AUTOMATED SURFACE

OBSERVING SYSTEM

Site Technical Manual

S100

AAI Systems Management Incorporated

ASOS Program Office

Silver Spring, Maryland

July 1998

U.S. DEPARTMENT OF COMMERCE

William M. Daley, Secretary

National Oceanic and Atmospheric Administration

D. James Baker, Administrator

National Weather Service

John J. Kelly, Jr. Director

This manual supersedes S100 dated May 92, which shall be destroyed in accordance with applicable

security regulations.
a

This manual contains certain material which is copyrighted by VAISALA

INC. and is reprinted courtesy of VAISALA INC. No person or entity is

authorized to copy or reprint this material without the written consent of:

VAISALA INC.

100 Commerce Way

Woburn, MA 01801

REGISTERED TRADEMARKS

PROCOMM PLUS is a registered trademark of Symantec Corporation.
CHANGE 1 INFORMATION

Change 1 consists of changes necessitated by the following task orders and ECPs:

TO 265 - RS 422 Pinout (ECP066)

TO 306 - DCP Power Expansion

TO 309 - ASOS Thunderstorm Sensor

TO 336 - ASOS Software Version 2.6

E93SM05F093- UPS Bypass

E94SM05F118- Wind Firmware Version 4.0

E94SM05F130- Wind Tower Watershield

E95SM05F139- High Speed Modems

E95SM05F150- Yagi Antenna

E95SM05F151- Temp Probe for DCP and SCA

E96SM05F158- RF Attenuators

E96SM05F161- Backup Sensors at Combined Sensor Group

E96SM05F163- Remote Wind Installation

E96SM05F166- Line Driver Replacement

E96SM05F167- Local OID and printer power by the UPS

E96SM05F168- Redesign Fiber Optic Cables

E96SM05F169- Press Vent Relocat on Alaska Shelters

E96SM05F174- Aluminum Pole for Freez Rain Snsr

E96SM05F176- DCP Pressure Sensor

E96SM05F181- Thunderstorm Sensor

E96SM05F185- SCA Solar Shield

E96SM05F186- Pressure Ports

E96SM05F187- Class I Delay Relay

E96SM05F189- Power Expansion at the ASOS DCP

E96SM05F190- Wind Sensor Direction Filter

E97SM05F195- SCA Thermostat Location

E97SM05F196- Temperature Probe Relocation

E97SM05F200- Visibility Firmware Version 039

E97SM05F202- Implementation of Software Version 2.4B

Change 1 also addresses and closes TPDRs

97-01 through 97-28

98-01 through 98-04

CHANGE 2 INFORMATION

Change 2 consists of changes necessitated by the following task orders and ECPs:

TO 347 - Uninterruptible Power Supply Replacement

E97SM05F203 - RF Modem Replacement

E97SM05F204 - Software Version 2.49

E98SM05F209 - SCA Combined Installation Alternative GTA Radio Antenna 

E98SM05F215 - Voice Software 4.0

Change 1 addresses and closes TPDRs

98-05 through 98-09

99-01 through 99-07
S100-ASOS Technical Manual Deficiency Report

INSTRUCTIONS: In a continuing effort to make our documents better, the NWS provides this form for

comments, suggestions for improvements, and identifying deficiencies. Be as specific as possible when

identifying deficiencies and recommended solutions. This form presented here can be completed

electronically within Adobe Reader and printed out. Return this form to the address provided below.

Return to:

NATIONAL WEATHER SERVICE

ASOS MAINTENANCE ASSURANCE W/OSO321

1325 EAST/WEST HIGHWAY, SSMC2

SILVER SPRING, MD 20910-3280

PAGE PARA/FIG/

TABLE

COMMENT

RECOMMENDED SOLUTION:

TYPE OF COMMENT: G Safety G Deficiency G Improvement

REMARK:

Name of Submitter:

Address:

City/State/Zip:

Date Submitted:

NWS USE ONLY

Date Rcvd Control No. Comment Publication Date
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NOTE: The portion of the text affected by the changes is indicated by a vertical line in the

outer margins of the page. Changes to illustrations are indicated by miniature

pointing hands. Changes to wiring diagrams are indicated by shaded areas.

Change 2 A

Dates of issue for original and changed pages are:

Original . . . 0 . . . March 97 Change . . . 1 . . . January 98

Change . . . 2 . . . December 98

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S100 ASOS Site Technical Manual

Change 2 i

TABLE OF CONTENTS

Chapter/Section/Paragraph Page

TABLE OF CONTENTS ....................................................................... i

LIST OF ILLUSTRATIONS ................................................................. xxiii

LIST OF TABLES ........................................................................ xxviii

SAFETY SUMMARY ..................................................................... xxxvi

LIST OF ABBREVIATIONS AND ACRONYMS .............................................. xxxviii

CHAPTER 1 SYSTEM OVERVIEW ........................................................... 1-1

SECTION I. DESCRIPTION AND LEADING PARTICULARS .............................. 1-1

1.1.1 INTRODUCTION ....................................................... 1-1

1.1.2 PURPOSE OF THIS MANUAL ............................................ 1-2

1.1.2.1 Chapter 1, System Overview ...................................... 1-2

1.1.2.2 Chapter 2, Acquisition Control Unit (ACU) ........................... 1-3

1.1.2.3 Chapter 3, Data Collection Package (DCP) ........................... 1-3

1.1.2.4 Chapters 4 through 13 and 16, Sensors and Subsystems ................. 1-3

1.1.2.5 Chapter 14, Single Cabinet ASOS (SCA) ............................ 1-3

1.1.2.6 Chapter 15, Port-Sharing Device (PSD) .............................. 1-3

1.1.2.7 Parts List ...................................................... 1-3

1.1.2.8 Maintenance Drawings ........................................... 1-3

1.1.3 SCOPE OF THIS MANUAL .............................................. 1-4

1.1.3.1 Section I, Description and Leading Particulars ........................ 1-4

1.1.3.2 Section II, Installation ........................................... 1-4

1.1.3.3 Section III, Operation ............................................ 1-4

1.1.3.4 Section IV, Theory of Operation ................................... 1-4

1.1.3.5 Section V, Maintenance .......................................... 1-4

1.1.4 ASOS SYSTEM DESCRIPTION ........................................... 1-4

1.1.5 SYSTEM CONFIGURATIONS ............................................ 1-5

1.1.6 RELATED PUBLICATIONS .............................................. 1-6

1.1.7 SYSTEM SPECIFICATIONS .............................................. 1-6

SECTION II. SYSTEM INSTALLATION ................................................ 1-9

SECTION III. OPERATION .......................................................... 1-11

1.3.1 INTRODUCTION ...................................................... 1-11

1.3.2 OPERATOR INTERFACE DEVICE (OID) CONTROLS AND INDICATORS ...... 1-11

1.3.3 PRINTER CONTROLS AND INDICATORS ................................ 1-13

1.3.4 MAINTENANCE SCREEN DESCRIPTIONS ................................ 1-13

1.3.4.1 Introduction .................................................. 1-13

1.3.4.2 Maintenance Screen Keypad ..................................... 1-15

1.3.4.3 Maintenance Screen Status Indicator Fields .......................... 1-15

1.3.4.4 Sensor Data Quality, Report Process, and Sensor Response Fields ........ 1-16

1.3.4.5 Maintenance Screen Description .................................. 1-18

1.3.4.6 Maintenance Action Selection .................................... 1-18

1.3.4.7 ACU Status Screen ............................................. 1-19

1.3.4.8 ACU VME Cards Screen ........................................ 1-20

1.3.4.9 CPU Screen .................................................. 1-20

1.3.4.10 Memory Screen .............................................. 1-22

1.3.4.11 Serial I/O Screen ............................................. 1-23
ASOS Site Technical Manual S100

TABLE OF CONTENTS - CONTINUED

Chapter/Section/Paragraph Page

ii Change 2

1.3.4.12 A/D Screen Description. ........................................ 1-24

1.3.4.13 Graphics Screen .............................................. 1-24

1.3.4.14 Voice Screen ................................................ 1-25

1.3.4.15 ACU Modem Screen .......................................... 1-26

1.3.4.16 ACU Power Screen ............................................ 1-27

1.3.4.17 ACU UPS Screen ............................................. 1-28

1.3.4.18 GTA Radio Screen ............................................ 1-30

1.3.4.19 Remote DCP Status Screen Description ............................ 1-31

1.3.4.20 DCP VME Cards Screen Description. ............................. 1-32

1.3.4.21 DCP #1, #2, #3 Power Screen ................................... 1-32

1.3.4.22 DCP UPS Screen ............................................. 1-33

1.3.4.23 Ceilometer and Ceilometer Sensor Dialogue Screens ................. 1-35

1.3.4.24 Freezing Rain Screen .......................................... 1-37

1.3.4.25 Present Weather Sensor Screen .................................. 1-37

1.3.4.26 Wind Speed and Direction Sensor Screen .......................... 1-39

1.3.4.27 Temperature/Dewpoint (Model 1088) Screen ....................... 1-41

1.3.4.28 Temperature/Dewpoint (Model H083) Screen ....................... 1-43

1.3.4.29 Visibility Sensor Screen ........................................ 1-44

1.3.4.30 Tipping Bucket Sensor Screen ................................... 1-45

1.3.4.31 Frozen Precipitation Screen ..................................... 1-46

1.3.4.32 Snow Depth Screen ........................................... 1-47

1.3.4.33 Sunshine Screen .............................................. 1-47

1.3.4.34 Thunderstorm Screen .......................................... 1-48

1.3.4.35 Pressure Sensor Screen. ........................................ 1-48

1.3.4.36 ACU/DCP Communications Status Screen ......................... 1-49

1.3.4.37 Trend Screen ................................................ 1-50

1.3.4.38 ADAS Summary Screen ........................................ 1-51

1.3.4.39 Processor Status Screen ........................................ 1-51

1.3.4.40 Maintenance Action Screen ..................................... 1-52

1.3.4.41 Preventive Maintenance Action Screen ............................ 1-53

1.3.4.42 Corrective Maintenance Action Screen ............................ 1-53

1.3.4.43 Calibration Maintenance Action Screen ............................ 1-53

1.3.4.44 Field Modification Kit Action Screen ............................. 1-53

1.3.5 SYSTEM POWER ON PROCEDURES ..................................... 1-53

1.3.6 SYSTEM SIGN-ON .................................................... 1-54

1.3.7 SYSTEM SIGNOFF .................................................... 1-54

1.3.8 RUNNING ASOS DIAGNOSTICS ........................................ 1-54

1.3.9 MONITORING/CONTROLLING SENSOR POWER FROM THE OID ........... 1-54

1.3.10 RECONFIGURING THE SYSTEM ....................................... 1-56

1.3.10.1 Configuring the OID ........................................... 1-56

1.3.10.2 Configuring the Remote Terminals ............................... 1-59

1.3.10.3 Deconfiguring and Reconfiguring Sensors to a Remote DCP ........... 1-59

1.3.11 DCP DOWNLOAD .................................................... 1-60

1.3.12 REVIEWING/PRINTING THE SYSTEM MAINTENANCE LOG .............. 1-61

1.3.13 ENTERING DATA INTO THE SYSTEM MAINTENANCE LOG .............. 1-62

1.3.14 REMOTE MAINTENANCE MONITORING ............................... 1-62

1.3.14.1 Remote OID Mode ............................................ 1-63

1.3.14.2 Direct Command Mode ........................................ 1-63

1.3.14.3 Monochrome Monitor Mode .................................... 1-65

1.3.14.4 ASCII Terminal Mode ......................................... 1-65

1.3.15 SYSTEM POWER OFF PROCEDURES ................................... 1-65

1.3.16 SITE CONFIGURATION SCREENS ...................................... 1-65
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1.3.16.1 Hardware Configuration Screen .................................. 1-66

1.3.16.2 Sensor Configuration Screen .................................... 1-67

1.3.16.3 Sensor-Algorithm Configuration Screen ........................... 1-67

1.3.16.4 Define Configuration Screen .................................... 1-68

1.3.16.5 ACU Serial Communications Screen .............................. 1-69

1.3.16.6 External Communications Screen ................................. 1-69

1.3.17 SITE SCREENS ...................................................... 1-70

1.3.17.1 Site Physical Screen ........................................... 1-70

1.3.17.2 Site Version Screen ........................................... 1-71

1.3.17.3 Site Normals Screen ........................................... 1-73

1.3.17.4 Site Pressure Screen ........................................... 1-73

1.3.17.5 Site Criteria Screen ............................................ 1-73

SECTION IV. SYSTEM THEORY OF OPERATION ...................................... 1-75

1.4.1 INTRODUCTION ...................................................... 1-75

1.4.2 ACQUISITION CONTROL UNIT (ACU) ................................... 1-75

1.4.3 PERIPHERALS ........................................................ 1-75

1.4.4 DATA COLLECTION PACKAGE (DCP) ................................... 1-76

1.4.5 SENSORS ............................................................ 1-77

1.4.6 ASOS OPERATION AND MONITORING CENTER (AOMC) .................. 1-77

1.4.6.1 ASOS/AOMC Interface ......................................... 1-77

1.4.6.2 ASOS Trouble Monitoring ....................................... 1-77

1.4.6.3 ASOS Site Specific Data ........................................ 1-77

1.4.6.3.1 File Upload and Download .............................. 1-78

1.4.6.3.2 Upload/Download Sequence ............................. 1-78

1.4.6.4 ASOS Time Synchronization ..................................... 1-78

1.4.6.4.1 AOMC Interface to ACTS .............................. 1-78

1.4.6.4.2 ASOS Synchronization Sequence ......................... 1-78

SECTION V. SYSTEM MAINTENANCE ............................................... 1-79

1.5.1 INTRODUCTION ...................................................... 1-79

1.5.2 MAINTENANCE ACTION RECORDING AND DOCUMENTATION ............ 1-79

1.5.3 PREVENTIVE MAINTENANCE (PM) ..................................... 1-81

1.5.3.1 Introduction .................................................. 1-81

1.5.3.2 Visual Inspection .............................................. 1-83

1.5.3.3 Cleaning ..................................................... 1-83

1.5.3.4 Corrosion Removal and Prevention, Steel Surfaces .................... 1-83

1.5.3.5 Refurbishment of Painted Aluminum Surfaces ........................ 1-84

1.5.4 CORRECTIVE MAINTENANCE ......................................... 1-87

1.5.4.1 Introduction .................................................. 1-87

1.5.4.2 System Diagnostics ............................................. 1-87

1.5.4.3 Fiberoptic Module Test ......................................... 1-87

1.5.4.4 Fiberoptic Cable Replacement .................................... 1-87

CHAPTER 2 ACQUISITION CONTROL UNIT (ACU) AND PERIPHERALS .......................... 2-1

SECTION I. DESCRIPTION AND LEADING PARTICULARS .............................. 2-1

2.1.1 INTRODUCTION ....................................................... 2-1

2.1.2 PHYSICAL DESCRIPTION ............................................... 2-2

2.1.2.1 Class I and Class II Systems ....................................... 2-2

2.1.2.2 ACU Cabinet. .................................................. 2-3

2.1.2.2.1 ACU Tie-Down ....................................... 2-3
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2.1.2.3 Controller Video Displays (CVD's) ................................. 2-3

2.1.2.4 Printer ........................................................ 2-3

2.1.2.5 FAA Handset .................................................. 2-3

2.1.2.6 Operator Interface Devices (OID's) ................................. 2-7

2.1.2.7 RF Antenna .................................................... 2-7

2.1.2.8 Observer Notification Device (OND) ................................ 2-7

2.1.2.9 Video Display Unit (VDU) ....................................... 2-7

2.1.2.10 Airline Displays ............................................... 2-7

2.1.3 ACU CONFIGURATIONS ................................................ 2-7

SECTION II. INSTALLATION ....................................................... 2-16

SECTION III. OPERATION .......................................................... 2-19

2.3.1 INTRODUCTION ...................................................... 2-19

2.3.2 CONTROLS AND INDICATORS ......................................... 2-19

2.3.2.1 Operator Interface Device (OID) .................................. 2-19

2.3.2.2 Printer ....................................................... 2-19

2.3.2.3 Controller Video Display (CVD) .................................. 2-19

2.3.2.4 Observer Notification Device (OND) ............................... 2-19

2.3.2.5 Card Rack Assembly ........................................... 2-19

2.3.2.6 Modem AC Power Rack ......................................... 2-19

2.3.2.7 Power Supply Assembly ......................................... 2-26

2.3.2.8 DC Power Supply Enclosure ..................................... 2-26

2.3.2.9 Codex ....................................................... 2-26

2.3.3 OPERATIONAL PROCEDURES .......................................... 2-32

2.3.3.1 ACU Power Up and Power Down Procedures ........................ 2-32

2.3.3.2 Providing Site ID and AOMC Phone Number ...................... 2-32.1

2.3.3.3 Refresh OID ................................................ 2-32.1

2.3.4 USING LAPTOP COMPUTER AS PRIMARY OID ......................... 2-32.2

SECTION IV. THEORY OF OPERATION .............................................. 2-33

2.4.1 ACU AND PERIPHERALS OVERVIEW ................................... 2-33

2.4.2 SIMPLIFIED BLOCK DIAGRAM DESCRIPTION ........................... 2-33

2.4.2.1 Data Processing ............................................... 2-33

2.4.2.1.1 Central Processing Units (CPU's) ......................... 2-33

2.4.2.1.2 Memory Board ....................................... 2-33

2.4.2.2 Data Input/Output .............................................. 2-33

2.4.2.2.1 Serial I/O Boards ..................................... 2-34

2.4.2.2.2 Analog to Digital (A/D) and VME Resistor Boards ........... 2-34

2.4.2.2.3 Digital I/O Board ..................................... 2-34

2.4.2.2.4 Digital Voice Processing ............................... 2-34

2.4.2.2.5 Video Controller Board ................................ 2-34

2.4.2.2.6 ACU/DCP Communication ............................. 2-37

2.4.2.2.7 Telephone Modems ................................... 2-37

2.4.2.3 Power Distribution and Control ................................... 2-37

2.4.3 DETAILED BLOCK DIAGRAM DESCRIPTION ............................ 2-37

2.4.3.1 General. ..................................................... 2-37

2.4.3.2 Card Rack Assembly ........................................... 2-38

2.4.3.2.1 Central Processing Unit (CPU) .......................... 2-38

2.4.3.2.2 Memory Board ....................................... 2-42

2.4.3.2.3 Serial I/O (SIO) Board ................................. 2-43

2.4.3.2.4 Voice Processor and Voice Recorder/Playback Boards ........ 2-44
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2.4.3.2.5 Video Board ......................................... 2-53

2.4.3.2.6 Digital I/O Board ..................................... 2-53

2.4.3.2.7 A/D Board and VME Resistor Board ...................... 2-53

2.4.3.3 Digital Voice Processor System ................................... 2-53

2.4.3.3.1 Voice Processor Board ................................. 2-54

2.4.3.3.2 Voice Recorder/Playback Board ......................... 2-54

2.4.3.3.3 Testing the Digital Voice Processing System ................ 2-57

2.4.3.4 Modem Communications ........................................ 2-57

2.4.3.4.1 Telephone Modems ................................... 2-57

2.4.3.4.2 RF Modems ......................................... 2-58

2.4.3.4.3 Line Drivers ......................................... 2-73

2.4.3.5 Pressure Sensors ............................................... 2-73

2.4.3.6 Local Sensor Fiberoptic Modems .................................. 2-74

2.4.3.7 Observer Notification Device and Peripheral Power ................... 2-74

2.4.3.8 ACU Power and Signal Monitoring ................................ 2-74

2.4.3.9 Power Distribution and Control ................................... 2-89

2.4.3.9.1 AC Distribution ...................................... 2-90

2.4.3.9.2 AC Distribution for Power Supply Assembly 62828-40124-10 . . 2-90

2.4.3.9.3 AC Distribution for Power Supply Assembly 62828-40265-10 . . 2-94

2.4.3.9.4 DC Power Distribution ................................. 2-97

SECTION V. MAINTENANCE ...................................................... 2-107

2.5.1 INTRODUCTION ..................................................... 2-107

2.5.2 PREVENTIVE MAINTENANCE ........................................ 2-107

2.5.2.1 Air Filter Cleaning ............................................ 2-107

2.5.2.2 Display Screen Cleaning ....................................... 2-107

2.5.2.3 ACU Cabinet Cleaning ......................................... 2-107

2.5.2.4 Check Memory Board LOW BATT Indicator ....................... 2-107

2.5.2.5 Check/Clean Batteries ......................................... 2-107

2.5.3 CORRECTIVE MAINTENANCE ........................................ 2-109

2.5.3.1 Introduction ................................................. 2-109

2.5.3.2 UPS Checks ................................................. 2-109

2.5.3.3 VME Card Rack Check ........................................ 2-117

2.5.3.4 ACU/DCP Communication System Checks ......................... 2-118

2.5.3.4.1 RF Communications .................................. 2-118

2.5.3.4.2 Line Driver Communications ........................... 2-119

2.5.3.5 Serial I/O Board Checks ........................................ 2-127

2.5.3.6 Diagnostics .................................................. 2-128

2.5.4 REMOVAL AND INSTALLATION PROCEDURES ......................... 2-128

2.5.4.1 General ..................................................... 2-128

2.5.4.2 Orienting DB-25 Adapters ...................................... 2-129

2.5.5 SETTING UP LEASED LINE MODEMS .................................. 2-155

2.5.5.1 Setting Up ACU Rack-Mounted Modems .......................... 2-155

2.5.5.2 Setting Up Stand Alone Modems ................................. 2-155

2.5.6 SETTING UP LINE DRIVER MODEMS .................................. 2-155

2.5.7 SETTING UP A DOT MATRIX PRINTER ................................. 2-158

2.5.7.1 ACU Serial Communications .................................... 2-158

2.5.8 ACU CPU AND SIO BOARD JUMPER CONFIGURATIONS ................. 2-163

2.5.9 JOHNSON DATA RF MODEM SETUP ................................... 2-163

CHAPTER 3 DATA COLLECTION PACKAGE .................................................. 3-1
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SECTION I. DESCRIPTION AND LEADING PARTICULARS .............................. 3-1

3.1.1 INTRODUCTION ....................................................... 3-1

3.1.2 PURPOSE ............................................................. 3-1

3.1.2.1 Class I and Class II Systems ....................................... 3-2

3.1.2.2 Optional Auxiliary Box .......................................... 3-2

3.1.3 PHYSICAL DESCRIPTION ............................................... 3-2

3.1.3.1 DCP Equipment Cabinet, Unit 2, 3, or 4 ............................. 3-2

3.1.3.1.1 Card Rack Assembly A1A2 .............................. 3-7

3.1.3.1.2 Circuit Breaker Rack 1A1A3 ............................. 3-7

3.1.3.1.3 DCP Uninterruptible Power Supply (UPS) ................... 3-7

3.1.3.1.3a Power Reset Assembly .......................... 3-8

3.1.3.1.3b UPS Bypass Circuit ............................ 3-8

3.1.3.1.4 DCP Heaters ......................................... 3-11

3.1.3.1.5 Faraday Box A3 ...................................... 3-11

3.1.3.2 AC Junction Box .............................................. 3-11

3.1.3.3 RF Antenna ................................................... 3-11

3.1.4 DCP CONFIGURATIONS ............................................... 3-11

SECTION II. INSTALLATION ....................................................... 3-15

SECTION III. OPERATION .......................................................... 3-17

3.3.1 INTRODUCTION ...................................................... 3-17

3.3.2 CONTROLS AND INDICATORS ......................................... 3-17

3.3.2.1 UPS Status Panel .............................................. 3-17

3.3.2.2 Card Rack Assembly A1A2 ...................................... 3-17

3.3.2.3 Circuit Breaker Rack A1A3 ...................................... 3-17

3.3.2.4 RF Modems ................................................ 3-18.1

3.3.3 OPERATIONAL PROCEDURES .......................................... 3-19

3.3.4 USING LAPTOP COMPUTER AS DCP OID ................................ 3-19

SECTION IV. THEORY OF OPERATION .............................................. 3-23

3.4.1 DATA COLLECTION PACKAGE (DCP) OVERVIEW ........................ 3-23

3.4.2 DCP BASIC BLOCK DIAGRAM DESCRIPTION ............................ 3-23

3.4.2.1 General ...................................................... 3-23

3.4.2.2 DCP Data Processing ........................................... 3-23

3.4.2.2.1 CPU Boards ......................................... 3-23

3.4.2.2.2 Memory Board ....................................... 3-23

3.4.2.3 DCP Input/Output .............................................. 3-23

3.4.2.3.1 DCP/ACU Communication .............................. 3-23

3.4.2.3.2 Serial I/O (SIO) Boards ................................. 3-24

3.4.2.3.3 Analog to Digital (A/D) and VME Resistor Boards ........... 3-24

3.4.2.3.4 Digital I/O Board ..................................... 3-24

3.4.2.4 DCP Power Distribution and Control ............................... 3-24

3.4.3 DCP DETAILED BLOCK DIAGRAM DESCRIPTION ........................ 3-29

3.4.3.1 General ...................................................... 3-29

3.4.3.2 DCP Card Rack Assembly ....................................... 3-29

3.4.3.2.1 Central Processing Units (CPU's) ......................... 3-29

3.4.3.2.2 Memory Board ....................................... 3-30

3.4.3.2.3 Serial I/O (SIO) Boards ................................. 3-37

3.4.3.2.4 A/D Boards, Digital I/O Board, and VME Resistor Board ...... 3-38

3.4.3.3 RF Modem Communications ..................................... 3-38

3.4.3.3.1 RF Modem Rack ...................................... 3-38
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3.4.3.3.2 Line Drivers ......................................... 3-39

3.4.3.3A. Pressure Sensors ...................................... 3-39

3.4.3.4 Fiberoptic Modules ............................................ 3-40

3.4.3.5 DCP Power and Signal Monitoring ................................ 3-40

3.4.3.6 Power Distribution and Control ................................... 3-57

3.4.3.6.1 AC Distribution - General ............................... 3-58

3.4.3.6.2 DC Power Distribution ................................. 3-82

SECTION V. MAINTENANCE ....................................................... 3-85

3.5.1 INTRODUCTION ...................................................... 3-85

3.5.2 PREVENTIVE MAINTENANCE ......................................... 3-85

3.5.2.1 Cabinet Cleaning and Inspection .................................. 3-85

3.5.2.2 Check/Clean Batteries .......................................... 3-85

3.5.3 CORRECTIVE MAINTENANCE ......................................... 3-86

3.5.3.1 Introduction .................................................. 3-86

3.5.3.2 UPS Checks .................................................. 3-87

3.5.3.3 VME Card Rack Check ......................................... 3-87

3.5.3.4 Serial I/O Board Checks ......................................... 3-97

3.5.3.5 DCP Equipment Cabinet Heater Troubleshooting ..................... 3-97

3.5.3.6 Diagnostics ................................................... 3-97

3.5.4 REMOVAL AND INSTALLATION PROCEDURES .......................... 3-98

3.5.5 DCP CPU AND SIO (RS-232) BOARD JUMPER CONFIGURATIONS .......... 3-129

3.5.6 SETTING UP LINE DRIVER MODULE ................................... 3-129

3.5.7 SETTING UP JOHNSON DATA RF MODEMS ............................. 3-129

CHAPTER 4 WIND SENSOR ................................................................. 4-1

SECTION I. DESCRIPTION AND LEADING PARTICULARS .............................. 4-1

4.1.1 INTRODUCTION ....................................................... 4-1

4.1.2 PHYSICAL DESCRIPTION ............................................... 4-1

4.1.2.1 Introduction ................................................... 4-1

4.1.2.2 System Physical Components ...................................... 4-1

4.1.3 WIND SENSOR CONFIGURATIONS ...................................... 4-1

4.1.3.1 Wind Speed Sensor ............................................. 4-2

4.1.3.1.1 Wind Speed Transducer ................................. 4-2

4.1.3.1.2 Wind Speed Cup Assembly ............................... 4-3

4.1.3.2 Wind Direction Sensor ........................................... 4-3

4.1.3.2.1 Wind Direction Transducer ............................... 4-3

4.1.3.2.2 Wind Direction Vane Assembly ........................... 4-4

4.1.3.3 Crossarm Assembly ............................................. 4-4

4.1.3.4 Wind Sensor Electronics Enclosure ................................. 4-4

SECTION II. INSTALLATION ........................................................ 4-5

4.2.1 INTRODUCTION ....................................................... 4-5

4.2.2 ASSEMBLY ........................................................... 4-5

4.2.2.1 Mounting Wind Sensor Electronics Enclosure ......................... 4-5

4.2.2.2 Installing Crossarm Support on Tower ............................... 4-5

SECTION III. OPERATION .......................................................... 4-11

4.3.1 INTRODUCTION ...................................................... 4-11

SECTION IV. THEORY OF OPERATION .............................................. 4-13
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4.4.1 INTRODUCTION ...................................................... 4-13

4.4.2 WIND SENSOR SENSING TECHNIQUES ................................. 4-13

4.4.2.1 Wind Speed and Direction ....................................... 4-13

4.4.2.2 Temperature .................................................. 4-13

4.4.3 BLOCK DIAGRAM DESCRIPTION ....................................... 4-13

4.4.3.1 Wind Speed Sensor ............................................ 4-13

4.4.3.2 Wind Direction Sensor .......................................... 4-14

4.4.3.3 Data Processing Board .......................................... 4-14

4.4.3.4 Fiberoptic Module ............................................. 4-15

4.4.3.5 Wind Sensor Power Distribution .................................. 4-15

4.4.3.6 Obstruction Lights ............................................. 4-15

SECTION V. MAINTENANCE ....................................................... 4-23

4.5.1 INTRODUCTION ...................................................... 4-23

4.5.2 PREVENTIVE MAINTENANCE ......................................... 4-23

4.5.2.1 Routine Inspection ............................................. 4-23

4.5.2.2 Obstruction Lights Check ........................................ 4-23

4.5.2.3 Mechanical Operation Inspection .................................. 4-23

4.5.2.4 Checking Wind Direction and Speed Data ........................... 4-23

4.5.2.5 Wind Direction Sensor Alignment Procedure ........................ 4-24

4.5.2.5.1 Solar Noon Wind Direction Sensor Alignment Procedure ...... 4-24

4.5.2.5.2 Davis Pelorus Instrument Wind Direction Sensor Alignment

Procedure ................................................... 4-24

4.5.2.6 Cleaning and Lubrication ........................................ 4-24

4.5.3 CORRECTIVE MAINTENANCE ......................................... 4-35

4.5.3.1 Diagnostics ................................................... 4-35

4.5.3.2 Troubleshooting ............................................... 4-35

4.5.3.3 Lowering and Raising the Wind Tower ............................. 4-35

4.5.3.4 Wind Direction and Wind Speed Sensors Removal and Installation ....... 4-35

4.5.3.5 Power Supply Removal and Installation ............................. 4-35

4.5.3.6 Fiberoptic Module Removal and Installation ......................... 4-35

4.5.3.7 Processor Board Removal and Installation ........................... 4-35

4.5.3.8 Wind Sensor Electronics Enclosure Removal and Installation ............ 4-36

4.5.3.9 Wind Tower Signal Cable W1 Removal and Installation ................ 4-36

4.5.3.10 Crossarm Assembly Removal and ................................ 4-36

4.5.3.11 Starting Torque Bearing Test .................................... 4-36

CHAPTER 5 TEMPERATURE/DEWPOINT SENSORS ........................................... 5-1

SECTION I. DESCRIPTION AND LEADING PARTICULARS .............................. 5-1

5.1.1 INTRODUCTION ...................................................... 5-1

5.1.2 PHYSICAL DESCRIPTION ............................................... 5-1

5.1.2.1 Introduction ................................................... 5-1

5.1.2.2 Physical Components ............................................ 5-1

5.1.2.3 Principles of Operation ........................................... 5-1

5.1.2.4 Aspirator 2MT4A1 .............................................. 5-2

5.1.2.5 Transmitter 2MT4A2 ............................................ 5-2

5.1.2.5.1 Transmit Logic Board 2MT4A2A1 ......................... 5-3

5.1.2.5.2 Calibrator Assembly 2MT4A2A2 .......................... 5-3

5.1.2.5.3 +5 Volt Power Supply 2MT4A2A3 ........................ 5-3

5.1.2.5.4 Auxiliary Power Supply 2MT4A2A4 ....................... 5-4

5.1.2.5.5 Autobalance Module 2MT4A2A5 ......................... 5-5
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5.1.2.5.6 Fiberoptic Module 2MT4A2A6 ........................... 5-5

5.1.3 TEMPERATURE/DEWPOINT SENSOR CONFIGURATIONS .................. 5-5

5.1.3.1 FRU’s Common to -30 and -40 Configurations ........................ 5-5

5.1.3.2 FRU’s Unique to Each Configuration ............................... 5-5

SECTION II. INSTALLATION ........................................................ 5-7

5.2.1 INTRODUCTION ...................................................... 5-7

5.2.2 TEMPERATURE/DEWPOINT SENSOR INSTALLATION ..................... 5-7

SECTION III. OPERATION .......................................................... 5-11

5.3.1 INTRODUCTION ...................................................... 5-11

5.3.2 CONTROLS AND INDICATORS ......................................... 5-11

5.3.3 TURN-ON PROCEDURES .............................................. 5-11

5.3.4 CHECKOUT PROCEDURES ............................................. 5-11

5.3.4.1 Model H083R Checkout ......................................... 5-11

5.3.4.2 Model 1088 Checkout .......................................... 5-11

5.3.5 RUNNING DIAGNOSTICS .............................................. 5-11

5.3.6 NORMAL OPERATING PROCEDURES ................................... 5-14

5.3.7 TURNOFF PROCEDURES .............................................. 5-14

SECTION IV. THEORY OF OPERATION .............................................. 5-15

5.4.1 INTRODUCTION ...................................................... 5-15

5.4.2 TEMPERATURE/DEWPOINT SENSOR MEASUREMENT SYSTEM CONCEPTS

DESCRIPTION ............................................................. 5-15

5.4.3 DETAILED BLOCK DIAGRAM DESCRIPTION ............................ 5-16

5.4.3.1 General ...................................................... 5-16

5.4.3.2 Aspirator 2MT4A1 ............................................. 5-16

5.4.3.3 Transmitter 2MT4A2 ........................................... 5-17

SECTION V. MAINTENANCE ....................................................... 5-29

5.5.1 INTRODUCTION ...................................................... 5-29

5.5.2 PREVENTIVE MAINTENANCE ......................................... 5-29

5.5.2.1 General ...................................................... 5-29

5.5.2.2 Aspirator Cleaning and Inspection ................................. 5-29

5.5.2.3 Optical Loop Adjustment ........................................ 5-31

5.5.2.4 Verify ASOS Temperature and Dewpoint Readings ................... 5-32

5.5.2.5 Deleted. ..................................................... 5-35

5.5.2.6 DC Power Supply Check ........................................ 5-36

5.5.2.7 Calibration ................................................... 5-38

5.5.3 CORRECTIVE MAINTENANCE ......................................... 5-39

5.5.3.1 Troubleshooting Procedures ...................................... 5-39

5.5.3.2 Running Diagnostics ............................................ 5-39

5.5.3.3 Dewpoint Sensor Assembly Removal and Installation .................. 5-39

5.5.3.4 Aspirator Housing Removal and Installation ......................... 5-39

5.5.3.5 Transmit Logic Board Removal and Installation ...................... 5-39

5.5.3.6 Autobalance Module Removal and Installation. ...................... 5-40

5.5.3.7 Power Supplies Removal and Installation ........................... 5-40

5.5.3.8 Fiberoptic Module Removal and Installation ......................... 5-40

CHAPTER 6 VISIBILITY AND DAY/NIGHT SENSOR ........................................... 6-1

SECTION I. DESCRIPTION AND LEADING PARTICULARS .............................. 6-1
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6.1.1 INTRODUCTION ....................................................... 6-1

6.1.2 PHYSICAL DESCRIPTION ............................................... 6-1

6.1.2.1 Upper Section .................................................. 6-1

6.1.2.1.1 Crossarm/Support ...................................... 6-1

6.1.2.1.2 Transmitter Assembly ................................... 6-1

6.1.2.1.3 Receiver Assembly ..................................... 6-2

6.1.2.1.4 Day/Night Assembly .................................... 6-2

6.1.2.2 Lower Section .................................................. 6-3

6.1.2.2.1 Electronics Enclosure ................................... 6-3

6.1.2.2.2 Enclosure Support ...................................... 6-3

6.1.2.3 Cabling ....................................................... 6-3

6.1.3 SPECIFICATIONS ...................................................... 6-3

6.1.3.1 Configurations ................................................. 6-4

SECTION II. INSTALLATION ........................................................ 6-5

6.2.1 INTRODUCTION ....................................................... 6-5

6.2.2 ASSEMBLY ........................................................... 6-5

6.2.2.1 Hinge Plate Assembly ........................................... 6-5

6.2.2.2 Enclosure Support .............................................. 6-5

6.2.2.3 Electronics Enclosure ............................................ 6-5

6.2.2.4 Crossarm Support ............................................... 6-5

6.2.2.5 Crossarm ...................................................... 6-5

6.2.2.6 Day/Night Sensor ............................................... 6-5

6.2.3 CABLES ............................................................. 6-10

SECTION III. VISIBILITY SENSOR OPERATION ....................................... 6-13

6.3.1 INTRODUCTION ...................................................... 6-13

6.3.2 CONTROLS AND INDICATORS ......................................... 6-13

6.3.3 TURN-ON PROCEDURES .............................................. 6-13

6.3.4 NORMAL OPERATION ................................................ 6-13

6.3.5 TURNOFF PROCEDURES .............................................. 6-13

SECTION IV. THEORY OF OPERATION .............................................. 6-15

6.4.1 INTRODUCTION ...................................................... 6-15

6.4.2 SIMPLIFIED BLOCK DIAGRAM DESCRIPTION ........................... 6-15

6.4.2.1 Principles of Operation .......................................... 6-15

6.4.2.2 Visibility Sensor Basic Block Diagram Description .................... 6-15

6.4.3 DETAILED BLOCK DIAGRAM DESCRIPTION ............................ 6-15

6.4.3.1 Transmitter Assembly ........................................... 6-16

6.4.3.2 Receiver Assembly ............................................. 6-16

6.4.3.3 Day/Night Assembly ........................................... 6-25

6.4.3.4 Processor Board ............................................... 6-25

6.4.3.5 Fiberoptic Module ............................................. 6-25

6.4.3.6 Power Distribution ............................................. 6-25

6.4.4 COMMAND DESCRIPTION ............................................. 6-26

6.4.4.1 Quick Reference ............................................... 6-26

6.4.4.1.1 Polled Mode ......................................... 6-26

6.4.4.1.2 Continuous Output Mode ............................... 6-26

6.4.4.1.3 Other ............................................... 6-26

6.4.4.2 Power Up/Reset Message ........................................ 6-31

6.4.4.3 V0 Command (Roll Call) ........................................ 6-31

6.4.4.4 V1 Command (Extinction Coefficient) .............................. 6-31
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6.4.4.5 V2 Command (Simulated Data) ................................... 6-31

6.4.4.6 V4 Command (Data Quality) ..................................... 6-32

6.4.4.7 VD Command (Standard Deviation of Zero Drift) ..................... 6-32

6.4.4.8 VD Command (Calibration Coefficients/Configuration Information) ...... 6-32

6.4.4.9 VL Command (Polled Mode, Extended Output Message) ............... 6-34

6.4.4.10 VG Command (Extended Diagnostics) ............................ 6-34

6.4.4.11 VH Command (Calibration Factors) .............................. 6-35

6.4.4.12 VP Command (Automatic Report) ................................ 6-35

6.4.4.13 VR Command (Reset Sensor) .................................... 6-36

SECTION V. MAINTENANCE ....................................................... 6-37

6.5.1 INTRODUCTION ...................................................... 6-37

6.5.2 PREVENTIVE MAINTENANCE ......................................... 6-37

6.5.2.1 General ...................................................... 6-37

6.5.2.2 Calibration ................................................... 6-37

6.5.3 CORRECTIVE MAINTENANCE ......................................... 6-37

6.5.3.1 General ...................................................... 6-37

6.5.3.2 AC and DC Power Troubleshooting ................................ 6-37

6.5.3.3 Heater ...................................................... 6-37

6.5.4 DIAGNOSTICS ........................................................ 6-38

6.5.4.1 Introduction .................................................. 6-38

6.5.4.2 Executing Diagnostics .......................................... 6-38

6.5.5 FRU REMOVAL AND INSTALLATION ................................... 6-39

6.5.5.1 Receiver Assembly Removal and Installation ........................ 6-39

6.5.5.2 Transmitter Assembly Removal and Installation ...................... 6-39

6.5.5.3 Processor Board Removal and Installation ........................... 6-39

6.5.5.4 Day/Night Assembly Removal and Installation ....................... 6-39

6.5.5.5 Electronics Power Supply Removal and Installation ................... 6-39

6.5.5.6 Fiberoptic Module Removal and Installation ......................... 6-39

6.5.5.7 Crossarm Assembly Removal and Installation ........................ 6-39

6.5.5.8 Electronics Enclosure Removal and Installation. ...................... 6-39

6.5.5.9 Regulator Board Removal and Installation ........................... 6-39

CHAPTER 7 PRESENT WEATHER SENSOR ................................................... 7-1

SECTION I. DESCRIPTION AND LEADING PARTICULARS .............................. 7-1

7.1.1 INTRODUCTION ....................................................... 7-1

7.1.2 PHYSICAL DESCRIPTION ............................................... 7-1

7.1.2.1 General ....................................................... 7-1

7.1.2.2 Frame Assembly ................................................ 7-1

7.1.2.3 Main Electrical Enclosure Assembly ................................ 7-2

7.1.3 PRESENT WEATHER SENSOR CONFIGURATIONS ......................... 7-2

SECTION II. INSTALLATION ........................................................ 7-3

7.2.1 INTRODUCTION ....................................................... 7-3

7.2.2 ASSEMBLY ........................................................... 7-3

7.2.3 INSTALLING THE PRESENT WEATHER SENSOR .......................... 7-3

SECTION III. OPERATION ........................................................... 7-7

7.3.1 INTRODUCTION ....................................................... 7-7

SECTION IV. THEORY OF OPERATION ............................................... 7-9
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7.4.1 INTRODUCTION ....................................................... 7-9

7.4.2 SIMPLIFIED BLOCK DIAGRAM DESCRIPTION ............................ 7-9

7.4.2.1 Principles of Operation ........................................... 7-9

7.4.2.2 Simplified Block Diagram Description .............................. 7-9

7.4.3 DETAILED BLOCK DIAGRAM DESCRIPTION ............................ 7-10

7.4.3.1 General ...................................................... 7-10

7.4.3.2 Transmitter Board (2MT2A1A1A1) ............................... 7-10

7.4.3.3 Transmitter Head (Part of Frame Assembly 2MT2A2) ................. 7-10

7.4.3.4 Receiver Head (Part of Frame Assembly 2MT2A2) ................... 7-10

7.4.3.5 Receiver AGC Board (2MT2A1A1A8) ............................. 7-11

7.4.3.6 Signal Processor Board No. 1 (2MT2A1A1A7) ...................... 7-11

7.4.3.7 Signal Processor Board No. 2 (2MT2A1A1A6) ...................... 7-12

7.4.3.8 Microprocessor Board (2MT2A1A1A3) ............................ 7-12

7.4.3.9 Fiberoptic Module (2MT2A1A2A1) ............................... 7-12

7.4.3.10 Power Distribution ............................................ 7-12

7.4.4 POLL/FRAME FORMATS ............................................... 7-21

7.4.4.1 Type A - Routine Data Poll ...................................... 7-21

7.4.4.2 Type B - Simulated Data Poll ..................................... 7-21

7.4.4.3 Type C - Full Raw Data Poll ..................................... 7-22

7.4.4.4 Field Description .............................................. 7-23

7.4.4.5 Status Field Encoding ........................................... 7-23

SECTION V. MAINTENANCE ....................................................... 7-27

7.5.1 INTRODUCTION ...................................................... 7-27

7.5.2 PREVENTIVE MAINTENANCE ......................................... 7-27

7.5.2.1 Checking Lens and Hood Heaters ................................. 7-27

7.5.2.2 Cleaning Transmitter and Receiver Lenses .......................... 7-27

7.5.2.3 Calibration ................................................... 7-27

7.5.2.4 Present Weather Sensor Spider Paint Application Procedure ............ 7-27

7.5.3 CORRECTIVE MAINTENANCE ......................................... 7-28

7.5.4 FRU REMOVAL AND INSTALLATION ................................... 7-28

7.5.4.1 Frame Head Assembly Removal and Installation ...................... 7-28

7.5.4.2 Heater Power Supply Removal and Installation ....................... 7-28

7.5.4.3 Analog Power Supply Removal and Installation ...................... 7-28

7.5.4.4 Digital Power Supply Removal and Installation ....................... 7-28

7.5.4.5 Circuit Board Removal and Installation ............................. 7-28

7.5.4.6 Fiberoptic Module Removal and Installation ......................... 7-28

7.5.4.7 Heater Bar Assembly Removal and Installation ....................... 7-28

7.5.4.8 Card Rack Assembly Removal and Installation ....................... 7-28

7.5.4.9 Main Electrical Enclosure Removal and Installation ................... 7-28

CHAPTER 8 PRESSURE SENSOR ............................................................ 8-1

SECTION I. DESCRIPTION AND LEADING PARTICULARS .............................. 8-1

8.1.1 INTRODUCTION ...................................................... 8-1

8.1.2 PHYSICAL DESCRIPTION .............................................. 8-1

8.1.3 PRESSURE SENSOR CONFIGURATIONS .................................. 8-1

8.1.3.1 Class I System Pressure Sensors .................................... 8-4

8.1.3.2 Class II System Pressure Sensors ................................... 8-4

8.1.3.3 Model 470T Extended Range Pressure Sensor ......................... 8-4

8.1.3.4 Single Cabinet ASOS Pressure Sensor ............................... 8-4

8.1.3.5 Data Collection Package Pressure Sensor ............................ 8-4
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SECTION II. INSTALLATION ........................................................ 8-5

8.2.1 INTRODUCTION ....................................................... 8-5

SECTION III. OPERATION .......................................................... 8-7

8.3.1 INTRODUCTION ....................................................... 8-7

8.3.2 TURN-ON PROCEDURES ............................................... 8-7

8.3.3 TURNOFF PROCEDURES ............................................... 8-7

8.3.4 NORMAL OPERATION ................................................. 8-7

SECTION IV. THEORY OF OPERATION ............................................... 8-9

8.4.1 INTRODUCTION ....................................................... 8-9

8.4.2 SIMPLIFIED BLOCK DIAGRAM DESCRIPTION ............................ 8-9

SECTION V. MAINTENANCE ....................................................... 8-11

8.5.1 INTRODUCTION ...................................................... 8-11

8.5.2 PREVENTIVE MAINTENANCE ......................................... 8-11

8.5.2.1 General ...................................................... 8-11

8.5.2.2 Pressure Sensor Cleaning and Inspection ............................ 8-11

8.5.2.3 Verifying Accuracy of Pressure Sensor Data ......................... 8-11

8.5.2.3.1 Use of the Portable Pressure Standard ..................... 8-11

8.5.3 CORRECTIVE MAINTENANCE ......................................... 8-13

8.5.3.1 Introduction .................................................. 8-13

8.5.3.2 Troubleshooting ............................................... 8-13

8.5.4 PRESSURE SENSOR REMOVAL AND INSTALLATION ..................... 8-14

8.5.5 PRESSURE SENSOR REPORT PROCESSING PROCEDURES ................. 8-14

8.5.6 CLEARING PRESSURE SENSOR DATA QUALITY FAILURES ............... 8-14

8.5.6.1 Effect of Data Quality Failures on Altimeter Report ................... 8-15

8.5.6.2 Clearing Pressure Sensor Data Quality Failures ....................... 8-15

CHAPTER 9 CLOUD HEIGHT SENSOR (CEILOMETER) ......................................... 9-1

SECTION I. DESCRIPTION AND LEADING PARTICULARS .............................. 9-1

9.1.1 INTRODUCTION ....................................................... 9-1

9.1.2 PHYSICAL DESCRIPTION ............................................... 9-1

9.1.2.1 General Description. ............................................. 9-1

9.1.2.2 System Components ............................................. 9-1

9.1.2.3 Ceilometer Configurations ........................................ 9-7

SECTION II. INSTALLATION ........................................................ 9-9

9.2.1 INTRODUCTION ....................................................... 9-9

9.2.2 ASSEMBLY ........................................................... 9-9

9.2.3 INSTALLING THE CEILOMETER ......................................... 9-9

SECTION III. OPERATION .......................................................... 9-13

9.3.1 INTRODUCTION ...................................................... 9-13

9.3.2 CONTROLS AND INDICATORS ......................................... 9-13

9.3.3 TURN-ON PROCEDURES .............................................. 9-13

9.3.4 TURNOFF PROCEDURES .............................................. 9-13

9.3.5 NORMAL OPERATION ................................................ 9-13

9.3.5.1 Startup Message. .............................................. 9-20

9.3.5.2 Digital Message No. 2 .......................................... 9-20

9.3.5.3 Digital Message No. 3 .......................................... 9-20
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9.3.6 CEILOMETER DIRECT DIALOGUE COMMANDS .......................... 9-24

9.3.6.1 Introduction. ................................................. 9-24

9.3.6.2 Line Open and Line Closed. ..................................... 9-24

9.3.6.3 Automatic Mode and Maintenance Mode. ........................... 9-25

9.3.6.4 Command Descriptions. ......................................... 9-26

9.3.6.4.1 AUTO (ON/OFF). ..................................... 9-26

9.3.6.4.2 PMOD (ON/OFF). .................................... 9-26

9.3.6.4.3 STA. ............................................... 9-26

9.3.6.4.4 ALIM. .............................................. 9-27

9.3.6.4.5 LASE (ON/OFF). ..................................... 9-28

9.3.6.4.6 SEQ (ON/OFF). ...................................... 9-28

9.3.6.4.7 FREQ. ............................................. 9-29

9.3.6.4.8 GAIN (0/2) .......................................... 9-29

9.3.6.4.9 HEAT (ON/OFF). ..................................... 9-30

9.3.6.4.10 BLOW (ON/OFF .................................... 9-30

9.3.6.4.11 SHUT (ON/OFF). ................................... 9-30

9.3.6.4.12 TIME (HH MM SS). .................................. 9-31

9.3.6.4.13 DATE (YYYY MM DD). ............................. 9-31

9.3.6.4.14 RESE .............................................. 9-31

9.3.6.4.15 CAL (time). ........................................ 9-32

9.3.6.4.16 HELP ............................................. 9-32

9.3.6.4.17 MEAS (time). ....................................... 9-33

9.3.6.4.18 TAB n (si ci). ....................................... 9-33

9.3.6.4.19 GRAP n (sc si ic). .................................... 9-34

9.3.6.4.20 MES. ............................................. 9-35

9.3.6.4.21 PAR. .............................................. 9-35

9.3.6.4.22 AN (Channel) ....................................... 9-38

9.3.6.4.23 NOIS .............................................. 9-38

SECTION IV. THEORY OF OPERATION .............................................. 9-39

9.4.1 INTRODUCTION ...................................................... 9-39

9.4.2 SIMPLIFIED BLOCK DIAGRAM DESCRIPTION ........................... 9-39

9.4.2.1 Principles of Operation. ......................................... 9-39

9.4.2.2 Simplified Block Diagram Description. ............................. 9-41

9.4.2.2.1 Measurement Circuit ................................... 9-41

9.4.2.2.2 Output Interfaces. .................................... 9-42

9.4.2.2.3 Internal Temperature Control. ........................... 9-42

9.4.2.2.4 Internal Monitoring .................................... 9-42

9.4.2.2.5 Power Supply Section .................................. 9-42

9.4.2.2.6 Window Conditioner ................................... 9-42

9.4.2.2.7 Solar Shutter Option ................................... 9-45

9.4.2.2.8 Snow Radiation Shield Option. ........................... 9-45

9.4.3 DETAILED BLOCK DIAGRAM DESCRIPTION ............................ 9-45

9.4.3.1 Introduction. .................................................. 9-45

9.4.3.2 Processor Board. .............................................. 9-45

9.4.3.3 Transmitter Board. ............................................. 9-59

9.4.3.4 Receiver Board. ............................................... 9-59

9.4.3.5 Light Monitor Board. ........................................... 9-60

9.4.3.6 Window Conditioner. ........................................... 9-61

9.4.3.7 High Voltage Power Supply. ..................................... 9-62

9.4.3.8 Unregulated Power Supply Board. ................................. 9-62

9.4.3.9 Fiberoptic Module. ............................................. 9-63
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9.4.3.10 I/O Connector Board. .......................................... 9-63

SECTION V. MAINTENANCE ....................................................... 9-65

9.5.1 INTRODUCTION ...................................................... 9-65

9.5.2 PREVENTIVE MAINTENANCE ......................................... 9-65

9.5.2.1 General. ..................................................... 9-65

9.5.2.2 Routine Inspection. ............................................. 9-65

9.5.2.3 Ceilometer Cleaning and Window Conditioner Checks. ................ 9-65

9.5.2.4 Calibration. ................................................... 9-65

9.5.2.5 Clean Snow Radiation Shield. .................................... 9-65

9.5.3 CORRECTIVE MAINTENANCE ......................................... 9-73

9.5.3.1 Fault Symptoms. .............................................. 9-72

9.5.3.2 Data Message Contains Alarm. ................................... 9-72

9.5.3.2.1 Hardware Alarm. ...................................... 9-72

9.5.3.2.2 Supply Voltage Alarm. ................................. 9-73

9.5.3.2.3 Laser Power Low Alarm. ............................... 9-75

9.5.3.2.4 Temperature Alarm. ................................... 9-76

9.5.3.3 RS-232C Interface Nonoperational. ......................... 9-78

9.5.3.4 Cloud Detection Missing. ........................................ 9-78

9.5.3.5 Superfluous Detection. .......................................... 9-79

9.5.4 BOARD VERIFICATION AND REPLACEMENT PROCEDURES .............. 9-80

9.5.4.1 Processor Board A1 Verification and Replacement. ................... 9-80

9.5.4.1.1 Verification. ......................................... 9-80

9.5.4.1.2 Replacement. ......................................... 9-80

9.5.4.2 Unregulated Power Supply Board A2 Verification and Replacement ...... 9-82

9.5.4.2.1 Verification .......................................... 9-82

9.5.4.2.2 Replacement. ........................................ 9-83

9.5.4.3 I/O Connector Board A3 Verification and Replacement. ................ 9-84

9.5.4.3.1 Verification. ......................................... 9-84

9.5.4.3.2 Replacement. ........................................ 9-84

9.5.4.4 Light Monitor Board A5 Verification and Replacement ................ 9-85

9.5.4.4.1 Verification. ......................................... 9-85

9.5.4.4.2 Replacement. ........................................ 9-85

9.5.4.5 Receiver Board A6 Verification and Replacement. .................... 9-86

9.5.4.5.1 Verification. ......................................... 9-86

9.5.4.5.2 Replacement. ......................................... 9-86

9.5.4.6 Transmitter Board A7 Verification and Replacement. .................. 9-88

9.5.4.6.1 Verification. ......................................... 9-88

9.5.4.6.2 Replacement. ........................................ 9-88

9.5.4.7 High Voltage Power Supply PS1 Verification and Replacement .......... 9-91

9.5.4.7.1 Verification. ......................................... 9-91

9.5.4.7.2 Replacement. ........................................ 9-91

9.5.4.8 Temperature Compensation Transformer T1 Verification and Replacement. 9-92

9.5.4.8.1 Verification. ......................................... 9-92

9.5.4.8.2 Replacement. ........................................ 9-92

9.5.4.9 Cabinet Heaters R1 and R2 Verification and Replacement. .............. 9-93

9.5.4.9.1 Verification. ......................................... 9-93

9.5.4.9.2 Replacement. ........................................ 9-93

9.5.4.10 External Air Temperature Sensor TS1 Verification and Replacement ..... 9-94

9.5.4.10.1 Verification. ........................................ 9-94

9.5.4.10.2 Replacement. ........................................ 9-94

9.5.4.10.3 Removal and Installation of Snow Radiation Shield .......... 9-95
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9.5.4.11 Window Conditioner Verification and Replacement. .................. 9-96

9.5.4.11.1 Verification. ........................................ 9-96

9.5.4.11.2 Replacement. ........................................ 9-96

9.5.4.12 Offset Calibration. ............................................ 9-97

9.5.4.13 Fiberoptic Module Removal and Replacement. ...................... 9-99

CHAPTER 10 LIQUID PRECIPITATION ACCUMULATION SENSOR (RAIN GAUGE) ............... 10-1

SECTION I. DESCRIPTION AND LEADING PARTICULARS ............................. 10-1

10.1.1 INTRODUCTION ..................................................... 10-1

10.1.2 PHYSICAL DESCRIPTION ............................................. 10-1

10.1.3 RAIN GAUGE CONFIGURATIONS ...................................... 10-1

SECTION II. INSTALLATION ....................................................... 10-5

10.2.1 INTRODUCTION ..................................................... 10-5

10.2.2 INSTALLATION ..................................................... 10-5

SECTION III. OPERATION .......................................................... 10-9

10.3.1 INTRODUCTION ..................................................... 10-9

SECTION IV. THEORY OF OPERATION ............................................. 10-11

10.4.1 INTRODUCTION .................................................... 10-11

10.4.2 DESCRIPTION OF OPERATION ....................................... 10-11

SECTION V. MAINTENANCE ...................................................... 10-13

10.5.1 INTRODUCTION .................................................... 10-13

10.5.2 PREVENTIVE MAINTENANCE ....................................... 10-13

10.5.3 CORRECTIVE MAINTENANCE ....................................... 10-13

10.5.3.1 Introduction. ................................................ 10-13

10.5.3.2 Rain Gauge Testing. .......................................... 10-13

10.5.3.3 Rain Gauge Removal and Installation. ........................... 10-13

10.5.3.4 Tipping Bucket Switch Removal and Installation. .................. 10-13

10.5.3.5 Fiberoptic Transmitter Removal and Installation. ................... 10-13

CHAPTER 11FREEZING RAIN SENSOR ...................................................... 11-1

SECTION I. DESCRIPTION AND LEADING PARAMETERS .............................. 11-1

11.1.1 INTRODUCTION ..................................................... 11-1

11.1.2 PHYSICAL DESCRIPTION ............................................. 11-1

11.1.2.1 Probe Assembly and Heat Sink. .................................. 11-1

11.1.2.2 Electronics Processor Board. .................................... 11-1

11.1.2.3 Fiberoptic Module. ............................................ 11-2

11.1.3 FREEZING RAIN SENSOR CONFIGURATIONS ........................... 11-2

SECTION II. INSTALLATION ....................................................... 11-5

11.2.1 INTRODUCTION ..................................................... 11-5

SECTION III. OPERATION .......................................................... 11-9

11.3.1 INTRODUCTION ..................................................... 11-9

11.3.2 CONTROLS AND INDICATORS ........................................ 11-9

11.3.3 POWER-ON ......................................................... 11-9

11.3.4 NORMAL OPERATION ............................................... 11-9

11.3.5 POWER OFF ......................................................... 11-9
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SECTION IV. THEORY OF OPERATION ............................................. 11-11

11.4.1 PRINCIPLES OF OPERATION ......................................... 11-11

11.4.1.1 Probe Assembly ............................................. 11-11

11.4.1.2 Heaters. ................................................... 11-12

11.4.1.3 Heat Sink. .................................................. 11-12

11.4.2 SIMPLIFIED BLOCK DIAGRAM DESCRIPTION ......................... 11-12

11.4.2.1 Electrical Input Requirements. ................................. 11-13

11.4.2.2 Communications Link. ........................................ 11-13

11.4.2.3 Microcontroller .............................................. 11-13

11.4.2.4 Watchdog Timer/Reset Power Monitor ........................... 11-13

11.4.2.5 Heater Control. ............................................. 11-13

11.4.3 COMMAND DESCRIPTION ........................................... 11-14

11.4.3.1 Quick Reference. ............................................ 11-14

11.4.3.2 Power Interruptions. .......................................... 11-14

11.4.3.3 Z1 Request (Send Routine Data). ................................ 11-14

11.4.3.4 Z3XX Request (Perform Deice Cycle). ........................... 11-15

11.4.3.5 Z4 Request (Perform Extended Diagnostics). ...................... 11-15

11.4.3.6 F5 Request (Field Calibration). ................................. 11-15

SECTION V. MAINTENANCE ...................................................... 11-17

11.5.1 INTRODUCTION .................................................... 11-17

11.5.2 PREVENTIVE MAINTENANCE ....................................... 11-17

11.5.2.1 Model 0872C2 Ground Fault Check ............................. 11-17

11.5.3 CORRECTIVE MAINTENANCE ....................................... 11-17

11.5.3.1 Using the Laptop Computer With the Freezing Rain Sensor ........... 11-18

11.5.3.2 Troubleshooting. ............................................ 11-18

11.5.3.3 Calibration. ................................................. 11-18

11.5.4 FRU REMOVAL AND INSTALLATION .................................. 11-18

CHAPTER 12 GROUND-TO-AIR RADIO ..................................................... 12-1

SECTION I. DESCRIPTION AND LEADING PARTICULARS ............................. 12-1

12.1.1 INTRODUCTION ..................................................... 12-1

12.1.2 PHYSICAL DESCRIPTION ............................................. 12-1

SECTION II. INSTALLATION ....................................................... 12-3

SECTION III. OPERATION .......................................................... 12-5

12.3.1 INTRODUCTION ..................................................... 12-5

12.3.2 CONTROLS AND INDICATORS ........................................ 12-5

12.3.2.1 General ..................................................... 12-5

12.3.2.2 Using the Front Panel Controls and Indicators ....................... 12-5

12.3.3 TURN-ON PROCEDURES ............................................. 12-8

12.3.4 TURNOFF PROCEDURES ............................................. 12-8

12.3.5 GTA RADIO CONFIGURING/OID CONTROL ............................. 12-8

12.3.5.1 Configuring the GTA Radio - General ............................. 12-9

12.3.5.2 Alternative Means of Adjusting Power and Frequency ................ 12-9

12.3.5.3 AOMC Frequency Storage ...................................... 12-9

SECTION IV. THEORY OF OPERATION ............................................. 12-11

12.4.1 INTRODUCTION .................................................... 12-11

12.4.2 SIMPLIFIED BLOCK DIAGRAM ....................................... 12-11
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12.4.3 DETAILED BLOCK DIAGRAM ........................................ 12-11

12.4.3.1 SIO Board .................................................. 12-11

12.4.3.2 Voice Recorder/Playback Board ................................ 12-11

12.4.3.3 Power Distribution Assembly ................................... 12-11

12.4.3.4 I/O Panel ................................................... 12-11

12.4.4 GTA RADIO SELF-TEST ............................................. 12-11

SECTION V. MAINTENANCE ...................................................... 12-15

12.5.1 INTRODUCTION .................................................... 12-15

12.5.2 PREVENTIVE MAINTENANCE ....................................... 12-15

12.5.2.1 RF Power Output Check ....................................... 12-15

12.5.2.2 Modulation Level Check ...................................... 12-15

12.5.2.3 VSWR at Transmitter Output Check ............................. 12-15

12.5.2.4 Frequency Stability Check ..................................... 12-15

12.5.2.5 Antenna Cable Insulation Verification ............................ 12-15

12.5.3 CORRECTIVE MAINTENANCE ....................................... 12-22

12.5.3.1 Troubleshooting ............................................. 12-22

12.5.3.1.1 Troubleshoot the GTA Radio RF ....................... 12-22

12.5.3.1.2 Troubleshoot the GTA Radio RS-232 Data Link ........... 12-23

12.5.3.1.3 GTA Radio BERT Program ........................... 12-23

12.5.3.2 Voice Recorder/Playback Board Check ........................... 12-23

12.5.3.3 Removal and Installation Procedure .............................. 12-23

CHAPTER 13 CODEX 3600 SERIES MODEM ................................................. 13-1

SECTION I. DESCRIPTION AND LEADING PARTICULARS ............................. 13-1

13.1.1 INTRODUCTION ..................................................... 13-1

13.1.2 PHYSICAL DESCRIPTION ............................................. 13-1

13.1.2.1 General Description ........................................... 13-1

13.1.2.2 System Components ........................................... 13-3

13.1.2.2.1 3600 Series Enclosure ................................. 13-4

13.1.2.2.2 Flex-Cartridge ....................................... 13-4

13.1.3 CODEX CONFIGURATIONS ........................................... 13-4

SECTION II. INSTALLATION ....................................................... 13-7

SECTION III. OPERATION .......................................................... 13-9

13.3.1 INTRODUCTION ..................................................... 13-9

13.3.2 CONTROLS AND INDICATORS ........................................ 13-9

13.3.2.1 STATUS Menu ............................................. 13-11

13.3.2.2 TEST Menu ................................................ 13-15

13.3.2.3 CONFIG Menu .............................................. 13-15

13.3.2.4 REMOTE Menu ............................................. 13-16

13.3.3 TURN-ON PROCEDURES ............................................ 13-16

13.3.4 TURNOFF PROCEDURES ............................................ 13-16

13.3.5 NORMAL OPERATION .............................................. 13-16

13.3.6 MONITORING AND VERIFYING CODEX 3600 SERIES MODEM AT OPERATOR

INTERFACE DEVICE ...................................................... 13-16

13.3.7 MONITORING AND VERIFYING CODEX 3600 SERIES MODEM BY VISUAL

INSPECTION ............................................................. 13-17

SECTION IV. THEORY OF OPERATION ............................................. 13-23
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13.4.1 INTRODUCTION .................................................... 13-23

13.4.2 TURBO POINT-TO-POINT AND V.33 COMMUNICATIONS ................ 13-23

13.4.3 MULTIPOINT-SLAVE (MP-S) OPERATING MODE ....................... 13-25

SECTION V. MAINTENANCE ...................................................... 13-27

13.5.1 INTRODUCTION .................................................... 13-27

13.5.2 PREVENTIVE MAINTENANCE ....................................... 13-27

13.5.2.1 Routine Inspection and Cleaning ................................ 13-27

13.5.3 CORRECTIVE MAINTENANCE ....................................... 13-27

13.5.3.1 Corrective Maintenance Philosophy .............................. 13-27

13.5.3.2 Bit Error Rate Tester ......................................... 13-27

13.5.3.3 CODEX 3600 Series Modem Troubleshooting ..................... 13-27

13.5.4 REMOVAL AND INSTALLATION PROCEDURES ........................ 13-28

13.5.4.1 General .................................................... 13-28

13.5.4.2 Codex 3600 Series Modem Removal and Installation ................ 13-28

CHAPTER 14 SINGLE-CABINET ASOS (SCA) AND ASSOCIATED EQUIPMENT ................... 14-1

SECTION I. DESCRIPTION AND LEADING PARTICULARS ............................. 14-1

14.1.1 INTRODUCTION ..................................................... 14-1

14.1.2 SITE DESCRIPTION .................................................. 14-1

14.1.3 PURPOSE OF CHAPTER .............................................. 14-1

14.1.4 SCOPE OF CHAPTER ................................................. 14-1

14.1.4.1 Section I, Description and Leading Particulars ...................... 14-1

14.1.4.2 Section II, Installation ......................................... 14-2

14.1.4.3 Section III, Operation .......................................... 14-2

14.1.4.4 Section IV, Theory of Operation ................................. 14-3

14.1.4.5 Section V, Maintenance ........................................ 14-3

14.1.5 RELATED PUBLICATIONS ............................................ 14-3

14.1.6 SCA FUNCTIONAL DESCRIPTION ...................................... 14-3

14.1.7 SCA CONFIGURATION ................................................ 14-5

14.1.8 SCA PHYSICAL DESCRIPTION ......................................... 14-5

14.1.8.1 Mounting Plate Assembly 7A1A1 ................................ 14-5

14.1.8.1.1 VME Rack 7A1A1A2 Description ....................... 14-5

14.1.8.1.2 Circuit Breaker Panel 7A1A1A3 Description ............... 14-5

14.1.8.1.3 AC Power Distribution Assembly 7A1A1A4 Description ..... 14-7

14.1.8.1.4 RF Modem Shelf 7A1A1A5 Description .................. 14-7

14.1.8.1.4A Uninterruptible Power Supply 7A1A1A6 Description 14-8

14.1.8.1.8 Optional Modems 7A1A1A11, A12 Description ............ 14-9

14.1.8.1.9 Power Reset Assembly 7A1A1A13 Description ............. 14-9

14.1.8.2 Faraday Box 7A1A3 Description ................................. 14-9

14.1.8.3 Power Supply Mounting Plate 7A1A4 ............................ 14-10

14.1.8.4 Modems 7A1A5, A6 Description ................................ 14-10

14.1.8.5 Optional Solar Shield ......................................... 14-11

14.1.9 AUXILIARY BOX PHYSICAL DESCRIPTION ............................ 14-11

14.1.9.1 Enclosure .................................................. 14-11

14.1.9.2 Auxiliary Box Standard Equipment .............................. 14-11

14.1.9.2.1 Mounting Plate Assembly 7A2A1 ....................... 14-12

14.1.9.2.2 Power Outlet Strip 7A2A1A4 Description ................ 14-12

14.1.9.2.3 Modem Shelf 7A2A1A5 Description .................... 14-12

14.1.9.3 Auxiliary Box Optional Equipment .............................. 14-12
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SECTION II. INSTALLATION ...................................................... 14-13

14.2.1 INTRODUCTION ..................................................... 14-1

14.2.2 SOLAR SHIELD (OPTIONAL) ......................................... 14-13

14.2.3 ALTERNATIVE GTA RADIO ANTENNA KIT ............................ 14-14

SECTION III. OPERATION ......................................................... 14-15

14.3.1 INTRODUCTION .................................................... 14-15

14.3.2 CONTROLS AND INDICATORS ....................................... 14-15

14.3.2.1 Circuit Breaker Panel 7A1A1A3, Controls and Indicators ............. 14-15

14.3.2.2 VME Rack 7A1A1A2, Controls and Indicators ..................... 14-15

14.3.2.3 Operator Interface Device (OID), Controls and Indicators ............ 14-16

14.3.2.4 Auxiliary Box 7A2, Controls and Indicators ....................... 14-16

14.3.3 MAINTENANCE DISPLAY PAGES ..................................... 14-18

14.3.4 OPERATING PROCEDURES .......................................... 14-18

SECTION IV. THEORY OF OPERATION ............................................. 14-19

14.4.1 INTRODUCTION .................................................... 14-19

14.4.2 SCA BLOCK DIAGRAM .............................................. 14-19

14.4.2.1 CPU CCA’s A1 and A2 ....................................... 14-21

14.4.2.2 Memory Board A3 ........................................... 14-23

14.4.2.3 Serial I/O (SIO) Boards A5 through A11 .......................... 14-23

14.4.2.4 A/D Board A13 ............................................. 14-26

14.4.2.5 VME Resistor Board A14 ..................................... 14-27

14.4.2.6 DIO Board A15 ............................................. 14-27

14.4.2.7 Digitized Voice Processor System ............................... 14-27

14.4.2.7.1 Voice Processor Board A20 ........................... 14-28

14.4.2.7.2 Voice Audio Board A21 .............................. 14-29

14.4.2.7.3 Digital Voice Processing System Self-Tests ............... 14-29

14.4.2.8 Pressure Sensor Shelf 7A1A1A7 ................................ 14-30

14.4.3 AC POWER DISTRIBUTION .......................................... 14-30

14.4.3.1 Power Reset Assembly A1A13 .................................. 14-30

14.4.4 SCA CABINET HEATERS ............................................ 14-35

14.4.5 AUXILIARY BOX CABINET HEATERS ................................. 14-36

14.4.6 DC POWER DISTRIBUTION AND MONITORING ........................ 14-36

14.4.7 SENSORS .......................................................... 14-40

14.4.8 PERIPHERALS ...................................................... 14-40

14.4.9 MODEMS .......................................................... 14-41

14.4.9.1 Telephone Modems .......................................... 14-41

14.4.9.2 RF Modems ................................................ 14-41

SECTION V. SCA MAINTENANCE .................................................. 14-43

14.5.1 GENERAL .......................................................... 14-43

14.5.1.1 Tools and Test Equipment ..................................... 14-43

14.5.1.2 Consumable Materials List ..................................... 14-43

14.5.1.3 Maintenance Action Recording and Documentation ................. 14-43

14.5.2 PREVENTIVE MAINTENANCE ....................................... 14-44

14.5.2.1 Desiccant .................................................. 14-44

14.5.3 CORRECTIVE MAINTENANCE ....................................... 14-45

14.5.3.1 Warmup and Initialization ..................................... 14-45

14.5.3.1.1 System Diagnostics .................................. 14-46

14.5.3.1.2 Preliminary Troubleshooting Checks .................... 14-46

14.5.3.2 Fiberoptic Module Test ....................................... 14-47
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14.5.3.3 Modem Setup ............................................... 14-48

14.5.3.3.1 Setting Up SCA Modems ............................. 14-48

14.5.3.3.2 Setting Up Stand-Alone (S/A) Modems .................. 14-48

14.5.3.4 FRU and Subassemblies Removal and Installation .................. 14-48

14.5.3.4.1 Removal and Replacement of VME 7A1A1A2 CCA’s ....... 14-49

14.5.3.4.2 Removal and Replacement of Memory Board 7A1A1A2A3 . . 14-49

14.5.3.4.3 Removal and Replacement of SCA UPS 7A1A1A6 ......... 14-49

14.5.3.4.4 Removal and Installation of Faraday Box 7A1A3 Subassemblies14-51

14.5.3.4.5 Removal and Installation of Alternative GTA Antenna. ...... 14-52

CHAPTER 15 PORT SHARING DEVICE ...................................................... 15-1

SECTION I. DESCRIPTION AND LEADING PARTICULARS ............................. 15-1

15.1.1 INTRODUCTION ..................................................... 15-1

15.1.2 PHYSICAL DESCRIPTION ............................................. 15-1

15.1.3 FUNCTIONAL DESCRIPTION .......................................... 15-1

SECTION II. INSTALLATION ....................................................... 15-3

SECTION III. OPERATION .......................................................... 15-5

15.3.1 INTRODUCTION ..................................................... 15-5

15.3.2 CONTROLS AND INDICATORS ........................................ 15-5

SECTION IV. THEORY OF OPERATION .............................................. 15-7

15.4.1 PSD FUNCTIONAL DESCRIPTION ...................................... 15-7

15.4.1.1 PSD Message Traffic Management ............................... 15-7

15.4.1.1.1 ASOS/RTA Communications ........................... 15-7

15.4.1.1.2 RTA/ABT Communications ............................ 15-7

15.4.1.1.3 PSD Connectivity .................................... 15-9

SECTION V. MAINTENANCE ...................................................... 15-11

15.5.1 INTRODUCTION .................................................... 15-11

15.5.2 PREVENTIVE MAINTENANCE ....................................... 15-11

15.5.3 CORRECTIVE MAINTENANCE ....................................... 15-11

15.5.3.1 General .................................................... 15-11

15.5.3.2 PSD Troubleshooting ......................................... 15-11

15.5.3.2.1 Determining SIO Board Assignments of the PSD ........... 15-11

15.5.3.2.2 Verifying ASOS Operating Condition ................... 15-12

15.5.3.2.3 Using the PSD Diagnostic (DIAG) Function .............. 15-12

15.5.3.2.4 PSD Hardware Connectivity Within the ACU ............. 15-12

15.5.3.2.5 Monitoring PSD Message Traffic ....................... 15-12

15.5.4 FIELD REPLACEABLE UNIT (FRU) REMOVAL AND REPLACEMENT ...... 15-14

15.5.4.1 PSD Memory Removal and Replacement ......................... 15-14

15.5.4.2 Modem Removal and Replacement .............................. 15-14

CHAPTER 16 THUNDERSTORM SENSOR .................................................... 16-1

SECTION I. DESCRIPTION AND LEADING PARAMETERS .............................. 16-1

16.1.1 INTRODUCTION ..................................................... 16-1

16.1.2 PHYSICAL DESCRIPTION ............................................. 16-1

16.1.3 THUNDERSTORM SENSOR CONFIGURATIONS ......................... 16-2
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SECTION II. INSTALLATION ....................................................... 16-3

16.2.1 INTRODUCTION ..................................................... 16-3

SECTION III. OPERATION .......................................................... 16-7

16.3.1 INTRODUCTION ..................................................... 16-7

16.3.2 CONTROLS AND INDICATORS ........................................ 16-7

16.3.3 TURN-ON PROCEDURES ............................................. 16-7

16.3.4 CHECKOUT PROCEDURES ............................................ 16-7

16.3.5 RUNNING DIAGNOSTICS ............................................. 16-7

16.3.6 NORMAL OPERATING PROCEDURES .................................. 16-7

16.3.7 TURNOFF PROCEDURES ............................................. 16-7

SECTION IV. THEORY OF OPERATION ............................................. 16-13

16.4.1 PRINCIPLES OF OPERATION ......................................... 16-13

16.4.2 SIMPLIFIED BLOCK DIAGRAM DESCRIPTION ......................... 16-13

16.4.2.1 Power and Power Supplies ..................................... 16-15

16.4.2.2 Communications ............................................. 16-15

16.4.2.3 Self-tests ................................................... 16-15

16.4.2.4 Lightning Categories ......................................... 16-16

16.4.2.5 Processing Strokes and Flashes ................................. 16-16

16.4.2.6 Signal Processing ............................................ 16-16

16.4.3 COMMAND DESCRIPTION ........................................... 16-17

16.4.3.1 Host Mode ................................................. 16-17

16.4.3.2 Send Present Weather Message ................................. 16-17

16.4.3.3 Send Status Message ......................................... 16-17

16.4.3.4 Perform Self-test ............................................. 16-19

16.4.3.4.1 Self-test Status Byte ................................. 16-19

16.4.3.5 Perform Reset ............................................... 16-20

16.4.3.6 Perform Type Test ........................................... 16-20

16.4.3.7 Send System Run Time ....................................... 16-20

16.4.4 DIAGNOSTIC TESTS ................................................ 16-20

16.4.4.1 Self-test .................................................... 16-21

16.4.4.2 Echo Test .................................................. 16-21

16.4.4.3 Watchdog Timer Test ......................................... 16-21

16.4.4.4 Switch Test ................................................. 16-21

16.4.4.5 Type Test .................................................. 16-21

SECTION V. MAINTENANCE ...................................................... 16-23

16.5.1 INTRODUCTION .................................................... 16-23

16.5.2 PREVENTIVE MAINTENANCE ....................................... 16-23

16.5.3 CORRECTIVE MAINTENANCE ....................................... 16-23

16.5.3.1 Using the Laptop Computer With the Thunderstorm Sensor ........... 16-23

16.5.3.2 Troubleshooting ............................................. 16-23

16.5.4 CALIBRATION. ..................................................... 16-23

16.5.5 FRU REMOVAL AND INSTALLATION ................................. 16-23

CHAPTER 17 MAINTENANCE DRAWINGS .................................................. 17-1

17.1 INTRODUCTION ............................................................. 17-1

17.2 DRAWING FORMAT .......................................................... 17-1

17.2.1 Unit Assembly Identification (1, Figure 1) .................................. 17-1

17.2.2 Subunit Assembly Identification (2) ....................................... 17-1
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17.2.3 Circuit Board Assembly Identification (3, Figure 1) ........................... 17-1

17.2.4 Functional Representation of Circuitry (4) .................................. 17-1

17.2.5 Intrafunctional Referencing (5) ........................................... 17-2

17.2.6 Bundled Signals (6) .................................................... 17-2

17.2.7 Cable/Connector Identification (7) ........................................ 17-2

17.2.8 Signal Names (8) ...................................................... 17-2

17.2.9 Supplementary Names (9, Figure 1) ....................................... 17-2

17.2.10 Connector Pin Numbers (10) ............................................ 17-2

17.2.11 Interfunctional Referencing (11) ......................................... 17-2

CHAPTER 18 STANDARD ASOS PARTS LIST ................................................ 18-1

18.1 INTRODUCTION ............................................................. 18-1

18.2 DESCRIPTION OF PARTS LIST ................................................. 18-1

18.2.1 Agency Stock Number (ASN) ............................................ 18-1

18.2.2 National Stock Number (NSN) ........................................... 18-1

18.2.3 Description .......................................................... 18-1

18.3 SOFTWARE VERSION COMPATIBILITIES ....................................... 18-1

LIST OF ILLUSTRATIONS

Figure Page

1.1.1. Typical ASOS ........................................................................ 1-5

1.3.1. OID Keyboard Controls and Indicators .................................................... 1-12

1.3.2. Maintenance Screens Hierarchy .......................................................... 1-14

1.3.3. Maintenance Screen ................................................................... 1-18

1.3.4. ACU Status Screen .................................................................... 1-19

1.3.5. ACU VME Cards Screen ............................................................... 1-20

1.3.6. CPU Screen ......................................................................... 1-21

1.3.7. Memory Screen ...................................................................... 1-22

1.3.8. Serial I/O Screen ..................................................................... 1-23

1.3.9. A/D Screen .......................................................................... 1-24

1.3.10. Graphics Screen ..................................................................... 1-24

1.3.11. Voice Screen ....................................................................... 1-25

1.3.12. ACU Modem Screen ................................................................. 1-27

1.3.13. ACU Power Screen .................................................................. 1-27

1.3.14. ACU UPS Screen .................................................................... 1-28

1.3.15. ACU GTA Radio Screen .............................................................. 1-30

1.3.16. Remote DCP Status Screen ............................................................ 1-31

1.3.17. DCP VME Cards Screen .............................................................. 1-32

1.3.18. DCP #1, #2, #3 Power Screen .......................................................... 1-32

1.3.19. DCP UPS Screen .................................................................... 1-33

1.3.20. Ceilometer Screen ................................................................... 1-35

1.3.21. Ceilometer Sensor Dialogue Screen ...................................................... 1-36

1.3.22. Freezing Rain Screen ................................................................. 1-37

1.3.23. Present Weather Sensor Screen ......................................................... 1-37

1.3.24. Wind Speed and Direction Sensor Screen ................................................. 1-40

1.3.25. Temperature/Dewpoint (Model 1088) Screen .............................................. 1-42

1.3.26. Temperature/Dewpoint (Model H083) Screen .............................................. 1-43

1.3.27. Visibility Sensor Screen ............................................................... 1-44

1.3.28. Tipping Bucket Sensor Screen .......................................................... 1-46
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1.3.29. Frozen Precipitation Screen ............................................................ 1-46

1.3.30. Snow Depth Screen .................................................................. 1-47

1.3.31. Sunshine Screen ..................................................................... 1-47

1.3.32 Thunderstorm Screen ................................................................. 1-48

1.3.33. Pressure Sensor Screen ................................................................ 1-48

1.3.34. ACU/DCP Communications Status Screen ................................................ 1-49

1.3.35. Trend Screen ....................................................................... 1-50

1.3.36. ADAS Summary Screen ............................................................... 1-51

1.3.37. Processor Status Screen ............................................................... 1-52

1.3.38. Maintenance Action Screen ............................................................ 1-52

1.3.39. Preventive Maintenance Action Screen ................................................. 1-52.1

1.3.40. Field Modification Kit Action Screen .................................................... 1-53

1.3.41. Site Configuration Screen .............................................................. 1-66

1.3.42. Hardware Configuration Screen ......................................................... 1-66

1.3.43. Sensor Configuration Screen ........................................................... 1-67

1.3.44. Sensor-Algorithm Configuration Screen .................................................. 1-68

1.3.45. Define Configuration Screen ........................................................... 1-68

1.3.46. ACU Serial Communications Screen ..................................................... 1-69

1.3.47. External Communications Screen ........................................................ 1-70

1.3.48. Site Physical Screen .................................................................. 1-70

1.3.49. Site Version Screen .................................................................. 1-71

1.3.50. SW Screen ......................................................................... 1-71

1.3.51. Sensor Firmware Version Screen ........................................................ 1-72

1.3.52. AOMC Screen ...................................................................... 1-72

1.3.53. Site Normals Screen .................................................................. 1-73

1.3.54. Site Pressure Screen .................................................................. 1-73

1.3.55. Site Criteria Screen ................................................................... 1-74

1.4.1. Typical ASOS Configuration - Basic Block Diagram ......................................... 1-76

1.5.1. Combined Zone Pedestal Locational ...................................................... 1-88

1.5.2. Fiberoptic Link Testing - Half Duplex Link ................................................. 1-89

2.1.1. ACU and Peripherals ................................................................... 2-1

2.1.2. ACU Cabinet Unit 1 Locational View ...................................................... 2-4

2.1.3. Card Rack Assembly 1A2 ............................................................... 2-8

2.1.4. Modem AC Power Rack 1A3 ............................................................. 2-8

2.1.5. Power Supply Assembly 1A4 ............................................................. 2-9

2.1.6. DC Power Supply Enclosure 1A5 ........................................................ 2-11

2.1.7. RF/Pressure Mounting Shelf 1A6 ......................................................... 2-12

2.1.8. Battery Box 1A8 ..................................................................... 2-14

2.1.9. I/O Panel Assembly 1A9 ............................................................... 2-15

2.3.1. Keyboard ........................................................................... 2-20

2.3.2. Controller Video Display (CVD) ......................................................... 2-21

2.3.3. Card Rack Assembly Controls and Indicators ............................................... 2-21

2.3.4. Modem AC Power Rack Controls and Indicators ............................................ 2-23

2.3.5. Power Supply Assembly 62828-40124-10 Controls and Indicators ............................... 2-27

2.3.6. Power Supply Assembly 62828-40265-10 with Deltek UPS 62828-90338-10 Controls and Indicators ... 2-28

2.3.7. Power Supply Assembly 62828-40265-10 with Deltek UPS 62828-xxxxx-xx Controls and Indicators ... 2-30

2.3.8. Johnson Data RF Modem Controls and Indicators ............................................ 2-32

2.4.1. ACU Simplified Block Diagram ......................................................... 2-35

2.4.2. ACU VMEbus Chassis and Connector Pin Assignments ....................................... 2-39

2.4.3. ACU Card Rack Assembly Detailed Block Diagram .......................................... 2-45

2.4.4. SIO Boards 4 Through 8 Ports and Pin Assignments .......................................... 2-49

2.4.5. Digital Voice Processor Detailed Block Diagram ............................................ 2-55
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Figure Page

Change 2 xxv

2.4.6. Leased Line and Public Switched Telephone Modem Communications Detailed Block Diagram ....... 2-59

2.4.7. ACU RF Modem/Line Driver Communications Link Detailed Block Diagram ...................... 2-65

2.4.8. Pressure Sensor Detailed Block Diagram ................................................... 2-75

2.4.9. Local Sensor Fiberoptic Modem Detailed Block Diagram ..................................... 2-77

2.4.10. Observer Notification Device and Peripheral Power ......................................... 2-79

2.4.11. ACU Power and Signal Monitoring Detailed Block Diagram .................................. 2-81

2.4.12. ACU AC Power Distribution Detailed Block Diagram for 62828-40124-10 ....................... 2-91

2.4.13. ACU AC Power Distribution Detailed Block Diagram for 62828-40265-10 ....................... 2-95

2.4.14. ACU DC Power Distribution Detailed Block Diagram ....................................... 2-99

2.5.1 Earthquake Mounting Installation ........................................................ 2-154

2.5.1A. DDS/MR64 Line Driver Switch and Jumper Location .................................... 2-158.1

2.5.2 Upper Cabinet Removal ............................................................... 2-160

3.1.1. DCP Communications Link - Simplified .................................................... 3-1

3.1.2. DCP Installation ....................................................................... 3-3

3.1.3. DCP Equipment Cabinet - Locational View ................................................ 3-4.2

3.1.4. VME Card Rack - Stuffing Chart .......................................................... 3-8

3.1.5. Circuit Breaker Module Rack - Stuffing Chart ................................................ 3-9

3.1.6. DCP Uninterruptible Power Supply - Locational View ........................................ 3-10

3.1.7. Faraday Box - Locational View .......................................................... 3-12

3.1.8. Typical AC Junction Box ............................................................... 3-13

3.1.9. Power Expansion DCP AC Junction Box - Locational View .................................. 3-14.1

3.3.1. Power Control Module Controls and Indicators .............................................. 3-18

3.3.2. Johnson Data RF Modem Controls and Indicators .......................................... 3-18.1

3.4.1. DCP Simplified Block Diagram .......................................................... 3-25

3.4.2. DCP Power Distribution and Control Simplified Block Diagram ................................ 3-27

3.4.3. DCP VMEbus Chassis and Connector Pin Assignments ....................................... 3-31

3.4.4. DCP VME Card Rack Detailed Block Diagram ............................................. 3-35

3.4.5. DCP RF Modem/Line Driver Communications Link Detailed Block Diagram ...................... 3-41

3.4.5a. DCP Pressure Sensors Detailed Block Diagram ............................................. 3-47

3.4.6. DCP Fiberoptic Modules Detailed Block Diagram ........................................... 3-49

3.4.7. DCP Power Monitoring and Digital I/O Diagram ............................................ 3-51

3.4.8. DCP AC and DC Power Distribution Detailed Block Diagram .................................. 3-59

3.4.9. AC Power Distribution Assembly A1A4 ................................................... 3-81

3.4.10. DC Power Distribution Assembly A4A1 .................................................. 3-84

4.1.1. Wind Sensor Locational Diagram ......................................................... 4-2

4.2.1. Wind Sensor Electronics Enclosure Installation ............................................... 4-6

4.2.2. Wind Sensors and Crossarm Installation .................................................... 4-9

4.4.1. Wind Speed and Wind Direction Sensing Technique ......................................... 4-14

4.4.2. Wind Sensor Block Diagram ............................................................ 4-17

4.4.3. Wind Sensor Obstruction Lights Detailed Block Diagram ...................................... 4-21

4.5.1. Wind Direction Sensor Alignment Tool .................................................... 4-25

4.5.2. Julian Calendar ....................................................................... 4-26

4.5.3. Wind Alignment Procedures ............................................................ 4-31

4.5.4. Davis Pelorus Instrument ............................................................... 4-32

4.5.5. True North Alignment ................................................................. 4-33

5.1.1. Temperature/Dewpoint Sensor Major Components ............................................ 5-2

5.1.2. Aspirator Component Location ........................................................... 5-3

5.1.3. Transmitter Component Location .......................................................... 5-4

5.2.1. Temperature/Dewpoint Sensor Installation Diagram ........................................... 5-8

5.3.1. Temperature/Dewpoint Sensor Controls and Indicators ........................................ 5-12

5.4.1. Dewpoint Temperature Thermal Control Loop .............................................. 5-15

5.4.2. H083R Temperature/Dewpoint Sensor Detailed Block Diagram ................................. 5-21
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xxvi Change 2

5.4.3. 1088 Temperature/Dewpoint Sensor Detailed Block Diagram .................................. 5-25

6.1.1. Visibility Sensor ....................................................................... 6-2

6.1.2. Visibility Sensor Electronics Enclosure ..................................................... 6-4

6.2.1. Electronics Enclosure Installation ......................................................... 6-6

6.2.2. Crossarm/Support and Day/Night Sensor Installation .......................................... 6-8

6.2.3. Day/Night Sensor Installation ............................................................ 6-9

6.4.1. Visibility Sensor Basic Block Diagram .................................................... 6-16

6.4.2. Visibility Sensor Detailed Block Diagram .................................................. 6-17

6.4.3. Visibility Sensor Electronics Enclosure Power Distribution Diagram ............................. 6-27

6.5.1. Visibility Sensor Calibration Data Sheet ................................................... 6-49

7.1.1. Present Weather Sensor ................................................................. 7-1

7.1.2. Present Weather Sensor ................................................................. 7-2

7.2.1. Present Weather Sensor Mounting Diagram ................................................. 7-6

7.2.2. Frame Assembly Mounting Plate Hardware .................................................. 7-6

7.4.1. Precipitation Effects on Received Signal .................................................... 7-9

7.4.2. Present Weather Sensor Simplified Block Diagram ........................................... 7-11

7.4.3. Present Weather Sensor Detailed Block Diagram ............................................ 7-13

7.4.4. Present Weather Sensor AC/DC Power Distribution .......................................... 7-17

7.4.5. OWI-240 Status Bit Identification ........................................................ 7-24

7.5.1. Present Weather Sensor Insect Treatment Areas ............................................. 7-36

8.1.1. ASOS ACU RF/Pressure Sensor Mounting Shelf ............................................. 8-2

8.1.2. ASOS DCP RF/Pressure Sensor Mounting Shelf ............................................. 8-3

8.4.1. ASOS Pressure Sensor Simplified Block Diagram ........................................... 8-10

9.1.1. Ceilometer (CT12K) ................................................................... 9-2

9.1.2. Ceilometer System Components .......................................................... 9-4

9.2.1. Ceilometer Mounting Diagram ........................................................... 9-11

9.2.2. Ceilometer Connections (Bottom) ........................................................ 9-12

9.3.1. Ceilometer Controls and Indicators ....................................................... 9-14

9.3.2. Sample Startup Message ............................................................... 9-20

9.3.3. Digital Message No. 2 ................................................................. 9-21

9.3.4. Digital Message No. 3 ................................................................. 9-23

9.3.5. Status (STA) Command Display ......................................................... 9-27

9.3.6. Alarm Limits (ALIM) Command Display .................................................. 9-28

9.3.7. Laser Control (LASE) Command Display .................................................. 9-28

9.3.8. Sequence Control (SEQ) Command Display ................................................ 9-28

9.3.9. Frequency Control (FREQ) Command Display .............................................. 9-29

9.3.10. Receiver Gain Control (GAIN) Command Display .......................................... 9-29

9.3.11. Heater Control (HEAT) Command Display ................................................ 9-30

9.3.12. Blower Control (BLOW) Command Display ............................................... 9-30

9.3.13. Solar Shutter Control (SHUT) Command Display ........................................... 9-31

9.3.14. Help Message (HELP) Command Display ................................................. 9-32

9.3.15. Measurement (MEAS) Command Display ................................................. 9-33

9.3.16. Data Tables (TAB) Command Display ................................................... 9-34

9.3.17. Graphic Output (GRAP) Command Display ............................................... 9-34

9.3.18. Parameter (PAR) Command Display ..................................................... 9-35

9.3.19. Noise (NOIS) Command Display ........................................................ 9-38

9.4.1. Ceilometer Laser Transmission/Reception Cycle ............................................. 9-40

9.4.2. Received Signal Sampling Noise Cancellation ............................................... 9-40

9.4.3. Ceilometer, Simplified Block Diagram .................................................... 9-43

9.4.4. Ceilometer Detailed Block Diagram ...................................................... 9-47

10.1.1. Liquid Precipitation Accumulation Sensor (Rain Gauge) ..................................... 10-2

10.2.1. Tipping Bucket Installation ............................................................ 10-8
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Figure Page

Change 2 xxvii

10.4.1. Liquid Precipitation Accumulation Sensor Wiring Diagram .................................. 10-12

11.1.1. Freezing Rain Sensor ................................................................. 11-2

11.1.2. Electronics Enclosure ................................................................. 11-3

11.2.1. Freezing Rain Sensor Installation ........................................................ 11-7

11.4.1. Magnetostrictive Oscillator Circuit ..................................................... 11-11

11.4.2. Freezing Rain Sensor Simplified Block Diagram ........................................... 11-12

11.4.3. Format of Z1 (Send Routine Data) Response .............................................. 11-14

12.1.1. Acquisition Control Unit (ACU) ........................................................ 12-2

12.3.1. GTA Radio Front Panel Controls and Indicators ............................................ 12-6

12.3.2. GTA Radio Rear Panel Connectors ...................................................... 12-7

12.4.1. GTA Radio Simplified Block Diagram .................................................. 12-12

12.4.2. GTA Radio, Detailed Block Diagram ................................................... 12-13

12.5.1. RF Power Output Check .............................................................. 12-16

12.5.2. Modulation Level Check ............................................................. 12-18

12.5.3. VSWR at Transmitter Output Check .................................................... 12-19

12.5.4. Frequency Stability Check ............................................................ 12-21

12.5.5. Coaxial Cable Insulation and Conductance, Test Setup ...................................... 12-22

12.5.6. Voice Recorder/Playback Board, Test Setup .............................................. 12-25

13.1.1. Codex Series 3600 Modem ............................................................ 13-2

13.1.2. Codex 3600 Series Modem Location in the ACU ........................................... 13-3

13.1.3. Codex 3600 Series Modem Dress Panel .................................................. 13-4

13.1.4. Codex 3600 Series Modem Components .................................................. 13-5

13.3.1. Codex 3600 Series Modem Controls and Indicators ......................................... 13-9

13.3.2. Top Level Software Menu ............................................................ 13-11

13.3.3. STATUS Menu - Top Level ........................................................... 13-11

13.3.4. STATUS Menu - GENERAL* Category ................................................. 13-12

13.3.5. STATUS Menu - DIAGNOS* Category ................................................. 13-13

13.3.6. STATUS Menu - CQMS* Category ..................................................... 13-14

13.3.7. STATUS Menu - PRT SEL* Category .................................................. 13-15

13.3.8. TEST Menu - Top Level ............................................................. 13-15

13.3.9. TEST Menu - SELF* Category ........................................................ 13-15

13.3.10. CONFIG Menu - Top Level .......................................................... 13-16

13.3.11. CONFIG Menu - DEVICE* Category .................................................. 13-17

13.3.12. CONFIG Menu - ANALOG* Category (Sheet 1 of 2) ...................................... 13-18

13.3.13. CONFIG Menu - PORTS* Category ................................................... 13-20

13.3.14. CONFIG Menu - NWK CTL* Category ................................................ 13-21

13.3.15. REMOTE Menu - Top Level ......................................................... 13-22

13.3.16. REMOTE Menu - MISC* Category .................................................... 13-22

13.4.1. ADAS Network Topology ............................................................ 13-23

13.4.2. ASOS/ADAS Point-to-Point and Multipoint Connections .................................... 13-24

13.5.1. BERT Test Setup ................................................................... 13-31

13.5.2. Disabling DC Power Through the DC Inhibit Switch ....................................... 13-34

13.5.3. Removing and Installing the Flex-Cartridge ............................................... 13-34

14.1.1. Typical ASOS Site, Single-Cabinet Configuration ........................................... 14-2

14.1.2. Single-Cabinet ASOS, Basic Block Diagram ............................................... 14-4

14.1.3. SCA Cabinet 7A1, Interior View ........................................................ 14-6

14.1.4. VME Rack 7A1A1A2, Front View ...................................................... 14-7

14.1.5. Pressure Sensor Shelf 7A1A1A7, Front View ............................................ 14-8.1

14.1.6. Faraday Box A3, Panel Views .......................................................... 14-9

14.1.7. Power Supply Assembly A4, Front View ................................................. 14-10

14.1.8. Auxiliary Box 7A2, Interior View ...................................................... 14-11

14.2.1. SCA Solar Shield (Optional) .......................................................... 14-13
ASOS Site Technical Manual S100

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Figure Page

xxviii Change 2

14.3.1. Circuit Breaker Panel 7A1A1A3, Controls ............................................... 14-16

14.3.2. VME CCA’s, Controls and Indicators ................................................... 14-17

14.3.3 Johnson Data RF Modem Controls and Indicators .......................................... 14-18

14.4.1. SCA Simplified Block Diagram ........................................................ 14-20

14.4.2. CPU, Simplified Block Diagram ....................................................... 14-21

14.4.3. Memory Board, Functional Block Diagram ............................................... 14-24

14.4.4. SIO Board, Functional Block Diagram .................................................. 14-24

14.4.5. A/D Board, Functional Block Diagram .................................................. 14-26

14.4.6. DIO Board, Function Block Diagram ................................................... 14-27

14.4.7. Digitized Voice Processor, Functional Block Diagram ...................................... 14-28

14.4.8. Pressure Sensor Shelf, Functional Diagram ............................................... 14-31

14.4.8A. SCA Power Reset Assembly ......................................................... 14-32

14.4.9. AC Power Distribution Diagram ..................................................... 14-32.1

14.4.10. SCA Cabinet, Heater Control Circuit ................................................... 14-35

14.4.11. Auxiliary Box, Heater Control Circuit .................................................. 14-36

14.4.12. DC Power Distribution Diagram ...................................................... 14-37

14.4.13. DC Power Distribution Assembly ..................................................... 14-40

14.5.1. VME CCA Locations ................................................................ 14-49

14.5.2. VME CCA Connector Pin Assignment .................................................. 14-50

14.5.3. Faraday Box Assembly A3, Parts Location Diagram ....................................... 14-52

15.1.1. PSD Communications ................................................................ 15-2

15.1.2. PSD Memory Board Location .......................................................... 15-2

15.4.1. PSD Message Traffic ................................................................. 15-8

15.4.2. PSD Hardware Connectivity Within the ACU .............................................. 15-9

15.4.3. RTA and ABT to PSD Physical Connections .............................................. 15-10

16.1.1. Thunderstorm Sensor ................................................................. 16-1

16.2.1. Thunderstorm Sensor Top and Bottom Mounting Brackets Assembly ........................... 16-5

16.2.2. Thunderstorm Sensor Antenna Seating ................................................... 16-6

16.2.3. Thunderstorm Sensor Antenna Cable Routing .............................................. 16-6

16.3.1. Power/Comm Module Controls and Indicators ............................................. 16-8

16.3.2. Analog Board and Processor Board Indicators ............................................. 16-9

16.4.1. Thunderstorm Sensor Modules ......................................................... 16-14

16.4.2. Functional Block Diagram ............................................................ 16-15

LIST OF TABLES

Table Page

1.1.1. ASOS Users .......................................................................... 1-1

1.1.2. System Specifications ................................................................... 1-6

1.3.1. Sensor Data Quality Algorithm Checks .................................................... 1-17

1.3.2. Maintenance Screen Field Descriptions .................................................... 1-18

1.3.3. ACU Status Screen Field Descriptions ..................................................... 1-19

1.3.4. CPU Screen Field Descriptions .......................................................... 1-21

1.3.5. Memory Screen Field Descriptions ....................................................... 1-22

1.3.6. Serial I/O Screen Field Descriptions ...................................................... 1-23

1.3.7. Graphics Screen Field Descriptions ....................................................... 1-25

1.3.8. Voice Screen Field Descriptions ......................................................... 1-26

1.3.9. ACU UPS Screen Field Descriptions ...................................................... 1-29

1.3.10. ACU GTA Radio Screen Field Descriptions ............................................... 1-30

1.3.11. Remote DCP Status Screen Field Descriptions ............................................. 1-31

1.3.12. DCP UPS Screen Field Descriptions ..................................................... 1-34
S100 ASOS Site Technical Manual

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Change 2 xxix

1.3.13. Ceilometer Screen Field Descriptions .................................................... 1-36

1.3.14. Present Weather Sensor Screen Field Descriptions .......................................... 1-38

1.3.15. Wind Speed and Direction Sensor Screen Field Descriptions .................................. 1-40

1.3.16. Temperature/Dewpoint (Model 1088) Screen Field Descriptions ............................... 1-42

1.3.17. Visibility and Day/Night Sensor Screen Field Descriptions .................................... 1-44

1.3.18. System Sign-On Procedures ............................................................ 1-54

1.3.19. System Signoff Procedures ............................................................. 1-54

1.3.20. Running ASOS Diagnostics ............................................................ 1-55

1.3.21. Monitoring/Controlling Sensor Power .................................................... 1-55

1.3.22. Configuring the OID Terminal .......................................................... 1-56

1.3.23. Sensor Decon and Recon Procedure ..................................................... 1-59

1.3.24. DCP Download Procedures ............................................................ 1-61

1.3.25. Reviewing/Printing the System Maintenance Log From the System Log Screen .................... 1-61

1.3.26. Printing the System Maintenance Log .................................................... 1-62

1.3.27. Making System Maintenance Log Entries ................................................. 1-62

1.3.28. Direct Command Mode Commands ...................................................... 1-64

1.3.29. Sensor Codes ....................................................................... 1-67

1.5.1. Tools and Test Equipment .............................................................. 1-80

1.5.2. Consumable Materials List .............................................................. 1-81

1.5.3. Maintenance Action Sequence ........................................................... 1-81

1.5.4. System Preventive Maintenance Schedule .................................................. 1-82

1.5.5. Visual Inspection Procedures ............................................................ 1-84

1.5.6. Facilities Maintenance Checklist ......................................................... 1-85

1.5.7. Cleaning Procedure ................................................................... 1-85

1.5.8. Corrective Maintenance Symptom Analysis ................................................. 1-86

1.5.9. Fiberoptic Link Testing - Half-Duplex Link ................................................ 1-88

1.5.10. Fiberoptic Link Testing - HO83 Link .................................................... 1-89

1.5.11. ASOS Fiberoptic Cables .............................................................. 1-90

1.5.12. Fiberoptic Cable Replacement ......................................................... 1-90

2.1.1. ACU Cabinet Major Assemblies .......................................................... 2-6

2.3.1. Card Rack Assembly Controls and Indicators ............................................... 2-22

2.3.2. Modem AC Power Rack Controls and Indicators ............................................ 2-23

2.3.3. Power Supply Assembly 62828-40124-10 Controls and Indicators ............................... 2-27

2.3.4. Power Supply Assembly 62828-40265-10 with Deltek UPS 62828-90338-10 Controls and Indicators ... 2-29

2.3.5. Power Supply Assembly 62828-40265-10 with Deltek UPS 62828-xxxxx-xx Controls and Indicators ... 2-31

2.3.6. Johnson Data RF Modem Controls and Indicators ............................................ 2-32

2.3.7. ACU and Peripherals Power Up Procedures .............................................. 2-32.1

2.3.8. ACU and Peripherals Power Down Procedures ............................................ 2-32.1

2.3.9. SID and AOMC Phone Number Entry ................................................... 2-32.2

2.3.10. Connecting Laptop Computer as Primary OID ........................................... 2-32.2

2.4.1. Port Assignments for SIO's 1 Through 3 ................................................... 2-44

2.5.1. ACU Preventive Maintenance Schedule .................................................. 2-107

2.5.2. Air Filter Cleaning ................................................................... 2-108

2.5.3. ACU Cabinet Cleaning ................................................................ 2-108

2.5.4. Corrective Maintenance Symptom Analysis ................................................ 2-109

2.5.5. UPS Fault Isolation (62828-40124-10) ................................................... 2-110

2.5.6. UPS (62828-40124-10) Pre-Service and Post-Service Procedures .............................. 2-114

2.5.7. UPS Fault Isolation (62828-90338-10) ................................................... 2-116

2.5.8. Card Rack Assembly Fault Isolation Procedures ............................................ 2-117

2.5.9. RF Failure Symptoms ................................................................. 2-120

2.5.10. ACU RF Communication Checkout Class II .............................................. 2-120

2.5.11. ACU RF Communication Checkout Class I ............................................... 2-122
ASOS Site Technical Manual S100

LIST OF TABLES - CONTINUED

Table Page

xxx Change 2

2.5.12. DCP RF Communication Checkout Class II .............................................. 2-123

2.5.13. DCP RF Communication Checkout Class I ............................................... 2-126

2.5.14. Modem/Line Driver Rack Power Supply Removal and Installation ............................. 2-129

2.5.15. RF Modem Removal and Installation .................................................... 2-130

2.5.16. RF Switch Removal and Installation .................................................... 2-132

2.5.17. VME Card Rack Circuit Board Removal and Installation .................................... 2-134

2.5.18. Modem/Line Driver Rack Circuit Board Removal and Installation ........................... 2-134.1

2.5.19. Power Supply Assembly Filter Board Removal and Installation ............................... 2-135

2.5.20. Power Supply Assembly Transformer Removal and Installation ............................... 2-135

2.5.21. Power Supply Assembly Fuse Removal and Installation ..................................... 2-137

2.5.22. Power Supply Assembly RS-232 Board Removal and Installation ............................. 2-137

2.5.23. Power Supply Assembly Inverter Board Removal and Installation ............................. 2-138

2.5.24. Power Supply Assembly Status Panel Removal and Installation ............................... 2-139

2.5.25. Power Supply Assembly OUTPUT POWER Switch Removal and Installation ................... 2-140

2.5.26. Power Supply Assembly Circuit Breaker Removal and Installation ............................ 2-140

2.5.27. DC Power Supply Removal and Installation .............................................. 2-141

2.5.28. DC Power Supply Fan Connector Board Removal and Installation ............................. 2-142

2.5.29. Blower Removal and Installation ....................................................... 2-143

2.5.30. Battery Box and Battery Removal and Installation ......................................... 2-145

2.5.31. Uninterruptible Power Supply Removal and Installation ..................................... 2-148

2.5.32. ACU Tie-Down Removal and Installation ................................................ 2-149

2.5.33. Stand-Alone Modem Setup Parameters .................................................. 2-156

2.5.34. Model DDS/MR64 ACU Rack Mount Line Driver Setup .................................... 2-157

2.5.35. Model KX-P2180 Printer Setup ........................................................ 2-159

2.5.36. Model KX-P1180 Printer Setup ........................................................ 2-159

2.5.37. Model KX-P3123 Printer Setup ........................................................ 2-160

3.1.1. DCP Equipment Cabinet Major Assemblies ................................................. 3-6

3.1.2. DCP Circuit Breakers ................................................................... 3-7

3.3.1. Power Control Module Controls and Indicators .............................................. 3-18

3.3.1A. Johnson Data RF Modem Controls and Indicators ........................................ 3-18.1

3.3.2. DCP Power Up Procedure .............................................................. 3-19

3.3.3. DCP Power Down Procedure ............................................................ 3-19

3.3.4. Connecting Laptop Computer as DCP OID ................................................. 3-20

3.4.1. Port Assignments for DCP SIO Boards .................................................... 3-38

3.5.1. DCP Preventive Maintenance Schedule .................................................... 3-85

3.5.2. DCP Equipment Cabinet Cleaning ........................................................ 3-85

3.5.2A. Desiccant Replacement Procedure ...................................................... 3-86

3.5.3. Corrective Maintenance Symptom Analysis ................................................. 3-87

3.5.4. DCP UPS Fault Isolation (62828-90057) ................................................... 3-88

3.5.5. DCP UPS (62828-90057) Pre-Service and Post-Service Procedures .............................. 3-93

3.5.6. UPS Fault Isolation (62828-90338-10 or 62828-xxxxx-xx) .................................... 3-95

3.5.7. DCP Card Rack Assembly Fault Isolation Procedures ......................................... 3-96

3.5.8. VME Card Rack Circuit Board Removal and Installation ...................................... 3-99

3.5.9. DCP UPS Filter Board Removal and Installation ............................................ 3-100

3.5.10. DCP UPS Transformer Removal and Installation .......................................... 3-101

3.5.11. DCP UPS Fuse Removal and Installation ................................................ 3-102

3.5.12. DCP UPS RS-232 Interface Board Removal and Installation ................................. 3-104

3.5.13. DCP UPS 1.5 KVA Inverter Board Removal and Installation ................................. 3-105

3.5.14. DCP UPS Fan Removal and Installation ................................................. 3-106

3.5.15. DCP UPS Status Panel Board Removal and Installation ..................................... 3-107

3.5.16. DCP UPS OUTPUT POWER Switch Removal and Installation ............................... 3-107

3.5.17. Battery Box and Battery Removal and Installation ......................................... 3-108
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LIST OF TABLES - CONTINUED

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Change 2 xxxi

3.5.18. DC Power Supply (+5 and ±12 VDC) Removal and Installation ............................... 3-111

3.5.19. RF Modem Removal and Installation .................................................... 3-113

3.5.20. RF Switch Removal and Installation .................................................... 3-114

3.5.21. RF Antenna Removal and Installation ................................................... 3-115

3.5.22. Fiberoptic Module Removal and Installation .............................................. 3-116

3.5.23. Power Control Module A1A3A1A2-A8 and A9-A18 Removal and Installation ................... 3-117

3.5.24. Solid State Relay Removal and Installation ............................................... 3-119

3.5.25. Heater HR1 Removal and Installation ................................................... 3-120

3.5.26. DCP Heater HR2 Removal and Installation ............................................... 3-121

3.5.27. DCP Thermostat Switch Removal and Installation ......................................... 3-121

3.5.28. DCP Fan Removal and Installation ..................................................... 3-122

3.5.29. Primary and Secondary Circuit Breakers A1A3A1CB1 and A10CB1 Removal and Installation ...... 3-124

3.5.30. Power Supply Assembly Diodes A4CR1 Through A4CR6 Removal and Installation ............... 3-125

3.5.31. Uninterruptible Power Supply Removal and Installation ..................................... 3-127

3.5.32. Line Driver Removal and Installation ................................................... 3-129

3.5.33. Model DDS/MR64 Stand Alone Line Driver Setup ......................................... 3-130

4.2.1. Mounting Wind Sensor Electronics Enclosure ................................................ 4-7

4.2.2. Installing Crossarm Support On Tower ..................................................... 4-8

4.5.1. Wind Sensor Preventive Maintenance Schedule ............................................. 4-27

4.5.2. Mechanical Operation Inspection ......................................................... 4-27

4.5.3. Solar Noon Wind Direction Alignment Procedure ............................................ 4-28

4.5.4. Davis Pelorus Alignment Procedure ....................................................... 4-30

4.5.5. Checking Wind Direction and Speed Data .................................................. 4-34

4.5.6. Wind Sensor Troubleshooting ........................................................... 4-35

4.5.7. Wind Sensor AC and DC Power Supply Checks ............................................. 4-36

4.5.8. Lowering and Raising Wind Tower ....................................................... 4-37

4.5.9. Wind Direction and Wind Speed Sensors Removal and Installation .............................. 4-39

4.5.10. Cup Assembly and Vane Assembly Removal and Installation .................................. 4-39

4.5.11. Power Supply Removal and Installation ................................................... 4-41

4.5.12. Fiberoptic Module Removal and Installation ............................................... 4-42

4.5.13. Processor Board Removal and Installation ................................................. 4-44

4.5.14. Wind Sensor Electronics Enclosure Removal and Installation .................................. 4-44

4.5.15. Wind Tower Signal Cable W1 Removal and Installation ...................................... 4-46

4.5.16. Crossarm Assembly Removal and Installation .............................................. 4-47

4.5.17. Starting Torque Bearing Test ........................................................... 4-49

5.2.1. Temperature/Dewpoint Sensor Preassembly ................................................. 5-7

5.2.2. Temperature/Dewpoint Sensor Installation .................................................. 5-9

5.3.1. Temperature/Dewpoint Sensor Controls and Indicators ........................................ 5-12

5.3.2. Temperature/Dewpoint Sensor Turn-On Procedures .......................................... 5-14

5.3.3. Temperature/Dewpoint Sensor Turnoff Procedures ........................................... 5-14

5.5.1. Temperature/Dewpoint Sensor Preventive Maintenance Schedule ............................... 5-29

5.5.2. Aspirator Cleaning .................................................................... 5-30

5.5.3. Model H083R Temperature/Dewpoint Sensor Optical Loop Adjustment .......................... 5-31

5.5.4. Model 1088 Temperature/Dewpoint Sensor Optical Loop Adjustment ............................ 5-32

5.5.5. Verification of ASOS H083R/1088 Sensor Readings Using Psychron Model 566-2 Psychrometer ...... 5-33

5.5.6. Maximum Allowable Difference Between ASOS H083R/1088 and Psychron Model 566-2 Dewpoint

Temperatures ............................................................................. 5-35

5.5.7. Deleted ............................................................................. 5-35

5.5.8. DC Power Supply Check ............................................................... 5-36

5.5.9. Model H083R Temperature/Dewpoint Sensor Calibration ..................................... 5-38

5.5.10. “T” Commands for Model 1088 Checkout ................................................. 5-38

5.5.11. Model 1088 Temperature/Dewpoint Sensor Calibration ...................................... 5-39
ASOS Site Technical Manual S100

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xxxii Change 2

5.5.12. Temperature/Dewpoint Sensor Troubleshooting ............................................ 5-40

5.5.13. Dewpoint Sensor Assembly Removal and Installation ........................................ 5-41

5.5.14. Aspirator Housing Removal and Installation ............................................... 5-42

5.5.15. Transmit Logic Board Removal and Installation ............................................ 5-43

5.5.16. Autobalance Module Removal and Installation ............................................. 5-44

5.5.17. +5V Power Supply Removal and Installation ............................................... 5-45

5.5.18. Auxiliary Power Supply Removal and Installation ........................................... 5-46

5.5.19. Fiberoptic Module Removal and Installation ............................................... 5-47

6.1.1. Visibility Sensor Accuracy ............................................................... 6-4

6.2.1. Enclosure Support Installation ............................................................ 6-6

6.2.2. Electronics Enclosure Installation ......................................................... 6-7

6.2.3. Day/Night Sensor Installation ............................................................ 6-9

6.2.4. Cable Installation ..................................................................... 6-10

6.5.1. Visibility Sensor Preventive Maintenance Schedule .......................................... 6-37

6.5.2. Visibility Sensor Cleaning and Inspection .................................................. 6-39

6.5.3. Visibility Sensor Calibration ............................................................ 6-39

6.5.4. DC Power Checks .................................................................... 6-50

6.5.5. AC Power Checks .................................................................... 6-50

6.5.6. Heater Troubleshooting ................................................................ 6-51

6.5.7. Receiver Assembly Removal and Installation ............................................... 6-52

6.5.8. Transmitter Assembly Removal and Installation ............................................. 6-54

6.5.9. Processor Board Removal and Installation .................................................. 6-56

6.5.10. Day/Night Assembly Removal and Installation ............................................. 6-56

6.5.11. Electronics Power Supply Removal and Installation ......................................... 6-57

6.5.12. Fiberoptic Module Removal and Installation ............................................... 6-58

6.5.13. Crossarm Assembly Removal and Installation .............................................. 6-59

6.5.14. Electronics Enclosure Removal and Installation ............................................ 6-61

6.5.15. Regulator Board Removal and Installation ................................................. 6-64

7.2.1. Installing Present Weather Sensor ......................................................... 7-3

7.4.1. Hex - Binary Nibble Conversion Chart .................................................... 7-24

7.4.2. Status Bit/FRU Summary ............................................................... 7-25

7.5.1. Lens and Hood Heater Touch Test ........................................................ 7-29

7.5.2. Present Weather Sensor Calibration ....................................................... 7-29

7.5.3. Present Weather Sensor Spider Paint Application Procedure ................................... 7-34

7.5.4. Present Weather Sensor Troubleshooting .................................................. 7-36

7.5.5. Present Weather Power Supply Test ...................................................... 7-37

7.5.6. Frame Head Assembly Removal and Installation ............................................. 7-38

7.5.7. Heater Power Supply Removal and Installation .............................................. 7-40

7.5.8. Analog Power Supply Removal and Installation ............................................. 7-41

7.5.9. Digital Power Supply Removal and Installation .............................................. 7-42

7.5.10. Circuit Board Removal and Installation ................................................... 7-44

7.5.11. Fiberoptic Module Removal and Installation ............................................... 7-44

7.5.12. Heater Bar Assembly Removal and Installation ............................................. 7-46

7.5.13. Card Rack Assembly Removal and Installation ............................................. 7-47

7.5.14. Main Electrical Enclosure Removal and Installation ......................................... 7-48

8.5.1. Pressure Sensor Preventive Maintenance Schedule ........................................... 8-11

8.5.2. Verifying Accuracy of Pressure Sensor Data ................................................ 8-13

8.5.3. Pressure Sensor Removal and Installation .................................................. 8-15

8.5.4. Turning Pressure Sensor Report Processing On .............................................. 8-17

8.5.5. Clearing Pressure Sensor Data Quality Failures .............................................. 8-17

9.1.1. Ceilometer Specifications ................................................................ 9-3

9.1.2. Ceilometer Configurations ............................................................... 9-7
S100 ASOS Site Technical Manual

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Change 2 xxxiii

9.2.1. Ceilometer Installation .................................................................. 9-9

9.3.1. Ceilometer Controls and Indicators ....................................................... 9-18

9.3.2. Ceilometer Turn-On Procedures .......................................................... 9-18

9.3.3. Ceilometer Turnoff Procedures .......................................................... 9-19

9.3.4. Ceilometer Parameters ................................................................. 9-35

9.5.1. Ceilometer Preventive Maintenance Schedule ............................................... 9-65

9.5.2. Cleaning and Inspection ................................................................ 9-66

9.5.3. Ceilometer Calibration Check Procedure ................................................... 9-67

9.5.3a Device Scale Calculation Procedure .................................................... 9-71.2

9.5.4. Snow Radiation Shield Cleaning Procedure ................................................. 9-71

9.5.5. Ceilometer Troubleshooting ............................................................. 9-73

9.5.6. General Hardware Alarm Messages ....................................................... 9-73

9.5.7. Initialization Error Messages ............................................................ 9-73

9.5.8. Power Supply Monitored Voltage Levels ................................................... 9-74

9.5.9. Monitored Power Test Points, Fuses, and Loads ............................................. 9-74

9.5.10. Power Supply General Troubleshooting Procedure .......................................... 9-75

9.5.11. Temperature Alarm References ......................................................... 9-77

9.5.12. Temperature Alarm With High Temperature ............................................... 9-78

9.5.13. Temperature Alarm With Reasonable Temperatures ......................................... 9-78

9.5.14. Ceilometer Equipment Cabinet Cover Removal and Installation ................................ 9-79

9.5.15. Processor Board Operating Voltage Checkpoints ........................................... 9-80

9.5.16. Processor Board Removal and Installation ................................................. 9-81

9.5.17. Unregulated Power Supply Voltage Limits ................................................ 9-83

9.5.18. Unregulated Power Supply Voltage Test Points and Loads .................................... 9-83

9.5.19. Unregulated Power Supply Board Removal and Installation ................................... 9-83

9.5.20. I/O Connector Board Voltage Test Points ................................................. 9-84

9.5.21. I/O Connector Board Removal and Installation ............................................. 9-84

9.2.22. Light Monitor Board Voltage Test Points ................................................. 9-85

9.5.23. Solar Shutter Driver Removal and Installation .............................................. 9-85

9.5.24. Light Monitor Board Removal and Installation ............................................. 9-86

9.5.25. Receiver Board Voltage Test Points ..................................................... 9-87

9.5.26. Receiver Board Removal and Installation ................................................. 9-87

9.5.27. Transmitter Board Voltage Test Points ................................................... 9-89

9.5.28. Transmitter Board Removal and Installation ............................................... 9-89

9.5.29. High Voltage Power Supply Removal and Installation ....................................... 9-91

9.5.30. Temperature Compensation Transformer Removal and Installation ............................. 9-92

9.5.31. Cabinet Heater Removal and Installation .................................................. 9-93

9.5.32. External Air Temperature Sensor Removal and Installation ................................... 9-94

9.5.33. Snow Radiation Shield Removal and Installation ........................................... 9-95

9.5.34. Window Conditioner Removal and Installation ............................................ 9-96

9.5.35. Offset Calibration Procedures .......................................................... 9-98

9.5.36. Fiberoptic Module Removal and Installation ............................................... 9-99

10.2.1. Liquid Precipitation Accumulation Sensor Installation Procedures .............................. 10-5

10.5.1. Rain Gauge Inspection and Calibration Check ............................................. 10-14

10.5.2. Liquid Precipitation Accumulation Sensor Fault Isolation .................................... 10-15

10.5.3. Liquid Precipitation Accumulation Sensor Removal and Installation ........................... 10-17

10.5.4. Tipping Bucket Switch Removal and Installation .......................................... 10-19

10.5.5. Fiberoptic Transmitter Removal and Installation ........................................... 10-21

11.2.1. Freezing Rain Sensor Installation Procedures .............................................. 11-5

11.5.1. Freezing Rain Sensor Inspection and Cleaning ............................................ 11-19

11.5.2. Using the Laptop Computer With the Freezing Rain Sensor .................................. 11-19

11.5.3. Freezing Rain Sensor Troubleshooting .................................................. 11-21
ASOS Site Technical Manual S100

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xxxiv Change 2

11.5.4. Depot Level Probe Assembly Heater Troubleshooting ...................................... 11-21

11.5.5. Depot Level Freezing Rain Sensor Calibration ............................................ 11-22

11.5.6. Electronics Enclosure Removal and Installation ........................................... 11-23

11.5.7. Depot Level Electronics Processor Board Removal and Installation ............................ 11-25

11.5.8. Depot Level Probe Assembly Removal and Installation ..................................... 11-27

11.5.9. Fiberoptic Module Removal and Installation .............................................. 11-29

12.3.1. GTA Radio Front Panel Controls and Indicators ............................................ 12-6

12.3.2. Display/Control Modes (Panels) ........................................................ 12-7

12.5.1. Periodic Performance Checks ......................................................... 12-15

12.5.2. RF Power Output Check .............................................................. 12-15

12.5.3. Modulation Level Check (Preferred) .................................................... 12-17

12.5.3a. Modulation Level Check (Alternative) ................................................ 12-17.1

12.5.4. VSWR at Transmitter Output Check .................................................... 12-18

12.5.5. Frequency Stability Check ............................................................ 12-20

12.5.6. Coax Cable Conductance and Insulation Check ............................................ 12-21

12.5.7. Corrective Maintenance Symptom Analysis ............................................... 12-23

12.5.8. Loss of Broadcast Weather Voice ...................................................... 12-23

12.5.9. GTA Radio Does Not Respond to ACU Data Test ......................................... 12-25

12.5.10. Voice Recorder/Playback Board Check ................................................. 12-25

12.5.11. GTA Radio Removal and Installation .................................................. 12-26

13.1.1. Codex 3600 Series Modem Specifications ................................................. 13-2

13.3.1. Codex 3600 Series Modem Controls and Indicators ......................................... 13-9

13.5.1. Codex 3600 Series Modem Quick Checks ................................................ 13-28

13.5.2. Codex 3600 Series Modem Signal Quality Test ............................................ 13-29

13.5.3. Codex 3600 Series Modem Self-Test .................................................... 13-30

13.5.4. BERT Test ........................................................................ 13-30

13.5.5. Codex 3600 Series Modem Removal and Installation ....................................... 13-32

13.5.6. Flex-Cartridge Removal and Installation ................................................. 13-33

13.5.7. Configuring the Codex 3600 Series Modem .............................................. 13-35

14.1.1. SCA (7A1) Major Components ......................................................... 14-6

14.1.2. Auxiliary Box (7A2) Major Components ................................................. 14-12

14.3.1. Circuit Breaker Panel 7A1A1A3 Controls and Indicators .................................... 14-16

14.3.2. VME Rack 7A1A1A2 Controls and Indicators ............................................ 14-17

14.3.3. Johnson data RF Modem Controls and Indicators .......................................... 14-18

14.4.1. SIO Port Assignments ............................................................... 14-25

14.4.2. Digitized Audio Connections .......................................................... 14-29

14.4.3. Modem Complement ................................................................ 14-41

14.5.1. Maintenance Documentation Procedures ................................................. 14-44

14.5.2. Visual Inspection Procedures .......................................................... 14-44

14.5.2A. Desiccant Replacement Procedure .................................................. 14-44.1

14.5.3. Facilities Maintenance Checklist ....................................................... 14-45

14.5.4. Cleaning Procedure ................................................................. 14-45

14.5.5. Symptom Analysis .................................................................. 14-46

14.5.6. Fiberoptic Link Testing - Half-Duplex Link .............................................. 14-47

14.5.7. Fiberoptic Link Testing - HO83 Link .................................................... 14-47

14.5.8. UPS 7A1A1A6 Removal Procedure .................................................... 14-49

14.5.9. UPS 7A1A1A6 Installation Procedure ................................................... 14-50

14.5.10. UPS DIP Switch Setup (Deltek UPS 62828-90338-10 Only) ................................ 14-50

14.5.11. Faraday Box Access Procedure ....................................................... 14-51

16.1.1. Operational specifications ............................................................. 16-2

16.2.1. Thunderstorm Installation Procedure ..................................................... 16-3

16.3.1. Power/Comm Module Controls and Indicators ............................................. 16-8
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Change 2 xxxv

16.3.2. Analog Board and Processor Board Controls and Indicators .................................. 16-10

16.3.3. Processor Board Switch Bank 101 Settings ............................................... 16-10

16.3.4. Processor Board Switch Bank 100 Settings ............................................... 16-10

16.3.5. Thunderstorm Sensor Turn-On Procedures ............................................... 16-11

16.3.6. Thunderstorm Sensor Turnoff Procedures ................................................ 16-11

16.4.1. Host Command Set .................................................................. 16-17

16.4.2. Response to Command A: Present Weather Message ....................................... 16-17

16.4.3. Response to Command B: Status Message ................................................ 16-18

16.4.4. Response to Command C: Self-test Message .............................................. 16-19

16.4.5. Self-test Status Byte ................................................................. 16-19

16.4.6. Response to Command E: Type Test Output .............................................. 16-20

16.4.7. Response to Command F: System Run Time Message ....................................... 16-20

16.4.8. SW100 Switches 1-3: Diagnostic Tests .................................................. 16-21

16.5.1. Thunderstorm Sensor Inspection and Cleaning ............................................ 16-24

16.5.2. Using the Laptop Computer With the Thunderstorm Sensor .................................. 16-24

16.5.3. Thunderstorm Sensor Troubleshooting .................................................. 16-26

16.5.4. Electro-optical Antenna Removal and Installation .......................................... 16-27

16.5.5. Electronics Module Removal and Installation ............................................. 16-28

16.5.6. Power/Comm Board Removal and Installation ............................................ 16-29

16.5.7. Fiberoptic Module Removal and Installation .............................................. 16-30

18.1. Software Compatibilities ................................................................ 18-1
ASOS Site Technical Manual S100

xxxvi Change 2

SAFETY SUMMARY

The following general safety precautions must be observed during all phases of operation, service, and repair of this

equipment. Failure to comply with these precautions or with specific warnings elsewhere in this manual violates

safety standards of design, manufacture, and intended use of the equipment. AAI assumes no liability for the

customer's failure to comply with these requirements.

KEEP AWAY FROM LIVE CIRCUITS 

Operating and maintenance personnel must at all times observe all safety regulations. Do not replace components

while the equipment is energized. Under certain conditions, dangerous potentials may exist when the power has

been turned off, due to charges retained by capacitors. To avoid injury, always remove power and discharge and

ground a circuit before touching it.

RESUSCITATION 

Personnel working with or near this system should be familiar with modern methods of resuscitation. Such

information may be obtained from the Bureau of Medicine and Surgery.

NEVER LOOK INTO THE CEILOMETER'S LASER TRANSMITTER WITH

MAGNIFYING OPTICS 

The ceilometer is intended for operation in an area restricted from public access, and pointing vertically up. 

Whenever this is not the case, care must be observed so as to prevent exposure to the laser beam through focusing

optics. Work area access by unauthorized persons during service operations must be prevented.

DO NOT SUBSTITUTE PARTS OR MODIFY INSTRUMENT

Because of the danger of introducing additional hazards, do not install substitute parts or perform any unauthorized

modification to the instrument. Return the instrument to the depot/AOMC for service and repair to ensure that safety

features are maintained.

TEST EQUIPMENT 

Ensure that all test equipment is calibrated within required dates and is in good operating condition. Ensure that all

test equipment is properly grounded before use.

ACCESSING EQUIPMENT 

Before attempting to service any ASOS equipment, notify airport security and gain access to the system by following

local procedures and adhere to all airport traffic regulations.

CROSSING RUNWAYS

 

Before crossing any runway, radio the tower and request clearance. Proceed only with clearance, and only after

illuminating the caution light mounted on top of your vehicle.

DANGEROUS PROCEDURE WARNINGS 

Warnings, such as the example below, precede potentially dangerous procedures throughout this manual. 

Instructions contained in the warnings must be followed.
S100 ASOS Site Technical Manual

Change 1 xxxvii

WARNING

Death or severe injury may result if power is not removed from the equipment prior to maintenance

activities. Ensure that output power switch is set to 0 (off) position and facility power is removed

from ACU.

EQUIPMENT CAUTIONS 

Cautions, such as the example below, precede procedures where failure to follow the specific instructions may result

in damage to the equipment. Instructions contained in the cautions must be followed.

CAUTION

Do not bend fiberoptic cables. Bending could break the optical fibers.

This equipment contains parts sensitive to damage by electrostatic discharge (ESD). Use ESD

precautionary procedures when touching, removing, or installing assemblies.
ASOS Site Technical Manual S100

xxxviii Change 1

LIST OF ABBREVIATIONS AND ACRONYMS

ACU - Acquisition Control Unit

AOMC - ASOS Operations Monitoring Center

ASOS - Automated Surface Observing System

ATC - Air Traffic Controller

AWIPS - Advanced Weather Information Processing System

A/D - Analog to digital

cps - Characters per second

CPU - Central Processing Unit

CRT - Cathode Ray Tube

CST - Continuous Self-Test

CVD - Controller Video Display

db - Decibel

DCP - Data Collection Package

DIO - Digital I/O

DMM - Digital multimeter

DRAM - Dynamic Random Access Memory

DTE - Data Terminal Equipment

EMI - Electromagnetic interference

EPROM - Erasable programmable read-only memory

ESD - Electrostatic discharge

FAA - Federal Aviation Administration

FRU - Field replaceable unit

GFI - Ground fault interrupt

GTA - Ground To Air

inHg - Inches of mercury

I/O - Input/output

LCD - Liquid crystal display

LDD - Lightning Detection Data

LED - Light emitting diode

LEDWI - Light emitting diode weather indication

NLQ - Near letter quality

NWS - National Weather Service

OID - Operator interface device

OND - Observer notification device

PM - Preventive maintenance

PSD - Port Sharing Device

P/N - Part number

RAM - Random access memory

rf - Radio frequency

RVR - Runway Visual Range

S/A - Stand-alone

SAL - System analog loopback

SAO - Surface aviation observation

SCA - Single Cabinet ASOS

SCC - Serial communication controller

SIO - Serial I/O

SRAM - Static random access memory

TCCC - Tower computer control complex

T/D - Temperature/dewpoint

TS - Temperature spread

UPS - Uninterruptible power supply

VDU - Video display unit

VF - Voice frequency
S100 ASOS Site Technical Manual

1-1

CHAPTER 1

SYSTEM OVERVIEW

SECTION I. DESCRIPTION AND LEADING PARTICULARS

1.1.1 INTRODUCTION

The Automated Surface Observing System (ASOS) automatically collects weather data and provides

accurate, 24-hour accumulated weather reports to local weather observers; weather forecasters; airport

personnel, including pilots and air traffic controllers (ATC's); and Federal Aviation Administration (FAA)

and National Weather Service (NWS) personnel. ASOS functions include: measurement of weather

elements, data processing and display, communication, and data storage (archiving). The ASOS is a flexible

system with a modular construction that allows deployment in a variety of configurationsfor operation with

or without the attendance of an observer. Unattended, the ASOS automatically collects, processes, and error

checks data and formats, displays, archives, and reports the weather elements included in a surface weather

observation. The ASOS also accepts inputs from observers (when present), who may also override or add

information to the automatically generated observation.Because ofthe flexibility oftheASOS,it can provide

useful weather information in text, video, and audio format to a variety of users. table 1.1.1 lists the users

with which the ASOS can interface. 

Table 1.1.1. ASOS Users

User Name Description

Automation of Field

Operations and Services

(AFOS)

National Weather Service (NWS) forecasters use the AFOS outputs from the acquisition

control unit(ACU)to performtheir duties. ASOS provides hourly surfacemeteorological

reports(METAR’s), Aerodrome Forecasts (TAF's), and special weather reports (SPECI's)

to any AFOS user. Local AFOS users receive data via direct connection (hardwire).

Remote AFOS users receive data through telephone lines. These terminals are not the

ASOS technician's responsibility.

Airline displays One-minute weather observations, in the International Civil Aviation Organization

(ICAO) METAR format are available from the ACU for distribution to up to 50 airline

displays located throughout the airport complex. The airline displays receive reports and

forecasts through coaxial cables connected to a single jack on the ACU. These terminals

are not the ASOS technician's responsibility. 

Controller Video

Displays (CVD’s)

Federal Aviation Administration (FAA) CVD’s serve air traffic controllers (ATC’s) in

the tower. Up to nine displays may receive data from a single ASOS. The CVD’s receive

METAR’s, 1-minute altimeter data, 5-second wind data, and density altitude data (when

greater than 1000 ft).

FAA radio ASOS produces a computer-generated voice message from the last METAR (hourly

surface observation report), or fromthe current 1-minute observation. The voice message

is generated continuously, with five seconds delay between the completion of one

message and the beginning of the next. The voice message is output to a radio

communications link for transmission to aircraft in the VHF frequency range. The

operator interface device (OID) provides FAA ATC's with the ability to select the

broadcast product (i.e., last METAR hourly report or current 1-minute observation).

Dial-In reports The ASOS computer-generated voice message (see FAA radio above) is also output for

up to eight telephone lines to provide audio reports for dial-in callers.
ASOS Site Technical Manual S100

1-2 Change 1

Table 1.1.1. ASOS Users -CONT

User Name Description

Operator Interface

Device (OID)

The OID is used to receive minute-by-minute data (including hourly, local, and special

observations) and all data requested from the OID. Up to three OID's are provided with

the ASOS. The primary OID has priority over the secondary OID's. When an observer is

signed on at the primary OID, changes to system data cannot be made via the secondary

OID's. One of the two secondary OID's can be equipped with an FAA handset. The

handset is used to generate voice messages which can be added to the continuous FAA

radio transmission. The FAA handset interfaces to the ACU via direct connection

(hardwire).

Remote users Up to five dial-in ports provided with the ACU can be used to allow remote users to

perform all OID functions and to send/receive information such as minute-by-minute

weather data, archive information, maintenance data, and diagnostics results. Users

interface with the ACU via telephone lines and a remote computer terminal. When

accessing the ASOS remotely via a modem hookup, the user cannot perform observer or

ATC level input functions. The five remote user ports are identified as follows:

a. User phone 1 (OID #4)

b. User phone 2 (OID #5)

c. User phone 1 spare (OID #6)

d. User phone 2 spare (OID #7)

e. OID spare (OID #8)

Video display units

(VDU's)

Up to four local VDU's provide 1-minute observations for various airport personnel.

VDU's are capable of operating up to 200 feet from the ACU.

Tower computer control complex (TCCC)For future use.

Advanced weather

information processing

system (AWIPS)

AWIPS usesthe AWIPS output from the acquisition control unit(ACU). ASOS provides

routine, hourly surface meteorological reports (METAR's), SPECI weather reports, and

SHEF reports to AWIPS. ASOS also provides the latest one-minute observation (OMO)

when requested by AWIPS. Local AWIPS users receive data via direct connection

(hardwire). Remote AWIPS users receive data through telephone lines.

FAA ADAS The FAA ADAS Data Acquisition System(ADAS) both transmits and receives messages

with the ASOS via the FAA ADAS port at the acquisition control unit (ACU). Messages

to the FAA ADAS are translated into the ADAS format before transmission. ASOS

provides METAR hourly reports and unscheduled SPECI reports to the FAA ADAS via

phone line. In addition, the FAA ADAS receives and disseminates Lightning Detection

Data (LDD) to the ASOS.

RVR Atselected sites, the acquisition control unit(ACU) provides a port to interface a Runway

Visual Range (RVR) computer. The RVR computer sends RVR data to ASOS at a

minimum rate of once per minute via a dedicated hardwire link or phone line.

1.1.2 PURPOSE OF THIS MANUAL

This manual provides site maintenance personnel with the primary source of technical information required

for the maintenance of the ASOS. The ASOS theory of operation and troubleshooting data are presented to

enable maintenance personnel to quickly remedy any problem and return the system to an operational

$ condition. This manual is divided into 16 chapters, partslist, and maintenance drawings which are described

$ in the following paragraphs.

1.1.2.1 Chapter 1, System Overview.Chapter 1 providessystemlevel maintenance data forthe ASOS. The

Chapteris divided into five sections: description, installation, operation, theory, and maintenance. Chapter 1

contains all system level maintenance procedures and, therefore, should be referenced first when fault

isolating the ASOS.
S100 ASOS Site Technical Manual

Change 1 1-3

1.1.2.2 Chapter 2, Acquisition Control Unit (ACU). Chapter 2 provides the physical description, theory

of operation, installation, and maintenance procedures for the ACU subsystem of the ASOS, including all

peripherals. Notice that the standard ASOS ACU includes a built-in local Data Collection Package (DCP)

function which can support up to three locally sited sensors, where sensor data and control are interfaced via

fiberoptic modules.

1.1.2.3 Chapter 3,DataCollectionPackage (DCP).Chapter 3 describesthe data collection package (DCP)

processing system. Theory of operation and installation, operating, and maintenance procedures are provided

for the rf link, uninterruptible power supply (UPS), modem, sensor processors, power supplies, and

environmental enclosure cooling system. Each DCP cabinet supports up to 16 sensors and is designed for

unsheltered installation remote from the ACU. At airports, DCP cabinets will generally be sited near the

approach end of runways. The standard ASOS ACU also can serve as a local DCP for up to three sensors

that are situated close to the shelter in which the ACU is installed. 

1.1.2.4 Chapters 4 through 13 and 16, Sensors and Subsystems. Chapters 4 through 13 and 16 provide $

maintenance information on theASOSsensors and subsystems, including: introduction, physical description,

specifications, installation, theory of operation, and maintenance. Chapter assignments are as follows: 

a. Chapter 4, Wind Sensors

b. Chapter 5, Temperature/Dewpoint (Model H083/1088) Sensors 

c. Chapter 6, Visibility Sensor

d. Chapter 7, Present Weather Sensor

e. Chapter 8, Ambient Pressure Sensor

f. Chapter 9, Cloud Height Sensor (Ceilometer) 

g. Chapter 10, Liquid Precipitation Accumulation Sensor (Rain Gauge) 

h. Chapter 11, Freezing Rain Sensor

i. Chapter 12, Ground-to-Air Radio

j. Chapter 13, Codex 3600 Series Modem

k. Chapter 16, Thunderstorm Sensor $

1.1.2.5 Chapter 14, Single Cabinet ASOS (SCA). Chapter 14 describes the Single Cabinet ASOS (SCA)

system. Theory of operation and installation, operating, and maintenance procedures are provided for the rf

link, uninterruptible power supply (UPS), modem, sensor processors, power supplies, and environmental

enclosure cooling system. The SCA cabinet contains both the ACU and DCP combined into one cabinet and

is designed for unsheltered installation. The SCA uses the same sensors and peripherals as the standard

ASOS.

1.1.2.6 Chapter 15, Port-Sharing Device (PSD). Chapter 15 describes the Port Sharing Device software

task that runs in the ACU. The PSD enables the single port on the remote terminal to AFOS to communicate

with both ASOS and the auxiliary backup terminal (ABT). 

1.1.2.7 Parts List. The parts list (located after the last chapter) provides a listing of all repair parts,

including assemblies,subassemblies, and parts common and peculiarto theASOS.The listing includes: item

name, Federal Stock Number (FSN), Federal manufacturer's code, manufacturer's part number, and

recommended initial stock quantities. A cross-reference from the FSN to manufacturer's stock numbers is

also included, which provides alternate sources for procurement where applicable. 

1.1.2.8 Maintenance Drawings. The maintenance drawings section (located after the parts list in volume

II) describes the formats used on oversize maintenance drawings contained in this manual. These drawings

include detailed block diagrams, power distribution drawings, and cabling diagrams.
ASOS Site Technical Manual S100

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1.1.3 SCOPE OF THIS MANUAL

Thismanual provides all information necessary for on-sitemaintenance support oftheASOS,which includes

preventive maintenance, operation, fault isolation, and removal/installation of field replaceable units (FRU's).

To enable site maintenance personnel to quickly locate the maintenance procedures for the various

subsystems of the ASOS, each subsystem is described in a separate Chapter as described in paragraph 1.1.2.

To further aid maintenance personnel, each Chapter follows the same format. Chapters consist of five major

sections whose order and basic content are as follows:

1.1.3.1 Section I, Description and Leading Particulars. Section I provides an introduction to the

system/subsystem and should be referenced to gain a general understanding of the system or to obtain

physical descriptions and locational information. 

1.1.3.2 Section II, Installation. Section II provides information on the method of replacing the individual

subsystem. This information is provided on the assumption that the subsystem was previously installed by

the factory installation team, and that all mounting hardware and electrical wiring are in place. 

1.1.3.3 Section III, Operation. Section III provides the procedures to power on/off, initialize, determine

operational status, and operate a system/subsystem. This information enables maintenance personnel to

effectively utilize the ASOS. Standard operating procedures are provided in the ASOS Software User's

Manual. 

1.1.3.4 Section IV, Theory of Operation. Section IV provides detailed theory of operation for a

system/subsystem and includes basic and detailed block diagrams. 

1.1.3.5 Section V, Maintenance. Section V provides corrective and preventive maintenance proceduresfor

a system/subsystem. Procedures are provided for cleaning and inspection, adjustment/calibration,

troubleshooting through the use of diagnostics, and removal/replacement of failed FRU's. Section V should

be referenced when troubleshooting or performing scheduled maintenance on the ASOS. 

1.1.4 ASOS SYSTEM DESCRIPTION

Figure 1.1.1 illustrates a typical ASOS installation. The systemconsists of an acquisition control unit(ACU),

up to three data collection packages (DCP's), sensors that gather weather information, and user terminals.

The ACU receivessensor data from the DCP(s); analyzes, compiles, and logsthe data; and providesthe data

to the various ASOS users. All interfacing with the ASOS is accomplished via the ACU. The DCP controls

the data collection process. It receives data from the individual sensors, formats the data, and transmits the

data to the ACU. The DCP also provides and controls all primary electrical powerto the sensors. The sensors

gather the weather information. The sensor complement can consist of up to 16 sensors per remote DCP.

These sensors perform specialized functions to gather raw data regarding weather and atmospheric

conditions. These data typically include temperature, wind, and precipitation. The sensors are then either

polled by the DCP or automatically transfer their data to the DCP where the data are incorporated into the

ASOS data processing scheme. In addition to the sensors connected to the remote DCP, up to six sensors can

be connected directly to the ACU. These sensors are referred to individually aslocal sensors, or collectively

as the local DCP. The first three local sensor slots are reserved for pressure sensors contained inside the

ACU. Any of the other types of ASOS sensors can be connected to local sensor ports 4, 5, and 6 of the ACU.
S100 ASOS Site Technical Manual

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Figure 1.1.1. Typical ASOS

1.1.5 SYSTEM CONFIGURATIONS

Each ASOS is configured tomeet the specific requirements at each individualsite. The present configuration

of a site can be reviewed by accessing the site configuration screens via the OID or a remote terminal. The

sitemaintenancemanual providesmaintenance documentation for all possible assemblies and subassemblies

in the ASOS but does not relate to any specific configuration. The technician should consult the

configuration screens and site specific documentation to make determinations such as sensor configuration,

number of OID and user terminals, sensor pad configuration, and facility power and signal cable routing. 
ASOS Site Technical Manual S100

1-6 Change 1

1.1.6 RELATED PUBLICATIONS

In addition to this manual, the ASOS is supported by the following manuals: 

a. ASOS Software User's Manual - Provides detailed information on ASOS operation and all

ASOS OID screens.

b. ASOS Ready Reference Guide - Provides operator reference information for system

operation.

c. Link MC70 User's Guide - Provides vendor support information for the OID.

d. Panasonic dot matrix printer model KX-P1180i, KX-P2180, or KX-P3123 Operating

Instructions Manual - Provides vendor support information for the dot matrix printer.

e. UDS 2440 Installation and Operation - Provides vendor support documentation for the

model 2440 stand-alone telephone modems.

f. UDS V.3225 Installation and Operation - Provides vendor support documentation for the

model V.3225 stand-alone telephone modems.

g. UDS V.3400 Installation and Operation - Provides vendor support documentation for the

model V.3400 stand-alone telephone modems.

h. Motorola DDS/MR64 Installation and Operation - Provides vendor support documentation

for the model DDS/MR64 line driver.

1.1.7 SYSTEM SPECIFICATIONS

ASOS system specifications are provided in table 1.1.2.

Table 1.1.2. System Specifications

Sensor Limits Accuracy Resolution

Wind Speed 0 to 125 knots ±2 knots or 5%, whichever is greater 1 knot

Wind

Direction

Winds $5 knots 

Winds 2 to 5 knots

±5°

- Winds must be displaced more than 5°

1 degree

Temperature -80°F to +130°F ±1.8° for readings between -58°F and 122°F. 

±3.6° for readings between -80°F and -58°F. 

±3.6° for readings between 122°F and 130°F.

 0.1°F

Dewpoint .0°F # TS < 10.8°F**

10.8°F # TS <14.4°F**

14.4°F # TS <16.2°F**

16.2°F # TS < 18.0°F**

±2° for dewpoint readings: Td > 32°F.

±3.4° for dewpoint readings: 32°F $ Td > -0.4°F.

$ ±4.5° for dewpoint readings: -0.4°F $ Td $ -31°F.

±2.2° for dewpoint readings: Td > 32°F.

±3.4° for dewpoint readings: 32°F $ Td >-0.4°F.

$ ±4.5° for dewpoint readings: -0.4°F $ Td $ -31°F.

±2.3° for dewpoint readings: Td > 32°F.

±3.6° for dewpoint readings: 32°F $ Td >-0.4°F.

$ ±4.5° for dewpoint readings: -0.4°F $ Td $ -31°F.

±2.5° for dewpoint readings: Td > 32°F.

±3.8° for dewpoint readings: 32°F $ Td >-0.4°F.

$ ±4.5° for dewpoint readings: -0.4°F $ Td $ -31°F.

 0.1°F

*,** See notes at the end of table
S100 ASOS Site Technical Manual

Change 1 1-7

Table 1.1.2. System Specifications -CONT

Sensor Limits Accuracy Resolution

Dewpoint

(cont)

18.0°F # TS < 19.8°F**

19.8°F # TS < 21.6°F**

21.6°F # TS < 23.4°F**

23.4°F # TS < 25.2°F**

25.2°F # TS < 27.0°F**

27.0°F # TS < 28.8°F**

28.8°F # TS <30.6°F**

30.6°F # TS < 36.0°F**

36.0°F # TS < 45.0°F**

45.0°F # TS < 54.0°F** 

54.0°F # TS < 63.0°F**

±2.7° for dewpoint readings: Td > 32°F.

±4.1° for dewpoint readings: 32°F $ Td > -0.4°F.

±4.5° for dewpoint readings: -0.4°F $ Td $ -31°F. $

±2.9° for dewpoint readings: Td > 32°F.

±4.5° for dewpoint readings: 32°F $ Td > -31°F.

±3.1° for dewpoint readings: Td > 32°F.

±5.0° for dewpoint readings: 32°F $ Td $ -31°F.

±3.2° for dewpoint readings: Td > 32°F.

±5.4° for dewpoint readings: 32°F $ Td $ -31°F.

±3.4° for dewpoint readings: Td > 32°F.

±5.8° for dewpoint readings: 32°F $ Td $ -31°F.

±3.6° for dewpoint readings: Td > 32°F.

±6.3° for dewpoint readings: 32°F $ Td $ -31°F.

±3.8° for dewpoint readings: Td > 32°F.

±6.7° for dewpoint readings: 32°F $ Td $ -31°F.

±4.5° for dewpoint readings: Td > 32°F.

±7.9° for dewpoint readings: 32°F $ Td $ -31°F.

±5.6° for dewpoint readings: Td > 32°F.

±7.9° for dewpoint readings: 32°F $ Td $ -0.4°F.

±9.9° for dewpoint readings: -0.4° $ Td $ -31°F.

±6.8° for dewpoint readings: Td > 32°F.

±11.9° for dewpoint readings: 32°F $ Td $ -31°F.

±7.9° for dewpoint readings: Td > 32°F.

±13.9° for dewpoint readings: 32°F $ Td $ -31°F.

Pressure 16.9" to 31.5" of mercury ±0.02" of mercury 0.0003"

Visibility*

Up to 11⁄4 miles

11⁄2 to 1-3/4 miles

2 to 21⁄2 miles

3 to 31⁄2 miles

4 to 10 miles

Up to 11⁄4 miles

11⁄2 to 13⁄4 miles

2 to 21⁄2 miles

3 to 31⁄2 miles

4 to 10 miles

For 80% of measurements

±1⁄4 mile

±1⁄4, -1⁄2 mile

±1⁄2 mile

±1⁄2, -1 mile

±1 report increment

For 98% of measurements

±1⁄2 mile

±1⁄2, -3⁄4 mile

±1 mile

+2 reporTable increments, -1 mile

+2 reporTable increments

--

Rain Accum 0 to 10.0"/hr ±0.02" or 4% of hourly total, whichever is greater 0.01"

Snow Depth 0 to 99" 0 - 5": ±1⁄2"

>5 - 99": ±1"

1⁄2"

1"

*,** See notes at the end of table
ASOS Site Technical Manual S100

1-8 Change 1

Table 1.1.2. System Specifications -CONT

Sensor Limits Accuracy Resolution

Frozen Precip

Water Equiv

0 to 40" ±0.04" or 1% of the total accumulation 0.01"

Freezing Rain 

Occurrence

-- Detection is reported whenever freezing rain

accumulates to 0.01". 

--

Ceilometer 0 to 12,650 ft ±100 ft or 5%, whichever is greater 50 ft

$ Thunderstorm 0-5, 5-10, 10-30 miles 100% for thunderstorms within 10 miles with 3 or more

$ cloud-to-ground discharges

--

Present

Weather

Occurrence 99% of time

Identification:

Rain 90% of time

Snow 97% of time

Precip 99% of time

0.01"/hr or 10%, whichever is greater

* Accuracy requirements for 80% of the measurements. For the remaining 20% of the measurements, double the

requirements.

** Temperature spread (TS) equals temperature minus dewpoint temperature.
S100 ASOS Site Technical Manual

1-9/ (1-10 blank)

SECTION II. SYSTEM INSTALLATION

System installation is not the site technician's responsibility. Information concerning installation of individual

sensors and removal/replacement of various FRU's in the ACU, DCP, and sensors is provided in the

appropriate ACU, DCP, or sensor Chapter of this manual. 
S100 ASOS Site Technical Manual

1-11

SECTION III. OPERATION

1.3.1 INTRODUCTION

Systemmaintenance operations are performed fromthe operator interface device (OID) terminal or fromthe

remote maintenance monitoring terminal (described in paragraph 1.3.14). From either of these terminals,

users can access the diagnostic program screens that are an integral part of the system; change the system

configuration; change output port assignments, parameters, and message formats; change communications

port characteristics; enable and disable communications ports; change the dialing mode between pulse and

tone; request 2-hour archive of 5-minute observations for 15 days; turn sensors on or off; turn sensor report

processing on or off; change selected site constants such as date, time, latitude, longitude, and elevation;

make log entries; and reset the system. By using the handset in conjunction with its designated OID terminal,

the technician can also record, play back, and control automated voice messages. The functions that a user

can perform on the ASOS depend on how the user signs on the system. There are four levels of users that

sign on to the system: observers, air traffic controllers (ATC's), system managers, and technicians. In

addition, an unsigned user has certain capabilities on the system. Some functions can be performed by more

than one type of user. For example, the technician and system manager have the same maintenance

capabilities under the MAINT (maintenance) function. The ASOS Software User's Manual identifies the

functions assigned to each type of user. This section provides control and indicator information for the OID

and printer, descriptions of all maintenance screens, and detailed systemmaintenance operating procedures.

Additional information on the other ASOS screens and operating procedures are provided in the ASOS

Software User's Manual. 

1.3.2 OPERATOR INTERFACE DEVICE (OID) CONTROLS AND INDICATORS

The OID is a standard cathode ray tube (CRT) terminal. The keyboard (Figure 1.3.1) is divided into four

functional areas: the main keypad, editing keypad, auxiliary keypad, and function keypad. The editing

keypad contains the arrow, REMOVE, and edit keys. The arrow keys are used to move the cursor to the

different fields on the screen. The REMOVE key is used to delete the character under the cursor. The edit

keys are used to move the cursor to a specific point on the screen when editing log entries. The auxiliary

keypad is used to access the maintenance/operator screens. The keypad on the OID screen overlays the

auxiliary keypad area such that the function in the upper left corner of the OID keypad is represented by key

7 and the function in the lower right corner of the OID keypad is represented by key 3. The function keypad

contains the HELP key, which is used to access the system help feature. Help can also be accessed by

pressing the 0 key on the auxiliary keypad. Function keys F12 and F20 control the system's audio alarm.

Pressing F12/F20 permanently disables the alarms. Pressing F12/F20 again enables the alarms. The audio

alarm can be disabled for the current alarm by pressing the F11 or F19 key. Additional information on the

OID and its use is provided in the ASOS Software User's Manual and the associated computer terminal

manual at your site. 
ASOS Site Technical Manual S100

1-12 Change 1

Figure 1.3.1. OID Keyboard Controls and Indicators

 11:18:06 07/04/96 1618Z ANYTOWN AIRPORT

SKY = OVC010

VISIBILITY = 3/4SM TEMP/DEWPT = 23.9/20.6 C 75/69 F

$ RVR = R17L/3800FT WIND DIR/SPD = 180/10

PRESENT WX = RA ALTIMETER = 29.90

REMARKS = RMK A02 P0010

$ METAR KANY 041556Z 18010KT 3/4SM R17L/3800 RA OVC010 24/21 A2990 RMK A02

SLP080 P0010 T02390206

PRINT

REVUE

SIGN AUX
S100 ASOS Site Technical Manual

1-13

1.3.3 PRINTER CONTROLS AND INDICATORS

The printer controls and indicators are described in the Panasonic dot matrix printer manual. 

1.3.4 MAINTENANCE SCREEN DESCRIPTIONS

1.3.4.1 Introduction. The ASOS technician uses the maintenance screens to interface with the ASOS

continuousself-test (CST) program, which runs continuously during normalsystemoperation. The program

monitors the operational status of all ASOS hardware by reading and writing diagnostic data between the

central processing unit(CPU) and the systemhardware components.The self-test isrepeated every 7minutes

and the results are entered into the system log. The technician interface screens provide a TEST key that is

used to specify testing for sensors and/or field replaceable units (FRU's). 

Certain items, specifically the wind sensor, the model 1088 temperature/dewpoint sensor, and telephone

modems in the ACU, provide internal detailed diagnostics. These detailed diagnostics are not run as part of

the normal CST cycle but are run on demand. If, during normal system data processing, a sensor failure is

detected by the sensor processing program, the sensor processing program issues a command to the sensor

to run its detailed diagnostic program. This command forces the sensor into an immediate detailed test. If

the sensor fails its detailed diagnostic, an FRU failure message is entered into the maintenance log. The

technician may also manually initiate the detailed diagnostics by pressing the TEST key on the wind sensor

or the 1088 screens. 

The telephone modems in the ACU may be configured for either dial-up operation (operating on the public

switched telephone network) or leased line operation. As mentioned above, the modems provide an internal

detailed diagnostic program, known as a system analog loopback (SAL) test. ASOS diagnostics test dial-up

modems by initiating the internal SAL. However, running the SAL test disrupts normal data transmission

(disconnects the telephone user). For this reason, the modems are tested every 7 minutes only when they are

not in use (on-line). If a modem is on-line when it is scheduled for testing, the test is skipped until the next

7-minute cycle. The technician can perform an on-demand test of a selected dial-up modem at any time by

pressing the TEST key on the modem maintenance screen, which immediately initiates the internal SAL.

Therefore, the technician must be aware that if the modemis on-line, pressing TEST will disrupt current data

transmission. Leased line modems are always on-line and therefore are not tested at all by the ASOS

software; neither can a technician test them on demand. 

The self-test/diagnostic programuses a series of easily accessible screensto display testresults and to enable

the technician to run specific portions of the diagnostic program. The screens are arranged in a hierarchical

mannersuch that the key element of the system is displayed on the first maintenance screen. The units under

each element of the system are accessed by placing the cursor on the element (i.e., ACU or DCP) and

pressing the SEL key. The elements in that area are displayed on the OID. The process of moving the cursor

and pressing the SEL key is repeated until the specific unit (i.e., sensor, board, or power supply screen) is

displayed on the OID. Figure 1.3.2 illustrates the hierarchy of the maintenance screens. 
ASOS Site Technical Manual S100

1-14 Change 1

Figure 1.3.2. Maintenance Screens Hierarchy
S100 ASOS Site Technical Manual

Change 1 1-15

1.3.4.2 Maintenance Screen Keypad. The maintenance screen keypad, which is located in the lower right

corner of each screen, enables the technician to access the different maintenance screens, print individual

screens, and perform on-demand diagnostic tests on an individual element of the ASOS hardware. The

keypad provides up to eight active key functions. The purpose of each of these keys is as follows:

a. PRINT -Enablesthe currently displayed screen to be printed on the printer. PRINT function

is not available to remote (dial-in) users (paragraph 1.3.14.1).

b. PREV/NEXT - Enables the cursor to be moved to the different fields on the currently

displayed screen.

c. SEL - Enablesthe selection of a specific maintenance screen indicated by the position ofthe

cursor.

d. TEST - For items with internal detailed diagnostic capability (1088, wind sensor, and ACU

telephone modems), initiates detailed testing. For all other hardware, selects items on

displayed screen for testing. T's are displayed on screen until items are tested during next

CST cycle. CST results (pass or fail) are then displayed.

e. EXIT - Returns the user to the 1-minute screen on the OID. 

f. CLEAR - Clears all countersfor the fail count fields on the screen displayed and all screens

summarized by this field.

g. BACK - Returns the user to the previous screen/keypad.

h. POWER - Appears on DCP Sensor Screens to enable the technician to control power to the

individual sensors.

1.3.4.3 Maintenance Screen Status Indicator Fields. The maintenance screen status indicator fields are

located to the right of each screen field. The status indicator field indicates the present operational status of

the respective hardware components displayed on a screen. These fields display either a P (pass), T (testing),

C (conditional), F (fail), or D (degraded) character depending on the present status of the unit or the result

ofthe last continuous diagnostic or on-demand diagnostic test. An * (asterisk) is placed in the field if the item

has not yet been tested. 

A numeric fail count may be displayed to the right of the status indicator field. The fail count increments

each time the statusfield transitionsfrom P to F. It also increments each time the statusfield transitionsfrom

T (when the TEST key is pressed) to F. The fail count does not increment if F status is continually displayed

by successive CST cycles. In most cases, the presence of a fail count generates the maintenance flag ($) in

the next METAR. Sensor report processing OFF also produces a $. The CLEAR key, when pressed, clears

all fail counts on the displayed screen and all screens beneath it on the maintenance hierarchy. 

The C (conditional) indication is displayed on a summary-type screen to indicate that a hardware item is

currently passing its CST but that failures have been generated (fail count(s) present on a lowerscreen in the

maintenance hierarchy). For example, on the DCP screen, a C status would appear for the visibility sensor

if the subordinate visibility screen showed the sensor passing CST but a fail count wasstill displayed. Using

the CLEAR key to erase the fail count would change the visibility status on the DCP screen from C to P. 
ASOS Site Technical Manual S100

1-16 Change 1

The system operates somewhat differently for tests associated with the serial input/output (SIO) boards and

telephone modems.Before describing thisin detail, it isimportant to make the following distinction between

fail counts and accumulated failures.

a. Fail Count - Numeric value displayed on modem or SIO screen. Indicates transitions from

P to F or T to F as described above (does not generate a $ in observation). 

b. Accumulated Failures - Internal count kept by the CST indicating the actual number of

failed test responses received (since the internal counter was last cleared). Accumulated

failures generate a $ as described below.

When there are fewer than five accumulated failures (and the test is currently passing), a $ is not placed in

the observation and a status of C (conditional) is reflected on the next higher screen. When the accumulated

failures reach five or more (and the test is currently passing), a status of D is displayed (and is reflected on

the next higher screen) and a $ is placed in the observation. 

At 0600 LST each day, the number of accumulated failures is summarized in the system (maintenance) log

as a code 9999 message. If the number of accumulated failures is less than five at this time, the system

automatically clears the accumulated failure counter, the displayed fail count, and the associated C status.

If the number of accumulated failuresisfive or more, the displayed fail count is cleared, but the accumulated

failure counter is not cleared and the D (degraded) status is still reported. 

The technician can use the CLEAR key for these tests. When pressed, the CLEAR key erases the number

of accumulated failures and the displayed fail count. As a result, the C or D statusis canceled (P is displayed)

and any associated $ is removed from the observation.

1.3.4.4 Sensor Data Quality, Report Process, and Sensor Response Fields. Each sensor screen contains

three additional testfields: data quality,report process, and sensorresponse.These fieldsidentify operational

data transmission status to the technician. The data quality field is controlled by the sensor processing

program; specifically, by the processing algorithm for the sensor. If the algorithm determines that the data

being received from the sensor are logically incorrect, the sensor processing program displays an F (fail)

status in the data quality field. Table 1.3.1 lists the failure conditions for each sensor. The report processing

field indicates whether or not a sensor algorithm is using the data being reported by the sensor. When report

processing is on (status = Y), the algorithm is using the sensor data to update the 1-minute screen. When

report processing is off (status = N), the algorithm ignores the sensor data, and the corresponding 1-minute

$ field reports missing (unless a value is manually entered by an observer). During sensor configuration,report

$ processing is off. The report processing statusis conditioned fromthe reviewsensorstatusscreen. The sensor

response field displays a failed status (F) whenever the sensor does not respond to a data request from the

sensor processing program or the self-test program and a passstatus(P) when the sensor isresponding when

polled. Sensor response is also called sensor status. 
S100 ASOS Site Technical Manual

Change 1 1-17

Table 1.3.1. Sensor Data Quality Algorithm Checks

Sensor Check

Wind direction a. Must vary more than 1 degree during 5-minute period in which the 2-minute

average wind speed exceeds 5 knots.

b. Must have at least 18 (of 24 total) samples present in current 2-minute period.

Temperature/dewpoint a. TA must vary by more than 0.1°F over a 60-minute period.

b. TA must not change more than 6°F over a 1-minute period.

c. TD cannot be more than 2 degrees greater than TA. 

d. TD must vary by more than 0.1°F over a 60-minute period. 

e. TD must not change more than 6°F over a 1-minute period. 

f. Must have at least 4 (of 5 total) samples present in current 5-minute period. 

g. In the event that the temperature/dewpoint sensor stops reporting, the system

reports the last values for 15 minutes. If a new temperature or dewpoint value is

not provided within 15 minutes, respective parameter is marked missing. At least

four readings in the last 5 minutes must be available before a new value can be

calculated. If new value for temperature or dewpoint is not computed in last 15

minutes, respective sensor is marked missing. Sensor must provide at least four

valid readings within 5 minutes for system to compute new value. 

Visibility a. Extinction coefficient must be between 65.6 and 0.00 /km. 

b. Must not drop from a reading of 7 miles or more to a reading of less than 2 miles

in 1 minute with a wind speed of less than 7 knots.

c. Must be greater than 2 miles if TA-TD is greater than 5°F. 

d. Must have at least 8 (of 10 total) samples present in current 10-minute period.

Day/night a. Sensor must report N (night) at midnight. 

b. Sensor must report D (day) at noon.

Present weather a. If sensor indicates snow, TA must indicate a temperature of less than 38°F. 

b. If sensor indicates liquid precipitation, TA must be greater than 28°F. 

c. Must have at least 8 (of 10 total) samples present in 10-minute period.

Liquid precipitation a. Rain gauge sends optical pulse to DCP with each tip of its tipping bucket. Pulses

must be greater than 50 milliseconds long.

b. Must indicate precipitation accumulation if the present weather sensor has

indicated 10 or more moderate or heavy occurrences of precipitation since the

previous hourly observation. 

Sky Must not be missing more than 2 consecutive ceilometer samples or more than 4 total

samples (of 60 total) in current 30-minute period. 

Pressure a. Sensor must report within ±0.04 inHg of other 1 or 2 pressure sensors. 

b. Must not be missing more than 1 sample (of 10 total) in current 1-minute period

or more than 2 samples in current 12-hour period. 

Freezing rain Must have at least 12 samples (of 15 total) samples present in current 15-minute period.

Snow depth a. Must indicate between 0 and 99 inches. 

b. Must not exceed a rate of change of 2 inches per minute. 

c. Must vary bymore than 0.5 inch when the present weathersensor report indicates

snow (S) or heavy snow (S+) over a 30-minute period and the 5-minute average

TA is less than 32°F.

Thunderstorm a. Number of lightning strikes for each range must be less than 4000. $

b. Must not be missing more than 3 consecutive thunderstorm samples in current $

15-minute period. $
ASOS Site Technical Manual S100

1-18 Change 1

1.3.4.5 Maintenance Screen Description. The maintenance screen (Figure 1.3.3) provides overall test

status information to the technician. It also enables the technician to access the next level status and test

screens. The function of each field is described in table 1.3.2. 

 11:21:56 11/21/97 1612Z ANYTOWN AIRPORT

ACU P DCP #1 P ACU/DCP COMMS * TREND PROC

$ DCP #2 P ADAS SUMMARY

DCP #3 P

MAINTENANCE

PRINT CLEAR PREV

SEL ACT

EXIT NEXT

Figure 1.3.3. Maintenance Screen

1.3.4.6 Maintenance Action Selection. An important function of the maintenance screen is the ACT key

on the MAINTENANCE keypad. This key permits the technician to access the maintenance action screens

from which maintenance tasks are started and documented in the system maintenance log. The technician

enters unit/assembly stock numbers and unit serial numbers to screens that specify preventive, corrective,

or calibration maintenance tasks. Field modification kit numbers are entered on a field modification kit

screen. 

Table 1.3.2. Maintenance Screen Field Descriptions

Field Description

ACU Displays the summary status of all hardware items in the ACU cabinet and any associated

local sensors. The SEL key enables the technician to select the ACU status screen, where

the individual status of ACU hardware and local sensors can be found. 

DCP #1

DCP #2

DCP #3

Displaysthe summary status of all hardware itemsin the respective data collection package

(DCP) along with its associated sensors. The SEL key enablesthe technician to accessthe

DCP status screen of interest, where the individual status of DCP hardware and

corresponding sensors can be found.

ACU/DCP COMMS Displays the status of the intercommunications devices in the ASOS configuration (DCP

to ACU communications). The SEL key enables the technician to select the ACU/DCP

communications status screen.

TREND Displays the communication status of the ACU and DCP radios (RF modems). The SEL

key enables the technician to select the trend screen, from which the technician can check

the communication link between the ACU and DCP(s).

$ ADAS SUMMARY Displays ADAS communication log entries per hour. The SEL key enables the technician

$ to select the ADAS summary screen.

PROC Displays the operationalstatus of the ACU and DCP processors. The SEL key enables the

technician to select the processor status screen, from which the technician may reset the

ACU or DCP.
S100 ASOS Site Technical Manual

Change 1 1-19

1.3.4.7 ACU Status Screen. The ACU status screen (Figure 1.3.4) displays the status of each ACU local

sensor and hardware area and provides menu commands to access sensor diagnostic and hardware status

functions. This screen pertains to the ACU only (the DCP has a separate, similar screen). The function of $

each field on the ACU status screen is described in table 1.3.3. Each sensor screen under the ACU status $

screen is similar to the same type sensor screen under the DCP status screen because the sensor tests (and $

sensors) are identical. Since most sensors are typically configured as part of the DCP at the majority of $

ASOS installation sites, the sensor screens are described in this section under the DCP status screen. These $

screens will not be covered again under the ACU status screen. However, the sensor screens that appear $

under the ACU statusscreen do not have the three sensor power-related items that appear on the DCP sensor

screens. The sensor power-related items consist of the POWER key that enables the technician to turn DCP

sensor power on and off, a POWER CONTROL statusfield that indicates whether sensor power is on or off,

and a POWER STATUS field that indicates the status of sensor power as a pass or fail condition. 

 11:21:56 11/21/97 1612Z ANYTOWN AIRPORT

LOCAL SENSORS: HARDWARE:

PRESSURE SENSOR #1 P

PRESSURE SENSOR #2 P VME CARDS RACK P

PRESSURE SENSOR #3 P

MODEM RACK P

ACU POWER P

ACU UPS P

GTA RADIO P

ACU STATUS

PRINT CLEAR PREV $

SEL

EXIT BACK NEXT

Figure 1.3.4. ACU Status Screen

Table 1.3.3. ACU Status Screen Field Descriptions $

Field Description $

LOCAL SENSORS Displays the status of each of the sensors configured as a local sensor in the ACU, and $

enables the technician to select a specific sensor screen. $

VME CARDSRACK Displaysthe summary status of all boardslocated in the ACU VME card rack, and enables $

the technician to select the ACU VME cards screen. $

MODEM RACK Displays the summary status of all modems located in the ACU modem rack, and enables $

the technician to select the ACU modem screen. $

ACU POWER Displays the status of all power-related functions in the ACU. Enables the technician to $

display individual status screens. $

ACU UPS Displays the summary status of the UPS in the ACU, and enables the technician to select $

individual status screens. $

GTA RADIO Displays the summary status of the GTA radio in the ACU, and enables the technician to $

select the ACU GTA radio screen. $
ASOS Site Technical Manual S100

1-20 Change 1

1.3.4.8 ACU VME Cards Screen. The ACU VME cards screen (Figure 1.3.5) pertains only to the ACU.

This screen displays the test status of each board in the VME card rack. The ACU VME cards screen also

enables the technician to select a specific board's diagnostic screen. 

11:21:56 11/21/97 1621Z ANYTOWN AIRPORT

 BOARD NAME

$ #1 CPU A P #13 A/D P

$ #2 CPU B P #14 A/D RESISTOR

 #3 MEMORY P #15 DIGITAL I/O

$ #4 #16 VIDEO CONTROLLER P

 #5 SIO #1 P #17

 #6 SIO #2 P #18

 #7 SIO #3 P #19

 #8 SIO #4 P #20 VOICE PROC #1 P

 #9 SIO #5 P #21 VOICE PROC #2 P

 #10 SIO #6 P

 #11 SIO #7 P

$ #12 SIO #8 P VME CARDS

PRINT CLEAR PREV

SEL

EXIT BACK NEXT

Figure 1.3.5. ACU VME Cards Screen

1.3.4.9 CPU Screen. The CPU screen (Figure 1.3.6) pertains to both the ACU and the DCP. The ACU

always contains two CPU's. The primary CPU operates the system while the other is the backup, or

redundant, CPU. Because this screen summarizes the status of both CPU's, the identical screen is displayed

regardless of whether the technician selects CPU A screen or the CPU B screen (from the VME cards

screen). The top half of the CPU screen displays the CST status for the primary CPU, while the bottom part

of the screen identifiesthe current redundantCPU and displaysthe pass/failstatus of itsinternal built-in test.

The function of each field on the CPU screen is described in table 1.3.4. 

The DCP contains either one or two CPU's, depending on site configuration. When the DCP contains two

CPU's, thisscreen operatesthe same as described above forthe ACU. When the DCP contains only oneCPU,

there is no redundant CPU and only the top part of the screen is applicable. 
S100 ASOS Site Technical Manual

Change 1 1-21

 11:21:56 11/21/97 1621Z ANYTOWN AIRPORT

 ACU

 PRIMARY CPU

DRAM P

EPROM P

BUS ERRORS P

SERIAL PORT #1

 LOOPBACK P

 XMIT ERRORS P

SERIAL PORT #2

 LOOPBACK P

 XMIT ERRORS P CPU

PRINT CLEAR $

REDUNDANT CPU B TEST STATUS P

EXIT BACK

Figure 1.3.6. CPU Screen

Table 1.3.4. CPU Screen Field Descriptions

Field Description

DRAM Displays the results of the dynamic random access memory (DRAM) test. This

test is based on an alternating pattern of 1's and 0's. The output status (P = pass

or F = fail) is displayed upon completion of a data comparison.

EPROM Displays the results of the erasable programmable read only memory (EPROM)

test. This test is based on a checksum. The checksum must be equal to the last

byte stored in the EPROM. The output status (P = pass or F = fail) is displayed

upon completion of the checksum comparison.

BUS ERRORS Displays the results of the bus errors test. The bus errors test is based on a

memory write to a specific address. The contents of the memory addressed are

then evaluated and the output status (P = pass or F = fail) is displayed. 

SERIAL PORT This test ensures that the CPU can communicate with its internal UART (two

ports). For each port, the CPU reads the UART interrupt sector register and tests

for bus errors. The status field indicates a P (pass) if no bus errors occurred and

indicates an F (fail) if bus errors were encountered. 

LOOPBACK Displays the results of the loopback test. This test ensures that the CPU can communicate

with its internal UART (two ports). For each port, the CPU reads the UART interrupt

sector register and tests for bus errors. The status field indicates a P (pass) if no bus errors

occurred and indicates an F (fail) if bus errors were encountered. 

XMIT ERRORS Displaysthe results of the XMIT errorstest. Thistest checksfor errors encountered during

data transmission (or incoming data) and is based on the UART status register contents.

The register contents are evaluated for parity errors, framing errors, and overrun errors on

incoming data. Ifsuch errors occur for two out of three consecutive CST cycles, an F (fail)

is displayed in the status field; otherwise, the status field indicates P (pass). 

REDUNDANT CPU Indicates which CPU is being used as the redundant CPU.

STATUS Indicates the status of the redundant CPU: P (pass) indicates functioning and F (fail)

indicates not operating correctly.
ASOS Site Technical Manual S100

1-22 Change 1

1.3.4.10 Memory Screen. The memory screen (Figure 1.3.7) pertains to both the ACU and DCP (although

DCP screen shows no EPROM line). This screen displays the results of the diagnostic test performed on the

major functional circuits on each memory board in the system. The function of each field on the memory

screen is described in table 1.3.5. 

 11:21:56 11/21/97 1621Z ANYTOWN AIRPORT

 ACU MEMORY

 EPROM P

 SRAM P

MEMORY

$

$ PRINT CLEAR $

TEST

EXIT BACK

Figure 1.3.7. Memory Screen

Table 1.3.5. Memory Screen Field Descriptions

Field Description

EPROM From the ACU memory board, displays the results of the EPROM test. This test

is based on checksum. The checksum must be equal to the last byte stored in the

EPROM. The output status (P = pass or F = fail) is displayed upon completion of

the checksum comparison. 

For the DCP memory board, thisfield is not displayed because the board contains

no EPROM. 

SRAM Displaysthe results of the SRAM test. Thistest indicates whether or not the CPU

can access the SRAM without encountering bus errors. The CPU reads from an

SRAM location and tests for bus errors. The status field indicates a P (pass) if no

bus errors occurred or an F (fail) if bus errors did occur. 
S100 ASOS Site Technical Manual

Change 1 1-23

1.3.4.11 Serial I/O Screen. The serial I/O screen (Figure 1.3.8) pertains to both the ACU and DCP. This

screen displays the results of the diagnostic test performed on the major functional circuits on a serial I/O

(SIO) board. The function of each field on the serial I/O screen is described in table 1.3.6. When fewer than

five LOOPBACK failures have been detected and the port is currently passing the LOOPBACK test, a $ is

not added to the observation and a status of C (conditional) is reflected on the next higher screen. When five

or more LOOPBACK failures have occurred and the port is currently passing this test, a status of D

(degraded) is displayed for the port (and is also reflected on the next higher screen) and a $ is added to the

observation. At 0600 LST each day, the number of accumulated failures is summarized in the system

(maintenance) log. The system operates identically for XMIT ERROR failures. The technician can use the

CLEAR key to reset the fail counts and clear the C or D status indication. Paragraph 1.3.4.3 provides

additional information on SIO test reporting. 

 11:21:56 11/21/97 1621Z ANYTOWN AIRPORT

 LOOPBACK XMIT ERR

 SIO #1

 PORT #1 P P

 PORT #2 P P

 PORT #3 P P

 PORT #4 P P

ACU SIO

PRINT CLEAR $

TEST

EXIT BACK

Figure 1.3.8. Serial I/O Screen

Table 1.3.6. Serial I/O Screen Field Descriptions

Field Description

LOOPBACK Displays the results of the loopback test. This test ensures that the CPU can

communicate with the two UART's (four ports total) on the SIO board. For each

port, reads the UART vector interrupt register and tests for bus errors. The status

field indicates a P (pass) if no bus errors occurred, an F (fail) if bus errors were

encountered, or a D if more than five errors have been detected and the test is

currently passing. 

XMIT ERRORS Displaysthe results of the XMIT errorstest. Thistest checksfor errors encountered during

data transmission (on incoming data) and is based on the UART status register contents.

The register contents are evaluated for parity errors, framing errors, and overrun errors on

incoming data. The status field indicates a P (pass) if no errors occurred, an F if errors

were detected, or a D if more than five errors occurred and the test is currently passing.
ASOS Site Technical Manual S100

1-24 Change 1

1.3.4.12 A/D Screen Description. The A/D screen (Figure 1.3.9) pertains to both the ACU and DCP, and

is essentially the same for both. The ACU contains one analog-to-digital (A/D) card which is used for

self-tests of powersupply voltages within the ACU cabinet. The DCP contains either one or two A/D boards.

The first DCP A/D board is used to self-test cabinet voltages and to sense whether the first eight sensors are

on or off. The second A/D board is installed in DCP's that contain more than eight sensors. 

The diagnostic test performstwo functional tests on each A/D board: register readback and reference voltage

tests. The register readback test sends control words to the control register on the board and reads the data

back via a status register also located on the A/D board. Failure of the register readback test indicates a

failure of the A/D board to properly store command data or a possible I/O failure. The reference voltage test

checks the operation of the A/D conversion circuits by checking the value of a +2.5 vdc precision reference

voltage in the ACU or DCP cabinet.

 11:21:56 11/21/97 1621Z ANYTOWN AIRPORT

 ACU

REGISTER

 READBACK P

REFERENCE

 VOLTAGE P

A/D

$

$ PRINT CLEAR $

TEST

EXIT BACK

Figure 1.3.9. A/D Screen

1.3.4.13 Graphics Screen. The graphics screen (Figure 1.3.10) pertains to the ACU only. This screen

displays the results of the diagnostic test performed on the major functional circuits on the video controller

board. The function of each field on the graphics screen is described in table 1.3.7.

 11:21:56 11/21/97 1621Z ANYTOWN AIRPORT

CRT CONTROLLER READBACK P

PARALLEL I/F TIMER READBACK P

LOOPBACK #1 P

LOOPBACK #2 P

RT CLOCK READBACK P

GRAPHICS

PRINT CLEAR

TEST

EXIT BACK

Figure 1.3.10. Graphics Screen
S100 ASOS Site Technical Manual

Change 1 1-25

Table 1.3.7. Graphics Screen Field Descriptions

Field Description

CRT CONTROLLER

READBACK

Displays the results of the CRT controller readback test. This test is based on

cursor position, which is stored in a register on the video controller board. This

register is read twice to ensure that the cursor remains stationary. The cursor

positions are compared and the output status (P = pass or F = fail) is displayed.

PARALLEL I/F

TIMER READBACK

Displays the results of the parallel I/F timer readback test. This test checks

hardware that is only used for diagnostic purposes. The parallel I/F timer

readback test is based upon a write/read routine. The data are evaluated and the

output status (P = pass or F = fail) is displayed. Failure of this test does not

necessitate the replacement of the video controller board. Failure of the CRT

controller readback test and/or the RT clock readback test in conjunction with

failure of this test indicates a real-time failure.

LOOPBACK Displays the results of the loopback tests. This test checks hardware that is only

used for diagnostic purposes. The loopback test is based upon a write/read

routine. The data are evaluated and the output status (P = pass or F = fail) is

displayed. Failure of this test does not necessitate the replacement of the video

controller board. Failure of the CRT controller readback test and/or the RT clock

readback test in conjunction with failure of this test indicates a real-time failure.

RT CLOCK

READBACK

Displays the results of the RT clock readback test. The RT clock readback test

tests clock calendar timing. Numbers from an RT clock chip are read and

evaluated, and the output status (P = pass or F = fail) is displayed. ASOS does

not use the RT clock on the video board.

1.3.4.14 Voice Screen. The voice screen (Figure 1.3.11) pertains only to the ACU. This screen displays the

results of the diagnostic test performed on the major functional circuits on the voice CPU/memory and voice

recorder/playback boards in the system. The function of each field on the voice screen is described in

table 1.3.8. 

 11:21:56 11/21/97 1621Z ANYTOWN AIRPORT

 CPU P

 AUDIO OUTPUT P

 AUDIO STATUS P

 TIMEOUT P

VOICE

PRINT CLEAR $

TEST

EXIT BACK

Figure 1.3.11. Voice Screen
ASOS Site Technical Manual S100

1-26 Change 1

Table 1.3.8. Voice Screen Field Descriptions

Field Description

CPU Displays the results of the CPU test. The CPU test specifically tests the

operational status of the voice CPU/memory board. Inputs to the status field are

based on a digital input received from the A/D converter. The CPU status is

evaluated and the output status (P = pass or F = fail) is displayed.

AUDIO OUTPUT Displays the results of the audio output test. The audio output test tests the

operation of the voice recorder/playback board and indirectly tests the voice

CPU/memory board. The audio output test is based on an internal audio test that

checks the audio circuitry and the output status (P = pass or F = fail) is displayed.

AUDIO STATUS Displays the results of the audio status test. The audio status test tests the

operation of the voice recorder/playback board and indirectly tests the voice

CPU/memory board. The audio status test is based upon a monitored audio line.

Inputs to the status field are based on a digital input received from the A/D

converter. The status is evaluated and the output status (P = pass or F = fail) is

displayed.

TIMEOUT Displays the results of the timeout test. The timeout test specifically tests the

operational status of the voice CPU/memory board watchdog timer. The status is

determined by the watchdog timer response, which is evaluated and the output

status (P = pass or F = fail) is displayed. 

1.3.4.15 ACU Modem Screen. The ACU modem screen (Figure 1.3.12) pertains only to the ACU. This

screen displays the port assignments for each modem and the status of the last internal system analog

loopback (SAL) test performed on the individual modems. The telephone modems in the ACU may be

configured for either dial-up operation (on the public switched telephone network) or leased line operation.

This screen displays only dial-up modems. The dial-up modems are tested (SAL is run) automatically every

7 minutes as long as they are not in use (on-line). If a modem is on-line when it is scheduled for testing, the

test is skipped until the next 7-minute cycle. The technician can perform an on-demand test of a selected

dial-up modem at any time by pressing the TEST key, which immediately initiates the internal SAL.

Therefore, the technician must be aware that if the modemis on-line, pressing TEST will disrupt current data

transmission. Leased line modems are not displayed on this screen because modems are always on-line and

therefore are not tested at all by the ASOS software; neither can a technician test them on-demand. The

STATUS field associated with each modem shows the current CST status for each modem. A status of P or

F indicates that the modem is currently passing or failing its internal SAL test. An associated fail count is

incremented each time that the status changes from P to F (or T to F). When fewer than five failures have

been detected and the modem is currently passing, a $ is not added to the observation and a status of C

(conditional)isreflected on the next higherscreen. When five or more failures have occurred and the modem

is currently passing, a status of D (degraded) is displayed for the modem (and is also reflected on the next

higher screen) and a $ is added to the observation. At 0600 LST each day, the number of accumulated

failures is summarized in the system (maintenance) log. The technician can use the CLEAR key to reset the

fail counts and clear the C or D status indication. If a test has not been performed for a particular modem,

an * is displayed in the status field. Paragraph 1.3.4.3 provides additional information on modem failure

reporting. 
S100 ASOS Site Technical Manual

Change 1 1-27

11:21:56 07/04/96 1621Z ANYTOWN AIRPORT

 MODEM PORT MODEM NAME STATUS FAILCOUNT

 #1 2-3 OID-4 USER #1 P

 #2 3-3 OID-5 USER #2 P

 #3 4-4 AFOS PHONE P

 #4 7-4 OID-6 USR SPR #1 P

 #5 8-1 OID-7 USR SPR #2 P

 #6 8-2 OID-8 SPARE P

 #7

 #8

 #9

 #10

 #11

 #12 ACU MODEM

 #13

PRINT CLEAR PREV #14

 #15 TEST #16

EXIT BACK NEXT

Figure 1.3.12. ACU Modem Screen

1.3.4.16 ACU Power Screen. The ACU powerscreen (Figure 1.3.13) pertains only to the ACU. Thisscreen

displays the status of all power-related functions within the ACU. The test result fields indicate the status

of the various power supplies as a P (pass) or F (fail) condition. 

 11:21:56 11/21/97 1621Z ANYTOWN AIRPORT

 POWER SUPPLIES:

 +2.5 REFERENCE P POWER SUPPLY A P

 +5 SUPPLY VOLTS P POWER SUPPLY B P

 +12 SUPPLY VOLTS P

 -12 SUPPLY VOLTS P

 +5 VME RACK P

 +12 VME RACK P

 -12 VME RACK P

 +5 RADIO A P

 +5 RADIO B P ACU PWR

 +12 RADIO A P

PRINT CLEAR $

 +12 RADIO B P

 -12 RADIO A P TEST -12 RADIO B P

EXIT BACK

Figure 1.3.13. ACU Power Screen
ASOS Site Technical Manual S100

1-28 Change 2

1.3.4.17 ACU UPS Screen. There are two types of power supply assemblies that may be installed in the

$ ACU: SOLA UPS, which is installed in ACU serial numbers 437 and below (40044-10), and Deltec UPS,

which is installed in serial numbers 438 and above (40044-30, -40, and -70). Figure 1.3.14 contains the two

types of OID screens available, and table 1.3.9 describes the function of each field on the ACU UPS screen.

$ 

 11:21:56 11/21/97 1621Z ANYTOWN AIRPORT

 BATTERY VOLTAGE: 53

 INPUT VOLTAGE: 116

 OUTPUT VOLTAGE: 116 UPS INLINE: 

 CMD UPS INLINE: 

 OUTPUT ENABLED: P

 ON AC LINE: P

 BATTERY STATUS: P

 TRIAC STATUS: P

 TEMPERATURE: P ACU UPS

 R3232 STATUS: P

PRINT CLEAR

 TIMEOUT: P TEST BYPAS

EXIT BACK

$ For SOLA UPS

 11:21:56 11/21/97 1621Z ANYTOWN AIRPORT

 BATTERY VOLTAGE: BATTERY MANAGEMENT: FLOATING 

 INPUT VOLTAGE: LINE REGULATION: NORMAL

 OUTPUT VOLTAGE: UPS INLINE: P 

 CMD UPS INLINE: OFF 

 UPS OPERATION: P

 ON AC LINE: P

 BATTERY STATUS: P

 INVERTER: P

 GROUND STATUS: P ACU UPS

 UTILITY P

PRINT CLEAR

 TIMEOUT: P TEST BYPAS

EXIT BACK

$ For Deltec UPS

Figure 1.3.14. ACU UPS Screen
S100 ASOS Site Technical Manual

Change 2 1-29

Table 1.3.9. ACU UPS Screen Field Descriptions

Field Description

SOLA UPS $

BATTERY VOLTAGE Displays a numeric value indicating the present backup battery voltage. 

INPUT VOLTAGE Displays a numeric value indicating the present input line voltage to the UPS. 

OUTPUT VOLTAGE Displays a numeric value indicating the present ac output voltage fromthe UPS to the rest

of the ACU. 

OUTPUT ENABLED Indicates that UPS output is on (pass) or off (fail). 

ON AC LINE Indicates whetherthe UPS is using facility (line) voltage (P) or generating ac voltage from

battery (in inverter mode) (F). 

BATTERY STATUS Indicates the present battery status in the ACU as a P (pass) or F (fail). 

TRIAC STATUS Indicates the present status of tap-changing TRIAC’s on the UPS 1.5 Kva inverter board

as a P (pass) or F (fail). 

TEMPERATURE Indicates present temperature status in the ACU as a P (pass) or F (fail). If fail, inverter

board is in overheat alarm and shuts off UPS. 

RS232 STATUS Indicates the present status of the UPS RS232 communications as a P (pass) or F (fail).

TIMEOUT Indicates the present status of the UPS watchdog timer as a P (pass) or F (fail). 

UPS INLINE Displays P when UPS is inline or F when UPS is bypassed.

CMD UPS INLINE Bypasses UPS when set to OFF or places UPS inline when set to ON.

Deltec UPS $

BATTERY VOLTAGE Displays a numeric value indicating the present backup battery voltage. 

INPUT VOLTAGE Displays a numeric value indicating the present input line voltage to the UPS. 

OUTPUT VOLTAGE Displays a numeric value indicating the present ac output voltage from the UPS to the rest

of the DCP.

UPS OPERATION Indicates that UPS is functioning in a normal (P) or abnormal (F) manner. 

ON AC LINE Indicates whetherthe UPS is using facility (line) voltage (P) or generating ac voltage from

the battery (in inverter mode) (F). 

BATTERY STATUS Indicates present battery status in the DCP as a P (pass) or F (fail). 

INVERTER Indicates whether the internal inverter is operating in overvoltage or undervoltage status.

GROUND STATUS F indicates a ground failure in facility wiring. 

UTILITY Checks for an overvoltage or unsynchronized signal from facility power. 

TIMEOUT Indicates the present status of the UPS watchdog timer as a P (pass) or F (fail).

BATTERY

MANAGEMENT

Indicates if the current from the batteries is FLOATING, RESTING, CHARGING, or

DISCHARGING.

LINE REGULATION Indicates if the UPS is maintaining a STEP-UP, STEP DOWN, or NORMAL status.

UPS INLINE Displays P when UPS is inline or F when UPS is bypassed.

CMD UPS INLINE Bypasses UPS when set to OFF or places UPS inline when set to ON.
ASOS Site Technical Manual S100

1-30 Change 1

1.3.4.18 GTA Radio Screen. The GTA radio screen (Figure 1.3.15) pertains only to the ACU and

applies to application software version 2.1 or higher. This screen displays the status of all GTA

radio-related functions in the ACU. Table 1.3.10 describes the function of each field on the ACU GTA

radio screen. 

 11:21:56 11/21/97 1621Z ANYTOWN AIRPORT

 RADIO ID NUMBER: 123456 RADIO RESPONSE: P

 TRANSMIT FREQUENCY: 125.375

 POWER LEVEL SETTING: 50

 MAX POWER SETTING: 189

 POWER SUPPLY STATUS:

 +5V P

 +12V P

 -12V P GTA RADIO

 -80V P

CLEAR VFWD STATUS 050 P

 VRFD STATUS 002 P TEST

EXIT BACK

Figure 1.3.15. ACU GTA Radio Screen

Table 1.3.10. ACU GTA Radio Screen Field Descriptions

Field Description

RADIO ID NUMBER Displays a numeric value indicating the designator specific to each radio.

TRANSMIT

FREQUENCY

Displays a numeric value indicating the current command value. This value will equal the

command frequency (117.975 to 136.975 in increments of 0.025). 

POWER LEVEL

SETTING

Displays a numeric digital value indicating the command power level. This value is equal

to commanded power level (0 to 255). 

MAX POWER

SETTING

Displays a numeric digital value indicating the maximumpower level. Each GTAradio has

a unique maximum power level (0 to 255). 

POWER SUPPLY

STATUS

Consists of four individual tests: +5V, +12V, -12V, and -80V. 

+5V Indicatesthat the internal measured operating voltage is within the tolerances of 3V to 7V.

+12V Indicates that the internal measured operating voltage is within the tolerances of 9.6V to

14.4V. 

-12V Indicates that the internal measured operating voltage is within the tolerances of -9.6V to

-14.4V. 

-80V Indicates that the internal measured operating voltage is within the tolerances of -96V to

-64V. 

VFWD STATUS Displays the digital value of the VFWD between 000 and 255.

VRFD STATUS Displays the digital value of the VRFD between 000 and 255.

RADIO RESPONSE Indicates if the ACU is capable of communicating with the radio.
S100 ASOS Site Technical Manual

Change 1 1-31

1.3.4.19 Remote DCP Status Screen Description. The remote DCP status screen (Figure 1.3.16)

displays the operational status of each sensor connected to the DCP as well as the status of all hardware

in the DCP pertaining only to the DCP. This screen pertains to the DCP only (the ACU has a separate,

similar screen). If the ASOS is equipped with optional uninterruptible power supplies (UPS's), each DCP

may contain either one or two UPS's. UPS #2 is provided only if the number of sensors connected to the

DCP provides a load too large for a single UPS. This second UPS would be mounted in a separate

cabinet, referred to as an auxiliary DCP, behind the basic DCP cabinet. The remote DCP status screen

also enables the technician to select the associated screen for each of the status fields on the screen. The

function of each field is described in table 1.3.11. 

 11:21:56 11/21/97 1621Z ANYTOWN AIRPORT

 SENSOR GROUP: HARDWARE:

 PRESENT WEATHER P VME P

 WIND SPEED/DIR P

 TEMP/DEWPOINT P DCP POWER P

 VISIBILITY #1 P

 VISIBILITY #2 P DCP UPS#1 P

 VISIBILITY #3 P

 CEILOMETER #1 P DCP UPS#2 P $

 CEILOMETER #2 P

 CEILOMETER #3 P

 TIPPING BUCKET P

 SNOW DEPTH P

 FREEZING RAIN P REMOTE DCP#1

 FROZEN PRECIP P

PRINT CLEAR PREV

 SUNSHINE P

 THUNDERSTORM P $

SEL $

EXIT BACK NEXT

Figure 1.3.16. Remote DCP Status Screen

Table 1.3.11. Remote DCP Status Screen Field Descriptions

Field Description

SENSOR GROUP Displays the status of each of the sensors connected to the DCP, and enables the

technician to select a specific sensor screen.

VME Displaysthe summary status of all boardslocated in the DCP VME card rack, and enables

the technician to select the DCP VME cards screen.

DCP POWER Displays the summary status of the DC power supplies in the DCP, and enables the

technician to select individual status screens.

DCP UPS #1 Displays the status of all power-related functions in the DCP. Enables the technician to

display individual status screens.
ASOS Site Technical Manual S100

1-32 Change 1

1.3.4.20 DCP VME Cards Screen Description. The DCP VME cards screen (Figure 1.3.17) pertains

only to the DCP. This screen displays the test status of each board in the VME card rack. The DCP VME

cards screen also enables the technician to select the diagnostic screen of a specific board. 

 11:21:56 11/21/97 1621Z ANYTOWN AIRPORT

 BOARD NAME

 #1 CPU A P

 #2 CPU B P

 #3 MEMORY P

 #4 SIO #1 P

 #5 SIO #2 P

$ #6 SIO #3 P

$ #7 SIO #4 P

 #8

 #9 A/D #1 P

 #10 A/D RESISTOR P

$ #11 A/D #2 P

 #12 DIGITAL I/O VME CARDS

$

$ PRINT CLEAR PREV $

SEL

EXIT BACK NEXT

Figure 1.3.17. DCP VME Cards Screen

1.3.4.21 DCP #1, #2, #3 Power Screen. The DCP #1, #2, #3 power screen (Figure 1.3.18) pertains to

the DCP only. This screen indicates the status of all power-related functions within the DCP's. The test

result fields indicate the status of the various power supplies as a P (pass) or F (fail) condition. 

11:21:56 11/21/97 1621Z ANYTOWN AIRPORT

POWER SUPPLIES:

 +2.5 REFERENCE P

 +5 SUPPLY #1 VOLTS P

 +5 SUPPLY #2 VOLTS P

 +12 SUPPLY #1 VOLTS P

 +12 SUPPLY #2 VOLTS P

 -12 SUPPLY #1 VOLTS P

 -12 SUPPLY #2 VOLTS P

DCP#1 PWR

$

$ PRINT CLEAR $

TEST

EXIT BACK

Figure 1.3.18. DCP #1, #2, #3 Power Screen
S100 ASOS Site Technical Manual

Change 2 1-33

1.3.4.22 DCP UPS Screen. There are two types of uninterruptible power supplies that may be installed in

the DCP: A SOLA UPS, which is installed in DCP serial numbers 438 and below, or a Deltec UPS, which $

is installed in serial numbers 439 and above. Figure 1.3.19 contains the two types of OID screens available,

and table 1.3.12 describes the function of each field on the DCP UPS screen. 

11:21:56 11/21/97 1621Z ANYTOWN AIRPORT

 BATTERY VOLTAGE: 72

 INPUT VOLTAGE: 116

 OUTPUT VOLTAGE: 118 UPS INLINE: P

 CMD UPS INLINE: OFF

 OUTPUT ENABLED: P

 ON AC LINE: P

 BATTERY STATUS: P

 TRIAC STATUS: P

 TEMPERATURE: P

 RS232 STATUS: P DCP#1 UPS#1

PRINT CLEAR

 TIMEOUT: P

TEST BYPAS

EXIT BACK

For SOLA UPS $

11:21:56 11/21/97 1621Z ANYTOWN AIRPORT

 BATTERY VOLTAGE: 56 BATTERY MANAGEMENT: FLOATING

 INPUT VOLTAGE: 120 LINE REGULATION: NORMAL

 OUTPUT VOLTAGE: 119 UPS INLINE: P

 CMD UPS INLINE: OFF

 UPS OPERATION P

 ON AC LINE: P

 BATTERY STATUS: P

 INVERTER: P

 GROUND STATUS: P

 UTILITY: P DCP#1 UPS#1

PRINT CLEAR

 TIMEOUT: P

TEST

EXIT BACK

For Deltec UPS $

Figure 1.3.19. DCP UPS Screen
ASOS Site Technical Manual S100

1-34 Change 2

Table 1.3.12. DCP UPS Screen Field Descriptions

Field Description

$ SOLA UPS

BATTERY VOLTAGE Displays a numeric value indicating the present backup battery voltage. 

INPUT VOLTAGE Displays a numeric value indicating the present input line voltage to the UPS. 

OUTPUT VOLTAGE Displays a numeric value indicating the present ac output voltage from the UPS to the rest

of the DCP. 

OUTPUT ENABLED Indicates that UPS output is on (P) or off (F). 

ON AC LINE Indicates whether the UPS is using facility (line) voltage (P) or generating ac voltage from

battery (in inverter mode) (F).

BATTERY STATUS Indicates present battery status in the DCP as a P (pass) or F (fail). 

TRIAC STATUS Indicates the present status of tap-changing TRIAC's on the UPS 1.5 Kva Inverter Board

as a P (pass) or F (fail).

TEMPERATURE Indicates the present temperature status of the UPS 1.5 Kva Inverter Board as a P (pass)

or F (fail). If fail, inverter board is in overheat alarm and shuts off UPS. 

RS232 STATUS Indicates the present status of the UPS RS232 communications as a P (pass) or F (fail). 

TIMEOUT Indicates the present status of the UPS watchdog timer as a P (pass) or F (fail).

UPS INLINE Displays P when UPS is inline or F when UPS is bypassed.

CMD UPS INLINE Bypasses UPS when set to OFF or places UPS inline when set to ON.

$ Deltec UPS

BATTERY VOLTAGE Displays a numeric value indicating the present backup battery voltage. 

INPUT VOLTAGE Displays a numeric value indicating the present input line voltage to the UPS. 

OUTPUT VOLTAGE Displays a numeric value indicating the present ac output voltage from the UPS to the rest

of the DCP. 

UPS OPERATION Indicates that UPS is functioning in a normal (P) or abnormal (F) manner. Normal

indicates that utility is OK, battery is OK, and UPS is operating from facility ac power.

Abnormal indicates failure of any of the above conditions. 

ON AC LINE Indicates whether the UPS is using facility (line) voltage (P) or generating ac voltage from

the battery (in inverter mode) (F). 

BATTERY STATUS Indicates present battery status in the DCP as a P (pass) or F (fail). 

INVERTER Indicates whether the internal inverter is operating in overvoltage or undervoltage status.

P indicates voltage within range, and F indicates voltage outside range. 

GROUND STATUS F indicates a ground failure in facility wiring. 

UTILITY Checks for an overvoltage or unsynchronized signal from facility power. 

TIMEOUT Indicates the present status of the UPS watchdog timer as a P (pass) or F (fail). 

BATTERY

MANAGEMENT

Indicates if the current from the batteries is FLOATING, RESTING, CHARGING, or

DISCHARGING. FLOATING indicates trickle charge, RESTING indicates no charge to

or discharge from battery, CHARGING indicates that UPS is charging battery, and

DISCHARGING indicates that battery is discharging. 

LINE REGULATION Indicates if the UPS is maintaining a STEP-UP, STEP DOWN, or NORMAL status.

UPS INLINE Displays P when UPS is inline or F when UPS is bypassed.

CMD UPS INLINE Bypasses UPS when set to OFF or places UPS inline when set to ON.
S100 ASOS Site Technical Manual

Change 1 1-35

1.3.4.23 Ceilometer and Ceilometer Sensor Dialogue Screens. The ceilometerscreen (Figure 1.3.20) and

the ceilometer sensor dialogue screen (Figure 1.3.21) pertain to the DCP when a ceilometer is configured

to the DCP and to the ACU when a ceilometer is configured as a localsensor. The ceilometerscreen displays

the current operating status ofthe selected ceilometer(cloud heightsensor) and providesthe meansfor direct

communication (direct dialogue mode) with the sensor. The ASOS polls the ceilometer for status reports

every 30 seconds. The reports comprise cloud height,sensor diagnostics, and operatingmode indicators. The

diagnostic and operating mode indicators are displayed along the left side of the screen. Table 1.3.13

describes the function of each field. Direct dialogue mode allows the technician to monitor and change

ceilometer parameters and obtain in-depth status and operating information regarding the sensor. The direct

mode also allows the technician to perform sensor troubleshooting procedures and specify sensor operating

parameters. Pressing the DIALG key displaysthe ceilometersensor dialogue screen.In direct dialogue mode

keyboard entries (ceilometer commands) are displayed in the ENTER COMMAND: field of the screen.

When the technician presses the enter key, the ceilometer CPU receives the ceilometer commands. Power

to the ceilometer can be toggled on or off by pressing the POWER key. The POWER CONTROL field

indicates the state of sensor power (ON/OFF) and POWER STATUS indicates the status of the power as a

P (pass) or F (fail) condition. Chapter 9, Section III provides detailed information on available ceilometer

commands and ceilometer output message interpretation. 

11:21:56 11/21/97 1621Z ANYTOWN AIRPORT

 HDW P DATA QUALITY P

 SUP. VOL. P REPORT PROCESS Y

 LASER PWR P SENSOR RESPONSE P

 TEMP P

 SLR SHTTR 0 POWER STATUS P

 BLOWER 1 POWER CONTROL ON

 HTR 1

 PUL FREQ 6

 GAIN 2

CEILOMETER #1

PRINT CLEAR DIALG $

TEST POWER

EXIT BACK

Figure 1.3.20. Ceilometer Screen
ASOS Site Technical Manual S100

1-36 Change 1

11:21:56 11/21/97 1621Z ANYTOWN AIRPORT

CEILOMETER #1

$

$ PRINT $

ENTER COMMAND PROCESSING

EXIT BACK

Figure 1.3.21. Ceilometer Sensor Dialogue Screen

Table 1.3.13. Ceilometer Screen Field Descriptions

Field Description

HARDWARE Indicates status of general hardware alarm bit sent by ceilometer. If ceilometer detects a

malfunction in its operation, this field is set to F to indicate that maintenance of the sensor

is required. 

SUP. VOL. Indicates status of the supply voltage alarm bit sent by ceilometer. This field is set to F

when ceilometer diagnostic detects a failure of any power supply reference in the sensor.

LASER PWR Indicates status of laser power low alarm bitsent by ceilometer. This field is set to F when

ceilometer diagnostic detects that transmitted laser power level is below its normal level.

TEMP Indicates status of temperature alarm bit sent by ceilometer. This field is set to F when

ceilometer detects a failure in heating system of the sensor. 

SLR SHTTR Indicates the present status of the ceilometer's optional solar shutter (0 = off, 1 = on). 

BLOWER Indicates present status of ceilometer's window conditioner blower (0 = off, 1 = on). 

HTR Indicates present status of ceilometer's window conditioner heater (0 = off, 1 = on). 

PUL FREQ Indicates the present transmitter pulse repetition frequency as follows: 

0 = 620 Hz 4 = 830 Hz

1 = 660 Hz 5 = 910 Hz

2 = 710 Hz 6 = 1000 Hz

3 = 770 Hz 7 = 1120 Hz

GAIN Indicates the present gain of the receiver amplifier as follows: 

0 = 250 (low)

2 = 930 (high)
S100 ASOS Site Technical Manual

Change 1 1-37

1.3.4.24 Freezing Rain Screen. The freezing rain screen (Figure 1.3.22) pertains to the DCP when a freezing rain

sensor is configured to the DCP and to the ACU when such a sensor is configured as a local sensor. The freezing rain

screen displaysthe current operationalstatus ofthe freezing rain sensor. The screen displaysthe presentstatus ofthe data

quality checks,report process, and sensorstatusfunctions. In addition, power to the sensor can be turned on and off using

the POWER key. The POWER CONTROL field on the screen indicates the state of sensor power (ON/OFF) and the

POWER STATUS field indicates the status of sensor power as a P (pass) or F (fail) condition. 

11:21:56 11/21/97 1621Z ANYTOWN AIRPORT

PROBE STATUS P DATA QUALITY P $

HEATER STATUS P REPORT PROCESS Y

ELECTRONICS STATUS P SENSOR RESPONSE P $

 POWER STATUS P $

 POWER CONTROL ON $

FREEZING RAIN

PRINT CLEAR $

TEST POWER $

EXIT BACK

Figure 1.3.22. Freezing Rain Screen

1.3.4.25 Present Weather Sensor Screen. The present weathersensorscreen (Figure 1.3.23) pertainsto the DCP when

a present weather sensor is configured to the DCP and to the ACU when such a sensor is configured as a local sensor.

This screen displays the current operational and self-test data being received from the sensor. The field of most

importance to the technician is the ERROR STATUS CODE field, which indicates, via a four-digit code, the status of

FRU's in the sensor. A status code of 0000 indicates that all FRU's are currently passing the present weather internal

self-test. A value other than 0000 indicates a failure of one or more FRU's. Definitionsfor all possible codes are provided

in table 1.3.14 along with definitions of all the other fields on the screen. The POWER key enablesthe technician to turn

sensor power on/off. POWER CONTROL indicates the state of sensor power as ON or OFF. POWER STATUS

indicates the status of sensor power as a P (pass) or F (fail). 

11:21:56 11/21/97 1621Z ANYTOWN AIRPORT

 ERROR STATUS CODE 0000 P DATA QUALITY P

 SIMULATED EVENT NP P REPORT PROCESS Y

 SIMULATED AMOUNT 1234 P SENSOR RESPONSE P

 SIMULATED DATA CKSUM 90 P

 CARRIER AVERAGE RAW DATA 450 POWER STATUS P $

 CHANNEL LOCK ON/OFF 111 POWER CONTROL ON

 LOW AVERAGE RAW DATA -40 $

 LOW CHANNEL BASELINE -10 $

 PEAK AVERAGE RAW DATA 076

 PARTICLE BASELINE 084 $

 HIGH AVERAGE RAW DATA 091 $

 HIGH CHANNEL BASELINE 090 $

 DIAG DATA CKSUM BA P PRESENT WEATHER

$

PRINT CLEAR $

$

TEST POWER

EXIT BACK

Figure 1.3.23. Present Weather Sensor Screen
ASOS Site Technical Manual S100

1-38 Change 1

Table 1.3.14. Present Weather Sensor Screen Field Descriptions

Field Description

ERROR STATUS

CODE

Displays the current status of the FRU's in the sensor. The definition of each code is

provided below: 

NOTE

The present weather sensor will attempt to reset itself whenever it

detects a failure. During thisreset process, theERRORSTATUSCODE

field displays the code 80 along with the detected error. For example,

the code 0280 identifies the failure as heater power supply (ASOS

Designator A1PS1) and indicates that the sensor is attempting to reset

itself. 

Code Definition

0000 All FRU's are functioning properly.

0080 Present weather sensor system reset is in process. This is only a status field that

informs the technician when the sensor is performing an automatic reset. Upon

completion of this process, the 8 changes back to a 0. 

0100 Frame Assembly malfunction

0200 Heater Power Supply (24V) malfunction

0300 Heater Power Supply (24V) and Frame Assembly

0400 Signal Processor #2 Card (SP2)

0500 Signal Processor #2 Card (SP2) and Frame Assembly

0600 Signal Processor #2 Card (SP2) and Heater Power Supply (24V)

0700 Heater Power Supply (24V), Frame Assembly, and Signal Processor #2 Card

(SP2)

0800 Signal Processor #1 Card (SP1)

0900 Frame Assembly and Signal Processor #1 Card (SP1)

0A00 Signal Processor #1 Card (SP1) and Heater Power Supply (24V)

0B00 Signal Processor #1 Card (SP1), Heater Power Supply (24V), and Frame

Assembly

0C00 Signal Processor #1 Card (SP1) and Signal Processor #2 Card (SP2)

0D00 Signal Processor #1 Card (SP1), Signal Processor #2 Card (SP2), and Frame

0E00 Signal Processor #1 Card (SP1), Signal Processor #2 Card (SP2), and Heater

Power Supply (24V) 

0F00 Signal Processor #1 Card (SP1), Signal Processor #2 Card (SP2), Frame, and

Heater Power Supply (24V) 

1000 Receiver AGC Card (AGC)

2000 Transmitter Card (TX)

3000 Receiver AGC Card (AGC)

Transmitter Card (TX)

4000 Analog Power Supply (15V)

5000 Receiver AGC Card (AGC)

Analog Power Supply (15V)

6000 Transmitter Card (TX)

Analog Power Supply (15V)

7000 Receiver AGC Card (AGC)

Transmitter Card (TX)

Analog Power Supply (15V)

8000 Transmitter/Digital Power Supply (5V) and Microprocessor Card (MPU)

9000 Receiver AGC Card (AGC) Transmitter/Digital Power Supply (5V) and

Microprocessor Card (MPU)

A000 Transmitter Card (TX) Transmitter/Digital Power Supply (5V) and

Microprocessor Card (MPU)
S100 ASOS Site Technical Manual

Change 1 1-39

Table 1.3.14. Present Weather Sensor Screen Field Descriptions -CONT

Field Description

ERROR STATUS

CODE (CONT)

Code Definition

B000 Receiver AGC Card (AGC) Transmitter Card (TX) Transmitter/Digital Power

Supply (5V) and Microprocessor Card (MPU)

C000 Analog Power Supply (15V)

Transmitter/Digital Power Supply (5V) and Microprocessor Card (MPU)

D000 Receiver AGC Card (AGC)

Analog Power Supply (15V)

 Transmitter/Digital Power Supply (5V) and Microprocessor Card (MPU)

E000 Transmitter Card (TX)

 Analog Power Supply (15V)

 Transmitter/Digital Power Supply (5V) and Microprocessor Card (MPU)

F000 Receiver AGC Card (AGC)

Transmitter Card (TX)

 Analog Power Supply (15V)

Transmitter/Digital Power Supply (5V) and Microprocessor Card (MPU)

SIMULATED EVENT Displays the results of simulated events test. The simulated events test consists of the

sensorsending a preset event back during diagnostic testing. This event is checked against

the correct value stored in the diagnostic test program. 

SIMULATED

AMOUNT

Displays the results of the simulated amounts test. The simulated amounts test consists of

the sensor sending a preset event back to the ACU during diagnostic testing. This event is

checked against the correct value stored in the diagnostic test program. 

SIMULATED DATA

CKSUM

Displays the results of the checksum error test. This test sums the ASCII bytes of data

being received from the sensor and compares this value to a checksum value received

directly from the sensor. If the two values do not match, the system assumes that a

communications error has occurred and indicates a fail status in the CKSUM field. 

CARRIER AVERAGE

RAW DATA

Displaysthe corresponding 1-minute averaged rawdata in tens ofmillivolts being received

from signal processor #1. These data are used to monitor signal strength and accidental

blockage or source failure. 

DIAG DATA CKSUM Displays the results of the checksum error test. This test sums the ASCII bytes of data

being received from the sensor and compares this value to a checksum value received

directly from the sensor. If the two values do not match, the system assumes that a

communications error has occurred and indicates a failstatusin the DIAG DATACKSUM

field.

1.3.4.26 Wind Speed and Direction Sensor Screen. The wind speed and direction sensor screen

(Figure 1.3.24) pertains to the DCP when a wind sensor is configured to the DCP and to the ACU when a

wind sensor is configured as a local sensor. This screen displays the current self-test data received from the

wind sensor. The diagnostic programperformstwo levels oftesting on the wind sensor. The first level is used

during the normal on-line diagnostic and provides the diagnostic program with the overall status of the

sensor,simulated wind direction and speed, and a data transmission checksum value. The data are evaluated

by the diagnostic program to determine if a fault exists in the wind sensor. If so, the diagnostic program

automatically executesthe second level test, which provides detailed self-test data on all circuitry in the wind

sensor. A technician performing an on-demand diagnostic can also execute the second level test by pressing

the TEST key with the wind speed and direction sensorscreen displayed on the OID. The data from both the

first and second level tests are displayed on the screen. The specific data received during these tests and a

description of each of the fields on the wind speed and direction sensor screen are provided in table 1.3.15.

When the on-demand test is exercised, the sensor cannot be brought back on line immediately. 
ASOS Site Technical Manual S100

1-40 Change 1

11:21:56 11/21/97 1621Z ANYTOWN AIRPORT

 SENSOR STATUS P POWER SUPPLY GROUND +0.0

 SIM WIND DIRECTION 123 P POWER SUPPLY +5.0 V +5.0

 SIM WIND SPEED 045 P ENCLOSURE TEMP +003C

 SIM DATA CKSUM 1C P EXTERNAL TEMP +000C

 WIND SPEED UNITS K DIAG DATA CHECK P

 SPEED ERROR P

 DIRECTION ERROR P DATA QUALITY P

 VOLTAGE ERROR P REPORT PROCESS Y

 SPEED SENSOR MISSING P SENSOR RESPONSE P

 DIR SENSOR MISSING P

 TEMPERATURE ERROR P POWER STATUS P

 FATAL ERROR P POWER CONTROL ON

 RAM CHECK P WIND LIGHT WEIGHT

$ ROM CHECK P $ PRINT CLEAR $

TEST POWER

EXIT BACK

Figure 1.3.24. Wind Speed and Direction Sensor Screen

Table 1.3.15. Wind Speed and Direction Sensor Screen Field Descriptions

Field Description

SENSOR STATUS Indicates the overall operational status of the wind sensor. Received during both first and

second levels of testing.

SIM WIND

DIRECTION

Displays the results of the simulated wind direction test. This test is performed by having

the wind sensor control processor send the value 123 instead of the actual wind direction

data. Received during both first and second levels of testing. 

SIM WIND SPEED Displays the results of the simulated wind speed test. This test is performed by having the

wind sensor control processor send the value 045 instead of the actual wind speed data.

Received during both first and second levels of testing. 

SIM DATA CKSUM Displays the results of the checksum test. Thistestsumsthe valuesreceived for sensor ID,

sensor status, and wind direction and speed and compares the value to a checksum value

received from the wind sensor. Failure of this test indicates a transmission error between

the sensor and the DCP. Received during second level testing. 

WIND SPEED UNITS The units field displays current units for wind speed as follows:

K = Knots

M = MPH

m = Meters/second

R = Revs/minute

P = Pulses/second

SPEED ERROR This field contains the speed error flag. If this parameter checks good, a P (pass) is

indicated in the status field. If this parameter checks bad, an F (fail) is indicated in the

field.

DIRECTION ERROR This field contains the direction error flag. If this parameter checks good, a P (pass) is

indicated in the status field. If this parameter checks bad, an F (fail) is indicated in the

field.

VOLTAGE ERROR Displays the operational status of the wind sensor's power supply. Indicates a pass or fail

status.

SPEED SENSOR

MISSING

This field contains the speed head missing flag. If this parameter checks good, a P (pass)

is indicated in the status field. If this parameter checks bad, an F (fail) and the associated

fail count are indicated in the status field.
S100 ASOS Site Technical Manual

Change 1 1-41

Table 1.3.15. Wind Speed and Direction Sensor Screen Field Descriptions -CONT

Field Description

SPEED SENSOR

MISSING

This field contains the speed head missing flag. If this parameter checks good, a P (pass)

is indicated in the status field. If this parameter checks bad, an F (fail) and the associated

fail count are indicated in the status field. 

DIR SENSOR

MISSING

This field contains the direction head missing flag. If this parameter checks good, a P

(pass) is indicated in the status field. If this parameter checks bad, an F (fail) and the

associated fail count are indicated in the status field. 

TEMPERATURE

ERROR

This field contains the internal temperature (too hot, too cold) failure flag.

FATAL ERROR Displays the results of an internal test performed on the wind sensor's processor. A fail

status in this field indicates the failure of the wind sensor's processor. Received during

second level testing. 

RAM CHECK Displays the results of the wind sensor's internal RAM test. During this test, the wind

sensor's internal processor checks its internal RAM by writing data to it and then reading

the data back. Received during second level testing. 

ROM CHECK Displays the results of the wind sensor's internal ROM test. During this test, the wind

sensor's internal processor performs a checksum type test on its internal ROM. Received

during second level testing. 

POWER SUPPLY

GROUND

Displays the results of the power supply ground test. This test measures the potential

difference between the ground terminal at the +5V power supply and the ground terminal

at the processor circuit board located in the wind direction assembly. The test detects poor

ground within the sensor. This condition may be the result of loose wires or corrosion.

Received during second level testing.

POWER SUPPLY

+5.0 V

Displays the results of wind sensor's +5V power supply test. Total failure of the +5V

powersupply resultsin a loss of all wind sensor data.Received during second level testing.

ENCLOSURE TEMP This field displays the enclosure temperature in degrees Fahrenheit. The allowable range

is 32 to 122 degrees F.

EXTERNAL TEMP For ASOS, always displays "000C" (not used).

DIAG DATA CHECK Displays the results of the level 1 checksum test. This test sums the values received for

sensor ID, sensor status, and wind direction and speed and compares the value to a

checksum value received from the wind sensor. Failure of thistest indicates a transmission

error between the sensor and the DCP. 

1.3.4.27 Temperature/Dewpoint (Model 1088) Screen. The temperature/dewpoint (model 1088) screen

(Figure 1.3.25) pertains to the DCP when a model 1088 sensor is configured to the DCP and to the ACU

when a model 1088 sensor is configured as a local sensor. This screen displays the current status of each of

the model 1088 diagnostic tests. The screen also displays the present status of the data quality checks,

operating status, and sensor status functions. The screen allows the technician to perform on-demand

diagnostic testing ofthemodel 1088 temperature/dewpointsensor. Pressing the TEST key causesthe sensor's

internal extended diagnostics to be executed within the sensor. The internal extended diagnostic issues a T2

command that isreceived by the sensor's calibrator assembly.In response, the calibrator assembly substitutes

known precision resistors in paths normally occupied by the temperature sensing elements. This simulates

ambient temperatures of 32 and 122 degrees Fahrenheit, and these calibration values are displayed with

decimal accuracy on the screen in respective SIMULATED TEMP DATA and SIMULATED DEWPOINT

DATA fields. Asshown on figure 1.3.25, these values correlate to the P (pass) condition, which is displayed

in the adjacent field. When this diagnostic capability is exercised, the sensor cannot be brought back on line

immediately. Pressing the POWER key turns sensor power on and off. The status of POWER CONTROL

indicatesifsensor power isturned on (ON/OFF). POWER STATUS indicatesthe status of the sensor power

as a P (pass) or F (fail) condition. table 1.3.16 describes each field on the temperature/dewpoint(model 1088)

screen. 
ASOS Site Technical Manual S100

1-42 Change 1

11:21:56 11/21/97 1621Z ANYTOWN AIRPORT

 SIMULATED TEMP DATA 0 DEG C 32.00 P TEMP QUALITY P

 SIMULATED TEMP DATA 50 DEG C 122.00 P DEW QUALITY P

 SIMULATED DEWPOINT DATA 0 DEG C 32.00 P REPORT PROCESS Y

 SIMULATED DEWPOINT DATA 50 DEG C 122.00 P SENSOR RESPONSE P

 ASPIRATOR FAN P

 0 DEGREE C CALIBRATION P POWER STATUS P

 50 DEGREE C CALIBRATION P POWER CONTROL ON

 REALTIME DIAGNOSTICS P

 MIRROR SERVO P

 CRITICAL VOLTAGE P

 DIRTY MIRROR P

 SIMULATED DATA ERROR P 1088

$

$ PRINT CLEAR $

TEST POWER

EXIT BACK

Figure 1.3.25. Temperature/Dewpoint (Model 1088) Screen

Table 1.3.16. Temperature/Dewpoint (Model 1088) Screen Field Descriptions

Field Description

SIMULATED

TEMPERATURE

DATA - 0 DEG C

Displays results of the simulated 0 degrees C temperature test. This test is performed by

switching a precision 100-ohm resistor into the measurement path of the model 1088 in

place of the temperature sensor. The value of the resistor is such that the model 1088

should return a reading of 0 degrees C if measurement circuitry is functioning properly. 

SIMULATED

TEMPERATURE

DATA - 50 DEG C

Displays results of the simulated 50 degrees C temperature test. This test is performed by

switching a precision 120-ohm resistor into the measurement path of the model 1088 in

place of the temperature sensor. The value of the resistor is such that the model 1088

should return a reading of 50 degrees C if measurement circuitry is functioning properly.

SIMULATED

DEWPOINT DATA - 

0 DEG C

Displays results of the simulated 0 degrees C dewpoint test. This test is performed by

switching a precision 100-ohm resistor into the measurement path of the model 1088 in

place of the dewpoint sensor. The value of the resistor is such that the model 1088 should

return a reading of 0 degrees C if measurement circuitry is functioning properly.

SIMULATED

DEWPOINT DATA - 

50 DEG C

Displays results of the simulated 50 degrees C dewpoint test. This test is performed by

switching a precision 120-ohm resistor into the measurement path of the model 1088 in

place of the dewpoint sensor. The value of the resistor is such that the model 1088 should

return a reading of 50 degrees C if measurement circuitry is functioning properly.

ASPIRATOR FAN Displays results of the aspirator fan motion test. The test ensures that the aspirator fan is

running by checking for airflow through the aspirator. The test monitors the value of two

thermal resistors; one in the airflow path and the other out of the airflow path. The cooling

effects of the moving air lowersthe resistance of the thermal resistor located in the airflow

path. If the two resistive values become equal, the system detects this condition as a loss

of airflow, indicating a fan failure.

0 DEG C

CALIBRATION

Indicates results of the model 1088 internal 0 degrees C calibration check. The simulated

temperature and temperature dewpoint resistors are used as the calibration references for

this test. 
S100 ASOS Site Technical Manual

Change 1 1-43

Table 1.3.16. Temperature/Dewpoint (Model 1088) Screen Field Descriptions -CONT

Field Description

50 DEG C

CALIBRATION

Indicates the results of the model 1088 internal 50 degrees C calibration check. The

simulated temperature and temperature dewpoint resistors are used as the calibration

references for this test.

REALTIME

DIAGNOSTICS

Indicates by the presence of a T in the status field when the system is performing a

real-time diagnostic (system diagnostic) or the model 1088 is performing an autobalance

cycle. 

MIRROR SERVO Indicates the status of the mirror servo control circuitry and the current position of the

test/operate mode switch in the model 1088. If the mode switch is in the test position, the

MIRROR SERVO field indicates a fail status. 

CRITICAL VOLTAGE Indicates that one of the power supplies in the model 1088 is out of tolerance.

DIRTY MIRROR Indicates the status of the dewpoint mirror in the aspirator. The test monitors the position

of the autobalance dial. If the dial indicates a reading between 450 and 500, the DIRTY

MIRROR field indicates a fail status. 

SIMULATED DATA

ERROR

Indicates a summary status of the simulated 0 and 50 degrees C temperature and dewpoint

status tests.

1.3.4.28 Temperature/Dewpoint (Model H083) Screen. The temperature/dewpoint (model H083) screen

(Figure 1.3.26) pertains to the DCP when a model H083 sensor is configured to the DCP and to the ACU

when a model H083 sensor is configured as a localsensor. Thisscreen displaysthe current operationalstatus

of the model H083 temperature/dewpointsensor. The model H083 sensor haslimited self-test capability and

supplies only one maintenance related field: THERMAL RUNAWAY. The THERMAL RUNAWAY field

indicates the status of the dewpoint mirror control servo loop. If a fault occurs within this loop that allows

the mirror temperature to rise above 65 degrees C, the sensor automatically issues a cooling command to the

mirror assembly and reportsthis condition to the diagnostic programby setting the THERMALRUNAWAY

status bit to F. Pressing the POWER key turns sensor power on and off. The status of POWER CONTROL

indicatesifsensor power isturned on (ON/OFF). POWER STATUS indicatesthe status of the sensor power

as a P (pass) or F (fail) condition. 

11:21:56 11/21/97 1621Z ANYTOWN AIRPORT

 TEMP QUALITY P

 DEW QUALITY P

 THERMAL RUNAWAY P REPORT PROCESS Y

 SENSOR RESPONSE P

 POWER STATUS P

 POWER CONTROL ON

HO83

 $

PRINT CLEAR $

$

TEST POWER

EXIT BACK

Figure 1.3.26. Temperature/Dewpoint (Model H083) Screen
ASOS Site Technical Manual S100

1-44 Change 1

1.3.4.29 Visibility Sensor Screen. The visibility sensor screen (Figure 1.3.27) pertains to the DCP when

a visibility sensor is configured to the DCP and to the ACU when such a sensor is configured as a local

sensor. This screen displays the current self-test data received from the visibility sensor. From these data,

the diagnostic program determines the operational status of the sensor. If the diagnostic program detects a

malfunction in the sensor, it invokesthe detailed diagnostic on the sensor. The systeminitiatesthis diagnostic

by issuing a command to the visibility sensor, which responds by displaying the data on the visibility sensor

screen. These data provide the detailed test results of the key sensor circuits. As a result, the functional

components of the system as well as the diagnostic circuitry are tested. The functions of each field on the

visibility sensor screen are provided in table 1.3.17. 

11:21:56 11/21/97 1621Z ANYTOWN AIRPORT

 SENSOR STATUS P DAY/NIGHT ELEC HEATER P

 SIMULATED EXT COEFF 12.34 P ENCLOSURE ELEC HEATER P

 SIMULATED PHOTO STATUS D P INSIDE AMBIENT TEMP 28.1 P

 SIMULATED DATA CKSUM E2 P CHECKSUM F9 P

 ADD CHECK P 

 RAM CHECK P VIS QUALITY P

 ROM CHECK P PHOTO QUALITY P

 EEPROM CHECK P REPORT PROCESS Y

 RECEIVER OP STATUS P SENSOR RESPONSE P

 TRANSMITTER OP STATUS P 

 DAY/NIGHT OP STATUS P POWER STATUS P

$ HEATER THERMOSTAT ON/OFF P POWER CONTROL ON

 RCVR HOOD HEATER P 

$ XMTR HOOD HEATER P VISIBILITY #1

$ RCVR WINDOW HEATER P $ PRINT CLEAR $ XMTR WINDOW HEATER P 

 DAY/NIGHT WINDOW HEATER P TEST POWER RCVR ELEC HEATER P

 XMTR ELEC HEATER P

EXIT BACK

Figure 1.3.27. Visibility Sensor Screen

Table 1.3.17. Visibility and Day/Night Sensor Screen Field Descriptions

Field Description

SENSOR STATUS The status field contains a symbol indicating visibility sensor status. A P is displayed for

pass and an F is displayed for fail.

SIMULATED EXT

COEFF

The simulated extinction coefficient value is 12.34/km. If value on screen matches this

value, a P (pass) is indicated in the status field. If value does not match this value, an F

(fail) and the associated fail count are indicated in the status field. 

SIMULATED PHOTO

STATUS

The simulated photometerstatusis D indicating day. Ifthe value on the screenmatchesthis

value, a P (pass) is indicated in the status field. If the value does not match this value, an

F (fail) and the associated fail count are indicated in the status field. 

SIMULATED DATA

CKSUM

If the simulated checksum of this test matches the correct value, a P (pass) is indicated in

the status field. If the value does not match this value, an F (fail) and the associated fail

count are indicated in the status field.

ADD CHECK In thistest, the processor writes data valuesto RAM locations. To each location, the value

that is written is equal to that location's address. After all locations are written to, the

processor reads back data and compares the stored data to the address. A P (pass) in the

statusfield indicates a match between the values written to and read from each address. An

F (fail) and associated fail count in the status field indicate that the values read from one

or more addresses did not match the values written to those addresses. 

RAM CHECK In the RAM test, the processor writes known valuesto selected addressesinRAM and then

reads them back. An F (fail) and the associated fail count are reported in the status field

if any of the values written to a given location in RAM are not the same when they are read

back. A P (pass) is reported in the status field if all the values written to a given location

in RAM are the same when they are read back.
S100 ASOS Site Technical Manual

Change 1 1-45

Table 1.3.17. Visibility and Day/Night Sensor Screen Field Descriptions -CONT

Field Description

ROM CHECK In the ROM test, the processor reads each address in ROM and calculates the checksum.

The last addressin ROM containsthe twos complement of the checksum of all other ROM

locations. When this value is added into the checksum of the rest of the ROM, a result of

zero should be obtained. A P (pass) in the statusfield indicates a healthy ROM. An F (fail)

and the associated fail count in the status field indicate a failed ROM.

EEPROM CHECK In the EEPROM test, the processor reads each address in EEPROM and calculates the

checksum. The last address in EEPROM contains the twos complement of the checksum

of all other EEPROM locations. When this value is added into the checksum of the rest of

the EEPROM, a result of zero should be obtained. When a recalibration occurs, the values

of the EEPROM are changed. The visibility sensor automatically writes the proper twos

complement value into the last location of EEPROM. A P (pass) in the status field

indicates that the EEPROM checksum is zero. An F (fail) and associated fail count in the

status field indicate that the EEPROM checksum value is other than zero.

RECEIVER OP

STATUS

The general operation of the receiver is continuously monitored as a part of taking

visibility measurements. This field indicates the receiver status (P = pass, F = fail). 

TRANSMITTER OP

STATUS

The number of flashes is continuously monitored as a part of taking visibility

measurements, and there should be two flashes per second. This field indicates the status

of the transmitter (P = pass, F = fail). 

DAY/NIGHT OP

STATUS

This field indicates the status of the day/night sensor (P = pass, F = fail).

HEATER $

THERMOSTAT $

This field indicates the status of the heater circuit (P = pass, F = fail).

RCVR HOOD

HEATER

This field indicates the status of the receiver hood heater (P = pass, F = fail).

XMTR HOOD

HEATER

This field indicates the status of the transmitter hood heater (P = pass, F = fail).

RCVR WINDOW

HEATER

This field indicates the status of the receiver window heater (P = pass, F = fail).

XMTR WINDOW

HEATER

This field indicates the status of the transmitter window heater (P = pass, F = fail).

DAY/NIGHT

WINDOW HEATER

This field indicates the status of the day/night window heater (P = pass, F = fail).

RCVR ELEC HEATER This field indicates the status of the receiver electronics heater (P = pass, F = fail).

XMTR ELEC HEATER This field indicates the status of the transmitter electronics heater (P = pass, F = fail).

DAY/NIGHT ELEC

HEATER

This field indicates the status of the day/night electronics heater (P = pass, F = fail).

ENCLOSURE ELEC

HEATER

This field indicates the status of the electronics enclosure heater (P = pass, F = fail). 

INSIDE AMBIENT

TEMP

This test monitors the temperature, in degrees C, inside the controller enclosure. The

allowable range is 20 to 70 degrees C. If the value on the screen is within this range, a P

(pass) is indicated in the status field. If the value is not within range, an F (fail) and the

associated fail count are indicated in the status field. 

VIS QUALITY This field indicates whether or not visibility data received from sensor is valid (logically

correct) when compared to the standard specified in the data quality monitoring algorithm.

A P (pass) (data quality meets the standard required by monitoring test algorithm) and an

F (fail) and the associated fail count (data quality does not meet the standard required by

monitoring test algorithm or sensor failed diagnostics) indicate pass/fail conditions. 

PHOTO QUALITY This field indicates whether or not photometer data received from the sensor is valid

(logically correct) when compared to the standard specified in the data quality monitoring

algorithm. A P (pass) (data quality meets the standard required by monitoring test

algorithm) and an F (fail) and the associated fail count (data quality does not meet the

standard required by monitoring test algorithm or sensor failed diagnostics) indicate

pass/fail conditions.

1.3.4.30 Tipping Bucket Sensor Screen. The tipping bucket sensor screen (Figure 1.3.28) pertains to the

DCP or ACU. The screen contains one sensor field that displays DATA QUALITY status as a P (pass) or

F (fail). Data quality is reckoned during moderate or heavy rain in a 10-minute period. During this time, if
ASOS Site Technical Manual S100

1-46 Change 1

at least one tip of the bucket occurs, a P status is indicated on the screen. If no tips occur during 10 minutes,

an F status is displayed. An F status can be cleared only if a tip occurs or if a deconfiguration is followed by

a reconfiguration. Deconfiguring the tipping bucket, however, may have an adverse effect on daily and

monthly summary data. While the sensor is deconfigured, estimated values are placed in the summaries for

a period of time. Eventually, missing will be reported on the summary screens. 

11:21:56 11/21/97 1621Z ANYTOWN AIRPORT

DATA QUALITY P 

TIPPING BUCKET

PRINT CLEAR

EXIT BACK

Figure 1.3.28. Tipping Bucket Sensor Screen

1.3.4.31 Frozen Precipitation Screen. The frozen precipitation screen (Figure 1.3.29) pertains to the DCP

when a frozen precipitation sensor is configured to the DCP and to the ACU when such a sensor is

configured as a localsensor.Currently, there is no frozen precipitation sensorin the operational baseline (this

screen is for future expansion). The frozen precipitation screen displays the current operational status of the

frozen precipitation sensor. The screen displays the present status of the data quality checks, report process,

and sensorstatusfunctions. In addition, power to the sensor can be turned on and off using the POWER key.

The POWER CONTROL field on the screen indicates the state of sensor power (ON/OFF) and the POWER

STATUS field indicates the status of sensor power as a P (pass) or F (fail) condition. 

11:21:56 11/21/97 1621Z ANYTOWN AIRPORT

DEW QUALITY P 

REPORT PROCESS Y 

SENSOR RESPONSE P 

POWER STATUS P 

POWER CONTROL ON 

FROZ PREC WATER

$ CLEAR

TEST POWER

EXIT BACK

NOTE: THIS SCREEN RESERVED FOR FUTURE EXPANSION.

Figure 1.3.29. Frozen Precipitation Screen
S100 ASOS Site Technical Manual

Change 1 1-47

1.3.4.32 Snow Depth Screen. The snow depth screen (Figure 1.3.30) pertains to the DCP when a snow

depth sensor is configured to the DCP and to the ACU when such a sensor is configured as a local sensor.

Currently, there is no snow depth sensor in the operational baseline (thisscreen isfor future expansion). The

snow depth screen displays the current operational status of the snow depth sensor. The screen displays the

present status of the data quality checks, report process, and sensor status functions. In addition, power to

the sensor can be turned on and off using the POWER key. The POWER CONTROL field on the screen

indicates the state of sensor power (ON/OFF) and the POWER STATUS field indicates the status of sensor

power as a P (pass) or F (fail) condition. 

11:21:56 11/21/97 1621Z ANYTOWN AIRPORT

DEW QUALITY P 

REPORT PROCESS Y 

SENSOR RESPONSE P 

POWER STATUS P 

POWER CONTROL ON 

SNOW DEPTH

CLEAR $

TEST POWER

EXIT BACK

NOTE: THIS SCREEN RESERVED FOR FUTURE EXPANSION.

Figure 1.3.30. Snow Depth Screen

1.3.4.33 Sunshine Screen. The sunshine screen (Figure 1.3.31) pertains to the DCP when a sunshine

sensor is configured to the DCP and to the ACU when such a sensor is configured as a local sensor.

Currently, there is no sunshine sensor in the operational baseline (this screen is for future expansion).

The sunshine screen displays the current operational status of the sunshine sensor. The screen displays

the present status of the data quality checks, report process, and sensor status functions. In addition,

power to the sensor can be turned on and off using the POWER key. The POWER CONTROL field on

the screen indicates the state of sensor power (ON/OFF) and the POWER STATUS field indicates the

status of sensor power as a P (pass) or F (fail) condition. 

11:21:56 11/21/97 1621Z ANYTOWN AIRPORT

DEW QUALITY P 

REPORT PROCESS Y 

SENSOR RESPONSE P 

POWER STATUS P 

POWER CONTROL ON 

SUNSHINE

CLEAR $

TEST POWER

EXIT BACK

NOTE: THIS SCREEN RESERVED FOR FUTURE EXPANSION.

Figure 1.3.31. Sunshine Screen
ASOS Site Technical Manual S100

1-48 Change 1

$ 1.3.4.34 Thunderstorm Screen. The thunderstorm screen (Figure 1.3.32) pertains to the DCP when a

$ thunderstorm sensor is configured to the DCP and to the ACU or SCA when such a sensor is configured

$ as a local sensor. The thunderstorm screen displays the current operational status and self-test data being

$ received from the sensor. Pressing the TEST key causes the sensor’s internal diagnostics to be executed

$ within the sensor. The screen displays the present status of the data quality checks, report process, and

$ sensor status functions. In addition, power to the sensor can be turned on and off using the POWER key.

$ The POWER CONTROL field on the screen indicates the state of sensor power (ON/OFF) and the

$ POWER STATUS field indicates the status of sensor power as a P (pass) or F (fail) condition.

$$ 11:21:56 11/21/97 1621Z ANYTOWN AIRPORT

$

$ SELFTEST C6 P DATA QUALITY P

$ INPUT VOLTAGE > 11 VOLT P REPORT PROCESS Y

$ INPUT VOLTAGE < 13 VOLT P SENSOR RESPONSE P

$ 5 VOLT SUPPLY P

$ 10 VOLT SUPPLY P POWER STATUS P

$ POWER CONTROL ON

$

$

$

$

$ THUNDERSTORM

$

$ PRINT CLEAR $

$

$ TEST POWER $

$

$ EXIT BACK $

$ Figure 1.3.32. Thunderstorm Screen

$ 1.3.4.35 Pressure Sensor Screen. The pressure sensor screen (Figure 1.3.33) pertains to the DCP when

$ pressure sensors are configured to the DCP and to the ACU or SCA when pressure sensors are configured

$ as local sensors. This screen displays the current operational status of the pressure sensor. Either sensor #1,

#2, or #3 can be called up by the technician. Data quality, report process, and sensor status functions are

displayed on this screen. 

11:21:56 11/21/97 1621Z ANYTOWN AIRPORT

DEW QUALITY P 

REPORT PROCESS Y 

SENSOR RESPONSE P 

PRESSURE #1

$

$ PRINT CLEAR $

TEST

EXIT BACK

Figure 1.3.33. Pressure Sensor Screen
S100 ASOS Site Technical Manual

Change 1 1-49

1.3.4.36 ACU/DCP Communications Status Screen. The ACU/DCP communications status screen

(Figure 1.3.34) shows the test status of the communications link between the ACU and the DCP. The

communications link can be either a radio link, using rf modems (radios) in the ACU and DCP, or may be

hardwired, using line drivers. Depending on site configuration, either one or two radios/line drivers may be

installed in both the ACU and the DCP. The first radio/line driver is referred to as radio/line driver A, and the

optional second radio/line driver is referred to as radio/line driver B. Where radio links are used, omnidirectional $

antennas are usually used at the ACU and at each DCP. At certain sites where co-channel interference has been $

experienced, yagi antenna arrays replace the omnidirectional antennas. The yagi antenna is a seven-element array, $

PN 62828-90413-2, with 10 dB gain and 14 dB front:back ratio. The yagis are usually oriented for vertical $

polarization, but may be oriented horizontally to further isolate ACU-DCP links. Additionally, five watt attenuators $

of 3 dB, 6 dB, 10 dB, 20 dB, or 30dB (PN 62828-90424-2, -3, -4, -5 and -6 respectively) may be installed to reduce $

transmit power into the yagi antennas. Combinations of these attenuators reduce interference to an $

accepTable level. $

11:21:56 07/04/96 1621Z ANYTOWN AIRPORT

 ACU DCP #1 DCP #2 DCP #3

 RADIO A

 OR L/D A P P P P

 RADIO B

 OR L/D B P P P P

 PRIMARY LINK A A A A

 DEGRADED COMMS P

 HARDFAIL COMMS P

ACU/DCP COMM

PRINT CLEAR

EXIT BACK

Figure 1.3.34. ACU/DCP Communications Status Screen

The ACU/DCP communications status screen shows the current test status for all radios/line drivers in the ACU

and in DCP's 1, 2, and 3. The PRIMARY LINK field at the bottom of the screen identifies which radio/line driver

in each cabinet is currently being used for data communication. The primary assignment does not change unless

there is a failure in the primary device, in which case, the backup radio/line driver (if available) becomes the new

primary device.

The system updates the status on the ACU/DCP communications status screen as the various links are tested during

CST. One ACU/DCP link is tested each minute. As there is no TEST key associated with this screen, the technician

cannot manually select to test the ACU/DCP communications links. 

RF noise, maintenance actions, and line-of-sight obstructions can cause temporary interruptions, or glitches, in

ACU/DCP communications. For this reason, the system software allows a certain amount of degradation in

ACU/DCP communication before appending a $ to the observation as described in the following paragraphs. 

When an ACU/DCP communications failure is detected, an F status indication is displayed in the appropriate field

in the upper half of the screen and the associated fail count is incremented. This fail count does not cause a $ in

the observation. 
ASOS Site Technical Manual S100

1-50 Change 1

At 6 a.m. (local standard time) each day, the system evaluates the ACU/DCP communications failures that occurred

over the last 24 hours. These failures are summarized on the trend screen and the fail counts on the ACU/DCP

communications status screen are cleared. If the number of communications failures exceeds 20 percent, the status

of the DEGRADED COMMS field on the ACU/DCP communications status screen is changed to C and a $ is

added to the observation to indicate the need for maintenance action. The maintenance technician can clear the C

status by pressing the CLEAR key. 

The HARDFAIL COMMS field is used to indicate a complete failure in ACU/DCP communications. An F

is placed in the appropriate field in the event that communications failures are detected continuously for a

period of 1 minute. When this occurs, the corresponding fail count is incremented and a $ is added to the

observation. The technician can clear these fail counts (and the $) by pressing the CLEAR key. 

1.3.4.37 Trend Screen. The trend screen (Figure 1.3.35)supplies performance information on the ACU and

DCP radios. At 6 a.m. local standard time each day, the fail counts from the ACU/DCP communications

status screen (Figure 1.3.34) are transferred to the trend screen. This screen lists the number of all radio or

line driver communications fail counts by date for the previous 31 days. Data are grouped into four clusters:

two for each radio/line driver. Each cluster consists of three columns. The first column in each cluster

providesthe date of occurrence using the mm/dd format. The second column displaysfail counts asindicated

on the ACU/DCP communications status screen (Figure 1.3.34), and the third column displays a percentage

value indicating the number of failed communication attempts compared to the number of tries. 

11:21:56 11/21/97 1621Z ANYTOWN AIRPORT

$ RADIO/LINE DRIVER A ACU FAILCOUNTS / PERCENTAGES RADIO/LINE DRIVER B

00/00 00000 00000% 06/30 00000 100.0% 00/00 00000 00000%

00/00 00000 00000% 07/01 00000 97.63% 00/00 00000 00000% 07/01 00000 44.22%

00/00 00000 00000% 07/02 00001 85.28% 00/00 00000 00000% 07/02 00000 13.07%

00/00 00000 00000% 07/03 00000 16.23% 00/00 00000 00000% 07/03 00000 0.000%

00/00 00000 00000% 07/04 00000 21.01% 00/00 00000 00000% 07/04 00000 0.000%

00/00 00000 00000% 07/05 00000 20.31% 00/00 00000 00000% 07/05 00000 0.000%

00/00 00000 00000% 07/06 00000 20.70% 00/00 00000 00000% 07/06 00000 0.000%

00/00 00000 00000% 07/07 00000 3.267% 00/00 00000 00000% 07/07 00000 0.013%

00/00 00000 00000% 07/08 00000 3.102% 00/00 00000 00000% 07/08 00000 0.000%

00/00 00000 00000% 07/09 00000 3.069% 00/00 00000 00000% 07/09 00000 0.000%

00/00 00000 00000% 07/10 00000 2.953% 00/00 00000 00000% 07/10 00000 0.000%

00/00 00000 00000% 07/11 00000 3.325% 00/00 00000 00000% 07/11 00000 0.000%

00/00 00000 00000% 00/00 00000 00000% TREND

$ 00/00 00000 00000% 00/00 00000 00000% $ PRINT CLEAR 00/00 00000 00000% 00/00 00000 00000%

EXIT BACK

Figure 1.3.35. Trend Screen
S100 ASOS Site Technical Manual

Change 1 1-51

1.3.4.38 ADAS Summary Screen. The ADAS summary screen (Figure 1.3.36) provides a record of $

communication status between ADAS and ASOS. This screen displays continuous hourly counts over a 24- $

hour period to indicate any of four status conditions that occur during each hour. These status conditions $

include the following : SP (ADAS has started polling ASOS), LP (ASOS has lost poll from ADAS), LNK $

(ADAS-ASOS link established), and DIS (ADAS has disconnected from ASOS). $

11:21:57 11/21/97 1621Z ANYTOWN AIRPORT $

 HRBEG SP LP LNK DIS HRBEG SP LP LNK DIS $

 12:00 000 000 000 000 00:00 000 000 000 000 $

 13:00 000 000 000 000 01:00 000 000 000 000 $

 14:00 000 000 000 000 02:00 000 000 000 000 $

 15:00 000 000 000 000 03:00 001 000 001 000 $

 16:00 000 000 000 000 04:00 000 001 000 001 $

 17:00 000 000 000 000 05:00 000 000 000 000 $

 18:00 000 000 000 000 06:00 000 000 000 000 $

 19:00 000 000 000 000 07:00 000 000 000 000 $

 20:00 000 000 000 000 08:00 000 000 000 000 $

 21:00 000 000 000 000 09:00 000 000 000 000 $

 22:00 000 000 000 000 10:00 000 000 000 000 $

 23:00 000 000 000 000 11:00 000 000 000 000 $

ADAS SUMMARY $

$

PRINT $

$

$

$

$

$

EXIT BACK $

Figure 1.3.36. ADAS Summary Screen $

1.3.4.39 Processor Status Screen. The processorstatusscreen (Figure 1.3.37) pertainsto both the ACU and

DCP. This screen enables the technician to observe the operational status of the ACU and DCP processors,

reinitialize the ACU and DCP's processors, and generate selective error message reports. The technician has

the option on the DCP's to perform either a hard or soft initialization. A hard initialization resets the DCP's

CPU's, clears memory and downloads the system software to the DCP. A soft initialization resets the CPU's

but does not clear memory. 

NOTE

Exercising the RESET function in the ACU field initializes a system reset

which forces the system into the power-up initialization sequence.

The START PRINT and END PRINT functions enable specific portions of the Maintenance Error Log to

be printed. To print specific portions of the log, the cursor is placed at the START PRINT field. The desired

error code number is entered to begin the report. The cursor is then placed at the END PRINT field and the

desired error code numberis entered to end the report. The designated portion ofthe log isthen automatically

printed on the printer. If a user error is detected when the START PRINT or END PRINT error code number

is entered, the system generates an audio alarm (beep), displays an error message, and then exits the mode.

The user must then reenter the START PRINT and END PRINT values. Possible errorsinclude non-numeric

characters and a start number greater than the end number. 
ASOS Site Technical Manual S100

1-52 Change 1

11:21:56 11/21/97 1621Z ANYTOWN AIRPORT

 ACU RUNNING

 DCP #1 INITIALIZING

 HARD

 SOFT

$ 

 DCP #2 INITIALIZING

 HARD

 SOFT

 DCP #3 RUNNING PROCESSOR STATS

 HARD

PRINT PREV

 SOFT

RESET CHANG START PRINT END PRINT 

 ____ ____

EXIT BACK NEXT

Figure 1.3.37. Processor Status Screen

1.3.4.40 MaintenanceAction Screen.Themaintenance action screen (Figure 1.3.38) enables the technician

to start the system maintenance log (START key) and to select four maintenance data entry screens from

which he enters unit stock numbers, serial numbers, and field modification kit numbers. These entries are

recorded in the system maintenance log (SYSLG) to correlate equipment identification with servicing tasks.

Preventivemaintenance (PREVT key), corrective maintenance (CORR key), calibration (CAL key), and field

maintenance kit (FMK key) screens are selected from the maintenance ACTION keypad. An ABORT key

returns the technician to the 1-minute screen and does not save entries on the screen. 

11:21:56 11/21/97 1621Z ANYTOWN AIRPORT

ACTION

$

$ PRINT PREVT CORR $

CAL FMK ABORT

EXIT BACK START

Figure 1.3.38. Maintenance Action Screen
S100 ASOS Site Technical Manual

Change 1 1-52.1/ (1-52.2 blank)

1.3.4.41 PreventiveMaintenance Action Screen. The preventive maintenance action screen (Figure 1.3.39)

is used by the technician to enter agency stock numbers (ASN's) and unit serial numbers into the system

maintenance log when preventive maintenance is being applied to units within ASOS. ASN's for ASOS

cabinets and FRU's are based on the assembly reference designator listed in the Parts List reference $

designator column (located after the last chapter). The reference designator is used in conjunction with the $

ASOS designator (S100) to determine the ASN as follows: S100-(reference designator). Examples of how $

this screen is used are illustrated by air filter cleaning in the ACU (paragraph 2.5.2.1) and check memory

board LOW BATT indicator (paragraph 2.5.2.4). For the cleaning task, the Parts List (located after the last $

chapter) shows the reference designator of the ACU blower filter to be 1FL1. Therefore, the agency stock $

number for this part is S100-1FL1. This number is typed in the AGENCY STOCK NUMBER field. $

Similarly, agency stock number S100-1A2A3 is typed to specify the LOW BATT indicator on the ACU

memory board. For the UNITS SERIAL NUMBERS field, numbers are acquired from visual inspection of

the assemblies and typed in the field. The preventive maintenance action screen prompts the technician to

verify if all entered data are correct. A Y entry storesthese numbersin the systemmaintenance log and clears

the screen for entry of numbers pertaining to the next unit used in preventive maintenance. Any additional

data relevant to the task may be entered directly on the SYSLG screen (paragraph 1.3.13). The preventive

maintenance action screen keypad is identical to the maintenance action screen keypad. 

11:21:56 11/21/97 1621Z ANYTOWN AIRPORT

PREVENTATIVE MAINTENANCE DATA

 AGENCY STOCK NUMBER: S100-1

 UNIT SERIAL NUMBER: 1

 ALL ENTERED DATA CORRECT (Y/N)?: N

ACTION

PRINT PREVT CORR $

CAL FMK ABORT

EXIT BACK START

Figure 1.3.39. Preventive Maintenance Action Screen

1.3.4.42 Corrective Maintenance Action Screen. The corrective maintenance action screen is identical

in layout to the preventive maintenance action screen (Figure 1.3.39). This screen is used by the technician

to enter agency stock numbers and unit serial numbers into the system maintenance log when ASOS

assemblies and units are repaired or removed and replaced. Pertinent agency stock numbers are acquired by $

referencing the Parts List (located after the last chapter). Unit serial numbers are acquired from engraved or $

stenciled identification data. Using the OID keyboard, the technician enters number data in the same manner

as described for the preventive maintenance action screen. If additional related data are to be entered, the

technician may enter the data directly on the SYSLG screen (paragraph 1.3.13).
S100 ASOS Site Technical Manual

Change 1 1-53

1.3.4.43 Calibration Maintenance Action Screen. The calibration maintenance action screen is identical

in layout to the preventive maintenance action screen (Figure 1.3.39). This screen is used by the technician

to enter agency stock numbers and unit serial numbers into the system maintenance log when ASOS

assemblies and units are calibrated. Pertinent agency stock numbers are acquired by referencing the Parts $

List(located afterthe last chapter).Unitserial numbers are acquired fromengraved orstenciled identification $

data. Using the OID keyboard, the technician enters number data in the same manner as described for the

preventive maintenance action screen. If additional related data are to be entered, the technician may enter

the data directly on the SYSLG screen (paragraph 1.3.13). 

1.3.4.44 Field Modification Kit Action Screen. The field modification kit action screen (Figure 1.3.40)

enables the technician to enter field modification kit numbers. When a field modification kit is installed in

ASOS, its number is entered on thisscreen and stored in the systemmaintenance log. A Y entered in the ALL

ENTERED DATA CORRECT (Y/N)? field stores the kit number and clears the screen. Any additional data

related to the field modification kit numbermay be entered directly on the SYSLG screen (paragraph 1.3.13).

The field modification kit action screen keypad is identical to the maintenance action screen keypad. 

11:21:56 11/21/97 1621Z ANYTOWN AIRPORT

FIELD MODIFICATION KIT MAINTENANCE DATA

 FIELD MODIFICATION KIT NUMBER:

ACTION

PRINT PREVT CORR $

CAL FMK ABORT

EXIT BACK START

Figure 1.3.40. Field Modification Kit Action Screen

1.3.5 SYSTEM POWER ON PROCEDURES

Chapters 2 and 3 provide procedures to power up the ACU peripherals and the DCP, respectively. When

powering up an entire system, these procedures are used to power up the ACU and its associated DCP's. It

does not matter which order the cabinets are powered up. After the ACU and DCP's are powered up, the

system performs whatever initialization is necessary and automatically begins normal operation. 
ASOS Site Technical Manual S100

1-54 Change 2

1.3.6 SYSTEM SIGN-ON

To sign on to the system as a maintenance technician, the procedure provided in table 1.3.18 is performed.

Table 1.3.18. System Sign-On Procedures

Step Procedure

1 At OID, ensure that 1-minute screen is displayed; if not, press EXIT key. 

2 Press SIGN key. The OID displays the message ENTER YOUR INITIALS.

3 Enter two or three alphabetic characters and press RETURN. The OID displays the message ENTER

PASSWORD. 

4 Enter your maintenance password and press RETURN. If the sign-on is successful, the system displays all

other users currently on the system; otherwise, the system displays an error message and sounds an alarm. 

NOTE

If an observer or ATC is presently signed on at any OID, neither the system manager nor

the technician can make any changes to system configuration, site physical characteristics

data, or passwords. 

5 The listing of users signed on to the system is only displayed for a brief period of time and then removed by

the system. Use the AUX-USERS subfunction to review the list again if desired. 

6 If signed on as a technician, the MAINT key is displayed in the keypad area of the screen and can be used

to access the technician interface screens.

1.3.7 SYSTEM SIGNOFF

To sign off the system, the procedure provided in table 1.3.19 is performed. 

Table 1.3.19. System Signoff Procedures

Step Procedure

1 At OID, ensure that 1-minute screen is displayed. If not, press EXIT key until the 1-minute screen is

displayed.

2 Press SIGN key. The OID displays the message ENTER YOUR INITIALS.

3 Enter the two or three alphabetic characters used to sign on the system and press RETURN. The OID

displays the message ENTER PASSWORD (or press RETURN to sign off). 

4 Press RETURN. If signed on as a technician or supervisor, the MAINT field is removed from the OID

keypad screen.

1.3.8 RUNNING ASOS DIAGNOSTICS

The ASOS diagnostics run continuously and repeat approximately every 7 minutes. Upon completion of a

diagnostic test, the system automatically logs the results in the maintenance log. In addition to the

continuously running diagnostic, the technician can run direct dialogue tests on certain sensors. Procedures

for running the direct dialogue tests are provided in the respective sensor chapter. To run specific parts of

the ASOS diagnostics, the procedures provided in table 1.3.20 are performed. 

1.3.9 MONITORING/CONTROLLING SENSOR POWER FROM THE OID

Electrical power to each sensor can be remotely monitored and controlled fromthe individualsensorscreens

at the OID. Turning sensor power off suspends all communications between the sensor and the ACU. The

system also logs a power off message in the maintenance log and displays an M in the sensor status field on

the 1-minute screen. Sensor powershould only be removed fromthe sensor at the DCP or at the actualsensor

for maintenance or emergency situations. When power is removed from a sensor in either manner, a sensor

power failure error is generated. To monitor sensor power status or to turn power on or off for a specific

$ sensor, the procedures provided in table 1.3.21 are performed. Power supplied to the local sensors cannot

$ be controlled via the sensor screens. 
S100 ASOS Site Technical Manual

Change 1 1-55

Table 1.3.20. Running ASOS Diagnostics

Step Procedure

NOTE

If an observer or ATC is presently signed on at any OID, neither the system manager nor the

technician can make any changes to system configuration, site physical characteristics data, or

passwords. 

1 Sign on the system as a technician using the procedure in table 1.3.18. 

2 At OID, press MAINT key. The maintenance screen is displayed on the OID and indicates the present status

of the system. 

3 To run a specific portion of the diagnostic test, use the PREV/NEXT keys to move the cursor to the

subassembly to be tested and press SEL key. The OID displays the appropriate status screen. 

4 Using the PREV/NEXT keys, move the cursor to the item to be tested and press SEL key. The OID displays

the item's status screen.

5 For units with built-in extended diagnostics(i.e., wind sensor, 1088 sensor, and ACU modems), the extended

diagnostics are initiated immediately and the results are reported when the diagnostics are complete. For all

other units, the T's remain on the screen until the unit is next tested during the CST, and the results of that

test are then reported. Typically, this requires less than 1 minute but should take no longer than a full CST

cycle (7 minutes). If the T's remain displayed longer, the unit is probably not responding to the CST checks.

The technician should ensure that the unit is properly installed in the system and turned on. If any unit fails,

or if the T's remain displayed even though the unit is installed and turned on, the technician should refer to

the applicable Chapter for specific troubleshooting and removal and replacement procedures.

6 Upon repair of the fault, repeat steps 1 through 5. 

7 To return to the next higher status screen, press BACK key.

Table 1.3.21. Monitoring/Controlling Sensor Power

Step Procedure

NOTE

If an observer or ATC is presently signed on at any OID, neither the system manager nor the

technician can make any changes to system configuration, site physical characteristics data, or

passwords. 

1 Sign on the system as a technician.

2 At OID, press MAINT key. The maintenance screen is displayed on the OID and indicatesthe present status

of the system. 

3 Using the PREV/NEXT keys, position the cursor on the selected DCP field and press SEL key. The OID

displays the remote DCP screen. 

4 Using the PREV/NEXT keys, position the cursor at the selected sensor field and press SEL key. The OID

displays the desired sensor screen. 

5 Press the POWER key on the keypad to toggle the sensor power on/off. The POWER CONTROL field on

the screen indicates the status of sensor power as on or off. 

6 To return to the remote DCP screen, press BACK key.
ASOS Site Technical Manual S100

1-56 Change 1

1.3.10 RECONFIGURING THE SYSTEM

Reconfiguration of the system requires both a hardware and software change. The technician can

reconFigure the hardware system at any time. Usually, hardware reconfiguration may be required as a result

of a system malfunction or a modification to the system. The hardware change consists of connecting the

cables from the input/output (I/O) boards in the DCP('s) to the fiberoptic boards that communicate with the

sensors. The hardware change must then be identified to the software system via the site configuration

screen. The site configuration (SITE CONFG) screens are used to perform the software change portion of

reconfiguration. The site configuration screens and their functions are described in paragraph 1.3.16. The

system should be reconfigured when adding new sensors. In addition to reconfiguring sensor input/output

channels, the technician may also identify the number of CPU's, UPS's, A/D's, I/O boards, modems, and

video boards presently in the system and at which OID the handset islocated. In the DCP, the only hardware

items that cannot be reconfigured are the UPS's. For a system so equipped, UPS #1 is always connected to

SIO #1 CHANNEL 1 and UPS #2 is always connected to SIO #3 CHANNEL 2.

1.3.10.1 Configuring the OID. The OID's must be properly configured to interface with the ASOS. The

ASOS requires terminals which communicate using a VT220 style format. The OID is configured using the

procedures provided in table 1.3.22. These procedures are provided specifically forthe Link MC70 terminal.

Additional information is contained in the terminal vendor manual located on-site. 

Table 1.3.22. Configuring the OID Terminal

Step Procedure

1 Apply power to the LINK MC70 OID.

NOTE

Press the HELP key 2 times in succession to repaint the screen. 

2 At the OID keyboard, press the F3 (SET-UP) key. The OID displays the terminal setup directory.

NOTE

The ENTER key referenced in this procedure is located in the auxiliary keypad

area of the keyboard. DO NOT use the ENTER key located in main keypad area.

3 Using the cursor keys, move right to the SCREEN submenu. 

4 Verify that the functions below are displayed:

WIDTH CHANGE CLEAR ON

SCREEN COLUMNS 80

SCREEN DATA LINES 24

PAGE COLUMNS 132

PAGE LINES 24/25

PAGE LINE MULTIPLIER 1

NUMBER OF PAGES 1

NUMBER OF SESSIONS 1

SESSION DISPLAY, SPLIT 1, FULL

POWER-ON TAB STOPS OFF

TAB STOPS

5 Using the cursor keys and ENTER key,select and toggle each field that does not contain the correct

information. 

6 Using the cursor keys, move right to the MODES submenu. 
S100 ASOS Site Technical Manual

Change 1 1-57

Table 1.3.22. Configuring the OID Terminal -CONT

Step Description

7 Verify that the functions below are displayed.

FEATURE LOCK OFF

CONTROLS MODE INTEPRT

RECEIVED CR CR

RECEIVED LF LF

TRANSMIT MODE 8-BIT

TRANSFER/PRINT/SEND

ANSWERBACK MESSAGE

BELL SETTINGS

PERSONALITY

8 Using the cursor keys and ENTER key, select and toggle each field that does not contain the correct

information. 

9 Using the cursor keys and ENTER key, select BELL SETTINGS. 

10 BELL TONE AND BELL VOLUME are user preference and may be set accordingly. Press SHIFT

UP-ARROW to return to the MODES submenu. 

11 Using the cursor keys and ENTER key, select PERSONALITY. 

12 Using the cursor keys and ENTER key,select VT320/VT220. If the entry is changed, an ARE YOU

SURE? (Y/N)Y verificationmessage is displayed. PressENTER. The systemreturns to the MODES

submenu. 

13 Using the cursor keys, move right to the DISPLAY submenu. 

14 Verify that the functions below are displayed:

SCREEN SAVER OFF

SCREEN SAVER MODE BLANK

REVERSE SCREEN OFF

SCROLL SPEED JUMP

TOP STATUS LINE BLANK

HOST MESSAGE OFF

SCREEN RESOLUTION 16x16

DISPLAY FUNCTIONS

CURSOR DISPLAY

15 Using the cursor keys and ENTER key, select and toggle each field that does not contain the correct

information. 

16 Using the cursor keys and ENTER key, select CURSOR DISPLAY. 

17 BLINK and CURSOR COLOR are user preference and may be set accordingly. Press SHIFT

UP-ARROW to return to the DISPLAY submenu. 

18 Using the cursor keys, move right to the ATTRIBUTES submenu. 

19 Verify that the functions below are displayed:

SETUP MENU COLOR BLUE

FOREGROUND COLOR WHITE

BACKGROUND COLOR

NORMAL COLORS

BOLD COLORS

DIM COLORS

BORDER COLOR

NORMAL ATTRIBUTES

BOLD ATTRIBUTES

DIM ATTRIBUTES
ASOS Site Technical Manual S100

Table 1.3.22. Configuring the OID Terminal -CONT

Step Description

1-58 Change 1

20 Using the cursor keys and ENTER key, select and toggle each field that does not contain the correct

information. 

21 Using the cursor keys, move right to the PORT submenu.

22 Verify that the functions below are displayed:

COMMUNICATIONS MODE FULL DPX

ON-LINE/LOCAL ON-LINE

TRACE BOTH

PORT A SETTINGS

PORT B SETTINGS

COMMUNICATIONS CARTRIDGE

SESSION RESOURCES

23 Using the cursor keys and ENTER key,select and toggle each field that does not contain the correct

information. 

24 Using the cursor keys and ENTER key, select PORT A SETTING.

25 Verify that the functions below are displayed:

TRANSMIT BAUD RATE 9600

RECEIVE BAUD RATE RCV=XMIT

DATA/STOP/PARITY BITS 8/1/NONE

RECEIVE HANDSHAKE NONE

TRANSMIT HANDSHAKE NONE

TRANSMIT LIMIT NONE

BREAK 250 MS

INTERFACE RS-232C

MODEM CONTROL ASCII

DISCONNECT DELAY OFF

26 Press SHIFT UP-ARROW to return to the PORT submenu. 

27 Using the cursor keys and ENTER key, select SESSION RESOURCES. 

28 Verify that the functions below are displayed:

PRTA PRTB BUF1 BUF2

SESSION 1 HOST AxPr ACTV

SESSION 2 ACTV

29 Press SHIFT UP-ARROW to return to the PORT submenu. 

30 Using the cursor keys, move right to the KEYBOARD submenu. 

31 Verify that the functions below are displayed:

KEY AUTOREPEAT OFF

KEYCLICK MEDIUM

KEYBOARD LANGUAGE US

NATIONAL MODE OFF

CHARACTER SET MULTNATL

CORNER KEY OFF

KEY DEFINITIONS LOCK OFF

KEY FUNCTIONS

KEY MODES

USER-DEFINED KEYS

32 Using the cursor keys and ENTER key, select and toggle each field that does not contain the correct

information. 

33 Using the cursor keys, move right to the EXIT submenu. 
S100 ASOS Site Technical Manual

Table 1.3.22. Configuring the OID Terminal -CONT

Step Description

Change 1 1-59

34 Verify that the functions below are displayed:

EXIT SETUP

EXIT SETUP AND CANCEL CHANGES

EXIT SETUP AND SAVE

RESTORE LAST SAVED

DEFAULT ALL

DEFAULT USER-DEFINED KEYS

35 Using cursor keys and ENTER key, select EXIT SETUP AND SAVE. An ARE YOU SURE?

(Y/N)Y verification message is displayed. Select ENTER. The OID exits the setup procedure.

1.3.10.2 Configuring the RemoteTerminals. The remote terminals provide qualified ASOS users with the

capability to accessthe ASOS from off-site locations(described in paragraph 1.3.14). When configuring the

remote terminal, the following parameter values are recommended: 

a. 2400 baud (300 to 28.8k baud also available dependent upon modem installed) $

b. No parity

c. 8 data bits

d. 1 stop bit

e. Full duplex

1.3.10.3 Deconfiguring and Reconfiguring Sensors to a Remote DCP. Configuring a sensor to a remote

DCP consists of assigning the sensor to an available SIO port on the DCP using the sensor configuration

screen. Similarly, deconfiguring a sensor consists of removing an assigned port from the same screen. When

a visibility sensor or ceilometer configuration is changed, the system requires the operator to access the

sensor algorithm configuration screen (paragraph 1.3.16.3) and ensure that algorithm parameters (sensor

location, priority, etc) are correct for the configured sensors. Whenever a sensor is configured to the system,

the technician must ensure that is properly installed and that it is physically connected to the specified port.

Table 1.3.23 provides a procedure for deconfiguring and reconfiguring a sensor to a remote DCP.

Deconfiguring a sensor resultsin the loss of archive data and accumulated daily/monthly summary data. For

this reason, the technician should not deconFigure any sensor unless permanently removing that sensor type

or unless instructed by specific maintenance procedures. Sensor report processing is turned off while $

configuring the sensor. $

Table 1.3.23. Sensor DeconFigure and ReconFigure Procedure

Step Procedure

SENSOR DECONFIGURATION

CAUTION

Deconfiguring sensor will result in loss of accumulated daily and monthly summary data. Do not

deconFigure sensor unless that type of sensor is being removed from system permanently (unless

instructed by other maintenance procedures). 

1 At OID, sign on to system as a technician.

2 Accesssensor configuration screen (paragraph 1.3.16.2) by pressing REVUE-SITE-CONFIG-SENSOR keys.

3 On sensor configuration screen, press CHANG key. A cursor is displayed over the first SIO port. Message

SYSTEM MODIFICATIONS flashes at top of screen. 
ASOS Site Technical Manual S100

1-60 Change 1

Table 1.3.23. Sensor DeconFigure and ReconFigure Procedure -CONT

Step Description

4 Using PREV and NEXT keys, move cursor to highlight code for sensor to be deconfigured. 

5 To deconFigure sensor, enter two asterisks (**) in place of highlighted sensor code. 

6 Press BACK key to cause system to accept new configuration. Message SYSTEM MODIFICATIONS is

removed when system has accepted change. 

7 If deconfigured sensor was visibility or ceilometer, press ALGOR key to display sensor-algorithm

configuration screen (paragraph 1.3.16.3). Review to ensure that sky/visibility algorithm, primary

assignments, priorities, etc, are correct per system manager specification. 

8 Press EXIT key to return to 1-minute screen.

SENSOR RECONFIGURATION

1 At OID, sign on to system as a technician.

2 Access sensor configuration screen (paragraph 1.3.16.2) by pressing REVUE-SITE-CONFIG-SENSOR keys.

3

NOTE

If no SIO ports are available, a new SIO board must be added to the system and must be

configured on the hardware configuration screen (paragraph 1.3.16.1). 

Select an available SIO port on which to conFigure sensor (available slots denoted by double asterisks(**)).

4 Ensure that sensor being configured is physically connected to the selected SIO port as follows: 

NOTE

If fiberoptic module corresponding to selected SIO slot is not installed in the system,

technician must install it in the DCP and then connect sensor to this module. 

a. Referring to port assignments for DCP SIO boards (Table 3.4.1), determine which

fiberoptic module in DCP corresponds to SIO port selected for sensor. 

b. Physically connect sensor being configured to this fiberoptic module. 

5 On sensor configuration screen, press CHANG key. A cursor is displayed over the first DCP SIO port.

Message SYSTEM MODIFICATIONS flashes at top of screen. 

6 Using PREV and NEXT keys, move cursor to highlight asterisks at SIO port selected for sensor. 

7 To conFigure sensor, enter two-character code for sensor being configured. A list of allowable codes is

provided in paragraph 1.3.16.2. 

8 Press BACK to cause system to accept new configuration. Message SYSTEM MODIFICATIONS is

displayed at top of OID until system has accepted change. 

9 If configured sensor is visibility or ceilometer, press ALGOR key to display sensor-algorithm configuration

screen (paragraph 1.3.16.3). Review to ensure that sky/visibility algorithm, primary assignments, priorities,

etc, are correct per system manager specification. 

10 Message SYSTEM MODIFICATIONS is removed when system has accepted change. 

11 Press EXIT key to return to 1-minute screen.

1.3.11 DCP DOWNLOAD

DCP initialization or download can be initiated by the technician via the PROC screen. The technician may

have to reinitialize the DCP after performing preventive or corrective maintenance or as an attempt to correct

a data communication problem within the system (e.g., such as the loss of data from a sensor or DCP).

System initialization is performed automatically when power is applied to the system. The DCP's are

initialized by performing the procedures provided in table 1.3.24. For systems with multiple remote DCP's,

performing a download to a system interrupts ACU communication with all others (until the download is

complete).
S100 ASOS Site Technical Manual

1-61

Table 1.3.24. DCP Download Procedures 

Step Procedure

1 At OID 1-minute screen, sign on as a technician. The MAINT key is displayed in the keypad area of the OID.

2 Press MAINT key. The OID displays the maintenance screen. 

3 Using PREV/NEXT keys, position the cursor over the PROC field and press SEL key. The OID displays the

processor status screen. 

4 Using PREV/NEXT keys, position the cursor over the selected DCP HARD field and press RESET key. The

respective status field displays INITIALIZING while the unit is initializing. The progress of the download

can be monitored by the PERCENT COMPLETE message displayed at the top of the screen. When the

download is complete, the DCP status field changes to RUNNING. 

5 Using EXIT key, return to 1-minute screen.

1.3.12 REVIEWING/PRINTING THE SYSTEM MAINTENANCE LOG

The system maintenance log contains maintenance data for the previous 31 days and the current day. A

four-digit error code is associated with each message that appears in the system log. The ASOS Software

Users Manual contains a complete listing by error code number of allsystem log error messages. Any ASOS

operator can review and print the system maintenance log one screen at a time without being signed on the

system. The entire log or portions of the log can be printed using the processor status (PROC) screen. Only

operators signed on as technicians or managers can change or add entries to the maintenance log. To

review/print the system maintenance log data from the system log screen, the procedure provided in

table 1.3.25 is performed. To print the complete system maintenance log or selected portions of the log, the

procedures provided in table 1.3.26 are performed using the processor status screen. 

Table 1.3.25. Reviewing/Printing the System Maintenance Log From the System Log Screen

Step Procedure

1

NOTE

A listing of the system log maintenance error codes is provided in the ASOS Software

User's Manual, Section 4. 

At 1-minute screen, press REVUE key. The OID displays the REVIEW keypad on the OID. 

2 Press SYSLG key. The OID displays the system log screen. 

3 Using PREV/NEXT keys, page through the maintenance data. 

4 To view the maintenance data for a specific date, press DATE key. The system displays the ENTER DATE:

MM/DD/YY prompt. Enter the desired date and press RETURN. The OID displaysthe maintenance log data

starting at the date specified. 

5 To search for maintenance codes, specific dates, or recent days, press FILTR key. The

Review-SYSLOG-FILTRfunction promptsthe user to enter a maintenance code,specific date, orrecent day.

After entering the desired filter values, press BACK key and if a match is found, that portion of the

maintenance log is displayed. When selecting specific date(s) on the filter screen, month and year must be

included (e.g., 03/01/91 and 03/05/91). 

6 To print the maintenance log data displayed on the OID, press PRINT key. The maintenance log data

displayed on the OID is printed on the printer.

7

NOTE

Maintenance log data can only be printed one OID screen at a time. Refer to table 1.3.26

to print larger portions. 

Press EXIT key to return to 1-minute screen.
ASOS Site Technical Manual S100

1-62 Change 1

Table 1.3.26. Printing the System Maintenance Log

Step Procedure

1

NOTE

A listing of the system log maintenance error codes is provided in the ASOS Software

User's Manual, Section 4. 

At OID 1-minute screen, sign on as a technician. The MAINT key is displayed in the keypad area of the OID.

2 Press MAINT key. The OID displays the maintenance screen. 

3 Using PREV/NEXT keys, position the cursor over the PROC field and press SEL key. The OID displays the

processor status screen. 

4 Using PREV/NEXT keys, position the cursor over the START PRINT field and press CHANG key. 

5 Enter the error number where the systemmaintenance log printout isto begin and press RETURN. The cursor

movesto the END PRINT field. Enter the error number where the printout isto end and press RETURN. The

requested system maintenance log data are printed on the printer. 

6 Press EXIT key to return to 1-minute screen.

1.3.13 ENTERING DATA INTO THE SYSTEM MAINTENANCE LOG

Data entry to the system maintenance log can only be made by operators who are signed on to the system as

technicians or system managers. The entry can be multiple lines and can be time tagged by using the DATE

function before entering the maintenance comment. The technician should make entries into the system

maintenance log whenever preventive or corrective actions are performed on the system; however, upon

successful repair of an FRU, the diagnostic automatically logs that the FRU has been repaired. Log entries

should clearly define the maintenance action performed. Data are entered into the system maintenance log

using the procedures provided in table 1.3.27. 

Table 1.3.27. Making System Maintenance Log Entries

Step Procedure

1 At 1-minute screen, sign on as a technician or system manager. 

2 At 1-minute screen, press REVUE key. The OID displays the REVIEW keypad on the OID. 

3 Press SYSLG key. The OID displays the system log screen. 

NOTE

If the log entry is being made at the current time, omit step 4. 

4 Press DATE key. The OID displays a prompt for month/day/ year. Enter the selected month (1 to 12), the

selected day of the month (1 to 31), and year and press RETURN. The system displays the log entry for the

date specified on the first line of the log screen. 

5 Press WRITE key, enter message using the OID keyboard, and then press EXIT or BACK. The message can

be a maximum of 200 characters. The entry is recorded in the system log (at the bottom of the log).

1.3.14 REMOTE MAINTENANCE MONITORING

The ASOS provides a remote maintenance monitor (RMM) capability that allows an off-site user, using a

terminal (or personal computer) and a telephone modem, to dial into the ASOS on one of its user ports. When

a call is made to the ASOS, the system requests the user to enter an access code. Depending on how the user

enters the access code, one of four modes may be selected: remote OID mode, direct command mode,

monochrome monitor mode, and ASCII terminal mode. Except for the last mode, a VT-220 (monochrome)

terminal or a VT-320 (color) terminal must be used. A personal computer may also be used, as long as a

VT-220/320 emulation program is employed. Paragraph 1.3.10.2 provides information on setting up serial

communications for an RMM terminal. The following paragraphs provide information on each of the four

available modes. 
S100 ASOS Site Technical Manual

Change 1 1-63

1.3.14.1 Remote OID Mode. This mode is accessed by dialing into the ASOS using a telephone modemand

a VT-320/220 terminal. After the telephone connection is made, the system prompts the user to enter a

remote access code. This code must be properly entered, using all uppercase letters, within 30 seconds. Up

to three attempts may be made. When the access code is properly entered, the 1-minute screen is displayed

and the remote terminal functions as an OID. The user may then operate the system as an unsigned user or

sign on to the system as a technician orsystem manager (observers and ATC's are not allowed from a remote

monitor). The user then has all of the same capabilities as provided by the local OID's, with the exception

that there is no print capability. When the user operates as an unsigned user, the ASOS disconnects the user

if there is no activity for a period of 5 minutes. 

1.3.14.2 Direct Command Mode. The direct command mode allows a remote user to directly access the

data in the various ASOS logs (communications, edit, system, OBS, daily summary log, etc). This mode is $

accessed in the same manner as the remote OID mode, except that the pound sign (#) is typed at the

beginning of the remote access code (#CODE). When the access code is properly entered, a CMD> prompt

is displayed. The user then enters commands as described in table 1.3.28 and the following paragraphs. 

a. All arguments are optional.If no arguments are entered, all entriesforthe selected command

are displayed. Any arguments entered indicate a range of data to be displayed. The default

arguments are as follows: 

start date 01/01/0000

start time 00:00

end date 12/31/9999

end time 23:59

b. For any of the commands where the user can enter dates and times(e.g., OBS, 5MIN, SHEF, $

SYSLOG,LEDWI, THUNDER,COMLOG, ADAS, ALDARS, and EDITLOG commands), $

the following logic applies. If the start date only is entered with the command, the default

start time is used and the end date and time are assumed to be the current system date and

time. If the start date and start time only are entered with the command, the end date and

time are assumed to be the current system date and time. If the start date, start time, and end

date only are entered with the command, the default end time is used. 

c. For the SYSLOG and COMLOG commands, in addition to the date and time arguments, the $

user can also enter a single code or two codes. Any code entry must be directly followed by

a C (i.e., 9999C). Entering a single code value indicates that all log entries with the $

designated code are to be displayed. Entering two code values indicates a range of codes to

be displayed. The user must enter the code value(s) as the last argument(s); however, the

code argument(s) can be entered with any combination of the remainder of the

SYSLOG/COMLOG valid arguments. $

d. For the ARC5MIN command, the user must enter a valid archive index (i.e., 1, 2, or 3).

Archive data are then displayed if available.

e. For the TREND command, the user must enter a valid device number (i.e., 0 = ACU, 1 =

DCP #1, 2 = DCP #2, and 3 = DCP #3). If device is enabled, data are displayed.

f. For any of the commands where the user can only enter dates (i.e., the DAILY and DSM

commands), the following logic applies. If the start date only is entered with the command,

the end date is assumed to be the current system date.
ASOS Site Technical Manual S100

1-64 Change 1

Table 1.3.28. Direct Command Mode Commands

Command Results

NOTE

The following commands can be entered for the direct command mode, where MM indicates a

month, DD indicates a day, HHMM indicates a time, I indicates an archive index, and CODE 1

and CODE2 indicate SYSLOG code:

12HR1 HHMM HHMM Outputs 12-hour screen one data.

12HR2 HHMM HHMM Outputs 12-hour screen two data.

12HRP HHMM HHMM Outputs 12-hour 15-minute precipitation data.

12HRC1 HHMM HHMM Outputs 12-hour ceilometer #1 data, if ceilometer #1 is configured.

12HRC2 HHMM HHMM Outputs 12-hour ceilometer #2 data, if ceilometer #2 is configured.

12HRC3 HHMM HHMM Outputs 12-hour ceilometer #3 data, if ceilometer #3 is configured.

12HR HHMM HHMM Outputs all 12-hour data.

5MIN MMDD HHMM MMDD HHMM Outputs 5-minute observation data. 

$ ADAS MMDD HHMM MMDD HHMM Outputs ADAS summary data.

$ ALDARS MMDD HHMM MMDD HHMM Outputs ALDARS lightning data.

ARC5MIN I Outputs archived 5-minute observation data. 

BYE Exits direct command mode.

$ CLOUD HHMM HHMM Outputs cloud layer cover factor data.

$ COMLOG MMDD HHMM MMDD

$ HHMM CODE1 CODE2

Outputs communications log data.

DAILY MMDD MMDD Outputs daily data.

$ DSM MMDD MMDD Outputs Daily Summary Message data.

$ EDITLOG MMDD HHMM MMDD

$ HHMM 

Outputs edit log data.

HELP Outputs help information for the direct command mode.

LEDWI MMDD HHMM MMDD HHMM ASOS maintains a 12-hour archive of present weather sensor

(LEDWI) reports (C command responses). This archive is not

available on normal OID screens, but is available remotely using this

LEDWI command. Refer to Chapter 7 for format of LEDWI C data.

MONTH Outputs monthly data.

$ MSM Outputs Monthly Summary Message data.

$ OBS MMDD HHMM MMDD HHMM Outputs observation data. 

SHEF MMDD HHMM MMDD HHMM Outputs SHEF observation data. 

SYSLOG MMDD HHMM MMDD HHMM

CODE1 CODE2

Outputs system log data.

$ THUNDER MMDD HHMM MMDD

$ HHMM

Outputs thunderstorm sensor data.

$ TREND D Outputs rf communication trend data.

$ XMODEM Toggles from/to Xmodem mode.

g. For any of the commands where the user can only enter times (i.e., the 12-hour and cloud

screens), the following logic applies.If no arguments are entered with the command, the end

date and time are assumed to be the time of the most recent 12-hour archive and the start

date and time are assumed to be the date and time of 13 hours prior to end time. If the start

time only is entered with the command, the end time is assumed to be the time of the most

recent 12-hour archive. 

h. All times entered are assumed to be local standard time. The user must append a Z to the

time entry to access Zulu time. All times, LST or UTC, are converted to the correct type

automatically before data are accessed (i.e., all 12-hour data are displayed with UTC times

and the remainder of the data are displayed with LST times). 
S100 ASOS Site Technical Manual

Change 1 1-65

i. The direct command mode also allows the user to enter any keystroke to exit a command

while data are being output and to use <CTRL Q> and <CTRL S> to stop and startscrolling.

j. For the XMODEM command, the user is prompted to direct DCM data to a file or a screen $

output. $

1.3.14.3 Monochrome Monitor Mode. The monochrome monitor mode is accessed in the same manner

as the remote OID mode, except that a dollar sign ($) is typed at the beginning of the remote access code

($CODE). The monitor then functions as an OID in the same manner as the remote OID mode but without

the color capabilities. 

1.3.14.4 ASCII Terminal Mode. The ASCII terminal mode is accessed in the same manner as the remote

OID mode, except that an asterisk (*) is typed at the beginning of the remote access code (*CODE). This

mode isfor use with all "dumb" terminals. The user has limited available options, which are displayed at the

bottomofthe screen. Number keys are used instead of keypad keys.The information scrolls acrossthe screen

in typical ASOS format excluding borders and colors, and is only available for review (not editing or

changing). When prompted, the user may enter dates and times in MMDD and HHMM format. 

1.3.15 SYSTEM POWER OFF PROCEDURES

Chapters 2 and 3 provide power-off procedures for the ACU/peripherals and the DCP, respectively. Should

it become necessary to power down the entire system, the ACU/peripherals and the DCP's are powered off

according to these procedures. It does not matter in what order the ACU and DCP's are powered down. 

1.3.16 SITE CONFIGURATION SCREENS

Site configuration screen (Figure 1.3.41) provides the technician and system manager access to the

configuration data specific to his site. This screen and its subfunctions can be used by the technician and

system manager as both a source of information and a tool in reconfiguration. The configuration screens

provide five standard key functions. The purpose of each is as follows: 

a. PRINT - Enables the currently displayed screen to be printed on the printer. 

b. PREV/NEXT - Enables the cursor to be moved to the different fields on the currently

displayed screen. 

c. BACK - Causes the previous screen to be displayed. 

d. CHANG - Causesthe screen function to go into an edit mode. After making change, BACK

or EXIT key must be pressed for system to incorporate change.

e. EXIT - Causes the current screen to be exited and the 1-minute screen to be displayed on

the OID. 

Ofspecial interest to the technician isthe sensor(SENSR) and hardware (HDWE) configuration screens. The

sensor screen is used to conFigure the sensor-to-serial I/O port scheme. The hardware screen is used to

identify the number of CPU's, UPS's, A/D's, I/O boards, modems, and video boards in the system. 
ASOS Site Technical Manual S100

1-66 Change 1

11:21:56 07/04/96 1621Z ANYTOWN AIRPORT

CONFIG

HDWE EXTRN

DEFIN SENSR COMMS

EXIT BACK

Figure 1.3.41. Site Configuration Screen

1.3.16.1 Hardware Configuration Screen. The hardware configuration screen (Figure 1.3.42) enablesthe

user to review and change the recorded quantities of CPU's, SIO's, UPS's, video cards, and A/D cards

presently in the ACU and DCP's. The VOICE PORT field permits the location of the FAA handset to be

specified as either OID-1 PRIMARY or OID-2 SECONDARY. This field must be set correctly to permit

entry of voice messages from the respective OID. The CHANG key is used to enter the change mode. The

user can change the hardware quantities using the arrow keys and keyboard. The DCP STATUS and VOICE

PORT fields are changed using the arrow keys and the sequence (SEQN) key. 

11:21:56 11/21/97 1621Z ANYTOWN AIRPORT

 DCP #1 DCP #2 DCP #3

 ACU ENABLED DISABLED DISABLED

 QUANTITIES QUANTITIES

 CPU 2 CPU 2

$ SIO 8 SIO 4

$ UPS 1 UPS 2

$ VIDEO CARD 1 A TO D 2

CONFIG

$ VOICE PORT OID-2 SECONDARY $ PRINT $

CHANG

EXIT BACK

Figure 1.3.42. Hardware Configuration Screen
S100 ASOS Site Technical Manual

Change 1 1-67

1.3.16.2 Sensor Configuration Screen. The sensor configuration screen (Figure 1.3.43) enablesthe user to review and

change the recorded sensor-to-serial I/O port scheme at the DCP's. By pressing the CHANG key, the user can change

the configuration using the arrow keys and the keyboard. The two-character field presented under each I/O port can have

one sensor assigned. A sensor-I/O port assignment is changed by typing over the existing sensor code. A list of sensor

codes is provided in table 1.3.29. Fields are provided to record local sensors and pressure sensors. These fields can be

changed in the same manner as sensor code assignments on the screen. By pressing the ALGOR key on the keypad, the

algorithm configuration screen is displayed. 

11:21:56 11/21/97 1621Z ANYTOWN AIRPORT

 SIO #1 SIO #2 SIO #3 SIO #4 SIO #5

 PORTS 2 3 4 1 2 3 4 1 3 4 1 2 3 4 1 2

 DCP #1 C1 V1 PW TB WS TD FR C2 TS ** $

 DCP #2

 DCP #3

 LOCAL SENSORS

   **  CONFIGURATION

PRINT $

 PRESSURE SENSORS

ALGOR CHANG P1 P2 **

EXIT BACK

Figure 1.3.43. Sensor Configuration Screen

Table 1.3.29. Sensor Codes

Sensor Code Definition

TD Temperature/dewpoint sensor

WS Wind speed/direction sensor

V1-V3 Visibility sensors

SD Snow depth sensor

FR Freezing rain sensor

FP Frozen precipitation sensor

SS Sunshine sensor

C1-C3 Ceilometer sensors

TB Tipping bucket sensors

PW Present weather sensors

TS Thunderstorm sensor $

P1-P3 Pressure sensors $

1.3.16.3 Sensor-AlgorithmConfiguration Screen. The sensor-algorithmconfiguration screen (Figure 1.3.44) enables

the user to review and change the recorded sky and visibility sensor algorithm configurations. These configurations are

single-sensor, backup, and meteorological discontinuity. In addition, the user can review and assign sensor specific

information such as primary and secondary sensors, sensor elevation, location, representative sensor, and priority.

Because setup of algorithms for a particular site is the responsibility of the system manager, the technician should make

no change to thisscreen except under direction of the system manager. Additional information on sensor algorithms can

be obtained from the ASOS User's Guide (an NWS publication) or by contacting the system manager. 
ASOS Site Technical Manual S100

1-68 Change 1

3:18:40 11/21/97 1818Z ANYTOWN AIRPORT

$ SKY ALGORITHM:

PRIM SENSOR #: 1 MET DISC SENSOR #: 2 BACKUP SENSOR #: 3

 ELEVATION: 277 ELEVATION: 277 ELEVATION: 277

 LOCATION: N LOCATION: E

$ VISIBILITY ALGORITHM:

PRIM SENSOR #: 1 MET DISC SENSOR #: 2 BACKUP SENSOR #: 3

 LOCATION: N LOCATION: E

ALGORITHM

PRINT

CHANG

EXIT BACK

Figure 1.3.44. Sensor-Algorithm Configuration Screen

1.3.16.4 Define Configuration Screen. The define configuration screen (Figure 1.3.45) enables the user

to review and change the recorded sensor and hardware configurations and types. New definitions should

be made only in conjunction with an actual change of hardware or other sensors. For the sensors and

hardware items, the configuration type, model number, or vendor is listed. By pressing the CHANG key,

the user is presented with a change keypad. The PREV/NEXT keys are used to select the field to be

changed. When the field to be changed is highlighted, a SEQN key on the change keypad is used to

sequence through all of the allowable entries for that field. When the new entry is displayed, the screen

can be exited and the new entry remains in the field. 

13:14:23 11/21/97 1814Z ANYTOWN AIRPORT

DEFINE CONFIGURATION

 SENSORS HARDWARE

 CEILOMETER PHASE I ACU MEMORY 1 MEGABYTE

 VISIBILITY BELFORT ASOS DCP MEMORY 1 MEGABYTE

 TEMP/DEW POINT 1088 RS 232 MODEM UDS

 PRESENT WX LEDWI SYNCH MODEM UDS

 WIND BELFORT ASOS ACU/DCP COMM PHASE I RADIO

 PRESSURE SETRA MODEL 470 RT CLOCK VIDEO CARD

 FREEZING RAIN PHASE II ACU POWER SUP ASTEC

 SNOW DEPTH PHASE II DCP POWER SUP R.O. ASSOC.

 HAIL PHASE II ACU UPS CPI

 SUNSHINE PHASE II DCP UPS CPI

 LIQUID PRECIP BELFORT ASOS GTA RADIO MOTOROLA VT-200

$ THUNDERSTORM LLP TSS 924 DEFINE CONFIG

PRINT

CHANG

EXIT BACK

Figure 1.3.45. Define Configuration Screen
S100 ASOS Site Technical Manual

Change 1 1-69

1.3.16.5 ACU Serial Communications Screen. The ACU serial communications screen (Figure 1.3.46)

provides access to the configuration and parameter data for each of the serial I/O communication ports.

This screen provides the recorded equipment-to-I/O port scheme currently in use in the system. The SIO

key is used to move the cursor to the next I/O port. By pressing the CHANG key, the user can change

data on the display using the keyboard. The equipment-to-I/O port scheme recorded for software use and

the hardware configuration must match for proper communication operations. In addition, the ACU serial

communications screen provides fields for communication status, baud rate, parity select, bits/character,

and stop bits for the configuration of any desired communication scheme. When configuring a GTA radio

to the ACU, there are two fields that must be completed: FREQUENCY and POWER LEVEL. These

two fields are mandatory and must be completed before exiting the COMMS screen. These fields may

also be changed at the front panel of the radio; when this is done, the ACU copies and reads the current

setting and stores it as a final setting and displays it on the ACU serial communications screen. The

figure applies only to systems operating application software version 2.1 or higher. For earlier versions,

radio adjustments must be made manually at the radio. 

13:19:45 07/04/96 1819Z ANYTOWN AIRPORT

PORT MOD FUNCTION PORT MOD FUNCTION PORT MOD FUNCTION

 1-1 4-1 UPS 7-1 GTA RADIO

 2 2 PRESSURE #3 2 VDU-1

 3 3 OID-2 SECONDARY 3 VDU-2

 4 4 PRINTER 4

 2-1 ACU-DCP A 5-1 LOCAL SENSOR #1 8-1

 2 PRESSURE #1 2 LOCAL SENSOR #2 2

 3 1 OID-4 USER #1 3 LOCAL SENSOR #3 3

 4 VOICE 4 LOCAL SENSOR #4 4

 3-1 ACU-DCP B 6-1 LOCAL SENSOR #5

 2 PRESSURE #2 2 LOCAL SENSOR #6

 3 2 OID-3 SECONDARY 3 LOCAL SENSOR #7

 4 OID-1 LOCAL 4 LOCAL SENSOR #8

 FUNCTION ACU-DCP A

 STATUS ENABLED HANDSHAKE RTS/CTS ACU SERIAL COMMS

 BAUD RATE 2400 CONNECTION RADIO

PRINT PREV

 PARITY SELECT NONE

 BITS/CHAR 8 SIO CHANG STOP BITS 1

EXIT BACK NEXT

Figure 1.3.46. ACU Serial Communications Screen

1.3.16.6 External Communications Screen. The external communications screen (Figure 1.3.47)

enables the user to review and change external communication information. This information is used by

the system software in communication with the various ASOS customers. The communication consists of

user address and codes, product type, message formats, and transmission parameters. By pressing the

CHANG key and using the keyboard, the user can change the external communications data fields. The

PRODUCT ID is automatically set depending on site commissioning status (site physical screen). 
ASOS Site Technical Manual S100

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08:28:48 11/21/97 1528Z ANYTOWN AIRPORT

 STATION ID (XXX): ANY WMO IDENTIFIER: KANY

 FORECASTOFFICE (CCC): ITB PRODUCT ID (NNN): MTR

AFOS: 15-MIN SHEF ID (NNN): RR6

 ADDRESS: RDC 1-HOUR SHEF ID (NNN): RR7

$ 15-MIN SHEF ADDRESS: DSM/MSM PRODUCT ID: DSM / MSM

 1-HOUR SHEF ADDRESS: ADAS:

 STATION IDS/PHONE NUMBERS ASOS ADDRESS: 100

$ STATION 1: ADAS TIMEOUT (SEC): 360

 12015551212 TCCC:

 STATION 2: TCCC ADDRESS: 100

 12015551213 AOMC:

 STATION 3: PRIMARY PHONE NO: 9,5551215

 12015551214 SECONDARY PHONE NO:

 MESSAGE FORMAT TYPE: I AOMC 1200 BAUD: NO

 PARITY SELECTION: NONE EXTERNAL

 REPLY REQUEST: NO

PRINT BUSY ATTEMPT TIME: 1

$ SEND REPLY TIME(SECS): 120 CHANG $ RECV REPLY TIME(MINS): 2

 BACKUP FOR ADAS: NO

EXIT BACK

Figure 1.3.47. External Communications Screen

1.3.17 SITE SCREENS

In addition to the site configuration screens, the technician can access the five other types of site screens. The

technician has the capability to review the site specific information on the physicals (PHYS), version (VERSN),

normals (NORML), pressure (PRESS), and criteria (CRIT) screens. These site specific screens are described in the

following paragraphs. 

1.3.17.1 Site Physical Screen. The site physical screen (Figure 1.3.48) provides access to the site specific physical

characteristics. In addition, the report time, edit time, transmit time, and SHEF transmit times are provided. Only the

system manager and technician can make changes to this screen. Only the system manager can make changes to the

“COMMISSIONED:” field.

08:28:48 11/21/97 1528Z ANYTOWN

AIRPORT

STATION

 NAME: ANYTOWN AIRPORT

 IDENTIFIER: LHX DATE: 12/19/91

 COMMISSIONED: NON TIME: 15:27:56 UTC

 ATTENDED: NO UTC TO LST OFFSET: -7

 OPEN 24 HOURS: YES METAR SWITCH DATE: 06/01/96 UTC

 OPENING TIME: METAR SWITCH TIME: 00:00:00 UTC

$ CLOSING TIME: DSM GENERATED: YES

$ ELEVATION: 4215 FEET PRIMARY DSM XMIT TIME: UTC

$ INTERMED DSM XMIT TIMES: UTC

$ FIELD ELEVATION: 4226 FEET UTC

$ PRESSURE SENSOR ELEVATION: 4193 FEET UTC

$ MSM GENERATED: YES

$ OBS HOURLY REPORT TIME: 55 MSM XMIT TIME: UTC

OBS EDIT TIME: 5:00 PHYSICAL

$ OBS HOURLY TRANSMIT TIME: 55:00 $ PRINT $ SHEF HOURLY TRANSMIT TIME: 22

$ LATITUDE: 38:57N $ CHANG $ LONGITUDE: 77:27W

$ MAG DECLINATION: 9W

EXIT BACK

Figure 1.3.48. Site Physical Screen
S100 ASOS Site Technical Manual

Change 1 1-71

1.3.17.2 Site Version Screen. The site version screen (Figure 1.3.49) provides access to software version (SW),

sensor firmware version (SENSR), and AOMC communications (AOMC) information. The SW screen $

(Figure 1.3.50) provides the current versions of software being used in the ASOS at the site. These fields are

automatically updated by the system. The sensor firmware version screen (Figure 1.3.51) provides an indication of $

the version of sensor firmware being used in the ASOS. An identifier consisting of up to seven characters is provided $

for each sensor. This identifier can be changed by pressing the CHANG key. The AOMC screen (Figure 1.3.52) $

provides access to AOMC communications information, consisting of upload/download statuses and dates. During

system operation, all changes made to the site specific screens are put in files to be routed to the AOMC for

recording purposes. When a file is pending, an upload request is displayed in the STATUS field. The technician or

system manager can manually upload or download this information if desired. Records of system changes can be

obtained from the AOMC. By using the PREV/NEXT keys, the user can select a desired field. Then, using the

UP-LD key, the user can cause an upload of status data (transmit to the AOMC). Using the DN-LD key, the user can

cause a download of status data (to the ASOS ACU). The CNCL key allows the user to cancel events that are not in

progress on the current cursor line. Automatic events cannot be canceled. If an observer or air traffic controller is

signed on to the system, downloads cannot be performed. 

08:28:48 11/21/97 1528Z ANYTOWN AIRPORT

VERSION

SW AOMC SENSR $

EXIT BACK

Figure 1.3.49. Site Version Screen

08:28:48 11/21/97 1528Z ANYTOWN AIRPORT

UNIT BOARD NAME DEVICE VERSION DATE

ACU CPU A PSOS OS EPROM 1.81 03/07/95

 CPU B PSOS OS EPROM 1.81 03/07/95

 MEMORY ACU APPLICATION EPROM 2.52 11/24/97 $

 MEMORY DCP APPLICATION EPROM 2.52 11/24/97 $

DCP-1 CPU A BOOT EPROM 1.90 11/03/97 $

 CPU B BOOT EPROM 1.90 11/03/97 $

 MEMORY DCP APPLICATION RAM 2.52 11/24/97 $

DCP-2 CPU A BOOT EPROM 1.90 11/03/97 $

 CPU B BOOT EPROM 1.90 11/03/97 $

 MEMORY DCP APPLICATION RAM 2.52 11/24/97 $

SOFTWARE VERSIONS

DCP-3 CPU A BOOT EPROM 1.90 11/03/97 $

PRINT $

 CPU B BOOT EPROM 1.90 11/03/97 $

 MEMORY DCP APPLICATION RAM 2.52 11/24/97 $

EXIT BACK

Figure 1.3.50. SW Screen

$
ASOS Site Technical Manual S100

1-72 Change 1

$ 8:28:48 11/21/97 1528Z ANYTOWN AIRPORT

$ SENSOR FIRMWARE VERSION

$

$ CEILOMETER XXXXXXX

$ VISIBILITY XXX

$ TEMP/DEW POINT XXXXX

$ PRESENT WX XXXXX

$ WIND XXXXXX

$ PRESSURE XXXXXXX

$ FREEZING RAIN XXXXXXX

$ LIQUID PRECIP XXXXX

$ THUNDERSTORM XXXXXX

$

$

$

$ FIRMWARE VERSION

$

$ PRINT $

$

$ CHANG $

$

$ EXIT BACK $

$ Figure 1.3.51. Sensor Firmware Version Screen

08:28:48 11/21/97 1528Z ANYTOWN AIRPORT

 DATA FILE STATUS LAST UPLOAD LAST DOWNLOAD

 SITE NORMAL COMPLETE 11/20/91 11:37:58

 PHYSICAL COMPLETE 11/20/91 09:38:01

 PRESSURE COMPLETE 11/20/91 09:38:11

 CRITERION COMPLETE 07/04/96 13:05:25 11/20/91 09:38:11

 CONFIG DEFINES COMPLETE 11/20/91 11:37:22

 RS-232 COMM COMPLETE 12/14/91 15:02:21 11/20/91 09:40:17

 SENSORS AUTO UPLOAD REQ 07/04/96 13:05:38

 HARDWARE AUTO UPLOAD REQ 07/04/96 13:04:11

 EXTERNAL COMM COMPLETE 07/04/96 13:05:51

 CMD VOICE/PASSW AUTO UPLOAD REQ

 VOICE AIRPORT NAME COMPLETE

$ VERSN SENSOR COMPLETE

AOMC COMMS STATUS

$

$ PRINT UP-LD PREV $

$

CNCL DN-LD $

EXIT BACK NEXT

Figure 1.3.52. AOMC Screen
S100 ASOS Site Technical Manual

Change 1 1-73

1.3.17.3 Site Normals Screen. The site normals screen (Figure 1.3.53) provides access to the site specific normals

for various weather parameters. Site normal data for 12 months are stored. Only the system manager can make

changes to this screen. 

08:28:48 11/21/97 1528Z ANYTOWN AIRPORT

 NORMALS FOR OCTOBER

DAY TMIN TMAX TAVG SUN DAY TMIN TMAX TAVG SUN DAY TMIN TMAX TAVG SUN

 1 49 74 61 708 11 44 70 57 683 21 40 66 53 659

 2 48 74 61 705 12 44 70 57 681 22 40 66 53 656

 3 48 73 61 703 13 43 69 56 678 23 40 65 53 654

 4 47 73 60 700 14 43 69 56 676 24 40 65 52 652

 5 47 72 60 698 15 43 68 55 673 25 39 64 52 649

 6 46 72 59 695 16 42 68 55 671 26 39 64 51 647

 7 46 72 59 693 17 42 68 55 668 27 39 64 51 645

 8 46 71 58 690 18 42 67 54 666 28 38 63 51 642

 9 45 71 58 688 19 41 67 54 663 29 38 63 51 640

10 45 70 57 685 20 41 66 54 661 30 38 62 50 638

 $

MONTHLY NORMAL HEATING DEG DAYS: 307 AVG/SUM: 42 68 55 20802 $

MONTHLY NORMAL COOLING DEG DAYS: 7 NORMALS

MONTHLY NORMAL PRECIP: 3.01

PRINT PREV SEASON HEATING DEGREE DAYS: 2915

SEASON COOLING DEGREE DAYS: 455

EXIT BACK NEXT

Figure 1.3.53. Site Normals Screen

1.3.17.4 Site Pressure Screen. The site pressure screen (Figure 1.3.54) provides access to the site specific pressure

data. Only the system manager can make changes to this screen.

13:10:48 11/21/97 1810Z ANYTOWN AIRPORT

PRESSURE REDUCTION RATIO (R)

 TEMP R TEMP R TEMP R TEMP R

 -70 1.0111 -65 1.0111 -60 1.0111 -55 1.0111

 -69 1.0111 -63 1.0111 -59 1.0111 -54 1.0111

 -68 1.0111 -63 1.0111 -58 1.0111 -53 1.0111

 -67 1.0111 -62 1.0111 -57 1.0111 -52 1.0111

 -66 1.0111 -61 1.0111 -56 1.0111 -51 1.0111

PRESSURE REDUCTION CONSTANT: 0.0000 PRESSURE

PRINT PAGE $

EXIT BACK

Figure 1.3.54. Site Pressure Screen

1.3.17.5 Site Criteria Screen. The site criteria screen (Figure 1.3.55) consists of three screens that define the

conditions that cause automatic special alerts, local alerts, and SHEF alerts to be generated by the system. By using

the PAGE key, the user can move between three screens in a circular fashion. Only the system manager can make

changes to this screen. 
ASOS Site Technical Manual S100

1-74 Change 1

08:28:48 11/21/97 1528Z ANYTOWN AIRPORT

CRITERIA FOR SPECIAL ALERTS

 SKY CONDITION:

 CEILING AT OR BELOW 3000 1500 1000 500 FEET

 USER’S CEILING AT OR BELOW 600 800 0 0 0 0

 LAYERS BELOW 1000 FEET

 USER’S LAYERS BELOW 800 0 0 0

$ VISIBILITY: 3 2 1 MILES

$ USER’S VISIBILITY 1/2 3/4 1 1/4

 RVR: 2400 FEET CRITERIA

$

$ PRINT PAGE $

EXIT BACK

Figure 1.3.55. Site Criteria Screen (Sheet 1 of 3)

13:10:48 11/21/97 1810Z ANYTOWN AIRPORT

CRITERIA FOR LOCAL ALERTS

 SKY CONDITION:

 CEILING AT OR BELOW 0 0 0 0 0 0 FEET

$ VISIBILITY: 1/2 MILES

CRITERIA

$

$ PRINT PAGE $

EXIT BACK

Figure 1.3.55 Site Criteria Screen (Sheet 2)

13:10:48 01/07/92 1810Z ANYTOWN AIRPORT

CRITERIA FOR SHEF ALERTS

 15-MINUTE ONSET THRESHOLD: 0.40 INCHES

 15-MINUTE TERMINATION THRESHOLD: 0.02 INCHES

CRITERIA

$

$ PRINT PAGE $

EXIT BACK

Figure 1.3.55. Site Criteria Screen (Sheet 3)
S100 ASOS Site Technical Manual

Change 1 1-75

SECTION IV. SYSTEM THEORY OF OPERATION

1.4.1 INTRODUCTION

This section describes the ASOS at the system level. Detailed information on the various subassemblies

is provided in the specific Chapter for that subassembly. Each ASOS is configured to meet the specific

requirements of a given site. Configuring a system entails identifying the specific sensors required and

the number and types of users that are to have access to the system. Regardless of the type of

configuration, the ASOS always contains four major units: acquisition control unit (ACU), data

collection package (DCP), sensors, and peripherals. Figure 1.4.1 illustrates a typical ASOS configuration.

ASOS configurations differ in the number of each component contained in the configuration. The major

differences are in the number of DCP's, sensors, and peripherals at the site. Regardless of the

configuration, each site is provided with only one ACU. There are two major types of ASOS systems: 

Class I and Class II. Class I systems are designed for small airports. Class II systems are designed for

larger, towered airports. Class II systems are provided with uninterruptible power supplies (UPS's) and $

UPS bypass circuits for the ACU and DCP(s) and redundant components in the ACU. $

1.4.2 ACQUISITION CONTROL UNIT (ACU)

The ACU is the central controlling element of the ASOS. It receives weather information from the

sensors via the DCP. The ACU processes the weather data via weather reporting algorithms and makes

these data available to the various users via the peripheral devices attached to the system. In Class II

systems, the ACU is equipped with the auxiliary UPS backup power supply. In addition, the Class II

ACU contains redundant rf modems or line drivers for increased system availability. 

1.4.3 PERIPHERALS

The peripheral devices consist of one to three operator interface devices (OID's), one to four video

display units (VDU's), one to nine controller video displays (CVD's), an FAA handset, and a printer. In

addition to these ASOS peripherals, the ACU may be equipped with a video driver option that allows it

to provide a video signal for distribution to up to 50 non-ASOS airline displays. All other output from the

system is via direct connection (hardwire) or modems, which are connected to the ACU via telephone

lines. The modem interface also services the AFOS. The OID is the primary operator input/output device

for the system. The observer uses the OID to monitor the weather data being reported by the system.

Observers also use the OID to enter weather observations into the system and to request weather

summaries from the system. The technician uses the OID to check system status, to reconFigure the

system, and to run the on-demand diagnostic test on specific elements of the system. The VDU and CVD

are display devices that provide weather data to other users of the system such as the air traffic

controllers (ATC's). The CVD's serve ATC's in the tower and the VDU's can be located throughout the

airport to be used by the various personnel. A digitized voice output is routed to a local transmitter,

which provides local weather and pressure data to pilots using the airport. The FAA handset enables

ATC's to augment messages onto the automatically generated digitized voice output of weather data. The

printer is the hard copy device for the system. It provides a hard copy output of data such as weather

summaries, observations, and log messages. The log messages identify the system status and changes $

made to the METAR observation by the observer. The system maintenance log provides the technician $

with the maintenance history of the system and provides the results of each self-test performed on the

system. If a unit in the ASOS fails its self-test, the log indicates the cause of the failure. 
ASOS Site Technical Manual S100

1-76 Change 1

Figure 1.4.1. Typical ASOS Configuration - Basic Block Diagram

1.4.4 DATA COLLECTION PACKAGE (DCP)

The DCP processes the weather data being received from the sensors and transfers the data to the ACU.

The DCP also controls both primary and heater sensor power. The system can utilize two types of DCP's:

a local and a remote. The remote DCP's are located on the sensor pads. Each remote DCP has the data

handling capability to support up to 16 sensors. However, the remote DCP optional UPS can only

$ provide power to nine sensors. Therefore, when using more than nine sensors on a sensor pad, an

auxiliary box (62828-40370) is required. The optional auxiliary box, which is considered part of the

remote DCP, contains the additional UPS. Many sites are equipped with more than one remote DCP.

When more than one remote DCP is used, they are usually placed at different locations at the airport with

some installed near the runways and one installed in the center of the airport. The units installed near the

runway are called touchdown zone DCP's. The units in the center of the airport are called the "combined

zone sensor group". At some sites, redundant ceilometer and visibility sensors are added to the combined

group to function as a backup sensor group.

DCP's and sensors installed in areas of meteorological discontinuity are called METDISCON Sensor

Groups (MDSG). Communications between the different DCP's are controlled by the ACU.

Communications between the ACU and DCP's are accomplished primarily via rf modems. The system

also has the capability of a direct wire hookup between the DCP's and the ACU. The local DCP is a

function contained within the ACU cabinet. The local DCP gives the ACU the capability of directly

$ controlling sensors. The pressure sensors in all of the systems are normally located in the ACU cabinet

$ (due to site specific requirements, pressure sensors may be located in the DCP). In addition to the

pressure sensors, the ACU can also handle up to three additional sensors via the local DCP. These

sensors are connected to the rear of the ACU via fiberoptic modems. 
S100 ASOS Site Technical Manual

Change 1 1-77

1.4.5 SENSORS

The sensor complement, like most other system components, reflects the requirements of the individual

sites. Some sites may be provided with more than one of the same type of sensor to function as

METDISCON or BACKUP sensors. The cloud height and visibility sensors are often duplicated at a site,

with a maximum of three each possible; PRIMARY (designated as C1 and V1), METDISCON

(designated as C2 and V2), and BACKUP (designated as C3 and V3). Usually, each touchdown zone is

provided with its own cloud height and visibility sensor. This ensures that the cloud and visibility

conditions at that specific runway are being reported accurately. 

Some airport sites will experience meteorological phenomena which are peculiar to one runway approach

only. At such locations, a meteorological discontinuity (METDISCON, or MDSG) sensor group will be

located, consisting of a DCP and three sensor pedestals. The MDSG is similar to the standard touchdown

zone installation (62828-40107), but the sensor complement will consist of a visibility sensor, a

ceilometer, or possibly, both. The MDSG DCP communicates with the ACU via UHF modems. 

1.4.6 ASOS OPERATION AND MONITORING CENTER (AOMC)

1.4.6.1 ASOS/AOMC Interface. The ASOS Operation and Monitoring Center (AOMC) is the central

monitoring and maintenance computer for all NWS ASOS sites. The AOMC performs three functions for

every NWS ASOS: the monitoring of ASOS hardware trouble, the maintenance of site specific data, and

ASOS time synchronization. 

1.4.6.2 ASOS Trouble Monitoring. The AOMC monitors all ASOS METAR’s through an NWS

computer system known as the gateway. If a particular ASOS outputs a maintenance flag ($) in METAR

or if the AOMC fails to receive a METAR during the proper time period, the AOMC notes a hardware

problem with that ASOS site. The AOMC operator then uses a remote maintenance monitor to further

investigate the problem and then notifies the appropriate maintenance personnel. 

1.4.6.3 ASOS Site Specific Data. For each NWS ASOS site, the AOMC maintains the latest

configuration of site specific data. The site specific data are contained in four site files, six configuration $

files, a command file, and a voice file as follows: 

a. Site - Normals

b. Site - Physicals

c. Site - Pressure

d. Site - Criterion

e. Configuration - Definitions

f. Configuration - RS-232 communications

g. Configuration - Sensors

h. Configuration - Hardware

i. Configuration - Externals

j. Configuration - Sensor Firmware Version $

k. Command - Voice/password

l. Voice - Airport name
ASOS Site Technical Manual S100

1-78

1.4.6.3.1 File Upload and Download. Site specific files can be either uploaded from the ASOS to the

AOMC or downloaded from the AOMC to the ASOS. Uploading and downloading is always initiated by

the ASOS (it places a phone call to the AOMC and requests a download or an upload). The ACU may

initiate an upload or download sequence automatically. For example, the ASOS initiates an upload after a

technician changes system configuration via the OID, or initiates a download request if it detects a loss of

site data. An upload or download may also be initiated manually via the site version - AOMC screen at

the OID (paragraph 1.3.17.2). 

1.4.6.3.2 Upload/Download Sequence. The ACU has between two and five telephone modems

dedicated to remote OID's (user ports 1 and 2, user spare ports 1 and 2, and the spare OID port). The

ACU uses these telephone modems to place calls to the AOMC. When an upload or download sequence

has been initiated (either automatically or manually), each available (not in use) OID modem places a

call every 2 minutes until a connection to the AOMC is made. After the connection is made, the ACU

either uploads files to the ACU or requests a file download from the AOMC. 

1.4.6.4 ASOS Time Synchronization. Each ASOS has an internal software clock. All ASOS software

clocks are synchronized to a time standard provided by the automated computer time service (ACTS).

The time synchronization of the ASOS clocks is accomplished with the aid of the AOMC. 

1.4.6.4.1 AOMC Interface to ACTS. The AOMC communicates with the ACTS to keep its own

internal software clock in synchronization with the time standard. Individual ASOS sites call the AOMC

as required to synchronize their internal software clocks. 

1.4.6.4.2 ASOS Synchronization Sequence. The ASOS time synchronization sequence begins when the

ACU is powered up or when an observer presses the RESET key on the edit screen. At first, the ACU

uses a hardware real-time clock (contained on the ACU memory board) as a default clock. As soon as

possible after the power up or reset, the ACU calls the AOMC to obtain the current standard time. The

ACU then initializes its software clock with the AOMC time and stops using its default hardware clock.

Ten hours later, the ACU again calls the AOMC to check its software clock against the standard time.

Based on the difference between the software clock and AOMC time, the ACU introduces a correction

factor into its software clock to adjust its accuracy. One week later, the ACU again calls the AOMC for a

time check and further adjusts its software clock. From this point, the ACU calls the AOMC once every 2

months to check and adjust its software clock. 
S100 ASOS Site Technical Manual

Change 1 1-79

WARNING

SECTION V. SYSTEM MAINTENANCE

Before attempting to service any ASOS equipment, the technician must perform the

following: 

Upon arrival at an airport, notify airport security and gain access to the

system by following local procedures. 

Adhere to all airport traffic regulations. 

Before crossing any runway, radio the tower and request clearance. 

Proceed only with clearance, and only after illuminating the caution light

mounted on top of your vehicle.

1.5.1 INTRODUCTION

This section contains corrective and preventive maintenance procedures for the ASOS. Preventive

maintenance identifies the quarterly and semiannual tasks required to keep the ASOS in peak operational

condition. Corrective maintenance provides detailed procedures for performing the system diagnostic test,

performing fault isolation, and removing and installing FRU's. The system diagnostic test is continuously

running and automatically prints system status that identifies the operational status of the system after each

cycle of the self-test. If the self-test detects a failure, the suspected FRU is identified in the system maintenance

log and printed on the printer. The technician's first step in system repair is to replace the indicated FRU. If the

system does not identify an FRU, the corrective maintenance table in this section is then used to isolate to a

faulty FRU. Table 1.5.1 lists the tools and test equipment required to perform maintenance on the system.

These are the preferred items that the technician should have available to perform maintenance on the system.

If the specific item listed in the table is not available, an equivalent item may be substituted. The specific tools

required for removal and installation of each FRU are specified within each procedure. Table 1.5.2 lists the

required consumables needed to maintain the ASOS. Although the Source column in table 1.5.2 provides a

recommended source for some of the items, the technician can substitute an equivalent product. 

1.5.2 MAINTENANCE ACTION RECORDING AND DOCUMENTATION

Whenever the technician performs maintenance tasks, all actions must be documented in the system

maintenance log. For the purpose of entering unit/assembly or modification kit identification numbers, the

process is initiated by the ACT key of the maintenance screen keypad. Next, the technician continues entry

process to the system maintenance log by activating the START key of the maintenance action screen

(paragraph 1.3.4.40), then performs the specified maintenance action under preventive maintenance, corrective $

maintenance, calibration, or field modification kit installation. When all actions are completed, the technician

accesses the corresponding PM, CM, CAL, or FMK screens (paragraphs 1.3.4.41 through 1.3.4.44) and enters $

appropriate identification numbers, which, in turn, are written to the system maintenance log. The technician

can write corresponding maintenance messages to the log at any time during the process by accessing the

SYSLG screen (paragraph 1.3.13). Table 1.5.3 provides a sequence to be followed when specified

maintenance tasks are to be performed by technicians at ASOS sites. In addition, the sensor firmware version $

screen allows the current version of sensor firmware to be documented (changed) if required by the specified $

maintenance action. $
ASOS Site Technical Manual S100

1-80 Change 1

Table 1.5.1. Tools and Test Equipment

Item Description Part No./Model No.

1 Common handtools (i.e., wrenches, screwdrivers,

nut drivers)

2 Digital multimeter (DMM) Fluke 77

3 Laptop computer ZEOS 286 (minimum)

4 PROCOMM software PROCOMM Plus, Datastorm Tech.

5 Precision torque gauge PN SO-3, SEEKONK Mfg.

6 STI LEDWI calibration kit Model STI200, Scientific Technology, Inc.

7 PorTable pressure standard Model 760-16B, Paroscientific, Inc 

8 Ceilometer calibration reflector Model CT-16, Vaisala, Inc.

9 RF UHF to BNC adapter (MIL-SPEC) MIL-SPEC 9183 UG-20/A/U 

10 Visibility sensor calibration kit 32041, Belfort Equipment Company

11 Black Box (Mini Sam)RS-232 Test Tool Model TS153B

12 Magnetic compass S&Y 183, Stocker and Yale

13 Laptop Interface cable 62828-90314-2

14 Laptop Null cable 62828-90314-1

15 Adapter - DB9 (male) to DB25 (female) Black Box TR-FA601

16 Adapter - DB9 (female) to DB25 (male) Black Box TR-FA600

17 In-line rf power meter Bird model 43 (with BNC connectors)

18 RF meter plug-in module Bird model 5d

19 Sun program disk (wind alignment)

20 Wind alignment tool CIMTECH 2767

21 Psychrometer Belfort 556-8

22 Laboratory beaker Fischer Scientific Model 2-540 (NSN 6640-00-264-8323)

23 Cable, RF (N to N) 62828-42016-30

24 Cable, RF (BNC to N) 62828-42024-30

$ 25 Davis Pelorus Instrument Davis Instrument Corp. Model 031

$ 26 Spotting Scope (Monocular) Bushnell Corp. Model 78-1545 (or equiv.)

27 Alignment protractor

$ 28 Tripod Bogen Photo Corp. Model G120 w/G1171 Head

29 Dual speed F420 wind speed calibrator ASN F850A-1

30 Ribbon Cable, Audio Adj 62828-42037

31 50 Ohm Load Bird 8362NM

32 Meter Element Bird 25-C (6625-00-980-8255)

33 Oscilloscope Tektronix TAS485 (6625-00-548-8181)

34 RF Frequency Counter HP5384A/34110/A

35 RF Load Sampler Bird 4274-025 (6625-01-080-5452)

36 Meter Element Bird 110-1 (6625-00-502-7502)

$ 37 Extender Board, VME Dawn VME Products 20800-188

38 Test Cable, BNC to BNC 62828-42046

39 Scanner w/AC Adapter Radio Shack PRO 36/273-1455 or equivalent

40 Wire brush (Commercial)

41 Scraper, w/razor blade (Commercial)

42 Gloves, rubber (Commercial)
S100 ASOS Site Technical Manual

Change 1 1-81

Table 1.5.2. Consumable Materials List

Item Quantity Source

Alcohol, anhydrous isopropyl, 91% 1 quart ASN-052-C-12

Applicator, cotton-tip 100 pieces

Bottle, squeeze

Brush, soft (1-inch paint) 1 each

Cloth, lint-free 10 pieces

Coating Compound, metal pretreatment 1 quart MIL-C-8514, or (DOD-P-15328)

Detergent, liquid 22 oz Joy dish washing liquid

DC-4,DowCorning, anti-corrosion dielectric

compound

1 tube

Filter-Coat 1 can

INSECTA paint 1 pint INSECTA Incorporated

Lacquer thinner, odorless 1 quart Parks 2215

Optical Gel Code 0608 4 oz R.P.Cargille 24231 (AMP 501555-1) $

Paint, Cabinet 1 quart Sherwin-Williams, Polane, No. 521-1719 F663W56,

Hi-Gloss White, Non-Textured Finish

Paint, Enamel, gloss-white 1 quart Rust-Oleum, or equal

Paint, Primer, for clean metal 1 quart Rust-Oleum, or equal

Paint, Primer, for rusty metal 1 quart Rust-Oleum, or equal

Paint, Primer, zinc-rich 1 quart Rust-Oleum, or equal

Paint, Wind Tower 1 quart FED-STD-595 Color 12197 (Orange) 17875 (White) $

Primer 1 quart Zinc Chromate, TT-P-1757, Type I, Color Y

RTV 732 Silicon Sealer 1 tube

Rust Stripper (for lightly rusted surfaces) 1 quart Rust-Oleum, or equal

Rust Reformer (for heavily rusted surfaces) 1 quart Rust-Oleum, or equal

Restorer, contact 1 can Radio Shack 64-2315

Tape, adhesive, electrical 2 rolls

Tissue, lens 50 pieces

Window cleaner 12 oz Windex glass cleaner with ammonia

Table 1.5.3. Maintenance Action Sequence

Step Procedure

1 Sign on system as a technician.

2 Select MAINT function and observe maintenance screen. Observe that MAINTENANCE keypad is

displayed in lower right corner. 

3 Press ACT key and observe that maintenance action screen is displayed. 

4 Press START key. This stores a maintenance action message in the system maintenance log, indicating the

start of a maintenance action to follow. 

5 Perform specified preventive maintenance, corrective maintenance, calibration, or field kit modification

tasks. Verify that all maintenance steps are complete and that appropriate units/assemblies or field

modification kits are identified. 

6 Reaccessmaintenance action screen. Use PREVT,CORR,CAL, and FMK keysto document all maintenance

tasks performed. If necessary, enter any additional relevant maintenance data or messages into SYSLG

screen (paragraph 1.3.13). 

7 Verify that system maintenance log has recorded complete and relevant maintenance notations regarding

each task performed.

8 Sign off ASOS.

1.5.3 PREVENTIVE MAINTENANCE (PM)

1.5.3.1 Introduction. ASOS preventive maintenance is performed at two intervals: 90 days and semiannually.

Table 1.5.4 provides the preventive maintenance schedule for each system major assembly.
ASOS Site Technical Manual S100

1-82 Change 2

Table 1.5.4. System Preventive Maintenance Schedule

Interval/Unit What To Do How To Do It

90 Days

ACU Clean air filters.

Clean CRT screens.

Clean cabinets.

Check memory board LOW BATT indicator.

Table 2.5.2

Table 1.5.7

Table 2.5.3 

Paragraph 2.5.2.4

Ceilometer Routine inspection and cleaning

Clean windows.

Check window conditioner.

Paragraph 9.5.2.2 

Table 9.5.2

Table 9.5.2 

CODEX modem Clean and inspect. Paragraph 13.5.2.1

DCP Clean cabinets. Table 3.5.2

Freezing rain sensor Clean and inspect. Table 11.5.1

GTA radio RF power output

Modulation level check

VSWR at transmitter output check

Frequency stability check

Table 12.5.2

Table 12.5.3

Table 12.5.4

Table 12.5.5

Present weather sensor Clean lenses.

Calibrate sensor.

Paragraph 7.5.2.2

Table 7.5.2 

Pressure sensor Clean and inspect.

Verify accuracy of pressure sensor data.

Paragraph 8.5.2.2

Table 8.5.2

SCA Perform visual inspection.

Clean CRT screens.

Table 14.5.2 

Table 14.5.4

System Perform visual inspection.

Clean peripherals.

$ Table 1.5.5 

Table 1.5.7

Temperature/dewpoint

sensor

Clean/inspect aspirator air passages.

Clean/inspect aspirator mirror.

Perform optical loop adjustments.

Verify temperature and dewpoint readings.

Table 5.5.2

Table 5.5.2

Table 5.5.3 or 5.5.4

Table 5.5.5

Thunderstorm sensor Clean and inspect. Table 16.5.1

Tipping bucket Clean and inspect. Table 10.5.1

Visibility sensor Clean lens assemblies.

Calibrate sensor.

Table 6.5.2

Table 6.5.3

Wind sensor Perform routine inspection.

Check obstruction lights.

Paragraph 4.5.2.1

Paragraph 4.5.2.2

Semiannually

ACU Check/clean batteries. Paragraph 2.5.2.5 

Ceilometer Check sensor calibration. Table 9.5.3

DCP Check/clean batteries, inspect desiccant (at special sites). Paragraph 3.5.2.2

SCA Check/clean batteries, inspect desiccant. Table 14.5.2

System Visual inspection and cleaning (as reqd). Table 1.5.5

Temperature/dewpoint

sensor

Check DC power supplies.

Calibrate sensor.

Table 5.5.8

Table 5.5.9 or 5.5.11

Wind sensor Mechanical operation inspection (bearings, cup balance, vane

balance).

Perform starting torque bearing test.

Check wind direction and speed data.

Check wind direction alignment.

Table 4.5.2

Table 4.5.17

Table 4.5.5

Paragraph 4.5.2.5

Annually

GTA radio Antenna cable conductance and insulation Table 12.5.6

Present weather sensor Treat with insect paint. Paragraph 7.5.2.4

System Visual inspection (as reqd)

Paint Refurbishment

Table 1.5.5

Paragraph 1.5.3.5

Thunderstorm sensor Replace desiccant. Table 16.5.1

Tipping bucket Inspect cable connector. Table 10.5.1

Wind sensor Inspect crossarm assembly cable connector. Table 4.5.2 
S100 ASOS Site Technical Manual

Change 1 1-83

1.5.3.2 Visual Inspection. Visual inspection is performed in two parts. The first part requires that power be

applied to the system; the second part requires that power be removed from the system. The visual inspection

procedure is provided in table 1.5.5. The DCP and sensor facilities must be inspected periodically. Table 1.5.6

specifies a checklist of items and the period for performing these tasks. 

1.5.3.3 Cleaning. Cleaning is required for the ACU, DCP, and sensor cabinets; the CRT and display screens on

the OID's, VDU, and CVD; and the printer and OID keyboard. The cleaning procedure is provided in table 1.5.7. 

1.5.3.4 Corrosion Removal and Prevention, Steel Surfaces. If corrosion (rust) is detected on steel parts such as

instrument subsystem pedestals, towers, wind tower base, or masts, proceed as follows: $

a. Wire brush affected areas thoroughly; then, wipe away all residue powder with a dry, clean

cloth.

b. Inspect rusted areas to determine whether remaining rust lies on surface, or whether it has

corroded deeply into the metal. If rust has penetrated below the surface, proceed with step d; if

not, proceed with step c.

CAUTION

Do not allow any chemicals used in this procedure to contact

the skin or eyes. Wear rubber gloves and safety glasses. If

any fluid splashes on exposed skin or eyes, flush with water

immediately. 

c. If rust is on or near the surface, proceed as follows:

1. Wearing rubber gloves, apply Rust Stripper with an applicator pad or a cloth. Apply

evenly over rusty surfaces; scrub vigorously.

2. Allow 30 minutes for Rust Stripper to work; then, wipe dry with a clean cloth.

3. Allow treated surfaces to air-dry for 30 minutes.

4. Using a clean, 2-inch paint brush, coat all treated and bare areas with zinc-rich primer.

5. Allow 1 hour drying time for primer.

6. Coat the entire surface with gloss white enamel.

7. Allow painted surfaces to dry for 8 hours; do not contact painted surfaces during drying

period.

d. If rust has penetrated below the surface, proceed as follows:

1. Wearing rubber gloves, apply Rust Reformer with an applicator pad or cloth. Apply

evenly over rusty surfaces, and scrub thoroughly.

2. When treated surfaces appear to be dry, wipe with a clean cloth.

3. Using clean, 2-inch paint brush, coat all treated and bare areas with rusty metal primer.
ASOS Site Technical Manual S100

1-84 Change 1

4. Allow 2 hours drying time.

5. Coat all treated surfaces with gloss-white enamel.

6. Allow 8 hours drying time; then, coat the entire surface with gloss-white enamel.

1.5.3.5 Refurbishment of Painted Aluminum Surfaces. Wherever paint has been damaged, or is

peeled or blistered, proceed as follows:

a. Scrape away all loose paint with a razor blade scraper. 

b. Using a 2-inch paint brush, coat the bare aluminum areas, and areas where yellow primer

is showing, with zinc-chromate primer.

c. Allow primer to dry for 4 hours.

$ d. Apply a coat of paint (refer to table 1.5.2 for proper paint) to primed areas.

$ e. If repainting of the entire surface is required, allow 8 hours drying time, then paint entire

$ surface.

Table 1.5.5. Visual Inspection Procedures

Step Procedure

1 With power applied, ensure that blower at the bottom of the ACU equipment cabinet, the fans on

the rear of the UPS's, and the muffin fans on the bottom of the DCP VME card rack are operating

properly. 

2 With power applied, at the wind sensor tower, cover the lightsensor on the tower light control box

and ensure that the clearance lights at the top of the tower illuminate. 

3 Remove power from the system and inspect the inner ACU, DCP, and sensor cabinets for signs of

pinched or chafed wiring, loose hardware, and proper connector mating. 

4 With power removed from the system, check the outside of all enclosures for signs of corrosion.

5 With power removed from the system, at the sensor pad, ensure that all hardware securing the

sensors to the pad is tight. Check each mounting column for visual signs of wear or corrosion.

Ensure that there are no cracks in the columns. 

NOTE

After performing the visual inspection procedure, reapply power to the system and wait

until the system initializes and successfully completes its diagnostic check before leaving

the area.
S100 ASOS Site Technical Manual

Change 1 1-85

WARNING

Table 1.5.6. Facilities Maintenance Checklist

Item/Task Period

EXTERNAL SURFACES $

Corrosion, Removal & Treatment Semiannually (para 1.5.3.4)

Fasteners, tighten Semiannually

Paint Yearly

FOUNDATIONS

Condition Yearly

FENCING

Condition Yearly

Paint Yearly

SIGNAGE

Condition Yearly

Paint Yearly

LIGHTNING PROTECTION SYSTEM

Condition (visual inspection) Semiannually

ROADS AND WALKWAYS

Condition Yearly

Snow removal Quarterly (in season)

LAND

Ground cover Yearly

Grass height Quarterly (in season)

Snow removal Quarterly (in season)

ELECTRICAL EQUIPMENT AND CABLES

Condition (visual inspection) Semiannually

Operation Quarterly

Table 1.5.7. Cleaning Procedure

Step Procedure

Ensure that power has been removed from a peripheral device before cleaning the device. 

Tools and Material Required:

Hand-held vacuum cleaner

Mild detergent and water

Lint-free cloths

1

NOTE

Wring out the cloth before washing the screens.

Using soft cloth dampened with a mixture of mild detergent and water, clean CRT and display screens and

external cases of the peripheral devices. Using lint-free cloth, dry screens and cases.

2 Using small hand-held vacuum cleaner, remove dust from the OID keyboard and the printer.
ASOS Site Technical Manual S100

1-86 Change 1

Table 1.5.8. Corrective Maintenance Symptom Analysis

Symptom What To Do How To Do It

 SYSTEM/ACU

 System is completely dead. Check ac and dc power. Reference ACU ac/dc power

distribution diagram

(Figure 2.4.12) and verify

presence of ac and dc

voltages.

Problemwith ACU uninterruptible powersupply

(UPS) in Class II system.

Check UPS. Paragraph 2.5.3.2

ACU computer does not initialize. Check VME card rack. Paragraph 2.5.3.3

Loss of ACU/DCP communications. Check ACU/DCP communication

link.

Paragraph 2.5.3.4

Failure of an SIO board or loss of communication with a peripheral or user.Check SIO boards. Paragraph 2.5.3.5

Printer malfunction Check printer. Refer to printer vendor

manual. 

DCP

DCP is completely dead. Check ac and dc power. Reference DCP ac/dc power

distribution diagram

(Figure 3.4.8) and verify

presence of ac and dc

voltages. Check fuses on DC

Power Distribu-tion

Assembly A4A1.

Problem with DCP UPS in Class II system. Check UPS. Paragraph 3.5.3.2

DCP computer will not initialize. Check VME cards. Paragraph 3.5.3.3

DCP cabinet overheats or becomes too cold. Check DCP heater circuit. Paragraph 3.5.3.4

CEILOMETER

Sensor will not respond. Check fiberoptic modules.

Troubleshoot sensor.

Paragraph 1.5.3.3

Paragraph 9.5.3.2

PRESENT WEATHER SENSOR

Sensor will not respond. Check fiberoptic modules.

Troubleshoot sensor.

Paragraph 1.5.3.3

Paragraph 7.5.3

PRESSURE SENSORS

All three pressure sensors read incorrectly. Clean pressure port. Paragraph 8.5.2.2 

One or two pressure sensors read incorrectly. Replace faulty sensor(s). Paragraph 8.5.5

Sensor will not respond. Troubleshoot sensor. Paragraph 8.5.3.2

TEMPERATURE/DEWPOINT SENSOR

Sensor will not respond. Check fiberoptic modules.

Troubleshoot sensor.

Paragraph 1.5.3.3

Paragraph 5.5.3.2

$ THUNDERSTORM SENSOR

$ Sensor will not respond. Check fiberoptic modules.

$ Troubleshoot sensor.

Paragraph 1.5.3.3

Paragraph 16.5.3.2

TIPPING BUCKET

Sensor fails to report rain accumulation. Test rain gauge. Paragraph 10.5.3.2

VISIBILITY SENSOR

Sensor will not respond. Check fiberoptic modules.

Troubleshoot sensor.

Paragraph 1.5.3.3

Paragraph 6.5.4

WIND SENSOR

Sensor will not respond. Check fiberoptic modules.

Troubleshoot sensor.

Paragraph 1.5.3.3

Paragraph 4.5.3.2
S100 ASOS Site Technical Manual

Change 1 1-87

1.5.4 CORRECTIVE MAINTENANCE

1.5.4.1 Introduction. Corrective maintenance involves the isolation, removal, and replacement of faulty FRU's. The

ASOS is equipped with a powerful automatic self-test program designed to isolate most faults to a single FRU.

However, due to system hardware configuration, there will be instances when the diagnostics can only isolate to a

group of FRU's, such as a sensor or an I/O channel. Obviously, the troubleshooting approach for these two types of

conditions is very different. When the FRU is specifically called out, the technician need only replace the faulty unit.

When a group of FRU's is called out, the technician must isolate the failed FRU by referencing the theory of

operation and associated drawings and following two basic procedures. 

The first procedure involves connector checks that ensure that all boards, cables, and connectors are present and

properly connected. The second procedure involves ac and dc power supply tests. Although the system monitors all

critical power supply voltages in the ACU, DCP, and sensors, failure of a power supply may result in a loss of

communications between the circuit powered by that supply and the rest of the system. Power supplies are tested by

both visual and mechanical inspection. Before measuring any voltages, the technician should visually inspect the

suspected area for obvious signs of power supply failure. During this inspection, the technician should pay particular

attention to circuit breakers, panel lights, and light emitting diode (LED) indicators on the units to ensure that they

are functioning normally. The physical checks involve checking fuses and the power supply voltages using a digital

multimeter (DMM). In most cases, these tests isolate the fault. 

To ensure proper operation of the system, the technician must allow the ASOS to automatically initialize upon the

application of primary power to the ACU and verify that the continuous self-test diagnostics run without failure.

Table 1.5.8 provides corrective maintenance symptom analysis information. 

1.5.4.2 System Diagnostics. The system diagnostics run continuously in the background of the ASOS operating

software. The diagnostics complete a check of the entire system every 7 minutes. The test data received via the

diagnostic program are displayed on the technician interface screens. These screens are described in Section III of

this chapter. Error messages are also entered into the system log and printed on the printer. 

1.5.4.3 Fiberoptic Module Test. The DCP communicates with its sensors via fiberoptic data links. The ACU can

also support up to three local sensors via fiberoptic links. Each fiberoptic link is made up of a fiberoptic module in

the DCP (or ACU), a corresponding module in the sensor, and two fiberoptic cables connecting the two fiberoptic

modules. The fiberoptic modules in the DCP (or ACU) and the sensors convert electrical RS-232 serial data to

optical data and vice versa. The fiberoptic links are not tested automatically by the CST and must therefore be tested

manually using an RS-232 test tool to check the electrical data paths. Data communication for all sensors except the

model HO83 temperature/dewpoint sensor and the rain gauge is half-duplex. That is, the DCP first polls the sensor

and the sensor then returns the requested data. Table 1.5.9 provides a procedure to manually test a fiberoptic link for

the half-duplex communications links. The HO83 data link is simplex (one-way only) communication. This sensor

outputs data to the DCP (or ACU) on a regular basis. The DCP (or ACU) then simply receives and processes the

data. The procedure to test an HO83 data link is provided in table 1.5.10. The rain gauge is not digital

communications at all. Rather, the rain gauge simply outputs an optical pulse to the DCP for each tip of its tipping

bucket. The rain gauge fiberoptic link is tested as part of the overall sensor test (described in paragraph 10.5.3).

1.5.4.4 Fiberoptic Cable Replacement. During initial installation, fiberoptic cable lengths were custom cut to $

lengths required to run between the sensor and the ACU/DCP or Single Cabinet ASOS (Figure 1.5.1). Replacement $

fiberoptic cables are available in standardized lengths (Table 1.5.11). When fault isolation identifies the fiberoptic $

cable as the failure, the technician refers to table 1.5.12 to remove the defective fiberoptic cable, measures the $

fiberoptic cable length, and round the length up to the nearest standard cable length as identified in table 1.5.11. At $

most sites, a maximum of two standard cables can be joined using the fiberoptic joiner (62828-90432) to achieve the $

required length. At sites with a remote wind sensor group, up to three cables can be joined. $

The replacement fiberoptic cable part numbers are identified as 62828-42100-XX where XX is the length of the $

cable (-10, -15, -20, -30, -40, -50, -100 for 10', 15’, 20', 30', 40', 50’ and 100' respectively). As an example, the fiber $

optic cable length for a rain gauge mounted on pedestal number 6 is 27.5'. After rounding up to the nearest standard $

length, the 62828-42100-30 (30 foot) fiberoptic cable is selected as the replacement cable. $

$
ASOS Site Technical Manual S100

1-88 Change 1

Figure 1.5.1. Combined Zone Pedestal Locational

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$ Table 1.5.9. Fiberoptic Link Testing - Half-Duplex Link

Step Procedure

1 At the OID, access sensor configuration screen. If the failing sensor is associated with a remote DCP,

determine the serial I/O (SIO) port to which the sensor is assigned. Refer to the list of Port Assignments for

DCP SIO Boards(Chapter 3, Section IV)to identify the corresponding fiberoptic module.Ifthe failing sensor

is associated with the ACU, use this screen to identify the corresponding ACU fiberoptic module. 

$ 2 At DCP (or ACU), connect RS-232 test tool (Figure 1.5.2) in line with fiberoptic module (DTE to modem)

$ for failing sensor (between fiberoptic module and corresponding DB-9 connector from cabinet harness). 

$ 3 On RS-232 test tool, verify periodic RxD signal activity from SIO board. If no activity, problem is in SIO

$ board in DCP (or ACU). If activity is present, proceed to step 4.

$ 4 On RS-232 test tool, verify TxD signal activity from fiberoptic module. If TxD signal is active, problem is

$ in SIO board. If no activity is present, proceed to step 5.

$ 5 Remove RS-232 test tool from fiberoptic module and reconnect DB-9 connector to module. 

$ 6 At failing sensor, connect RS-232 test tool in line with the sensor fiberoptic module (DTE to modem)

$ between fiberoptic module and corresponding DB-9 connector from cabinet harness. 

$ 7 On RS-232 test tool, verify periodic activity on TxD signal from fiberoptic module in DCP (or ACU). If

$ signal is active, continue with step 8. If signal is not active, proceed to step 9. 

$ 8 On RS-232 test tool, verify periodic activity on RxD signal from sensor. If no activity, problem is in sensor

$ serial data interface circuits. If both TxD and RxD signals are active, proceed to step 9.

$ 9 Remove RS-232 test tool from sensor fiberoptic module and reconnect DB-9 connector to module. One at

$ a time, remove and replace the following units and retest system until the problem is corrected:

$ a. Fiberoptic module in DCP (or ACU)

$ b. Fiberoptic module in sensor

$ c. Fiberoptic cable
S100 ASOS Site Technical Manual

Change 1 1-89

SIO Board Fiberoptic

Module

ACU/DCP/SCA

RS-232

SENSOR

Sensor SIO

Circuits RS-232

Tx Rx

Rx Tx

Tx

Rx

Rx

Tx

Tx

Rx

Rx

Tx

Fiberoptic

Module

RS-232

TESTER

STEPS 2-4

RS-232

TESTER

STEPS 6-8

9801502

Figure 1.5.2. Fiberoptic Link Testing - Half-Duplex Link

Table 1.5.10. Fiberoptic Link Testing - HO83 Link

Step Procedure

1 In the HO83 sensor, connect RS-232 test tool in line with sensor fiberoptic module (between fiberoptic

module and corresponding DB-9 connector from cabinet harness). 

2 Verify periodic activity of RxD signal on RS-232 test tool. If signal is active, proceed to step 3. If not,

problem is in serial data interface in HO83 sensor. 

3 Remove RS-232 test tool from HO83 fiberoptic module and reconnect DB-9 connector to module. 

4 At OID, accesssensor configuration screen. If HO83 sensor is associated with a remote DCP, determine SIO

port to which the sensor is assigned. Refer to the list of Port Assignments for DCP SIO Boards (Chapter 3,

Section IV) to identify the corresponding fiberoptic module. If HO83 sensor is associated with the ACU, use

this screen to identify the corresponding ACU fiberoptic module. 

5 In DCP (or ACU), connect RS-232 test tool in line with fiberoptic module for HO83 sensor (between

fiberoptic module and corresponding DB-9 connector from cabinet harness). 

6 Verify periodic activity of TxD signal on RS-232 test tool. If signal is active, problem is in DCP (or ACU) $

SIO board. If signal is not active, proceed with step 7. 

7 Remove RS-232 test tool from fiberoptic module and reconnect DB-9 connector to module. One at a time,

remove and replace the following units and retest system until the problem is corrected: 

a. Fiberoptic module in DCP (or ACU)

b. Fiberoptic module in sensor

c. Receive fiberoptic cable between DCP (or ACU) and sensor.
ASOS Site Technical Manual S100

1-90 Change 1

WARNING

$ Table 1.5.11. ASOS Fiberoptic Cables

$ Pedestal Typical

$ Sensor

Req.

Length

New

Length

New Part Number

(Ref Des)

Old Part Number

(Ref Des)

$ 6 Rain Gauge 27.5' 30' 62828-42100-30 (W120) 62828-42040-60 (W23)

$ 4 Temp/Dew 25.5' 30' 62828-42100-30 (W118) 62828-42040-40 (W21)

$ 2 LEDWI 18' 20' 62828-42100-20 (W116) 62828-42040-20 (W19)

$ N/A Thunderstorm 8' 10' 62828-42100-10 (W124) N/A

$ 1 Ceilometer 19.5' 20' 62828-42100-20 (W115) 62828-42040-10 (W18)

$ 3 Freezing Rain 25.5' 30' 62828-42100-30 (W117) 62828-42040-30 (W20)

$ 5 Visibility 28' 40' 62828-42100-40 (W119) 62828-42040-50 (W22)

$ N/A Wind 26' TBD 62828-42100-xx (W121) 62828-42040-80 (N/A)

$ 7 Ceilometer 36.5' 50' 62828-42100-50 (W122) N/A

$ 9 Reserved 42.5' 50' 62828-42100-50 N/A

$ 11 Visibility 48' 50' 62828-42100-50 (W123) N/A

$

$ Table 1.5.12. Fiberoptic Cable Replacement

$ Step Procedure

$ Fiberoptic Cable Removal

$ Tools required:

$ Small flat-tipped screwdriver

$ No. 1 Phillips screwdriver

$

$

$

$ Death or severe injury may result if power is not removed from cabinet prior to maintenance

$ activities. Ensure that UPS POWER switch is set to 0 (off) position and facility power is removed

$ from cabinet.

$ 1 If applicable, set UPS POWER switch to off (0) position.

$ 2 Set primary Circuit Breaker Module to OFF position.

$ 3 At ac junction box, remove facility power from equipment cabinet by setting cabinet circuit breaker to off.

$ 4 Using Phillips screwdriver, remove 22 screws and flat washerssecuring shielded cover assembly to Faraday

$ box. Lower Faraday box cover.

$ 5 Accessing underside of fiberoptic module through Faraday box, disconnect fiberoptic transmit (TX) and

$ receive (RX) cables.

$ 6 Remove fiberoptic cable from cabinet.

$ 7 At the sensor associated with the faulty fiberoptic cable, access underside of fiberoptic module and

$ disconnect fiberoptic transmit (TX) and receive (RX) cables.

$ 8 Remove fiberoptic cable from sensor.

$ 9 Remove fiberoptic cable from raceway.

$ 10 Measure length of faulty fiberoptic cable, round the length up to the nearest standard cable length as

$ identified in the parts list and order replacement cable.
S100 ASOS Site Technical Manual

Change 1 1-91/ (1-92 blank)

WARNING

Table 1.5.12. Fiberoptic Cable Replacement -CONT

Step Procedure

FIBEROPTIC CABLE INSTALLATION $

Tools required: $

 Small flat-tipped screwdriver $

 No. 1 Phillips screwdriver $

$

$

$

Death or severe injury may result if power is not removed from cabinet prior to maintenance $

activities. Ensure that UPS POWER switch is set to 0 (off) position and facility power is removed $

from cabinet. $

$

NOTE $

Replacement fiberoptic cables must be properly marked prior to installation. $

1 At equipment cabinet end of the replacement fiberoptic cable, apply the appropriate information to the wrap $

around tags using the following definitions: $

$

a. On marker FOM#: line, write three letter code for ACU, DCP, or SCA followed by the fiberoptic $

modem number (1-3 for ACU, 1-16 for DCP, 1-13 for SCA). $

$

b. On marker SENSOR: line, write two character software code for sensor as follows: $

C1, C2, C3 for Ceilometer 1 thru 3 $

V1, V2, V3 for Visibility 1 thru 3 $

PW for Present Weather $

FR for Freezing Rain $

WS for Wind Sensor $

TD for Temperature/Dewpoint $

TB for Tipping Bucket $

TS for Thunderstorm $

$

c. On marker COUPLED? Y N line, circle Y if replacement cable uses two cables connected by a $

fiberoptic joiner or circle N if one cable is used. $

2 Repeat step 1 for sensor end of replacement fiberoptic cable. $

3 If applicable, at UPS, ensure that UPS POWER switch is set to off (0) position. $

4 Ensure that power is removed from equipment cabinet. $

5 $

$

$

CAUTION $

Bending the fiberoptic cable during installation beyond the minimum bend radius of 1.8 $

inches could damage the cable. The minimum bend radius for long term storage is 1.2 $

inches. Ensure that the minimum bend radius is not exceeded. $

$

NOTE $

If two standard fiberoptic cables are joined to form the replacement cable, connect TX to $

RX at each fiberoptic joiner (62828-90432). $

$

Couplers, if used, must be installed in an area that will not contact standing water. $

$

Route replacement fiberoptic cable between sensor and equipment cabinet. Ensure that sufficient length of $

cable remains at each end to connect to the fiberoptic modems. Store excess cable in Faraday box, raceway, $

or sensor as applicable. $

6 At sensor, using tags as a guide, connect fiberoptic TX and RX cables to module connector. $

7 At equipment cabinet, using tags as a guide, connect fiberoptic TX and RX cables to appropriate module $

connector though opened Faraday box. $

8 Using Phillips screwdriver, install screws and flat washers securing shielded cover assembly to Faraday box. $

9 Apply facility power to equipment cabinet by setting circuit breaker in ac junction box to on position. $

10 Set primary Circuit Breaker Module to ON position. $

11 If applicable, set UPS POWER switch to 1 (on) position. $
S100 ASOS Site Technical Manual

2-1

Figure 2.1.1. ACU and Peripherals

CHAPTER 2

ACQUISITION CONTROL UNIT (ACU) AND PERIPHERALS

SECTION I. DESCRIPTION AND LEADING PARTICULARS

2.1.1 INTRODUCTION

The acquisition control unit(ACU) and associated peripherals(Figure 2.1.1) provide central control and user

interface for the Automated Surface Observing System (ASOS). The ACU is used for data acquisition,

processing, quality checks, storage, formatting, and output. The ACU is also used to control system self-test

and diagnostics and to interfacewith all operator displays and external communicationswith the system. This

Chapter providesthe physical description, installation procedures, operation procedures, theory of operation,

and maintenance procedures for the ACU and associated peripherals.
ASOS Site Technical Manual S100

2-2 Change 1

2.1.2 PHYSICAL DESCRIPTION

As shown in figure 2.1.1, a typical ACU/peripheral installation contains the following major units:

a. ACU Cabinet, Unit 1

b. Up to 17 Controller Video Displays (CVD's), Units 81 through 89 (first CVD location) and

91 through 98 (second CVD location)

c. Printer, Unit 12

d. FAA Handset, Unit 5

e. Up to three Operator Interface Devices (OID's), Units 11, 21, and 31

f. Optional Observer Notification Device (OND), Unit 6

g. Up to ten Video Display Units(VDU's), Units 41 through 44 (first VDU location), Units 51

through 53 (second VDU location), Units 61 and 62 (third VDU location), and Unit 71

(fourth VDU location)

The ACU communicates with the data collection package (DCP) via either a radio frequency (rf) modemlink

$ or via a direct line link. When an rf modem link is used, an RF Antenna (1E1) is also connected to the ACU.

$ Most sites use omnidirectional antennas. Yagi antennas and attenuators are installed at sites where cochannel interference is experienced. In addition to the above listed equipment, the ACU may be equipped

with a video driver option that allows it to drive external airline displays which are not part of the actual

ASOS.

2.1.2.1 ClassI and ClassII Systems. Throughout thisChapter and Chapter 3, a distinction is made between

Class I systems and Class II systems. The Class I system is the basic model ASOS. This model will be

installed at most Class I (non-towered) airports and other observation sites. The Class II ASOS is almost

identical to the Class I system, except that all Class II systems have the following additional features to

increase system availability and performance:

$ a. Uninterruptible power supplies (UPS's) and UPS bypass circuits in the ACU and DCP that

allow the ASOS to operate in the event of a loss of facility ac power.

b. A third (redundant) pressure sensor in the ACU (Class I system has two). This third sensor

allows the ASOS to continue to report altimeter settings and pressure data even if one of its

three pressure sensors fails.

c. Redundant communications equipment for ACU/DCP data communications. This includes

a second rf modem (or line driver) in both the ACU and DCP, and a second CPU in the

DCP.

d. Electromagnetic interference (EMI) shielded ACU and DCP cabinets

These features are available as options for Class I systems.
S100 ASOS Site Technical Manual

Change 1 2-3

2.1.2.2 ACU Cabinet. The ACU cabinet (Figure 2.1.2) measures 70 inches high, 25 inches wide, and 32

inches deep. For Class II systems, honeycombed rf filters in the front and rear doors of the cabinet and rf

gaskets on the doors provide EMIshielding for up to 100 decibels(db). The cabinet containsfive equipment

racks, a battery box, a blower, and a connector panel. Brief descriptions of these components are provided

in table 2.1.1. 

2.1.2.2.1 ACU Tie-Down. In earthquake prone areas, the ACU is anchored down (at sites not using

equipment shelters) with two sections of construction "U" channel and attaching hardware (including

associated materials). The ACU tie-down installation method is determined by the material that the ACU is

being attached to (wood or concrete). The ACU tie-down installation procedure (including all parts and tools

needed)is contained in table 2.5.32. ACU’sinstalled in equipmentsheltersthat are in earthquake prone areas

will use a different anchoring scheme, which is as yet undetermined. 

2.1.2.3 Controller Video Displays (CVD's). The ACU can drive up to nine CVD's located in the airport

control tower for use by air traffic controllers. Each CVD is a liquid crystal display (LCD) that may be either

a free standing unit or panel mounted. The CVD displays the following information:

a. Wind direction and speed

b. Altimeter setting

c. Most recent hourly meteorological report (METAR) data

2.1.2.4 Printer. The printer is a dot matrix type printer that features several fonts and print quality modes.

The features, operation, and maintenance of this printer are explained in the corresponding printer operation

manual. Refer to paragraph 2.5.7 for printer setup procedures. The following types of information are

automatically printed:

a. Initials of persons signed on and off system

b. 1-minute observations before and after editing

c. Equipment and communications failures $

d. Reason for alarms

e. Daily and monthly summaries

f. Hourly meteorological reports (METAR’s) and SPECI’s at end of day (15 minutes past

midnight)

g. Edits to meteorological reports (METAR’s) by the observer $

The printer also produces hard copies of OID displays in response to user requests.

2.1.2.5 FAA Handset. The FAA handset allows operators to monitor audio weather reports generated by

the ASOS and to append verbal comments to the audio reports.
ASOS Site Technical Manual S100

2-4

Figure 2.1.2. ACU Cabinet Unit 1 Locational View (Sheet 1 of 2)
S100 ASOS Site Technical Manual

Change 1 2-5

Figure 2.1.2. ACU Cabinet Unit 1 Locational View (Sheet 2)
ASOS Site Technical Manual S100

2-6 Change 2

Table 2.1.1. ACU Cabinet Major Assemblies

Unit Name Figure Purpose

1A1 Codex

Modem

- ADAS modem, refer to Chapter 13.

1A2 Card Rack

Assembly

2.1.3 Contains up to 16 circuit boards that perform all of the data processing and

input/output (I/O) functions associated with the ACU. 

 1A3 Modem AC

Power Rack

2.1.4 Contains up to 10 modems, which are used for all telephone communications with

the ACU. May also contain up to two line drivers for ACU/DCP communication

(when rf modems are not used).

1A4

$

$

$

Power

Supply

Assembly

2.1.5 Provides an uninterruptible powersupply (UPS) that supplies power to the ACU in

the event of main facility power loss. The UPS supplies ac power for the ACU

cabinet, printer, and primary OID for a minimum of 10 minutes. Power Supply

Assembly 1A4 is installed in Class II systems and in Class I systems where it has

been installed as an option. Power Supply Assembly 1A4 may be one of two

different assemblies. Power supply assembly, part number 62828-40124-10

(Figure 2.1.5, sheet 1), is installed in systems having serial numbers 437 and below

$ and contains UPS part number 62828-90057. Systems having serial numbers 438

and above contain power supply assembly 62828-40265-10 (sheet 2). This assembly

$ contains either UPS part number 62828-90338-10 or 62828-90338-20.

1A5 DC Power

Supply

Enclosure 

2.1.6 Rack containing two dc power supplies. Each power supply provides +5V, +12V,

and -12V for the ACU cabinet.

1A6 RF/Pressure

Mounting

Shelf 

2.1.7 Slide-mounted shelf containing rf modems and pressure sensors. For Class I

systems, the shelf contains one rf modem (unless communication is by line driver)

and two pressure sensors. For Class II systems, the shelf contains a second rf

modem, an rf modemswitch, and a third pressure sensor. For ClassIIsystems using

line driver communication, rf modems are not installed and an LD1/LD2 switching

board replaces the rf modem switch.

1A7 Power

Distribution

Assembly 

- Terminal strip that distributes ac and dc power within the ACU. Contains Power

Reset Relay K1 and in Class II systems contains UPS Bypass Relays K2 and K3.

1A8 Battery Box 2.1.8 Contains either four or five 12-volt batteries for the UPS. Battery Box 1A8 may be

one of three different assemblies. Battery box part number 62828-40063-10

contains five batteries, which are used with power supply assembly part number

62828-40124-10. Battery box part number 62828-40063-30, referred to as the

interim battery box, contains four batteries and packing material and is used with

power supply assembly part number 62828-40265-10. Battery box part number

62828-40262-20, referred to as the production model battery box, is similar to part

number 62828-40063-30 but is physically smaller. It contains four batteries and is

also used with power supply assembly part number 62828-40265-10.

1A9 I/O Panel

Assembly

2.1.9 The main interface panel for all external connections to the ACU. Main facility

power is applied to the systemvia AC INPUT POWERconnectorJ41 on this panel.

PERIPHERAL POWER connector J40 is controlled by the UPS (in Class II

systems) and supplies UPS ac power to the primary OID and printer.

 B1 Blower - Cools the ACU cabinet.
S100 ASOS Site Technical Manual

2-7

2.1.2.6 Operator Interface Devices (OID's). The OID consists of a display and a keyboard and provides

full control over all aspects of the ASOS. The ACU may have multiple OID's. One local OID, also known

asthe primary OID, islocated within 100 feet of the ACU. Two secondary OID's(notshown) may be located

up to 3 milesfrom the ACU. Communication using remote OID'sis accomplished over telephone lines using

modems. There are four types of OID users: observers, air traffic controllers, system managers, and

technicians. Different log-on sequences and passwords for each type of user allow tailored control of the

appropriate systems. Only those displays pertinent to the particular user are available to that user.

2.1.2.7 RF Antenna. The rf antenna enables ACU/DCP communications and operates within the ASOS

operating frequency (410.075 or 410.950 MHZ). Because the rf antenna is an omnidirectional antenna, its

use reduces the placement restrictions of the DCP's. Most sites use the omnidirectional antennas. Yagi $

antennas and attenuators are installed at sites where co-channel interference is experienced. $

2.1.2.8 Observer Notification Device (OND). One of the ASOS configurations includes an OND, which

is an alarm light, similar to the on-the-air indicators used in radio stations. The OND light blinks on and off

to alert the observer or air traffic controller that a report (METAR or SPECI) is soon to be transmitted and

that it may be edited during the pretransmission period. The OND light blinks until the edit time ends and

the report is transmitted.

2.1.2.9 Video Display Unit (VDU). Up to four VDU's can be placed at various locations in the airport. The

VDU is a 12-inch diagonal monochrome cathode ray tube (CRT) display. The VDU displays the current

ASOS 1-minute weather observations and the most recently transmitted METAR.

2.1.2.10 Airline Displays.The ACU can have a number of airline displays distributed throughout the airport

complex. These displays are industrial terminals without keyboards that are not a part ASOS. Each airline

display presents ASOS 1-minute weather observations and other OID displays.

2.1.3 ACU CONFIGURATIONS

The ACU (P/N 62828-40044) has six possible configurations as shown below:

-10 Class II system as described in paragraphs 2.1.2 and 2.1.2.1. The -10 system uninterruptible power

supply is built by SOLA. The SOLA battery box contains five 12V lead-acid batteries.

-20 Standard Class I system as described in paragraphs 2.1.2 and 2.1.2.1.

-30 ClassIIsystemas described in paragraphs 2.1.2 and 2.1.2.1. The -30 system’s uninterruptible power

supply is built by DELTEC. The DELTEC battery box contains four 12V lead-acid batteries.

-40 Class I system as described in paragraphs 2.1.2 and 2.1.2.1. The -40 system includes an

uninterruptible power supply built by DELTEC.

-50 ClassIsystem as described in paragraphs 2.1.2 and 2.1.2.1. The -50 systemincludes a third pressure

sensor installed for improved reliability.

-60 Class I system as described in paragraphs 2.1.2 and 2.1.2.1. The -60 system includes an

uninterruptible power supply built by DELTEC and a third pressure sensor installed for improved

reliability.
ASOS Site Technical Manual S100

2-8

Figure 2.1.3. Card Rack Assembly 1A2

Figure 2.1.4. Modem AC Power Rack 1A3
S100 ASOS Site Technical Manual

2-9

Figure 2.1.5. Power Supply Assembly 1A4 (Sheet 1 of 2)
ASOS Site Technical Manual S100

2-10 Change 2

Figure 2.1.5. Power Supply Assembly 1A4 (Sheet 2)
S100 ASOS Site Technical Manual

2-11

Figure 2.1.6. DC Power Supply Enclosure 1A5
ASOS Site Technical Manual S100

2-12 Change 2

Figure 2.1.7. RF/Pressure Mounting Shelf 1A6 (Sheet 1 of 2)
S100 ASOS Site Technical Manual

2-13

Figure 2.1.7. RF/Pressure Mounting Shelf 1A6 (Sheet 2)
ASOS Site Technical Manual S100

2-14

Figure 2.1.8. Battery Box 1A8
S100 ASOS Site Technical Manual

2-15/ (2-16 blank)

Figure 2.1.9. I/O Panel Assembly 1A9
ASOS Site Technical Manual S100

SECTION II. INSTALLATION

Installation of a complete acquisition control unit (ACU) is not the responsibility of the site technician. The

proceduresforremoving and replacing individual field replaceable units(FRU's) are contained in Section V.
S100 ASOS Site Technical Manual

2-19

SECTION III. OPERATION

2.3.1 INTRODUCTION

System maintenance control is performed from the operator interface device (OID), where the user can

monitor self-test results, initiate diagnostic tests, review and update the maintenance logs, conFigure the

system, and control power to sensors at remote data collection packages (DCP's). In addition to the OID

displays, various units within the acquisition control unit (ACU) contain controls and indicators that can be

used during system maintenance. This section describes these ACU controls/indicators. Refer to Chapter 1

for system related operating procedures and a complete description of all maintenance display pages.

2.3.2 CONTROLS AND INDICATORS

2.3.2.1 Operator Interface Device (OID). The OID is a standard cathode ray tube (CRT) terminal. The

keyboard (Figure 2.3.1) is divided into four functional areas: the main keypad, editing keypad, auxiliary

keypad, and function keypad. The editing keypad contains the arrow, REMOVE, and edit keys. The arrow

keys are used to move the cursor to the different fields on the display. The REMOVE key is used to delete

the character under the cursor. The edit keys are used to move the cursor to a specific point on the page when

editing log entries. The auxiliary keypad is used to access the maintenance/observer displays. The keypad

on the OID display overlays the auxiliary keypad area such that key 7 represents the function in the upper

left corner of the OID keypad and key 3 represents the function in the lower right corner of the OID keypad.

The function keypad contains the HELP key, which is used to access the system help feature. Help can also

be accessed by pressing the 0 key on the auxiliary keypad. Function keys F12 and F20 control the system's

audio alarm. Pressing F12/F20 disables the alarms until the user signs off the system. Pressing F12/ F20

again enables the alarm. The audio alarm can be disabled for the current alarm by pressing the F11 or F19

key. Additional information on the OID and its use is provided in the ASOS Software User's Manual.

2.3.2.2 Printer. The model KX-P1180, KX-P2180, or KX-P3123 printer controls and indicators are

described in the correspondingPrinterOperationManual. Paragraph 2.5.7 providesthe procedures for setting

up the model KX-P1180, KX-P2180, and KX-P3123 printers.

2.3.2.3 Controller Video Display (CVD). The CVD (Figure 2.3.2) contains a brightness control and a

contrast/reset control. The brightness control is used to adjust the overall intensity of the video display.

Turning the contrast/reset control adjuststhe contrast between the light and dark areas on the screen. Pressing

the contrast/reset control resets the CVD.

2.3.2.4 Observer Notification Device (OND). The OND is an alarm light. When the ASOS generates an

observer alert message, the light blinks on and off for a maximum of 5 minutes.

2.3.2.5 Card Rack Assembly. Of the nine types of boards (maximum) in the card rack assembly, five

contain controls/indicators. These boards are illustrated on figure 2.3.3 and each control/indicator is

described in table 2.3.1.

2.3.2.6 Modem AC Power Rack. The modem ac power rack contains up to 10 telephone modems (models

2440, V.3225, V.3400) and up to two DDS/MR64 or D19.2 line drivers. The modem rack also contains an

ac power supply module that provides power to all modems and line drivers installed in the rack. The

modems, the line drivers, and the power supply module are illustrated on figure 2.3.4 and controls and

indicators are described in table 2.3.2.
ASOS Site Technical Manual S100

2-20

Figure 2.3.1. Keyboard

 11:18:06 07/04/96 1618Z ANYTOWN AIRPORT

 SKY = OVC100

 VISIBILITY = 1 3/4SM TEMP/DEWPT = 12.2 /7.8 C 54 /46 F

 RVR = R17L/3800FT WIND DIR/SPD = 180/10

 PRESENT WX = RA ALTIMETER = 29.90

 REMARKS = RMK P0019

 METAR KANY 041558Z AUTO 18010KT 1 3/4SM R17L/3800 RA OVC100 12/08 A2990

PRINT

REVUE

SIGN AUX
S100 ASOS Site Technical Manual

2-21

Figure 2.3.2. Controller Video Display (CVD)

Figure 2.3.3. Card Rack Assembly Controls and Indicators
ASOS Site Technical Manual S100

2-22

Table 2.3.1. Card Rack Assembly Controls and Indicators

Control/

Indicator

Type Description

NOTE

The controls and indicators contained on the VME cards are not the primary troubleshooting

indicators. The technician should refer to the maintenance pages first and use the VME card

indicators only for secondary reference.

CPU

FAIL Light emitting diode

(LED) 

When illuminated, indicates that the CPU has failed its internal self-test. When

the CPU self-test is in process, the FAIL and PASS indicators flash. 

PASS LED When illuminated, indicatesthat the CPU has passed itsinternalself-test. When

the CPU self-test is in process, the FAIL and PASS indicators illuminate.

HALT LED When illuminated, indicates that the CPU has entered the halt state

(nonprocessing state).

ABORT Pushbutton switch When pressed, halts program execution without resetting the CPU. This switch

is for developmental use only. It should not be used in the field. If it is pressed,

press the RESET switch.

 RESET Pushbutton switch When pressed, resets the CPU and the VMEbus. Resetting the CPU does not

affect the contents of the dynamic random access memory (DRAM).

 Memory Board

B1 LED When illuminated, indicatesthat the bank 1 memorymodule is being addressed.

B2 LED When illuminated, indicatesthat the bank 2 memorymodule is being addressed.

B3 LED When illuminated, indicatesthat the bank 3 memorymodule is being addressed.

LOW

BATT

LED When illuminated, indicates that backup battery on board is low and memory

board must be replaced (may also illuminate if J22 jumper is not installed).

Video Controller Board

SVME

676

LED Software programmable. Not used during normal operation. The initialization

routine turns this indicator off to conserve energy.

Voice CPU/Memory Board 

ALARM LED When illuminated, indicatesthat the watchdog timer on the voice CPU/memory

board detected a CPU hardware or software failure. 

RESET Pushbutton switch When pressed, resetsthe CPU and does not reset the VME system. No messages

are broadcast until a play message string command is successfully received.

Voice Recorder/Playback Board

ALARM LED When illuminated, indicates that no audio output has occurred for 30 to 60

seconds.
S100 ASOS Site Technical Manual

2-23

Figure 2.3.4. Modem AC Power Rack Controls and Indicators

Table 2.3.2. Modem AC Power Rack Controls and Indicators

Control/

Indicator

Type Description

NOTE

The controls and indicators contained on the modems and line drivers are not the primary

troubleshooting indicators. The technician should refer to the maintenance pages first and use the

modem indicators only for secondary reference.

2440 Modem

TD LED Transmit data. When illuminated, indicates that data are being transmitted from

ACU computer to the respective voice frequency (VF) line.

RD LED Receive data. When illuminated, indicates that data are being received on-line

and are being transferred to ACU computer.

MC LED Modem check. When illuminated, indicatesthat modem is off-line, in talk mode,

errors detected during diagnostics, or data are being retransmitted.

HS LED High-speed. When illuminated, indicates that modem is operating at maximum

configured speed, which is 2400 bps. When extinguished, indicates that modem

is operating at medium speed (1200 bps). When flashing, indicates that modem

is operating in low speed (0 to 300 bps). 

TR LED Terminal ready. When illuminated, indicates that ACU computer is on-line and

ready for data transfers.

MR/RI LED Modem ready. When illuminated, indicates that modem is operational and is

connected to the telephone line.When flashing, indicatesthatmodemisreceiving

a ring signal.
ASOS Site Technical Manual S100

2-24

Table 2.3.2. Modem AC Power Rack Controls and Indicators -CONT

Control/

Indicator

Type Description

TALK/DATA Pushbutton

switch

Talk/data mode select. Used in conjunction with 1-LINE LCD to allow manual

phone calls for either data or voice communication. Not used for ASOS.

YES Pushbutton

switch

Used in conjunctionwith 1-LINELCDto answer modem configuration questions.

Not used for ACU rack-mounted modems.

NO Pushbutton

switch

Used in conjunctionwith 1-LINE LCD to answer modem configuration questions.

Not used for ACU rack-mounted modems.

1-LINE

LCD

Liquid crystal

display 

Displays menu of options available for manual modem configuration and test.

Because ACU rack-mounted modems are configured and tested automatically by

ACU computer, LCD is not used.

 AC Power Supply Module

Circuit

breakers

Pushbuttons or

rocker switches

Left and right circuit breakers provide overcurrent protection for left and right

sides of modem rack, respectively.

POWER Indicator When illuminated, indicates that ac power supply module is on. 

V.3325 Modem

TD LED Transmit data. When illuminated, indicates that data are being transmitted from

ACU computer to the respective VF line.

RD LED Receive data. When illuminated, indicates that data are being received on-line

and are being transferred to ACU computer.

RS LED Request to send. When illuminated, indicatesthat ACU computer (via a serial I/O

board) has issued a request to send signal to the modem on pin 4 of the RS-232

interface. This occurs when the serial I/O board is ready to send data to the

modem. 

CD LED Carrier detect. When illuminated, indicates that modem has connected with

another modem on-line.

CS LED Clear to send. When illuminated, indicates that modem has given a clear to send

signal on pin 5 of the RS-232 interface. This indicates that modem is ready to

receive data from ACU computer (via a serial I/O board).

QM LED Quality monitor. When illuminated, indicates low quality of modem

communications signals.

TALK/DATA Pushbutton

switch 

Talk/data mode select. Used in conjunction with 2-LINE LCD to allow manual

phone calls for either data or voice communication. Not used for ASOS.

YES Pushbutton

switch

Used in conjunction with 2-LINE LCD to answer modem configuration questions.

Not used for ASOS.

NO Pushbutton

switch

Used in conjunction with 2-LINE LCD to answer modem configuration questions.

Not used for ASOS.

2-LINE LCD Liquid crystal

display

Displays menu of options available for manual modem configuration and test.

Because modems are configured and tested automatically by ACU computer,

LCD is not used for ASOS.

V.3400 Modem

TD LED Transmit data. When illuminated, indicates that data are being transmitted from

ACU computer to the respective VF line.

RD LED Receive data. When illuminated, indicates that data are being received on-line

and are being transferred to ACU computer.

RS LED Request to send. When illuminated, indicatesthat ACU computer(via a serial I/O

board) has issued a request to send signal to the modem on pin 4 of the RS-232

interface. This occurs when the serial I/O board is ready to send data to the

modem. 
S100 ASOS Site Technical Manual

Table 2.3.2. Modem AC Power Rack Controls and Indicators -CONT

Control/

Indicator

Type Description

2-25

CD LED Carrier detect. When illuminated, indicates that modem has connected with

another modem on-line.

CS LED Clear to send. When illuminated, indicates that modem has given a clear to send

signal on pin 5 of the RS-232 interface. This indicates that modem is ready to

receive data from ACU computer (via a serial I/O board).

TR LED Terminal Ready indicator. Illuminates when DTE asserts Data Terminal Ready.

TALK/DATA Pushbutton

switch 

Talk/Data mode select. Used in conjunction with 2-LINE LCD to allow manual

phone calls for either data or voice communication. Not used for ASOS.

YES Pushbutton

switch

Used in conjunction with 2-LINE LCD to answer modem configuration questions.

Not used for ASOS.

NO Pushbutton

switch

Used in conjunction with 2-LINE LCD to answer modem configuration questions.

Not used for ASOS.

2-LINE LCD Liquid crystal

display

Displays menu of options available for manual modem configuration and test.

Because modems are configured and tested automatically by ACU computer,

LCD is not used for ASOS.

D19.2 Line Driver

PWR LED Power indicator. When illuminated, indicatesthat power is applied to line driver.

Mode switch Seven-position

rotary switch

Selects line driver mode of operation. In the ASOS, this switch is kept in the

DATA position. The LL/TP and RL/TP are used for manually testing the line

drivers. The line driver modes are listed below for reference purposes.

DATA- Normal operation

RT- Remote terminal loopback

LL- Local line loopback

RL- Remote terminal loopback

TP- Test pattern

LL/TP- Local line with test pattern

RL/TP- Remote loopback with test pattern

TM LED Test mode. Illuminates or blinks when line driver is placed in the test mode by the

ACU computer.

TD LED Transmit data. When illuminated, indicates that data are being transmitted from

ACU computer to DCP over dedicated lines.

RD LED Receive data. When illuminated, indicatesthat data are being received fromDCP

over dedicated lines and are being transferred to ACU computer.

CS LED Clear to send. When illuminated, indicates that line driver has given a clear to

send signal on pin 5 of the RS-232 interface. This indicates that line driver is

ready to receive data from ACU computer (via a serial I/O board).

NS LED No signal. When illuminated, indicates that no signal is present on ACU/DCP

dedicated line.

OS LED Out of service. When illuminated, indicates that line driver has received an out

of service code from the corresponding line driver in the DCP.

TP/ER LED Test pattern/error. When line driver is placed in test mode, indicator illuminates

to indicate that an error has been received.

DDS/MR64 Line Driver

TD LED Transmit data. When illuminated, indicates that data are being transmitted from

ACU computer to DCP over dedicated lines.

RD LED Receive data. When illuminated, indicatesthat data are being received fromDCP

over dedicated lines and are being transferred to ACU computer.
ASOS Site Technical Manual S100

Table 2.3.2. Modem AC Power Rack Controls and Indicators -CONT

Control/

Indicator

Type Description

2-26 Change 2

CS LED Clear to send. When illuminated, indicates that line driver has given a clear to

send signal on pin 5 of the RS-232 interface. This indicates that line driver is

ready to receive data from ACU computer (via a serial I/O board)

NS LED No signal. When illuminated, indicates that no signal is present on ACU/DCP

dedicated line.

OS LED Out of service. When illuminated, indicates that line driver has received an out

of service code from the corresponding line driver in the DCP.

TM LED Test Mode. When illuminated, indicates that the DDS/MR64 is in Test mode. 

HOME Pushbutton

switch 

Data mode or Set mode select. Used in conjunction with 1-LINE LCD when in

Set mode for manual modem configuration.

YES Pushbutton

switch

Used in conjunction with 1-LINE LCD to answer modem configuration questions.

NO Pushbutton

switch

Used in conjunction with 1-LINE LCD to answer modem configuration questions.

1-LINE LCD Liquid crystal

display

Displays menu of options available for manual modem configuration and test. 

2.3.2.7 Power Supply Assembly. The powersupply assembly (Figure 2.3.5) monitors ac input power to the

ACU and supplies normal/emergency output power to all equipment in the ACU cabinet including

$ peripherals within 100 feet of the ACU. The controls and indicators for the SOLA uninterruptible power

$ supply (UPS) contained in power supply 62828-40124-10 are illustrated on figure 2.3.5 and described in

$ table 2.3.3. Powersupply 62828-40265-10 can contain either Deltek UPS 62828-90338-10 (figure 2.3.6 and

$ table 2.3.4) or Deltek UPS 62828-90338-20 (figure 2.3.7 and table 2.3.5).

2.3.2.8 DC Power Supply Enclosure. Each of the two +5V and ±12V power supplies has a power (I/O)

switch and a power on indicator lamp. The on/off switches are normally kept in the on position, and the

power supplies are turned on and off via the UPS.

2.3.2.9 Codex Modem. The Codex 3600 Series modem is Government-furnished equipment (GFE) that

interfaces with the Federal Aviation Administration (FAA) ADAS via the Data Multiplexer Network. Refer

to Chapter 13.

$ 2.3.2.10 RF Modems. RF data modems provide communications between the ACU and DCP cabinets. Only

$ the Johnson Data rf modem (62828-40506-X) has controls and indicators as shown on figure 2.3.8 and

$ described in table 2.3.6.
S100 ASOS Site Technical Manual

2-27

Figure 2.3.5. Power Supply Assembly 62828-40124-10 Controls and Indicators

Table 2.3.3. Power Supply Assembly 62828-40124-10 Controls and Indicators

Control/

Indicator

Type Description

OUTPUT

POWER 

Rocker switch When set to on (1), turns UPS on and applies ac power to ACU cabinet and

peripherals.

OUTPUT LED When illuminated, indicates that UPS is on and that ac power is being supplied

to ACU loads.

BATTERY LED When illuminated, indicates that ACU backup batteries in Battery Box 1A8 are

fully charged. When blinking, indicates that batteries are low and UPS is

recharging them.

AC FAIL LED When illuminated, indicates that ACU primary power source has failed and that

UPS is supplying backup ac power to ACU loads. The UPS beeps every 10

seconds while backup power is being used.

ALARM LED When illuminated, indicatesthat UPS has overheated, backup battery is dead (less

than 40 vdc), backup battery is overvoltage (greater than 78 vdc), or there issome

other problem with UPS components.

Circuit breaker Pushbutton

switch

Provides overload protection for the UPS and its loads. Pushbutton switch pops

out when circuit breaker trips; press in to reset the breaker.
ASOS Site Technical Manual S100

2-28 Change 2

Figure 2.3.6. Power Supply Assembly 62828-40265-10 with Deltek UPS 62828-90338-10

Controls and Indicators
S100 ASOS Site Technical Manual

Change 2 2-29

Table 2.3.4. Power Supply Assembly 62828-40265-10 with Deltek UPS 62828-90338-10 $

Controls and Indicators

Control/ Indicator Type Description

ON LED When illuminated, indicates that output voltage is available.

AC INPUT LEDs (three) When top LED is illuminated, indicates that line is too high

(overvoltage condition) and that UPS is in battery operation. When

middle LED is illuminated, indicates that the line is OK. When

bottom LED is illuminated, indicates that line is too low

(undervoltage condition) and that the UPS is in battery operation.

SITE WIRING FAULT LED When illuminated, indicates that there is either no existing ground

wire connection or that the line and neutral wires are reversed in the

line receptacle.

BATTERY LED's (four

green, one red)

When illuminated, indicate the condition of the battery charge.

BATTERY SERVICE LED When illuminated, indicates when a potential battery failure is

detected. If reset is pushed, continues to flash until service is

performed.

ALARM SILENCE/

RESET

Pushbutton The alarm sounds at any new alarm condition. If the problem is

resolved or if ALARM SILENCE/RESET is pushed, the buzzer

sounds.

LOAD LED's (five) When the top LED is illuminated, indicates when the load current

or wattage exceeds full load. The bottom four (green) LED's show

either the load current or load wattage (whichever is higher) in

increments of approximately one-fourth of full rating.

COMMUNICATION LED Turns on after the UPS receives a command code from a computer

to establish communication. Flashes during data transfer via the

COMM PORT.

UPS ON/OFF SWITCH Rocker switch When set to on (1), turns on UPS and applies ac power to ACU

cabinet and peripherals.

SETUP DIP SWITCHES DIP switches Switches 1, 2, 3, 4, 5, 7, and 8 are user-defined switches. OFF is

default position.

Switch Function Default Position $

1 Line Voltage Select OFF $

2 Line Voltage Select OFF $

3 Site Warning Alarm OFF $

4 Back Alarm OFF $

5 Low/Auto Shutdown OFF $

6 Not Used OFF $

7 ASOS Protocol OFF - Firmware vsn 2.1 & up $

ON - Firmware below vsn 2.1 $

8 Frequency Select OFF $

COMM PORT Connector Allows the UPS to report status to the ACU.

BATTERY BOX

CONNECTOR

Connector Allows external batteries to be connected to the UPS.

OUTPUT RESET Pushbutton Provides overload protection for the UPS and its loads. Pops out

when circuit breaker trips; pressed in to reset the breaker.

5-15R Receptacles

(four)

Used to provide power to additional equipment.

5-20R Receptacles

(two) 

Used to provide power to additional equipment.
ASOS Site Technical Manual S100

2-30 Change 2

Figure 2.3.7. Power Supply Assembly 62828-40265-10 with Deltek UPS 62828-90338-20

Controls and Indicators
S100 ASOS Site Technical Manual

Change 2 2-31

Table 2.3.5. Power Supply Assembly 62828-40265-10 with Deltek UPS 62828-90338-20 $

Controls and Indicators $$

Control/ Indicator Type Description $

ON LED LED When illuminated, indicates that output voltage is available. $

INPUT VOLTAGE LEVEL LEDs $

Red $

Green $

Green $

Red $

Reading LEDs from top to bottom: $

1 (top) - Line voltage is too high: UPS battery providing power. $

2 - Line voltage is normal: AC input providing power. $

3 - Line voltage is lower than normal: AC input providing power. $

4 (bot) - Line voltage is too low: UPS battery providing power. $

SITE WIRING FAULT LED When illuminated, indicates that there is either no existing ground $

wire connection or that the line and neutral wires are reversed in the $

line receptacle. $

BATTERY LEVEL LEDs $

Green $

Green $

Green $

Red $

Reading LEDs from top to bottom: $

1 (top) - Batteries are fully charged. $

2 - Battery charge is approximately 2/3 of full charge. $

3 - Battery charge is approximately 1/3 of full charge. $

4 (bot) - Low battery (3 - 5 minutes of battery backup remaining). $

BATTERY SERVICE LED When illuminated, indicates when a potential battery failure is $

detected. An audio alarm will be also be sounding. $

TEST/ALARM SILENCE $

BUTTON $

Pushbutton The alarm sounds at any new alarm condition. If the problem is

resolved or if ALARM SILENCE/RESET is pushed, the buzzer $

sounds. $

LOAD LEVEL LED's $

Red $

Green $

Green $

Green $

Reading LEDs from top to bottom: $

1 (top) - Load current exceeds full load. $

2 - Load current is at maximum. $

3 - Load current is at 2/3 of maximum. $

4 (bot) - Load current is at 1/3 of maximum. $

COMMUNICATION LED Turns on after the UPS receives a command code from a computer $

to establish communication. Flashes during data transfer via the $

COMM PORT. $

ON BUTTON Pushbutton When pressed, applies ac power to UPS receptacles. $

OFF/STANDBY BUTTON Pushbutton When pressed, removes power from UPS receptacles, but the $

batteries will continue to charge. To completly remove power, the $

UPS must be unplugged. $

COMM PORT Connector Allows the UPS to report status to the ACU. $

BATTERY CONNECTOR Connector Allows external batteries to be connected to the UPS. $

NETWORK TRANSIENT $

PROTECTOR $

Connector Not used in ASOS.

LOAD SEGMENTS #1 $

AND #2 $

Receptacles Six 5-15R receptacles used to provide power to equipment. Each $

segment is protected by a RESET button that pops out when an $

overload condition exists. $

LOAD SEGMENT #3 Receptacles Two 5-20R receptacles used to provide power to equipment. $
ASOS Site Technical Manual S100

2-32 Change 2

Figure 2.3.8. Johnson Data RF Modem Controls and Indicators

$

$$ Table 2.3.6. Johnson Data RF Modem Controls and Indicators

Index

Control/

Indicator Description

$ 1 SMA Connector RF output (requires SMAM-to-BNCF adapter)

$ 2 HDB-15 Connector High density 15 pin female power/communications connector (requires

$ adapter cable 62828-42110-10)

$ 3 RX LED (Yellow) Illuminates when receiving data

$ 4 TX LED (Red) Illuminates when transmitting data

$ 5 PWR LED (Green)

$ (Flashing)

Illuminates when power is applied

$ Illuminates when setup mode is active

2.3.3 OPERATIONAL PROCEDURES

The primary operational procedures associatedwith theACUand peripherals are the application and removal

of power. Also, the technician may occasionally have to enter the site ID and AOMC phone number, and

refresh the OID screen. The following paragraphs describe each of these procedures. 

$ 2.3.3.1 ACU Power Up and Power Down Procedures. Tables 2.3.7 and 2.3.8 provide the procedures to

apply and remove power from the ACU and its peripherals. 
S100 ASOS Site Technical Manual

Change 2 2-32.1

Table 2.3.7. ACU and Peripherals Power Up Procedures $

Step Procedure

1 At OID, set powerswitch located on monitor base to ON position. The power-on indicator located in the left

front of the CRT illuminates.

2 If ACU has a UPS, ensure that UPS POWER switch is set to off (0) position.

3 At ACU DC Power Supply Enclosure 1A5, ensure that ON/OFF switches on power supplies PS1 and PS2

are set to ON (1) position.

4 Set facility power circuit breaker for ACU to on position. If Class I ACU, power is applied to ACU cabinet

components when facility power is applied.

5 If ACU has a UPS, set UPS POWER switch to on (1) position. Power is applied to components in Class II

ACU cabinet.

6 With power applied to OID and ACU and after a brief warmup delay, OID displays the 1-minute display. If

the display is not being updated, press the HELP key twice to refresh the screen. The data fields may contain

the letter M, indicating that the sensor(s) are notreporting measurement data.Ifthe message NEED SID AND

AOMC PHONE message is displayed at the top of the screen, the system has lost its memory and requires

a download of site specific data from the AOMC. In this case, perform the following procedures:

a. Sign on system as a technician.

b. Call up the REVUE SITE CONFIG EXTERN display on the OID and enter the phone

number of the AOMC in the AOMC PHONE NUMBER field. 

c. Call up the REVUE SITE PHYS display on the OID and enter the three to five-character

SID code for the ASOS site in the STATION IDENTIFIER field. The system then calls

the AOMC and receives a download of site specific data. After the download is complete,

the system automatically initializes to the proper configuration and begins normal

operation.

7 Ensure that any other peripheral devices(VDU's, CVD's, printer, etc) associated with the ACU are turned on.

Table 2.3.8. ACU and Peripherals Power Down Procedures $

Step Procedure

1 Turn printer off by setting power switch, located on right side of printer, to off position.

2 Turn off OID by setting power switch on monitor base to OFF position.

3 If ACU has a UPS, set UPS POWER switch to OFF position.

4 Set facility power circuit breaker for ACU to OFF position.

5 Turn off any other peripheral devices (VDU's, CVD's, etc) associated with the ACU. 

2.3.3.2 Providing Site ID and AOMC Phone Number. If the ACU loses its site specific data, it requests

a download of site specific data from the AOMC. If the ACU has also lost its site ID (SID) code and the

AOMC phone number, it displays the prompt NEED SID AND AOMC PHONE on the top line of the OID.

In this case, the technician must enter the site ID and the AOMC phone number at the OID so that the ACU

can call the AOMC and request the download. Table 2.3.9 provides procedures to enter the SID code and $

the AOMCphone number. Afterthe download is complete, the systemautomatically initializesto the proper

configuration and begins normal operation.

2.3.3.3 Refresh OID. In the event that power is removed from the ACU cabinet, the OID retains the last

display on its screen. If, after power returns to the ACU, the OID screen is not updated, the screen must be

refreshed by pressing the HELP key twice. This reestablishes ACU/OID communication and allows the

system to function normally.
ASOS Site Technical Manual S100

2-32.2 Change 2

2.3.4 USING LAPTOP COMPUTER AS PRIMARY OID

Some sites may not have a primary OID connected directly to the PRIMARY OID connector (J22) of ACU

I/O Panel Assembly 1A9. This may be because another local OID serves as primary (e.g., tower OID) or

because a particular site has no local OID at all. In either case, the technician may connect the laptop

$ computer to the PRIMARY OID connector (as described in table 2.3.10) to perform all technician-related

tasks. SIO port 3-4 must be properly configured for a primary OID on the ACU serial communications page

before the system will be able to communicate with the laptop computer. If not, the technician must access

the ACU serial communications page from another OID (a remote OID as described in paragraph 1.3.14 if

no other is available) and set up port 3-4 as follows:

FUNCTION: OID (any available, 1-8)

STATUS: ENABLED 

BAUD RATE: 9600

PARITY SELECT: NONE

BITS/CHAR: 8

STOP BITS: 1

HANDSHAKE: NONE

CONNECTION: HARDWIRED

$ Table 2.3.9. SID and AOMC Phone Number Entry

Step Procedure

1 To determine ifsystemrequires download ofsite specific data fromAOMC, verify that message NEED SID

AND AOMC PHONE is displayed at top of OID screen.

2 Sign on system as a technician.

3 Call up the REVUE SITECONFIG EXTERN display on the OID and enterthe phone number ofthe AOMC

in the AOMC PHONE NUMBER field. 

4 Call up the REVUE SITE PHYS display on the OID and enter the three to five-character SID code for the

ASOS site in the STATION IDENTIFIER field. The system then callsthe AOMC and receives a download

of site specific data. After the download is complete, the system automatically initializes to the proper

configuration and begins normal operation.

$ Table 2.3.10. Connecting Laptop Computer as Primary OID

Step Procedure

NOTE

SIO port 3-4 (corresponds to PRIMARY OID connector J22 on I/O Panel Assembly 1A9) must

be configured as a hardwired OID port on ACU serial communications page before laptop

computer can be recognized as an OID. Paragraph 2.3.4 provides setup parameters. 

INITIALIZATION

Tools required:

 Laptop computer with

 PROCOMM Plus installed

 Laptop interface (Y-shaped) cable

 DB-9 to DB-25 adapter
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Change 2 2-32.3/ (2-32.4 blank)

Table 2.3.10. Connecting Laptop Computer as Primary OID -CONT $

Step Procedure

1 Connect RS-232 (COM1) port of laptop computer to PRIMARY OID connectorJ22 on I/O Panel Assembly

1A9 using the following support items:

(1) Laptop interface (Y-shaped) cable 

(2) One DB-9 to DB-25 adapter

2 Turn on laptop computer and initialize to PROCOMM Plus program. When program initializes, press any

key to enter terminal mode (blank) screen.

3 On laptop computer, set CAPS LOCK to ON.

4 Using ALT-S command (setup facility), set up the following TERMINAL OPTIONS:

(1) Terminal emulation: VT220

(2) Duplex: FULL

(3) Soft flow control (XON/XOFF): OFF

(4) Hard flow control (CTS/RTS): OFF

(5) Line wrap: OFF

(6) Screen scroll: OFF

(7) CR translation: CR

(8) BS translation: NON-DESTRUCTIVE

(9) Break length (milliseconds): 350

(10) Enquiry: OFF

(11) EGA/VGA true underline: OFF

(12) Terminal width: 80

(13) ANSI 7 or 8 bit commands: 8 BIT

5 Return (exit) to terminal mode (blank) screen.

6 Using ALT-P command (line/port option), set CURRENT SETTINGS as follows:

(1) Baud rate: 9600

(2) Parity: NONE

(3) Data bits: 8

(4) Stop bits: 1

(5) Port: COM1

7 Return (exit) to terminal mode (blank) screen.

8 ACU begins communication and 1-minute display is displayed on laptop screen. Laptop computer now functions as an OID. If display is not correct, set NUM LOCK key to ON and press 0 (help) twice to refresh

screen.

9 Sign on and operate OID in usual manner. Ensure that NUM LOCK is set to ON when using number keys

with function keypad on screen and that NUM LOCK is set to OFF when entering alphanumeric characters

(e.g., initials and password during sign-on).

SIGNOFF

1 From 1-minute display, sign offin usual manner. Ensure that NUM LOCK isset to ON when using SIGN key

on display and that NUM LOCK is set to OFF when entering initials for signoff.

DISCONNECTING LAPTOP PRIMARY OID

1 Sign off OID as described above.

2 Using ALT-X (exit) command, exit Procomm Plus.

3 Turn off laptop computer.

4 Disconnect cables and adapter between laptop computer and I/O Panel Assembly 1A9.
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SECTION IV. THEORY OF OPERATION

2.4.1 ACU AND PERIPHERALS OVERVIEW

The task of central control and dissemination of all data is performed by the acquisition control unit (ACU),

which isthe central receiving point of allsensor data. The ACU receivessensor data fromthe data collection

packages(DCP's), processesthe data according to preprogrammed instructions(algorithms), and outputsthe

appropriate information to the various peripheral devices and users. In addition, the ACU controls a speech

processor that communicates using digitized human speech. Another important feature of the ACU is the

conduct of all diagnostic routines and themeaningful interpretation ofresultstomaintenance personnel. This

section describes ACU theory of operation at the simplified block diagramand detailed block diagramlevels.

The Codex modem, when furnished, is described in Chapter 13.

2.4.2 SIMPLIFIED BLOCK DIAGRAM DESCRIPTION

A simplified block diagram of the ACU is depicted on figure 2.4.1. The major subassemblies of the ACU

are the card rack assembly, the modem ac power rack, the power supply assembly, the dc power supply

enclosure, the rf/pressure mounting shelf, the I/O panel assembly, and the battery box. The ACU's major

functions are grouped into three functional areas: data processing, data input/output, and power distribution

and control. These functional areas are discussed in the following paragraphs.

2.4.2.1 Data Processing. The data processing functional area is responsible for system timing and control,

data processing, data formatting and storage, and data quality checks. All hardware required for data

processing is contained in the card rack assembly and includes two central processing units (CPU's) and a

memory board.

2.4.2.1.1 Central Processing Units (CPU's). The CPU boards provide central processing and control for

the entire ASOS.BothCPU boards are identical. TheCPU boards are programmed to performself-tests once

per second during real-time operation and constantly monitor each other. If a self-test error is detected, the

faulty CPU is flagged off-line and the other CPU assumes the processing duties. 

2.4.2.1.2 Memory Board. The memory board contains the ASOS operational software used by the CPU's.

The memory board also stores archive data, the maintenance log, and site specific constants. The board

contains up to 6 megabytes of memory with a battery backup for random access memory (RAM) in the event

of a power failure.

2.4.2.2 Data Input/Output. The data input/output (I/O) functional area is responsible for data acquisition

and communications between the data processing functional area and the ASOS users (Chapter 1). Due to

the large number and variety of ASOS communications, the I/O functional area is the largest and most

complex of the ACU system. Communications between ASOS users and the data processing functional area

are established through telephone lines, modems, and I/O boards. Communications between the ACU and

DCP are established through I/O boards and rf modems (or optional line drivers). Communications between

the pressure sensors and the data processing functional area are established through I/Oboards. Five different

types of I/O boards exist: serial I/O, analog to digital (A/D), digital I/O, digital voice processing, and video

controller. The type of I/O board used is dependent on the requirements of the user. The modems (up to 10)

contained in the modem ac power rack are used for remote communications via telephone lines. The

rf/pressure mounting shelf contains up to two rf modems (primary and secondary). The rf modems are used

to establish an rf communications link between the ACU and the DCP's when no direct lines are available.

When direct lines are available at the DCP, communications are accomplished through line drivers (short
ASOS Site Technical Manual S100

2-34 Change 1

haul modems) located in the modem ac power rack. ACU I/O hardware is described in the following

paragraphs.

2.4.2.2.1 SerialI/O Boards. From three to eightserial I/O (SIO) boards are used to interface the ACU CPU

boards with other communications equipment. SIO board 1 is a model XVME 401 interface, which provides

four RS-422 serial I/O ports. SIO board 1 is dedicated to the FAA tower computer control complex (TCCC),

the FAA ADAS, and RVR. All other SIO boards are model XVME 490/1, each of which provides four

RS-232 ports. SIO boards 2 and 3 are dedicated to the two (in Class II) rf modems or line drivers, the first

two pressure sensors, modems 4 and 5 in the modem ac power rack (these correspond to user phone 1 and

2 ports), the digital voice system, and the primary operator interface device (OID). SIO boards 4 through 8

are optional. Unlike the first three SIO boards, their individual I/O ports are not dedicated to specific pieces

of equipment.Rather, their ports are assigned to various equipments by the ACU serial communications page

on the OID. They may interface any piece of equipment requiring RS-232 communications, such as the

printer, a local video display unit (VDU), a controller video display (CVD), AFOS hardwire and spare, or

the other modems in the modem ac power rack, etc. 

2.4.2.2.2 Analog to Digital (A/D) and VME Resistor Boards. The A/D board converts analog signals to

digital data so that the data can be read by the CPU. These boards convert analog dc power monitor signals

from the dc power supplies and the rf modems into digital data. The CPU then reads the data to determine

the power status of the dc powersupplies and the rf modems. The VME resistor board scales the dc voltages

before they are applied to the A/D board.

2.4.2.2.3 DigitalI/O Board. The digital I/O board containsfour digital I/O portsthat allow the CPU to read

and write control signals from and to the ACU. In particular, the digital I/O board inputs status signals from

the dc power supplies and the voice processor board (via the VME resistor board). In Class II systems, the

digital I/O board outputs a control signal to control an rf modem switch (or line driver relay) that switches

between the primary and secondary rf modems (or line driver). The digital I/O board in the Class II system

also monitors and controls the UPS bypass circuit.

2.4.2.2.4 Digital Voice Processing. Digital voice processing consists ofthree operations: producing a verbal

report from a stored vocabulary based on current ASOS data, recording an operator-generated addendum up

to 90 seconds long, and producing an output consisting of the automatically generated data and the operator

input. Outputs are available for the FAA handset, dial-up reports, and FAA radio communications for

aircraft. Voice processing is accomplished with two dedicated boards: a voice processor board and a voice

recorder/playback board. The voice processor board containstheCPU forthe digital voice system. Itreceives

digital voice filesfromthe ASOS CPU, creates voice reports consistent with the data reported by the sensors,

and receives operator-generated digitized audio from the voice recorder/playback board. The voice

recorder/playback board receives digitized voice from the voice processor board and converts the data into

audio. Audio is output for dial-in weather requests, for the FAA handset at OID port 5C, and to the GTA

radio for pilot use. In addition, the voice recorder/playback board receives input voice audio from the FAA

handset, digitizes the input audio, and transfers the digitized audio to the voice processor board for storage

in RAM.

2.4.2.2.5 Video Controller Board. The video controller board is an option that can be installed in the ACU

to allow it to drive external airline displays that are not part of the ASOS. The video controller board outputs

a composite RS-170 video signal required to drive the airline video displays. 
S100 ASOS Site Technical Manual

Figure 2.4.1. ACU Simplified Block Diagram

Change 1 2-35/ (2-36 blank)
S100 ASOS Site Technical Manual

Change 1 2-37

2.4.2.2.6 ACU/DCP Communication. Communications between the ACU and DCP are established via an rf

modem or line driver link. For Class II systems using an rf modem link, the communication system consists of two

rf modems, an rf modem switch, and an rf antenna. The CPU communicates with one of the modems via an SIO

board RS-232 data link. The modem, in turn, communicates with the DCP via the rf antenna. The two rf modems

are identical, with one serving as the primary communications link and the other as a backup. The rf switch selects

which modem uses the antenna. In the event that the primary rf modem fails (transmitter or receiver), all

communications are automatically switched to the secondary rf modem. For Class I systems, a single rf modem

provides the data link (rf switch is not required). The line driver communication link is similar, except that

communication with the DCP is over a direct line rather than the airwaves. For Class II systems, two line drivers

are installed in the modem ac power rack, and an LD1/LD2 switching board (installed in the rf/pressure mounting

shelf) switches between primary and secondary line drivers. For Class I systems, a single line driver handles all

ACU/DCP communication.

2.4.2.2.7 Telephone Modems. Telephone modems are used to provide communication between the ACU and

remote users or other devices (refer to Chapter 1, Section I for a list of the ASOS users who can receive/transmit

data over modems). The modem ac power rack can contain up to 10 modems. Three different models may be

installed in the modem rack: model 2440 (2400 baud), model V.3225 (9600 baud), and model V.3400 (28800

baud). The model 2440 modem is used for USER PHONE #1 (modem 4, refer to figure 2.1.4), USER PHONE

#2 (at some sites), and most other applications. The model V.3225 is used with optional OID #2 (port 3B) and

optional OID #3 (port 3C). The model V.3400 is used for USER PHONE #2 instead of the model 2440 at selected

sites. 

Modems 4 and 5 are included in every installation and are dedicated to the USER PHONE #1 and #2

communication ports. These two modems communicate with the CPU via specific ports on SIO boards 2 and 3,

respectively. All of the other modems are provided as needed for communications options. These modems may

be connected to any port on SIO boards 4 through 8, depending upon how the ACU communications are

configured on the ACU serial communications page of the OID.

2.4.2.3 Power Distribution and Control. The power distribution and control functional area consists of Power

Distribution Rail A7, DC Power Supply Enclosure A5, and Power Supply Assembly A4 (Class II systems only).

The power distribution rail consists of a terminal strip that distributes ac and dc power and a power reset relay that

delays power application to the ACU for three seconds after site power is interrupted. The dc power supply

enclosure contains two identical power supplies that generate +5 volts, -12 volts, and +12 volts. These two power

supplies are wired in parallel to provide a guaranteed output in the event that either supply fails. Special circuits

built into the power supplies prevent a failed power supply from dragging down the operational power supply.

Class II systems contain an uninterruptible power supply (UPS) bypass circuit mounted on Power Distribution Rail

A7. The UPS bypass circuit provides additional power source control and monitoring. In the event of a power

failure, the UPS is capable of supplying backup ac power to the ACU under full load for a minimum of 10

minutes. Special line loss circuitry in the UPS constantly monitors the input voltage for a power loss. When a

power loss is detected, the circuitry allows Battery Box A8 to drive an inverter (dc to ac conversion), which

supplies ac power to the ACU. ACU components requiring ac power are the dc power supplies and the modem

ac power rack. The primary OID, the printer, and the FAA modems also receive UPS backup power via

PERIPHERAL POWER connector J40 on the I/O panel assembly. Any additional peripherals connected to the

UPS place an extra load on the UPS and reduce its capability to supply power. The UPS and Battery Box A8 are

not included in Class I systems. For these systems, ac power for internal ACU equipment and the PERIPHERAL

POWER connection is supplied directly from the input power applied to ACU INPUT POWER connector J41.

2.4.3 DETAILED BLOCK DIAGRAM DESCRIPTION

2.4.3.1 General. This section contains descriptions and detailed block diagrams of the ASOS ACU. The card rack

assembly is described using a detailed block diagram. The circuit cards dedicated to processing ASOS sensor data

are also described. Descriptions of the rf and telephone modems, digital pressure sensors, and local sensor fiber

optic modems include theory of operation and associated diagrams. 
ASOS Site Technical Manual S100

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Peripherals associated with the ACU, and connected through the connector panel, are the printer, CVD's,

VDU's, OID's, airline displays, OND, and FAA handset. Repair of a faulty ACU peripheral consists of

replacing the failed peripheral. Accordingly, the theory of operation of peripherals is presented on a general

level. The drawings associated with peripherals are intended to provide the technician with the information

necessary to conduct continuity checks when a connector is suspected of being faulty or needs replacement.

Power distribution and control is described using detailed block diagrams of the distribution of dc and ac

voltages to the ACU, including the UPS in the power supply assembly.

2.4.3.2 Card Rack Assembly. The card rack assembly contains up to 17 circuit boards that perform all of

the data processing and input/output functions. The following circuit boards are used specifically to process

data: CPU's A and B, and the memory board provide the computational system for the ACU. The following

circuit boards perform the ACU input/output functions: serial I/O (SIO) boards (up to eight), the A/D board

(in conjunction with the VME resistor board), the digital I/O board, the voice processor and voice

recorder/playback boards, and the video controller board. All of the circuit boards are designed to

accommodate the VMEbus backplane construction. Figure 2.4.2 illustrates the VMEbus chassis, backplane

configuration, and connector pin assignments as required by the VMEbus specification. One or two 96-pin

bus connectors are located on the rear edge of the board and are labeled P1 and P2. The 96-pin connectors

consist of 3 rows of pins (32 pins per row) labeled rows A, B, and C. The pin connections for P1 contain the

standard address, data, and controlsignals necessary forsystembus communication. The P1 pin assignments

are listed by pin number order. The pin connections for P2 vary according to the function provided by the

circuit board.The following paragraphs provide detailed information on the circuit boards and their dedicated

functions, and reference figure 2.4.3 (ACU Card Rack Assembly Detailed Block Diagram).

2.4.3.2.1 Central Processing Unit (CPU). The CPU executes the ASOS operational software. All

operational software resides in the erasable programmable read-only memory (EPROM) on the memory

board. Execution of the operational software involves data processing, data formatting, data quality checks,

and data storage. The card rack assembly contains two CPU circuit boards, both of which are identical and

contain a 68010 series microprocessor running at 10 MHZ, memory (EPROM and dynamic random access

memory (DRAM)), two RS-232 ports, and a 16-bit timer. During system operation, one of the CPU's

functions asthe primary CPU, which performs all processing and I/O functions. The other (secondary) CPU

provides a redundant processor. If, at any time, the primary CPU fails, it is taken off-line and the secondary

CPU becomes the primary CPU. Initially, CPU A is the primary CPU. Two pushbutton switches labeled

RESET and ABORT are provided on the front ofthe circuit board. ABORT halts programexecution without

resetting the CPU. This switch is used for development purposes and should not be used in the field. In the

event that ABORT is pressed, RESET should be pressed to reset the CPU and activate SYSRESET, thereby

resetting the entire backplane via the VMEbus.Resetting theCPU does not affect the contents ofthe DRAM.

The following paragraphs provide a detailed block diagram description of the CPU and its various modes

of operation.

The CPU consists of nine functional areas (Figure 2.4.3): the system resource function, dual UART and

timer, RS-232 driver and receiver logic, CPU clock, CPU, interrupt logic, VME interface logic, address

buffer and decode, and memory. The system resource function on CPU A providesthe system clock,system

reset, bus arbitration, and bus timer functions for the entire VMEbus. Because CPU A is the bus controller,

the system resource function on CPU B is not used. 

The dual UART and timer providestwo RS-232 serial communication channels(channels A and B), a timer,

and two I/O and control ports. The RS-232 driver and receiver logic interfaces UART channels A and B to

external devices via connector JK1 on the CPU by providing standard transmit and receive lines. On both

CPU A and CPU B, the two channels are not used. On CPU A, however, a loopback jumper is
S100 ASOS Site Technical Manual

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Figure 2.4.2. ACU VMEbus Chassis and Connector Pin Assignments (Sheet 1 of 3)
ASOS Site Technical Manual S100

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Figure 2.4.2. ACU VMEbus Chassis and Connector Pin Assignments (Sheet 2)
S100 ASOS Site Technical Manual

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Figure 2.4.2. ACU VMEbus Chassis and Connector Pin Assignments (Sheet 3)
ASOS Site Technical Manual S100

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installed between the channel B transmit and receive lines (pins 14 and 16 of connector JK1). This jumper

identifies CPU A as the initial primary CPU. When power is first applied to the ACU, both CPU's issue a

message from their respective UART channel B. CPU A then receives the message back via the installed

loopback jumper. Both CPU's then examine their receive lines. When CPU A detects that it has received the

signal via the loopback jumper, it assumes the role of the primary CPU. When CPU B detects that it has not

received its transmitted signal, it assumes the role of the secondary CPU. The secondary CPU continuously

monitors the primary CPU status by examining a memory location in the memory board used to store a free

running count. The primary CPU updatesthis count on a periodic basis. Failure to update the count indicates

a CPU failure. The secondary CPU then becomes the primary CPU.

The CPU clock provides the 10 MHZ clock signal required by the CPU. The CPU executes the ASOS

operational software. The interrupt logic monitors the dedicated interrupt lines and informs the CPU when

an interrupt line is active. The interrupts are prioritized and processed on a first come, first serve basis. The

VME interface logic provides the standard address, data, and control signals necessary for system bus

communication. The address buffer and decode providesthe address. The onboard memory consists of 128K

bytes of EPROM and 512K bytes of DRAM. The operating system software for the CPU is contained in the

EPROM. The refresh circuitry for the DRAM is not disabled during a RESET; therefore, the CPU may be

reset without affecting the memory contents.

The ACU continuous self-test (CST) checks the status of the CPU's once per minute. CST results are

displayed on the CPU page of the OID. The CST checks the following areas of both the primary and

secondary CPU: DRAM, EPROM, BUS ERRORS, SERIAL PORT #1 and #2 LOOPBACK, and SERIAL

PORT #1 and #2 XMIT ERRORS. For the primary CPU, test pass/fail status is displayed for each of these

areas. For the secondary (redundant) CPU, test status is displayed for the overall board only. The technician

can manually run the CPU test from the CPU page at any time. A T status is displayed for each test category

until the test is run again during the next CST cycle. After the cycle, the latest teststatusis displayed and the

fail count (if applicable) is incremented. 

The DRAM test is based on an alternating pattern. Data are output to the DRAM and read back, the returned

data are evaluated, and the test status is displayed. The EPROM test is based on a checksum. The checksum

is compared to the last byte in the EPROM, the result is evaluated, and the test status is displayed. The BUS

ERRORS test is based on a memory write to a specific address, with the contents of the addressed memory

evaluated and the test status displayed. 

The SERIAL PORT #1 and #2 LOOPBACK tests ensure that the CPU can communicate with its internal

UART. The CPU readsthe UART interrupt vector register and checksfor bus errors. Teststatusis displayed

as P (pass) if no bus errors occurred.

For the SERIAL PORT #1 and #2 XMIT ERRORS test, the CPU reads the contents of the status register for

the corresponding port. This register contains information on transmission errors detected by the UART

during RS-232 communications. Specifically, the CPU checks the status register for parity errors, framing

errors, and overrun errors that may have occurred. If such errors occur for three consecutive CST cycles, an

F (fail) is displayed for the test status; otherwise, test status is P (pass). 

2.4.3.2.2 Memory Board. The XVME-110 memory board contains three memory banks. Each bank is

independently configured via jumpers to specify VME address/memory chip size, device speed, device

pinout, and backup power. The following paragraphs provide a detailed block diagram description of the

memory board.

The memory board consists of nine functional areas (Figure 2.4.3): banks 1, 2, and 3 memory devices;

VME/bank address decode and control; battery backup; data buffer; bus cycle control; address buffer and

decode logic; and the system real-time clock. The first bank contains up to 4 Mbytes of EPROM. The

EPROM contains the operational software program run by the CPU. It also contains the DCP software load

that istransferred to a DCP in the event that a DCP losesits programload and requiresreinitialization. Banks
S100 ASOS Site Technical Manual

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2 and 3 contain up to 2 Mbytes of static random access memory (SRAM). The SRAM provides storage for

ASOS weather archives. The address and controlsignals used to address memory locations are generated by

the VME/bank address decode and control. The memory boards are configured with a battery backup to

provide an alternate power source in the event of a power loss. The data buffer, bus cycle control, and

address buffer and decode logic provide the standard address, data, and controlsignals necessary for system

bus communication.The real-time clockmaintains clock calendartiming, which is accessed by theCPUupon

initialization. When initialized, the CPU maintains a clock via software.

The ACU continuous self-test (CST) checks the status of the memory board once per minute. CST results

are displayed on the memory page of the OID. The CST performs an EPROM test and an SRAM test. The

technician can manually run the memory test from the memory page at any time. A T status is displayed for

each test category until the test is run again during the next CST cycle. After the cycle, the latest test status

is displayed and the fail count (if applicable) is incremented. 

The EPROM test is based on a checksum, which is compared to the last byte in the EPROM. The result is

evaluated and the teststatusis displayed. The SRAM test ensuresthat theCPU can read data fromthe SRAM

on the memory board without encountering bus errors.

2.4.3.2.3 Serial I/O (SIO) Board. The card rack assembly contains one XVME-491 SIO board and up to

seven XVME-490/1 SIO boards. The XVME-491/1 SIO board (SIO board 1) provides four RS-422 serial

ports, while each of the XVME-490/1 SIO boards(SIO boards 2 through 8) providesfour RS-232 ports. The

SIO boards communicate with the CPU on a character-by-character basis. The CPU must process interrupts

on each and every transmitted and received character. The following paragraphs provide a detailed block

diagram description of the SIO board.

The SIO board consists ofsix functional areas(Figure 2.4.4): two serial communication controllers(SCC's),

interrupt logic, data buffer, bus cycle control, and address buffer and decode logic. The SCC's provide a

variety of communicationmodes.Upon power up, theCPUinitializesthe SCC'sto the proper communication

modes. Interrupts are generated via the interrupt logic. An interrupt can signify that a received character is

available, that the transmit buffer is empty, or an external/ status change. The data buffer, bus cycle control,

and address buffer and decode logic provide the standard address, data, and control signals necessary for

system bus communication. 

The four ports of each of SIO boards 1 through 3 are factory assigned to specific devices. Their ports are

dedicated to these devices via corresponding connectors on the ACU main wiring harness. Although these

ports can be reassigned via the ACU serial communications page of the OID, the technician should not

reassign them; assigning these ports to other FRU's would invalidate their corresponding harness markers.

Table 2.4.1 identifies each ofthe ports of these SIO boards and liststhe corresponding harness connector and

the device to which it is connected.

Unlike SIO boards 1 through 3, SIO boards 4 through 8 are optional. Most systems will not have all of these

SIO boards installed. As such, the ports of these SIO boards are not factory assigned to specific devices.

Rather, these ports are assigned to various devices during the initial configuration of the system. This

assignment is made via the ACU serial communications page of the OID. Figure 2.4.4 identifies all of the

ports of SIO boards 4 through 8 and identifies the W014 (or W016) connector that corresponds to each. The

devices to which these connectors mate depend upon the device assigned to that port by the ACU serial

communications page. Figure 2.4.4 also identifies the pin-to-pin wiring between each of the SIO boards and

their respective connectors.
ASOS Site Technical Manual S100

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Table 2.4.1. Port Assignments for SIO's 1 Through 3

SIO Board Port W014/16

Connector

Device Function

1

(RS-422)

Note 1

1 P16 1A9J29 FAA ADAS

2 P17 1A9J27 FAA TCCC

3 P18 1A9J42 RVR

4 P19 N/A Spare

 2

(RS-232)

1 P21 1A6A4 or

1A3A13

RF Modem A

Line Driver A

2 P22 A6A1 Pressure Sensor #1

3 P23 1A3A4 Modem #4 (User Phone #1)

4 XA20-P2 1A2A20 Voice Processor Board

3

(RS-232)

1 P26 1A6A5 or

1A3A14

RF Modem B (Class II only)

Line Driver B (Class II only

2 P27 1A6A2 Pressure Sensor #2

3 P28 1A3A5 Modem #5 (User Phone #2)

4 P29 1A9J22 Primary OID

Note 1- ACU S/N 288 and below use crossover connector cables (W77) between W014/16 and the device connectors

to conFigure the RS-422 ports for DTE I/O. ACU S/N 289 and above are factory wired for DTE I/O. 

The ACU CST checks the status of the SIO boards once per minute. CST results are displayed on the ACU

SIO display pages of the OID (there is one page for each of the eight SIO boards). The CST performs a

LOOPBACK test and an XMIT ERRORS test on each of the four ports of an SIO board. The technician can

manually run the SIO test from an SIO page at any time. A T status is displayed for both test categories until

the test is run again during the next CTS cycle. After the cycle, the latest test status is displayed and the fail

count (if applicable) is incremented. 

For the LOOPBACK test, the CPU reads an interrupt vector register on the SIO board to ensure that it can

communicate with the SIO port. For the XMIT ERRORS test, the CPU reads the contents of the SCC status

register for the corresponding port. Thisregister containsinformation on transmission errors detected by the

SCC during RS-232 communications. Specifically, the CPU checks the status register for parity errors,

framing errors, and overrun errorsthat may have occurred. For both LOOPBACK and XMIT ERRORS tests,

CST status is displayed as either P (pass), F (fail), or D (degraded). A status of D is displayed if five or more

errors have been detected and the port is currently passing the test. At 0600 LST each day, the number of

accumulated failuresissummarized in the system(maintenance)log. Paragraph 1.3.4.3.3 provides additional

information on SIO test reporting.

2.4.3.2.4 Voice Processor and Voice Recorder/PlaybackBoards.The voice processor board and the voice

recorder/playback board make up the digital voice processing system of the ACU. Both of these boards are

connected to the VMEbus for power and system reset purposes. Communication between the CPU and the

digital voice systemis accomplished via the RS-232 link between SIO board 2 and the voice processor board

(rather than over the VMEbus). The voice processor board communicates with the voice recorder/playback

board via a 50-pin ribbon cable connected between the front panels of both boards. Voice outputs from the

digital voice system are passed to the I/O panel where they are made available for dial-up reports, the FAA

handset, and FAA radio communications for aircraft. Additional information on these boards is provided in

the digital voice processor detailed block diagram description (paragraph 2.4.3.3).
S100 ASOS Site Technical Manual

Figure 2.4.3. ACU Card Rack Assembly

Detailed Block Diagram (Sheet 1 of 2)

2-45/ (2-46 blank)
S100 ASOS Site Technical Manual

Figure 2.4.3. ACU Card Rack Assembly

Detailed Block Diagram (Sheet 2)

Change 1 2-47/(2-48 blank)
 S100 ASOS Site Technical Manual

Figure 2.4.4. SIO Boards 4 Through 8 Ports

and Pin Assignments (Sheet 1 of 2)

2-49/ (2-50 blank)
S100 ASOS Site Technical Manual

Figure 2.4.4. SIO Boards 4 Through 8 Ports

and Pin Assignments (Sheet 2)

2-51/ (2-52 blank)
S100 ASOS Site Technical Manual

Change 1 2-53

2.4.3.2.5 Video Board. The video board is an option that is installed on systems connected to airline video

displays. The video board functions asthe interface between the VMEbus and the airline video displays. The

airline video displays are updated once per minute. The video display is memory mapped.

The video board consists of eight functional areas: data buffer, bus cycle control, address buffer and decode

logic, memory, video timing and control, clock, RTC battery backup, and interrupt logic. The data buffer,

bus cycle control, and address buffer and decode logic provide the standard address, data, and controlsignals

necessary forsystembus communication.Thememory providesthe storage forthe display information.Each

character location has a specific memory location. The data stored in memory are used to select a specific

character and how it is displayed. The video timing and control provides the sync signals (horizontal and

vertical) and display timing signals as well as memory address refresh. These discrete video signals are

combined and output as a composite video signal. The clock and battery backup are not used.

The ACU CST checks the status of the video board once per minute. CST results are displayed on the video

(graphics) page of the OID. The CST performs five tests: CRT CONTROLLER READBACK, PARALLEL

I/F TIMER READBACK, LOOPBACK #1 and #2, and RT CLOCK READBACK. The technician can

manually run the video memory test from the video page at any time. A T status is displayed for each test

category until the test is run again during the next CST cycle. After the cycle, the latest test status is

displayed and the fail count (if applicable) is incremented.

The CRT CONTROLLER READBACK test readsthe contents of a register in a CRT controller in the video

timing and control area of the board. The status word is evaluated and the test status is displayed. The

PARALLEL I/F TIMER READBACK test checks the operation of a parallel interface on the board. This

parallel interface is not used. The LOOPBACK #1 and #2 tests check the status of two RS-422 SCC's

provided by the board. These SCC's are not used by the system. The RT CLOCK READBACK tests clock

timing. This clock is not used by the system.

2.4.3.2.6 DigitalI/O Board. The digital I/O board provides address buffer and control, a data buffer, timing

and interrupt control, two dual I/O port IC's(#1 and #2), and four transceivers. The CPU communicates with

the digital I/O board over the VMEbus via the address buffer and decode, the data buffer, and the timing and

interrupt control. The two dual I/O port IC's provide a total of four ports (ports A1, B1, A2, and B2), each

of which communicates with external devices via a dedicated transceiver. Port A1 is configured as an input

only port. This port is used by the CPU to input a watchdog timer signal from the voice processor board and

to input status bits for the dc power supplies (via the VME resistor board) and the UPS bypass circuit. Port $

B1 is configured as an output only port. This port is used by the CPU to output control signals to the voice

recorder/playback board, the rf modem switch (or line driver relay), and the UPS bypass circuit. Ports A2 $

and B2 on the DIO board are not used in the ACU. The ACU CST does not check the status of the digital

I/O board.

2.4.3.2.7 A/D Board and VME Resistor Board. The A/D board and the VME resistor board make up the

ACU power and signal monitoring function. The A/D board, in conjunction with the VME resistor board,

receives dc power monitor signals and converts them to digital values that may be read by the CPU via the

VMEbus. A detailed description of these boards is provided in the ACU power and signal monitoring

description (paragraph 2.4.3.8).

2.4.3.3 Digital Voice Processor System. The digital voice processor (Figure 2.4.5) is made up of Voice

Processor Board A20 and Voice Recorder/Playback Board A21. These two boards operate together as a

systemand are tested together. They are both connected to the VMEbusfor power and systemreset purposes,

but they do not communicate with the CPU via the VMEbus. CPU/voice system communication is

accomplished via the RS-232 link between SIO board 2 and the voice processor board.
ASOS Site Technical Manual S100

2-54

2.4.3.3.1 Voice Processor Board. The voice processor board contains a Z80XXX series (Z80 thousand

series) microprocessor and the necessary memory to execute onboard instructions. These instructions are

used to reconstruct digitized human voice, create voice reports, and receive operator-generated digitized

audio from the voice recorder/playback board. The voice processor board communicates with the VMEbus

directly for power and systemreset and indirectly via SIO board 2 forsystem communication. The following

paragraph provides a detailed block diagram description of the voice processor board.

The voice processor board consists of nine functional areas (Figure 2.4.5): system reset/power interface,

DRAM, EPROM vocabulary, CPU, audio board interface, timing and control logic, serial communications

controller,RS-232 driver and receiver logic, and watchdog timer and alarm. The system reset/power interface

generates an internal reset when the system reset signal from the VMEbus is received or the RESET

pushbutton switch on the front of the board is pressed and power is applied. The internal reset disables

message broadcast until a play message string is received from the CPU via SIO board 2. The VMEbus

interface for power and ground requirements is also provided by the system reset/power interface. The

DRAMprovides 1Mbyte ofmemory formessage/file storage.Thisisthe area where digitizedmessagesfrom

the FAA handset are stored. These messages are appended to the automatically generated observation

messages. The EPROM vocabulary consists of 512 Kbytes of EPROM for voice files. The onboard CPU

executes the operational software to execute new message strings and to monitor the eight telephone lines.

The audio board interface provides the communication path to the voice recorder/playback board via the

50-pin connector on the front of the board. The necessary timing and interface signals required by the CPU

and peripherals are provided by the timing and control logic. The serial communications controller provides

the RS-232 serial communication channel, and the RS-232 driver and receiver logic provides the standard

RS-232 receive and transmit lines. The watchdog timer and alarm provides an alarm signal to the primary

CPU (via Digital I/O Board 1A2A15) when a CPU software or hardware failure occurs.

2.4.3.3.2 Voice Recorder/Playback Board. The voice recorder/playback board receives digitized voice

from the voice processor board and converts it into audio. Audio is output as a weather data message for

dial-in weather requests and to a VHF transmitter for airline use. In addition, the voice recorder/playback

board receives audio signals from the FAA handset and transmits the digitized audio to the voice processor

board for processing. The following paragraph provides a detailed block diagram description of the voice

recorder/playback board.

The voice recorder/playback board consists of six functional areas (Figure 2.4.5): CPU board interface,

power interface logic, radio transmitter output logic, record and playback logic, telephone line output logic,

and audio alarm output logic. Pinouts for the output of the voice recorder/processor board (XA21-P2) are

provided on the table on figure 2.4.5. The signal mnemonics and pins associated with row A and row C of

XA21-P2 are listed with the associated plug connector. For example, the RING signal of the FAA handset

line can be monitored at pin 20 of XA21-P2 or pin 2 of plug 68 (P68). The CPU board interface provides the

communication path to the voice processor board via the 50-pin connector on the front of the board. The

VMEbus interface for power and ground requirements is provided by the power interface logic. The radio

transmitter output logic and the record and playback logic digitize audio input and synthesize digitized voice

to audio. The interface circuits to the telephone outputs and line output peripherals are provided by the

telephone line output logic. The audio alarmoutput logic provides an audio alarmindicator. One ofthe audio

line outputs is continually monitored by the alarm circuit. A loss of audio for a predetermined period causes

the indicator on the voice recorder/playback board to illuminate. Chapter 12 provides information on GTA

radio pin-to-pin connections. 
S100 ASOS Site Technical Manual

Figure 2.4.5. Digital Voice Processor Detailed

Block Diagram

2-55/ (2-56 blank)
S100 ASOS Site Technical Manual

Change 1 2-57

2.4.3.3.3 Testing the Digital Voice Processing System. The ACU CST checks the status of the digital

voice processing system once per minute. CST results are displayed on the voice page of the OID. The CST

performs four tests on the voice processing system: CPU, AUDIO OUTPUT, AUDIO STATUS, and

TIMEOUT. The technician can manually run the voice processing test from the VOICE page at any time.

A T status is displayed for the four test categories until the test is run again during the next CST cycle. After

the cycle, the latest test status is displayed and the fail count (if applicable) is incremented. 

The CPU test checks the operational status of the voice processor board. The TIMEOUT test checks the

operational status of the watchdog timer. The AUDIO OUTPUT and AUDIO STATUS tests check the

operation of the voice recorder/playback board and indirectly test the voice processor board. The AUDIO

OUTPUT test is based on an internal audio test that checks the audio circuitry. The AUDIO STATUS test

is based upon a monitored audio line. The status of each test is evaluated and the test status is displayed.

2.4.3.4 Modem Communications. Three different types of modem communications are provided in the

ACU cabinet: modems for telephone communications, rf communications, and dedicated line

communications. The system is configured with rf modems or line drivers (commonly referred to as short

haul modems); it does not contain both. The following paragraphs provide a detailed block diagram

description of the modems and their modes of operation.

2.4.3.4.1 Telephone Modems. Modem AC Power Rack 1A3 can contain up to 10 telephone modems

(Figure 2.4.6) which operate in a 2-wire full duplex mode over both leased lines and the public switched

network. The modems provide communications to external devices over leased line or public switched

telephone network at data rates of 2400, 9600, or 28800 baud (models 2440, V.3225, and V.3400

respectively). All data transfers are under the control of the SIO boards, which communicate with the data

terminal equipment (DTE) ports of the modems using RS-232 protocol. 

In most cases, the modems used are model 2440 devices, which operate at data rates of up to 2400 baud.

Modems 1A3A4 and A5 are provided in all systems, and are dedicated as USER PHONE #1 (model 2440)

and #2 (model 2440 or V.3400). These modems are controlled by port 3 of SIO boards 2 (A6) and 3 (A7).

The outputs of these modems are connected to J15 and J16 of I/O Panel Assembly 1A9. Sheet 1 of

figure 2.4.6 illustrates the installation of the model 2440 and V.3400 modems. 

All of the other modems are optional and are installed in the system as required to provide the following

ports:

a. AFOS phone 

b. OID spare

 c. ADAS $

d. VDU's

 e. AWIPS

 f. User Phone #1 spare

 g. User Phone #2 spare

 h. Printer

These modems are controlled by SIO boards 4 through 8. Their outputs are connected to connectors J12

through J14 and J17 through J21 of I/O Panel Assembly 1A9.

As stated above, model 2440 modems are used for most ASOS telephone communication applications. The
ASOS Site Technical Manual S100

2-58 Change 2

exceptions are USER PHONE #2 at selected sites which uses the 28800 baud modem (model V.3400) and

optionalsecondary OID's(OID #2, port 3B, and OID #3, port 3C) which use the 9600 baud modem(V.3225).

When secondary OID ports are active, model V.3225 modems are installed in modem rack slots A2 and A3.

Leased line connections are made at connectors J13 and J14 of I/O Connector Panel 1A9. Sheet 2 of

figure 2.4.6 illustrates the configuration of an ACU that has been modified to accept V.3225 modems (9600

baud) in slots A2 and A3. This modification is performed for ACU's (Class I and Class II) having serial

numbers 364 and below. Sheet 3 of figure 2.4.6 shows the configuration of an ACU for which the V.3225

modems were built in as original equipment. This configuration applies to Class I and Class II ACU's with

serial numbers 365 and above.

The ACU CST checks the status of the telephone modems configured for dial-up operation (leased line

modems are always on-line and cannot be tested). CST results for the dial-up modems are displayed on the

MODEM RACK page of the OID. Each modem is tested once every 7 minutes, as long as the modem is not

busy (no user islogged onto the system). If the modem is busy during a CST cycle, the CST is not performed.

Thisis because running the CST on an active modem disruptsthe communications and valuable information

may be lost.

The test that is performed during CST is an analog self-test loopback test. The CPU initiates the test, but the

entire test is performed inside the modem. The transmitter in the modem is internally linked to the receiver.

The modem then generates a test pattern, transmits it over the loopback, receives the data, and checks for

errors. The modem completes the test by reporting its pass/fail status back to the CPU. The CPU then

displays the status on the MODEM RACK page. A status of D (degraded) is displayed for a modem if five

or more failures have been detected and the modem is currently passing its loopback test. At 0600 LST each

day, the number of accumulated failures is summarized in the system (maintenance) log. Chapter 1,

Section III provides additional information on SIO test reporting.

In addition to the regular CST testing, the technician may manually initiate a test of a dial-up modem from

the MODEM RACK page. When a test is ordered, the modem immediately tests itself as described above.

As mentioned before, if the modem is busy when the test is ordered, current communications are disrupted

as the test is performed. For this reason, the technician should ensure that the modem is not in use before

manually issuing a test command. The LCD indicator on the front of the modem which should indicate

OFF-LINE can be used to verify that the modem is not in use.

$ 2.4.3.4.2 RF Modems. Three different rf modems are used in two ACU configurations. The modems are

$ 62828-90013-XX (AAI Corporation), 62828-90315-XX (Motorola, Inc), or 62828-40506-X (Johnson Data).

$ ACU -10 cabinets(62828-40044-10)serial number 185 and below and ACU -20 cabinets(62828-40044-20)

$ serial number 245 and below were originallymanufactured with AAIrf modems.The -10 cabinets with serial

$ numbers 186 and above and the -20 cabinets with serial numbers 246 and above were manufactured with

$ Motorola modems.

$

$ Normally, a system built with AAI modems continuesto operate with the modems untilsufficientspares can

$ no longer be obtained. When this occurs, the entire site (ACU and DCP) must be modified to operate with

$ Motorola modems. This modification is accomplished by the installation of FMK 18886. This FMK

$ an be ordered through NLSC using ASN S100-FMK18886. Each kit contains adapter cables W050 (to route

$ signals and power from the existing harness to the new modems) and two modems (the quantity required to

$ complete a Class I system). Two FMK's must be ordered to upgrade a Class II system. All AAI modems

$ removed from a system must be returned to the National Reconditioning Center.

$

$
S100 ASOS Site Technical Manual

Change 2 2-58.1/ (2-58.2 blank)

NOTE $

$

When an AAI modem (62828-90013-XX) fails, ASN S100-FMK18886 must be ordered to $

replace the modem with the Motorola modem (62828-90315-XX). AAI modems cannot be $

replaced with the Johnson Data modems (62828-40506-X ). $

$

When aMotorola modem (62828-90315-XX)fails and spare Motorola modems are not $

available, a Johnson Data modem (62828-40506-X), an adapter cable (62828-42110-10), $

and a SMAM-to-BNCF adapter must be ordered to replace the failing rf modem. $

$

When spare Motorola rf modems can no longer be obtained, Johnson Data modems are used. When the $

failure occursin the ACU, a modem(62828-40506-X), an adapter cable (62828-42110-10), and a SMAM-to- $

BNCF adapter must be ordered. The Johnson Data modems are compatible with the Motorola modems $

(Motorola and Johnson Data modems can coexist within the ACU). When the Motorola rf modem fails in $

a Class II DCP, two modems, adapter cables and adapters must be ordered. $

$

Figure 2.4.7 illustrates the ACU and rf modem configurations as follows: $

Sheet 1- original equipment AAI rf modem (-10 ACU s/n #185 and -20 ACU s/n #245) $

Sheet 2- as sheet 1 but shown modified for Motorola rf modems $

Sheet 3- as sheet 2 but shown with Johnson Data modems $

Sheet 4- original equipment Motorola rf modem (-10 ACU s/n $186 and -20 ACU s/n $246) $

Sheet 5- as sheet 4 but shown with Johnson Data modems $

$

For a Class II system, the ACU rf communications equipment consists of two rf modems (A and B), an rf $

modem switch, and an omnidirectional antenna (Figure 2.4.7,sheets 1 through 6). Omnidirectional antennas $

are usually used in the ACU-DCP rf link. $

Sheet 3 of figure 2.4.7 illustrates the configuration of systems with Motorola modems built in as original

equipment. Effectivity for this configuration is -10 cabinets with serial number 186 and above and -20

cabinets with serial number 246 and above.
S100 ASOS Site Technical Manual

Figure 2.4.6. Leased Line and Public Switched

Telephone ModemCommunications Detailed

Block Diagram (Sheet 1 of 3)

Change 1 2-59/ (2-60 blank)
S100 ASOS Site Technical Manual

Figure 2.4.6. Leased Line and Public Switched

Telephone Modem Communications Detailed

Block Diagram (Sheet 2)

2-61/ (2-62 blank)
S100 ASOS Site Technical Manual

Figure 2.4.6. Leased Line and Public Switched

Telephone Modem Communications Detailed

Block Diagram (Sheet 3)

2-63/ (2-64 blank)
AAI MODEMS

S100 ASOS Site Technical Manual

Figure 2.4.7. ACU RF Modem/Line Driver

Communications Link Detailed Block Diagram

(Sheet 1 of 6)

Change 2 2-65/ (2-66 blank)
S100 ASOS Site Technical Manual

SYSTEM CONVERTED FROM AAI Figure 2.4.7. ACU RF Modem/Line Driver

 MOTOROLA MODEMS Communications Link Detailed Block 

Diagram (Sheet 2 of 6)

Change 2 2-67/ (2-68 blank)
S100 ASOS Site Technical Manual

 SYSTEM CONVERTED FROM AAI TO MOTOROLA Figure 2.4.7. ACU RF Modem/Line Driver

MODEMS EQUIPED WITH JOHNSON DATA MODEMS Communications Link Detailed Block

Diagram (Sheet 3 of 6)

Change 2 2-68.1/ (2-68.2 blank)
MOTOROLA MODEMS

S100 ASOS Site Technical Manual

Figure 2.4.7. ACU RF Modem/Line Driver

Communications Link Detailed Block Diagram.

(Sheet 4 of 6)

 Change 2 2-69/ (2-70 blank)
S100 ASOS Site Technical Manual

Figure 2.4.7. ACU RF Modem/Line Driver 

 CONVERTED FROM MOTOROLA MODEMS Communications Link Detailed Block Diagram

 TO JOHNSON DATA MODEMS (Sheet 5 of 6)

 Change 2 2-70.1/ (2-70.2 blank)
S100 ASOS Site Technical Manual

Figure 2.4.7. ACU RF Modem/Line Driver

Communications Link Detailed Block Diagram

(Sheet 6 of 6)

Change 2 2-71/ (2-72 blank)
S100 ASOS Site Technical Manual

Change 2 2-73

For a Class II system, the ACU rf communications equipment consists of two rf modems (A and B), an rf modem

switch, and an omnidirectional antenna (Figure 2.4.7, sheets 1 through 6. Omnidirectional antennas are usually $

used in the ACU-DCP rf link. However, at certain sites where RFI was experienced, yagi antennas are used at one

or both ends of the link. A yagi can only be used at the ACU if all DCP's are illuminated within the yagi’s 10-

degree beamwidth. A seven-element yagi, PN 62828-90413-2, provides 10 dB gain over the 406 - 420 MHz band

and has a front:back ratio of 14 dB. Additionally, at sites where cochannel interference is particularly troublesome,

five watt attenuators of 3 dB, 6 dB, 10 dB, 20 dB, or 30 dB (PN 62828-90424 -2, -3, -4, -5, and -6, respectively)

may be inserted in the antenna line(s) to reduce transmit power into the antennas. The rf modems are

identical, with one modem serving as the primary communications link and the other as a backup. The test

is based on a loop test. The ACU transmits a predefined pattern acrossthe communicationslink, and the DCP

verifies modems operate in the UHF frequency range in half duplex mode. The primary CPU communicates

with rf modem A via SIO board 2 and with modem B via SIO board 3. The rf switch selects which modem

usesthe antenna. The switch is controlled by the CPU via DIO board A15. In the event that the primary CPU

senses a failure in its primary rf link (no data received for a period of 2-1/2 minutes), it writes a selection

word to the DIO board to toggle the rf switch. The other modem then becomes the primary modem and

controls all rf communications between the DCP and ACU. For a Class I system, the rf communications

circuitry is similar, except there is no redundant rf system (there is only one rf modem and no rf switch).

The ACU CST checks the status of the ACU/DCP communications link once per minute. CST results are

displayed on the ACU/DCP COMM page of the OID. This test performs two checks: RADIO A OR L/D A

and RADIO B OR L/D B. The RADIO A OR L/D A test checks the A link between the ACU and up to three

DCP's. The RADIO B OR L/D B test does the same for link B (Class II systems only). The CST also

identifies which link (modem or line driver) (A or B) is currently serving as the primary link in the ACU and all

DCP's.

The rf communications the reception of the pattern by responding with an OK or ERROR acknowledgment. An

incorrect reception signifies an error and a failed indication. A failed indication is also displayed if the DCP fails

to respond at all to the ACU transmission.

2.4.3.4.3 Line Drivers. If dictated by the configuration, two line drivers and an LD1/LD2 switching board

(Figure 2.4.7, sheet 6) are used in place of rf modems and the rf modem switch. The line drivers in the ACU are $

connected by a direct line to corresponding line drivers in the DCP. The line drivers are commonly referred to as

short haul modems and perform a function similar to that of the rf modems. Diagnostically, the line driver is tested

in lieu of the rf modem and the status is displayed on the ACU/ DCP COMM page. The diagnostic test is the same

as that used for the rf modems. 

Normally, a system built with UDS D19.2 line drivers continues to operate with the line drivers until sufficient

spares can no longer be obtained. When this occurs, the entire site (ACU and DCP) must be modified to operate

with Motorola DDS/MR64 line drivers as detailed in Field Modification Kit FMK 086. This FMK can be ordered

through NLSC. Each kit contains two line drivers required to update a Class I system. Order two kits to upgrade

a Class II system. All UDS line drivers removed from a system must be returned to the National Reconditioning

Center. 

2.4.3.5 Pressure Sensors. The rf/pressure mounting shelf is a slide-mounted rack containing up to three

barometric pressure sensors (Figure 2.4.8). Three pressure sensors are installed in Class II systems, while Class

I systems have pressure sensors 1 and 2 only. The pressure sensors provide barometric pressure in inches of

mercury (inHg). The primary CPU communicates with pressure sensors 1 and 2 via RS-232 ports of SIO boards

2 and 3. Pressure sensor 3, when installed, communicates with the CPU via one of the optional SIO boards (4

through 8). An adapter cable (W026) is used for pressure sensor 3 data. This cable adapts the 25-pin RS-232

connector for the optional SIO port to the 9-pin RS-232 connector on the pressure sensor. The pressure connection

is provided at the connector panel and is labeled PRESSURE PORT.

Pressure sensors that are installed in Class I ACU cabinets (without optional UPS) must be equipped with

threshold detectors, which may be either internal (built into the sensor) or external. A threshold detector

ensures that the pressure sensor resets completely in the event of a dc power undervoltage fluctuation (when
ASOS Site Technical Manual S100

2-74 Change 1

its power drops below 4.55 vdc). Threshold detectors are notrequired on ClassIIsystems because the ACU's

uninterruptible powersupply preventssuch fluctuations.Internal threshold detectors were built into pressure

sensors with serial numbers 358495, 358509, and 363914 and above. Internal detectors are being added to

all other sensors when they are returned to the depot for repair. In these cases, a label is applied to the

repaired sensor, indicating that an internal detector has been added. External threshold detectors are installed

on Class I systems via FMK #027. The external detector is a small module that is mounted to the sensor's

DB-9 power connector (J2). The external detector then becomes part of the pressure sensor and should not

be removed (it is not an FRU). As part of the FMK, a label is placed on the pressure sensor stating

"EXTERNAL THRESHOLD DETECTOR REQUIRED". FMK 27 can be ordered through NLSC. Order

S100-FMK27 for threshold detector and labels. Special authorization is required when ordering this kit.

The ACU CST displays the current status of the pressure sensors on the OID PRESSURE #1, #2, and #3

pages. Status is provided for three parameters: DATA QUALITY, REPORT PROCESSING, and SENSOR

RESPONSE. The DATA QUALITY field displays the current status (pass/fail) of data quality checks

performed by pressure sensor algorithm software. The REPORT PROCESSING field indicates Y if report

processing is currently turned on (system reports sensor data) or indicates N if report processing has been

manually turned off (system reports manually entered pressure data or "missing" if no manual data). The

SENSOR RESPONSE field indicates an F if the CPU does not receive pressure sensor data responses.

2.4.3.6 Local Sensor Fiberoptic Modems. The localsensor fiberoptic modems provide fiberoptic portsfor

three additional local sensors (Figure 2.4.9). These fiberoptic modems are connected to RS-232 ports on the

optional SIO boards (4 through 8). Adapter cables (W011) are used to adapt the 25-pin RS-232 connectors

for the SIO ports to the 9-pin RS-232 connectors on the fiberoptic modems. Electrical data transmitted from

an SIO board are converted to optical data and are then transferred to the connected device. Optical data

received from the connected device are converted to electrical data and transmitted to the SIO board as

received data. 

2.4.3.7 Observer Notification Device and Peripheral Power. Figure 2.4.10 illustrates detailed wiring for

the observer notification device (OND) and peripheral powerstripW006.The OND is controlled by theCPU

via a digital output signal from DIO Board A15. When the OND is to flash, the CPU repeatedly toggles this

signal on and off. The printer, primary OID, and FAA modems (not part of the ASOS) may receive their

power from power strip W006, which is connected to PERIPHERAL POWER connector J40 on I/O Panel

Assembly 1A9. In Class IIsystems, connector J40 receives power from the UPS in Power Supply Assembly

1A4. As such, backup power is supplied to these peripherals in the event of a loss of primary ac power. The

OND operates on 12 vdc, and therefore has a 12 vdc converter built into its power cord that plugs directly

into any available ac wall outlet. 

2.4.3.8 ACU Power and SignalMonitoring. The circuitry shown on the ACU power and signal monitoring

detailed block diagram (Figure 2.4.11) interfaces with both analog voltage signals and digital data points to

$ allow monitoring by system software. The hardware is used by the diagnostic software to read the status of

$ dc power supply output voltages, the power applied to the rf modems, as well as UPS bypass circuit in Class

$ II systems. Sheets 1 through 3 of figure 2.4.11 show three different configurations of power monitoring

circuitry, depending on the rf modem installation (paragraph 2.4.3.4.2). Sheet 1 shows the configuration for

original equipment AAIrf modems,sheet 2 illustrates a systemthat has beenmodified for Motorolamodems,

and sheet 3 shows the configuration for original equipment Motorola modems. The following paragraphs

describe the operation of the ACU power and signal monitoring circuitry.
2-75/ (2-76 blank)

S100 ASOS Site Technical Manual

Figure 2.4.8. Pressure Sensor Detailed Block

Diagram
S100 ASOS Site Technical Manual

Figure 2.4.9. Local Sensor Fiberoptic Modem

Detailed Block Diagram

2-77/ (2-78 blank)
S100 ASOS Site Technical Manual

Figure 2.4.10. Observer Notification Device

and Peripheral Power

2-79/ (2-80 blank)
S100 ASOS Site Technical Manual

Figure 2.4.11. ACU Power and Signal

Monitoring Detailed Block Diagram

(Sheet 1 of 4)

2-81/ (2-82 blank)
S100 ASOS Site Technical Manual

Figure 2.4.11. ACU Power and Signal

Monitoring Detailed Block Diagram (Sheet 2)

2-83/ (2-84 blank)
S100 ASOS Site Technical Manual

Figure 2.4.11. ACU Power and Signal

Monitoring Detailed Block Diagram (Sheet 3)

2-85/ (2-86 blank)
S100 ASOS Site Technical Manual

Figure 2.4.11. ACU Power and Signal

Monitoring Detailed Block Diagram (Sheet 4)

Change 1 2-87/ (2-88 blank)
S100 ASOS Site Technical Manual

2-89

The ACU power and signal monitoring circuitry consists of an A/D board, VME resistor board, and digital

I/O board. The A/D board and DIO board each provide an interface to the VMEbus for access by the CPU

(P1). These VMEbusinterfaces contain control and statuslogic that identifies and conducts all VMEbus data

transfers with the boards. The A/D board and DIO board also provide second interfacesfor analog and digital

user-defined devices (P2).

The A/D board contains 16 input analog channels numbered from 0 to 15 on the user interface port (P2). An

analog multiplexer, under software control, selects 1 of the 16 possible analog signals for application to the

A/D converter. The selected analog signal is converted to a 12-bit digital data value by the A/D converter

that is then read by the computer over the VMEbus via the I/O control and status logic. 

The analog input channels of the A/D board receive monitor signals corresponding to dc power supply

outputs, rf modem power, and VMEbus (card rack assembly) power. All of these analog power signals are

input via the VME resistor board. The VME resistor board scales ±12 vdc power signals down to ±6 vdc

levels for the A/D converter. The 5 vdc power signals are passed through the VME resistor board unscaled.

The voltages monitored at the actual power supply outputs are typically more than +5V and ±12V due to

adjustments for losses between the power supplies and the loads.

The VME resistor board contains a precision voltage source that outputs a 2.5 ±0.1 vdc reference voltage.

This reference voltage is input on channel 0 of the A/D board. The CPU selects this signal for conversion

during the ACU CST to test the operation of the A/D converter on the A/D board. 

The digital I/O board allows the CPU to monitor the status of four digital status bits. These bits are the $

watchdog timer from the voice processor board, two status bits from the two dc power supplies, and UPS $

bypass status (Class II only). All signals except the UPS bypass status are routed through the VME resistor $

board before being applied to the digital I/O board. The powersupply status bits(PS1/2GOOD) are normally

at a logic 1 level. When a failure occurs in one of the power supplies, the corresponding status bit goes to

logic 0. On the VME resistor board, a pulldown resistor is connected to each of the powersupply status bits.

The pulldown resistor ensures that the status bit goes to logic 0 to indicate a failure when the corresponding

power supply is removed from the system.

The ACU CST checks the status of the A/D board once per minute. The overall status of this board is

displayed on the A/D page of the OID. The CST providestwo testsfor this board: REGISTER READBACK

and REFERENCE VOLTAGE. The technician can manually run the A/D testfromthe A/D page at any time.

A T status is displayed for all test categories until the test is run again during the next CST cycle. After the

cycle, the latest test status is displayed and the fail count (if applicable) is incremented. 

The REGISTER READBACK test checks the ability of the CPU to write and read data to and from the

board. The REFERENCE VOLTAGE test is based on the A/D board properly converting the 2.5 vdc

reference voltage from the VME resistor board.

In addition to testing the A/D board, the CST also checks the status of each of the monitored power supply

lines. The results of these checks are displayed on the ACU PWR page of the OID. The pass/fail status of

all monitored 5 vdc and ±12 vdc lines is displayed, along with the status of the 2.5 vdc reference voltage.

Also given is the pass/fail indication for each of the two dc power supplies. The power supply checks are

based on the status of the PSXGOOD bits input via the digital I/O board.

2.4.3.9 Power Distribution and Control. This paragraph contains detailed descriptions and detailed block

diagrams of the ac/dc power distribution. The ACU is divided into two types of power distribution: ac and

dc. The following paragraphs describe both the ac and dc power distribution.
ASOS Site Technical Manual S100

2-90 Change 1

2.4.3.9.1 AC Distribution. Class II ACU cabinets contain Power Supply Assembly 1A4, which provides

UPS functions. Some Class I ACU's also contain a UPS as an option. Power Supply Assembly 1A4 can be

one of two types, depending on the ACU serial number. The ACU's that have power supply assemblies

installed are listed below with the effective serial numbers.

 a. Power supply assembly 62828-40124-10 is installed in ACU serial numbers 437 and below.

 b. Power supply assembly 62828-40265-10 is installed in ACU serial numbers 438 and above.

$ Power Distribution Assembly A7 provides the ACU with proper reset and UPS bypass capability. The

$ assembly consists of a solid state Time Delay Relay A7K1, Digital I/O Module A7K2 (Class II only), and

$ Power Relay A7K3 (Class II only). During initial turn-on, power is applied to solid state Time Delay Relay

$ A7K1 which delays power application for approximately three seconds then distributes power throughout

$ the ACU in Class I systems or applies power to Power Relay A7K3 normal closed contacts and Power

$ Supply Assembly A4. Power to Power Relay A7K3 normally closed contacts is routed through Power

$ Distribution Assembly A7 where it is distributed to the ACU assemblies. 

$

$ After power is applied to Class II ACU assemblies, ASOS operational software monitors Power Relay A7K3

$ bypass status via Digital I/O Module A7K2 and Digital I/O Board A2XA15. When UPS status is good, Power

$ Relay A7K3 is energized via Digital I/O Board A1A2XA15 and Digital I/O Module A7K2 to route power from

$ the UPS output applied to Power Relay A7K3 normal open contacts to the ACU. 

The following paragraphs describe ac power distribution for the two power supply assemblies.

2.4.3.9.2 AC Distribution for Power Supply Assembly 62828-40124-10 (Figure 2.4.12). Facility power

is provided to the ACU via ACU INPUT POWER connector J41 on the I/O panel assembly. Input power is

$ applied to Power Distribution Assembly 1A7 Power Reset Relay K1 which provides a three second delay

$ to allow the pressure sensors and rf modems to stabilize after power is interrupted and then distributed

throughout the ACU. For both Class I and Class II ACU's, blower B1 receives its ac power directly from the

power distribution assembly.

For Class II systems (serial number 437 and below), a UPS is provided by Power Supply Assembly A4 and

Battery Box A8 (serial number 437 and below). The UPS is not a unit in itself, but is the collection of the

following eight units: 

 a. Circuit breaker 1A4CB1

 b. 1.5 KVA Filter Board 1A4A3

 c. 1.5 KVA Inverter Board 1A4A4

 d. 1.5 KVA transformer 1A4T1

 e. Battery Box 1A8

 f. Fuse 1A4F1

 g. RS-232 Interface Board 1A4A2

 h. Status Panel Board 1A4A1
S100 ASOS Site Technical Manual

Figure 2.4.12. ACU AC Power Distribution

Detailed Block Diagram for 62828-40124-10

Change 2 2-91/ (2-92 blank)
S100 ASOS Site Technical Manual

Change 1 2-93

Input ac power is applied through circuit breaker CB1 to 1.5 KVA Filter Board A3. The filter board filters

the input line voltage and routes it to 1.5 KVA Inverter Board A4 on the WHT/BLK (neut) and BLK/RED

(line) wires of W030. 

During normal(noninterrupted power) operation, the inverter boardmonitorsthe input voltage fromthe filter

board and regulates it to provide a constant 120 vac output signal. The inverter board uses transformer T1

to perform this regulation. The secondary coil of T1 has multiple taps that are routed to tap-switching triacs

on the inverter board. If the inverter board senses that the input line voltage is low, it causes one of the triacs

to switch in a T1 secondary tap thatsteps up the voltage to the required level. The stepped-up voltage is then

output from the BLK/WHT terminal of the inverter board to connector S10 of 1.5 KVA Filter Board A3.

Similarly, if the inverter board senses that the input ac voltage is high, the T1 secondary tap is changed to

step the voltage down to the required level, and the stepped-down voltage is output to the filter board. The

filter board filters the ac voltage and outputs the regulated voltage from connector J7 as the UPS ac output

signal. 

When the inverter board senses a loss of itsinput ac signal, it usestransformer T1 to convert dc voltage from

Battery Box A8 to a backup ac signal. Battery Box A8 contains five 12 vdc batteries wired in series to

provide a total of 60 vdc. This dc voltage is applied through fuse F1 to the RED terminal of the inverter

board, where it is then routed to the center tap of the primary coil of T1. When the inverter board senses a

lossin the input ac signal fromthe inverter board, it alternatingly switchesin the two other two primary leads

of T1 (BLU2 and YEL2). This causes alternating current in the T1 primary, which is induced to the

secondary coil of T1. The inverter board then uses its tap-switching triacs, as described above, to output a

regulated ac voltage to the filter board. 

The regulated, filtered UPS ac output signal from the filter board is routed to Power Distribution Assembly

A7 for distribution to ACU assemblies. Unitsthatreceive the UPS output voltage fromthe power distribution

assembly are the dc power supply enclosure, the card rack assembly, and the modem ac power rack. UPS ac

voltage is also routed to PERIPHERAL POWER connectorJ40 on the I/O panel assembly to provide backed

up ac power to the primary OID, the printer, and to FAA modems. 

RS-232 Interface Board A2 allows the CPU to monitor the operational status of the UPS. The inverter board

contains circuitry to monitor the status of the ac input and output voltages, battery voltages, tap-switching

triac status, etc. DuringCST, theCPU communicates with the inverter board, via theRS-232 interface board,

to obtain these status data. The CPU analyzesthese UPS data and displays the results on the ACU UPS page

of the OID. 

The ACU CST checks the status of the UPS once per minute. CST results are displayed on the ACU UPS

page of the OID. The CST performs 10 tests on the UPS. These tests are based on information determined

by the 1.5 KVA inverter board and communicated to the CPU via the RS-232 interface board. The technician

can manually run the UPS test fromthe UPS page at any time. A T is displayed for the 10 test categories until

the test is run again during the next CST cycle. After the cycle, the latest test status is displayed and the fail

count (if applicable) is incremented. 

The BATTERY VOLTAGE test indicates the current voltage provided by the battery box. The INPUT

VOLTAGE test indicatesthe current value (in vac) ofthe facility input voltage being received by the inverter

board from the 1.5 KVA filter board. The OUTPUT VOLTAGE test indicates the current value (in vac) of

the regulated ac voltage being output from the inverter board to the filter board. The OUTPUT ENABLED

test indicates whether or not the UPS output is currently enabled or disabled via the OUTPUT POWER

switch on the status panel. The ON AC LINE test indicates the power source on which the UPS is operating

(P = facility input (ac line), F = UPS operating on battery backup). The BATTERY STATUS test indicates

the condition of the battery box supply. The TRIAC STATUS test indicates the operating condition of the

tap changing triacs on the inverter board. The TEMPERATURE test checks for an overheat condition as

detected by a sensor on the inverter board. The RS-232 test checks for transmission errors encountered by
ASOS Site Technical Manual S100

2-94 Change 1

the RS-232 interface board. Finally, the TIMEOUT test indicates a failure in the event that the CPU receives

no response at all from the RS-232 interface board. 

In a Class I ACU that does not contain a UPS (UPS is an option in a Class I ACU), jumpers are installed

between the UPS input and UPS output terminals on Power Distribution Assembly 1A7. That is, wires are

installed between terminals A7-18C and -23A (115 vac), and between terminals -19C and -22C (neutral) to

bypass the Class II UPS described above. 

2.4.3.9.3 AC Distribution for Power Supply Assembly 62828-40265-10 (Figure 2.4.13). Facility power

is provided to the ACU via ACU INPUT POWER connector J41 on the I/O panel assembly. Input power is

applied to Power Distribution Assembly 1A7 for distribution throughout the ACU. For bothClassI andClass

IIACU's, blowerB1 receivesits ac power directly fromthe power distribution assembly. ForClassIIsystems

(serial number 438 and above), facility power is provided by Power Supply Assembly 1A4 and Battery Box

1A8.

Input ac power is applied through connector P97. During normal (noninterrupted power) operation, the UPS

assembly monitors the input signal internally and maintains a steady output voltage.

When the UPS detects a loss in its input ac voltage, it inverts dc voltage from Battery Box 1A8 to a backup

ac voltage. Battery Box 1A8 contains four 12-vdc batteries wired in series to provide a total of 48 vdc.

The regulated, filtered UPS ac output signal from the UPS is routed to Power Distribution Assembly 1A7

for distribution to ACU assemblies. The dc power supply enclosure and the modem ac power rack receive

the UPS output voltage from the power distribution assembly. UPS ac voltage is also routed to

PERIPHERAL POWER connector J40 on the I/O panel assembly to provide backed-up ac power to the

primary OID, the printer, and FAA modems. An UPS bypass circuit has been added to ClassII ACU's, which

allows the ACU to operate from unconditioned ac power input in the event that the UPS fails or is

undergoing maintenance. The bypass circuit includes three relays. A 1-second time-delay relay, A7K1,

ensures that whenever primary power is interrupted briefly, it cannot be reapplied for 1 second, so that

power-up reset circuits in ACU FRU's will correctly reset those FRU's. Solid-state relay A7K2 allows

software control of the UPS bypass function;software control can be disabled by jumpering terminals 1 and

2. A7K2 normally connects the coil of ac power relay A7K3, a triple-pole, double-throw relay, to UPS

output, so that it will be energized whenever UPS is providing an output. When the software command is

active, A7K2 contacts open to release A7K3, bypassing the UPS and connecting the unconditioned primary

ac power input to ac power distribution. The third set of A7K3 contacts, when the relay is released, sends

a ground signal to the DIO board to indicate that unconditioned primary input power is selected.

The RS-232 COMM PORT on the UPS allows the CPU to monitor the operational status of the UPS. The

UPS contains circuitry to monitor the status of the ac input and output voltages, battery voltages, etc. During

CST, the CPU communicates with the UPS to obtain these status data. The CPU analyzes these UPS data

and displays the results on the ACU UPS page of the OID.

The ACU polls the UPS approximately every 2 minutes with a dump status command to obtain a current

status of the UPS. BATTERY VOLTAGE status (provided as a numerical value) indicates the current

voltages provided by the battery box. INPUT VOLTAGE status (provided as a numerical value) indicates

the current value (in vac) of the facility input voltage being received by the UPS. OUTPUT VOLTAGE

status (provided as a numerical value) indicates the current value (in vac) of the regulated ac voltage being

output from the UPS. UPS OPERATION status indicates whether or not the UPS is functioning in a normal

(indicated by a P (utility is OK, battery is OK, and UPS is in its normal state)) or abnormal operation

(indicated by an F). The ON AC LINE status indicates the power source on which the UPS is operating 
S100 ASOS Site Technical Manual

Figure 2.4.13. ACU AC Power Distribution

Detailed Block Diagram for 62828-40265-10

Change 2 2-95/ (2-96 blank)
S100 ASOS Site Technical Manual

2-97/ (2-98 blank)

(P = facility input (ac line), F = UPS operating on battery backup). BATTERY STATUS (P for pass or F for

fail) indicates whether battery power is low from the battery box supply. INVERTER status indicates

whether the internal inverter is operating in overvoltage or undervoltage status. GROUND STATUS (P for

pass or F for fail) checks for a ground failure. UTILITY status (P for pass or F for fail) indicates an

overvoltage or unsynchronized signal from facility power. TIMEOUT status (P for pass or F for fail)

indicates a failure in the event that the CPU receives no response at all from the UPS. BATTERY

MANAGEMENT status (provided as a word description) indicates if the current from the batteries is

FLOATING (trickle charge), RESTING (not charging or discharging), CHARGING, or DISCHARGING.

Finally, LINE REGULATION status (provided as a word description) indicates if the UPS is maintaining

a STEP-UP, STEP DOWN, or NORMAL voltage from facility power.

In a ClassI ACU without a UPS (UPS is an option in a Class I ACU), jumpers are installed between the UPS

input and output terminals on Power Distribution Assembly 1A7; that is, wires are installed between

terminals-18Cand -23A (115 vac) and between terminals-19Cand -22C(neutral)to bypasstheClassIIUPS

described above.

2.4.3.9.4 DC Power Distribution. Figure 2.4.14, sheets 1 through 6, illustrate dc power distribution. Sheet $

1 shows the common dc circuitry for all rf modem installations. Sheets 2 through 6 show five different $

configurations of dc power distribution wiring, depending on the rf modeminstallation (paragraph 2.4.3.4.2) $

as follows: $

$

Sheet 2- original equipment AAI rf modem configuration $

Sheet 3- as sheet 2 but shown modified for Motorola rf modems $

Sheet 4- as sheet 3 but shown with Johnson Data modems $

Sheet 5- original equipment Motorola rf modem configuration $

Sheet 6- as sheet 5 but shown with Johnson Data modems $

$
S100 ASOS Site Technical Manual

Figure 2.4.14. ACU DC Power Distribution

Detailed Block Diagram (Sheet 1 of 6)

Change 2 2-99/ (2-100 blank)
S100 ASOS Site Technical Manual

 AAI MODEMS Figure 2.4.14. ACU DC Power Distribution $

Detailed Block Diagram (Sheet 2 of 6)

Change 2 2-101/ (2-102 blank)
S100 ASOS Site Technical Manual

 SYSTEM CONVERTED FROM AAI Figure 2.4.14. ACU DC Power Distribution

 MODEMS TO MOTOROLA MODEMS Detailed Block Diagram (Sheet 3 of 6)

Change 2 2-102.1/ (2-102.2 blank)
S100 ASOS Site Technical Manual

SYSTEM CONVERTED FROM AAI MODEMS TO MODEMS

EQUIPPED WITH JOHNSON DATA MODEMS

Figure 2.4.14. ACU DC Power Distribution

Detailed Block Diagram (Sheet 4 of 6)

Change 2 2-103/ (2-104 blank)
S100 ASOS Site Technical Manual

MOTOROLA MODEMS Figure 2.4.14. ACU DC Power Distribution

Detailed Block Diagram (Sheet 5 of 6)

Change 2 2-105/ (2-106 blank)
S100 ASOS Site Technical Manual

SYSTEM CONVERTED FROM MOTOROLA Figure 2.4.14. ACU DC Power Distribution

MODEMS TO JOHNSON DATA MODEMS Detailed Block Diagram (Sheet 6 of 6)

Change 2 2-106.1/ (2-106.2 blank)
S100 ASOS Site Technical Manual

2-107

SECTION V. MAINTENANCE

2.5.1 INTRODUCTION

This section contains the preventive and corrective maintenance procedures for the acquisition control unit

(ACU) cabinet. Preventive maintenance ensures that the ACU cabinet remains operational. Corrective

maintenance allows fault isolation to a faulty field replaceable unit (FRU). The procedures for removal and

replacement of a faulty FRU are also provided in this section. Malfunctions within the ACU cabinet are

identified by the ASOS continuous self-test (CST). Maintenance information for the pressure sensor is

located in Chapter 8. Maintenance information for the Codex modem is located in Chapter 13. 

2.5.2 PREVENTIVE MAINTENANCE

Preventive maintenance consists of those proceduresthat are performed on a scheduled basisto maintain the

ACU cabinet in an operational state. All preventive maintenance tasks for the ACU cabinet are provided in

table 2.5.1.

Table 2.5.1. ACU Preventive Maintenance Schedule

Interval What To Do How To Do It

90 days Clean air filters Paragraph 2.5.2.1

Clean cathode ray tube (CRT)/display screens on the OID's, VDU's and

CVD's

Paragraph 2.5.2.2

Clean ACU cabinet Paragraph 2.5.2.3

Check memory board LOW BATT indicator Paragraph 2.5.2.4

Semiannually Check/clean batteries Paragraph 2.5.2.5

2.5.2.1 Air Filter Cleaning. Due to continuous air flow through the ACU cabinet, the air filters can become

clogged with dust and foreign matter resulting in an unsTable thermal condition. Periodic air filter cleaning

prevents this condition from occurring. Refer to table 2.5.2 for the air filter cleaning procedure.

2.5.2.2 Display Screen Cleaning. Cleaning the display screens is required to remove dust and dirt that

accumulate on the screens. The display screen cleaning procedure is provided in Chapter 1, Section V.

2.5.2.3 ACU Cabinet Cleaning. Cleaning the ACU cabinet is required to remove dust and dirt that

accumulate on the external surface and to remove any internal debris. The ACU cabinet cleaning procedure

is provided in table 2.5.3.

2.5.2.4 CheckMemoryBoardLOWBATTIndicator.TheLOWBATTindicator onACUMemoryBoard

1A2A3 should be checked every 90 days or whenever the technician visits the site. If the LOW BATT

indicator is illuminated, the backup battery on the board has failed and ACU Memory Board 1A2A3 must

be replaced.

2.5.2.5 Check/Clean Batteries. For Class II systems, there are two types of battery packs depending on

which power supply assembly is installed. The power supply assembly 62828-40124-10 configuration has

five batteries in Battery Box 1A8; the power supply assembly 62828-40265-10 configuration has only four

batteries. The batteries should be checked and cleaned semiannually or whenever the CST indicates that the

batteries have failed or are low. The individual batteries should be removed from the battery box in

accordance with the battery removal procedure of table 2.5.30. The batteries should be checked for leakage

or corrosion on the terminals and replaced in accordance with the installation procedure of table 2.5.30. If

a battery is found to be leaking, it should be replaced. If battery terminals are corroded, they should be

cleaned with a terminal brush or other wire brush before the battery is reinstalled.
ASOS Site Technical Manual S100

2-108

WARNING

WARNING

Table 2.5.2. Air Filter Cleaning

Step Procedure

Tools and material required:

Vacuum cleaner

Mild detergent and water

Lint-free cloths

Phillips screwdriver

ACU cabinet power isleft on when cleaning the air filter. Death or severe injury may result if hands

and tools are not kept clear of moving blower parts and cabinet power wiring when cleaning filter.

NOTE

There are two types of cabinets for the ACU. One type has a partial length front door with the

fan/blower assembly mounted behind an air intake grill. The other type of cabinet has a full length

door with the fan/blower assembly immediately accessible with the door open.

1 If the ACU cabinet has a partial length front door, remove six Phillips screws and lockwashers securing air

intake grill to lower front of cabinet. Remove air intake grill. Proceed to step 3.

2 If cabinet has a full length front door, open front door. Loosen knurled knobs on either side of shield in front

of fan/blower B1 and remove shield.

3 Remove filter.

4 Clean filter using detergent solution.

5 Dry filter. 

6 Vacuum air intake grill (both types of cabinets) and blower shield (full length door cabinet).

7 Reinstall filter.

8 If full length door cabinet, install blower shield in front of blower and hand tighten two knobs on shield.

9 If partial length front door cabinet, position air intake grill in front of fan/blower assembly. Install Phillips

screws and lockwashers securing grill to cabinet.

Table 2.5.3. ACU Cabinet Cleaning

Step Procedure

Tools and material required:

Hand-held vacuum cleaner

Mild detergent and water

Lint-free cloths

Death or severe injury may result if power is not removed from ACU prior to performing

maintenance activities inside the cabinet. Ensure that UPS POWER switch is set to 0 (off) position

and facility power is removed from ACU.

NOTE

Wring out cloth before washing surfaces.

1 Set UPS POWER switch to 0 (off) position.

2 Remove facility power from ACU cabinet.

3 Clean external surfaces using lint-free cloth dampened with a mixture of mild detergent and water.

4 Dry surfaces using lint-free cloth.

5 Using hand-held vacuum cleaner, remove any loose debris inside ACU cabinet.

6 Apply facility power to ACU cabinet.

7 Set UPS POWER switch to 1 (on) position.
S100 ASOS Site Technical Manual

2-109

2.5.3 CORRECTIVE MAINTENANCE

2.5.3.1 Introduction. Corrective maintenance involves the isolation, removal, and replacement of faulty

FRU's. The ASOS is equipped with a powerful automatic self-test program that is designed to isolate most

faultsto a single FRU. However, because of the systemhardware configuration, there will be instances when

the diagnostics can only isolate to a group of FRU's,such as a sensor or an I/O channel. The troubleshooting

approach for single FRU and group FRU types of conditions is different.

When the FRU is specifically called out, the technician need only replace the faulty unit. When a group of

FRU's is called out, the technician must isolate the failed FRU by referencing the theory of operation and

associated drawings and following two basic procedures. The first procedure involves connector checks,

which ensure that all boards, cables, and connectors are present and properly connected. The second

procedure involves ac and dc power supply tests. Although the system monitors all critical power supply

voltages in the ACU, data collection package (DCP), and sensors, failure of a power supply may result in a

loss of communications between the system and its FRU's.

Power supplies are tested through both visual and mechanical inspection. Before measuring any voltages,

the technician should visually inspect the suspected area for obvious signs of power supply failure. During

this inspection, the technician should pay particular attention to circuit breakers, panel lights, and light

emitting diode (LED) indicators on the units to ensure that they are functioning normally. The physical

checks involve checking fuses and the power supply voltages using a DMM. In most cases, these tests will

isolate the fault.

After an FRU has been replaced, the technician must allow the ASOS to automatically initialize upon the

application of primary power to the ACU and verify that the continuous self-test diagnostics run without

failure. The technician should also display the corresponding maintenance page on the OID and ensure that

the FRU passesits CST checks. Table 2.5.4 provides corrective maintenance symptom analysisinformation

for the ACU.

Table 2.5.4. Corrective Maintenance Symptom Analysis

Symptom What To Do How To Do It

System is completely dead. Check ac and dc power. Reference ACU AC/DC power distribution diagram figure 2.4.12 and

verify ac and dc voltages.

Problem with ACU uninterruptible power

supply (UPS) if installed.

Check UPS. Paragraph 2.5.3.2

ACU computer does not initialize. Check VME card rack. Paragraph 2.5.3.3

Loss of ACU/DCP Check ACU/DCP communications link.Paragraph 2.5.3.4

Failure of an SIO board or loss of

communication with a peripheral or user

Check SIO boards.

Check modems.

Paragraph 2.5.3.5

Paragraph 2.5.5

Printer malfunction Check printer Paragraph 2.5.7 and printer vendor

manual 

2.5.3.2 UPS Checks. In a Class II system with serial number 437 and below, and in certain Class I systems

which have been retrofitted per FMK # 088, for all components except the fan/blower assembly. If power

is not applied to the ACU when the UPS POWER switch is set to ON (1), but the blower still operates, there

could be a failure in the UPS. During operation, there are a number of tools available to fault isolate the UPS.

The CST continually checks the status of the UPS and provides status information on the ACU UPS page

of the OID. Error messages are printed on the printer and entered into the maintenance log. Also, the status
ASOS Site Technical Manual S100

2-110 Change 2

LED's on the UPS status panel provide valuable information for analyzing UPS problems. Table 2.5.5

$ provides procedures for troubleshooting the SOLA UPS. Table 2.5.6 provides procedures to prepare this

$ SOLA UPS for maintenance and to return the UPS to operation following service.

$ In a ClassIIsystem with serial number 438 and above, a Deltek UPS (either UPS 62828-90338-10 or 62828-

$ 90338-20) provides the same functions except that the troubleshooting procedures are conducted primarily

from the OID page. Table 2.5.7 provides the procedures for troubleshooting the Deltek UPS based on

observed symptoms. 

Table 2.5.5. UPS Fault Isolation (62828-40124-10)

Step Symptom Checks/Corrective Actions

1 UPS will not turn on.

Indicators on Status Panel Board 1A4A1 are all

extinguished.

Ensure that facility power is being applied to ACU. 

On back of Power Supply Assembly 1A4, check circuit breaker CB1. If tripped,

reset CB1 and cycle OUTPUT POWER switch on status panel off and back on.

Remove power from UPS and remove UPS cover per table 2.5.6.

Visually inspect 1.5 KVA Filter Board 1A4A3 for damage. Replace filter board

if damaged.

Apply facility power to ACU cabinet. 

Using digital multimeter (DMM), verify 120 ±10% vac between terminal 1 of

circuit breaker CB1 and WHT terminal of 1.5 KVA Filter Board 1A4A3. If

voltage is not present, replace CB1.

Verify 120 ±10% vac between WHT/BLK and BLK/RED terminals of 1.5 KVA

Filter Board 1A4A3. If voltage is not present, replace A3.

Replace 1.5 KVA Inverter Board 1A4A4.

If problem persists, replace transformer 1A4T1.

2 UPS will not turn on.

BATTERY indicator on

status panel is on or

blinking, but OUTPUT

indicator is off.

This is normal situation with OUTPUT POWER switch set to off (0); therefore,

ensure that OUTPUT POWER switch on Status Panel Board 1A4A1 is in the on

(1) position. 

Remove power from UPS and remove UPS cover per table 2.5.6.

Inspect ribbon cable on Status Panel Board 1A4A1 for damage or loose

connections.

Set OUTPUT POWER switch to on (1) position. Using DMM, ensure continuity

across terminals of switch. Replace switch if no continuity.

Set OUTPUT POWER switch to off (0) position. 

Reinstall UPS cover per table 2.5.6. 

To ensure that problem was not due to cable connectors, set OUTPUT POWER

switch to on (1) position and attempt to operate UPS again.

If problem is not corrected, replace Status Panel Board 1A4A1.

If problem persists, replace 1.5 KVA Inverter Board 1A4A4.
S100 ASOS Site Technical Manual

2-111

Table 2.5.5. UPS Fault Isolation (62828-40124-10) - CONT

Step Symptom Checks/Corrective Actions

3 UPS operates, but

CPU cannot communicate with RS-232 Interface Board 1A4A2.

Failure indicated for

TIMEOUT test or RS232 test on ACU UPS

page at OID.

From ACU serial communications page on OID, determine which SIO board and

port the UPS is assigned.

Select ACU SIO page corresponding to board to which UPS is assigned.

From ACU SIO page, press TEST key to runCST on this SIO board. If port assigned

to UPS fails LOOPBACK or XMIT ERRORS test, replace SIO board. If both tests

pass, continue.

At rear of UPS (Power Supply Assembly 1A4), disconnect W014/W016 connector

from UPS RS-232 connector (1A4A2-J20).

Insert RS-232 test box between UPS RS-232 connector and corresponding

W014/W016 connector.

Select ACU UPS page at OID.

From ACU UPS page, press TEST key to run CST on UPS.

On RS-232 tester, ensure that transmit (TxD) and receive (RxD) signals are being

passed between the UPS and the SIO board (at least once per minute). If both signals

are active, replace the following (in order) and retry UPS:

a. SIO board to which UPS is connected

b. RS-232 Interface Board 1A4A2

If transmit signal is missing, replace SIO board.

If receive signal is missing, check/replace W078. If W078 P1-3 to P2-2 check

measures continuity, continue.

Remove power from UPS and remove UPS cover per table 2.5.6.

Inspect ribbon cable between RS-232 interface board and 1.5 KVA Inverter Board

1A4A4. Ensure that ribbon cable is not twisted or damaged. Reseat connectors to

ensure proper connection.

After checking ribbon cable, replace cover per table 2.5.6 and operate system again.

If problem is not corrected, replace RS-232 Interface Board 1A4A2.

If problem persists, replace 1.5 KVA Inverter Board 1A4A4.

4 ALARM indicator on

status panel is illuminated. 

Overheat condition likely.

On UPS status panel, set OUTPUT POWER switch to off (0) position.

Inspect inside of ACU cabinet to ensure proper ventilation around UPS and that

ACU blower is operating. Replace if necessary. 

Allow UPS to cool.

Set UPS OUTPUT POWER switch to on (1) position. If UPS fails to turn on and

ALARM indicator remains illuminated, set UPS OUTPUT power switch to off (0)

position and proceed to step 5.
ASOS Site Technical Manual S100

Table 2.5.5. UPS Fault Isolation (62828-40124-10) - CONT

Step Symptom Checks/Corrective Actions

2-112

WARNING

WARNING

WARNING

5 With UPS cool,

ALARM indicator on

UPS status panel is

illuminated when facility power is applied

to ACU. UPS does not

output power.

Ensure that connector W030-P1 is securely attached to connectorJ1 on Battery Box

1A8. Attempt to operate UPS again by setting OUTPUT POWER switch to on (1)

position.

Remove power from UPS and remove UPS cover per table 2.5.6.

Ensure thatW030-P1 connectoris disconnected fromBatteryBox

1A8 before attempting to test fuse 1A4F1 for continuity. Failure

to disconnect the battery box may result in injury to personnel or

damage to equipment.

Ensure that connector W030-P1 is disconnected from Battery Box 1A8.

Inspect UPS fuse 1A4F1 and test for continuity using DMM. If fuse is good, proceed

to nextstep. Iffuse is open, replace fuse.If, after replacing fuse, problempersists and

fuse again opens, replace 1.5 KVA Inverter Board 1A4A4.

Exercise extreme caution in connecting UPS battery and taking

measurement with UPS cover off. Death or severe injury may

occur if contact is made with battery terminal or wires.

Connect battery cable W030-P1 to connector J1 on Battery Box 1A8.

Using DMM, measure dc voltage at battery terminals (RED+ and BLK-) of Inverter

Board 1A5.

Disconnect battery cable W030-P1 from connector J1 on Battery Box 1A8.

If indication was less than 40 ±4 vdc, replace batteries BT1 through BT5 in Battery

Box 1A8. If problem persists, replace 1.5 KVA Inverter Board 1A4A4.

If battery voltage was above 40 ±4 vdc, replace 1.5 KVA Inverter Board 1A4A4.

6 After 24 hours of

continuous charging

(UPS has operated

continually on facility

power), BATTERY

indicator on UPS

status panel blinks,

indicating low battery.

Remove power from ACU and remove UPS cover per table 2.5.6.

Ensure thatW030-P1 connector is disconnected fromBatteryBox

1A8 before attempting to test fuse 1A4F1 for continuity. Failure

to disconnect battery box may result in injury to personnel or

damage to equipment.

Inspect UPS fuse 1A4F1 and test for continuity using DMM. If fuse is good, proceed

to nextstep.Iffuse is open, replace fuse.If, after replacing fuse, problempersists and

fuse again opens, replace 1.5 KVA Inverter Board 1A4A4.

Replace batteries BT1 through BT5 in Battery Box 1A8.

If problem persists, replace 1.5 KVA Inverter Board 1A4A4.

If problem persists, replace transformer 1A4T1.
S100 ASOS Site Technical Manual

Table 2.5.5. UPS Fault Isolation (62828-40124-10) - CONT

Step Symptom Checks/Corrective Actions

2-113

WARNING

7 One or more indicators on Status Panel

Board 1A4A1 do not

illuminate.

Remove power from UPS and remove UPS cover per table 2.5.6.

Inspect ribbon cable on Status Panel Board 1A4A1 for damage or loose connections.

After checking ribbon cable, reinstall UPS cover per table 2.5.6 and operate system

again. 

If problem persists, replace KVA Status Panel Board 1A4A1.

If problem persists, replace 1.5 KVA Inverter Board 1A4A4.

8 UPS beeps when

OUTPUT POWER

switch is set to off (0)

position.

Replace 1.5 KVA Inverter Board 1A4A4.

NOTE

Failure (step 9) may be result of circuit breaker CB1 tripping

below its rated value. If problem persists after performing the

following corrective actions, CB1 may be faulty.

9 UPS circuit breaker

1A4CB1 continually

trips when facility

power is applied to

ACU cabinet.

Remove power from ACU and remove UPS cover per table 2.5.6.

Inspect 1.5 KVA Filter Board 1A4A3 and 1.5 KVA Inverter Board 1A4A4 forsigns

of damage. Replace if necessary.

On 1.5 KVA Filter Board 1A4A3, disconnect CB1 output wire from BLK terminal.

Reset CB1.

Apply facility power to ACU cabinet. If CB1 trips, replace CB1. 

Remove facility power from ACU cabinet.

Reconnect CB1 wire to BLK terminal of 1.5 KVA Filter Board 1A4A3.

On 1.5 KVA Inverter Board 1A4A4, disconnect input wires from WHT/BLK and

BLK/RED terminals.

Apply facility power to ACU cabinet. If CB1 trips, replace 1.5 KVA Filter Board

1A4A3.

Remove facility power from ACU cabinet. 

Reconnect wiresto WHT/BLK and BLK/RED terminals of 1.5 KVA Inverter Board

1A4A4.

On 1.5 KVA Filter Board 1A4A3, disconnect connector from J10.

Ensure that W030-P1 connectoris disconnected fromBatteryBox

1A8 before attempting to disconnect transformer T1. Failure to

disconnect battery boxmay result in injury to personnel or damage

to equipment.
ASOS Site Technical Manual S100

Table 2.5.5. UPS Fault Isolation (62828-40124-10) - CONT

Step Symptom Checks/Corrective Actions

2-114

WARNING

On 1.5 KVA Inverter Board 1A4A4, tag and disconnect 10 transformer 1A4T1 wires

from their terminals.

Apply facility power to ACU cabinet. If CB1 trips, replace 1.5 KVA Inverter Board

1A4A4. 

Remove facility power from ACU cabinet.

Reconnect 10 transformer wiresto respective connectors on 1.5 KVA InverterBoard

1A4A4.

Apply facility power to ACU cabinet. If CB1 trips, replace transformer 1A4T1.

Remove facility power from ACU cabinet.

Reconnect connector to J10 on 1.5 KVA Filter Board 1A4A3.

Disconnect W014/W016 connector P13 from connectorJ7 on 1.5 KVA Filter Board

1A4A3.

Apply facility power to ACU cabinet. If CB1 trips, replace 1.5 KVA Filter Board

1A4A3. If not, problem is not in UPS components, but a short circuit probably exists

in ACU cabinet wiring or in one of the loads connected to the UPS output.

10 Failure indicated for

TRIAC test on ACU

UPS page at the OID.

Replace 1.5 KVA Inverter Board 1A4A4.

If problem persists, replace transformer 1A4T1.

Table 2.5.6. UPS (62828-40124-10) Pre-Service and Post-Service Procedures

Step Procedure

PRE-SERVICE: REMOVING UPS POWER AND REMOVING COVER

Tools required:

 Small flat-tipped screwdriver

 No. 2 Phillips screwdriver

Ensure that power is completely removed from the UPS by performing the following steps. Death

or severe injury may result if power is not completely removed from the UPS prior to removing the

cover on Power Supply Assembly 1A4 and performing maintenance on UPS subassemblies.

1 Set OUTPUT POWER switch S1 on UPS status panel to off (0) position. OUTPUT indicator on status panel

extinguishes. 

2 Remove facility power from the ACU cabinet.

3 On Battery Box 1A8, disconnect cable connector W030-P1 from battery box connectorJ1. To remove cable

connector, squeeze tabs on side of connector inward while rocking the connector free.

4 Wait at least 30 seconds while UPS capacitors discharge through bleeders and other drains.

5 Remove screws, lockwashers, and flat washers that hold Power Supply Assembly 1A4 drawer to ACU

cabinet. Pull power supply assembly drawer out of cabinet to its fully extended and locked position. 

6 Remove three screws and washers at lower front of Power Supply Assembly 1A4 cover. 

7 Remove three screws and washers at top rear of Power Supply Assembly 1A4 cover. 
S100 ASOS Site Technical Manual

2-115

WARNING

Table 2.5.6. UPS (62828-40124-10) Pre-Service and Post-Service Procedures -CONT

Step Procedure

8 CAUTION

Status panel ribbon cable is delicate. Use caution when lifting cover and disconnecting

cable to prevent damage to status panel cable.

Carefully raise cover approximately 6 inches and disconnect status panel ribbon cable from J4 on 1.5 KVA

Inverter Board 1A4A4. 

9 Lift cover from off Power Supply Assembly 1A4.

POST-SERVICE: INSTALLING UPS COVER AND APPLYING POWER TO UPS

Tools required:

 Small flat-tipped screwdriver

 No. 2 Phillips screwdriver

Ensure that facility power is removed from ACU and that cable W030-P1 is disconnected from

Battery Box 1A8 before performing maintenance on UPS. Death or severe injury may result if

power is not completely removed from UPS prior to maintenance activities.

CAUTION

Status panel ribbon cable is delicate. Use caution when connecting cable and lowering cover to

prevent damage to status panel cable. Ribbon connector is not keyed. Ensure that pin 1 on cable

mates with pin 1 on board.

1 While holding cover approximately 6 inches above its normal position, carefully connectstatus panel ribbon

cable to connector J4 on 1.5 KVA Inverter Board 1A4A4. Pin 1 on ribbon connector is marked with ink dot

or other marking. Ensure that this mates with pin 1 of inverter board.

2 Lower cover into position on Power Supply Assembly 1A4, taking care not to disturb or pinch status panel

ribbon cable.

3 Secure cover to Power Supply Assembly 1A4 by installing six screws and washers in bottom front and top

rear of cover.

4 Release locks on power supply assembly slide rails and slide assembly back into ACU cabinet.

5 Using screws, lockwashers, and flat washers, secure power supply assembly drawer to ACU cabinet. 

6 On UPS Status Panel Assembly 1A4A1, ensure that OUTPUT POWER switch is set to OFF (0) position.

7 Connect battery cable W030-P1 to connector J1 on Battery Box 1A8. 

8 Apply facility power to ACU cabinet.
ASOS Site Technical Manual S100

2-116 Change 2

$ Table 2.5.7. UPS Fault Isolation (62828-90338-10 or 62828-90338-20)

Step Symptom Checks/Corrective Actions

1

$

$

$

$

$

$

UPS will not start. Line cord is not connected.

Connect line cord.

$ UPS power switch is OFF.

Turn switch ON.

Wall socket is dead. Test wall socket. Nominal input voltage is too high or too

low for voltage setting.

$ DIP Switch Settings (UPS 62828-90338-10 only)

Voltage S1 S2

 127 ON OFF

 120 OFF OFF (Default)

 110 OFF ON

$ Using multimeter, check input voltage and set DIP switches(UPS 62828-90338-

$ 10 only) properly in accordance with the above table.

Battery fuse or circuit is open.

$ Turn UPS power switch to OFF.

Replace battery fuse or set circuit breaker to ON.

$ Turn UPS power switch to ON.

2

$

$

$

Alarm continues after

ALARM SILENCE

button is pushed.

Overheat condition likely.

$ On UPS, set power switch to off position.

Inspect inside of ACU cabinet to ensure proper ventilation around UPS and that

ACU blower is operating. Replace if necessary.

Allow UPS to cool.

$ Set power switch to on position. If UPS fails to turn on and alarm continues, set

$ UPS power switch to off position and proceed to step 3.

3 With UPS cool, ALARM

continues when facility

power is applied to ACU.

UPS does not output

power.

Ensure that connector P1 is securely attached to UPS. Attempt to operate UPS

$ again by setting UPS power switch to on position.

4 Battery service LED is

red.

Replace batteries BT1 through BT4. If problem persists, replace UPS.

5 Top LED above load

symbol is solid red. 

Determine if load(s) is defective or too many loads are connected to the UPS.

Overload condition because of excessive current.

6 All LED's above load

symbol are on. 

High dc charging voltage.

Turn UPS off and disconnect all loads connected to UPS (modem power supply,

ACU DC#1, ACU DC #2, GTA Radio, and Codex modem). Connect loads one

at a time back into UPS and turn power back on after each one is plugged in until

problem returns. If problem persists, remove and replace UPS.

$ 7

$

$

$ Red LED (top or bottom)

$ above ac input voltage

$ symbol is lit.

$ Line voltage is either too high or too low. UPS in battery operation. Correct input

voltage if possible or be prepared to lose power to load in approximately 2 to 5

minutes after impending low battery LED turns on.
S100 ASOS Site Technical Manual

Change 2 2-117

Table 2.5.7. UPS Fault Isolation (62828-90338-10 or 62828-90338-20) - CONT $

Step Symptom Checks/Corrective Actions

8 Red LED (top or bottom) $

above ac input symbol is $

flashing. $

Line voltage has returned to normal, but RESET was not pushed. $

Wait until power returns to normal, then press RESET.

2.5.3.3 VME Card Rack Check. The ACU VME cards page displays overall status of the ACU card rack

boards. The ASOS is configured with redundant hardware for increased system availability. The technician

must examine the maintenance log periodically to replace redundant faulty units to reduce the possibility of

redundant malfunctions. When a single board is identified as a faulty FRU, it must be replaced. Failure of

all or multiple boardsindicates that a failure on any board tied to VMEbus could exist. Thisis a catastrophic

failure and requires the technician to isolate the malfunctioning board through board removal and

replacement. Table 2.5.8 provides procedures to isolate the faulty FRU in the event of such a failure. 

Table 2.5.8. Card Rack Assembly Fault Isolation Procedures

Step Procedure

1 Remove power from system by setting UPS POWER switch to OFF (0) position and remove facility power

fromACU cabinet. Visually inspect both front and rear ofCard Rack Assembly 1A2 for damage, loose power

connections, etc. 

2

NOTE

Reference paragraph 2.5.4 for the proper removal and installation procedures for the card

rack circuit boards. Refer to paragraph 2.5.8 for proper jumper settings.

Remove CPU B (1A2A2) from card rack. At the rear of card rack, install jumpers across A2-IACK (slot 2,

row A, pins 21 and 22).

3 Apply facility power to ACU cabinet and set UPS POWER switch to ON (1) position. If system initializes

properly, CPU B is suspect. Verify jumpers on board and reinstall to confirm board is bad. If system does

not initialize properly, proceed to step 4.

4 Replace CPU A (1A2A1). Apply facility power to ACU cabinet and set UPS POWER switch to ON (1)

position. If system initializes properly, CPU A is suspect.Verify jumpers on board and reinstall to confirm

board is bad. If system does not initialize properly, proceed to step 5.

5 Replace Memory Board 1A2A3. Apply facility power to ACU cabinet and set UPS POWER switch to ON

(1) position. If system initializes properly, Memory Board 1A2A3 is suspect. Remove J22 on suspect board

for 30 seconds and reinstall jumper. Verify jumpers on board and reinstall to confirm board is bad. Ifsystem

does not initialize properly, proceed to step 6.

6 One at a time, replace each SIO board in slots A4 through A21 and apply power to system. If system

initializes, board most recently replaced is suspect. Verify jumpers are set correctly on suspect SIO and

reinstall to confirm board is bad. If system fails to initialize, card rack itself is bad or multiple failures exist.
ASOS Site Technical Manual S100

2-118

2.5.3.4 ACU/DCP Communication System Checks. The communication link between the ACU and the

DCP can be either via rf modems orline drivers. For ClassIIsystems, redundant hardware is used to increase

system availability. The ACU CST continually monitors the status of the communication link between the

ACU and the DCP. When the ACU is requesting sensor weather data from the DCP, it makes up to three

attempts to communicate before logging a failure. For example, if the DCP does not respond to the first

request, the ACU requests a second time. If the DCP still does not respond, the ACU requests a third time.

If the DCP still fails to respond, a communications failure is noted and the requested data are lost. When the

ACU is requesting other types of data (DCP CST results, sensor CST results, etc), only one request is made.

If the DCP fails to respond, a failure is logged and no retry is made. The status of the link is reported on the

ACU/DCP COMMS page at the OID. Also, when malfunctions are detected, error messages are printed on

the printer and entered into the maintenance log. The following paragraphs describe checks ofthe ACU/DCP

communications link.

2.5.3.4.1 RF Communications. In the ClassIIsystem, the primary (A orB) rf modemin the ACU maintains

communication with the primary CPU/rf modem set (A or B) in the DCP. Every minute, the ACU checks its

secondary modem to ensure that it can communicate with the DCP. If the ACU primary or secondary rf

modemcannot communicate with the DCP, then an errormessage is printed and entered into themaintenance

log, and an F is indicated for the modem on the ACU/DCP COMMS page. Because these are not sensor

weather data, no retries are made before logging the failure (as described above).

The ACU can determine the status of the current primary CPU/rf modem link in the DCP and display this

status on the ACU/DCP COMMS page on the OID. However, because the DCP'ssecondary link is not in use,

the ACU cannot determine itsstatus. Assuch, it is normalforthe ACU/DCP COMMS status page to indicate

P (pass) for the primary DCP link and * (not yet tested) for the secondary link. If the current DCP primary

link fails, the DCP will automatically reset and the other link becomes the new primary link (see below). In

this case, an ACU/DCP COMMS FAILURE message is entered in the maintenance log and the failure of the

first link is noted on the ACU/DCP COMMS page. The status for the new primary link will be shown as P

on the ACU/DCP COMMS page (assuming that the new link is operational).

ACU/DCP communications are half-duplex (one way at a time). The ACU polls the DCP for data, and the

DCP responds. The DCP never initiates a communication. In the event that the DCP does not receive any

ACU communications for a period of 2 minutes and 40 seconds, the DCP resets itself. When this occurs, the

formersecondary CPU initializesitself asthe new primary CPU. When this CPU receives a synchronization

message from the ACU (transmitted once per minute at second #59), it sends a message to the ACU that it

has switched systems and reset. A message DCP # ___ HAS RESET TO THE BOOT PROMS is printed on

the printer and is entered into themaintenance log. When the DCP receivesthe nextsynchronizationmessage

from the ACU, the DCP completes its initialization and begins normal operation with the new primary

CPU/rf modem set. 

In a configuration with more than one DCP, the ACU examines the status of all ACU/DCP links in

identifying the source of the failure. That is, a loss of communications with all DCP's indicates that the

problem is in the ACU. A loss of communications with a single DCP in the multiple configuration indicates

that the fault lies in the failing DCP. 

When a complete communication breakdown occurs in a single DCP system, the technician must determine

whether the failure is in the ACU or the DCP. This is most easily accomplished using an in-line rf power

meter to determine if the ACU and the DCP are transmitting from their respective rf modems. Because the

DCP will not transmit anything unless it first receives an inquiry from the ACU, the ACU transmissions

should be checked first. 
S100 ASOS Site Technical Manual

2-119

Table 2.5.9 provides a list of ACU/DCP communication symptoms and references the technician to

additional procedures that may be used to isolate rf system faults. Procedures are provided for both Class I

and Class II ACU's and DCP's.

2.5.3.4.2 Line Driver Communications. For a line driver communications link, the system performs the

same checks and issuesthe same error messages. The operation of the ACU/DCP COMMS page isthe same.

Because there are no rf antennasin a line driversystem, the technician should carefully check all connections

for the ACU-DCP cable before replacing equipment in either cabinet.

NOTE

Normally, a system built with UDS D19.2 line drivers continues to operate with the line

drivers until sufficient spares can no longer be obtained. When this occurs, the entire site

(ACU and DCP) must be modified to operate with Motorola DDS/MR64 line drivers. Two

line drivers are required to update a ClassIsystem. Four line drivers are required to upgrade

a Class II system. All UDS line drivers removed from a system must be returned to the

National Reconditioning Center. 

When a problem is suspected with ACU or DCP line drivers, the technician should make the following

checks of the line drivers.

 a. Ensure that power is applied to the line driver. If not, determine reason for power

interruption to line driver.

b. Check for proper connection of RS-232 and telephone cables to line driver.

 c. For the D19.2 line drivers perform the following:

(1) Ensure that front panel switch on each line driver is in DATA position.

(2) Ensure that TM indicator on front panel of line driveris not illuminated or blinking.

If TM indicator is on or blinking perform the following:

(a) Ensure that all ACU and DCP line driver rotary switches are in DATA

position.

(b) Disconnect RS-232 cable and telephone cable from line driver.

(c) Temporarily remove power from line driver and reapply power (in ACU,

remove it from modem rack and then insert it).

(d) If indicator does not extinguish, replace line driver. If problem is not

corrected, replace associated line driver in other cabinet.

 d. For the DDS/MR64 line drivers perform the following:

(1) Ensure that “ERROR” is not displayed on each line driver LCD. If LCD displays

“ERROR” perform the following:

(a) Disconnect RS-232 cable and telephone cable from line driver.
ASOS Site Technical Manual S100

2-120 Change 1

(b) Temporarily remove power from line driver and reapply power (in ACU,

remove it from modem rack and then insert it).

(c) If indicator does not extinguish, refer to paragraph 2.5.3.4 and verify line

driver configuration.

(d) If “ERROR” isstill displayed on LCD, replace line driver.If problemis not

corrected, replace associated line driver in other cabinet.

Table 2.5.9. RF Failure Symptoms

Symptom Corrective Action

ACU loses communication with

all DCP's in multiple-DCP

system.

a. Check ACU rf system:

 Table 2.5.10 (Class II)

 Table 2.5.11 (Class I)

b. Replace ACU antenna.

ACU loses communication with

one DCP in a multiple-DCP

system.

a. Check DCP rf system:

 Table 2.5.12 (Class II)

 Table 2.5.13 (Class I)

b. Replace DCP antenna.

ACU loses communication with

DCP in single-DCP system.

a. Check ACU rf system:

 Table 2.5.10 (Class II)

 Table 2.5.11 (Class I)

b. Check DCP rf system:

 Table 2.5.12 (Class II)

 Table 2.5.13 (Class I)

c. Replace DCP antenna.

d. Replace ACU antenna.

Table 2.5.10. ACU RF Communication Checkout Class II

Step Test Corrective Action

NOTE

This procedure disables one ACU rf modem (A or B) while testing the other. This procedure

must be performed twice (once with only rf modem A enabled and once with rf modem B

enabled) to fully test the ACU communication systems.

Throughout the procedure, inspect all applicable rf cables and connections as possible source of

failure.

1 Using an rf scanner, select site transmit frequency.

Adjust squelch and volume and verify that polling

tone is generated by the ACU radio.

 If ACU is transmitting, check DCP communications. Refer to table 2.5.12.

2 At OID (from the 1-minute display), press

REVUE-SITE-CONFIG-COMMS keys to select

communications configuration (ACU serial communication) page (Figure 1.3.41). 
S100 ASOS Site Technical Manual

2-121

Table 2.5.10. ACU RF Communication Checkout Class II -CONT

Step Test Corrective Action

3 Using CHANGE function, disable one of the two

ACU-DCP links (A or B).

4 At ACU I/O Panel Assembly 1A9, install an in-line rf

power meter between the ACU antenna cable and

ANTENNA output connector J39.

5 Watch the rf power meter to ensure that the ACU

transmits at least once per minute (synchronization

messages are sent out during second 59 each minute).

If ACU is not transmitting, proceed with step 6.

If ACU is transmitting at least once per minute,

reconnect cable to ANTENNA connector. Then insert

power meter in line at connector at base of ACU

antenna. If transmissions are not detecTable at the

antenna, then problem is in cabling from ACU to

antenna. If transmissions are still detected at the

antenna, then problem is in ACU antenna or in DCP.

6 Remove rf power meter and reconnect antenna cable

to ANTENNA connector J39. 

7 At ACU RF/Pressure Mounting Shelf 1A6, install rf

power meter between output of rf modem switch

1A6S1 and output cable W012.

NOTE

Output coaxial cable is an FRU and connections should be checked before replacing other FRU's.

8 Watch the rf power meter to ensure that the ACU

transmits at least once per minute.

If ACU is transmitting at least once per minute, check

output coaxial cable and replace rf surge protector

1A9J39 on I/O Panel Assembly 1A9.

If ACU is not transmitting, proceed with step 9.

9 Remove rf power meter and reconnect cable to rf

modem switch S1.

10 Install rf power meter in line at the output BNC

connector of currently enabled rf modem. Ensure that

modem transmits at least once per minute.

If modem is not transmitting, continue with step 11. If

modem is transmitting, proceed to step 12.

11 Insert RS-232 tester in line at connectorJ1 of enabled

rf modem. Verify activity on TxD, RTS, and CTS

signals at input to rf modem.

If RTS signal is not active at least once per minute,

replace SIO board corresponding to enabled modem

(SIO #2 for modem A, SIO #3 for modem B).

If RTS is active and CTS is not, replace failing rf

modem.

If RTS and CTS are active, but TxD signal is not

active at least once per minute, replace SIO board

corresponding to failing modem.

If RTS, CTS, and TxD signals are all active, replace

failing modem.
ASOS Site Technical Manual S100

Table 2.5.10. ACU RF Communication Checkout Class II -CONT

Step Test Corrective Action

2-122

12 Using DMM, ensure correct logic level between rf

modem switch terminals 1A6S1-TTL and S1-COM

as follows:

Enabled

Modem S1-TTL

A Logic 0 (0.0 to 1.0 vdc)

B Logic 1 (3.0 to 5.0 vdc)

If voltage is not correct for enabled radio, replace DIO

board 1A2A15.

NOTE

Coaxial cable at output of rf modem

is an FRU and connection should be

checked.

Check coaxial cable between rf modem and rf modem

switch.

If voltage is correct and cable looks good, replace rf

modem switch 1A6S1.

13 Remove all test equipment and reconnect all cables.

14 At ACU serial communications page of OID, use

CHANGE function to enable the ACU-DCP link (A

or B) previously disabled. 

Table 2.5.11. ACU RF Communication Checkout Class I

Step Test Corrective Action

NOTE

Throughout the procedure, inspect all applicable rf cables and connections as possible source of

failure.

1 Using an rf scanner, select site transmit frequency.

Adjust squelch and volume and verify that polling

tone is generated by the ACU radio.

If ACU istransmitting, check DCP communica-tions.

Refer to table 2.5.13.

2 At ACU I/O Panel Assembly 1A9, install an in-line rf

power meter between the ACU antenna cable and

ANTENNA output connector J39. 

3 Watch the rf power meter to ensure that the ACU

transmits messages at least once per minute

(synchronizationmessages are sent out during second

59 each minute). 

If ACU is not transmitting, proceed with step 4.

If ACU is transmitting at least once per minute,

reconnect cable to ANTENNA connector. Then insert

power meter in line at connector at base of ACU

antenna. If transmissions are not detecTable at the

antenna, then problem is in cabling from ACU to

antenna. If transmissions are still detected at the

antenna, then problem is in ACU antenna or in DCP.

4 Remove rf power meter and reconnect antenna cable

to ANTENNA connector J39. 

5 At ACU RF/Pressure Mounting Shelf 1A6, install rf

power meter between output BNC connector of RF

Modem 1A6A4 and output cable W032.

NOTE

Output coaxial cable is an FRU and connections should be checked before replacing other FRU's.
S100 ASOS Site Technical Manual

2-123

Table 2.5.11. ACU RF Communication Checkout Class I -CONT

Step Test Corrective Action

6 Watch the rf power meter to ensure that the rf modem

transmits at least once per minute.

If the rf modem is transmitting at least once per

minute, check coaxial cable, then replace rf surge

protector 1A9J39 on I/O Panel Assembly 1A9.

If rf modem is not transmitting, proceed with step 7.

7 Insert RS-232 tester in line at connector J1 of RF

Modem 1A6A4. Verify activity on TxD, RTS, and

CTS signals at input to rf modem.

If RTS signal is not active at least once per minute,

replace SIO board 2. 

If RTS is active and CTS is not, replace failing rf

modem.

If RTS and CTS are active, but TxD signal is not

active at least once per minute, replace SIO board 2.

If RTS, CTS, and TxD signals are all active, replace

RF Modem 1A6A4. 

Table 2.5.12. DCP RF Communication Checkout Class II

Step Test Corrective Action

NOTE

This procedure tests one rf link (A or B) at a time. This procedure must be performed twice (once

for link A and once for link B) to fully test the DCP communications system.

Examine PASS indicators on CPU's A and B to determine which CPU/rf modem link is currently

primary (PASS indicator is illuminated steadily on primary).

Throughout this procedure, the technician may have to manually reset the DCP to maintain primary

assignment on link being tested. The DCP is manually reset by pressing the RESET switch on the

CURRENT primary CPU. For example, the technician can test rf modem B when the A

CPU/modem is currently primary by resetting the A CPU, which causes the B CPU to take over

primary assignment. RF modem B may then be tested.

Throughout the procedure, inspect all applicable rf cables and connections as possible source of

failure.

1 Select link (A or B) to be tested first. If necessary,

reset DCP to toggle primary assignment to selected

link under test.

2 Examine PASS indicator on opposite (secondary)

CPU. This indicator should flash after DCP receives

synchronization message from ACU (may have to

wait up to 1 minute for this to occur).

If PASS LED on secondary CPU flashes, link under

test is receiving sync message. Proceed to step 8.

If PASS LED does not flash (and DCP resets after 2

minutes and 40 seconds), continue with step 3.

3 On selected rf modemunder test, insert RS-232 tester

in line with cable from CPU and modem connector

J1.

4 Ensure that selected link under test is still primary

(press CPU RESET if necessary).

NOTE

Cable between CPU and rf modem is an FRU and should be checked before replacing other FRU's.
ASOS Site Technical Manual S100

2-124

Table 2.5.12. DCP RF Communication Checkout Class II -CONT

Step Test Corrective Action

5 5 Verify activity of RxD signal on RS-232 tester at

least once per minute (ACU sends synchronization

messages during second 59 each minute).

If RxD signal is active, check cable between CPU

and rf modem under test, then replace CPU.

If RxD signal is not active, continue with step 6.

6 Using DMM, ensure correct logic level between rf

modem switch terminals A1A5S1-TTL (white wire)

and S1-COM (black wire) as follows:

 Link

 Under

Test S1-TTL

 A Logic 0 (0.0 to1.0 vdc)

 B Logic 1 (3.0 to5.0 vdc)

If voltage is not correct for current primary link,

replace DIO Board A1A2A12.

If voltage is correct, proceed to step 7.

7 Press RESET to toggle primary assignment to

opposite CPU/rf modem. Wait to see if ACU/DCP

communications resume on opposite link.

If communications resume, fault is due to one of the

following:

a. Cable between first rf modem and rf

 modem switch (check connections).

b. First rf modem

c. RF modem switch

If communications do not resume, fault is due to one

of the following:

a. RF modem switch

b. Cabling from DCP antenna to rf

modem switch

c. RF surge protector A1A3J8

d. Both radios failed (or cables

between radios and rf modem

switch)

e. DCP antenna

f. ACU antenna

8 On selected rf modemunder test, insert RS-232 tester

in line with cable from CPU and modem connector

J1.

NOTE

Cable between CPU and rf modem is an FRU and should be checked before replacing other FRU's.
S100 ASOS Site Technical Manual

Table 2.5.12. DCP RF Communication Checkout Class II -CONT

Step Test Corrective Action

2-125

9 Ensure that selected link is still primary, and verify

activity on RTS, CTS, and TxD signals on RS-232

tester (at least once per minute).

If RTS signal is not active, replace corresponding

CPU board.

If RTS is active but CTS is not, replace rf modem.

If RTS and CTS are active but TxD is not, replace

corresponding CPU.

10 At output of same rf modem, connect an in-line rf

power meter between output BNC connector and

output cable. 

11 Ensure that selected link under test is still primary

(press CPU RESET if necessary).

12 Watch the rf power meter to ensure that the rf modem

transmits messages at least once per minute.

If rf modem is transmitting, continue with step 13.

If rf modem is not transmitting, replace rf modem.

13 Remove rf power meter and reconnect modem output

cable.

14 Install rf power meter between output of rf modem

switch A1AS1 and output cable W013.

15 Ensure that selected link under test is still primary

(press CPU RESET if necessary).

NOTE

Coaxial cable between rf modem and switch is an FRU and should be checked before replacing

other FRU's.

16 Watch the rf power meter and ensure that system

transmits from rf modem switch at least once per

minute.

If transmissions are indicated, continue with step 17.

If transmissions are not indicated, check coaxial

cable, then replace rf modem switch.

17 Remove rf power meter and reconnect rf switch

output cable.

18 At Faraday Box A1A3, install rf power meter

between output of rf surge suppressor A3J8 and

output cable W010.

19 Ensure that selected link under test is still primary

(press CPU RESET if necessary).

NOTE

Coaxial cable between rf modem switch and surge suppressor is an FRU and should be checked

before replacing other FRU's.

20 Watch the rf power meter and ensure that system

transmits from the rf surge suppressor at least once

per minute.

If transmissions are indicated, continue with step 21.

If transmissions are not indicated, replace rf surge

suppressor. 

21 Remove rf power meter and reconnect cable to surge

suppressor.

22 Insert power meter in line at connector at base of

DCP antenna.
ASOS Site Technical Manual S100

Table 2.5.12. DCP RF Communication Checkout Class II -CONT

Step Test Corrective Action

2-126

23 Ensure that selected link under test is still primary

(press CPU RESET if necessary).

NOTE

Cables between DCP rfsurge suppressor and DCP antenna are FRU's and should be checked before

replacing other FRU's.

24 Watch the rf power meter and ensure that system

transmits to the antenna at least once per minute.

If transmissions are not indicated at the base of the

antenna, then problem is in cabling from surge

suppressor to antenna.

If transmissions are indicated, then problem is in the

DCP antenna or the ACU antenna. 

Table 2.5.13. DCP RF Communication Checkout Class I

Step Test Corrective Action

NOTE

Throughout the procedure, inspect all applicable rf cables and connections as possible source of

failure.

1 Examine PASS indicator on CPU A1A2A1 to ensure

that it is steadily illuminated. 

If PASS indicator is not illuminated steadily, press

RESET switch on the CPU. If CPU does not

initialize, replace CPU.

2 On rf modem A1A5A1, insert RS-232 tester in line

with cable from CPU and modem connector J2.

3 Verify activity of RxD signal on RS-232 tester at

least twice per minute.

If RxD signal is active, proceed to step 4.

If RxD signal is not active, fault is due to one of the

following: 

a. Cabling/connections from DCP antenna to rf

 modem

b. RF surge protector A3J8

c. RF Modem A1A5A1

d. DCP antenna

e. ACU antenna

NOTE

Cable between CPU and rf modem is an FRU and should be checked before replacing other FRU's.

4 Verify activity on RTS, CTS, and TxD signals on

RS-232 tester (at least twice per minute).

If RTS signal is not active, replace CPU A1A2A1.

If RTS is active, but CTS is not, replace rf modem.

If RTS and CTS are active, but TxD is not, replace

CPU.

5 At output of rf modem, connect an in-line rf power

meter between output BNC connector and output

cable. 
S100 ASOS Site Technical Manual

2-127

Table 2.5.13. DCP RF Communication Checkout Class I -CONT

Step Test Corrective Action

6 Watch the rf power meter to ensure that the rf modem

transmits messages at least once per minute.

If rf modem is transmitting, continue with step 7.

If rf modem is not transmitting, replace rf modem.

7 Remove rf power meter and reconnect modemoutput

cable.

8 At Faraday Box A1A3, install rf power meter

between output of rf surge suppressor A3J8 and

output cable W010.

NOTE

Coaxial cable between rf modem and surge suppressor is an FRU and should be checked before

replacing other FRU's.

9 Watch the rf power meter and ensure that system

transmits from the rf surge suppressor at least twice

per minute.

If transmissions are indicated, continue with step 11.

If transmissions are not indicated, replace rf surge

suppressor. 

10 Remove rf power meter and reconnect cable to surge

suppressor.

11 Insert power meter in line at connector at base of

DCP antenna.

NOTE

Cables between DCP rfsurge suppressor and DCP antenna are FRU's and should be checked before

replacing other FRU's.

12 Watch the rf power meter and ensure that system

transmits to the antenna at least twice per minute. 

 

If transmissions are not indicated at the base of the

antenna, then problem is in cabling from surge

suppressor to antenna. 

If transmissions are indicated, then problem is in the

DCP antenna or the ACU antenna. 

2.5.3.5 Serial I/O Board Checks. The ACU continuous self-test (CST) checks the operation of the SIO

boards once per minute. A LOOPBACK test and a TRANSMIT ERRORtest is performed on each ofthe four

ports of each SIO board. When a failure is discovered, an error message is printed on the printer and entered

into the maintenance log. The error message identifies the SIO board and port, the type of test failed, and

gives instructions to replace the board. Also, an F indication is displayed on the appropriate ACU SIO page

at the OID. For this type of SIO board failure, the technician need only replace the identified board to repair

the system.

In addition to the definitive SIO board failures described above, general communicationsfailures may occur

between the CPU and some device (peripheral, local sensor, or user). These failures may be the fault of an

SIO board, but they may also be the fault of the device, or equipment in between the SIO and the device (e.g.,

telephone modems, cable connections, etc). Often the CPU itself may detect such communication failures.

In such case, a general error message, such as PRIMARY OID COMMUNICATION FAILURE or AFOS

PHONE PORT DOWN is printed on the printer and entered into the maintenance log.

When such general loss of communication occurs, the technician should first access the ACU serial

communications page on the OID and determine to which SIO port the failing device is assigned. The ACU

functional diagrams and the descriptions of Section IV of this Chapter should be referenced to determine all

of the equipment cables between the corresponding SIO board and the device which lost communications.

The technician should then inspect all cable connections associated with the failing port.

If all cable connections appear to be good and the port is still not operating, an RS-232 test box can be used
ASOS Site Technical Manual S100

2-128

to check communication between the SIO port and the next device in line with it (e.g. modem, printer, OID,

etc). The RS-232 test box is inserted between the connector for the failing SIO Port and the device which

lost communications.

When using the RS-232 test box, the technician must verify the activity of the applicable RS-232 signals. In

all cases, the transmit data (TxD) and receive data (RxD) signals must be active to indicate correct

communication. Depending on the device being investigated, two handshaking signals may also be required:

request to send (RTS) and clear to send (CTS). In order to determine whether the RTS and CTS signals

should be present for a given application, the technician must access the ACU serial communications page

at the OID, select the port that is being investigated, and look at the HANDSHAKING field. This field will

indicate either NONE or CTS/RTS. If CTS/RTS is indicated, the technician must ensure that these signals

are present on the RS-232 tester. If NONE is indicated, the technician need only verify the TxD and RxD

signals.

2.5.3.6 Diagnostics. The ACU CST runs continuously in the background of the ASOS operating software

as described in Chapter 1. The CST completes a check of the system every minute with the exception of the

modem rack. The CST checks each of the individual telephone modems in the modem rack once every 7

minutes, as long asthe modems are not busy (testing a busy modem would disrupt communication). The test

data received via the diagnostic program are displayed on the technician interface display pages, which are

described in Chapter 1, Section III. If the CST detects a failure, the unit is tagged as faulty and a message

is entered into the maintenance log. Where redundant hardware is present (i.e., CPU's, rf modems, pressure

sensors, or line drivers), the faulty FRU is bypassed via software and the failure is entered into the

maintenance log and a maintenance flag ($) is added to the next METAR.

2.5.4 REMOVAL AND INSTALLATION PROCEDURES

2.5.4.1 General. The following chart is provided to facilitate safe and efficient removal of assembliesfound

to be defective through performance of the preventive maintenance and troubleshooting procedures.

Procedures provided for replacement of duplicate assemblies,such asthe VME cards and dc powersupplies,

are sufficient for maintenance of all units and are described for one assembly only. Only those assemblies

and subassemblies whose replacement procedures are not obvious have been provided in this chapter. The

removal/installation sequence of attaching hardware (screws, washers, nuts, etc) is reflected by the relative

order of their presentation in the applicable step.

Unit to Be Replaced Removal/Installation/

Table reference 

Modem/line driver rack power supply 2.5.14

RF modem 2.5.15

RF switch 2.5.16

VME card rack circuit board 2.5.17

Modem/line driver rack circuit board 2.5.18

Power supply assembly filter board 2.5.19

Power supply assembly transformer 2.5.20

Power supply assembly fuse 2.5.21

Power supply assembly RS-232 board 2.5.22

Power supply assembly inverter board 2.5.23

Power supply assembly status panel 2.5.24

Power supply assembly OUTPUT POWER switch 2.5.25

Power supply assembly circuit breaker 2.5.26
S100 ASOS Site Technical Manual

Unit to Be Replaced Removal/Installation/

Table reference 

2-129

WARNING

WARNING

DC power supply 2.5.27

DC power supply fan connector board 2.5.28

Blower 2.5.29

Battery box and battery 2.5.30

Uninterruptible power supply 2.5.31

ACU tie-downs 2.5.32

Pressure sensor See Chapter 8

GTA Radio See Chapter 12

Codex modem See Chapter 13

2.5.4.2 Orienting DB-25 Adapters. On I/O Panel 1A9, DB-25 adapters J22 through J31 and J42 (p/n

62828-90148-1) are combination EMI filter/surge suppressor devices. The manufacturer of these adapters

placesits part number label on the surge suppressor end of the device. When installing a new DB-25 adapter,

the maintenance technician must orient the new adapter so that its surge suppressor (label) end faces the

outside of the ACU cabinet (EMI end is inside cabinet).

Table 2.5.14. Modem/Line Driver Rack Power Supply Removal and Installation

Step Procedure

REMOVAL

Tools required:

 Small flat-tipped screwdriver

 Death orsevere injurymay result if power is notremoved fromACU prior to maintenance activities.

Ensure that UPS POWER switch isset to 0 (off) position and facility power is removed from ACU.

1 Set UPS POWER switch to 0 (off) position. 

2 Remove facility power from ACU cabinet.

3 Disconnect ac power cord from rear of modem/line driver rack.

4 Using small flat-tipped screwdriver, loosen power supply holding screw on rear of modem/line driver rack.

5 Lower modem/line driver rack hinged front panel.

6

 CAUTION

Power supply module is heavy. Grasp handle with one hand while supporting bottom of

power supply module with other hand.

Grasp power supply handle and slide out of modem/line driver rack.

INSTALLATION

Tools required:

 Small flat-tipped screwdriver

Death orsevere injurymay result if power is notremoved fromACU prior to maintenance activities.

Ensure that UPS POWER switch is set to 0 (off) position and facility power isremoved from ACU.

1 Verify that UPS POWER switch is set to 0 (off) position. 
ASOS Site Technical Manual S100

2-130 Change 2

WARNING

Table 2.5.14. Modem/Line Driver Rack Power Supply Removal and Installation - CONT

Step Procedure

2 Verify that facility power is removed from ACU cabinet. 

3 Position power supply in guide strips and slide into modem/line driver rack.

4 Close hinged front panel.

5 Using small flat-tipped screwdriver, tighten power supply holding screw on rear of modem/line driver rack.

6 Connect ac power cord to modem/line driver rack.

7 Apply facility power to ACU cabinet.

8 Set UPS POWER switch to 1 (on) position.

Table 2.5.15. RF Modem Removal and Installation

Step Procedure

REMOVAL

Tools required:

 No. 1 Phillips screwdriver

 No. 2 Phillips screwdriver

 Small flat-tipped screwdriver

CAUTION

Damage to rf modems may result if power is not removed from ACU prior to removal or

installation. Ensure that UPS POWER switch isset to 0 (off) position and facility power isremoved

from ACU.

NOTE

Refer to paragraph 2.4.3.4.2 for replacement rf modem information.

1 Set UPS POWER switch to 0 (off) position. 

2 Remove facility power from ACU cabinet.

3

Pressure sensors in RF/Pressure Mounting Shelf 1A6 are safety-critical devices. Pressure

sensors may output erroneous readings if damaged or if plastic vent tubing is damaged or

obstructed. Throughout this procedure, exercise caution to avoid damage to pressure

sensors and vent tubing.

Using No. 2 Phillips screwdriver, remove two screws, lockwashers, and flat washers securing rf/pressure

mounting shelf slide mount to frame. Slide mounting shelf out until slides lock in fully extended position.

$ 4 Using figure 2.1.7, locate rf modem to be removed.

$ 5

$

$ At rf modem to be removed, use small flat-tipped screwdriver to remove D connectors (two for AAI model,

$ one for Motorola and Johnson Data models) from rf modem.

$ 6

$

$ Remove BNC connector from modem rf output connector. If modem being removed is Johnson Data model

$ then remove SMAM-to-BNCF adapter.
S100 ASOS Site Technical Manual

Change 2 2-131

WARNING

Table 2.5.15. RF Modem Removal and Installation - CONT

Step Procedure

7 Using No. 1 Phillips screwdriver, remove two screws, lockwashers, and flat washers from the bottom of

mounting shelf that secure rf modem to shelf. Remove rf modem from mounting shelf.

NOTE $

When an AAI modem (62828-90013-XX) fails, and a replacement AAI modem is not $

available, ASN S100-FMK18886 must be ordered to replace themodemwith the Motorola $

modem (62828-90315-XX). AAI modems cannot be replaced with the Johnson Data $

modems (62828-40506-X ). $

$

When a Motorola modem (62828-90315-XX) fails and spare Motorola modems are not $

available, a Johnson Data modem (62828-40506-X), an adapter cable (62828-42110-10), $

and a SMAM-to-BNCF adapter must be ordered to replace the failing rf modem. $

INSTALLATION

Tools required:

 No. 1 Phillips screwdriver

 No. 2 Phillips screwdriver

 Small flat-tipped screwdriver

CAUTION

Damage to rf modems may result if power is not removed from ACU prior to removal or

installation. Ensure that UPS POWER switch isset to 0 (off) position and facility power isremoved

from ACU.

1 Verify that UPS POWER switch is set to 0 (off) position. 

2 Verify that facility power is removed from ACU cabinet.

2.1 If rf modem to be installed is a Johnson Data model, ensure that bottom mounting plate is removed from the $

modem. If necessary, remove bottom mounting plate using a No. 2 Phillips screwdriver and discard. $

3

Pressure sensors in RF/Pressure Mounting Shelf 1A6 are safety-critical devices. Pressure

sensors may output erroneous readings if damaged or if plastic vent tubing is damaged or

obstructed. Throughout this procedure, exercise caution to avoid damage to pressure

sensors and vent tubing.

Using No. 2 Phillips screwdriver, remove two screws, lockwashers, and flat washers securing rf/pressure

mounting shelf slide mount to frame. Slide mounting shelf out until slides lock in fully extended position.

4 Position replacement rf modem on mounting shelf and use No. 1 Phillips screwdriver to install two screws, $

lockwashers, and flat washers securing rf modem to mounting shelf. Screws are installed from bottom side $

of mounting shelf. $

4.1 If replacement modem is a Johnson Data modem (62828-40506-X), install adapter cable (62828-42110-10) $

and a SMAM-to-BNCF adapter to rf modem. $

5 Install BNC connector to modem rf output connector (or to SMAM-to-BNCF adapter). $

6 Using small flat-tipped screwdriver, install and secure power/signal D connectors to rf modem. $
ASOS Site Technical Manual S100

2-132 Change 2

WARNING

WARNING

Table 2.5.15. RF Modem Removal and Installation - CONT

Step Procedure

7

Pressure sensors in RF/Pressure Mounting Shelf 1A6 may output erroneous values if

plastic vent tubing binds or crimps when shelf is closed. Exercise caution when closing

shelf to prevent damage to pressure sensor vent tubing.

While taking care not to damage or crimp pressure sensor vent tubing, release mounting shelfslide locks and

push mounting shelf back into cabinet. After closing shelf, ensure that pressure sensor tubing is properly

connected to sensor and to PRESSURE VENT on I/O Panel Assembly 1A9 and is not damaged or crimped.

8 Using No. 2 Phillips screwdriver, install two screws, lockwashers, and flat washers securing mounting shelf

to frame.

9 Apply facility power to ACU cabinet.

10 Set UPS POWER switch to 1 (on) position.

Table 2.5.16. RF Switch Removal and Installation

Step Procedure

REMOVAL

Tools required:

 No. 1 Phillips screwdriver

 No. 2 Phillips screwdriver

CAUTION

Equipment damage may occur if power is not removed from ACU prior to removal or installation.

Ensure that UPS POWER switch is set to 0 (off) position and facility power is removed.

1 Set UPS POWER switch to 0 (off) position. 

2 Remove facility power from ACU cabinet.

3

Pressure sensors in RF/Pressure Mounting Shelf 1A6 are safety-critical devices. Pressure

sensors may output erroneous readings if damaged or if plastic vent tubing is damaged or

obstructed. Throughout this procedure, exercise caution to avoid damage to pressure

sensors and vent tubing.

Using No. 2 Phillips screwdriver, remove two screws, lockwashers, and flat washers securing rf/pressure

mounting shelf slide mount to frame.

4 At rf switch, tag and remove three BNC connectors.

5 Disconnect rf switch in-line connector (A6-P1) from ACU harness connector P92.

6 Using No. 1 Phillips screwdriver, remove two screws, flat washers, and lockwashers securing rf switch to

standoffs. Remove rf switch.
S100 ASOS Site Technical Manual

Change 2 2-133

WARNING

WARNING

Table 2.5.16. RF Switch Removal and Installation - CONT

Step Procedure

INSTALLATION

Tools required:

 No. 1 Phillips screwdriver

 No. 2 Phillips screwdriver

 Large flat-tipped screwdriver

CAUTION

Equipment damage may occur if power is not removed from ACU prior to removal or installation.

Ensure that UPS POWER switch is set to 0 (off) position and facility power is removed.

1 Verify that UPS POWER switch is set to 0 (off) position. 

2 Verify that facility power is removed from ACU cabinet.

3

Pressure sensors in RF/Pressure Mounting Shelf 1A6 are safety-critical devices. Pressure

sensors may output erroneous readings if damaged or if plastic vent tubing is damaged or

obstructed. Throughout this procedure, exercise caution to avoid damage to pressure

sensors and vent tubing.

Using No. 2 Phillips screwdriver, remove two screws, lockwashers, and flat washers securing rf/pressure

mounting shelf slide mount to frame.

4 Position rf switch near standoffs at rear of rf/pressure mounting shelf.

5 Using No. 1 Phillips screwdriver, install two screws, flat washers, and lockwashers securing rf switch to

standoffs.

6 Connect rf switch in-line connector (A6-P1) to ACU harness connector P92.

7 Using markers as a guide, install three BNC connectors on rf switch.

8

Pressure sensors in RF/Pressure Mounting Shelf 1A6 may output erroneous values if

plastic vent tubing binds or crimps when shelf is closed. Exercise caution when closing

shelf to prevent damage to pressure sensor vent tubing.

While taking care not to damage or crimp pressure sensor vent tubing, release mounting shelfslide locks and

push mounting shelf back into cabinet. After closing shelf, ensure that pressure sensor tubing is properly

connected to sensor and to PRESSURE VENT on I/O Panel Assembly 1A9 and is not damaged or crimped.

9 Using No. 2 Phillips screwdriver, install two screws, lockwashers, and flat washers securing mounting shelf

to frame.

10 Apply facility power to ACU cabinet.

11 Set UPS POWER switch to 1 (on) position.
ASOS Site Technical Manual S100

2-134 Change 2

Table 2.5.17. VME Card Rack Circuit Board Removal and Installation

Step Procedure

REMOVAL

Tools required:

 Small flat-tipped screwdriver

 CAUTION

Damage to equipment may result if power is not removed prior to removal or installation. Ensure

that UPS POWER switch is set to 0 (off) position and facility power is removed.

To avoid damage to circuit boards, use proper electrostatic discharge (ESD) handling procedures

to include the use of a grounding strap when performing the following procedures.

1 Set UPS POWER switch to 0 (off) position. 

2 Remove facility power from ACU cabinet.

3 Using figure 2.1.3, locate circuit board to be removed.

4 If removing Voice Processor Board 1A2A20 or Voice Recorder/Playback Board 1A2A21, disconnect cable

from the front of the boards by exerting an outward force on the cable release tabs located at the top and

bottom of the connector.

5 Using small flat-tipped screwdriver, loosen captive screws located at the top and bottom of the board.

6

CAUTION

When removing a CPU board from the rack, support the board via the handles. Failure to

support the board properly when it releasesfromthe rear connector may result in the board

hitting the bottom of the card rack.

If the board is equipped with extractor handles, press handles in opposite directions to release the board. If

the board does not have extractor handles, gently rock the board while exerting an outward pressure and

remove board from the rack.

7

CAUTION

JumperJ22 on ACUmemory board must be disconnected before shipping orstoring board.

Failure to comply may result in discharge of battery.

If board removed is ACU Memory Board A1A2A3, remove jumper J22 from board. Install jumper on one

pin only of J22 for shipping or storage.

INSTALLATION

Tools required:

 Small flat-tipped screwdriver

 CAUTION

Damage to equipment may result if power is not removed prior to removal or installation. Ensure

that UPS POWER switch is set to 0 (off) position and facility power is removed.

To avoid damage to circuit boards, use proper ESD handling procedures to include the use of a

ground strap when performing the following procedures.

1 Verify that UPS POWER switch is set to 0 (off) position. 

2 Verify that facility power is removed from ACU cabinet.
S100 ASOS Site Technical Manual

Change 2 2-134.1/ (2-134.2 blank)

Table 2.5.17. VME Card Rack Circuit Board Removal and Installation -CONT

Step Procedure

3 If board being installed is CPU A or B (1A2A1 or 1A2A2) or RS-232 SIO board #2 through #7 (1A2A6

through 1A2A12), conFigure board jumpers for slot into which it is being installed (paragraph 2.5.6).

4

NOTE

Jumper J22 on ACU memory board must be properly installed to enable battery backup

circuit.

If board installed is ACU MemoryBoard 1A2A3, remove jumper clip from storage position (one pin) ofJ22

and install across both pins of J22.

5 Holding the board by the handles, position board with the component side to the right and carefully slide

board into the card rack on its guides. Align board with the rear connector and press into place.

6 Using small flat-tipped screwdriver, tighten captive screws located at the top and the bottom of the board.

7 If installing Voice Processor Board 1A2A20 or Voice Recorder/Playback Board 1A2A21, connect cable

attached to the front of the boards as follows:

 a. Position connector extraction tabs to their fully extended position.

 b. Locate cable keys and position keys to the right; install cable in the connector.

8 Apply facility power to ACU cabinet.

9 Set UPS POWER switch to 1 (on) position.

Table 2.5.18. Modem/Line Driver Rack Circuit Board Removal and Installation

Step Procedure

REMOVAL

NOTE

ACU power need not be turned off for a modem/ line driver circuit board interchange. This allows

normal operation of ACU during removal and replacement.

1 Using figure 2.1.4, locate circuit board to be removed.

2 Lower modem/line driver rack hinged front panel.

3 Using the handle located at the middle of the board, gently rock board until free from the rear connector.

Remove board.

INSTALLATION

NOTE

ACU power need not be turned off for a modem/ line driver circuit board interchange. This allows

normal operation of ACU during removal and replacement.

1 On circuit board being installed, verify that switch settings and jumper installations match those of

previously removed board.

2 Position component side of the board to the right and align on the guides, then slide board into slot.

3 Ensure that edge connector of board is aligned with the rack connector, then apply enough pressure to set

the board into the rack connector.

4 Close modem/line driver rack hinged front panel.
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Table 2.5.19. Power Supply Assembly Filter Board Removal and Installation

Step Procedure

REMOVAL

Tools required:

 No. 2 Phillips screwdriver

Ensure that power is completely removed from UPS by performing the procedure in table 2.5.6.

Death or severe injury may result if power is not completely removed from UPS prior to removing

the cover in front of UPS components and performing maintenance on UPS subassemblies.

1 Remove power supply assembly cover in accordance with table 2.5.6.

2 At 1.5 KVA Filter Board 1A4A3, remove harness connectors from board connectors J7 and J10.

3 Tag and remove five single wires from 1.5 KVA Filter Board 1A4A3.

4 Using Phillips screwdriver, remove four screws, flat washers, and lockwashers securing 1.5 KVA Filter

Board 1A4A3 to standoffs.

5 Remove filter board from power supply assembly.

 INSTALLATION

Tools required:

 No. 2 Phillips screwdriver

Ensure that power is completely removed from UPS by performing the procedure in table 2.5.6.

Death or severe injury may result if power is not completely removed from UPS prior to removing

the cover in front of UPS components and performing maintenance on UPS subassemblies.

1 Verify that power supply assembly cover is removed in accordance with table 2.5.6.

2 Position 1.5 KVA Filter Board 1A4A3 on standoffs with connectors J7 and J10 on bottom.

3 Using Phillips screwdriver, install four screws, flat washers, and lockwashers securing 1.5 KVA Filter

Board 1A4A3 to standoffs.

4 Using tags as a guide, install five wires on 1.5 KVA Filter Board 1A4A3.

5 Install harness connectors on board connectors J7 and J10.

6 Install power supply assembly cover in accordance with table 2.5.6.

Table 2.5.20. Power Supply Assembly Transformer Removal and Installation

Step Procedure

REMOVAL

Tools required:

 No. 2 Phillips screwdriver

 3/8-inch nut driver

Ensure that power is completely removed from UPS by performing the procedure in table 2.5.6.

Death or severe injury may result if power is not completely removed from UPS prior to removing

the cover in front of UPS components and performing maintenance on UPS subassemblies.

1 Remove power supply assembly cover in accordance with table 2.5.6.
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Table 2.5.20. Power Supply Assembly Transformer Removal and Installation -CONT

Step Procedure

2 At 1.5 KVA Inverter Board 1A4A4, tag and remove seven transformer wires with solderless (spade)

connectors from spade connectors on inverter board.

3 Using 3/8-inch nut driver, tag and remove three transformer wiresfrom standoffs on 1.5 KVA Inverter Board

1A4A4.

4 Using Phillips screwdriver, remove four screws and flat washers securing transformer to power supply

assembly.

5

Transformer is heavy equipment (weighs approximately 45 pounds) and requirestwo-man

or mechanical lift. Failure to comply may result in injury to personnel or damage to

equipment.

Carefully remove transformer from power supply assembly drawer.

INSTALLATION

Tools required:

 No. 2 Phillips screwdriver

 3/8-inch nut driver

Ensure that power is completely removed from UPS by performing the procedure in table 2.5.6.

Death or severe injury may result if power is not completely removed from UPS prior to removing

the cover in front of UPS components and performing maintenance on UPS subassemblies.

1 Verify that power supply assembly cover is removed in accordance with table 2.5.6.

2

Transformer is heavy equipment (weighs approximately 45 pounds) and requirestwo-man

or mechanical lift. Failure to comply may result in injury to personnel or damage to

equipment. 

Position transformer on power supply assembly with three heavy gauge wires on the right.

3 Using Phillips screwdriver, install four screws and flat washers securing transformer to power supply

assembly.

4 Using 3/8-inch nut driver and tags as a guide, install three transformer wiresto standoffs on 1.5 KVA Inverter

Board 1A4A4.

5 On 1.5 KVA Inverter Board 1A4A4, using tags as a guide, install seven transformer wires to spade

connectors on 1.5 KVA Inverter Board 1A4A4.

6 Install power supply assembly cover in accordance with table 2.5.6.
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Table 2.5.21. Power Supply Assembly Fuse Removal and Installation

Step Procedure

REMOVAL

Tools required:

Fuse puller

Ensure that power is completely removed from UPS by performing the procedure in table 2.5.6.

Death or severe injury may result if power is not completely removed from UPS prior to removing

the cover in front of UPS components and performing maintenance on UPS subassemblies.

1 Remove power supply assembly cover in accordance with table 2.5.6.

2 Using fuse puller, remove fuse F1 from fuse holder A4XF1.

INSTALLATION

Ensure that power is completely removed from UPS by performing the procedure in table 2.5.6.

Death or severe injury may result if power is not completely removed from UPS prior to removing

the cover in front of UPS components and performing maintenance on UPS subassemblies.

1 Verify that power supply assembly cover is removed in accordance with table 2.5.6.

2 Install replacement fuse F1 in fuse holder A4XF1.

3 Install power supply assembly cover in accordance with table 2.5.6.

Table 2.5.22. Power Supply Assembly RS-232 Board Removal and Installation

Step Procedure

REMOVAL

Tools required:

 Small flat-tipped screwdriver

 3/16-inch nut driver

Ensure that power is completely removed from UPS by performing the procedure in table 2.5.6.

Death or severe injury may result if power is not completely removed from UPS prior to removing

the cover in front of UPS components and performing maintenance on UPS subassemblies.

1 Remove power supply assembly cover in accordance with table 2.5.6.

2 Disconnect RS-232 board ribbon connector A4A2-P1 fromconnectorJ2 on 1.5 KVA Inverter Board 1A4A4

by grasping connector with thumb and index finger and exerting an upward force on connector.

3 Using small flat-tipped screwdriver, loosen retaining screws on serial port (DB-25) connector (at rear of

RS-232 board) and remove connector from RS-232 board.

4 Using 3/16-inch nut driver, remove two lugs (standoffs) securing RS-232 board to power supply assembly

chassis.

5 Remove RS-232 board from power supply assembly.
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Table 2.5.22. Power Supply Assembly RS-232 Board Removal and Installation -CONT

Step Procedure

INSTALLATION

Tools required:

 Small flat-tipped screwdriver

 3/16-inch nut driver

Ensure that power is completely removed from UPS by performing the procedure in table 2.5.6.

Death or severe injury may result if power is not completely removed from UPS prior to removing

the cover in front of UPS components and performing maintenance on UPS subassemblies.

1 Verify that power supply assembly cover is removed in accordance with table 2.5.6.

2 Carefully position RS-232 board in power supply assembly with component side to the right.

3 Using 3/16-inch nut driver, install two lugs (standoffs) securing RS-232 board to power supply assembly

chassis.

4 Install RS-232 ribbon board connector A4A2-P1 to connectorJ2 on 1.5 KVA Inverter Board 1A4A4. Ensure

that pin 1 on ribbon connector (marked with ink dot or other marking) mates with pin 1 of Inverter Board

1A4A4.

5 Install connector harnessserial port(DB-25) connectortoRS-232 board. Using smallflat-tipped screwdriver,

tighten retaining screws.

6 Install power supply assembly cover in accordance with table 2.5.6.

Table 2.5.23. Power Supply Assembly Inverter Board Removal and Installation

Step Procedure

REMOVAL

Tools required:

 No. 2 Phillips screwdriver

 3/8-inch nut driver

Ensure that power is completely removed from UPS by performing the procedure in table 2.5.6.

Death or severe injury may result if power is not completely removed from UPS prior to removing

the cover in front of UPS components and performing maintenance on UPS subassemblies.

1 Remove power supply assembly cover in accordance with table 2.5.6.

2 Remove RS-232 ribbon connector A2-P1 from inverter board connector A4J2.

3 Tag and remove 10 wires with solderless (spade) connectors from inverter board terminals.

4 Tag seven wires attached to the four inverter board standoffs.

5 Using 3/8-inch nut driver, remove four nuts, four flat washers, four lockwashers, and seven wires from four

inverter board standoffs.

6 Remove four screws, flat washers, lockwashers, and nuts securing mounting bracket to insulator (insulator

is located on top of two heat sinks).

7 Using Phillips screwdriver, remove three screws and flat washers securing inverter board to power supply

assembly chassis.

8 Carefully slide inverter board forward and remove from power supply assembly.
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Table 2.5.23. Power Supply Assembly Inverter Board Removal and Installation -CONT

Step Procedure

INSTALLATION

Tools required:

 No. 2 Phillips screwdriver

 3/8-inch nut driver

Ensure that power is completely removed from UPS by performing the procedure in table 2.5.6.

Death or severe injury may result if power is not completely removed from UPS prior to removing

the cover in front of UPS components and performing maintenance on UPS subassemblies.

1 Verify that power supply assembly cover is removed in accordance with table 2.5.6.

2 Carefully position inverter board into card guides, with insulator under mounting bracket.

3 Using Phillips screwdriver, install three screws and flat washers securing inverter board to power supply

assembly chassis.

4 Using Phillipsscrewdriver, installfourscrews,flatwashers, lockwashers, and nutssecuringmounting bracket

to insulator. Insulator is located on top of two heat sinks.

5 Using 3/8-inch nut driver and tags as a guide, install four nuts, four flat washers, four lockwashers, and seven

wires to four inverter board standoffs.

6 Using tags as a guide, install 10 wires with solderless (spade) connectors to inverter board terminals.

7 Install RS-232 connector A2-P1 on inverter board connector A4-J2. Ensure that pin 1 on ribbon connector

(marked with ink dot or other marking) mates with pin 1 of inverter board.

8 Install power supply assembly cover in accordance with table 2.5.6.

Table 2.5.24. Power Supply Assembly Status Panel Removal and Installation

Step Procedure

REMOVAL

Tools required:

 5/16-inch nut driver

Ensure that power is completely removed from UPS by performing the procedure in table 2.5.6.

Death or severe injury may result if power is not completely removed from UPS prior to removing

the cover in front of UPS components and performing maintenance on UPS subassemblies.

1 Remove power supply assembly cover in accordance with table 2.5.6.

2 Tag and remove two wires from OUTPUT POWER switch S1.

3 Using 5/16-inch nut driver, remove two nylon nuts and spaces securing status panel to power supply

assembly cover.

4 Remove status panel from power supply assembly cover.

INSTALLATION

Tools required:

 5/16-inch nut driver

Ensure that power is completely removed from UPS by performing the procedure in table 2.5.6.

Death or severe injury may result if power is not completely removed from UPS prior to removing

the cover in front of UPS components and performing maintenance on UPS subassemblies.
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WARNING

WARNING

$ Table 2.5.24. Power Supply Assembly Status Panel Removal and Installation - CONT

Step Procedure

1 Verify that power supply assembly cover is removed in accordance with table 2.5.6.

2 Position status panel on mounting screws.

3 Using 5/16-inch nut driver, install two nylon nuts and spacers securing status panel to power supply

assembly cover.

4 Using tags as a guide, install two wires to OUTPUT POWER switch S1.

5 Install power supply assembly cover in accordance with table 2.5.6.

Table 2.5.25. Power Supply Assembly OUTPUT POWER Switch Removal and Installation

Step Procedure

REMOVAL

Ensure that power is completely removed from UPS by performing the procedure in table 2.5.6.

Death or severe injury may result if power is not completely removed from UPS prior to removing

the cover in front of UPS components and performing maintenance on UPS subassemblies.

1 Remove power supply assembly cover in accordance with table 2.5.6.

2 At rear of OUTPUT POWER switch, tag and remove two wires.

3 Press plastic tabs on both sides of switch while pushing switch out the front of power supply assembly

cover.

INSTALLATION

Ensure that power is completely removed from UPS by performing the procedure in table 2.5.6.

Death or severe injury may result if power is not completely removed from UPS prior to removing

the cover in front of UPS components and performing maintenance on UPS subassemblies.

1 Verify that power supply assembly cover is removed in accordance with table 2.5.6.

2 Push switch through the front of power supply assembly cover until plastic tabs lock switch into place.

3 At rear of OUTPUT POWER switch using tags as a guide, install two wires.

4 Install power supply assembly cover in accordance with table 2.5.6.

Table 2.5.26. Power Supply Assembly Circuit Breaker Removal and Installation

Step Procedure

REMOVAL

Tools required:

 Small flat-tipped screwdriver

 9/16-inch nut driver

Ensure that power is completely removed from UPS by performing the procedure in table 2.5.6.

Death or severe injury may result if power is not completely removed from UPS prior to removing

the cover in front of UPS components and performing maintenance on UPS subassemblies.
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Table 2.5.26. Power Supply Assembly Circuit Breaker Removal and Installation -CONT

Step Procedure

1 Remove power supply assembly cover in accordance with table 2.5.6.

2 Using small flat-tipped screwdriver, remove two wires from circuit breaker.

3 Using 9/16-inch nut driver, remove nut and washer securing circuit breaker to power supply assembly

chassis.

4 Carefully remove circuit breaker from chassis.

INSTALLATION

Tools required:

 Small flat-tipped screwdriver

 9/16-inch nut driver

Ensure that power is completely removed from UPS by performing the procedure in table 2.5.6.

Death or severe injury may result if power is not completely removed from UPS prior to removing

the cover in front of UPS components and performing maintenance on UPS subassemblies.

1 Verify that power supply assembly cover is removed in accordance with table 2.5.6.

2 Install circuit breaker in power supply assembly chassis.

3 Using 9/16-inch nut driver, install nut and washer securing circuit breaker chassis.

4 Using small flat-tipped screwdriver, install two wires on circuit breaker.

5 Install power supply assembly cover in accordance with table 2.5.6.

Table 2.5.27. DC Power Supply Removal and Installation

Step Procedure

REMOVAL

Tools required:

 Small flat-tipped screwdriver

NOTE

ACU power need not be turned off for dc power supply interchange. This allows normal operation

of ACU during removal and replacement.

1 Using figure 2.1.6, locate dc power supply to be removed. 

2

NOTE

On/off switch has a built-in lock that prevents removing power supply while switch is in

1 (on) position. Switch must be set to 0 (off) before power supply can be removed.

At dc power supply, set front panel on/off switch to 0 (off) position.

3

CAUTION

Wait 1 minute before removing power supply from chassis to allow internal capacitors

to discharge through drain circuits.

Using small flat-tipped screwdriver, remove two panel screws securing dc power supply to Power Supply

Enclosure 1A5.

4 Grasp dc power supply handle and slide out of enclosure.
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Table 2.5.27. DC Power Supply Removal and Installation -CONT

Step Procedure

INSTALLATION

Tools required:

 Small flat-tipped screwdriver

 NOTE

ACU power need not be turned off for dc power supply interchange. This allows normal operation

of ACU during removal and replacement.

1 Set replacement power supply front panel on/off switch to 0 (off) position.

2 Position dc power supply in Power Supply Enclosure 1A5 and slide into enclosure.

3 Using small flat-tipped screwdriver, install two panel screws securing dc power supply to enclosure.

4 Set power supply front panel on/off switch to 1 (on) position.

Table 2.5.28. DC Power Supply Fan Connector Board Removal and Installation

Step Procedure

REMOVAL

Tools required:

 Small flat-tipped screwdriver

 No. 1 Phillips screwdriver

 No. 2 Phillips screwdriver

 3/8-inch nut driver

Death orsevere injurymay result if power is notremoved fromACU prior to maintenance activities.

Ensure that UPS POWER switch is set to 0 (off) position and facility power is removed from ACU.

1 Set UPS POWER switch to 0 (off) position. 

2 Remove facility power from ACU cabinet.

3

NOTE

On/off switch has a built-in lock that prevents removing power supply while switch is in

1 (on) position. Switch must be set to 0 (off) position before power supply can be

removed.

Set front panel on/off switch on dc power supplies to 0 (off) position.

4

CAUTION

Wait 1 minute before removing power supplies from chassis to allow internal capacitors

to discharge through drain circuits.

Using small flat-tipped screwdriver, remove four panel screws securing dc power supplies to DC Power

Supply Enclosure 1A5.

5 Remove dc power supplies from enclosure.

6 Using No. 1 Phillips screwdriver at rear of powersupply enclosure, remove four screws securing connectors

J2A and J2B to dc power supply fan connector board. Remove connectors J2A and J2B.

7 At dc power supply fan connector board, tag and remove wires from terminal boards TB1A and TB1B.

8 Using No. 2 Phillips screwdriver, remove wires from terminal boards TB2A and TB2B.

9 Using 3/8-inch nut driver, tag and remove wires from output studs A and B.

10 Using No. 1 Phillips screwdriver, remove 12 screws, flat washers, and lockwashers securing fan connector

board to dc power supply enclosure.

11 Remove fan connector board from dc power supply enclosure.
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Table 2.5.28. DC Power Supply Fan Connector Board Removal and Installation -CONT

Step Procedure

INSTALLATION

Tools required:

 Small flat-tipped screwdriver

 No. 1 Phillips screwdriver

 No. 2 Phillips screwdriver

 3/8-inch nut driver

Death orsevere injurymay result if power is notremoved fromACU prior to maintenance activities.

Ensure that UPS POWER switch is set to 0 (off) position and facility power isremoved from ACU.

1 Verify that UPS POWER switch is set to 0 (off) position. 

2 Verify that facility power is removed from ACU cabinet.

3 Position fan connector board on rear of DC Power Supply Enclosure 1A5 with connectorJ2A in the top right

corner.

4 Using No. 1 Phillips screwdriver, install 12 screws, flat washers, and lockwashers securing fan connector

board to dc power supply enclosure. Ensure that two green chassis ground wires are connected.

5 Install connectors J2A and J2B on fan connector board.

6 Using No. 1 Phillipsscrewdriver, installfourscrewssecuring connectorsJ2A and J2Bto fan connector board.

7 Using 3/8-inch nut driver and tags as a guide, install wires on output studs A and B.

8 Using No. 2 Phillips screwdriver, install wires on fan connector board terminal boards TB2A and TB2B.

9 Install wires on terminal boards TB1A and TB2A.

10 Set front panel on/off switch on dc power supplies to 0 (off) position.

11 Slide dc power supplies into Power Supply Enclosure 1A5.

12 Using small flat-tipped screwdriver, install four panel screws securing dc power supplies to enclosure.

13 Set dc power supplies front panel on/off switches to 1 (on) position.

14 Apply facility power to ACU cabinet.

15 Set UPS POWER switch to 1 (on) position.

Table 2.5.29. Blower Removal and Installation

Step Procedure

REMOVAL

Tools required:

 No. 2 Phillips screwdriver

 Diagonal cutting pliers

 Small screwdriver

Death orsevere injurymay result if power is notremoved fromACU prior to maintenance activities.

Ensure that UPS POWER switch isset to 0 (off) position and facility power is removed from ACU.

1 Set UPS POWER switch to 0 (off) position. 

2 Remove facility power from ACU cabinet.
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Table 2.5.29. Blower Removal and Installation -CONT

Step Procedure

3

NOTE

Blower may have either long power cord or short power cord. If blower has long power

cord, it is connected directly to Power Distribution Assembly 1A7 at rear of ACU. If

blower has short power cord, it is butt-spliced into extension that connects to 1A7.

If blower has short power cord, at rear of cabinet, tag ac power wires at butt splice connection to blower

power cord.

4 If blower has short power cord, using diagonal cutting pliers, cut cabinet harness ac power cord near butt

splice connectors.

5 If blower has long power cord, using small screwdriver, disconnect three blower power wires from

Power Distribution Assembly 1A7.

6

NOTE

There are two types of cabinets for the ACU. One type has a partial length front door with

the blower mounted behind an air intake grill. The other type of cabinet has a full length

door with the blower accessible with the door open.

If ACU cabinet has a partial length front door, using Phillips screwdriver, remove six Phillips screws and

lockwashers securing air intake grill to lower front of cabinet. Remove air intake grill.

7 If ACU cabinet has a full length front door, open front door. Loosen knurled knobs on either side of shield

in front of blower B1 and remove shield.

8 Remove air filter from blower.

9 Using Phillips screwdriver, remove four screws, lockwashers, and flat washers securing blower to ACU

cabinet.

10 Remove blower from cabinet.

INSTALLATION

Tools required:

 No. 2 Phillips screwdriver

 Wire stripper

 Crimping tool

 Butt splice connectors M7928/5-3

 Small screwdriver

Death orsevere injurymay result if power is notremoved fromACU prior to maintenance activities.

Ensure that UPS POWER switch isset to 0 (off) position and facility power is removed from ACU.

1 Verify that UPS POWER switch on UPS status panel is set to 0 (off) position.

2 Verify that facility power is removed from ACU cabinet.

3

NOTE

There are two types of cabinets for the ACU. One type has a partial length front door with

the blower mounted behind an air intake grill. The other type of cabinet has a full length

door with the blower accessible with the door open.

Slide blower into ACU cabinet. Using Phillipsscrewdriver, installfourscrews,flat washers, and lockwashers

securing blower to cabinet.
S100 ASOS Site Technical Manual

Table 2.5.29. Blower Removal and Installation -CONT

Step Procedure

2-145

WARNING

4

NOTE

Blower may have either long power cord or short power cord. If blower has long power

cord, it is connected directly to Power Distribution Assembly 1A7 at rear of ACU. If

blower has short power cord, it is butt-spliced into extension that connects to 1A7.

If blower has long power cord, using small screwdriver, connect three blower power wires to Power

Distribution Assembly 1A7 as follows:

BLK 1A7-18D

 WHT 1A7-19D

GRN 1A7-20D

5 If blower hasshort power cord, using crimping tool and buttsplice connectors(with tags as a guide), connect

blower ac power wires to cabinet harness ac power extension wires.

6 Install air filter in blower.

7 If ACU cabinet has a partial length front door, position air intake grill in front of blower. Using Phillips

screwdriver, install six Phillips screws and lockwashers securing air intake grill to lower front of cabinet.

8 If ACU cabinet has a full length front door, install blower shield in front of blower and hand tighten two

knurled knobs on shield.

9 Apply facility power to ACU cabinet.

10 Set UPS POWER switch to 1 (on) position.

Table 2.5.30. Battery Box and Battery Removal and Installation

Step Procedure

REMOVAL

Tools required:

 Two 5/16-inch box wrenches

 No. 2 Phillips screwdriver

 Small screwdriver

Death or severe injury may result if power is not removed from ACU prior to performing

maintenance activities. Ensure that UPS POWER switch is set to 0 (off) and facility power is

removed from ACU.

Severe injury may result if the negative and positive battery terminals are shorted together. Exercise

caution while removing batteries.

1 Set UPS POWER switch to 0 (off) position. 

2 Remove facility power from ACU cabinet.

3 Disconnect Battery Box 1A8.

a. For battery box, part number 62828-40063-10, connector J1, squeeze tabs on side of connector

 inward while rocking connector free.

b. For battery box, 62828-40062-30 or 62828-90360-10, pull battery box connector P1 out of

 UPS PRA BATTERY BOX connector.
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Table 2.5.30. Battery Box and Battery Removal and Installation -CONT

Step Procedure

4 Wait at least 30 seconds while UPS capacitors discharge through bleeders and other drains.

NOTE

ACU blower 1B1 must be removed to access Battery Box 1A8.

5 Using small screwdriver, tag and remove three blower ac power wires from AC Power Distribution

Assembly 1A7 terminals 1A7-18D, -19D, and -20D.

6

NOTE

There are two types of cabinets for the ACU. One type has a partial length front door

with the blower mounted behind an air intake grill. The other type of cabinet has a full

length door with the blower accessible with the door open. 

If ACU cabinet has a partial length front door, using Phillips screwdriver, remove six Phillips screws and

lockwashers securing air intake grill to lower front of cabinet. Remove air intake grill.

7 If ACU cabinet has a full length front door, open front door. Loosen knurled knobs on either side of

shield in front of blower B1 and remove shield.

8 Remove air filter from blower.

9 Using Phillips screwdriver, remove four screws, lockwashers, and flat washers securing blower to ACU

cabinet.

10 Remove blower from ACU cabinet.

11

Pressure sensors in RF/Pressure Mounting Shelf 1A6 are safety-critical devices. Pressure

sensors may output erroneous readings if plastic vent tubing to I/O panel assembly is

damaged or crimped. Throughout this procedure, exercise caution to avoid damage to

pressure vent tubing.

 Disconnect retaining strap securing Battery Box 1A8 to inside of ACU cabinet.

12

Battery box is heavy equipment (weighs from 60 to 70 pounds) and should be slid, not

lifted. If lifted, two-man or mechanical lift is required. Failure to comply may result in

injury to personnel or damage to equipment.

Slide Battery Box 1A8 from ACU cabinet through blower opening.

13

CAUTION

When lifting top of battery tray, do not pull the attached wires off the connector.

Lift top of battery box and position so that battery terminals can be accessed.

14

Batteries contain corrosive fluid. Do not tip batteries during removal.

Severe injury may result if the negative and positive battery terminals are shorted together.

Exercise caution while removing batteries.

Using two 5/16-inch box wrenches, remove bolt, flat washers, lockwasher, and nut from negative terminal

of batteryBT1 (connected to top of battery box via black wires).Remove black wiresfromnegative terminal.
S100 ASOS Site Technical Manual

Table 2.5.30. Battery Box and Battery Removal and Installation -CONT

Step Procedure

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WARNING

WARNING

15 Using two 5/16-inch box wrenches, remove bolt, flat washers, lockwasher, and nut from positive terminal of

battery BT5 (connected to top of battery box via red wires). Remove red wires from positive terminal.

16 Remove top of battery box.

17 Using two 5/16-inch box wrenches,remove bolt, lockwasher,flat washers, and nutfrombattery terminals and

remove all jumper wires.

18 Using strap tied around battery BT5 or packing material, remove from battery box.

19 Remove and retain strap.

20 Remove additional batteries.

INSTALLATION

Tools required:

 Two 5/16-inch box wrenches

Death or severe injury may result if power is not removed from ACU prior to performing

maintenance activities. Ensure that UPS POWER switch is set to 0 (off) and facility power is

removed from ACU.

1 Verify that UPS POWER switch is set to 0 (off) position. 

2 Verify that facility power is removed from ACU.

3 Tie previously removed strap around battery BT5 or packing material to facilitate future removal. Leave

approximately 2 inches of slack between top of battery or packing material and strap.

4 Using figure 2.1.8, install batteries in battery box.

5

NOTE

Refer to figure 2.4.12 or 2.4.13 for wiring diagram of battery box.

Using markers as a guide and two 5/16-inch box wrenches, install jumpersto battery terminals,securing with

bolt, flat washer, lockwasher, and nut.

6 Position top of battery box so that red wires can be connected to positive terminal and black wires can be

connected to negative terminal.

7 Using two 5/16-inch box wrenches, install bolt,flat washers, lockwasher, and nutsecuring wiresto respective

terminals.

8 Position top over battery box and press into place.

9

Battery box is heavy equipment (weighs approximately 75 pounds) and should be slid, not

lifted. If lifted, two-man or mechanical lift is required. Failure to comply may result in

injury to personnel or damage to equipment.

Pressure sensorsin RF/Pressure Mounting Shelf 1A6 are safety-critical devices. Pressure

sensors may output erroneous readings if plastic vent tubing to I/O panel assembly is

damaged or crimped. Throughout this procedure, exercise caution to avoid damage to

pressure vent tubing.

Slide battery box into ACU cabinet through blower opening. While taking care not to damage or crimp

pressure sensor vent tubing, position box with connector J1 to right and two rear corners in contact with

vertical plates.

10 Secure battery box in position by installing retaining strap to left and right vertical plates.
ASOS Site Technical Manual S100

Table 2.5.30. Battery Box and Battery Removal and Installation -CONT

Step Procedure

2-148 Change 2

WARNING

11

NOTE

There are two types of cabinets for the ACU. One type has a partial length front door with

the blower mounted behind an air intake grill. The other type of cabinet has a full length

door with the blower accessible with the door open.

Slide blower into ACU cabinet. Using Phillipsscrewdriver, install fourscrews,flat washers, and lockwashers

securing blower to cabinet.

12 Install air filter in blower.

13 If ACU cabinet has a partial length front door, position air intake grill in front of blower. Using Phillips

screwdriver, install six Phillips screws and lockwashers securing air intake grill to lower front of cabinet.

14 If ACU cabinet has a full length front door, install blower shield in front of blower and hand tighten two

knurled knobs on shield.

15 Using small screwdriver and tags as a guide, install three blower ac power wires to AC Power Distribution

Assembly 1A7 terminals 1A7-18D, -19D, and -20D.

16 Ensure that pressure sensor vent tubing is properly connected to pressure sensors and PRESSURE VENT on

I/O Panel Assembly 1A9 and is not damaged or crimped.

17

NOTE

Ensure that battery plug is fully seated and locked into place.

Connect Battery Box 1A8.

a. For battery box, part number 62828-40063-10, position W030 cable connector P1 on top of

 battery box connector J1 and press connector into place.

b. For battery box, part number 62828-40062-30 or 62828-90360-10, insert battery box

 connector into UPS PRA BATTERY BOX connector.

18 Apply facility power to ACU cabinet.

19 Set UPS POWER switch to 1 (on) position.

Table 2.5.31. Uninterruptible Power Supply Removal and Installation

Step Procedure

REMOVAL

Tools required:

 Phillips screwdriver

Death or severe injury may result if power is not removed from the ACU prior to performing

maintenance activities. Ensure that UPS POWER switch is set to 0 (off) and that facility power is

removed from the ACU.

Severe injury may result if the negative and positive battery terminals are shorted together. Exercise

caution while removing batteries.

$ 1 Set UPS power switch to off position.

2 Remove facility power from ACU cabinet.

3 Disconnect UPS from wiring harness by removing connectors P97, P1, and P13.

4 Using screwdriver, disconnect cable W78 connector P2 from COMM PORT by removing two screws.
S100 ASOS Site Technical Manual

Change 2 2-149

WARNING

WARNING

Table 2.5.31. Uninterruptible Power Supply Removal and Installation -CONT

Step Procedure

5 Using screwdriver, remove four screws securing shelf, then slide UPS shelf out of ACU.

6 Unstrap UPS from shelf.

7 Lift and pull UPS off shelf.

INSTALLATION

Tools required:

 Phillips screwdriver

Death or severe injury may result if power is not removed from the ACU prior to performing

maintenance activities. Ensure that UPS powerswitch isset to off and that facility power isremoved $

from the ACU.

Severe injury may result ifthe negative and positive battery terminals are shorted together. Exercise

caution while removing batteries.

1 Verify that UPS power switch is set to off position. $

2 Verify that facility power is removed from ACU.

3 Slide UPS shelf out of ACU.

4 Place UPS on shelf.

5 Secure UPS onto shelf with strap.

6 Slide shelf into ACU cabinet; using Phillips screwdriver, install four screws securing shelf in place.

7 Using Phillips screwdriver, connect cable W78 connector P2 to COMM PORT by securing two screws.

8 Connect UPS to wiring harness by connecting connectors P97, P1, and P13.

9 Apply facility power to ACU.

10 Set UPS power switch to on position. $

Table 2.5.32. ACU Tie-Down Removal and Installation

Step Procedure

INSTALLATION

Tools and materials required:

Small Flat-blade screwdriver 

3/4-inch open end wrench 

No. 2 Phillips screwdriver 

3/8 inch power drill (wood installation)

1⁄2-inch power (hammer type preferred) drill (concrete installation)

Various wood, metal, and masonry bits

Scotchbrite (or equivalent) pad

Denatured alcohol

Earthquake mounting kit (part number 62828-40306-100)

Death or severe injury may result if power is not removed from ACU prior to performing FMK

instructions. Ensure that OUTPUT POWER switch is set to 0 (off) and facility power is removed

from ACU. 
ASOS Site Technical Manual S100

2-150

Table 2.5.32. ACU Tie-Down Removal and Installation -CONT

Step Procedure

NOTE

If this installation is being performed for the first time it is necessary to use the materials and

instructions found in FMK #078. If this installation is being performed to reinstall an ACU that

already has earthquake mounts, it will be necessary to replace the lag bolts, washers, lag shields

(used for concrete installation only), and conductive adhesive (see the following chart for

information):

CAGE

ITEM QTY CODE PART NUMBER NOMENCLATURE

 1 2 0J8A4 62828-40270-1 Channel, Mounting

 2 4 0J8A4 62828-90410-1 Screw, Lag Bolt Hx-Hd

 3 4 0J8A4 62828-90329-2 Washer, Flat-metal, Rd

 4 1 3796X 72-00192 Adhesive, Conductive, w/primer

 5 4 88367 1155 Lag Shield 

This procedure is based upon a UPS installation: where no UPS is installed, skip all steps which

refer to the UPS or to the battery box.

1 Set OUTPUT POWER switch on UPS status panel to 0 (off) position. OUTPUT indicator on status panel

extinguishes.

2 Remove facility power from ACU cabinet.

3 Disconnect Battery Box 1A8.

a. For battery box, part number 62828-40063-10, connector J1, squeeze tabs on side of connector

 inward while rocking connector free.

b. For battery box, part number 62828-40062-30, pull battery box connector P1 out of UPS

 PRA BATTERY BOX connector.

4 Wait at least 30 seconds while UPS capacitors discharge through bleeders and other drains.

NOTE

ACU blower 1B1 must be removed to access Battery Box 1A8.

5 Using small screwdriver, tag and remove three blower ac power wires from AC Power Distribution

Assembly 1A7 terminals 1A7-18D, -19D, and -20D.

6

NOTE

There are two types of cabinets for the ACU. One type has a partial length front door with

the blower mounted behind an air intake grill. The other type of cabinet has a full length

door with the blower accessible with the door open. 

If ACU cabinet has a partial length front door, using Phillips screwdriver, remove six Phillips screws and

lockwashers securing air intake grill to lower front of cabinet. Remove air intake grill.

7 If ACU cabinet has a full length front door, open front door. Loosen knurled knobs on either side of shield

in front of blower B1 and remove shield.

8 Remove air filter from blower.

9 Using Phillips screwdriver, remove four screws, lockwashers, and flat washers securing blower to ACU

cabinet.

10 Remove blower from ACU cabinet.

11 Disconnect strap securing Battery Box 1A8 to inside of ACU cabinet.
S100 ASOS Site Technical Manual

Table 2.5.32. ACU Tie-Down Removal and Installation -CONT

Step Procedure

2-151

WARNING

12

Battery box is heavy equipment (weighs from 60 to 70 pounds) and should be slid, not

lifted. If lifted, two-man or mechanical lift is required. Failure to comply may result in

injury to personnel or damage to equipment. 

Slide Battery Box 1A8 from ACU cabinet through blower opening.

13 Verify all cables connected to the I/O panel assembly are properly marked. Disconnect all cables from the

I/O panel assembly.

14 If 1A9 is ported through tubing, disconnect pressure tubing from 1A9.

15 Secure ACU to floor. Determine the type of material that the ACU is to be mounted to (concrete or wood).

Follow the instructions for that material type. 

CONCRETE

 NOTE

Perform the following steps if the material that the

ACU is to be mounted is composed of concrete.

a. Place "U" channel pieces in ACU as shown in figure 2.5.1, Section A-A and mark

bottom of ACU (in four places, as shown) in preparation for drilling mounting holes.

b. Use a center punch to define hole centers to be drilled.

c. Using 2X4 boards as supports, lift the ACU above the floor. Drill four holes, 0.397 inch

in diameter, through bottom of cabinet. 

 d. Place ACU in its exact position. Using the four holes drilled through the bottom of the

ACU as a guide, mark the floor in preparation for drilling.

e. Move ACU out of position and drill four holes 0.625 inch in diameter into the concrete

to a depth of 2.88 inches each.

 f. Blow each hole clean of dust and insert an anchor (lag shield) into each hole until it is

flush with the surface. 

 h. Using sandpaper, remove paint and primer from around holes drilled in the ACU; clear

a 0.75-inch diameter circle surrounding each hole diameter on the interior and exterior

surfaces of the cabinet.

i. Move ACU back into position and prepare all surfaces to be bonded. These surfaces

include the bottom edge of each lag bolt, both sides of each washer, the area around

each "U" channel hole, and the paint-free areas around the holes drilled in the ACU

cabinet. Prepare all surfaces to be bonded using the following instructions:

 (1) Scour all surfaces to be bonded with a Scotchbrite (or equivalent) pad.

 

 (2) Clean all surfaces to be bonded with denatured alcohol.

(3) Apply primer to all surfaces to be bonded; allow to air dry for 2 hours.

 j. Place the two "U" channel pieces into position and secure the ACU to the floor with the

lag bolts and flat washers. The bottom edge of each lag bolt, each washer, and the

paint-free areas around the holes drilled in the ACU cabinet should be coated with

conductive adhesive immediately prior to use. 
ASOS Site Technical Manual S100

Table 2.5.32. ACU Tie-Down Removal and Installation -CONT

Step Procedure

2-152

WOOD

NOTE

If the material that the ACU is to be mounted to is composed of wood,

perform the following steps.

 a. Place "U" channel pieces in ACU as shown in figure 2.5.1, Section A-A and mark bottom

of ACU (in four places, as shown) in preparation for drilling mounting holes.

 b. Use a center punch to define hole centers to be drilled.

 c. Using 2X4 boards as supports, lift the ACU above the floor. Drill four holes, 0.397 inch

in diameter through bottom of cabinet. 

 d. Determine the position of the ACU. The chosen position must allow the lag bolts to be

screwed into the floor joists when the lag bolts are installed.

 e. Place ACU in its exact position. Using the four holes drilled through the bottom of the

ACU as a guide, mark the floor in preparation for drilling.

 f. Move ACU out of position and drill four holes 0.312 inch in diameter through the wood

floor and into the joists to a depth of 2.88 inches each.

 g. Blow each hole clean of sawdust.

 h. Using sandpaper, remove paint and primer from around holes drilled in the ACU; clear a

0.75-inch diameter circle surrounding each hole diameter, on the interior and exterior

surfaces of the cabinet.

i. Move ACU back into position and prepare all surfaces to be bonded. These surfaces

include the bottom edge of each lag bolt, both sides of each washer, the area around each

"U" channel hole, and the paint-free areas around the holes drilled in the ACU cabinet.

Prepare all surfaces to be bonded using the following instructions:

 (1) Scour all surfaces to be bonded with a Scotchbrite (or equivalent) pad.

 

 (2) Clean all surfaces to be bonded with denatured alcohol.

 (3) Apply primer to all surfaces to be bonded and allow to air dry for 2 hours.

 j. Place the two "U" channel pieces into position and secure the ACU to the floor with the

lag bolts and flat washers. The bottom edge of each lag bolt, each washer, and the paint

free areas around the holes drilled in the ACU cabinet should be coated with conductive

adhesive immediately prior to use. 

16 Vacuum inside of ACU cabinet and remove all foreign matter.

17 Slide battery box into ACU cabinet through blower opening. While taking care not to damage or crimp

pressure sensor vent tubing, position box with connector J1 to right and two rear corners in contact with

restraining angles.

18 Secure battery box in position by hooking restraining strap to left and right angles. 

19 Slide blower into ACU cabinet. Using Phillipsscrewdriver, installfourscrews, flat washers, and lockwashers

securing blower to cabinet.

20 Install air filter in blower.
S100 ASOS Site Technical Manual

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Table 2.5.32. ACU Tie-Down Removal and Installation -CONT

Step Procedure

21 If ACU cabinet has a partial length front door, position air intake grill in front of blower. Using Phillips

screwdriver, install six Phillips screws and lockwashers securing air intake grill to lower front of cabinet.

22 If ACU cabinet has a full length front door, install blower shield in front of blower and hand tighten two

knurled knobs on shield.

23 Using small screwdriver and tags as a guide, install three blower ac power wires to AC Power Distribution

Assembly 1A7 terminals 1A7-18D, -19D, and -20D.

24 If pressure tubing was disconnected from 1A9 (in step 14), reconnect it and ensure that it is not damaged or

crimped.

25

NOTE

Ensure that battery plug is fully seated and locked into place.

Connect Battery Box 1A8.

 a. For battery box, part number 62828-40063-10, position W030 cable connector P1 on top of

 battery box connector J1 and press connector into place.

 b. For battery box, part number 62828-40062-30, insert battery box connector into UPS PRA

 BATTERY BOX connector.

26 Reconnect all cables to the I/O Panel Assembly.

27 Apply facility power to ACU cabinet.

28 (Class II Systems Only) Set UPS POWER switch to 1 (on) position.

CHECK OUT SYSTEM

1 Sign on at OID as a technician.

2 Check 12 HR pages to ensure that data is being collected from sensors.

3 Ensure that all peripherals connected to the system are operational.

4 Clear all failures on MAINT pages for the ACU and DCP that were caused by powering system down.

5 Update maintenance log to reflect addition of ACU tie-downs.
ASOS Site Technical Manual S100

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Figure 2.5.1 Earthquake Mounting Installation
S100 ASOS Site Technical Manual

2-155

2.5.5 SETTING UP LEASED LINE MODEMS

Leased lines are used to allow the ACU to communicate with peripherals (OID's, VDU's, CVD's, and

printers) located at various positions throughout the ASOS site. For each leased line peripheral, two

telephone modems are used: one at the ACU and one at the peripheral. At the ACU, a rack-mounted modem

is installed in Modem AC Power Rack 1A3. At the peripheral, a stand-alone (S/A) modem is used.

2.5.5.1 Setting Up ACU Rack-Mounted Modems. After a rack-mounted modem is installed in the ACU,

it is configured via the ACU serial communications page. From this page, the modem is assigned a function,

assigned to an SIO port, assigned a baud rate, and specified for leased line operation. Baud rates for the

model 2440 modem are 2400 for OID's, VDU's, and printers and 1200 for CVD's. The baud rate is 9600 for

the model V.3225 modemand 28800 forthemodel V.3400 modem. After a rack-mounted modemisinstalled

and configured on the ACU serial communications page, the ACU program automatically programs the

modem for operation. No other action is required on the part of the technician.

2.5.5.2 Setting Up Stand Alone Modems. After a stand alone modem is installed at the peripheral end, it

must be manually programmed to operate in leased line mode with the proper parameters. This is

accomplished using the LCD display and the YES and NO pushbutton switches on the front panel of the

modem (same as rack-mounted modems shown on figure 2.3.4). The LCD display presents main menus,

submenus, and configuration options to the technician. The NO pushbutton is used to sequence through the

main menus and the YES pushbutton is used to branch to submenus and to select appropriate options. The

Installation and Operation Manual for the stand-alone modem provides detailed information on all menus,

submenus, and options available with the modem and provides instructions on their use. Table 2.5.33

identifies the settings that must be manually made for models 2440 and V.3225 stand-alone modems. The

model V.3400 does not require manual setup. This table addresses only the settings that must be checked or

changed by the technician. They do not address options that are automatically set by the factory or are not

required for ASOS operation. The actual menu and option titles that appear on the modem LCD display may

vary, depending on the modem's internal firmware.

2.5.6 SETTING UP LINE DRIVER MODEMS

The model D19.2 line drivers are obsolete and are replaced by the model DDS/MR64. If a D19.2 line driver

fails at a site and spare D19.2 line drivers are not available, then all the D19.2 line drivers must be replaced

with the DDS/MR64 line drivers. After installation, the ACU and DCP DDS/MR64 line drivers must be

manually programmed to operate with the ASOS parameters by using the LCD display and the YES and NO

pushbutton switches on the front panel ofthemodem(same asrack-mountedmodemsshown on figure 2.3.4).

The LCD display presentsmainmenus,submenus, and configuration optionsto the technician. The YES/NO

pushbuttons are used to sequence through the main menus and submenus and to select appropriate options.

The Installation and Operation Manual for the stand-alone line driver provides detailed information on all

menus,submenus, and options available with the modemand providesinstructions on their use. Table 2.5.34

identifies the options and switch settings that must be manually made for the model DDS/MR64 line driver

in the ACU (refer to paragraph 3.5.6 for the model DDS/MR64 line driver in the DCP). This table addresses

only the settings that must be checked or changed by the technician. The table does not address options that

are automatically set by the factory or are notrequired for ASOS operation. The actual menu and option titles

that appear on the modem LCD display may vary, depending on the modem's internal firmware.
ASOS Site Technical Manual S100

2-156 Change 2

Table 2.5.33. Stand-Alone Modem Setup Parameters

Step Procedure

MODEL 2440 SETUP PARAMETERS

NOTE

The factory settings (step 1) should be performed first and the SAVE operation (step 6) performed

last. The order in which other settings are made may vary.

Actual menu, submenu, and option names appearing on LCD display may vary due to version of

modem firmware. Titles shown in parentheses indicate possible alternates.

1 Using OPTIONS? main menu and FACTORY? submenu, select FACTORY 1 settings.

2 Using OPTIONS? main menu and SPKR OPTS? submenu, set speaker control always to OFF.

3

$

$

Using OPTIONS? main menu and TELE OPTS? submenu, set the following:

a. LINE TYPE? (or PRIV/PSTN?) to LEASED (or PRIVATE) for OID or VDU

$ to Dial (for AFOS Dial Line)

b. ANS/ORIG? to ANSWER mode

4

$

Using DATA OPTS? main menu and DTE OPTS? submenu, set DTE RATE? to one of the following

baud rates:

a. 2400 for OID, VDU, or printer

b. 1200 for CVD

$ c. 300 for AFOS Dial Line

5 Using DATA OPTS? main menu and AT CMDS? submenu (or STAT OPTS? main menu and

ACU OPTS? submenu), set AT CMDS (or ACU) to D (i.e., disabled).

6 Using SAVE? main menu, save above settings in modem for permanent use after power up.

MODEL V.3225 DIAL UP SETUP PARAMETERS

NOTE

The MODEM is configured by using the front panel push buttons. Use the NO push button to cycle

through the menu options and the YES push button to select the submenus. Configuration options are

selected by pressing YES or NO push buttons when prompted by LCD display with “CHANGE?”.

Pressing YES activates the configuration option.

Factory option set #1 configures the modem for dial up.

 Actual menu, submenu, and option names appearing on LCD display may vary due to version of

modem firmware.

1 Using MODIFY CONFIGURATION? menu and LOAD/STORE OPTION SET? submenu, load factory

option set #1 and answer YES to the ARE YOU SURE? prompt. Modem then prompts to STORE

PRESENT OPTIONS? Answer YES.

MODEL V.3225 LEASE LINE SETUP PARAMETERS

NOTE

This setup procedure is typical. Modem firmware versions may differ which may cause additional

LCD messages to be displayed between steps within this table.

The factory settings (step 1) should be performed first and the STORE PRESENT OPTIONS (step

4) performed last. The order in which other settings are made may vary. 

1 Using MODIFY CONFIGURATION? menu and LOAD/STORE OPTION SET? submenu, load factory

option set #1 and answer YES to the ARE YOU SURE? prompt. Modem then prompts to STORE

PRESENT OPTIONS? Answer NO at this time (this is performed as last step).
S100 ASOS Site Technical Manual

2-157

Table 2.5.33. Stand-Alone Modem Setup Parameters -CONT

Step Procedure

2 Using MODIFY CONFIGURATION? menu and CHANGE MODEM PARAMETERS? submenu,

perform the following:

a. Ensure that DCE RATE is set for 9600 TRELLIS.

b. Set NORMAL ORIGINATE? FORCED ANSWER mode to FORCED ANSWER.

c. Ensure that V.32 FAST TRAIN option is set to DISABLED.

d. Ensure that AUTO RETRAIN option is set to ENABLED.

e. Change LINE TYPE from DIAL to LEASE.

3 Using MODIFY CONFIGURATION? menu and CHANGE DTE PARAMETERS? submenu, perform

the following:

a. Ensure that DTE RATE is 9600.

b. Set AT COMMAND SET to DISABLED (D).

c. Set CTS STATE to CTS FOLLOWS DCD.

4 Using MODIFY CONFIGURATION? menu and LOAD/STORE OPTION SET?, perform STORE

PRESENT OPTIONS and answer YES to the ARE YOU SURE? prompt. LCD temporarily displays

OPTIONS PERMANENT prompt. Programming is then complete. LCD displays V.32 9600 IDLE or

TRAINING until leased line connection is established, then changes to V.32 9600 ON LINE.

Table 2.5.34. Model DDS/MR64 ACU Rack Mount Line Driver Setup

Step Procedure

NOTE

D19.2 line drivers and DDS/MR64 line drivers are not compatible. If a D19.2 line driver fails and the

failed line driver must be replaced with a DDS/MR64 line driver, all D19.2 installed in the system

must be replaced with DDS/MR64 line drivers.

Ensure that the line driver LCD does not display “ERROR”, if “ERROR” cannot be cleared the line

driver may be defective.

The line driver is configured by using the front panel push buttons. Use the NO push button to cycle

through the menu options and the YES push button to select the submenus. Configuration options are

selected by pressing YES or NO push buttons when prompted by LCD display with “CHANGE?”.

Pressing YES activates the configuration option.

1 Use front panel push buttons to conFigure the DDS/MR64 line driver as follows:

Display Press Configures Option

“NO SIGNAL ASYNC DTE RATE” or 

“ASYNC RA 1200 2.4K BPS LINE” HOME (start configuration process)

TEST NO N/A

“SYNC DTE CHANGE?” YES ASYNC DTE

 “RATE ADAPTER DISABLED - CHANGE?” NO DISABLE

“CHANGE TIMING ?” YES INT

“CHG LINE RATE?” YES 2400 BPS

“BITS PER WORD=09 CHANGE?” YES 10
ASOS Site Technical Manual S100

2-158 Change 2

Table 2.5.34. Model DDS/MR64 ACU Rack Mount Line Driver Setup -CONT

Step Procedure

1 Display Press Configures Option

(cont) “CHANGE CONTROL OPTIONS?” YES N/A

“CHANGE RTS CONTROL?” YES NORMAL RTS

“CHANGE SYNC BUFFER OPT?:” YES SYNC BUFFER DIS

“CHANGE REMOTE LB OPT?” YES RMT LB ENABLED

“CHANGE DSR OPTION?” YES DSR OPT ENABLED

“CHANGE SYS STATUS OPT?” YES SS OPT DISABLED

“CHANGE CA OTP?” YES CA OPT DISABLED

“CHANGE RTS-CTS DELAY?” YES RTS-CTS NORMAL

“CHANGE DTE RL OPT?” YES DTE RL DISABLED

“CHANGE DTE LL OPT?” YES DTE LL DISABLED

“CHANGE DTE TP OPT?” YES DTE TP DISABLED

“CHANGE DTE RT OPT?” YES DTE RT DISABLED

“CHANGE 64K SCRAM OPT? YES SCRAMBLER DIS

“LOAD FACTORY OPTION SET? NO N/A

“SAVE NEW CONFIGURATION?” YES N/A

2 Remove power from ACU.

$ 3 Remove line driver from modem rack and set jumpers (Figure 2.5.1A) as follows:

SW1- RS232 Enable JP1 EN JP2 CH GND

SW2- V.35 Enable

SW3-1 OFF SW3-2 ON SW3-3 OFF SW3-4 OFF

SW3-5 OFF SW3-6 OFF SW3-7 OFF SW3-8 OFF

SW4-1 OFF SW4-2 OFF SW4-3 ON SW4-4 ON

4 Reinsert line driver into modem rack and restore power to ACU.

2.5.7 SETTING UP A DOT MATRIX PRINTER

2.5.7.1 ACU Serial Communications. The dot matrix printer used with ASOS can be a Panasonic model

KX-P1180, KX-P2180, or KX-P3123. For any ofthese printers, the technician must ensure that it is properly

configured on the ACU serial communications page (Figure 1.3.44). As a minimum, the printer parameters

on this page should be set as follows:

 BAUD RATE: 2400 for remote printer (9600 for local printer)

 PARITY SELECT: NONE

 BITS/CHAR: 8

 STOP BITS: 1

 HANDSHAKE: XON/XOFF

After specifying the ACU serial communications parameters, the printer must be manually set up using its

front panel controls and indicators. Table 2.5.35 provides the procedure to perform this setup for the

KX-P2180. Table 2.5.36 provides the KX-P1180 setup procedure. Table 2.5.37 provides the KX-P3123

setup procedure.
S100 ASOS Site Technical Manual

Change 2 2-158.1/ (2-158.2 blank) $

Figure 2.5.1A. DDS/MR64 Line Driver Switch and Jumper Location
S100 ASOS Site Technical Manual

2-159

Table 2.5.35. Model KX-P2180 Printer Setup

Step Procedure

1 Turn POWER switch OFF.

2 While pressing and holding FUNCTION switch, turn POWER switch ON. The ON LINE/FUNCTION

indicator blinks. Initial setup mode is active.

3 Press and release SUPER QUIET switch until ROW indicators are as follows:

 FONT OFF

 PITCH ON

 FORM LENGTH OFF

 FONT ON

4 Press TEAR OFF key to toggle interface from parallel to serial. The indicator over the first column

illuminates.

5 Press and release SUPER QUIET switch until ROW indicators are as follows:

 FONT OFF

 PITCH ON

 FORM LENGTH ON

 FONT ON

6 Press TEAR OFF key to toggle protocol from DTR to XON/XOFF. The indicator over the first column

illuminates.

7 Press FUNCTION switch to exit initial setup mode. The ON LINE/FUNCTION indicator stops blinking.

8 Press SUPER QUIET switch to enter quiet mode.

9 Press FUNCTION switch to enter function mode. The ON LINE/FUNCTION indicator blinks.

10 Press and release TEAR OFF key until column indicator is blinking over MACRO.

11 Press LOAD PARK switch to save the macro. A beep is heard and the column indicator stops blinking.

12 Press FUNCTION switch to exit function mode. The ON LINE/FUNCTION indicator stops blinking.

Table 2.5.36. Model KX-P1180 Printer Setup

Step Procedure

Tools Required:

 No. 2 Phillips screwdriver

1 Turn POWER switch OFF.

2 While pressing and holding FUNCTION switch, turn POWER switch ON. The ON LINE/FUNCTION

indicator blinks. Initial setup mode is active.

3 Press and release SUPER QUIET switch until ROW indicators are as follows:

 FONT OFF

 PITCH ON

FORM LENGTH OFF

 FONT ON

4 Press TEAR OFF key to toggle interface from parallel to serial. The indicator over the first column

illuminates.

5 Ensure that printer POWER switch is set to OFF.

6 Ensure that RS-232 serial data cable is disconnected from back of printer and that printer power cable is

disconnected from facility output.

7 Remove smoked plastic cover, top cover (with paper guide), and platen knob from printer.
ASOS Site Technical Manual S100

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Figure 2.5.2 Upper Cabinet Removal

Table 2.5.36. Model KX-P1180 Printer Setup -CONT

Step Procedure

8 Remove upper cabinet from printer by performing the following steps (Figure 2.5.2):

a. Raise rear of printer to gain access to underside.

b. Insert No. 2 Phillips screwdriver into center of release openings. Push screwdriver in to

 release hooks.

c. While hooks are released, separate upper cabinet from lower cabinet.

9 On serial interface board at rear of printer, set DIP switch SW1-8 to ON position. This selects XON/XOFF

protocol.

10 Install upper cabinet, platen knob, smoked plastic cover, and top cover onto printer.

11 Connect RS-232 serial data cable to rear of printer.

12 Connect printer power cable to facility outlet.

13 Turn printer POWER switch to ON.

Table 2.5.37. Model KX-P3123 Printer Setup

Step Procedure

DEFAULT CONFIGURATION

NOTE

It is not necessary to set up a NEW printer that you have just removed from the box if you intend to

use it in the local mode (connected directly to the printer port, J25); the configuration for this mode

should have been setup at the factory. The "local" mode is not the same as the factory settings mode

mentioned below.

FACTORY SETTINGS

NOTE

If you suspect that the printer settings have been accidently changed, you should reset the printer to

the "factory settings" mode using the following procedure, prior to performing the printer setup

procedure (otherwise continue to step 1under printer setup procedure):
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Table 2.5.37. Model KX-P3123 Printer Setup -CONT

Step Procedure

1 Turn power switch OFF.

2 While pressing the FUNCTION key on the printer, turn the powerswitch on to enter the setup mode. The ON

LINE/FUNCTION will start blinking. Row indicators R1 (FONT), R2 (PITCH), R3 (FORM LENGTH), &

R4 (OTHERS) will be blinking.

3 Press LF. You will hear a beep.

4 Press FUNCTION to exit the function mode.

PRINTER SETUP

1 Turn power switch off.

2 While pressing the FUNCTION key on the printer, turn the power switch on to enter the setup mode. The

ON LINE/FUNCTION willstart blinking. Row indicators R1 (FONT), R2 (PITCH), R3 (FORM LENGTH),

& R4 (OTHERS) will be blinking.

3

PRINTER (INTERFACE) SETUP

Press and release SUPER QUIET until row indicators are as follows:

R1 FONT ON

R2 PITCH ON

R3 FORM LENGTH OFF

R4 OTHERS ON

4 Press TEAR OFF to toggle interface from PARALLEL to SERIAL. The indicator over C1 will light

(column indicator C3 is already lit).

REMOTE PRINTER (ONLY) BAUD RATE SETUP

NOTE

If the printer you are setting up is a remote printer (a printer using a modem), you must

perform the following steps (otherwise, go to step 5):

 a. Press and release SUPER QUIET until row indicators are as follows:

 R1 FONT OFF

 R2 PITCH OFF

 R3 FORM LENGTH ON

 R4 OTHERS ON 

b. Press LF to select 2400 baud. Column indicator C4 will be illuminated.

5

PRINTER (PROTOCOL) SETUP

Press and release SUPER QUIET until row indicators are as follows:

 R1 FONT ON

 R2 PITCH ON

 R3 FORM LENGTH ON

 R4 OTHERS ON

6 Press TEAR OFF to toggle protocol from DTR to XON/XOFF. The indicators over columns C1,C2, and C3

will be illuminated.

7 Press FUNCTION to exit initial setup mode. The ON LINE/FUNCTION indicator will be illuminated.
ASOS Site Technical Manual S100

Table 2.5.37. Model KX-P3123 Printer Setup -CONT

Step Procedure

2-162

8

PRINTER (HANDSHAKE) SETUP

 Verify that HANDSHAKE on the OID COMMS page is set to XON/XOFF by the AOMC.

NOTE

If HANDSHAKE is not set correctly (to XON/XOFF) on the OID COMMS page by the

AOMC, it is possible to overwrite the printer buffer. To verify and/or change the selection

for HANDSHAKE, you must:

a. Sign on to the OID as a technician.

b. Press REVUE SITE CONFIG COMMS. If XON/XOFF appears as the HANDSHAKE selection,

press EXIT to return to the 1-minute page; otherwise, you must continue to step c. 

c. Using the PREV and NEXT keys, move the cursor to the PRINTER port.

d. Press CHANG and move cursor to HANDSHAKE.

e. Press SEQN until XON/XOFF is selected.

f. Press EXIT to exit COMMS page and return to the 1-minute page.

OPTIONAL PROCEDURES

NOTE

The following optional printer procedures are presented to enable the technician to optimize the

KX-P3123 printer capabilities.

PRINT CURRENT SETTINGS (OPTIONAL)

 NOTE

To print the current configuration of the printer, the following procedure is

performed:

 a. Turn power switch off.

 b. While pressing the FUNCTION key on the printer, turn the power switch on to enter the setup

mode. The ON LINE/FUNCTION willstart blinking. Row indicatorsR1 (FONT), R2 (PITCH),

R3 (FORM LENGTH), & R4 (OTHERS) will be blinking.

 c. Press TEAR OFF, LOAD/PARK ON LINE, or FF. The printer will print all current settings. 

 d. Press FUNCTION to exit the function mode.

SUPER QUIET MODE (OPTIONAL)

NOTE

To allow the printer to function with reduced printer noise (but also with reduced

printer speed), the following procedure should be performed:

 a. Be sure power is on. Make sure that the ON LINE/FUNCTION indicator is not blinking. If it is

blinking, press FUNCTION.

 b. To enter super quiet mode, press SUPERQUIET. You will hear a beep and the SUPERQUIET

indicator will illuminate.

 c. Press FUNCTION. The ON LINE/FUNCTION indicator will start blinking.
S100 ASOS Site Technical Manual

Table 2.5.37. Model KX-P3123 Printer Setup -CONT

Step Procedure

Change 2 2-163/ (2-164 blank)

 d. Press and release TEAR OFF until only Row R4 (OTHERS) is illuminated and column C3

(MACRO #1) is blinking.

 e. Press LOAD PARK to set macro. You will hear a beep and the column indicator C3 will stop

blinking and stay lit.

f. Press TEAR OFF to save macro. You will hear two beeps and indicator C3 will start blinking.

 g. Press FUNCTION to exit the function mode. The ON LINE/FUNCTION indicator will stop

blinking.

ZERO SLASH SETUP (OPTIONAL)

 NOTE

This procedure causes a slash to be placed across the number 0 (zero) when it is

printed.

 a. Press and release SUPER QUIET until the row indicators are as follows:

 R1 FONT OFF

 R2 PITCH OFF

 R3 FORM LENGTH OFF

 R4 OTHERS ON

 b. Press LOAD PARK; C2 indicator will illuminate.

2.5.8 ACU CPU AND SIO BOARD JUMPER CONFIGURATIONS

When replacing a CPU board, the technician must conFigure jumpers on a basic XVME-601/6 CPU board

(manufacturer’s P/N 70601-006)forthe slot it isto be installed. This changestheCPU part numberto 62828-

47006-XX, where XX is determined by the slot number. Similarly, when replacing a RS-232 SIO board , the

technicianmust conFigure jumpers on a basicXVME-490/1 board (manufacturer’s P/N70490-001)to create

the 62828-47014-XX part that corresponds to the slot it is installed. The following altered item drawings

(located on the following pages) define the jumper configurations for the following ACU and DCP circuit

boards:

Part Number Title

62828-47006 CPU Circuit Card Assembly

-10 ASSY ACU Primary CPU

-20 ASSY ACU Secondary CPU

-30 ASSY DCP Primary CPU

-40 ASSY DCP Secondary CPU

62828-47008 Circuit Card Assembly, ACU Memory

62828-47013 Circuit Card Assembly, SIO RS-422

62828-47014 Circuit Card Assembly, SIO RS-232

62828-47016 Circuit Card Assembly, Analog/Digital

62828-47018 Circuit Card Assembly, Voice Processor

62828-47028 Circuit Card Assembly, Memory, DCP

62828-47033 Circuit Card Assembly, Digital I/O

62828-47003 Circuit Card Assembly, VME Resistor

2.5.9 JOHNSON DATA RF MODEM SETUP $

$

Johnson Data rf modem frequencies are assigned and setup at the depot. Order rf modem part number $

62828-40506-1 for 410.075 MHz or 62828-40506-2 for 410.950 Mhz. $
 Change 2 2-165/ (2-166 blank)
2-167/ (2-168 blank)
2-169/ (2-170 blank)
2-171/ (2-172 blank)
$ Change 2 2-172.1/ (2-172.2 blank)
Change 1 2-173/ (2-174 blank) $
2-175/ (2-176 blank)
Change 1 2-177/ (2-178 blank) $
2-179/ (2-180 blank)
Change 1 2-181/ (2-182 blank) $
2-183/ (2-184 blank)
Change 1 2-185/ (2-186 blank) $
2-187/ (2-188 blank)
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2-191/ (2-192 blank)
Change 1 2-193/ (2-194 blank) $
2-195/ (2-196 blank)
Change 1 2-197/ (2-198 blank) $
Change 1 2-199/ (2-200 blank) $
S100 ASOS Site Technical Manual

Change 1 3-1

Figure 3.1.1. DCP Communications Link - Simplified

CHAPTER 3

DATA COLLECTION PACKAGE

SECTION I. DESCRIPTION AND LEADING PARTICULARS

3.1.1 INTRODUCTION

Each ASOS may have up to three data collection packages(DCP's) and theirsensor complements. The DCP's

are designated Unit 2, Unit 3, and Unit 4. This section defines the purpose of the DCP and describes its

physical configuration. Locational illustrations are provided to identify DCP assemblies and subassemblies

applicable to maintenance personnel. 

3.1.2 PURPOSE

An Automated Surface Observing System (ASOS) typically utilizes between one and three remotely located

(i.e., outside) DCP's, which function as data links between ASOS sensors and the acquisition control unit

(ACU). As illustrated on figure 3.1.1, data exchanges between the DCP and externally mounted sensors are

accomplished via fiberoptic cabling, while data transfers between the DCP and ACU are accomplished via

radio frequency (rf) communication. However, the system can be configured for hardwire communications

between the ACU and DCP. A single DCP may handle data exchanges for up to 16 sensors.
ASOS Site Technical Manual S100

3-2 Change 2

3.1.2.1 ClassI and ClassII Systems. Throughout this chapter and Chapter 2, a distinction is made between

Class Isystems and Class IIsystems. The Class I DCP is the basic model DCP. This model will be installed

at most Class I (non-towered) airports and other observation sites. The Class II DCP is very similar to the

Class I system, except that the Class II DCP has several additional features to increase system availability

and performance. These additional features are identified as follows:

a. There are two types of uninterruptible powersuppliesthat may be installed in the DCP: UPS

62828-90057, which isinstalled in serial number 438 and below, and UPS 62828-90338-10,

which is installed in serial numbers 439 and above. The UPS allows the DCP to operate in

the event of a loss of facility power.

b. Redundant communications equipment for ACU/DCP data communications. This includes

a second CPU and a second rf modem (or line driver) in the DCP. 

c. Electromagnetic interference (EMI) shielded DCP equipment cabinet.

d. UPS bypass circuit for additional power monitoring and control capability.

e. At designated sites that have pressure sensors mounted in the DCP, a third (redundant)

pressure sensor is added. The third sensor allows ASOS to continue to report altimeter

settings and pressure data when one of the three pressure sensors fails.

Although the above-mentioned features are standard for Class II DCP's, they are also available as options

for Class I DCP's.

$ 3.1.2.2 Optional Auxiliary Box. Because of lack ofspace within the 62928-40070-20 ClassI DCP cabinet,

$ an auxilliary box is used to house the optional UPS. The auxiliary box is mounted behind the main DCP

$ cabinet. Also, if more than nine sensors are connected to a ClassII DCP, a second UPS isrequired to provide

$ the back-up ac power for sensors 10 through 17. This second UPS will be mounted in an auxiliary box. Refer

$ to chapter 14 for descriptions and troubleshooting of the auxiliary box.

$

3.1.3 PHYSICAL DESCRIPTION

Figure 3.1.2 illustrates three types of DCP installations; combined sensor group (shown with backup sensors),

touchdown zone pad, and remote wind sensor pad. Each type consists of the following major units: the DCP

equipment cabinet, an externally mounted ac junction box, and an rf antenna. For a Class II installation having

more than nine sensors, an auxiliary DCP equipment cabinet housing a second UPS can be added to meet sensor

power requirements. 

3.1.3.1 DCP Equipment Cabinet, Unit 2, 3, or 4. Figure 3.1.3 illustrates a typical Class II DCP equipment

cabinet. The Class I DCP equipment cabinet is similar but does not contain the UPS components, UPS bypass

$ circuit, or the backup battery box. The Class II DCP contains one of three types of UPS. A SOLA UPS

62828-90057 is installed in serial numbers 438 and below and has components that are behind a UPS cover (sheet

$ 1). Either of two interchangeable Deltek UPS’s, 62828-90338-10 or 62828-90338-20 is installed in serial numbers

$ 439 and above; their components are installed inside the UPS box and cannot be removed (sheet 2). In addition

to the UPS components and the battery box, the DCP equipment cabinet also contains a card rack assembly, a

circuit breaker module rack, an rf modem mounting plate, four dc power supplies, power reset relay, and a Faraday

box. At selected sites, the DCP also contains pressure sensors. Many of these assemblies are mounted on, and

identified with, a large mounting plate assembly (A1). The Faraday box contains two distribution strips/buses,

interconnecting electrical and fiberoptic cabling, and electromagnetic interference (EMI) filters. Brief descriptions

of the DCP assemblies are provided in table 3.1.1. Additional information for selected DCP assemblies is provided

in the following paragraphs.
S100 ASOS Site Technical Manual

Change 1 3-3 Combined Sensor Group (With Backup Sensors) Figure 3.1.2. DCP Installation (Sheet 1 of 3)
ASOS Site Technical Manual S100

3-4 Change 1

Remote Wind Sensor Pad

Figure 3.1.2. DCP Installation (Sheet 2)
ASOS Site Technical Manual S100

3-4.1 Change 1 Touchdown Zone Pad Figure 3.1.2. DCP Installation (Sheet 3)
ASOS Site Technical Manual S100

3-4.2 Change 1

Figure 3.1.3. DCP Equipment Cabinet - Locational View (Sheet 1 of 2)

(POWER RESET AND UPS BYPASS)
S100 ASOS Site Technical Manual

Change 1 3-5

Figure 3.1.3. DCP Equipment Cabinet - Locational View (Sheet 2)
ASOS Site Technical Manual S100

3-6 Change 2

Table 3.1.1. DCP Equipment Cabinet Major Assemblies

Unit Nomenclature Purpose

A1 Mounting Plate

Assembly

Main mounting plate in DCP equipment cabinet.

A1A2 Card Rack Assembly Contains up to 12 circuit boards that perform all data processing and I/O

functions associated with the DCP.

A1A3 Circuit Breaker Rack Hinged rack assembly containing up to 18 circuit breaker modules. Left

row modules (A1 through A9) are allocated for DCP and first eight

sensors. Right row modules (A10 through A18) are allocated for optional

auxiliary DCP (if Class II system) and sensors 9 through 16. 

A1A4 AC Power Distribution

Assembly

A terminal strip/bus that distributes ac power (facility or UPS) to DCP

assemblies and associated sensors.

A1A5 RF Modem Mounting

Plate 

For Class II system with rf communication link to ACU, contains rf

modem A (A1A5A1), rf modem B (A1A5A2), and an rf modem switch

(A1A5S1). For Class I rf link system, contains only rf modem A. For

Class II system with line driver link to ACU, contains line driver A

(A1A5A1), line driver B (A1A5A2), and an LD1/LD2 switching board

(A1A5A3). For Class I line driver system, contains only line driver A.

Only on Class I Antarctica systems and selected sites, contains two

pressure sensors (A1A5A3 and A1A5A4), third sensor added for Class II

systems (A1A5A5).

UPS cover Contains UPS status panel and shields individual UPS assemblies (refer

to figure 3.1.6 sheet 1). UPS 62828-90057 is installed in serial numbers

438 and below. DCP UPS is installed in Class II systems.

A1A6 UPS Uninterruptible power supply part numbers 62828-90057, 62828-

$ 90338-10, or 62828-90338-20 provide backup ac power.

A1A9 Power Reset Assembly Contains power delay relay K1 and Class II systems UPS Bypass relays

K2 and K3.

A1HR1, HR2 Heater assemblies Two heater assemblies provide heating for the DCP equipment cabinet.

Heater HR1 is mounted below the card rack assembly and contains two

375-watt metal bar elements. HR2 is a 350-watt silicon strip heater

element that is mounted behind the battery box in a Class II system.

Heater HR2 is not installed in Class I systems. 

$ A2 Battery Box Contains either four or five 12-volt batteries for UPS. Battery Box A2

$ may be one of three different assemblies. Part number 62828- 40062-10

$ contains five batteries and is used with SOLA UPS 62828-90057 in DCP

$ serial numbers 438 and below. Part number 62828-40062-30, referred to

$ as the interim battery box, contains four batteries and packing material

$ and is used with Deltek UPS 62828-90038-10 or 62828-90338-20 in DCP

$ serial numbers 439 and above. Part number 62828-90360-10, referred to

$ as the production model battery box, is similar to 62828-40063-30 but is

$ physically smaller. It contains four batteries and is also used with Deltek

$ UPS 62828-90038-10 or 62828-90338-20 in DCP serial numbers 439 and

$ above.

A1S1-S3 Thermal switches Control activation of DCP heater elements.

A1K1, K2 Solid state relays Used in conjunction with thermostats to control cabinet heater operation.

A3 Faraday Box Central signal/power distribution point for DCP associated circuitry.

Power, rf signals, and sensor fiberoptics are routed through this box. 

A4 Power Supply Assembly Mounting plate that physically holds dc power supplies and dc power

distribution assembly to DCP equipment cabinet.

A4PS1,PS2 5 vdc power supplies Source of +5 vdc power for DCP cabinet.

A4PS3,PS4 ±12 vdc power supplies Source of ±12 vdc power for DCP cabinet.

A4A1 DC power A terminal strip/bus that distributes dc power to circuitry within the DCP

equipment cabinet.
S100 ASOS Site Technical Manual

Change 2 3-7

3.1.3.1.1 Card Rack Assembly A1A2. The 12-slot card rack assembly providessystem interconnection for

up to 12 circuit board assemblies. These circuit board assemblies provide data processing and input/output

(I/O) functions for the DCP. Figure 3.1.4 identifies the specific boards located in each position of the rack.

CPU B isinstalled in ClassIIsystems only to provide a redundant processor in the event that there is a failure

in CPU A or its associated ACU communications link. All DCP's contain at least one serial I/O (SIO) board

(SIO #1), but up to four additional SIO's may be installed, depending on the number of sensors supported

by the DCP. Similarly, all DCP's contain at least one analog to digital converter board (A/D board #1), but

A/D board #2 is added when the DCP supports more than eight sensors.

3.1.3.1.2 CircuitBreaker Rack 1A1A3.Circuit breakerrack 1A1A3 (Figure 3.1.5) contains up to 18 circuit

breaker modules that control power application to the DCP, DCP sensors (16 maximum), and the optional

auxiliaryDCP.CircuitBreaker Module A1 isthe primarymodule.It applies powerto the UPS (ClassIIDCP)

or DCP electronics (Class I) and to the first group of eight sensors associated with it. Circuit breaker A10

is optional. It applies power to an optional second UPS and to a second group of sensors that may be

connected to the DCP. Primary Circuit Breaker Modules A1 and A10 are not field replaceable units (FRU's)

themselves. Rather, the individual circuit breakers on these modules are the FRU's. Each module installed

in slots A2 through A9 and A11 through A18 is dedicated to one of the installed sensors and applies power

to that sensor. These sensor-dedicated modules are FRU's, and their piece parts (circuit breakers, module

board) are not. These modules are equipped with relays that permit software control of power to the sensor

electronics. The modules installed in slots A2 through A9 and A11 through A18 may contain any of the

module models. The model installed in a given slot is determined by the type of sensor that the module is

controlling. Each of the modelsis defined by a different dash number appended to its basic part number. All

of the modules have at least one circuit breaker for the corresponding sensor electronics and heaters. Several

of the modules provide a second breaker for the sensor's heater circuits. This heater breaker provides a

separate run forsensors with high power heaters. The circuit breaker module models are identified asshown

in table 3.1.2.

Table 3.1.2. DCP Circuit Breakers

Sensor Type Dash Number Heater Breaker

Ceilometer (CHI) -10 Yes (obsolete, replaced with -80)

Temperature/dewpoint (T/D) -20 No

Visibility -30 No

Wind -40 No

Light emitting diode weather indication (LEDWI)

(present weather indicator)

-50 Yes

Tipping bucket (no power) -60 Heater only

Freezing rain -70 Yes (obsolete, replaced with -90)

Ceilometer (CHI) -80 Yes

Freezing rain -90 Yes

Thunderstorm -100 Yes

3.1.3.1.3 DCP Uninterruptible Power Supply (UPS). For Class II systems, there are three types of $

uninterruptible power supplies that may be installed. SOLA UPS 62828-90057 is installed in DCP’s with $

serial numbers 438 and below. Either Deltek UPS 62828-90338-10 or 62828-90338-20 is installed in DCP’s $

with serial numbers 439 and above. A UPS is included in the DCP to provide a backup ac power source for $

the DCP and up to nine sensors. If more than nine sensors are associated with a Class II DCP, a secondary

UPS is installed in an optional auxiliary box. The UPS generates its ac backup power from the dc power

provided by Battery Box A2. UPS 62828-90057 is not a unit in itself but is a collection of seven FRU's

mounted on Mounting Plate Assembly A1 and the UPS cover. These FRU's are illustrated and identified on

figure 3.1.6. UPS 62828-40338-10 is an FRU that is mounted on Mounting Plate Assembly A1.
ASOS Site Technical Manual S100

3-8 Change 1

Figure 3.1.4. VME Card Rack - Stuffing Chart

$ 3.1.3.1.3a Power Reset Assembly. PowerReset Assembly A1A9 (ClassI andClassIIsystems)islocated

$ in the top center of the cabinet, above the circuit breaker rack. The power reset assembly consists of Time

$ Delay Relay A1A9K1. The time delay relay ensures that the DCP resets properly after power is interrupted

$ by delaying power application approximately three seconds.

$ 3.1.3.1.3b UPS Bypass Circuit. The UPS bypass circuit (Class II systems) is co-located with the Power

$ Reset Assembly A1A9 in the top center of the cabinet. The UPS bypass circuit consists of Digital I/O

$ Module A1A9K2 and Power Relay A1A9K3. The ASOS application software monitors and controls the

$ power relay which routes site power or UPS output power to the cabinet.
S100 ASOS Site Technical Manual

3-9

Figure 3.1.5. Circuit Breaker Module Rack - Stuffing Chart
ASOS Site Technical Manual S100

3-10

Figure 3.1.6. DCP Uninterruptible Power Supply - Locational View
S100 ASOS Site Technical Manual

Change 1 3-11

3.1.3.1.4 DCP Heaters. Heater A1HR1 is installed in both Class I and Class II systems. It contains two 375-watt

heater elements for a combined total of 750 watts. For a Class II system, HR2 is also installed to provide heating for

the battery box and the UPS components. HR2 is a 350-watt element. Three thermal switches (A1S1 through S3) are

used in conjunction with two solid state relays (A1K1 and K2) to control the heaters. Power is applied to one element

of HR1 and to HR2 (if installed) as the internal DCP temperature drops below 50 degrees Fahrenheit. If the internal

temperature continues to fall below 40 degrees Fahrenheit, the second element of HR1 is activated. Overheat

protection prevents application of heater power when temperatures exceed 80 degrees Fahrenheit. Heater operation

is disabled if facility ac input power loss necessitates operation of the UPS. 

3.1.3.1.5 Faraday Box A3. Figure 3.1.7 illustrates the parts/assembly locations associated with the Faraday box,

which provides the signal and power interfaces for DCP operations. Up to 16 fiberoptic modules (A3A1 through A16,

one per sensor) may be located on top of the box. These modules provide digital/optical data conversions necessary

for DCP communication with individual sensor assemblies. Each fiberoptic module possesses a distinct transmit and

receive channel. The rf output connection to the externally mounted antenna assembly is located on top of the box.

The left side of the shielded box assembly contains two DB-25 connectors (J5 and J6) which carry sensor power lines

while the five remaining connectors (J1 through J4 and J9) are EMI filter equipped and route ac power throughout

the DCP. Two ac distribution panels (A17 and A18), with surge suppression capability, are located inside the Faraday

box and provide the necessary ac interconnections between the input facility power, the DCP, and its sensors. 

3.1.3.2 AC Junction Box. The ac junction box (Figure 3.1.8), located external to the DCP equipment cabinets,

provides the main control point for the facility ac site power. The box consists of a standard circuit breaker box which

contains one dual (2-phase) 40-ampere main circuit breaker, two 30-ampere circuit breakers, two 15-ampere circuit

breakers, and a 15-ampere ground fault interrupter (GFI) circuit breaker. The four secondary breakers provide power

to the clearance lights, primary DCP, auxiliary DCP, and utility GFI outlet located on the side of the box. The GFI

outlet provides additional safety for the technician when working on the equipment and should be used to supply

power to any test equipment or support equipment used at the sensor pad. For the power expanded DCP $

(Figure 3.1.9), a dual 30-ampere circuit breaker replaces one 30-ampere circuit breaker and the 40-ampere main circuit $

breaker. $

3.1.3.3 RF Antenna. The rf antenna enables ACU/DCP communications and operates on the ASOS rf frequencies

(410.075 or 410.950 MHZ). The antenna itself is usually an omnidirectional antenna, but it is mounted onto its mast $

in such a manner as to provide some directional gain (in the direction of the ACU antenna). At certain sites where RFI $

was experienced, yagi antennas are used at one or both ends of the link. A yagi can only be used at the ACU if all $

DCP's are illuminated within the yagi’s 10-degree beamwidth. A seven-element yagi, PN 62828-90413-2, provides $

10 dB gain over the 406 - 420 MHz band and has a front:back ratio of 14 dB. Additionally, at sites where cochannel $

interference is particularly troublesome, five watt attenuators of 3 dB, 6 dB, 10 dB, 20 dB, or 30 dB (PN 62828- $

90424-2, -3, -4, -5 and -6, respectively) may be inserted in the antenna line(s) to reduce transmit power into the $

antennas. $

3.1.4 DCP CONFIGURATIONS

There are seven possible configurations for the DCP, which are described below. In addition, there is a special

application version of the DCP, which contains three pressure sensors.

-10 Class II DCP with an uninterruptible power supply (UPS) built by SOLA

-20 Standard Class I DCP (small cabinet) $

-30 Class II DCP with an enclosure built by Electrorack, an extension on the Faraday box, and an UPS

built by SOLA

-40 Class I DCP with an enclosure built by Electrorack, an extension on the Faraday box, and the old

style backplate

-50 Class II DCP with the new backplate, an UPS by Deltec, and the new harness

-60 Class I DCP with the new backplate, and the new harness

-70 Class I DCP with an UPS built by Deltec
ASOS Site Technical Manual S100

3-12

Figure 3.1.7. Faraday Box - Locational View
S100 ASOS Site Technical Manual

Change 1 3-13

Figure 3.1.8. Typical AC Junction Box (Sheet 1 of 2)
ASOS Site Technical Manual S100

3-14 Change 1

Figure 3.1.8. Typical AC Junction Box (Sheet 2)
ASOS Site Technical Manual S100

Change 1 3-14.1/ (3-14.2 blank)

Figure 3.1.9. Power Expansion DCP AC Junction Box - Locational View
S100 ASOS Site Technical Manual

3-15/ (3-16 blank)

SECTION II. INSTALLATION

Installation of the DCP is not the responsibility of the site technician. The removal and installation

procedures for the individual field replaceable units (FRU's) within the DCP are contained in Section V.
S100 ASOS Site Technical Manual

Change 2 3-17

SECTION III. OPERATION

3.3.1 INTRODUCTION

This section provides the information necessary for maintenance personnel to correctly interpret and utilize

the controls and indicators associated with data collection package (DCP) assemblies. The operational

procedures for the application and removal of DCP input power are also provided.

3.3.2 CONTROLS AND INDICATORS

This paragraph describesthe DCP maintenance controls and indicators. The assemblies within the DCP that

contain maintenance-related controls and indicators are the status panel of the uninterruptible power supply

(UPS), the card rack assembly, and the power control module rack. 

3.3.2.1 UPS Status Panel. The status panel in UPS 62828-90057 (ClassIIsystems with DCP serial numbers $

438 and below) provides an OUTPUT POWER switch and several LED indicators. UPS’s 62828-90338-10 $

and 62828-90338-20 (ClassIIsystems only with serial number 439 and above) provide an on/offswitch and $

several LED indicators. Descriptions ofthese controls and indicators are provided fortheir ACU counterpart

in Chapter 2, Section III of this manual and are not repeated here.

3.3.2.2 Card Rack Assembly A1A2. The card rack assembly contains three circuit board assemblies (two

distinct types) with controls and indicators: CPU's A and B (slots A1 and A2, respectively) and the memory

board (slot A3). Descriptions of the controls and indicators for the CPU boards are provided for their ACU

counterparts in Chapter 2, Section III of this manual and are not repeated here. The memory board contains

two LED indicators labeled BANK 1 and BANK 2. These indicators are illuminated when their respective

memory banks are being accessed by the CPU. 

3.3.2.3 Circuit Breaker Rack A1A3. The circuit breaker module located in slot A1 controlsthe application

of power to the UPS (Class II DCP) or DCP electronics (Class I) and to the first group of eight sensors.

Similarly, the module in slot A10 controlsthe application of power to the optionalsecond UPS (ClassII) and

to the second group of eight sensors. The modules in slots A2 through A9 and A11 through A18 control the

application of power to the electronics and heaters of the individual sensors. These modules are equipped

with relays that allow system software to control power to the sensor electronics. Table 3.3.1 describes the

control/indicator functions of a typical power control module asillustrated by figure 3.3.1. Slots A2 through

A9 and A11 through A18 contain differentmodels of circuit breakermodules.The types of modulesinstalled

in slots A2 through A9 and A11 through A18 depends on the type of sensor being controlled from that slot.

Each of the models is defined by a dash number appended to its basic part number. All of the modules have

at least one circuit breaker for the corresponding sensor electronics and heaters. Several models also provide

a separate, second breaker for the sensor's heater circuits. This heater breaker provides a separate run for

sensors with high-current heaters. The circuit breaker module models are identified as follows:

Dash Heater Software

Sensor Type Number Breaker Controlled

Ceilometers (CHI) -10 Yes Yes (obsolete, use -80)

Temperature/dewpoint (T/D) -20 No Yes

Visibility -30 No Yes

Wind speed/direction -40 No Yes

Present weather -50 Yes Yes

Tipping bucket (no electronics) -60 Heater only No

Freezing rain -70 Yes Yes (obsolete, use -90)

Ceilometer -80 Yes Yes

Freezing rain -90 Yes Yes

Thunderstorm -100 Yes Yes
ASOS Site Technical Manual S100

3-18

Figure 3.3.1. Power Control Module Controls and Indicators

Table 3.3.1. Power Control Module Controls and Indicators

Control/

Indicator

Type Description

NOTE

Modules that do not utilize both of the circuit breakers described below contain a void in the

associated module position.

POWER Circuit

breaker

When set to on (left) position, ac power is applied to the DCP or sensor associated with

specific rack slot assignment. The circuit breaker modules in slots A1 and A10 (if

installed) are not software-controllable via the operator interface device (OID). All

remaining modules(except the -60, which is heater only) may be controlled fromthe OID

when this breaker is in on position. 

When set to off (right) position, ac power is removed and the DCP and/or sensor is

disabled. Software control cannot enable a module when this breakerisset to off position.

HEATER Circuit

breaker

When set to on (left) position, ac power is applied to the associated sensor's heater

circuitry. 

When set to off (right) position, ac power is removed from sensor circuitry.
S100 ASOS Site Technical Manual

Change 2 3-18.1/ (3-18.2 blank)

3.3.2.4 RF Modems. RF data modems provide communications between the ACU and DCP cabinets. Only $

the Johnson Data rf modem (62828-40506-X) has controls and indicators as shown on figure 3.3.2 and $

described in table 3.3.1A. $

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

Figure 3.3.2. Johnson Data RF Modem Controls and Indicators $

$

$

$

Table 3.3.1A. Johnson Data RF Modem Controls and Indicators $

Index $

Control/ $

Indicator Description

1 SMA Connector RF output (requires SMAM-to-BNCF adapter) $

2 HDB-15 Connector High density 15 pin female power/communications connector (requires $

adapter cable 62828-42110-10) $

3 RX LED (Yellow) Illuminates when receiving data $

4 TX LED (Red) Illuminates when transmitting data $

5 PWR LED (Green) $

 (Flashing) $

Illuminates when power is applied

Illuminates when setup mode is active

$
S100 ASOS Site Technical Manual

3-19

3.3.3 OPERATIONAL PROCEDURES

Operational procedures associated with the DCP equipment cabinet consist of the application and removal

of power. Power up and power down procedures for the DCP equipment cabinet are provided in tables 3.3.2

and 3.3.3, respectively.

3.3.4 USING LAPTOP COMPUTER AS DCP OID

OID display pages are used fortesting and other maintenance functions associated with the DCP and sensors.

Forthisreason, the ASOS provides a DCP OID capability. This capability allows a laptop computer(or other

VT220/320 terminal) to function as an OID. The laptop computer is connected to DCP SIO port 1-1, which

is not used in a Class I DCP but is the UPS port in a Class II DCP. As such, when connecting the laptop

computer to a Class II DCP, the technician must disconnect the SIO port connector from the UPS so that the

laptop computer can be connected. After connecting and initializing the laptop computer, the system

automatically signs the user on to OID #8, as a technician, with the initials DCP. When finished using the

DCP OID, the technician signs off of the system from the 1-minute display in the normal manner. The

technician mustsign off of the DCP OID before removing power fromthe DCP for any maintenance actions.

If the DCP is turned off before the technician signs off, the technician may not be able to initialize the DCP

OID after restoring power. Table 3.3.4 provides a procedure to connect the laptop computer to the DCP and

initialize the computer as the DCP OID.

Table 3.3.2. DCP Power Up Procedure

Step Procedure

1 If DCP is a Class II DCP, ensure that UPS POWER switch is set to off (0) position.

2 Ensure that all circuit breaker module switches in Circuit Breaker Rack A1A3 (slots A1 through A18) are

set to off (right) position.

3 Set DCP circuit breaker, located in ac junction box, to on position.

4 Set primary Circuit Breaker Module A1A3A1 to ON (left) position. If Class I DCP, power is applied to

DCP when this breaker is turned on.

5 If Class II DCP, set UPS POWER switch to on (1) position.

6 To apply powerto individualsensors,set corresponding circuit breaker module switchesinCircuitBreaker

Rack A1A3 (slots A2 through A9 and A11 through A18) to on (left) position.

Table 3.3.3. DCP Power Down Procedure

Step Procedure

1 In Circuit Breaker Rack A1A3, set sensor circuit breakers in slots A2 through A9 and A11 through A18

to off (right) position.

2 If Class II DCP, set UPS POWER switch to off (0) position.

3 Set primary Circuit Breaker Module A1A3A1 to OFF (right) position.

4 Set DCP circuit breaker, located in ac junction box, to off position.
ASOS Site Technical Manual S100

3-20 Change 1

WARNING

Table 3.3.4. Connecting Laptop Computer as DCP OID

Step Procedure

Tools required:

 Laptop computer with PROCOMM Plus installed

 Laptop interface (Y-shaped) cable

$ Laptop null cable

 DB-9 to DB-25 adapter

 Large flat-tipped screwdriver

 Small flat-tipped screwdriver

120 vac is present in cabinet if DCP has not been powered down prior to connecting DCP OID. To

avoid death or severe injury, exercise extreme caution when connecting DCP OID.

1

$

INITIALIZATION

a. If Class I DCP, locate DB-25 connector for SIO port 1-1 (W017-P22). Proceed to step d.

b. If Class II DCP, using large flat-tipped screwdriver, loosen knurled captive screw at top of Circuit

Breaker Module Rack A1A3. Lower circuit breaker module rack to gain access to UPS SIO

connector.

c. Using small flat-tipped screwdriver, disconnect SIO port 1-1 connector (W015-P22) from UPS

RS-232 Interface Board A1A8.

d. Connect RS-232 (COM1) port of laptop computer to DCP SIO port 1-1 connector

(W015/W017-P22) using the following support items:

(1) Laptop interface (Y-shaped) cable

(2) One DB-9 to DB-25 adapter

$ (3) Laptop null cable

e. Raise circuit breaker module rack and secure captive screw.

f. Turn on laptop computer and initialize to PROCOMM Plus program. When program initializes,

press any key to enter terminal mode (blank) screen.

g. Using ALT-S command (setup facility), set up the following TERMINAL OPTIONS:

(1) Terminal emulation: VT220

(2) Duplex: FULL

(3) Soft flow control (XON/XOFF): OFF

(4) Hard flow control (CTS/RTS): OFF

(5) Line wrap: OFF

(6) Screen scroll: OFF

(7) CR translation: CR

(8) BS translation: NON-DESTRUCTIVE

(9) Break length (milliseconds): 350

(10) Enquiry: OFF

(11) EGA/VGA true underline: OFF

(12) Terminal width: 80

(13) ANSI 7 or 8 bit commands: 8 BIT

h. Return (exit) to terminal mode (blank) screen.
S100 ASOS Site Technical Manual

3-21

Table 3.3.4. Connecting Laptop Computer as DCP OID - CONT

Step Procedure

I. Using ALT-P command (line/port option), set CURRENT SETTINGS as follows:

(1) Baud rate: 9600

(2) Parity: NONE

(3) Data bits: 8

(4) Stop bits: 1

(5) Port: COM1

j. Return (exit) to terminal mode (blank) screen.

k. On laptop computer, set CAPS LOCK to ON and NUM LOCK to OFF.

l. Press <CTRL>A (no carriage return).

m. Type OID (no carriage return). The systemresponds with STANDBY while OID initializes. After

a short delay, the 1-minute display is displayed on the laptop screen. If display is not correct, set

NUM LOCK to ON and press 0 (help) twice to refresh screen. Technician is automatically signed

on to OID #8, as a technician, with initials DCP (there is no need for manual sign-on).

n. Laptop computer now functions as an OID. Set NUM LOCK to ON to use laptop number keys

as OID function keypad in usual manner. Set NUM LOCK to OFF to type alphabetic characters.

2 SIGNOFF

NOTE

The technician must sign off of the DCP OID before removing power from the DCP for

any maintenance actions. If the technician does notsign off before the DCP isturned off,

the technician may not be able to initialize the DCP OID after restoring power.

From 1-minute display, sign off in usual manner (select SIGN key, enter DCP as initials, and press return

twice). Ensure that NUM LOCK is set to ON when using SIGN key on display and set to OFF when

entering initials for signoff.

3 DISCONNECTING DCP OID

Tools required:

 Large flat-tipped screwdriver

 Small flat-tipped screwdriver

a. Sign off DCP OID as described above.

b. Using ALT-X (exit) command, exit PROCOMM Plus.

c. Turn off laptop computer.
ASOS Site Technical Manual S100

Table 3.3.4. Connecting Laptop Computer as DCP OID - CONT

Step Procedure

3-22

WARNING

120 vac is present in cabinet if DCP has not been powered down prior to connecting

DCP OID. To avoid death or severe injury, exercise extreme caution when connecting

DCP OID.

d. If Class I DCP, disconnect cables and adapter between laptop computer and DCP harness

connector W017-P22. Place unused connector P22 in position that it will not be damaged or

interfere with other equipment. Procedure is then complete for Class I DCP. For Class II DCP,

perform steps e through h.

e. IfClassII DCP, using large flat-tipped screwdriver, loosen knurled captive screw at top ofCircuit

Breaker Module Rack A1A3. Lower circuit breaker rack to gain access to UPS SIO connector.

f. Disconnect cables and adapter between laptop computer and DCP harness W015-P22. 

g. Using smallflat-tipped screwdriver, install connector W015-P22 to UPSRS-232 Interface Board

A1A8.

h. Raise circuit breaker module rack and secure captive screw.
S100 ASOS Site Technical Manual

Change 1 3-23

SECTION IV. THEORY OF OPERATION

3.4.1 DATA COLLECTION PACKAGE (DCP) OVERVIEW

The DCP collects information directly from the remote weather sensors and provides the collected data to

the acquisition control unit (ACU) for processing. The DCP also provides ac power for each interfaced

sensor.

3.4.2 DCP BASIC BLOCK DIAGRAM DESCRIPTION

3.4.2.1 General. Figure 3.4.1 provides an overall block diagram of the DCP. The major subassemblies of

the DCP are the card rack assembly, the rf modem mounting plate, the Faraday box, the uninterruptible

power supply, the power supply assembly, and the battery box. The DCP's major functions are grouped into

three functional areas: data processing, input/output, and power distribution and control. The following

paragraphs provide a basic block diagram description of these functional areas. 

3.4.2.2 DCP Data Processing. The data processing functional area is responsible for system timing and

control, data processing, data formatting and storage, and data quality checks. All hardware required for data

processing is contained in the card rack assembly and includes one (ClassIsystems) or two (ClassII) central

processing unit (CPU) boards and a memory board. The following paragraphs provide brief descriptions of

these data processing boards. 

3.4.2.2.1 CPU Boards. The CPU board(s) provide central processing and control for the DCP and its

corresponding sensors. For Class IIsystems, one CPU functions as the primary CPU, and the second serves

as the secondary CPU. Both CPU boards perform self-tests once per second during real-time operation and

constantly monitor each other. If a self-test error is detected, the faulty CPU is flagged off-line and the other

CPU assumes the processing duties. For Class I systems, only one CPU board is provided. 

3.4.2.2.2 Memory Board. The memory board stores the DCP execuTable code, which is downloaded from

the ACU during DCP initialization. The memory board also saves data before a systemshutdown. The board

can contain up to 1 megabyte of memory with a battery backup for random access memory (RAM) in the

event of facility ac input power loss.

3.4.2.3 DCP Input/Output. The DCP input/output (I/O) functional area is responsible for communication

between the data processing functional area, the ACU, and the remote weather sensors. This area also

monitors ac and dc power supplies and controls power to the sensors.

3.4.2.3.1 DCP/ACU Communication. Communications between the DCP and ACU are established via an

rf modemorline driverlink. ForClassIIsystems using an rf modemlink, the communication systemconsists

of two rf modems, an rf modem switch, and an rf antenna. At certain sites where RFI was experienced, yagi $

antennas are used at one or both ends of the link. A yagi can only be used at the DCP if the ACU is $

illuminated within the yagi’s 10-degree beamwidth. Additionally, five watt attenuators of 3 dB, 6 dB, 10 dB, $

20 dB, or 30 dB (PN 62828-90424-2, -3, -4, -5 and -6, respectively) may be inserted in the antenna line(s) $

to reduce transmit power into the antennas. Each of the two Class II CPU's communicates with one of the $

modems via a direct RS-232 data link, and the modem, in turn, communicates with the ACU via the rf

antenna. For Class I systems, a single rf modem connected to the single Class I CPU provides the data link,

and an rf switch is not required. The line driver communication link is similar, except that communication

with the ACU is over a direct line rather than the airwaves. For Class II systems, two line drivers are

provided, and an LD1/LD2 switching board switches between primary and secondary line drivers. For Class

I systems, a single line driver handles all DCP/ACU communication.
ASOS Site Technical Manual S100

3-24 Change 1

3.4.2.3.2 Serial I/O (SIO) Boards. Five XVME 490/1 type SIO boards provide communication between

$ theCPU, optional pressure sensors, and the remote sensors (sensors mounted external to the DCP). The DCP

has one SIO board as a minimum configuration. Up to four additional SIO boards may be added, depending

$ on the number of sensors connected to the DCP. Each SIO board provides four RS-232 serial ports. For

$ remote sensors, the SIO boards communicate with fiberoptic modems contained in the Faraday box, which

$ in turn communicate with the individualsensors and the auxiliaryDCP equipment cabinet. Optional pressure

$ sensors use cables W73, W74, and W75 instead of fiberoptic modems to communicate with the SIO boards.

In Class II systems, one SIO port is also used to communicate with the uninterruptible power supply (UPS)

in the power distribution and control functional area.

3.4.2.3.3 Analog to Digital (A/D) and VME Resistor Boards. One or two A/D boards convert analog data

to digital so that the data can be read by the CPU. One A/D board is used if the DCP supports eight or fewer

sensors. The second A/D board is required for a DCP that has nine or more sensors. These boards convert

analog dc and ac power monitorsignalsto dc data. The CPU'sthen read the data to determine the operational

status of the dc power supplies and to monitor the ac power being used by the remote sensors. The VME

resistor board scales the dc voltages before they are applied to the A/D boards. 

3.4.2.3.4 DigitalI/O Board. The digital I/O board containsfour digitalI/O portsthat allow theCPU'sto read

and write control data from and to DCP assemblies. The primary use of the digital I/O ports is to allow the

system software to control the application of ac power to the sensors via the power control modules. In Class

II systems, the CPU's also use the digital I/O board to select between primary and secondary rf modems (or

$ line drivers) by controlling the rf switch (or line driver relay) and to control and monitor the UPS bypass

$ circuit.

3.4.2.4 DCP Power Distribution and Control. The power distribution and control functional area isshown

in simplified form in figure 3.4.2. The power distribution area consists of several assemblies located

throughout the DCP equipment cabinet. Facility ac input power is applied to the DCP via the Faraday box,

which provides electromagnetic interference (EMI) shielding and surge protection. The ac power is then

$ routed through a time delay relay, through an input circuit breaker module in the circuit breaker rack, to the

$ ac distribution strip. For Class II systems, ac power is then routed to a UPS bypass circuit and to the DCP

uninterruptible powersupply (UPS). The UPS is not a unit in itself but is a group ofseveral field replaceable

units (FRU's) that are collectively referred to as the UPS. The UPS provides backup ac power to the DCP

$ assemblies and up to nine sensors for a minimum of 10 minutes. Special line loss circuitry within the UPS

monitors the applied ac power. If an ac input power loss is detected, the UPS uses the battery backup source

(via a dc-to-ac conversion) to continue providing ac power to the DCP. The power outputs of the UPS are

returned to the ac distribution strip. For both Class I and Class II systems, ac power is distributed from the

ac distribution strip to DCP assemblies, including the sensor circuit breaker modules and the dc power

supplies. The dc power supplies provide +5 vdc and ±12 vdc for the DCP assemblies via the dc distribution

strip. Assembliesrequiring dc power include the rf modems (or line drivers) and the card rack assembly. DC

power is also applied to the control circuitry for the DCP heaters and to the sensor circuit breaker modules.

While the actual configuration of the sensor circuit breaker modules varies according to the sensors

interfaced, the function of these modules is to provide circuit breaker control for the external sensor

electronics and heater (if applicable). In addition, special control and monitoring circuitry in each circuit

breaker module allows system software to remove ac power from the associated sensor and to check the

amount of electrical current being used by the sensor. The sensed current level and dc power supply outputs

are monitored by the system software through the card rack assembly. The ac power outputs of the sensor

circuit breaker modules are routed to the external weather sensors through the Faraday box.
S100 ASOS Site Technical Manual

Figure 3.4.1. DCP Simplified Block Diagram

Change 1 3-25/ (3-26 blank)
S100 ASOS Site Technical Manual

Figure 3.4.2. DCP Power Distribution and

Control Simplified Block Diagram

Change 1 3-27/ (3-28 blank)
S100 ASOS Site Technical Manual

3-29

3.4.3 DCP DETAILED BLOCK DIAGRAM DESCRIPTION

3.4.3.1 General. This paragraph contains detailed block diagrams and descriptions of the ASOS DCP. A

description of the card rack assembly includes a detailed block diagram and a description of the circuit

boards dedicated to the processing of ASOS sensor data. A description of the rf modems includes diagrams

and theory of operation. The sensor fiberoptic modules are described including the theory of operation and

associated diagrams. Repair of a faulty DCP peripheral consists of replacing the failed peripheral.

Accordingly, the theory of operation of peripherals is presented at a general level. The drawings associated

with peripherals are intended to provide the technician with the information necessary to conduct continuity

checks when a connector is suspected of being faulty or needs replacement. Power distribution and control

are described using detailed block diagrams for the distribution of dc and ac voltages to the DCP, including

the UPS.

3.4.3.2 DCP Card Rack Assembly. The DCP card rack assembly contains up to 12 circuit boards that

perform all of the data processing and I/O functions. The CPU's and memory board are used specifically to

process data. The SIO boards, the A/D boards, the VME resistor board, and the digital I/O board performthe

DCP I/O functions. All of the circuit boards are designed to accommodate the VMEbus backplane

construction. Figure 3.4.3 illustrates the VMEbus chassis, backplane configuration, and connector pin

assignments asspecified by theVMEbusspecification dictated byBICC-VEROElectronics,Inc.Two 96-pin

bus connectors on the back edge of the board are labeled P1 and P2. The 96-pin bus connector consists of

three rows of pins (32 pins per row) labeled rows A, B, and C. The pin connections for P1 contain the

standard address, data, and controlsignals necessary forsystembus communication. The P1 pin assignments

are listed by pin number order. The pin connections for P2 vary according to the function provided by the

circuit board.The following paragraphs provide detailed information on the circuit boards and their dedicated

functions. 

3.4.3.2.1 Central Processing Units (CPU's). The CPU's execute the ASOS operational software upon

initialization. All operational software resides in battery backed up RAM on Memory Board A1A2A3.

Execution ofthe operationalsoftware involves data processing, data formatting, data quality checks, and data

storage. For a ClassII DCP, the VME card rack containstwo CPU circuit boards, both of which are identical

and contain a 68010 series (68 thousand series) microprocessor running at 10 MHZ, memory (EPROM and

dynamic random access memory (DRAM)), two RS-232 ports, and a 16-bit timer. During system operation,

one of the CPU's functions as the primary CPU, which performs all processing and I/O functions. The other

(secondary) CPU provides a redundant processor. If at any time the primary CPU fails, it is taken off-line

and the secondary CPU becomes the primary CPU. Initially, CPU A is the primary CPU. Two pushbutton

switches labeled RESET and ABORT are provided on the front of the circuit board. ABORT halts program

execution without resetting the CPU. This switch is used for development purposes and should not be used

in the field. If ABORT is pressed, RESET should be pressed to reset the CPU and activate SYSRESET,

thereby resetting the entire backplane via the VMEbus. Resetting the CPU does not affect the contents of the

DRAM. The following paragraphs provide detailed block diagram descriptions of the CPU and the various

modes of operation.

The CPU consists of nine functional areas (Figure 3.4.4): the system resource function, UART and timer,

RS-232 driver and receiver logic, CPU, CPU clock, interrupt logic, VME interface logic, address buffer and

decode, and memory. The system resource function of CPU A provides the system clock, system reset, bus

arbitration, and bus timer functions for the entire VMEbus. Therefore, because CPU A is the bus controller,

the system resource function of CPU B is not used.
ASOS Site Technical Manual S100

3-30

The dual UART and timer provides two RS-232 serial communication channels, a timer, and two ports. The

RS-232 driver and receiverlogic providesthe standardRS-232 receive and transmit lines. TheRS-232 driver

and receiver logic interfaces UART channel A of its CPU to one of the two rf modems (A5A1 and A2) via

connector JK1 on the CPU's. UART channel B on both CPU's are not used. On CPU B, however, a loopback

jumper is installed between the channel B transmit and receive lines (pins 14 and 16 of JK1). This jumper

identifies CPU B asthe initialsecondaryCPU. When the DCP isfirst initialized, both CPU'sissue a message

to their respective UART channel B. CPU B then receives the message back via the installed loopback

jumper. Both CPU's then examine their receive lines. When CPU B detectsthat it has received the signal via

the loopback jumper, it assumes the role of secondary CPU. When CPU A detects that it has not received

its transmitted signal, it assumes the role of primary CPU.

The CPU clock provides the 10 MHZ clock signal required by the CPU, which executes the ASOS

operational software. The interrupt logic monitors the dedicated interrupt lines and informs the CPU when

an interrupt line is active. The interrupts are prioritized and processed on a first-come, first-serve basis. The

VME interface logic provides the standard address, data, and control signals necessary for system bus

communication. The address buffer and decode provides the memory address and system address. The

onboard memory consists of 128K bytes of EPROM and 512K bytes of DRAM. The refresh circuitry for the

DRAM is not disabled during a RESET; therefore, the CPU may be reset without affecting the memory

contents.

The DCP continuous self-test (CST) checks the status of the CPU's once per minute. CST results are

displayed on the CPU display page of the OID. The CST checks the following areas of both the primary and

secondary CPU: DRAM, EPROM, BUS ERRORS, SERIAL PORT #1 and #2 LOOP-BACK, and SERIAL

PORT #1 and #2 XMIT ERRORS. For the primary CPU, test pass/fail status is displayed for each of these

areas. For the secondary (redundant) CPU, test status is displayed for the overall board only. The technician

can manually select to run the CPU test from the CPU page at any time. When this is done, a T status is

displayed for each test category until the test is run again during the next CTS cycle. After the cycle, the

latest test status is displayed and the fail count (if applicable) is incremented.

The DRAM test is based on an alternating pattern. Data are output to the DRAM and read back and the

returned data are evaluated and the test status is displayed. The EPROM test is based on a checksum. The

checksum is compared to the last byte in the EPROM and the result is evaluated and the test status is

displayed. The BUS ERRORS test is based on a memory write to a specific address, with the contents of the

addressed memory evaluated and the test status displayed.

The SERIAL PORT #1 and #2 LOOPBACK tests ensure that the CPU can communicate with its internal

UART. The CPU readsthe UART interrupt vector register and checksfor bus errors. Teststatusis displayed

as P (pass) if no bus errors occurred. 

For the SERIAL PORT #1 and #2 XMIT ERRORS test, the CPU reads the contents of the status register for

the corresponding port. This register contains information on transmission errors detected by the UART

during RS-232 communications. Specifically, the CPU checks the status register for parity errors, framing

errors, and overrun errors that may have occurred. If such errors occur for three consecutive CST cycles, an

F (fail) is displayed for the test status; otherwise, test status is P (pass).

3.4.3.2.2 Memory Board. The XVME-100 memory board can contain up to 1M byte of static RAM

(SRAM) memory arranged into two banks (up to 512K bytes of memory per bank). Each bank can contain

up to four 128K x 8 bit memory devices. Each bank isindependently configured via jumpersto specify VME

address/memory chip size, device speed, device pinout, and backup power. The following paragraphs a

provide detailed block diagram description of the memory board.
S100 ASOS Site Technical Manual

Figure 3.4.3. DCP VMEbus Chassis and

Connector Pin Assignments (Sheet 1 of 2)

3-31/ (3-32 blank)
S100 ASOS Site Technical Manual

Figure 3.4.3. DCP VMEbus Chassis and

Connector Pin Assignments (Sheet 2)

3-33/ (3-34 blank)
S100 ASOS Site Technical Manual

Figure 3.4.4. DCP VME Card Rack Detailed

Block Diagram 

Change 1 3-35/ (3-36 blank)
S100 ASOS Site Technical Manual

3-37

The memory board consists of seven functional areas (Figure 3.4.3): two banks (1 and 2), VME/bank address and

decode logic, battery backup, data buffer, bus cycle control, and address buffer and decode logic. The address and

control signals used to address memory locations are generated by the VME/bank address decode and control

logic. The memory board is configured with a battery backup to provide an alternate power source in the event

of facility ac input power loss. The data buffer, bus cycle control, and address buffer and decode logic provide the

standard address, data, and control signals necessary for system bus communication. 

The DCP CST checks the status of the memory board once per minute. CST results are displayed on the memory

display page of the OID. The CST performs an SRAM test on the DCP memory board. The technician can

manually select to run the memory test from the memory page at any time. When this is done, a T status is

displayed for the SRAM test category until the test is run again during the next CTS cycle. After the cycle, the

latest test status is displayed and the fail count (if applicable) is incremented. 

The SRAM test ensures that the CPU can read data from the SRAM on the memory board without encountering

bus errors. The results are evaluated and the test status is displayed.

3.4.3.2.3 Serial I/O (SIO) Boards. Each of the five (maximum) XVME 490/1 type SIO boards used in the DCP

provide four RS-232 serial ports. The XVME 490/1 SIO boards communicate with the Faraday box and the DCP

UPS. The SIO boards communicate with the CPU on a character-by-character basis. The CPU processes interrupts

on each and every transmitted and received character. The following paragraphs provide a detailed block diagram

description of the SIO board.

The SIO board consists of six functional areas (Figure 3.4.4): two serial communication controllers (SCC's),

interrupt logic, data buffer, bus cycle control, and address buffer and decode logic. Each of the SCC's provides two

communication ports. Upon power up, the SCC's are initialized to the proper communication modes. Interrupts

are generated via the interrupt logic. An interrupt can signify that a received character is available, that the transmit

buffer is empty, or an external/ status change. The data buffer, bus cycle control, and address buffer and decode

logic provide the standard address, data, and control signals necessary for system bus communication. 

The four ports of each of the DCP SIO boards are factory assigned to specific devices. The ports are connected

to these devices via corresponding connectors on the DCP main harness. Table 3.4.1 identifies each of the ports

of the DCP SIO boards and lists the corresponding harness connector and the device to which it is connected.

The DCP CST checks the status of the SIO boards once per minute. CST results are displayed on the DCP SIO

display pages of the OID (there is one page for each of the five SIO's). The CST performs a LOOPBACK test and

an XMIT ERRORS test on each of the four ports of an SIO board. The technician can manually select to run the

SIO test from an SIO page at any time. When this is done, a T status is displayed for both test categories until the

test is run again during the next CTS cycle. After the cycle, the latest test status is displayed and the fail count (if

applicable) is incremented. 

For the LOOPBACK test, the CPU reads an interrupt vector register on the SIO board to ensure that it can

communicate with the SIO port. For the XMIT ERRORS test, the CPU reads the contents of the SCC status

register for the corresponding port. This register contains information on transmission errors detected by the SCC

during RS-232 communications. Specifically, the CPU checks the status register for parity errors, framing errors,

and overrun errors that may have occurred. For both LOOPBACK and XMIT ERRORS tests, CST status is

displayed as either P (pass), F (fail), or D (degraded). A status of D is displayed if five or more errors have been

detected and the port is currently passing the test. At 0600 LST each day, the number of accumulated failures is

summarized in the system (maintenance) log. Paragraph 1.3.4.3.3 provides additional information on SIO test

reporting.
ASOS Site Technical Manual S100

3-38 Change 2

Table 3.4.1. Port Assignments for DCP SIO Boards

SIO

Board

Port W015/17

Connector

Device Function1

$ 1 1 P22 A1A8 or A1A6 UPS #1 RS-232 Interface Board (Class II)

2 P6 A1A3A1 Fiberoptic Module #1

3 P7 A1A3A2 Fiberoptic Module #2

4 P8 A1A3A3 Fiberoptic Module #3

 2 1 P9 A1A3A4 Fiberoptic Module #4

2 P10 A1A3A5 Fiberoptic Module #5

3 P11 A1A3A6 Fiberoptic Module #6

4 P12 A1A3A7 Fiberoptic Module #7

 3 1 P13 A1A3A8 Fiberoptic Module #8

2 None None UPS #2 RS-232 Interface Board (future use)

3 P14 A1A3A9 Fiberoptic Module #9

4 P15 A1A3A10 Fiberoptic Module #10

 4 1 P16 A1A3A11 Fiberoptic Module #11

2 P17 A1A3A12 Fiberoptic Module #12

3 P18 A1A3A13 Fiberoptic Module #13

4 P19 A1A3A14 Fiberoptic Module #14

 5 1 P20 A1A3A15 Fiberoptic Module #15

2 P21 A1A3A16 Fiberoptic Module #16

3 None None Not used

4 None None Not used

1 Depending upon port availability at selected sites with pressure sensors located in the DCP, connectors P6 - P21

could be connected to W73, W74, or W75 for pressure sensors P1, P2, and P3 respectively.

3.4.3.2.4 A/D Boards, Digital I/O Board, and VME Resistor Board. The two A/D boards, the digital I/O board,

and the VME resistor board collectively make up the DCP power monitoring and digital I/O function. The A/D

boards, in conjunction with the VME resistor board, receive dc power monitor signals and convert them to digital

values that may be read by the CPU via the VME bus. The digital I/O board provides digital input and output ports

for use by the CPU. The CPU uses the output ports to write control signals to various FRU's in Circuit Breaker

Rack A1A3 and in the rf modem mounting plate. The CPU uses the input ports to read configuration data from the

VME resistor board. A detailed description of these boards is provided in the DCP power monitoring and digital

I/O description (paragraph 3.4.3.5).

3.4.3.3 RF Modem Communications. Two different types of ACU/DCP communications may be provided by

the DCP equipment cabinet: rf communications or direct line communications. RF modems are installed in the

DCP to facilitate rf communications. Line drivers are installed for direct line communications. The following

paragraphs provide a detailed block diagram of the rf communications equipment and its operation.

3.4.3.3.1 RF Modem Rack.As described for ACU rf modems (paragraph 2.4.3.4.2), three different 

types of modems are used in the DCP cabinets. The modems are 62828-90013-XX (AAI Corporation),

62828-90315-XX (Motorola, Inc), or 62828-40506-X (Johnson Data). Sheets 1 through 5 of figure 3.4.5 document

the possible installations of these three types of modems as follows: 

$ Sheet 1- original equipment AAI rf modem (-10 DCP s/n #189 and -20 DCP s/n #251)

$ Sheet 2- as sheet 1 but shown modified for Motorola rf modems

$ Sheet 3- as sheet 2 but shown with Johnson Data modems

$ Sheet 4- original equipment Motorola rf modem (-10 DCP s/n >190 and -20 DCP s/n >251)

$ Sheet 5- as sheet 4 but shown with Johnson Data modems

$
S100 ASOS Site Technical Manual

Change 2 3-39

NOTE $

When an AAI modem (62828-90013-XX) fails, ASN S100-FMK18886 must be ordered to $

replace the modem with the Motorola modem (62828-90315-XX). AAI modems cannot be $

replaced with the Johnson Data modems (62828-40506-X ). $

When a Motorola modem (62828-90315-XX) fails and spare Motorola modems are not $

available, a Johnson Data modem (62828-40506-X), an adapter cable (62828-42110-10), and a $

SMAM-to-BNCF adapter must be ordered to replace the failing rf modem. $

For a Class II system, the DCP rf communications equipment consists of two rf modems (A and B), an rf switch

assembly, and a shared omnidirectional antenna (Figure 3.4.5, sheets 1 through 5). The rf modems are identical,

with one serving as the primary communications link and the other as the secondary. The modems operate in the

UHF frequency range in half-duplex mode. CPU A (A1) communicates with rf modem A via the CPU's built-in

RS-232 port (connector JK1). CPU B (A2) communicates with rf modem B. The rf switch selects which modem

is to use the antenna. This switch is controlled by the CPU's via Digital I/O Board A12. In the event that the

primary CPU senses a failure in its rf link (no data received for a period of 2 minutes and 40 seconds), primary

control is handed over to the other CPU. The new primary CPU then writes a selection word to the digital I/O

board to toggle the rf switch. The new primary CPU and its modem then control all rf communications between

the DCP and the ACU. For a Class I system, the rf communications circuitry is similar, except that there is no

redundant rf system (there is only one CPU, one rf modem, and no rf switch).

The DCP CST checks the status of the ACU/DCP communications link once per minute. CST results are

displayed on the ACU/DCP COMM page of the OID. This test performs two checks: RADIO A OR L/D A and

RADIO B OR L/D B. RADIO A OR L/D A checks the ACU radio A link for up to three DCP's. RADIO B OR

L/D B does the same for ACU radio link B (Class II systems). The CST also identifies which link (modem or line

driver) (A or B) is currently serving as the primary link in the ACU and all DCP's.

The rf communications test is based on a loop test. The ACU transmits a predefined pattern across the

communications link and the DCP verifies the reception of the pattern by responding with an OK or ERROR

acknowledgment. An incorrect reception signifies an error and a failed indication. A failed indication is also

displayed if the DCP fails to respond at all to the ACU transmission.

3.4.3.3.2 Line Drivers. If dictated by the configuration, line drivers and an LD1/LD2 switching board

(Figure 3.4.5, sheet 4) are used in place of rf modems and the rf modem switch. The line drivers in the DCP are

connected by a direct line to corresponding line drivers in the ACU. The line drivers are commonly referred to as

short haul modems and perform a function similar to that of the rf modems. Diagnostically, the line driver is tested

in lieu of the rf modem and the status is displayed on the ACU/ DCP COMM status page. The diagnostic test is

the same as that used for the rf modems. The self-test/diagnostic program utilizes the ACU/DCP COMM status

page to display test results.

3.4.3.3A. Pressure Sensors. The pressure sensors are mounted in the upper right corner of the DCP. The pressure

sensors provide barometric pressure in inches of mercury (inHg). The CPU communicates with pressure sensors

via available SIO board RS-232 ports (Figure 3.4.5a). An adapter cable (W026) is used for pressure sensor data

which adapts the 25-pin RS-232 connector for the optional SIO port to the 9-pin RS-232 connector on the pressure

sensor. The sensor pressure connections are routed through the desiccant assembly to the pressure port located on

top of the DCP.

The pressure sensor tray contains a small printed circuit card to monitor the internal temperature of the DCP to

insure that the DCP does not output pressure data when the internal temperature of the DCP is outside of the

calibration range of the pressure sensors.

DCP firmware changes the pressure data to missing if the temperature inside the DCP is below 35/F ±3/F or above

150/F ±3/F and will automatically (no technician intervention required) report pressure when temperature is $

between 35/F to 150/F. The pressure sensor maintenance screen displays why the pressure is marked missing. A
S100 ASOS Site Technical Manual

3-40 Change 2

remark is entered into the syslog when the sensor is marked missing and when it recovers.

3.4.3.4 Fiberoptic Modules. Up to 16 fiberoptic modules provide digital/optical data conversions necessary for

DCP communication with up to 16 individual sensor assemblies. All fiberoptic communications are controlled by

the primary CPU through VMEbus and the five SIO boards (Figure 3.4.6). Transmit data (TXD) output from an

SIO channel are applied to the drive circuit of the corresponding fiberoptic module. The transmit data are

converted from electrical to optical and output to the sensor through the module's Tx port. Conversely, optical data

applied to the Rx port of the fiberoptic module are converted from optical to electrical and output to the SIO as

receive data (RXD).

3.4.3.5 DCP Power and Signal Monitoring. The circuitry shown on the DCP power monitoring and digital I/O

detailed block diagram (Figure 3.4.7) allows the system software to monitor both analog voltage signals and digital

data points. Digital output ports are also provided whereby the system software can control the application of ac

power to the sensors. The following paragraphs describe the operation of the DCP power monitoring and digital

I/O circuitry.

The DCP power monitoring and digital I/O function consists of one or two A/D boards, one VME resistor board,

and one digital I/O board. DCP's supporting between one and eight sensors require only one A/D board. The

second A/D board is installed only in DCP's supporting more than eight sensors. These boards are very similar to

the A/D board, the VME resistor board, and the digital I/O board in the ACU, and they perform the same function.

The A/D board, the VME resistor board, and the digital I/O board provide an interface to the VMEbus for access

by the system computer (P1). The VMEbus contains control and status logic that identifies and conducts all

VMEbus data transfers with the boards. The A/D boards and the digital I/O board also provide second interfaces

for analog and digital user-defined devices (P2). 

A/D Board A9 is the primary A/D board and is used for DCP's that have eight or fewer sensors. The A/D board

contains 16 input analog channels numbered from 0 to 15 on the user interface port (P2). An analog multiplexer,

under software control, selects 1 of the 16 possible analog signals for application to the A/D converter. The

selected analog signal is converted to a 12-bit digital data value by the A/D converter that is then read by the

computer over the VMEbus via the control and status logic. 

Analog input channels 1 through 6 of A/D Board A9 receive power supply monitor signals via VME Resistor

Board A10. 

The VME resistor board scales the ±12 vdc signals from the power supplies down to ±6 vdc levels for the A/D

converter. The 5 vdc signals from the power supplies are passed through the VME resistor board unscaled. The

voltages monitored at the actual power supply outputs are typically more than +5V and ±12V due to adjustments

for losses between the power supplies and the loads.

The VME resistor board contains a precision voltage source that outputs a 2.5 ±0.1 vdc reference voltage. This

reference voltage is input on channel 0 of both A/D boards. The CPU selects this signal for conversion during the

DCP CST to test the operation of the A/D converters on the A/D boards.

Analog input channels 8 through 15 of A/D Board A9 receive the current sensing output voltages of the circuit

breaker modules associated with the first eight sensors (modules A1A3A2 through A9). These voltage levels

represent the amount of ac current being used by the sensor associated with the circuit breaker module. 

Digital I/O Board A12 contains two I/O port integrated circuits, identified as I/O port numbers 1 and 2. The

primary CPU communicates with these ports via the VMEbus and address buffer and decode logic, a data buffer,

and interrupt timing and control logic on the digital I/O board. The two I/O port IC's provide a total of four ports

(ports A1, B1, A2, and B2), each of which communicates with external devices via a dedicated transceiver. Ports

A1, B1, and A2 are defined as output only ports, and port B2 is configured for input.

Output ports A1 and A2 allow the system software to control the application of ac power to up to 16 sensors via
S100 ASOS Site Technical Manual

Change 2 3-40.1/ (3-40.2 blank)

the circuit breaker modules. The computer writes control data to these I/O ports, which then output CONTROL

bits that remove ac power from the associated sensor. Output port B1 is similarly used by the computer to send

a control signal to the rf modem switch (or LD1/LD2 switching board).

VME Resistor Board A10 contains DCP SELECT switch S1. Because a single ACU can control up to three

independent DCP's, this switch is set to identify its DCP as number 1, 2, or 3. The computer reads this identifier

through input port B2 provided by Digital I/O Board A12. 
AAI MODEMS

S100 ASOS Site Technical Manual

Figure 3.4.5. DCP RF Modem/Line Driver

Communications Link Detailed Block Diagram

(Sheet 1 of 6)

Change 2 3-41/ (3-42 blank)
SYSTEM CONVERTED FROM AAI

TO MOTOROLA MODEMS

S100 ASOS Site Technical Manual

Figure 3.4.5. DCP RF Modem/Line Driver

Communications Link Detailed Block Diagram

(Sheet 2)

Change 2 3-43/ (3-44 blank)
S100 ASOS Site Technical Manual

SYSTEM CONVERTED FROM AAI TO MOTOROLA MODEMS Figure 3.4.5. DCP RF Modem/Driver 

EQUIPPEDWITHJOHNSONDATAMODEMS Communications Link Detailed Block Diagram

(Sheet 3)

Change 2 3-44.1/ (3-44.2 blank)
MOTOROLA MODEMS

S100 ASOS Site Technical Manual

Figure 3.4.5. DCP RF Modem/Line Driver

Communications Link Detailed Block Diagram

(Sheet 4)

Change 2 3-45/ (3-46 blank)
S100 ASOS Site Technical Manual

CONVERTED FROM MOTOROLA MODEMS TO JOHNSON DATA MODEMS Figure 3.4.5. DCP RF Modem/Line Driver

CommunicationsLinkDetailed block Diagram

(Sheet 5)

Change 2 3-46.1/ (3-46.2 blank)
S100 ASOS Site Technical Manual

Figure 3.4.5. DCP RF Modem/Line Driver

CommunicationsLinkDetailed block Diagram

(Sheet 6)

Change 2 3-46.3/ (3-46.4 blank)
S100 ASOS Site Technical Manual

Figure 3.4.5a. DCP Pressure Sensors Detailed

Block Diagram

Change 2 3-47/ (3-48 blank)
S100 ASOS Site Technical Manual

Figure 3.4.6.DCPFiberopticModulesDetailed

Block Diagram

Change 1 3-49/ (3-50 blank)
S100 ASOS Site Technical Manual

Figure 3.4.7. DCP Power Monitoring and

Digital I/O Diagram (Sheet 1 of 3)

Change 2 3-51/ (3-52 blank)
S100 ASOS Site Technical Manual

Figure 3.4.7. DCP Power Monitoring and

Digital I/O Diagram (Sheet 2 of 3)

Change 2 3-53/ (3-54 blank)
S100 ASOS Site Technical Manual

Figure 3.4.7. DCP Power Monitoring and

Digital I/O Diagram (Sheet 3 of 3)

3-55/ (3-56 blank)
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Change 2 3-57

3.4.3.6 Power Distribution and Control.AC and dc power distribution are described using figure 3.4.8 which

consists of several sheets that are divided to depict distinct sections of the power distribution circuitry. The ac

wiring from the facility input power source to the DCP equipment cabinet is shown as well as the routing through

the DCP Faraday box. The ac power distribution throughout the DCP, including the power reset assembly, UPS

bypass circuit, UPS, and circuit breaker modules, is also depicted, with point-to-point wiring integrity. The dc

power distribution circuitry throughout the DCP is shown, including fiberoptic modules and rf modems.

As previously described, there are three configurations for rf modem installation in the DCP. Sheets 7 and 9 of $

figure 3.4.8 show power distribution for original equipment AAI rf modems. Sheet 11 shows the differences for $

a system that has been modified for Motorola modems. Sheet 11A shows the differences for a system that has been $

modified for Motorola modems and equipped with Johnson Data modems. Sheet 8 corresponds to a system built $

with Motorola modems as original equipment.

Facility power is provided to the DCP via the ac junction box. The ac junction box contains a circuit breaker panel

with circuit breakers for the DCP, auxiliary DCP, clearance lights, and a ground fault interrupt (GFI) receptacle.

In addition, a main circuit breaker is provided for disconnecting all ac power. The DCP ac power is routed to the

DCP power reset assembly and then distributed within the DCP Faraday box. 

Power Reset Assembly A9 provides the DCP with proper power reset and (in Class II systems) UPS bypass

capability. The assembly consists of a solid state Time Delay Relay A9K1, Digital I/O Module A9K2 (Class II

only), and Power Relay A9K3 (Class II only). During initial turn-on, power is applied to solid state Time Delay

Relay A9K1 which delays power application for approximately three seconds then distributes power throughout

the DCP in Class I systems. In Class II systems power is applied to Power Relay A9K3 normal closed contacts

and the UPS. Power to Power Relay A9K3 normally closed contacts is routed through AC Distribution Strips A17

and A18 where it is distributed to DCP assemblies. 

After power is applied to Class II DCP assemblies, ASOS operational software monitors Power Relay A9K3

bypass status via Digital I/O Module A9K2 and Digital I/O Board A2XA12. When UPS status is good, Power

Relay A9K3 is energized via Digital I/O Board A1A2XA12 and Digital I/O Module A9K2 to route power from

the UPS output applied to Power Relay A9K3 normal open contacts to the DCP. 

AC Distribution Strips A17 and A18 are used to break out the power for separate wiring, with AC Distribution

Strip A17 designated for 110 vac (hot) distribution and AC Distribution Strip A18 designated for ac neutral

distribution. Earth ground is provided by the rails upon which the individual distribution terminals are mounted.

AC power is provided to the rest of the DCP via connectors J1 through J4 and J9. AC power for each of the

sensors as well as their heaters is applied to the Faraday box at connectors J5 and J6. These connectors are wired

to AC Distribution Strips A17 and A18 to provide separate ac power lines to the individual sensors external to the

DCP. Individual distribution terminals (#3 through #26) provide built-in surge protection for these ac runs.

Faraday box connectors J1 through J4 and J9 provide ac power to the rest of the DCP over an internal wiring

harness. Connectors J1 and J3 provide ac power for the primary (first eight) sensors and their internal heaters,

respectively. Connectors J2 and J4 of the Faraday box provide ac power for the optional secondary (second group

of eight) sensors and their internal heaters. Connector J9 provides ac power for the heaters in the DCP equipment

cabinet itself. Circuit breakers A1 and A10 in Circuit Breaker Rack A1A3 are used to control the primary and

secondary power inputs. The outputs of these circuit breakers provide ac power to separate terminals on AC Power

Distribution Assembly A1A4. AC neutral lines from connectors J1 and J2 are connected directly to AC Power

Distribution Assembly A1A4.

AC Power Distribution Assembly A1A4 is the breakout point for the ac power wiring within the DCP. This power

distribution strip provides separate power wiring to assemblies within the DCP and provides room for additional

wiring to a secondary UPS.

A secondary UPS is an option that would be installed in an auxiliary DCP equipment cabinet in the event that

more than nine sensors were attached to a Class II DCP.
ASOS Site Technical Manual S100

3-58 Change 2

3.4.3.6.1 AC Distribution - General. Class II DCP cabinets contain uninterruptible power supplies, which

$ provide UPS functions. Uninterruptible power supplies can be one of three types depending on the serial number

$ of the DCP.

$ a. SOLA UPS 62828-90057 is installed in DCP serial numbers 438 and below.

$ b. Deltek UPS 62828-90338-10 or 62828-90338-20 is installed in DCP serial numbers 439 and

$ above.

Class I DCP's have no uninterruptible power supplies. The following paragraphs describe the ac power

distribution for the two uninterruptible power supplies.

3.4.3.6.1.1 AC Distribution for Uninterruptible Power Supply 62828-90057-10 (Figure 3.4.8, Sheet 3). For

Class II systems, a UPS is mounted in the DCP to provide a backup ac power source for the DCP and up to nine

sensors. If more than nine sensors are attached to the DCP, an optional secondary UPS is provided in an auxiliary

DCP equipment cabinet. The UPS is not a unit in itself, but is the collection of the following FRU's:

a. 1.5 KVA Filter Board A1A6

b. 1.5 KVA Inverter Board A5

c. 1.5 KVA Transformer A1T1

d. Battery Box A2

e. Fuse A1F1

f. RS-232 Interface Board A1A8

g. Status Panel Board A1A7

h. UPS Fan A1B1

1.5 KVA Filter Board A1A6 receives the primary ac input power from the Faraday box via Circuit Breaker

Module A1A3A1 and AC Power Distribution Assembly A1A4. 1.5 KVA Filter Board A1A6 filters the input line

voltage and routes it to 1.5 KVA Inverter Board A5 on the WHT/BLK (neut) and BLK/RED (line) wires of W031.

During normal (noninterrupted power) operation, the inverter board monitors the input voltage from the filter

board and regulates it to provide a constant 120 vac output signal. The inverter board uses transformer T1 to

perform this regulation. The secondary coil of T1 has multiple taps that are routed to tap-switching triacs on the

inverter board. If the inverter senses that the input line voltage is low, it causes one of the triacs to switch in a T1

secondary tap that steps up the voltage to the required level. The stepped-up voltage is then output from the

BLK/WHT terminal of the inverter board to connector J10 of 1.5 KVA Filter Board A1A6. Similarly, if the

inverter board senses that the input ac voltage is high, the T1 secondary tap is changed to step down the voltage

to the required level, and the stepped-down voltage is output to the filter board. The filter board filters the inverter

board ac voltage and outputs the regulated voltage from connector J7 as the UPS output ac signal.

When the inverter board senses a loss of its input ac signal, it uses transformer T1 to convert dc voltage from

Battery Box A2 to a backup ac signal. Battery Box A2 contains five 12 vdc batteries wired in series to provide a

total of 60 vdc. This dc voltage is applied through fuse A1F1 to the RED terminal of the inverter board, where it

is then routed to the center tap of the primary coil of transformer T1. When the inverter board senses a loss in the

input ac signal from the filter board, it alternatingly switches in the other two primary leads of transformer T1

(BLU2 and YEL2). This causes alternating current in the primary, which is induced to the secondary coil of

transformer T1. The inverter board then uses its tap-switching triacs, as described above, to output a regulated ac

voltage to the filter board.
S100 ASOS Site Technical Manual

Figure 3.4.8. DCP AC and DC Power

Distribution Detailed Block Diagram (Sheet 1

of 12) $

Change 1 3-59/ (3-60 blank)
S100 ASOS Site Technical Manual

Figure 3.4.8. DCP AC and DC Power

Distribution Detailed Block Diagram (Sheet 2)

Change 1 3-60/ (3-62 blank)
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Figure 3.4.8. DCP AC and DC Power

Distribution Detailed Block Diagram (Sheet 3)

Change 1 3-63/ (3-64 blank)
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Figure 3.4.8. DCP AC and DC Power

Distribution Detailed Block Diagram (Sheet 4)

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Figure 3.4.8. DCP AC and DC Power

Distribution Detailed Block Diagram (Sheet 5)

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S100 ASOS Site Technical Manual

Figure 3.4.8. DCP AC and DC Power

Distribution Detailed Block Diagram (Sheet 6)

Change 1 3-69/ (3-70 blank)
DCP WIRED FOR AAI MODEMS

S100 ASOS Site Technical Manual

Figure 3.4.8. DCP AC and DC Power

Distribution Detailed Block Diagram (Sheet 7)

Change 1 3-70/ (3-72 blank)
DCP WIRED FOR MOTOROLA MODEMS

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Figure 3.4.8. DCP AC and DC Power

Distribution Detailed Block Diagram (Sheet 8)

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Figure 3.4.8. DCP AC and DC Power

Distribution Detailed Block Diagram (Sht 9)

Change 1 3-75/ (3-76 blank)
“AS BUILT” BOTH HEATERS ACTIVATE AT 40° AND

DEACTIVATE AT 60°

S100 ASOS Site Technical Manual

Figure 3.4.8. DCP AC and DC Power

Distribution Detailed Block Diagram (Sht 10)

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S100 ASOS Site Technical Manual

Figure 3.4.8. DCP AC and DC Power Distribution

Detailed Block Diagram (Sheet 11)

Change 1 3-79/ (3-80 blank)

S100 ASOS Site Technical Manual
SYSTEM CONVERTED FROM AAI TO MOTOROLA MODEMS Figure 3.4.8. DCP AC and DC Power

EQUIPPED WITH JOHNSON DATA MODEMS Distribution Detailed Block Diagram (Sheet 11A)

Change 2 3-80.1/ (3-80.2 blank)
S100 ASOS Site Technical Manual

Figure 3.4.8. DCP AC and DC Power Distribution

Detailed Block Diagram (Sheet 12)

Change 2 3-80.3/ (3-80.4 blank) $
S100 ASOS Site Technical Manual

3-81

Figure 3.4.9. AC Power Distribution Assembly A1A4

The regulated, filtered UPS ac output signal from the filter board is routed to AC Power Distribution

Assembly A1A4 for distribution to DCP assemblies. Units that receive the UPS output voltage from the

distribution assembly are the dc power supplies, the card cage assembly, and circuit breaker rack (for use by

sensor electronics only).

RS-232 Interface Board A1A8 allows the CPU to monitor the operational status of the UPS. The inverter

board contains circuitry to monitor the status of the ac input and output voltages, battery voltages,

tap-switching triac status, etc. During CST, the CPU communicates with the inverter board via the RS-232

interface board to obtain status data. The CPU analyzes the UPS data and displays the results on the OID

DCP UPS page OID. A UPS bypass circuit in class II DCP’s allows operation on primary input power if the

UPS isinoperative or when commanded by software. The digital output line operatessolid-state relay A9K2

which operatestriple-pole, double-throw relay A9K3. Relay A9K3 selects ac power from the unconditioned

input or from UPS output. A jumper can be placed across the solid-state relay contacts to inhibit the UPS

bypass function. The third set of A9K3 contacts closes a ground signal path to the processor via the DIO

board. A 3-second time-delay relay (A9K1) has also been included to ensure correct power-up reset in DCP

equipment. The TD relay is energized by unconditioned primary ac power input. The TD relay releases with

minimal delay uponmomentary interruption of power, butrequires powerto be restored for at least 3 seconds

before power is reapplied to DCP equipment and to the UPS input.

The above paragraphs describe the distribution of primary ac power for a DCP on a ClassIIsystem. Because

a Class I DCP does not contain a UPS, jumpers are installed between the UPS input and UPS output

terminals on AC Distribution Strip A1A4. That is, jumpers are installed between terminals 1B and 12A (115

vac), and between 9B and 17C (Neutral).

3.4.3.6.1.2 AC Distribution for Uninterruptible Power Supply 62828-90338-10 or 62828-90338-20 $

(Figure 3.4.8, Sheet 4). For Class II systems, a UPS is mounted in the DCP to provide a backup ac power $

source for the DCP and up to nine sensors. If more than nine sensors are connected to the DCP, an optional

secondary UPS is provided in an auxiliary DCP equipment cabinet. The UPS is an FRU. $

Input ac power is applied through connector P45. During normal (noninterrupted power) operation, the UPS
ASOS Site Technical Manual S100

3-82 Change 1

assembly monitors the input signal internally and maintains a steady output voltage.

When the UPS assembly detects a loss of its input ac signal, it converts dc voltage from Battery Box A2 to a

backup signal. Battery Box A2 contains four 12-vdc batteries wired in series to provide a total of 48 vdc.

The UPS regulated, filtered ac output signal is routed to Power Distribution Assembly A1A4 for distribution to

DCP assemblies. Units that receive the UPS output voltage from the power distribution assembly are the dc power

supply enclosure, card cage assembly, and circuit breaker rack (for use by sensor electronics only).

The RS-232 COMM PORT on the UPS allows the CPU to monitor the operational status of the UPS. The UPS

contains circuitry to monitor the status of the ac input and output voltages, battery voltages, etc. During CST, the

CPU communicates with the UPS to obtain these status data. The CPU analyzes these UPS data and displays the

results on the DCP UPS page of the OID.

The ACU polls the DCP UPS every minute with a dump status command to obtain a current status of the UPS.

BATTERY VOLTAGE status (provided as a numerical value) indicates the current voltages provided by the

battery box. INPUT VOLTAGE status (provided as a numerical value) indicates the current value (in vac) of the

facility input voltage being received by the UPS. OUTPUT VOLTAGE status (provided as a numerical value)

indicates the current value (in vac) of the regulated ac voltage being output from the UPS. UPS OPERATION

status indicates whether or not the UPS is functioning in a normal (indicated by a P (utility is OK, battery is OK,

and UPS is in its normal state)) or abnormal operation (indicated by an F). ON AC LINE status indicates the power

source on which the UPS is operating (P = facility input (ac line), F = UPS operating on battery backup).

BATTERY status (provided as either P for pass or F for fail) indicates if the battery power is low from the battery

box supply. INVERTER status indicates whether the internal inverter is operating in overvoltage or undervoltage

condition. GROUND status (provided as either P for pass or F for fail) checks for a ground failure. UTILITY status

(P for pass or F for fail) indicates an overvoltage or unsynchronized signal from facility power. When the UPS is

on battery power and facility power returns, the UPS must synchronize the phasing from the inverter to match the

phasing of the facility power before switching to UPS operation under facility power. TIMEOUT status (P for pass

or F for fail) indicates a failure in the event that the CPU receives no response from the UPS. BATTERY

MANAGEMENT status (provided as a word description) indicates if the current from the batteries is FLOATING

(trickle charge), RESTING (not charging or discharging), CHARGING, or DISCHARGING. Finally, LINE

REGULATION status (provided as a word description) indicates whether the UPS is maintaining a STEP-UP,

STEP DOWN, or NORMAL voltage from facility power.

$ A UPS bypass circuit in class II DCP’s allows operation on primary input power if the UPS is inoperative or when

$ commanded by software. The digital output line operates solid-state relay A9K2 which operates triple-pole,

$ double-throw relay A9K3. Relay A9K3 selects ac power from the unconditioned input or from UPS output. A

$ jumper can be placed across the solid-state relay contacts to inhibit the UPS bypass function. The third set of A9K3

$ contacts closes a ground signal path to the processor via the DIO board. A 3-second time-delay relay (A9K1) has

$ also been included to ensure correct power-up reset in DCP equipment. The TD relay is energized by

$ unconditioned primary ac power input. The TD relay releases with minimal delay upon momentary interruption

$ of power, but requires power to be restored for at least 3 seconds before power is reapplied to DCP equipment and

$ to the UPS input.

Because the Class I DCP does not contain a UPS, jumpers are installed between the UPS input and output

terminals on AC Distribution Strip A1A4; that is, jumpers are installed between terminals 1B and 12A (115 vac)

and between terminals 9B and 17C (neutral) to bypass the Class II UPS described above.

3.4.3.6.2 DC Power Distribution. Circuit Breaker Modules A2 through A9 and A11 through A18 control

the application of ac power to each of the weather sensors. Circuit Breaker Modules A2 through A9 are

designated for use as the primary DCP sensors (sensors 1 through 8). Circuit Breaker Modules A11 through

A18 are designated for use by auxiliary DCP sensors. A full complement of circuit breaker modules may not

be present, depending on the number ofsensors connected for the DCP. Two different types ofsensor circuit
S100 ASOS Site Technical Manual

3-83

breaker modules are available to match the power requirements of the individual sensors. The main

difference between the two types of circuit breaker modules is the number of circuit breakers they contain.

Those sensors which require ac powerfortheir electronics and their heaters are provided with circuit breaker

modules containing two circuit breakers. Sensors that have no electronics or no heaters are provided with

circuit breaker modules containing only one circuit breaker. Figure 3.4.8 illustrates a typical circuit breaker

module and uses dashed lines to indicate that one or two circuit breakers may be used. Eight slots in Circuit

Breaker Rack A1A3 are reserved for those sensors with both electronics and heaters. AC Power Distribution

Assembly A1A4 provides the ac power source for application to the sensors. Circuit breaker CB2 in the

circuit breaker module controls the application of ac power to the sensor heaters directly. Circuit breaker

CB1 in the circuit breaker module is incorporated into a control and monitor circuit that allows software

control of power to the sensor. A control signal from the CPU is applied via Digital I/O Board A1A2A12 to

energize a normally closed relay on the circuit breaker module and disrupt ac power to the associated sensor.

In addition, the circuit breaker module contains a current sensing circuit that produces a voltage level

indicating the amount of ac current being used by the sensor load. This sensed current signal is applied to

one of the two A/D boards (A1A2A9 or A1A2A11) in the card rack assembly for monitoring by the CPU.

The ac power outputs of the circuit breaker modules are applied to connectors J5 and J6 of the Faraday box

for application to the external sensors.

DC power for the DCP is provided by four power supplies located on Power Supply Assembly A4 in the

DCP. These power supplies receive ac input power originating at AC Power Distribution Assembly A1A4

through DC Power Distribution Assembly A4A1. The terminal blocks on the dc distribution assembly

provide fuse protection for the power supply ac inputs. The power supplies are wired in parallel at DC

Distribution Assembly A4A1, with two supplies providing +5 vdc power (A4PS1 and A4PS2) and two

supplies providing ±12 vdc power (A4PS3 and A4PS4). The power supply outputs are connected to DC

Distribution Assembly A4A1 via diodes for current protection and isolation. DC Distribution Assembly

A4A1 breaks out the dc power for separate runs to those DCP assemblies requiring dc power. Figure 3.4.10

identifies the dc power voltages provided according to the individual terminal blocks. The outputs of each

of the power supplies are also distributed to VME Resistor Board A1A2A10 in the circuit card rack. The

VME resistor board scalesthese powersupplymonitoring signals and passesthemon to A/DBoard A1A2A9

for monitoring by the CPU.

The DCP equipment cabinet heating system consists of two solid state relays, three thermal switches, and $

one or two heaters. Heater HR1 (Class I and Class II systems) contains two heating elements totaling $

750-watts. Heater HR2 is a 350-watt silicon strip element provided in Class II systems only. The DCP $

equipment cabinet heaters are controlled by the three thermal switches and the two solid state relays. The $

solid state relay terminals are connected to these switches to control the application of power to the cabinet $

heaters. Switch S1 controls power to switches S2 and S3. Switch S2 controls power to half of HR1 and to $

HR2. Switch S3 controls power to the remaining half of HR1. Switch S1 closesto provide power to switches $

S2 and S3 when internal cabinet temperature falls to 40°F. At 40°F, S2 and S3 close to provide power to the $

heaters. When internal cabinet temperature climbs to 60°F, switches S2 and S3 open to remove power from $

cabinet heaters. Switch S1 also opens at 60°F disabling switches S2 and S3 to prevent over temperature $

conditions (should S2 or S3 fail to open). Both heaters will come on at 40°F and go off at 60°F. $

$

In the special application DCP equipped with pressure sensors, S1 enables switches S2 and S3 when the $

temperature falls to 60°F. At 50°F, switches S2 and S3 close to turn on all heater power. When the $

temperature climbs to 70°F, switches S2 and S3 open to remove heater power. Should either S2 or S3 fail $

to open and cabinet temperature climbs to 80°, switch S1 opens to disable switches S2 and S3 and remove $

power from the heaters. $
ASOS Site Technical Manual S100

3-84 Change 1

Figure 3.4.10. DC Power Distribution Assembly A4A1
S100 ASOS Site Technical Manual

Change 2 3-85

WARNING

SECTION V. MAINTENANCE

3.5.1 INTRODUCTION

This section contains the preventive and corrective maintenance procedures for the data collection package (DCP).

Preventive maintenance identifies the periodic tasks required to maintain the DCP in peak operational condition.

Corrective maintenance procedures are provided for performance of appropriate diagnostic routines, fault isolation

procedures, and the removal and installation of faulty DCP field replaceable units (FRU's).

3.5.2 PREVENTIVE MAINTENANCE

Preventive maintenance consists of those procedures that are performed on a scheduled basis. All preventive

maintenance tasks for the DCP and auxiliary DCP are identified in table 3.5.1. If the performance of any

preventive maintenance tasks indicates a malfunction, corrective maintenance must be performed as described in

paragraph 3.5.3. 

Table 3.5.1. DCP Preventive Maintenance Schedule

Interval What To Do How To Do It

90 days Clean and inspect cabinets. Paragraph 3.5.2.1 

Semiannually Check/clean batteries. Paragraph 3.5.2.2

3.5.2.1 Cabinet Cleaning and Inspection. Cleaning of the DCP equipment cabinet is required to remove dust

and dirt that accumulates on the external surface and to remove any internal debris. At selected sites where

pressure sensors are installed in the DCP, the desiccant is inspected. The DCP equipment cabinet cleaning and

inspection procedure is provided in table 3.5.2.

3.5.2.2 Check/Clean Batteries. For Class II systems, there are three types of battery packs in Battery Box A2. $

Battery pack 62828-40062-10 contains five batteries and is used with SOLA UPS 62828-90057. Battery pack $

62828-40062-30 (4 batteries) or 62828-90360-10 (5 batteries) are used with either of the Deltek UPS, 62828- $

90038-10 or 62828-90338-20. The batteries should be checked and cleaned semiannually or whenever the CST $

indicates that the batteries have failed or are low. The individual batteries should be removed from the battery box

per the battery removal procedure of table 3.5.17. The batteries should be checked for leakage or corrosion on the

terminals and replaced according to the installation procedure of table 3.5.17. If a battery is found to be leaking,

it should be replaced. If battery terminals are corroded, they should be cleaned with a terminal brush or other wire

brush before the battery is reinstalled.

Table 3.5.2. DCP Equipment Cabinet Cleaning

Step Procedure

Tools and material required:

 Hand-held vacuum cleaner

 Mild detergent and water

 Lint-free cloths

Death or severe injury may result if power is not removed from DCP equipment cabinet prior to

performing maintenance activities inside the cabinet. Ensure that UPS POWER switch is set to 0 (off)

and DCP primary circuit breaker module is set to off and that facility power is removed.

NOTE

Wring out cloth before washing surfaces.

1 Set UPS POWER switch S1 to off (0) position.

2 Set primary Circuit Breaker Module A1A3A1 to OFF position.
ASOS Site Technical Manual S100

3-86 Change 1

Table 3.5.2. DCP Equipment Cabinet Cleaning -CONT

Step Procedure

3 Remove facility power from the DCP by setting DCP circuit breaker in ac junction box to off.

4 Clean external surfaces using lint-free cloth dampened with a mixture of mild detergent and water.

5 Dry surfaces using lint-free cloth.

6 Using hand-held vacuum cleaner, remove any loose debris inside DCP equipment cabinet.

$ 6.1

$

Inspect desiccant in desiccant dryer (Dryer, figure 3.1.3 sheet 2). If indicated by color, remove and replace

desiccant (refer to table 3.5.2A).

7 Apply facility power to DCP by setting DCP circuit breaker in ac junction box to on position.

8 Set primary Circuit Breaker Module A1A3A1 to on position.

9 Set UPS POWER switch on UPS status panel to 1 (on) position.

$$ Table 3.5.2A. Dessicant Replacement Procedure

$ Step Procedure

$ Tools and material required:

$ Hand-held vacuum cleaner

$ Mild detergent and water

$ Lint-free cloth(s).

$

$ CAUTION

$ Before handling the desiccant, the Material Safety Data Sheet (MSDS) for Davidson Blue Indicating

$ Gel issued by W.R. Grace & Co., P.O. Box 2117, Baltimore, MD 21203 (telephone: 410-659-9000)

$ or the current supplier should be obtained from the supervisor and read. 

$

$ NOTE

$ Wring out cloth before washing screens.

$

$ 1 At DCP cabinet, loosen dryer clamp ring, slide off metal bowl guard, and unscrew bowl from top housing.

$ 2 Pour out used desiccant into plastic bag and seal bag for proper disposal.

$ 3

$

Open new container and refill bowl, shaking or tapping bowl to settle desiccant to 1/2 inch from top of bowl.

$ CAUTION

$ Do not install the bowl without installing the metal bowl guard.

$ 4 Replace bowl and bowl guard and clamp ring onto unit. Ensure that clamp ring is securely in place.

$

3.5.3 CORRECTIVE MAINTENANCE

3.5.3.1 Introduction. Corrective maintenance involves the isolation, removal, and replacement of faulty FRU's.

The ASOS is equipped with a powerful automatic self-test program that is designed to isolate most faults to a

single FRU. However, because of the system hardware configuration, there will be instances when the diagnostics

can only isolate to a group of FRU's, such as a sensor or an I/O channel. The troubleshooting approach for single

FRU and group FRU types of conditions is different.

When the FRU is specifically called out, the technician need only replace the faulty unit. When a group of FRU's

is called out, the technician must isolate the failed FRU by referencing the theory of operation and associated

drawings and following two basic procedures. The first procedure involves connector checks, which ensure that

all boards, cables, and connectors are present and properly connected. The second procedure involves ac and dc

power supply tests. Although the system monitors all critical power supply voltages in the ACU, DCP, and sensors,

failure of a power supply may result in a loss of communications between the circuit powered by that supply and

the rest of the system.
S100 ASOS Site Technical Manual

Change 1 3-87

Power supplies are tested through both visual and mechanical inspection. Before measuring any voltages, the

technician should visually inspect the suspected area for obvious signs of power supply failure. During this

inspection, the technician should pay particular attention to circuit breakers, panel lights, and light emitting diode

(LED) indicators on the units to ensure that they are functioning normally. The physical checks involve checking

fuses and the power supply voltages using a digital multimeter (DMM). In most cases, these tests will isolate the

fault.

After an FRU has been replaced, the technician must allow the ASOS to automatically initialize upon the

application of primary power to the ACU and verify that the CST diagnostics run without failure. The

technician should also display the corresponding maintenance page and the OID and ensure that the FRU

passes its CST. Table 3.5.3 provides corrective maintenance symptom analysis information.

3.5.3.2 UPS Checks. In a Class IIsystem with serial number 438 and below, the UPS provides ac power for

all electronics in the DCP and associated sensors, but not for the heaters in the DCP and sensors. If power

is not applied to the DCP when the UPS POWER switch on the UPS is set to ON (1) but the heaters still

operate, there could be a failure in the UPS. During operation, there are a number of tools available to fault

isolate the UPS. The CST continually checks the status of the UPS and provides status information on the

DCP UPS page of the OID. Error messages are printed on the printer and entered into the maintenance log.

Also, the status LED's on the UPS status panel provide valuable information for analyzing UPS problems.

Table 3.5.4 provides methods for troubleshooting the UPS based on observed symptoms. Table 3.5.5

provides a procedure to prepare the UPS for maintenance and to return the UPS to operation following

service.

In a Class II system with serial number 439 and above, the UPS provides the same functions except the

troubleshooting procedures are conducted primarily fromthe OID page. Table 3.5.6 provides proceduresfor

troubleshooting the UPS based on observed symptoms.

3.5.3.3 VME Card Rack Check. The DCP VME cards page displaysthe overallstatus ofthe DCP card rack

boards. In a Class II system, the DCP is configured with redundant hardware for increased system

availability. The technician must examine the maintenance log periodically to replace redundant faulty units

to reduce the possibility of redundant malfunctions. When the CST identifies a single board as a faulty FRU,

it must be replaced. Failure of all or multiple boards indicates that a failure on any board tied to VMEbus

could exist. This is a catastrophic failure and requires the technician to isolate the malfunctioning board

through board removal and replacement. Table 3.5.7 provides procedures to isolate the faulty FRU.

Table 3.5.3. Corrective Maintenance Symptom Analysis

 Symptom What to Do How to Do It

System is completely dead Check ac and dc power. Reference DCP ac/dc power distribution

diagramfigure 3.4.8 and verify presence of

ac and dc voltages. Check fuses on DC

Power Distribution Assembly A4A1.

Loss of communication with ACU Check ACU/DCP rf

communications link.

Table 2.5.7

Problem with DCP uninterruptible power

supply (UPS) in Class II system

Check UPS. Paragraph 3.5.3.2

DCP computer does not initialize Check VME card rack. Paragraph 3.5.3.3

Loss of communication with a sensor Check circuit breaker

module.

Inspect Circuit Breaker Rack A1A3 for

tripped sensor module.

Check DCP/sensor

fiberoptic link.

Paragraph 1.5.4.3

Check DCP SIO board. Paragraph 3.5.3.4

DCP equipment cabinet overheats or

becomes too cold.

Check DCP heater

circuit.

Paragraph 3.5.3.5
ASOS Site Technical Manual S100

3-88 Change 1

Table 3.5.4. DCP UPS Fault Isolation (62828-90057)

 Step Symptom Checks/Corrective Actions

$ 1 UPS will not turn on.

Indicators on Status

Panel Board A1A7 are

all extinguished.

$ Ensure that facility power is applied to DCP, UPS bypass, and UPS.

Check Circuit Breaker Module A1A3A1. If tripped, reset A1A3A1 and cycle

OUTPUT POWER switch on status panel off and back on.

Remove power from UPS and remove UPS cover per table 3.5.5.

Visually inspect 1.5 KVA Filter Board A1A6 for damage. Replace filter board

if damaged.

Loosen screw at top of Circuit Breaker Rack A1A3 and swing rack down on

hinges to access AC Power Distribution Assembly A1A4.

Apply facility power to DCP by setting DCP circuit breaker in ac junction box to

ON. 

Using DMM, verify 120 ±10% vac between terminals 1A and 9A of AC Power

Distribution Assembly A1A4. If voltage is not present, replace Circuit Breaker

CB1 on circuit breaker Module A1A3A1.

Verify 120 ±10% vac between WHT/BLK and BLK/RED terminals of 1.5 KVA

Filter Board A1A6. If voltage is not present, replace A1A6.

Replace 1.5 KVA Inverter Board A5.

If problem, persists, replace transformer A1T1.

2 UPS will not turn on.

BATTERY indicator on

status panel is on or

blinking but OUTPUT

indicator is off.

This is normal situation with OUTPUT POWER switch set to off (0). Therefore,

ensure that OUTPUT POWER switch on Status Panel Board A1A7 is set to on

(1) position.

Remove power from UPS and remove UPS cover per table 3.5.5.

Inspect ribbon cable on Status Panel Board A1A7 for damage or loose

connections.

Set OUTPUT POWER switch to on (1) position. Using DMM, ensure continuity

across terminals of switch. Replace switch if no continuity.

Set OUTPUT POWER switch to off (0) position. 

Install UPS cover per table 3.5.5. 

To ensure that problem was not due to cable connections, set OUTPUT POWER

switch to on (1) position and attempt to operate UPS again.

If problem is not corrected, Replace Status Panel Board A1A7.

If problem persists, replace 1.5 KVA Inverter Board A5.
S100 ASOS Site Technical Manual

3-89

Table 3.5.4. DCP UPS Fault Isolation (62828-90057) - CONT

 Step Symptom Checks/Corrective Actions

3 UPS operates, but CPU

cannot communicate with

RS-232 Interface Board

A1A8. 

Failure indicated for

TIMEOUT test or

RS-232 test on DCP UPS

page at OID.

Select DCP #1 SIO page on OID.

From DCP #1 SIO page, press TEST key to run CST on this SIO board. If port

#1 (the UPS port) fails LOOPBACK test or XMIT ERRORS test, replace SIO

board #1 (A1A2A4). If both tests pass, continue.

Loosen screw on top of Circuit Breaker Rack A1A3 and swing rack down on

hinges to access UPS RS-232 connector.

Disconnect W015 connector P22 from J20 of RS-232 Interface Board A1A8.

Insert RS-232 test box between W015-P22 and J20 of RS-232 Interface Board

A1A8.

Select DCP UPS page at OID.

From DCP UPS page, press TEST key to run CST on UPS.

OnRS-232 tester, ensure that transmit(TxD) and receive (RxD)signals are being

passed between the UPS and the SIO board (at least once per minute). If both

signals are active, replace one of the following (in order) and retry UPS.

a. SIO board #1 (A1A2A4)

b. UPS RS-232 Interface Board A1A8

If transmit signal is missing, replace SIO board #1 (A1A2A4).

If receive signal is missing, continue.

Remove power from UPS and remove UPS cover per table 3.5.5.

Inspect ribbon cable between RS-232 Interface Board A1A8 and 1.5 KVA

Inverter Board A5. 

Ensure that ribbon cable is not twisted or damaged. Reseat connectors to ensure

proper connection.

After checking ribbon cable, replace cover per table 3.5.5 and operate system

again.

If problem is not corrected, replace RS-232 Interface Board A1A8.

If problem persists, replace 1.5 KVA Inverter Board A5.
ASOS Site Technical Manual S100

Table 3.5.4. DCP UPS Fault Isolation (62828-90057) - CONT

 Step Symptom Checks/Corrective Actions

3-90

WARNING

WARNING

4 ALARM indicator on

Status PanelBoard A1A7

is illuminated.

Overheat condition is likely. 

On UPS Status Panel Board A1A7, set OUTPUT POWER switch to off (0).

Inspect inside of DCP equipment cabinet to ensure proper ventilation around

UPS. 

Ensure that connector W031-P1 is securely attached to connector J1 on Battery

Box A2.

Allow UPS to cool.

Set UPS OUTPUT POWER switch to on (1) position. 

If UPS operates after allowing to cool, check operation of UPS fan A1B1 by

setting Circuit Breaker Module A1A3A1 to OFF. AC FAIL indicator on Status

Panel Board A1A7 illuminates and UPS enters inverter mode to provide battery

backup power. While UPS is operating in inverter mode, ensure that UPS fan

A1B1 is operating. If not, proceed to step 11.

If, after cooling, UPS failsto turn on and ALARM indicator remainsilluminated,

proceed to step 5.

5 With UPS cool, ALARM

indicator on UPS Status

Panel Board A1A7 is

illuminated.

Set UPS OUTPUT POWER switch to off (0) position.

Ensure connector W031-P1 is securely attached to connector J1 on Battery Box

A2.

Attempt to operate UPS by setting OUTPUT POWER switch to on (1) position.

Remove power from UPS and remove UPS cover per table 3.5.5.

Ensure that W031-P1 connector is disconnected from Battery

Box A2 before attempting to test fuse A1F1 for continuity.

Failure to disconnect battery box may result in injury to

personnel or damage to equipment.

Ensure that connector W031-P1 is disconnected from Battery Box A2.

Inspect UPS fuse A1F1 and test for continuity using DMM. If fuse is good,

proceed to nextstep. Iffuse is open, replace fuse.If, after replacing fuse, problem

persists and fuse again opens, replace 1.5 KVA Inverter Board A5.

Exercise extreme caution when connecting UPS battery and

taking measurements with UPS cover off. Death or severe

injury may result if contact is made with battery terminals or

wires.

Connect battery cable W031-P1 to connector J1 on Battery Box A2.

Using DMM, measure dc voltage at battery terminals (RED + and BLK -) of 1.5

KVA Inverter Board A5. Disconnect battery cable W031-P1 from connector J1

on Battery Box A2.
S100 ASOS Site Technical Manual

Table 3.5.4. DCP UPS Fault Isolation (62828-90057) - CONT

 Step Symptom Checks/Corrective Actions

3-91

WARNING

If indication was less than 55 vdc, replace batteries BT1 through BT5 in Battery

Box A2. If problem persists, replace 1.5 KVA Inverter Board A5.

If battery voltage is above 55 vdc, replace 1.5 KVA Inverter Board A5.

6 After 24 hours of

continuous charging

(UPS has operated

continually on facility

power), BATTERY

indicator on UPS Status

Panel Board A1A7

blinks, indicating a low

battery. 

Remove power from UPS and remove UPS cover per table 3.5.5.

Ensure that W031-P1 connector is disconnected from Battery

Box A2 before attempting to test fuse A1F1 for continuity.

Failure to disconnect battery box may result in injury to

personnel or damage to equipment.

Inspect UPS fuse A1F1 and test for continuity using DMM. If fuse is good,

proceed to nextstep. Iffuse is open, replace fuse. If, after replacing fuse, problem

persists and fuse again opens, replace 1.5 KVA Inverter Board A5.

Replace batteries BT1 through BT5 in Battery Box A2.

If problem persists, replace 1.5 KVA Inverter Board A5.

If problem persists, replace transformer A1T1.

7 One or more indicators

on Status Panel Board

A1A7 do not illuminate.

Remove power from UPS and remove UPS cover per table 3.5.5.

Inspect ribbon cable on Status Panel Board A1A7 for damage or loose

connections.

After checking ribbon cable, install UPS cover per Table 3.5.5 and operate

system again. 

If problem persists, replace Status Panel Board A1A7.

If problem persists, replace 1.5 KVA Inverter Board A5.

 8 UPS beeps when OUTPUT POWER switch is

set to on (1) position.

Replace 1.5 KVA Inverter Board A5.

NOTE

Failure may be the result of Circuit Breaker Module A1A3A1

tripping below its rated value. If problem persists after

performing the following corrective actions, A1A3A1 may be

faulty.
ASOS Site Technical Manual S100

Table 3.5.4. DCP UPS Fault Isolation (62828-90057) - CONT

 Step Symptom Checks/Corrective Actions

3-92

WARNING

9 Primary Circuit Breaker

Module A1A3A1

continually trips when

power is applied to DCP

equipment cabinet from

ac junction box.

With primaryCircuitBreakerModule A1A3A1 set to off,removeCircuit Breaker

Modules A1A3A2 through A9.

Apply power to DCP and set Circuit Breaker Module A1A3A1 to on. If breaker

does not trip, then there is a short circuit in circuit breaker modules or in

associated sensors. If breaker still trips, problem is in UPS; continue. 

Remove power from UPS and remove UPS cover per Table 3.5.5.

Inspect 1.5 KVA Filter Board A1A6 and 1.5 KVA Inverter Board A5 for signs

of damage. Replace if necessary.

On 1.5 KVA Filter Board A1A6, disconnect Circuit Breaker Module A1A3A1

load wire from BLK terminal.

Reset Circuit Breaker Module A1A3A1. 

Apply facility power to DCP by setting DCP circuit breaker in ac junction box to

ON. If Circuit Breaker Module A1A3A1 trips, replace circuit breaker CB1 on

module.

Remove facility power from DCP by setting DCP circuit breaker in ac junction

box to off.

Reconnect wire to BLK terminal of 1.5 KVA Filter Board A1A6.

On 1.5 KVA Inverter Board A5, disconnect input wires from WHT/BLK and

BLK/RED terminals.

Apply facility power to DCP by setting DCP circuit breaker in ac junction box to

ON. If Circuit Breaker Module A1A3A1 trips, replace 1.5 KVA Filter Board

A1A6.

Remove facility power from DCP by setting DCP circuit breaker in ac junction

box to off. 

Reconnect wires to WHT/BLK and BLK/RED terminals of 1.5 KVA Inverter

Board A5.

On 1.5 KVA Filter Board A1A6, disconnect connector from J10.

Ensure that W031-P1 connector is disconnected from Battery

Box A2 before attempting to disconnect transformer T1.

Failure to disconnect battery box may result in injury to

personnel or damage to equipment.

On 1.5 KVA Inverter Board A5, tag and disconnect 10 transformer T1 wiresfrom

their terminals.
S100 ASOS Site Technical Manual

Table 3.5.4. DCP UPS Fault Isolation (62828-90057) - CONT

 Step Symptom Checks/Corrective Actions

3-93

WARNING

Apply facility power to DCP by setting DCP circuit breaker in ac junction box to

on. If Circuit Breaker Module A1A3A1 trips, replace 1.5 KVA Inverter Board

A5. 

Remove facility power from DCP by setting DCP circuit breaker in ac junction

box to off.

Reconnect 10 transformer wires to respective connectors on 1.5 KVA Inverter

Board A5.

Apply facility power to DCP by setting DCP circuit breaker in ac junction box to

on. If Circuit Breaker Module A1A3A1 trips, replace transformer T1.

Remove facility power from DCP by setting DCP circuit breaker in ac junction

box to off. 

Reconnect connector to J10 on 1.5 KVA Filter Board A1A6.

Disconnect W015 connector P13 from connector J7 on 1.5 KVA Filter Board

A1A6.

Apply facility power to DCP by setting DCP circuit breaker in ac junction box to

on. If Circuit Breaker Module A1A3A1 trips, replace 1.5 KVA Filter Board

A1A6. If not, problem is not in UPS components, but a short circuit probably

exists in the DCP equipment cabinet wiring.

10 Failure indicated for

TRIAC test on DCP UPS

page at the OID.

Replace 1.5 KVA Inverter Board A5.

If problem persists, replace transformer T1.

11 UPS fan A1B1 does not

turn on when UPS is in

inverter mode.

Replace fan A1B1.

If problem persists, replace 1.5 KVA Inverter Board A5. 

12 UPS fan A1B1 does not

turn off when UPS is not

in inverter mode.

Replace 1.5 KVA Inverter Board A5.

Table 3.5.5. DCP UPS (62828-90057) Pre-Service and Post-Service Procedures

Step Procedure

PRE-SERVICE: REMOVING UPS POWER AND REMOVING COVER

Tools required:

 Small flat-tipped screwdriver

 No. 2 Phillips screwdriver

Ensure that power is completely removed from UPS by performing the following steps. Death or

severe injury may result if power is not completely removed from UPS prior to removing the cover

in front of UPS components and performing maintenance on UPS subassemblies.

1 Set UPS POWER switch to off (0) position.

2 Set primary Circuit Breaker Module A1A3A1 to OFF position.
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WARNING

WARNING

Table 3.5.5. DCP UPS (62828-90057) Pre-Service and Post-Service Procedures - CONT

Step Procedure

3 Remove facility power from DCP equipment cabinet by setting DCP circuit breaker in ac junction box to off.

4

Sparks are generated when battery box connector J1 is connected or disconnected.

Explosive fumes from battery box may be present when DCP cabinet is opened. Ensure

that DCP cabinet is ventilated for at least 5 minutes before connecting or disconnecting J1.

On Battery Box A2, disconnect cable connector W031-P1 from battery box connector J1. To remove cable

connector, squeeze tabs on side of connector inward while rocking the connector free.

5 Wait at least 30 seconds while UPS capacitors discharge through bleeders and other drains.

6

CAUTION

Be sure to hold UPS cover in place while removing screws and flat washers that secure

cover to cabinet. Damage to UPS equipment may result if cover falls while being removed.

While holding DCP cover in place, remove eight screws, lockwashers, and flat washers securing UPS cover

to DCP.

7

CAUTION

Status panel ribbon cable is delicate. Use caution when lifting cover and disconnecting

cable to prevent damage to status panel cable.

Carefully pull cover approximately 6 inches from DCP and disconnect status panel ribbon cable from

connector J4 on 1.5 KVA Inverter Board A5.

8 Remove cover from DCP.

POST-SERVICE: INSTALLING UPS COVER AND APPLYING POWER TO UPS

Tools required:

 Small flat-tipped screwdriver

 No. 2 Phillips screwdriver

Ensure that facility power is removed from DCP and that cable W031-P1 is disconnected from

BatteryBox A2 before performing maintenance on UPS. Death orsevere injury may result if power

is not completely removed from UPS prior to maintenance activities.

CAUTION

Status panel ribbon cable is delicate. Use caution when connecting cable and lowering cover to

prevent damage to status panel cable.

Ribbon connector is not keyed. Ensure that pin 1 on cable mates with pin 1 on board.

1 While holding cover approximately 6 inches in front of its normal position, carefully connect status panel

ribbon cable to connector J4 on 1.5 KVA Inverter Board A5. Pin 1 on ribbon connector is marked with ink

dot or other marking. Ensure that mark mates with pin 1 of inverter board.

2 Position cover in front of UPS components, taking care not to disturb or pinch status panel ribbon cable.
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WARNING

Table 3.5.5. DCP UPS (62828-90057) Pre-Service and Post-Service Procedures - CONT

Step Procedure

3

CAUTION

Be sure to hold UPS cover in place while installing screws and flat washers. Damage to

UPS equipment may result if cover falls while being installed. 

While holding cover in position, install eight screws, lockwashers, and flat washers securing cover.

4 Ensure that UPS POWER switch is set to off (0) position.

5

Sparks are generated when battery box connector J1 is connected or disconnected.

Explosive fumes from battery box may be present when DCP cabinet is opened. Ensure

DCP cabinet is ventilated for at least 5 minutes before connecting or disconnecting J1.

Connect battery cable W031-P1 to connector J1 on Battery Box A2.

6 Apply facility power to DCP equipment cabinet by setting DCP circuit breaker in ac junction box to on

position.

7 Set Circuit Breaker Module A1A3A1 to ON position.

Table 3.5.6. UPS Fault Isolation (62828-90338-10 or 62828-90338-20) $

Step Symptom Checks/Corrective Actions $

1 UPS will not start. Line cord is not connected. Connect line cord. $

$

UPS power switch is OFF. Turn switch ON. $

$

Input power is missing or incorrect. $

$

Using multimeter, check input voltage and set DIP switches(UPS 62828-90338- $

10 only) properly: $

$

DIP Switch Settings (UPS 62828-90338-10 only) $

$

Voltage S1 S2 $

 127 ON OFF $

 120 OFF OFF (Default) $

 110 OFF ON $

$

Battery fuse or circuit is open. $

$

Turn UPS power switch to OFF. Replace battery fuse or set circuit breaker to $

ON. Turn UPS power switch to ON. $

2 Alarm continues after $

ALARM SILENCE $

button is pushed. $

Overheat condition likely. $

On UPS, set power switch to off position.

$

Inspect inside of DCP cabinet to ensure proper ventilation around UPS and that $

DCP fan is working properly. Replace if necessary. $

$

Allow UPS to cool. $

$

Set power switch to on position. If UPS fails to turn on and alarm continues, set $

UPS power switch to off position and proceed to step 3. $

Table 3.5.6. UPS Fault Isolation (62828-90338-10 or 62828-90338-20) - CONT $
ASOS Site Technical Manual S100

3-96 Change 2

$ Step Symptom Checks/Corrective Actions

$ 3

$

$

$

With UPS cool, ALARM

$ continues when power is

$ applied to DCP. UPS does

$ not output power.

$ Ensure that connector P1 is securely attached to UPS. Attempt to operate UPS

$ again by setting UPS power switch to on position.

$ 4

$

$ Battery service LED is

$ red.

Replace batteries. If problem persists, replace UPS.

$ 5

$

$

$ Top LED above load

$ symbol is solid red. 

Determine if load(s) is defective or too many loads are connected to the UPS.

$ Overload condition because of excessive current.

$ 6

$

$

$

$

$ All LED's above load

$ symbol are on. 

High dc charging voltage.

$ Turn UPS off and disconnect all loads connected to UPS. Connect loads one at

$ a time back into UPS and turn power back on after each one is plugged in until

$ problem returns. If problem persists, remove and replace UPS.

$ 7

$

$

$ Red LED (top or bottom)

$ above ac input voltage

$ symbol is lit.

$ Line voltage is either too high or too low. UPS in battery operation. Correct input

$ voltage if possible or be prepared to lose power to load in approximately 2 to 5

$ minutes after impending low battery LED turns on.

$ 8 Red LED (top or bottom)

$ above ac input symbol is

$ flashing.

$ Line voltage has returned to normal, but RESET was not pushed.

Wait until power returns to normal, then press RESET.

Table 3.5.7. DCP Card Rack Assembly Fault Isolation Procedures

Step Procedure

1 Remove power from system by setting OUTPUT POWER switch on UPS status panel to off (0) position

and setting Circuit Breaker Module A1A3A1 to OFF. Visually inspect Card Rack Assembly A1A2 for

damage, loose power connections, etc. 

NOTE

Reference paragraph 3.5.4 for the proper removal and installation

procedures for the card rack circuit boards.

2 Replace CPU A (A1A2A1). Apply power to system by setting OUTPUT POWER switch and Circuit

Breaker Module A1A3A1 to ON. Ifsysteminitializes properly, CPU A is bad. Ifsystemdoes not initialize,

proceed to step 3.

3 Replace MemoryBoard A1A2A3. Apply powerto systemby setting OUTPUT POWERswitch andCircuit

Breaker Module A1A3A1 to ON. If system initializes, Memory Board A1A2A3 is bad. Ifsystem does not

initialize, proceed to step 4.

4 If DCP isClassII, replace CPU B (A1A2A2). Apply power to systemby setting OUTPUT POWERswitch

and Circuit Breaker Module A1A3A1 to ON. If system initializes, CPU B is bad. If system does not

initialize, proceed to step 5.

5 One at a time, replace each of the boards in slots A4 through A12 and apply power to the system. If the

system initializes, board most recently replaced is bad. If system fails to initialize, card rack itself is bad.
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3.5.3.4 Serial I/O Board Checks. The DCP CST checks the operation of the SIO boards once per minute.

A LOOPBACK test and a TRANSMIT ERROR test is performed on each of the four ports of each SIO

board. When a failure is discovered, an error message is printed on the printer and entered into the

maintenance log. The error message identifies the SIO board and port, identifies the type of test failed, and

gives instructions to replace the board. Also, an F indication is displayed on the appropriate DCP SIO page

at the OID. For this type of SIO board failure, the technician need only replace the identified board to repair

the system.

In addition to the definitive SIO board failures described above, general communicationsfailures may occur

between the DCP and one of its sensors. In these cases, the problem is either the fault of the sensor, an SIO

port in the DCP, or in the fiberoptic link between the DCP and the sensor. 

When such a loss in sensor communication occurs, the technician should first refer to the DCP fiberoptic

modules detailed block diagram (Figure 3.4.6) to determine which SIO board is connected to the fiberoptic

link for the failing sensor. The technician should then inspect all cable connections associated with the SIO

board and the failing sensor. 

If all cable connections appear to be good and the port is still not operating, an RS-232 test box can be used

to check communication between the SIO board and the fiberopticmodule or UPS that it communicates with.

Paragraph 1.3.5.3 describes testing RS-232 signals for the fiberoptic modules. The DCP UPS fault isolation

procedure of Table 3.5.4 doesthe same for UPS communications. TheRS-232 test box isinserted in line with

connector P1 on the fiberoptic module. 

When using theRS-232 test box, the technician must verify the activity of the applicableRS-232 signals. For

the sensor and UPS communications, these signals are the transmit data (TxD) and receive data (RxD)

signals. Handshaking signals are not used for sensor communications and therefore need not be checked.

However, the technician should check the 5 vdc and signal ground signals applied to the fiberoptic module

being tested.

3.5.3.5 DCPEquipment CabinetHeaterTroubleshooting. Failuresinvolving the DCP equipment cabinet

heaters may be quite subtle in nature and may not become immediately evident. Basically, heater

malfunctions present themselves in one of two possible symptoms. If the heaters do not come on as they are

supposed to, then the cabinet temperature becomestoo low. If the heaters come on and do notshut off asthey

are supposed to, then the cabinet becomes too hot. The difficulty in recognizing the fault symptoms is due

to the fact that the symptoms are dependent on the ambient temperature at the installation site. For example,

if the temperature at the site is quite cold and the heaters malfunction such that they are always on, the

malfunction will not be noticeable until the temperature rises to the point where the heaters should turn off.

Troubleshooting the DCP heating is performed using the DCP power distribution detailed block diagramand

its accompanying text. The heaters are controlled by thermal switches and solid state relays. The ac power

for the heaters should be verified at the inputs to solid state relays. The state (open or closed) of the thermal

switches should then be checked. If the cabinet is overheating, then the heaters are stuck on and the thermal

switches and the solid state relays are closed (they should be open). If the cabinet temperature is too low,

then the heaters are not coming on and the thermal switches and solid-state relays are open (they should be

closed). The proper operation of the heaters themselves is checked by feeling the heat output by each of the

heater strips.

3.5.3.6 Diagnostics. The diagnostics on the DCP equipment cabinet run continuously in the background of

the ASOS operating software as described in Chapter 1. The diagnostics complete a check of the system

every 7 minutes. The test data received via the diagnostic program are displayed on the technician interface

display pages, which are described in Chapter 1, Section III. If the diagnostics detect a failure, on-demand

diagnostics of the affected unit are performed immediately and are repeated three times. If the unit fails at

least two of the three tests, the unit is tagged as faulty and a message is entered into the maintenance log.

Where redundant hardware is present (i.e., CPU's, rf modems, and line drivers), the faulty FRU is removed

from the system and replaced with the operational unit via software. The technician must examine the

maintenance log periodically, even if the system is up in operation, to replace redundant faulty units.
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3.5.4 REMOVAL AND INSTALLATION PROCEDURES

The following chart is provided to facilitate safe and efficient removal and installation procedures for those

assemblies and subassemblies found to be defective as a result of preventive maintenance and

troubleshooting. Thissection does not include any obviousreplacement procedures. Priorto the removal and

installation ofthe assemblies as described in the following paragraphs,maintenance personnelshould ensure

that electrical power is removed from the DCP by setting the UPS OUTPUT POWER switch to off, setting

the primary Circuit Breaker Module A1A3A1 to OFF, and setting the DCP breaker in the ac junction box

(mounted beside the DCP) to off, as specified in the individual procedures. Procedures that are provided for

the replacement of duplicate assemblies, such as VME cards and dc power supplies, are sufficient for

maintenance of all similar units and are described for one assembly only. Removal/installation sequences

of attaching hardware (screws, washers, nuts, etc) are reflected by the relative order of their presentation in

the applicable step. Removal and installation of assemblies in the auxiliary DCP can be accomplished by

substituting auxiliary DCP for DCP in the applicable procedural steps of the DCP removal and installation

tables and by setting the circuit breaker located in slot A10 of the power control module rack to the off

position.

Unit to Be Replaced Removal/Installation/

 table Reference

VME card rack circuit board 3.5.8

DCP UPS filter board 3.5.9 

DCP UPS transformer 3.5.10 

DCP UPS fuse 3.5.11

DCP UPS RS-232 interface board 3.5.12

DCP UPS 1.5 KVA inverter 3.5.13

DCP UPS fan 3.5.14

DCP UPS status panel board 3.5.15

DCP UPS OUTPUT POWER switch 3.5.16

Battery box and battery 3.5.17

DC power supply (+5 and +12) 3.5.18

RF modem 3.5.19

RF switch 3.5.20

RF antenna 3.5.21

Fiberoptic module 3.5.22

Power control module A1A3A2-A9 and A11-A18 3.5.23

Solid state relay 3.5.24

Heater HR1 3.5.25

DCP heater HR2 3.5.26

DCP thermostat switch 3.5.27

DCP fan 3.5.28

Primary and secondary circuit breakers A1A3A1CB1 and A1A3A10CB1 3.5.29

Power supply assembly diodes A4CR2-CR6 3.5.30

$ Uninterruptible power supply 3.5.31

$ Line Driver 3.5.32
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Table 3.5.8. VME Card Rack Circuit Board Removal and Installation

Step Procedure

REMOVAL

Tools required:

 Small flat-tipped screwdriver

CAUTION

Damage to equipment may result if power is not removed prior to removal or installation. Ensure

that UPS POWER switch is set to off (0) position and primary Circuit Breaker Module A1A3A1

is set to OFF.

1 Set UPS POWER switch to off (0) position.

2 Set primary Circuit Breaker Module A1A3A1 to OFF.

3 Referring to figure 3.1.4, locate the slot containing board to be removed.

4

CAUTION

To avoid damage to circuit boards, use proper ESD handling proceduresto include the use

of a grounding strap when performing the following procedures.

Disconnect any cablesthat may be attached to front of board by pulling cable connectorstraight out of circuit

board connector.

5 Using small flat-tipped screwdriver, loosen two captive screws located at top and bottom of board front.

6

CAUTION

When removing a CPU board from rack, exert even force on both board handles. Failure

to apply even force to both handles may result in board hitting bottom of card rack.

If board is equipped with extractor handles, press handlesin opposite directionsto release the board. If board

does not have extractor handles, gently rock board vertically while gently pulling board from rack.

7

CAUTION

Jumper J34 on DCP Memory Board A1A2A3 must be moved to storage position

(J34-A) prior to storing or shipping board. Failure to comply may result in discharge of

battery.

If board removed is DCP Memory Board A1A2A3, move battery jumper from operational position

(J34-B) to storage position (J34-A).

INSTALLATION

Tools required:

 Small flat-tipped screwdriver

CAUTION

Damage to equipment may result if power is not removed prior to removal or installation. Ensure

that UPS POWER switch is set to off (0) position and primary Circuit Breaker Module A1A3A1

is set to OFF.

To avoid damage to circuit boards, use proper ESD handling procedures to include the use of a

grounding strap when performing the following procedures.

1 Ensure that UPS POWER switch is set to off (0) position.

2 Ensure that primary Circuit Breaker Module A1A3A1 is set to OFF.

3 If board being installed is CPU A or B (A1A2A1 or A2) or SIO board #1 through #5 (A1A2A4 through A8),

configure board jumpers for slot into which it is being installed (described in paragraph 3.5.5).

4

NOTE

Jumper J34 on DCP Memory Board A1A2A3 must be moved to operational position

(J34-B) to enable battery backup circuit.

If board installed is DCP Memory Board A1A2A3, move battery jumper from storage position (J34-A) to

operational position (J34-B).
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WARNING

WARNING

Table 3.5.8. VME Card Rack Circuit Board Removal and Installation - CONT

Step Procedure

5 Using two handles located at top and bottom of board, position board with component side facing right and

carefully slide board into rack card guides. Align card with rack connector and press into place.

6 Using small flat-tipped screwdriver, tighten captive screws located at top and bottom of board.

7 If installing CPU A or CPU B, connect RS-232 cable to connector JK1 on front of CPU board.

8 Set primary Circuit Breaker Module A1A3A1 to ON.

9 Set UPS POWER switch to on (1) position.

Table 3.5.9. DCP UPS Filter Board Removal and Installation

Step Procedure

REMOVAL

Tools required:

 No. 2 Phillips screwdriver

 No. 1 offset Phillips screwdriver

Ensure that power is completely removed from UPS by performing procedure in table 3.5.5. Death

or severe injury may result if power is not completely removed from UPS prior to removing cover

in front of UPS components and performing maintenance on UPS subassemblies.

1 Remove DCP UPS cover in accordance with table 3.5.5.

2 At 1.5 KVA Filter Board A1A6, remove harness connectors from board connectors J5 and J10.

3 Tag and remove five single wires from 1.5 KVA Filter Board A1A6.

4 Using Phillips screwdrivers, remove four screws, flat washers, and lockwashers securing 1.5 KVA Filter

Board A1A6 to standoffs.

5 Remove filter board from DCP.

INSTALLATION

Tools required:

 No. 2 Phillips screwdriver

 No. 1 offset Phillips screwdriver

Ensure that power is completely removed from UPS by performing the procedure in table 3.5.5.

Death or severe injury may result if power is not completely removed from UPS prior to removing

cover in front of UPS components and performing maintenance on UPS subassemblies.

1 Verify that DCP UPS cover is removed in accordance with table 3.5.5.

2 Position 1.5 KVA Filter Board A1A6 on standoffs with connectors J5 and J10 positioned to the right.

3 Using Phillips screwdriver, install four screws, flat washers, and lockwashers securing filter board to

standoffs.

4 Using tags as a guide, install five wires on filter board.

5 Install harness connectors on board connectors J5 and J10.

6 Install DCP UPS cover in accordance with table 3.5.5.
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WARNING

WARNING

WARNING

Table 3.5.10. DCP UPS Transformer Removal and Installation

Step Procedure

REMOVAL

Tools required:

 No. 2 Phillips screwdriver

 3/8-inch socket with ratchet

 9/16-inch socket with ratchet

Ensure that power is completely removed from UPS by performing the procedure in table 3.5.5.

Death or severe injury may result if power is not completely removed from UPS prior to removing

the cover in front of UPS components and performing maintenance on UPS subassemblies.

1 Remove DCP UPS cover in accordance with table 3.5.5.

2 On 1.5 KVA Inverter Board A5, tag and remove seven transformer wires with solderless (spade) connectors

from spade connectors on inverter board.

3 Using 3/8-inch socket with ratchet, tag and remove three transformer wires from standoffs on 1.5 KVA

Inverter Board A5.

4

Transformer is heavy equipment (weighs approximately 45 pounds) and requires a

two-man or mechanical lift. Failure to comply may result in injury to personnel or damage

to equipment.

CAUTION

Hold transformer in place while removing nuts and flat washers securing it to mounting

plate. Damage to equipment may result if transformer falls while being removed.

Using 9/16-inch socket with ratchet, remove four nuts and flat washers securing transformer to Mounting

Plate Assembly A1.

5 Remove transformer from DCP.

INSTALLATION

Tools required:

 No. 2 Phillips screwdriver

 3/8-inch socket with ratchet

 9/16-inch socket with ratchet

Ensure that power is completely removed from UPS by performing the procedure in table 3.5.5.

Death or severe injury may result if power is not completely removed from UPS prior to removing

cover in front of UPS components and performing maintenance on UPS subassemblies.

NOTE

This procedure applies to part number 62828-90057 only (installed in DCP's with serial numbers

438 and below).

1 Verify that DCP UPS cover is removed in accordance with table 3.5.5.
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WARNING

WARNING

WARNING

Table 3.5.10. DCP UPS Transformer Removal and Installation -CONT

Step Procedure

2

Transformer is heavy equipment (weighs approximately 45 pounds) and requires a

two-man or mechanical lift. Failure to comply may result in injury to personnel or damage

to equipment.

CAUTION

Hold transformer in place while installing nuts and washers securing it to mounting plate.

Damage to equipment may result if transformer falls while being installed.

Position transformer on mounting plate assembly studs with three heavy gauge wires on bottom.

3 Using 9/16-inch socket with ratchet, install four nuts and washers securing transformer to mounting plate

assembly.

4 Using 3/8-inch socket with ratchet and using tags as a guide, connect three transformer wires to standoffs on

1.5 KVA Inverter Board A5.

5 On 1.5 KVA Inverter Board A5 using tags as a guide, connect seven transformer wires to spade connectors

on inverter board.

6 Install DCP UPS cover in accordance with table 3.5.5.

Table 3.5.11. DCP UPS Fuse Removal and Installation

Step Procedure

REMOVAL

Tools required:

 Fuse puller

Death orsevere injurymay result if power is not removed from DCP prior to maintenance activities.

Ensure that UPS POWER switch isset to 0 (off) position, facility power isremoved from DCP, and

battery box connector is disconnected.

1 Set UPS POWER switch to off (0) position.

2 Set primary Circuit Breaker Module A1A3A1 to off position.

3 Remove facility power from DCP equipment cabinet by setting DCP circuit breaker in ac junction box to off.

4

Sparks are generated when battery box connector J1 is connected or disconnected.

Explosive fumes from battery box may be present when DCP cabinet is opened. Ensure

DCP cabinet is ventilated for at least 5 minutes before connecting or disconnecting J1.

At DCP battery box, disconnect W031-P1 from J1.

5 Wait at least 30 seconds while UPS capacitors discharge through bleeders and other drains.

6 Using fuse puller, remove fuse F1 from fuse holder A1XF1.
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WARNING

WARNING

WARNING

Table 3.5.11. DCP UPS Fuse Removal and Installation -CONT

Step Procedure

INSTALLATION

Death or severe injury may result if power is not removed from DCP prior to maintenance

activities. Ensure that OUTPUT POWER switch is set to 0 (off) position, facility power is

removed from DCP, and battery box connector is disconnected.

1 Ensure that UPS POWER switch is set to off (0) position.

2 Ensure that primary Circuit Breaker Module A1A3A1 is set to off position.

3 Ensure that DCP circuit breaker in ac junction box is set to off position.

4

Sparks are generated when battery box connector J1 is connected or disconnected.

Explosive fumes from battery box may be present when DCP cabinet is opened. Ensure

DCP cabinet is ventilated for at least 5 minutes before connecting or disconnecting J1.

Ensure that battery box connector W031-P1 is disconnected from battery box.

5 Install replacement fuse F1 in fuse holder A1XF1.

6

Sparks are generated when battery box connector J1 is connected or disconnected.

Explosive fumes from battery box may be present when DCP cabinet is opened. Ensure

that DCP cabinet is ventilated for at least 5 minutes before connecting or disconnecting

J1.

At the DCP battery box, connect W031-P1 to J1.

7 Apply facility power to DCP equipment cabinet by setting DCP circuit breaker in ac junction box to on

position.

8 Set primary Circuit Breaker Module A1A3A1 to on position.

9 Set UPS POWER switch to 1 (on) position.
ASOS Site Technical Manual S100

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WARNING

WARNING

Table 3.5.12. DCP UPS RS-232 Interface Board Removal and Installation

Step Procedure

REMOVAL

Tools required:

 Large flat-tipped screwdriver

 Small flat-tipped screwdriver

 3/16-inch nut driver

Ensure that power is completely removed from UPS by performing the procedure in table 3.5.5.

Death or severe injury may result if power is not completely removed from UPS prior to removing

cover in front of UPS components and performing maintenance on UPS subassemblies.

NOTE

This procedure applies to part number 62828-90057 only (installed in DCP's with serial numbers

438 and below).

1 Remove DCP UPS cover in accordance with table 3.5.5.

2 Disconnect RS-232 interface board ribbon connector A1A8-P1 from connector J2 on 1.5 KVA Inverter Board

A5 by grasping connector with thumb and index finger and executing upward force on connector.

3 Using large flat-tipped screwdriver, loosen captive screw and lower circuit breaker module rack.

4 Using small flat-tipped screwdriver, loosen retaining screws and remove connector W015-P22 from RS-232

interface board.

5 Using 3/16-inch nut driver, remove two lugs (standoffs) and flat washers securing RS-232 interface board

to mounting bracket.

6 Remove RS-232 interface board from DCP.

INSTALLATION

Tools required:

 Large flat-tipped screwdriver

 Small flat-tipped screwdriver

 3/16-inch nut driver

Ensure that power is completely removed from UPS by performing the procedure in table 3.5.5.

Death or severe injury may result if power is not completely removed from UPS prior to removing

cover in front of UPS components and performing maintenance on UPS subassemblies.

1 Verify that DCP UPS cover is removed in accordance with table 3.5.5.

2 Carefully position RS-232 interface board in mounting bracket.

3 Using 3/16-inch nut driver, install two lugs (standoffs) and flat washers securing RS-232 interface board to

mounting bracket.

4 Using small flat-tipped screwdriver, install connector W015-P22 to RS-232 interface board.

5 Connect RS-232 interface board ribbon connector A1A8-P1 to connectorJ2 on 1.5 KVA Inverter Board A5.

Ensure that pin 1 on ribbon connector (marked with ink dot or other marking) mates with pin 1 of inverter

board.

6 Raise circuit breaker module rack and secure captive screw.

7 Install DCP UPS cover in accordance with table 3.5.5.
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WARNING

WARNING

Table 3.5.13. DCP UPS 1.5 KVA Inverter Board Removal and Installation

Step Procedure

REMOVAL

Tools required:

 No. 2 Phillips screwdriver

 3/8-inch nut driver

 7/16-inch nut driver

Ensure that power is completely removed from UPS by performing the procedure in table 3.5.5.

Death or severe injury may result if power is not completely removed from UPS prior to removing

cover in front of UPS components and performing maintenance on UPS subassemblies.

1 Remove DCP UPS cover in accordance with table 3.5.5.

2 Remove RS-232 ribbon cable connector A1A8-P1 from 1.5 KVA inverter board connector J2.

3 Remove blower cable connector A1B1-P3 from 1.5 KVA inverter board connector J11.

4 Tag and remove 10 wires with solderless (spade) connectors from 1.5 KVA inverter board.

5 Tag seven wires connected to four 1.5 KVA inverter board standoffs.

6 Using 3/8-inch nut driver, remove four nuts, four flat washers, four lockwashers, and seven wires from four

1.5 KVA inverter board standoffs.

7 Remove two screws, lockwashers, and flat washers securing mounting bracket to back of cabinet.

8 If cabinet is type with left door support blocking inverter board removal, using 7/16-inch nut driver, remove

nut from door support and lower support out of the way.

9 Using Phillips screwdriver, remove three screws securing 1.5 KVA inverter board to mounting plate.

10 Carefully slide 1.5 KVA inverter board forward and remove from DCP.

11 Using Phillips screwdriver, remove four screws, flat washers, lockwashers, and nuts securing mounting

bracket to insulator on top of inverter board heat sinks.

INSTALLATION

Tools required:

 No. 2 Phillips screwdriver

 3/8-inch nut driver

 7/16-inch nut driver

Ensure that power is completely removed from UPS by performing the procedure in table 3.5.5.

Death or severe injury may result if power is not completely removed from UPS prior to removing

cover in front of UPS components and performing maintenance on UPS subassemblies.

1 Verify that DCP UPS cover is removed in accordance with table 3.5.5.

2 Using Phillipsscrewdriver, installfourscrews,flat washers, lockwashers, and nutssecuringmounting bracket

to insulator on top of inverter board heat sinks.

3 Carefully install 1.5 KVA inverter board into card guides.

4 Using Phillipsscrewdriver, install three screws and flat washerssecuring 1.5 KVAinverter board tomounting

plate.

5 If cabinet left door support was disconnected and lowered during removal, using 7/16-inch nut driver, install

nut securing support to cabinet door.

6 Using Phillips screwdriver, install two screws, lockwashers, and flat washers securing mounting bracket to

back of cabinet.
ASOS Site Technical Manual S100

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WARNING

WARNING

Table 3.5.13. DCP UPS 1.5 KVA Inverter Board Removal and Installation - CONT

Step Procedure

7 Using 3/8-inch nut driver and using tags as a guide, install four nuts, four flat washers, four lockwashers, and

seven wires to four 1.5 KVA inverter board standoffs.

8 Using tags as a guide, install 10 wires with solderless (spade) connectors to 1.5 KVA inverter board

terminals.

9 Install connectors A1A8-P1 and A1B1-P3 on 1.5 KVA inverter board connectors J2 and J11, respectively.

Ensure that pin 1 of ribbon connector A1A8-P1 (marked with ink dot or other marking) mates with pin 1 of

inverter board.

10 Install DCP UPS cover in accordance with table 3.5.5.

Table 3.5.14. DCP UPS Fan Removal and Installation

Step Procedure

REMOVAL

Tools required:

 No. 2 Phillips screwdriver

Ensure that power is completely removed from UPS by performing the procedure in table 3.5.5.

Death or severe injury may result if power is not completely removed from UPS prior to removing

cover in front of UPS components and performing maintenance on UPS subassemblies.

1 Remove 1.5 KVA Inverter Board A5 in accordance with table 3.5.13.

2 Using Phillipsscrewdriver,remove fourscrews, lockwashers, and flat washerssecuring fan to mounting plate

assembly.

3 Remove fan from DCP.

INSTALLATION

Tools required:

 No. 2 Phillips screwdriver

Ensure that power is completely removed from UPS by performing the procedure in table 3.5.5.

Death or severe injury may result if power is not completely removed from UPS prior to removing

cover in front of UPS components and performing maintenance on UPS subassemblies.

NOTE

This procedure applies to part number 62828-90057 only (installed in DCP's with serial numbers

438 and below).

1 Verify that DCP UPS cover is removed in accordance with table 3.5.5.

2 Verify that 1.5 KVA Inverter Board A5 is removed in accordance with table 3.5.13.

3 Orient fan so that airflow will be toward front of cabinet (across UPS components). Install fan on mounting

plate assembly. Install four screws, lockwashers, and flat washers securing fan.

4 Install 1.5 KVA Inverter Board A5 in accordance with table 3.5.13.
S100 ASOS Site Technical Manual

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WARNING

WARNING

WARNING

Table 3.5.15. DCP UPS Status Panel Board Removal and Installation

Step Procedure

REMOVAL

Tools required:

 5/16-inch nut driver

Ensure that power is completely removed from UPS by performing the procedure in table 3.5.5.

Death or severe injury may result if power is not completely removed from UPS prior to removing

cover in front of UPS components and performing maintenance on UPS subassemblies.

NOTE

This procedure applies to part number 62828-90057 only (installed in DCP's with serial numbers

438 and below).

1 Remove DCP UPS cover in accordance with table 3.5.5.

2 Tag and disconnect two wires from UPS POWER switch.

3 Using 5/16-inch nut driver, remove two nylon nuts and spacers securing status panel board to DCP UPS

cover.

4 Remove status panel board from DCP UPS cover.

INSTALLATION

Tools required:

 5/16-inch nut driver

Ensure that power is completely removed from UPS by performing the procedure in table 3.5.5.

Death or severe injury may result if power is not completely removed from UPS prior to removing

cover in front of UPS components and performing maintenance on UPS subassemblies.

1 Verify that DCP UPS cover is removed in accordance with table 3.5.5.

2 Position status panel board on mounting screws.

3 Using 5/16-inch nut driver, install two nylon nuts and spacerssecuring status panel board to DCP UPS cover.

4 Using tags as a guide, connect two wires to UPS POWER switch.

5 Install DCP UPS cover in accordance with table 3.5.5.

Table 3.5.16. DCP UPS OUTPUT POWER Switch Removal and Installation

Step Procedure

REMOVAL

Ensure that power is completely removed from UPS by performing the procedure in table 3.5.5.

Death or severe injury may result if power is not completely removed from UPS prior to removing

cover in front of UPS components and performing maintenance on UPS subassemblies.

NOTE

This procedure applies to part number 62828-90057 only (installed in DCP's with serial numbers

438 and below).

1 Remove DCP UPS cover in accordance with table 3.5.5.

2 Press plastic tabs on both sides of switch while pushing switch out front of panel.
ASOS Site Technical Manual S100

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WARNING

WARNING

Table 3.5.16. DCP UPS OUTPUT POWER Switch Removal and Installation -CONT

Step Procedure

INSTALLATION

Ensure that power is completely removed from UPS by performing the procedure in table 3.5.5.

Death or severe injury may result if power is not completely removed from UPS prior to removing

cover in front of UPS components and performing maintenance on UPS subassemblies.

NOTE

This procedure applies to part number 62828-90057 only (installed in DCP's with serial numbers

438 and below).

1 Verify that DCP UPS cover is removed in accordance with table 3.5.5.

2 Push switch through front of status panel until plastic tabs lock switch into place.

3 At rear of switch, using tags as a guide, connect two wires to switch.

4 Install DCP UPS cover in accordance with 3.5.5.

Table 3.5.17. Battery Box and Battery Removal and Installation

Step Procedure

REMOVAL

Tools required:

 Medium flat-tipped screwdriver

 Two 5/16-inch box wrenches

 5/8-inch nut driver

 3/8-inch nut driver

 No. 2 Phillips screwdriver

Death orsevere injury may result if power is not removed fromDCP prior to maintenance activities.

Severe injury may result if the negative and positive battery terminals are shorted together. Exercise

caution while removing batteries.

NOTE

This procedure applies to part number 62828-90057 only (installed in DCP's with serial numbers

438 and below).

1 Set UPS POWER switch to off (0) position.

2 Set primary Circuit Breaker Module A1A3A1 to OFF position.

3 Remove facility power from the DCP equipment cabinet by setting DCP circuit breaker in ac junction box

to off.
S100 ASOS Site Technical Manual

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WARNING

WARNING

Table 3.5.17. Battery Box and Battery Removal and Installation - CONT

Step Procedure

4

Sparks are generated when battery box connector J1 is connected or disconnected.

Explosive fumes from battery box may be present when DCP cabinet is opened. Ensure

DCP cabinet is ventilated for at least 5 minutes before connecting or disconnecting J1.

Disconnect Battery Box A2.

a. For battery box part number 62828-40062-10,squeeze tabs on side of connectorJ1 inward

while rocking connector free.

b. For battery box part number 62828-40062-30 or 62828-90360-10, pull battery box

connector P1 out of UPS PRA BATTERY BOX connector.

5 Loosen hose clamp on battery box vent tube and remove tubing from top of battery box.

6 Wait at least 30 seconds while UPS capacitors discharge through bleeders and other drains.

7 Slide battery box forward as far as possible so that rear of box rests on front edge of DCP cabinet while box

is retained by lanyards on either side.

8 Slide retaining straps off of left and right top of battery box.

9

CAUTION

When lifting top of battery box, do not pull the attached wires off the connector.

Carefully lift top of battery box and position top to gain access to battery terminals.

10

Batteries contain corrosive fluid. Do not tip batteries during removal.

Using two 5/16-inch wrenches, remove bolt, flat washers, lockwasher, and nut from negative terminal of

battery BT1 (connected to top of battery box via black wires). Remove black wires from negative terminal.

11 Using two 5/16-inch box wrenches, remove bolt, flat washers, lockwasher, and nut from positive terminal of

battery (connected to top of battery box via red wires). Remove red wiresfrom positive terminal, and remove

top of battery box.

12 Using two 5/16-inch box wrenches, remove bolt, lockwasher, flat washers, and nuts from battery terminals.

Remove all jumper wires.

13 Using strap tied around battery BT5 or packing material, remove battery from battery box.

14 Remove strap from battery and retain strap.

15 Remove additional batteries.

16 If battery box itself isto be replaced, remove two lanyardsfrombattery box by using Phillipsscrewdriver and

3/8-inch nut driver to remove screws, two flat washers, and nut (four places).

17 If battery box itself is to be replaced, remove retaining straps by using Phillips screwdriver and 3/8-inch nut

driver to remove screws, two flat washers, and nut securing straps to box.
ASOS Site Technical Manual S100

Table 3.5.17. Battery Box and Battery Removal and Installation - CONT

Step Procedure

3-110

WARNING

INSTALLATION

Tools required:

 Medium flat-tipped screwdriver

 Two 5/16-inch box wrenches

 No. 2 Phillips screwdriver

 3/8-inch nut driver

 5/8-inch nut driver

Death orsevere injurymay result if power is not removed from DCP prior to maintenance activities.

Severe injurymay result ifthe negative and positive battery terminals are shorted together. Exercise

caution while removing batteries.

1 Ensure that UPS POWER switch is set to off (0) position.

2 Ensure that primary Circuit Breaker Module A1A3A1 is set to OFF position.

3 Ensure that DCP circuit breaker in ac junction box is set to off position.

4 If battery box itself is to be replaced, install retaining straps on new box using Phillips screwdriver and

3/8-inch nut driver to installscrews, two flat washers, and nutsecuring strapsto box. Ensure thatscrew heads

are inside box and nuts are outside.

5 If battery box itself isto be replaced, install two lanyards on new box using Phillipsscrewdriver and 3/8-inch

nut driver to install screws, two flat washers, and nut (four places). Ensure that screw heads are inside box

and nuts are outside.

6 Slide empty battery box forward asfar as possible so that rear of box rests on front edge of DCP cabinet while

box is retained by lanyards on either side.

7 Using figure 2.1.1, install batteries in battery box.

8 Tie previously removed strap around batteryBT5 or packingmaterial to facilitate future removal. Leave slack

in strap to allow approximately 2 inches of clearance between the top of battery and strap.

9 Using strap around battery BT5 or packing material, install in battery box.

10

NOTE

Refer to figure 3.4.8 (sheet 3) for wiring diagram of battery box.

Using markers as a guide and two 5/16-inch box wrenches, install jumpers on battery terminals,securing with

bolt, flat washers, and nut.

11 Position top of battery box to allow connection of red wires to positive terminal and black wires to negative

terminal.

12 Using markers as a guide and two 5/16-inch box wrenches, install bolts, flat washers, lockwashers, and nuts

securing wires to their respective terminals.

13 Install top on battery box and press into place.

14 Pull two retaining straps over top of battery box to secure top.

15 Using flat-tipped screwdriver, install battery box vent tube.
S100 ASOS Site Technical Manual

Table 3.5.17. Battery Box and Battery Removal and Installation - CONT

Step Procedure

3-111

WARNING

WARNING

WARNING

16

Sparks are generated when battery box connector J1 is connected or disconnected.

Explosive fumes from battery box may be present when DCP cabinet is opened. Ensure

that DCP cabinet is ventilated for at least 5 minutes before connecting or disconnecting J1.

NOTE

Ensure that battery cable connector is fully seated and locked in place.

Connect Battery Box A2.

a. For battery box part number 62828-40062-10, position cable W030 connector P1 on top

of battery box connector J1 and press connector into place.

b. For battery box part number 62828-40062-30 or 62828-90360-10, insert battery box

connector into UPS PRA BATTERY BOX connector.

17 Apply facility power to DCP equipment cabinet by setting DCP circuit breaker in ac junction box to on

position.

18 Set primary Circuit Breaker Module A1A3A1 to ON position.

19 Set UPS POWER switch to 1 (on) position.

Table 3.5.18. DC Power Supply (+5 and ±12 VDC) Removal and Installation

Step Procedure

REMOVAL

Tools required:

 Small flat-tipped screwdriver

 No. 2 Phillips screwdriver

 3/8-inch socket and ratchet

Death orsevere injurymay result if power is not removed from DCP prior to maintenance activities.

1 Set UPS POWER switch to off (0) position.

2 Set primary Circuit Breaker Module A1A3A1 to OFF position.

3 Remove facility power from the DCP equipment cabinet by setting DCP circuit breaker in ac junction box

to off.

4

Sparks are generated when battery box connector J1 is connected or disconnected.

Explosive fumes from battery box may be present when DCP cabinet is opened. Ensure

that DCP cabinet is ventilated for at least 5 minutes before connecting or disconnecting J1.

At DCP battery box, disconnect connector W031-P1 from J1.
ASOS Site Technical Manual S100

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WARNING

WARNING

Table 3.5.18. DC Power Supply (+5 and ±12 VDC) Removal and Installation -CONT

Step Procedure

5 Referring to figure 3.1.3, locate power supply to be removed.

6 Disconnect cable connectors W024-P1 through W024-P4.

7 Using 3/8-inch socket and ratchet, remove six nuts, lockwashers, and flat washers securing Power Supply

Assembly A4 to DCP equipment cabinet.

8 Carefully remove Power Supply Assembly A4 from DCP equipment cabinet.

9 Using No. 2 Phillipsscrewdriver, remove four countersunk screws securing powersupply to mounting plate.

10 If +5 vdc power supply, remove terminal strip cover.

11 Using small flat-tipped screwdriver, tag and disconnect wires from power supply terminal strip.

12 If +5 vdc power supply, tag and remove wires from terminal studs using 3/8-inch socket and ratchet.

INSTALLATION

Tools required:

 Small flat-tipped screwdriver

 No. 2 Phillips screwdriver

 3/8-inch socket and ratchet

Death orsevere injurymay result if power is not removed from DCP prior to maintenance activities.

1 Ensure that UPS POWER switch is set to off (0) position.

2 Ensure that primary Circuit Breaker Module A1A3A1 is set to OFF position.

3 Ensure that DCP circuit breaker in ac junction box is set to off position.

4

Sparks are generated when battery box connector J1 is connected or disconnected.

Explosive fumes from battery box may be present when DCP cabinet is opened. Ensure

that DCP cabinet is ventilated for at least 5 minutes before connecting or disconnecting J1.

At DCP battery box, ensure that connector W031-P1 is disconnected from J1.

5 If +5 vdc power supply, using wire tags/markers as a guide, connect wires to terminal studs using 3/8-inch

socket and ratchet and install terminal strip cover.

6 Using small flat-tipped screwdriver and using wire tags/ markers as a guide, connect wires to power supply

terminal strip. 

7 Using No. 2 Phillips screwdriver, install four countersunk screws securing power supply to mounting plate.

8 Carefully position Power Supply Assembly A4 back in DCP equipment cabinet, ensuring that bottom of A4

plate rests on mounting support on bottom of right wall.

9 Using 3/8-inch socket, install six nuts, lockwashers, and flat washers securing power supply mounting plate

assembly.

10 Connect cables to connectors W024-P1 through W024-P4.
S100 ASOS Site Technical Manual

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WARNING

Table 3.5.18. DC Power Supply (+5 and ±12 VDC) Removal and Installation -CONT

Step Procedure

11

Sparks are generated when battery box connector J1 is connected or disconnected.

Explosive fumes from battery box may be present when DCP cabinet is opened. Ensure

that DCP cabinet is ventilated for at least 5 minutes before connecting or disconnecting J1.

At DCP battery box, connect connector W031-P1 to J1.

12 Apply facility power to DCP equipment cabinet by setting DCP circuit breaker in ac junction box to on

position.

13 Set primary Circuit Breaker Module A1A3A1 to ON position.

14 Set UPS POWER switch to 1 (on) position.

Table 3.5.19. RF Modem Removal and Installation

Step Procedure

REMOVAL

Tools required:

 Small flat-tipped screwdriver

 Short No. 2 Phillips screwdriver

CAUTION

Damage to rf modems may result if power is not removed fromDCP prior to removal or installation.

Ensure that UPS POWER switch is set to 0 (off) position and DCP primary circuit breaker module

is set to off.

1 Set UPS POWER switch to off (0) position.

2 Set primary Circuit Breaker Module A1A3A1 to OFF position.

3 Remove facility power from the DCP equipment cabinet by setting DCP circuit breaker in ac junction box

to off.

4 Using Phillips screwdriver, remove two screws, flat washers, and lockwashers securing rf modem mounting

plate to mounting bracket.

5 Slide rf modem mounting plate forward to access rf modem connectors. $

6 Disconnect BNC connectors from rf modems. If modem being removed isJohnson Data model then remove $

SMAM-to-BNCF adapter. $

7 Using smallflat-tipped screwdriver,remove D connectors(two for AAImodel, one forMotorolamodel)from $

rf modems and Johnson Data models) . $

8 Remove rf modem mounting plate from guides. $

9 Remove two mounting screws, lockwashers, and flat washers securing rf modem to mounting plate. $
ASOS Site Technical Manual S100

Step Procedure

3-114 Change 2

$ 10

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$ Remove rf modem.

$ NOTE:

$ A common anomaly with ACU/DCP communications is a failed DCP Radio B (or Line

$ Driver B) after a completed download. The workaround for this specific failure is to

$ deconfigure and then reconfigure Radio B (or Line Driver B). Proceed to the

$ Hardware Configuration page (REVUE-SITE-CONFG-HDWE), sequence the DCP

$ CPU to 1, press EXIT, then repeat this procedure and sequence the DCP CPU to 2.

$

$ NOTE:

$ When an AAI modem (62828-90013-XX) fails, and a replacement AAI modem is not available,

$ ASN S100-FMK18886 must be ordered to replace the modem with the Motorola modem

$ (62828-90315-XX). AAI modems cannot be replaced with the Johnson Data modems (62828-

$ 40506-X ). When a Motorola modem (62828-90315-XX) fails and spare Motorola modems are not

$ available, a Johnson Data modem (62828-40506-X), an adapter cable (62828-42110-10), and a

$ SMAM-to-BNCF adapter must be ordered to replace the failing rf modem.

INSTALLATION

Tools required:

 Small flat-tipped screwdriver

 Short No. 2 Phillips screwdriver

CAUTION

Damage to rf modems may result if power is not removed from DCP prior to removal or

installation. Ensure that UPS POWER switch is set to 0 (off) position and DCP primary circuit

breaker module is set to off.

1 Ensure that UPS POWER switch is set to off (0) position.

2 Ensure that primary Circuit Breaker Module A1A3A1 is set to OFF position.

3 Ensure that DCP circuit breaker in ac junction box is set to off position.

4 Using Phillips screwdriver, install two mounting screws, lockwashers, and flat washers securing rf modem

to mounting plate.

5 Slide rf modem mounting plate partway into guides to hold it in place for cable connection.

6 Using small flat-tipped screwdriver, install D connectors (two for AAI model, one for Motorola model) to

rf modems.

7 Connect BNC connectors to rf modems.

8 Slide rf modem mounting plate fully into guides.

9 Using Phillips screwdriver, install two screws, flat washers, and lockwashers securing rf modem mounting

plate to mounting bracket.

10 Apply facility power to DCP equipment cabinet by setting DCP circuit breaker in ac junction box to on

position.

11 Set primary Circuit Breaker Module A1A3A1 to ON position.

12 Set UPS POWER switch to 1 (on) position.
S100 ASOS Site Technical Manual

Change 1 3-115

Table 3.5.20. RF Switch Removal and Installation

Step Procedure

REMOVAL

Tools required:

 No. 1 Phillips screwdriver

CAUTION

Damage to rf modems may result if power is notremoved fromDCP prior to removal or installation.

Ensure that UPS POWER switch is set to 0 (off) position and DCP primary circuit breaker module

is set to off.

1 Set UPS POWER switch to off (0) position.

2 Set primary Circuit Breaker Module A1A3A1 to OFF position.

3 Remove facility power from DCP equipment cabinet by setting DCP circuit breaker in ac junction box to

off.

4 At rf switch, tag and remove three BNC connectors.

5 Disconnect rf switch in-line connector (A1A5-P1) from DCP harness connector P43.

6 Using Phillips screwdriver, remove two screws, flat washers, and lockwashers securing rf switch to

standoffs.

INSTALLATION

Tools required:

 No. 1 Phillips screwdriver

CAUTION

Damage to rf modems may result if power is not removed from DCP prior to removal or installation.

Ensure that UPS POWER switch is set to 0 (off) position and DCP primary circuit breaker module is

set to off.

1 Ensure that UPS POWER switch is set to off (0) position.

2 Ensure that primary Circuit Breaker Module A1A3A1 is set to OFF position.

3 Ensure that DCP circuit breaker in ac junction box is set to off position.

4 Using Phillips screwdriver, install two screws, flat washers, and lockwashers securing rf switch to standoffs.

5 Connect rf switch in-line connector (A1A5-P1) to DCP harness connector P43.

6 Install three BNC connectors on rf switch.

7 Apply facility power to DCP equipment cabinet by setting DCP circuit breaker in ac junction box to on.

8 Set primary Circuit Breaker Module A1A3A1 to ON position.

9 Set UPS POWER switch to 1 (on) position.
ASOS Site Technical Manual S100

3-116 Change 1

Table 3.5.21. RF Antenna Removal and Installation

Step Procedure

REMOVAL

Tools required:

 Flat-tipped screwdriver

CAUTION

Damage to rf modems may result if power is not removed from DCP prior to removal or installation.

Ensure that UPS POWER switch is set to 0 (off) position and DCP primary circuit breaker module is

set to off.

1 Set UPS POWER switch to off (0) position.

2 Set primary Circuit Breaker Module A1A3A1 to OFF position.

3 Remove facility power from DCP equipment cabinet by setting DCP circuit breaker in ac junction box to off.

$ 4 Disconnect coaxial cable from rf antenna. If yagi antenna, observe antenna polarization relative to ground (vertical

$ or horizontal) and note antenna orientation towards ACU or DCP rf modem antenna.

5 Using flat-tipped screwdriver and 3/8-inch nut driver, remove screw, two flat washers, lockwasher, and nut (two

$ places) securing antenna to mounting bracket. Remove antenna.

INSTALLATION

Tools required:

 Flat-tipped screwdriver

CAUTION

Damage to rf modems may result if power is not removed from DCP prior to removal or installation.

Ensure that UPS POWER switch is set to 0 (off) position and DCP primary circuit breaker module is set

to off.

1 Ensure that UPS POWER switch is set to off (0) position.

2 Ensure that primary Circuit Breaker Module A1A3A1 is set to OFF position.

Table 3.5.21. RF Antenna Removal and Installation -CONT

Step Procedure

$ 2.1 Install replacement antenna. If yagi, orient vertically or horizontally as observed in removal step 4.

3 Using flat-tipped screwdriver and 3/8-inch nut driver, install screw, two flat washers, lockwasher, and nut (two

places) securing antenna to mounting bracket. Ensure that one flat washer is installed under screw head on top side

and one under lockwasher on underside of mounting bracket.

4 Connect coaxial cable to rf antenna.

$ 4.1

$

Ensure that antenna orientation is pointed towards the ACU or DCP rf modem antenna (±10°) as noted in removal

step 4

5 Apply facility power to DCP equipment cabinet by setting DCP circuit breaker in ac junction box to on position.

6 Set primary Circuit Breaker Module A1A3A1 to ON position.

7 Set UPS POWER switch to 1 (on) position.
S100 ASOS Site Technical Manual

3-117

WARNING

WARNING

Table 3.5.22. Fiberoptic Module Removal and Installation

Step Procedure

REMOVAL

Tools required:

 Small flat-tipped screwdriver

 No. 1 Phillips screwdriver

Death or severe injury may result if power is not removed from DCP prior to maintenance activities.

Ensure that UPS POWER switch is set to 0 (off) position and facility power is removed from DCP.

1 Set UPS POWER switch to off (0) position.

2 Set primary Circuit Breaker Module A1A3A1 to OFF position.

3 Remove facility power from DCP equipment cabinet by setting DCP circuit breaker in ac junction box to off.

4 Using Phillips screwdriver, remove 22 screws and flat washers securing shielded cover assembly to Faraday box.

Lower Faraday box cover.

5 Using flat-tipped screwdriver, loosen two integral screws securing connector to top of fiberoptic module. Remove

connector from receptacle on fiberoptic module.

6 Accessing underside of faulty fiberoptic module through Faraday box, tag and disconnect fiberoptic transmit (TX)

and receive (RX) cables.

7 Using small flat-tipped screwdriver, remove four screws and washers securing fiberoptic module to top of Faraday

box.

8 Remove faulty fiberoptic module.

INSTALLATION

Tools required:

 Small flat-tipped screwdriver

 No. 1 Phillips screwdriver

Death or severe injury may result if power is not removed from DCP prior to maintenance activities.

Ensure that UPS POWER switch is set to 0 (off) position and facility power is removed from DCP.

1 Ensure that UPS POWER switch is set to off (0) position.

2 Ensure that primary Circuit Breaker Module A1A3A1 is set to OFF position.

3 Ensure that DCP circuit breaker in ac junction box is set to off position.

4 Orient new fiberoptic module to match previously mounted assemblies and align over mounting holes in top

of Faraday box.

5 Using small flat-tipped screwdriver, install four screws and washers securing fiberoptic module to top of

Faraday box.

6 Using tags as a guide, connect fiberoptic TX and RX cablesto appropriate module connector though opened

Faraday box. 

7 Install connector into receptacle on top of fiberoptic module and secure two integralscrews using flat-tipped

screwdriver.

8 Using Phillips screwdriver, install 22 screws and flat washers securing shielded cover assembly to Faraday

box.

9 Apply facility power to DCP equipment cabinet by setting DCP circuit breaker in ac junction box to on

position.

10 Set primary Circuit Breaker Module A1A3A1 to ON position.

11 Set UPS POWER switch to 1 (on) position.
ASOS Site Technical Manual S100

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WARNING

WARNING

WARNING

WARNING

Table 3.5.23. Power Control Module A1A3A1A2-A8 and A9-A18 Removal and Installation

Step Procedure

REMOVAL

Tools required:

 Large flat-tipped screwdriver

Death orsevere injurymay result if power is not removed from DCP prior to maintenance activities.

Ensure that UPS POWER switch isset to 0 (off) position, facility power isremoved from DCP, and

battery box connector is disconnected.

1 Set UPS POWER switch to off (0) position.

2 Set primary Circuit Breaker Module A1A3A1 to OFF position.

3 Remove facility power from DCP equipment cabinet by setting DCP circuit breaker in ac junction box to off.

4

Sparks are generated when battery box connector J1 is connected or disconnected.

Explosive fumes from battery box may be present when DCP cabinet is opened. Ensure

that DCP cabinet is ventilated for at least 5 minutes before connecting or disconnecting J1.

At DCP battery box, disconnect connector W031-P1 from J1.

5 Using flat-tipped screwdriver, loosen two captive screws securing module retaining strip to power control

module rack.

6 Remove module retaining strip from assembly.

7 Release module from connector by placing fingers behind module faceplate and pressing outward. Remove

module from rack.

INSTALLATION

Tools required:

 Large flat-tipped screwdriver

Death orsevere injurymay result if power is not removed from DCP prior to maintenance activities.

Ensure that UPS POWER switch isset to 0 (off) position, facility power isremoved from DCP, and

battery box connector is disconnected.

1 Ensure that UPS POWER switch is set to off (0) position.

2 Ensure that primary Circuit Breaker Module A1A3A1 is set to OFF position.

3 Ensure that DCP circuit breaker in ac junction box is set to off position.

$ 4

Sparks are generated when battery box connector J1 is connected or disconnected.

Explosive fumes from battery box may be present when DCP cabinet is opened. Ensure

that DCP cabinet is ventilated for at least 5 minutes before connecting or disconnecting J1.

Ensure that battery box connector W031-P1 is disconnected from battery box.

$ 5 Alignmodule with rack-mounted guides.Carefully pushmodule into rack untilfirmly seated in rack-mounted

connector.

6 Hand-tighten two captive screws securing module retaining strip to power control module rack.
S100 ASOS Site Technical Manual

Table 3.5.23. Power Control Module A1A3A1A2-A8 and A9-A18 Removal and Installation

Step Procedure

3-119

WARNING

WARNING

WARNING

7

Sparks are generated when battery box connector J1 is connected or disconnected.

Explosive fumes from battery box may be present when DCP cabinet is opened. Ensure

that DCP cabinet is ventilated for at least 5 minutes before connecting or disconnecting J1.

At DCP battery box, connect connector W031-P1 to J1.

8 Apply facility power to DCP equipment cabinet by setting DCP circuit breaker in ac junction box to on

position.

9 Set primary Circuit Breaker Module A1A3A1 to ON position.

10 Set UPS POWER switch to 1 (on) position.

Table 3.5.24. Solid State Relay Removal and Installation

Step Procedure

REMOVAL

Tools required:

 Small flat-tipped screwdriver

 No. 2 Phillips screwdriver

Death orsevere injurymay result if power is not removed from DCP prior to maintenance activities.

Ensure that UPS POWER switch is set to 0 (off) position and facility power is removed from DCP.

1 Set UPS POWER switch to off (0) position.

2 Set primary Circuit Breaker Module A1A3A1 to OFF position.

3 Remove facility power from DCP equipment cabinet by setting DCP circuit breaker in ac junction box to off.

4 Loosen captive screw in upper center of power control module rack and lower rack assembly.

5 Using flat-tipped screwdriver, remove wires from relay module connectors 1 through 4.

6 Using Phillips screwdriver, remove two screws, lockwashers, and flat washers securing relay module to

Mounting Plate Assembly A1.

INSTALLATION

Tools required:

 Small flat-tipped screwdriver

 No. 2 Phillips screwdriver

Death orsevere injurymay result if power is not removed from DCP prior to maintenance activities.

Ensure that OUTPUT POWER switch is set to 0 (off) position and facility power is removed from

DCP.

1 Ensure that UPS POWER switch is set to off (0) position.

2 Ensure that primary Circuit Breaker Module A1A3A1 is set to OFF position.

3 Ensure that DCP circuit breaker in ac junction box is set to off position.

4 Using Phillipsscrewdriver, install two screws, lockwashers, and flat washerssecuring relay module to DCP.

5 Using flat-tipped screwdriver and wiremarkers as a guide, install wires on relaymodule connectors 1 through

4.

6 Raise circuit breaker module rack and secure captive screw.
ASOS Site Technical Manual S100

3-120 Change 2

WARNING

WARNING

Table 3.5.24. Solid State Relay Removal and Installation - CONT

Step Procedure

7 Apply facility power to DCP equipment cabinet by setting DCP circuit breaker in ac junction box to on

position.

8 Set primary Circuit Breaker Module A1A3A1 to ON position.

9 Set UPS POWER switch to 1 (on) position.

Table 3.5.25. Heater HR1 Removal and Installation

Step Procedure

REMOVAL

Tools required:

 No. 2 Phillips screwdriver

 3/8-inch nut driver

 7/16-inch nut driver

Death orsevere injury may result if power is notremoved fromDCP prior to maintenance activities.

Ensure that UPS POWER switch is set to 0 (off) position and facility power is removed from DCP.

1 Set UPS POWER switch to off (0) position.

2 Set primary Circuit Breaker Module A1A3A1 to OFF position.

3 Remove facility power from DCP equipment cabinet by setting DCP circuit breaker in ac junction box to off.

4 Using Phillips screwdriver, remove three screws, lockwashers, and flat washers securing heat grill to

mounting plate.

5 Using 3/8-inch nut driver, remove three wires from heater.

6 Using Phillips screwdriver, remove six screws and flat washers securing three heater mounting brackets.

7 Using 7/16-inch nut driver,remove two nuts,flatwashers, and lockwasherssecuring heaterto mounting plate.

8 Remove heater from DCP.

INSTALLATION

Tools required:

 No. 2 Phillips screwdriver

 3/8-inch nut driver

 7/16-inch nut driver

Death orsevere injury may result if power is not removed fromDCP prior to maintenance activities.

Ensure that UPS POWER switch is set to 0 (off) position and facility power is removed from DCP.

1 Ensure that UPS POWER switch is set to off (0) position.

2 Ensure that primary Circuit Breaker Module A1A3A1 is set to OFF position.

3 Ensure that DCP circuit breaker in ac junction box is set to off position.

4 Position heater in DCP over mounting holes.

5 Using 7/16-inch nut driver, install two nuts, lockwashers, and flat washerssecuring heater to mounting plate.

6 Using Phillips screwdriver, install six screws and flat washers securing three heater mounting brackets.

7 Using 3/8-inch nut driver and using markers as a guide, install wiring to heater.

8 Using Phillips screwdriver, install three screws, lockwashers, and flat washers securing heater grill to

mounting plate.
S100 ASOS Site Technical Manual

3-121

WARNING

Table 3.5.25. Heater HR1 Removal and Installation - CONT

Step Procedure

9 Apply facility power to DCP equipment cabinet by setting DCP circuit breaker in ac junction box to on

position.

10 Set primary Circuit Breaker Module A1A3A1 to ON position.

11 Set UPS POWER switch to 1 (on) position.

Table 3.5.26. DCP Heater HR2 Removal and Installation

Step Procedure

REMOVAL

Tools required:

 No. 2 Phillips screwdriver

 Diagonal cutting pliers

1 Remove Battery Box A2 from DCP equipment cabinet in accordance with table 3.5.17.

2 Disconnect heater HR2 in-line connector (A1-P1) from DCP harness connector P44.

3 Using Phillipsscrewdriver, remove three screws, flat washers, and lockwasherssecuring heater to mounting

plate assembly.

4 Remove heater from DCP.

INSTALLATION

Tools required:

 No. 2 Phillips screwdriver

 Wire stripper

 Crimping tool

 Butt splice connectors - M7928/5-3

Death orsevere injurymay result if power is not removed from DCP prior to maintenance activities.

Ensure that UPS POWER switch is set to 0 (off) position and facility power is removed from DCP.

1 Ensure that UPS POWER switch is set to off (0) position.

2 Ensure that primary Circuit Breaker Module A1A3A1 is set to OFF position.

3 Ensure that DCP circuit breaker in ac junction box is set to off position.

4 Ensure that Battery Box A2 is removed from DCP in accordance with table 3.5.17.

5 Position heater in DCP. Using Phillips screwdriver, install three screws, flat washers, and lockwashers

securing heater to mounting plate assembly.

6 Connect heater HR2 in-line connector (A1-P1) to DCP harness connector P44.

7 Install DCP battery in accordance with table 3.5.17.
ASOS Site Technical Manual S100

3-122

WARNING

WARNING

Table 3.5.27. DCP Thermostat Switch Removal and Installation

Step Procedure

REMOVAL

Tools required:

 Small flat-tipped screwdriver

 Solder iron

Death orsevere injury may result if power is notremoved fromDCP prior to maintenance activities.

Ensure that UPS POWER switch is set to 0 (off) position and facility power is removed from DCP.

1 Set UPS POWER switch to off (0) position.

2 Set primary Circuit Breaker Module A1A3A1 to OFF position.

3 Remove facility power from DCP equipment cabinet by setting DCP circuit breaker in ac junction box to off.

4 Loosen captive screw in top of circuit breaker rack and lower rack to facilitate thermostat removal.

5 Tag wires to be removed from faulty thermostat.

6 Using solder iron, remove wires from faulty thermostat.

7 Using flat-tipped screwdriver, remove two screws, flat washers, lockwashers, and nuts securing thermostat

to mounting bracket.

8 Remove thermostat from DCP.

INSTALLATION

Tools required:

 Small flat-tipped screwdriver

 Solder iron

Death orsevere injury may result if power is notremoved fromDCP prior to maintenance activities.

Ensure that UPS POWER switch is set to 0 (off) position and facility power is removed from DCP.

1 Ensure that UPS POWER switch is set to off (0) position.

2 Ensure that primary Circuit Breaker Module A1A3A1 is set to OFF position.

3 Ensure that DCP circuit breaker in ac junction box is set to off position.

4 Position thermostat in mounting bracket.

5 Using flat-tipped screwdriver, install two screws, flat washers, lockwashers, and nuts securing thermostat to

mounting bracket.

6 Using solder iron, install wires on thermostat.

7 Raise circuit breaker module rack and secure captive screw.

8 Apply facility power to DCP equipment cabinet by setting DCP circuit breaker in ac junction box to on

position.

9 Set primary Circuit Breaker Module A1A3A1 to ON position.

10 Set UPS POWER switch to 1 (on) position.
S100 ASOS Site Technical Manual

3-123

WARNING

WARNING

Table 3.5.28. DCP Fan Removal and Installation

Step Procedure

REMOVAL

Tools required:

 No. 1 Phillips screwdriver

 No. 2 Phillips screwdriver

 Small flat-tipped screwdriver

 5/16-inch open-end wrench

Death orsevere injury may result if power is notremoved fromDCP prior to maintenance activities.

Ensure that UPS POWER switch is set to 0 (off) position and facility power is removed from DCP.

1 Set UPS POWER switch to off (0) position.

2 Set primary Circuit Breaker Module A1A3A1 to OFF position.

3 Remove facility power from DCP equipment cabinet by setting DCP circuit breaker in ac junction box to off.

4 Loosen captive screw in top of circuit breaker rack and lower rack to facilitate fan removal.

5 Remove rf modem mounting plate (with modem(s) attached) in accordance with table 3.5.19.

6 Using flat-tipped screwdriver, remove fan wiring (four wires) from ac power distribution assembly.

7 Using Phillips screwdriver, remove screw and flat washer securing two ground wires to fan A2B2.

8 Using Phillips screwdriver, remove four screws, nuts, flat washers, and lockwashers securing fan assembly

to card rack assembly.

9 Remove fan assembly from DCP.

10 Using Phillipsscrewdriver,remove fourscrews, nuts,flat washers, and lockwasherssecuring fan to mounting

plate.

11 Remove fan from mounting plate.

INSTALLATION

Tools required:

 No. 1 Phillips screwdriver

 No. 2 Phillips screwdriver

 Small flat-tipped screwdriver

Death orsevere injurymay result if power is not removed from DCP prior to maintenance activities.

Ensure that UPS POWER switch is set to 0 (off) position and facility power is removed from DCP.

1 Ensure that UPS POWER switch is set to off (0) position.

2 Ensure that primary Circuit Breaker Module A1A3A1 is set to off position.

3 Ensure that DCP circuit breaker in ac junction box is set to off position.

4 Ensure that Circuit Breaker Rack A1A3 is lowered.

5 Ensure that rf modem mounting plate is removed.

6 Position fan on mounting plate.

7 Using Phillips screwdriver, install four screws, flat washers, lockwashers, and nuts securing fan and guard

to mounting plate.

8 Position fan assembly in DCP under card rack assembly.

9 Using Phillips screwdriver, install four screws, nuts, flat washers, and lockwashers securing fan assembly

to card rack assembly.

10 Using Phillips screwdriver, install screw and flat washer securing two ground wires to fan A2B2.

11 Using flat-tipped screwdriver, install fan wiring (four wires) to ac power distribution assembly.
ASOS Site Technical Manual S100

Table 3.5.28. DCP Fan Removal and Installation

Step Procedure

3-124

WARNING

WARNING

12 Raise circuit breaker module rack and secure captive screw.

13 Install rf modem mounting plate (with modem(s) attached) in rf mounting bracket in accordance with

table 3.5.19.

14 Apply facility power to DCP equipment cabinet by setting DCP circuit breaker in ac junction box to on

position.

15 Set primary Circuit Breaker Module A1A3A1 to ON position.

16 Set UPS POWER switch to 1 (on) position.

Table 3.5.29. Primary and Secondary Circuit Breakers A1A3A1CB1 and A10CB1

 Removal and Installation

Step Procedure

REMOVAL

Tools required:

 Large flat-tipped screwdriver

 No. 1 Phillips screwdriver

Death orsevere injury may result if power is notremoved fromDCP prior to maintenance activities.

Ensure that UPS POWER switch isset to 0 (off) position, facility power isremoved from DCP, and

battery box connector is disconnected.

1 Set UPS POWER switch to OFF (0) position.

2 Set primary Circuit Breaker Module A1A3A1 to OFF position.

3 Remove facility power from DCP equipment cabinet by setting DCP circuit breaker in ac junction box to off.

4

Sparks are generated when battery box connector J1 is connected or disconnected.

Explosive fumes from battery box may be present when DCP cabinet is opened. Ensure

DCP cabinet is ventilated for at least 5 minutes before connecting or disconnecting J1. 

At DCP battery box, disconnect connector W031-P1 from J1.

5 Using flat-tipped screwdriver, loosen two captive screws securing module retaining strip to rack.

6 Remove module retaining strip from assembly.

7 Slide primary module A1A3A1 or secondary module A1A3A10 forward to gain accessto solderless(spade)

connectors behind circuit breaker CB1.

8 Disconnect spade connectors from circuit breaker CB1 and slide module out of rack.

9 Using Phillips screwdriver, remove two screws, lockwashers, and flat washers securing circuit breaker CB1

to module faceplate.
S100 ASOS Site Technical Manual

Table 3.5.29. Primary and Secondary Circuit Breakers A1A3A1CB1 and A10CB1

 Removal and Installation

Step Procedure

3-125

WARNING

WARNING

WARNING

WARNING

INSTALLATION

Tools required:

 Large flat-tipped screwdriver

 No. 1 Phillips screwdriver

Death orsevere injurymay result if power is not removed from DCP prior to maintenance activities.

Ensure that UPS POWER switch isset to 0 (off) position, facility power isremoved from DCP, and

battery box connector is disconnected.

1 Ensure that UPS POWER switch is set to OFF (0) position.

2 Ensure that DCP circuit breaker in ac junction box is set to off position.

3

Sparks are generated when battery box connector J1 is connected or disconnected.

Explosive fumes from battery box may be present when DCP cabinet is opened. Ensure

DCP cabinet is ventilated for at least 5 minutes before connecting or disconnecting J1.

Ensure that battery box connector W031-P1 is disconnected from battery box.

4

Circuit breaker must be oriented so that power is removed from DCP when switch is in

right position. Death or severe injury may result if circuit breaker is not properly oriented.

Position circuit breaker CB1 on module faceplate. Ensure that breaker is oriented so that breaker turns off

to right position (looking toward faceplate). In this position, LOAD connector of circuit breaker CB1 is on

right and LINE connector is on left. 

5 Using Phillips screwdriver, install two screws, lockwashers, and flat washers securing circuit breaker CB1

to module faceplate.

6 Slide module into position in Circuit Breaker Rack A1A3 far enough to connect wires to back of circuit

breaker CB1.

7 Using markers as a guide, connect solderless (spade) connectors to LINE and LOAD terminals of circuit

breaker CB1.

8 Slide module fully into circuit breaker rack.

9 Hand-tighten two captive screws securing module retaining strip to rack.

10

Sparks are generated when battery box connector J1 is connected or disconnected.

Explosive fumes from battery box may be present when DCP cabinet is opened. Ensure

that DCP cabinet is ventilated for at least 5 minutes before connecting or disconnecting J1.

At DCP battery box, connect connector W031-P1 to J1.

11 Apply facility power to DCP equipment cabinet by setting DCP circuit breaker in ac junction box to on

position.

12 Set primary Circuit Breaker Module A1A3A1 to ON position.

13 Set UPS POWER switch on UPS status panel to 1 (on) position.
ASOS Site Technical Manual S100

3-126

WARNING

Table 3.5.30. Power Supply Assembly Diodes A4CR1 Through A4CR6 Removal and Installation

Step Procedure

REMOVAL

Tools required:

 3/8-inch socket and ratchet

 3/8-inch open end wrench

 Diagonal cutting pliers

Death orsevere injurymay result if power is not removed from DCP prior to maintenance activities.

1 Set UPS POWER switch to off (0) position.

2 Set primary Circuit Breaker Module A1A3A1 to off position.

3 Remove facility power from the DCP equipment cabinet by setting circuit breaker in ac junction box to off.

4 At DCP battery box, disconnect connector W031-P1 from J1.

5 At Power Supply Assembly A4, disconnect harness connectors W024-P1 through W024-P4.

6 Using 3/8-inch socket and ratchet, remove six nuts, lockwashers, and flat washers securing Power Supply

Assembly A4 to DCP equipment cabinet.

7 Carefully remove Power Supply Assembly A4 from DCP equipment cabinet.

8 Lay Power Supply Assembly A4 flat on a suiTable work surface at a location where soldering can be

performed.

9 Locate diode to be removed (CR1 through CR6).

10

NOTE

Anode of diode is canister end. Cathode is end with threaded shaft.

Using diagonal cutting pliers, cut wire soldered to anode of diode (cut as close to anode terminal as possible).

11

CAUTION

Diode is mounted to bracket using two film washers, one plastic insulator ring, one flat

washer, and one 3/8-inch nut. Throughout this procedure, care must be taken not to damage

or lose these parts.

Using 3/8-inch open end wrench, remove nut from cathode of diode.

12 Carefully slide wire with terminal lug from threaded cathode shaft.

13 Carefully remove diode from mounting bracket, retaining flat washer, two film washers, and plastic

insulator ring.

INSTALLATION

Tools required:

 3/8-inch socket and ratchet

 3/8-inch open end wrench

 Wire stripping tool

 Digital multimeter

 Soldering iron

 Solder, tin/lead alloy (specification QQ-S-571)

NOTE

Diode mounting hardware (two film washers, plastic insulator ring, metal flat washer, and 3/8-inch

nut) is part of diode mounting kit 62828-90167-1. If hardware is damaged or lost, a new mounting

kit must be obtained.

1 Place one film washer over diode-threaded shaft and seat against base of canister.
S100 ASOS Site Technical Manual

3-127

WARNING

Table 3.5.30. Power Supply Assembly Diodes A4CR1 Through A4CR6

Removal and Installation - CONT

Step Procedure

2 Insert diode (with film washer) into position in mounting bracket and hold in position (threaded cathode

shaft faces center of Power Supply Assembly A4).

3 While holding diode in position, slide plastic insulator ring over threaded shaft and seat into position

between threaded shaft and surrounding mounting bracket.

4 Slide second film washer over threaded shaft and seat flat against mounting bracket.

5 Slide metal flat washer over threaded shaft and seat flat against second film washer.

6 Slide terminal lug of cathode wire over threaded shaft and seat flat against metal flat washer.

7 Using 3/8-inch open end wrench, install nut onto threaded shaft to secure diode to mounting bracket.

8 Using digital multimeter, verify that diode is properly insulated from mounting bracket by verifying no

continuity between anode terminal and bracket and between cathode shaft and bracket.

9 Using wire stripping tool, strip approximately 1⁄2 inch of insulation from anode wire that was previously

cut from diode.

10 Using soldering iron and solder, tin exposed end of anode wire.

11 Using soldering iron and solder, solder anode wire to anode terminal of diode.

12

Death or severe injury may result if power is not removed from DCP prior to

performing maintenance activities.

Ensure that OUTPUT POWER switch S1 on UPS status panel is set to off (0) position and OUTPUT

indicator is extinguished.

13 Ensure that primary Circuit Breaker Module A1A3A1 is set to OFF position.

14 Ensure that DCP circuit breaker in ac junction box is set to off position. 

15 At DCP battery box, ensure that connector W031-P1 is disconnected from J1.

16 Carefully position Power Supply Assembly A4 in DCP equipment cabinet, ensuring that bottom of A4

plate rests on mounting support at bottom of right wall.

17 Using 3/8-inch socket and ratchet, install six nuts, lockwashers, and flat washers securing power supply

mounting plate assembly.

18 Connect cables to connectors W024-P1 through W024-P4.

19 At DCP battery box, connect connector W031-P1 to J1.

20 Apply facility power to DCP equipment cabinet by setting DCP circuit breaker in ac junction box to on

position.

21 Set primary Circuit Breaker Module A1A3A1 to ON position.

22 Set UPS POWER switch to 1 (on) position.
ASOS Site Technical Manual S100

3-128

WARNING

WARNING

Table 3.5.31. Uninterruptible Power Supply Removal and Installation

Step Procedure

REMOVAL

Tools required:

 Phillips screwdriver

$ Death or severe injury may result if power is not removed from the DCP prior to performing

$ maintenance activities. Ensure that UPS POWER switch isset to off position and that facility power

$ is removed from the DCP.

Severe injury may result if the negative and positive battery terminals are shorted together. Exercise

caution while removing batteries.

$ 1 Set UPS power switch to off position.

$ 2 Remove facility power from DCP cabinet.

3 Disconnect UPS from wiring harness by removing connectors P45, P1, and P33.

4 Using screwdriver, disconnect COMM PORT connector P2 by removing two screws.

5 Unstrap UPS from backplate.

6 Lift and pull UPS off of backplate.

INSTALLATION

Tools required:

 Phillips screwdriver

$ Death or severe injury may result if power is not removed from the DCP prior to performing

$ maintenance activities. Ensure that UPS POWER switch isset to off position and that facility power

$ is removed from the DCP.

$ 1 Verify that UPS power switch is set to off position.

$ 2 Verify that facility power is removed from DCP.

3 Place UPS on backplane.

4 Secure UPS onto backplane with strap.

5 Using screwdriver, connect COMM PORT connector P2 by securing two screws.

6 Connect UPS to wiring harness by connecting connectors P45, P1, and P33.

7 Apply facility power.

$ 8 Set UPS power switch to on position.
S100 ASOS Site Technical Manual

Change 2 3-129

3.5.5 DCP CPU AND SIO (RS-232) BOARD JUMPER CONFIGURATIONS

When replacing a DCP CPU board, the technician must configure jumpers on a basic XVME-601/6 CPU

board (manufacturer's P/N 70601-006) for the slot in which it is to be installed. This changes the CPU part

number to 62828-47006-XX, where XX is determined by the slot number. Similarly, when replacing a

DCP-RS-232 SIO board, the technician must configure jumpers on a basic XVME-490/1 board

(manufacturer's P/N 70490-001) to create the 62828-47014-XX part that corresponds to the slot in which it

is to be installed. Altered item drawings for selected DCP circuit boards, which define the jumper

configurations, are located at the end of Chapter 2, Section V (paragraph 2.5.8).

3.5.6 SETTING UP LINE DRIVER MODEMS

The model D19.2 line drivers are obsolete and are replaced by the model DDS/MR64. If a D19.2 line driver

fails at a site and spare D19.2 line drivers are not available, then all the D19.2 line drivers must be replaced

with the DDS/MR64 line drivers. After installation, the DDS/MR64 line drivers must be manually

programmed to operate with the ASOS parameters by using the LCD display and the YES and NO

pushbutton switches on the front panel ofthemodem(same asrack-mountedmodemsshown on figure 2.3.4).

The LCD display presents main menus,submenus, and configuration optionsto the technician. The YES/NO

pushbuttons are used to sequence through the main menus and submenus and to select appropriate options.

The Installation and Operation Manual for the stand-alone line driver provides detailed information on all

menus,submenus, and options available with the modemand providesinstructions on their use. Table 3.5.33 $

identifiesthe settingsthat must be manuallymade for the model DDS/MR64 line driver. Thistable addresses $

only the settings that must be checked or changed by the technician. The table does not address options that

are automatically set by the factory or are notrequired for ASOS operation. The actual menu and option titles

that appear on the modem LCD display may vary, depending on the modem's internal firmware.

3.5.7 JOHNSON DATA RF MODEM SETUP $

$

Johnson Data rf modem frequencies are assigned and setup at the depot. Order rf modem part number $

62828-40506-1 for 410.075 MHz or 62828-40506-2 for 410.950 MHz. $

$
ASOS Site Technical Manual S100

3-130 Change 2

WARNING

WARNING

$ Table 3.5.32. Line Driver Removal and Installation

Step Procedure

REMOVAL

Tools required:

 Small flat-tipped screwdriver

 No. 2 Phillips screwdriver

Death or severe injury may result if power is not removed from DCP prior to maintenance activities.

Ensure that UPS POWER switch is set to 0 (off) position and facility power is removed from DCP.

1 Set UPS POWER switch to off (0) position.

2 Set primary Circuit Breaker Module A1A3A1 to OFF position.

3 Remove facility power from DCP equipment cabinet by setting DCP circuit breaker in ac junction box to off.

4 At DCP line driver, remove cables from line driver DDS and DDE connectors.

5 At AC Power Distribution Assembly A1A4, remove line driver power connections as follows:

LD #1 (2A1A5A1) A1A4-12D (115VAC) LD#2 (2A1A5A2) A1A2-13D (115VAC)

A1A4-17D (NEUT) A1A4-18D (NEUT)

A1A4-23C (GND) A1A4-23D (GND)

6 Remove and retain hardware securing line driver from 2A1A5 bracket. Remove line driver.

INSTALLATION

Tools required:

 Small flat-tipped screwdriver

 No. 2 Phillips screwdriver

Death or severe injury may result if power is not removed from DCP prior to maintenance activities.

Ensure that OUTPUT POWER switch is set to 0 (off) position and facility power is removed from DCP.

1 Ensure that UPS POWER switch is set to off (0) position.

2 Ensure that primary Circuit Breaker Module A1A3A1 is set to OFF position.

3 Ensure that DCP circuit breaker in ac junction box is set to off position.

4 Remove cover from Line Driver and set switches and install jumpers per table 3.5.32. Replace cover.

5 At DCP, use hardware retained from removal step 6 to secure line driver to 2A1A5 bracket.

6 Install cables to line driver DDS and DDE connectors.

7 At AC Power Distribution Assembly A1A4, connect line driver power connections as follows:

LD #1 (2A1A5A1) A1A4-12D (115VAC) LD#2 (2A1A5A2) A1A2-13D (115VAC)

A1A4-17D (NEUT) A1A4-18D (NEUT)

A1A4-23C (GND) A1A4-23D (GND)

8 Apply facility power to DCP equipment cabinet by setting DCP circuit breaker in ac junction box to on position.

9 Set primary Circuit Breaker Module A1A3A1 to ON position.

10 Set UPS POWER switch to 1 (on) position.
S100 ASOS Site Technical Manual

Change 2 3-131

Table 3.5.33. Model DDS/MR64 Stand Alone Line Driver Setup $

Step Procedure

NOTE

D19.2 line drivers and DDS/MR64 line drivers are not compatible. If a D19.2 line driver fails and

the failed line driver must be replaced with a DDS/MR64 line driver, all D19.2 installed in the

system must be replaced with DDS/MR64 line drivers.

Ensure that the line driver LCD does not display “ERROR”, if “ERROR” cannot be cleared the line

driver may be defective.

The line driver is configured by using the front panel push buttons. Use the NO push button to cycle

through the menu options and the YES push button to select the submenus. Configuration options

are selected by pressing YES or NO push buttons when prompted by LCD display with

“CHANGE?”. Pressing YES activates the configuration option.

1 Use front panel push buttons to configure the DDS/MR64 line driver as follows:

Display Press Configures Option

“NO SIGNAL ASYNC DTE RATE” or 

“ASYNC RA 1200 2.4K BPS LINE” HOME (start configuration process)

TEST NO N/A

“SYNC DTE CHANGE?” YES ASYNC DTE

 “RATE ADAPTER DISABLED - CHANGE?” NO DISABLE

“CHANGE TIMING ?” YES DDS

“CHG LINE RATE?” YES 2400 BPS

“BITS PER WORD=09 CHANGE?” YES 10

“CHANGE CONTROL OPTIONS?” YES N/A

“CHANGE RTS CONTROL?” YES NORMAL RTS

“CHANGE SYNC BUFFER OPT?:” YES SYNC BUFFER DIS

“CHANGE REMOTE LB OPT?” YES RMT LB ENABLED

“CHANGE DSR OPTION?” YES DSR OPT ENABLED

“CHANGE SYS STATUS OPT?” YES SS OPT DISABLED

“CHANGE CA OTP?” YES CA OPT DISABLED

“CHANGE RTS-CTS DELAY?” YES RTS-CTS NORMAL

“CHANGE DTE RL OPT?” YES DTE RL DISABLED

“CHANGE DTE LL OPT?” YES DTE LL DISABLED

“CHANGE DTE TP OPT?” YES DTE TP DISABLED

“CHANGE DTE RT OPT?” YES DTE RT DISABLED

“CHANGE 64K SCRAM OPT? YES SCRAMBLER DIS

“LOAD FACTORY OPTION SET? NO N/A

“SAVE NEW CONFIGURATION?” YES N/A

2 Remove power from line driver.
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$ Table 3.5.33. Model DDS/MR64 Stand Alone Line Driver Setup -CONT

Step Procedure

3

NOTE

In order to set internal jumpers, the line driver must be removed from the DCP and the line

driver cover must be removed.

Remove cover from line driver as follows:

a. Place line driver on its side on a flat surface and place small screwdriver blade in one of

the rear latch slots.

b. Gently push screwdriver while lightly twisting srewdriver back and forth to release lock

prong from lock clip. Assist removal by using fingers to pry cover from chassis.

c. Repeat steps a and b for remaining three latches.

4 Set line driver internal jumpers as follows (refer to figure 2.5.1A):

SW1- RS232 Enable JP1 EN JP2 CH GND

SW2- V.35 Enable

SW3-1 OFF SW3-2 ON SW3-3 OFF SW3-4 OFF

SW3-5 OFF SW3-6 OFF SW3-7 OFF SW3-8 OFF

SW4-1 OFF SW4-2 OFF SW4-3 ON SW4-4 ON

5 Replace line driver cover by aligning rear panel slot guides and front panel lock tabs then pressing cover to

the chassis until the lock prongs engage the lock clips.

6 Reinstall line driver, connect power and signal cables, and apply power to the line driver.
S100 ASOS Site Technical Manual

4-1

CHAPTER 4

WIND SENSOR

SECTION I. DESCRIPTION AND LEADING PARTICULARS

4.1.1 INTRODUCTION

This Chapter provides field service information for the wind sensor (an updated Model 2000 manufactured

by Belfort Equipment Company). This information includes wind sensor physical description, sensor

configurations, installation, operation, theory of operation, and preventive and corrective maintenance. 

4.1.2 PHYSICAL DESCRIPTION

4.1.2.1 Introduction. The wind sensor measures current wind speed and direction relative to true north and

computes 5-second averages of these measurements. Wind measurement data are output in response to

request signals from the data collection package (DCP). Each response message includes diagnostic status

signals generated by the sensor's internal, continuously running self-test.

4.1.2.2 System Physical Components. The wind sensor (Figure 4.1.1) consists of four major components:

wind speed sensor,wind direction sensor, crossarmsupport, andwind sensor electronics enclosure.The wind

speed sensoris made up oftwo components: a wind speed transducer and a cup assembly. Similarly, the wind

direction sensor consists of a wind direction transducer and a vane assembly. All four of these items are field

replaceable units (FRU's). The wind sensor crossarm assembly and electronics enclosure are also FRU's, as

well as a processor board and power supply within the electronics enclosure. The wind speed sensor, wind

direction sensor, and crossarm support are all mounted on a tipping tower to allow them to operate free from

ground obstructions while still being easy to maintain.

The housings of the wind speed and direction sensors are fabricated out of Admiralty brass. The cups and

vane are made of corrosion resistant stainless steel. All electrical connections to the sensors are through the

crossarm support. 

The wind sensor electronics enclosure provides electrical power to the wind sensor and a communications

data link between the sensor and the DCP. The electronics enclosure houses the sensor's data processing

board, power supply, fiberoptic module, and power input box (rf filter assembly). The wind sensor

electronics enclosure is mounted on the sensor tower support. 

Wind speed is measured by a rotating three-cup device that drives a photointerrupter device. Wind direction

is measured by a direction vane assembly coupled to a precision potentiometer. The outputs from the wind

direction and wind speed sensors are processed and converted to an RS-232C message format by a

microprocessor module located in the wind sensor electronics enclosure. The RS-232C format is then

converted to an optical signal by the fiberoptic module located in the wind sensor electronics enclosure for

output to the DCP.

4.1.3 WIND SENSOR CONFIGURATIONS

This Section defines the configurations of the variousfield replaceable units(FRU’s) that make up the wind

sensor. All versions of the FRU’s making up the wind sensor are interchangeable with one possible

exception. Some early model vane and cup assemblies do not fit well on some later model transducer

assemblies. (See the concentricity procedure in table 4.5.10.)
ASOS Site Technical Manual S100

4-2

Figure 4.1.1. Wind Sensor Locational Diagram

4.1.3.1 Wind Speed Sensor. The wind speed sensor has six possible configurations dependent upon the

combination of three versions of wind speed transducers and two versions of wind speed cup assemblies.

4.1.3.1.1 Wind Speed Transducer. There are three versions of wind speed transducers; Mod 0, Mod 1, and

Mod 2, the latest production configuration. 
S100 ASOS Site Technical Manual

4-3

The Mod 0 wind speed transducer is considered obsolete. It can be identified by the manufacturer’s part

number 32228 stamped onto the identification plate on the side ofthe unit. The Mod 0 wind speed transducer

issubject to bearing failures, excessive torque, and moisture problems; for these reasons, it issuggested that

any remaining Mod 0 units be replaced with Mod 1 or preferably, Mod 2 wind speed transducers upon failure

of the unit.

The Mod 1 wind speed transducer can be identified by the manufacturer’s part number 32228 MOD 1

stamped onto the identification plate on the side of the unit. The Mod 1 unit corrected the internal problems

of the Mod 0 transducer; however, the relatively flat top of the Mod 0 and Mod 1 transducers can allow ice

buildup which could degrade the performance of the unit in severe cold weather. For this reason, it is

recommended that the Mod 1 wind speed transducer not be used in climates where icing is prevalent.

The Mod 2 wind speed transducer can be identified by the manufacturer’s part number 33079 stamped onto

the identification plate on the side of the unit and by the unit's steeply sloping top. The Mod 2 wind speed

transducer operates well in all climates and is the recommended replacement for any failed wind speed

transducer.

4.1.3.1.2 Wind Speed Cup Assembly. There are two versions of wind speed cup assemblies; basic and Rev.

C.

The basic version of the wind speed cup assembly can be identified by the relatively short (0.125"), steep

(45°) rain shield flair. This unit is susceptible to moisture problems during severe weather and should be

replaced with the Rev. C version when a failure occurs.

The Rev. C version of the wind speed cup assembly can be identified by the relatively long (0.156"),shallow

(20°) rain shield flair. Rev. C is the preferred version of the wind speed cup assembly and should be used

whenever possible.

4.1.3.2 Wind Direction Sensor. The wind direction sensor hassix possible configurations dependent upon

the combination of three different versions of wind direction transducers and two different versions of wind

direction vane assemblies.

4.1.3.2.1 Wind Direction Transducer. There are three versions of wind direction transducers; Mod 0, Mod

1, and Mod 2. 

The Mod 0 wind direction transducer can be identified by the manufacturer’s part number 32229 stamped

onto the identification plate on the side of the unit. The Mod 0 wind direction transducer issubject to bearing

failures, excessive torque, and moisture problems; for these reasons it is suggested that any remaining Mod

0 units be replaced with Mod 1 or preferably the Mod 2 wind direction transducers upon failure of the unit.

The Mod 1 wind direction transducer can be identified by the manufacturer’s part number 32229 MOD 1

stamped onto the identification plate on the side of the unit. The Mod 1 unit corrected the internal problems

of the Mod 0 transducer; however, the relatively flat top allows ice to build up and degrade the performance

of the unit in severe weather. For this reason, it is recommended that the Mod 1 wind direction transducer

not be used in climates where icing is prevalent.

Mod 2 of the wind direction transducer can be identified by the manufacturer’s part number 33080 stamped

onto the identification plate on the side of the unit and by the unit's steeply sloping top. The current

configuration wind direction transducer operates well in all climates and is the recommended replacement

for any failed wind direction transducer.
ASOS Site Technical Manual S100

4-4

4.1.3.2.2 Wind Direction Vane Assembly. There are two versions of the wind direction vane assembly;

basic and Rev. C.

The basic version ofthe wind direction vane assembly can be identified by the relatively short(0.125"),steep

(45°) rain shield flair. This unit is susceptible to moisture problems during severe weather and should be

replaced with the Rev. C version when a failure occurs.

The Rev. C version of the wind direction vane assembly can be identified by the relatively long (0.156"),

shallow (20°) rain shield flair.Rev.Cisthe preferred version ofthe wind direction vane assembly and should

be used whenever possible.

4.1.3.3 Crossarm Assembly. There are three versions of crossarm assemblies; basic, Rev. F, and Rev. G.

The basic version ofthe crossarmassembly can be identified by the front opening condulet and the aluminum

adapters at the crossarm ends (sensor must be removed to view adapter). The aluminum adapters are subject

to corrosion and the crossarms are subject to cracking at or near the condulet if mishandled. (Example:

Releasing the tipping tower suddenly and allowing the sensors to attain a high rate of acceleration prior to

being stopped could damage the crossarm assembly. It is best to control the tower's progress during the

righting process with the rope installed for that purpose.) It is suggested that the crossarm assembly be

replaced with the Rev. G version if the basic version is damaged or badly corroded.

The Rev. F version of the crossarm assembly can be identified by the front opening condulet and the brass

adapters at the crossarm ends (sensor must be removed to view adapter). The brass adapters were added to

reduce corrosion. The crossarms are subject to cracking at or near the condulet if mishandled. (Example:

Releasing the tipping tower suddenly and allowing the sensors to attain a high rate of acceleration prior to

being stopped could damage the crossarm assembly. It is best to control the tower's progress during the

righting process with the rope installed for that purpose.) It is suggested that the crossarm assembly be

replaced with the Rev. G version if the Rev. F version is damaged.

The Rev. G version of the crossarm assembly can be identified by the top opening on the condulet (the

condulets on the other versions open on the side). The Rev. G crossarm has been built stronger to prevent

damage caused by acceleration. This crossarm is the preferred version and is recommended as the

replacement for failed units.

4.1.3.4 Wind Sensor Electronics Enclosure. There are two different versions of wind sensor electronics

enclosures; basic and Rev. J. 

The basic version of the wind sensor electronics enclosure can be identified by the two line filters present

on the side of the Faraday box, inside the enclosure.

The Rev. J version of the wind sensor electronics enclosure can be identified by the single line filter present

on the side of the Faraday box, inside the enclosure. The other line filter was removed to reduce system

complexity.
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4-5

SECTION II. INSTALLATION

4.2.1 INTRODUCTION

The modular design of the ASOS wind sensor enables simple assembly. The four basic components of the

wind sensor (wind speed sensor, wind direction sensor, crossarm support, and wind sensor electronics

enclosure) are secured to each other by bolts. The entire assembly mounts on the tower and is secured by

locking bolts.

4.2.2 ASSEMBLY

The wind speed sensor and wind direction sensor are prewired to mating connectors; there are no

interconnecting cables. The wind sensor may be assembled prior to installation, or it can be assembled after

the crossarm support is installed on the tower. The following paragraphs provide procedures for assembling

the wind sensor and installing it on the tower.

4.2.2.1 Mounting Wind Sensor Electronics Enclosure. The wind sensor electronics enclosure is mounted

on the tower as shown on figure 4.2.1 using the procedures provided in table 4.2.1. Power and signal cables

are connected through flexible conduits located at the bottom of the enclosure. The power connectionsfrom

the DCP to the wind sensor power input box located in the electronics enclosure are identical for the oneand two-filter configurations. Section IV contains an illustration showing block diagrams for both

configurations.

4.2.2.2 Installing Crossarm Support on Tower. The wind sensor was designed to mate with the tower top

section. During installation of the crossarm support on the tower, the tower top section is accessed by

lowering it to the horizontal position. Table 4.2.2 lists the procedures to install the crossarm support.

Paragraph 4.5.3.3 provides procedures for lowering and raising the tower. The crossarm support post fits

inside of the top section post. The crossarm support is aligned by pointing the wind direction sensor end of

the crossarm support to due north. The direction survey is performed only once upon installation of the

crossarm support. The shorter arm of the crossarm support (wind direction arm) is mechanically aligned to

north when it is attached to the crossarm support given that the crossarm support is aligned and secured to

the tower. Signal and power cables from the crossarm support are fed to the wind sensor electronics

enclosure through the tower and a conduit. The wind direction and wind speed sensors should be installed

after the crossarm support is mounted on the tower. Installation and removal of these sensors is described

in paragraph 4.5.3.4.
ASOS Site Technical Manual S100

4-6

Figure 4.2.1. Wind Sensor Electronics Enclosure Installation (Sheet 1 of 2)
S100 ASOS Site Technical Manual

Change 1 4-7

Figure 4.2.1. Wind Sensor Electronics Enclosure Installation (Sheet 2)

WARNING

 K

Table 4.2.1. Mounting Wind Sensor Electronics Enclosure

Step Procedure

Tools required:

 Large flat-tipped screwdriver

 No. 1 Phillips screwdriver

 Large adjusTable wrench

Death or severe injury may result if power is not removed from wind sensor prior to maintenance

activities. Ensure that circuit breaker (located in DCP) supplying power to wind sensor is set to off

(right) position.

1 Inside DCP equipment cabinet, ensure that circuit breaker on wind sensor power control module is set to off

(right) position.

2 Referencing figure 4.2.1, position wind sensor electronics enclosure on tower.

3 Tighten four bolts, washers, and nuts securing electronics enclosure to tower.

4 Using large flat-tipped screwdriver, open electronics enclosure access door.

5 Using Phillips screwdriver, remove six screws securing access cover to electronics enclosure power input

box.
ASOS Site Technical Manual S100

4-8

Table 4.2.1. Mounting Wind Sensor Electronics Enclosure -CONT

Step Procedure

6 Remove access cover from power input box.

7 Carefully slide ac power and signal cables through holes in bottom of electronics enclosure. Using large

adjusTable wrench, secure flexible conduits to enclosure.

8 Connect ac power wiring to terminal board TB1 in power input box according to the following connection

chart:

Wire color Terminal Function

Black TB1-1 110 vac

White TB1-2 Neutral

Green TB1-3 Chassis ground 

If power input box has two filters and surge suppressors, ensure that the following jumpers are also in place:

From To

TB1-1 (black) TB1-4

TB1-2 (white) TB1-5

9 Remove protective plastic covers from fiberoptic cable connectors on underside of fiberoptic module.

10 Referring to stencils on fiberoptic module, connect transmitter cable (TX) to transmitter connector (XMTR)

and receiver cable (RX) to receiver connector (RCVR).

11 Install access cover on power input box.

12 Using Phillips screwdriver, install six screws securing access cover to power input box.

13 Connect connectors P1 and P2 of tower signal cable W1 to connectors J1 and J2 in electronics enclosure.

14 Using large flat-tipped screwdriver, close and secure electronics enclosure access door.

Table 4.2.2. Installing Crossarm Support On Tower

Step Procedure

Tools required:

 7/16-inch wrench

 1⁄2-inch wrench

 RTV732 sealant (or equivalent)

 Wind tower shims (62828-40224)

1 Lower tower in accordance with paragraph 4.5.3.3 to gain safe access to top of tower.

2 Connect connector P3 of tower signal cable to connector J1 of crossarm support.

3 Install crossarm support in top of tower.

4 Rotate crossarm support such that wind direction sensor end of crossarm support points due north and holes

in tower are aligned with holes in crossarm support.

5 Referencing figure 4.2.2, install two bolts, flat washers, and nuts securing crossarm support. Install the

required number of wind tower shims to remove any excessive play between crossarm support and tower.

Tighten two bolts to secure crossarm assembly to tower.

6 Using RTV732 sealant or equivalent, seal seam around base of crossarm support.

7 Raise tower in accordance with paragraph 4.5.3.3.
S100 ASOS Site Technical Manual

4-9/ (4-10 blank)

Figure 4.2.2. Wind Sensors and Crossarm Installation
S100 ASOS Site Technical Manual

4-11/ (4-12 blank)

SECTION III. OPERATION

4.3.1 INTRODUCTION

The wind sensor is precalibrated and requires no adjustment after it has been properly installed on the tower.

ASOS uses the wind speed and wind direction sensors in a polled mode of operation where the wind sensor

is automatically polled by the data collection package (DCP) to read the wind speed and wind direction data.

A sensorstatusflag isincluded with the wind speed and wind direction data to indicate the results(pass/fail)

of the wind sensor's internal diagnostics. The diagnostic test responses received from the wind sensor are

displayed on the wind speed and direction sensor page, which is explained in Chapter 1. All communications

with the wind sensor are performed via this diagnostic page. There are no special operating procedures for

the wind sensor.
S100 ASOS Site Technical Manual

4-13

SECTION IV. THEORY OF OPERATION

4.4.1 INTRODUCTION

The wind sensor consists of four basic components: the wind speed sensor assembly, wind direction sensor,

crossarmsupport, and wind sensor electronics enclosure. The ASOS wind speed and wind direction sensors,

which use a separate cup and vane design, are updated versions of the Belfort Model F420 seriessensor. The

ASOS Model 2000 series sensors have additional capabilities for digital sensing, diagnostics, and digital

communications. The wind speed and wind direction sensors are mounted to the crossarm support, which

is physically aligned to north during installation and then secured to the tower. The sensors are easily

removed fromthe crossarmsupportforreplacement by unscrewing captive bolts.The housings ofthe sensors

are keyed such that a replaced sensor on the crossarm support maintains true north alignment. The wind

sensor electronics enclosure, which houses the data processing board, power supply, power input box (rf

filter assembly), fiberoptic module, and tower signal cable W1 are mounted on the tower support. The data

processing board, power supply, and fiberoptic module are field replaceable units (FRU's) that are easily

removed for replacement by removing screws and disconnecting wires. 

4.4.2 WIND SENSOR SENSING TECHNIQUES

4.4.2.1 Wind Speed and Direction. Figure 4.4.1 illustrates the sensing technique for both wind speed and

wind direction. Wind speed is measured using an anemometer, which has a photointerrupter device installed

on its shaft. The number of pulses produced by the photointerrupter in a given amount of time is directly

proportional to the wind speed. Wind direction is determined using a precision potentiometer connected

directly to the shaft of the wind vane. The voltage level of the potentiometer wiper is directly proportional

to the wind direction. A micro controller on the data processing board collects data fromboth the wind speed

and wind direction sensors, calculates wind speed and wind direction, formats the data for output, and

communicates with the data collection package (DCP). The micro controller also runs diagnostic tests both

continuously and upon demand from the DCP. The continuous diagnostic provides go/no go type testing of

the wind sensor. The on-demand diagnostic performs a detailed operational checkout of the wind sensor.

4.4.2.2 Temperature.The temperature stabilizationwithin thewind sensor electronics enclosure is provided

by a thermostatically controlled heating element. This heater provides additional warming to the interior of

the electronics enclosure such that wind sensor operation is not hampered by cold weather conditions.

4.4.3 BLOCK DIAGRAM DESCRIPTION

Wind sensor block diagrams are illustrated on figure 4.4.2. Sheet 1 is the block diagram for the wind sensor

with the basic version of the electronics enclosure. Sheet 2 depicts the REV J version of the enclosure. The

paragraphs below provide a block diagram level description of each of the functional areas.

4.4.3.1 Wind Speed Sensor. The sensingmechanismofthe wind speed sensor consists of a photointerrupter

mounted in the sensor housing (Figure 4.4.1). A slotted disk is attached directly to the wind cup assembly

shaft. As the shaft rotates, the slots in the disk pass between a light source and light detector. An electrical

pulse is output by the light detector each time the slot passes by. The electrical pulses created by the

photointerrupter are input to the micro controller via a cable running inside the crossarm support. The micro

controller counts the pulses for a period of time and then calculates the corresponding wind speed.
ASOS Site Technical Manual S100

4-14

Figure 4.4.1. Wind Speed and Wind Direction Sensing Technique

4.4.3.2 Wind Direction Sensor. The sensing mechanism of the wind direction sensor is a precision

potentiometer (Figure 4.4.2). The potentiometer is connected directly to the wind vane assembly shaft such

that it rotates in unison with the wind vane. The voltage level output of the potentiometer is received by the

data processing board, which compares the output to a reference voltage to determine the wind direction

vector.

4.4.3.3 Data Processing Board. The wind sensor data processing board is located in the wind sensor

electronics enclosure. The data processing board containsthe wind sensor micro controller, which performs

all of the data processing functions of the wind sensor apart from the actual sensing of the environment

described above, including the following functions:

a. Accepts data from the photointerrupter and potentiometer to compute the

wind speed and wind direction.
S100 ASOS Site Technical Manual

4-15/ (4-16 blank)

b. Accepts diagnostic data from the wind sensor electronics, temperature

sensors, and power supply and warns the ASOS of a failure.

c. Performs self-test diagnostics and data quality checks (continuous and on-demand tests).

d. Communicates with the ASOS DCP.

4.4.3.4 Fiberoptic Module. The fiberoptic module located in the wind sensor electronics enclosure is the

physical communication link between the wind sensor and the ASOS DCP. The wind sensor is capable of

responding to an interrogation from the ASOS once every 5 seconds. The wind sensor receives ASCII

commands from the ASOS through the fiberoptic module and formats the appropriate response. The

fiberopticmodule usesseparate optical cablesfortransmitting (TX) and receiving (RX) data.The data format

includes the following:

a. 1 start bit

b. 8 data bits

c. 1 stop bit

d. No parity

e. 2400 baud

f. Full duplex

g. Serial asynchronous

h. Configured as data terminal equipment (DTE)

4.4.3.5 Wind Sensor Power Distribution. Power for the wind sensor is provided from the DCP to the

powerinput box and the powersupply located in the wind sensor electronics enclosure.If one filter protrudes

from the top of the power input box, the sensor is a one-filter configuration as illustrated on figure 4.4.2,

sheet 2. If two filters protrude from the top of the power input box as illustrated on figure 4.4.2, sheet 1, the

sensor is a two-filter configuration. DCP cables are connected to the sensor in an identical manner for both

configurations. The power input box contains line surge protectors and rf filters to provide electromagnetic

interference (EMI) protection. Low pass filters on the power lines are also used to filter out high frequency

noise. The power supply converts the filtered 120V, 60 Hz ac power into 5 vdc power required by the wind

sensor electronics.

4.4.3.6 Obstruction Lights. Figure 4.4.3 provides a detailed block diagram of the obstruction lights at the

top of the wind sensor pole. The obstruction lights are controlled by a photo control (day/night switch)

mounted above the ac junction box (beside the DCP). Power from this switch is routed through the Faraday

box in the DCP where it is passed to an underground conduit to the wind sensor. At the wind sensor pad,

power is passed through a flexible conduit to the junction box on the side of the wind sensor pole. From this

junction box, power is routed up through the pole to the obstruction lights.
S100 ASOS Site Technical Manual

Figure 4.4.2. Wind Sensor Block Diagram

(Sheet 1 of 2)

Change 1 4-17/( 4-18 blank)
S100 ASOS Site Technical Manual

Figure 4.4.2. Wind Sensor Block Diagram

(Sheet 2)

Change 1 4-19/ (4-20 blank)
S100 ASOS Site Technical Manual

Figure 4.4.3. Wind Sensor Obstruction Lights

Detailed Block Diagram

4-21/ (4-22 blank)
S100 ASOS Site Technical Manual

4-23

SECTION V. MAINTENANCE

4.5.1 INTRODUCTION

The wind sensor is designed to be easily maintained. There are two categories of wind sensor maintenance:

preventive maintenance and corrective maintenance. Preventive maintenance consists of tasks and teststhat

ensure continued operation. Corrective maintenance consists of tasks that are followed to solve a problem

with the unit.In both cases, the tasks are easy to perform. Furthermore, in the case of corrective maintenance,

the wind sensor helps the technician locate the problem via diagnostics. 

4.5.2 PREVENTIVE MAINTENANCE

The basic preventive maintenance concept includes routine inspection of the wind sensor, inspection of

moving parts for damage or clogging from debris, checking of the obstruction lights, and a semiannual

performance inspection of the bearings and cups. The wind sensor preventive maintenance schedule is

provided in table 4.5.1.

4.5.2.1 Routine Inspection. Routine inspection is performed every 90 days or whenever a technician is at

the site. Routine inspection consists of checking the cups and vane for physical damage and ensuring that

they move freely in the wind. Any debris from insects, animals, or any other cause that shows up as a

performance degradation or a potential performance degradation should be removed. Any otherirregularities

should be noted and any problems should be corrected. The maintenance log should be reviewed to ensure

there are no electronic problems with the system.

4.5.2.2 Obstruction Lights Check. An operational check of the obstruction lights at the top of the wind

sensor pole is performed every 90 days or whenever a technician is at the site. The obstruction lights are

checked by using an opaque object to cover the photo control, which is located on top of the ac junction box

beside the DCP. The obstruction lights should illuminate.

4.5.2.3 Mechanical Operation Inspection. Inspect the cup and vane assemblies for damage, free spin, and

absence of drag to demonstrate that the bearings are operating properly and that the assemblies have not

undergone any trauma since being originally balanced. Annually inspect crossarmassembly cable connector

for corrosion. Table 4.5.2 provides the inspection procedures for the assemblies.

4.5.2.4 Checking Wind Direction and Speed Data. Semiannually, or sooner if there is a degradation of

performance, the technician should check the alignment of the wind direction sensor using the procedure in

table 4.5.3 or 4.5.4 and then check the data being output by the wind sensor. The wind direction data check

is performed after the mechanical bearing and balance checks described above, and after the wind direction

sensor has been properly aligned using the procedure in table 4.5.3 or 4.5.4. These checks use the DCP OID

to observe data being reported by the direction and speed sensors. Table 4.5.5 provides the procedure to

check wind direction and speed data. Wind speed performance is verified by testing the ASOS wind speed

transducer, using a dual speed-driven F420 wind speed calibrator (ASN F850A-1). The calibrator uses a

60-cycle synchronousmotorto provide 300, 600, and 900 rpmtestspeeds. The test verifiessensor electronics

and throughput for the wind speed data collection package (DCP). Test results are reviewed and verified by

the ASOS technician at the OID. The ASOS technician enters the results of the test in the ASOS SYSLOG.

If the wind speed transducer fails to meet the specified calibration values, the wind speed transducer is

replaced.
ASOS Site Technical Manual S100

4-24 Change 1

4.5.2.5 Wind Direction Sensor Alignment Procedure. The wind direction sensor's alignment to true north

must be checked every 180 days or whenever maintenance is performed on the direction sensor or the

crossarm assembly. Wind direction sensor alignment may be performed in two ways. The preferred method

uses an NWS F420 translucent plastic orientation plate and adapter head to directly align the sensor based

on the shadow cast at solar noon. The secondary method uses a Davis pelorus instrument to determine the

offset ofthe wind sensor crossarmwith respect to true north; the wind direction sensoristhen adjusted based

on the crossarm offset. The secondary method should be used when use of the preferred method is not

possible. The following paragraphs provide the procedures for both of these methods. 

4.5.2.5.1 Solar Noon Wind Direction Sensor Alignment Procedure. The preferred method of aligning

the wind direction sensor is to use a special alignment tool (Figure 4.5.1) at the time of solar noon to cast a

shadow at a known reference point on the tool. To perform this procedure, the maintenance technician must

be able to calculate when solar noon will occur at the site. To do this, a special software program is used.

The program is called SUN and runs on any laptop or PC. In order for the program to calculate solar noon

for a given site, the maintenance technician must input the site's latitude and longitude, the Julian date, and

the site's Greenwich Mean Time (GMT). Greenwich Mean Time is also called ZULU or UTC time. Latitude

and longitude can be obtained from the ASOS site survey or the OID's site physicals page. Julian dates are

shown on the Julian calendar, figure 4.5.2. With these inputs, the SUN program will provide the time that

solar noon will occur for that day at thatspecific site. Because the sun casts a shadow at 0 degrees on the tool

at solar noon, the technician must be aware of the time constraints of this procedure. When performing the

procedure, the technician must calculate the time at which solar noon will occur, install the alignment tool

on the wind tower, and raise the tower to a vertical position 20 minutes before solar noon occurs. At 20

minutes before solar noon, the shadow cast on the tool by the sun is checked; the shadow should occur at 5

$ degrees. If the shadow is not at the 5-degree mark on the “E” side of the calibration template, the technician

must lower the tower, align the wind sensor's housing, and raise the tower as quickly as possible. For every

$ 4 minutes that expire after 20 minutes before solar noon, the shadow moves approximately 1 degree;

$ therefore, at 10 minutes before solar noon, the shadow is approximately at the 2.5-degree mark on the “E”

$ side of the calibration template. When adjusting the wind sensor's housing, it is easy to adjust the housing

in the wrong direction. If the tower is tilted to the west after servicing and the shadow is too far west at 20

minutes before solar noon, the technician must turn the housing down toward the west mark by the number

of degrees that it is out. For example, if at 20 minutes before solar noon the shadow is pointing to

$ approximately 12 degrees on the “E” side of the calibration template, the technician lowers the tower over

$ to the west and corrects the alignment by adjusting the housing 7 degrees to the east. This is accomplished

by moving the housing clockwise toward the "W" mark on the orientation plate of the tool. If the error is to

the east, the technician corrects the alignment by moving the housing to the "E" mark. The solar noon

alignment procedure is detailed in table 4.5.3.

4.5.2.5.2 Davis Pelorus Instrument Wind Direction Sensor Alignment Procedure. The secondary

method of aligning the wind direction sensor uses a Davis pelorus instrument and a monocular to determine

the offset of the wind sensor crossarm from true north. The wind direction sensor is then adjusted by the

amount of the offset to align it to true north. To align the wind direction sensor to true north using the Davis

pelorus instrument, perform the procedure in table 4.5.4.

4.5.2.6 Cleaning and Lubrication. The only cleaning required is to remove any debris from the wind

sensor. Because all bearings are sealed, there is no requirement for lubrication. When any field replaceable

unit (FRU) is removed, the connectors should be inspected for dirt and corrosion and cleaned if necessary.
S100 ASOS Site Technical Manual

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Figure 4.5.1. Wind Direction Sensor Alignment Tool
ASOS Site Technical Manual S100

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Figure 4.5.2. Julian Calendar
S100 ASOS Site Technical Manual

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Table 4.5.1. Wind Sensor Preventive Maintenance Schedule

Interval What To Do How To Do It

90 days

Visual inspection Paragraph 4.5.2.1 

Check obstruction lights Paragraph 4.5.2.2

Semiannually

Mechanical operation inspection Table 4.5.2

Starting torque bearing test Paragraph 4.5.3.11 and table 4.5.17

Wind direction alignment Table 4.5.3

Check wind direction and speed data Table 4.5.5

Cleaning and lubrication Paragraph 4.5.2.6

Annually Inspect crossarm cable connector Table 4.5.2

Table 4.5.2. Mechanical Operation Inspection

Step Procedure

1 Remove any dirt from assemblies using soap, water, and a soft cloth.

2 Inspect cup assembly and vane assembly for any physical damage such as bent or dented cups, bent arm

assemblies, bent fins, or seriously cracked or chipped paint.

3 Inspect hub to ensure that shroud is not bent or rubbing sensor housing.

4 Inspect end of each cup arm (on wind speed assembly) to ensure that ends are sealed.

5 Place sensors on a level table in an upright position.

6 Slowly spin cups (and vane). The cup and vane assemblies should rotate freely with no apparent drag,

resistance, or noise (squeaking).

7 When rotated on the housing, the cup assembly and vane assembly should exhibit no wobble, which indicates

bent parts.

8 Slowly spin cup assembly (and vane assembly). The cup and vane assemblies should slowly come to a stop

with no noticeable drag. (Any air currents may prevent the assemblies from stopping completely.) If there

is drag, replace FRU.

9 Tug lightly on the end of the cup and vane assembly. Verify that there is #1/16th inch windshaft endplay. If

endplay >1/16th-inch, replace the FRU.

10 Annually inspect connector between collector assembly and lower case for corrosion. Remove corrosion if

present and apply thin coat of DC-4 anti-corrosion compound to connector pins.
ASOS Site Technical Manual S100

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WARNING

Table 4.5.3. Solar Noon Wind Direction Alignment Procedure

Step Procedure

Tools Required:

 Laptop computer w/ASOS calibration program installed

 3⁄4-inch socket and ratchet

 3⁄4-inch open-end wrench

 1⁄2-inch open-end wrench

 7/16-inch wrench

 NWS F420 direction adapter head

 NWS F420 opaque plastic orientation plate

 Alignment protractor

Before proceeding, ensure safe clearance of wind tower from dangerous areas of the runways,

taxiways, or restricted zones.

NOTE

Synchronize your watch with Local Tower Time before starting this procedure.

1 Using Julian calendar (Figure 4.5.2), determine Julian date.

2 If the ACU has been downloaded from the AOMC at the OID, access the site physical page and record site's

latitude and longitude. If the ACU has not been downloaded from the AOMC, obtain this information from

the site survey document.

3 At the DOS prompt, enter: ASOS; then, execute menu # 1 to run the solar noon program.

4 Enter latitude and longitude in degrees, minutes, and seconds as prompted. Press <ENTER>.

5 To transfer control to the left half of menu, press F10.

6 Press N. Obtain Julian date from figure 4.5.2 and enter in right half of menu; then, press <ENTER>.

7 Solar noon, in local standard time, will be displayed on the next menu line; record result.

NOTE

When using the ASOS calibration program to determine solar noon at a specified site,

adjust the displayed solar noon value by subtracting 1 hour from the result for the

following regions:

Time Zone Longitude

Eastern <75° 00'00" W

Central <90° 00'00" W

Mountain <105° 00'00" W

Pacific <120° 00'00" W

8 To quit, press F10 (to transfer control to the left side of the menu) and press Q.

9

NOTE

Steps 5 through 8 should be performed approximately 30 minutes before solar noon.

Using procedure in table 4.5.8, lower wind tower.

10 Using 1⁄2-inch open-end wrench, remove lightning rod from wind tower so that its shadow does not interfere

with direction reading.

11 Using procedure in table 4.5.10, remove wind direction sensor.

12 Note two scribed lines on north end of crossarm, one on the direction sensor mounting adapter and one on

the pipe that is part of the crossarm.
S100 ASOS Site Technical Manual

Change 1 4-29

Table 4.5.3. Solar Noon Wind Direction Alignment Procedure -CONT

Step Procedure

13 Place direction adapter head onto alignment pin on mounting adapter and tighten thumbscrew. Place

translucent plastic adapter on mounting adapter and secure with supplied thumb nut. Place indicator tube in

center of mounting adapter.

14 Using procedure in table 4.5.8, raise wind tower to vertical position.

15

NOTE

The NWS translucent plastic plate and adapter with rod act as a sundial. The plate is

divided into degrees east and west. The shadow cast by the rod onto the plate is easily

visible from beneath the tower.

At 20 minutes before true solar noon, determine if shadow is pointing to 5-degree east mark on translucent

plate. If it is not, perform the following:

a. Using procedure in table 4.5.8, lower tower.

b. Locate scribed line on direction sensor mounting adapter.

c. Position alignment protractor immediately beneath mounting adapter (at junction with

crossarm assembly) so that 0-degree mark of protractor aligns with scribed line on

mounting adapter.

d. Using 7/16-inch wrench, loosen hex head bolts on direction sensor mounting adapter.

NOTE

The approximate solar motion is 1 degree per 4 minutes (duration is longer during the

summer as latitude approaches 90°; duration is shorter during winter). Experience has

shown that the time it takes to lower tower, make the required adjustment, and raise the

tower is between 3 and 5 minutes.

e. Rotate direction head the number of degrees it was off the 5-degree mark.

f. Using 7/16-inch wrench, tighten two mounting adapter bolts.

g. Using procedure in table 4.5.8, raise tower to vertical position and verify that shadow on

translucent plastic plate is now within the 5-degree west mark. For every 4 minutes that

have expired after 20 minutes before true solar noon, the shadow moves approximately 1

degree.

16 At 10 minutes before solar noon, verify that shadow is centered between the 5-degree on the “E” side of $

the calibration template and 0-degree marks (2.5 degrees). $

17 Using procedure in table 4.5.8, lower tower.

18 Remove alignment tool. Using procedure in table 4.5.10, reinstall direction sensor.

19 Coat threads of lightning rod with antiseize compound. Using 1⁄2-inch open-end wrench, install lightening

rod on wind tower.

20 Using procedure in table 4.5.8, raise wind tower to vertical position.
ASOS Site Technical Manual S100

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WARNING

Table 4.5.4. Davis Pelorus Alignment Procedure

Step Procedure

Tools Required:

 Davis pelorus with tripod

 3⁄4-inch socket and ratchet

 3⁄4-inch open-end wrench

 1⁄2-inch open-end wrench

 7/16-inch wrench

 NWS F420 direction adapter head

 NWS F420 opaque plastic orientation plate

 Alignment protractor

Before proceeding, ensure safe clearance of wind tower from dangerous areas of the runways,

taxiways, or restricted zones.

1 Move 100 ft. to 200 ft. away from south side of wind sensor crossarm (side with three-cup anemometer).

2 Select a position aligned with crossarm assembly using figure 4.5.3 as a guide. A monocular can aid in

obtaining this alignment, especially at 200 feet.

3 Position Davis pelorusinstrument tripod on a flatsurface at the position selected in step 1. Use the level builtin the Davis pelorus instrument to level the instrument.

4 Rotate the entire instrumentso that the instrument’s north and south white markings are in alignment with the

wind sensor crossarm. The north markings should point directly towardsthe wind tower. Use the instrument

sight assembly to obtain the exact orientation as shown in figure 4.5.4.

5 Determine true north by using the Solar Noon shadow or by using a compass and allowing for local magnetic

deviation. Refer to table 4.5.3 to determine Solar Noon. Using a compassrequiresthat the north reading from

the compass be corrected by adding orsubtracting a few degreesto correct for the local deviation of magnetic

north from true north.

6 While maintaining the Davis pelorus instrument alignment with the wind tower, rotate the sight assembly to

align with true north as shown in figure 4.5.5.

7 Measure and record the difference in degrees, CW or CCW, of true north with respect to the Davis pelorus

instrumentmarkings of north. Thisisthe heading error. A CCW heading error correspondsto true north being

on the left side of the instrument (Figure 4.5.5).

8 If the heading error is less than or equal to 2 degrees, then direction alignment need not be adjusted. If the

heading error is greater than 2 degrees, then it must be corrected by performing the following steps.

9 Using the procedures in tables 4.5.7 and 4.5.9, lower the wind tower and remove the wind direction sensor.

10 Observe the two scribed lines on the north end of the crossarm (one on the direction sensor mounting adapter

and one on the pipe part of the crossarm).

11 Position alignment protractor at interSection of crossarm pipe and sensor mounting adapter so that the

protractor zero degree mark aligns with the scribed lines on the crossarm pipe and the mounting adapter.

12 Using a 7/16-inch wrench, loosen hex head bolts on the direction sensor mounting adapter.

13 If the heading error calculated in step 7 is CW, rotate the mounting adapter CW (looking down at the sensor)

to the exact number of degrees recorded in step 7; if heading error is CCW, rotate mounting adapter CCW.

14 Using a 7/16-inch wrench, tighten two mounting adapter boltsthen recheck heading error using a protractor.

If necessary, remark the two scribed lines on the north end of the crossarm.

15 Using the procedure in table 4.5.10, install the wind direction sensor.

16 Using the procedure in table 4.5.8, raise wind tower to a vertical position.
S100 ASOS Site Technical Manual

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Figure 4.5.3. Wind Alignment Procedures
ASOS Site Technical Manual S100

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Figure 4.5.4. Davis Pelorus Instrument
S100 ASOS Site Technical Manual

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Figure 4.5.5. True North Alignment
ASOS Site Technical Manual S100

4-34

Table 4.5.5. Checking Wind Direction and Speed Data

Step Procedure

NOTE

Laptop computerinitialized asDCP OID (paragraph 3.3.4), or any other available OID, may be used

for the following procedure.

1 At OID, displaysensorstatus page (sequentially pressREVUE-SENSOR-STAT function keysfrom1-minute

display).

2 On sensor status page, set report processing for wind sensor to OFF.

3 Display first page of sensor 12-hour page (shows 5-second wind data) on OID (sequentially press

REVUE-SENSOR-12 HR function keys from 1-minute display).

4 Inside DCP equipment cabinet,set circuit breaker on wind sensor power control module to on (left) position.

5 At wind direction sensor, rotate direction vane to align tail of vane to alignment (north) mark on body of

direction sensor. Hold in position for 2 minutes.

6 On sensor 12-hour page at OID, verify that 5-second wind data for test period indicates 180 ±10 degrees.

7 Remove cup assembly from wind speed transducer. Refer to the procedure in table 4.5.10 for cup assembly

removal.

8 Remove ASOS wind speed transducer using procedure of table 4.5.9.

9 Connect ASN S100-TE321 test cable between transducer and adapter head.

10 Place transducer in position onto calibrator blocks.

11 Couple transducerto F420 wind speed calibrator using flexible coupler No. L050. The 3:1 gearspeed reducer

is to be used when running the 600-rpm check.

NOTE

Note the time after completion of each rpm test. This will aid in locating the results at the

OID.

12 While the transmitter is coupled to the F420 calibrator, run calibrator at speeds of 300, 600, and 900 rpm.

The time for each speed will be 2 minutes and 15 seconds. Ensure that calibrator is turning transmitter in

same direction as 3- cup rotor is normally driven. 

13 On 12-hour page of OID, note data in WIND column. Use completion time recorded earlier to locate and

verify calibration data. The calibration values that must be met are listed below. These knot values are valid

only with Version 2.07 wind processor firmware.

RPM Knots

300 27 ±2 knots

600 52 ±2 knots

900 77 ±3 knots

If calibration values are not met, replace wind speed transducer. Repeat test; if the test still fails, follow

standard procedures to locate and repair fault.

14 Remove F420 wind speed calibrator, remove calibrator blocks, disconnect ASN S100-TE321 test cable,

connect transducer to the adapter head, and install cup assembly to transducer by repeating steps 11, 10, 9,

8, and 7.

15 Inside DCP equipment cabinet, set circuit breaker on wind sensor power control module to off (right)

position.

16 Raise wind sensor tower and apply power to wind sensor in accordance with table 4.5.8.

17 AT OID, display sensor status page (sequentially press REVUE-SENSOR-STAT function keys from

1-minute display).

18 On sensor status page, set report processing for wind sensor to ON.
S100 ASOS Site Technical Manual

4-35

4.5.3 CORRECTIVE MAINTENANCE

4.5.3.1 Diagnostics. The ASOS implements diagnostics such that the type of repair is known to the

technician before traveling to the field. The ASOS wind speed and wind direction sensors are provided with

two types of diagnostics: continuous self-testing which runs automatically, and specific built-in tests which

are executed upon demand from the ASOS. The results of both diagnostics are displayed on the wind

speed/direction sensor page as described in Chapter 1.

4.5.3.2 Troubleshooting. The majority of wind sensor problems can be isolated by the diagnosticstest. For

these faults, the technician need only replace the faulty FRU asisindicated in the maintenance log. However,

if a failure inhibits the diagnostics from running, it becomes the technician's responsibility to manually

troubleshoot and repair the wind sensor. The troubleshooting procedures outlined in table 4.5.6 provide a

basis from which the technician can isolate and repair the fault. Upon completing the repair of the wind

sensor, the technician must run the on-demand diagnostics to ensure that the fault is corrected.

Table 4.5.6. Wind Sensor Troubleshooting

What To Do How To Do It

Perform visual inspection of wind sensor. Paragraph 4.5.2.1

Perform fiberoptic module test. Paragraph 1.5.3.3

At DCP, verify that wind sensor ac power control module circuit breaker

is set to on (left) position.

 ---

Perform wind sensor ac and dc power supply checks. Table 4.5.7

If unit still does not function, troubleshoot wind sensor wiring. Figure 4.4.2

4.5.3.3 Lowering and Raising the Wind Tower. Before performing certain corrective maintenance tasks,

the wind tower must be lowered and secured using the polypropylene rope attached to the top of the wind

tower. Technicians muststay clear ofthe tower while it is being lowered orraised. When the towerissecured

in its horizontal position, the lightning rod must be covered to avoid severe cuts or punctures from its sharp

tip. After performing maintenance actions, the tower must be raised and secured in the upright position.

Table 4.5.8 provides the procedures to lower and raise the wind tower. This procedure is referenced as

necessary from subsequent maintenance procedures.

4.5.3.4 WindDirection andWind Speed Sensors Removal and Installation.The wind direction and wind

speed sensors are removed and installed in the same manner. Wind direction and wind speed sensorsremoval

and installation procedures are provided in table 4.5.9. The wind speed transducer, cup assembly, direction

transducer, and vane assembly are all FRU's. For this reason, the cup assembly or the vane assembly must

be removed from its respective transducer before replacing one of the four FRU's. Table 4.5.10 provides

proceduresto remove and install a cup assembly or vane assembly. The cup assembly and vane assemblymay

be removed while the sensor is mounted on the crossarmassembly or after the sensor has been removed from

the crossarm assembly.

4.5.3.5 Power SupplyRemoval and Installation.Removal and installation procedures for the power supply

are provided in table 4.5.11.

4.5.3.6 Fiberoptic Module Removal and Installation. Removal and installation procedures for the

fiberoptic module are provided in table 4.5.12.

4.5.3.7 ProcessorBoard Removal and Installation.Removal and installation proceduresforthe processor

board are provided in table 4.5.13.
ASOS Site Technical Manual S100

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WARNING

4.5.3.8 Wind Sensor Electronics Enclosure Removal and Installation. Removal and installation

procedures for the wind sensor electronics enclosure are provided in table 4.5.14.

4.5.3.9 Wind Tower Signal Cable W1 Removal and Installation. Removal and installation procedures

for the tower signal cable W1 are provided in table 4.5.15.

4.5.3.10 Crossarm Assembly Removal and Installation. Removal and installation procedures for the

crossarm assembly are provided in table 4.5.16.

4.5.3.11 Starting Torque Bearing Test. A performance check of the wind sensor includes performing a

starting torque bearing test. The starting torque of the wind speed and wind direction housings is measured

to detect bearing condition. As the bearings in each housing age, they tend to show an increase in friction

which can be easily measured. Bearings that measure within the allocated starting torque values will ensure

that the wind cups and vanes are responsive at low wind speeds. The starting torque bearing test is performed

every 6 months and prior to installation of a new cup or vane assembly using the procedures in table 4.5.17.

Table 4.5.7. Wind Sensor AC and DC Power Supply Checks

Step Procedure

Tools required:

 No. 1 Phillips screwdriver

NOTE

AC and dc power supply checks should be performed on wind sensor as part of troubleshooting

procedure when a malfunction interrupts communications between sensor and ASOS.

1 Inside DCP equipment cabinet, set circuit breaker on wind sensor power control module to off (right)

position.

2 At wind sensor, open electronics enclosure access door.

3 At electronics enclosure, useNo. 1 Phillipsscrewdriverto remove six screwssecuring powerinput box access

cover.

4 Remove access cover from power input box.

5 Inside DCP equipment cabinet,set circuit breaker on wind sensor power control module to on (left) position.

6

Dangerous voltages are present withinwind sensor electronics enclosurewhenwind sensor

is powered on.

Using digital multimeter (DMM), measure ac voltage between terminals 1 and 2 on terminal board TB1 in

power input box. Voltage should be 110 vac ±10%. If correct voltage is not obtained, troubleshoot ac wiring

back to DCP.

7 Using DMM, measure ac voltage between LINE OUT and NEUTRAL studs on line protector (E2) in power

input box. Voltage should be 110 vac ±10%. If correct voltages are not obtained, replace wind sensor

electronics enclosure.

8 Check fuse F2 (heater fuse) and replace if blown. If fuse blows again, replace wind sensor electronics

enclosure.

9 Using DMM, measure dc voltage between power supply (PS1) terminals marked +OUT and -OUT. Voltage

should be between 4.5 and 5.5 vdc. If correct voltage is not obtained, remove power, disconnect wires from

+OUT and -OUT terminals, reapply power, and check voltage outputs again. If correct voltage is still not

obtained, replace power supply PS1.
S100 ASOS Site Technical Manual

4-37

WARNING

Table 4.5.7. Wind Sensor AC and DC Power Supply Checks -CONT

Step Procedure

10 Inside DCP equipment cabinet, set circuit breaker on wind sensor power control module to off (right)

position.

11 Install load wires to +OUT and -OUT terminals of power supply PS1.

12 Loosen screw securing data processing board A2 to vertical support post and remove data processing board

from its edge connector.

13 Inside DCP equipment cabinet,set circuit breaker on wind sensor power control module to on (left) position.

14 Using DMM, measure dc voltage between power supply (PS1) terminals marked +OUT and -OUT. Voltage

should be between 4.5 and 5.5 vdc. If correct voltage is obtained, replace data processing board A2. If correct

voltage is still not obtained, replace wind sensor electronics enclosure.

15 Inside DCP equipment cabinet, set circuit breaker on wind sensor power control module to off (right)

position.

16 Install data processing board on vertical support post and tighten screw.

17 Install power input box access cover and using No. 1 Phillips screwdriver, install six screws securing cover.

18 Inside DCP equipment cabinet,set circuit breaker on wind sensor power control module to on (left) position.

Table 4.5.8. Lowering and Raising Wind Tower

Step Procedure

LOWERING TOWER

Tools required:

 3⁄4-inch socket and ratchet

 3⁄4-inch open-end wrench

1 Inside DCP cabinet, set circuit breaker on wind sensor circuit breaker module to off (right) position. 

2 Select direction (east or west) to which tower is to be lowered.

3 At opposite side of tower (west or east), use socket, ratchet, and open-end wrench to remove two nuts,

lockwashers, and bolts securing top horizontal retaining beam (Figure 4.1.1) to vertical supports. Remove

top horizontal retaining beam.

4 Release lower end of tower guide rope. 

5

Wind tower is counterbalanced and swings freely when horizontal retaining beams are

removed. Death or severe injury may result if personnel are not kept out of travel path of

wind tower. Throughout this procedure, use guide rope to control tower, and ensure that

personnel are kept out of travel path of tower.

Tower may move unpredictably in heavy winds or if counterbalance is distorted (due to

ice accumulation, FRU's removed from sensor, etc). Use caution when lowering tower

under such conditions.

While maintaining control oftower guide rope, use socket, ratchet, and open-end wrench to carefully remove

two nuts, lockwashers, and bolts securing bottom horizontal retaining beam to vertical supports. Remove

bottom horizontal retaining beam.

6 Using tower guide rope,slowly lowertower until itstravel isstopped by remaining upper horizontal retaining

beam.
ASOS Site Technical Manual S100

4-38

WARNING

WARNING

WARNING

Table 4.5.8. Lowering and Raising Wind Tower -CONT

Step Procedure

7

Tower must be secured in horizontal position using tower guide rope before removing

sensors, crossarm assembly, counterbalance weights, or before performing other

maintenance that affects counterbalance of tower. Failure to comply may result in death

or severe injury.

Secure tower in horizontal position by securing free end of tower guide rope to stationary object (such as

nearest sensor pedestal).

8

The lightning rod is very sharp and can inflict serious injuries to technicians servicing the

sensors. Prior to servicing the sensors while the tower is in the horizontal position, the

lightning rod must be covered.

Devise or obtain a covering having hollow dimensions suiTable to enclose lightning rod (7 inches deep by

1-1/2 inchesin diameter). The cover can be made of plastic,styrofoam, wood, cardboard, orsuiTable packing

material. Cover lightning rod.

RAISING TOWER

Tools required:

 3/4-inch socket and ratchet

 3/4-inch open-end wrench

1 Inside DCP equipment cabinet, ensure that circuit breaker on wind sensor power control module is set to off

(right) position.

2

Death orsevere injury may result if personnel are not kept out of travel path of wind tower.

Throughout this procedure, use guide rope to control tower, and ensure that personnel are

kept out of travel path of tower. 

Tower may move unpredictably in heavy winds or if counterbalance is distorted (due to

ice accumulation, FRU'sremoved from sensor, etc). Use caution when raising tower under

such conditions. 

 Remove lightning rod cover.

3 Release tower guide rope from stationary object.

4 Using tower guide rope, slowly raise tower to upright position.

5

NOTE

Bolts are installed from outboard side of vertical supports. Lockwashers and nuts are

installed from inboard side.

While maintaining control of tower guide rope, use socket, ratchet, and open-end wrench to carefully install

two bolts, lockwashers, and nuts securing bottom horizontal retaining beam to vertical supports.

6 Secure free end of tower guide rope to tower.

7 Using socket, ratchet, and open-end wrench, install two bolts, lockwashers, and nuts securing top horizontal

retaining beam to vertical supports.

8 Inside DCP equipment cabinet,set circuit breaker on wind sensor power control module to on (left) position.
S100 ASOS Site Technical Manual

4-39

Table 4.5.9. Wind Direction and Wind Speed Sensors Removal and Installation

Step Procedure

REMOVAL

Tools required:

 7/16-inch wrench

1 Remove power from wind sensor and lower wind tower in accordance with table 4.5.8.

2

CAUTION

When removing wind direction sensor, loosen only captive bolts on sensor itself. Do not

loosen or adjust bolts securing mounting flange to crossarm. Failure to comply may alter

sensor alignment.

At base of sensor, use 7/16-inch wrench to loosen two captive bolts (Figure 4.2.1) until bolts are free of

sensor housing. Ensure that bolts are disengaged from threads.

3 Firmly grasp sensor and pull straight off of crossarm support mounting flange.

INSTALLATION

1

CAUTION

When installing wind direction sensor, tighten only captive bolts on sensor itself. Do not

tighten or adjust bolts securing mounting flange to crossarm assembly. Failure to comply

may alter sensor alignment.

Install new sensor by aligning guide pins and connector on sensor with mounting holes and receptacle in

crossarm support mounting flange.

2

CAUTION

Bolts securing sensor to crossarm support must be tightened as directed below. Failure to

follow these procedures may result in cross threading of holes in sensor and damage to

internal connectors.

Tighten each captive bolt 1⁄2 turn.

3 Using 7/16-inch wrench, alternately tighten each captive bolt 1⁄2 turn at a time.Continue this process until both

bolts are tight.

4 Raise wind sensor tower and apply power to wind sensor in accordance with table 4.5.8.

Table 4.5.10. Cup Assembly and Vane Assembly Removal and Installation

Step Procedure

REMOVAL

Tools required:

 Large flat-tipped screwdriver

 1/8-inch hex key wrench

1 If removing cup or vane assembly while respective sensor is still mounted to crossarm assembly, remove

power from wind sensor and lower wind tower in accordance with table 4.5.8.

2

NOTE

Cone-shaped cap on top of cup assembly or vane assembly is lefthand thread. Turn

screwdriver clockwise to loosen and counterclockwise to tighten.

Using large flat-tipped screwdriver, remove cone-shaped cap securing cup assembly or vane assembly to

transducer shaft and remove Seeloc washer.
ASOS Site Technical Manual S100

4-40

Table 4.5.10. Cup Assembly and Vane Assembly Removal and Installation -CONT

Step Procedure

3 Using hex key wrench, loosen setscrew securing cup assembly or vane assembly to transducershaft. Lift cup

assembly or vane assembly from transducer shaft.

NOTE

The Mod 0 wind speed transducer is subject to bearing failures, excessive torque, and

moisture problems; for these reasons it is suggested that any remaining Mod 0 units, upon

failure of the unit, be replaced with Mod 1, or preferably, the Mod 2 wind speed

transducers.

The Mod 1 wind speed transducer can be identified by the manufacturers part number

32228 MOD 1 stamped onto the identification plate on the side of the unit. The Mod 1 unit

corrected the internal problems of the Mod 0 transducer; however, the relatively flat top

of the Mod 0 and Mod 1 transducers can allow ice buildup which could degrade the

performance of the unit in severe cold weather. For thisreason, it isrecommended that the

Mod 1 wind speed transducer not be used in climates where icing is prevalent.

INSTALLATION

Tools required:

 1/8-inch hex key wrench

 Test fixture S100-TE329 (NLSC)

1 If installing cup assembly or vane assembly while respective transducer is mounted to crossarm assembly,

ensure that power is removed from wind sensor and tower is lowered in accordance with table 4.5.8.

2 Attach the 0.374-in. diameter dowel(p/o testfixture S100-TE329)to the wind vane hub. Tighten the setscrew

enough to hold the drill blank from rotating but do not overtighten. Slide the clearance gauge (p/o test fixture

S100-TE329) onto the dowel.

3 Invert the wind vane assembly so that gravity causes the clearance gauge to fall into the skirt. Observe that

the clearance gauge falls freely to the bottom of the skirt and is fully seated on the hub. 

4 Repeat step 3 several times, and observe whether the clearance gauge contacts skirt sidewalls and/or fails to

contact the hub. If either ofthese unsatisfactory conditions exists, the wind vane assembly should be rejected:

it cannot be used on the MOD 2 wind bottle.

5 Remove the test fixture from the wind vane. If the wind vane passed the test of steps 3 and 4 above, attach

it to a MOD 2 bottle and manually spin the wind vane while looking upward to inspect clearance; verify that

there is no contact between skirt sidewalls and bottle neck.

6 Position vane assembly on shaft of corresponding transducer. Install wind direction vane, ensuring that

setscrews are aligned with flat surface of wind direction bottle shaft. Using hex key wrench, tighten the

setscrew that secures vane assembly to transducer shaft.

7 Attach the 0.374-in. diameter dowel to the windspeed cup hub by sliding the dowel into the center hole and

tightening the setscrew until the dowel can not rotate but do not overtighten.

8 Slide clearance gauge onto dowel.

9 Hold the windspeed cup assembly inverted so that gravity causes the clearance gauge to fall into the skirt.

Observe that the clearance gauge falls freely to the bottom of the skirt and is fully seated on the hub. 

10 Repeatstep 9 several times and observe whether the clearance gauge contactsthe skirtsidewalls, and/or, fails

to contact the hub. If either of these unsatisfactory conditions exists, the windspeed cup assembly should be

rejected: it cannot be used on the MOD 2 wind bottle.
S100 ASOS Site Technical Manual

Table 4.5.10. Cup Assembly and Vane Assembly Removal and Installation -CONT

Step Procedure

4-41

WARNING

11 Remove the test fixture from the windspeed cup assembly. If the windspeed cup assembly passed steps 9 and

10 above, attach the windspeed cup to the MOD 2 (or current configuration) bottle. Hold this assembly

upright and manually spin the cup assembly while looking upward under the skirt to verify that the skirt

sidewalls do not contact the bottle neck.

NOTE

If either the wind vane assembly or the windspeed cup assembly were to fail the above

concentricity tests, they should be identified accordingly and returned to NRC.

12 Position cup assembly on shaft of corresponding transducer. Using hex keywrench, tighten setscrewsecuring

cup assembly to transducer shaft.

13 Install Seeloc washer on transducer shaft.

14

NOTE

Cone-shaped cap on top of cup assembly or vane assembly is lefthand threaded. Turn

screwdriver clockwise to loosen; counterclockwise to tighten. 

Using large flat-tipped screwdriver, install cone-shaped cap securing cup assembly or vane assembly to

transducer shaft.

15 If transducer is already mounted to crossarm assembly, raise wind tower and apply power to wind sensor in

accordance with table 4.5.8.

Table 4.5.11. Power Supply Removal and Installation

Step Procedure

REMOVAL

Tools required:

 Large flat-tipped screwdriver

 Small flat-tipped screwdriver

 No. 0 Phillips screwdriver

 No. 1 Phillips screwdriver

Death or severe injury may result if power is not removed from sensor prior to maintenance

activities. Ensure that circuit breaker (located in DCP)supplying power to sensor isset to off (right)

position.

1 Inside DCP equipment cabinet, set circuit breaker on wind sensor power control module to off (right)

position.

2 Using large flat-tipped screwdriver, open wind sensor electronics enclosure access door.

3 Using flat-tipped screwdriver, tag and remove wires from power supply terminals.

4 Using No. 0 Phillipsscrewdriver, loosen screwsecuring data processing board to support post(standoff)such

that data processing board is freed from post.

5 Using No. 1 Phillips screwdriver, remove two screws and flat washers securing power supply angle mount

to wind sensor electronics enclosure.Carefully lift powersupply with angle mount from electronics enclosure.

6 Using No. 0 Phillips screwdriver, remove four screws, lockwashers, and flat washerssecuring power supply

to angle mount.
ASOS Site Technical Manual S100

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WARNING

WARNING

Table 4.5.11. Power Supply Removal and Installation -CONT

Step Procedure

INSTALLATION

Tools required:

 Large flat-tipped screwdriver

 Small flat-tipped screwdriver

 No. 0 Phillips screwdriver

 No. 1 Phillips screwdriver

Death orsevere injurymay result if poweris notremoved fromsensor prior to maintenance

activities. Ensure that circuit breaker (located in DCP) supplying power to sensor is set to

off (right) position.

1 Inside DCP equipment cabinet, ensure that circuit breaker on wind sensor power control module is set to off

(right) position.

2 Using No. 0 Phillips screwdriver, install four flat washers, lockwashers, and screws securing power supply

to angle mount.

3 With terminals positioned to the left, slide power supply with angle mount into position.

4 Using No. 1 Phillips screwdriver, install two flat washers and screws securing power supply angle mount to

wind sensor electronics enclosure.

5 Using flat-tipped screwdriver and tags as a guide, connect wires to power supply terminals.

6 Using No. 0 Phillips screwdriver, install screw securing data processing board to support post (standoff) on

power supply mounting angle.

7 Close and secure wind sensor electronics enclosure access door.

8 Inside DCP equipment cabinet,set circuit breaker on wind sensor power control module to on (left) position.

Table 4.5.12. Fiberoptic Module Removal and Installation

Step Procedure

REMOVAL

Tools required:

 Large flat-tipped screwdriver

 Medium flat-tipped screwdriver

 Small flat-tipped screwdriver

 No. 1 Phillips screwdriver (short)

Death or severe injury may result if power is not removed from sensor prior to maintenance

activities. Ensure that circuit breaker (located in DCP)supplying power to sensor isset to off (right)

position.

1 Inside DCP equipment cabinet, set circuit breaker on wind sensor power control module to off (right)

position.

2 Using large flat-tipped screwdriver, open wind sensor electronics enclosure access door.

3 Using small flat-tipped screwdriver, loosen two retaining screws on DB-9 connector located on top of

fiberoptic module. Remove DB-9 connector.

4 Remove six screws and lockwashers securing power input box access cover. 

5 Remove access cover from power input box.
S100 ASOS Site Technical Manual

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WARNING

Table 4.5.12. Fiberoptic Module Removal and Installation -CONT

Step Procedure

6 Using counterclockwise (ccw) rotation, remove two fiberoptic cables from rear of fiberoptic module. Install

protective plastic covers over fiberoptic connectors.

NOTE

Screws referenced in next step are located inside power input box.

7 At wind sensor electronics enclosure, use No. 1 Phillipsscrewdriver to remove fourscrews, lockwashers, flat

washers, and nuts securing fiberoptic module mounting plate to power input box. Remove fiberoptic

mounting plate and gasket.

8 Using smallflat-tipped screwdriver, remove four screws, lockwashers, and gaskets securing fiberoptic module

to mounting plate.

INSTALLATION

Tools required:

 Large flat-tipped screwdriver

 Medium flat-tipped screwdriver

 Small flat-tipped screwdriver

 No. 1 Phillips screwdriver (short)

Death or severe injury may result if power is not removed from sensor prior to maintenance

activities. Ensure that circuit breaker (located in DCP)supplying power to sensor isset to off (right)

position.

1 Inside DCP equipment cabinet, ensure that circuit breaker on wind sensor power control module is set to off

(right) position.

2 Using smallflat-tipped screwdriver, install gaskets, four lockwashers, and screwssecuring fiberoptic module

to mounting plate.

3 With DCP connector toward the front, position fiberoptic module mounting plate and gasket on power input

box. Using No. 1 Phillips screwdriver, install four nuts, flat washers, lockwashers, and screws securing

fiberoptic module to power input box.

4 Remove protective plastic covers from fiberoptic connectors and connect receive (RX) cable to front

connector and transmit (TX) cable to rear connectors to fiberoptic module.

5 Install power input box access cover and secure using six lockwashers and screws.

6 Installsignal cable to DB-9 connector on fiberoptic module. Using smallflat-tipped screwdriver, tighten two

retaining screws.

7 Using large flat-tipped screwdriver, close and secure wind sensor electronics enclosure access door.

8 Inside DCP equipment cabinet,set circuit breaker on wind sensor power control module to on (left) position.
ASOS Site Technical Manual S100

4-44

WARNING

WARNING

WARNING

Table 4.5.13. Processor Board Removal and Installation

Step Procedure

REMOVAL

Tools Required:

 Large flat-tipped screwdriver

 No. 1 Phillips screwdriver

Death or severe injury may result if power is not removed from sensor prior to maintenance

activities. Ensure that circuit breaker (located in DCP)supplying power to sensor isset to off (right)

position.

1 Inside DCP equipment cabinet, set circuit breaker on wind sensor power control module to off (right)

position.

2 Using large flat-tipped screwdriver, open wind sensor electronics enclosure access door.

3 Using No. 1 Phillips screwdriver, remove screw securing processor board to standoff.

4 Carefully remove processor board by pulling it free from its connector.

INSTALLATION

Tools required:

 No. 1 Phillips screwdriver

 Large flat-tipped screwdriver

Death or severe injury may result if power is not removed from sensor prior to maintenance

activities. Ensure that circuit breaker (located in DCP)supplying power to sensor isset to off (right)

position.

1 Inside DCP equipment cabinet, ensure that circuit breaker on wind sensor power control module is set to off

(right) position. 

2 Insert processor board into its corresponding connector inside electronics enclosure.

3 Using No. 1 Phillips screwdriver, install screw securing processor board to standoff. 

4 Using large flat-tipped screwdriver, close and secure wind sensor electronics enclosure access door.

5 Inside DCP equipment cabinet,set circuit breaker on wind sensor power control module to on (left) position.

Table 4.5.14. Wind Sensor Electronics Enclosure Removal and Installation

Step Procedure

REMOVAL

Tools required:

 Large flat-tipped screwdriver

 No. 1 Phillips screwdriver

 Large adjusTable wrench

Death or severe injury may result if power is not removed from sensor prior to maintenance

activities. Ensure that circuit breaker (located in DCP)supplying power to sensor isset to off (right)

position.

1 Inside DCP equipment cabinet, set circuit breaker on wind sensor power control module to off (right)

position.
S100 ASOS Site Technical Manual

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WARNING

Table 4.5.14. Wind Sensor Electronics Enclosure Removal and Installation -CONT

Step Procedure

2 Using large flat-tipped screwdriver, open wind sensor electronics enclosure access door.

3 Using No. 1 Phillips screwdriver, remove six screws securing access cover to power input box. Remove

access cover.

4 Disconnect ac power input wires from terminals TB1-1, TB1-2, and TB1-3 inside power input box.

5 Using ccw rotation, disconnect two fiberoptic cables from underneath fiberoptic module. Install protective

plastic covers over fiberoptic cable connectors.

6 Disconnect connectors P1 and P2 of tower signal cable W1 from connectors J1 and J2 in electronics

enclosure.

7 Using large adjusTable wrench, disconnect both flexible conduits from electronics enclosure.

8 Carefully retract flexible conduits while sliding signal and ac power cables out of electronics enclosure.

9 While supporting electronics enclosure, loosen four captive bolts securing electronics enclosure to tower.

10 Remove electronics enclosure.

INSTALLATION

Tools required:

 Large flat-tipped screwdriver

 No. 1 Phillips screwdriver

 Large adjusTable wrench

Death or severe injury may result if power is not removed from sensor prior to maintenance

activities. Ensure that circuit breaker (located in DCP)supplying power to sensor isset to off (right)

position.

1 Inside DCP equipment cabinet, ensure that circuit breaker on wind sensor power control module is set to off

(right) position.

2 Position wind sensor electronics enclosure on tower. 

3 Tighten four captive bolts securing electronics enclosure to tower.

4 Using large flat-tipped screwdriver, open electronics enclosure access door.

5 Using No. 1 Phillips screwdriver, remove six screws securing power input box access cover. Remove access

cover.

6 Carefully slide ac power and signal cables through holes in bottom of electronics enclosure. Using large

adjusTable wrench, secure flexible conduits to electronics enclosure.

7 Connect ac power wiring to terminal board TB1 in power input box according to the following connection

chart:

Wire color Terminal Function

Black TB1-1 110 vac

White TB1-2 Neutral

Green TB1-3 Chassis ground

If power input box has two filters and surge suppressors, ensure that the following jumpers are also in place:

From To

TB1-1 (black) TB1-4

TB1-2 (white) TB1-5

8 Remove protective plastic covers from two fiberoptic cable connectors underneath fiberoptic module.

9 Referring to stencils on fiberoptic module, connect transmitter cable (TX) to transmitter connector (XMTR)

and receiver cable (RX) to receiver connector (RCVR).

10 Install access cover on power input box and using No. 1 Phillips screwdriver, install six screws securing

cover.

11 Connect connectors P1 and P2 of tower signal cable W1 to connectors J1 and J2 in electronics enclosure.

12 Using large flat-tipped screwdriver, close and secure electronics enclosure access door.
ASOS Site Technical Manual S100

Table 4.5.14. Wind Sensor Electronics Enclosure Removal and Installation -CONT

Step Procedure

4-46

WARNING

13 Inside DCP equipment cabinet,set circuit breaker on wind sensor power control module to on (left) position.

Table 4.5.15. Wind Tower Signal Cable W1 Removal and Installation

Step Procedure

REMOVAL

Tools required:

 Large flat-tipped screwdriver

 Medium flat-tipped screwdriver

 No. 1 Phillips screwdriver

 No. 3 Phillips screwdriver

 Large adjusTable wrench

 Electrical fishtape (optional)

Death or severe injury could result if power is not removed from sensor prior to maintenance

activities. Ensure thatsensor circuit breakersCB1 andCB2 (located in DCP) are off(right position).

NOTE

It is recommended that two persons work together to accomplish this procedure.

1 Open AC Junction Box; turn off circuit breaker for obstruction lights.

2 Open DCP; set wind sensor power control module circuit breaker off (toward right).

3 Open wind sensor electronics enclosure door.

4 Unplug two signal cable connectors W1P1 and W1P2.

5 Attach pullcord or pullwire to cable connectors to aid in installation of replacement cable.

6 Remove cover of pivot junction box. (See figure 4.2.1.)

7 Remove tower access plate.

8 Pull cable W1 (and pullcord) back through pivot pipe to access plate opening.

NOTE

Obstruction light wires might have to be removed temporarily from pivot pipe to allow

enough space for connectors to pass.

9 Remove crossarm. (Refer to table 4.5.16.) If tower is being lowered toward the side with the access plate

(usually on the eastside), be careful not to pinch cable between access plate opening edge and top horizontal

retaining beam.

10 Pull cable W1 (and pullcord) back through top of tower and detach pull cord.

11 If installation will not be accomplished immediately, proceed as follows:

a. Tie off both ends of pullcord.

b. Connect obstruction light wires.

c. Install tower access plate.

d. Install pivot junction box cover.

e. Raise tower. (Refer to table 4.5.8.)

f. Close all three enclosures.

g. Turn on obstruction lights circuit breaker.
S100 ASOS Site Technical Manual

4-47

WARNING

WARNING

Table 4.5.15. Wind Tower Signal Cable W1 Removal and Installation -CONT

Step Procedure

INSTALLATION

Tools required:

 Large flat-tipped screwdriver

 Medium flat-tipped screwdriver

 No. 1 Phillips screwdriver

 No. 3 Phillips screwdriver

 Large adjusTable wrench

 Electrical fishtape (optional)

Death or severe injury may result if power is not removed from sensor prior to maintenance

activities. Ensure that circuit breaker (located in DCP)supplying power to sensor isset to off (right)

position.

1 Repeat/check removal steps 1, 2, 3, 6, 7, and 9.

2 Use vinyl electrical tape to cover and protect connectors while pulling the cable. Use the pullcord installed

in Removal step 5, or use an electrician's fishtape to pull replacement W1 cable into tower, pivot pipe, and

flex conduit. Ensure that W1P3 will be positioned at tower top while W1P1 and W1P2 will be at the wind

electronics enclosure.

3 Install crossarm. (Refer to table 4.5.16.)

4 At the tower access opening, leave slack in the cable to form a drip loop.

5 In the wind electronics enclosure, connect plugs W1P1 and W1P2 into A1J1 and A1J2, respectively.

6 Install tower access plate and pivot junction box cover.

7 Set circuit breakers on; verify that obstructions lights and wind sensor are operating.

8 Close all three enclosures and verify that obstruction lights and wind sensor continue operating.

Table 4.5.16. Crossarm Assembly Removal and Installation

Step Procedure

REMOVAL

Tools required:

 7/16-inch wrench

Death or severe injury may result if power is not removed from sensor prior to maintenance

activities. Ensure that circuit breaker (located in DCP) supplying power to sensor is set to the off

(right) position.

1 Inside DCP equipment cabinet, ensure that circuit breaker on wind sensor circuit breaker module isset to off

(right) position.

2 Using the procedures in table 4.5.8, lower wind tower.

3 At base of wind direction sensor, use 7/16-inch wrench to loosen two captive bolts (Figure 4.2.1) until bolts

are free of sensor housing. Ensure that bolts are disengaged from threads.

4 Firmly grasp wind direction sensor and pull straight off crossarm support mounting flange.

5 At base of wind speed sensor, use 7/16-inch wrench to loosen two captive bolts (Figure 4.2.1) until bolts are

free of sensor housing. Ensure that bolts are disengaged from threads.

6 Firmly grasp wind speed sensor and pull straight off crossarm support mounting flange.

7 Referring to figure 4.2.2, remove two bolts, flat washers, and nuts securing crossarm support to tower.
ASOS Site Technical Manual S100

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WARNING

Table 4.5.16. Crossarm Assembly Removal and Installation -CONT

Step Procedure

8 Carefully slide vertical section of crossarm support off top of tower and remove and retain any shims which

may be present. Disconnect connector W1P3 of tower signal cable from connector J1 of crossarm support

and remove crossarm from tower.

9 Clean off any RTV732 sealant that may remain on tower mounting post.

INSTALLATION

Tools required:

 RTV732 sealant (or equivalent)

 DC-4 anti-corrosion compound

 Wind tower shims (62828-40224)

 7/16-inch wrench

Death or severe injury may result if power is not removed from sensor prior to maintenance

activities. Ensure that circuit breaker (located in DCP) supplying power to sensor is set to the off

(right) position.

1 Inside DCP equipment cabinet, ensure that circuit breaker on wind sensor circuit breaker module isset to off

(right) position.

2

NOTE

Crossarm is mounted to top of tower such that wind direction sensor end of crossarm

points due north and holes in tower are aligned with holes in crossarm support.

Lower wind tower in accordance with table 4.5.8 to gain safe access to top of tower.

3 Apply thin coat of DC-4 anti-corrosion compound to connector pins and connect tower connector W1P3

signal cable to crossarm support connector J1.

4 Install crossarm support in top of tower.

5 Rotate crossarmsupportsuch that wind direction sensor end of crossarmsupport(lower arm) points due north

and holes in tower are aligned with holes in crossarm support.

6 Referencing figure 4.2.2, install two bolts, flat washers, and nuts securing crossarm support to tower. Install

the required number of wind towershimsto remove any excessive play between crossarm support and tower.

Tighten two bolts securing crossarm support to tower.

7 Using RTV732 sealant or equivalent, seal seam around base of crossarm support.

CAUTION

When installing wind direction sensor, tighten only captive bolts on sensor itself. Do not

tighten or adjust bolts securing mounting flange to crossarm assembly. Failure to comply

may alter sensor alignment.

8 Install wind direction sensor by aligning guide pins and connector on sensor with mounting holes and

receptacle in crossarm support mounting flange.

CAUTION

Bolts securing sensor to crossarm support must be tightened as directed below. Failure to

follow these procedures may result in cross threading of holes in sensor and damage to

internal connectors.

9 Tighten each captive bolt 1⁄2 turn.

10 Using 7/16-inch wrench, alternately tighten each captive bolt 1⁄2 turn at a time.Continue this process until both

bolts are tight.

11 Install wind speed sensor by aligning guide pins and connector on sensor with mounting holes and receptacle

in crossarm support mounting flange.
S100 ASOS Site Technical Manual

Table 4.5.16. Crossarm Assembly Removal and Installation -CONT

Step Procedure

4-49/ (4-50 Blank)

12

CAUTION

Bolts securing sensor to crossarm support must be tightened as directed below. Failure to

follow these procedures may result in cross threading of holes in sensor and damage to

internal connectors.

Tighten each captive bolt 1⁄2 turn.

13 Using 7/16-inch wrench, alternately tighten each captive bolt 1⁄2 turn at a time.Continue this process until both

bolts are tight.

14 Raise wind tower in accordance with table 4.5.8.

15 Align wind direction sensor by performing procedure in table 4.5.3.

16 Inside DCP equipment cabinet, ensure that circuit breaker on wind sensor module is set to on (left) position.

Table 4.5.17. Starting Torque Bearing Test

Step Procedure

Tools required:

 Precision torque gauge (Seekonk model SO-3)

1 Using procedures in table 4.5.9, remove wind speed and wind direction sensors from crossarm support.

2 Position wind speed sensor on a flat surface in an area protected from wind or any air movement.

3 Using flat blade bit attached to torque gauge, install torque gauge in slot of nut that secures cups to housing

shaft.

4 Holding torque gauge vertical, slowly turn clockwise and read indicated torque at which cups just begin to

turn. Record reading.

5 Repeat step 4 two more times.

6 Repeat steps 4 and 5, but this time turn torque gauge in a counterclockwise direction.

7 Average six recorded values to determine starting torque of sensor. If value is greater that 0.25 inch-ounce,

replace sensor.

8 Repeat steps 2 through 7 for wind direction sensor.

9 Using procedures in table 4.5.9, install wind speed and wind direction sensors.
S100 ASOS Site Technical Manual

5-1

CHAPTER 5

TEMPERATURE/DEWPOINT SENSORS

SECTION I. DESCRIPTION AND LEADING PARTICULARS

5.1.1 INTRODUCTION

This chapter providesfield service information for the model H083R and 1088 temperature/dewpoint sensors

(hygrothermometers). The only difference between the H083R and 1088 sensors is that the 1088 sensor is

equipped with diagnostic circuitry and software. The H083R has no automatic diagnostic capability. The

information in this chapter includes physical description, installation, operation, theory of operation, and

preventive and corrective maintenance for both sensors. Any differences between the sensors are clearly

noted in the text and drawings. A separate functional drawing for each sensor is provided.

5.1.2 PHYSICAL DESCRIPTION

5.1.2.1 Introduction. Each of the model H083R and 1088 hygrothermometers, developed by the Technical

Services Laboratory for the National Weather Service (NWS), functions as a thermometer and dewpoint

indicator. The sensors indicate dewpoint and ambient temperatures in the range of -80 to +130 degrees

Fahrenheit (°F). Resolution is 0.1°F.

Temperature/dewpoint sensor accuracies are as follows:

Ambient temperature ±1 degree, -58°F to +122°F

±2 degrees through remainder of operational range

Dewpoint temperature ±2°F RMSE, +30°F to +86°F

±3°F RMSE, -10°F to +30°F

±4°F RMSE, -30°F to -10°F

5.1.2.2 Physical Components. Each of the sensors consists of two separate components, as shown in

figure 5.1.1: an aspirator and a transmitter. The aspiratoris mounted to the transmitter via a mounting bracket

assembly. The transmitter is mounted to the sensor mounting pole via a 3-3/4 circular mounting sleeve. The

transmitter is connected to the data collection package (DCP) via a power cable and two fiberoptic cables.

The DCP receives temperature, dewpoint, and diagnostic data (model 1088 only) from the sensor via the

fiberoptic cables. The DCP formats the temperature/dewpoint measurement data and diagnostic data and

transmitsthese data to the acquisition control unit(ACU) via eitherline drivers or an rf communicationslink.

The ACU processes the measurement data via the measurement algorithm and outputs the measurement

results to the various ASOS peripheral devices.

5.1.2.3 Principles of Operation. The model H083R and 1088 hygrothermometers both use a chilled mirror

method to measure dewpoint. By definition, the dewpoint of a sample of air is the temperature at which the

water vapor in the air condenses. In the chilled mirror method, a mirror is cooled to the point where a fine

film of condensate is present on the mirror's surface.

The temperature of the mirror at this condition is equal to the dewpoint temperature. The presence of

condensation is detected by the reflection of an infrared light off the surface of the mirror. Internal circuits

of the model H083R and model 1088 refrigerate a small mirror, and by using an optical feedback loop,

maintain the mirror at exactly the temperature at which the mirrorsurface isslightly clouded with condensed
ASOS Site Technical Manual S100

5-2

Figure 5.1.1. Temperature/Dewpoint Sensor Major Components

water vapor from the sampled air. A precision thermal sensor embedded in the mirror measures the

temperature. A similar thermal sensor located in a sample of the ambient air measures the ambient air

temperature.

5.1.2.4 Aspirator 2MT4A1. The aspirator (figure 5.1.2) consists of two FRU’s: Housing Assembly A1A2

(with built-in fan) and Dewpoint Sensor Assembly A1A1. The dewpointsensor assembly consists of a sensor

card (ambient and dewpoint sensing circuitry), its mounting frame, and the aspirator cable (connects to

transmitter). The dewpoint sensor assembly contains additional diagnostic circuitry that monitors airflow

through the aspirator and is used to detect a fan failure. Thisfan failure circuitry is monitored by model 1088

only.

5.1.2.5 Transmitter 2MT4A2.The transmitter(figure 5.1.3) consists of an outer protective housing, chassis

subassembly, transmit logic board, calibrator assembly, +5 volt power supply, auxiliary power supply, ac

input terminal block, signal out terminal block, line filter, main power switch, heat/cool switch, power fuse,

autobalance module, and fiberoptic module.
S100 ASOS Site Technical Manual

5-3

Figure 5.1.2. Aspirator Component Location

5.1.2.5.1 Transmit Logic Board 2MT4A2A1. The transmit logic board controls mirror heating and

cooling to maintain dewpoint temperature at the mirror surface. It also processes the absolute and dewpoint

temperature resistance sensor information into a serial digital data stream for transmission to the DCP. The

transmit logic board contains a numeric data display for use in servicing the equipment. During system

calibration, the transmit logic board receives a calibrated resistive value from the calibrator assembly in lieu

of the ambient and dewpoint temperature resistive outputs. The model 1088 transmit logic board also

contains self-test circuitry that enables it to test its power supplies and measurement circuits.

5.1.2.5.2 Calibrator Assembly 2MT4A2A2. The calibrator assembly consists of calibrator select switch

S1 and associated calibratorresistors.The calibrator assembly enables the selection of fixed resistance values

in place of the resistive temperature sensors for alignment and troubleshooting of the instrument's circuits.

The model 1088 contains additional self-test selection circuitry that enables automatic selection of the

calibrator resistors during diagnostic testing.

5.1.2.5.3 +5 Volt Power Supply 2MT4A2A3. The +5 volt power supply provides regulated 5V,

1.5-ampere power to the auxiliary power supply for the generation of ±12V power. It also provides the main

logic power supply voltage for the circuits on the transmit logic board.
ASOS Site Technical Manual S100

5-4

Figure 5.1.3. Transmitter Component Location

5.1.2.5.4 Auxiliary Power Supply 2MT4A2A4. The auxiliary power supply supplies power to the

thermoelectric pump in the dewpoint sensor assembly and supplies ±12V power to the system. It also

provides power to the lamp in the mirror/dewpoint sensor circuit. The auxiliary power supply receives a

thermocontrolsignalfromthe transmitterlogic board and a powersupply inputsignalfromthe +5 volt power

supply. The thermocontrol signal controls the polarity of the control voltage applied to the thermoelectric

pump. When the thermocontrol signal is positive, the pump signal is positive, indicating a heat condition.

When the thermocontrol signal is negative, a cooling condition is indicated. Two models of auxiliary power

supplies are used: 1063-2031 and 1063-06B. The applicable model number is stenciled in the upper right

corner of the power supply board. The only difference between the models is how they generate the ±12V

outputs. Themodel 1063-2031 uses an internal oscillator, which is powered by the +5 volt powersupply. The

model 1063-06B uses full wave rectifier power from the 115 vac input.
S100 ASOS Site Technical Manual

5-5/ (5-6 blank)

5.1.2.5.5 Autobalance Module 2MT4A2A5. The autobalance module automatically compensates for

accumulated dirt and other visible contamination on the mirrorsurface, thereby increasing the time between

maintenance cycles. The autobalance module is activated once each day to readjust the bias voltage on the

mirror/dewpoint sensor circuit.

5.1.2.5.6 Fiberoptic Module 2MT4A2A6. The fiberoptic module handles the data transfers between the

sensor and the DCP. For the 1088 sensor, data communication is half-duplex; i.e., the DCP polls the sensor

for data and the 1088 responds. For the H083R, data communication is simplex (one way only), where the

sensor outputs data at regular intervals.

5.1.3 TEMPERATURE/DEWPOINT SENSOR CONFIGURATIONS

The temperature/dewpointsensor(P/N 62828-90114) hastwo possible configurations: the -30 (1088-20) and

the -40 (R1063-20, Refurbished H083R). All FRU’s in all configurations work similar to the descriptions

given in Section 5.1.2. It should be noted however, that some FRU’s are interchangeable between

configurations and some are not. For this reason, the following information is given. See the parts list

(located after the last chapter in volume II) for a complete listing of all parts in this sensor.

5.1.3.1 FRU’s Common to -30 and -40 Configurations. There are six FRU’s that are common to both

configurations:

Power Supply, 5VDC 62828-90114-4

Power Supply, AUX 62828-90114-3

Autobalance Assy. 62828-90114-2

Aspirator Assy. 62828-90114-15

Dew Point Sensor Assy 62828-90114-21

Aspirator Housing Assy 62828-90114-22

5.1.3.2 FRU’s Unique to Each Configuration. The following FRU’s are unique to a particular

configuration:

 -10 (Modified by ECP F004 to become -30.)

 -20 (Modified by ECP F004 to become -40.)

 -30 Transmitter Enclosure 62828-90114-18

Transmitter Logic Card 62828-90114-16

Calibration Assy. 62828-90114-17

 -40 Transmitter Enclosure 62828-90114-19

Transmitter Logic Card 62828-90114-23

Calibration Assy. 62828-90114-24
S100 ASOS Site Technical Manual

5-7

SECTION II. INSTALLATION

5.2.1 INTRODUCTION

This Section provides instructions for installing the aspirator and transmitter on the sensor pads. These

procedures assume that allsupportstructures and cabling have been previously installed. The installation of

the model H083R and model 1088 temperature/dewpoint sensors is identical.

5.2.2 TEMPERATURE/DEWPOINT SENSOR INSTALLATION

Before the temperature/dewpoint sensor is installed on the sensor pad, the aspirator and transmitter must be

connected to each other using the supplied support arm and the procedures provided in table 5.2.1. The

temperature/dewpoint sensor can then be installed on the sensor pad using the procedures provided in

table 5.2.2.

Table 5.2.1. Temperature/Dewpoint Sensor Preassembly

Step Procedure

Tools and materials required:

No. 1 Phillips screwdriver

5/16-inch nut driver/wrench

3/8-inch nut driver/wrench

1⁄2-inch nut driver/wrench

No. 2 Phillips screwdriver

Cable tie wraps

1 Remove aspirator, transmitter,solarshield, and support arm assembly angle brackets with attached hardware

from shipping crate.

 2 Referencing figure 5.2.1, assemble left and right side angle brackets as follows:

a. Separate three different sized angle irons.

b. Locate two long angle irons with an X stamped on one end.

c. Position angle irons on work surface.

d. Locate medium sized angle iron with an X stamped on it.

e. Position medium sized angle iron on top of two long angle irons as shown. Using two

screws and locknuts, connect angle irons. Do not tighten locknuts.

f. Repeat steps b through e for angle irons stamped with an O.

 3 Connect mounting bracket stamped with an O to hinged side of transmitter. Install two 1⁄2-inch standoffs

securing bracket. Do not tighten standoffs.

4 Connect mounting bracketstamped with an X to the otherside of the transmitter. Install two 1⁄2-inch standoffs

securing bracket. Do not tighten standoffs.

5 Position aspirator on mounting brackets with nameplate facing outward (away from transmitter). Install four

3/8-inch locknuts securing aspirator on mounting brackets. Do not tighten locknuts.

6 Using No. 1 Phillipsscrewdriver, install fourscrews and 5/16-inch locknutssecuring small angle ironsto top

and bottom of support brackets. Do not tighten locknuts.

7 Using 5/16-inch nut driver and No. 1 Phillipsscrewdriver, tighten locknutssecuring medium and small angle

irons to bracket assembly.

8 Using 3/8-inch nut driver, tighten four locknuts securing mounting bracket to aspirator. 
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Figure 5.2.1. Temperature/Dewpoint Sensor Installation Diagram

Table 5.2.1. Temperature/Dewpoint Sensor Preassembly -CONT

Step Procedure

9

CAUTION

Overtightening standoffs may cause threads to break off. Take care not to overtighten

standoffs when securing them to transmitter.

Using 1⁄2-inch nut driver, tighten four standoffs securing mounting bracket to transmitter. Take care not to

overtighten standoffs.

10 Position solar shield over transmitter with longest side facing aspirator (figure 5.2.1).

11 Using No. 2 Phillips screwdriver, install four screws, lockwashers, and flat washers securing solar shield to

standoffs on transmitter.

12 Connect connector P1 to connector J1 on transmitter.

13 Using cable tie wraps, secure aspirator cable to support arm assembly as shown on figure 5.2.1. Be sure to

leave service loop to allow removal of dewpoint sensor assembly without cutting tie wraps.
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WARNING

Table 5.2.2. Temperature/Dewpoint Sensor Installation

Step Procedure

Tools required:

 1⁄2-inch wrench

 Large adjustable wrench

 Flat-tipped screwdriver

 No. 1 Phillips screwdriver

Death or severe injury may result if power is not removed from sensor prior to maintenance

activities. Ensure that circuit breaker (located in DCP)supplying power to sensor isset to off (right)

position. 

 1 Inside DCP equipment cabinet, ensure that circuit breaker on temperature/dewpoint sensor power control

module is set to off (right) position.

2

NOTE

Sensor must be mounted so that aspirator assembly is toward the south, over either grass

or bare earth (whichever is the norm for the area, no gravel).

Slide transmitter on sensor pad mounting pole and orient sensor so that aspirator faces south (transmitter

access door opens north). Using 1⁄2-inch wrench, install three mounting bolts securing sensor to mounting

pole. Tighten nuts against mounting column to lock mounting bolts in position.

 3 Open transmitter access door.

4 Carefully slide ac power and fiberoptic cables through hole in bottom of transmitter. Using large adjustable

wrench, secure flexible conduit to transmitter.

5 Using No. 1 Phillips screwdriver, remove two screws and plastic washers securing plastic safety shield over

ac terminal board.

6 Connect ac power wiring to transmitter terminal board TB1 according to the following connection chart:

Wire color Terminal Function

Black TB1-1 110 vac

White TB1-2 Neutral

Green TB1-3 Chassis ground

7 Using No. 1 Phillips screwdriver, install two screws and plastic washers securing plastic safety shield over

ac terminal board.

8 Connect RX connector of fiberoptic cable to RX connector underneath fiberoptic module in transmitter (RX

connector on module is nearest DB-9 electrical connector). Connect TX connector on fiberoptic cable to

remaining connector on fiberoptic module.

9 At transmitter, set the following controls to the indicated positions:

Control Position

Power on/off switch On (up) 

Mode switch OPR 

Autobalance dial 000

10 Inside DCP equipment cabinet, set circuit breaker on temperature/dewpoint sensor power control module to

on (left) position.

11 At temperature/dewpoint sensor, set power switch to on (up) position. Ensure that display on transmitter is

illuminated and that fan in aspirator is operating (fan makes an audible sound). If the correct indications are

not observed, remove power from sensor immediately and troubleshootsensor using procedures provided in

Section V of this chapter.

12 Using procedures provided in paragraph 5.5.2.6, check temperature/dewpoint sensor dc power supplies.
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$ Table 5.2.2. Temperature/Dewpoint Sensor Installation -CONT

Step Procedure

13 Using procedures provided in paragraph 5.5.2.2, inspect and clean aspirator air passage and mirror.

14 Using procedures provided in paragraph 5.5.2.3, perform optical loop adjustment.

15 Using procedures provided in paragraph 5.5.2.7, calibrate temperature/dewpoint sensor.

16 Using procedures provided in table 5.5.7, perform fan fail monitoring circuit adjustment for model 1088

sensor only. Skip this step for model H083R sensor.

17 Using six holddown clips, close access door at transmitter.

18 At OID, using procedures provided in paragraph 1.3.10, configure the system to accept sensor inputs.

19 Using procedures provided in Chapter 1, perform diagnostic testing of the sensor.

20 After allowing sensor to stabilize its operation, observe 1-minute display to verify sensor operation and data

reporting.
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SECTION III. OPERATION

5.3.1 INTRODUCTION

Automatic operation of the temperature/dewpointsensor is controlled by the acquisition control unit (ACU)

via the data collection package (DCP).This Section providesturn-on and turnoff procedures and information

on operation, checkout, and diagnostic testing of the sensor.

5.3.2 CONTROLS AND INDICATORS

The temperature/dewpoint sensor contains maintenance controls and indicators on the transmit logic board

and the calibrator assembly. Descriptions of the test data displayed as part of the system diagnostic test

program are provided in Chapter 1. The temperature/dewpoint sensor controls/indicators are illustrated on

figure 5.3.1 and described in table 5.3.1.

5.3.3 TURN-ON PROCEDURES

The temperature/dewpointsensor is designed for continuous operation and normally remains on at all times,

except for maintenance or repair. The temperature/dewpoint sensor turn-on procedures are provided in

table 5.3.2.

5.3.4 CHECKOUT PROCEDURES

5.3.4.1 Model H083R Checkout. The ACU via the DCP continuously monitors the model H083R

temperature/dewpoint sensor data for proper format and temperature limits. If the ACU detects a failure, it

flags the temperature/dewpoint sensor off-line. Actual testing of the model H083R temperature/dewpoint

sensor must be performed manually using the procedures provided in Section V of this chapter.

5.3.4.2 Model 1088 Checkout. The ACU via the DCP continuously monitors the model 1088

temperature/dewpoint sensor diagnostic output for failure indications. If the ACU detects a failure, it flags

the temperature/dewpoint sensor off-line and enters the appropriate message in the system log. The

technician can review the sensor's test data via Temperature/Dewpoint Sensor (Model 1088) Page on the

OID, and can prompt specific responses by entering T commands per table 5.5.10. (Byte/bit formats for

response words are given in the model 1088 vendor's manual.) For most failures, the diagnostic identifies

the faulty field replaceable unit (FRU). If the diagnostic failsto indicate the faulty FRU, the troubleshooting

procedures provided in Section V of this chapter should be performed for the model 1088 sensor.

5.3.5 RUNNING DIAGNOSTICS

The ASOS contains diagnostic pagesfor both themodel H083Rand 1088 sensors.Because themodel H083R

does not contain any detailed diagnostics, the display page for this model only provides data on transmission

status and watchdog timerfailures. Themodel 1088, however, does contain a complete diagnostic test, which

can be performed by using an on-demand diagnostic test as explained in Chapter 1. 
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Figure 5.3.1. Temperature/Dewpoint Sensor Controls and Indicators

Table 5.3.1. Temperature/Dewpoint Sensor Controls and Indicators

Control/

 Indicator 

Type Description

Transmit Logic Board 2MT4A2A1

TD+ Variable

resistor

Sets gain of dewpoint temperature scaling amplifier.

TDO Variable

resistor

Sets offset of dewpoint temperature scaling amplifier such that with a -5.0V

signal applied to scaling amplifier input, output is 0 volts.

TA+ Variable

resistor

Sets gain of ambient temperature scaling amplifier.

TAO Variable

resistor

Sets offset of ambient temperature scaling amplifiersuch that with a -5.0V signal

applied to scaling amplifier input, output is 0 volts.

NOTE

When DISPLAY SWITCH S2 (model 1088 only) is pressed, normal sensor data transmissions to

the DCP are interrupted and the sensor processing algorithm or diagnostic program may log the

sensor as missing. 

Monitor

Display

Seven-segment 

display

Displays ambient temperature and dewpoint temperature values for sensor

maintenance and calibration. Temperature/dewpoint or ambient temperature

readings are selected via DISPLAY SELECT switch S1. For model 1088,

DISPLAY SELECT switch S2 must be pressed to display selected temperature.
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Table 5.3.1. Temperature/Dewpoint Sensor Controls and Indicators -CONT

Control/

 Indicator 

Type Description

DISPLAY

SELECTOR

S1

Two-position

slide switch

Selects either ambient temperature (TA) or dewpoint temperature (TD) valuesfor

display on the seven-segment display.

NEG.

temperature

Light emitting

diode (LED)

When illuminated, indicates that values being displayed on seven- segment

display are negative.

COOL LIMIT LED When illuminated, indicates that system is in a maximum cooling condition.

HEAT LIMIT LED When illuminated, indicates that system is in a maximum heating condition.

SI GAIN Variable

resistor

Enables indirect sensor amplifier gain adjustment. During system calibration, SI

GAIN is adjusted until SI LEVEL indicator illuminates.

SD GAIN Variable

resistor

Enables direct sensor amplifier gain adjustment. During system calibration, SD

GAIN is adjusted until SD LEVEL indicator illuminates and then extinguishes.

SI LEVEL LED Indicates when indirect signal (SI) is above threshold. With a dry mirror, should

be off. For normal operation, should be on.

SD LEVEL LED Indicates when direct signal (SD) is above threshold. With a dry mirror, should

be on. For normal operation, should be off (or flickering).

FAN FAIL

(model 1088)

LED When illuminated, indicates a fan failure. Also used during fan sensor calibration

to set threshold level of detection circuit.

FAN FAIL

(model 1088)

Variable

resistor

Enables detection threshold of fan sensor circuit to be adjusted.

NOTE

When DISPLAY SWITCH S2 is pressed, normal sensor data transmissions to the DCP are

interrupted and the sensor processing algorithm or diagnostic program may log the sensor as

missing. 

DISPLAY

SWITCH S2

(model 1088)

Momentary

switch

When pressed, causes monitor display to indicate current dewpoint temperature

or ambient temperature, as selected by DISPLAY SELECTOR switch S1.

TEST

(model H083R)

Momentary

toggle switch

When pressed, enablesthe temperature dewpoint mirror temperature to be forced

to a high or low temperature for testing purposes. When released, returns to the

center position, which enablesthe systemto return automatic temperature control

of the mirror.

MODE

(model H083R)

Four-position

rotary switch

Enables precision resistors to be substituted in place of the resistive temperature

sensors for testing and checking the accuracy of the instrument circuits. During

normal operation of the sensor, must be set to OPR.

Calibrator Assembly 2MT4A2A2

MODE

(model 1088)

Six-position

rotary switch

When set to TEST 0 or TEST 50, enables precision resistors to be substituted in

place of resistive temperature sensors for testing and checking accuracy of

instrument circuits. During normal operation of the sensor, must be set to OPR.

When set to HEAT or COOL, enables the temperature dewpoint mirror

temperature to be forced to a high or low temperature for testing purposes. 

When set to SENSORTEST, disables mirror cool circuitry, which enables mirror

temperature to stabilize at ambient air temperature. Under this condition, TD and

TA readings should be the same (±1 degree). This verifies that TD and TA

sensors function properly.

Autobalance Dial Indicates current autobalance setting and allows manual reset of autobalance

during calibration.

FUSE Two-ampere

main power

fuse

Controls 115 vac power to aspirator and transmitter.

POWER Two-position

toggle switch

Controls 115 vac power to aspirator and transmitter. Power is applied when set

to the up position.
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Table 5.3.2. Temperature/Dewpoint Sensor Turn-On Procedures

Step Procedure

Tools required:

 Large flat-tipped screwdriver

1 Using large flat-tipped screwdriver, open temperature/dewpoint sensor transmitter access door.

2 On calibrator assembly, ensure that MODE switch is set to OPR and POWER switch is set to on (up)

position.

3 Inside DCP equipment cabinet, set circuit breaker on temperature/dewpoint sensor power control module to

on (left) position. Model H083R monitor display on transmit logic board illuminates and begins to update

at 18.75-second interval. After approximately 5 minutes, the display stabilizes. Model 1088 monitor display

illuminates and displays the word OFF.

4 Using large flat-tipped screwdriver, close and secure temperature/dewpoint sensor transmitter access door.

5.3.6 NORMAL OPERATING PROCEDURES

The temperature/dewpoint sensor is in continuous operation under the control of the DCP. The temperature

and dewpoint temperature readings are displayed in the TEMP/DEWPT field on the 1-minute display at the

OID.

5.3.7 TURNOFF PROCEDURES

The temperature/dewpoint sensor should be turned off for maintenance purposes only using the procedures

provided in table 5.3.3.

Table 5.3.3. Temperature/Dewpoint Sensor Turnoff Procedures

Step Procedure

Tools required:

 Large flat-tipped screwdriver

1 Inside DCP equipment cabinet,set circuit breaker on temperature/dewpoint sensor power control module to

off (right) position.

 2 Using large flat-tipped screwdriver, open temperature/dewpoint sensor transmitter access door.

 3 On calibrator assembly, set POWER switch to OFF (down) position.

4 Using large flat-tipped screwdriver, close and secure temperature/dewpoint sensor transmitter access door.
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Figure 5.4.1. Dewpoint Temperature Thermal Control Loop

SECTION IV. THEORY OF OPERATION

5.4.1 INTRODUCTION

This Section describes how the model H083R and 1088 hygrothermometers convert physical stimuli

(temperature and dewpoint), as received from the aspirator, into usable data for transmission to the data

collection package (DCP). System theory of operation for both sensors is identical and is divided into two

parts. The first part describes how the ambient temperature and dewpoint temperature measurements are

performed within the aspirator. The second part describes the temperature/dewpoint sensor on a detailed

block diagram level. The model 1088 diagnostic circuitry is explained separately.

5.4.2 TEMPERATURE/DEWPOINT SENSOR MEASUREMENT SYSTEM CONCEPTS

DESCRIPTION

The temperature/dewpoint sensor uses a temperature-controlled mirror with an imbedded heat sensor and

an optical system to detect temperature dewpoint levels. The temperature dewpoint sensor system is

illustrated on figure 5.4.1 and contains a thermo/mirrormodule; an opticalsystemconsisting of a lamp, direct

sensor, and indirect sensor; and a temperature module control circuit consisting of amplifier/detectors, a

summing amplifier, and power amplifiers.
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A light beam from a small infrared diode (CR1) is directed at the surface of a mirror at an angle of 45

degrees. Two photo transistors, Q1 and Q2, are mounted as shown to receive the reflected light. Transistor

Q1, the direct sensor, is placed so that it receives a high degree of light when the mirror is clear. Transistor

Q2, the indirect sensor, is placed so that it is sensitive to light that is scattered when the mirror is clouded

with visible condensation. As the degree of cloudiness of the mirror surface increases, transistor Q1 tends

to receive less light and Q2 tends to receive more light.

A pair of identical signal amplifier/detectors, U5A and U6A, drives a differential control amplifier, U6B.

The output of this high-gain amplifier is negative when the mirror is clear and positive when the mirror is

clouded because of the relative difference between the outputs of transistors Q1 and Q2.

The output of amplifier U6B, through a power amplifier, drives the mirror cooling module, U1. This device

is an electronic heat pump that operates much like a thermocouple in reverse. With a dc voltage applied

across the terminals, the module produces a temperature difference between its flat surfaces. Depending on

the polarity of the applied voltage, the thermal module can produce a heating or cooling effect.

The feedback loop is effectively closed by the physical phenomenon offormation of condensate on themirror

as it is cooled by the thermal module. When the sensor is first turned on, the mirror is clear and transistor

Q1 receives a high level of directly reflected light, and transistor Q2 receives little scattered light. This

condition causes a large negative unbalance signal at the output of amplifier U6B, causing a heavy current

to flow through the thermal module in the cooling direction. The unbalanced condition remains, typically

for approximately 1 minute, until the mirror surface temperature has reached the dewpoint temperature. At

the dewpoint temperature, the output of transistor Q1 decreases and the output of Q2 increases because of

the visible effect of condensation on the mirror. The system then stabilizes at the dewpoint temperature,

maintaining just enough cooling effect to keep the signal levels from transistors Q1 and Q2 in balance, with

amplifier U6B and the power amplifier supplying just enough cooling current to maintain the mirror

temperature at the dewpoint. If the dewpoint of the air changes or if the circuit is disturbed by noise, the loop

makes the necessary corrections to restabilize at the dewpoint. The system is designed for continuous

operation.

The basic operation of both the model H083R and 1088 hygrothermometers is performed by the simplified

circuitry illustrated on figure 5.4.1. The remainder of the system contains the circuitry necessary to monitor

the temperatures of the mirror and the ambient temperature. The system encodes that information and

transmits it to the DCP. The system contains additional circuits for calibration and display of maintenance

data. These circuits are described in the detailed block diagram description of the temperature/dewpoint

sensor provided in paragraph 5.4.3. 

5.4.3 DETAILED BLOCK DIAGRAM DESCRIPTION

5.4.3.1 General. The temperature/dewpoint sensor (figure 5.4.2 for H083R and 5.4.3 for 1088) makes

ambient and dewpoint temperature readings, encodes the readings into a digital format, and transmits the

digitally encoded measurement data to the DCP. The temperature/dewpoint sensor consists of two major

assemblies: the aspirator and the transmitter.

5.4.3.2 Aspirator 2MT4A1. The aspirator contains two thermo resistors. One thermo resistor measures

ambient temperature and the other measures dewpoint temperature. The ambient temperature resistor is

mounted directly in the incoming air stream and is connected to the transmitter via a cable. The dewpoint

temperature resistor is embedded in the mirror, whose temperature is electronically controlled to remain at

the dewpoint. Temperature control of the mirror is performed by optical sensors and a thermoelectric heat

pump. Opticalsensor direct and indirect outputsignals are sent to the transmitter, which sends controlsignals

via the auxiliary power supply to the thermoelectric heat pump to control the temperature of the mirror. The
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5-17

control signals are applied to the thermoelectric heat pump via pins P and R of connector J1. A positive

voltage at pin J1-R indicates a heating condition; a negative voltage indicates a cooling condition.

5.4.3.3 Transmitter 2MT4A2. The transmitter contains the system power supply, control circuits, and

calibration circuits. The transmitter receives the temperature data and converts the data into digital

measurement data, which are transmitted to the DCP.

Calibrator Assembly MT4A2A2 routes the ambient sensor (TA) and the dewpoint sensor (TD) or special

calibrator signals to the transmit logic board measurements circuits. In the model H083R, during system

calibration or troubleshooting, the calibrator assembly enablesthe selection of one of three standard resistor

values. These three valuessimulate temperatures of -50, 0, and +50 degrees Celsius(°C). When in the -50°C

position, TA indicates-50 and TD indicates-55.5. The reason for the difference isthat the dewpoint channel

has been compensated to indicate dewpoint, not frost point, below 0°C. In the model 1088, during system

calibration or troubleshooting, the calibrator assembly enables the selection of one of two standard resistor

values. These values simulate temperatures of 0°C (32°F) and +50°C (122°F). The °F values are displayed

on the monitor display (122 displayed as 22.0). In addition, the model 1088 sensor contains a calibration

select circuit that enables the sensor to automatically select the calibration resistors when it runs its

diagnostic test. The circuit consists of four relays that are controlled by calibration select signals, which are

received from the transmit logic board. These control signals are active when the mode select switch is set

to the OPR position. When a calibration check of model 1088 is performed automatically, the resulting TA

and TD values are retained on the 1088 OID page.

The temperature input amplifiersreceive the TA and TD sensor input signals and are configured asstandard

operational amplifiers. The TA and TD sensor resistive inputs serve as the feedback resistors for the

amplifiers. A 6.2V reference signal is fed through 1240-ohm input resistors to the amplifiers. The output of

the amplifiers depends on the ratio of the input resistors to the resistance of the TA and TD sensors. At 0°C,

the sensor'sresistance is 100 ohms; therefore, the output of the amplifiersis-0.5V. These signals are applied

to the TA and TD scaling circuits, which offset the inputs by 0.5V such that a -0.5V input signal results in

a 0V output from the scaling circuits. The gain of the scaling amplifiers is set such that a ±50°C input from

the sensors results in a ±2V output signal from the scaling amplifiers. The TA0 and TD0 offset variable

resistors enable the offset of the scaling circuit to be set at +0.5V. The TA+ and TD+ gain variable resistors

enable the gain of the amplifiers to be set to 20. Proper adjustment of these resistors is performed during

sensor calibration.

The TD/TA select logic receivesthe TA and TD signalsfrom the scaling amplifiers and a temperature select

signal from the temperature processing control processing unit (CPU). Based on the state of the temperature

select signal, the TD/TA select logic selects either the TA or TD signal and applies it to the analog to digital

(A/D) temperature converter.

The A/D temperature converter measures the TD/TA input and converts it to a 12-bit digital word, which is

routed to the temperature processing CPU. The measurement cycle is started by the CPU, which issues a

RUN command. During this measurement cycle, the A/D converter activates the status line with a busy

signal, which remains active until the measurement cycle is completed. When the busy status is removed,

the CPU activates the hold signal and reads the digitally encoded temperature data from the A/D converter.

The cycle is then repeated. In addition to performing the measurement function, the A/D temperature

converter also provides a 2.458 MHZ system clock signal to the measurement processing and displayCPU's.

The heat pump control circuitreceivesthe sensor direct and sensor indirectsignalsfromthe mirror/dewpoint

temperature sensor circuit and sums these signals to generate heat/ cool commands for application to the

auxiliary power supply. The heat pump control circuit also applies a signal to the heat limit detect circuit,

which monitors the heat pump control circuit heat/cool circuitry. If either circuit fails, the heat limit detect
ASOS Site Technical Manual S100

5-18

circuit activates an error signal to the CPU, which responds by sending an error message to the DCP. The

CPU also monitors the TD sensor measurement data. If this measurement indicates a TD reading of 65°C

or greater, the CPU activates the cool protect command to force the heat pump control circuit into a cool

condition to protect the mirror assembly. During system calibration, the heat pump control circuit is

overridden by heat/cool switch S2 on the model H083R or the mode switch on the model 1088. Overriding

the heat pump control circuit in this manner illuminates one of the heat limit indicators on the transmit logic

board. This is a normal condition due to the 12V drive signal being applied to pin 5 during calibration.

The auxiliary power supply provides the heat/cool current to the thermoelectric heat pump, ac lamp voltage

to the LED in the mirror/dewpoint temperature sensor circuit, and ±12V power to the autobalance module

and transmit logic board. Two types of auxiliary powersupplies are used in the temperature/dewpointsensor.

Although the power supplies perform the same functions and are interchangeable, the circuitry used to

generate the ±12V outputs is different. The part numbers of these two supplies are the only way to

distinguish between the two. The heat/cool current to the thermoelectric heat pump is controlled by the

heat/cool command from the heat pump control circuit. When the heat/cool command is positive, the

auxiliary power supply outputs a pulsating positive dc signal to the thermoelectric heat pump. When the

heat/cool command is negative, the auxiliary power supply outputs a negative cool signal to the

thermoelectric heat pump. Auxiliary power supply P/N 1063-2031 generates the ±12V outputs by utilizing

an internal oscillator, which is driven by the +5V input from the +5 volt power supply. Auxiliary power

supply P/N 1063-06B generates the ±12V output by utilizing a full wave rectifier, which is powered by the

115 vac input.

The maintenance display circuit consists of a display CPU, display select switch S1, display switch S2

(model 1088 only), a polarity indicator, and a 3-digit display. The display CPU receives the serial

temperature data from the temperature processing CPU. The display CPU converts the data into the proper

format to drive the 3-digit display. The display select switch enables either TD or TA temperature data to

be displayed by routing the respective data strobe to the 3-digit display. For model 1088, display switch S2

must be pressed in order to display TA or TD as selected by display select switch S1. As shown on sheet 2

of figure 5.4.3, pressing display switch S2 also opens the path of serial data to the DCP. This may cause the

DCP to miss responses to data requests. As such, the DCP CST may register transmission errors for the SIO

port corresponding to the model 1088 sensor. Thisis a normal occurrence when display switch S2 is pressed

and should not be considered as an actual sensor failure.

The temperature processing CPU controls measurement of the TA and TD data, transmits the TA and TD

data to the display CPU and DCP, monitors the heat pump control circuit, and activates the autobalance

circuit. 

The autobalance module cancels the effects of contaminations on the mirror by applying a fixed dc offset

voltage to the heat pump control circuit. The dc offset voltage cancels the indirect sensor error signal being

received from the mirror/dewpoint temperature sensor circuit. The autobalance circuit is activated once every

24 hours by the temperature processing CPU. The balance cycle is initiated by the CPU, which activates the

heat command signal that is applied to the heat pump control circuit, forcing the circuit into a heat mirror

cycle. The heat command signal remains active for 5 minutes to ensure that all moisture has been driven off

the mirror. The CPU then enables the balance enable signal, which in turn activates the autobalance circuit.

If the mirror is dirty, the heat/cool signal remains in a heating state because the sensor circuit is still trying

to clear the mirror. This positive signal is applied to the motor control circuit, which in turn generates a

balance offset dc voltage. This voltage is applied back to the heat pump control circuit. The enable signal

remains active for 15 seconds, which is adequate time for the autobalance circuit to stabilize. At the end of

the cycle, the balance offset signal remains fixed and acts as an offset value to cancel the effects of the

indirect sensor signal trying to drive the thermoelectric heat pump into a heat condition. Each time the

autobalance circuit is activated, it attempts to eliminate the effects of contaminations on the mirror by
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repeating this cycle. During maintenance, after the mirroris cleaned, the technician must physically reset the

autobalance circuit by returning the autobalance bias resistor to its zero position.

The model 1088 sensor diagnostic circuitry (figure 5.4.3) consists of a critical voltage monitoring circuit,

a fan fail monitoring circuit, a dirty mirror monitoring circuit, and remote select logic circuitry. The model

1088 critical voltage monitoring circuit uses comparator circuitry to monitor the outputs from the +5 volt

power supply and the auxiliary power supply. The critical voltage monitoring circuit receives +12V, -12V,

+5V, and -5V values and compares the sum of these voltages to a fixed reference voltage. If any of the

voltages falls below a predefined value, the comparator generates a critical voltage error signal, which is

monitored by the temperature processing CPU. 

The model 1088 fan fail monitoring circuit uses a comparator circuit to monitor the values of two thermal

resistors located in the aspirator. Only one of these resistors is located in the airflow of the fan. The cooling

effect of the airflow creates a resistive difference between the two resistors. The comparator monitors these

resistive values. If the two values become equal, the fan fail monitoring circuit generates a fail signal and

applies it to the temperature processing CPU.

The model 1088 dirty mirror monitoring circuit monitors the balance offset signal at pin 5 of the transmit

logic board. When this signal exceeds approximately 0.5V, the dirty mirror monitoring circuit activates the

dirty mirror signal and applies it to the temperature processing CPU. The 0.5V balance offset signal is

reached when the value on the autobalance dial is between 450 and 550.

The model 1088 remote select logic circuitry enables the temperature processing CPU to select the TEST

0, TEST 50, and SENSOR TEST functions during the automatic diagnostic. The CPU activates one of the

relay controlsignals, which applies a 5V drive signal to the respective selectrelay on the calibrator assembly.

The CPU monitors the position of the calibrate switch via the op mode error signal, which is applied from

the calibrator assembly to pin 7 on the transmit logic board. During normal system operation, the op mode

error signal should be at a logic 0, indicating that the calibrate switch is set to the OPR position.
S100 ASOS Site Technical Manual

Figure 5.4.2. H083R Temperature/Dewpoint

Sensor Detailed Block Diagram (Sheet 1 of 2)

5-21/ (5-22 blank)
S100 ASOS Site Technical Manual

Figure 5.4.2. H083R Temperature/Dewpoint

Sensor Detailed Block Diagram (Sheet 2)

5-23/ (5-24 blank)
S100 ASOS Site Technical Manual

Figure 5.4.3. 1088 Temperature/Dewpoint

Sensor Detailed Block Diagram (Sheet 1 of 2)

5-25/ (5-26 blank) 
S100 ASOS Site Technical Manual

Figure 5.4.3. 1088 Temperature/Dewpoint

Sensor Detailed Block Diagram (Sheet 2)

5-27/ (5-28 blank) 
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SECTION V. MAINTENANCE

5.5.1 INTRODUCTION

This Section contains the preventive and corrective maintenance procedures for the temperature/dewpoint

sensor. Preventive maintenance consists of checking/cleaning the aspirator air passages and mirror and

calibrating the instrument. Corrective maintenance consists of those procedures required to fault isolate to

a faulty field replaceable unit (FRU) in the temperature/dewpoint sensor. Malfunctions within the

temperature/dewpoint sensor are identified by the ASOS diagnostic test. When performing preventive and

corrective maintenance on the model 1088 sensor, display switch S2 must be pressed to display TA or TD

readings. Pressing this switch interrupts serial data to the DCP, which may result in SIO port failure

indications. This is normal, and these failures should be cleared by the technician after completing

maintenance actions.

5.5.2 PREVENTIVE MAINTENANCE

5.5.2.1 General. A list of the preventive maintenance functions for the temperature/dewpoint sensor is

provided in table 5.5.1.

Table 5.5.1. Temperature/Dewpoint Sensor Preventive Maintenance Schedule

 Interval What To Do How To Do It

90 days

Clean/inspect aspirator air passages. Paragraph 5.5.2.2

Clean/inspect aspirator mirror. Paragraph 5.5.2.2

Perform optical loop adjustment. Paragraph 5.5.2.3

Verify temperature and dewpoint readings. Paragraph 5.5.2.4

Semiannually

Test and adjust fan fail monitoring circuit (1088 only). Paragraph 5.5.2.5

Check dc power supplies. Paragraph 5.5.2.6

Calibrate sensors. Paragraph 5.5.2.7

5.5.2.2 Aspirator Cleaning and Inspection. Because of the continuous flow of outside air through the

aspirator, the air passages on the aspirator may become clogged with dust, leaves, etc. The optical mirror also

gradually acquires a film of contamination, which, if not removed, impairs performance. The performance

of the dewpoint sensor is directly dependent on the use of the proper cleaning agents and procedures for the

mirror.Many dewpointmaintenance problems can be traced directly to improper mirror cleaning even though

they appearto be hardware failures.The various contaminantsthat can accumulate on themirrorsurface have

different effects on sensor performance. Contaminants that consist primarily of particles such as dust and

pollen have the least effect on performance; the sensor tolerates a substantial layer of these contaminates

because they have a relatively small effect on the formation of the dew layer. There are other types of

contaminants, however, that have a disastrous effect on the sensor. The contaminants known to cause serious

performance problems are cleaning compounds such as detergents, soaps, and ammonia; oily substances such

as skin oil and petroleum products; and substances that have an affinity for water (e.g., any of the various

salts including common salt). By interfering with the formation of the dew layer, these contaminants cause

performance problems that include mirror icing and elevated dewpoint temperatures. To prevent these

problems, the aspirator must be cleaned using the procedure provided in table 5.5.2.
ASOS Site Technical Manual S100

5-30

Table 5.5.2. Aspirator Cleaning

Step Procedure

Tools and materials required:

Large flat-tipped screwdriver

Cotton swabs

Distilled water

Kit Carnauba Wax (Northern Labs Inc.)

Isopropyl alcohol (ASN 052-C-12)

CAUTION

Internal components of aspirator are delicate and must be handled with care. Excessive mechanical

shocks can cause permanent damage.

NOTE

Laptop computer initialized as DCP OID (Chapter 3) or any other available OID may be used for

the following procedure.

Wax the mirror after every cleaning. Do not wax the mirror if the mirror has not been cleaned. In

a cold environment, the waxing procedure should be performed in a warm enclosed area.

1 At OID, sign on as a maintenance technician and display sensor status page (sequentially press

REVUE-SENSOR-STAT function keys from 1-minute display).

2 On sensor status page, set report processing for temperature/dewpoint sensor to OFF.

3 Using large flat-tipped screwdriver, open transmitter access door and remove ac power by setting POWER

switch to OFF (down) position.

4 Remove dewpointsensor assembly from aspirator by loosening captive screw on side of unit. Slide dewpoint

sensor assembly downward and out of aspirator housing.

5 Clean unit air passages by wiping with clean rag or blowing clean with compressed air. 

6

CAUTION

Do notscratchmirrorsurface when cleaning. Under no circumstancesshould soap orsoapy

detergent be used on the mirror. Soap seriously impairsthe ability of the mirror surface to

form a film of condensate necessary for dewpoint detection.

Apply power to sensor by setting POWER switch to ON (up) position.

7 Set DISPLAY SELECTOR switch to TD position. While monitoring seven-segment display, heat mirror

above ambient temperature (for model H083R, use TEST switch; for model 1088, use MODE switch).

Remove power from sensor by setting POWER switch to OFF (down) position.

8 Set autobalance potentiometer to 0 position.

9 Using clean cotton swab and distilled water, thoroughly wet mirror surface and wash with gentle circular

motion. Using clean dry swab, immediately wipe the wet surface until dry and all loosened material is

removed. Continue the wet swab and dry swab process until it no longer has a cleaning effect. The use of the

dry swab is essential to the cleaning process because it removes the loosened contaminants which would

otherwise remain on the mirror. For colder temperatures, it may be necessary to disconnect dewpoint sensor

assembly from transmitter enclosure and perform the cleaning in a warmer place.

10 Repeat step 9 using the approved isopropyl alcohol (ASN 052-C-12). Repeat the wet swab and dry swab

process until it no longer has a cleaning effect.

11 Use a clean swab to apply a small amount of wax to mirror surface. Use a circular motion to ensure that a

thin, even coat of wax is applied to the mirror surface. Use care to prevent wax from getting into the optic

block holes for the LED and photo transistors.

12 Allow wax to dry to a hazy finish.

13 Use a clean swab to buff mirror to a smooth, shiny surface free of any excess wax.
S100 ASOS Site Technical Manual

Step Procedure

5-31

14 Use another clean swab to clean up any access wax around the mirror especially around the edge of the card

around the mirror and on the optical block. Confirm that the optic block holes for the LED and photo

transistors are not blocked by wax.

15 Install sensor/fan assembly in aspirator housing and secure with captive screw.

16 At transmitter, apply ac power to sensor by setting POWER switch to ON (up) position. Seven-segment

display illuminates and fan in aspirator begins to operate.

17 Repeat step 7 to heat mirror to 20 degrees Fahrenheit (°F) above ambient temperature or 52°F, whichever

is higher.

18 Using procedures provided in paragraph 5.5.2.3, perform optical loop adjustment.

5.5.2.3 Optical Loop Adjustment. The optical loop adjustment consists of adjusting the gains of the direct

and indirect sensor amplifiers so that the mirror thermocontrol loop can properly maintain the mirror

temperature at dewpoint.The optical loop adjustment should be performed whenever the aspirator or transmit

logic board isserviced orreplaced. Optical loop adjustment proceduresforthemodel H083Randmodel 1088

are provided in tables 5.5.3 and 5.5.4, respectively.

Table 5.5.3. Model H083R Temperature/Dewpoint Sensor Optical Loop Adjustment

Step Procedure

Tools required:

 Small flat-tipped screwdriver

 Large flat-tipped screwdriver

CAUTION

Internal components of aspirator are delicate and must be handled with care. Excessive mechanical

shocks can cause permanent damage.

1 Clean aspirator using the procedure in table 5.5.2. Do not reapply ac power.

2 Install the sensor/fan assembly in aspirator housing and secure with captive screw.

3 Using large flat-tipped screwdriver, open temperature/dewpoint sensor transmitter access door.

4 Reset autobalance variable resistor to zero.

5 Apply power to sensor by setting POWER switch to ON (up) position.

6

NOTE

The adjustments made in this Section must be performed with a completely dry mirror.

Ensure that mirror is dry by heating it for a minimum of 1 minute initially, then keeping

the mirror temperature above ambient (TA) using the HEAT position of the TEST switch.

The measurements and adjustments described in steps 6 and 7 must not be made while

heating the mirror. Therefore, it is necessary to monitor the mirror temperature (TD), via

the seven-segment display, and heat as necessary to ensure that TD is greater than TA,

while making the measurements and adjustments between the heating cycles.

Turn SD GAIN variable resistor (R21) CCW until SD LEVEL LED (CR5) extinguishes then turn CW until

SD LEVEL LED illuminates.

7 Adjust SI GAIN variable resistor (R22) CW until SI LEVEL LED (CR9) illuminates, then turn CCW until

SI LEVEL LED extinguishes.

8 Ensure that CALIBRATOR switch is set to OPR position.

9 Using large flat-tipped screwdriver, close and secure temperature/dewpoint sensor transmitter access door.

10 On sensor status page at OID, turn on report processing for temperature/dewpoint sensor.
ASOS Site Technical Manual S100

5-32

Table 5.5.4. Model 1088 Temperature/Dewpoint Sensor Optical Loop Adjustment

Step Procedure

Tools required:

 Small flat-tipped screwdriver

 Large flat-tipped screwdriver

CAUTION

Internal components of aspirator are delicate and must be handled with care. Excessive mechanical

shocks can cause permanent damage.

1 Clean aspirator using the procedure in table 5.5.2. Do not reapply ac power.

2 Install the sensor/fan assembly in aspirator housing and secure with captive screw.

3 Using large flat-tipped screwdriver, open temperature/dewpoint sensor transmitter access door.

4 Reset autobalance variable resistor to zero.

5 Apply power to sensor by setting POWER switch to ON (up) position.

6

NOTE

The adjustments made in this Section must be performed with a completely dry mirror.

Ensure that mirror is dry by heating it for a minimum of 1 minute initially, then keeping

the mirror temperature above ambient (TA) using the HEAT position of the TEST switch.

The measurements and adjustments described in steps 6 and 7 must not be made while

heating the mirror. Therefore, it is necessary to monitor the mirror temperature (TD), via

the seven-segment display, and heat as necessary to ensure that TD is greater than TA,

while making the measurements and adjustments between the heating cycles.

Turn SD GAIN variable resistor (R21) CCW until SD LEVEL LED (CR5) extinguishes then turn CW until

SD LEVEL LED illuminates.

7 Adjust SI GAIN variable resistor (R22) until SI LEVEL LED (CR9) illuminates, then back off until SI

LEVEL LED extinguishes.

8 Ensure that MODE switch is set to OPR position.

9 Using large flat-tipped screwdriver, close and secure temperature/dewpoint sensor transmitter access door.

10 On sensor status page at OID, turn on report processing for temperature/dewpoint sensor.

5.5.2.4 Verify ASOS Temperature and Dewpoint Readings. The Temperature and Dewpoint Readings

Test is a confidence test, which verifies that ASOS H083R/1088 air temperature and dewpoint temperature

readings compare reasonably with readingstaken by a Psychron Model 566-2 psychrometer. The 90-day test

consists of recording psychrometer temperatures and recording ASOS H083R/1088 temperatures.

Psychrometer temperatures are converted to air and dewpoint temperatures. These temperatures are then

compared with ASOS H083R/1088 corresponding results to determine if the ASOS readings are within

tolerance. The test procedure is provided in table 5.5.5.
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5-33

Table 5.5.5. Verification of ASOS H083R/1088 Temperature/Dewpoint Sensor Readings Using

 Psychron Model 566-2 Psychrometer

Step Procedure

Test Equipment Required:

 Laptop Computer

 Psychron Model 566-2

 Laptop Computer with BASIC 

 Software Program "PSYCHRO411"

CAUTION

For Psychron Model 566-2, the center contact post of each battery must be inserted first to ensure

correct rotation of the fan.

OBTAINING AND CONVERTING PSYCHRON MODEL 566-2 READINGS

INITIAL PREPARATION

 1 Open sliding door halfway, remove water bottle, and close sliding door.

 2 Remove sliding air intake.

3 Examine wet-bulb wick to ensure that it is clean. If it is clean, proceed to step 7. If it is dirty, remove old

wicking, clean thermometer bulb, and install new wick by performing the following steps.

4 Slip a length oftubular wicking over bulb. Secure at top of bulb with a thread at the constriction between bulb

and stem, using a loop and square knot.

5 Form a loop in a second thread and place it approximately in middle of bulb. Tighten thread and pull toward

bottom of bulb, stretching wick firmly and snugly against bulb. Tie with a double loop and square knot.

6 Clip ends of thread and cut off excess wicking about 1/8 inch below bottom of bulb.

7 Thoroughly saturate wet-bulb wick, ensuring that water does not contact eitherthermometertube or dry-bulb.

8 If water has contacted dry-bulb, remove and dry the dry-bulb, then reinstall it.

9 Replace sliding air intake, ensuring that small circular holesin air intake are positioned against thermometer

holder. Replace water bottle.

OPERATION

1

NOTE

The following position is recommended during operation.

While standing at the ASOS H083R/1088 unit, hold Psychron Model 566-2 at temperature/dewpoint sensor

aspirator intake.
ASOS Site Technical Manual S100

5-34 Change 1

Table 5.5.5. Verification of ASOS H083R/1088 Temperature/Dewpoint Sensor Readings Using 

Psychron Model 566-2 -CONT

Step Procedure

2

CAUTION

The air intake and both exhaust ports must be entirely free of obstruction. Because the

instrument samples the air to which it is exposed, care must be taken to use the

psychrometer far enough away from any source that may cause erroneous thermometer

indications.

Turn switch knob clockwise to start aspiration.

3 If thermometer illumination is desired, turn knob to extreme clockwise position.

4

CAUTION

Ensure that motor is turned off after each observation as unnecessary usage greatly

shortens the life of the batteries.

When wet-bulb temperature stabilizes at a minimum value, observe readings of both thermometers as well

astime of readings, and switchmotor off by turning knob fully counterclockwise. For a wet-bulb temperature

below 32 degrees Fahrenheit, check ifthe wick isfrozen. If wet-bulb temperature stabilization does not occur

within 2-1/2 minutes of aspiration, the fan motor is probably running too slow due to weak batteries.

VERIFYING ASOS H083R/1088 TEMPERATURE (Ta)/DEWPOINT (Td $ ) READINGS

1

NOTE

Wet-bulb temperature is not the dewpoint temperature. Wet-bulb temperature is used to

derive the dewpoint temperature.

Convert the psychrometer readings to a dewpoint (Td $ ) temperature using the ASOS calibration program.

2 At the DOS prompt, type: ASOS then, enter menu item 3 to execute the psychrometer calculation program.

3

NOTE

Steps 3 through 7 are the written procedures that are performed in the psychrometer

calculation program. Follow the instructions in the calculation program and use steps 3

through 7 as a reference. When the calculation program is complete, return to step 8 of

this procedure.

Enter the station pressure in inches of mercury and hit return.

4 Enter the dry- and wet-bulb temperature readings obtained from Psychron Model 566-2 and hit return after

each entry.

5 If a wet-bulb temperature is entered which is higher than the dry-bulb temperature (Ta $ ) , the program will

beep to alert the user that an invalid entry was entered. The cursor will return to the dry-bulb temperature

location to enable the user to reenter the correct values.

6 If the wet-bulb temperature is below freezing, the program will beep and ask the user if the wick is frozen.

Enter a "y" or an "n" (The answer is not case sensitive).

7 The dewpoint temperature and relative humidity will be displayed on the subsequent lines.

8 Record the calculated dewpoint temperature for comparison with ASOS H083R/1088 dewpoint temperature.

9 Obtain ASOS H083R/1088 temperature (Ta) /dewpoint (Td $ ) readings. Record air temperature and dewpoint

temperature in °F from the OID. Use 5-minute observation reading (from REVIEW-RPT-5MIN screen)

closest in time to the time of the psychrometer readings.
S100 ASOS Site Technical Manual

Table 5.5.5. Verification of ASOS H083R/1088 Temperature/Dewpoint Sensor Readings Using 

Psychron Model 566-2 -CONT

Step Procedure

Change 1 5-35

10 After air temperatures and dewpoint temperatures for ASOS H083R/1088 and Psychron Model 566-2 have

been obtained, use the following criteria to verify validity of ASOS H083R/1088 readings:

a. If the difference between the ASOS H083R/1088 air temperature and the Psychron Model

566-2 air temperature is within ±5°F, the ASOS H083R/1088 reading is valid. If the

difference is more than ±5°F, the ASOS H083R/1088 temperature reading is invalid and

corrective maintenance should be performed. For corrective maintenance, perform

procedure under "Symptom: Either the ambient or dewpoint temperature reading is

incorrect" in table 5.5.12.

b. For dewpoint comparison, use table 5.5.6 to determine maximum allowable difference

between ASOS H083R/1088 dewpoint temperature and Psychron Model 566-2 dewpoint

temperature recorded in step 8.

c. If the difference between the ASOS H083R/1088 dewpoint temperature and the Psychron

Model 566-2 dewpoint temperature is within the maximum allowable difference

(determined from table 5.5.6), the ASOS H083R/1088 reading is valid.

d. If the difference between the dewpoint temperatures exceeds the maximum allowable

difference, the ASOS H083R/1088 reading is invalid and corrective maintenance should

be performed. For corrective maintenance instructions, refer to the procedure in

table 5.5.12, entitled: "Symptom: Either the ambient or dewpoint temperature reading is

incorrect."

Table 5.5.6. Maximum Allowable Difference Between ASOS H083R/1088 and

Psychron Model 566-2 Dewpoint Temperatures

Dewpoint Depression If Dewpoint >32/F If Dewpoint #32/F

(Ta - Td) #23/F 6/ 10/

 23/F < (Ta - Td) <36/F 9/ 16/

36/F # (Ta - Td) 16/ 26/

Example: If the ASOS H083R/1088 air temperature (Ta) and dewpoint temperature (Td) are 55/F and 30/F $

respectively, the (Ta- Td) spread would be 25 and the maximum allowable difference between the ASOS

H083R/1088 dewpoint and the Psychron Model 566-2 dewpoint would be ±16/F.

5.5.2.5 Deleted. $

Table 5.5.7. Deleted $

This space intentionally left blank. $
ASOS Site Technical Manual S100

5-36 Change 1

WARNING

$ This space intentionally left blank.

5.5.2.6 DC Power Supply Check. The dc power supplies are checked by first checking fuse F1 on the

transmitter and then testing the 5V and ±12V outputs from the 5-volt power supply and auxiliary power

supply, respectively. The power supplies require no adjustment. If a power supply fails the check, it must

be replaced. The outputs of the dc power supplies are checked using the procedures provided in table 5.5.8.

Table 5.5.8. DC Power Supply Check

Step Procedure

TEST

Dangerous voltages(110 vac) are present within themodelsH083Rand 1088 temperature/dewpoint

sensors. Exercise standard safety procedures.

1 At temperature/dewpoint power control module in DCP,remove power fromsensor by setting circuit breaker

on power control module to the off (right) position.

2 At transmitter, open access door.

3 Check fuse F1.

4 Apply power to sensor by setting circuit breaker on power control module to the on (left) position.

5 NOTE

Power supply checks are made with full heater power applied. For the model H083R

sensor, the TEST switch must be manually held in HEAT position while voltage

measurements are being made.

Ensure that POWER switch S1 is set to ON (up) position. For model 1088 sensor, place MODE switch in

HEAT position. For model H083R, hold TEST switch in HEAT position.

6 At terminal board TB1, set DMM for ac reading and connect between pins 1 and 2. DMM should indicate

120 ±10 vac. If correct indication is not obtained, check DCP. If correct indication is obtained, proceed to

step 7.

7 At +5V power supply, connect DMM between pins 1 and 3. DMM should indicate 120 ±10 vac. If correct

indication is not obtained, replace transmitter. If correct indication is obtained, proceed to step 8.
S100 ASOS Site Technical Manual

5-37

Table 5.5.8. DC Power Supply Check - CONT

Step Procedure

8 At +5V power supply, set DMM for dc reading and connect between pins 6 (+) and 5 (-). DMM should

indicate +5 ±0.5V. If correct indication is not obtained, perform the following:

a. Remove power from sensor and remove transmitter board.

b. Reapply power and check power supply output at pins 6 and 5. If normal indication is

obtained, replace transmitter board. If normal indication is not obtained, proceed to step

c.

c. Remove power from sensor and disconnect connector X6 from Fiberoptic Module A5.

d. Reapply power and check power supply output at pins 6 and 5. If normal indication is

obtained, replace fiberoptic module. If not, proceed to step e.

e. Remove power from sensor and disconnect aspirator cable P1 from J1.

f. Reapply power and check power supply output at pins 6 and 5. If normal indication is

obtained, replace dewpoint sensor. If not, proceed to step g.

g. Remove power and replace +5V power supply. 

h. Reapply power and check power supply output at pins 6 and 5. If normal indication is

obtained, remove power from sensor and connect or install the units removed or

disconnected above. Reapply power and check power supply output. If normal indication

is not obtained, replace transmitter.

9

NOTE

When connecting DMM, use pin 9 as ground for the model 1088 and pin 7 as ground for

the model H083R.

At transmit logic board, connect DMM between pins 6 (+) and ground. DMM should indicate +12 ±0.5 vdc.

Connect DMM between pins 12 (+) and ground. DMM should indicate -12 ±0.5 vdc. If correct indication

is not obtained, perform the following:

a. Remove power from sensor and remove transmitter board.

b. Reapply power and check power supply outputs at pins 6 and ground and 12 and ground.

If normal indications are obtained, replace transmitter board. If not, proceed to step c.

c. Remove power from sensor and disconnect aspirator cable P1 from J1.

d. Reapply power and check power supply outputs at pins 6 and ground and 12 and ground.

If normal indications are obtained, replace dewpoint sensor. If not, proceed to step e.

e. Remove power from sensor and replace auxiliary power supply. 

f. Reapply power and check power supply outputs at pins 6 and ground and 12 and ground.

If normal indications are obtained, remove power from sensor and connect or install the

units removed or disconnected above. Reapply power and check power supply outputs. If

normal indication is not obtained, replace transmitter. 
ASOS Site Technical Manual S100

5-38

5.5.2.7 Calibration.The temperature/dewpointsensormust be calibrated semiannually orwhenever an FRU

is replaced. The temperature/dewpoint sensor calibration procedures for the model H083R and model 1088

are provided in tables 5.5.9 and 5.5.11, respectively. For the model 1088 sensor, a calibration check can be

performed automatically using extended diagnostics (pressing TEST key on 1088 page at OID), or the

individual functions can be commanded by "T" commands from the 1088 page as listed in table 5.5.10. The

results of the last automatic calibration check are retained on the 1088 page.

Table 5.5.9. Model H083R Temperature/Dewpoint Sensor Calibration

Step Procedure

Tools required:

 Large flat-tipped screwdriver

 Small flat-tipped screwdriver

NOTE

Laptop computer initialized on DCP OID (Chapter 3, Section III), or any other available OID, may

be used for the following procedure.

1 At OID, display sensorstatus page (sequentially pressREVIEW-SENSR-STAT function keysfrom1-minute

display).

2 On sensor status page, turn report processing for temperature/dewpoint sensor to off.

3 Using large flat-tipped screwdriver, open temperature/dewpoint sensor transmitter access door. With power

on, set the calibrate switch to 0 position.

4 At transmit logic board, set DISPLAY SELECTOR switch S1 to TA position.

5 Adjust TA0 trimpotfor a 32.0 ±0.1 indication on transmit logic board seven-segment display. Thisrepresents

0°C.

6 Set DISPLAY SELECTOR switch S1 to TD position and adjust TD0 trimpot for a 32.0 ±0.1 indication on

transmit logic board seven-segment display. This represents 0°C.

7 Set the calibrate switch to +50 position. Set DISPLAY SELECTOR switch S1 to TA position. 

8 Adjust TA+ trimpot for a 22.0 ±0.1 indication on transmit logic board seven-segment display.

9 Set DISPLAY SELECTOR switch S1 to TD position and adjust TD+ trimpot for a 22.0 ±0.1 indication on

transmit logic board seven-segment display.

10 Set the calibrate switch to -50 position. Verify that transmit logic board seven-segment display indicates-67.7

±0.5.

11 Set DISPLAY SELECTOR switch S1 to TA position and verify that transmit logic board seven-segment

display indicates -58 ±0.5.

12 Using large flat-tipped screwdriver, close and secure temperature/dewpoint sensor transmitter access door.

13 On sensor status page at OID, turn report processing for temperature/dewpoint sensor to on.

Table 5.5.10. “T” Commands for Model 1088 Checkout

Command Function

T1 Prompts current ambient temp (Ta) &dewpoint(Td); but during Autobalance cycle, promptsMirror

Temp response.

T2 At minute 50, prompts response of cal values Ta & Td @ 0°C, and again @50°C, so that the next

following hourly observation will have been validated prior to transmission.

T3 Prompts Ta & Td diagnostic response in case of fail.

T4 Prompts diagnostic response in case of failure.

T5 Initiates an abbreviated, 24-hour cycle response, beginning with the Autobalance cycle. (Inhibits

T6 and overrides all other commands.)

T6 Initiates mirror heat cycle.

T7 Initiates Autobalance cycle.
S100 ASOS Site Technical Manual

5-39

Table 5.5.11. Model 1088 Temperature/Dewpoint Sensor Calibration

Step Procedure

Tools required:

 Large flat-tipped screwdriver

 Small flat-tipped screwdriver

NOTE

Laptop computer initialized on DCP OID (Chapter 3, Section III), or any other available OID, may

be used for the following procedure.

1 At OID, display sensorstatus page (sequentially pressREVIEW-SENSR-STAT function keysfrom1-minute

display).

2 On sensor status page, turn report processing for temperature/dewpoint sensor to off.

3 Using large flat-tipped screwdriver, open temperature/dewpoint sensor transmitter access door. With power

on, set MODE switch to TEST 0 position.

4 On transmit logic board, set DISPLAY SELECTOR switch S1 to TA position and press and hold DISPLAY

switch S2.

5 Adjust TA0 trimpot for a 32.0 ±0.1 indication on transmit logic board seven-segment display.

6 Set DISPLAY SELECTOR switch S1 to TD position, press and hold DISPLAY switch S2, and adjust TD0

trimpot for a 32.0 ±0.1 indication on transmit logic board seven-segment display.

7 Set MODE switch to TEST 50 position. Set DISPLAY SELECTOR switch S1 to TA position and press and

hold DISPLAY switch S2. 

8 Adjust TA+ trimpot for a 22.0 ±0.1 indication on transmit logic board seven-segment display.

9 Set DISPLAY SELECTOR switch S1 to TD position, press and hold DISPLAY switch S2, and adjust TD+

trimpot for a 22.0 ±0.1 indication on transmit logic board seven-segment display.

10 Set MODE switch to OPR position.

11 Using large flat-tipped screwdriver, close and secure temperature/dewpoint sensor transmitter access door.

12 On sensor status page at OID, turn report processing for temperature/dewpoint sensor to on.

5.5.3 CORRECTIVE MAINTENANCE

5.5.3.1 Troubleshooting Procedures. Unlike the model 1088, the model H083R temperature/dewpoint

sensor does not contain internal diagnostics. Therefore, standard troubleshooting procedures must be used.

The troubleshooting procedures provided in table 5.5.12 assist the technician in isolating a fault to an FRU

in the sensor. These procedures may also be used on the model 1088 if the diagnostic fails to identify the

correct FRU.

5.5.3.2 Running Diagnostics. The model 1088 ASOS diagnostic program monitors the ambient and

dewpoint temperature readingsreceived fromthe temperature/dewpoint sensor. If the acquisition control unit

(ACU) does not receive data from the sensor or the sensor readings are outside acceptable limits, the ACU

flags the sensor as malfunctioning and marks it off-line. The fault condition is verified by running the

temperature/dewpoint sensor diagnostic as described in Chapter 1, Section V.

5.5.3.3 Dewpoint Sensor Assembly Removal and Installation. The dewpoint sensor assembly removal

and installation procedures are provided in table 5.5.13.

5.5.3.4 Aspirator Housing Removal and Installation. The aspirator housing removal and installation

procedures are provided in table 5.5.14.

5.5.3.5 Transmit Logic Board Removal and Installation. The transmit logic board removal and

installation procedures are provided in table 5.5.15.
ASOS Site Technical Manual S100

5-40

WARNING

5.5.3.6 AutobalanceModule Removal and Installation.The autobalancemodule removal and installation

procedures are provided in table 5.5.16.

5.5.3.7 Power Supplies Removal and Installation. The +5 volt power supply and auxiliary power supply

removal and installation procedures are provided in tables 5.5.17 and 5.5.18, respectively.

5.5.3.8 Fiberoptic Module Removal and Installation. The fiberoptic module removal and installation

procedures are provided in table 5.5.19.

Table 5.5.12. Temperature/Dewpoint Sensor Troubleshooting

Step Procedure

Dangerous voltages(110 vac) are present within the model 1088 and H083R temperature/dewpoint

sensors. Exercise standard safety procedures.

Symptom -No measurement data being received from sensor. Seven-segment display is not illuminated.

1 At transmitter, check fuse F1. Replace fuse if blown. If fuse blows a second time, fault isolate to either the

+5V power supply, the auxiliary power supply, or the fan in the aspirator, and replace fuse.

2 With power applied to transmitter, remove power connector from J1 and connect DMM between pins A and

B. DMM should indicate 120 ±10 vac. If correct indication is not obtained, troubleshoot cabling between

DCP and sensor. If correct indication is obtained, install power connector and proceed to step 3. 

3 Ensure that POWER switch S1 is set to on (up) position.

4 At +5V power supply, connect DMM between pins 1 and 3. DMM should indicate 120 ±10 vac. If correct

indication is not obtained, replace transmitter. If correct indication is obtained, proceed to step 5.

5 At +5V power supply, connect DMM between pins 6 (+) and 5 (-). DMM should indicate +5 ±0.5 vdc. If

correct indication is not obtained, replace +5 Volt Power Supply 2A3. If correct indication is obtained,

proceed to step 6.

6

NOTE

When connecting DMM, use pin 9 as ground for the model 1088 and pin 7 as ground for

the model H083R.

At transmit logic board, connect DMM between pin 6 (+) and ground. DMM should indicate +12 ±0.5 vdc.

Connect DMM between pin 12 (+) and ground. DMM should indicate -12 ±0.5 vdc. If either reading is

incorrect, replace auxiliary power supply.

Symptom -No measurement data being received at ACU. Seven- segment display on transmitter logic board

is illuminated, but readings are incorrect.

1 At +5V power supply, connect DMM between pins 6 and 5. DMM should indicate +5 ±0.5V. If correct

indication is not obtained, replace +5 Volt Power Supply 2A3. If correct indication is obtained, proceed to

step 2.

2 At auxiliary power supply, connect DMM between pins 13 and 10. DMM should indicate +12 ±0.5V.

Connect DMM between pins 12 and 10. DMM should indicate -12 ±0.5V. If either indication is incorrect,

replace auxiliary power supply.

3 On transmit logic board, set monitor display switch to TA position. If seven-segment display indicates the

correct outside temperature, troubleshoot sensor-DCP fiberoptic link per Chapter 1, Section V).
S100 ASOS Site Technical Manual

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WARNING

WARNING

Table 5.5.12. Temperature/Dewpoint Sensor Troubleshooting -CONT

Step Procedure

4 At transmitter, set the calibrate switch to 0 position. Seven-segment display should indicate 32.0 ±0.3. Set

the calibrate switch to -50 position. Seven-segment display should indicate -58 ±0.5. If either indication is

incorrect, replace transmit logic board. If one of the indications is correct, a dirty or faulty calibrator switch

is suspect. Clean the switch contacts and retest. If correct indication is still not obtained, replace

temperature/dewpoint sensor.

Symptom -Either the ambient or dewpoint temperature reading is incorrect.

1 At transmitter, set the calibrate switch to 0 position. Set monitor display switch to display the incorrect

temperature value (TA or TD). Seven-segment display should indicate 32.0 ±0.3. If correct indication is not

obtained,replace transmit logic board. If correct indication is obtained and sensor ismeasuring the TA values

incorrectly, replace temperature/dewpointsensor in the aspirator. Ifsensor is measuring TA values correctly

and SI LEVEL LED is flashing, replace temperature/dewpoint sensor. If SI LEVEL LED is not flashing or

if either or both of the LIMIT LED's are illuminated, replace transmit logic board.

Table 5.5.13. Dewpoint Sensor Assembly Removal and Installation

Step Procedure

REMOVAL

Tools required:

 Diagonal cutting pliers

 Death or severe injury may result if power is not removed from sensor prior to maintenance

activities. Ensure that circuit breaker (located in DCP)supplying power to sensor isset to off (right)

position. 

1 Inside DCP equipment cabinet, set circuit breaker on temperature/dewpoint sensor power control module to

off (right) position. 

2 Disconnect connector P1 of dewpoint sensor assembly cable from connector J1 of Transmitter A2.

3 Using diagonal cutting pliers, remove tie wrapssecuring dewpointsensor assembly cable to aspiratorsupport

bracket.

4

CAUTION

Dewpointsensor assembly components are delicate and must be handled with care. Sensor

can be permanently damaged by excessive mechanical shocks.

Remove dewpointsensor assembly from aspirator by loosening captive screw on side of unit. Slide dewpoint

sensor assembly downward and out of aspirator housing.

INSTALLATION

Materials required:

 Cable tie wraps

Death or severe injury may result if power is not removed from sensor prior to maintenance

activities. Ensure that circuit breaker (located in DCP)supplying power to sensor isset to off (right)

position. 

1 Inside DCP equipment cabinet, ensure that circuit breaker on temperature/dewpoint sensor power control

module is set to off (right) position.

2 Align key on dewpoint sensor assembly with slot in aspirator housing, and slide dewpoint sensor assembly

into aspirator housing. Secure with captive screw.
ASOS Site Technical Manual S100

5-42

WARNING

WARNING

Table 5.5.13. Dewpoint Sensor Assembly Removal and Installation -CONT

Step Procedure

3 Connect connector P1 of dewpoint sensor assembly to connector J1 of Transmitter A2.

4 Using cable tie wraps, secure cable of dewpoint sensor assembly as shown on figure 5.2.1. Be sure to leave

service loop to allow removal of dewpoint sensor assembly without cutting tie wraps.

5 Perform temperature/dewpoint sensor optical loop adjustment in accordance with table 5.5.3 (for model

H083R) or table 5.5.4 (for model 1088).

6 Calibrate temperature/dewpointsensor in accordance with table 5.5.9 (for model H083R) or table 5.5.11 (for

model 1088).

7 Perform fan fail monitoring circuit test and adjustment in accordance with table 5.5.7 (model 1088 only).

Table 5.5.14. Aspirator Housing Removal and Installation

Step Procedure

REMOVAL

Tools required:

 No. 1 Phillips screwdriver

 5/16-inch nut driver

 3/8-inch nut driver

Death or severe injury may result if power is not removed from sensor prior to maintenance

activities. Ensure that circuit breaker (located in DCP)supplying power to sensor isset to off (right)

position. 

1 Inside DCP equipment cabinet, set circuit breaker on temperature/dewpoint sensor power control module to

off (right) position. 

2 Remove Dewpoint Sensor Assembly A1A1 from aspirator housing in accordance with table 5.5.13. To

prevent damage, store dewpoint sensor assembly in a safe place.

3 Using No. 1 Phillipsscrewdriver and 5/16-inch nut driver, loosen (but do notremove) hardware securing four

angle irons on top, bottom, left, and right of aspirator mounting brackets.

4 Using 3/8-inch nut driver, remove four locknuts securing aspirator housing to mounting brackets. Carefully

remove aspirator housing.

INSTALLATION

Tools and materials required:

 No. 1 Phillips screwdriver

 5/16-inch nut driver 

 3/8-inch nut driver 

Death orsevere injury may result if power is notremoved from sensor prior to maintenance activities. Ensure

that circuit breaker (located in DCP) supplying power to sensor is set to off (right) position. 

1 Inside DCP equipment cabinet, ensure that circuit breaker on temperature/dewpoint sensor power control

module is set to off (right) position.

2 To facilitate mounting of aspirator housing, ensure that hardware securing four angle irons to aspirator

mounting brackets have been loosened (but not removed).

3 Position aspirator housing on mounting brackets with nameplate facing outward (away from transmitter).

4 Using 3/8-inch nut driver, install four locknuts securing aspirator on mounting brackets. Do not tighten

locknuts.

5 Using 5/16-inch nut driver and No. 1 Phillips screwdriver, tighten locknuts securing angle irons to aspirator

mounting brackets.
S100 ASOS Site Technical Manual

Change 1 5-43

WARNING

WARNING

Table 5.5.14. Aspirator Housing Removal and Installation -CONT

Step Procedure

6 Using 3/8-inch nut driver, tighten four locknuts securing mounting brackets to aspirator housing.

7 Install Dewpoint Sensor Assembly A1A1 into aspirator housing in accordance with table 5.5.13.

8 Perform temperature/dewpoint sensor optical loop adjustment in accordance with table 5.5.3 (for model

H083R) or table 5.5.4 (for model 1088).

9 Calibrate temperature/dewpointsensor in accordance with table 5.5.9 (for model H083R) or table 5.5.11 (for

model 1088).

10 Perform fan fail monitoring circuit adjustment in accordance with table 5.5.7 (model 1088 only).

Table 5.5.15. Transmit Logic Board Removal and Installation

Step Procedure

REMOVAL

Tools required:

 Large flat-tipped screwdriver

Death or severe injury may result if power is not removed from sensor prior to maintenance

activities. Ensure that circuit breaker (located in DCP)supplying power to sensor isset to off (right)

position.

1 Inside DCP equipment cabinet, set circuit breaker on temperature/dewpoint sensor power control module to

off (right) position.

2 Using large flat-tipped screwdriver, open temperature/dewpoint sensor transmitter access door.

3 Grasp ejector ears at top corners of board and turn outward to force the board out of its socket.

 4 Slide board out on its guides.

INSTALLATION

Tools required:

 Large flat-tipped screwdriver

Death or severe injury may result if power is not removed from sensor prior to maintenance

activities. Ensure that circuit breaker (located in DCP)supplying power to sensor isset to off (right)

position.

1 Inside DCP equipment cabinet, ensure that circuit breaker on temperature/dewpoint sensor power control

module is set to off (right) position.

2 Slide new board on guides and press ejector ears toward socket until board is firmly seated.

3 Using large flat-tipped screwdriver, close and secure temperature/dewpoint sensor transmitter access door.

4 Inside DCP equipment cabinet, set circuit breaker on temperature/dewpoint sensor power control module to

on (left) position.

5 Perform temperature/dewpoint sensor optical loop adjustment in accordance with table 5.5.3 (for model

H083R) or table 5.5.4 (for model 1088).

6 Calibrate temperature/dewpointsensor in accordance with table 5.5.9 (for model H083R) or table 5.5.11 (for

model 1088).
ASOS Site Technical Manual S100

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WARNING

WARNING

Table 5.5.16. Autobalance Module Removal and Installation

Step Procedure

REMOVAL

Tools required:

 Large flat-tipped screwdriver

 No. 0 Phillips screwdriver

 No. 2 Phillips screwdriver

Death or severe injury may result if power is not removed from sensor prior to maintenance

activities. Ensure that circuit breaker (located in DCP)supplying power to sensor isset to off (right)

position.

1 Inside DCP equipment cabinet, set circuit breaker on temperature/dewpoint sensor power control module to

off (right) position.

2 Using large flat-tipped screwdriver, open temperature/dewpoint sensor transmitter access door.

3 Using No. 0 Phillips screwdriver, remove two screws and lockwashers securing connector J2 to calibrator

assembly.

4 Using No. 2 Phillips screwdriver, remove two screws and lockwashers securing autobalance module to top

of calibrator assembly. Remove autobalance module.

INSTALLATION

Tools required:

 Large flat-tipped screwdriver

 No. 0 Phillips screwdriver

 No. 2 Phillips screwdriver

Death or severe injury may result if power is not removed from sensor prior to maintenance

activities. Ensure that circuit breaker (located in DCP)supplying power to sensor isset to off (right)

position.

1 Inside DCP equipment cabinet, ensure that circuit breaker on temperature/dewpoint sensor power control

module is set to off (right) position.

2 Position autobalance module in upper right corner of transmitter. Using No. 2 Phillips screwdriver, install

two screws and lockwashers securing autobalance module to calibrator assembly.

3 Connect connector J2 to connector located on side of calibrator assembly. Using No. 2 Phillips screwdriver,

install two screws and lockwashers securing connector J2.

4 Using large flat-tipped screwdriver, close and secure temperature/dewpoint sensor transmitter access door.

5 Inside DCP equipment cabinet, set circuit breaker on temperature/dewpoint sensor power control module to

on (left) position.

6 Perform temperature/dewpoint sensor optical loop adjustment in accordance with table 5.5.3 (for model

H083R) or table 5.5.4 (for model 1088).

7 Calibrate temperature/dewpointsensor in accordance with table 5.5.9 (for model H083R) or table 5.5.11 (for

model 1088).
S100 ASOS Site Technical Manual

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WARNING

WARNING

Table 5.5.17. +5V Power Supply Removal and Installation

Step Procedure

REMOVAL

Tools required:

 Large flat-tipped screwdriver

 No. 2 Phillips screwdriver

Death or severe injury may result if power is not removed from sensor prior to maintenance

activities. Ensure that circuit breaker (located in DCP)supplying power to sensor isset to off (right)

position.

1 Inside DCP equipment cabinet, set circuit breaker on temperature/dewpoint sensor power control panel to

off (right) position.

2 Using large flat-tipped screwdriver, open temperature/dewpoint sensor transmitter access door.

3 Disconnect 2X1 and lift +5V power supply out of chassis.

4 Using Phillips screwdriver, remove four corner mounting screws and insulated flat washers securing +5V

power supply.

INSTALLATION

Tools required:

 Large flat-tipped screwdriver

 No. 2 Phillips screwdriver

Death or severe injury may result if power is not removed from sensor prior to maintenance

activities. Ensure that circuit breaker (located in DCP)supplying power to sensor isset to off (right)

position.

1 Inside DCP equipment cabinet, ensure that circuit breaker on temperature/dewpoint sensor power control

module is set to off (right) position.

2 Position +5V power supply on four corner mounting posts.

3 Connect 2X1 and using Phillips screwdriver, install four insulated flat washers and corner mounting screws

securing +5V power supply to corner mounting posts. 

4 Using large flat-tipped screwdriver, close and secure temperature/dewpoint sensor transmitter access door.

5 Perform temperature/dewpoint sensor optical loop adjustment in accordance with table 5.5.3 (for model

H083R) or table 5.5.4 (for model 1088).

6 Calibrate temperature/dewpointsensor in accordance with table 5.5.9 (for model H083R) or table 5.5.11 (for

model 1088).
ASOS Site Technical Manual S100

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WARNING

WARNING

Table 5.5.18. Auxiliary Power Supply Removal and Installation

Step Procedure

REMOVAL

Tools required:

 Large flat-tipped screwdriver

 No. 0 Phillips screwdriver

 No. 2 Phillips screwdriver

Death or severe injury may result if power is not removed from sensor prior to maintenance

activities. Ensure that circuit breaker (located in DCP)supplying power to sensor isset to off (right)

position.

1 Inside DCP equipment cabinet, set circuit breaker on temperature/dewpoint sensor power control panel to

off (right) position.

2 Using large flat-tipped screwdriver, open temperature/dewpoint sensor transmitter access door.

3 Using No. 0 Phillips screwdriver, remove two screws and lockwashers securing autobalance module

connector J2 to calibrator assembly. 

4 Using No. 0 Phillips screwdriver, remove two screws and lockwashers securing autobalance module to top

of calibrator assembly. Remove autobalance module.

5 Using No. 2 Phillips screwdriver, remove four screws and lockwashers securing auxiliary power supply to

transmitter mounting plate.

6 Disconnect connector X2 from auxiliary power supply. Remove auxiliary power supply.

INSTALLATION

Tools required:

 Large flat-tipped screwdriver

 No. 0 Phillips screwdriver

 No. 2 Phillips screwdriver

Death or severe injury may result if power is not removed from sensor prior to maintenance

activities. Ensure that circuit breaker (located in DCP)supplying power to sensor isset to off (right)

position.

1 Inside DCP equipment cabinet, ensure that circuit breaker on temperature/dewpoint sensor power control

module is set to off (right) position.

2

CAUTION

When positioning auxiliary powersupply in transmitter, do not crimp wires attached to the

calibrator assembly.

Connect connector X2 to auxiliary power supply and position auxiliary power supply over four mounting

holes in transmitter mounting plate.

3 Using No. 2 Phillips screwdriver, install four screws and lockwashers securing auxiliary power supply to

transmitter mounting plate.

4 Position autobalance module in upper right corner of transmitter. Using No. 0 Phillips screwdriver, install

two screws and lockwashers securing autobalance module to top of calibrator assembly.

5 Connect connector J2 to the connector located on side of calibrator assembly. Using No. 0 Phillips

screwdriver, install two screws and lockwashers securing connector J2.

6 Using large flat-tipped screwdriver, close and secure temperature/dewpoint sensor transmitter access door.
S100 ASOS Site Technical Manual

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WARNING

WARNING

Table 5.5.18. Auxiliary Power Supply Removal and Installation -CONT

Step Procedure

7 Inside DCP equipment cabinet, set circuit breaker on temperature/dewpoint sensor power control module to

on (left) position.

8 Perform temperature/dewpoint sensor optical loop adjustment in accordance with table 5.5.3 (for model

H083R) or table 5.5.4 (for model 1088).

9 Calibrate temperature/dewpointsensor in accordance with table 5.5.9 (for model H083R) or table 5.5.11 (for

model 1088).

Table 5.5.19. Fiberoptic Module Removal and Installation

Step Procedure

REMOVAL

Tools required:

 Large flat-tipped screwdriver

 Small flat-tipped screwdriver

 No. 1 Phillips screwdriver

 No. 0 Phillips screwdriver

Death or severe injury may result if power is not removed from sensor prior to maintenance

activities. Ensure that circuit breaker (located in DCP)supplying power to sensor isset to off (right)

position.

1 Inside DCP equipment cabinet, set circuit breaker on temperature/dewpoint sensor power control panel to

off (right) position.

2 Using large flat-tipped screwdriver, open temperature/dewpoint sensor transmitter access door.

3 Using small flat-tipped screwdriver, loosen two retaining screws on connector located on side of fiberoptic

module. Remove connector.

4 Using CCW rotation, remove two fiberoptic cables from bottom of fiberoptic module. Install protective

plastic covers over board connectors.

5 Using No. 1 Phillipsscrewdriver, remove two screws and lockwasherssecuring fiberoptic module mounting

bracket to calibrator assembly.

6 Using No. 0 Phillips screwdriver, remove two screws, lockwashers, and gaskets securing fiberoptic module

to mounting bracket. Remove fiberoptic module.

INSTALLATION

Tools required:

 Large flat-tipped screwdriver

 Small flat-tipped screwdriver

 No. 1 Phillips screwdriver

 No. 0 Phillips screwdriver

Death or severe injury may result if power is not removed from sensor prior to maintenance

activities. Ensure that circuit breaker (located in DCP)supplying power to sensor isset to off (right)

position.

1 Inside DCP equipment cabinet, ensure that circuit breaker on temperature/dewpoint sensor power control

module is set to off (right) position.
ASOS Site Technical Manual S100

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Table 5.5.19. Fiberoptic Module Removal and Installation -CONT

Step Procedure

2 Position fiberoptic module and gaskets over mounting holes in mounting bracket. Using No. 0 Phillips

screwdriver, install two screws and lockwashers securing fiberoptic module to mounting bracket.

3 Using No. 1 Phillips screwdriver, install two screws and lockwashers securing fiberoptic module mounting

bracket to calibrator assembly.

4 Remove any protective covers from fiberoptic connectors and install the receive (RX) and transmit (TX)

connectors on fiberopticmodule.RXcable mates with fiberoptic connector nearest DB-9 electrical connector.

5 Install signal cable on connector on fiberoptic module and using small flat-tipped screwdriver, tighten two

retaining screws.

6 Using large flat-tipped screwdriver, close and secure temperature/dewpoint sensor transmitter access door.
S100 ASOS Site Technical Manual

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CHAPTER 6

VISIBILITY AND DAY/NIGHT SENSOR

SECTION I. DESCRIPTION AND LEADING PARTICULARS

6.1.1 INTRODUCTION

The ASOS visibility and day/nightsensor, hereinafter referred to asthe visibility sensor, providesthe means

to automatically calculate the current visibility level and indicate current day/night conditions. The visibility

sensor measures ambient meteorological optical range (visibility) using the forward scatter technique. This

technique involves transmitting a flash of xenon light through a section of the atmosphere (which scatters

the light) and measuring the scattered light level to determine the loss. An extinction coefficient is calculated

from the amount of light received from the scattered xenon flash lamp light source. This coefficient is then

translated into a value of visibility. The visibility sensor also computes and outputs a day or night indication

as derived from an ambient light sensor. Both extinction coefficient and day/night data are output for use by

the ASOS in response to requestsignalsfromthe data collection package (DCP).Each responsemessage also

includes sensor operating status signals generated by the visibility sensor through a continuously running

self-test.

6.1.2 PHYSICAL DESCRIPTION

The visibility sensor (Figure 6.1.1) is mounted on a single support. All of the processing and sensing

electronics are mounted to the support, thereby eliminating the need for careful alignment between separate

stations. The components of the visibility sensor are divided into two separate sections: an uppersection and

a lower section. The upper section contains all of the sensing elements. The lower section contains all of the

processing, communications, and diagnostic electronics as well as the power supplies and electromagnetic

interference (EMI) protection. The following paragraphs provide detailed descriptions of the two sections

and the cabling of the entire unit.

6.1.2.1 Upper Section. The upper section is mounted above the electronics enclosure and contains all of

the sensing elements of the visibility sensor: crossarm/support, transmitter hood assembly, receiver hood

assembly, and day/night assembly.

6.1.2.1.1 Crossarm/Support.The crossarmand support hold the sensing elements at the appropriate height

and relative orientation. The support is a pole mounted to the top ofthe enclosure mounting support with four

bolts. The crossarmis mounted to the top of the support with four bolts. Two mounts provided on the support

allow for the attachment of a scatter plate. The scatter plate is a calibration tool that, when mounted to the

support (thereby extended into the scatter volume), creates an artificially high amount of scattered light for

the receiver to detect. The location of the scatter plate mounts is such that the scatter plate is firmly held in

the scatter volume. The crossarm is a welded assembly that consists of the hoods, arms, and plenum. The

arms connect all of the other crossarm components. The hoods contain the transmitter and receiver units.

They also contain heaters to prevent snow and ice buildup as well as fogging and icing of the lenses. The

plenum is a small enclosed cavity where the support is attached and through which the sensor cables are

passed to the electronics enclosure.

6.1.2.1.2 Transmitter Assembly. The transmitter assembly flashes a xenon bulb to produce visible light

forscattering. Light isfocused into the scatter volume by a fixed lensincluded with the transmitter assembly.

The transmitter assembly consists of two basic parts: the canister and the cap. The canister is a field

replaceable unit (FRU) that can be quickly and easily replaced for maintenance. The canister is an aluminum
ASOS Site Technical Manual S100

6-2

Figure 6.1.1. Visibility Sensor

cylinder that contains all of the transmitter electronics and interface wiring in a single package. The canister

slides into the transmitter hood and is keyed for correct insertion. Once the canister is fully inserted into the

hood, the transmitter is aligned and ready to be connected to the system. The cap protects the canister by

covering the end of the hood.

6.1.2.1.3 Receiver Assembly. The receiver assembly is the unit that detects the transmitted xenon light

afterit isscattered by the atmosphere. The light is detected by a positive-intrinsic-negative (PIN) photodiode

mounted in the receiver canister. Light is focused onto the photodiode by a fixed lens included with the

receiver assembly. The photodiode converts the light energy into an electrical current signal for processing.

The receiver assembly consists of two basic parts: the canister and the cap. The canister is an FRU that can

be quickly and easily replaced for maintenance. The canister is an aluminum cylinder that contains all of the

receiver electronics and interface wiring in a single package. The canister slides into the receiver assembly

and is keyed for correct insertion. After the canister isfully inserted into the assembly, the receiver is aligned

and ready to be connected to the system (presupposing previous factory alignment and calibration). The cap

protects the canister by covering the end of the assembly.

6.1.2.1.4 Day/Night Assembly. The day/night assembly is a photometer designed to indicate daytime or

nighttime conditions. The sensor mounts to the support pole just above the flange. Signal and power cables

are contained within the hollow support. The connection for the signal cable is made inside the electronics

enclosure. The connection for the power cable is made inside the plenum with free-hang connectors. The
S100 ASOS Site Technical Manual

6-3

day/night assembly detects light via a photodiode mounted behind a clear window. The photodiode is

positioned such that its field of view is 6 degrees above the horizon. A heater located on the inside of the

small day/night assembly prevents the accumulation of snow or ice. The day/night assembly (an FRU) can

be easily removed from the day/night mount for repair. The assembly is connected to the electronics

enclosure by a cable. Removal is accomplished by unscrewing the assembly mounting screws, unplugging

one connector, and removing the signal cable out through the support pole.

6.1.2.2 Lower Section. The lower section, which mates directly with the standard flange, consists of the

electronics enclosure and the enclosure support. A flange at the top of the enclosure support mates with the

bottom part of the upper section support.

6.1.2.2.1 Electronics Enclosure. The electronics enclosure (Figure 6.1.2) houses all of the processing and

diagnostic electronics. The enclosure also houses all of the EMI filtering and power supplies. All of the

internal components are accessed through a hinged front door. All external cables are connected to the

enclosure at the bottom. The enclosure is mounted to the support with four bolts. Four mounting flanges are

welded to the enclosure for this purpose. The power input box within the electronics enclosure contains

either one filter and surge suppressor or two filters and surge suppressors. The two-filter configuration is

illustrated in the figure. To determine the configuration, one or two filters are observed protruding from the

top of the power input box. Visibility sensors with serial numbers A0358 and above have one filter; those

numbered A0357 and below have two filters. The power input box wiring for the one- and two-filter

configurations is illustrated in Section IV.

6.1.2.2.2 Enclosure Support. The enclosure support is a pipe with flanges at each end and mounting

brackets for the enclosure box. The electronics enclosure attaches to the enclosure mounting brackets with

four bolts. The visibility sensor is aligned relative to north by properly positioning the support on the

mounting flange. The bottomflange is provided with holes at 30-degree intervalsto allow for this alignment.

The top flange mates with the bottom flange of the upper section support.

6.1.2.3 Cabling. Signal cables run between the electronics enclosure and the transmitter and receiver

sections. These cables carry all of the data signals and DC power for the sensing sections and are physically

located internal to the support. The heater power is included with these cables. Day/night sensor cables run

internal to the support through an opening in the enclosure support. The sample trigger cable is the coax

cable thatruns between the transmitter and receiversections. This cable runsinternally through the crossarm.

6.1.3 SPECIFICATIONS

The visibility sensor meets the full range of ASOS outdoor environmental requirements during continuous

operation. The visibility sensor is capable of providing an extinction coefficient equivalent to visibilities up

to and including 10 miles, with sufficient accuracy and resolution to allow the acquisition control unit(ACU)

to report the standard reporTable increments. The visibility sensor agrees with the 1,500-foot baseline

NationalWeather Service (NWS)transmissometer according to table 6.1.1. The day/night assembly provided

with the visibility sensor indicates day or night condition according to the ambient light level and operates

for ambient light levels up to 50 foot candles(fc). The day/nightsensor alwaysindicates day for illumination

greater than 3 fc and always indicates night for illumination less than 0.5 fc. The transition from indicating

day to indicating night occurs once in the region from 3 to 0.5 fc (as illumination decreases). The transition

from indicating night to indicating day occurs once in the region from 0.5 to 3 fc (as illumination increases).

The day/night assembly is mounted such that it points in the same direction as the receiver. The design is

such that snow and ice buildup is prevented from affecting operation.
ASOS Site Technical Manual S100

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Figure 6.1.2. Visibility Sensor Electronics Enclosure

6.1.3.1 Configurations. There is only one configuration of the visibility sensor. This configuration is

described in Section II.

Table 6.1.1. Visibility Sensor Accuracy*

Visibility of NWS Standard

Transmissometer

Sensor Accuracy (Percent of All Data)

At Least 80% No More than 18% No More than 2%

0 to 1-1⁄4 ±1⁄4 ±1⁄2 ±1

1-1⁄2 to 1-3⁄4 +1⁄4, -1⁄2 +1⁄2, -3⁄4 ±1

2 to 2-1⁄2 ±1⁄2 ±1 ±1

3 to 3-1⁄2 +1⁄2, -1 +2 RI**/-1 +2 RI**/-1

4 to 10+ ±1 RI** ±2 RI** ±2 RI**

 *All units in miles except where noted with double asterisk.

**ReporTable increments (RI's) are used as units instead of miles.
S100 ASOS Site Technical Manual

6-5

SECTION II. INSTALLATION

6.2.1 INTRODUCTION

The modular design of the ASOS visibility sensor allows for simple assembly. All elements are wired with

keyed connectors and are secured to each other with bolts. The entire single-pedestal assembly is secured

to the standard mounting flange with locking bolts. The sensor head is mounted to the top of the pole and

is interfaced with the electronics enclosure via supplied cables. When assembled, the scatter volume (the

volume of air through which the flash transfers) is approximately 10 feet high in the air. The electronics

enclosure is mounted on the support structure several feet off the ground to provide easy access for the

servicing technician.

6.2.2 ASSEMBLY

6.2.2.1 Hinge Plate Assembly. The hinge plate assembly provides easy access to the visibility sensor's

receiver and transmitter assemblies by permitting the visibility sensor to be lowered to a horizontal position.

The hinge plate has a locking pin to secure the sensor in an upright position and a cable lanyard to support

the sensor when it is lowered.

6.2.2.2 Enclosure Support. The base ofthe enclosure support consists of a flange containing 12 holes. Each

of the holes is offset 30 degrees from adjacent holes to allow proper positioning of the enclosure support on

the mounting hinge. The enclosure support is mounted on top ofthe hinge plate assembly using four 5/8-inch

hex head bolts and associated hardware (figure 6.2.1 and table 6.2.1). Alignment of the enclosure support

on the hinge plate is important to the operation of the unit. The visibility sensor should be installed such that

the receiver optics and the day/night assembly are pointed away from direct sunlight. In the northern

hemisphere, this aligns the receiver and day/night sensor to face north. Precise alignment of the visibility

sensor may not be possible and is not considered critical; however, for the best performance, the hole pattern

that provides the closest receiver alignment to face north should be selected.

6.2.2.3 Electronics Enclosure. Figure 6.2.1 identifies and locates the components used to install the

electronics enclosure on the enclosure support. Installation procedures are provided in table 6.2.2.

6.2.2.4 Crossarm Support. The crossarm support is mounted on top of the enclosure support such that the

calibration plate mounts face to the right of the enclosure. The crossarm support is secured to the enclosure

support using four e - 11 by 2-1⁄2-inch HHCS's as shown on figure 6.2.2.

6.2.2.5 Crossarm. The crossarm is mounted to the top of the crossarm support such that the transmitter and

receiver hoods are to the right of the electronics enclosure (on the same side of the support pole as the

calibration plate mounts). The crossarm comes prewired for the head assemblies. As such, the wires from

the crossarm need to be routed through the interior of the support pole prior to securing the crossarm to the

support pole. The crossarm is secured to the crossarm support pole using four 3/8 - 16 by 1-3⁄4-inch HHCS's

as shown on figure 6.2.2.

6.2.2.6 Day/Night Sensor. The day/nightsensorisinstalled by feeding the day/night heater and signal wires

through the support columns, attaching the sensor ground and cable connections, and mounting the day/night

sensor to the crossarm support such that the day/night sensor is pointed 6 degrees above the horizon

(Figure 6.2.3). This installation procedure is described in table 6.2.3.
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Figure 6.2.1. Electronics Enclosure Installation

Table 6.2.1. Enclosure Support Installation

Step Procedure

1 Open hinge plate and position on mounting pedestal. For most sites, orient hinge plate so that when facing

the door of enclosure, sensor tilts to right, away from other sensors (hinge side of plate is on right). 

2

NOTE

The lanyard must be oriented so that when the hinge plate is opened, the lanyard falls in

hinge plate cutouts.

Using one e-inch bolt, one nut, one lockwasher, and three flat washers, secure opening edge of hinge plate

to pedestal, attaching one end of cable lanyard. Bolt isinserted from top down through pedestal with one flat

washer under bolt head. On the underside of pedestal, lanyard loop must be secured between two flat washers

with lockwasher and nut on outside. Do not fully tighten hardware.

3 Install three more sets of mounting hardware (i.e., bolt, two flat washers, lockwasher, and nut) on hinge plate.

Tighten all four sets of mounting hardware. 
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WARNING

WARNING

Table 6.2.1. Enclosure Support Installation -CONT

Step Procedure

4 Install washer on each bolt and slide four mounting bolts up through top of hinge plate. Temporarily install

nut on each bolt and close hinge plate. Install hinge plate locking pin to hold hinge plate in closed position.

5 Remove nuts from four enclosure support mounting holes.

6 Position enclosure support on top of four mounting bolts taking care to properly position enclosure support.

7

NOTE

The lanyard must be oriented so that when the hinge plate is opened, the lanyard falls in

hinge plate cutouts.

Using two flat washers, one lock washer, and one nut, secure front of hinge plate to enclosure support pole,

attaching other end of cable lanyard. Lanyard loop must be secured between two flat washerswith lockwasher

and nut on outside. Do not fully tighten hardware.

8 Install remaining sets of mounting hardware (i.e., flat washer, lockwasher, and nut) on rear, left, and right of

sensor support pole. 

9

With locking pin removed from hinge plate, sensor pole is not firmly locked in upright

position. Death or severe injury may result if personnel are not kept out of travel path of

sensor.

Lower enclosure support pole on hinge plate as follows:

a. Remove locking pin from front part of hinge plate.

b. From hinge side of sensor pole, firmly grasp pole with both hands and carefully lower

support pole on hinge until lanyard catches and supports weight of pole.

10 Tighten all four sets of hardware securing support pole to hinge plate.

11

With locking pin removed from hinge plate, sensor pole is not firmly locked in upright

position. Death or severe injury may result if personnel are not kept out of travel path of

sensor. 

Raise enclosure support pole on hinge plate as follows:

a. From behind hinged side of pole, firmly grasp support pole with both hands and carefully

raise pole on hinge into upright position. 

b. Install locking pin into front of hinge plate.

Table 6.2.2. Electronics Enclosure Installation

Step Procedure

1

NOTE

Do not tighten screws in next step. Box flanges must be allowed to slip onto bolts.

Install two sets of 1⁄2 - 18 by 1-1⁄4-inch HHCS hardware into holes on lower bracket of enclosure support.

2 Position enclosure such that lower mounting flanges slip onto bolts and enclosure is resting on bolts.

3 Position box such that upper mounting flanges align with holes in upper mounting bracket.

4 Install hardware as shown on figure 6.2.1. Firmly tighten all four sets of bolts.
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Figure 6.2.2. Crossarm/Support and Day/Night Sensor Installation
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Figure 6.2.3. Day/Night Sensor Installation

Table 6.2.3. Day/Night Sensor Installation

Step Procedure

Tools required:

 7/16-inch wrench

1 Using 1⁄4-inch bolts and mounting hardware provided, mount day/night sensor on crossarm support pole

approximately 12 inches above flange and sensor window facing same direction asreceiver hood. Position

sensor so that it points approximately 15 degrees above the horizon.

2 Connect day/night sensor signal and power cable A5W1-P1 to lower cable W2-P1 and route lower cable

through support column and out access hole below electronics enclosure.

3 Using two 1⁄4-inch bolts and flat washers, secure day/night sensor conduit connector to enclosure support

pole.

4 Pass day/night sensor lower cable (W2) through lower conduit and into electronics enclosure.
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WARNING

Table 6.2.3. Day/Night Sensor Installation -CONT

Step Procedure

5 Connect day/night sensor signal and power cable to connector J6 on backplane within electronics

enclosure.

6 Secure lower conduit to support pole and electronics enclosure.

6.2.3 CABLES

All cables between the enclosure and the transmitter, receiver, and day/night sensor run through the interior

of the support poles. All cables enter or exit the enclosure at the bottom of the enclosure. All cables to the

transmitter or receiver connect directly to the modules within their respective hoods. Cable installation is

easy and quick. After all of the cables are attached to their appropriate connectors, cable ties are installed

as necessary. Table 6.2.4 provides details on installing the visibility sensor cables.

Table 6.2.4. Cable Installation

Step Procedure

Receiver and Transmitter Cable Installation

Tools required:

 7/16-inch wrench

 Large pliers

 Flat-tipped screwdriver

 No. 1 Phillips screwdriver

1 Remove large nut from end of flexible conduit and install conduit in right bottom side hole in main

electrical enclosure. Install large nut securing conduit to main electrical enclosure. Do not tighten nut at

this time.

2 Route receiver cable through support column and lower conduit into main electrical enclosure.

3 Connect receiver cable to connector J5 on motherboard located within main electrical enclosure.

4 Route transmitter cable through support column and lower conduit into main electrical enclosure.

5 Connect transmitter cable to connector J4 on motherboard located within main electrical enclosure.

6 Route ground wire through support column and lower conduit into main electrical enclosure.

7 Using 7/16-inch wrench, connect ground wire to wire lug E3 (located on top of power input box).

8 Remove mounting hardware from mounting bracket attached to flexible conduit. Discard nuts.

9

CAUTION

Exercise care not to crimp wires when installing gasket.

Locate EMI gasket and position gasket on rear of mounting bracket. Using 7/16-inch wrench, install two

bolts, flat washers, and lockwashers securing mounting plate to column.

10 Using large pliers, tighten large nut securing conduit to main electrical enclosure.

Connecting System Cables to Enclosure

1

Ensure that all power is disconnected from visibility sensor (turned off at DCP) before

connecting cables.

Using No. 1 Phillips screwdriver, open power input box within electronics enclosure by removing six

Phillips screws that secure access cover.
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Table 6.2.4. Cable Installation -CONT

Step Procedure

2 Route ac power wires and fiberoptic cablesfromflexible conduit through opening in bottomof powerinput

box.

3 Secure flexible conduit to bottom of electronics enclosure.

4 Using flat-tipped screwdriver, connect ac power wires to terminal board TB1 within power input box

according to following chart:

Wire Connection

Black (ac hot) TB1-1

White (ac neut) TB1-2

Green (ground) TB1-3

If power input box has two filters and surge suppressors, ensure that following jumpers are also in place:

From To

TB1-1 (ac hot) TB1-4

TB1-2 (ac neut) TB1-5

5 Connect transmit (TX) fiberoptic cable to TX connector on fiberoptic module.

6 Connect receive (RX) fiberoptic cable to RX connector on fiberoptic module.

7 Install access cover on power input box and secure using six Phillips screws.

8 Secure pedestal ground wire to ground stud located at bottom of electronics enclosure.

9 Close and secure sensor's electronics enclosure.
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SECTION III. VISIBILITY SENSOR OPERATION

6.3.1 INTRODUCTION

Once the visibility sensorisinstalled and calibrated, only regularly scheduled maintenance isrequired unless

a failure is detected by the ASOS. All operations, including diagnostics, are handled automatically by the

ASOS.

6.3.2 CONTROLS AND INDICATORS

There are no maintenance significant controls and indicators on the visibility sensor. The sensor is designed

for continuous operation and requires no operator or technician intervention.

6.3.3 TURN-ON PROCEDURES

The visibility sensor contains no power switch. Upon application of 120 vac, 60 Hz power from the data

collection package (DCP), the sensor commences its startup sequence. Power is controlled via the visibility

sensor circuit breaker module in the DCP.

6.3.4 NORMAL OPERATION

During normal operation, the DCP pollsthe visibility sensor once per minute for visibility data. Once polled,

the visibility sensor quickly responds with the visibility data reports as described in Chapter 1. This polling

is automatically performed by the ASOS system software and requires no user intervention. The diagnostic

function of the sensor is also automatically performed by software, and occurs once each minute as

controlled by the ASOS system software. The technician may also initiate a test of the sensor directly by

exercising the TEST selection from the visibility sensor page display at the operator interface device (OID).

This action is normally performed only in instances where a failure of the sensor has been detected.

6.3.5 TURNOFF PROCEDURES

The visibility sensor contains no power switch. Heater and electronics power is controlled via the visibility

sensor circuit breaker module in the DCP.
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SECTION IV. THEORY OF OPERATION

6.4.1 INTRODUCTION

This section provides a detailed description of how the visibility sensor functions to calculate the visibility

level and detect day/night conditions. The operating principles of the sensor are introduced, followed by

simplified block diagram descriptions of the sensor and its components. The theory describesthe individual

functional areas to a level of detail necessary for the isolation of a faulty FRU.

6.4.2 SIMPLIFIED BLOCK DIAGRAM DESCRIPTION

The following paragraphs describe the basic operation of the visibility sensor. The physical principles upon

which the sensor bases it operation are described, followed by a simplified block diagram of the sensor. The

simplified block diagram description introduces the basic system components and their functional

relationships.

6.4.2.1 Principles of Operation. The Belfort visibility sensor is a forward-scatter class sensor that projects

a pulsed beam of xenon light into a sample volume of the atmosphere. Aerosols in the illuminated sample

region scatter light into a receiver, which looks toward the sample volume at an angle of approximately 45

degrees.It has been empirically shown that the amount oflightscattered forward at approximately 45 degrees

is proportional to the extinction coefficient regardless of the type or size of scattering media. The spacing

of the detector fromthe transmitter and the optical focusing afford a large unobstructed sample volume (0.75

cubic feet). The downward-looking hoods aid in preventing ice and snow buildup and create an unattractive

environment for birds and insects that cause contamination of the optical path. The use of xenon as a light

source hasseveralsignificant advantages. The bulb has an extremely long life expectancy (intensity half-life

of 10.5 years). Also, the use of visible light accurately simulates human perception of visibility. The xenon

light source has a component of blue light (short wave lengths) that allows scatter to occur from hazes and

other small particles that are prevalent under higher visibility conditions. This permits the visibility sensor

to report accurately under these conditions as well as during fog, rain, and snow. The opticalsystemincludes

filtering to reduce the overabundance of blue and ultraviolet light and hence permits proportional levels of

radiation at all critical wave lengths to fill the scatter volume.

6.4.2.2 Visibility Sensor Basic Block Diagram Description. The basic visibility measuring system is

depicted in figure 6.4.1. The six major functional blocks are the transmitter assembly, receiver assembly,

day/night assembly, processor board, current sense board, and fiberoptic module. Each functional block is

a field replaceable unit (FRU) that can be easily removed and replaced for sensor repairs. All operations of

the visibility sensor are directed by the processor board. The processor board sends commands to the

transmitter assembly to initiate a flash, and then receives data from the receiver assembly to measure the

scattered light. After data are received from the receiver assembly, age detect (part of the transmitter

assembly) data, day/night data, and voltage monitor data are collected. The processor board combines all of

these data to compute the extinction coefficient to determine visibility and detects daytime or nighttime

conditions. The processor board then communicatesthese results via the fiberoptic module to the DCP. The

software that controls the operations of the sensor, runs diagnostics, monitors heater operations, and

calculates the proper output values is located on the processor board.

6.4.3 DETAILED BLOCK DIAGRAM DESCRIPTION

The following paragraphs describe the operation of the visibility sensor components to a detailed block

diagram level. The simplified version of the operating theory provides the level of detail required to

understand the operation of each FRU and is intended to assist the maintenance technician in servicing the

unit. The detailed block diagram is provided in figure 6.4.2. The functional operation of each component is

depicted and point-to-point signal wiring is shown.
ASOS Site Technical Manual S100

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Figure 6.4.1. Visibility Sensor Basic Block Diagram

6.4.3.1 Transmitter Assembly. The transmitter assembly flashes a xenon flashlamp at a 2 Hz rate. The high

voltage switching supply (located in the transmitter assembly) charges the energy storage (a storage

capacitor) to full voltage. The trigger circuitsends a signal to the light pack to fire the xenon flashlamp. Light

from the flashlamp is received by two detectors: the receiver assembly (paragraph 6.4.3.2) and the

photodarlington transistor. The timing for the receiver sample is initiated by the photodarlington transistor,

which outputs an electrical pulse when the xenon flash is generated. The photodarlington transistor output

signal is used by the receiver assembly to detect the scattered light. Separate heater elementsfor the window

and the hood are also provided in the transmitter assembly.

6.4.3.2 Receiver Assembly. The receiver assembly is used to detect the forward scattered light level from

transmitted flashes and report the data to the controller board. The receiver diode receives scattered light

fromthe sample volume through a lens. The light pulse strikesthe receiver diode, causing the diode to create

an electrical pulse proportional to the amplitude and duration ofthe scattered light pulse. The electricalsignal

from the diode is bandpassfiltered and amplified and then input to a sample and hold circuit. The logic input

to the sample and hold circuit is timed to catch the received signal at its peak. The sample and hold circuit

is normally in the sample mode. The trigger signal from the transmitter assembly, created from the xenon

light pulse, places the sample and hold circuit in the hold mode where it can take the light measurement.

Once the received pulse is sampled at the peak of the signal and held there by the sample and hold circuit,

an analog-to-digital converter transforms the voltage level into a digital value. The measured data is loaded

into a first-in first-out (FIFO) memory, which, when full, isread by the processor board through a serial data

interface for further processing. The processor board then places the sample and hold circuit back into the

sample mode. After 33.3 milliseconds, the sample and hold circuit returns to the hold mode to measure the

background (dark) light. The new data are then read in the same manner. Both light and dark measurements

are required to calculate the extinction coefficient. This procedure isrepeated for every flash. Separate heater

elements for the window and the hood are also provided in the receiver assembly.
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Figure 6.4.2. Visibility Sensor Detailed Block

Diagram (Sheet 1 of 4)

6-17/ (6-18 blank)
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Figure 6.4.2. Visibility Sensor Detailed Block

Diagram (Sheet 2)

6-19/ (6-20 blank)
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Figure 6.4.2. Visibility Sensor Detailed Block

Diagram (Sheet 3)

6-21/ (6-22 blank)
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Figure 6.4.2. Visibility Sensor Detailed Block

Diagram (Sheet 4)

6-23/ (6-24 blank)
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6-25

6.4.3.3 Day/Night Assembly. The day/night assembly is essentially an ambient light photometer. It detects

light using a PIN receiver diode in the assembly such that light is received from the sky with a 6-degree

viewing angle. The day/night receiver diode receives light through a window (not a lens) mounted in the

day/night assembly. The light strikes the day/night receiver diode, causing the diode to create an electrical

signal proportional to the amplitude of the ambient light. The electrical signal is then bandpass filtered and

amplified. The voltage signal is then sent to the processor board for further processing. Separate heater

elements for the window and the hood are also provided in the day/night assembly. 

6.4.3.4 Processor Board. The processor board directs all of the actions of the visibility sensor. Its primary

task is to take measurements of the sample volume and calculate the visibility extinction coefficient and

day/night condition. 

The extinction coefficient for the sample volume of atmosphere is proportional to the ratio of light energy

received by the receiver diode to the light energy input to the sample volume by the xenon flash transmitter.

Two measurements are performed during each sample cycle (1⁄2 second). During the first measurement (the

light measurement), the transmittersends a triggersignal to the receiver assembly asthe flashlamp fires. The

sample and hold circuit in the receiver assembly responds to the trigger signal to latch the receiver signal at

its peak. This peak level is converted into a digital value that is read by the processor. The data collected

during this first measurement period are directly proportional to the amount of light that was scattered into

the receiver. 

During the second measurement (the dark measurement), the sample and hold isreturned to the sample mode

by the processor. In the absence of the flash (no scattered signal reaching the receiver), the receiver level is

sampled and held. This measurement is then converted to a digital form and read by the processor. The

receiver data collected during this second measurement period are directly proportional to the amount of

ambient background light (background noise) that was observed by the receiver. The difference between the

two measurements is used to determine extinction coefficient. The subtraction cancels the effects of any

possible offsets in the receiver assembly. The day/night signal is converted to digital form on the processor

board. The processor uses the day/night data to determine if the ambient light indicates day. The day/night

sensor alwaysindicates day forillumination greaterthan 3 fc, and alwaysindicates nightforillumination less

than 0.5 fc. The transition from indicating day to indicating night occurs once in the region from 3 to 0.5 fc

(as illumination decreases). The transition from indicating night to indicating day occurs once in the region

from 0.5 to 3 fc (as illumination increases). The day/night assembly is calibrated before installation. Two

calibration factors are supplied with the calibrated day/night assembly: edge of day, which indicates the

transition point for daytime, and edge of night, which indicates the transition point for nighttime.

The processor board also monitors the operation of the heaters. The board monitors the electrical current

levels used by the heaters. The signals sensed indicate whether the associated heater element is on or off.

When it is cold enough for the heaters to turn on (temperatures less than 40 degrees Fahrenheit), the heaters

cycle on and off. The processor periodically verifies the operation of the heaters as a part of its normal

processing.

6.4.3.5 Fiberoptic Module. A fiberoptic link provides for two-way serial communication between the

visibility sensor and the DCP. The fiberoptic module performs the electrical-to-optical and

optical-to-electrical conversions required. The electrical interface between the controller board and the

fiberoptic module is an RS-232C serial interface. The fiberoptic link with the DCP consists of separate

transmit and receive optic fibers.

6.4.3.6 Power Distribution. Both ac and dc power are present in the visibility sensor electronics enclosure

(Figure 6.4.3). If one filter protrudes from the top of the power input box, the sensor is a one-filter

configuration as illustrated on figure 6.4.3, sheet 2. If two filters protrude from the top of the power input

box as illustrated on figure 6.4.3, sheet 1, the sensor is a two-filter configuration. DCP cables are connected

to the sensor in an identical manner for either configuration. Two types of ac power are applied from the
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DCP: electronics ac and heater ac. The electronics ac power is passed through surge suppression and EMI

filter circuits and is applied to electronics power supply PS1. The ±15 vdc and +5 vdc output by the

electronics power supply are applied to the sensor electronics via the electronics assembly. The heater ac

power is passed through surge suppression and EMI filter circuits and applied to the heater power supply.

The +24 vdc output of the heater power supply is applied to the electronics assembly where it is distributed

to all of the heaters.

Take note that the F2 fuse in figure 6.4.3 is a 1⁄4 amp fast blow fuse. Furthermore, the S1 temperature sensor

in figure 6.4.3 is a cut-off switch that will open at 30°F and closes at 50°F. Should the electronics enclosure

drop below 30°F, all power to the sensor will be terminated.

6.4.4 COMMAND DESCRIPTION

The visibility sensor responds to V commands issued by the DCP during normal operation and by the

technician during calibration. The following paragraphs describe visibility sensor commands.

6.4.4.1 Quick Reference.

6.4.4.1.1 Polled Mode.

a. The V1 command reports sensor status, extinction coefficient, and day/night status.

b. The VL command reports sensor serial number; sensor status; day/night status; enclosure

temperature; flash, dark, and day/night measurements; visibility in miles; and extinction

coefficient in inverse kilometers.

6.4.4.1.2 Continuous Output Mode. The VP command sets the delay between output messages (delay of

zero = >off) that report the measurement values of the most recentsample, visibility in miles, and extinction

coefficient in inverse kilometers.

6.4.4.1.3 Other.

a. V0 displays sensor status and current firmware revision.

b. V2 is used as a communications check, causing known and unchanging valuesfor extinction

coefficient to be reported.

c. V3 is used to enter heater calibration mode. (Refer to table 6.5.3, step 9.)

d. V4 enables/disables the data quality algorithm.

e. VD calculates the standard deviation of the sensor's "zero drift".

f. VF allows the entry/modification of calibration coefficients and configuration information.

g. VH allows the entry/modification of initialization coefficients.

h. VG invokes extended diagnostics.

I. VE clears and initializes the EEPROM (nonvolatile RAM).

NOTE

If VE is performed, the sensor must be recalibrated unless calibration constants have been

recorded otherwise (i.e., written down) and known to have not changed. The calibration

constants must be reentered after VE or the sensor will not operate properly.
S100 ASOS Site Technical Manual

Figure 6.4.3. Visibility Sensor Electronics

Enclosure Power Distribution Diagram (Sheet

1 of 2)

6-27/ (6-28 blank)
S100 ASOS Site Technical Manual

Figure 6.4.3. Visibility Sensor Electronics

Enclosure Power Distribution Diagram (Sheet 2)

6-29/ (6-30 blank)
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6.4.4.2 Power Up/Reset Message.

***VIS VER 021***

Total message length is 21 characters. The time for total message transmission at 2400 bps is 0.07 second.

6.4.4.3 V0 Command (Roll Call).

Byte Description Value

1 Start of transmission STX

2 Carriage return CR

3 Line feed LF

4 Sensor identification V

5 Sensor status P/F

6-8 ROM version XXX

9-10 Checksum (in ASCII) CHECKSUM

11 End of transmission ETX

12 Carriage return CR

13 Line feed LF

Total message length is 13 characters. A sensorstatus of P indicatesthat the sensor has passed all diagnostic

tests. A sensor status of F indicates that the sensor has failed one or more diagnostic tests. More information

as to the nature of the failure is available by sending a VG command to the sensor.

6.4.4.4 V1 Command (Extinction Coefficient).

Byte Description Value

1 Start of transmission STX

2 Carriage return CR

3 Line feed LF

4 Sensor ID V

5 Sensor status P/F

6-10 Extinction coefficient XXX.X

11 Day/night status D/N

12-13 Checksum (in ASCII) CHECKSUM

14 End of transmission ETX

15 Carriage return CR

16 Line feed LF

The total message length is 16 characters. The extinction coefficient consists of five charactersincluding the

number and the decimal point. The position of the decimal point shifts, depending on the value of extinction

coefficient to yield the most accurate reading in the available space. The extinction coefficient range is

186.4/km (52.8 feet) to 0.018/km (100 miles).

6.4.4.5 V2 Command (Simulated Data).

Byte Description Value

1 Start of transmission STX

2 Carriage return CR

3 Line feed LF

4 Sensor ID V

5 Sensor status P/F

6-10 Extinction coefficient 12.34
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Byte Description Value

11 Simulated day/night status D

12-13 Checksum (in ASCII) CHECKSUM

14 End of transmission ETX

15 Carriage return CR

16 Line feed LF

The total message length is 16 characters. This message is constant except that the sensor status reports the

actual pass/fail status of the instrument to avoid confusion.

6.4.4.6 V4 Command (Data Quality).

Data quality? (Y or N)[Y]>Y

New Cksum=9f

Old Cksum=9f

---> End of v4 >---

***************************************

This command is used to enable or disable the use of the data quality algorithm during visibility

measurements. This data quality algorithm is designed to ignore errant readings that are caused by debris

passing through the scatter volume temporarily (e.g., windblown leaves, windblown snow, birds, etc). The

data quality algorithm causes the sensor to appear stuck temporarily if there is a sudden and significant

change in ambient visibility but the sensor output data conform to the actual conditions within a 3-minute

period.

6.4.4.7 VD Command (Standard Deviation of Zero Drift). The firmware includes a function that

calculates the standard deviation of the sensor indication about zero when in the zero state. This is the best

possible means of determining zero drift and, thus, the overall accuracy ofthe individual instrument. The VD

command calculates the standard deviation of a number of zero state samples. The number of samples is

selecTable in the range of 2 to 65,535 with 120 samples as the default. To invoke VD, the opaque filter is

placed on the receiver and the instrument is allowed to settle for at least 3 minutes. After settling time, the

technician types VD. When prompted for the number of samples, the desired number is entered or ENTER

is pressed to accept the default. The function then displays a countdown of the samples being used for the

calculation. The results of the VD command are std_dev and VIS. std_dev is the calculated standard

deviation of zero drift, which is consistent with the classical mathematical definition. VIS is the maximum

visibility (in miles) at which there is a 90-percent statistical probability of being 10 percent accurate. The

VIS output of the VD command should be no less than 100 miles. The value of FI calculated by the VZ

command should be in the range of +1.0 to -1.0.

NOTE

It is normal for the extinction coefficient and visibility readings to go negative when in the

zero state. This does not happen in actual ambient visibility and should not be construed as

a malfunction of the device.

6.4.4.8 VDCommand (Calibration Coefficients/Configuration Information). The VF command, invoked

by typing VF, allows the technician to enter the calibration coefficients and configuration information

required for proper operation. The VF command responds as follows:

**************************************

E2PROM chk_sum = 0

E0 = 19.399999...==>

F0 = 1.000000...==>
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WINDOW = 113.999999...==>

VIS_SER_NO? 1...==>

Day/Night installed? (Y or N)[Y]>

Heaters installed? (Y or N)[Y]>

--------------------------------------

E0 = 19.399999

F0 = 1.000000

WINDOW = 113.999999

VIS_SER_NO = 1

D/N installed = Y

Htrs installed = Y

New Cksum=9f

Old Cksum=9f

---> End of vF <---

**************************************

a. E0 is the factory-initialized value for the standard extinction coefficient obtained from the

calibration filter/scatter plate set. E0 is changed only when a new scatter plate/filter

combination is used.

b. F0 is the factory-initialized value for the extinction coefficient adjustment factor. F0 is

changed only when an FRU replacement calibration is performed. F0 is not used for

measurement calculations; it is for reference only.

c. WINDOW is the time constant (in seconds) of the window averaging filter for extinction

coefficient data. This should be set to 114. (The processor stores 114 as 113.999999 in

floating point format.)

d. VIS_SER_NO? is the serial number of the visibility meter, which is shown on the Belfort

ID marker.

e. Day/Night installed? allows the sensor to be configured with or without the day/night

option. If day/night is not configured in, all day/night diagnostics pass and day/night status

reads X instead of D or N.

f. Heaters installed? allows the sensor to be configured with or without the cold weather

option. If heaters are not configured in, all heater diagnostics (except transmitter and

receiver window heaters) pass.

g. Values are changed by entering a new value at the ...==> prompt.

h. The information below the dashed line is a verification of the data entered. The information

also contains EEPROM checksum information.

i. If no data are to be changed in a particular field, <ENTER> is pressed. <ESC> is pressed

to abort the remainder of the data entry.
ASOS Site Technical Manual S100

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6.4.4.9 VL Command (Polled Mode, Extended Output Message).

SER001 AOK Night 26.1 001031 001024 000024 Vis: 23.40 Ext: 0.079646

The total message length is 72 characters (including CR/LF at the end). This message reports the serial

number of the sensor,sensorstatus, day/nightstatus, enclosure internal temperature, value of the latest flash

and dark measurements, value of the latest day/night measurement, visibility in miles, and extinction

coefficient in inverse kilometers.

6.4.4.10 VG Command (Extended Diagnostics).

VPN 0.06553PPPP PPP PP PPP PPPP 26.4 9f

Byte Description Value

1 Start of transmission STX

2 Carriage return CR

3 Line feed LF

4 Sensor ID V

5 Sensor status P/F

6 Day/night status D/N

7-13 Latest extinction coefficient XXX.XXX

14 ADD check P/F

15 RAM check P/F

16 ROM check P/F

17 EEPROM check P/F

18 Space

19 Receiver operational status P/F

20 Transmitter operational status P/F

21 Day/night operational status P/F

22 Space

23 Receiver hood heater P/F

24 Transmitter hood heater P/F

25 Space

26 Receiver window heater P/F

27 Transmitter window heater P/F

28 Day/night window heater P/F

29 Space

30 Receiver electronics heater P/F

31 Transmitter electronics heater P/F

32 Day/night electronics heater P/F

33 Enclosure electronics heater P/F

34 Space

35-39 Inside ambient temperature XXX.X

40 Space

41-42 Checksum XX

43 End of transmission ETX

44 Carriage return CR

45 Line feed LF

The total message length is 45 characters. The processor is dedicated full-time to the test during the check

period and is not available to output visibility data.
S100 ASOS Site Technical Manual

6-35

6.4.4.11 VH Command (Calibration Factors).

FE = 0.873497...==>

FI = 0.408333...==>

EDGE_OF_DAY = 90.000000...==>

EDGE_OF_NIGHT = 30.000000...==>

DAY_NIGHT_ZERO = 10...==>

--------------------------------------

FE = 0.873497

FI = 0.408333

EDGE_OF_DAY = 90

EDGE_OF_NIGHT = 30

DAY_NIGHT_ZERO = 10

New Cksum=9f

Old Cksum=9f

---> End of vH <---

**************************************

a. FE is a calibration constant and is a multiplier in the equation that calculates the extinction

coefficient. FE is directly proportional to the extinction coefficient.

b. FI is the zero offset. FI is subtracted out of the measurement data as a part of the extinction

coefficient calculation.

c. EDGE_OF_DAY is the digital measurement that corresponds to an ambient light level of

3 foot-candles.

d. EDGE_OF_NIGHT is the digital measurement that corresponds to an ambient light level

of 0.5 foot-candle.

e. DAY_NIGHT_ZERO is the minimum reading that the processor should obtain from the

day/night sensor. DAY_NIGHT_ZERO is used for diagnostics.

6.4.4.12 VP Command (Automatic Report). The VP command is used to provide a periodic output

message that reports several operating values including the extinction coefficient in inverse kilometers and

visibility in miles. This command also provides the capability to alter the delay between messages in

increments of 1 second. The delay should be set to zero to turn off the output message. The following is an

example of the response to the VP command:

Delay? 0...==>60

New Cksum=7c

Old Cksum=2e

---> End of vP <---

**************************************

001031 001024 000107 000024 N 004095 23.4 0.079646

001031 001024 000107 000024 N 004095 23.4 0.079646
ASOS Site Technical Manual S100

6-36

The columns of data in the VP output message are as follows:

(1) The latest flash measurement

(2) The latest dark measurement

(3) Flash - dark + K (K is an arbitrary constant)

(4) The latest day/night measurement

(5) The latest day/night status

(6) Reserved

(7) The latest visibility in miles

(8) The latest extinction coefficient in inverse kilometers

6.4.4.13 VR Command (Reset Sensor). The VR command invokes a reset of the processor, which

initializes the visibility meter.
S100 ASOS Site Technical Manual

6-37

SECTION V. MAINTENANCE

6.5.1 INTRODUCTION

The visibility sensor requires a few, simple maintenance procedures. In general, the maintenance schedule

depends upon the influence of local environmental factors near and about the installation site. Corrective

maintenance is divided into two areas. The troubleshooting procedure is used when data transfer

communications with the sensor have failed. The diagnostic procedure is used when data communications

with the sensor are available. The source of any faults can thereby be quickly detected and identified.

6.5.2 PREVENTIVE MAINTENANCE

6.5.2.1 General. The preventive maintenance schedule for the visibility sensor is provided in table 6.5.1.

Routine cleaning and inspection ofthe sensor, as described in table 6.5.2,should be performed every 90 days

and whenever the maintenance technician visits the site. The maintenance log should be updated and any

problems noted at each interval.

Table 6.5.1. Visibility Sensor Preventive Maintenance Schedule

Interval What To Do How To Do It

90 days

Routine cleaning and inspection Table 6.5.2

Calibration Table 6.5.3

6.5.2.2 Calibration. The visibility sensor must be calibrated every 90 days or after any corrective

maintenance action.Before the sensor can be calibrated, it must be properly installed andmust passits ASOS

diagnostics checks. Table 6.5.3 provides the procedure to calibrate the visibility sensor. Calibration is

performed using the laptop computer to issue "V_" commands and receive the sensor's responses. Paragraph

6.4.4 provides a detailed description of these responses.

6.5.3 CORRECTIVE MAINTENANCE

6.5.3.1 General. Corrective maintenance is performed only when a malfunction occurs. Manual

troubleshooting as well as diagnostic testing procedures are provided for the sensor. The troubleshooting

procedure is used when data transfer communications with the sensor have failed. The diagnostics procedure

is used to automatically isolate faults when communications with the sensor are available.

6.5.3.2 AC and DC Power Troubleshooting. The dc and ac power checks used in troubleshooting are

provided in tables 6.5.4 and 6.5.5, respectively. After all dc and ac power checks have been performed and

the sensor communications are still not possible or are error prone, the fiberoptic module must be checked

using the procedures in Chapter 1. If the fiberoptic module checks good, the failure must be located in the

RS-232 link with the processor board. The processor board must then be removed and replaced.

6.5.3.3 Heater Troubleshooting. The visibility sensor has heater elements located in the main electrical

enclosure, the day/ night sensor, the transmit head assembly, and the receiver head assembly. The heater

power supply supplies power to all of these heater assemblies. A temperature sensor switch, located in the

lower right corner of the main electrical enclosure, controls the application of heater power to the heating

elements.During normalsystemoperation, the temperature sensorswitch closeswhen the temperature within

the main electrical enclosure is below 40 degrees Fahrenheit and applies 24 voltsto the heater elements. The

processor board monitorsthe currentflow through the heater elements and reportsthisstatus on the visibility

sensor maintenance page. Five faults can affect proper operation of the heater circuitry: failure of the heater
ASOS Site Technical Manual S100

6-38

power supply, failure of one or more of the heater elements, failure of the regulator circuit board (3A1),

failure of the processor card monitor circuit, or failure of the temperature sensor. The current status of the

visibility sensor's maintenance page should be reviewed prior to troubleshooting the heater control circuit.

The troubleshooting procedures provided in table 6.5.6 can then be used to troubleshoot the sensor.

$ Common visibility heater specifications, all with tolerances of +/- 5%:

$

$ Window Heater - 115 ohms

$ Hood Heater - 12 ohms

$ Electronics Heater - 53.6 ohms thru 63 ohms

$ Day/Night Window Heater - 115 ohms

$ Day/Night Electronics Heater - 100 ohms

$

$ With all heaters on, nominal current draw is 2.4966 amps (maximum is 2.7594 amps).

6.5.4 DIAGNOSTICS

6.5.4.1 Introduction. The visibility sensor is provided with a continuous self-test (CST) that runs

automatically as a part of normal ASOS operation. The technician can also selectively run a diagnostic test

on demand. The operation of the CST software does not interfere with the collection, processing, storage,

or reporting of data. All of the diagnostic capabilities of the sensor may be exercised by the technician from

the OID. Processor Board, PN 32194-1, with V036 firmware loaded, contains a "V3" command. V3 guides

the technician in a step-by-step procedure to measure current draw of each heater element, using a supplied

jumper. Procedural instructions are included in the firmware so that the OID displays each procedural step.

No special test equipment or fixtures are needed to perform the "V3" measurement, and the visibility sensor

need not be in ASOS mode. Sensor calibration is not required after the "V3" measurement.

The diagnostic capability of the visibility sensor is designed to check and monitor the major signal paths of

the sensor to detect any possible failures. Each of the sensor heaters is monitored by current sensors. The

outdoor temperature is monitored, and if the range is such that heaters are to be operational, software

algorithms look for cycling (on and off) of the heaters. Every power supply output voltage is monitored by

the processor board through a multiplexer and sensing circuit. If any level is out of range, a software flag is

set to notify the technician to replace the corresponding FRU.

Signals generated by the various detectors are monitored to check for out-of-range values. Any discrepancies

result in the setting of a software flag that notifies the technician to replace the associated FRU. In addition,

random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only

memory (EEPROM), and address self-test checks are run by the processor board to continually monitor its

own operation. All diagnostics are available to the technician at the OID during normal operation.

6.5.4.2 Executing Diagnostics. The visibility sensor executes its own diagnostic routine during normal

operation to detect any failures in operation. The results of this diagnostic routine are reported to the ASOS

system software as a part of its normal data gathering process. Any failures that are detected are displayed

at the OID as well as reported in the maintenance log. The visibility sensor page displayed at the OID also

allows the technician to perform a detailed diagnostic test on the sensor. The test is initiated by selecting the

TEST option fromthe display. The results of the test process are then displayed forthe technician at the OID.

A description of the visibility sensor page and its fields is provided in Chapter 1.
S100 ASOS Site Technical Manual

6-39

WARNING

6.5.5 FRU REMOVAL AND INSTALLATION

FRU removal and installation are easily accomplished with simple handtools.

6.5.5.1 Receiver Assembly Removal and Installation. The procedures required to remove and install the

visibility sensor receiver assembly are provided in table 6.5.7.

6.5.5.2 Transmitter Assembly Removal and Installation. The procedures required to remove and install

the visibility sensor transmitter assembly are provided in table 6.5.8.

6.5.5.3 Processor Board Removal and Installation. The procedures required to remove and install the

processor board are provided in table 6.5.9.

6.5.5.4 Day/Night Assembly Removal and Installation. The proceduresrequired to remove and install the

day/night assembly are provided in table 6.5.10.

6.5.5.5 Electronics Power Supply Removal and Installation. The procedures required to remove and

install the electronics power supply are provided in table 6.5.11.

6.5.5.6 Fiberoptic Module Removal and Installation. The procedures required to remove and install the

fiberoptic module are provided in table 6.5.12.

6.5.5.7 Crossarm Assembly Removal and Installation. The proceduresrequired to remove and install the

crossarm assembly are provided in table 6.5.13.

6.5.5.8 Electronics Enclosure Removal and Installation. The procedures required to remove and install

the electronics enclosure are provided in table 6.5.14.

6.5.5.9 Regulator Board Removal and Installation. The procedures required to remove and install the

regulator board are provided in table 6.5.15.

Table 6.5.2. Visibility Sensor Cleaning and Inspection

Step Procedure

Death or severe injury may result if power is not removed from the sensor prior to maintenance activities. Ensure

that circuit breaker supplying power to the sensor is in the OFF (right) position.

1 Inspect ac and signal wiring that supplies the visibility sensor enclosure and ac and signal cables that route

from enclosure to sensor's transmitter, receiver, and day/night assemblies.

2 Ensure that all visibility sensor cable connectors are secure.

3 Inspect inside of transmitter, receiver, and day/night assembly housings (assemblies) for dirt, spider webs,

birds' nests, or any other obstructing material that may disrupt optical path.

4

NOTE

Spider webs can float in air currents and attach across sample volume. Webs may be

almost invisible to the human eye but can severely effect performance of sensor.

Using a soft cloth, remove any evidence of window fouling. Gently brush cloth over critical areas that may

appear to be clean,such aslip of assembly and support pole where scatter plate attaches. Make several passes

through sensing volume with an arm or pole to ensure that there is no contamination.

5 Using soft cloth and a commercially available glass cleaner, clean protective glass windows of transmitter,

receiver, and day/night assemblies.
ASOS Site Technical Manual S100

6-40

Table 6.5.3. Visibility Sensor Calibration

Step Procedure

NOTE

Before running the Visibility Calibration Check, check continuity of all nine visibility sensor

heaters per table 6.5.6.

Figure 6.5.1 provides a sample visibility sensor calibration data sheet. Copies of this form should

be made and used to record values as directed in this procedure.

Tools required:

 Laptop computer with PROCOMM Plus installed

 Visibility sensor calibration kit

 Laptop interface (Y-shaped) cable

 Large flat-tipped screwdriver

 Small flat-tipped screwdriver

 Window cleaner and soft cloth

 Dark opaque cloth

 Tape measure

CAUTION

Adverse weather conditions can affect the accuracy of the visibility calibration. Calibration should

only be performed under the following conditions: winds less than 10 knots, ambient visibility

greater than 2.5 miles, and no precipitation or blowing snow.

INITIAL SETUP PROCEDURE

1 Inside equipment cabinet,set circuit breaker on visibility sensor circuit breaker module to off(right) position.

2 During initial installation or TX/RX replacement only, verify that TX and RX canisters are fully seated in

hood. This can be verified by measuring the distance from the back of the hood down to the end of TX or RX

canister body. The distance should be at least 1.0 inch. If not, slide canister out 1 inch and then push canister

back in until fully seated. 

3 Using large flat-tipped screwdriver, open visibility sensor electronics enclosure access door.

4 Using small flat-tipped screwdriver, disconnect visibility sensor DB-9 connector from fiberoptic module

inside electronics enclosure.

5 Using laptop computer interface (Y-shaped) cable, connect RS-232C (COM1) port of laptop computer to

DB-9 connector removed from fiberoptic module. 

6 Turn on laptop computer and initialize PROCOMM Plus program. After program initializes, press any key

to enter terminal mode (blank) screen.

7 Using ALT-S command (setup facility), set up the following TERMINAL OPTIONS:

a. Terminal emulation: VT220

b. Duplex: FULL

c. Soft flow control (XON/XOFF): OFF

d. Hard flow control (CTS/RTS): OFF

e. Line wrap: OFF

f. Screen scroll: ON

g. CR Translation: CR

h. BS Translation NON-DESTRUCTIVE

i. Break length (milliseconds): 035

j. Enquiry: OFF

k. EGA/VGA true underline: OFF

l. Terminal width: 80

m. ANSI 7 or 8 bit commands: 8 BIT
S100 ASOS Site Technical Manual

6-41

Table 6.5.3. Visibility Sensor Calibration -CONT

Step Procedure

8 Press ESC key to exit to terminal mode (blank) screen.

9 Using ALT-P command (line/port option), set CURRENT SETTINGS as follows:

a. Baud rate: 2400

b. Parity: NONE

c. Data bits: 8

d. Stop bits: 1

e. Port: COM1

10 Press ESC key to exit to terminal mode (blank) screen.

11 Set laptop computer CAPS LOCK to ON.

12 Inside equipment cabinet, set circuit breaker on visibility sensor circuit breaker module to on (left) position.

13 Verify that laptop computer displays sensor initialization message shown below:

***VIS VER XXX - 6220***

The XXX refers to sensor firmware version number and 6220 refers to sensor model number. Record

firmware version number on calibration data sheet.

14 At laptop computer, enter VG <CR>. Sensor enters Extended Diagnostics (VG) mode and responds with:

VPXXXXXXXXPPPP PPP PP PPP PPPP XXXX XX

Sensor status bytes reported above should be all P's for pass. Values marked with X above may be any value

(don't care), depending on prevailing visibility, ambient temperature, etc.

15 At laptop, press CTRL A then enter VF. Sensor responds with Need Password to disable ASOS mode:

PASSWORD?...==>. 

NOTE

CTRL A putsthe sensor into Maintenance Mode. Be sure to press CTRL A again to put the sensor back into

ASOS Mode before leaving.

16 Enter EIEIO <CR>. Sensor enters Calibration Coefficients/Configuration Information (VF) mode and

displays information shown below (one line at a time). The table below also shows correct values for each

line. If data in any line are incorrect, enter correct value at ==> prompt and enter <CR>. If data are correct

or correct value is XXXXXX (don't care), enter <CR> to accept data as is. Thisshould be performed at each

line of VF command.

Sensor Response Correct Value

E2PROM chk_sum = XX

EO = XXXXXXXXX...==> Note 1

FO = XXXXXXXX....==> XXXXXX

WINDOW = 113.999999...==> 113.9999999

VIS_SER_NO? XXXX...==> Note 2

Day/Night installed? (Y or N) [Y]> Y

Heaters installed? (Y or N) [Y]> Y

Note 1 - EnterBelfortCalibration Kit extinction coefficient(EXCO) value labeled on scatter plate and filters

in EO field. EXCO is usually a 4-digit number (i.e., 1.572) and should be entered as such. EO is a

9-digit floating point field; therefore, up to 8 digits and a decimal point may be entered.
ASOS Site Technical Manual S100

Table 6.5.3. Visibility Sensor Calibration -CONT

Step Procedure

6-42

Note 2 - Verify that sensor serial number on nameplate located on electronics enclosure door is the same as

entered here. If not, enter correct serial number. Up to four digits may be entered in this field.

After entering final <CR>, sensor retransmits corrected data entered above as well as the following:

New Cksum = XX

Old Cksum = XX

---> End of vF <---

17 At laptop computer, enter VH. Sensor enters Calibration Factors (VH) mode and responds with information

shown below (one line at a time). The table below also shows correct values for each line. If data in any line

are incorrect, enter the correct value at the ==> prompt and enter <CR>. If data are correct or correct value

is XXXXXX (don't care), enter <CR> to accept data as is. This should be performed at each line of VH

command. Record values for FE and FI on calibration data sheet.

Sensor Response Correct Value

FE = 0.918000...==> Note 1

FI = XXXXXXX...==> -1.0 to +1.0 (Note 2)

EDGE_OF_DAY = 90.000000...==> 90.0

EDGE_OF_NIGHT = 30.000000...==> 30.0

DAY_NIGHT_ZERO = 5...==> 5

Note 1 - FE value will be whatever calibration constant was entered into sensor during last calibration, and

will typically range from 0.50 to 1.80.

Note 2 - If FI value is not between -1.0 and +1.0, noise is probable problem. Perform the following:

a. Check all grounds on crossarm and electronics enclosure.

b. There is a very small chance that the problem is in the processor board. Replace

and retest.

c. In fewer cases, the site ground, as a function of soil conditions and conductivity,

is a factor.

After entering final <CR>, sensor retransmits corrected data entered above as well as the following:

New Cksum = XX

Old Cksum = XX

---> End of vH <---

18 At laptop computer, enter VP. Sensor responds with request for delay. Enter 5 <CR> to put sensor into

Automatic Reporting (VP) mode. Automatic Reporting mode transmits data to laptop computer every 5

seconds. Data are presented in eight columns as follows:

XXXXXX XXXXXX XXXXXX XXXXXX X XXXXXX XXXX XXXXXXXX
S100 ASOS Site Technical Manual

Table 6.5.3. Visibility Sensor Calibration -CONT

Step Procedure

6-43

Columns of data in VP output message are as follows:

 Group Contents

1 Latest flash measurement

2 Latest dark measurement

3 (Flash counts - dark counts) + 100

4 Latest day/night measurement

5 Latest day/night status

6 Reserved

7 Latest visibility in miles

8 Latest extinction coefficient (EXCO) in /km

Automatic Reporting mode and EXCO of column 8 is used throughout the rest of this procedure to aid in

validating calibration steps.

VISIBILITY ZERO ADJUSTMENT

1 At visibility sensor, place opaque filter from calibration kit over receiver window.

NOTE

You can also install the calibration plate now to save time.

Verify the dark measurement in column 2 of VP is 512 ±5. If dark measurement is not within tolerance, the

problem is in the receiver. Perform the following:

a. Check opaque filter for cracks. This can best be done by removing opaque filter from

receiver, installing it on transmitter, and looking for light leaks when the transmitter

flashes. Ensure that O-ring is in place.

b. Remove and replace receiver assembly.

2 With the opaque filter in place, wait 5 minutesfor reading of column 8 of VP to stabilize to a value near zero.

Reading may be considered stable when column 8 changes less than ±0.01 over six consecutive VP updates.

If value in column 8 does not stabilize, noise is probable problem. Perform the following:

a. Check all grounds on crossarm and electronics enclosure.

b. Check opaque filter for cracks or leaks by removing opaque filter from receiver, installing

it on transmitter, and looking for light leaks when transmitter flashes. Ensure that O-ring

is in place.

c. There is a possibility that the problem is in the processor board. Replace and retest.

d. In fewer cases, the site ground, as a function ofsoil conditions and conductivity, is a factor.
ASOS Site Technical Manual S100

Table 6.5.3. Visibility Sensor Calibration -CONT

Step Procedure

6-44

3 At laptop computer, enter VZ. Sensor enters Zero State Calibration (VZ) mode and displays the following:

FROM VZ->

OLD FI = XXXXXXXXX

SAMPLE: XXX

SAMPLE field counts down from 120 to 0 over a 1-minute period. Sensor then prompts to accept (Y) or

reject (N) new zero calibration value FI. The perfect FI value is 0.00. If new FI value is between ±1.0, record

new FI value and enter Y. Entering an N or doing nothing leaves the old number in FI. If new FI value is not

between ±1.0, noise is probable problem. Performtroubleshooting actions described in step 2.If newFI value

is >1.00, replace the receiver.

4 With opaque filter still in place, verify that sensor EXCO in column 8 of VP is between -0.005 and +0.005.

Record this EXCO value on calibration data sheet. If EXCO is not within tolerance, repeat step 2. If

acceptable EXCO value cannot be achieved, noise is probable problem. Perform troubleshooting actions

described in step 2.

5 At laptop computer, enter VF. Sensor enters VF mode (as in initial setup procedure, step 15). Enter <CR>

to bring up FO data line. Enter value of FI obtained in step 2 in FO line followed by <CR>. Enter <CR> four

additional timesto exit VF mode. This processstores zero calibration value for future reference; it is not used

by sensor for measurement purposes.

6 At laptop computer, enter VD. Sensor responds with request for number of samples as shown below:

From VD ->

Number of samples? 120...==>

To accept default of 120, press <CR>. Sensor enters Standard Deviation of Zero Drift (VD) mode and counts

down from 120 to 0 over a 1-minute period. Sensor then displays the following:

std_dev = XXXXXXXX

Standard deviation VIS: XXXXXXXXXX

---> End of vD <---

Value of standard deviation VIS should be greater than 100. Record this value on calibration data sheet. If

standard deviation VIS is not greater than 100, noise is probable problem. Perform troubleshooting actions

as described in step 2.

7 Remove opaque filter from receiver and store in calibration kit.

VISIBILITY CALIBRATION CHECK

1 Remove two neutral density filtersfromcalibration kit. Verify that calibration plate is not warped or cracked.

If it is, obtain complete new calibration kit (plate and both filters) before proceeding. Clean neutral density

filters and calibration plate with soft cloth and windowcleaner. Also, clean transmitter and receiver windows

before installing filters. Install neutral density filter marked with TX over transmitter window and filter

marked with RX over receiver window.

NOTE

During initial installation or when visibility head is replaced only, verify that calibration

plate is centered equidistant between TX andRX heads. Use tape measure to measure from

front tip of each head to upper corner of calibration plate. Distance should be ±1⁄4 inch

between sides.

2 Record EXCO value marked on calibration plate on calibration data sheet. Install calibration plate (with side

labeled TOP upward) to top sensor support pole using knurled knobs. Using tape measure, ensure that

calibration plate is mounted equidistant (±1 inch) between transmitter and receiver heads.
S100 ASOS Site Technical Manual

Table 6.5.3. Visibility Sensor Calibration -CONT

Step Procedure

6-45

3 Wait 5 minutes and observe that column 8 of VP is within ±5% of value of EXCO written on calibration plate

and filters.

4 At laptop computer, enter VS. Sensor enters Span State Calibration (VS) mode and displays the following:

FROM VS->

OLD FE = XXXXXXXXX

SAMPLE: XXX

SAMPLE field counts down from 120 to 0 over a 1-minute period. Sensor then prompts to accept (Y) or

reject (N) new span calibration value FE. If new FE value is between 0.5 and 4.0, enter Y. Entering N or

doing nothing leaves old number in FE.

Record newFE value on calibration data sheet. If new FE value is not between 0.5 and 4.0, problemis optical

in nature. Perform the following:

a. Pull transmitter and receiver assemblies and inspect and clean windows. Ensure that no

foreign objects are in the optical path. 

b. Check for damage on calibration kit, including both calibration plate and neutral density

filters. Ensure that both plate and filters are clean and have correct part number.

c. Remove and replace transmitter assembly.

d. Remove and replace receiver assembly.

5 Record final EXCO value from column 8 of VP on calibration data sheet. If step 4 was performed and

adjustment was made, wait 10 minutes for EXCO value to stabilize before recording value.

DAY/NIGHT SENSOR CHECK

1 Cover window of day/night sensor with dark cloth.

2 Observe that column 4 of VP decreases below 30 and that column 5 switches from D (day) to N (night).

SENSOR HEATER CALIBRATION

NOTE

Whenever the visibility crossarm, transmit canister, receiver canister, or day/nightsensor have been

replaced, the Heater Power Supply Check and the Heater Calibration procedure must be run, but

first, check continuity of all nine heater elements per table 6.5.6.

Heater Power Supply Check

1 Disconnect hood/electronics heater thermostat from backplane connector J7.

2 Jumper contacts on electronics assembly backplane connector J7 together using jumper assembly supplied

with visibility calibration kit. This connection enables the hood and electronics heaters.

3 Set DMM for dc volts and connect DMM (-) terminal to heater powersupply capacitor C2 negative terminal.

Connect DMM (+) lead to C2 positive terminal.

4 Adjust R4 at heater supply board for 24.00 vdc ±0.25 as read on DMM. If DMM shows no voltage, check

ac power supply fuse (F2) and replace if necessary; otherwise, replace electronics power supply and repeat

steps 3 and 4.

Heater Calibration

5 Unlatch two fasteners and carefully remove transmitter assembly cap from back of transmitter assembly.

6 Using small flat-head screwdriver, slide locking mechanism (plate in front of connector) in transmitter

assembly to unlock connector DB-9. Do not disconnect connector.

7 Repeat steps 5 and 6 for receiver assembly.
ASOS Site Technical Manual S100

Table 6.5.3. Visibility Sensor Calibration -CONT

Step Procedure

6-46

8 Enter V3. The sensor enters heater calibration mode and displays the following instructions:

HEATER "CALIBRATION"

PLEASE INSERT A JUMPER ACROSS THE CONTACTS OF J7 ON THE BACKPLANE.

PRESS <ENTER> WHEN DONE

NOTE

Ensure the canisters are warm to the touch.

9 Jumper contacts on backplane connecter J7 together using jumper assembly supplied with visibility

calibration kit. This connection enables hood and electronics heaters. Press <ENTER>. The system displays

the following:

READING ALL OF THE HEATERS FOR 10 SECONDS.

RCV_HTR_VOLTS_AVE X.XXX

XMT_HTR_VOLTS_AVE X.XXX (where X.XXX is the average voltage measured)

PLEASE DISCONNECT THE "CANISTER" CONNECTOR IN THE RECEIVER HOOD.

PRESS <ENTER> WHEN DONE

10 Disconnect connector DB-9 in receiver hood which was loosened in step 6. Press <ENTER>. The system

displays the following:

READING THE RECEIVER CROSSARM HEATERS FOR 10 SECONDS.

........DONE

RX_XARM_HTR X.XXX (where X.XXX equals the average voltage read)

PLEASE RECONNECT THE "CANISTER" CONNECTOR IN THE RECEIVER HOOD AND

DISCONNECT THE HEATER CONNECTOR FROM THE RECEIVER HOOD

PRESS <ENTER> WHEN DONE

11 Using small flat-head screwdriver, reconnect connector DB-9 in receiver hood and disconnect heater

connector from receiver hood (molex connector). Press <ENTER>. The system displays the following:

READING THE RECEIVER HEATER ELECTRONICS HEATER FOR 10 SECONDS.

....... DONE

RX_EL_HTR X.XXX (where X.XXX equals the average voltage measured)

PLEASE RECONNECT THE HEATER CONNECTOR ON THE RECEIVER HOOD AND

DISCONNECT THE "CANISTER" CONNECTOR ON THE TRANSMITTER HOOD.

PRESS <ENTER> WHEN DONE
S100 ASOS Site Technical Manual

Table 6.5.3. Visibility Sensor Calibration -CONT

Step Procedure

6-47

12 Reconnect heater connector on receiver hood and disconnect connector DB-9 on transmitter hood, whichwas

loosened in step 6. Press <ENTER>. The system displays the following:

READING THE TRANSMITTER CROSSARM FOR 10 SECONDS.

........DONE

TX_XARM_HTR X.XXX (where X.XXX equals the average voltage read)

PLEASE RECONNECT THE "CANISTER" CONNECTOR ON THE TRANSMITTER HOOD

AND DISCONNECT THE HEATER CONNECTOR FROM THE TRANSMITTER HOOD.

PRESS <ENTER> WHEN DONE

13 Using small flat-head screwdriver, reconnect connector DB-9 in transmitter hood and disconnect heater

connector from transmitter hood. Press <ENTER>. The system displays the following:

READING THE HEATER ELECTRONICS FOR 10 SECONDS.

....... DONE

TX_EL_HTR X.XXX (where X.XXX equals the average voltage measured)

NEW CKSUM = NN

OLD CKSUM = NN

RX_HD = X.XX (receiver hood heater average voltage)

RX_EL = X.XX (receiver electronics heater average voltage) 

RX_WN = X.XX (receiver window heater average voltage)

TX_HD = X.XX (transmitter hood heater average voltage)

TX_EL = X.XX (transmitter electronics heater average voltage)

TX_WN = X.XX (transmitter window heater average voltage)

DN_WN = X.XX (day/night sensor window heater average voltage)

DON'T FORGET TO RECONNECT THE HEATER POWER CONNECTOR ON BOTH HOODS.

NOTE

Press ENTER before removing J7 jumper. You want to settle the current levels before

J7 jumper is removed.

DON'T FORGET TO RECONNECT THE HEATER THERMOSTAT TO BACKPLANE J7.

14 Reconnect heater power connectors on both hoods and reconnect heater thermostat to backplane connector

J7.

15 Enter VG. The system displays the following:

VFXXXXXXXXPPPP PFPOPP PPP PPPP XXXX XX

 ^ ^ 

NOTE: The symbol ^ denotes the bytes indicating failure. These symbols will not appear on the display.

16 Enter VG again. The system displays the following:

VPXXXXXXXXPPPP PPPOPP PPP PPPP XXXX XX

 ^ ^ 

17 At DCP, turn visibility sensor circuit breaker to OFF.
ASOS Site Technical Manual S100

Table 6.5.3. Visibility Sensor Calibration -CONT

Step Procedure

6-48

18 Using small flat-head screwdriver at receiver assembly DB-9 connector, press up on locking mechanism to

lock connector DB-9.

19 Repeat step 18 for transmitter assembly.

20 Install transmitter assembly cap and latch two fasteners.

21 Install receiver assembly cap and latch two fasteners.

22 Perform teardown procedure.

TEARDOWN

1

NOTE

Step 1 must be performed to reset sensor to ASOS operational mode.

To exit calibration procedure, press CTRL-A. Sensor responds with:

RESET TO ASOS MODE

NEW CKSUM = XX

OLD CKSUM = XX

2 Repeat initial setup procedure step 13 to verify that all sensor diagnostics pass.

3 At laptop computer, press ALT-X (exit) to exit PROCOMM Plus.

4 Turn off laptop computer.

5 Inside equipment cabinet,set circuit breaker on visibility sensor circuit breaker module to off(right) position.

6 Disconnect cables between laptop computer and visibility sensor. 

7 Using small flat-tipped screwdriver, connect visibility sensor DB-9 connector to fiberoptic module.

8 Using large flat-tipped screwdriver, close and secure visibility sensor electronics enclosure access door.

9 Remove calibration plate and two filters and store in calibration kit.

10 Clean transmitter, receiver, and day/night windows to remove any fingerprints. 

11 Inside equipment cabinet, set circuit breaker on visibility sensor circuit breaker module to on (left) position.
S100 ASOS Site Technical Manual

6-49

VISIBILITY SENSOR CALIBRATION PROCEDURE

DATA SHEET

SITE SID: ______________________ OPERATOR: _______________________

SENSOR S/N: ______________________ DATE: _______________________

REF.

STEP

PARAMETER EXPECTED

VALUE

RECORDED

VALUE

INITIAL SETUP PROCEDURE

13 Firmware Ver. $034

17 FE Value 0.50 - 1.80

17 Current FI Value #1.0

VISIBILITY ZERO ADJUSTMENT

2 New F1 Value between ±1.0

3b Zero EXCO <±0.005

5 Standard Deviation VIS >100

VISIBILITY CALIBRATION CHECK

2 Cal Plate EXCO XXXXX

4* New FE Value 0.50 - 1.80

5 Sensor EXCO ±5% of Cal Plate

DAY/NIGHT SENSOR CHECK

2 D/N Switch Yes

(*) Only fill in a new FE value if step 4 (Span State Calibration) was performed; otherwise, mark

with N/A.

Figure 6.5.1. Visibility Sensor Calibration Data Sheet
ASOS Site Technical Manual S100

6-50

WARNING

WARNING

Table 6.5.4. DC Power Checks

Step Procedure

Dangerous voltage levels are present within visibility sensor's electronics enclosure.

NOTE

If output of any power supply is low, problem may be due to an overload by one or more of the

FRU(s). In such a case, technician should disconnect load and recheck power supply output. If

power supply output still fails, replace power supply. If power supply output is then good,

troubleshoot to faulty load FRU using visibility sensor diagrams (figures 6.4.2 and 6.4.3).

1 Perform ac power check in accordance with table 6.5.5.

2 Using digital multimeter (DMM), connect positive lead to terminal TB1-4 on electronics power supply PS1

and negative lead on terminal TB1-3. Voltage should be +5 ±0.5 vdc. If correct voltage is not present, replace

power supply PS1.

3 Using DMM, connect positive lead to terminal TB1-7 on electronics powersupply PS1 and negative lead on

terminal TB1-6. Voltage should be +15 ±1.5 vdc. If correct voltage is not present, replace powersupply PS1.

4 Using DMM, connect positive lead to terminal TB1-5 on electronics powersupply PS1 and negative lead on

terminal TB1-6. Voltage should be -15 ±1.5 vdc. If correct voltage is not present, replace powersupply PS1.

5 Using DMM, connect positive lead to terminal TB1-5 on heater power supply and negative lead on terminal

TB1-4. Voltage should be +24 ±5 vdc. If correct voltage is not present, troubleshoot heater power supply

using procedures in paragraph 6.5.3.3.

Table 6.5.5. AC Power Checks

Step Procedure

Dangerous voltage levels are present within visibility sensor electronics enclosure.

1 Using DMM, measure ac voltage between terminals 1 and 2 on electronics power supply PS1 in electronics

enclosure. Voltage should be 104 to 127 vac. If correct voltage is not present, check fuse F2 (1⁄4 amp, 250V)

on heater power supply and replace if blown. If fuse is good and correct voltage is still not present, proceed

to step 2.

2 Open power input box within electronics enclosure by removing six Phillips screws securing access cover

to power input box.

3 Using DMM, measure ac power input between terminals 1 and 2 ofterminal TB1 in powerinput box. Voltage

should be 104 to 127 vac. If correct voltage is not present, troubleshoot power wiring back to DCP.

4 Using DMM, measure ac output between terminals L0 and N ofline protector E2 in powerinput box. Voltage

should be 104 to 127 vac. If correct voltage is not present, replace electronics enclosure in accordance with

procedure in table 6.5.14. If voltage is 104 to 127 vac in a two-filter configuration, use DMM to measure

output between terminals LO and N of line protector E1 in power input box. If correct voltage is not present,

replace electronics assembly in accordance with procedure in table 6.5.14.

5 Install cover on power input box and secure using six Phillips screws.
S100 ASOS Site Technical Manual

Change 2 6-51

WARNING

Table 6.5.6. Heater Troubleshooting

Step Procedure

Death or severe injury may result if power is not removed from sensor prior to

performing maintenance activities. Dangerous voltages (110 vac) are present

within the visibility sensor. Exercise standard safety procedures.

1 Only one or two of the heater tests failed.

a. Using functional diagram (Figure 6.4.2), check for approximately 24 volts between heater

input terminal and ground. If 24 volts is not present, proceed to step 2.

b. If 24-volt signal is present, set circuit breakers for Visibility Heaters and Visibility

Electronics OFF.

c. At visibility sensor electronics assembly, disconnect connector/wires at the following points

to check continuity of individual heater elements:

Connector/TB Pins/Terminals Heater Element

W2P3 1 - 2 Xmtr Hood

W2P3 1 - 3 Xmtr Window

W3P3 1 - 2 Rcvr Hood

W3P3 1 - 3 Rcvr Window

W2P2 E8 - E9 D/N Window & D/N Elec

Htr Pwr Sup TB1 1 - 2 Xmtr Elec Encl, Rcvr Elec Encl, Vis Sens

Elec Encl

d. Perform the following resistance checks: $

$

J5 - P1 Receiver Connector on Main Board - remove connector from the main board and $

measure on J5 which is wired to RX head. $

$

Pins 10 and 12 - 115 ohms - Receiver Window Heater $

$

Pins 11 and 12 - 12 ohms with both RX head connectors in place $

58 ohms with only the white heater connector separated $

14 ohms with only the DB-9 Canister connector removed from RX $

canister. $

$

$

$

$

$

$

$

$

$
ASOS Site Technical Manual S100

6-51.1 Change 2

Table 6.5.6. Heater Troubleshooting -CONT

Step Procedure

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$ J4 - P1 TransmitterConnector on MainBoard -remove connector fromthe main board and

$ measure on J4 which is wired to TX head.

$

$ Pins 3 and 5 - 115 ohms - Transmitter Window Heater

$

$ Pins 4 and 5 - 12 ohms with both TX head connectors in place

$ 58 ohms with only the white heater connector separated

$ 14 ohms with only the DB-9 Canister connector removed from TX

$ canister.

$

$

$

$

$

$

$

$

$

$

$

$ J6 - P1 Day/Night Sensor on Main board - remove connector from the main board and

$ measure on J6 which is wired to D/N Sensor.

$

$ Pins 5 and 6 - 145 ohms heaters in D/N Sensor

$

$

$

$

$

$

$

$
S100 ASOS Site Technical Manual

Change 2 6-51.2

Table 6.5.6. Heater Troubleshooting -CONT

Step Procedure

e. If continuity or resistance tests fail, replace applicable FRU. $

$

f. If continuity and resistance checks pass, use figure 6.4.2 and check heater wiring. Repair $

as necessary. $

$

g. Set circuit breakers for visibility Heaters and Visibility Electronics ON. $

2 All heater elements fail to operate and the temperature of the main electrical enclosure is below 40 degrees $

Fahrenheit. $

$

a. Check fuse F2 on heater power supply and fuse F1 on regulator circuit board (3A1) (15 $

amp, 32V). $

$

b. If fuse F2 on heater power supply is blown, replace fuse and reapply power to unit. If fuse $

blows again, remove power and disconnect wires from 3A1-TB1 on regulator circuit $

board. Replace fuse and reapply power. If fuse blows again, replace main electrical $

enclosure. $

$

c. If fuse F1 on regulator circuit board is blown, remove power, disconnect wires from $

3A1-TB2, and replace fuse. Reapply power. If fuse blows again, replace regulator circuit $

board. If not, remove power and using DMM, measure resistance across terminals TB1-4 $

and TB1-5. DMM should indicate greater than 200 ohms. If reading is low, while $

observing DMM, disconnect connectorJ6.If correctreading is obtained,replace day/night $

sensor. If correct reading is still not obtained, connect connector J6 and disconnect $

connectors J4 and J5. If correct reading is obtained after disconnecting $
ASOS Site Technical Manual S100

6-52

WARNING

Table 6.5.6. Heater Troubleshooting -CONT

Step Procedure

connector J4, connect connector J4 and disconnect connector J3 at transmitter assembly.

If correct reading is obtained, replace transmitter assembly. If not, replace crossarm

assembly. If correct reading is obtained after disconnecting connector J5, connect

connectorJ5 and disconnect connectors P2 and P3 at receiver assembly. If correct reading

is obtained, replace receiver assembly. If not, replace crossarm assembly.

d. If fuses test good, use DMM and check for continuity across temperature sensor located

in lower right corner of main electrical enclosure. If continuity check fails, replace main

electrical enclosure. 

e. If continuity check passed, apply power to sensor and use DMM to check for the presence

of 24 ±2.4 volts dc between each temperature sensor terminal and ground. 

f. If 24-volt test failed, use DMM to measure voltage across terminals on capacitor C1 on

heater powersupply. Capacitor C1 islocated in lower right corner of heater powersupply.

If DMM indicates 24.00 ±2.4 volts, replace regulator circuit board (3A1), which islocated

on heater power supply.

g. If correct voltage reading is not obtained in step 2f, disconnect wires from terminal board

3A1TB1 on regulator circuit board and repeat measurement across capacitor C1. If correct

reading is obtained, replace regulator circuit board (3A1). If not, replace main electrical

enclosure.

Table 6.5.7. Receiver Assembly Removal and Installation

Step Procedure

REMOVAL

Tools required:

 No. 1 Phillips screwdriver

 Small flat-tipped screwdriver

CAUTION

Damage to equipment may result if power is not removed from sensor prior to maintenance

activities. Ensure that circuit breaker supplying power to sensor is set to off (right) position.

1 Inside equipment cabinet, ensure that circuit breaker on visibility sensor circuit breaker module is set to off

(right) position.

2 Locate receiver assembly (south end).

3

With locking pin removed from hinge plate,sensor is not locked in upright position. Death

or severe injury may result if personnel are not kept out of travel path of sensor.

Lower visibility sensor on hinge plate as follows:

a. Remove locking pin from hinge plate.

b. From hinge side of sensor, firmly grasp support pole with both hands and carefully lower

sensor on hinge until lanyard catches and supports weight of sensor.
S100 ASOS Site Technical Manual

6-53

Table 6.5.7. Receiver Assembly Removal and Installation -CONT

Step Procedure

4

CAUTION

Do not strain crossarm wiring harness when removing or installing receiver assembly.

Failure to comply may result in damage to hood or lens heater wiring.

Unlatch two fasteners and carefully remove receiver assembly cap from back of receiver assembly.

5 Disconnect molex-type cable connector.

6 Disconnect trigger signal coax wire from receiver coax connector.

7 Using Phillips screwdriver, remove screw securing green ground wire to receiver module. Disconnect green

wire.

8 Using small flat-tipped screwdriver, slide locking mechanism (plate at front of connector) downward to

unlock DB-9 connector. Disconnect DB-9 connector.

9 Grasp receiver module and slide module out of assembly.

INSTALLATION

Tools required:

 Small flat-tipped screwdriver

 No. 1 Phillips screwdriver

CAUTION

Damage to equipment may result if power is not removed from sensor prior to maintenance

activities. Ensure that circuit breaker supplying power to sensor is set to off (right) position.

1 Inside equipment cabinet, ensure that circuit breaker on visibility sensor circuit breaker module is set to off

(right) position.

CAUTION

Do not strain crossarm wiring harness when removing or installing receiver assembly.

Failure to comply may result in damage to hood or lens heater wiring.

2 Slide receiver module into assembly, seating module as far forward as possible (at least 1 inch down from

back of hood).

3 Connect DB-9 connector to receiver module. Using small flat-tipped screwdriver, press up on locking

mechanism to lock DB-9 connector.

4 Connect green ground wire to receiver module. Using Phillips screwdriver, install screw securing green

ground wire to receiver module.

5 Connect trigger signal coax wire to receiver module.

6 Connect molex-type cable connector.

7 Slide receiver assembly cap over back of receiver assembly, being careful not to crush any wiring, and latch

two fasteners securing cap.
ASOS Site Technical Manual S100 Table 6.5.7. Receiver Assembly Removal and Installation -CONT

Step Procedure

6-54

WARNING

WARNING

8

With locking pin removed from hinge plate, sensor is not locked in upright position. Death or severe injury

may result if personnel are not kept out of travel path of sensor.

Raise visibility sensor on hinge plate as follows:

a. Frombehind hinged side ofsensor, firmly grasp support pole with both hands and carefully

raise sensor on hinge into upright sensor.

b. Install locking pin into front of hinge plate. 

9 Calibrate visibility sensor in accordance with table 6.5.3.

Table 6.5.8. Transmitter Assembly Removal and Installation

Step Procedure

REMOVAL

Tools required:

 No. 1 Phillips screwdriver

 Small flat-tipped screwdriver

CAUTION

Damage to equipment may result if power is not removed from sensor prior to maintenance

activities. Ensure that circuit breaker supplying power to sensor is set to off (right) position.

1 Inside equipment cabinet, ensure that circuit breaker on visibility sensor circuit breaker module is set to off

(right) position.

2 Locate transmitter assembly. This is most easily accomplished by looking in assembly and locating clear

colored window (receiver is yellow).

3

With locking pin removed from hinge plate, sensor is not locked in upright position. Death or severe injury

may result if personnel are not kept out of travel path of sensor.

Lower visibility sensor on hinge plate as follows:

a. Remove locking pin from hinge plate.

b. From hinge side of sensor, firmly grasp support pole with both hands and carefully lower

sensor on hinge until lanyard catches and supports weight of sensor.

CAUTION

Do not strain crossarm wiring harness when removing or installing transmitter assembly.

Failure to comply may result in damage to hood or lens heater wiring.

4 Unlatch two fasteners and carefully remove transmitter assembly cap from back of transmitter assembly.

5 Disconnect molex-type cable connector.

6 Disconnect trigger signal coax wire from transmitter coax connector.
S100 ASOS Site Technical Manual

6-55

WARNING

Table 6.5.8. Transmitter Assembly Removal and Installation -CONT

Step Procedure

7 Using Phillips screwdriver, remove screw securing green ground wire to transmitter module. Disconnect

green wire.

8 Using small flat-tipped screwdriver, slide locking mechanism (plate at front of connector) downward to

unlock DB-9 connector. Disconnect DB-9 connector.

9 Grasp transmitter module and slide module out of assembly.

INSTALLATION

Tools required:

 Small flat-tipped screwdriver

 No. 1 Phillips screwdriver

CAUTION

Damage to equipment may result if power is not removed from sensor prior to maintenance

activities. Ensure that circuit breaker supplying power to sensor is set to off (right) position.

1 Inside equipment cabinet, ensure that circuit breaker on visibility sensor circuit breaker module is set to off

(right) position.

2

CAUTION

Do not strain crossarm wiring harness when removing or installing transmitter assembly.

Failure to comply may result in damage to hood or lens heater wiring.

Position the flat (on side of transmitter module) to right and slide transmitter module into assembly, seating

module as far forward as possible (at least 1 inch down from back of hood).

3 Connect DB-9 connector to transmitter module. Using small flat-tipped screwdriver, press up on locking

mechanism to lock DB-9 connector.

4 Connect green ground wire to transmitter module. Using Phillips screwdriver, install screw securing green

ground wire to transmitter module.

5 Connect trigger signal coax wire to receiver module.

6 Connect molex-type cable connector.

7 Slide transmitter assembly cap over back of transmitter assembly, being careful not to crush any wiring, and

latch two fasteners securing cap.

8

With locking pin removed from hinge plate, sensor is not locked in upright position. Death or severe injury

may result if personnel are not kept out of travel path of sensor.

Raise visibility sensor on hinge plate as follows:

a. Frombehind hinged side ofsensor,firmly grasp support pole with both hands and carefully

raise sensor on hinge into upright sensor.

b. Install locking pin into front of hinge plate.

9 Calibrate visibility sensor in accordance with table 6.5.3.
ASOS Site Technical Manual S100

6-56

WARNING

WARNING

WARNING

Table 6.5.9. Processor Board Removal and Installation

Step Procedure

REMOVAL

Tools required:

 Large flat-tipped screwdriver

 No. 1 Phillips screwdriver

Death or severe injury may result if power is not removed from sensor prior to maintenance activities. Ensure that

circuit breaker supplying power to sensor is set to off (right) position.

1 Inside equipment cabinet, ensure that circuit breaker on visibility sensor circuit breaker module is set to

off (right) position.

2 Using large flat-tipped screwdriver, open visibility sensor electronics enclosure access door.

3 Using Phillips screwdriver, remove screw securing processor board to standoff.

4 Carefully remove processor board by pulling it free from backplane connector XA1.

INSTALLATION

1

Tools required:

 No. 1 Phillips screwdriver

 Large flat-tipped screwdriver

Death or severe injury may result if power is not removed from sensor prior to maintenance activities.

Ensure that circuit breaker supplying power to sensor is set to off (right) position.

Inside DCP cabinet, ensure that circuit breaker on visibility sensor circuit breaker module is set to off

(right) position.

2 Install processor board into backplane connector XA1.

3 Using Phillips screwdriver, install screw securing processor board to standoff.

4 Calibrate visibility sensor in accordance with table 6.5.3.

Table 6.5.10. Day/Night Assembly Removal and Installation

Step Procedure

REMOVAL

Tools required:

 7/16-inch socket and ratchet

Death or severe injury may result if power is not removed from sensor prior to maintenance activities. Ensure that

circuit breaker supplying power to sensor is set to off (right) position.

1 Inside equipment cabinet, ensure that circuit breaker on visibility sensor circuit breaker module is set to off

(right) position.

2 Using 7/16-inch socket and ratchet, remove two bolts and flat washers securing flexible conduit connector

for day/night sensor to enclosure support pole.
S100 ASOS Site Technical Manual

6-57

WARNING

WARNING

Table 6.5.10. Day/Night Assembly Removal and Installation -CONT

Step Procedure

3 Disconnect day/night sensor cable connector A5W1-P1 from wiring harness located in support column

W2-P2, being careful not to drop internal harness inside column.

4 Loosen three bolts, flat washers (two each), lockwashers, and nuts securing day/night sensor to crossarm

support column. Remove sensor from column.

INSTALLATION

Tools required:

 7/16-inch socket and ratchet 

Death or severe injury may result if power is not removed from sensor prior to maintenance activities. Ensure that

circuit breaker supplying power to sensor is set to off (right) position.

1 Inside equipment cabinet, ensure that circuit breaker on visibility sensor circuit breaker module is set to off

(right) position.

2 Mount day/night sensor on crossarm support column (with sensor window facing same direction as receiver

hood). Tighten three bolts, flat washers (two each), lockwashers, and nuts securing sensor to column.

3 Connect day/night sensor cable connector A5W1-P1 to wiring harness located in support column W2-P2.

4 Using 7/16-inch socket and ratchet, install two bolts and flat washers securing flexible conduit connector to

support column.

5 Calibrate visibility sensor in accordance with table 6.5.3.

Table 6.5.11. Electronics Power Supply Removal and Installation

Step Procedure

REMOVAL

Tools required:

 Large flat-tipped screwdriver

 Flat-tipped screwdriver

 No. 0 Phillips screwdriver

 No. 1 Phillips screwdriver

Death or severe injury may result if power is not removed from sensor prior to maintenance activities. Ensure that

circuit breaker supplying power to sensor is set to off (right) position.

1 Inside equipment cabinet,set circuit breaker on visibility sensor power control module to off (right) position.

2 Using large flat-tipped screwdriver, open visibility sensor electronics enclosure access door.

3 Using flat-tipped screwdriver, tag and disconnect wires from power supply terminals.

4 Using No. 1 Phillips screwdriver, remove two screws, lockwashers, and flat washers securing power supply

angle mount to visibility sensor electronics enclosure. Carefully lift power supply with angle mount from

electronics enclosure.

5 Using No. 0 Phillips screwdriver, remove four screws, lockwashers, and flat washerssecuring power supply

to angle mount.
ASOS Site Technical Manual S100

6-58

WARNING

WARNING

Table 6.5.11. Electronics Power Supply Removal and Installation -CONT

Step Procedure

INSTALLATION

Tools required:

 Large flat-tipped screwdriver

 Flat-tipped screwdriver

 No. 0 Phillips screwdriver

 No. 1 Phillips screwdriver

Death or severe injury may result if power is not removed from sensor prior to maintenance activities. Ensure that

circuit breaker supplying power to sensor is set to off (right) position.

1 Inside equipment cabinet, ensure that circuit breaker on visibility sensor circuit breaker module is set to off

(right) position.

2 Using No. 0 Phillips screwdriver, install four flat washers, lockwashers, and screws securing power supply

to angle mount.

3 With terminals positioned downward, slide power supply with angle mount into position.

4 Using No. 1 Phillips screwdriver, install two lockwashers, flat washers, and screws securing power supply

angle mount to visibility sensor electronics enclosure.

5 Using flat-tipped screwdriver and tags as a guide, connect wires to power supply terminals.

6 Calibrate visibility sensor in accordance with table 6.5.3.

Table 6.5.12. Fiberoptic Module Removal and Installation

Step Procedure

REMOVAL

Tools required:

 Large flat-tipped screwdriver

 Medium flat-tipped screwdriver

 Small flat-tipped screwdriver

 No. 1 Phillips screwdriver (short)

Death or severe injury may result if power is not removed from sensor prior to maintenance activities. Ensure that

circuit breaker supplying power to sensor is set to off (right) position.

1 Inside equipment cabinet, set circuit breaker on visibility sensor power control module to off (right)

position.

2 Using large flat-tipped screwdriver, open visibility sensor electronics enclosure access door.

3 Using small flat-tipped screwdriver, loosen two retaining screws on DB-9 connector located on top of

fiberoptic module. Remove connector DB-9.

4 Remove six screws and lockwashers securing power input box access cover. 

5 Remove access cover from power input box.

6 Using clockwise (cw) rotation, remove two fiberoptic cables from underneath fiberoptic module. Install

protective plastic covers over fiberoptic connectors.
S100 ASOS Site Technical Manual

6-59

WARNING

WARNING

Table 6.5.12. Fiberoptic Module Removal and Installation -CONT

Step Procedure

7 At visibility electronics enclosure, use No. 1 Phillips screwdriver to remove four screws, lockwashers, and

flatwasherssecuring fiberopticmodulemounting plate to power input box. Remove fiberoptic mounting plate

and gasket.

8 Using small flat-tipped screwdriver, remove four screws, four lockwashers, and gasket securing fiberoptic

module to mounting plate.

INSTALLATION

Tools required:

 Large flat-tipped screwdriver

 Medium flat-tipped screwdriver

 Small flat-tipped screwdriver

 No. 1 Phillips screwdriver (short)

Death or severe injury may result if power is not removed from sensor prior to maintenance activities. Ensure that

circuit breaker supplying power to sensor is set to off (right) position.

1 Inside equipment cabinet, ensure that circuit breaker on visibility sensor circuit breaker module is set to off

(right) position.

2 Using small flat-tipped screwdriver, install four lockwashers, four screws, and gasket securing fiberoptic

module to mounting plate. Ensure that DB-9 connector on module is oriented toward RCVR stencil on plate.

3 With DB-9 connector toward the front, position fiberoptic module mounting plate and gasket on power input

box. Using No. 1 Phillips screwdriver, install four flat washers, lockwashers, and screws securing fiberoptic

module to power input box.

4 Remove protective plastic covers from fiberoptic connectors and connect transmit (TX) cable to rear

connector and receive (RX) cable to front connector of fiberoptic module.

5 Install power input box access cover and secure using six lockwashers and screws.

6 Installsignal cable on connector DB-9 on fiberoptic module and using small flat-tipped screwdriver, tighten

two retaining screws.

7 Using large flat-tipped screwdriver, close and secure visibility sensor electronics enclosure access door.

8 Inside equipment cabinet, set circuit breaker on visibility sensor circuit breaker module to on (left) position.

Table 6.5.13. Crossarm Assembly Removal and Installation

Step Procedure

REMOVAL

Tools required:

 Large flat-tipped screwdriver

 7/16-inch wrench

Death or severe injury may result if power is not removed from sensor prior to maintenance activities. Ensure that

circuit breaker supplying power to sensor is set to the off (right) position.
ASOS Site Technical Manual S100

6-60

WARNING

WARNING

Table 6.5.13. Crossarm Assembly Removal and Installation -CONT

Step Procedure

1 Inside equipment cabinet, ensure that circuit breaker on visibility sensor circuit breaker module is set to off

(right) position.

2 Using large flat-tipped screwdriver, open visibility sensor electronics enclosure access door.

3 In electronics enclosure, disconnect transmitter cable from connector J4 on motherboard.

4 In electronics enclosure, disconnect receiver cable from connector J5 on motherboard.

5 On power input box, using 7/16-inch wrench, disconnect crossarm green ground wire from stud E3.

6 Using 7/16-inch wrench, disconnect flexible conduit from electronics enclosure and support column.

7 Carefully feed the cables disconnected above out of conduit.

8

With locking pin removed from hinge plate, sensor is not locked in upright position. Death or severe injury

may result if personnel are not kept out of travel path of sensor.

Lower visibility sensor on hinge plate as follows:

a. Remove locking pin from hinge plate.

b. From hinge side of sensor, firmly grasp support pole with both hands and carefully lower

sensor on hinge until lanyard catches and supports weight of sensor.

9 Mark the orientation of receiver and transmitter heads on crossarm support column.

10 While supporting crossarm assembly and using 7/16-inch socket, remove four bolts, lockwashers, and flat

washerssecuring crossarm assembly to crossarm support. Remove crossarm assembly and carefully pull three

cables out of crossarm support.

INSTALLATION

Tools required:

 7/16-inch wrench

Death or severe injury may result if power is not removed from sensor prior to maintenance activities. Ensure that

breaker supplying power to sensor is to the off (right) position.

1 Inside equipment cabinet, ensure that circuit breaker on visibility sensor circuit breaker module is set to off

(right) position.

2

NOTE

Crossarm is mounted to top of crossarm support such that transmitter and receiver hoods

are to the right of electronics enclosure (on the same side of support pole as calibration

plate mounts).

At top of crossarm support, carefully feed wires coming out of base of crossarm assembly through interior

of crossarm support and out of access hole located on bottom of electronics enclosure.

3 Using the marks placed on crossarmsupport column during removal of crossarmassembly, position crossarm

assembly such that transmitter and receiver hoods are to the right of electronics enclosure. Ensure that

receiver assembly is pointed away from direct sunlight. In the northern hemisphere, receiver should point

north.

4 While supporting crossarm assembly and using 7/16-inch socket, install four bolts, flat washers, and

lockwashers securing crossarm assembly to crossarm support.
S100 ASOS Site Technical Manual

Table 6.5.13. Crossarm Assembly Removal and Installation -CONT

Step Procedure

6-61

WARNING

WARNING

5 At base of enclosure support, route receiver, transmitter, and ground cables through flexible conduit into

electronics enclosure.

6 Using cable marker as a guide, connect transmitter cable to connector J4 on motherboard.

7 Using cable marker as a guide, connect receiver cable to connector J5 on motherboard.

8 Using 7/16-inch wrench, connect green ground cable to stud E3 on power input box.

9 Using 7/16-inch wrench, install two bolts, lockwashers, and flat washers securing lower conduit to support

pole and electronics enclosure. Ensure that EMI gasket is in place.

10 Verify that TX and RX canisters are fully seated in hood by measuring the distance from the back of the hood

down to the end of TX or RX canister body. The distance should be at least 1.0 inch. If not, slide canister out

1 inch and then push canister back in until fully seated.

11

With locking pin removed from hinge plate, sensor is not locked in upright position. Death or severe injury

may result if personnel are not kept out of travel path of sensor.

Raise visibility sensor on hinge plate as follows:

a. Frombehind hinged side ofsensor,firmly grasp support pole with both hands and carefully

raise sensor on hinge into upright sensor.

b. Install locking pin into front of hinge plate.

12 Calibrate visibility sensor in accordance with table 6.5.3.

Table 6.5.14. Electronics Enclosure Removal and Installation

Step Procedure

REMOVAL

Tools required:

 Large flat-tipped screwdriver

 7/16-inch wrench

 No. 1 Phillips screwdriver

 9/16-inch wrench

 Large pliers

 1⁄2-inch socket with ratchet

Death or severe injury may result if power is not removed from sensor prior to maintenance activities. Ensure that

circuit breaker supplying power to sensor is set to the off (right) position.

1 Inside equipment cabinet, ensure that circuit breaker on visibility sensor circuit breaker module is set to off

(right) position.

2 Using large flat-tipped screwdriver, open visibility sensor electronics enclosure access door.

3 In electronics enclosure, disconnect receiver cable from connector J5 on motherboard.

4 In electronics enclosure, disconnect day/night sensor cable from connector J6 on motherboard.

5 In electronics enclosure, disconnect transmitter cable from connector J4 on motherboard.

6 Using 7/16-inch wrench, disconnect green ground wire from stud E3 located on top of power input box.
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WARNING

Table 6.5.14. Electronics Enclosure Removal and Installation -CONT

Step Procedure

7 Using Phillips screwdriver, remove six screws securing access cover to power input box and remove access

cover.

8 Disconnect the following ac power wires from terminal board TB1:

Wire Connection

Black (ac hot) TB1-1

White (ac neut) TB1-2

Green (ground) TB1-3

9 Disconnect transmit (TX) fiberoptic cable from TX connector on fiberoptic module.

10 Disconnect receive (RX) fiberoptic cable from RX connector on fiberoptic module.

11 Using 9/16-inch wrench, remove pedestal ground wire from ground stud located at bottom of electronics

enclosure.

12 Using large pair of pliers, remove flexible conduit from base of electronics enclosure. Carefully pull wires

out of enclosure.

13 Install access cover on power input box. Using Phillipsscrewdriver, installsix screws securing access cover.

14 Using 1⁄2-inch socket and ratchet, loosen but do not remove four bolts securing electronics enclosure to

support.

15 While supporting electronics enclosure, remove top two mounting bolts, four flat washers, two lockwashers,

and two nuts and remove electronics enclosure from support.

INSTALLATION

Tools required:

 Large flat-tipped screwdriver

 7/16-inch wrench

 No. 1 Phillips screwdriver

 9/16-inch wrench

 1⁄2-inch socket with ratchet

Death or severe injury may result if power is not removed from sensor prior to maintenance activities. Ensure that

circuit breaker supplying power to sensor is set to the off (right) position.

1 Inside equipment cabinet, ensure that circuit breaker on visibility sensor circuit breaker module is set to off

(right) position.

NOTE

Do not tighten bolts in next step. Electronics enclosures box flanges must be allowed to

slip onto bolts.

2 Ensure that bolt, two flat washers, lockwasher, and nut are installed in holes on lower bracket of enclosure

support.

3 Position electronics enclosure such that lower mounting flanges slip onto bolts and enclosure is resting on

bolts.

4 Position electronics enclosure such that upper mounting flanges align with holes in upper mounting bracket.

5 Install mounting bolt, two flat washers, lockwasher, and nut in each flange. Using 1⁄2-inch socket and ratchet,

tighten four mounting bolts.

6 Using large flat-tipped screwdriver, open visibility electronics enclosure access door.

7 Remove protective plastic covers from fiberoptic cables. Connect transmit (TX) cable to rear connector of

fiberoptic module and receive (RX) cable to front connector.
S100 ASOS Site Technical Manual

Table 6.5.14. Electronics Enclosure Removal and Installation -CONT

Step Procedure

6-63

8 Using Phillips screwdriver, remove six screws securing access cover to power input box and remove access

cover.

9 Route ac power wires into power input box.

10 Using flat-tipped screwdriver, connect the following ac power wires to terminal board TB1:

Wire Connection

Black (ac hot) TB1-1

White (ac neut) TB1-2

Green (ground) TB1-3

on the 2-filter configuration, ensure that the following jumpers are also in place:

From To

TB1-1 (ac hot) TB1-4

TB1-2 (ac neut) TB1-5

11 Install access cover on power input box. Using Phillipsscrewdriver, installsix screws securing access cover.

12 Using 9/16-inch wrench, connect pedestal ground wire to ground stud located at bottom of electronics

enclosure.

13 Feed wires coming out of conduit through large access hole in bottom of electronics enclosure. Position

conduit in hole and install large nut securing conduit to electronics enclosure.

14 Using cable marker as a guide, in electronics enclosure, connect receiver cable to connector J5 on

motherboard.

15 Using cable marker as a guide, in electronics enclosure, connect transmitter cable to connector J4 on

motherboard.

16 Using cable marker as a guide, in electronics enclosure, connect day/night sensor cable to connector J6 on

motherboard.

17 Using 7/16-inch wrench, connect green ground wire to stud E3 located on top of power input box.

18 Inside equipment cabinet, set circuit breaker on visibility sensor circuit breaker module to on (left) position.

19 Calibrate visibility sensor in accordance with table 6.5.3.
ASOS Site Technical Manual S100

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WARNING

WARNING

Table 6.5.15. Regulator Board Removal and Installation

Step Procedure

REMOVAL

Tools required:

 Large flat-tipped screwdriver

 No. 1 Phillips screwdriver

Death or severe injury may result if power is not removed from sensor prior to maintenance activities. Ensure that

circuit breaker supplying power to sensor is set to the off (right) position.

1 Inside equipment cabinet, ensure that circuit breaker on visibility sensor circuit breaker module is set to off

(right) position.

2 Using large flat-tipped screwdriver, open visibility sensor electronics enclosure access door.

3 At regulator board, tag and disconnect wires from terminal board TB1 and TB2.

4 Using Phillips screwdriver, remove fours screws, flat washers, and lockwashers securing regulator board to

heater power supply board. Remove regulator board.

INSTALLATION

Tools required:

 No. 1 Phillips screwdriver

Death or severe injury may result if power is not removed from sensor prior to maintenance activities. Ensure that

circuit breaker supplying power to sensor is set to the off (right) position.

1 Inside equipment cabinet, ensure that circuit breaker on visibility sensor circuit breaker module is set to off

(right) position.

2 Using Phillips screwdriver, install four screws, lockwashers, and flat washers securing regulator board to

heater power supply board.

3

NOTE

The red wire terminals are marked with red paint.

Using tags as a guide, connect wires to terminal board TB1 and TB2.

4 Calibrate visibility sensor in accordance with table 6.5.3.
S100 ASOS Site Technical Manual

7-1

Figure 7.1.1. Present Weather Sensor

CHAPTER 7

PRESENT WEATHER SENSOR

SECTION I. DESCRIPTION AND LEADING PARTICULARS

7.1.1 INTRODUCTION

The ASOS present weather sensor is a fully automated sensor that monitors and reports the current

precipitation state. The present weather sensor uses weather-particle-induced optical scintillation of an

infrared emitter diode (IRED) system to identify precipitation state and type (rain, snow, drizzle, etc) and

measure precipitation intensity. The ASOS present weather sensor reports three precipitation conditions to

the ACU: rain, snow, and precipitation undetermined. The present weather sensor also reports the intensity

of the precipitation as light (-), moderate, or heavy (+). The omission of the plus or minus indication

identifies the current precipitations as moderate. Refer to the ASOS Ready Reference Guide for present

weather code designators.

7.1.2 PHYSICAL DESCRIPTION

7.1.2.1 General. The present weather

sensor (Figure 7.1.1) contains two major

assemblies: a U-shaped frame assembly

and a main electrical enclosure assembly.

The transmitter and receiver sensor heads

are mounted at opposite ends of the frame

assembly, 1 meter apart. The main

electrical enclosure assembly houses all

associated electronics components

including the power supplies. A cable

assembly is routed through the U-shaped

frame assembly and connects the main

electrical enclosure to the transmitter and

receiver heads. The cable assembly has

two connectors:J4 and J5. ConnectorJ4 is

connected to the receiver and connectorJ5

is connected to the transmitter. A hinge

plate assembly is used to attach the sensor

to the mounting support and enables the

sensor to be lowered to a horizontal

position for easier maintenance of the

frame assembly.

7.1.2.2 Frame Assembly. The frame

assembly holds the transmitter and

receiver heads, which contain the optical

subassembliesthat determine the different

types of precipitation. An IRED with a die size 0.4 mm square is used as a source of infrared radiation. The

transmitter and receiver heads use 175 mm/ f3.5 cemented achromatic lenses. A 1 mm horizontally-oriented

slot and an infrared filter (No. 87C) are located behind the receiver lens. A positive-intrinsic-negative (PIN)

photodiode with a 2.75mmsquare area providesinfrared detection. The frame assembly isreplaced as a field

replaceable unit (FRU).
ASOS Site Technical Manual S100

7-2

Figure 7.1.2. Present Weather Sensor

7.1.2.3 Main Electrical Enclosure Assembly. The main electrical enclosure assembly (Figure 7.1.2)

contains the subassemblies that generate the transmit frequency supplied to the transmitter head and the

measurement and processing circuits that process the measurement data received from the receiver head. A

fiberoptic module supplies an RS-232 communicationslink between the present weathersensor and the data

collection package (DCP). The main electrical enclosure assembly also contains the system power supplies

and temperature control circuitry. The signal processing circuitry consists of five printed circuit boards

housed in a card rack. The board complement consists of a transmitter board, two signal processor boards

(SP1 and SP2), a receiver AGC board, and a microprocessor board.

7.1.3 PRESENT WEATHER SENSOR CONFIGURATIONS

There is currently only one configuration of present weather sensor fielded. It is described in Section 7.1.2.
S100 ASOS Site Technical Manual

7-3

WARNING

SECTION II. INSTALLATION

7.2.1 INTRODUCTION

The ASOS present weather sensor, commonly referred to as the LEDWI or Light Emitting Diode Weather

Identifier, has a lightweight, modular design which allows for easy installation. The sensor is normally

shipped partially assembled in three separate boxes. The boxes contain the sensor frame, main electronics

enclosure, andmounting column.Thissection providesinstructionsforinstalling all ofthese present weather

sensor assemblies. The procedures assume that the sensor pad support pedestal has been previously installed.

7.2.2 ASSEMBLY

The main electrical enclosure, frame assembly, and mounting column are preassembled units and do not

require any additional assembly prior to installation. The present weather sensor is mounted to the support

column using a hinge plate assembly. The hinge plate assembly provides easy access to the present weather

sensor receiver and transmitter assemblies by permitting the present weather sensor to be lowered to a

horizontal position. 

7.2.3 INSTALLING THE PRESENT WEATHER SENSOR

The present weather sensor is installed on the sensor pad support pedestal shown in Section 7.2.1 using the

procedures in table 7.2.1.

Table 7.2.1. Installing Present Weather Sensor

 Step Procedure

Tools required:

 15/16-inch wrench

 3/4-inch wrench

 9/16-inch wrench

 Large flat-tipped screwdriver

 No. 1 Phillips screwdriver

Death or severe injury may result if power is not removed from sensor prior to performing

installation procedures. Ensure that heater and primary power circuit breakers supplying

power to sensor are set to off (right) positions.

1 Inside equipment cabinet, ensure that circuit breakers on present weather sensor circuit breaker module are

set to off (right) position.

2 Open hinge plate and position on mounting pedestal. For most sites, orient hinge plate so that sensor will tilt

backward away from walkway (hinge is opposite walkway).

NOTE

Lanyard must be oriented so that when hinge plate is opened, lanyard falls in hinge plate

cutouts.

3 Using one 5/8-inch bolt, one nut, one lockwasher, and three flat washers, secure front of hinge plate to

pedestal, attaching one end of cable lanyard. Bolt is inserted from top down through pedestal, with one flat

washer under bolt head. On the underside of pedestal, lanyard opening must be secured between two flat

washers, with lockwasher and nut on outside. Do not fully tighten hardware.
ASOS Site Technical Manual S100

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WARNING

Table 7.2.1. Installing Present Weather Sensor - CONT 

 Step Procedure

4 Install three more sets of mounting hardware (bolt, two flat washers, lockwasher, and nut) on rear, left, and

right mountings of hinge plate. Tighten all four sets of mounting hardware. 

5 Install washer on each bolt and slide four mounting bolts up from bottom of the top hinge plate. Temporarily

install nut on each bolt and close hinge plate. Install hinge plate locking pin to hold hinge plate in closed

position.

6 Remove nutsfrom four mounting bolts. Position enclosure support on top of four mounting bolts, taking care

to properly position enclosure support so that it faces sensor pad walkway.

7 Using two flat washers, one lockwasher, and one nut, secure front of hinge plate to sensor support pole,

attaching other end of cable lanyard. Lanyard opening must be secured between two flat washers, with

lockwasher and nut on outside. Do not fully tighten hardware.

NOTE

Lanyard must be oriented so that when hinge plate is opened, lanyard

falls in hinge plate cutouts.

8 Install remaining sets of mounting hardware (flat washers, lockwasher, and nut) on rear, left, and right of

sensor support pole. Tighten all four sets of mounting hardware.

With locking pin removed from hinge plate,sensor is not firmly locked in upright

position. Death or severe injury may result if personnel are not kept out of travel

path of sensor.

9 Lower sensor support pole on hinge plate as follows:

a. Remove locking pin from front part of hinge plate.

b. From rear ofsensor, firmly grasp support pole with both hands and carefully lowersupport

pole on hinge until lanyard catches and supports weight of support pole.

10 Tighten bolts securing sensor mounting post to hinge plate.

11 Referring to Section 7.2.2 and using 3/4-inch wrench, install but do not tighten three 1⁄2-inch mounting bolts

and three rubber strips using six flat washers, nine neoprene washers, nine lockwashers, and three nuts to

secure frame mounting plate to top of mounting column. Be sure to orient two flanges so that two 10-32

mounting holes for short grounding strap are aligned.

12 Tighten three mounting bolts quarter turn past finger tight (enough to slightly compress split lockwashers,

but not enough to compress neoprene washers to less than 75% of original thickness).

13 Install 10-32 X 0.5 screw, lockwasher, and flat washer securing ground strap to flanges on mounting plate

and mounting column.

14 Feed frame assembly cables from bottom of frame assembly down into mounting column and gently lower

the frame assembly on to mounting column (Figure 7.2.1).

15 At mounting column access hole (below mount for main electrical enclosure), pull free ends of two frame

assembly cables and frame assembly ground wire out of mounting column.

16 Position frame so that sensor head piece with horizontal slotted mask is facing north (±10°). Raise frame

assembly up so thatstem of frame is approximately 1/4 inch above bottom of mounting plate (not protruding

out of mounting base).

17 Tighten four hex capscrewsin collar of mounting base to secure frame. Do not overtighten screws; otherwise,

lower end of mounting frame will become distorted and difficult to remove from mounting base.
S100 ASOS Site Technical Manual

Table 7.2.1. Installing Present Weather Sensor - CONT 

 Step Procedure

7-5

WARNING

18 Position main electrical enclosure on channel of mounting column. Using 9/16-inch wrench, install 3/8-inch

bolt, two flat washers, lockwasher, and nut securing enclosure.

With locking pin removed fromhinge plate,sensor is not firmly locked in upright

position. Death or severe injury may result if personnel are not kept out of travel

path of sensor.

19 Raise present weather sensor on hinge plate as follows:

a. From rear of sensor, firmly grasp support pole with both hands and carefully raise sensor

on hinge into upright position.

b. Install locking pin into front of hinge plate.

20 Connect frame cable connectors P4 and P5 to connectors J4 and J5 on main electrical enclosure.

21 Connect frame assembly (long white) ground wire and site ground wire to ground wire stud located on bottom

of main electrical enclosure.

22 Using large flat-tipped screwdriver, open main electrical enclosure access door.

23 Using No. 1 Phillips screwdriver, remove four screws and lockwashers securing access cover to ac junction

box.

24 Remove access cover from ac junction box.

25 Connect ac power wiring to terminal board in ac junction box according to the following connection chart:

Wire color Terminal Function

Black TB1-1 120 vac (electronics)

White TB1-2 Neutral (electronics)

Green TB1-3 Chassis ground

Red TB1-4 120 vac (heater)

Yellow TB1-5 Neutral (heaters)

26 Remove protective plastic covers from fiberoptic cable connectors on underside of fiberoptic module.

27 Connect RX connector on fiberoptic cable to RX connector on fiberoptic module (RX connector on module

is nearest DB-9 electrical connector). Connect TX connector on fiberoptic cable to remaining connector on

fiberoptic module.

28 Using large adjustable wrench and hardware supplied, connect flexible conduit to main electrical enclosure.

29 Using No. 1 Phillips screwdriver, install four screws and lockwashers securing access cover to ac junction

box.

30 Calibrate present weather sensor in accordance with table 7.5.2.
ASOS Site Technical Manual S100

7-6

Figure 7.2.1. Present Weather Sensor Mounting Diagram

Figure 7.2.2. Frame Assembly Mounting Plate Hardware
S100 ASOS Site Technical Manual

7-7/ (7-8 blank)

SECTION III. OPERATION

7.3.1 INTRODUCTION

The present weathersensor is designed to operate continuously under complete control of the data collection

package (DCP).The present weathersensormust be calibrated every 90 days. During this procedure, the low,

high, and particle channels are adjusted and the carrier channel is monitored. Information to properly adjust

the associated controls is contained within the calibration procedure. The sensor's self-test diagnostic data

are displayed on the present weather maintenance page. Information defining the purpose of each field on

that display is provided in Chapter 1, Section III.
S100 ASOS Site Technical Manual

7-9

Figure 7.4.1. Precipitation Effects on Received Signal

SECTION IV. THEORY OF OPERATION

7.4.1 INTRODUCTION

This section describes how the ASOS present weather sensor functions to detect and identify precipitation.

The operating theory is presented in two levels of detail. The first level introducesthe principles of operation

and describes sensor operation on a simplified block diagram level. The second level describes the sensor's

individual functional areas in a detailed block diagram that allows isolation of faulty field replaceable units

(FRU's).

7.4.2 SIMPLIFIED BLOCK DIAGRAM DESCRIPTION

The following paragraphs describe the basic operation of the present weather sensor, and the physical

principles upon which the sensoris designed. A simplified block diagramofthe sensor's operation introduces

the basic sensor components and describes their functional relationships.

7.4.2.1 Principles of Operation. The ASOS present weather sensor detects the presence of precipitation

by using an infrared light beam. A simplified illustration of the sensing technique is provided in

Section 7.4.1. The infrared light is pulsed by the transmitter at a high rate (50 kHz) and passed through a

volume of air where it is then detected by the receiver. The receiver uses a horizontal slit aperture, which

maximizesitssensitivity to vertically falling precipitants.When there is no precipitation, the light pulses pass

directly through the air. Thus, the frequency of the light pulses at the receiver is the same as the frequency

of the light pulses transmitted. Also, with no precipitation, the power level received by the receiver is at a

maximum. If there is any precipitation such as rain or snow in the volume of air, some of the light pulses are

blocked by the precipitation particles. The result is a modulation of the light signal, which changes the

frequency composition ofthe signal detected at the receiver. The physical properties ofthe precipitation such

as the particle size, number, and falling velocity directly affect the frequency composition of the received

signal. In actuality, the physical properties of the light pulses and the precipitation particles cause more of

a partial shadowing than actual blocking of the light pulses. The effects, however, are still the same. Thus,

by measuring the frequency components and power levels at the receiver, the presence and type of

precipitation can be determined.

7.4.2.2 Simplified Block Diagram Description. A simplified block diagram of the present weather sensor

is provided in Section 7.4.2. The transmitter modulator in the main electrical enclosure assembly generates

a 50 kHz transmit signal, which is output to the transmitter head. The infrared transmitter generates light

pulses that are formed into a semicoherent beam by optics in the transmitter head. The transmitted light

signal passes through a sample volume of air where it is detected by the receiver head. Optics in the receiver

head focus incoming light onto an infrared detector where it is converted back into an electrical signal. The

received signal isthen amplified and output to an automatic gain control (AGC). The AGC compensates the
ASOS Site Technical Manual S100

7-10

received signal to overcome effects of temperature changes, component aging, dusty optics, and haze or fog.

AGCoutput is demodulated and sent to the signal processors. Signal processorsfilter the demodulated signal

to determine itsfrequency component content. There are actually four channels ofsignal processing: the low

band (25 to 250 Hz) channel, the high band (1 to 4 kHz) channel, the particle count channel, and the carrier

channel. The use of these channels is summarized as follows:

a. The particle count channel and the high and low band channels are used for precipitation

state (yes/no) identification. 

b. The ratio of high band to low band signal strength is used for precipitation type (snow/rain)

identification.

c. The strength of the high band signal is used to determine intensity of rain (R-, R, or R+). 

d. The strength of the low band signal is used to determine intensity of snow (S-, S, or S+).

e. The carrier channel is tuned to the carrier signal to monitor the received signal strength and

detect accidental beam blocking or light source failure. 

The outputs of the signal processing channels are applied to the microprocessor control logic where they are

converted to digital formand processed. The microprocessorsamples channel data once every 5 seconds and

continually runs a present weather algorithm(once per minute). As part of the algorithm, the microprocessor

maintains an adaptive baseline of 1-minute averages of the three data channels (low band, high band, and

particle count).Because ofthis adaptive baselining technique, the sensorrequiresseveralminutesto stabilize

(establish its baseline) after power up or calibration adjustments. When polled by the DCP, the

microprocessor outputs its present weather data in RS-232 format to the fiberoptic module. The fiberoptic

module relays all of the data messages between the present weather sensor and the DCP using a fiberoptic

data link.

7.4.3 DETAILED BLOCK DIAGRAM DESCRIPTION

7.4.3.1 General. The present weather sensor (Figure 7.4.3) detects current precipitation conditions via an

infrared light beam. The infrared beamistransmitted through a sample volume of air, detected by an infrared

receiver, and then analyzed for frequency components that indicate precipitation. The results of these

processes are then transferred in digital format to the DCP.

7.4.3.2 Transmitter Board (2MT2A1A1A1). The transmitter board in the card rack assembly of the main

electrical enclosure assembly generates the carrier frequency signal for the transmitter head. A voltage

controlled oscillator (VCO) generates a 50 kHz signal that is amplified and output to trigger the transmitter's

infrared light emitting diode (LED).

7.4.3.3 Transmitter Head (Part of Frame Assembly 2MT2A2). The transmitter head houses the emitter

board and transmitter optics. The carrier frequency modulation signal input fromthe transmitter board in the

main electrical enclosure assembly card rack assembly is applied to an infrared LED.The LEDemitsinfrared

light pulses at the carrier frequency rate (50 kHz). The light pulses are then shaped into a semicoherent light

beam by the transmitter optics and passed through a sample volume of air.

7.4.3.4 Receiver Head (Part of Frame Assembly 2MT2A2). The receiver head housesthe receiver optics,

infrared detector, and signal preamplifier. The receiver optics focus the incoming infrared light signal onto

a photodiode. This photodiode produces a low level electrical signal that contains all of the characteristics

of the precipitation effects on the light beam. The low level electrical signal is then amplified and output to

the receiver AGC board in the main electrical enclosure assembly card rack assembly. 
S100 ASOS Site Technical Manual

7-11

Figure 7.4.2. Present Weather Sensor Simplified Block Diagram

7.4.3.5 Receiver AGC Board (2MT2A1A1A8). The receiver AGC board is located in the card rack

assembly in the main electrical enclosure assembly. The receiver AGC board adjusts the signal level input

from the receiver head and demodulates the received signal. The receiver AGC board uses a variable

feedback amplifier to automatically adjust the signal level to an optimum level for output to the signal

processor boards. This AGC amplifier circuit senses the amplitude of the incoming signal and adjusts the

feedback (gain) of the amplifier to generate a normalized signal for further processing. The signal is then

demodulated to separate the carrier signal component from the modulation signal component. These two

signals are then output to the signal processor boards for further processing.

7.4.3.6 Signal Processor Board No. 1 (2MT2A1A1A7). Signal processor board No. 1 contains the signal

processing channelsforthe carriersignal and the low band (25 to 250 Hz) frequency components.The carrier

channel is filter tuned to the carrier frequency and converts the carrier frequency component to a dc voltage

signal for output to the microprocessor board. The carrier channel is used by the sensor to verify the presence

of the carrier signal. If there is no signal output from this channel, then the sensor reports a failure due to

optical path blockage or a transmitter/receiver failure. The low band frequency channel is tuned to the

frequency band from 25 to 250 Hz. This channel converts any signal components in the low band range into

a dc voltage signal that is output to the microprocessor board. The sensor uses this channel, in conjunction
ASOS Site Technical Manual S100

7-12

with the particle count and high band channels, to determine the state (yes/no) of precipitation. The ratio of

this channel with respect to the high band channel is used to determine the type (rain/snow) of precipitation.

Finally, the strength of the low band output signal is used to determine intensity of snow (S-, S, or S+).

7.4.3.7 Signal Processor Board No. 2 (2MT2A1A1A6). Signal processor board No. 2 contains the signal

processing channels for the particle count signal and the high band (1 to 4 kHz) frequency components. The

output of the particle count channel is used to detect the start (yes/no) of a precipitation event. The high band

frequency channel is tuned to the frequency band from 1 to 4 kHz. This channel converts any signal

components in the high band range into a dc voltage signal that is output to the microprocessor board. The

sensor usesthis channel, in conjunction with the particle count and low band channels, to determine the state

(yes/no) of precipitation. The ratio of this channel to the low band channel is used to determine the type

(rain/snow) of precipitation. Finally, the strength ofthe high band outputsignal is used to determine intensity

of rain (R-, R, or R+).

7.4.3.8 MicroprocessorBoard (2MT2A1A1A3).Themicroprocessor board contains all of the control logic

within the present weather sensor. The microprocessor control logic operates under sensor software control

to sample the outputs of each of the signal processor channels and determine the presence and type of

precipitation. The sampling of the signal processor channels is performed one channel at a time. The signal

outputs of each of the channels are selected through an analog multiplexer for application to an

analog-to-digital (A/D) converter. The A/D converter converts the analog voltage signal input into a digital

output, which is then read and processed by the microprocessor control logic. This same circuit is used to

monitor the power supply voltages used by the sensor electronics assemblies.

7.4.3.9 Fiberoptic Module (2MT2A1A2A1). The fiberoptic module provides a two-way serial data

communication link between the present weather sensor and the DCP. The module converts the optical data

from the DCP to RS-232 serial data for the sensor's microprocessor control logic. The module also converts

RS-232 data from the sensor's microprocessor control logic to optical data to be sent to the DCP. The

fiberoptic link with the DCP consists of separate transmit and receive fiberoptic cables.

7.4.3.10 Power Distribution. The present weather sensor has two ac power inputs from the DCP

(Figure 7.4.4). One ac power input is the power source for the sensor's bar heater assembly. The second ac

power input is the power source for the sensor's digital and analog electronics. The heater power input from

the DCP is controlled by two thermostats. The first (failsafe) thermostat closes at 80 degrees F to enable the

heater circuit. The second thermostat then turns on the heater when enclosure temperature drops to 40

degrees and turns the heater off when the enclosure temperature rises to 60 degrees. The failsafe thermostat

then opens to disable the heater circuit when the temperature of the enclosure rises to 110 degrees. Heater

power supply PS1 generates +24 vdc heater power, which isrouted to the card rack assembly. From the card

rack assembly, the +24 vdc power is routed as +24V CONTINUOUS power to the lens heaters of both the

transmitter and the receiver. The heater power supply also contains a relay that is controlled by

Microprocessor Board A1A3. This relay switches +24 vdc power and routes it back to the card rack

assembly, where it is applied as +24V HTR SW to the hood heaters on both the transmitter and receiver

heads. This allows the microprocessor to control the hood heaters on the transmitter and receiver heads.

Analog power supply PS2 provides +12 vdc and -12 vdc for Signal Processor Board No. 1 A1A7, Signal

Processor Board No. 2 A1A6, Receiver AGC Board A1A8, and the receiver head. Digital power supply PS3

provides +12 vdc,-12 vdc, and +5 vdc powerfor TransmitterBoard A1A1 and MicroprocessorBoard A1A3.
S100 ASOS Site Technical Manual

Figure 7.4.3. Present Weather Sensor Detailed

Block Diagram (Sheet 1 of 2)

7-13/ (7-14 blank)
S100 ASOS Site Technical Manual

Figure 7.4.3. Present Weather Sensor Detailed

Block Diagram (Sheet 2)

7-15/ (7-16 blank)
S100 ASOS Site Technical Manual

Figure 7.4.4. Present Weather Sensor AC/DC

Power Distribution (Sheet 1 of 2)

7-17/ (7-18 blank)
S100 ASOS Site Technical Manual

Figure 7.4.4. Present Weather Sensor AC/DC

Power Distribution (Sheet 2)

7-19/ (7-20 blank)
S100 ASOS Site Technical Manual

7-21

7.4.4 POLL/FRAME FORMATS

The present weather sensor responds to three different types of single character ASCII polls issued by the

DCP orthe technician during calibration. The poll charactertransmitted to the present weathersensorshould

be a single character only (transmitted at 1200 baud, 1 start bit, 8 data bits, no parity, and 1 stop bit), not

followed by any other characters or control codes. The poll codes and description are listed below:

 DCP Request Description

A Send routine data

B Send simulation data

C Send data and raw data

The type A poll (short message format) is used for normal operation. This poll is issued once every 60

seconds by the DCP, and in response, the present weathersensortransmits a 17-characterstring that contains

present weather, precipitation amount, sensor status, and frame checksum information. The type B poll

(simulation data) is used for field test and diagnostic purposes during calibration. This mode outputs a fixed

(never changing) string of 17 characters in the same format as above, but with fixed dummy data. The type

C poll is a long (45 characters) output format which includes present weather, precipitation intensity, and

full raw data along with status and checksum data. This poll is used for performing normal polls along with

acquiring raw sensor data for evaluation or diagnostic purposes. Each of the three poll types are discussed

in more detail in the sections below. The various fields, portions of which are common to all formats, are

described in paragraph 7.4.4.4. Paragraph 7.4.4.5 details the status code field of the type C poll.

7.4.4.1 Type A - Routine Data Poll. This paragraph explains the format of the present weather sensor data

frame that istransmitted in response to the type A poll. The present weathersensor ASCII routine data string

is 17 bytes long and is formatted as follows:

Format [STX] W w w P p p p p S s s s s c c [CR]

Byte 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17

Byte Description Value

1 Start of transmission [STX]

2 Weather type marker W

3-4 Present weather field ww

5 Precipitation amount marker P

6-9 Precipitation amount field pppp

10 Status field marker S

11-14 Status field ssss

15-16 Checksum field cc

17 Carriage return [CR]

7.4.4.2 Type B - Simulated Data Poll. This paragraph explains the format of the present weather sensor

data frame that is transmitted in response to the type B poll. The present weather sensor ASCII diagnostic

data string is 17 bytes long and is formatted as follows:

Format [STX] W N P P 1 2 3 4 S 5 6 7 8 9 0 [CR]

Byte 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
ASOS Site Technical Manual S100

7-22

Byte Description Value

1 Start of transmission [STX]

2 Weather type marker W

3-4 Present weather (dummy data) NP

5 Precipitation amount marker P

6-9 Precipitation amount (dummy data) 1234

10 Status field marker S

11-14 Status field (dummy data) 5678

15-16 Checksum field (dummy data) 90

17 Carriage return [CR]

7.4.4.3 Type C - Full Raw Data Poll. This paragraph explainsthe format of the present weathersensor data

frame that istransmitted in response to the type C poll. The present weathersensor ASCIIfullraw data string

is 45 bytes long and is formatted as follows:

Format [STX] W w w P p p p p S s s s s c c X

Byte 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17

Format n n n z z z L n n n b b b K n n n

Byte 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34

Format b b b H n n n b b b [CR]

Byte 35 36 37 38 39 40 41 42 43 44 45

Byte Description Value

1 Start of transmission [STX]

2 Weather type marker W

3-4 Present weather field ww

5 Precipitation amount marker P

6-9 Precipitation amount field pppp

10 Status field marker S

11-14 Status field ssss

15-16 Checksum field cc

17 Carrier raw data field marker X

18-20 Carrier 1 min average raw data nnn

21-23 Low/particle/high lock indicator zzz

24 Low raw data field marker L

25-27 Low 1 min average raw data nnn

28-30 Low baseline bbb

31 Particle raw data field marker K

32-34 Particle 1 min average raw data nnn

35-37 Particle baseline bbb

38 High raw data field marker H

39-41 High 1 min average raw data nnn

42-44 High baseline bbb

45 Carriage return [CR]
S100 ASOS Site Technical Manual

7-23

7.4.4.4 Field Description. This paragraph describes the format of the various fixed fields as they are used

in the three formats above.

a. The capital letters W, P, S, X, L, K, and H above serve as place markers for the weather,

precipitation,status, carrier, low, particle, and high data fields to follow. These markers are

fixed in position and coding. They are included within the format to simplify manual

interpretation of the sensor output.

b. w w is a 2-byte field indicating present weather. The weather code contained in this field

will be one of the following:

L- Light drizzle S- Light snow

L_ Moderate drizzle S_ Moderate snow

R- Light rain S+ Heavy snow

R_ Moderate rain P? Unknown precipitation

R+ Heavy rain ER Error condition

__ No precipitation P_ Mixed precipitation

-- Startup code

The _ (underline) character represents an ASCII space character and is shown only for

readability. The -- code will be output in this and other data fields during approximately the

first 60 seconds after reset or power up of the sensor.

c. p p p p is a 4-byte field indicating the precipitation amount of equivalent water content for

snow. Zero isformatted asfour zeros(0000). The number is a floating point format, varying

from0.01 to 9999. Units aremillimeters-per-hourrain rate, averaged over a 1-minute period.

d. s s s s is a four-character field containing ASCII encoded hex value reserved for error and

status codes. Each character represents a 4-bit field of binary information. The 4-bit field

contains status information of the FRU’s. Paragraph 7.4.4.5 contains detailed breakdown.

e. c c is a 2-byte field containing ASCII encoded 8 bit hex value for a modulo 256 checksum

of the data between but not including [STX] and c c.

f. n n n is a 3-byte ASCII numeric field indicating the corresponding 1-minute averaged raw

data in tens of millivolts. Leading/unused positions are filled with zeros. Valid values are

-99 to 999. Overflows and underflows are represented as 999 and -99, respectively.

g. z z z is a three-character ASCII numeric field indicating the lock on (0) or off (1) status of

the low, particle counting, and high channels, respectively.

h. b b b is a 3-byte ASCII numeric field indicating the respective data channel adaptive

baseline value in tens of millivolts for the current algorithm (1 minute) processing cycle.

Leading/unused positions are filled with zeros. Valid values are -99 to 999.

7.4.4.5 Status Field Encoding. The status field, denoted by s s s s (4 bytes) in the present weather sensor

data output format, is a 4-byte field of sensor status bytes. Each status byte is represented in the data field

as an ASCII-encoded hex-formatted nibble (O-F). Each of the 4 bits, represented by each of the 4 nibbles,

represents the status of a particular field replaceable unit (FRU) or of a particular system condition. Each

status byte character must be converted to binary in orderto identify which bits are set or cleared. Table 7.4.1

shows what the corresponding binary nibble is for each of the 16 possible hex characters that may be seen

in the status string.
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7-24

Table 7.4.1. Hex - Binary Nibble Conversion Chart

ASCII -Encoded

Hex Character

Binary Nibble

 (msb) (lsb) 

0 0 0 0 0

1 0 0 0 1

2 0 0 1 0

3 0 0 1 1

4 0 1 0 0

5 0 1 0 1

6 0 1 1 0

7 0 1 1 1

8 1 0 0 0

9 1 0 0 1

A 1 0 1 0

B 1 0 1 1

C 1 1 0 0

D 1 1 0 1

E 1 1 1 0

F 1 1 1 1

Each bit is set (bit = 1) to indicate that a problem exists in that FRU or that a specified event or condition

is true. A bit will be cleared (bit = 0) if that FRU is good or that condition is false. The actual meaning of

each bit is given on Section 7.4.5. The bits shown as 0 are low and are reserved for future use. The RESET

bit will normally be low (0), except after power-up or system reset (hardware or software reset). Upon such

an event and for 5 minutes afterward, the RESET bit will be high (1). ASOS disregards data taken during

these 5 minutes. (This time is required for the present weather sensor averaging routine to stabilize.) In

normal operation (excluding the first 5 minutes after reset or power-up), the status bytes will be all low

(0000). A non-zero character in any of the four positions indicates the suspected failure of an FRU which

causes ASOS to take action to alert maintenance personnel of a problem. In addition, data from the present

weather sensor will be disregarded and a missing report issued. (Note that the present weather sensor does

not necessarily stop outputting data when a status bit flags an error condition.) A summary of the active

status bits and the corresponding FRU's and assembly numbers are provided in table 7.4.2.

NOTE

Byte 0 is transmitted first.

Output String

Position

Relative

Position

Character 11 FRU8 FRU7 FRU2 FRU3 Byte 1

Character 12 FRU4 FRU5 FRU9 FRU1 Byte 2

Character 13 RESET 0 0 0 Byte 3

Character 14 0 0 0 0 Byte 4

Bit 3 Bit 2 Bit 1 Bit 0

 

Figure 7.4.5. OWI-240 Status Bit Identification
S100 ASOS Site Technical Manual

7-25/ (7-26 blank)

Table 7.4.2. Status Bit/FRU Summary

FRU Number Item Reference Designator

FRU1 Frame assembly 2MT2A2

FRU2 Transmitter board 2MT2A1A1A1

FRU3 Receiver AGC board 2MT2A1A1A8

FRU4 Signal processor board #1 2MT2A1A1A7

FRU5 Signal processor board #2 2MT2A1A1A6

FRU6 Microprocessor board 2MT2A1A1A3

FRU7 Analog power supply 2MT2A1PS2

FRU8 Digital power supply 2MT2A1PS3

FRU9 Heater power supply 2MT2A1PS1
S100 ASOS Site Technical Manual

7-27

SECTION V. MAINTENANCE

7.5.1 INTRODUCTION

This section provides the preventive and corrective maintenance procedures for the present weather sensor.

Preventive maintenance consists of checking the lens and hood headers, cleaning lenses on the transmitter

and receiver heads, and calibrating the sensor. Corrective maintenance is performed by running the system

diagnostic test on the sensor to identify any faulty module. Failure of a powersupply may prevent the system

diagnostic test from running. Therefore, additional procedures are provided for checking power supply

voltages. Detailed removal and installation procedures are provided for each field replaceable unit (FRU)

in the present weather sensor.

7.5.2 PREVENTIVE MAINTENANCE

Preventive maintenance for the present weather sensor is performed every 90 days and consists of checking

the lens and hood heaters, cleaning the lenses on the transmitter and receiver heads, and calibrating the

sensor. Once each year the sensor must be treated with the insect paint.

7.5.2.1 Checking Lens and Hood Heaters. The present weather sensor lens and hood heaters are not

automatically tested by the sensor'sinternal diagnostics. Assuch, the maintenance technician must manually

check the heaters every 90 days and whenever a problem with the heaters is suspected. The lens heaters are

on all the time. Hood heaters are turned on whenever the sensor is reporting snow (S) or heavy snow (S+)

or whenever the beam is completely blocked. Since checking the heatersrequires a touch test of the lens, the

transmitter and receiver lenses should be cleaned after this test (paragraph 7.5.2.2). Table 7.5.1 providesthe

procedure to check the operation of the present weather sensor lens and hood heaters.

7.5.2.2 Cleaning Transmitter and Receiver Lenses. Generally, moderate dust buildup and scratches on

the transmitter and receiver lenses will not effect sensor accuracy or sensitivity. However, as preventive

maintenance, the lenses on the transmitter and receiver heads should be cleaned every 90 days. Individual

sites may require more frequent cleaning if there are a significant number of problems noted due to dirty

lenses. Before cleaning the lenses, power should be removed from the present weather sensor by setting the

circuit breakers on sensor circuit breaker module (located in the DCP) to the off (right) position. After

removing power, a soft optics brush should be used to remove dust or dirt that may scratch the lenses. The

lenses are then cleaned using lint-free lens cleaning tissues and lens cleaning solution. A drop of cleaning

solution is applied to the tissues, and the lenses are then cleaned by wiping each lens in a circular fashion.

7.5.2.3 Calibration. The present weather sensor must be calibrated every 90 days or after any corrective

maintenance action. Before calibration, the sensor must be properly installed and must pass its ASOS

diagnostic checks. Table 7.5.2 provides the procedures to calibrate the present weather sensor. Calibration

is accomplished using the laptop computer to issue present weather sensor B and C commands and receive

the sensor's responses. Paragraph 7.4.4 contains a detailed description of the sensor responses.

7.5.2.4 Present Weather Sensor Spider Paint Application Procedure. This procedure is used to treat

(paint) the present weathersensor with an insecticide material. The sensorshould be painted once each year.

The entire sensor head (excluding hoods),sensor pole, and pedestal must be painted. The purpose isto create

a long, treated path over which climbing insects have to traverse before reaching the optical path of the

present weathersensor. The insecticide, a product called INSECTA, is a milky white, latex based liquid that,

when dry, is relatively benign to humans but deadly to spiders and insects. The insecticide is present in

crystalsthat are released when an insect walks on the treated surface. The present weathersensorspider paint

application procedure is provided in table 7.5.3.
ASOS Site Technical Manual S100

7-28

7.5.3 CORRECTIVE MAINTENANCE

The present weather sensor calibration should be checked using the INITIAL CALIBRATION check of

table 7.5.2 prior to further corrective maintenance. The present weather sensor contains elaborate fault

isolation circuitry and software that enable fault isolation to an FRU. Although these diagnostics are very

reliable, if they fail to execute properly, the technician should troubleshoot the sensor using the procedures

in table 7.5.4. Each procedure should be performed in the order listed until the problem is corrected. If the

sensor cannot be repaired using these procedures, the sensor's detailed block diagrams should be referenced

and troubleshooting performed. After repair, the on-demand testshould be performed on the present weather

sensor to verify system operation. The system should then be monitored until the continuous self-test (CST)

completes its routine test of the complete system. After the completion of CST, the system maintenance log

should be reviewed to ensure that the system is operating properly.

7.5.4 FRU REMOVAL AND INSTALLATION

7.5.4.1 Frame Head Assembly Removal and Installation. The procedures required to remove and install

the present weather sensor frame assembly are provided in table 7.5.6.

7.5.4.2 Heater Power Supply Removal and Installation. The procedures required to remove and install

the present weather sensor heater power supply are provided in table 7.5.7.

7.5.4.3 Analog Power Supply Removal and Installation. The procedures required to remove and install

the present weather sensor analog power supply are provided in table 7.5.8.

7.5.4.4 Digital Power Supply Removal and Installation. The procedures required to remove and install

the present weather sensor digital power supply are provided in table 7.5.9.

7.5.4.5 CircuitBoardRemoval and Installation.The proceduresrequired to remove and install the present

weather sensor circuit boards are provided in table 7.5.10.

7.5.4.6 Fiberoptic Module Removal and Installation. The procedures required to remove and install the

present weather sensor fiberoptic module are provided in table 7.5.11.

7.5.4.7 Heater Bar Assembly Removal and Installation. The procedures to remove and install the heater

bar assembly are provided in table 7.5.12.

7.5.4.8 Card Rack Assembly Removal and Installation. The procedures to remove and install the card

rack assembly are provided in table 7.5.13.

7.5.4.9 Main Electrical Enclosure Removal and Installation. The procedures to remove and install the

main electrical enclosure are provided in table 7.5.14.
S100 ASOS Site Technical Manual

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WARNING

Table 7.5.1. Lens and Hood Heater Touch Test

Step Procedure

While lens and hood heaters will be hot, they will not cause burns to skin if

lightly touched for short periods of time. 

NOTE

Laptop computer initialized as DCP OID (Chapter 3, Section III), or any other

available OID, may be used for the following procedure.

1 At OID, displaysensorstatus page (sequentially press REVUE-SENSOR-STAT) function keys from 1-minute

display.

2 On sensor status page, set report processing for present weather sensor to OFF.

3 Briefly touch part of transmitter and receiver lenses where heater is attached fromoutside. Verify that heaters

are warmer than ambient temperature.

4 Block beam between transmitter and receiver head for 3 to 5 minutes. 

5 Briefly touch transmitter and receiver hood heaters and verify that heaters are warmer than ambient

temperature. If lens (window) and/or hood heaters are not working, check 24-volt dc power supply for

discontinuity in heater circuit as follows:

a. Check 24-volt heater power supply located on the left side of LEDWI electronic box.

Connect a DMM at power supply 2MT2A1PS1 V+ and V- pins. If 24 volts dc is not

present, replace power supply; otherwise, check lens and hood heaters for continuity.

b. Remove connectors J4 and J5 from electrical enclosure. Measure resistance on J5

connector(transmitter) between pinsCand D (lens heater) and pins G and H (hood heater).

Measure resistance on J4 connector (receiver) between pins D and E (lens heaters) and

pins G and H (hood heater). Reference Section 7.4.4.

6 Clean transmitter and receiver lenses in accordance with paragraph 7.5.2.2. 

7 On sensor status page at OID, set report processing for present weather sensor to ON.

Table 7.5.2. Present Weather Sensor Calibration

Step Procedure

Tools required:

 Large flat-tipped screwdriver

 STI LEDWI calibration kit

 Small flat-tipped screwdriver

 Laptop interface (Y-shaped) cable

 Laptop computer with PROCOMM Plus installed

NOTE

Power to the LEDWI must be cycled OFF, then ON anytime the beam is interrupted. This occurs

during optics cleaning and when the adjustable tube is installed and removed.

INITIAL SETUP PROCEDURE

1 Inside DCP equipment cabinet,set circuit breakers on present weathersensor circuit breaker module to off

(right) position.

2 Clean lenses on transmitter and receiver heads in accordance with paragraph 7.5.2.2.

3 Install adjustable tube from calibration kit between transmitter and receiver heads.
ASOS Site Technical Manual S100

7-30

Table 7.5.2. Present Weather Sensor Calibration -CONT

Step Procedure

4 Using large flat-tipped screwdriver, open present weather sensor main electrical enclosure access door.

NOTE

After removing transmitter board, place it inside and at the bottom of the electrical

enclosure to keep it warm and dry.

5 At present weather sensor main electrical enclosure, remove transmitter board from top slot of card rack

and install TST-200 test modulator board from calibration kit into same slot.

6 Using small flat-tipped screwdriver, disconnect DB-9 connector from fiberoptic module inside main

electrical enclosure.

7 Using laptop computer interface (Y-shaped) cable, connect RS-232C (COM1) port of laptop computer to

DB-9 connectorremoved fromfiberoptic module.Close electrical enclosure door asfar as possible without

damaging interface cable.

8 Turn on laptop computer and initialize PROCOMM Plus program. After program initializes, press any key

to enter terminal mode (blank) screen.

9 Using ALT-S command (setup facility), set up the following TERMINAL OPTIONS:

a. Terminal emulation: VT220

b. Duplex: FULL

c. Soft flow control (XON/XOFF): OFF

d. Hard flow control (CTS/RTS): OFF

e. Line wrap: OFF

f. Screen scroll: OFF

g. CR translation: CR/LF

h. BS translation: NON-DESTRUCTIVE 

I. Break length (milliseconds): 350

j. Enquiry: OFF

k. EGA/VGA true underline: OFF

l. Terminal width: 80

m. ANSI 7 or 8 bit commands: 8 BIT

10 Press ESC key to exit to terminal mode (blank) screen.

11 Using ALT-P command (line/port option), set CURRENT SETTINGS as follows:

a. Baud rate: 1200

b. Parity: NONE

c. Data bits: 8

d. Stop bits: 1

e. Port: COM1

12 Press ESC key to return to terminal mode (blank) screen.

13 Using ALT-F1 (open log) command, open log file to record calibration data. In response to prompt for file

name, use the following format:

PWMMDD.CAL

where MMDD is current month/date.
S100 ASOS Site Technical Manual

Table 7.5.2. Present Weather Sensor Calibration -CONT

Step Procedure

7-31

14 On laptop computer, set CAPS LOCK to ON.

CAUTION

The installation of the TST-200 test modulator board causes the hood heaters to be

turned on continuously. Temperature of the hood and lens area can exceed 200 degrees

Fahrenheit. Do not touch the hood or lens. Serious burns may result. Use extreme

caution while installing and removing the calibration tube.

15 Inside DCP equipment cabinet,set circuit breakers on present weathersensor circuit breaker module to on

(left) position. Wait at least 2 minutes for sensor to warm up and stabilize before proceeding.

16 At laptop computer, type B. Computer displays the following report:

WNPP1234S567890

Verify that report is correct. Wait 10 minutes before proceeding.

INITIAL CALIBRATION CHECK

1 Ten minutes after above step is completed, type C. Verify that sensor reports:

WS+PxxxxSxxxxxxXxxx000L---xxxK---xxxH---xxx

Data denoted by xx indicatesthat those values are irrelevant to this procedure and should be ignored. Data

denoted by --- are values that will be adjusted as necessary during this procedure.

2 Subtract displayed value of high channel (H---) from value oflow channel (L---). Record difference (L-H).

3 Compare displayed values oflow channel, high channel, particle channel, and low/high difference with the

following tolerances:

Low Channel (L-) 240 +/- 4

Particle Channel (K-) 400 +/-10

High Channel (H-) 174 +/- 4

Difference Channel (L-H) 66 +/- 8

IMPORTANT !!! If all values are within tolerance and the difference between the L (low channel) and the

H (high channel) is 66 ±8, proceed to transmit modulator calibration procedure. If not, continue with signal

processing calibration procedure below.
ASOS Site Technical Manual S100

Table 7.5.2. Present Weather Sensor Calibration -CONT

Step Procedure

7-32

SIGNAL PROCESSING CALIBRATION PROCEDURE

NOTE

When making the following adjustments, turn potentiometers no more than 1/4 turn, wait 3 minutes

for sensor data averaging, and issue C command again. Repeat as necessary to bring value into

specified tolerance. Electronics enclosure door should be closed as much as possible between

potentiometer adjustments.

 Do not adjust carrier frequency. This will adversely affect sensor operation; also, adjusting carrier

value could mask other malfunctions such as lens fogging, optical misalignment, or degradation of

the signal processing cards 1 and 2, the transmitter, and the AGC card.

 

 If L value, H value, or L-H value was out of tolerance in previous check, both L and H values should

be adjusted in the following steps. This is to keep L-H value within 66 ±8 tolerance. If K value was

out of tolerance but other values were in tolerance, only K value need be adjusted below.

1 Low channel (L---) adjustment. Adjust LO potentiometer on signal processor No. 1 (SP1) printed circuit

board for L indication of 240 ±4. Adjust LO potentiometer clockwise (cw) to decrease reading or

counterclockwise (ccw) to increase reading. The second three digits in L field are not used in calibration.

2 Particle channel (K---) adjustment. Adjust PAR potentiometer on signal processor No. 2 (SP2) printed

circuit board for K indication of 400 ±10. Adjust PAR potentiometer cw to decrease reading or ccw to

increase reading. The second three digits in K field are not used in calibration. 

3 High channel (H---) adjustment. Adjust HI potentiometer on signal processor No. 2 (SP2) printed circuit

board for H indication of 174 ±4. Adjust HI potentiometer cw to decrease reading or ccw to increase

reading. The second three digits in H field are not used in calibration. 

 

NOTE

If L and H values were adjusted to proper tolerances, L-H value will automatically be

within tolerance.

4 If adjustments were made to L and/or H value, recalculate L-H value and ensure that L-H value is within

66 ±8 tolerance. Repeat L and H adjustments as necessary to bring L-H value within tolerance.

TRANSMIT MODULATOR CALIBRATION CHECK PROCEDURE

1 Inside DCP equipment cabinet,set circuit breakers on present weathersensor circuit breaker module to off

(right) position.

2 Inside present weathersensor main electrical enclosure, remove TST-200 test modulator board and install

transmitter board.

3 Inside DCP equipment cabinet,set circuit breakers on present weathersensor circuit breaker module to on

(left) position. Wait at least 5 minutes for sensor to warm up and stabilize before proceeding.

4 Five minutes after above step is completed, type C. Verify that sensor reports:

W+P0000SxxxxxxX---000LxxxxxxKxxxxxxHxxxxxx

Data denoted by xx indicatesthat those values are irrelevant to this procedure and should be ignored. Data

denoted by --- is the carrier channel value.
S100 ASOS Site Technical Manual

Table 7.5.2. Present Weather Sensor Calibration -CONT

Step Procedure

7-33

5 Verify that first three digits after X (carrier value) is above 350, then proceed to teardown procedure. If

value is below 350, remove and replace the following FRU's, in order, and retest carrier channel for value

above 350.

a. Receiver/AGC Board - AlAlA8

 b. Transmitter Board - AlAlA1

c. Signal Processor 1 - AlAlA7

d. Microprocessor Board - AlAlA3

e. Frame Assembly A2 (This check can be completed with new frame assemblies

resting on the ground. The cables must be connected to the electrical enclosure

and the calibration tube installed.) 

TEARDOWN PROCEDURE

1 At laptop computer, use ALT-F1 command to close log.

2 At laptop computer, use ALT-X (exit) command to exit PROCOMM Plus.

3 Turn off laptop computer.

4 Inside DCP equipment cabinet, set circuit breaker on present weather sensor circuit breaker module to off

(right) position. 

5 Disconnect cables between laptop computer and present weather sensor.

6 Using small flat-tipped screwdriver, install present weather sensor DB-9 connector on fiberoptic module.

7 Using large flat-tipped screwdriver, close and secure present weather sensor main electrical enclosure

access door.

CAUTION

The installation of the TST-200 test modulator board causes the hood heaters to be

turned on continuously. Temperature of the hood and lens area can exceed 200 degrees

Fahrenheit. Do not touch the hood or lens. Serious burns may result. Use extreme

caution while installing and removing the calibration tube. The tube that is removed in

the next step may be hot.

8 Remove adjustable tube from sensor heads. 

9 Inside DCP equipment cabinet,set circuit breakers on present weathersensor circuit breaker module to on

(left) position.
ASOS Site Technical Manual S100

7-34

WARNING

WARNING

WARNING

Table 7.5.3. Present Weather Sensor Spider Paint Application Procedure

Step Procedure

Tools and materials required:

Water 

Clean cloths 

Eye protection 

Plastic gloves 

INSECTA liquid 

Hand soap 

Follow the recommended directions in this procedure and on the bottle of

INSECTA regarding the handling and disposal of INSECTA.

NOTE

INSECTA should be applied after replacing present weather sensor head or

installing newsensor if ambient temperature is above 55 degrees Fahrenheit (°F).

If temperature is below 55°F, it is necessary to remove present weather sensor

head and mounting pole and treat indoors at room temperature. Ensure that there

is adequate ventilation before painting indoors. The procedure is the same

whether present weather sensor is painted indoors or outdoors.

1 Inside DCP equipment cabinet, set circuit breakers on present weather sensor circuit breaker module to off

(right) position. 

Death or severe injury may result if personnel are not kept out of travel path of sensor.

With locking pin removed fromhinge plate,sensor is not firmly locked in upright position.

2 Lower present weather sensor on hinge plate as follows:

a. Remove locking pin from front part of hinge plate.

b. From rear of sensor, firmly grasp support pole with both hands and carefully lower sensor

on hinge until lanyard catches and supports weight of sensor.

CAUTION

When washing sensor head and pole, take care not to wash or otherwise contact sensor

lenses. Failure to comply may result in damage to lenses.

3 Thoroughly wash present weathersensor head and pole with water to remove surface dirt and dry using clean

cloth.

 

Eye protection and plastic gloves must be worn when performing the following steps and

any exposed skin must be covered.

4 Remove cap from INSECTA bottle and screw on applicator brush with black seal installed in applicator.
S100 ASOS Site Technical Manual

7-35

WARNING

Table 7.5.3 Present Weather Sensor Spider Paint Application Procedure -CONT

Step Procedure

5 Squeeze bottle until milky white liquid saturates brush.

NOTE

When painting surfaces, do not paint the inside or outside of the black hoods on the present

weather sensor head. Apply an even, thick coat of INSECTA but avoid applying so much

that it runs.

6 Using Section 7.5.1 as a guide, brush INSECTA on all white surfaces of present weather sensor head, both

mounting plates (upper surface of top plate and lower surface of bottom plate), and pole. Also paint the

18-inch high galvanized mounting pedestal and hinge plate. It is not necessary to paint the main electrical

enclosure box.

7 Allow treated surfaces to dry 2 to 3 hours before touching.

8 Using clean water and rags, clean up any spills and applicator brush.

 

With locking pin removed from hinge plate,sensor is notfirmly locked in upright position.

Death or severe injury may result if personnel are not kept out of travel path of sensor.

9 Raise present weather sensor on hinge plate as follows:

a. From rear of sensor, firmly grasp support pole with both hands and carefully raise sensor

on hinge into upright position.

b. Install locking pin into front of hinge plate.

10 Dispose of dirty rags, plastic gloves, and INSECTA bottle, when it is empty, by sealing in plastic bag and

placing bag in trash can.

11 Use soap and water to thoroughly wash hands to remove any traces of INSECTA.

12 Inside DCP equipment cabinet, set circuit breakers on present weather sensor circuit breaker module to on

(right) position.
ASOS Site Technical Manual S100

7-36

Figure 7.5.1. Present Weather Sensor Insect Treatment Areas

Table 7.5.4. Present Weather Sensor Troubleshooting

What to Do How To Do It

Check system maintenance log and replace indicated FRU. Tables 7.5.6 - 7.5.9

Perform fiberoptic module test. Chapter 1, Section V

Perform present weather sensor power supply test Table 7.5.5

Replace Microprocessor Board A1A3. Table 7.5.10
S100 ASOS Site Technical Manual

7-37

WARNING

Table 7.5.5. Present Weather Power Supply Test

Step Procedure

Tools required:

 Large flat-tipped screwdriver

 No. 1 Phillips screwdriver

 Digital multimeter (DMM)

Hazardous voltages are present in present weather sensor. Exercise proper safety

procedures to avoid possible injury or death.

NOTE

Because the microprocessor board is powered by digital power supply PS3, this power

supply is tested first. If microprocessor is operating, it will report most failures of heater

power supply PS1 and analog power supply PS2 during system continuous self-test

(CST). 

1 Using large flat-tipped screwdriver, open present weather sensor main electrical enclosure access door.

2 Using No. 1 Phillipsscrewdriver, remove four screws and lockwasherssecuring access cover to ac junction

box.

3 Remove access cover from ac junction box.

4 With power applied to present weather sensor, use DMM to check for 115 vac power between terminals 1

and 2 and between terminals 4 and 5 of terminal board TB1 inside ac junction box. If power is present,

proceed to step 5. If not, ensure that all cables are connected properly and then troubleshoot ac power cables

between DCP and present weather sensor. 

5 Using DMM, verify 115 vac between terminals 1 and 2 of filter block TB2 on top of ac junction box. If

power is present, proceed to step 6. If not, replace ac junction box.

6 At card rack assembly, disconnect digital power supply connector P15 from connector J15.

7 Using DMM, check the following pins for indicated voltages:

 Negative lead Positive lead Reading

P15-1 P15-4 +5.0 vdc ±0.2 vdc

P15-2 P15-9 +12.0 vdc ±0.2 vdc

P15-2 P15-7 -12.0 vdc ±0.2 vdc

 

If any reading is incorrect, replace digital power supply PS3. If all readings are correct, reconnect P15 to

J15 and proceed to step 8.

8 At card rack assembly, disconnect analog power supply connector P19 from connector J19.

9 Using DMM, check the following pins for indicated voltages:

 Negative lead Positive lead Reading

P19-4 P19-1 -12.0 vdc ±0.2 vdc

P19-4 P19-7 +12.0 vdc ±0.2 vdc

 

If either reading is incorrect, replace analog power supply PS2. If both readings are correct, reconnect P19

to J19 and proceed to step 10.

10 At card rack assembly, disconnect heater power supply connector P17 from connector J17.
ASOS Site Technical Manual S100

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WARNING

WARNING

Table 7.5.5. Present Weather Power Supply Test -CONT

Step Procedure

11 Using DMM, check the following pins for indicated voltages:

 Negative lead Positive lead Reading

P17-1 P17-5 +24.0 vdc ±0.2 vdc

 

If reading is incorrect, replace heater power supply PS1. If reading is correct, connect P17 to J17.

12 Using No. 1 Phillips screwdriver, install four screws and lockwashers securing access cover to ac junction

box.

13 Using large flat-tipped screwdriver, close and secure present weathersensor main electrical enclosure access

door.

Table 7.5.6. Frame Head Assembly Removal and Installation

Step Procedure

REMOVAL

Tools required:

 3/16-inch hex key wrench

 15 feet of rope

 5/8-inch wrench

 Sensor support device

Death orsevere injurymay result if power is notremoved fromsensor prior to maintenance

activities. Ensure that circuit breakers (located in DCP) supplying heater and primary

power to sensor are set to off (right) position.

1 Inside DCP equipment cabinet, set circuit breakers on present weather sensor circuit breaker module to off

(right) position.

2 Remove frame assembly (long white) ground wire fromground wire stud located on bottomofmain electrical

enclosure.

3 Disconnect frame cable connectors P4 and P5 from connectors J4 and J5 on main electrical enclosure. Feed

all exposed cabling into access opening in sensor mounting column.

 

Death or severe injury may result if personnel are not kept out of travel path of sensor.

With locking pin removed fromhinge plate,sensor is notfirmly locked in upright position.

4 Lower present weather sensor on hinge plate as follows:

a. Remove locking pin from front part of hinge plate.

b. From rear of sensor, firmly grasp support pole with both hands and carefully lower sensor

on hinge until lanyard catches and supports weight of sensor.

5 Using 3/16-inch hex key wrench at collar of frame mounting base plate, loosen four hex capscrews securing

frame stem to mounting plate.
S100 ASOS Site Technical Manual

7-39

WARNING

Table 7.5.6. Frame Head Assembly Removal and Installation -CONT

Step Procedure

6 Gently raise frame assembly out of collar of mounting base plate, carefully pulling frame assembly cabling

out behind it.

INSTALLATION

Tools required:

 3/16-inch hex key wrench

 15 feet of rope

 5/8-inch wrench

 Sensor support device

Death or severe injury may result if power is not removed from sensor prior to

maintenance activities. Ensure that heater and primary power circuit breakers (located

in DCP) supplying power to sensor are set to off (right) position.

1 Inside DCP equipment cabinet, ensure that circuit breakers on present weathersensor circuit breaker module

are set to off (right) position.

2 Feed cables from sensor frame down through collar of frame assembly mounting base plate (down into

mounting column) and gently lower stem of frame into collar of base plate.

3 At mounting column access hole (below main electrical enclosure), pull free ends of two frame assembly

cables and frame assembly ground wire out of mounting column.

4 Position frame assembly so thatsensor headpiece with horizontalslotted mask isfacing north (±10 degrees).

Raise frame assembly so that stem of frame is approximately 1/4 inch above bottom of mounting plate (not

protruding out of mounting base).

5 Using 3/16-inch hex key wrench, tighten four hex capscrews in collar of mounting base to secure frame

assembly. Do not overtighten screws; otherwise, lower end of mounting plate will become distorted and

difficult to remove from mounting base.

6 Raise present weather sensor on hinge plate as follows:

a. From rear of sensor, firmly grasp support pole with both hands and carefully raise sensor

on hinge into upright position.

b. Install locking pin into front of hinge plate.

7 Connect frame cable connectors P4 and P5 to connectors J4 and J5 on main electrical enclosure.

8 Connect frame assembly (long white) ground wire to ground wire stud located on bottom of main electrical

enclosure. 

9 Check operation of window heaters and hood heaters in accordance with paragraph 7.5.2.1.

10 Clean transmitter and receiver lenses in accordance with paragraph 7.5.2.2.

11 Calibrate present weather sensor in accordance with table 7.5.2.
ASOS Site Technical Manual S100

7-40

WARNING

WARNING

Table 7.5.7. Heater Power Supply Removal and Installation

Step Procedure

REMOVAL

Tools required:

 Large flat-tipped screwdriver

 No. 1 Phillips screwdriver

 Long-nosed pliers

 Long flat-tipped screwdriver

Death orsevere injurymay result if power is notremoved fromsensor priorto maintenance

activities. Ensure that circuit breakers (located in DCP) supplying heater and primary

power to sensor are set to off (right) position.

1 Inside DCP equipment cabinet, set circuit breakers on present weather sensor circuit breaker module to

off (right) position.

2 Using large flat-tipped screwdriver, open present weather sensor main electrical enclosure access door.

NOTE

Heater power supply A1PS1 is located on left side of main electrical enclosure.

3 Locate twisted pair of wires connecting heater power supply to terminals 1 and 2 of terminal board on top

of ac junction box. Using No. 1 Phillips screwdriver, disconnect heater power supply wires from terminal

board, but leave other wires connected to terminal board.

4 Using long-nosed pliers to grasp connector, on left side of card rack assembly, disconnect heater power

supply cable from connector J17.

5 While supporting heater power supply, use long flat-tipped screwdriver to loosen four captive screws

securing power supply to main electrical enclosure.

NOTE

Do not detach heater power supply from its own mounting plate.

6 Remove heater power supply from main electrical enclosure.

INSTALLATION

Tools required:

 Long flat-tipped screwdriver

 Long-nosed pliers

 No. 1 Phillips screwdriver

 Large flat-tipped screwdriver

Death orsevere injurymay result if poweris notremoved fromsensor priorto maintenance

activities. Ensure that circuit breakers (located in DCP) supplying heater and primary

power to sensor are set to off (right) position. 

1 Inside DCP equipment cabinet, ensure that circuit breakers on present weather circuit breaker module are

set to off (right) position.

2 Using long flat-tipped screwdriver, install new heater power supply and tighten four captive screws

securing power supply to main electrical enclosure.

3 Using long-nosed pliers to grasp connector, on left side of card rack assembly, connect heater power

supply cable to connector J17.
S100 ASOS Site Technical Manual

7-41

WARNING

Table 7.5.7. Heater Power Supply Removal and Installation -CONT

Step Procedure

4 Using No. 1 Phillips screwdriver, connect two twisted pair wires from heater power supply to terminals 1

and 2 of terminal board on top of ac junction box. Leave other wires connected to terminals.

5 Check heater power supply in accordance with table 7.5.5, step 11. If power supply does not read 24vdc,

adjust R11 for 24vdc ±.2vdc.

6 Using large flat-tipped screwdriver, close and secure present weather sensor main electrical enclosure

access door.

Table 7.5.8. Analog Power Supply Removal and Installation

Step Procedure

REMOVAL

Tools required:

 Large flat-tipped screwdriver

 No. 1 Phillips screwdriver

 Long-nosed pliers

 Long flat-tipped screwdriver

Death or severe injury may result if power is not removed from sensor prior to

maintenance activities. Ensure that circuit breakers(located in DCP) supplying heater and

primary power to sensor are set to off (right) position.

1 Inside DCP equipment cabinet, set circuit breakers on present weather sensor circuit breaker module to off

(right) position.

2 Using large flat-tipped screwdriver, open present weather sensor main electrical enclosure access door.

NOTE

Analog power supply A1PS2 is located toward top of main electrical enclosure.

3 Locate twisted pair of wires connecting analog power supply to terminals 1 and 2 of terminal board on top

of ac junction box. Using No. 1 Phillips screwdriver, disconnect analog power supply wires from terminal

board, but leave other wires connected to terminal board.

4 Using long-nosed pliers to grasp connector, on left side of card rack assembly, disconnect analog power

supply cable from connector J19.

5 While supporting analog power supply, use long flat-tipped screwdriver to loosen four captive screws

securing power supply to main electrical enclosure.

NOTE

Do not detach analog power supply from its own mounting plate.

6 Remove analog power supply from main electrical enclosure.
ASOS Site Technical Manual S100

7-42

WARNING

WARNING

Table 7.5.8. Analog Power Supply Removal and Installation -CONT

Step Procedure

INSTALLATION

Tools required:

 Long flat-tipped screwdriver

 Long-nosed pliers

 No. 1 Phillips screwdriver

 Large flat-tipped screwdriver

Death or severe injury may result if power is not removed from sensor prior to maintenance

activities. Ensure that circuit breakers (located in DCP) supplying heater and primary power to

sensor are set to off (right) position. 

1 Inside DCP equipment cabinet, ensure that circuit breakers on present weather circuit breaker module are set

to off (right) position.

2 Using long flat-tipped screwdriver, install new analog powersupply and tighten four captive screws securing

power supply to main electrical enclosure.

3 Using long-nosed pliersto grasp connector, on left side of card rack assembly, connect analog power supply

cable to connector J19.

4 Using No. 1 Phillips screwdriver, connect two twisted pair wires from analog power supply to terminals 1

and 2 of terminal board on top of ac junction box. Leave other wires connected to terminals.

5 Check analog power supply in accordance with table 7.5.5, Step 9.

6 Calibrate present weather sensor in accordance with table 7.5.2.

7 Using large flat-tipped screwdriver, close and secure present weathersensor main electrical enclosure access

door.

Table 7.5.9. Digital Power Supply Removal and Installation

Step Procedure

REMOVAL

Tools required:

 Large flat-tipped screwdriver

 No. 1 Phillips screwdriver

 Long-nosed pliers

 Long flat-tipped screwdriver

Death orsevere injurymay result if power is notremoved fromsensor prior to maintenance

activities. Ensure that circuit breakers (located in DCP) supplying heater and primary

power to sensor are set to off (right) position.

1 Inside DCP equipment cabinet, set circuit breakers on present weather sensor circuit breaker module to off

(right) position.

2 Using large flat-tipped screwdriver, open present weather sensor main electrical enclosure access door.

NOTE

Digital power supply A1PS3 is located in middle of main electrical enclosure.
S100 ASOS Site Technical Manual

7-43

WARNING

Table 7.5.9. Digital Power Supply Removal and Installation -CONT

Step Procedure

3 Locate twisted pair of wires connecting digital power supply to terminals 1 and 2 of terminal board on top

of ac junction box. Using No. 1 Phillips screwdriver, disconnect digital power supply wires from terminal

board, but leave other wires connected to terminal board.

4 Using long-nosed pliers to grasp connector, on left side of card rack assembly, disconnect digital power

supply cable from connector J15.

5 While supporting digital power supply, use long flat-tipped screwdriver to loosen four captive screws

securing power supply to main electrical enclosure.

NOTE

 Do not detach digital power supply from its own mounting plate.

6 Remove digital power supply from main electrical enclosure.

INSTALLATION

Tools required:

 Long flat-tipped screwdriver

 Long-nosed pliers

 No. 1 Phillips screwdriver

 Large flat-tipped screwdriver

Death or severe injury may result if power is not removed from sensor prior to

maintenance activities. Ensure that circuit breakers (located in DCP) supplying

heater and primary power to sensor are set to off (right) position. 

1 Inside DCP equipment cabinet, ensure that circuit breakers on present weather circuit breaker module are set

to off (right) position.

2 Using long flat-tipped screwdriver, install new digital powersupply and tighten four captive screws securing

power supply to main electrical enclosure.

3 Using long-nosed pliers to grasp connector, on left side of card rack assembly, connect digital power supply

cable to connector J15.

4 Using No. 1 Phillipsscrewdriver, connect two twisted pair wiresfromdigital powersupply to terminals 1 and

2 of terminal board on top of ac junction box. Leave other wires connected to terminals.

5 Check digital power supply in accordance with table 7.5.5, Step 7.

6 Calibrate present weather sensor in accordance with table 7.5.2.

7 Using large flat-tipped screwdriver, close and secure present weathersensor main electrical enclosure access

door.
ASOS Site Technical Manual S100

7-44

WARNING

WARNING

WARNING

Table 7.5.10. Circuit Board Removal and Installation

Step Procedure

REMOVAL

Tools required:

 Large flat-tipped screwdriver

 Small flat-tipped screwdriver

Death or severe injury may result if power is not removed from sensor prior to

maintenance activities. Ensure that circuit breakers(located in DCP)supplying heater and

primary power to sensor are set to off (right) position.

1 Inside DCP equipment cabinet, set circuit breakers on present weather sensor circuit breaker module to off

(right) position.

2 Using large flat-tipped screwdriver, open present weather sensor main electrical enclosure access door.

3 At card rack assembly, locate circuit board to be removed. Using small flat-tipped screwdriver, loosen

captive screws and remove circuit card.

INSTALLATION

Tools required:

 Large flat-tipped screwdriver

 Small flat-tipped screwdriver

Death or severe injury may result if power is not removed from sensor prior to

maintenance activities. Ensure that circuit breakers(located in DCP)supplying heater and

primary power to sensor are set to off (right) position. 

1 Inside DCP equipment cabinet, ensure that circuit breakers on present weather circuit breaker module are

set to off (right) position.

2 Position new circuit card in correct slot and using small flat-tipped screwdriver, tighten captive screws.

3 Calibrate present weather sensor in accordance with table 7.5.2.

4 Using large flat-tipped screwdriver, close and secure present weathersensor main electrical enclosure access

door.

Table 7.5.11. Fiberoptic Module Removal and Installation

Step Procedure

REMOVAL

Tools required:

 Large flat-tipped screwdriver

 Small flat-tipped screwdriver

 No. 1 Phillips screwdriver

Death orsevere injurymay result if power is notremoved fromsensor priorto maintenance

activities. Ensure that circuit breakers (located in DCP) supplying heater and primary

power to sensor are set to off (right) position.
S100 ASOS Site Technical Manual

7-45

WARNING

Table 7.5.11. Fiberoptic Module Removal and Installation -CONT

Step Procedure

1 Inside DCP equipment cabinet, set circuit breakers on present weather sensor power control module to off

(right) position.

2 Using large flat-tipped screwdriver, open present weather sensor main electrical enclosure access door.

3 Using small flat-tipped screwdriver, loosen two retaining screws on DB-9 connector located on top of

fiberoptic module. Remove connector DB-9.

4 UsingNo. 1 Phillipsscrewdriver,remove fourscrews and lockwasherssecuring ac junction box access cover.

5 Remove access cover from ac junction box.

6 Disconnect two fiberoptic cables from underneath fiberoptic module. Install protective plastic covers over

fiberoptic connectors.

NOTE

Screws referenced in next step are located inside ac junction box.

7 Using small flat-tipped screwdriver, remove four screws, four lockwashers, and two gaskets securing

fiberoptic module to ac junction box.

INSTALLATION

Tools required:

 Small flat-tipped screwdriver

 No. 1 Phillips screwdriver

 Large flat-tipped screwdriver

Death orsevere injurymay result if power is notremoved fromsensor priorto maintenance

activities. Ensure that circuit breakers (located in DCP) supplying heater and primary

power to sensor are set to off (right) position.

1 Inside DCP equipment cabinet, ensure that circuit breakers on present weathersensor circuit breaker module

are set to off (right) position.

2 With DB-9 connector toward the front, position fiberoptic module mounting plate and gasket on ac junction

box. Using small flat-tipped screwdriver, install four lockwashers, four screws, and two gaskets securing

fiberoptic module to ac junction box.

NOTE

Screws referenced in next step are installed inside (beneath module) ac junction box.

3 Remove protective plastic coversfromfiberoptic connectors and installreceive (RX) cable to front connector

and transmit (TX) cable to rear connector on fiberoptic module.

4 Install access cover on ac junction box and using No. 1 Phillips screwdriver, install four screws and

lockwashers securing access cover.

5 Install signal cable on connector DB-9 on fiberoptic module and using small flat-tipped screwdriver, tighten

two retaining screws.

6 Using large flat-tipped screwdriver, close and secure present weathersensor main electrical enclosure access

door.

7 Inside DCP equipment cabinet, set circuit breakers on present weather sensor circuit breaker modules to on

(left) position.
ASOS Site Technical Manual S100

7-46

WARNING

WARNING

Table 7.5.12. Heater Bar Assembly Removal and Installation

Step Procedure

REMOVAL

Tools required:

 Large flat-tipped screwdriver

 7/16-inch socket with ratchet

 10-inch extension bar

Death orsevere injurymay result if poweris notremoved fromsensor prior to maintenance

activities. Ensure that circuit breakers (located in DCP) supplying electronics and heater

power to sensor are set to the off (right) position.

1 Inside DCP equipment cabinet, ensure that electronics and heater circuit breakers on present weather sensor

circuit breaker module are set to off (right) position.

2 Using large flat-tipped screwdriver, open present weather sensor main electrical enclosure access door.

NOTE

Heater bar is located on left side of main electrical enclosure.

3 Disconnect heater bar from main cable.

CAUTION

When removing nut from rear of heater bar, exercise care not to damage thermal switches

or wires located on rear of ac junction box.

4 At heater bar, using 7/16-inch socket with ratchet and 10-inch extension bar, remove two nuts, lockwashers,

and flat washers and remove heater bar.

INSTALLATION

Tools required:

 7/16-inch socket with ratchet

 10-inch extension bar

 Large flat-tipped screwdriver

Death or severe injury may result if power is not removed from sensor prior to

maintenance activities. Ensure that circuit breakers (located in DCP) supplying

electronics and heater power to sensor are set to the off (right) position.

1 Inside DCP equipment cabinet, ensure that electronics and heater circuit breakers on present weather sensor

circuit breaker module are set to off (right) position.

CAUTION

When installing nut from rear of heater bar, exercise care not to damage thermal switches

or wires located on rear of ac junction box.

2 Using 7/16-inch socket with ratchet and 10-inch extension bar, install two nuts, flat washers, and lockwashers

securing heater bar to main electrical enclosure supports.

3 Connect cable from heater bar to the associated main harness connector.

4 Using large flat-tipped screwdriver, close and secure present weathersensor main electrical enclosure access

door.

5 Inside DCP equipment cabinet, set circuit breakers on present weather sensor circuit breaker module to on

(left) position.
S100 ASOS Site Technical Manual

7-47

WARNING

WARNING

Table 7.5.13. Card Rack Assembly Removal and Installation

Step Procedure

REMOVAL

Tools required:

 Large flat-tipped screwdriver

 Small flat-tipped screwdriver

 Long-nosed pliers

 No. 2 Phillips screwdriver

Death orsevere injurymay result if power is notremoved fromsensor priorto maintenance

activities. Ensure that circuit breakers (located in DCP) supplying electronics and heater

power to sensor are set to the off (right) position.

1 Inside DCP equipment cabinet, ensure that electronics and heater circuit breakers on present weather sensor

circuit breaker module are set to off (right) position.

2 Using large flat-tipped screwdriver, open present weather sensor main electrical enclosure access door.

3 At card rack assembly, using small flat-tipped screwdriver, loosen captive screws on each circuit board and

remove circuit board.

4 Using long-nosed pliers to grasp connectors, tag and disconnect cables located on left side of card rack.

5 Using small flat-tipped screwdriver, loosen two retaining screws on DB-9 connector located on top of

fiberoptic module. Remove cable.

6 While supporting card rack and using No. 2 Phillips screwdriver, remove four screws, flat washers, and

lockwashers and remove card rack.

INSTALLATION

Tools required:

 Small flat-tipped screwdriver

 Large flat-tipped screwdriver

 Long-nosed pliers

 No. 2 Phillips screwdriver

Death orsevere injurymay result if poweris notremoved fromsensor prior to maintenance

activities. Ensure that circuit breakers (located in DCP) supplying electronics and heater

power to sensor are set to the off (right) position.

1 Inside DCP equipment cabinet, ensure that electronics and heater circuit breakers on present weather sensor

circuit breaker module are set to off (right) position.

2 Using No. 2 Phillips screwdriver, install four screws, lockwashers, and flat washers securing card rack to

main electrical enclosure.

3 Using long-nosed pliers and tags as a guide, connect main harness cables to connectors on left side of card

rack. These connectors are keyed and can only be installed one way.

4 Using Section 7.1.2 as a guide, install circuit boardsin card rack. Tighten captive screw securing each board

to card rack.

5 Calibrate present weather sensor in accordance with table 7.5.2.
ASOS Site Technical Manual S100

7-48

WARNING

WARNING

Table 7.5.14. Main Electrical Enclosure Removal and Installation

Step Procedure

REMOVAL

Tools required:

 No. 1 Phillips screwdriver

 Large adjustable wrench

 Large flat-tipped screwdriver

 Small flat-tipped screwdriver

 7/16-inch wrench

 9/16-inch wrench

Death orsevere injurymay result if power is notremoved fromsensor prior to maintenance

activities. Ensure that circuit breakers (located in DCP) supplying electronics and heater

power to sensor are set to the off (right) position.

1 Inside DCP equipment cabinet, ensure that electronics and heater circuit breakers on present weather sensor

circuit breaker module are set to off (right) position.

2 Using No. 1 Phillips screwdriver, remove four screws and lockwashers securing cover to ac junction box.

Remove cover.

3 Using large adjustable wrench, disconnect flexible conduit from main electrical enclosure.

4 Using large flat-tipped screwdriver, open present weather sensor main electrical enclosure access door.

5 Using small flat-tipped screwdriver, tag and disconnect power input wires from terminal strip located inside

ac junction box.

6 Disconnect two fiberoptic cables from underneath fiberoptic module. Install protective plastic covers over

fiberoptic cable connectors. Pull fiberoptic and power cables out of enclosure.

7 Disconnect frame cable connectors P4 and P5 from connectors J4 and J5 on main electrical enclosure.

8 Using 7/16-inch wrench, disconnect frame assembly (long white) ground wire and site ground wire from

ground stud located on bottom of main electrical enclosure.

9 Using 9/16-inch wrench, loosen but do not remove two bottom bolts securing main electrical enclosure to

mounting column.

10 While supporting main electrical enclosure and using 9/16-inch wrench, remove two bolts, four flat washers,

two lockwashers, and two nuts securing top of main electrical enclosure to mounting column and remove

main electrical enclosure.

INSTALLATION

Tools required:

 9/16-inch wrench

 7/16-inch wrench

 Large flat-tipped screwdriver

 No. 1 Phillips screwdriver

 Large adjustable wrench

 Small flat-tipped screwdriver

Death orsevere injurymay result if power is notremoved fromsensor priorto maintenance

activities. Ensure that circuit breakers (located in DCP) supplying electronics and heater

power to sensor are set to the off (right )position

1 Inside DCP equipment cabinet, ensure that electronics and heater circuit breakers on present weather

sensor circuit breaker module are set to off (right) position
S100 ASOS Site Technical Manual

7-49 (7-50 blank)

Table 7.5.14. Main Electrical Enclosure Removal and Installation - CONT

Step Procedure

2 Position main electrical enclosure on two mounting bolts located in channel of mounting column.

3 Using 9/16-inch wrench, install two bolts, four flat washers, two lockwashers, and two nuts securing main

electrical enclosure to mounting column. Tighten two mounting bolts located on bottom of main electrical

enclosure.

4 Connect frame cable connectors P4 and P5 to connectors J4 and J5 on main electrical enclosure.

5 Using 7/16-inch wrench, connect frame assembly (long white) ground wire and site ground wire to ground

stud located on bottom of main electrical enclosure.

6 Using large flat-tipped screwdriver, open main electrical enclosure access door.

7 Using No. 1 Phillips screwdriver, remove four screws and lockwashers securing access cover to ac junction

box. Remove cover.

8 Route ac power wiring and fiberoptic cables through access hole in bottom of main electrical enclosure into

ac junction box.

9 Using large adjustable wrench and hardware supplied, connect flexible conduit to main electrical enclosure.

10 Using small flat-tipped screwdriver, connect ac power wiring to terminal board in ac junction box according

to the following connection chart:

Wire color Terminal Function

Black TB1-1 120 vac (electronics)

White TB1-2 Neutral (electronics)

Green TB1-3 Chassis ground

Red TB1-4 120 vac (heater)

Yellow TB1-5 Neutral (heaters)

11 Remove protective plastic covers from fiberoptic cable connectors underneath fiberoptic module and from

fiberoptic cables.

12 Connect RX connector on fiberoptic cable to RX connector on fiberoptic module. Connect TX connector on

fiberoptic cable to remaining connector on fiberoptic module.

13 Using No. 1 Phillips screwdriver, install four screws and lockwashers securing access cover to ac junction

box.

14 Calibrate present weather sensor in accordance with table 7.5.2.
S100 ASOS Site Technical Manual

Change 1 8-1

CHAPTER 8

PRESSURE SENSOR

SECTION I. DESCRIPTION AND LEADING PARTICULARS

8.1.1 INTRODUCTION

This chapter describes the operation and maintenance of the ASOS pressure sensor. The ASOS pressure

sensor configuration consists of two or three model 470 digital pressure transducers, manufactured by

Setra Corporation. Each pressure transducer is a highly accurate pressure measurement instrument that

uses advanced microcomputer-based electronics and firmware, resulting in a 0.02% full scale accuracy. 

8.1.2 PHYSICAL DESCRIPTION

Two or three pressure sensors are mounted on the rf/pressure mounting shelf inside the acquisition

control unit (ACU) or data collection package (DCP) as shown in figures 8.1.1 and 8.1.2. Refer to $

Chapter 14 for the position of pressure sensors in the Single Cabinet ASOS (SCA). The Class II ASOS

system contains three pressure sensors. The Class I system typically contains two pressure sensors, but a

third pressure sensor is available as an option. The pressure sensors share a common 3/8-inch tygon

sensor tube for sensing barometric pressure. This configuration ensures reliable reporting of barometric

pressure information. The tygon air tube is routed to the pressure drawer from a pressure port located on

the connector panel. At some sites, the pressure port on the connector panel may be connected to an

outside pressure vent via additional tubing. This outside vent eliminates the barometric pressure effects

of inside environmental factors (such as heating and air-conditioning systems) on the pressure readings.

During normal operation, the ASOS reads the pressure value from each of the sensors and compares the

values to verify the accuracy of the measured data. 

Pressure sensors that are installed in Class I ACU cabinets must be equipped with threshold detectors,

which may be either internal (built into the sensor) or external. A threshold detector ensures that the

pressure sensor resets completely in the event of a dc undervoltage fluctuation (when its power drops

below 4.55 vdc). Threshold detectors are not required on Class II systems because the ACU’s

uninterruptible power supply prevents such fluctuations. Internal threshold detectors were built into

pressure sensors with serial numbers 358495, 358509, and 363914 and above. Internal detectors are

added to all sensors when (and if) the internal circuit boards are replaced during depot repair. In these

cases, a label is applied to the repaired sensor, indicating that an internal detector has been added.

External threshold detectors are installed in Class I systems via FMK #027. The external detector is a

small module that is mounted to the sensor’s DB-9 power connector (J2). The external detector then

becomes part of the pressure sensor and should not be removed (it is not an FRU). As part of the FMK, a

label is placed on the pressure sensor stating: “EXTERNAL THRESHOLD DETECTOR REQUIRED”.

8.1.3 PRESSURE SENSOR CONFIGURATIONS

There are two possible configurations of the pressure sensor: the model 470 (part number 90110-10),

which has an operating temperature range of 55°F to 100°F and the model 470T (part number 90110-20)

which has an extended operating temperature range of 35°F to 150°F. Each sensor configuration has

three possible variations: the sensor with no threshold detector, the sensor with an internal threshold

detector, and the sensor with an external threshold detector. 
ASOS Site Technical Manual S100

8-2

Figure 8.1.1. ASOS ACU RF/Pressure Sensor Mounting Shelf
S100 ASOS Site Technical Manual

Change 1 8-3

Figure 8.1.2. ASOS DCP RF/Pressure Sensor Mounting Shelf $
ASOS Site Technical Manual S100

8-4 Change 1

8.1.3.1 Class I System Pressure Sensors. Model 470 pressure sensors that are installed in Class I ACU

cabinets must be equipped with threshold detectors, which may be either internal (built into the sensor)

or external. A threshold detector ensures that the pressure sensor resets completely in the event of a dc

power undervoltage condition. Internal threshold detectors were built into pressure sensors with serial

numbers 358495, 358509, and 363914 and above. Internal threshold detectors are being added to sensors

when they are returned to the depot for repair. External threshold detectors were installed on Class I

systems via FMK #027. The external detector is a small module that is mounted to the sensor's DB-9

power connector (J2). The external threshold detector then becomes part of the pressure sensor and

should not be removed (it is not an FRU). As part of the FMK, a label is placed on the pressure sensor

stating "EXTERNAL THRESHOLD DETECTOR REQUIRED". 

8.1.3.2 Class II System Pressure Sensors. Model 470 pressure sensors that are installed in Class II

systems do not require threshold detectors because the uninterruptible power supply in the ACU prevents

dc power undervoltage fluctuations. Model 470 pressure sensors with threshold detectors can be installed

in Class II systems.

8.1.3.3 Model 470T Extended Range Pressure Sensor. The extended range of the model 470T allows

it to be installed in the data collection package (DCP), SCA, or in other locations exposed to temperature

extremes. The Model 470T has three possible variations as well (no threshold detector, internal threshold

detector, and external threshold detector). If an external threshold detector is required in a particular

application, the pressure sensor must be labeled "EXTERNAL THRESHOLD DETECTOR

REQUIRED". Once an external threshold detector is installed, it becomes a permanent part of the 470T

pressure sensor (it is not an FRU). The 470T can be installed in Class I and Class II systems. The 470T is

the replacement unit of choice if a pressure sensor should fail. There are special applications that require

the pressure sensors be installed in the DCP; the 470T pressure sensor must be used in these cases. 

8.1.3.4 Single Cabinet ASOS Pressure Sensor. Refer to Chapter 14 for a description of pressure

sensors installed in the SCA.

$ 8.1.3.5 Data Collection Package Pressure Sensor. Refer to Chapter 3 for a description of pressure

$ sensors installed at special application DCP sites.
S100 ASOS Site Technical Manual

Change 1 8-5/(8-6) blank)

SECTION II. INSTALLATION

8.2.1 INTRODUCTION

The ASOS pressure sensor is installed in the acquisition control unit (ACU), data collection package $

(DCP), or in the Single Cabinet ASOS (SCA) at the factory. Thus, there are no user installation $

procedures required. The procedures for removal and installation of an individual pressure transducer are

provided as part of the maintenance procedures contained in Section V. 
S100 ASOS Site Technical Manual

Change 1 8-7/(8-8) blank)

SECTION III. OPERATION

8.3.1 INTRODUCTION

The ASOS pressure sensor is an automatic sensor without controls or indicators. The ASOS acquisition $

control unit (ACU), data collection package (at special application sites), or Single Cabinet ASOS (at $

single cabinet sites) processor reads each of the pressure transducers to obtain barometric pressure data. $

This function is performed automatically by the ASOS software and requires no operator intervention.

The barometric pressure data displayed and reported by the ASOS are described in the ASOS Ready

Reference Guide. 

8.3.2 TURN-ON PROCEDURES

The ASOS pressure sensor is designed for continuous operation and normally remains powered on at all

times. There are no power control switches on the pressure transducers. All power is provided by the

ACU's dc power supplies (or Single Cabinet ASOS dc power supplies at single cabinet sites). 

8.3.3 TURNOFF PROCEDURES

The ASOS pressure sensor is normally turned off only for maintenance purposes. Power is removed from

the pressure transducers either by turning off cabinet power or by unplugging the pressure sensor power

connector (J2). The pressure sensor should only be turned off for removal and installation of a faulty

pressure sensor. These procedures are included in the maintenance procedures provided in Section V. 

8.3.4 NORMAL OPERATION

During normal operation, each of the pressure transducers is polled every 10 seconds by ASOS for

barometric pressure data. The ASOS software checks each of the barometric pressure data reports to

determine accurate barometric pressure data as well as to detect the failure of any one of the pressure

transducers. This processing is automatically performed by the ASOS such that no user actions are

required. The reported barometric pressure data become part of the ASOS weather database that is

reported to the weather observer.
S100 ASOS Site Technical Manual

Change 1 8-9

SECTION IV. THEORY OF OPERATION

8.4.1 INTRODUCTION

This section provides a brief description of how the ASOS pressure sensor functions to sense the ambient

barometric pressure. Each ASOS barometric pressure transducer is considered a field replaceable unit

(FRU); therefore, only a simplified block diagram description is provided in this chapter. This

description is intended to provide basic familiarity with the operation of a pressure transducer and does

not describe the detailed operation of the internal electronics of the pressure sensor. Additional

information on the operation of the pressure sensor within the ACU is provided in Chapter 2, within the $

DCP is provided in Chapter 3, and within the Single Cabinet ASOS (SCA) in Chapter 14. $

8.4.2 SIMPLIFIED BLOCK DIAGRAM DESCRIPTION

The ASOS pressure sensor is actually a configuration of separate barometric pressure sensing devices. A

simplified block diagram of the ASOS pressure sensor configuration is provided on figure 8.4.1. The

ambient barometric pressure is input to each pressure transducer through a shared tygon sensor tube. This

ensures that each pressure transducer receives the same barometric pressure input level. A transducer

assembly internal to each unit converts the pressure level into an electrical signal level. This level is then

monitored and translated by a microprocessor-based circuit within the pressure sensor to produce a

barometric pressure value. Each pressure transducer is polled individually by the central processing unit

(CPU) and sends its calculated barometric pressure value in a data transfer over an RS-232 interface.

This same RS-232 interface provides the means for the CPU to send and receive other commands and

data to/from the pressure sensor. Each of the pressure transducers receives its electrical power supply

from the power distribution circuit. 

As previously described, pressure sensors installed on Class I systems must be equipped with

undervoltage threshold detectors. Where internal detectors are not built into the sensor, an external

detector is mounted to the power connector (J2) of the sensor. The external detector is then considered

part of the sensor itself and should not be removed by the technician. 
ASOS Site Technical Manual S100

8-10 Change 1

PRESSURE SENSOR

ACU 1A6A1

DCP 1A5A3

SCA 1A7A1

(TRANSDUCER 1)

PRESSURE SENSOR

ACU 1A6A1

DCP 1A5A4

SCA 1A7A2

(TRANSDUCER 2)

PRESSURE SENSOR

ACU 1A6A3

DCP 1A5A5

SCA 1A7A3

(TRANSDUCER 3)*

AIR PRESSURE

AIR PRESSURE

AIR PRESSURE

RS-232

INTERFACE

TO/FROM

DATA INPUT/

OUTPUT

FUNCTION

RS-232

INTERFACE TO/FROM

DATA INPUT/

OUTPUT

FUNCTION

FROM AC/DC

POWER

DISTRIBUTION

RS-232

INTERFACE

TO/FROM

DATA INPUT/

OUTPUT

FUNCTION

* INSTALLED ON CLASS II SYSTEMS

** REQUIRED WHEN SENSORS THAT

DO NOT HAVE INTERNAL THRESHOLD

DETECTORS ARE INSTALLED ON

CLASS I SYSTEM

EXTERNAL

THRESHOLD

DETECTORS **

9708401

Figure 8.4.1. ASOS Pressure Sensor Simplified Block Diagram
S100 ASOS Site Technical Manual

Change 1 8-11

SECTION V. MAINTENANCE

8.5.1 INTRODUCTION

This section provides the preventive and corrective maintenance procedures for the ASOS pressure

sensor. Preventive maintenance consists of checking and cleaning the pressure sensor and verifying the

accuracy of pressure sensor data. Corrective maintenance consists of the procedures required to

troubleshoot and fault isolate the pressure sensor. This section also provides the procedures to remove

and install a pressure sensor, to turn on pressure sensor report processing, and to clear pressure sensor

data quality failures. 

8.5.2 PREVENTIVE MAINTENANCE

8.5.2.1 General. A list of the pressure sensor preventive maintenance functions is provided in table

8.5.1. 

Table 8.5.1. Pressure Sensor Preventive Maintenance Schedule

Interval What To Do How To Do It

90 days Clean and inspect pressure sensor.

Check DCP/SCA desiccant. 

Verify accuracy of pressure sensor data. $

Paragraph 8.5.2.2

Paragraph 3.5.2.1, 14.5.2.1 $

Paragraph 8.5.2.3

8.5.2.2 Pressure Sensor Cleaning and Inspection. Pressure sensor accuracy relies on the tygon tubing

from the sensors to the PRESSURE VENT inlets. At some sites, external copper tubing may also be used

to vent the PRESSURE VENT to the outdoor environment. For proper performance, all tubing must be

clear of obstructions and not be crimped or pinched by any other structures. All pressure vent tubing

must be visually inspected to ensure that there is no foreign matter in the tube and that the tube is not

pinched or cut. Any damaged tubing must be replaced. The DCP and SCA use desiccant dryers. Refer to $

paragraphs 3.5.2.1 and 14.5.2.1 respectively for desiccant dryer information. The drawer should also be $

cleaned to remove any dirt or dust that may be present. 

8.5.2.3 Verifying Accuracy of Pressure Sensor Data. A technician must verify the accuracy of data

from the pressure sensors as follows: 

a. Every 90 days $

b. Whenever pressure sensor report processing has been turned off (paragraph 8.5.5) 

c. Whenever a pressure sensor data quality failure has occurred (paragraph 8.5.6) 

d. After performing pressure sensor corrective maintenance (troubleshooting, replacing a

pressure sensor, etc) 

Pressure sensor data are verified by comparing pressure sensor output data (as shown on the sensor status

page at the OID) against a calibrated portable pressure standard. Table 8.5.2 provides procedures to

verify output data from the pressure sensors. 

8.5.2.3.1 Use of the Portable Pressure Standard. The portable pressure standard used with ASOS is

Paroscientific model 760-16B, part number 1107-101. This portable pressure standard incorporates a

6-volt, 3 ampere-hour sealed lead acid battery for portable operation. Some characteristics of the battery

circuit and operation of the portable pressure standard are listed below. 
ASOS Site Technical Manual S100

8-12

a. A nominal charge for the battery is 6.3 to 6.7 volts. 

b. The expected life of the battery is 100 hours between charges. 

CAUTION

The portable pressure standard must not be used when a

low battery indication is given. Readings may continue

to be taken if the portable pressure standard is plugged

into an ac power outlet. The battery will also be charged

during this period. 

c. A low battery voltage (i.e., 5.1 volts) is indicated by decimals being placed after each

numeric digit being displayed. 

(1) Example of a good reading: 14.4567 psi 

 (2) Example of a low voltage display reading: 1.4.4.5.6.7 

d. The model 760-16B portable pressure standard charges at a controlled rate up to 180

mA. A partially discharged battery (5.1-volt low battery) takes approximately 6 to 8

hours to become fully charged. 

e. A fully discharged battery (0 to 3 volts) may not necessarily recover when charged. In

this case, the LCD display shows a series of dashes. If the battery does not accept a

charge, the portable pressure standard is to be returned to the pressure laboratory at the

address listed below: 

National Weather Service 

1325 East/West Highway

Silver Spring, MD 20910

RM 2378 Attn: Bernard Morningstar

All units being returned must be shipped Federal Express Overnight. 

f. The charging circuit is on when the portable pressure standard is plugged into an ac

power outlet. The ON/OFF switch does not have to be ON.

g. The LCD power-on sequence with a fully charged battery goes through a stage where all

LCD segments are ON (8.8:8.8:8.8), then OFF -----, then the pressure reading is

displayed. 

h. The front panel ZERO SET switch is actually a mathematical TARE switch. This means

that a software zero will be set for the portable pressure standard. When switched ON, it

reads the pressure displayed and subtracts that amount from subsequent measurements.

The display then indicates the difference from the original value. When the ZERO SET

switch is switched OFF, this function is disabled. For use with ASOS, the ZERO SET

switch must be left in the OFF position before turning the standard on. 
S100 ASOS Site Technical Manual

Change 1 8-13

8.5.3 CORRECTIVE MAINTENANCE

8.5.3.1 Introduction. Corrective maintenance consists of fault isolation and removal and replacement of

faulty pressure sensors. The pressure sensors are considered critical reporting items. For this reason,

corrective maintenance for a pressure sensor typically generates a data quality failure, which essentially

takes the sensor off-line. The system WILL NOT automatically clear the data quality failure following

the maintenance action. The technician MUST use a portable pressure standard to verify the accuracy of

pressure sensor data (paragraph 8.5.2.3), then manually clear the data quality failure (paragraph 8.5.6)

before the system will place the sensor back on-line.

8.5.3.2 Troubleshooting. Troubleshooting the pressure sensors consists of isolating faults to a particular

pressure sensor, the internal plastic (and, at some sites, external copper) sensor tubing, power to the

sensor, or the serial input/output (SIO) interfaces to the sensors. The pressure sensor maintenance page

(Chapter 1, Section III) indicates when the corresponding sensor fails the sensor response check and the

system data quality check. A sensor response failure indicates a pressure sensor power failure or an SIO

interface failure. The ac/dc power distribution description in Chapter 2 (ACU), Chapter 3 (DCP), or $

Chapter 14 for SCA provides pressure sensor power troubleshooting information. The pressure sensor

and SIO descriptions in Chapter 2 (ACU), Chapter 3 (DCP), or Chapter 14 for SCA describe $

troubleshooting pressure sensor SIO interfaces. A data quality failure may indicate that the sensor is

reporting data that are out of tolerance with the other pressure sensors in the system (paragraph 8.5.6)

and should therefore be replaced. 

Table 8.5.2. Verifying Accuracy of Pressure Sensor Data

Step Procedure

Tools required:

 Portable pressure standard

CAUTION

The portable pressure standard LCD displaywillfreeze at temperatures below15°F (-10°C). When

using the pressure standard outdoors in a cold climate, ensure that the pressure standard is placed

in a location that will prevent the LCD from freezing.

1 Open portable pressure standard and remove cap from PRESSURE INPUT port. Ensure that ZERO SET

switch is in OFF position. Position pressure standard near cabinet, at same elevation as pressure sensor.

CAUTION

Do not use portable pressure standard on battery power when a low battery indication is

given (decimals or dashes on LCD display). In such cases, pressure standard may be used

if plugged into an ac outlet (standard also recharges during this period).

2 Turn on portable pressure standard. If standard is at room temperature, allow approximately 5 minutes for

portable pressure standard to stabilize. If standard is not at room temperature, allow it to warm up before

proceeding.

3 If PRESSURE VENT on I/O Connector Panel 1A9 (at rear of ACU cabinet) is vented to outside by copper

tubing, perform steps 4 through 6. If PRESSURE VENT is not vented or if sensor is installed in the DCP $

or SCA, proceed to step 7. $

4 At OID, displaysensorstatus page (sequentially press REVIEW-SENSR-STAT function keys from 1-minute

screen).

5 On sensor status page, set report processing for pressure sensors to OFF.

6 Disconnect outside vent tubing from PRESSURE VENT inlet of I/O Control Panel 1A9.

7 At OID, display second page (shows pressure data) of sensor 12-hour set (sequentially press

REVUE-SENSR-12HR-PAGE function keys from 1-minute screen).

8 On 12-hour page, compare most recent reading for pressure sensors 1, 2, and 3 (if applicable) with value

displayed on portable pressure standard.
ASOS Site Technical Manual S100

8-14

Table 8.5.2. Verifying Accuracy of Pressure Sensor Data -CONT

Step Procedure

9 Ensure that all sensor values are within ±0.020 of the value on the portable pressure standard. If individual

sensor is out of tolerance, replace sensor. If all sensors are out of tolerance (by the same amount), inspect

and clear all pressure sensor vent tubing and recheck. If all sensors are still out of tolerance, portable

pressure sensor may be out of calibration.

10 If external copper vent tubing was previously disconnected, connect external tubing to PRESSURE VENT

inlet on I/O Connector Panel 1A9.

11 Turn pressure sensor report processing on in accordance with table 8.5.4.

12 Turn off portable pressure standard, install cap on PRESSURE INPUT port, and install lid.

8.5.4 PRESSURE SENSOR REMOVAL AND INSTALLATION

The replacement of a faulty pressure transducer is easily accomplished using simple handtools. When a

pressure sensor is replaced, the loss of sensor data results in a data quality failure for that sensor. Before

the system places the new sensor on-line, the technician MUST use a portable pressure standard to verify

the accuracy of the new sensor (paragraph 8.5.2.3) and clear the data quality failure (paragraph 8.5.6).

The procedures required to remove and install a pressure sensor are provided in table 8.5.3. 

8.5.5 PRESSURE SENSOR REPORT PROCESSING PROCEDURES

Report processing for the pressure sensors may be turned off in one of two ways: 

a. Like other sensors, report processing for pressure sensors may be turned off (from OID

sensor status page) by an observer, air traffic controller, technician, or system manager. 

b. Unlike other sensors, the system automatically turns off report processing for the

pressure sensors whenever an observer edits the ALTIMETER field on the 1-minute

screen. 

Whenever pressure sensor report processing is off (for either reason), the system assumes that the

pressure data may not be accurate and therefore should not be used. The system then allows only a

technician to turn back on pressure sensor report processing. Before turning pressure sensors report

processing on, the technician MUST use a portable pressure standard to verify that pressure sensors are

providing accurate data (paragraph 8.5.2.3). Table 8.5.4 provides procedures to turn on pressure sensor

report processing.

8.5.6 CLEARING PRESSURE SENSOR DATA QUALITY FAILURES

ASOS software performs the following two data quality checks against the data received by the pressure

sensors. Data quality failures, when they occur, are indicated on the maintenance page for the failing

sensor (Chapter 1, Section III) and on the sensor status page (REVUE-SENSR-STAT). 

a. A data quality failure occurs if the data from one pressure sensor is more than ±0.040

inHg apart from the other(s). In a system with three pressure sensors, the out-of-tolerance

sensor is logged as a data quality failure. In a system with two pressure sensors, it is

impossible to determine which of the two is out of tolerance, so the system logs both as

data quality failures.

b. Each pressure sensor is polled for data once every 10 seconds. If a pressure sensor fails

to respond more than once in a 1-minute period or fails to respond more than twice in a

12-hour period, a data quality failure is logged for that sensor. Because corrective

maintenance tasks such as troubleshooting or replacing a pressure sensor require longer

than 20 seconds, such tasks typically generate data quality failures. 
S100 ASOS Site Technical Manual

Change 1 8-15

WARNING

8.5.6.1 Effect of Data Quality Failures on Altimeter Report. If a data quality failure occurs in a

system with only two pressure sensors, the ASOS stops reporting altimeter settings (altimeter goes

missing). In a three-sensor system, a single data quality failure does not interrupt altimeter reporting. The

ASOS continues to report altimeter settings based on the data from the two remaining pressure sensors.

8.5.6.2 Clearing Pressure Sensor Data Quality Failures. For other ASOS sensors (visibility,

ceilometer, etc.), the system automatically clears data quality failures after the sensor reports a sufficient

number of valid data samples. The pressure sensors, because they are critical to aircraft safety, require

the technician to take a positive action to clear the data quality failure and bring the sensor on-line. This

is achieved by deconfiguring and reconfiguring the pressure sensor from the sensor configuration page

(paragraph 1.3.16.2) of the OID. Prior to this action, however, the technician MUST use a portable

pressure standard to verify that the sensor is reporting accurate data (as described in paragraph 8.5.2.3).

Table 8.5.5 provides procedures to clear a pressure sensor data quality failure by deconfiguring and

reconfiguring the sensor.

Table 8.5.3. Pressure Sensor Removal and Installation

Step Procedure

REMOVAL

Tools required:

 Large flat-tipped screwdriver

 Small flat-tipped screwdriver

 No. 2 Phillips screwdriver

Pressure sensors are safety-critical devices. Pressure sensors may output erroneous readings if

damaged or if plastic vent tubing is damaged or obstructed. Throughout this procedure, exercise

caution to avoid damage to pressure sensors and vent tubing.

NOTE

Internal threshold detectors were built into pressure sensors with serial numbers 358495, 358509,

and 363914 and above. Othersensorsmodified with internal detectors are labeled assuch. All other

sensors, when used on Class I systems, require external threshold detectors.

1

NOTE

In the DCP and SCA, the pressure mounting shelf is not secured. Proceed to step 2. $

Using large flat-tipped screwdriver, remove fourscrews, lockwashers, and flat washerssecuring rf/pressure

mounting shelf slide mount to frame.

2 Slide mounting shelf out until slides lock in fully extended position.

3 Locate pressure sensor to be removed.

4 Using small flat-tipped screwdriver, remove power and signal cables from pressure sensor.

5 Disconnect pressure sensor tube from pressure sensor.

6 Using Phillips screwdriver, remove four screws, lockwashers, and flat washers securing pressure sensor to

shelf. Remove pressure sensor.

7 If pressure sensor is equipped with an external threshold detector, disconnect detector fromsensor. Pack and

ship detector in container with sensor.
ASOS Site Technical Manual S100

8-16

WARNING

WARNING

WARNING

Table 8.5.3. Pressure Sensor Removal and Installation -CONT

Step Procedure

INSTALLATION

Tools required:

 Large flat-tipped screwdriver

 No. 2 Phillips screwdriver

 Small flat-tipped screwdriver

Pressure sensors are safety-critical devices. Pressure sensors may output erroneous readings if

damaged or if plastic vent tubing is damaged or obstructed. Throughout this procedure, exercise

caution to avoid damage to pressure sensors and vent tubing. 

NOTE

Internal threshold detectors were built into pressure sensors with serial numbers 358495, 358509,

and 363914 and above. Othersensors modified with internal detectors are labeled assuch. All other

sensors, when used on Class I systems, require external threshold detectors. 

$ In the DCP and SCA, the pressure mounting shelf is not secured. Proceed to step 2.

1 Slide mounting shelf out until slides lock in fully extended position. 

NOTE

If installing pressure sensor on a Class I system, ensure that replacement sensor is

equipped with an undervoltage threshold detector (internal or external). 

If replacement sensor requires an external threshold detector, install detector onto pressure sensor power

connector (J2). 

2 Position pressure sensor over four mounting holesin mounting shelf. Using Phillipsscrewdriver, install four

screws, lockwashers, and flat washers securing pressure sensor to shelf. 

3 Using small flat-tipped screwdriver, install power and signal cables to pressure sensor.

4 Connect pressure sensor tube to pressure sensor.

Pressure sensors may output erroneous valuesif plastic vent tubing binds or crimps when

shelf is closed. Exercise caution when closing shelf to prevent damage to pressure sensor

vent tubing. 

5

$ NOTE

$ In the DCP and SCA, the pressure mounting shelf is not secured. Proceed to step 7.

$

While taking care not to damage or crimp pressure sensor vent tubing, release mounting shelfslide locks and

push mounting shelf back into cabinet. After closing shelf, ensure that pressure tubing is properly connected

to PRESSURE VENT on ACU I/O Panel Assembly 1A9 and is not damaged or crimped.

6 Using large flat-tipped screwdriver, install four screws, lockwashers, and flat washers securing mounting

shelf to frame (ACU only).

7

Accuracy of pressure sensor data is critical to aircraft safety. Technician must verify the

accuracy of pressure sensor data after installing pressure sensor. 

Verify accuracy of data from all pressure sensors in accordance with table 8.5.2. 

8 At OID, display sensorstatus page (sequentially press REVUE-SENSR-STAT function keysfrom 1-minute

screen).

9 Check DATA QUALITY status of pressure sensor just installed. Ifstatusis F (fail), clear data quality failure

in accordance with table 8.5.5. 
S100 ASOS Site Technical Manual

Change 1 8-17

WARNING

WARNING

Table 8.5.4. Turning Pressure Sensor Report Processing On

Step Procedure

Accuracy of pressure sensor data is critical to aircraft safety. Technician must verify the

accuracy of pressure sensor data before turning pressure sensor report processing on. 

1 Verify the accuracy of data from all pressure sensors in accordance with table 8.5.2. 

2 At OID, display sensorstatus page (sequentially press REVUE-SENSR-STAT function keysfrom1-minute

screen). 

3 Using PREV and NEXT keys, move cursor to select one of the pressure sensors. 

4 Press PROC function key. Message SYSTEM MODIFICATIONS flashes at top of screen and system

prompts for technician to enter initials. 

5 Enter two- or three-character initials. After entering initials, RPT PROC field for all pressure sensors

changes to ON and SYSTEM MODIFICATION message is removed. 

 6 Press EXIT to return to 1-minute screen. System begins reporting ALTIMETER data within 1 minute

(provided that at least two pressure sensors have report processing on and pass data quality verification). 

Table 8.5.5. Clearing Pressure Sensor Data Quality Failures

Step Procedure

SENSOR DECONFIGURATION

Accuracy of pressure sensor data is critical to aircraft safety. Technician must verify the

accuracy of pressure sensor data before clearing data quality failure. 

1 Verify accuracy of data from all pressure sensors in accordance with table 8.5.2. 

2 At OID, display sensorstatus page (sequentially press REVUE-SENSR-STAT function keysfrom1-minute

screen). 

3 From sensor status page, determine which pressure sensor (#1, #2, or #3) has data quality failure. 

4 At OID, display sensor configuration page (sequentially press REVUE-SITE-CONFIG-SENSR function

keys from 1-minute screen). 

5 On sensor configuration page, press CHANG key. A cursor is displayed and message SYSTEM

MODIFICATIONS flashes at top of screen. 

6 Using PREV and NEXT keys, move cursor to highlight code (P1, P2, or P3) for pressure sensor with data

quality failure. 

7 To deconfigure sensor, enter two asterisks (**) in place of highlighted sensor code.

8 Press BACK key. Cursor and SYSTEM MODIFICATIONS message are removed from screen. 

9 Press EXIT key to return to 1-minute screen and cause system to accept change. 

SENSOR RECONFIGURATION

1 At OID, again displaysensor configuration page (sequentially press REVUE-SITE-CONFIG-SENSR keys).

2 On sensor configuration page, press CHANG key. Cursor is displayed and message SYSTEM

MODIFICATIONS flashes at top of screen.

3 Using PREV and NEXT keys,move cursorto highlight asterisks(**) entered when sensor was deconfigured.

4 To reconfigure sensor, enter two-character code (P1, P2, or P3) for pressure sensor in place of asterisks.
ASOS Site Technical Manual S100

8-18

Table 8.5.5. Clearing Pressure Sensor Data Quality Failures -CONT

Step Procedure

5 Press BACK key. Cursor and SYSTEM MODIFICATIONS message are removed from screen. 

6 Press EXIT key to return to 1-minute screen and cause system to accept change.

7 Display sensorstatus page (sequentially press REVUE-SENSR-STAT function keysfrom1-minute screen).

Verify that data quality field shows pass status for pressure sensor just reconfigured (within 2 minutes).

8 Press exit to return to 1-minute screen. System begins reporting ALTIMETER data within 4 minutes after

reconfiguring (provided that at least two pressure sensors have report processing on and pass data quality

verification).
This chapter contains certain material which is copyrighted by VAISALA INC. and is reprinted courtesy of VAISALA INC. No person or entity is

authorized to copy or reprint this material without the written consent of: VAISALA INC., 100 Commerce Way, Woburn, MA 01801.

S100 ASOS Site Technical Manual

9-1

CHAPTER 9

CLOUD HEIGHT SENSOR (CEILOMETER)

SECTION I. DESCRIPTION AND LEADING PARTICULARS

9.1.1 INTRODUCTION

The ASOS cloud height sensor, hereinafter referred to as the ceilometer, senses and reports cloud levels in

the atmosphere. The ceilometer is a VAISALA model CT12K that uses invisible laser radiation to detect

cloud levels. The ceilometer basically works by transmitting a pulse of laser light into the atmosphere and

sensing the light return as it is reflected back toward the ceilometer by objects in its path. By timing the

interval between the transmission and reception, the height of particles(such as water droplets or ice crystals

in clouds) above the ceilometeris calculated and reported to the data collection package (DCP). This chapter

provides information on the physical description, installation, operation, theory of operation, and both

preventive and corrective maintenance for the ceilometer.

9.1.2 PHYSICAL DESCRIPTION

9.1.2.1 General Description. The CT12K ceilometer (figure 9.1.1) consists of a single housing assembly

mounted on a support pedestal. The pedestal is high enough to provide clearance in deep snow

accumulations, and is hinged in the middle to facilitate maintenance. (A quick-release pin secures the hinge

plates together.) The cabinet houses the sensor optics and electronics. The equipment cover protects the

equipment cabinet assembly from the environment. The top of the equipment cover provides two window

openings for the ceilometer optics. A window conditioner is mounted on the top of the equipment cover to

protect the windows from dust and precipitation. The warm airflow output by the window conditioner and

two internal heaters warm the entire ceilometer during periods of cold temperatures. The physical and

operational specifications of the ceilometer are provided in table 9.1.1.

9.1.2.2 System Components. The equipment cabinet assembly contains all of the physical system

components of the ceilometer (figure 9.1.2), which are divided into two subassemblies: the optics

subassembly and the electronics subassembly. The optics subassembly, which contains the optics housing

as a frame, consists of a transmitter board, a receiver board, associated optics adjustment hardware, a light

monitor board, transmitter and receiver lenses, a temperature compensation transformer, two temperature

control heaters, and an optional solar shutter. The optics subassembly is mounted on the electronics

subassembly with six screws and is electrically connected using seven separate cables and four attached

connectors. The electronics subassembly uses an equipment base, high voltage power supply housing, and

board frame as its mechanical structure and consists of a high voltage power supply, processor board,

unregulated powersupply board,I/Oconnector board, and fiberopticmodule.An external temperature sensor

(and snow shield, if required) and the four connectors are mounted to the equipment base and connect to the

various internal subassemblies via cables.
This chapter contains certain material which is copyrighted by VAISALA INC. and is reprinted courtesy of VAISALA INC. No person or entity is

authorized to copy or reprint this material without the written consent of: VAISALA INC., 100 Commerce Way, Woburn, MA 01801.

ASOS Site Technical Manual S100

9-2

Figure 9.1.1. Ceilometer (CT12K)
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Table 9.1.1. Ceilometer Specifications

Parameter Specification

PHYSICAL:

Height

Width

Depth

Weight

52.8 in. (with pedestal), 29.1 in. (without pedestal)

22.8 in.

16.5 in.

156 lb (with pedestal), 135 lb (without pedestal)

ELECTRICAL:

AC power 116V ±10%, 45 to 65 Hz, 800 watts (7 amperes) max

TRANSMITTER OPTICS:

Laser source

Diode wavelength

Operating mode

Initial transmitted pulse energy

Peak pulse power

Pulse width @ 50% peak 

Repetition rate

Average power

Maximum irradiance

Laser classification

Laser source dimensions

Transmitter optics focal length

Transmitter effective lens dia

Transmitter beam divergence

Lens transmittance

Window transmittance

Gallium Arsenide (GaAs)

904 nm nominal

Pulsed

6.6 microwatts ±5% (factory-adjusted)

40 watts (typical)

135 nanoseconds (typical)

620 to 1,120 Hz, processor-controlled for constant average power

5 milliwatts

50 microwatts/cm2 measured with 7 mm dia aperture

Class I in compliance with FDA CFR 1040.10 (Subsection e,3)

50 mil sq (1.3 x 1.3 mm)

14.45 inches (367 mm)

4.65 inches (118 mm)

±2.5 mrad maximum

90% typical

97% typical, clean

RECEIVER OPTICS:

Detector

 Responsivity at 904 nm

Surface diameter

 Interference filter

 50% pass band

 Transmissivity @ 904 nm

 Focal length

 Reception lens effective diameter

 Field of view divergence

 Lens transmittance

 Window transmittance

Silicon Avalanche Photodiode

40 A/W (factory adjustment)

0.0314 in. (0.8 mm)

904 nm 

880 to 940 nm typical

85% typical, 60% minimum

5.91 inches (150 mm)

4.65 in. (118 mm)

±2.7 mrad

90% typical

97% typical, clean

OPTICAL SYSTEM:

Lens distance, transmitter - receiver

Laser beam, entering receiver field of view

Laser beam 90% within receiver field of

view

12.2 in. (301 mm)

100 feet (30 meters)

1,000 feet (300 meters)

PERFORMANCE:

Measurement range

Resolution

12,000 ft acquisition time

System bandwidth

Tolerance of precipitation

0 to 12,650 feet

50 feet

30 seconds maximum

10 MHZ at low gain (-3 db), 3 MHZ at high gain (-3 db)

To 0.3 inch (7.5 mm) per hour, range-limited

ENVIRONMENTAL CONDITIONS:

Ambient temperature

Humidity

Salt spray

Wind

Shock

-60 to +120 degrees F (-51 to +49 degrees C)

100% relative humidity

MIL-STD-810C Method 509.1

100 kt (50 m/s)

4 inches (10 cm) drop
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ASOS Site Technical Manual S100

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Figure 9.1.2. Ceilometer System Components (Sheet 1 of 3)
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S100 ASOS Site Technical Manual

9-5

Figure 9.1.2. Ceilometer System Components (Sheet 2)
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Figure 9.1.2. Ceilometer System Components (Sheet 3)
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S100 ASOS Site Technical Manual

9-7/ (9-8 blank)

9.1.2.3 Ceilometer Configurations. Some ceilometers are equipped with a solar shutter assembly on the

transmit side of the ceilometer (figure 9.1.2). Solar shutters are installed on ceilometers used in tropical

regions from 30 degrees North latitude to 30 degrees South latitude. The shutter protects the transmit laser

from damage by direct sunlight. The solar shutter closes over the transmit lens during times when direct

sunlight can enter the lens system. Ceilometers equipped with solar shutters are also equipped with tropical

receiver assemblies. The tropical receiver assembly has a different filter and mounting block than the filter

installed on the standard receiver assembly. The ceilometer is installed in one of four configurations with

each configuration assigned a unique part number. (Refer to the Parts List located after the last chapter in

volume II.)The part numbersidentify the original and refurbished configurations both with and withoutsolar

shutters. Original and refurbished configurations with solar shutters are identical as are original and

refurbished configurations without solar shutters. Table 9.1.2 identifies the different ceilometer

configurations and associated receiver assemblies. Some ceilometers are equipped with a snow radiation

shield (part number 50-20663 Rev. H) covering the ambient air temperature sensor on the bottomof the unit.

The snow shield preventssunlight, reflected by snow, frominadvertently causing heating of the temperature

sensor. The snow shield will require cleaning each Fall, prior to the winter season. See table 9.5.33 for the

snow radiation shield removal and installation procedure.

Table 9.1.2. Ceilometer Configurations

Ceilometer Configuration Part Number RCVR Assy

Nomenclature

Part No.

Original with no solar shutter 62828-90112-10 Standard 62828-90112-4

Original with solar shutter PN 62828-90112-9 62828-90112-20 Tropical 62828-90112-4

Refurbished - no solar shutter 62828-90112-30 Standard 62828-90112-4

Refurbished - with solar shutter PN 62828-90112-9 62828-90112-40 Tropical 62828-90112-4

Refurbished - with solar shutter PN 62828-90112-9

& tropical filter

62828-90112-50 Tropical 62828-90112-11

Refurbished - with solar shutter PN 62828-90112-9

& tropical filter

62828-90112-60 Tropical 62828-90112-11

Ceilometer FMK#073, Rev A, snow shield

installation

50-20663

(CAGEC 65653)
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S100 ASOS Site Technical Manual

9-9

WARNING

WARNING

SECTION II. INSTALLATION

9.2.1 INTRODUCTION

The ceilometer has a modular design which allows for easy installation. The ceilometer is normally shipped

partially assembled in two boxes. The boxes contain the ceilometer, electronics box, mounting column, and

blower assembly. This section provides instructions for installing all of the ceilometer assemblies. The

procedures assume that the support pedestal has been installed.

9.2.2 ASSEMBLY

The ceilometer, electronics box, mounting column, and blower assembly are preassembled units and do not

require any additional assembly prior to installation.

NOTE

If pedestal is equipped with a hinge, leave the hinge closed and pinned during installation.

9.2.3 INSTALLING THE CEILOMETER

The ceilometerisinstalled on the support pedestal using the proceduresin table 9.2.1 and referencing figures

9.2.1 and 9.2.2.

Table 9.2.1. Ceilometer Installation

Step Procedure

1

Tools required:

 5/8-inch socket, flat screwdriver

Death orsevere injurymay result if power is notremoved fromsensor priorto maintenance

activities. Ensure that heater and primary power circuit breakers (located in DCP) are set

to off (right) position.

Inside DCP equipment cabinet, ensure that circuit breakers on ceilometer circuit breaker module are set to

off (right) position.

2 Install four bolts and washers securing mounting column to bottom of ceilometer. If ceilometer is to be

equipped with a snow radiation shield, it should be installed using the procedure in table 9.5.33.

3

Ceilometer is heavy equipment (weighs approximately 150 pounds) and requirestwo-man

or mechanical lift. Failure to comply may result in injury to personnel or damage to

equipment.

Carefully lift mounting column with ceilometer attached and position base over mounting flange of support

pedestal.

4 Orient the receiver side of ceilometer to face away from the sun (in the northern hemisphere, face toward

north and in the southern hemisphere, face toward south).
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ASOS Site Technical Manual S100

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Table 9.2.1. Ceilometer Installation -CONT

Step Procedure

5 Install 5/8-inch hardware securing mounting column to support pedestal flange.

6 Pass free end of site cablesthrough interface conduit hole (figure 9.2.2) on bottom of electronics box and up

through enclosure.

7 Connect site conduit connector to interface conduit hole (figure 9.2.2) on bottom of electronics box.

8 Connect transmit fiberoptic cable to TX connector on fiberoptic modemand connect receive fiberoptic cable

to RX connector on fiberoptic modem (RX connector on module is nearest DB-9 electrical connector).

9 Connect site wiring (TB-1) in electronics box and secure Faraday box cover plate. On high voltage power

supply PS1, set CB1 and CB2 circuit breakers to ON position. On Processor Board A1, set A1S1 to

NORMAL (middle position). On Unregulated Power Supply Board A2, set A2S1 to ON position and A2S2

to NORMAL position.

10 Attach ground wire to ground stud located on bottom of electronics box (figure 9.2.2).

11 Remove any temporary dust coversfromthe optics and carefully install lens cover assembly over ceilometer.

12 Snap latches closed securing lens cover.

13 Carefully install blower assembly and route blower assembly electrical wire down the side to blower

power connector J2 on bottom of ceilometer (figure 9.2.2).

14 Tighten screws securing blower assembly to lens cover.

15 Connect blower ac power cable to blower power connector J2 on ceilometer.

16 At DCP circuit breaker module, apply power to ceilometer.
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Figure 9.2.1. Ceilometer Mounting Diagram
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ASOS Site Technical Manual S100

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Figure 9.2.2. Ceilometer Connections (Bottom)
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S100 ASOS Site Technical Manual

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SECTION III. OPERATION

9.3.1 INTRODUCTION

The normal operation of the ceilometer is fully automatic and requires no operator intervention. The digital

data message sent by the ceilometer to report cloud information is automatically issued as a response to

sensor polling by the data collection package (DCP) at predetermined timed intervals. This data message is

transferred fromthe ceilometerto the DCP and ultimately to the acquisition control unit(ACU) for broadcast

and display.

9.3.2 CONTROLS AND INDICATORS

The ceilometer isintended for continuous operation and normally remains on at all times, with the exception

of maintenance or repair requirements. The digital communicationsinterface with the ceilometer allows the

system to automatically detect and report the majority of possible malfunctions through software displays.

As such, the ceilometer contains only a few controls and indicators which require setting or monitoring by

the technician. These controls and indicators are illustrated on figure 9.3.1 and described in table 9.3.1.

9.3.3 TURN-ON PROCEDURES

The ceilometer is designed for continuous operation and normally remains on at all times, except for

maintenance or repair activities. The turn-on procedures for the ceilometer require that the cover of the

equipment cabinet assembly be removed, power applied, proper operation of the ceilometer verified, power

removed, the cover installed, and power applied. These procedures prohibit the dangers involved with

installing the ceilometer equipment cover with the system powered on. The ceilometer turn-on procedures

are provided in table 9.3.2.

9.3.4 TURNOFF PROCEDURES

The ceilometer is normally turned off only for maintenance purposes using the procedures provided in table

9.3.3. These procedures remove electrical power from the ceilometer equipment to ensure safe disassembly

of the ceilometer and safe removal/replacement of field replaceable units (FRU’s).

9.3.5 NORMAL OPERATION

The ceilometer normally operatesin automatic mode with the polling mode on (PMOD ON), which requires

no operator intervention. A digital message is sent from the ceilometer to the DCP each time that the DCP

pollsthe ceilometer with a SEND command. The content ofthese messages may be viewed on the ceilometer

page of the OID. A description of the OID display is provided in Chapter 1. There are three possible message

outputs from the ceilometer, which are described in the following paragraphs.
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ASOS Site Technical Manual S100

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Figure 9.3.1. Ceilometer Controls and Indicators (Sheet 1 of 4)
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S100 ASOS Site Technical Manual

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Figure 9.3.1. Ceilometer Controls and Indicators (Sheet 2)
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ASOS Site Technical Manual S100

9-16

Figure 9.3.1. Ceilometer Controls and Indicators (Sheet 3)
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Figure 9.3.1. Ceilometer Controls and Indicators (Sheet 4)
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ASOS Site Technical Manual S100

9-18

Table 9.3.1. Ceilometer Controls and Indicators

Control/Indicator Description Normal Condition

PS1 CB1 ON/OFF AC power circuit breaker ON (up)

PS1 CB2 ON/OFF Window conditioner ac power

circuit breaker

ON (up)

PS1 DS1 LINE VOLTAGE AC power indicator On (illuminated)

A1S1 Reset/normal/(spare) switch Normal = middle, Reset = up

A1D4 Processor alarm indicator Normally off (extinguished)

A1D5 Processor OK indicator Blinking once per second

A2S1 HEATING SYSTEM ON

(auto)/OFF

Internal heating switch ON (right)

A2S2 INTERFACE CONTROL

NORMAL/LINE

Switch NORMAL (left)

A5D4 Laser power indicator Illuminates except if optional solar

shutter is on

Table 9.3.2. Ceilometer Turn-On Procedures

Step Procedure

1 Inside DCP equipment cabinet, set circuit breakers on ceilometer circuit breaker module to off (right)

position.

2 At ceilometer, disconnect windowconditioner cable fromconnectorJ2 on the underside of equipment cabinet

assembly.

3 Loosen four knurled screws securing window conditioner to equipment cabinet assembly.

4 Lift window conditioner from equipment cabinet assembly and carefully place assembly on the ground.

5 Unfasten two latches at lower edge of ceilometer equipment cabinet assembly.

6

CAUTION

The glass windows on the cover of the equipment cabinet assembly are specially

manufactured optics. Damage to thesewindows, including scratches and cracks,mayresult

in operational failure of the ceilometer.

Carefully lift cover from equipment cabinet assembly and place cover on the ground.

7 Verify that all interface cables other than the window conditioner powersupply cable are connected properly

to the underside of equipment cabinet assembly.

8 Observe that LINE VOLTAGE indicator PS1 DS1 is extinguished.

9 Set MEASUREMENT EQUIPMENT circuit breaker PS1 CB1 and WINDOW CONDITIONER circuit

breaker PS1 CB2 to OFF position.

10 Inside DCP equipment cabinet,set circuit breakers on ceilometer circuit breaker module to on (left) position.

11 At ceilometer, observe that LINE VOLTAGE indicator PS1 DS1 is illuminated, indicating the application

of ac power.
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Table 9.3.2. Ceilometer Turn-On Procedures -CONT

Step Procedure

12 Set MEASUREMENT EQUIPMENT circuit breaker PS1 CB1 to ON position and observe the following:

a. Processor alarm indicator A1D4 illuminates for approximately 5 seconds, indicating that

a system reset is in progress.

b. After processor alarm indicator A1D4 extinguishes, processor OK indicator A1D5 begins

blinking approximately once each second to indicate that system software is operating.

13 Inside DCP equipment cabinet, set circuit breakers on ceilometer circuit breaker module to off (right)

position.

14 At ceilometer, observe that LINE VOLTAGE indicator PS1 DS1 is extinguished.

15 Set WINDOW CONDITIONER circuit breaker PS1 CB2 to ON position.

16

CAUTION

Glass windows on equipment cabinet assembly cover are specially manufactured optics.

Damage to these windows, including scratches and cracks, may result in ceilometer

operational failure.

Install cover on ceilometer equipment cabinet assembly and secure two latches.

17 Install window conditioner on equipment cabinet assembly and tighten four knurled screws securing window

conditioner.

18 Connect window conditioner cable to connector J2 on the underside of equipment cabinet assembly.

19 Inside DCP equipment cabinet,set circuit breakers on ceilometer circuit breaker module to on (left) position.

Table 9.3.3. Ceilometer Turnoff Procedures

Step Procedure

1 Inside DCP equipment cabinet, set circuit breakers on ceilometer circuit breaker module to off (right)

position.

2 At ceilometer, disconnect windowconditioner cable fromconnectorJ2 on the underside of equipment cabinet

assembly.

3 Loosen four knurled screws securing window conditioner to equipment cabinet assembly.

4 Lift window conditioner from equipment cabinet assembly and carefully place assembly on the ground.

5 Unfasten two latches at lower edge of ceilometer equipment cabinet assembly.

6

CAUTION

Glass windows on equipment cabinet assembly cover are specially manufactured optics.

Damage to these windows, including scratches and cracks, may result in ceilometer

operational failure.

Carefully lift cover from equipment cabinet assembly and place cover on the ground.

7 Observe that LINE VOLTAGE indicator PS1 DS1 is extinguished.

8 Set MEASUREMENT EQUIPMENT circuit breaker PS1 CB1 and WINDOW CONDITIONER circuit

breaker PS1 CB2 to off (right) position.
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9.3.5.1 Startup Message. Upon startup, the ceilometer automatically performs a series of self-tests during

its initialization sequence. The results of these tests and ceilometer operating status are reported in a data

message. A sample startup message is provided on figure 9.3.2.

9.3.5.2 Digital Message No. 2. This message contains the measured cloud return and internal monitoring

data that are the normalsensor output for the ASOS configuration. The message is output every time that the

DCP polls the ceilometer. The same message is output in response to the SEND 2 and MES commands in

maintenance mode. The message consists of 13 lines and is shown on figure 9.3.3.

9.3.5.3 Digital Message No. 3. This message consists of status line 1 (identical to that described for digital

message No. 2) and one single range gate data line indicating the presence or absence of backscatter in the

range gate. This message is output in response to the SEND 3 command in maintenance mode. The message

format is shown on figure 9.3.4.

VAISALA CT12K VERSION 2.46 SN:97023 DATA MEMORY OK

SEQUENCE OK

?

EEPROM OK

CT12K STATUS

00 ///// ///// ///// ///// 0000000010

POWER STATUS

P10D 8.5 P20I 21.1 M201 -20.4 P25V 27.3

M20A -20.6 P20A 19.3 P12M 12.9 P10X 9.8

PXHV 140 P10R 10.1 MRHV -380

SIGNAL STATUS

LLAS 145 LSKY 0 GND 0

TEMPERATURE STATUS

TL 30 TE 18 TI 32 TB 20

HEATER OFF

BLOWER OFF

AUTOMATIC MODE

GAIN 0

LASER FREQUENCY 3

NOTE

All values shown are for sample purposes only. Values for version, serial

number, and parameters may vary from unit to unit.

Figure 9.3.2. Sample Startup Message
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Message format: <status data line 1>

<status data line 2>

<data table line 1>

<data table line 2>

!

!

<data table line 13>

Status Data Line 1 format:

 

NSB_H1H1H1H1H1_T1T1T1T1T1_H2H2H2H2H2_T2T2T2T2T2_S1S2S3S4S5S6S7S8S9S10

 

N =0 No significant backscatter (clear sky)

N =1 One layer detected

N =2 Two layers detected

N =3 Sky is fully obscured but no cloud base can be detected from echo signal received (e.g., fog or precipitation)

N =4 Sky is partially obscured and no cloud base is detected

 

S = 0 No alarm status bits S1...S4 ON for more than 5 minutes

S = 1 At least one alarm status S1...S4 ON for more than 5 minutes

B =_ Space if S = 0

B = 'bel' character if S = 1. Because 'bel' is a nonprinting character, the alarming line appears one character shorter

in a printout than normally.

N = 0 or 4: H1=H2=T1=T2 = ///// (not defined)

 

N = 1 or 2: H1H1H1H1H1= Lowest detected cloud height in 5 digits. Leading zeros not suppressed.

 

T1T1T1T1T1 = Range of backscatter of first layer; ///// if not defined

 

N = 2: H2H2H2H2H2 = Second cloud height; ///// if not defined

 

T2T2T2T2T2 = Range of backscatter of second layer; ///// if not defined

 

N = 3: H1H1H1H1H1 = Calculated vertical visibility

 

T1T1T1T1T1 = Signal range (i.e., height of highest detected backscatter)

STATUS INDICATORS:

S1 = 1: Hardware alarm

S2 = 1: Supply Voltage alarm

S3 = 1: Laser power low

S4 = 1: Temperature alarm

S5 = 1: Solar shutter On

S6 = 1: Blower On

S7 = 1: Heater On

S8 = 0: Unit is feet

1: Unit is meters

S9 = 1: Not used (permanently set to 1)

S10 = 1: Polling Mode on

Figure 9.3.3. Digital Message No. 2 (Sheet 1 of 2)
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ASOS Site Technical Manual S100

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Status Data Line 2 format:

G_F_N.NN_SUM_IIN_LAS_TL.x_OF.FS_XX_PP

G = 0 Gain used is 250

G = 2 Gain used is 930

F = 0 Laser pulse frequency used is 620 Hz (minimum)

!

!

!

F = 7 Laser pulse frequency is 1120 Hz (maximum)

N.NN = Noise RMS voltage is units of ADC increments, computed from the latest 12 s measurement period. One digit,

two decimals.

SUM = Sum of total backscattered power per unitsolid angle (i.e., range and instrument normalization applied). Three

digits, no decimals. Leading zeros replaced by space characters.

IIN = Algorithm related internal processing information. Three digits.

LAS = Measured Laser Power in units of ADC increments (LLAS). Three digits.

TL.x = Internal variable indicating transmitter temperature. Two digits, one decimal; preceded by minus sign

if negative. Degrees Celsius.

OF.FS = Offset of zero signal relative to Data Table minimum (=0), in units of ADC increments. Two digits,

two decimals.

XX = Algorithm related internal processing information. Two digits.

PP = A 2-digit number representing calculated extinction coefficient values of 10 lowest range gates

(0...500 ft). This 2-digit number determines if the obscuration is ground based.

Data Table Line format:

HHD0D1D2D3 .......................D19

Data scaled to hexadecimal number 0...FE (decimal 0...254). Overflow indicated by FF. Leading zero replaced

by space character.

Data values are presented for each 50 ft range gate.

Height offirst value in line in thousands offeet. Two digits; leading zero replaced by space. Twenty 50 ft values

per line starting with 0 ft, next line 1000 ft. 13 lines altogether. Last line (12,000 ft) has 10 values.

Sample Message:

10_04200_00150_/////_/////_0000011010 (Status Data Line 1)

2_3_0.08_36_12_168_23.9_4.56_20_10 (Status Data Line 2)

_0DD...................DD (Data Table Line 1)

_1 !

_2 !

_3 !

_4 !

_5 !

_6 (DATA VALUES) !

_7 !

_8 !

_9 !

10 !

11 !

12DD..............DD (Data Table Line 13)

Figure 9.3.3. Digital Message No. 2 (Sheet 2)
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Message format: <status data line 1>

<backscatter data line>

Status Data Line 1 format:

NSB_H1H1H1H1H1_T1T1T1T1T1_H2H2H2H2H2_T2T2T2T2T2_S1S2S3S4S5S6S7S8S9S10

N = 0 No significant backscatter (clear sky)

N = 1 One layer detected

N = 2 Two layers detected

N = 3 Sky is fully obscured but no cloud base can be detected from echo signal received (e.g., fog or precipitation)

N = 4 Sky is partially obscured and no cloud base is detected

S = 0 No alarm status bits S1...S4 ON for more than 5 minutes

S = 1 At least one alarm status S1...S4 ON for more than 5 minutes

B = _ Space if S = 0

B = 'bel' character if S = 1. Because 'bel' is a nonprinting character, the alarming line appears one character shorter

in a printout than normally.

N = 0 or 4: H1=H2=T1=T2 = ///// (not defined)

N = 1 or 2: H1H1H1H1H1 = The lowest detected cloud height in 5 digits. Leading zeros not suppressed.

T1T1T1T1T1 = Range of backscatter of first layer; ///// if not defined

N = 2: H2H2H2H2H2 = Second cloud height; ///// if not defined

T2T2T2T2T2 = Range of backscatter of second layer; ///// if not defined

N = 3: H1H1H1H1H1 = Calculated vertical visibility

T1T1T1T1T1 = Signal range (i.e., height of highest detected backscatter)

STATUS INDICATORS:

S1 = 1: Hardware alarm

S2 = 1: Supply Voltage alarm

S3 = 1: Laser power low

S4 = 1: Temperature alarm

S5 = 1: Solar shutter On

S6 = 1: Blower On

S7 = 1: Heater On

S8 = 0: Unit is feet

1: Unit is meters

S9 = 1: Not used (permanently set to 1)

S10 = 1: Polling Mode on

Figure 9.3.4. Digital Message No. 3 (Sheet 1 of 2)
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Backscatter Data Line format:

D1D2D3D4..................D64

Dn Where n=1 to 64 is single ASCII-coded hexadecimal character 0...F where each bit of the 4-bit nibble of the

hex character expressed in binary form represents one range gate.

With EMOD ON, range gate bit is 1 if ceilometer determined extinction coefficient at that range gate exceeds

a value corresponding to a horizontal visibility of approximately 10 km (6 miles) except for three lowest range

gates which have higher thresholds.

D1represents the four lowest 50 ft range gates (i.e., 0 ft, 50 ft, 100 ft, 150 ft), D2represents the four next 50 ft

range gates (i.e., 200 ft, 250 ft, 300 ft, 350 ft), etc.

For example:

0 (0000) indicates no detectable backscatter in four adjacent range gates.

F (1111) indicates backscatter in all four range gates.

8 (1000) indicates backscatter in the lowest range gate only.

1 (0001) indicates backscatter in the highest range gate only.

All other characters indicate a gate-by-gate combination of backscatter according to the binary nibble, converted

to hexadecimal.

Sample Message:

10_04200_00150_/////_/////_0000011010 (Status Data Line 1)

0001FFF80000000000007A000.. ..000 (Backscatter Data Line)

Figure 9.3.4. Digital Message No. 3 (Sheet 2)

9.3.6 CEILOMETER DIRECT DIALOGUE COMMANDS

9.3.6.1 Introduction.Themaintenance proceduresforthe ceilometerrely heavily on the sensor's diagnostic

capability. The maintenance technician is provided with the capability to communicate directly with the

ceilometer's microprocessor to issue commands and receive messages. This function is referred to as direct

dialogue mode. Direct dialogue mode can be invoked from the operator interface device (OID) ceilometer

page using the DIALG key select. Fromthis point, the technician can issue commands(ENTERCOMMAND

area) and receive (Direct Dialogue Message Received) messages using the OID. Technicians should be

patient when operating in dialogue mode from an OID. The processing of some commands may take up to

90 seconds. Chapter 1 provides additional information on using direct dialogue mode from the OID. The

technician uses direct dialogue mode to control and monitor the ceilometer locally.

9.3.6.2 Line Open and Line Closed. A single serial data interface is used for both ceilometer measurement

data reports and maintenance communications with the sensor. To distinguish between these two uses, the

interface has two states: 
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LINE CLOSED - Normal operation state. This is the default state upon power up.

Measurement data messages are transmitted automatically when

sensor is in Automatic Mode (paragraph 9.3.6.3). All commands

other than SEND <CR> and OPEN <CR> (to OPEN the line) are

ignored.

LINE OPEN - Direct dialogue mode. Ceilometer accepts and executes all

commands entered at the > prompt.

The following examples show the command syntaxes and ceilometer responses for opening and closing the

line:

Line Opened Line Closed

for Direct Dialogue for Normal Operation

<ENTER> >CLOS

LINE OPENED FOR LINE CLOSED

OPERATOR COMMANDS

(measurement data messages resume)

>(ready for input)

NOTE

In Automatic Mode (paragraph 9.3.6.3), the line automatically closes if no

entries are made within 1 minute.

Line may be opened in the middle of a message; however, the > prompt does not

appear until the current message display is completed.

9.3.6.3 Automatic Mode and Maintenance Mode. There are two basic operating modesto the ceilometer:

Automatic Mode - There are two options under Automatic Mode:

Polling Mode Off (PMOD OFF): A measurement cycle and data message

report is output at specified intervals. Internal monitoring and controls are

updated every 15 seconds. The digital data messages are not displayed if

the line is opened for direct dialogue.

Polling Mode On (PMOD ON): This is the normal operating mode for the

ASOS ceilometer. The measurement cycles and internal monitoring

function normally. Data outputs only occur when a SEND command is

received by the sensor (from the DCP).

Maintenance Mode - Used for checking sensor operation. Measurement cycles are halted.

Internal settings and controls may be operated and checked using specific

commands.
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The following examples show the command syntaxes and ceilometer responses for invoking the ceilometer

operating mode:

To Invoke Maintenance Mode To Invoke Automatic Mode

>AUTO OFF >AUTO ON

WAIT FOR SEQUENCE STOP AUTOMATIC MODE

MAINTENANCE MODE >(ready for next input)

>(ready for next input)

NOTE

The current measurement cycle is completed before switching to

Maintenance Mode. The mode selected remains in effect over a sensor

power down or restart.

9.3.6.4 Command Descriptions. The following paragraphs describe each of the commands available to

themaintenance technician for use in direct dialogue with the ceilometer. Each command is briefly described,

although only a few are of practical use to the maintenance technician due to the ASOS configuration. The

use of these commands for troubleshooting and maintenance purposes is provided specifically in the

maintenance section of this chapter.

9.3.6.4.1 AUTO (ON/OFF). This command is used to define the operating mode of the ceilometer.

Automatic mode is the normal operating mode and is automatically selected by the ASOS system software

during normal operation. The maintenance technician can also select this mode by entering AUTO ON. As

previously described (paragraph 9.3.6.3), the polling mode option can be either on or off while the sensor

is in automatic mode. For the ceilometer to operate with ASOS, the polling mode option must be set to on

using the PMOD command (paragraph 9.3.6.4.2). AUTO OFF is used to select the maintenance mode of

operation for the ceilometer. This mode allows the technician to perform sensor checks and operations

manually. During maintenance mode, the normal measurement cycle is halted and no measurement reports

are generated. The maintenance mode also doubles as the standby mode so that the ceilometer halts

operations until further commands are entered.

9.3.6.4.2 PMOD (ON/OFF). This command allows the technician to turn polled mode on and off. The

polled mode option is a subset of Automatic Mode (paragraph 9.3.6.3). For ASOS operation, polled mode

must be set to on. In this case, the ceilometer outputs data only in response to SEND command requests

(polls) from the DCP. When polled mode is turned off, the ceilometer automatically outputs data at regular

intervals.

9.3.6.4.3 STA. This command allowsthe technician to request a statusreportfromthe ceilometer and is used

to obtain more detailed information from the ceilometer when an alarm is reported at the ceilometer OID

display. The status data display reports the monitored voltage levels, signal and temperature levels, heater

and blower status, operating mode, receiver gain, and laser pulse repetition frequency. An asterisk (*)

immediately following any value on the status data display indicates an alarm value. A sample of the STA

command display is shown on figure 9.3.5.
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>STA

CT12K STATUS

00 ///// ///// ///// ///// 0000000010

POWER STATUS

P10D 8.5 P20I 21.5 M20I -20.7 P25V 27.9

M20A -20.9 P20A 19.3 P12M 13.1 P10X 9.9

PXHV 140 P10R 10.2 MRHV -382

SIGNAL STATUS

LLAS 155 LSKY 1 GND 0

TEMPERATURE STATUS

TL 30 TE 20 TI 34 TB 22

HEATER OFF

BLOWER OFF

AUTOMATIC MODE

GAIN 2

LASER FREQUENCY 3

>(next input)

NOTE

All values shown are for sample purposes only.

Figure 9.3.5. Status (STA) Command Display

9.3.6.4.4 ALIM. This command allows the technician to request the alarm limit message. Alarms are

generated by comparingmeasured values against the alarmlimit values. Voltage levels produce alarms when

the measured voltage is below the alarm limit voltage value. Temperatures (in degrees Celsius) produce

alarms when the measured value exceeds the limit value. The laser power level is in units of the

analog-to-digital (A/D) converter circuit and produces an alarm when the measured value is less than the

limit value. The sky light power level is of no practical significance and is allowed to be the full range of 0

through 255. The electrical ground reference is measured for self-test purposes and produces an alarm if the

measured value exceeds the alarm limit value. The alarm limit values for all of the displayed values can be

temporarily changed using the ALIM command. ALIM is entered, followed by the alarm limit to change,

followed by the new value. For example, to change the external temperature alarm value to 105 degrees, the

following command is entered: ALIM TE 105. Alarm limits that are changed in this manner are temporary;

they are not retained by the system. Limits are returned to the default values by resetting the ceilometer or

cycling power to the ceilometer. An example of the ALIM command display is shown on figure 9.3.6.
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>ALIM

ALARM LIMITS

POWER LIMITS

P20I 15.0 P10X 7.5 M20A 15.0 P10R 7.0

MRHV -150 P12M 8.0 P10D 6.0 P25V 20.0

PXHV 52 P20A 15.0 M20I -15.0

SIGNAL LIMITS

LLAS 155 LSKY 255 GND 4

TEMPERATURE LIMITS

TI 100 TE 100 TL 70 TB 80

>ALIM PXHV 54

NEW LIMIT 54.0

>(ready for input)

NOTE

All values shown are for sample purposes only.

Figure 9.3.6. Alarm Limits (ALIM) Command Display

9.3.6.4.5 LASE (ON/OFF). This command controls the laser enable signal to the laser transmitter. This

command is only possible in maintenance mode. LASE OFF disables the laser trigger enable signal, which

prevents the ceilometer from transmitting. LASE ON enables the laser trigger signal to be generated;

however, the SEQ command is also required to provide the timing sequence signals for a transmission. The

command is automatically cleared after eachmeasurement cycle. An example ofthe LASEcommand display

is shown on figure 9.3.7.

>LASE ON

LASER IS ENABLED

>(ready for input)

Figure 9.3.7. Laser Control (LASE) Command Display

9.3.6.4.6 SEQ (ON/OFF). The SEQ command controls the timing sequence generator circuit of the

ceilometer. This command is only possible in maintenance mode. SEQ OFF disablesthe sequence generator

and thereby halts the transmit and receive cycles. SEQ ON enables the sequence generator to produce the

required timing signals; however, transmission cycles also require theLASEcommand to output laser pulses.

The command is automatically cleared after each measurement cycle. An example use of the SEQ command

display is shown on figure 9.3.8.

>SEQ ON

SEQ ON

>(ready for input)

Figure 9.3.8. Sequence Control (SEQ) Command Display

9.3.6.4.7 FREQ. This command is used to check and specify the pulse repetition frequency for the laser

pulse transmissions. The command may only be used in maintenance mode. The frequency is selected by
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entering a number (from 0 to 7) after the FREQ command. Entering the command alone allows the current

frequency to be displayed. An example of the FREQ command display is shown on figure 9.3.9.

>FREQ

LASER FREQ COUNT 2

>FREQ 5

LASER FREQ COUNT 5

>(next input)

NOTE

The allowable values for selecting the ceilometer nominal frequencies are:

Frequency

 Number (in Hz)

0 620

1 660

2 710

3 770

4 830

5 910

6 1000

7 1120

Figure 9.3.9. Frequency Control (FREQ) Command Display

9.3.6.4.8 GAIN (0/2). This command specifies the gain of the receiver measurement amplifier. GAIN 0

specifies a gain of 250; GAIN 2 specifies a gain of 930. When the GAIN command alone is entered, the

present gain (0 or 2) is returned. This command is only available in maintenance mode. An example of the

GAIN command display is shown on figure 9.3.10.

>GAIN

GAIN SELECT

0

>GAIN 2

GAIN SELECT

2

>(ready for input)

Figure 9.3.10. Receiver Gain Control (GAIN) Command Display
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9.3.6.4.9 HEAT (ON/OFF). This command allows the technician to interrogate and control the operation

of the window conditioner heater. When the HEAT command alone is entered, the present status (heater on

or heater off) of the window conditioner isreturned. The HEAT OFF command forces the heater off; HEAT

ON forces the heater on. The HEAT ON command, however, only functions if the window conditioner

blower is on. An example of the HEAT command display is shown on figure 9.3.11.

>HEAT

HEATER OFF

>HEAT ON

HEATER ON

>(ready for input)

Figure 9.3.11. Heater Control (HEAT) Command Display

9.3.6.4.10 BLOW (ON/OFF). This command allowsthe technician to interrogate and control the operation

of the window conditioner blower. When the BLOW command alone is entered, the present status (blower

on or blower off) of the window conditioner is returned. The BLOW OFF command forces the blower unit

off; BLOW ON forces the blower on. The BLOW OFF command also disables the window conditioner

heater to protect the sensor from overheating. An example of the BLOW command display is shown on

figure 9.3.12.

>BLOW

BLOWER OFF

>BLOW ON

BLOWER ON

>(ready for input)

Figure 9.3.12. Blower Control (BLOW) Command Display

9.3.6.4.11 SHUT (ON/OFF). This command is used to interrogate and control the optional solar shutter of

the ceilometer. When the SHUT command alone is entered, the present status (shutter on or shutter off) of

the solar shutter is returned. The SHUT OFF command forces the solar shutter open; SHUT ON forces the

shutter closed. If the ceilometer is not equipped with the optional solar shutter, the message NO SHUTTER

is returned. An example of the SHUT command display is shown on figure 9.3.13.
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>SHUT

SHUTTER IS OFF

>SHUT ON

SHUTTER IS ON

>(ready for input)

NOTE

In Automatic Mode, the command is canceled within 15 seconds due to the automatic

operation sequence.

The SHUT OFF cannot cancel an ON state controlled by Light Monitor Board A5.

If ceilometer is not equipped with optional solar shutter, message NO SHUTTER is returned.

Figure 9.3.13. Solar Shutter Control (SHUT) Command Display

9.3.6.4.12 TIME(HH MM SS). This command is used to interrogate and set the ceilometer'sinternal clock.

The time is entered in the following format: HH MM SS

where: HH = Hours (0 to 23)

MM = Minutes (0 to 59)

SS = Seconds (0 to 59)

Spaces are used to separate the number groups, and the seconds group can be omitted. The time counting

starts from zero following a system reset or cycling of power. The clock does not need to be set for the

ceilometer to operate properly.

9.3.6.4.13 DATE (YYYY MM DD). This command is used to interrogate and set the ceilometer's internal

calendar. The date is entered in the following format: YYYY MM DD

where: YYYY = Year (four digits, such as 1990)

MM = Month (1 to 12)

DD = Day (1 to 31)

Spaces are used to separate the number groups. The system automatically accounts for leap years. The date

starts from zero following a system reset or cycling of power. The calendar does not need to be set for the

ceilometer to operate properly.

9.3.6.4.14 RESE. This command allows the technician to reset the ceilometer. The command halts all

operations of the ceilometer and in approximately 5 seconds, initializes the ceilometer to the startup

sequence.
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9.3.6.4.15 CAL (time). This command is used to perform offset calibration for the ceilometer. The offset

calibration is required following the replacement of any parts of the ceilometer. The time field specified is

in seconds, with values from 120 to 240 recommended. The ceilometer performs an automatic calibration

sequence for the time interval, stores the values in electrically erasable programmable read-only memory

(EEPROM), and displays the values. Instructions for using this command are provided in Section V.

9.3.6.4.16 HELP. This command results in a display of the ceilometer command set. The commands TAB,

GRAP, CAL, SERN, and SEND are not listed. Each command is followed by a brief description of its

function. An example of the HELP command display is shown on figure 9.3.14.

>HELP

VAISALA CT 12K VERSION 2.46 SN: 87023

TIME (HH MM(SS))

DATE (YYYY MM DD)

MES AUTOMATIC DATA MESSAGE

PAR DISPLAY PARAMETERS

STA STATUS MESSAGE

CONF SYSTEM CONFIGURATION

CLIM <LIMIT> CLOUD LIMIT

SLIM <LIMIT> SIGNAL LIMIT

DEV SET/DISPLAY DEVICE SCALE

TOTAL <SIGNAL SUM> SET /DISPLAY THE NORMALIZED SIGNAL SUM LIMIT

NSCA SET/DISPLAY NOISE SCALE

SCAL SET/DISPLAY OUTPUT SCALE

LNOR SET/DISPLAY THE LASER POWER NORM

PMOD ON/OFF POLLING MODE

AUTO ON/OFF AUTOMATIC MODE

BAUD <RATE> SET/DISPLAY BAUD RATE (300, 1200, OR 2400)

RESET

LASE ON/OFF LASER ENABLE DISABLE

SEQ ON/OFF SEQUENCE START STOP

MEAS <TIME S> LASER MEASUREMENT

HOFF <HEIGHT> SET/DISPLAY OFFSET VALUE FOR THE MEASURED HEIGHTS

FREQ 0...7 SET/DISPLAY LASER PULSE FREQUENCY

NOIS SAMPLE NOISE DISPLAY

AN 0...17 ANALOG TEST

GAIN SELECT GAIN 0/2

HEAT ON/OFF BLOWER HEATER CONTROL

BLOW ON/OFF BLOWER CONTROL

SHUT ON/OFF SOLAR SHUTTER MANUAL CONTROL

ALIM <ID><VALUE> SET/DISPLAY ALARM LIMITS

RECT RECORDER TEST OUTPUT UNTIL ESC

NOTE

Software version and serial number display may vary from those shown.

Figure 9.3.14. Help Message (HELP) Command Display
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9.3.6.4.17 MEAS (time). This command is used to manually force the ceilometer to take measurement

samplings for the time specified. This command is only available in maintenance mode. The time field is

specified in seconds, with 1 second the default value if none is specified. Upon completion of the

measurement sequence, the raw range gate data values are available in table 0 of the ceilometer. The TAB

command can be referenced for information on this table. An example of the MEAS command display is

shown on figure 9.3.15.

>MEAS 12

BACK SCATTERED POWER

(12 sec. terminal inactivity)

INPUT DATA AV 15.9488

>(ready for input)

NOTE

Values shown are for example purposes only.

Figure 9.3.15. Measurement (MEAS) Command Display

9.3.6.4.18 TAB n (si ci). This command displays the contents of the ceilometer internal data tables. The

value specified in the field n selects the data table as follows:

n Data table

0 Raw data in flash A/D converters

1 Intermediate calculation table

2 Final range and instrument normalized data values

3 Static offset data table

4 Instrument-only normalized data table

The si entry specifies the starting index (range from 0 to 253) that corresponds to the 50-foot range gate

number from which output data start. Zero is the default value if none is specified. The ci entry specifies the

cycling index (1 to 254) that corresponds to the number of range gatesselected for continuous cyclic output.

If not specified, the output is once. When specified, the output cycles continuously until aborted by the ESC

key. The output ofthe table starts with the latest cloud heights and penetration in the formin Digital Message

Status Line 1. Non-cloud obstruction heights are not indicated. Output lines contain the height of the first

sample in the line, followed by five samples. An example of the TAB command display is shown on figure

9.3.16.
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>TAB 3 17 13

LASER PULSE COUNT 10907

///// ///// ///// /////

850 16.0043 16.0010 15.9978 15.9945 15.9913

1100 15.9880 15.9848 15.9815 15.9783 15.9750

1350 15.9745 15.9740 15.9735

///// ///// ///// /////

850 16.0043 16.0010 15.9978 15.9945 15.9913

1100 15.9880 15.9848 15.9815 15.9783 15.9750

1350 15.9745 15.9740 15.9735

///// ///// ///// /////

850 16.0043 16.0010 15.9978 15.9945 15.9913

<ESC>

>(ready for input)

NOTE

All values shown are for sample purposes only.

Figure 9.3.16. Data Tables (TAB) Command Display

9.3.6.4.19 GRAP n (sc si ic). This command produces a semigraphic output of the internal measurement

data. The n field specifies the data table to be graphed (refer to TAB command). The sc field is the scaling

factor that specifies how many horizontal character positions equal the value 1.0000 in the table. If none is

specified, 200 is the default value. The si field is the start index, which is the same as for si for the TAB

command. If si is not specified, 10 (500 feet) is the default value. The ic field is the index counter (from 0

to 254) that specifies how many range gates (50-foot increments) are displayed. If not specified, the output

is to end of range. Output is only once, with no cycling available. Output may be aborted using the ESC key.

The display of range gate data is output one gate per line, starting from the start index. Each line contains

the height points, one per character position, and an asterisk (*) as a mark for the data value of that range

gate. An example of the GRAP command display is shown on figure 9.3.17.

>GRAP 0 100 0 12

 0 .......*

 50 *

100 ..............*

150 *

200 ....*

250 .......*

300 ..............*

350 ..............*

400 ....*

450 ....*

500 .......*

550 .........*

>(ready for input)

NOTE

All values shown are for sample purposes only.

Figure 9.3.17. Graphic Output (GRAP) Command Display
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9.3.6.4.20 MES. This command outputs the data message from the ceilometer. In automatic mode, the

message is that of the last completed measurement. In maintenance mode, a correctly formatted message is

output, but only internal monitoring data are updated. The MEAS command is required to update the

measurement data.

9.3.6.4.21 PAR. This command allows the technician to view the ceilometer system parameters. The

resulting display shows each of the parameters, followed by its command and value. An example of the PAR

command display is shown on figure 9.3.18. The value of any parameter is changed by entering the

corresponding parameter command and the selected value or state. These parameters become stored in

nonvolatile memory in the ceilometer and become the default values used by the system following a reset

or cycling of power. Descriptions and examples for each parameter are provided in table 9.3.4.

>PAR

SYSTEM PARAMETERS

CLOUD LIMIT CLIM 0.1000

SIGNAL LIMIT SLIM 0.2000

DEVICE SCALE DEV 1.2400

NOISE SCALE NSCA 4.5000

OUTPUT SCALE SCAL 100.0000

LASER NORM LNOR 164

TOTAL SIGNAL TOTAL 10.0000

HEIGHT OFFSET HOFF 0

DATA UNIT FT

POLLED MESSAGES, PMOD ON

NOTE

Standard values are shown for example purposes; actual values may vary.

Figure 9.3.18. Parameter (PAR) Command Display

Table 9.3.4. Ceilometer Parameters

Parameter Definition Description

 CLIM Cloud limit

EXAMPLE:

Sets the minimum increase in calculated extinction coefficient in ceilometer specific

units that must be present over a short range for cloud base condition.

>CLIM

CLOUD LIMIT CLIM 0.1600

>CLIM .1

CLOUD LIMIT CLIM 0.1000

SLIM Signal limit

EXAMPLE:

Setsthe minimum in calculated extinction coefficient value in ceilometerspecific units

that must be present in one range gate for cloud base condition.

>SLIM

SIGNAL LIMIT SLIM 0.2600

>SLIM .25

SIGNAL LIMIT SLIM 0.2500
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Table 9.3.4. Ceilometer Parameters -CONT

Parameter Definition Description

 DEV Device scale

EXAMPLE:

Multiplying scaling factor applied to allrange gate values after normalization and prior

to application of cloud detection algorithms and output.

>DEV

DEVICE SCALE DEV 1.20000

>DEV 1

DEVICE SCALE DEV 1.0000

NSCA Noise scale

EXAMPLE:

Multiplying scaling factor which, whenmultiplied with the RMS noise calculated from

the 12-second measurement scan, sets the limit for discriminating between true signal

and noise. Decreasing NSCA increases sensitivity but causes more noise hits.

>NSCA

NOISE SCALE NSCA 2.5000

>NSCA 3

NOISE SCALE NSCA 3.0000

 SCAL Scale

EXAMPLE:

Multiplying scaling factor used to scale the value of PP.

>SCAL

OUTPUT SCALE SCAL 20.0000

>SCAL 10

OUTPUT SCALE SCAL 10.000

LNOR Laser normal

power level

EXAMPLE:

Device specific parameter for 100% nominal laser power, in units of monitor A/D

converter. Measured laser power (LLAS) is compared with this value for laser power

control and measurement normalization.

>LNOR

LASER NORM LNOR 162

>LNOR 164

LASER NORM LNOR 164

TOTA Total signal

sum limit

EXAMPLE:

Limit for determining full, partial, or no obscuration. For every 12-second scan, all

range and equipment normalized range gate backscatter values are added to provide

current signal sum (SUM). If SUM exceeds TOTA, full obscuration is concluded. If

SUM is less than TOTA but greater than 0.4 x TOTA (40% of TOTA), partial

obscuration is concluded. If SUM is less than 0.4 x TOTA, no significant obscuration

is detected.

>TOTA

TOTAL SIGNAL LIMIT 6.00

CURRENT SIGNAL SUM 25.63

>TOTA 5

TOTAL SIGNAL LIMIT 5.00

CURRENT SIGNAL SUM 25.63
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S100 ASOS Site Technical Manual

Table 9.3.4. Ceilometer Parameters -CONT

Parameter Definition Description

9-37

HOFF Height Offset

EXAMPLE:

Parameter for offsetting heights reported when ceilometer is installed considerably

higher (positive value) or lower (negative value) than the desired level of interest (i.e.,

ceilometer is mounted on a rooftop, and the reports are to be in feet above runway

ground level). The HOFF value must be in the same units asthe data output (either feet

or meters).

>HOFF

HEIGHT OFFSET HOFF 0

CONF Configuration

EXAMPLE:

Determines if the output is in feet (F) or meters (M) and indicates whether a solar

shutter is installed (Y) or not (N). This command is interactive; i.e., the operator is

prompted with questions.

>CONF

SELECT UNIT M/F ?F

SHUTTER OPTION Y/N ?N

END OF CONFIGURATION

SEND Send message

EXAMPLE:

Selects the digital signal message data output format (refer to paragraphs 9.3.5.2 and

9.3.5.3).

>SEND

AUTOMATIC MESSAGE: 3

>SEND 2

AUTOMATIC MESSAGE: 2

>SEND 2

AUTOMATIC MESSAGE: 2

AUTO Automatic

mode

EXAMPLE:

Sets the ceilometer operating mode to automatic or maintenance mode (refer to

paragraph 9.3.6.3).

>AUTO

MAINTENANCE MODE

>AUTO ON

AUTOMATIC MODE

PMOD Polled mode

EXAMPLE:

Sets the polled mode (subset of automatic mode) to on or off (refer to paragraph

9.3.6.3). For ASOS operator, polled mode should be ON.

>PMOD ON

POLLED MESSAGES, PMOD ON

>PMOD OFF

AUTOMATIC MESSAGES, PMOD OFF

 SERN Serial No.

EXAMPLE:

Arbitrary serial number option. Only numbers from 0 to 999999 are allowed. Has no

effect on operation.

>SERN

VAISALA CT 12K VERSION 2.44 SN:0

>SERN 87023 NEW

VAISALA CT 12K VERSION 2.44 SN:87023
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9.3.6.4.22 AN (Channel). This command provides a continuous display output of analogmonitored signals.

The value displayed is the A/D converter output and is in the range of 0 to 255. Output is aborted using the

ESC key. If no channel number isspecified, the A/D converter internalself-test channel is displayed (normal

value is 125 to 131). The channel number specifies which analog signal is monitored and displayed as

follows:

Channel Signal Normal value

 0 P20I 192 ±32

 1 P20A 179 ±32

 2 P25V 172 ±27

 3 P10D 131 ±33

 4 P10R 155 ±33

 5 P10X 155 ±33

 6 P12M 196 ±41

 7 PXHV* 82 ±20

 8 LLAS 77 to 230

 9 LSKY 0 to 255

 10 TE* 152 ±3

 11 TB* 152 ±3

 12 TI* 152 ±3

 13 TL* 152 ±3

 14 M20I 184 ±32

 15 MRHV* 158 ±41

 16 M20A 184 ±32

 17 GND 0 to 1

* These voltages are temperature dependent and may vary from the given ranges depending

on the installation temperature.

9.3.6.4.23 NOIS. This command provides a continuous output of the highest, average, and lowest receiver

data measurementsample recorded after the final phase of the last completed scan. This givesthe light noise

levels detected by the receiver. The data displayed are in units of the A/D converter. Data updates are

instantaneous in maintenance mode, and once every 12 seconds in automatic mode. The message output is

terminated by the escape key <ESC>. An example of the NOIS command display is shown on figure 9.3.19.

>NOIS

NOISE MEASUREMENT

19 16 13

19 16 13

19 16 13

!

!

!

<ESC>

>(ready for input)

Figure 9.3.19. Noise (NOIS) Command Display
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SECTION IV. THEORY OF OPERATION

9.4.1 INTRODUCTION

This section provides a detailed explanation of how the CT12K ceilometer functions to detect clouds,

calculate their heights, and report the results. The operating theory is presented on two levels. The first level

describes the principles of operation for the ceilometer and identifies the basic functional areas on a block

diagram level. The second level describes the individual functional areas to a level of detail that enables

isolation of a faulty field replaceable unit (FRU).

9.4.2 SIMPLIFIED BLOCK DIAGRAM DESCRIPTION

The following paragraphs describe the basic operation of the ceilometer and the basic physical principles

used by the ceilometer during operation. A simplified block diagram including the ceilometer components

is also provided to describe the basic system configuration and operation sequences.

9.4.2.1 Principles of Operation. The CT12K ceilometer operating principles are based on measuring the

amount of time it takes a pulse of light to travel from the ceilometer transmitter through the atmosphere,

reflect off a cloud, and return to the ceilometer receiver. By starting a timer when the transmitter outputs a

pulse oflight and stopping the timer when the receiver detectsthe reflected pulse return, the distance traveled

by the pulse (at the speed of light) can be calculated. Because the total distance traveled includes a path from

the transmitter to the cloud and back again, the actual height of the cloud (from the transmitter) is actually

one-half of the total distance. The calculation can be expressed as: h = ct/2

where: h = Height of cloud

c = Speed of light (9.8356 x 108 feet/second)

t = Time from transmission to reception

Example: Cloud return detected 24.4 microseconds (:s) after transmission indicates a cloud at 12,000 ft.

In practical application, particles in the atmosphere reflect and scatter the transmitted light pulse. These

particles (dust, smoke, or water droplets) have a degrading effect on the reception of the light pulse.

However, these effects can also be useful in detecting the presence of fog or precipitation. Therefore, the

signals transmitted and received are related as depicted on figure 9.4.1. The ceilometer compensates for the

attenuation effects on the pulse due to particles in the atmosphere to minimize their influence. The CT12K

ceilometer samples the return signal at a 100-nanosecond rate to cover a time frame of 25.4 :s. As a result,

the ceilometer is able to detect clouds up to a height of 12,500 feet with a 50-foot resolution. This resolution

is considered adequate since visibility within the densest clouds is on the order of 50 feet.

For safety and economic reasons, the laser power used by the ceilometer is so low that components of

ambient light (noise) typically exceed the laser light pulse received at the ceilometer receiver. To overcome

this problem, the ceilometer uses several transmission/reception cycles in its measurements and sums the

results. As a result of this technique, the actual pulse return is strengthened in detection (because it is

relatively constant), while the noise tends to cancel itself out (because it is random in nature). This concept

is illustrated on figure 9.4.2, which shows three separate transmission and reception cycles. Sample 1

provides a relatively clean return, with the majority of the received signal due to the cloud return. Sample

2 provides a noisy return, where the cloud return is virtually indistinguishable from the noise. Sample 3

provides a moderate noise level, where the cloud return is presented amidst the noise. The sum of these three

samples results in a significantly higher return signal level over only one range of time. This distinction in

the sum is produced due to the cloud return component present in each sample as compared to the noise

component, which varied in each sample. Compensationssuch asthis are also applied to the samplesto filter

out returns due to other obstructions in the light pulse path.
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Figure 9.4.1. Ceilometer Laser Transmission/Reception Cycle

Figure 9.4.2. Received Signal Sampling Noise Cancellation
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9.4.2.2 Simplified Block Diagram Description. A simplified block diagram of the CT12K ceilometer is

provided on figure 9.4.3. The operation of the ceilometer is basically performed by seven functional areas:

the measurement circuit, output interfaces, internal temperature control, internal monitoring, power supply

section, window conditioner, and solar shutter option.

9.4.2.2.1 Measurement Circuit. The measurement circuit isthe main operational part ofthe ceilometer and

functionsto actuallymeasure the atmosphere.Themeasurement circuit involvesthe processor, its operational

software, and its memory. The processor begins a measurement cycle by signaling the lasersequence control

to issue a laser trigger pulse. The pulse frequency and duration are also specified. The laser transmitter

executes the trigger signal to force a laser diode to emit a short, high intensity pulse of infrared single-wave

radiation. The laser pulse is focused through the transmitter optics to produce a parallel beam. The laser

power monitor senses the emitted laser pulse as it leaves the enclosure and outputs a voltage signal (back to

the processor)that is proportional to the average power level of the laser. The emitted laser pulse then travels

through the atmosphere and small amounts of the radiation are backscattered by any non-gaseous particles

in the atmosphere. The reflected signals are then detected by the receiver.

The receiver optics are designed to focus the incoming light onto a silicon avalanche photodiode. Because

only the wavelength of the transmitted pulse (904 nanometers (nm)) is needed, a filter built into the receiver

circuit blocks out the majority of the extraneous signals. The photodiode converts the light signals into a

small electrical current. The preamplifier in the receiver circuit converts this current into a larger voltage

signal for easier processing by the system. Data acquisition circuitry in the measurement function contains

another amplifier, an analog to digital (A/D) converter, and a sample accumulator circuit. At the same

moment that the transmitter emits a pulse, the data acquisition circuit is initialized to start sampling the

received light. The received light is converted to an electrical voltage signal by the receiver and sampled by

the A/D converter to produce a digital value. This digital value is then stored in the sample accumulator and

the nextsample is processed. As a result, a digitized sample of incoming light is stored in memory every 100

nanoseconds for 25.4 :s (254 total samples). This represents backscattered returns from 0 to 12,650 feet in

the atmosphere, with each sample resulting from returns 50 feet above the previous return.

As described in the principles of operation, the received light signal is typically buried within noise signals.

The noise effects, due to their random nature, can be overcome by taking multiple samples and summing

them. Hence, the ceilometer emits several pulses to conduct its sampling. Before the second pulse (and all

successive pulses) are transmitted, the digitized sample results from the previous transmission are stored in

a sample summing memory circuit. When the next pulse is transmitted, the received signals are digitized as

before and stored in the sample memory. When all 254 samples are stored, they are added to the contents in

the sample summing memory to accumulate the results. This process continues until the desired number of

pulses (as directed by the processor) have been processed. Typically, the number of samples taken falls into

the number of thousands. For example, 10,000 pulses can be processed and accumulated to provide results

that permitseparation of cloud signal returnsfromnoise. Statistically, thisresultsin providing signal returns

from clouds that are approximately 100 times stronger than the noise level, and thus easily discerned. After

the sampling, digitizing, and summing process, the summing memory contains the raw profile of the

atmosphere. The data are then transferred to the processor memory and the sample accumulator is cleared

to begin the next acquisition cycle.

Before the next acquisition cycle begins, the processor uses the A/D converter to check the average laser

power measured by the laser power monitor during the transmission cycle. Based on the laser power value

measured, the processor calculates a new value for the pulse frequency to adjust the average laser power as

close as possible to the optimum value. Average laser power is thus controlled automatically by adjusting

the pulse repetition rate.In addition, before the next acquisition cycle, the processor checksthe measurement
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ASOS Site Technical Manual S100

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signal and noise levels and selectsthe gain to be used for the next cycle. High gain is desirable, but the active

resolution range of the A/D converter must not be exceeded. The processor then starts a new measurement

cycle and begins to process the raw data just accumulated to construct the cloud data for report to the DCP.

9.4.2.2.2 OutputInterfaces. The CT12K ceilometer provides two different output interfaces. An RS-232C

interface isthe primary interface used on the ceilometerfor both sensorreporting and maintenance purposes.

The ASOS configuration for the ceilometer adds a fiberoptic modem module interfaced to the RS-232C

interface to provide the fiberoptic data link with the DCP.

9.4.2.2.3 Internal Temperature Control. The internal temperature of the ceilometer cabinet is controlled

by two heaters in the cabinet. The two heaters are connected to control circuitry that enables one of three

possible configurations depending on the heating requirements of the cabinet. The temperature controller

monitors the ceilometer internal air temperature and generates a corresponding voltage level. This voltage

level is applied to voltage comparatorsthat are set for reference voltages equal to 32 degrees Fahrenheit (°F)

(0 degrees Celsius (°C)) and 68°F (20°C). The output of the comparators drives relays that apply power to

the heaters. When the air temperature is above 68°F, power is removed from both heaters. When the

temperature is between 32°F and 68°F, the heaters are powered and configured in series, providing

approximately 20 watts of heating power. When the temperature falls below 32°F, the heaters are powered

and configured in parallel, providing approximately 80 watts of heating power. Without heating, the cabinet

internal temperature is typically 10°F to 20°F above the ambient temperature. With full heating, the cabinet

internal temperature is typically 40°F to 60°F above the ambient temperature.

9.4.2.2.4 Internal Monitoring. Internal monitoring consists of the circuitry required to monitor voltage

levels and signals produced by the ceilometer during normal operation. The analog monitoring section

includes a signal selector and an A/D converter. The signal selector is used to select which of the input

voltage signals is applied to the A/D converter. The A/D converter processes the selected analog voltage to

produce a digital data value. This data value is then applied to the processor for analysis to detect

malfunctioning assemblies and components.

9.4.2.2.5 Power Supply Section. The power supply section consists of a high voltage power supply and

an unregulated power supply that provide the unregulated power to all of the electronics assemblies in the

ceilometer. All of the assemblies are provided with local voltage regulators. The temperature control

transformer is used to provide the power required by the cabinet heaters.

9.4.2.2.6 Window Conditioner. The window conditioner consists of a heater and blower that provide warm

airflow across the optics windows of the ceilometer. This airflow keeps the windows clean and dry and

permits optimum performance of the system. A temperature sensor in the window conditioner monitors the

operation of both the heater and the blower and reports to the internal monitoring circuit. For safety

considerations, the heateris provided with a thermostat that isset to remove powerif the temperature reaches

250°F (120°C).
S100 ASOS Site Technical Manual

Figure 9.4.3. Ceilometer, Simplified Block

Diagram 

9-43/( 9-44 blank)
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9.4.2.2.7 Solar Shutter Option. The solar shutter is an optional assembly to the CT12K ceilometer. It is

installed on ceilometers located in the region of 30 degrees North latitude to 30 degrees South latitude to

protect the transmit laser from the effects of direct sunlight. A tropical receiver board (part No.

62828-90112-11) is installed in ceilometers that are equipped with the solar shutter assembly (table 9.1.2).

The tropical receiver board has a different filter and mounting block than the receiver board filter used on

ceilometers without a solar shutter. The solar shutter closes during periods when direct sunlight can enter

the transmitter lens system and when a laser pulse is not being transmitted. The solar shutter assembly

consists of a control solenoid and a flap that are located above the transmitter and a light sensor and

electronics that are installed on the light monitor board. The light sensor and control electronics determine

when the shutter should be shut and activate the solenoid to move the shutter.

9.4.2.2.8 Snow Radiation Shield Option. The snow radiation shield is an optional assembly to the CT12K

ceilometer. It isinstalled on ceilometersthat are susceptible to having their external ambient air temperature

sensorsinadvertently heated by snowreflected solarradiation. The snow radiation shield consists ofstainless

steel plating bent into a rectangular box shape with the short sides left open to allow for airflow into the

resultant enclosure. The snow radiation shield is painted white to reflect solar radiation. Figure 9.1.2 shows

the snow radiation shield in place. Table 9.5.33 contains installation and removal procedures for the snow

radiation shield.

9.4.3 DETAILED BLOCK DIAGRAM DESCRIPTION

9.4.3.1 Introduction. The ceilometer is composed of two basic subsystems: the optics subsystem and the

electronics subsystem. The optics subsystem consists of the windows and lenses required for laser

transmission and light energy reception. The optics subsystem supports several separate, but interrelated,

electronics assemblies. A detailed block diagram of these assemblies is illustrated on figure 9.4.4 and

described in the following paragraphs.

9.4.3.2 Processor Board. Processor Board A1 is the main control circuit for the ceilometer. The processor

board is a microprocessor-based design that performs all of the following functions:

a. Provides software-controlled laser pulse triggering.

b. Buffers and amplifies (software-controlled gain) backscatter reflections sensed by the

receiver board.

c. Samples, converts, and stores amplified echo signals.

d. Processes the stored echo signal data to calculate cloud base levels and other relevant

atmospheric information.

e. Transfers data and commands through the onboard RS-232C serial interface.

f. Monitors unregulated power supply voltages, transmitter and receiver board operating

voltages, laser power level, ambient light level, and operating temperatures throughout the

ceilometer.

g. Controlsthe operation of the window conditioner and the optionalsolarshutter via the light

monitor board.

h. Automatically controls internal heating of the ceilometer.
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The electrical power required by the processor board is derived from dc power inputs provided by the

unregulated power supply board. Voltage regulator circuits on the processor board stabilize these dc power

inputs for use by the processor board electronics. In addition, some of these regulated voltages are output by

the processor board for application to the I/O connector board. Several onboard precision voltage references

are also derived for measurement needs by circuits on the processor board.

The main data processing is performed by the central processing unit(CPU) and itsrelated control logic. The

operating system and programmed instruction set are stored in erasable programmable read-only memory

(EPROM) for use by the CPU. A section of random access memory (RAM) provides the CPU with data

workspace and temporary data storage. OnboardEEPROM is used for nonvolatile data storage for ceilometer

scaling factors and other important parameters.

Through an integral asynchronous communications port, the processor board maintains serial data

communications with the DCP. System timing sequences are also maintained onboard, with a special

watchdog timer provided to force system resets in the event of a temporary processor hangup. Two light

emitting diodes (LED's) on the processor board indicate the operating status of the CPU. A green LED

flashes at an approximate 1-second interval to indicate that the system is operating normally. A red LED

illuminates when the CPU is in a reset condition.

The primary function of the processor board is to initiate laser transmissions, collect the reflected cloud

echoes, and process the received signals to detect and report the presence of clouds. The transmit/receive

cycles of the ceilometer are synchronized by a timing sequencer located on the processor board. The

transmission cycle is started by activating the pulse trigger generator circuit. This circuit outputs a trigger

pulse signal that fires the laser located on the transmitter board. The pulse trigger generator is controlled by

a signal from the CPU and output control latch that allowsthe processor to enable and disable the generation

of laser pulse transmissions.

The echo signal from the receiver board is first amplified and then converted into digital format by an A/D

converter. The conversion processis performed synchronousto transmission cycles and produces a digitized

sample corresponding to every 50 feet above the ceilometer. Each sample is stored in a specific RAM

location dedicated for currentsamples. After all 254 samples(12,650 feet total) have been taken, the samples

are added to the sums of previous cycles. The resulting accumulated values for each 50-foot increment are

then stored in a section ofRAM reserved forsummed samples. Afterthe required number oftransmit/receive

cycles have been completed, the CPU readsthe accumulated sample sums and processesthe data to generate

the cloud report data that are transmitted to the DCP.

The processor board also monitorsthe ceilometer powersupply voltages and other importantsystemsignals.

The checking of these signalsis an integral part of the self-test capability of the ceilometer, which is capable

of detecting and isolating the majority of faults that may occur within the system. The voltages and signals

are monitored by an analog multiplexer and A/D converter circuit. The CPU selects the signal to be

monitored using control lines to the multiplexer. The selected signal is then patched to the input of the A/D

converter where it is digitized. The CPU reads the resulting digitized signal data and processes the data to

determine if within tolerance limits or other suitable parameters. The actual signals monitored by the

processor board are identified and described in the paragraphs for each of the other ceilometer components.
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Figure 9.4.4. Ceilometer Detailed Block

Diagram (Sheet 1 of 6)

9-47/ (9-48 blank)
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Figure 9.4.4. Ceilometer Detailed Block

Diagram (Sheet 2)

9-49/ (9-50 blank)
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Figure 9.4.4. Ceilometer Detailed Block

Diagram (Sheet 3)

9-51/ (9-52 blank)
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Figure 9.4.4. Ceilometer Detailed Block

Diagram (Sheet 4)

9-53/ (9-54 blank)
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Figure 9.4.4. Ceilometer Detailed Block

Diagram (Sheet 5)

9-55/ (9-56 blank)
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Figure 9.4.4. Ceilometer Detailed Block

Diagram (Sheet 6)

9-57/ (9-58 blank)
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The processor board is designed to be easily maintained. In addition to the automatic self-test capability of

the system, test points are provided throughout the board (78 total). Many of these test points allow fault

isolation down to the component level; however, for ASOS applications, only a subset of these test points

is required for isolating faulty field replaceable units (FRU’s). The actual test points are identified as a part

of the corrective maintenance procedures provided in Section V.

9.4.3.3 Transmitter Board. Transmitter Board A7 generates the infrared laser light pulses used by the

ceilometer to detect clouds. The laser pulses output by the transmitter board are focused by the ceilometer

optics for transmission into the atmosphere. Each laser pulse is generated under processor control as a part

of the overall ceilometer operating sequence. The operation of the transmitter board is also monitored for

report back to the processor board.

The transmitter board receives high voltage power from the high voltage power supply and low voltage

power from the unregulated power supply. The low voltage power (+10VX) is used to bias the high power

pulse generator circuits. The high voltage (+260 vdc) power is applied to an on-board high-voltage regulator.

This regulator circuit provides stable high-voltage power for transmitter board circuitry. Both the low- and

high-voltages for the transmitter board are monitored by the processor board for diagnostic purposes. The

low voltage power (+10VX) is monitored by the processor board directly fromthe unregulated powersupply

board. The high-voltage regulator circuit on the transmitter board is monitored using a scaled test signal

(PXHV), which is routed to the processor board via the unregulated power supply board.

The laser light pulses are produced by the infrared laser diode on the transmitter board. When the ceilometer

is to produce a laser pulse, a pulse trigger generator on the processor board outputs a laser trigger pulse to

the transmitter board. This pulse causes the high power pulse generator on the transmitter board to output

a high voltage firing pulse to the infrared laser diode. The firing pulse causes the diode to emit a pulse of

infrared light. The light pulse is then output to the atmosphere via the ceilometer optics.

The operation of the infrared laser diode is affected by temperature. As the temperature of the diode

increases, a greater voltage is required to fire the diode. For this reason, the transmitter board contains a

temperature compensating circuit. A temperature sensor monitors the operating temperature of the laser

diode. This sensor outputs a temperature compensation feedback signal that is applied to the high voltage

regulator circuit, where it adjusts the voltage output by the regulator. This design provides continual

compensation for the temperature of the laser diode to obtain consistent performance. The temperature of

the laser diode is also monitored by the processor board using two laser temperature signals (TL+ and TL-)

provided by the temperature sensor circuit. These signals are routed to the unregulated power supply board,

where they are passed to the processor board. This allows the processor board to detect proper operation of

the laser diode transmitter automatically.

9.4.3.4 Receiver Board. Receiver Board A6 detectsreflections of the transmitted laser pulses. Light energy

from the sky above the ceilometer is focused by the ceilometer optics onto a photodiode located on the

receiver board. The receiver board converts this light energy to an electrical voltage signal for output to the

processor board. The processor board uses this voltage signal to determine the presence and location of

clouds. The operation of the receiver board is also monitored and reported to the processor board. A tropical

receiver board (part No. 62828-90112-11) is installed on ceilometers that are equipped with a solar shutter

and a standard receiver board (part No. 62828-90112-4) is installed on ceilometers without a solar shutter.

The difference between the tropical and standard receiver boards is that the tropical receiver board is

equipped with a type of filter that protects the transmitter optics from the effects of direct sunlight.
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The operation of the receiver board requires both a high voltage power supply and a low voltage power

supply. The low voltage power (+10 vdc) is applied from the unregulated power supply board to the local

voltage regulator on the receiver board. This power source is used to derive the +5 vdc power required by

the receiver board circuitry. A high voltage bias for the photodiode (ranging from -250 to -425 vdc) is

provided by the high voltage power supply in the ceilometer. Both of these power sources are monitored by

the CPU on the processor board. The low voltage power (+10VR) is monitored directly fromthe unregulated

powersupply board. The high voltage power isrouted from the regulated high-voltage powersupply, passed

through the receiving board scaling resistors, unregulated power supply board (MRHV), and is applied to

the processor board. This allows the CPU to detect power supply failures involving the receiver board.

The focused light energy on the receiver photodiode causes the photodiode to generate a low level electrical

current. The more light energy applied to the photodiode, the more electrical current output. This low level

dc current is applied to a preamplifier circuit that produces a corresponding voltage level output to the

processor board. The processor board samples the receiver board output voltage to detect the presence of

cloud reflections resulting from the laser pulse transmissions.

The response of the photodiode on the ceilometer receiver board is highly sensitive to both bias voltage and

temperature. A diode temperature sensor monitors the photodiode level and adjusts the photodiode bias

voltage circuit to compensate for the photodiode operating temperature. As a result, the receiver operates

with constant sensitivity and improved performance.

9.4.3.5 Light Monitor Board. Light Monitor Board A5 is located between the laser transmitter lens and

the instrument cover window. The circuit functions to monitor both the average power level of the laser

transmission pulses as well as the ambient light level of the sky. In addition, the light monitor board is used

to drive the optional solar shutter. All electrical power required by the circuitry is derived from the

unregulated powersupply board. Local voltage regulators on the light monitor board control the powerinput

to provide stable dc supply power.

The average laser power level is detected by a photodiode that is pointed toward the laser transmitter. The

photodiode converts a portion of the laser-radiated light pulses into low-level electrical current pulses, the

peaks of which are passed through Schottky diode D2 and filtered by capacitor C2. D2 blocks the low-level

photovoltage produced by ambient light entering the transmitter optics, but laser light pulses are passed by

D2 and converted to an analog voltage which varies proportionally with pulse intensity, duration, and

repetition rate.

This dc voltage is applied to the noninverting input of differential comparator U1A. Threshold voltage for

U1A is applied by Monitor Gain Adjust potentiometer R6, which also provides offset compensation. The dc

output voltage of differential comparator U1A, which can be measured at TP1, is termed the Laser Power

Signal (LLAS). LLAS isrouted through the unregulated powersupply board for application to the processor

board. The CPU on the processor board monitors the laser power level via an A/D converter. The LLAS

voltage also drives a red LED (D4) located on the light monitor board.

The ambient light level of the sky is processed in a similar manner. Photodiode D3 is pointed skyward to

convert ambient skylight into electrical current, which develops a positive dc voltage level across resistor

R4 and capacitor C3. Voltage follower U1B provides a voltage gain of 1 for the high-impedance photodiode

but a low-impedance output to drive the analog Sky Light (LSKY\) signal line, which is routed to the

processor board, via the unregulated power supply board, for monitoring by the CPU.
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The sky light voltage (LSKY) is also applied to the solar shutter driver circuit on the light monitor board.

This positive voltage level, compared in differential comparator U1D to a threshold level derived from

potentiometer R13, determines whether the solar shutter (if installed) should be closed to protect the laser

transmitter. Normally, R13 is adjusted for 2.0V at TP4, which corresponds to an incident skylight power of

32W/m2. If LSKY exceeds reference voltage level (indicating considerable direct sunlight into the

ceilometer) the solar shutter solenoid will be deactivated to close the shutter and protect transmitter optics.

When the solar shutter solenoid is activated, it opens; conversely, when deactivated, it closes. This design

protects transmitter optics in the event of a malfunction or power loss to the ceilometer.

The processor board also controls activation of the solar shutter in response to the Sky Light (LSKY) signal

from the light monitor board to protect the transmitter against focused skylight from zenith. It uses fail-safe

logic so that the microprocessor can close the shutter when it should be closed but cannot open the shutter

when it should be closed as determined by the sky light monitor circuit on the light monitor board. The

SOLAR SHUTTER ON signal (SSON) is generated by the output control latch on the processor board.

SSON is routed through the unregulated power supply board to the solar shutter driver circuit on the light

monitor board, where it is applied to the base of PNP transistor Q1. When SSON is high (inactive state), Q1

is on to drive PNP Darlington pair Q2 to saturation. Q2 collector current then keeps solar shutter solenoid

K1 energized to hold the shutter open - provided that the skylight monitor circuit is not detecting excessive

ambientskylight.Because SSON signal is active (low), transistor Q1 will be off and the shutter will normally

be closed unlessthe processor opensit by activating SSON; if analog signal LSKY is ofsufficient amplitude

(positive), then the inverting input of differential comparator U1D will cause its output to swing negative,

thereby cutting Darlington pair Q2 off to keep the shutter solenoid deenergized (closed), regardless of the

state of SSON from the processor board. This feature prevents the transmitter optics from being damaged

by focused light during transmission cycles.

9.4.3.6 Window Conditioner. Window Conditioner B1 performs two functionsfor the ceilometer: it keeps

the windows on the ceilometer clear of precipitation and dust and assists in regulating the cabinet

temperature of the ceilometer. The window conditioner is controlled by the processor board via two power

relays in the high voltage power supply.

AC power for the window conditioner is controlled by high voltage power supply circuit breaker CB2 and

relays K1 and K2. The circuit breaker provides current limiting protection for the window conditioner while

also providing a convenient means to manually remove power from the window conditioner. Relays K1 and

K2 control the heater and blower components of the window conditioner, respectively. These relays are

configured such that power cannot be applied to the window conditioner heater unless the blower is on. The

heater assembly in the window conditioner provides 600 watts nominal heating power. The blower housing

is designed to move air over the heater and sweep it across the windows. The combination of warmed,

moving air evaporates moisture from the windows while helping to prevent dust and dirt buildup on the

window surface.

The operation of the window conditioner is controlled by the processor board. As a part of this processing,

the processor board monitors the external air temperature using the external temperature sensor located on

the underside of the ceilometer. The sensed temperature signals (TE+ and TE-) report the air temperature

to the processor board via the unregulated powersupply board. In response to thisinput and other processing

criteria, the processor outputs the WINDOW BLOWER ON signal (BON) and WINDOW HEATER ON

signal(HON). These signals are routed through the unregulated powersupply board and are applied to relays

K1 and K2 in the high voltage power supply. HON and BON energize their respective relays and thereby

connect ac power to the window conditioner heater and blower.
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ASOS Site Technical Manual S100

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The operation of the window conditioner is also monitored by the processor board. A temperature sensor in

the window conditioner provides a voltage signal that is routed from the window conditioner and through

the high voltage power supply and unregulated power supply board and is applied to the processor board

(TB+ and TB-). The processor board monitors this signal to determine the desired operating mode for the

window conditioner, as well asto detect failures of the window conditioner. As an additional precaution, the

window conditioner also contains a safety thermostat. The safety thermostat removes ac power from the

heater in the event of a malfunction that causes an overtemperature condition (256 ±6°F or 124 ±3°C) in the

window conditioner. The processor board receives no direct report of safety thermostat operation.

 The ceilometer operating software continually monitors the external temperature and blower temperature

to switch the window conditioner heater and blower on and off as required. These two data inputs are also

used to determine malfunctions involving the window conditioner. In addition, the software uses time

references to switch the blower on and off by itself during periods when window heating is not necessary.

This keeps the windows free from dust and debris. The heat and airflow are also used to regulate cabinet

temperature conditions. In cold weather (below 14°F or -10°C), the heater and blower are constantly on to

help heat the ceilometer cabinet. In hot weather (above 86°F or 30°C), the heater remains off and the blower

remains on. This helps to combat heating of the ceilometer by solar radiation.

9.4.3.7 High Voltage Power Supply. High voltage power supply PS1 is the ac line power entry point for

the ceilometer. The high voltage power supply performs three basic functions. First, the ac input power is

transformed into low voltage ac power needed to supply the ceilometer electronics. Second, the ac input

power is rectified, filtered, and partially regulated to generate the high power dc voltages required by the

transmitter and receiver boards. Finally, the ac line power is switched and controlled for application to the

ceilometer window conditioner.

The ac line power is input to the ceilometer at connector J1. The power is then routed to the high voltage

powersupply for application to terminalstrip J5, LINE VOLTAGE indicator DS1, and circuit breakers CB1

and CB2. The ac power indicator is wired in front of the circuit breakers to show the presence of ac power

regardless of the state of the circuit breakers. The circuit breakers double as on/off switches and circuit

protectors. The dual pole configuration of the circuit breakers allows the use of a floating or nonspecified

line voltage. Circuit breaker CB2 controlsthe application of ac power for the window conditioner power via

relays K1 and K2. Operation of these relays is described in the operating theory for the window conditioner.

Circuit breaker CB1 controls the application of ac power for the ceilometer electronics. The ac power is

distributed by terminal strip J5, where surge protectors R1 through R3 are located. This power is distributed

to transformers T1 and T2 and to the temperature control transformer via terminal strip J3. Transformer T1

supplies the low voltage ac power to the unregulated power supply board. Transformer T2 provides the ac

power required by the high voltage powersupply board. These ac power lines are current-protected by fuses.

The values of these fuses are critical to the operation of the ceilometer and are noted as such on the detailed

block diagram. 

The high voltage power supply board in the high voltage power supply generates the high voltage dc power

required by the ceilometer transmitter and receiver boards. The transmitter power is derived by full wave

rectifying the ac input voltage. This produces an unregulated dc power level in the range of +260V. The

receiver power is also generated by rectifying the ac input power. The resulting dc power is then partially

regulated and compensated for temperature effects to provide an output dc power source of +250 to +425

vdc.

9.4.3.8 Unregulated Power Supply Board. Unregulated Power SupplyBoard A2 is a centralsupport board

for the ceilometer. The board rectifies and filtersseveral low voltage ac powersourcesfor use by the various

electronics. The board also provides signal routing between the ceilometer component boards and contains

the relays that control ceilometer cabinet heating.
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The unregulated power supply board receives low voltage ac power from the ceilometer high voltage power

supply at connector J10 and from the temperature compensation transformer at connector J3. All of the ac

power inputs are fuse protected, rectified, and filtered. All of the resulting dc voltages are unregulated; line

inputs and load fluctuations cause variations in the actual dc voltages obtained. The dc power is applied to

the other ceilometer electronics where local voltage regulatorsstabilize the power. The dc voltages produced

on the unregulated power supply board are also applied to the processor board where they are monitored as

a part of the automatic testing of the ceilometer.

Ceilometer cabinet temperature is controlled by two relays (K1 and K2) located on the unregulated power

supply board. The relays are controlled by a cabinet temperature sensor circuit located on the processor

board. This circuit monitors the ceilometer internal cabinet temperature and reports the temperature to the

processor via the monitor multiplex A/D conversion circuit. The circuit also generates the heater control

signals required to energize relays K1 and K2 on the unregulated power supply board. These control signals

are generated independently from the processor and are not controllable by software. The relays function to

switch 20 vac power input from temperature compensation transformer T1 to the two cabinet heater

elements. At temperatures above approximately 68°F (20°C), power to both heaters is removed. At cabinet

temperatures between 32°F and 68°F (0°C and 20°C), relay K1 is activated. This connects the two cabinet

heaters in series and provides two 10-watt sources of heat. At cabinet temperatures below 32°F (0°C), relay

K1 is off and relay K2 is activated. This connects the two cabinet heaters in parallel and provides two

40-watt sources of heat. An override switch (S1) is provided on the unregulated power supply board. By

setting the switch to the off position, relays K1 and K2 cannot be activated, and power is removed from the

cabinet heaters. This switch is intended for temporary maintenance activities, and is therefore kept in the on

position for normal operation.

9.4.3.9 Fiberoptic Module. The fiberoptic module added to the ceilometer for the ASOS provides the data

communications link with the DCP. The fiberoptic module is interfaced to connector J4 on the ceilometer,

which is normally reserved for the ceilometer maintenance terminal. For the ASOS, however, the

maintenance terminal is not required for normal operation, which allows connectorJ4 to be available for the

fiberoptic module. The fiberoptic module converts electrical data signals (RS-232 serial data) to light pulse

signals that are transferred to the DCP. The RS-232 interface data transmit signal (TXD) originates on the

processor board and carries the data messages from the ceilometer to the DCP. The signal is routed through

the unregulated power supply board to interface connector J4. Switch S2 on the unregulated power supply

board is normally set to connect the TXD signal to provide the MTXD signal to the fiberoptic module. In

the other position, switch S2 passes the received data signal (IRXD) from the I/O connector board to the

fiberoptic module. The TXD signal is also connected to the I/O connector board. The RS-232 interface data

received signal (MRXD) is input from the fiberoptic module and carries the data messages from the DCP

to the ceilometer. The MRXD signal is routed through the unregulated power supply board and is applied

to the processor board. The MRXD signal is also applied to the I/O connector board.

9.4.3.10 I/O Connector Board. I/O Connector Board A3 is the communications link circuit of the

ceilometer. In the ASOS configuration, the I/O connector board provides the RS-232 interface required for

the fiberoptic module. All data transmissions from the ceilometer originate from the processor board. The

RS-232 serial transmitted data signal (TXD) is routed from the processor board to the I/O connector board

via the unregulated power supply board. The data signal is applied to a standard DB-9 connector for output

to the fiberoptic module. The ceilometer receives data via the same circuitry used for transmitting data. The

data signal isinputfromthe fiberoptic module and applied to the DB-9 connector on the I/O connector board.

The received data signal is output as IRXD and routed through the unregulated power supply board to the

processor board.
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Change 1 9-65

SECTION V. MAINTENANCE

9.5.1 INTRODUCTION

This section provides the preventive and corrective maintenance procedures for the ceilometer. Preventive

maintenance consists ofthose procedures performed on a periodic basisto keep the ASOS operational, which

includes routine cleaning and inspection. Corrective maintenance consists of those procedures required to

isolate a fault in the ceilometer down to the field replaceable unit (FRU) level.

9.5.2 PREVENTIVE MAINTENANCE

9.5.2.1 General. Preventive maintenance for the ceilometer consists of two basic procedures, which are

listed in table 9.5.1. The maintenance log should be updated after each procedure to record any problems or

repairs that were required.

Table 9.5.1. Ceilometer Preventive Maintenance Schedule

Interval What To Do How To Do It

90 days

Routine inspection and cleaning Paragraph 9.5.2.2

Ceilometer cleaning and window conditioner checks Paragraph 9.5.2.3

Semiannually Check ceilometer calibration Paragraph 9.5.2.4

Annually Clean snow radiation shield Paragraph 9.5.2.5

9.5.2.2 Routine Inspection. Routine visual inspection of the ceilometershould be performed every 90 days

or each time the technician visitsthe installation site. Thisinspection consists of checking the ceilometer for

signs of physical damage, wear, mold, mildew, or corrosion.

CAUTION

Mold or mildew can form at base of ceilometer near top of the mounting pole. Examine for

mold or mildew. If present, remove with a putty knife and scrub area with a detergent/water

solution. Treat any rust present in accordance with paragraph 1.5.3.4.

Any debris from insects, animals, or such that may potentially degrade performance should be removed. All

power and signal cabling to the ceilometer should be checked to ensure that it is secure and undamaged.

9.5.2.3 Ceilometer Cleaning and Window Conditioner Checks. Cleaning the ceilometer windows,

blowers, and exhaust screens and checking the operation of the window conditioner are maintenance

procedures vital to optimum ceilometer performance. These procedures are provided in table 9.5.2.

9.5.2.4 Calibration. The calibration of the ceilometer must be checked every 180 days or after replacing

Transmitter Board A7 or Receiver Board A6. Before the sensor can be calibrated, it must be properly

installed and must pass its ASOS diagnostic checks. Table 9.5.3 provides the procedure to check ceilometer

calibration.

9.5.2.5 Clean Snow Radiation Shield. The snow radiation shield must be cleaned annually, in the fall, prior

to the winter season. The snow radiation shield cleaning procedure is contained in table 9.5.4.
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ASOS Site Technical Manual S100

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WARNING

Table 9.5.2. Cleaning and Inspection

Step Procedure

1

Do not look into the ceilometer optics with magnifying glass, binoculars, or any other

magnifying optics. The transmitter emits an invisible infrared laser pulse that can cause

damage to human eyes.

Death orsevere injurymay result if poweris notremoved fromsensor prior to maintenance

activities. Ensure that heater and primary power circuit breakers (located in DCP) are set

to off (right) position.

Inside DCP equipment cabinet, set circuit breakers on ceilometer circuit breaker module to off (right)

position.

2 Visually inspect ceilometer windows for damage (scratches, chips, or cracks) and dirt (film, streaks, or

particles). Replace damaged windows by replacing the ceilometer electronics assembly.

3 Disconnect window conditioner by unplugging the cable from connector J2 located on the underside of the

equipment cabinet assembly.

4 Loosen four knurled screws securing window conditioner to equipment cabinet assembly.

5 Carefully lift window conditioner from equipment cabinet assembly and gently set on the ground. Check that

heater resistance between pins B and C of the window conditioner cable is 22 ±3 ohms. If resistance is not

within tolerance, replace window conditioner assembly.

6 Using soft brush or clean linen cloth, gently dust off all loose particles from windows.

7 Using cleaning alcohol, soak window surfaces, allowing the surface to remain damp for a few minutes.

8

CAUTION

Avoid rubbing window surface to prevent scratching the window.

Gently wipe cleaning alcohol from windows. Turn cloth over and wipe the surface dry.

9 Inspect window conditioner for signs of obvious wear or damage.

10 Check thickness of rubber foam stripslocated on the underside of the heater/blower subassembly base plate.

Replace compressed or worn strips using NWS ASN K220-1B1MP1. Brown burn marksin top of equipment

cover indicates that the rubber foam strips need to be replaced.

11 Remove heater/blower subassembly and inspect for insects or other debris, especially at the blower exhaust

screens. Remove any accumulated foreign material.

12

CAUTION

Be aware of razor-sharp edges on subassembly screens.

Carefully install window conditioner on equipment cabinet assembly and tighten four knurled screws.

13 Connect window conditioner cable to connector J2 on the underside of equipment cabinet assembly.

14 The operation of the blower can be observed by listening to the sound of the blower motor and feeling the

air movement across the surface of the windows.
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Table 9.5.3. Ceilometer Calibration Check Procedure

Step Procedure

Tools required:

 CTX-16 ceilometer calibration kit

 Small flat-tipped screwdriver

 Laptop interface (Y-shaped) cable

 Laptop null cable

 Laptop computer with PROCOMM Plus installed

 Two jumper wires

INITIAL SETUP PROCEDURE

1 Remove ceilometer window conditioner, clean windows, and reinstall window conditioner in accordance

with table 9.5.2.

2

CAUTION

The CTX-16 reflector hood attenuates the ceilometer laser beam and reflects it back to

the receiver. Damage to inside surfaces of hood will alter the transmissivity

characteristics and recalibration may be necessary. Use special care when assembling

or disassembling instrument.

Open CTX-16 calibration kit and remove folded reflector hood. Unfold hood and set it on its edge. 

3

CAUTION

Do not disturb position of hex nuts at ends of two male and two female rods. Hex nuts

at end of four rods are factory adjusted so that after reflector hood is assembled, two top

panels are at a 90-degree angle to each other.

Remove two female rods and two male rods from calibration kit. Do not disturb position of hex nuts on

ends of four rods. Connect one female rod to one male rod at their knurled ends. Repeat to connect second

pair of rods.

4 Insert both ends of one male/female rod assembly through holes on one side of reflector hood. Secure ends

of rod assembly by loosely installing two 3/8-inch wingnutsfromcalibration kit. Repeat to install other rod

assembly on other side of calibration reflector. Tighten all wingnuts.

5 Mount CTX-16 calibration reflector hood on top of ceilometer.

6 Inside DCP equipment cabinet, identify fiberoptic module dedicated to ceilometer. If necessary, perform

the following:

a. Refer to sensor configuration page on OID (sequentially press REVUE-SITECONFG-SENSOR function keys from 1-minute display).

b. Refer to Chapter 3, Section IV to identify corresponding fiberoptic module.

7 Using smallflat-tipped screwdriver, disconnect DB-9 connector from ceilometer fiberoptic module in DCP.

8 Using small flat-tipped screwdriver, install jumper between TB1-1 (on orange terminal block) on

ceilometer fiberoptic module (A1) and TB1-1 on adjacent fiberoptic module. Install second jumper

between terminals TB1-2 of ceilometer fiberoptic modules and adjacent module containing first jumper.

9 Using laptop interface (Y-shaped) cable and laptop null cable, connect RS-232C (COM1) port of laptop

computer to DB-9 connector of ceilometer fiberoptic module.

10 Turn on laptop computer and initialize the PROCOMM Plus program. After program initializes, press any

key to enter terminal mode (blank) screen.
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Table 9.5.3. Ceilometer Calibration Check Procedure - CONT

Step Procedure

11 Using ALT-S command (setup facility), set up the following TERMINAL OPTIONS:

a. Terminal emulation: VT220

b. Duplex: FULL

c. Soft flow control (XON/XOFF): OFF

d. Hard flow control (CTS/RTS): OFF

e. Line wrap: ON

f. Screen scroll: ON

g. CR translation: CR

h. BS translation: NON-DESTRUCTIVE 

I. Break length (milliseconds): 350

j. Enquiry: OFF

k. EGA/VGA true underline: OFF

l. Terminal width: 80

m. ANSI 7 or 8 bit commands: 7 BIT

12 Press ESC key to exit to terminal mode (blank) screen.

13 Using ALT-P command (line/port option), set CURRENT SETTINGS as follows:

a. Baud rate: 2400

b. Parity: NONE

c. Data bits: 7

d. Stop bits: 1

e. Port: COM1

14 Press ESC key to exit to terminal mode (blank) screen.

CALIBRATION PROCEDURE

NOTE

All commands used in this procedure (except SEND) require an open line to ceilometer. Line, when

opened, times out after 30 seconds. Throughout this procedure, it may be necessary to use OPEN

command before issuing other commands.

1 Turn Caps Lock ON. Type OPEN <CR>. Ceilometer responds with LINE OPENED FOR OPERATOR

COMMANDS. Type PAR <CR>. Parameter values are displayed. Verify that the values are as follows:

CLIM 0.1000

SLIM 0.2000

NSCA 4.5000

SCAL 100.0000

TOTAL 10.0000

HOFF 0

DATA UNIT FT

POLLED MESSAGES

If the stored parameter values do not agree with those listed above, enter the above values.

2 Mount CTX-16 calibration reflector. Allow ceilometer to be powered up for at least 10 minutesin automatic

mode so that laser power can stabilize. Perform the following steps as one sequence within 60 secondsso that

laser power does not change significantly during test.

3 Type AUTO OFF <CR> to set ceilometer to maintenance mode.

4 Type GAIN 0 to set ceilometer to Gain 0.

5 Activate measurement cycle in ceilometer by typing MEAS 12 command and using MES command to

observe output. Use commands at least twice to verify that measurement is stable.
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Table 9.5.3. Ceilometer Calibration Check Procedure - CONT

Step Procedure

Change 1 9-69

6 Use the STA command and from output, record values for FREQ and LLAS.

7 Type LNOR <CR>. Ceilometer responds with current laser normal (LNOR) value (e.g., LASER NORM

LNOR 134). Subtract 5 from LNOR value and record LNOR - 5 value (e.g., 134 - 5 = 129).

8 Using FREQ value recorded above, obtain corresponding relative frequency percentage as follows:

 RELATIVE

 FREQ FREQUENCY (%)

0 -0.195

1 -0.143

2 -0.078

3 0.0

4 +0.078

5 +0.182

6 +0.299

7 +0.455

9 Calculate and record adjusted LLAS value by multiplying recorded LLAS value by relative frequency value

obtained above, and subtracting result from original LLAS value. That is:

LLAS (adj) = LLAS - [(relative freq) * LLAS]

For example, if LLAS is 117 at FREQ = 5, then 

LLAS (adj) = 117 - [(.182)(117)] = 117 - 21 = 96

Ifsign of relative frequency value is negative, then negative value sign must be included in calculation (result

is added instead of subtracted).

For example, if LLAS is 117 at FREQ = 2, then

LLAS (adj) = 117 - [(-0.078)(117)] = 117 + 9 = 126

10 Calculate and record percentage difference of operating laser power (LLAS) from nominal (LNOR - 5) by

subtracting LLAS (adj) value from LNOR - 5 value, dividing result by LLAS (adj) value, and multiplying

by 100 to obtain percentage. That is:

PCT DIFF = [((LNOR-5) - LLAS (adj))/LLAS(adj)] * 100

For example, if LNOR = 134, then LNOR - 5 = 129. If LLAS(adj) is 96 as above, then:

PCT DIFF = [((129 - 96)/96] *100 = 0.34 * 100 = 34%
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Table 9.5.3. Ceilometer Calibration Check Procedure - CONT

Step Procedure

9-70 Change 2

11 Type MES <CR>. Ceilometer responds with printout of two statuslinesfollowed by 13 data lines(numbered

0 through 12) in the following format:

30 00050 00050 ///// ///// 0000010011

0 3 0.01 747 7 100 22.0 1.46 10 98

 0D1B61F 2 7 5 5 0 2 2 4 1 0 2 3 2 1 1 2 3

 1 

 2

 3

 4

 5

 6 (DATA PRINTOUT)

 7

 8

 9

10 

11

12 6 6 6 7 7 6 7 7 6 7

12 Using reflector response percentage table supplied with calibration kit, locate first two digits from data line

0 (e.g., D1 above) on list along top of form.

13 Locate second two digits from line 0 (e.g., B6 above) on list along left side of reflector response percentage

table.

14 Record sensitivity (S) value at intersection of top column and left row noted above.

15 Type DEV <CR>. Ceilometer responds with current device scale (DEV) value (e.g., DEVICE SCALE DEV

1.0908). Record displayed DEV value. If DEV value is lost, refer to table 9.5.3a.

16 Calculate and record scaled sensitivity value for ceilometer by multiplying S value obtained from reflector

response percentage table by DEV value obtained above.

For example, if value from table was 71 and DEV was as above:

S (scaled) = (71) * (1.0908) = 77.4

17 Calculate final sensitivity by adding PCT DIFF value (from calibration step 10 above) to S (scaled) value.

That is: 

S (final) = S (scaled) + PCT DIFF

For example:

S (final) = 77.4 + 34 = 111.4

18 Verify that S (final) value is 100 ±15%.

19 If S (final) value is not within tolerance, replace transmitter board and recalibrate. If resulting S (final) value

is still not within tolerance, replace receiver board.

20 Type AUTO ON to return ceilometer to automatic mode.

NOTE

Failure to perform step 20 to return the ceilometer to automatic mode will result in the

ceilometer erroneously reporting the calibration values obtained in this calibration

procedure as cloud data. ASOS will not detect this false condition.
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Table 9.5.3. Ceilometer Calibration Check Procedure - CONT

CALCULATIONS

1 At DOS prompt, type ASOS <CR> to initialize the ASOS calibration program.

2 Enter menu item 4 of the ASOS calibration program.

3 Enter the recorded LLAS, FREQ, and LNOR values when prompted, pressing <CR> after each entry.

4 The program will calculate the adjusted LLAS (LLAS [adj]) and percentage difference (PCT DIFF) and

display them on the next line. Record these values.

5 Enter the recorded LLAS, FREQ, and LNOR values when prompted, pressing <CR> after each entry.

6 Enter the DEV value at the prompt and press <RT>.

7 The program calculates the scaled sensitivity and displays the result on the next line.

8 The program will then calculate and display the final sensitivity and verify that the S (final) value is 100

±15%. If the value is within tolerance, a message will appear stating that the value is within tolerance. If the

value is higher or lower than the tolerance, the program will beep and display a warning message.

TEARDOWN

1 Remove, disassemble, and store reflector hood, hardware, and instructions in calibration kit carrying case.

2 At laptop computer, use ALT-X (exit) command to exit PROCOMM Plus.

3 Turn off laptop computer.

4 Disconnect cables between laptop computer and fiberoptic module.

5 Remove two jumpers between fiberoptic modules.

6 Using small flat-tipped screwdriver, install DB-9 connector to ceilometer fiberoptic module in DCP.

Table 9.5.3a. Device Scale Calculation Procedure

NOTE

 All lenses and windows must be cleaned before starting this procedure.

1 Mount CTX-16 Calibration Reflector hood on top of ceilometer. Allow ceilometer to be powered up for at

least 15 minutes in the Automatic Mode so that Laser Power can stablilize. Perform the following steps as

one sequence within 60 seconds so that the Laser Power does not change significantly during test.

2 Type AUTO OFF <CR> to set ceilometer to enter maintenance mode.

3 Type DEV 1.0000 <CR>.

4 Type GAIN 0 <CR> to set ceilometer Gain

5 Type MEAS 12 to activate measurement cycle.
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ASOS Site Technical Manual S100

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 Table 9.5.3a. Device Scale Calculation Procedure - CONT

6 Type MES <CR>. Ceilometer responds with a printout of status lines followed by 13 data lines

(numbered 0 thru 12) in the following format:

30 0050 0050 //// //// 0000010011

0 3 0.01 747 7100 22.0 1.46 10 98

0D1B61F 2 7 5 5 0 2 2 4 1 0 2 3 2 1 1 2 3

1

2

3

4

5

6

7

8

9

10

11

12 6 6 6 7 7 6 7 7 6 7

7 Using the Reflector Response Percentage Table supplied with the Calibration Kit, locate the first two

digits from the data line 0 (e.g., D1, above and underlined) along TOP of percentage table.

8 Locate second two digits from data line 0 (e.g., B6, above and underlined) along LEFT side of

percentage table.

9 Record SENSITIVITY (S) value at intersection of TOP column and LEFT row.

10 This value is (S) WITH COVERS, record this value.

11 Type AUTO ON >CR< to set ceilometer to automatic mode.

12 Remove CTX-16 Calibration Reflector Hood.

13 Turn DCP ceilometer circuit breakers to OFF.

14 Remove both ceilometer equipment cabinet covers as described in table 9.5.13. Turn DCP ceilometer

circuit breakers to ON.

15 Mount CTX-16 Calibration Reflector Hood on top of ceilometer.

16 Repeat Steps 1 thru 12, this second value is (S) WITHOUT COVERS, record this value.

17 Calculate the DEVICE SCALE factor by dividing (S) WITHOUT COVERS by (S) WITH COVERS.

Example: 105 / 98 = 1.0714 (DEV)

18 Type OPEN <CR>.

19 Type DEV X.XXXX <CR> (X.XXXX is the value in step 17). Record this value for future reference. If

the DEV exceeds 1.2500 the window cover needs to be replaced.

20 Turn DCP ceilometer circuit breakers to OFF.

21 Reinstall ceilometer equipment cabinet covers as described in table 9.5.13.

22 Turn DCP ceilometer circuit breakers to ON.
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Table 9.5.4. Snow Radiation Shield Cleaning Procedure

Step Procedure

1

Tools required:

 Clean clothes

 Portable vacuum cleaner

 3-inch brush 

Remove snow radiation shield from the ceilometer using the procedure in table 9.5.33.

2 Clean bottom of ceilometer and entire snow radiation shield with a damp cloth.

3 Remove dust and debris from external temperature sensor housing using a portable vacuum cleaner and 3-

inch brush.

4 Install snow radiation shield onto ceilometer using the procedure in table 9.5.33.

9.5.3 CORRECTIVE MAINTENANCE

The ceilometer is supported by a set of internal automatic diagnostics that are executed by the ceilometer

processor board and reported in the data messages transferred to the DCP and ultimately reported to the

ACU. These diagnostic messages provide the basis for all corrective maintenance for the ceilometer. If

the operation of the ceilometer is questionable, yet no alarm messages are received, an intermittent fault

or data transfer fault may exist. In either case, the maintenance technician must perform troubleshooting

of the ceilometer to isolate and replace the faulty FRU and return the system to operation.
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9.5.3.1 Fault Symptoms. The symptoms of a fault involving the ceilometer generally fall under one of

the following four categories:

a. Data Message Contains Alarm. This symptom is reported to the operator on the

ceilometer page display at the operator interface device (OID).

b. RS-232C Interface Nonoperational. This symptom is evidenced by loss of reports (data

missing) from the ceilometer, which may be consistent or intermittent.

c. Cloud Detection Missing. This symptom is evidenced by the ceilometer reporting no

clouds present, when the observer knows that there is cloud cover.

d. Superfluous Detection. This symptom is evidenced by conflicts in ceilometer reports,

such as drastic, unrealistic changes in the detected cloud bases.

The troubleshooting and repair procedures for the ceilometer are performed by identifying the fault

symptom from one of those listed in table 9.5.5. The table defines the detailed fault isolation procedures

to be followed. These procedures are provided in the following paragraphs. These procedures isolate the

fault to the FRU level. The replacement procedures for each FRU are provided at the end of this section.

9.5.3.2 Data Message Contains Alarm. When the automatic self-test routine of the ceilometer detects a

malfunction, it is reported to the operator on the OID ceilometer page display. The alarm status indicators

include: hardware alarm, supply voltage alarm, laser power low alarm, and temperature alarm. In addition

to these alarms, the same display indicates the status of the following ceilometer components: solar

shutter (optional) on/off, blower on/off, heater on/off, pulse frequency (pulse repetition frequency) value,

and gain (receiver amplifier gain) value.

9.5.3.2.1 Hardware Alarm. A hardware alarm is indicated by an F in the HARDWARE field on the

OID ceilometer page. When a general hardware alarm is detected by the system, the maintenance

technician should open a line of communication (direct dialogue mode) with the ceilometer and request

status from the processor. Direct dialogue mode is entered by using the DIALG key at the OID display.

Direct dialogue mode is also available when using the maintenance laptop computer. The status of the

ceilometer is requested by entering the STA command in the ENTER COMMAND area on the display.

The status message reply from the ceilometer may contain one or more of the messages listed in table

9.5.6. The status message displayed should be located in the table and the verification and replacement

procedures provided for the identified FRU’s performed. If none of these messages apply, the direct

dialogue RESET command should be entered at the OID (or ceilometer power is cycled for a moment).

When the ceilometer initialization sequence is complete, the startup message should be observed. If the

ceilometer initialization sequence detects an error, the message received may contain one of the messages

identified in table 9.5.7. The error message should be located in the table and the verification and

replacement procedures provided for the identified FRU’s performed. If no error message is displayed,

the system may have detected a temporary or intermittent fault. If so, the ceilometer should be reset and

its operation observed. If an intermittent fault is still observed, troubleshooting should be performed

using the theory of operation as the basis for fault analysis and the verification and replacement

procedures for isolating the fault and replacing the FRU performed.
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Table 9.5.5. Ceilometer Troubleshooting

Symptom What to Do How to Do It

Data message contains hardware alarm Isolate fault using direct dialogue. Paragraph 9.5.3.2.1

Data message contains supply voltage alarm Isolate fault using direct dialogue. Paragraph 9.5.3.2.2

Data message contains laser power low alarm Isolate fault using direct dialogue. Paragraph 9.5.3.2.3

Data message contains temperature alarm Isolate fault using direct dialogue. Paragraph 9.5.3.2.4

No response from ceilometer module Check fiberoptic. Chapter 1, Section IV

Replace fiberoptic module. Paragraph 9.5.4.13

Check ceilometer RS-232C interface. Paragraph 9.5.3.3

Check ac/dc power. Paragraph 9.5.3.2.2

Replace Processor Board, A1. Paragraph 9.5.4.1

Ceilometer not detecting clouds Troubleshoot Paragraph 9.5.3.4

Superfluous cloud detections Troubleshoot Paragraph 9.5.3.5

Table 9.5.6. General Hardware Alarm Messages

Message Suspect FRU

SKY MONITOR SUSPECTED A5, A6, or A1

AD MONITOR ERROR A1

SEQUENCE ERROR A1

INTERNAL HEATING SUSPECTED T1, R1, R2, A1, or A2

BLOWER/HEATER ERROR B1, PS1, TS1, or A1

SHUTTER CONTROL SUSPECTED K1 or A5

Table 9.5.7. Initialization Error Messages

Message Suspect FRU

EX XXXXX XX XX (X=hex char.) A1

OFFSET ERROR A1

AMPLIFIER ERROR A1

NOISE ERROR A1, A6, or W8

SEQ RAM NOT CLEARED A1

SEQ PULSE COUNTER ERROR A1

ANALOG MONITOR ERROR A1

LASER POWER LOW A7, A5, K1, or PS1

SEQUENCE HALT A1

EEPROM ERROR A1

SIGNAL ERROR A1

9.5.3.2.2 Supply Voltage Alarm. A supply voltage alarm is indicated by an F in the SUPPLY VOLTAGE

field on the OID ceilometer page. When a supply voltage alarm is detected by the system, the maintenance

technician should open a line of communication (direct dialoguemode) with the ceilometer and requeststatus

(STA command) from the processor board. The displayed status message contains one or more voltagesthat

are detected as being below the alarm limit (as set by the ALIM command). The voltage(s) that triggered the

alarm are identified by an asterisk (*) after the voltage value. Table 9.5.8 provides the voltage levels that

should be detected at each power supply monitoring point. The voltage points are also depicted on the
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ASOS Site Technical Manual S100

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detailed block diagram(figure 9.4.4 sheet 3). If the voltage displayed is within the specified limits, the alarm

limit specified for the system should be checked (using the ALIM command). If the specified alarm limit is

correct (within the normal operating range specified in the table), connector faults or line voltage variances

are possible. If a specified voltage point is out of limit, reference should be made to table 9.5.9, which

identifies the ac power inputs, fuses, and loads associated with each monitored dc power point. The

maintenance technician should manually check the power supply points at the ceilometer installation site to

isolate the fault. Table 9.5.10 provides a general troubleshooting procedure for the power supplies.

Table 9.5.8. Power Supply Monitored Voltage Levels

Voltage Point Normal Value Alarm Limit Acceptable Max

P20I +20 vdc +15 vdc +24 vdc

P10X +10 vdc +7.5 vdc +12 vdc

M20A -20 vdc -15 vdc -24 vdc

P10R +10 vdc +7 vdc +13 vdc

MRHV* -300 vdc -150 vdc -450 vdc

P12M +12 vdc +8 vdc +15 vdc

P10D +10 vdc +6.5 vdc +12 vdc

P25V +25 vdc +20 vdc +30 vdc

PXHV* +130 vdc +52 vdc +200 vdc

P20A +20 vdc +15 vdc +24 vdc

M20I - 20 vdc -15 vdc -24 vdc

 * These voltages are temperature-dependent and are adjusted at 72°F (22°C) to the values

marked on the respective circuit boards.

Table 9.5.9. Monitored Power Test Points, Fuses, and Loads

Voltage Point Check Fuses Voltage Test Point AC Input at A2 Power Loads

 P10D A2F3 A2TP4 8 vac A1

P20I A2F6 or F7 A2TP3 30 vac A1

 M20I A2F6 or F7 A2TP2 30 vac A1

P25V A2F1 A2TP1 20 vac R1, R2, A1, A5, T1, or PS1

M20A A2F4 or F5 A2TP5 30 vac A1

P20A A2F4 or F5 A2TP6 8 vac A1

 P12M A2F8 A2TP7 10 vac A1

P10X A2F9 A2TP9 8 vac A1 or A7

PXHV PS1F1 PS1 A1 J8 N/A A7

 P10R A2F2 A2TP8 8 vac A1 or A6

MRHV PS1F2 PS1 TP1-TPGND N/A A6
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Table 9.5.10. Power Supply General Troubleshooting Procedure

Step Procedure

1 Check fuse(s) and replace if blown.

2 If replaced fuse blows, remove circuit load(s).

3 If fuse blows without load, suspect unregulated power supply board A2 (except for high voltage power

points PXHV and MRHV, where power supply PS1 is suspect).

4 Replace suspected FRU as cause of blown fuse.

5 If voltage at test point islow and its ac input is okay, suspect unregulated powersupply A2 (except for high

voltage points PXHV and MRHV, where power supply PS1 is suspect).

6 If single or several ac inputs are low while ac line input is 103 vac or better, suspect power supply PS1

(except for P25V ac point, where temperature compensation transformer T1 is suspect).

7 If PXHV at high voltage power supply PS1 connector J8 is above alarm limit but alarm persists, check for

bad ground connection through W9.

8 If MRHV at high voltage power supply board PS1A1 test points TP1 and TP2 is above alarm limit but

alarm persists, check for bad ground connection through W8.

9 If all voltages check within limits but alarm persists, suspect processor board A1.

10 If input line voltage is below 103 vac, check ac input power from DCP.

9.5.3.2.3 Laser Power Low Alarm. A laser power low alarm is indicated by an F in the LASER POWER

field on the OID ceilometer page. This alarm displays when the light monitor board detects a low value of

average laser power (LLAS). A laser power low alarm normally indicates a failure of either the transmitter

board or the light monitor board. When a laser power low alarm is detected by the system, the maintenance

technician should open the direct dialogue mode with the sensor and request the sensor status (STA)

command. The measured value for LLAS is included in the status display.

9.5.3.2.3.1 LLAS Value Close to Zero. If the LLAS value (indicated in the STA display) is close to zero,

the following should be performed:

a. Inspect to ensure that there are no obstructions between the transmitter lens and the light

monitor board (especially at the solar shutter, if installed).

b. Check the value of the laser normal (LNOR) parameter through direct dialogue using the

PAR or LNOR command. Verify that displayed LNOR is same as factory-calibrated mark

on the transmitter board (record number from transmitter board for future use). The LNOR

value should be entered as required to match the transmitter board marking.

c. If there is no obstruction and the LNOR parameters match, check the supply voltages to the

transmitter board and the light monitor board.

d. Check the voltages on Transmitter Board A7 test points TP4, TP7, TP3, and TP6-TP5 in

accordance with paragraph 9.5.4.6.1. 

e. Ensure that laser is on (AUTO ON) and check the following test points on Light Monitor

Board A5: 

(1) Measure TP3 (+) to TP5 (-) (GND) for 17 ±1 vdc. If not in range, measure cathode

of diode D7 (or connector J2-1) for +25 vdc. If +25 vdc is present but TP3 is not

present or out of tolerance, replace Light Monitor Board A5. If +25 vdc is not

present, suspect Unregulated Power Supply Board A2.
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(2) If ceilometer is providing positive cloud detection (with clouds in sky), measure

TP1 (+) to TP5 (-) (GND) for between 1.5 and 4 vdc (with laser on). If not correct,

suspect Light MonitorBoard A5.Ifin tolerance,suspectUnregulated Power Supply

Board A2 or Processor Board A1. 

f. If above checks do not identify fault, replace Transmitter Board A7 and recheck laser power

level. If fault remains, replace Light Monitor Board A5.

9.5.3.2.3.2 LLAS Value Not Close to Zero. If the LLAS value (indicated in the STA display) is below the

alarm limit but not close to zero, the following should be performed:

a. Using direct dialogue, check that the pulse repetition frequency parameterisset tomaximum

(FREQ = 7). If it is, verify LNOR is the proper value. Replace Transmitter Board A7 if

LNOR was correct.

b. Check that the value of the laser temperature (TL in STA output) is less than 140 degrees

F. If temperature is above this value, interrupt operation (AUTO OFF) for a few minutes to

allow ceilometer to cool. After cooling,set AUTO ON and allow ceilometer to run for a few

minutes and check the temperature and power alarm again. If the temperature again is high,

the transmitter board is suspect. 

c. If TL value is well below 140 degrees F and the alarm persists, check calibration of

ceilometerin accordancewith paragraph 9.5.2.4.If ceilometer calibration is out of tolerance,

replace Transmitter Board A7. If ceilometer calibration is within tolerance, proceed to next

step.

d. Ensure that laser is on (AUTO ON). If ceilometer is not reporting cloud detection (while

clouds are present), replace transmitter board. If ceilometer isreporting clouds, measure the

following on Light Monitor Board A5: 

(1) Measure TP3 (+) to TP5 (-) (GND) for 17 ±1 vdc. If not in range, measure cathode

of diode D7 for +25 vdc. If +25 vdc is present but TP3 is not present or out of

tolerance, replace Light Monitor Board A5. If +25 vdc is not present, suspect

Unregulated Power Supply Board A2.

(2) If ceilometer is providing positive cloud detection, measure TP1 (+) to TP5 (-)

(GND) for between 1.5 and 4 vdc (with laser on). If not correct, suspect Light

Monitor Board A5. If in tolerance,suspect Unregulated Power Supply Board A2 or

Processor Board A1. 

e. If above checks do not identify fault, replace Transmitter Board A7 and recheck laser power

level. If fault remains, replace Light Monitor Board A5.

9.5.3.2.4 Temperature Alarm. A temperature alarm is indicated by an F in the TEMPERATURE field on

the OID ceilometer page. Temperature alarms result when the processor board senses component

temperatures or temperature differences that are above the specified alarm limit parameters (ALIM). When

a temperature alarm is detected, the maintenance technician should open direct dialogue with the ceilometer

to request status (STA). The resulting status display identifies the detected temperature alarm sensed point

by an asterisk (*) after the sensed value. Table 9.5.11 lists the temperature references, their normal stable
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value range, and their alarm limit values. If the sensed temperature is within the limits of the table, the alarm

limit parameter (ALIM) should be checked. If both of these values are correct, a wiring or connector fault

is probable. If the sensed temperature is abnormal or out of limits, the associated sensor and wiring should

be checked. The temperature sensors convert heat energy to electrical energy, using the following formula

to convert temperatures expressed in degrees Celsius to the equivalent temperatures expressed in degrees

Fahrenheit:

T(degrees Fahrenheit) = 1.8 x T(degrees Celsius) + 32

Atemperature alarmoccursifthe sensed voltage exceedsthe preset alarmlimit. An open temperature sensing

circuit indicates an approximate temperature reading of 200°C (a sensed voltage of 5 vdc). The voltage

output of an operational temperature sensor is expressed as:

V = (T(degrees Celsius) + 273) x 10 mV

Table 9.5.11. Temperature Alarm References 

Temperature

Reference Normal Range (Stabilized) Alarm Limit(Specified)

TE Up to 5°C above ambient 100°C

TI +5°C to +15°C above ambient when ambient is above 0°C, or +10°C to

+30°C above ambient when ambient is below 0°C

100°C

TL Equal to TI (±5°C) 70°C

TB

Up to 20°C above TE when unit is in sunshine with heaters and blower both

off. Up to 5°C above TE when heaters are off and blower is on. Between 5°C

and 10°C above TE with both heaters and blower on.

80°C

The following are typical values for reference purposes:

 Temperature (T) Sensor

Degrees Degrees Voltage

Fahrenheit Celsius (vdc) 

 +140 +60 +3.33 

 +104 +40 +3.13 

 +68 +20 +2.93

 +32 +0 +2.73 

 -4 -20 +2.53 

 -40 -40 +2.33 

If, after sufficient stabilization time (minutes for the TE and TB references and hours for the TI and TL

references), the temperature alarm persists, the course of action is determined by the category of the sensed

temperature. If a high temperature is sensed (close to 200°C may indicate an open circuit), table 9.5.12

should be referenced for voltage test points. If the sensed temperature seems to be within reasonable range

yet the alarm persists, table 9.5.13 should be used for fault isolation procedures. The cables and connectors

referenced in these tables are depicted in the ceilometer detailed block diagram (figure 9.4.4).
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Table 9.5.12. Temperature Alarm With High Temperature

Temperature

Reference

Check Test Points

TL A7, TP6 - TP5; A2J1, A13 - C13; connectors A7J2, A2J8, A2J1, and A1J1; Cable W7

TE A2J9, 1 - 2;A2J1, a14 - c14; connectors TS1P1, A2J9, A2J1, and A1J1

TI None, replace A1

TB B1E1, 8 - 9; A2J1, a15 - c15; connectors B1E1, B1P1, W2J2, W2P1, PS1J2, PS1P2, A2J11,

A2J1, and A1J1; cables W2 and B1W1

Table 9.5.13. Temperature Alarm With Reasonable Temperatures

Temperature

Reference

 Procedure

TL > 70°C (158°F) If ambient temperature is close to 49°C (120°F) and solar radiation is intense, check that

window conditioner blower is on and heat is off. If not, troubleshoot window conditioner.

TB > 80°C (176°F) or

TB-TE > 40°C (72°F)

Check that the window conditioner or blower is on and functional. If not, troubleshoot

window conditioner.

9.5.3.3 RS-232C Interface Nonoperational. The RS-232C interface of the ceilometer is the primary data

communications interface for the ASOS configuration. This interface is connected to a fiberoptic module

added to the ceilometer to provide the fiberoptic link with the DCP. A failure in this link could cause a total

loss of communications with the ceilometer or cause intermittent data transfer errors with the sensor. If

communications with the ceilometer become difficult, the maintenance technician should troubleshoot the

data link starting at the DCP. (Chapter 1 providesinstructionsfor testing the DCP fiberoptic modules.) If the

DCP tests okay, the ceilometer must be checked. Before the RS-232C interface is checked at the ceilometer,

the ceilometer equipment cabinet covers must be removed as described in table 9.5.14 to gain access to the

electronics. Once the covers are removed, the line voltage indicator(DS1) and the equipment circuit breakers

(CB1 and CB2) on high voltage power supply (PS1) are checked. The line voltage indicator should be

illuminated and both circuit breakers in the ON (up) position. If power is available to the ceilometer, the

ERRORand OK indicators(D4 and D5) on ProcessorBoard A1 should be checked.The OK indicatorshould

be flashing (about 1 Hz rate) and the ERROR indicator should be extinguished. If the ERROR indicator is

illuminated, then reset the processor board using the RESET switch located on the board. If the ERROR

indicator remains illuminated, then replace the processor board. If both the ERROR and OK indicators are

extinguished, then perform power checks on the processor board (refer to paragraph 9.5.4.1) and the

unregulated powersupply board (referto paragraph 9.5.4.2). Should the indicators and power check out okay,

the ceilometer detailed block diagram(figure 9.4.4)should be referenced to check the wiring and connectors

along the RS-232C data path.

9.5.3.4 Cloud Detection Missing. If clouds are definitely present and within the detectable range of the

ceilometer but are not reported by the ceilometer, the message reports from the ceilometer must be checked

for any alarm messages. It may be necessary to reset the ceilometer (by using the RESET command in direct

dialogue mode or by cycling power) and check the status messages upon initialization. Using direct dialogue

with the ceilometer, the parameters should be checked (using the PAR command) to verify that they are

correct for the current configuration of the system. Any incorrect value should be adjusted as required. The

ceilometer windows and lensesshould be checked for possible obstructions. If these activities do not correct

the problem, the transmitter, receiver, and processor boards are suspect. The technician should check for

proper operation by referring to the theory of operation provided in Section IV and to the board verification

and replacement procedures provided in this section.
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WARNING

WARNING

Table 9.5.14. Ceilometer Equipment Cabinet Cover Removal and Installation

Step Procedure

REMOVAL

Tools required:

 None

Death or severe injury may result if power is not removed from sensor prior to maintenance

activities. Ensure that heater and primary power circuit breakers (located in DCP) are set to off

(right) position.

CAUTION

Prevent dust, precipitation, dirt, or other obstructionsfromaccumulating on the ceilometer windows

and lenses. Damage to the optics may render the ceilometer inoperable.

1 Inside DCP equipment cabinet, set circuit breakers on ceilometer circuit breaker module to off (right)

position.

2 Disconnect window conditioner by unplugging cable from connector J2 located on the underside of the

equipment cabinet assembly.

3 Loosen four knurled screws securing window conditioner to equipment cabinet assembly.

4 Carefully remove window conditioner by lifting from equipment cabinet assembly and gently set on the

ground.

5 Release two latches at the lower edge of the ceilometer equipment cabinet cover.

6 Carefully raise equipment cabinet cover over the ceilometer electronics assembly and set on the ground.

INSTALLATION

Death or severe injury may result if power is not removed from sensor prior to maintenance

activities. Ensure that heater and primary power circuit breakers (located in DCP) are set to off

(right) position.

1 Inside DCP equipment cabinet, ensure that circuit breakers on ceilometer circuit breaker module are set to

off (right) position.

2 Carefully install ceilometer equipment cabinet cover over ceilometer electronics assembly and lower to its

normal position.

3 Secure two latches at lower edge of ceilometer equipment cabinet cover.

4 Carefully install window conditioner on equipment cabinet assembly.

5 Tighten four knurled screws securing window conditioner to equipment cabinet assembly.

6 Connect window conditioner cable to connector J2 located on underside of equipment cabinet assembly.

7 Inside DCP equipment cabinet,set circuit breakers on ceilometer circuit breaker module to on (left) position.

9.5.3.5 Superfluous Detection. If repeated miss-hits are reported by the ceilometer with no apparent cause,

the system could possibly be experiencing intermittent malfunctions. The first step in isolation of these

malfunctions is to check the alarm messages received from the ceilometer. It may be necessary to reset the

ceilometer (by using the RESET command or by cycling power) to check the status messages reported by

systeminitialization. The ceilometer parametersshould also be checked (using the PAR command) to verify

that they are correct for the current configuration of the system. If the system checks out without alarms or

parameter problems and the malfunction persists, the maintenance technician should refer to the theory of

operation provided in this chapter as well as the board verification and replacement procedures to

troubleshoot the system.
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9.5.4 BOARD VERIFICATION AND REPLACEMENT PROCEDURES

The following paragraphs provide detailed proceduresto verify the operation of the ceilometer circuit boards.

Procedures are also provided for the removal and replacement of each board. To performthe verification and

replacement procedures, the ceilometer equipment cabinet cover must be removed to gain access to the

electronics. Table 9.5.14 provides the procedures to remove and install the ceilometer equipment cabinet

cover.

9.5.4.1 Processor Board A1 Verification and Replacement.

9.5.4.1.1 Verification. The processor board is a microprocessor-based design that functions as the central

control element of the ceilometer. In some instances, the actual malfunction may be caused by a temporary

condition that confuses the processing software. Therefore, it is recommended that the ceilometer first be

reset (using the RESET command, cycling power, or activating the reset switch on the processor board) and

then observed to check if the condition is corrected. The microprocessor-based design also provides the

onboard processor capability of detecting the majority of faults through self-test diagnostics. These tests

report detected failuresthrough hardware alarmmessagesthat are displayed as previously described. Several

onboard voltage regulator circuits provide electrical power and reference voltages to the processor board.

The source power for these local regulators is monitored by the sensor software and can be observed using

the STA (status) command in the direct dialogue mode. The local regulator outputs can be checked at the

points provided in table 9.5.15. If any of the onboard voltagesis out of tolerance, the processor board should

be replaced.

9.5.4.1.2 Replacement. The processor board removal and installation procedures are provided in table

9.5.16.

Table 9.5.15. Processor Board Operating Voltage Checkpoints

Checkpoint Voltage Description

J6 pin 8 +5 ±0.25 Logic supply

J5 pin 10 +12.2 ±0.8 Interface supply

J5 pin 9 -12.2 ±0.8 Interface supply

J9 pin 5 +9 ±0.5 Flash A/D supply

J14 pin 2 +12.7 ±0.8 Analog high supply

J19 pin 6 -12.7 ±0.8 Analog high supply

J19 pin 3 +6.1 ±0.3 Analog low supply

J19 pin 4 -6.1 ±0.3 Analog low supply

J6 pin 7 +5 ±0.05 Monitor A/D reference

J9 pin 4 +8.3 ±0.1 Flash A/D high reference

J9 pin 3 +1.7 ±0.05 Flash A/D low reference

J9 pin 2 +0.9 ±0.1 Flash A/D input

J16 pin 10 +7.1 ±0.3 Level shift source

J16 pin 9 +1.9 ±0.3 Level shift return

J19 pin 7 -4.3 ±0.3 Amplifier test point 2

J19 pin 5 +3 ±0.5 Amplifier test point 1
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Table 9.5.16. Processor Board Removal and Installation

Step Procedure

REMOVAL

Tools required:

None

NOTE

A laptop computer initialized as DCP OID (Chapter 3, Section III) or any other available OID may

be used for the following steps.

1 Using ceilometer dialog page, enter the following command:

 

LNOR

For measurement normalization during installation of the new processor board, record LNOR parameter

displayed; then, enter the following command:

DEV

2 Record LNOR and DEV values returned. If the values are not returned, proceed to step 3.

3 Disconnect ac power from ceilometer and remove ceilometer equipment cabinet covers as described in table

9.5.14.

4 Unplug cable W8 from connector J22 on the processor board.

5 Unplug cable W9 from connector J26 on the processor board.

6 Disconnect processor board A1 from unregulated power supply board.

7 Remove processor board from ceilometer.

INSTALLATION

1

Tools required:

 None

Ensure that all jumpers on new processor board are positioned the same as the processor board being

replaced.

2 Connect new processor board into its connector on unregulated power supply board.

3 Connect cables W8 and W9 to connectors J22 and J26, respectively, on the processor board.

4 Apply power to the ceilometer and observe LED indicators D4 and D5 on Processor Board A1. The red LED

(D4) should be extinguished and the green LED (D5) should blink about once per second.

5 Using the PAR (parameter) command, verify that the following system parameters values are stored:

CLIM 0.1000

SLIM 0.2000

NSCA 4.5000

SCAL 100.0000

TOTAL 10.0000

HOFF 0

DATA UNIT FT

POLLED MESSAGES

If stored parameter values do not agree with those listed above, then enter the above values.
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Table 9.5.16. Processor Board Removal and Installation -CONT

Step Procedure

6 If LNOR and DEV values were recorded in step 2 of removal procedure, proceed to step 7.

If LNOR and DEV values were not recorded in step 2 of removal procedure, or have not been previously

recorded, disconnect AC power form the ceilometer. Remove U5 from new processor board installed in step

1 above, and U5 from processor board removed in Removal step 7; swap U5's. Reapply power, use the

ceilometer dialogue page to enter the following commands:

LNOR

DEV

Record LNOR and DEV.

Disconnect AC power form the ceilometer, and swap U5's to their original boards. Reapply power.

7 Use ceilometer dialogue page to enter the following commands:

LNOR XXX (where XXX is the LNOR value recorded in step 6 of the installation procedure, or

step 2 of the removal procedure, or the logged values).

DEV X.XXXX (where X.XXXX is the DEV value recorded in step 6 of the installation procedure,

or step 2 of the removal procedure, or the logged values).

8 If LNOR for the system cannot be retrieved by the above methods, the ceilometer transmitter board must be

replaced with a newboard using the transmitter board removal and installation procedures. This will establish

a new correct LNOR for the system.

9 Install ceilometer equipment cabinet covers as described in table 9.5.14 and apply power to ceilometer.

10 Perform the offset calibration procedures as described in table 9.5.35.

9.5.4.2 Unregulated Power Supply Board A2 Verification and Replacement.

9.5.4.2.1 Verification. Malfunctions involving the unregulated power supply board are generally detected

by supply voltage alarms reported by the ceilometer. A supply voltage alarm is indicated by an F in the

SUPPLY VOLTAGE field on the OID ceilometer page. When a supply voltage alarm is detected by the

system, the technician should open a direct dialogue line with the ceilometer (select OID dialogue page) and

requeststatus(STA command)fromthe processor board. The displayed status message contains one ormore

voltages that are detected as being below the alarm limit (as set by the alarm command). The voltage(s) that

triggered the alarm are identified by an asterisk (*) after the voltage value. Table 9.5.17 providesthe voltage

levels that should be detected at each power supply monitoring point. If the voltage displayed is within the

limits shown in the table, the technician should check the alarm limit entered into the system (using the

ALIM command). If the system alarm limit is correct (within the normal operating range specified in the

table), connector faults or line voltage variances are possible. If one specific voltage point is out of limit,

reference should be made to table 9.5.18, which identifies the ac power inputs, fuses, and loads associated

with each monitored dc power point. The technician should check corresponding fuses and manually check

the power supply points at the ceilometer to isolate the fault. Table 9.5.10 provides additional information

on checking system power supplies. In addition to the power supplies, the unregulated power supply board

provides an extensive number ofsignal paths between the other circuit boardsin the ceilometer. These signal

paths can be verified by checking their continuity using an ohmmeter. The temperature control relays on the

unregulated power supply board can only be checked by simulating heating conditions using a cold spray to

cool the temperature sensor (U16 on Processor Board A1). The operation of the relays may be heard, and

after the relays are energized, the voltage outputs can be checked using a multimeter.
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9.5.4.2.2 Replacement. The unregulated power supply board removal and installation procedures are

provided in table 9.5.19.

Table 9.5.17. Unregulated Power Supply Voltage Limits

 Voltage Point Normal Value Alarm Limit Acceptable Max

P20I +20 vdc +15 vdc +24 vdc

P10X +10 vdc +7.5 vdc +12 vdc

M20A -20 vdc -15 vdc -24 vdc

P10R +10 vdc +7 vdc +13 vdc

P12M +12 vdc +8 vdc +15 vdc

P10D +10 vdc +6.5 vdc +12 vdc

P25V +25 vdc +20 vdc +30 vdc

P20A +20 vdc +15 vdc +24 vdc

M20I -20 vdc -15 vdc -24 vdc

Table 9.5.18. Unregulated Power Supply Voltage Test Points and Loads

Voltage Point Check Fuses Voltage Test Point AC Input at A2 Power Loads

 P10D A2F3 A2TP4 8 vac A1

 P20I A2F6 or F7 A2TP3 30 vac A1

 M20I A2F6 or F7 A2TP2 30 vac A1

 P25V A2F1 A2TP1 20 vac R1, R2, A1, A5, T1, or

PS1

 M20A A2F4 or F5 A2TP5 30 vac A1

 P20A A2F4 or F5 A2TP6 8 vac A1

P12M A2F8 A2TP7 10 vac A1

P10X A2F9 A2TP9 8 vac A1 or A7

 P10R A2F2 A2TP8 8 vac A1 or A6

Table 9.5.19. Unregulated Power Supply Board Removal and Installation

Step Procedure

REMOVAL

Tools required:

 No. 1 Phillips screwdriver

 Needle-nosed pliers

1 Disconnect ac power from ceilometer and remove ceilometer equipment cabinet covers as described in table

9.5.14.

2 Disconnect Processor Board A1 and I/O Connector Board A3 from unregulated power supply board as

described in tables 9.5.16 and 9.5.21.

3 Disconnect all cables and wiring harnesses from unregulated power supply board connectors.

4 Remove four screws securing unregulated power supply board to frame.

5 Unplug unregulated power supply board from two plastic standoffs, using pliers to press plastic springs.
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Table 9.5.19. Unregulated Power Supply Board Removal and Installation -CONT

Step Procedure

INSTALLATION

Tools required:

 No. 1 Phillips screwdriver

 Needle-nosed pliers

1 Ensure that new unregulated power supply board has switch S1 set to ON position and switch S2 set to

NORMAL position.

2 Install new unregulated power supply board on two plastic standoffs using pliers to press plastic springs.

3 Install four screws securing unregulated power supply board to frame.

4 Connect all cables and wiring harnesses to unregulated power supply board connectors as required.

5 Connect Processor Board A1 and I/O Connector Board A3 to unregulated power supply board as described

in tables 9.5.16 and 9.5.21.

6 Install the ceilometer equipment cabinet covers as described in table 9.5.14 and apply power to ceilometer.

7 Perform the offset calibration procedures provided in table 9.5.35.

9.5.4.3 I/O Connector Board A3 Verification and Replacement.

9.5.4.3.1 Verification. The supply voltage test points for the I/O connector board are identified in table

9.5.20. The only supply voltage on the board isthe +5 vdc supply. Continuity checks on the RS-232 transmit

(TXD) and receive (RXD) data signal paths can be performed by referring to detailed block diagram, figure

9.4.4.

9.5.4.3.2 Replacement. The removal and replacement procedures for the I/O connector board are provided

in table 9.5.21.

Table 9.5.20. I/O Connector Board Voltage Test Points

Voltage Reference Test Point Value

+5V J2-9 +5 vdc

GND J2-5 Ground ref

Table 9.5.21. I/O Connector Board Removal and Installation

Step Procedure

REMOVAL

Tools required:

None 

1 Disconnect ac power from ceilometer and remove ceilometer equipment cabinet covers as described in

table 9.5.14.

2 Disconnect cable W3 from connector J2 on I/O connector board.

3 Unplug I/O Connector Board A3 from Unregulated Power Supply Board A2.

INSTALLATION

1 Plug I/O Connector Board A3 on unregulated power supply board.

2 Connect cable W3 to connector J2 on output interface board.

3 Install ceilometer equipment cabinet covers as described in table 9.5.14 and apply power to ceilometer.
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9.5.4.4 Light Monitor Board A5 Verification and Replacement.

9.5.4.4.1 Verification. Before the light monitor board can be checked, there should be no obstructions that

would prevent the board from monitoring the laser transmitter light or the ambient sky light. The supply

voltage test points for the light monitor board are listed in table 9.5.22. Both the laser power level voltage

and the sky light level voltage are monitored by the processor board. If either of these circuits should

malfunction, the processor board issues an alarm message for display. The solar shutter driver and optional

solar shutter can be verified using the SHUT ON and SHUT OFF commands in direct dialogue with the

ceilometer if the shutter option is installed. The solar shutter driver can be further checked by covering D3

and checking that the voltage at TP4 is approximately 2v ±0.1v. Adjustment is made at R13 if necessary.

Driver Q2 should be fully conducting (i.e.,solenoid is energized and flap is open); if it is not, force on signal

SSON is verified as low. If force is low, A5 should be replaced; otherwise, A1, A2, or W5 may be faulty.

Processor control status should be verified as SHUTTEROFF. If the shutter driver must be replaced, the

procedure in table 9.5.23 is performed.

9.5.4.4.2 Replacement. The light monitor board removal and installation procedures are provided in table

9.5.24.

Table 9.2.22. Light Monitor Board Voltage Test Points

Voltage reference Test point Value

P25V J2-1 +25 vdc

+17V TP3 +17 vdc (±1 vdc)

GNDP TP5 Ground ref

Table 9.5.23. Solar Shutter Driver Removal and Installation

Step Procedure

REMOVAL

Tools required:

 No. 10 flat-tipped screwdriver

 Allen wrench (.050)

1 Disconnect power from ceilometer and remove ceilometer equipment cover as described in table 9.5.14.

NOTE

The shutter flap is in the closed position when ceilometer power is OFF. The flap is open

when power is ON and the light intensity threshold is not exceeded.

2 Place protective cloth over lensto protect lensfrom any tools or hardware that may be inadvertently dropped

on lens during removal procedure.

3 Disconnect solar shutter driver (i.e., solenoid) cable from connector J1 on light monitor board.

4 Loosen sleeve at solenoid end of flexible coupling using .050 Allen wrench.

5 Remove two screws that secure solenoid to ceilometer frame and remove solenoid from ceilometer.

6 Move flap back and forth by hand to ensure that flap is unobstructed.

INSTALLATION

1 Slide armature of solenoid into coupling sleeve. Leave sleeve loose.

2 Secure solenoid to frame with two machine screws.

3 Tighten sleeve on coupling.

4 Reconnect solenoid cable to connector J1 on light monitor board.

5 Replace ceilometer equipment cover in accordance with procedure in table 9.5.14.

6 Turn ON ceilometer power.
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ASOS Site Technical Manual S100

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Table 9.5.24. Light Monitor Board Removal and Installation

Step Procedure

REMOVAL

Tools required:

 No. 1 Phillips screwdriver

1 Disconnect power from ceilometer and remove ceilometer equipment cabinet covers as described in table

9.5.14.

2 Disconnect cable W5 from connector J1 on light monitor board.

3 Disconnect solar shutter relay solenoid cable (if installed) from connector J2 on light monitor board.

4 Place protective cloth over lensto protect lensfrom any tools or hardware that may be inadvertently dropped

during this procedure.

5 Remove two screws securing light monitor board to optics frame assembly.

6 Lift light monitor board from electronics assembly.

INSTALLATION

1 Place protective cloth over lensto protect lensfrom any tools or hardware that may be inadvertently dropped

during this procedure.

2 Install new light monitor board. Install two screws securing light monitor board to optics frame assembly.

3 Connect solar shutter relay solenoid cable (if installed) to connector J2 on light monitor board.

4 Connect cable W5 to connector J1 on light monitor board.

5 Install ceilometer equipment cabinet covers as described in table 9.5.14 and apply power to ceilometer.

9.5.4.5 Receiver Board A6 Verification and Replacement.

9.5.4.5.1 Verification. The same verification and replacement procedure is used for the standard and

tropical receiver boards. The supply voltage test points for the receiver board are listed in table 9.5.25. In

addition to these supply voltages, the high voltage power can be checked at test point TP2. The value of the

high voltage power is temperature dependent. The receiver board is factory calibrated at 25°C (77°F) and

the TP2 voltage for this temperature is identified by a sticker located on the board. With the

voltage/temperature relationship of 2.3 volts/°C (1.3 volts/°F), the voltage that should be measured at test

point TP2 can be calculated using the following equations:

V(TP2) = Vb + ((Tp(°C) - 25) x 2.3) 

V(TP2) = Vb + ((Tp(°F) - 77) x 1.3) 

where: V(TP2) = Voltage measured at TP2

 Vb = Voltage on board sticker

 Tp = Present temperature

If the voltage level measured is not close to the calculated level, high voltage powersupply PS1 or cable W10

is suspect. The receiver photodiode can also be checked by measuring the voltage between test points TP1

and TP2. With the receiver lens covered, this value should be less than 1 millivolt. With the lens uncovered

in bright daylight, the level may be as high as 0.5 volt, but not significantly higher. Artificial light may be

used in instances when bright daylight is not available.

9.5.4.5.2 Replacement.The receiver board removal and installation procedures are provided in table 9.5.26.

Use extreme care when removing the receiver board. Damage to fiberoptic connectors can be prevented by

removing the receiver housing.
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WARNING

Table 9.5.25. Receiver Board Voltage Test Points

Voltage Reference Test Point Value

High voltage is accessible on the receiver board.

+5V TP3 +5 vdc (+0.5 vdc)

P10R J1-1 +10 vdc (+2 vdc)

GNDR TP GND Ground ref

Table 9.5.26. Receiver Board Removal and Installation

Step Procedure

REMOVAL

Tools required:

 9/32-inch open end wrench

1 Disconnect ac power from ceilometer and remove ceilometer equipment cabinet covers as described in

table 9.5.14.

2

CAUTION

Use extreme care when removing receiver board. Damage to fiberoptic connectors can

be prevented by removing receiver housing.

Disconnect cable W8 from connector J3 on receiver board.

3 Disconnect cable W6 from connector J1 on receiver board.

4 Disconnect cable W10 from connector J2 on receiver board.

5 Remove hex spacer nuts securing receiver board to optics frame assembly.

6

CAUTION

Avoid touching the mirror-like infrared light interference filter when installing receiver

board.

Upon removal of receiver board from optics frame assembly, immediately store board

in a bag or box to protect light filter from damage.

Carefully lower receiver board to clear the long screws and remove board from optics frame assembly.

INSTALLATION

Tools required:

 9/32-inch open end wrench

1

CAUTION

Avoid touching the mirror-like infrared light interference filter when installing receiver

board.

NOTE

Install tropical receiver board (part No. 62828-90112-11 on ceilometers equipped with

solar shutter assembly and standard receiver board (part No. 62828-90112-4) on

ceilometers that are not equipped with solar shutter assembly.

Install receiver board in optics frame assembly by raising into position over the long screws.

2 Install hex spacer nuts securing receiver board to optics frame assembly.
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Table 9.5.26. Receiver Board Removal and Installation -CONT

Step Procedure

3 Connect cable W10 to connector J2 on receiver board.

4 Connect cable W6 to connector J1 on receiver board.

5 Connect cable W8 to connector J3 on receiver board.

6 Install ceilometer equipment cabinet covers as described in table 9.5.14 and apply power to ceilometer.

7 Perform offset calibration procedures as provided in table 9.5.35.

8 Verify ceilometer calibration in accordance with table 9.5.4.

9.5.4.6 Transmitter Board A7 Verification and Replacement.

9.5.4.6.1 Verification. The absence of laser power can be detected by persistent missing cloud returns or

by a low monitored laser power level (LLAS). The ceilometer processor board monitors the LLAS voltage

signal and issues an alarm message when LLAS is low. The supply voltage test points for the transmitter

board are listed in table 9.5.27. If the voltage level measured at TP4 is too low, Unregulated Power Supply

Board A2 or wiring harness W7 is suspect. If the high voltage input at TP7 is too low, high voltage power

supply PS1 or cable W11 is suspect. In addition to these supply voltages, the high voltage power can be

checked at test point TP3. This voltage should be checked with laser power off (use AUTO OFF command).

The value of the high voltage power at TP3 is temperature dependent. The transmitter board is factory

calibrated at 21°C (70°F) and the TP3 voltage for this temperature is identified by a sticker located on the

board. With the voltage/temperature relationship of 1.8 volt/°C (1.0 volt/°F), the voltage that should be

measured at test point TP3 can be calculated using the following equations:

V(TP3) = Vb + ((Tp(°C) - 21) x 1.8) 

V(TP3) = Vb + (Tp(°F) - 70)

where: V(TP3) = Voltage measured at TP3

 Vb = Voltage on board sticker

 Tp = Present temperature

If the voltage level measured is not close to the calculated level, high voltage powersupply PS1 or cable W11

is suspect. If the high voltage measured at TP7 is okay, but TP3 is close to zero, power should be removed

from the unit for a few seconds and then reapplied. TP7 and TP3 should then be rechecked. If TP3 is still

close to zero, Transmitter Board A7 should be replaced. The laser temperature sensor voltage can be

measured across TP6-TP5. At 70°F, the voltage at TP6 should be +2.94 vdc. The voltage level at TP6-TP5

is temperature sensitive, with a temperature coefficient of 5.5 mv/°F (10 mv/°C). If the voltage measured at

TP6 is too low, Processor Board A1, Unregulated Power Supply Board A2, or cable harness W7 is suspect.

9.5.4.6.2 Replacement. The transmitter board removal and installation procedures are provided in table

9.5.28.
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WARNING

Table 9.5.27. Transmitter Board Voltage Test Points

Voltage reference Test point Value

High voltage is present on the transmitter board.

+10VX TP4 +10 (±1.5) vdc

+260V TP7 +260 (±40) vdc

GNDX TP GND Ground ref

Table 9.5.28. Transmitter Board Removal and Installation

Step Procedure

REMOVAL

Tools required:

 9/32-inch open end wrench

1 Disconnect ac power from ceilometer and remove ceilometer equipment cabinet covers as described in table

9.5.14. Remove transmitter cover (black knob underneath).

2 Disconnect cable W11 from connector J3 on transmitter board.

3 Disconnect cable W7 from connector J2 on transmitter board.

4 Disconnect cable W9 from connector J1 on transmitter board.

5 Remove three hex spacer nuts securing transmitter board to optics frame assembly.

6 Carefully lower transmitter board to clear the long screws and remove from optics frame assembly.

INSTALLATION

Tools required:

 9/32-inch open end wrench

1 Install transmitter board in optics frame assembly by raising into position over the long screws.

2 Install three hex spacer nuts securing transmitter board to optics frame assembly.

3 Connect cable W9 to connector J1 on transmitter board.

4 Connect cable W7 to connector J2 on transmitter board.

5 Connect cable W11 to connector J3 on transmitter board.

6 Note the diffuser value marked on the diffuser and install diffuser over transmitter lens such that the four

notches in the diffuser ring are lined up with the three pairs of support screws on the lens plate (diffuser ring

must rest flat on the lens plate).

7 Install ceilometer equipment cabinet covers as described in table 9.5.14 and apply power to ceilometer.

8 Allow ceilometer to warm up for at least 1⁄2 hour with equipment cabinet covers in place.

NOTE

LNOR is used by the system to adjust the laser output power to a standard value. Standard laser

poweris essential to uniformcloud detection. The uniformpower provides a consistentresult among

LBC’s and the sky condition is reported consistently between ASOS systems. LNOR should be

determined only when a new transmitter board is installed. That value of LNOR should be used

throughout the life of that transmitter board. A new LNOR should not be determined using a

transmitter that has been used in the system. New transmitter cards have a calibrated standard output

power and can be used to establish LNOR for the LBC system.

Laptop computer, initialized as DCP OID (Chapter 3, Section III) or any other available OID, may

be used for the following steps.
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WARNING

Table 9.5.28. Transmitter Board Removal and Installation - CONT

Step Procedure

9 At OID, display ceilometer dialogue page.

10 Using ceilometer dialogue page, enter the following commands:

AUTO OFF (which enters maintenance mode)

FREQ 3

SEQ ON

LASE ON

AN LLAS

11 Observe laser power level values displayed to visually estimate the average value. If the average displayed

value does not match the value listed on the diffuser (tolerance = ±3), terminate the output by pressing ESC

and enter the following commands according to the observed display values:

If displayed average is less than diffuser value, enter:

FREQ 4

SEQ ON

LASE ON

AN LLAS

If displayed average is greater than diffuser value, enter:

FREQ 2

SEQ ON

LASE ON

AN LLAS

12 Observe the values displayed to visually estimate the average value. Repeat steps 10 and 11 as necessary,

each time increasing or decreasing the FREQ value by one, until the average value matches the diffuser

value (±3).

13 When the displayed average value and the diffuser value match, do not terminate the output display on the

maintenance monitor terminal.

14

The high voltage ac and dc power are accessible on the ceilometer electronics assembly.

Use extreme caution when removing the equipment cabinet covers with power applied

to the ceilometer.

Remove equipment cabinet covers.

15

CAUTION

When removing diffuser from lens plate, avoid scratching the lens or hitting the light

monitor board.

Carefully remove diffuser from lens plate.

16 Observe LLAS values displayed on screen to visually estimate the average value displayed.

17 Terminate the display output.

18 Increase the average value determined in step 16 by adding five (LLAS + 5).

19 Using ceilometer dialogue page, enter the following command: LNOR XXX

where: XXX = the value obtained in step 18

Record the LNOR value in a permanent log book for the transmitter card.

20 Observe that the system displays the same value. If not, repeat step 19.
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S100 ASOS Site Technical Manual

Table 9.5.28. Transmitter Board Removal and Installation - CONT

Step Procedure

Change 1 9-91

21 Using ceilometer dialogue page, enter the following command to return ceilometer to normal operation:

AUTO ON

22 Install equipment cabinet covers and perform offset calibration procedures as provided in table 9.5.35.

23 Verify ceilometer calibration in accordance with table 9.5.3.

9.5.4.7 High Voltage Power Supply PS1 Verification and Replacement.

9.5.4.7.1 Verification. The operation of the high voltage power supply is verified by checking the input ac

power and the power supply outputs. The point-to-point wiring of the high voltage power supply is depicted

on the ceilometer detailed block diagram(figure 9.4.4),which should be referenced when checking the power

supply. The operation of the window conditioner heater and blower relays that are a part of the high voltage

powersupply can also be verified.The following commands are entered at themaintenancemonitorterminal:

AUTO OFF (to enter the maintenance mode), BLOW ON, and HEAT ON. These commands instruct the

processor to activate the relays and turn the window conditioner blower and heater on.

9.5.4.7.2 Replacement. The high voltage power supply removal and installation procedures are provided

in table 9.5.29.

Table 9.5.29. High Voltage Power Supply Removal and Installation

Step Procedure

REMOVAL

Tools required:

 5mm hex key wrench

1 Disconnect ac power from ceilometer and remove ceilometer equipment cabinet covers as described in table

9.5.14.

2 Disconnect cable W1 from connector J1 on high voltage power supply.

3 Disconnect cable W2 from connector J2 on high voltage power supply.

4 Disconnect temperature compensation transformer T1 wiring harness from connector J3 on high voltage

power supply.

5 Disconnect cable W10 from connector J7 on high voltage power supply.

6 Disconnect cable W11 from connector J8 on high voltage power supply.

7 Using Allen (hex) key, remove four screws from front and two screws from rearsecuring high voltage power

supply to frame assembly.

8 Slide high voltage power supply out from front of cabinet.
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ASOS Site Technical Manual S100

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Table 9.5.29. High Voltage Power Supply Removal and Installation -CONT

Step Procedure

INSTALLATION

Tools required:

 5mm hex key wrench

1 Install high voltage power supply from front of cabinet.

2 Using Allen (hex) key, install four screws at front and two screws at rear securing high voltage power supply

to frame assembly.

3 Connect cable W11 to connector J8 on high voltage power supply.

4 Connect cable W10 to connector J7 on high voltage power supply.

5 Connect temperature compensation transformer T1 wiring harnessto connectorJ3 on the high voltage power

supply.

6 Connect cable W2 to connector J2 on high voltage power supply.

7 Connect cable W1 to connector J1 on high voltage power supply.

8 On high voltage power supply PS1, adjust R13 to its maximum (fully clockwise) limit.

9 Install ceilometer equipment cabinet covers as described in table 9.5.14 and apply power to ceilometer.

10 Perform the offset calibration procedures as provided in table 9.5.35.

9.5.4.8 Temperature Compensation Transformer T1 Verification and Replacement.

9.5.4.8.1 Verification.The temperature compensation transformeris verified by checking the voltage output

to the unregulated power supply board. The transformer output (secondary) should provide 20 vac (±3 vac).

The input voltage to the transformer can be verified at connector J3 of the high voltage power supply. These

voltage levels are provided on the ceilometer detailed block diagram (figure 9.4.4).

9.5.4.8.2 Replacement.The temperature compensation transformerremoval and installation procedures are

provided in table 9.5.30.

Table 9.5.30. Temperature Compensation Transformer Removal and Installation

Step Procedure

REMOVAL

Tools required:

 Diagonal cutting pliers

 No. 2 Phillips screwdriver

1 Disconnect ac power from ceilometer and remove ceilometer equipment cabinet covers as described in

table 9.5.14.

2 Disconnect wiring harness from connector J3 on unregulated power supply board.

3 Disconnect wiring harness from connector J3 on high voltage power supply.

4 Open cable clamp securing transformer secondary wiring harness to optics frame assembly.

5 Cut wiring bundle ties securing transformer primary wiring harness to optics frame assembly.

6 Lift plastic feed-through bushing that guides transformer secondary wiring harness through the top of optics

frame assembly.

7 Feed transformer secondary wiring harness through the top of optics frame assembly.

8 Remove two screws securing temperature compensation transformer to optics frame assembly and remove

transformer.
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S100 ASOS Site Technical Manual

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Table 9.5.30. Temperature Compensation Transformer Removal and Installation -CONT

Step Procedure

INSTALLATION

Tools and materials required:

Diagonal cutting pliers 

 No. 2 Phillips screwdriver

Cable ties 

1 Install new temperature compensation transformer using two screws to secure the transformer to the optics

frame assembly.

2 Feed transformer secondary wiring harness through the top of optics frame assembly.

3 Install plastic feed-through bushing that guides transformer secondary wiring harness through the top of optics

frame assembly.

4 Close cable clamp securing transformer secondary wiring harness to optics frame assembly.

5 Connect transformer secondary wiring harness to connector J3 on unregulated power supply board.

6 Connect transformer primary wiring harness to connector J3 on high voltage power supply.

7 Install wiring bundle ties securing transformer primary wiring harness to optics frame assembly.

8 Install ceilometer equipment cabinet covers as described in table 9.5.14 and apply power to ceilometer.

9.5.4.9 Cabinet Heaters R1 and R2 Verification and Replacement.

9.5.4.9.1 Verification. The cabinet heaters are resistive heater elements whose operation can be verified by

checking their resistance values. The heater elements must be disconnected from unregulated power supply

board connectorsJ2 and J4 before resistance is measured. The resistance measured acrossthe heater element

should read 10 ohms ±5%.

9.5.4.9.2 Replacement. The cabinet heaterremoval and installation procedures are provided in table 9.5.31.

Table 9.5.31. Cabinet Heater Removal and Installation

Step Procedure

REMOVAL

Tools required:

 No. 1 Phillips screwdriver

1 Disconnect ac power from ceilometer and remove ceilometer equipment cabinet covers as described in table

9.5.14.

2 Disconnect heater element wiring harness from unregulated power supply board (connectorJ2 for heater R1

and connector J4 for heater R2).

3 Pull out feed-through bushing from hole in optics frame assembly.

4 Remove two screws securing heater to optics frame assembly. Remove heater.

INSTALLATION

1 Transfer as much of the heat conducting silicon grease as possible fromreplaced heater to newheater, adding

more grease as necessary.

2 Install heater on optics frame assembly and secure using two screws.

3 Install feed-through bushing in hole in optics frame assembly.

4 Connect heater element wiring harness to unregulated power supply board (connector J2 for heater R1 and

connector J4 for heater R2).

5 Install ceilometer equipment cabinet covers as described in table 9.5.14 and apply power to ceilometer.
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authorized to copy or reprint this material without the written consent of: VAISALA INC., 100 Commerce Way, Woburn, MA 01801.

ASOS Site Technical Manual S100

9-94

9.5.4.10 External Air Temperature Sensor TS1 Verification and Replacement.

9.5.4.10.1 Verification. The external air temperature sensor is verified by checking power (voltage and

current)levels where it interfaces with the unregulated powersupply board (connectorJ9). The voltage level

present across the sensor is a function of the air temperature. At 70°F (21°C), the voltage level between pins

J9-1(+) and J9-2(-) should be approximately 2.94 ±0.020 vdc. The voltage level that should be measured at

other temperatures can be calculated according to the following equations:

Vt = 2.94 + (Ta - 70) x 0.0055 for Fahrenheit

Vt = 2.94 + (Ta - 21) x 0.010 for Celsius

where: Vt = Voltage measured for that temperature

Ta = Present air temperature

If the voltage measured does not match the calculated value, the sensor should be disconnected from

connector J9 of the unregulated power supply board, and the voltage level across pins 1 and 2 of connector

J9 should be checked. The voltage should measure approximately 5 vdc. The current level measured across

shorted pins 1 and 2 of connector J9 should measure 2 milliamps. If either the voltage or current level is not

correct, Processor Board A1 or Unregulated Power Supply Board A2 is suspect. If both voltage and current

level are correct, the sensor TS1 should be replaced.

9.5.4.10.2 Replacement. The external air temperature sensor removal and installation procedures are

provided in table 9.5.32.

Table 9.5.32. External Air Temperature Sensor Removal and Installation

Step Procedure

REMOVAL

Tools required:

 Diagonal cutting pliers

1 Disconnect ac power from ceilometer and remove ceilometer equipment cabinet covers as described in table

9.5.14.

2 Disconnect temperature sensor wiring harness from connector J9 on unregulated power supply board.

3 Cut wiring harness bundle ties.

4 Remove air filter from cabinet air vent.

5 Lift temperature sensor from cabinet air vent.

INSTALLATION

Materials Required:

Cable ties

1 Install temperature sensor in cabinet air vent.

2 Install air filter in cabinet air vent.

3 Connect temperature sensor wiring harness to connector J9 on Unregulated Power Supply Board A2.

4 Install new wiring harness bundle ties securing temperature sensor wiring harness as required.

5 Install ceilometer equipment cabinet covers as described in table 9.5.14 and apply power to ceilometer.
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S100 ASOS Site Technical Manual

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9.5.4.10.3 Removal and Installation of Snow Radiation Shield. The snow radiation shield is held in place

by a tab on the edge of the shield. It is installed on the under side of the ceilometer with one edge parallel

to the edge of the ceilometer base and the other edge with the tab against the pedestal top plate. The tab fits

between the top of the pedestal and the bottom of the ceilometer. It is mounted at the end opposite from the

fan cable and connector. It is mounted midway between the sides and over top of the ambient air sensor

housing which protrudes out of the bottom of the ceilometer. See figure 9.1.2. The snow radiation shield

removal and installation procedures are provided in table 9.5.33. 

Table 9.5.33. Snow Radiation Shield Removal and Installation

Step Procedure

REMOVAL

Tools required:

 5mm hex key 

1 Coordinate with site observer, if applicable, and make an entry in SYSLOG.

2 Locate end of ceilometer opposite fan cable entry on bottom of ceilometer. Remove two screws that secure

ceilometer to pedestal on that end of ceilometer.

3 On end of the ceilometer where fan cable enters ceilometer base, loosen, but do notremove two screws which

secure this end to pedestal. Loosen so there is about 1/16 inch between head of screw and pedestal.

4 Ensure that thumbscrews which secure blower assembly and two latches which secure ceilometer cover to

base plate are in place and tight.

5 Locate end of ceilometer where temperature sensor housing is located (same end where two screws were

removed). Ceilometer will be tilted away from this end.

6 In one hand, hold snow radiation shield. With other hand, lift at side of ceilometer while placing your

shoulder against side of ceilometer to aid in lifting and pushing (if lifting hand is at end of ceilometer, it will

be in the way when shield is being removed.). Tilt ceilometer away from you. 

7 Remove shield from between inside edge of ceilometer and pedestal top assembly. Lower ceilometer.

8 Install two screws that were removed in step 3.

9 Tighten four screws that secure ceilometer to pedestal.

10 Coordinate with site observer, if applicable, and clear any maintenance flags generated, making an entry in

SYSLOG.

INSTALLATION

Tools required:

 5mm hex key 

1 Coordinate with site observer, if applicable, and make an entry in SYSLOG.

2 Locate end of ceilometer opposite fan cable entry on bottom of the ceilometer. Remove two screws that

secure ceilometer to pedestal on that end of ceilometer. 

3 On end of ceilometer where fan cable enters ceilometer base, loosen, but Do not remove two screws which

secure this end to pedestal. Loosen so there is about 1/16 inch between head of screw and pedestal.

4 Ensure thumbscrews which secure blower assembly and two latches which secure ceilometer cover to base

plate are in place and tight.

5 Locate end of ceilometer where temperature sensor housing is located (same end where two screws were

removed). Ceilometer will be tilted away from this end.
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authorized to copy or reprint this material without the written consent of: VAISALA INC., 100 Commerce Way, Woburn, MA 01801.

ASOS Site Technical Manual S100

9-96

WARNING

Table 9.5.33. Snow Radiation Shield Removal and Installation -CONT

Step Procedure

6 In one hand, hold snow radiation shield so that tab is toward pedestal, and ceilometer is tilted away. With

other hand, lift at side of ceilometer while placing shoulder against side of ceilometer to aid in lifting and

pushing. (If lifting hand were at the end of ceilometer, it would be in the way when shield is put in place.) 

7 Insert shield between inside edge of ceilometer and pedestal top assembly so tab fits over top of pedestal.

Lower ceilometer to secure snow radiation shield.

8 Check that shield is positioned midway with respect to sides of ceilometer. Move as necessary by sliding.

9 Install two screws that were removed in step 3.

10 Tighten four screws that secure ceilometer to pedestal.

11 Coordinate with site observer, if applicable, and clear any maintenance flags generated, making an entry in

SYSLOG.

9.5.4.11 Window Conditioner Verification and Replacement.

9.5.4.11.1 Verification. The operation of the window conditioner blower and heater can be verified through

software commands to the ceilometer using direct dialogue in maintenance mode. In maintenance mode

(AUTO OFF), the window conditioner BLOW ON and HEAT ON commandsforce the window conditioner

blower and heater on. Within a few minutes, the blower temperature displayed (TB) should read

approximately 12°F (7°C) above the ambient temperature display (TE). If the temperature rises considerably

more, blower operation is suspect. If the temperatures read approximately the same value, heater operation

issuspect. The isolation of the fault to the window conditioner can be performed by resistance checks across

the blower and heater circuits. These circuits are depicted in point-to-point wiring on the ceilometer detailed

block diagram (figure 9.4.4). With the window conditioner cable disconnected from connector J2 on the

ceilometer, the blower circuit and the heater circuit should measure approximately 60 ohms and 22 ohms,

respectively. If these resistance levels check okay, high voltage power supply PS1, Processor Board A1, or

Unregulated Power Supply Board A2 is suspect.

9.5.4.11.2 Replacement. The window conditionerremoval and installation procedures are provided in table

9.5.34.

Table 9.5.34. Window Conditioner Removal and Installation 

Step Procedure

REMOVAL

Tools required:

 Diagonal cutting pliers

 Small flat-tipped screwdriver

Death or severe injury may result if power is not removed from sensor prior to maintenance

activities. Ensure that heater and primary power circuit breakers (located in DCP) are set to off

(right) position.

CAUTION

Prevent dust, precipitation, dirt, or other obstructionsfromaccumulating on the ceilometer windows

and lenses. Damage to the optics may render the ceilometer inoperable.

1 Inside equipment cabinet, set circuit breakers on ceilometer circuit breaker module to off (right) position.
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authorized to copy or reprint this material without the written consent of: VAISALA INC., 100 Commerce Way, Woburn, MA 01801.

S100 ASOS Site Technical Manual

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WARNING

Table 9.5.34. Window Conditioner Removal and Installation -CONT

Step Procedure

2 Disconnect window conditioner by unplugging cable from connector J2 located on underside of equipment

cabinet assembly.

3 Loosen four knurled screws securing window conditioner to equipment cabinet assembly.

4 Carefully remove window conditioner by lifting from equipment cabinet assembly and gently set on the

ground.

5 Remove window conditioner cable from the guiding clamp inside the cover.

6 Remove four screws securing heater-blower to cover housing.

7 Remove heater-blower from cover housing.

INSTALLATION

Tools required:

 Small flat-tipped screwdriver

Death or severe injury may result if power is not removed from sensor prior to maintenance

activities. Ensure that heater and primary power circuit breakers (located in DCP) are set to off

(right) position.

1 Inside equipment cabinet, ensure that circuit breakers on ceilometer circuit breaker module are set to off

(right) position.

2 Install new heater-blower in cover housing and install four screws securing heater-blower.

3 Install window conditioner cable in the guiding clamp inside the cover.

4 Carefully install window conditioner on equipment cabinet assembly.

5 Tighten four knurled screws securing window conditioner to equipment cabinet assembly.

6 Connect window conditioner cable to connector J2 located on the underside of the equipment cabinet

assembly.

7 Inside equipment cabinet, set circuit breakers on ceilometer circuit breaker module to on (left) position.

9.5.4.12 Offset Calibration. The ceilometerinstrument offset has been factory calibrated and under normal

circumstancesrequires no need forrecalibration. However, the replacement of any part ofthe ceilometerthat

has an effect on internal noise behavior requires recalibration after restoring to operation. Parts influencing

noise behavior are:

a. Processor Board A1

b. Unregulated Power Supply Board A2

c. Receiver Board A6

d. Transmitter Board A7

e. High voltage power supply PS1

f. Receiver low-voltage cable W6

g. Transmitter low-voltage cable W7

h. Receiver signal cable W8

i. Transmitter control cable W9

A recalibration may also be performed to correct operations where the cloud data are excessively noisy. The

procedures for performing the offset calibration are provided in table 9.5.35.
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ASOS Site Technical Manual S100

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Table 9.5.35. Offset Calibration Procedures

Step Procedure

Tools and materials required:

Small flat-tipped screwdriver

Laptop computer w/Procomm

Y-interface cable

Laptop null cable

Dark non-reflective cloth

1 Inside equipment cabinet, identify fiberoptic module dedicated to ceilometer. If necessary, perform the

following on an OID:

a. Refer to sensor configuration page on OID (sequentially press REVUE-SITECONFG-SENSOR function keys from 1-minute display).

b. Refer to Chapter 3, Section IV to identify corresponding fiberoptic module.

2 Using small flat-tipped screwdriver, disconnect DB-9 connector from ceilometer fiberoptic module.

3 Using small flat-tipped screwdriver, install jumper between TB1-1 (on orange terminal block) on ceilometer

fiberoptic module (A1) and TB1-1 on adjacent fiberoptic module. Install second jumper between terminals

TB1-2 of ceilometer fiberoptic modules and adjacent module containing first jumper.

4 Using laptop interface (Y-shaped) cable and laptop null cable, connect RS-232C (COM1) port of laptop

computer to DB-9 connector of ceilometer fiberoptic module.

5 Turn on laptop computer and initialize the PROCOMM Plus program. After program initializes, press any

key to enter terminal mode (blank) screen.

6 Using ALT-S command (setup facility), set up the following TERMINAL OPTIONS:

a. Terminal emulation: VT220

b. Duplex: FULL

c. Soft flow control (XON/XOFF): OFF

d. Hard flow control (CTS/RTS): OFF

e. Line wrap: ON

f. Screen scroll: ON

g. CR translation: CR

h. BS translation: NON-DESTRUCTIVE 

i. Break length (milliseconds): 350

j. Enquiry: OFF

k. EGA/VGA true underline: OFF

l. Terminal width: 80

m. ANSI 7 or 8 bit commands: 7 BIT

7 Press ESC key to exit to terminal mode (blank) screen.

8 Using ALT-P command (line/port option), set CURRENT SETTINGS as follows:

a. Baud rate: 2400

b. Parity: NONE

c. Data bits: 7

d. Stop bits: 1

e. Port: COM1

9 Press ESC key to exit to terminal mode (blank) screen.

10 Turn Caps Lock ON.

11 From the laptop computer, check that noise conditions are such that the difference between the two smallest

numbers(average and minimum)seen with command NOIS are 8 or higher (with GAIN of 2) and 2 or higher

(with GAIN of 0.) Use artificial light into the receiver if necessary.
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Table 9.5.35. Offset Calibration Procedures -CONT

Step Procedure

12 With equipment in normal operating configuration, cover the transmitter aperture of the window conditioner

with a dark, nonreflecting cloth.

13

NOTE

This procedure requires stable ambient light conditions. If performed outdoors, wait for

a clear sky or a long break in the clouds if there is broken cloud cover. If performed

indoors, use a steady light source such as a desk lamp positioned over the receiver.

From the ceilometer dialogue page, perform the following command sequence:

AUTO OFF

GAIN 0

LASE ON

SEQ ON

CAL 240

14 After 4 minutes, the unit has performed the calibration and responds with:

OFFSET TO EEPROM

and starts listing the offset values obtained. The listing may be interrupted by pressing the <ESC> key.

15 From the ceilometer dialogue page, enter the following commands to return the unit to normal operation:

AUTO ON

CLOS

16 Observe the performance of the unit for a period of time to verify its operation.

17 At laptop computer, use ALT-X (exit) command to exit PROCOMM Plus.

18 Turn off laptop computer.

19 Disconnect cables between laptop computer and fiberoptic module.

20 Remove two jumpers between fiberoptic modules.

21 Using small flat-tipped screwdriver, install DB-9 connector to ceilometer fiberoptic module in DCP.

9.5.4.13 Fiberoptic Module Removal and Replacement. The fiberoptic module removal and replacement

procedures are provided in table 9.5.36.

Table 9.5.36. Fiberoptic Module Removal and Installation

Step Procedure

REMOVAL

Tools required:

Small flat-tipped screwdriver

1 Disconnect ac power from ceilometer and remove ceilometer equipment cabinet covers as described in table

9.5.14.

2 Using small flat-tipped screwdriver, loosen two retaining screws on DB-9 connector located on top of

fiberoptic module. Remove connector DB-9.

3 Using clockwise (cw)rotation, remove two fiberoptic cablesfromfiberopticmodule.Install protective plastic

covers over fiberoptic connectors.

4 Using small flat-tipped screwdriver, remove four screws, four lockwashers, and two gaskets securing

fiberoptic module to mounting plate.
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ASOS Site Technical Manual S100

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Table 9.5.36. Fiberoptic Module Removal and Installation -CONT

Step Procedure

INSTALLATION

Tools required:

Small flat-tipped screwdriver

1 Ensure that ac power is disconnected and ceilometer equipment cabinet covers are removed as

described in table 9.5.14.

2 Using small flat-tipped screwdriver, install four screws, four lockwashers, and two gaskets

securing fiberoptic module to mounting plate.

3 Remove protective plastic covers from fiberoptic connectors and connect receive (RX) cable to

receive connector on fiberoptic module (nearest DB-9 connector) and transmit (TX) cable to

transmit connector on fiberoptic module.

4 Install signal cable on connector DB-9 on fiberoptic module and using small flat-tipped

screwdriver, tighten two retaining screws.

5 Install ceilometer equipment cabinet covers as described in table 9.5.14 and apply power to

ceilometer.
S100 ASOS Site Technical Manual

Change 2 10-1

CHAPTER 10

LIQUID PRECIPITATION ACCUMULATION SENSOR

(RAIN GAUGE)

SECTION I. DESCRIPTION AND LEADING PARTICULARS

10.1.1 INTRODUCTION

The liquid precipitation accumulation sensor(rain gauge)is a heated tipping bucketrain gauge manufactured

by the Frise Engineering Company. The rain gauge is a custom ASOS configuration, modified Model

7405HA. This section describes the modified Model 7405HA used in the ASOS and its physical attributes.

10.1.2 PHYSICAL DESCRIPTION

The rain gauge (Figure 10.1.1) is a free-standing receptacle for measuring precipitation. The rain gauge

contains an open top, which measures approximately 1 foot in diameter, that allows precipitation to fall into

the upper portion, referred to as the collector. The collector is heated to melt any frozen precipitation, such

as snow or hail, for collection. Collected water is funneled to a mechanical device (tipping bucket), which

incrementally measuresthe accumulation and causesthe momentary closure of a switch (either a reed switch

or a mercury switch) for each increment. The tipping bucket is designed to measure in increments of 0.01

inch of rain. As water is collected, the tipping bucket fills to the point where it tips over. This action empties

the bucket in preparation for additional measurements, closes the momentary switch, and signals another 0.01

inch of precipitation to the DCP. Water discharged by the tipping bucket passes out ofthe rain gauge through

a lower funnel to the ground below. The physical design provides for the adaptation of the rain gauge to the

standard ASOS mounting flange, with the collector portion located approximately 48 inches above the

ground. Atspecified sites, a 48-inch diameter wind shield isinstalled around the rain gauge. The wind shield

reduces wind updrafts and wind streamlines that alter rain trajectories.

10.1.3 RAIN GAUGE CONFIGURATIONS

Four configurations of the rain gauge (part number 90116) have been manufactured. Some earlier $

configuration gauges have been, and the rest are being, upgraded to the newest (-40) configuration. $

-10 This configuration can be identified by the mercury switch, mounted in a bracket to the

bucket frame assembly. The mercury switch requires special consideration and handling

during adjustment and shipping. If the mercury switch fails, itshould be replaced by the reed

switch.

-20 This configuration can be identified by the reed switch and bracket mounted to the bucket

frame assembly, the funnel extension added to the top funnel, and the brass stops on the

tipping bucket.

-30 This configuration is identical to the -20 assembly except that the tipping bucket has

polyethylene stopsinstead of brassstops. The brassstops were susceptible to sticking to the

bucket frame. For this reason, brass stops have been replaced with polyethylene stops

secured by a screw and adhesive. $
ASOS Site Technical Manual S100

10-2 Change 2

$ -40 This configuration replaces the magnet and magnet holder with a magnet/holder

$ combination. It also uses a self-tapping screw to mount the polyethylene stop to the bucket

$ instead of a screw and adhesive.

Figure 10.1.1. Liquid Precipitation Accumulation Sensor (Rain Gauge) (Sheet 1 of 3)
S100 ASOS Site Technical Manual

10-3

Figure 10.1.1. Liquid Precipitation Accumulation Sensor (Rain Gauge) (Sheet 2)
ASOS Site Technical Manual S100

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Figure 10.1.1. Liquid Precipitation Accumulation Sensor (Rain Gauge) (Sheet 3)
S100 ASOS Site Technical Manual

10-5

WARNING

SECTION II. INSTALLATION

10.2.1 INTRODUCTION

The rain gauge is a relatively simple, single-unit sensor that mounts directly on a sensor pedestal at the site.

The only preparation required is assembly of the supportstand, installation of the tipping bucketswitch, and

installation of the tipping bucket. The only cabling required is the connection of heater power and one

fiberoptic signal line.

10.2.2 INSTALLATION

Installation procedures for the rain gauge are provided in table 10.2.1. Figure 10.2.1 provides an illustration

of the tipping bucket and tipping bucket switch installation. Locational drawings of the wind shield and the

fiberoptic transmitter are provided in Section I of this chapter. A wiring diagram for the sensor is provided

in Section IV of this chapter.

Table 10.2.1. Liquid Precipitation Accumulation Sensor Installation Procedures

Step Procedure

Tools required:

 15/16-inch wrench

 Small flat-tipped screwdriver

 Digital multimeter (DMM)

 Large flat-tipped screwdriver

 Large adjustable wrench

Death or severe injury may result if power is not removed from sensor prior to maintenance

activities. Ensure that heater circuit breaker (located in DCP) supplying power to sensor isset to off

(right) position.

1 Inside DCP equipment cabinet, ensure that circuit breaker on rain gauge circuit breaker module is set to off

(right) position.

2 Using 15/16-inch wrench, installfour 5/8 - 11 bolts, flat washers(two places), lockwashers, and nutssecuring

rain gauge base plate and windshield mounting plate (if required) to sensor pedestal.

3 Install three 1/4 - 20 hex head bolts and flat washers securing three sensor legs to sensor base plate. Do not

tighten legs to base plate. Legs should be free to rotate and will be tightened after lower case is installed.

4 Using small flat-tipped screwdriver, remove Bottom Plate A2A2 from Lower Case A2.

5 At flexible conduit for rain gauge pedestal, remove large nut from end of conduit using large adjustable

wrench. Ensure that gasket (rubber gasket with metal gasket holder) is in place on metal conduit cap (rubber

gasket toward sensor).

6 Route ac wiring and fiberoptic cable from DCP through wiring hole (not the center drain hole) in Bottom

Plate A2A2 and slide threaded end of flexible conduit cap through same hole. Using large adjustable wrench,

secure flexible conduit to bottom plate by attaching nut to conduit cap.

7 Apply thin coat of DC-4 anti-corrosion compund to connector pins in cable connector between collector

assembly and lower case pins.
ASOS Site Technical Manual S100

10-6

Table 10.2.1. Liquid Precipitation Accumulation Sensor Installation Procedures -CONT

Step Procedure

8 Connect heater ac wiring from DCP to terminal block (Figure 10.4.1) on Bottom Plate A2A2 as follows:

 Wire Terminal

Jumper 1 to 2

Green (ground) 3

Red (ac line) 4

Yellow (ac neut) 5

9 Connect fiberoptic cable from DCP to Transmitter Board A2A2A1 on Bottom Plate A2A2.

10 Install Bottom Plate A2A2 on Lower Case A2.

11 Position Lower Case A2 on sensor support legs.

12 Secure sensor earth ground to grounding stud on Bottom Plate A2A2.

13 Install six 1/4 - 20 hex head bolts and jamnuts (two each leg) in holes in leg supports on lower case

14 Level lower case and secure in position by tightening six 1/4 - 20 hex head bolts and jamnuts as necessary.

15 Mount Tipping Bucket Frame A2A1 to top of lower case.

16 Install two 8-32 X 5/8 screws and washers securing Tipping Bucket Frame A2A1.

17 Adjust Tipping Bucket Frame 2MT6A2A1 using a level and adjust legs if required.

CAUTION

Tipping bucket mercury switch is verysensitive.Care should be taken whenmoving switch

to keep the wire leads up to avoid getting the mercury pool stuck in top of switch.

18 Mount tipping bucket on tipping bucket frame with magnet facing switch.

19 Tip bucket several times by hand to ensure that it moves freely. As the bucket tips and the magnet passes the

switch, a momentary contact occurs in the switch. Visually inspect the magnet during tipping to ensure that

it passes within 0.25 inch of the switch but does not contact the switch. (Adjustswitch position, if necessary,

to achieve required spacing.)

20 Connect an ohmmeter between the two output connectors on the back of the reed switch.

21 While tipping the bucket by hand, observe the ohmmeter. As bucket tips, magnet should cause switch to

momentarily close and then open, causing the ohmmeter output to display a momentary short circuit reading.

Ensure that switch operates properly for both tipping directions. If switch does not close and open properly,

adjust by moving up or down in bracket and adjust bracket by loosening screws securing bracket to frame.

22 Using collector locating pin and alignment arrow on lower case as a guide, mount collector on lower case and

tighten two retaining knobs on sides of lower case.

23 If sensor is equipped with wind shield, perform the following:

a. Install three windshield support poles to windshield base plate by sliding poles over three

base plate pins. 

b. Obtain three nylon sections of windshield, three sections of bottomring, and three sections

of top ring.

NOTE

Top side of each nylon section is side where individual nylon strips are widest.

c. Slide one section of top ring through top of each section of nylon shield. 

d. Slide one section of bottom ring through bottom of each section of nylon shield.
S100 ASOS Site Technical Manual

Table 10.2.1. Liquid Precipitation Accumulation Sensor Installation Procedures -CONT

Step Procedure

10-7/ (10-8 blank)

Figure 10.2.1. Tipping Bucket Installation

e. Using large flat-tipped screwdriver, loosen two setscrews in connector at the top of each

support pole.

f. Install top ring of one wind shield section into connectors at top of support poles. Secure

each end of section by tightening two setscrews. Repeat for other two sections of wind

shield.

g. Install bottom ring of windshield by sliding each section into a bottom section of the

windshield. Connect all three bottom ring sections together and tighten all setscrews.

24 Inside DCP equipment cabinet, set circuit breaker on rain gauge circuit breaker module to on (left) position.

25 Check tipping bucket calibration in accordance with table 10.5.1.
S100 ASOS Site Technical Manual

10-9/ (10-10 blank)

SECTION III. OPERATION

10.3.1 INTRODUCTION

The rain gauge is fully automatic, and has no controls or indicators. The internal electronics monitor the

bucket for tips. Each time a tip occurs, a pulse signal is issued to the data collection package (DCP) via the

fiberopticmodule.The heaters are thermostatically controlled to provide automatic heating ofthe rain gauge,

as required.
S100 ASOS Site Technical Manual

10-11

SECTION IV. THEORY OF OPERATION

10.4.1 INTRODUCTION

The rain gauge for the ASOS operates in the same manner as all tipping bucket rain gauges, but has been

modified to transmit light pulses for each tip of the bucket back to the ASOS data processing system. With

the rain gauge part of a computer-based system, compensation can be made for rain-rate dependent errors,

which results in increased rain gauge accuracy and dependability. This section describes the tipping bucket

sensor and the error correction. A wiring diagram of the sensor is provided as figure 10.4.1 to depict the

sensor's operation.

10.4.2 DESCRIPTION OF OPERATION

The tipping bucket is located under a funnel in the collector housing. The bucket is a two-chamber container

that pivots. Precipitation flows through the funnel into one compartment until 0.01 inch of rain (18.5 grams)

is accumulated. That amount of weight causes the bucket to tip on its pivots, dumping the collected water

and moving the other chamber under the funnel. The tipping motion activates a switch, thereby establishing

a momentary closure for each 0.01 inch of rain. Rain gauge output is one electrical pulse for each 0.01 inch

of precipitation collected. Fiberoptic Transmitter A2A2A1 converts the electrical pulse to a light pulse

suitable for fiberoptic transmission to the data collection package (DCP). Power to produce the light pulses

is supplied by a 3.6-volt lithium battery, which is part of Fiberoptic Transmitter A2A2A1. A pulse is

transmitted each time the tipping bucket fills. The sensor is heated by two electrical heaters: a 150-watt,

110-volt flexible heating element is cemented to the back of the collector funnel, and a 175-watt, 110-volt

band heater is mounted on the drain tube. Each heater is controlled by its own thermostat, which is set to

close (turn the heater on) at temperatures below 40°F. A third thermostat(located on the sensor bottomplate)

is normally closed and opens at temperatures below -20°F. This thermostat removes power from the heaters

to conserve energy under conditions when precipitation would not normally occur. The thermostat closes

again as the temperature rises above -12°F to return power to the heaters. The DCP provides all of the

required heater ac power. A safety switch is mounted on the rim of the lower case. This switch removes

power from the collector heater female plug when the collector is removed, thus removing a potential

electrical hazard. The safety switch does not remove power from the drain tube heater. As such, the

technician must ensure that rain gauge power isremoved at the DCP circuit breaker module before servicing

the rain gauge. Also, the technician must use caution to avoid thermal burns when working near the heaters.
ASOS Site Technical Manual S100

10-12

Figure 10.4.1. Liquid Precipitation Accumulation Sensor Wiring Diagram
S100 ASOS Site Technical Manual

10-13

SECTION V. MAINTENANCE

10.5.1 INTRODUCTION

Preventive maintenance for the rain gauge consists of keeping both the collector and discharge water flow

paths free of obstructions. Occasional cleaning and inspection of the tipping bucket is also necessary to

ensure that the bucket operates properly. Due to its simple design, troubleshooting is performed via manual

inspection.

10.5.2 PREVENTIVE MAINTENANCE

The frequency of an inspection and maintenance schedule depends on the environment of the rain gauge

installation. Any malfunctions or damage that are detected should be corrected using the corrective

maintenance procedure provided in this chapter. The maintenance log should be updated after each visit to

record any maintenance required by the rain gauge. Recommended routine maintenance consists of visually

inspecting the rain gauge and checking its calibration every 90 daysto ensure proper operation and inspecting

the connector between the collector assembly and the lower case annually for corrosion. Table 10.5.1

provides a procedure to accomplish this.

10.5.3 CORRECTIVE MAINTENANCE

10.5.3.1 Introduction. Corrective maintenance of the rain gauge consists of a visual inspection, testing the

heater circuit, testing the fiberoptic module interfaced to the rain gauge, and removing and installing the rain

gauge. Faults within the rain gauge are automatically detected by the data quality algorithm. If the present

weather sensor is reporting moderate or heavy liquid precipitation and the rain gauge fails to indicate any

accumulation, the system diagnostics log a rain gauge failure.

10.5.3.2 Rain Gauge Testing. Rain gauge testing includes visual inspection as defined in preventive

maintenance, checking for proper heater operation, and testing the fiberoptic module in the DCP, which

receives data from the rain gauge. A faulty rain gauge is isolated using the procedures provided in

table 10.5.2.

10.5.3.3 Rain Gauge Removal and Installation. When a fault is isolated to the rain gauge (other than a

tipping bucket switch or fiberoptic transmitter failure), the entire sensor must be replaced. The replacement

sensor uses the same mounting hardware as the faulty sensor. The rain gauge removal and installation

procedures are provided in table 10.5.3.

10.5.3.4 TippingBucket Switch Removal and Installation. The proceduresrequired to remove and install

the rain gauge tipping bucket switch are provided in table 10.5.4.

10.5.3.5 FiberopticTransmitterRemoval and Installation.The proceduresrequired to remove and install

the rain gauge fiberoptic transmitter are provided in table 10.5.5.
ASOS Site Technical Manual S100

10-14 Change 2

WARNING

WARNING

Table 10.5.1. Rain Gauge Inspection and Calibration Check

Step Procedure

INSPECTION

Tools required:

Large flat-tipped screwdriver

Carpenter's level

Laboratory beaker

Water

NOTE

Laptop computer initialized as DCP OID (Chapter3, Section III), or any other available OID, may

be used for the following procedure.

1 At OID, display sensor status page (sequentially press REVIEW-SENSOR-STAT function keys from

1-minute display).

2 On sensor status page, set report processing for tipping bucket to OFF.

Death orsevere injurymay result if power is notremoved fromsensor priorto maintenance

activities. Ensure that heater circuit breaker (located in DCP) supplying power to sensor

is set to off (right) position.

3 Inside DCP equipment cabinet,set circuit breaker on rain gauge circuit breaker module to off(right) position.

4 Ifsensor is equipped with wind shield, remove one section of wind shield to accessrain gauge by performing

the following:

a. Using large flat-tipped screwdriver, loosen setscrews securing one section of bottom ring.

b. Using large flat-tipped screwdriver, loosen setscrews securing one section of top ring to

two support poles. Remove section of wind shield.

5 Ensure that rain gauge Collector A1 is free of obstructions.

6 Loosen two knurled retaining knobs securing collector to lower case. 

7

Heater on underside of collector funnel may be hot. Do not touch heater when removing

collector. Failure to comply may result in thermal burns. 

Lift Collector A1 straight up and remove from lower case.

8 Ensure that lower funnel is free of obstructions.

9 Check Tipping Bucket Frame A2A1 for level and adjust legs if required.

10 Ensure that tipping bucket is clean and tips freely.

11 Ensure that tipping bucket switch is intact and operating.

12 Using collector pin and alignment arrow on lower case as a guide, mount collector on lower case and tighten

two retaining knobs on sides of lower case.

13 Annually inspect cable connector between collector assembly and lower case for corrosion. Remove corrosion

if present and apply thin coat of DC-4 anti-corrosion compund to connector pins.

CALIBRATION CHECK

$ 1 Using laboratory beaker, pour 195 milliliters of water slowly into rain gauge over a 1-minute period. Ensure

that this causes 10 ±1 tips.
S100 ASOS Site Technical Manual

10-15

WARNING

Table 10.5.1. Rain Gauge Inspection and Calibration Check -CONT

Step Procedure

2 At OID, display second page of 12-hour archive (sequentially press REVUE-SENSOR-12 HR function keys

from 1-minute display). Verify that precipitation amount (total for 2 adjacent minutes) matches the number

of tips that occurred as follows:

 No. of tips

9

10

11

Precipitation

0.09 to 0.10

0.10 to 0.11

0.11 to 0.12

WRAP UP

1 If sensor is equipped with windshield, install open section of wind shield by performing the following: 

a. Install top ring of wind shield in connectors at top of two support poles. Using large

flat-tipped screw driver, tighten two setscrews securing each end of section.

b. Connect bottom ring of windshield to two adjacent sections.

c. Using large flat-tipped screwdriver, tighten two setscrews securing each end of section.

2 Inside DCP equipment cabinet, set circuit breaker on rain gauge circuit breaker module to on (left) position.

3 At OID, display sensor status page (sequentially press REVIEW-SENSOR-STAT function keys from

1-minute display).

4 On sensor status page, set report processing for tipping bucket to ON.

Table 10.5.2. Liquid Precipitation Accumulation Sensor Fault Isolation

Step Procedure

Tools required:

 RS-232 Test Tool

 Digital multimeter (DMM)

 Small flat-tipped screwdriver

1 Visually inspect rain gauge using guidelines of table 10.5.1, steps 1 through 11.

2 In conditions of freezing temperatures, check input funnel of rain gauge for the presence of ice. If ice is

present, perform the following:

The nominal resistance of both heaters is approximately 0.010 ohm.

a. At power control module in DCP, ensure that rain gauge heater circuit breaker isset to ON

position.

AC power is present at rain gauge when DCP power control module is set to ON position.

Use extreme care when working on equipment with ac power applied.

NOTE

Do not short the leads to the tipping bucket switch or cause the tipping bucket switch to

be closed for long periods of time. Do not leave the DMM connected across the tipping

bucketswitch for longer than 30 secondsto measure current flow. These actions will drain

the battery at a faster rate and shorten the life expectancy of the battery.

b. At rain gauge, remove the sensor's bottom plate and referring to wiring diagram in

Section IV, connect DMM across heater ac input. DMM should indicate between 107 and

130 volts ac. If so, replace rain gauge. If reading is not correct, replace rain gauge heater

circuit breaker module in DCP (refer to Chapter 3).
ASOS Site Technical Manual S100

10-16

Table 10.5.2. Liquid Precipitation Accumulation Sensor Fault Isolation -CONT

Step Procedure

3 Place leads of DMM (in current mode) across terminals of tipping bucket switch (with switch open). A

current of 8 mA or higher is an indication of a good battery. If the current is below 8 mA, replace Fiberoptic

Transmitter A2A2A1.

4 Check operation of tipping bucket switch by performing the following:

a. Using small flat-tipped screwdriver, disconnect one leg of tipping bucket switch A2A1S1

from terminal on side of Tipping Bucket Frame A2A1.

b. Connect DMM across both legs of tipping bucket switch.

c. Rock tipping bucket back and forth to actuate tipping bucket switch. Ensure that DMM

indicates continuity when switch is actuated. If continuity is not observed, replace tipping

bucket switch A2A1S1.

d. If tipping bucket switch is operating properly, reconnect free leg of switch to terminal.

5 Check operation of rain gauge/DCP fiberoptic link by performing the following:

a. At OID, accesssensor configuration page. Determine the SIO port to which the rain gauge

is assigned. Refer to the list of port assignments for DCP SIO boards (Chapter3,

Section IV) to identify the corresponding fiberoptic module. 

b. In DCP, connect RS-232 test tool in line with rain gauge fiberoptic module (between

fiberoptic module and corresponding DB-9 connector from cabinet harness).

c. Actuate tipping bucket switch A2A1S1 in rain gauge and verify that RxD indicator on

RS-232 test tool illuminates. If RxD indicator illuminates (and rain gauge data are not

being received by the system), replace corresponding SIO board in DCP. If RxD indicator

on test tool fails to illuminate while the tipping bucket switch is actuated, remove and

replace the following, in order, until the problem is corrected:

(1) Fiberoptic module in DCP

(2) Fiberoptic transmitter in rain gauge

Table 10.5.3. Liquid Precipitation Accumulation Sensor Removal and Installation

Step Procedure

REMOVAL

Tools required:

 Large flat-tipped screwdriver

 Small flat-tipped screwdriver

 7/16-inch socket

 Adjustable wrench

NOTE

Laptop computer initialized as DCP OID (Chapter 3, Section III), or any other available OID, may

be used for the following procedure.

1 At OID, display sensor status page (sequentially press REVIEW-SENSOR-STAT function keys from

1-minute display).
S100 ASOS Site Technical Manual

10-17

WARNING

Table 10.5.3. Liquid Precipitation Accumulation Sensor Removal and Installation -CONT

Step Procedure

2 On sensor status page, set report processing for tipping bucket to OFF.

Death orsevere injurymay result if power is notremoved fromsensor prior to maintenance

activities. Ensure that heater circuit breaker (located in DCP) supplying power to sensor

is set to off (right) position. 

3 Inside DCP equipment cabinet,set circuit breaker on rain gauge circuit breaker module to off(right) position.

4 If sensor is equipped with windshield (Figure 10.2.1, sheet 1), remove one section of windshield to access

rain gauge by performing the following: 

a. Using large flat-tipped screwdriver, loosen setscrews securing one section of bottom ring.

b. Using large flat-tipped screwdriver, loosen setscrews securing one section of top ring to

two support poles. Remove section of wind shield.

5 Loosen two knurled retaining knobs securing Collector A1 to lower case.

6 Lift Collector A1 straight up and remove from Lower Case A2.

7 Carefully remove tipping bucket by tilting and lifting from Bucket Frame A2A1.

8 Using small flat-tipped screwdriver, remove two screws securing Bucket Frame A2A1 to lower case.

CAUTION

If tipping bucket switch is of the mercury type it is very sensitive. Remove the bracket and

switch assembly together, holding the assembly with the switch lead wires up; otherwise,

the mercury pool could getstuck in the top end ofthe switch. The mercury switch isreadily

identifiable by the transparent vial which is vertically positioned in its bracket, while the

reed switch is opaque and cylindrical and is mounted horizontally in its bracket.

9 Carefully lift Bucket Frame A2A1 to gain access to terminal board located on side.

10 Disconnectsensor wiring harness(two wiresfrom fiberoptic transmitter) from Bucket Frame A2A1 terminal

board.

11 To remove tipping bucket switch A2A1S1:

a. Disconnect terminals from terminal board.

b. Remove screwsfromswitch bracket and remove assembly intact; ifswitch ismercury, hold

assembly with wires up.

12 Using 7/16-inch socket, loosen six 1/4 - 20 bolts and jamnuts (two on each leg) securing lower case to legs.

13 Using small flat-tipped screwdriver, remove four screws securing Bottom Plate A2A2 to lower case.

14 Disconnect heater ac input wiring from terminals 3, 4, and 5 on bottom plate terminal board.

15 Disconnect fiberoptic cable from bottom plate Fiberoptic Transmitter A2A2A1.

16 Disconnect flexible conduit and remove wires through hole in bottom plate.

17 Remove lower case from sensor support legs.

18 Remove 1/4 - 20 bolt and flat washer securing each sensor support leg to base plate. Remove three sensor

support legs.
ASOS Site Technical Manual S100

Table 10.5.3. Liquid Precipitation Accumulation Sensor Removal and Installation -CONT

Step Procedure

10-18

WARNING

INSTALLATION

Tools required:

 7/16-inch socket

 Small flat-tipped screwdriver

 Adjustable wrenches

1 At OID, ensure that report processing for tipping bucket is set to OFF.

Death orsevere injurymay result if power is notremoved fromsensor prior to maintenance

activities. Ensure that heater circuit breaker (located in DCP) supplying power to sensor

is set to off (right) position. 

2 Inside DCP equipment cabinet, ensure that circuit breaker on rain gauge circuit breaker module is set to off

(right) position. 

3 Install three 1/4 - 20 bolts and flat washerssecuring sensor support legs to base plate. Legs should be free to

rotate and will be tightened after sensor is mounted.

4 Using 7/16-inch socket, install, but do not tighten, six 1/4 - 20 bolts and jamnuts in mounting holes on lower

case leg brackets.

5 Using small flat-tipped screwdriver, remove four screws securing bottom plate to lower case.

6 Using large adjustable wrench at flexible conduit for rain gauge pedestal, remove large nut from end of

conduit. Ensure that gasket (rubber gasket with metal gasket holder) is in place on metal conduit cap (rubber

gasket toward sensor).

7 Route ac wiring and fiberoptic cable from DCP through wiring hole (not center drain hole) in Bottom Plate

A2A2 and slide threaded end offlexible conduit cap through same hole. Using large adjustable wrench, install

attaching nut to conduit cap securing flexible conduit to bottom plate.

8 Connect heater ac wiring from DCP to terminal block on Bottom Plate A2A2 as follows:

Wire Terminal

Jumper 1 to 2

Green (ground) 3

Red (ac line) 4

Yellow 5

9 Connect fiberoptic cable to bottom plate Fiberoptic Transmitter A2A2A1.

10 Using small flat-tipped screwdriver, install four screws securing bottom plate to lower case.

11 Position Lower Case A2 on sensor support legs.

12 Connect sensor earth ground to grounding stud on Bottom Plate A2A2.

13 Level lower case and tighten three bolts securing legs to base plate and six bolts securing lower case to legs.

CAUTION

If tipping bucket switch is of the mercury type, be careful to hold the switch and bracket

assembly with the wire leads upward; otherwise, the mercury pool could get stuck in the

top end of the switch.

14 Place tipping bucketswitchA2A1S1 intact with itsmounting bracket on tipping bucket frame and secure with

mounting screws.

15 Connect terminal lugs of tipping bucket switch to Bucket Frame A2A1 terminal board. If a mercury type

tipping bucket switch is to be replaced connect the capacitor to Bucket Frame A2A1 terminal board.
S100 ASOS Site Technical Manual

Table 10.5.3. Liquid Precipitation Accumulation Sensor Removal and Installation -CONT

Step Procedure

10-19

WARNING

16 Connectsensor wiring harness(two wiresfromfiberoptic transmitter)toBucket Frame A2A1 terminal board.

CAUTION

If tipping bucket switch is of the mercury type it is very sensitive. Care should be taken

when handling the switch and bracket assembly to keep the lead wires up; otherwise, the

mercury pool could get stuck in the top end of the switch.

17 Position Bucket Frame A2A1 on brackets in top of lower case.

18 Using small flat-tipped screwdriver, install two screws securing bucket frame to brackets.

19 Install tipping bucket in bucket frame with magnet facing tipping bucket switch.

20 Tip the tipping bucket several times by hand to ensure that it moves freely in Bucket Frame A2A1. At each

tip, the magnet's passing the tipping bucket switch causes a momentary contact in switch. Magnetshould not

touch switch.

If necessary, position of mercury switch can be adjusted by loosening screwssecuring switch to frame casting

and again tightening them after moving switch and bracket assembly.

If necessary, position of reed type switch can be adjusted by loosening plastic nutssecuring switch to bracket

assembly and again tightening them after moving switch.

21 Using locating pin and arrows on outside of Collector A1 as guides, carefully mount collector on lower case.

22 Tighten two knurled retaining knobs.

23 Perform rain gauge inspection and calibration check in accordance with table 10.5.1.

Table 10.5.4. Tipping Bucket Switch Removal and Installation

Step Procedure

REMOVAL

Tools required:

 Large flat-tipped screwdriver

 Small flat-tipped screwdriver

 Adjustable wrench

NOTE

Laptop computer initialized as DCP OID (Chapter 3, Section III), or any other available OID, may

be used for the following procedure.

1 At OID, display sensor status page (sequentially press REVIEW-SENSOR-STAT function keys from

1-minute display).

2 On sensor status page, set report processing for tipping bucket to OFF.

 

Death orsevere injurymay result if poweris notremoved fromsensor prior to maintenance

activities. Ensure that heater circuit breaker (located in DCP) supplying power to sensor

is set to off (right) position. 

3 Inside DCP equipment cabinet,set circuit breaker on rain gauge circuit breaker module to off(right) position.
ASOS Site Technical Manual S100

10-20

WARNING

WARNING

Table 10.5.4. Tipping Bucket Switch Removal and Installation -CONT

Step Procedure

4 Ifsensor is equipped with wind shield, remove one section of wind shield to accessrain gauge by performing

the following:

a. Using large flat-tipped screwdriver, loosen setscrews securing one section of bottom ring.

b. Using large flat-tipped screwdriver, loosen setscrews securing one section of top ring to

two support poles. Remove section of wind shield.

5 Loosen two knurled retaining knobs securing Collector A1 to lower case.

6

Heater on underside of collector funnel may be hot. Do not touch heater when removing

collector. Failure to comply may result in thermal burns.

Lift Collector A1 straight up and remove from Lower Case A2.

7 Carefully remove tipping bucket by tilting and lifting from Bucket Frame A2A1.

8 Using small flat-tipped screwdriver, remove two screws securing Bucket Frame A2A1 to lower case.

CAUTION

If tipping bucket switch is of the mercury type, it is very sensitive. Care should be taken

when moving switch to avoid getting mercury stuck in top of switch.

9 Carefully lift Bucket Frame A2A1 to gain access to terminal board located on side.

10 Remove tipping bucket switch A2A1S1 by:

a. Disconnecting the two terminal lugs from the terminal board. 

b. If the tipping bucketswitch is of the mercury type, remove the capacitor from the terminal

board and pull the switch from mounting socket. 

c. If the tipping bucket switch is of the reed type, remove the switch from mounting bracket

by loosening the two plastic retaining nuts with an adjustable wrench and then remove one

of the plastic nuts from the reed switch. Remove the reed switch from the mounting

bracket. 

INSTALLATION

Tools required:

 Small flat-tipped screwdriver

 Adjustable wrench

1 At OID, ensure that report processing for tipping bucket is set to OFF.

2

Death orsevere injurymay result if power is notremoved fromsensor priorto maintenance

activities. Ensure that heater circuit breaker (located in DCP) supplying power to sensor

is set to off (right) position.

Inside DCP equipment cabinet, ensure that circuit breaker on rain gauge circuit breaker module is set to off

(right) position.

3 Ensure that tipping bucket is removed from Bucket Frame A2A1.
S100 ASOS Site Technical Manual

Table 10.5.4. Tipping Bucket Switch Removal and Installation -CONT

Step Procedure

10-21

WARNING

4 Ensure that Bucket Frame A2A1 is loosened from lower case to gain access to terminal board on side of

frame.

CAUTION

Ifthe tipping bucketswitch is ofthe mercury type, it is very sensitive. Care should be taken

when moving switch to avoid getting mercury stuck in top of switch.

5 Slide tipping bucket switch A2A1S1 into mounting bracket.

6 If tipping bucketswitch is of the mercury type, connect capacitor and mercury switch terminal lugsto Bucket

Frame A2A1 terminal board.

If tipping bucket switch is of the reed type, install plastic retaining nuts on switch on either side of mounting

bracket. Adjust switch to allow magnet to pass within 1/4" of switch. Install switch terminal lugs to Bucket

Frame A2A1 terminal board.

7 Position Bucket Frame A2A1 on brackets in top of lower case.

8 Install tipping bucket in bucket frame with magnet facing tipping bucket switch.

9 Using small flat-tipped screwdriver, install two screws securing bucket frame to brackets.

10 Tip the tipping bucket several times by hand to ensure that it moves freely in Bucket Frame A2A1. At each

tip, the magnet's passing the tipping bucketswitch causes a momentary contact in switch. Magnet should not

touch switch. 

If necessary, position of mercury switch can be adjusted by loosening screwssecuring switch to frame casting

and again tightening them after moving switch and bracket assembly.

If necessary, position of reed type switch can be adjusted by loosening plastic nutssecuring switch to bracket

assembly and again tightening them after moving switch.

11 Using locating pin and arrow on outside of Collector A1 as guides, carefully mount collector on lower case.

12 Tighten two knurled retaining knobs.

13 Perform rain gauge inspection and calibration check in accordance with table 10.5.1.

Table 10.5.5. Fiberoptic Transmitter Removal and Installation

Step Procedure

REMOVAL

Tools required:

 Flat-tipped screwdriver

 Small flat-tipped screwdriver

 7/16-inch socket 

NOTE

Laptop computer initialized as DCP OID (Chapter 3, Section III), or any other available OID, may

be used for the following procedure.

1 At OID, display sensor status page (sequentially press REVIEW-SENSOR-STAT function keys from

1-minute display).

2 On sensor status page, set report processing for tipping bucket to OFF.

Death orsevere injurymay result if power is notremoved fromsensor priorto maintenance

activities. Ensure that heater circuit breaker (located in DCP) supplying power to sensor

is set to off (right) position. 
ASOS Site Technical Manual S100

10-22

WARNING

WARNING

Table 10.5.5. Fiberoptic Transmitter Removal and Installation - CONT

Step Procedure

3 Inside DCP equipment cabinet,set circuit breaker on rain gauge circuit breaker module to off(right) position.

4 Ifsensor is equipped with wind shield, remove one section of wind shield to accessrain gauge by performing

the following: 

a. Using large flat-tipped screwdriver, loosen setscrews securing one section of bottom ring.

b. Using large flat-tipped screwdriver, loosen setscrews securing one section of top ring to

two support poles. Remove section of wind shield.

5 Loosen two knurled retaining knobs securing Collector A1 to lower case.

Heater on underside of collector funnel may be hot. Do not touch heater when removing

collector. Failure to comply may result in thermal burns.

6 Lift Collector A1 straight up and remove from Lower Case A2.

7 Carefully remove tipping bucket by tilting and lifting from Bucket Frame A2A1.

8 Using small flat-tipped screwdriver, remove two screws securing Bucket Frame A2A1 to lower case.

CAUTION

If tipping bucket switch is of the mercury type, it is very sensitive. Care should be taken

when moving switch to avoid getting mercury stuck in top of switch.

9 Carefully lift Bucket Frame A2A1 to gain access to terminal board located on side.

10 Using smallflat-tipped screwdriver, disconnectsensor wiring harness(two wiresfromfiberoptic transmitter)

from bucket frame terminal board. 

11 Remove Bucket Frame A2A1 (with tipping bucket switch) from lower case.

12 Using 7/16-inch socket, loosen six 1/4 - 20 bolts and jamnuts (two each leg) securing lower case to legs.

13 Using small flat-tipped screwdriver, remove four screws securing Bottom Plate A2A2 to lower case.

14 Remove Lower Case A2 from sensor support legs to gain access to Fiberoptic Transmitter A2A2A1.

15 Disconnect fiberoptic cable from bottom plate Fiberoptic Transmitter A2A2A1.

16 Using small flat-tipped screwdriver, remove four screws, plastic spacers, lockwashers, and nuts securing

Fiberoptic Transmitter A2A2A1 to mounting shelf on Bottom Plate A2A2.

 INSTALLATION

Tools required:

 Small flat-tipped screwdriver

 Carpenter's level

 7/16-inch socket

 Adjustable wrench

1 At OID, ensure that report processing for tipping bucket is set to OFF.

Death orsevere injurymay result if poweris notremoved fromsensor priorto maintenance

activities. Ensure that heater circuit breaker (located in DCP) supplying power to sensor

is set to off (right) position.

2 Inside DCP equipment cabinet, ensure that circuit breaker on rain gauge circuit breaker module is set to off

(right) position.

3 Using small flat-tipped screwdriver, install four screws, plastic spacers, lockwashers, and nuts securing

Fiberoptic Transmitter A2A2A1 to mounting shelf on Bottom Plate A2A2.

4 Connect fiberoptic cable to bottom plate Fiberoptic Transmitter A2A2A1.
S100 ASOS Site Technical Manual

Table 10.5.5. Fiberoptic Transmitter Removal and Installation - CONT

Step Procedure

10-23/ (10-24 blank)

5 Position Lower Case A2 on sensor support legs.

6 Feed two wires from fiberoptic transmitter through tube in Lower Case A2.

7 Using small flat-tipped screwdriver, install four screws securing Bottom Plate A2A2 to lower case.

8 Level lower case and using 7/16-inch socket, tighten six 1/4 - 20 bolts and jamnuts securing lower case to

legs. 

CAUTION

If tipping bucket switch is of the mercury type, it is very sensitive. Care should be taken

when moving switch to avoid getting mercury stuck in top of switch.

9 Position Bucket Frame A2A1 (with tipping bucket switch) on brackets in top of lower case.

10 Using small flat-tipped screwdriver, connect two wires from fiberoptic transmitter to terminal board on side

of Bucket Frame A2A1.

11 Install tipping bucket in bucket frame with magnet facing tipping bucket switch.

12 Using flat-tipped screwdriver, install two screws securing Bucket Frame A2A1 to brackets.

13 Tip the tipping bucket several times by hand to ensure that it moves freely in Bucket Frame A2A1. At each

tip, the magnet's passing the tipping bucketswitch causes a momentary contact in switch. Magnet should not

touch switch. 

If necessary, position of mercury switch can be adjusted by loosening screwssecuring switch to frame casting

and again tightening them after moving switch and bracket assembly.

If necessary, position of reed type switch can be adjusted by loosening plastic nutssecuring switch to bracket

assembly and again tightening them after moving switch.

14 Using locating pin and arrow on outside of Collector A1 as guides, carefully mount collector on lower case.

15 Tighten two knurled retaining knobs.

16 Perform rain gauge inspection and calibration check in accordance with table 10.5.1.
S100 ASOS Site Technical Manual

11-1

CHAPTER 11

FREEZING RAIN SENSOR

SECTION I. DESCRIPTION AND LEADING PARAMETERS

11.1.1 INTRODUCTION

The ASOS freezing rain sensor is manufactured by Rosemount Aerospace, Inc. of Burnsville, Minnesota,

uses an ultrasonically vibrating probe to detect the presence of icing conditions. The vibrating frequency of

the probe decreases with the accumulation of ice. The sensor communicates with the data collection package

(DCP) via a fiberoptic serial data link. The DCP polls the sensor for status once every 60 seconds, and the

sensor responds with the current operating frequency of its probe. The DCP, in turn, passes the frequency

data to the acquisition control unit(ACU). When the ACU receives a frequency fromthe freezing rain sensor

indicating ice formation, the ACU confirms that the present weather sensor (also known as a light emitting

diode weather indicator (LEDWI)) is indicating precipitation. The indications from these two sensors

confirmice formation on the freezing rain sensor probe.In addition to probe frequency data, the freezing rain

sensor provides built in-test (BIT) results that are interpreted by the ASOS continuous self-test (CST) to

detect sensor failures.

11.1.2 PHYSICAL DESCRIPTION

The freezing rain sensor (figure 11.1.1) consists of Electronics Enclosure 2MT3A1 installed on a mounting

pole. The mounting pole itself is considered to be part of the supporting structure for the sensor and does not

have a reference designator. The electronics enclosure (figure 11.1.2) contains all of the sensor field

replaceable units (FRU’s), which include Probe Assembly A1A1, Electronics Processor Board A1A2, and

the Fiberoptic Module A1A2A1.

11.1.2.1 Probe Assembly and Heat Sink. Probe Assembly A1A1 is mounted to a heat sink made of 4.5

pounds of anodized aluminum, which, in turn, is mounted to the electronics enclosure. Heaters are built into

the tip of the probe assembly and strut. After ice has accumulated on the probe to a predetermined thickness,

ASOS instructs the sensor to turn on the probe assembly heaters to deice the probe. During deicing,

maximum heater power is 400 watts. The deicing system is capable of completely melting approximately

3.8mm of ice on the probe and strut within 30 seconds at -20 degrees Celsius (°C). The heat sink dissipates

the heat from the probe assembly following a deice cycle. The heat sink provides a recovery time (i.e., the

time required forthe sensor to revert to ambient temperature) of 10 minutesfollowing a deice cycle. The heat

sink also thermally isolates the probe assembly from the electronics, which allows accurate measurement at

temperatures at or close to 0°C (32°F).

11.1.2.2 Electronics Processor Board. Electronics Processor Board A1A2 is the central controller for the

freezing rain sensor. The electronics processor board is a microcontroller-based device with its controller

program stored as firmware on an erasable programmable read only memory (EPROM) chip. The primary

functions of the Electronics Processor board are to stimulate and read the probe assembly, control the probe

assembly heaters, communicatewith theDCPvia the fiberopticmodule, and performsensor calibrationwhen

commanded. The Electronics Processor board also performs BIT on itself and the probe assembly and

performs sensor calibration when commanded by the technician. The results of BIT are reported to the DCP

and are ultimately displayed to the technician on the freezing rain page at the operatorinterface device (OID).

The technician uses the laptop computer to issue calibration and other freezing rain sensor commands. 
ASOS Site Technical Manual S100

11-2

Figure 11.1.1. Freezing Rain Sensor

11.1.2.3 Fiberoptic Module. Fiberoptic Module A1A2A1 enables communication between the DCP and the

electronics processor board. The fiberoptic module is identical to the one used in the DCP and other ASOS

sensors. It converts DCP fiberoptic data signals to RS-232 format for the Electronics Processor board and

vice versa. 

11.1.3 FREEZING RAIN SENSOR CONFIGURATIONS

There are two configurations of the freezing rain sensor; the 0872C2 and 0872C3. The 0872C2 model

freezing rain sensor uses a floating ground which requires a ground fault check (paragraph 11.5.2.1) prior

to initial power-on and all maintenance activities. The 0872C3model uses a chassis ground and does not

require a ground fault check. 
S100 ASOS Site Technical Manual

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Figure 11.1.2. Electronics Enclosure
ASOS Site Technical Manual S100

11-4

WARNING

SECTION II. INSTALLATION

11.2.1 INTRODUCTION

To install the freezing rain sensor, the mounting pole is first installed onto the site pedestal. The electronics

enclosure is then installed on the mounting pole, and finally, electrical connections are made. Following

installation, the sensor must be inspected in accordance with the instructions contained in Section V.

Table 11.2.1 provides the step-by-step freezing rain sensor installation procedure as shown in figure 11.2.1.

Table 11.2.1. Freezing Rain Sensor Installation Procedures

Step Procedure

Tools and Materials Required:

Two 15/16-inch wrenches

7/16-inch wrench and torque driver

11/32-inch wrench

Large flat-tipped screwdriver

Large pliers (12 inch, 2-1/4 inch capacity, curved jaw)

7/16-inch hex key wrench and torque driver

 Cable ties

 Death or severe injury may result if power is not removed from sensor prior to maintenance activities. Ensure 

that circuit breakers (located in DCP) supplying power to sensor are set to off (right) position. The circuit breakers

are labeled.

CAUTION

This sensor requires that a proper ground be established and maintained for safe operation. DO NOT apply AC

power or perform maintenance until the ground condition is verified in accordance with paragraph 11.5.2.1.

NOTE

Freezing rain sensor installation should only be accomplished when environmental conditions are as specified for

field calibration; otherwise, the unit cannot be field-calibrated immediately after installation.

1 Ensure that circuit breakers on freezing rain sensor circuit breaker module inside DCP equipment cabinet are

set to off (right) position.

2 Position sensormounting pole onto sitemounting pedestal. Orient mounting pole so that electronics enclosure

opens toward walkway.

3 Using two 15/16-inch wrenches, four bolts, eight washers, four lockwashers, and four nuts, secure mounting

pole to pedestal. For each bolt, use one washer on top side of mounting pole flange and one on bottom side

of pedestal flange. Place lockwasher on underside of bottom washer and secure with nut.

4 Ensure that plastic probe cap and protective shipping cover are installed oversensor Probe Assembly A1A1.

5 Position electronics enclosure on mounting pole.

6 While supporting electronics enclosure and using a 7/16-inch hex key wrench, secure enclosure to pole by

tightening four captive bolts. Using torque driver, torque bolts to 45 inch-pounds.
S100 ASOS Site Technical Manual

11-5

Table 11.2.1. Freezing Rain Sensor Installation Procedures -CONT

Step Procedure

7 Using flat-tipped screwdriver, loosen four captive bolts securing hinged sensor access door and open door.

8 Locate and remove ESD protective conduit cap from next to the external ground stud. 

9 Route ac power wiring and fiberoptic cables through access hole in bottom of electronics enclosure.

10 Using large pliers and supplied hardware, connect flexible conduit to electronics enclosure.

11 Using pliers and split bolt connector, connect 10 Americanwire gauge (AWG)sensor ground wire to raceway

ground strap.

12

NOTE

When installing site ground wire to sensor, ensure that sufficient slack exists to allow

ground wire to be secured to sensor mounting pole.

Using 7/16-inch wrench, remove sensor-supplied nut from ground stud located at bottom right of enclosure.

Use nut to connect other end of sensor ground wire to ground stud. Torque nut to 7 foot-pounds. 

13 Using cable ties, secure sensor ground wire and cable conduit to mounting pole.

CAUTION

Electronics Processor Board A1A2 is a Class I electrostatic discharge (ESD) component.

To avoid damage to electronics processor board, use proper ESD handling procedures

including the use of a ground strap while performing the following steps.

14 Using small flat-tipped screwdriver, release catches holding plastic cover in front of ac terminal board

connector J1. Remove plastic cover.

15 On model 0872C3 only, using 11/32 inch wrench, connect green wire (chassis ground) to E1.

16 Using flat-tipped screwdriver, connect ac power wiring to ac terminal board connector J1 as follows: 

Wire color Terminal Function 

Black J1-1 115 vac (electronics)

White J1-2 Neutral (electronics)

Green J1-3 Chassis ground (model 0872C2 only)

Red J1-4 115 vac (heater)

Yellow J1-5 Neutral (heater)

17 Install protective plastic cover in front of ac terminal board connector J1. 

18 Remove plastic covers from fiberoptic cables and connect transmit (TX) cable to TRANSMIT connector of

fiberoptic module and receive (RX) cable to RECEIVE connector.

19 Using large flat-tipped screwdriver, close and secure freezing rain sensor access door.

20 Remove plastic probe cap and protective shipping coverfromprobe assembly, taking care not to touch probe.

21 Check sensor frequency using either OID REVUE-SENSOR-12HR page or laptop computer (Z1 command).

If ambient temperature is 0°C ±10°C, verify that frequency is 40,000 ±10 hertz.
ASOS Site Technical Manual S100

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Figure 11.2.1. Freezing Rain Sensor Installation
S100 ASOS Site Technical Manual

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SECTION III. OPERATION

11.3.1 INTRODUCTION

Only regularly scheduled maintenance is required after freezing rain sensor installation, unless a failure is

detected by the ASOS. All operations, including diagnostics, are handled automatically by the ASOS.

11.3.2 CONTROLS AND INDICATORS

There are no maintenance significant controls and indicators on the freezing rain sensor. The sensor is

designed for continuous operation and requires no operator or technician intervention.

11.3.3 POWER-ON

The freezing rain sensor contains no powerswitch. Upon application of 115 vac, 60 Hz powerfromthe DCP,

the sensor beginsitsstartup sequence. Power is controlled via the freezing rain sensor circuit breaker module

in the DCP.

11.3.4 NORMAL OPERATION

During normal operation, the DCP polls the freezing rain sensor once per minute for data. After it is polled,

the sensor responds with the data. This polling is automatically performed by ASOS software and requires

no user intervention. The diagnostic status of the sensor is also reported to ASOS once each minute. Results

of diagnostic interrogations are displayed on the freezing rain page at the OID.

11.3.5 POWER OFF

The freezing rain sensor contains no power switch. Heater and electronics power is controlled via the

freezing rain sensor circuit breaker module in the DCP.
S100 ASOS Site Technical Manual

11-11

Figure 11.4.1. Magnetostrictive Oscillator Circuit

SECTION IV. THEORY OF OPERATION

11.4.1 PRINCIPLES OF OPERATION

The ASOS freezing rain sensor uses an ultrasonic axially vibrating probe to detect the presence of icing

conditions. This sensing probe is a nickel alloy tube mounted in the strut at its midpoint with 1 inch

(25.4mm) exposed to the atmosphere.Thistube exhibitsmagnetostrictive properties and expands and relaxes

under the influence of a variable magnetic field. A magnetic bias field is provided by a magnet mounted

inside the strut and modulated by a drive coil surrounding the lower half of the tube. A magnetostrictive

oscillator (MSO) circuit (figure 11.4.1) is created by the addition of a pickup coil and operational amplifier.

The ultrasonic axial movement of the tube resulting from the activation of the drive coil causes a current to

be induced in the pickup coil. The current from the pickup coil drives the operational amplifier, which

provides the signal for the drive coil. The oscillation frequency of the circuit is determined by the natural

resonant frequency of the sensor tube, which is tuned to approximately 40,000 hertz. As the ice detector

encounters an icing environment, ice collects on the sensing probe. The added mass of accreted ice causes

the frequency of the sensing probe to decrease in accordance with the laws of classical mechanics. A

0.02-inch (0.5mm) thickness of ice on the probe causes the operating frequency of the probe to decrease by

approximately 133 hertz. The ice detector control circuitry utilizes a microprocessor to monitor probe

frequency when instructed by ASOS. The ice detector deicesitself through internal heating elementsin both

the strut and probe. After the ice detector is deiced, the sensing probe cools quickly and is ready to sense ice

formation again.

11.4.1.1 Probe Assembly. The probe assembly consists of the probe (sensing element), the strut, and the

deice collar. The strut contains pickup and drive coils, cartridge heaters, a magnet, and a retaining spring.

The probe assembly minimizes the flat area around the probe and contains radial grooves machined in the

conical portion of the strut. This design prevents water droplets from collecting around the probe nodal area

in still air conditions. The deice collar aids in breaking up ice that may form on the heat sink (refer to

paragraph 11.4.1.3). The sensor watershedding ability eliminatesfalse signals due to water refreezing at the

base when the atmosphere does not contain liquid water to actually form ice on the probe element.
ASOS Site Technical Manual S100

11-12

Figure 11.4.2. Freezing Rain Sensor Simplified Block Diagram

11.4.1.2 Heaters. Deicing is accomplished using a heater brazed in the interior of the probe. A pair of

cartridge heaters deice the strut. During deicing, the maximum power drain is 400 watts. The deicing system

is capable of completely melting approximately 3.8mm of ice on the strut and probe within 30 seconds at

-20°C.

11.4.1.3 Heat Sink. The heatsink consists of a 4.5-pound (2.05 kilograms) mass of anodized 6061 aluminum

that separates the electronics and probe strut. The heat sink provides heat dissipation for the probe and strut

during deicing. The purpose of the heat sink is to achieve a recovery time (defined as the time required for

the sensor to revert to ambient temperature after being deiced). The heat sink thermally isolates the sensing

element from the electronics heat, which allows accurate measurement at temperatures at or close to 0°C.

11.4.2 SIMPLIFIED BLOCK DIAGRAM DESCRIPTION

Figure 11.4.2 provides a simplified block diagram of the freezing rain sensor. All circuitry is contained on

Electronics Processor Board A1A2 or in Probe Assembly A1A1.
S100 ASOS Site Technical Manual

11-13

11.4.2.1 Electrical Input Requirements. The sensor utilizes 115vac (103.5 to 126.5 vrms), 55- to 65-hertz

input power. Normal operation continues for power interruptions of less than 10 milliseconds. Power

interruptions greater than 10 milliseconds cause the sensor to go into a reset condition. Under this condition,

the sensor resumes operation automatically after power is reapplied and the power up test sequence

completes. Terminals 1 and 2 and terminals 4 and 5 are on separate circuit breakers, respectively. The ac

power terminal connections for the sensor are as follows:

 Terminal Function

1 115 vac, hot, electronics

2 115 vac, neutral, electronics

3 Chassis ground (model 0872C2 only)

4 115 vac, hot, heater

5 115 vac, neutral, heater

E1 Chassis ground(model 0872C3 only)

11.4.2.2 CommunicationsLink.The freezing rain sensor communicates with the DCP via fiberoptic cables.

In the sensor, Fiberoptic Module A1A2A1 providesthe interface between opticalsignals of the DCP and the

RS-232 electrical signals applied to the sensor Electronics Processor board. The DCP polls the sensor for

data every 60 seconds. The sensor responds with the requested ice condition and self-test status.

11.4.2.3 Microcontroller. The sensor uses an M80C51FB 8-bit microcontroller. This chip contains an

internalRS-232 interface, which greatly simplifiesthe interface to the DCP. The unit'sfirmware is contained

on a separate ultraviolet erasable programmable read only memory (UVEPROM) chip mounted on a socket.

This permits the unit's software to be easily changed in the field by removing the UVEPROM chip from its

socket and replacing it with a chip containing the new program. An electrically erasable programmable read

only memory (EEPROM) is used to store data and tables used in computation. The unit also features a

nonvolatile read and write memory (RAM) chip that permits any detected failure codes to be stored in the

unit. A failed unit can be brought back to a repair facility and the failure code read to determine how the unit

failed.

11.4.2.4 Watchdog Timer/Reset Power Monitor. A single chip combines the function of watchdog timer

and power monitor. The purpose of the watchdog timer is to monitor the operation of the microcontroller.

The microcontroller must output a pulse into the watchdog timer approximately every second or the

watchdog timer causes the microcontroller to go into a reset condition, which reinitializes the

microcontroller.The powermonitor circuit causesthemicrocontrollerto reset any time that the voltage drops

below 4.65 vdc, which is the lower operational voltage for the memory circuits. Any time that the voltage

drops below 4.25 vdc, it is possible for the memory circuits to lose memory. The power monitor maintains

the microcontroller in a reset condition until the supply voltage is above 4.65 vdc.

11.4.2.5Heater Control.The heater control circuit consists of amechanicalrelaywith a solid-state interface

circuit to the microcontroller. When ice has accreted on the probe to a predetermined thickness (typically

2.0mm), ASOS instructs the heater circuit to furnish 115 vac to the heaters in the probe and strut, causing

the ice to melt. A mechanical relay is used instead of a solid state relay to avoid any leakage current that

might flow through the heater circuit when the relay isin a deenergized state. A leakage current would cause

some heating of the probe, which would have an adverse effect on freezing rain detection, especially around

0°C ambient air temperature. There is a feedback circuit to the microcontroller to ensure that the relay is

operating properly.
ASOS Site Technical Manual S100

11-14

11.4.3 COMMAND DESCRIPTION

The freezing rain sensor responds to commands issued by the DCP during normal operation and by the

technician during maintenance. The following paragraphs describe these commands.

11.4.3.1 Quick Reference. There are four different requests that the freezing rain sensor responds to over

its RS-232 communications link. These commands are summarized as follows: 

Command Description

Z1 Send routine data

Z3XX Perform deice cycle for "XX" seconds (minimum 01 second, maximum 60)

Z4 Perform extended diagnostics

F5 Field calibration

11.4.3.2 Power Interruptions. After a power interruption (greater than 50 milliseconds), the freezing rain

sensor takes 30 seconds to initialize and an additional 15 seconds to calculate an averaged frequency for

output. If a Z1 command is issued within 30 seconds of power-on, the sensor does not respond. If the sensor

failsto respond to anyZcommand, an additional 30 secondsisrequired before the command can be reissued.

11.4.3.3 Z1 Request (Send Routine Data). The Z1 command is the request sent from the DCP once per

minute to obtain sensor data. The sensor responds to the Z1 command with the sensor frequency normalized

over a 1-minute period. The sensor provides status (pass/fail/deice), a failure code, and a checksum value.

Figure 11.4.3 illustrates the format of the sensor response. The Z1 request should not be issued more often

than once per minute. If it is, the sensor response will be unchanged from the previous response until the

1-minute normalization period has passed. 

If a BIT failure is detected (F in status byte), the sensor does not respond correctly to Z1 or Z3 commands.

The sensor will, however, respond to Z4 and F5 commands. 

If the Z1 request is issued within 5 minutes of a deice cycle, the sensor responds with "ZD 40000CB", a

software-generated response that does not indicate the actual frequency of the sensor.

Z1 RESPONSE 

ZXYZZZZZHH

X Sensor status

P - Pass BIT

F - Fail BIT

D - Recent deice command 

Y Fail code (displayed only if sensor status = F)

1 - Probe Failure

2 - Probe Deicing Heater Failure

3 - Electronics Failure

ZZZZZ Normalized frequency between 38,400 and 40,100

HH Checksum value (hexadecimal)

Figure 11.4.3. Format of Z1 (Send Routine Data) Response
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WARNING

11.4.3.4 Z3XX Request (Perform Deice Cycle). This command causes the freezing rain sensor to initiate

a deice cycle. The probe and strut heaters are activated for 1 to 60 seconds as determined by the number

typed after "Z3". All communication with the sensor is locked out for 2 minutes following a Z3 command.

The operator should wait for at least 5 minutes before attempting any other command. 

Seriousinjury could result if the probe is contacted within 30 minutes after

issuing the Z3 command. Do not touch the probe for 30 minutes after

issuing the Z3 command.

The sensor responds to a Z3 command with "ZDOKHH". "OK" indicates that sensor heaters are operating

satisfactorily, and "HH" is a checksum value. The heater did not turn on properly if the sensor does not

respond. If "OK" indication is not received, a Z4 command should be issued to determine if the heater failed.

The probe assembly becomes hot following a Z3 command; therefore personnel should wait at least 30

minutes after the command before touching the probe assembly. The heat generated in response to a Z3

command may damage the probe assembly, especially if the ambient temperature is above the sensor normal

operating range. For thisreason, the following guidelines must be followed when turning the heater on using

the Z3 command.

Temperature Range Duration

Below 5°C (41°F) Do not turn heater on for more than 45 seconds. 

Between 5 and 15°C Do not turn heater on for more than 5 seconds.

(41 and 59°F)

Above 15°C (59°F) Do not turn heater on.

11.4.3.5 Z4 Request (Perform Extended Diagnostics). The Z4 command causes the freezing rain sensor

to perform an on-demand self-test. The test performed is an extended version of the test regularly performed

with the Z1 command. Specifically, the Z4 command performs a more detailed check of the sensor memory

circuits and exercises more of the heater circuitry. The format for the Z4 response is "ZXYHH". "X"

represents sensor status (P, F, or D), "Y" is the fail code (1, 2, or 3), and "HH" is the checksum value.

11.4.3.6 F5 Request (Field Calibration). The F5 command causes the freezing rain sensor to perform an

automatic calibration. Sensor calibration is not a periodic task and is not authorized for field use. Calibration

is performed only at the National Reconditioning Center (NRC) after replacing the probe assembly,

electronics processor board, or if frequency is outside the range of 39,990 to 40,010 Hz. Calibration is

performed only when the probe is clean and dry and environmental conditions are acceptable.

The format of the sensor's response to the F5 command is "ZXYZZZZZ". "X" indicates sensor status (P or

F), "Y" isthe fail code (1, 2, or 3), and "ZZZZZ" isthe calibration frequency. The calibration frequency must

be between 39,900 and 40,100 hertz. A failure isindicated if the calibration frequency is outside these limits.

After issuing the F5 command, the maintenance technician must wait at least 3 minutes before issuing any

other command and the calibration frequency must be 40,000 ±10 Hz.
S100 ASOS Site Technical Manual

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SECTION V. MAINTENANCE

11.5.1 INTRODUCTION

This section provides preventive and corrective maintenance procedures for the freezing rain sensor.

Preventive maintenance consists of sensor inspection and cleaning (if necessary). Corrective maintenance

consists of fault isolation using the ASOS freezing rain page and removing and replacing the sensor.

11.5.2 PREVENTIVE MAINTENANCE

The freezing rain sensor is inspected and the probe is cleaned if necessary every 90 days. Table 11.5.1

providesthe procedure forsensorinspection and cleaning. The probe is cleaned only when it is contaminated

with foreign materialsuch as dirt, oil,fingerprints, etc.If environmental conditions are acceptable, the output

frequency of the sensor is checked. If the output frequency is out of tolerance, the sensor must be replaced.

Every six months, the model 0872C2 ground path conductivity must be measured as described in paragraph

11.5.2.1.

11.5.2.1 Model 0872C2 Ground Fault Check. Verify the freezing rain sensor ground path as follows:

a. At equipment cabinet, set freezing rain sensor circuit breaker to off (right) position.

b. At model 0872C2 freezing rain sensor, check internal chassis ground inside freezing rain

enclosure by verifying J1-3 (green wire) is tight.

c. Second ground is electronics enclosure (case) ground and is 10 American Wire Gauge

(AWG) ground wire connected to single barrel lug on electronics enclosure (case). Check

ground wire connection at raceway ground wire. Check for corrosion on both lugs. If

corrosion is detected, clean by using a wire brush. 

d. Third ground is mounting pole connected to pedestal and provides earth ground. Check that

all bolts and nuts are installed and tight.

e. After the ground connections are checked and verified, set the freezing rain circuit breaker

in the DCP to the ON position.

 CAUTION

Do not touch sensor case until voltage check has been completed in step h.

g. At the OID, go to the REVUE-SITE-CONFG-SENSR page. Configure the freezing rain

sensor in the appropriate position.

h. Using a DVM, check the AC and DC voltages between the case of the freezing rain

enclosure and the 10 AWG copper wire located at the raceway. If the voltage measures more

than 0.25 volts AC or DC, remove power from the freezing rain sensor by turning OFF the

circuit breaker in the DCP. Call Bobby McCormick at 301-713-1835 X 120 and report the

problem.

11.5.3 CORRECTIVE MAINTENANCE

Freezing rain sensor corrective maintenance consists of troubleshooting failures and sensor removal and

replacement.In orderto communicate with the sensor for calibration (and troubleshooting), the maintenance

technician must connect a laptop computer to the sensor. 
ASOS Site Technical Manual S100

11-18

11.5.3.1 Using the Laptop Computer With the Freezing Rain Sensor. In order to communicate with the

sensorfor calibration and othertasks, the maintenance technician must use the laptop computer.Table 11.5.2

provides the procedure to set up the laptop computer to communicate with the sensor. Paragraph 11.4.3

provides detailed descriptions of individual sensor commands.

11.5.3.2 Troubleshooting. The FREEZING RAIN maintenance page at the OID is the primary

troubleshooting tool for the freezing rain sensor. Although diagnostic commands can be issued directly from

the laptop computer, these commands provide no additional information other than what is displayed on the

OID. Table 11.5.3 provides a summary of troubleshooting actions for different failure indications.

Table 11.5.4 provides additional troubleshooting steps for heater failures. The heater checks should be

performed only after a heater failure is indicated on the freezing rain page (or by a Z1 or Z3 command) or

if a "no response" condition occurs after a Z3 command is issued. Remove and replace the electronics

enclosure when fault isolation identifies the sensor as the source of the failure.

11.5.3.3 Calibration. The sensor is calibrated at the authorized repair facility by using the laptop computer

to issue an F5 command (paragraph 11.4.3.6). Sensor field calibration is not authorized. The freezing rain

sensor should be calibrated only when sensor F1 frequency is less than 39,990 hertz or greater than 40,010

hertz. Calibration may be performed only when the probe assembly is clean and dry and when environmental

conditions are acceptable. Calibration should not be performed under any of the following conditions:

a. When ice, snow, or liquid water is visible on the probe or at the base of the probe or when

the probe is dirty. These substances cause the frequency of the probe to deteriorate.

b. When ambient temperature is below -10°C (14°F) or above +10°C (50°F). Temperatures

outside this range cause contraction or expansion of the metallic probe, thereby modifying

its frequency.

c. Within 20 minutes of a Z3 request. A Z3 request initiates a deice cycle and the probe needs

time to return to ambient temperature.

d. When a fail condition is indicated on the freezing rain sensor page on the OID (or by Z1 or

Z4 commands). The sensor cannot be calibrated in a failed condition or when responding

to data requests or when performing self-diagnostics.

e. More than once every 90 days. More frequent calibration under normal operating conditions

is unnecessary.

Table 11.5.5 provides the procedure to calibrate the freezing rain sensor.

11.5.4 FRU REMOVAL AND INSTALLATION

Removal and installation procedures identified on the following chart by table number are provided to

facilitate safe and efficient removal of sensor FRU’s. 

Unit to be replaced Table

Electronics enclosure 11.5.6 (field level)

Electronics Processor board 11.5.7 (depot level)

Probe assembly 11.5.8 (depot level)

Fiberoptic module 11.5.9 (depot level)
S100 ASOS Site Technical Manual

11-19

WARNING

WARNING

Table 11.5.1. Freezing Rain Sensor Inspection and Cleaning

Step Procedure

Tools and Materials Required:

Soft cotton cloth

Isopropyl alcohol (ASN 052-C-12)

Laptop computer with PROCOMM Plus installed

Laptop interface (Y-shaped) cable

Large flat-tipped screwdriver

No. 1 Phillips screwdriver

Death or severe injury may result if power is not removed from sensor prior to maintenance

activities. Ensure that circuit breakers (located inside DCP equipment cabinet) supplying power to

sensor are set to off (right) position.

1 Set circuit breakers on freezing rain sensor circuit breaker module inside DCP equipment cabinet to off(right)

position. The freezing rain sensor circuit breaker module is labeled.

2

Freezing rain sensor probe assembly will be hot ifsensor recently completed a deice cycle. Ensure that probe

assembly has cooled before cleaning probe.

At freezing rain sensor, inspect surface of probe for contaminants such as dirt, oil, fingerprints, etc. If any

contaminants are present, clean probe using isopropyl alcohol and soft cotton cloth. 

3 Set circuit breakers on freezing rain sensor circuit breaker module inside DCP equipment cabinet to on (left)

position.

4 Check sensor frequency using either REVUE-SENSOR-12HR page of OID or laptop computer (Z1

command).

5

NOTE

If temperature is out of range, frequency tolerance (±10 hertz) may not be applicable. Do

not perform calibration when temperature is out of range.

If ambient temperature is 0°C ±10°C, verify that frequency is 40,000 ±10 hertz. If frequency is out of

tolerance, remove and replace the electronics enclosure.

Table 11.5.2. Using the Laptop Computer With the Freezing Rain Sensor

Step Procedure

INITIAL SETUP PROCEDURE

Tools Required:

 Laptop computer with PROCOMM Plus installed

 Laptop interface (Y-shaped) cable

 Laptop null cable

 Large flat-tipped screwdriver

 No. 1 Phillips screwdriver

1 Set circuit breakers on freezing rain sensor circuit breaker module inside DCP equipment cabinet to off

(right) position.
ASOS Site Technical Manual S100

11-20

WARNING

Table 11.5.2. Using the Laptop Computer With the Freezing Rain Sensor -CONT

Step Procedure

2

Probe Assembly A1A1 will be hot ifsensor recently completed a deice cycle. Ensure that probe assembly has

cooled before proceeding to step 2.

Using flat-tipped screwdriver, loosen four captive bolts securing hinged sensor access door and open door.

3 Using No. 1 Phillips screwdriver, disconnect DB-9 connector from fiberoptic module inside electronics

enclosure.

4 Using laptop computer null cable and interface (Y-shaped) cable, connect RS-232C (COM1) port of laptop

computer to DB-9 connector removed from fiberoptic module. 

5 Turn on laptop computer and initialize PROCOMM Plus program. After program initializes, press any key

to enter terminal mode (blank) screen.

6 Using ALT-S command (setup facility), set up the following terminal options:

a. Terminal emulation: VT220

b. Duplex: FULL

c. Soft flow control (XON/XOFF): OFF

d. Hard flow control (CTS/RTS): OFF

e. Line wrap: OFF

f. Screen scroll: ON

g. CR translation: CR

h. BS translation: NON-DESTRUCTIVE

I. Break length (milliseconds): 035

j. Enquiry: OFF

k. EGA/VGA true underline: OFF

l. Terminal width: 80

m. ANSI 7 or 8 bit commands: 8 BIT

7 Press ESC key to exit to terminal mode (blank) screen.

8 Using ALT-P command (line/port option), set current settings as follows:

a. Baud rate: 2400 or 9600 (depending on modem used)

b. Parity: NONE

c. Data bits: 8

d. Stop bits: 1

e. Port: COM1

9 Press ESC key to exit to terminal mode (blank) screen

10 Set laptop computer CAPS LOCK to ON.

11 Set circuit breakers on freezing rain sensor circuit breaker module inside DCP equipment cabinet to on (left)

position

12

NOTE

After a power interruption, the freezing rain sensor takes 30 seconds to initialize and an

additional 15 seconds to calculate an averaged frequency. If a Z1 command is issued

within 30 seconds of power-on, the sensor will not respond. If the sensor fails to respond

to any Z command, allow an additional 30 seconds and reissue the command.

The freezing rain sensor is now available for legal commands from the laptop computer. Refer to paragraph

11.4.3 for detailed descriptions of sensor commands and for specific restrictions on their use. 
S100 ASOS Site Technical Manual

Table 11.5.2. Using the Laptop Computer With the Freezing Rain Sensor -CONT

Step Procedure

11-21

WARNING

WARNING

TEARDOWN

1 At laptop computer, press ALT-X (exit) to exit PROCOMM Plus.

2 Turn off laptop computer.

3 Set circuit breakers on freezing rain sensor circuit breakermodule insideDCP equipment cabinet to off(right)

position.

4 Disconnect cables between laptop computer and freezing rain sensor. 

5 Using No. 1 Phillips screwdriver, connect freezing rain sensor DB-9 connector to fiberoptic module.

6 Using large flat-tipped screwdriver, close and secure freezing rain sensor access door.

7 Set circuit breakers on freezing rain sensor circuit breaker module inside DCP equipment cabinet to on (left)

position.

Table 11.5.3. Freezing Rain Sensor Troubleshooting

Symptom What to Do

Sensor does not respond.

(Field Level)

Connect laptop computer and issue Z1 command. 

If sensor responds, perform fiberoptic module test (Chapter 1, Section V).

If sensor fails to respond, replace sensor (Electronics Processor Board A1A2 failure).

PROBE STATUS failure

(Depot Level)

Replace Probe Assembly A1A1.

If failure continues, replace Electronics Processor Board A1A2.

ELECTRONICS STATUS

failure (Depot Level)

Replace Electronics Processor Board A1A2.

HEATER STATUS failure

(Depot Level)

Perform heater resistance test (table 11.5.4).

If resistance is out of tolerance, replace Probe Assembly A1A1. 

If resistance is within tolerance, replace Electronics Processor Board A1A2.

Table 11.5.4. Depot Level Probe Assembly Heater Troubleshooting

Step Procedure

Tools and Materials Required:

 Large flat-tipped screwdriver

Tweezers 

 Digital multimeter 

Death or severe injury may result if power is not removed from sensor prior to maintenance

activities. Ensure that circuit breakers (located in DCP) supplying power to sensor are set to off

(right) position.

1 At equipment cabinet, set freezing rain sensor circuit breaker module to off (right) position.

2

Probe Assembly A1A1 will be hot if sensor recently completed a deice cycle. Ensure

that probe assembly has cooled before proceeding to step 2. 

Using flat-tipped screwdriver, loosen four captive bolts securing hinged cover to sensor and open cover.
ASOS Site Technical Manual S100

11-22

Table 11.5.4. Depot Level Probe Assembly Heater Troubleshooting -CONT

Step Procedure

3

CAUTION

Use caution when removing probe connectors. Heater on Electronics processor board may

be damaged if too much side pressure is exerted.

Using tweezers, disconnect probe assembly electrical connectorsJ3 and J4 fromelectronics processor board.

(Refer to figure 11.1.2). To disconnect connector J4, press latch and pull connector straight out. 

4 Using digital multimeter, measure resistance between pins 1 and 2 of connector J4. Verify that resistance is

42 ±5 ohms. If resistance is out of tolerance, replace Probe Assembly A1A1. If resistance is within tolerance,

replace Electronics Processor Board A1A2.

Table 11.5.5. Depot Level Freezing Rain Sensor Calibration

Step Procedure

Tools and Materials Required:

Laptop computer with PROCOMM Plus installed

Laptop interface (Y-shaped) cable

Laptop null cable

Large flat-tipped screwdriver

No. 1 Phillips screwdriver

CAUTION

Probe must be clean and dry and environmental conditions must be acceptable (paragraph 11.5.3.3).

Sensor calibration under less than optimum conditions may result in inaccurate sensor operation.

1 Connect and initialize laptop computer for communication to freezing rain sensor in accordance with

table 11.5.2.

2 At laptop computer, type Z4 <CR>. Verify that sensor responds with "ZP HH". If failure (F) is indicated,

troubleshoot and repair sensor (based on indicated error code) before performing calibration.

3 Type F5 <CR>. Sensor responds with "ZPXXXXX" where "XXXXX" is the calibration frequency between

39,990 and 40,010 hertz.

4 Wait a minimum of 3 minutes, then type Z1 <CR>. Sensor responds with "ZP XXXXXHH". If failure (F)

is indicated, troubleshoot and repair sensor (based on indicated error code) before performing calibration.

5 Verify that frequency ("XXXXX")is 40,000 ±10 hertz. Iffrequency is out oftolerance, replace the following

FRU’s in order and recalibrate until the required tolerance is met. Allow at least 1 hour for probe to obtain

ambient temperature when replacing probe or sensor.

a. Probe Assembly A1A1

b. Electronics Processor Board A1A2

c. Freezing rain sensor

6 Disconnect laptop computer and return sensor to operation in accordance with table 11.5.2. 
S100 ASOS Site Technical Manual

11-23

WARNING

WARNING

Table 11.5.6. Electronics Enclosure Removal and Installation

Step Procedure

REMOVAL

Tools and Materials Required:

Flat-tipped screwdriver

7/16-inch wrench

Large pliers (12 inch, 2-1/4 inch capacity, curved jaw)

3/16-inch hex key wrench 

Death or severe injury may result if power is not removed from sensor prior to maintenance

activities. Ensure that circuit breakers (located in DCP) supplying power to sensor are set to off

(right) position.

NOTE

Electronics enclosure replacementshould be accomplished onlywhen environmental conditions are

as specified for field calibration; otherwise, the unit cannot be field-calibrated immediately after

replacement.

1 Set circuit breakers on freezing rain sensor circuit breaker module inside DCP equipment cabinet to off

(right) position.

2

Probe Assembly A1A1 will be hot ifsensor recently completed a deice cycle. Ensure that probe assembly has

cooled before proceeding to step 2.

Place plastic probe cap protective cover over probe assembly.

3 Using flat-tipped screwdriver, loosen four captive bolts securing hinged sensor access door and open

door. 

CAUTION

Electronics Processor Board A1A2 is a Class I ESD component. To avoid damage to

electronics processor board, use proper ESD handling procedures, including the use of a

ground strap, when performing the following steps.

4 Remove two fiberoptic cables from underneath fiberoptic module by turning counterclockwise (ccw).

Install protective plastic covers over fiberoptic connectors.

5 Using small flat-tipped screwdriver, release catches holding plastic cover over ac terminal board

connector J1. Remove plastic cover.

6 Using flat-tipped screwdriver, remove five ASOS power and chassis ground wires from terminal board

connectorJ1. Do not disconnectsensor chassis ground wire fromterminal No. 3. Afterremoving ASOS wires

and fiberoptic cables, reinstall terminal screws. 

7 Install protective plastic cover over ac terminal board connector J1. 

8 Using 7/16-inch wrench, remove pedestal ground wire from ground stud located at bottom right of

enclosure. 

9 Using large pliers, remove flexible conduit from base of electronics enclosure. Carefully pull wires and

fiberoptic cables out of enclosure.

10 Using large flat-tipped screwdriver, close and secure freezing rain sensor access door.

11 While supporting electronics enclosure and using 3/8-inch hex key wrench, loosen three captive screws on

mounting pole behind enclosure. When enclosure is free from screws, carefully lift enclosure off mounting

pole.
ASOS Site Technical Manual S100

11-24

WARNING

Table 11.5.6. Electronics Enclosure Removal and Installation -CONT

Step Procedure

INSTALLATION

Tools and Materials Required:

 Flat-tipped screwdriver

 7/16-inch wrench and torque driver

 Large pliers

 3/8-inch hex key wrench and torque driver

Death or severe injury may result if power is not removed from sensor prior to maintenance

activities. Ensure that circuit breakers (located in DCP) supplying power to sensor are set to off

(right) position.

NOTE

Electronics enclosure replacementshould be accomplished onlywhen environmental conditions are

as specified for field calibration (refer to paragraph 11.4.3.6); otherwise, the unit cannot be

field-calibrated immediately after replacement.

1 Ensure that circuit breakers on freezing rain sensor circuit breaker module inside DCP equipment cabinet

are set to off (right) position. Circuit breaker module will be labeled.

2 Ensure that protective tube is installed over Probe Assembly A1A1 of replacement enclosure.

3 Position electronics enclosure on mounting pole.

4 While supporting electronics enclosure and using 3/8-inch hex key wrench, secure enclosure to pole by

tightening three captive bolts. Using torque driver, torque bolts to 45 inch-pounds.

5 Using flat-tipped screwdriver, loosen four captive bolts securing hinged sensor access door and open

door.

6 Route ac power wiring and fiberoptic cables through access hole in bottom of electronics

enclosure.

7 Using large pliers and hardware supplied, connect flexible conduit to electronics enclosure.

8 Using 7/16-inch wrench, remove sensor-supplied nut from ground stud located at bottom right of enclosure.

(Refer to figure 11.1.2.) Use nut to connect sensor pedestal 10 AWG ground wire to ground stud. Do not

torque nut more than 7 foot-pounds. 

9

CAUTION

Electronics Processor Board A1A2 is a Class I ESD component. To avoid damage to

electronics processor board, use proper ESD handling procedures, including the use of a

ground strap, when performing the following steps.

Using small flat-tipped screwdriver, release catches holding plastic cover over ac terminal board connector

J1. Remove plastic cover.

10 On model 0872C3 only, using 11/32 inch wrench, connect green wire (chassis ground) to E1.

11 Using flat-tipped screwdriver, connect ac power wiring to ac terminal board connector J1 as follows: 

Wire color Terminal Function 

Black J1-1 115 vac (electronics)

White J1-2 Neutral (electronics)

Green J1-3 Chassis ground (model 0872C2 only)

Red J1-4 115 vac (heater)

Yellow J1-5 Neutral (heater)

12 Install protective plastic cover over ac terminal board connector J1. 
S100 ASOS Site Technical Manual

Table 11.5.6. Electronics Enclosure Removal and Installation -CONT

Step Procedure

11-25

WARNING

WARNING

13 Remove plastic covers from fiberoptic cables and connect transmit (TX) cable to TRANSMIT connector

of fiberoptic module and receive (RX) cable to RECEIVE connector.

14 Remove protective cover from probe assembly.

15 Check sensor frequency using either OID REVUE-SENSOR-12HR page or laptop computer (Z1

command).If ambient temperature is 0°C ±10°C, verify that frequency is 40,000 ±10 hertz.

Table 11.5.7. Depot Level Electronics Processor Board Removal and Installation

Step Procedure

REMOVAL

Tools and Materials Required:

Flat-tipped screwdriver

 Small flat-tipped screwdriver

 No. 3 Phillips screwdriver

Tweezers

Death or severe injury may result if power is not removed from sensor prior to maintenance

activities. Ensure that circuit breakers (located in DCP) supplying power to sensor are set to off

(right) position.

CAUTION

Processor board is a Class I ESD component. To avoid damage to circuit boards, use proper ESD

handling procedures, including the use of a ground strap, when performing the following steps. 

NOTE

Electronics processor board replacement should be accomplished only when environmental

conditions are as specified for field calibration; otherwise, the unit cannot be field-calibrated

immediately after replacement.

1 Set circuit breakers on freezing rain sensor circuit breaker module inside DCP equipment cabinet to off(right)

position. Circuit breaker module will be labeled.

2

Probe Assembly A1A1 will be hot if sensor recently completed a deice cycle. Ensure that

probe assembly has cooled before proceeding to step 2. 

Using flat-tipped screwdriver, loosen four captive bolts securing cover sensor and open cover. Cover is

hinged to enclosure.

3

CAUTION

Electronics Processor Board A1A2 is a Class I ESD component. To avoid damage to

electronics processor board, use proper ESD handling procedures, including the use of a

ground strap, when performing the following steps.

Remove two fiberoptic cables from underneath fiberoptic module by turning ccw. Install protective plastic

covers over fiberoptic connectors.

4 Using small flat-tipped screwdriver, release catches holding plastic cover over ac terminal board connector

J1. Remove plastic cover.
ASOS Site Technical Manual S100

11-26

WARNING

Table 11.5.7. Depot Level Electronics Processor Board Removal and Installation - CONT

Step Procedure

5 Using flat-tipped screwdriver, remove five power and chassis ground wires from terminal board connector

J1.

6

CAUTION

Use caution when removing probe connectors. Heater on electronics processor board may

be damaged if too much side pressure is exerted.

Disconnect probe assembly electrical connectorsfromelectronics processor board connectorsJ3 and J4. Use

tweezers to press latch and pull connector straight out. 

7

CAUTION

Use caution when removing capacitor connectors. Heater on electronics processor board

may be damaged if too much side pressure is exerted.

NOTE

Capacitors C7 and C9 are matched to Probe Assembly A1A1 and should be retained to use

on the replacement electronics processor board.

Disconnect and tag select capacitors C7 and C9 of Electronics processor board. Use tweezers to press latch

and pull connector with capacitor mounted straight out. 

8 Using No. 3 Phillips screwdriver, remove four screws securing Electronics Processor Board A1A2 to

electronics enclosure.

INSTALLATION

Tools and Materials Required:

Flat-tipped screwdriver

 Small flat-tipped screwdriver

 No. 3 Phillips screwdriver

Tweezers

Death or severe injury may result if power is not removed from sensor prior to maintenance

activities. Ensure that circuit breakers (located in DCP) supplying power to sensor are set to off

(right) position.

CAUTION

Processor board is a Class I ESD component. To avoid damage to circuit boards, use proper ESD

handling procedures, including the use of a ground strap, when performing the following steps. 

NOTE

Electronics processor board replacement should be accomplished only when environmental

conditions are as specified for field calibration; otherwise, the unit cannot be field-calibrated

immediately after replacement.

1 Ensure that circuit breakers on freezing rain sensor circuit breaker module inside DCP equipment cabinet are

set to off (right) position.

2 Position Electronics Processor Board A1A2 in electronics enclosure so that terminal board connector J1 is

toward bottom and screw holes in board align with holes in enclosure.

3 Using No. 3 Phillips screwdriver, install four screws securing Electronics processor board to electronics

enclosure.

4

NOTE

Select capacitors C7 and C9 should be retained from previously removed board.

Using tweezers and tags as a guide, install select capacitors C7 and C9 onto Electronics Processor board. 
S100 ASOS Site Technical Manual

Table 11.5.7. Depot Level Electronics Processor Board Removal and Installation - CONT

Step Procedure

11-27

WARNING

WARNING

5 Using tweezers, install probe assembly electrical connectors onto Electronics Processor board connectorsJ3

and J4.

6 On model 0872C3 only, using 11/32 inch wrench, connect green wire (chassis ground) to E1.

7 Using flat-tipped screwdriver, connect ac power wiring to ac terminal board connector J1 as follows: 

Wire color Terminal Function 

Black J1-1 115 vac (electronics)

White J1-2 Neutral (electronics)

Green J1-3 Chassis ground (model 0872C2 only)

Red J1-4 115 vac (heater)

Yellow J1-5 Neutral (heater)

8 Install protective plastic cover over ac terminal board connector J1. 

9 Remove protective plastic covers from fiberoptic cables. Connect transmit (TX) cable to TRANSMIT

connector of fiberoptic module and receive (RX) cable to RECEIVE connector.

10 Calibrate freezing rain sensor in accordance with table 11.5.5.

Table 11.5.8. Depot Level Probe Assembly Removal and Installation

Step Procedure

REMOVAL

Tools and Materials Required:

Flat-tipped screwdriver 

 No. 1 Phillips screwdriver

Tweezers

Death or severe injury may result if power is not removed from sensor prior to maintenance

activities. Ensure that circuit breakers (located in DCP) supplying power to sensor are set to off

(right) position.

NOTE

Probe assembly replacement should be accomplished only when environmental conditions are as

specified for field calibration; otherwise, the unit cannot be field-calibrated immediately after

replacement.

1 Set circuit breakers on freezing rain sensor circuit breaker module inside DCP equipment cabinet to off(right)

position.

2

Probe Assembly A1A1 will be hot if sensor recently completed a deice cycle. Ensure that

probe assembly has cooled before proceeding with step 2.

Place protective cover over probe assembly. 

3 Using flat-tipped screwdriver, loosen four captive bolts securing cover to sensor and open cover. Cover is

hinged to enclosure.
ASOS Site Technical Manual S100

11-28

WARNING

Table 11.5.8. Depot Level Probe Assembly Removal and Installation - CONT

Step Procedure

4

CAUTION

Use caution when removing probe connectors. Heater on electronics processor board may

be damaged if too much side pressure is exerted.

Using tweezers, disconnect probe assembly electrical connectors from electronics processor board connectors

J3 and J4. For connector J4, press latch and pull connector straight out. 

5

CAUTION

Probe assembly cables and connectors are fragile. Remove cables and connectors slowly

so that cables do not catch as they are guided through the housing or heat sink.

NOTE

An O-ring that is used between the probe assembly and heat sink may come out when

probe assembly isremoved. Retain O-ring for installation of replacement probe assembly.

Using No. 1 Phillipsscrewdriver, remove fourscrews securing Probe Assembly A1A1 to heatsink. Carefully

lift probe assembly from heat sink, guiding cables through housing and heat sink. Retain O-ring.

6

CAUTION

Use caution when removing capacitor connectors. Heater on electronics processor board

may be damaged if too much side pressure is exerted.

NOTE

Select capacitors C7 and C9 are a matched set and are packed and shipped with replaced

probe assembly. New capacitors should be obtained from probe replacement kit. 

Disconnect and tag select capacitorsC7 and C9 fromelectronics processor board. Use tweezersto presslatch

and pull connector with capacitor mounted straight out.

INSTALLATION

Tools and Materials Required:

Flat-tipped screwdriver 

 No. 1 Phillips screwdriver

Tweezers

Death or severe injury may result if power is not removed from sensor prior to maintenance

activities. Ensure that circuit breakers (located in DCP) supplying power to sensor are set to off

(right) position.

NOTE

Probe assembly replacement should be accomplished only when environmental conditions are as

specified for field calibration; otherwise, the unit cannot be field-calibrated immediately after

replacement.

1 Ensure that circuit breakers on freezing rain sensor circuit breaker module inside DCP equipment cabinet are

set to off (right) position.

2

NOTE

Replacement capacitors C7 and C9 are provided with replacement probe assembly.

Obtain probe assembly field replaceable kit (P/N 00872-0277). Ensure that kit contains replacement

capacitors C7 and C9 and that protective cover is installed over probe assembly.
S100 ASOS Site Technical Manual

Table 11.5.8. Depot Level Probe Assembly Removal and Installation - CONT

Step Procedure

11-29

WARNING

3

CAUTION

Electronics Processor Board A1A2 is a Class I ESD component. To avoid damage to

electronics processor board, use proper ESD handling procedures, including the use of a

ground strap, when performing the following steps.

Using tweezers, install replacement select capacitors C7 and C9 onto electronics processor board. 

4 Place O-ring into channel on top of heat sink.

5

CAUTION

Probe assembly cables and connectors are fragile. Use caution so that cables do not catch

as they are guided through the heat sink or housing. 

While holding probe assembly with one hand, carefully guide two cables though hole in heat sink and into

electronics enclosure.

6 Using No. 1 Phillips screwdriver, install four screws securing probe assembly to heat sink. 

7 Using tweezers, install probe assembly electrical connectors onto electronics processor board connectors J3

and J4.

8 Remove protective cover from probe assembly.

9 Calibrate freezing rain sensor in accordance with table 11.5.5.

Table 11.5.9. Fiberoptic Module Removal and Installation

Step Procedure

REMOVAL

Tools and Materials Required:

Flat-tipped screwdriver 

 Small flat-tipped screwdriver

 No. 1 Phillips screwdriver

Death or severe injury may result if power is not removed from sensor prior to maintenance

activities. Ensure that circuit breakers (located in DCP) supplying power to sensor are set to off

(right) position.

1 Set circuit breakers on freezing rain sensor circuit breakermodule insideDCP equipment cabinet to off(right)

position.

2 Using flat-tipped screwdriver, loosen four captive bolts securing hinged sensor access door and open door.

3 Using No. 1 Phillipsscrewdriver, loosen two retaining screws on DB-9 connector located on top offiberoptic

module. Remove DB-9 connector.

4 Install signal cable on fiberoptic module DB-9 connector. Using No. 1 Phillips screwdriver, tighten two

retaining screws.

5 Using small flat-tipped screwdriver, remove four screws securing fiberoptic module to mounting plate.
ASOS Site Technical Manual S100

11-30

WARNING

Table 11.5.9. Fiberoptic Module Removal and Installation -CONT

Step Procedure

INSTALLATION

Tools and Materials Required:

Flat-tipped screwdriver

 Small flat-tipped screwdriver

 No. 1 Phillips screwdriver

Death or severe injury may result if power is not removed from sensor prior to maintenance

activities. Ensure that circuit breakers (located in DCP) supplying power to sensor are set to off

(right) position.

2 With DB-9 connector toward the front (RECEIVE) and using small flat-tipped screwdriver, install four

screws to secure fiberoptic module to mounting plate. 

3 Remove plastic coversfromfiberoptic connectors and connect transmit(TX) cable to TRANSMIT connector

and receive (RX) cable to RECEIVE connector.

4 Remove two fiberoptic cables from underneath fiberoptic module by turning ccw. Install protective plastic

covers over fiberoptic connectors.

5 Using large flat-tipped screwdriver, close and secure freezing rain sensor access door.

6 Set circuit breakers on freezing rain sensor circuit breaker module inside DCP equipment cabinet to on (left)

position.
S100 ASOS Site Technical Manual

Change 2 12-1

CHAPTER 12

GROUND-TO-AIR RADIO

SECTION I. DESCRIPTION AND LEADING PARTICULARS

12.1.1 INTRODUCTION

This chapter provides field service information for the ground-to-air (GTA) radio system that is installed at

selected sites. The GTA radio continuously transmits regularly updated information to pilots and other

listeners. The system manager may select either 1-minute data, hourly METAR’s or SPECI’s for broadcast.

This chapter includes a physical description, installation and operation instructions, theory of operation, and

preventive and corrective maintenance procedures.

12.1.2 PHYSICAL DESCRIPTION

The GTA radio is installed in the acquisition control unit (ACU) at location 1A10 below the RF/pressure

mounting shelf (figure 12.1.1). Chapter 2 provides a complete description of the ACU. The I/O panel

assembly is the interface for the GTA radio to the antenna with connector J43 as the GTA radio output

connection plug to the antenna. Connector J43 is a surge suppressor that is located on the I/O panel next to

connector J39. Connector J43 provides protection for the GTA radio system from outside interference.

Peripheral cable assembly W79, installed on the back of the ACU behind location 1A4, provides power for

the radio. The radio interfaces with the voice recorder/playback board via cable W076. The radio is also

connected to the SIO board via the same adapter cable for RS-232 communications. The RS-232 cable

applies serial data to the radio for self-test and setup information. 

The antenna is a Government-furnished Collinear antenna, the dipole elements are mounted one above the

other in a common axis. These dipoles are sealed in a single fiberglassradome that provides both mechanical

stability and environmental protection. The Collinear antenna is lightweight, rugged, and weatherproof and

provides a vertically polarized, omnidirectional azimuth pattern with 6 dBof gain.The antenna operates over

a frequency range of 116 to 137 MHz. An antenna cable connects the antenna to connector J43. The length

of the cable varies from site to site. 

At some single-cabinet combined ASOS sites, an alternative GTA Antenna Kit (62828-40507-10) may be $

installed in lieu of the collinear antenna. This alternative antenna is a ground-plane antenna mounted near $

the top of the wind tower. The type and location of this antenna reduces GTA radio voice-modulated $

transmission interference with the Present Weather Sensor. Refer to Chapter 14 for descriptions and $

replacement procedures for this antenna. $
ASOS Site Technical Manual S100

12-2

Figure 12.1.1. Acquisition Control Unit (ACU)
S100 ASOS Site Technical Manual

12-3/ (12-4 blank)

SECTION II. INSTALLATION

The site technician is notresponsible for the installation of the GTA radio; however, installation instructions

are provided in AAI Systems Management, Inc. Field Modification Kit 051. Section V containsremoval and

replacement procedures for the GTA radio.
S100 ASOS Site Technical Manual

12-5

SECTION III. OPERATION

12.3.1 INTRODUCTION

The GTA radio normally operates in automatic mode, which requires no operator intervention. A message

is continuously transmitted overthe air waves via the GTA radio antenna. Maintenance control of the system

is performed from the operator interface device (OID) where the user can monitor self-test results, adjust

broadcast power level and frequency, initiate diagnostic tests, review and update the maintenance log, and

configure the GTA radio. In addition to the OID displays, the GTA radio contains controls and indicators

that can be used during system maintenance. 

12.3.2 CONTROLS AND INDICATORS

12.3.2.1 General. The GTA radio contains only a few controls and indicators, which may require setting

or monitoring by the technician. There is a liquid crystal display (LCD) on the front panel of the radio that

provides an alphanumeric display showing operatingmodes,frequency, messages, andmeasurements.These

controls and indicators are illustrated on figure 12.3.1 and described in table 12.3.1. Figure 12.3.2 illustrates

rear panel connectors.

12.3.2.2 Using the Front Panel Controls and Indicators. The following paragraphs describe the

procedures used to enable and disable the display so that configuration changes can be made to the GTA

radio.

When the GTA radio is powered up, the display is enabled and the frequency select mode is displayed as

shown in table 12.3.2. The pushbuttons are also enabled, and the operator can make configuration and mode

changes using the MOD and up and down arrow pushbuttons. Table 12.3.2 describes all possible modes for

the GTA radio.

If the pushbuttons and display are disabled (i.e., display is blank), the display can be enabled by pressing the

enable (ENB) pushbutton. The enable displaymode is displayed asshown in table 12.3.2.This display shows

the current operating frequency and prompts the operator to press the ENB pushbutton two more times. If

the ENB pushbutton is not pressed a second time within 10 seconds or if any other pushbutton is pressed,

the display and pushbuttons return to the disabled mode.

The ENB pushbutton is pressed twice in quick succession. The display and pushbuttons are then enabled and

frequency select mode is displayed as shown in table 12.3.2. If the presses occur more than 1/2 second apart

or if any other pushbutton is pressed, the display and pushbuttons return to the disabled mode.

After it is enabled, the display can be disabled by pressing the ENB pushbutton three times; if no pushbutton

presses occur for 2 minutes, timeout occurs and the display and pushbuttons are automatically disabled.
ASOS Site Technical Manual S100

12-6

Figure 12.3.1. GTA Radio Front Panel Controls and Indicators

Table 12.3.1. GTA Radio Front Panel Controls and Indicators

Control/Indicator Type Description

XMIT Green light emitting diode

(LED) indicator

Illuminates when the transmitter is keyed.

MIC Audio connector Not used by ASOS.

ENB Pushbutton Enablesthe operatorinterface pushbutton switches and display

if the display is blank and the switches are disabled. Disables

the interface switches and display if they are active.

MOD Pushbutton Selects between the display/control modes.

Down arrow Pushbutton Used in conjunction with the MOD switch to make changes to

the operating parameters of the GTA radio. Decrements the

parameter by one unit.

Up arrow Pushbutton Used in conjunction with the MOD switch to make changes to

the operating parameters of the GTA radio. Increments the

parameter by one unit.

DC PWR Green LED indicator Not used by ASOS.

AC PWR Green LED indicator Illuminates when ac power is applied to the GTA radio.

AC/PWR ON 

(120 VAC/60 HZ)

Power switch/circuit breaker Applies ac power to the GTA radio and provides overcurrent

protection for the ac line.

DC/PWR ON 

(24 VDC)

Power switch/circuit breaker Not used by ASOS.

LCD 2 x 16 alphanumeric display Shows operating modes, frequency, messages, and measurements

VSWR RedLEDindicator Illuminateswhen voltage standing wave ratio (VSWR) exceeds

2.8:1. (This indicator is not installed on all units.)
S100 ASOS Site Technical Manual

12-7

Figure 12.3.2. GTA Radio Rear Panel Connectors

Freq 119.600 MHz Press

ENB twice

Frequency -- MHz

119.600

OOOG

Signal Meter

Freq 119.600 MHz

+5V Level 4.78

Freq 119.600 MHz

+12V Level +11.6

Table 12.3.2. Display/Control Modes (Panels)

Mode LCD Display Function

Disabled

Disables any mode or configuration from the

pushbuttons. The ENB pushbutton is the only

active pushbutton when display is disabled.

Enable display

Displayed after ENB pushbutton is pressed

once. Two additional presses enable pushbuttons and display for configuration changes.

Frequency select

Displays current operating frequency and

allows operator to change operating frequency

using pushbuttons.

Monitor Functions

Signal strength meter

The bar graph displays relative transmit signal

strength. The maximum number of bars is 16.

+5V test

Displays internal measured operating voltage

for +5V supply line.

+12V test

Displays internal measured operating voltage

for +12V supply line.
ASOS Site Technical Manual S100

12-8

Freq 119.600 MHz

-12V Level -11.6

Freq 119.600 MHz

+80V Level +79.7

Freq 119.600 MHz

Xmit Timeout 00

OOOOOG

Xmit Power 105

Freq 119.600 MHz

Mod Index 90

Freq 119.600 MHz

Warp Setting 16

Table 12.3.2. Display/Control Modes (Panels) -CONT

Mode LCD Display Function

-12V test

$ Displays internal measured operating voltage

for -12V supply line.

+80V test

$ Displays internal measured operating voltage

for +80V supply line.

Transmit timeout

adjust

$ Allows operator to set duration of timeout in

10-second intervals from 0 to 300 seconds. In

ASOS environment, transmission is continuous. Timeout is not used.

Transmit power adjust

$ Allows operatorto adjust transmit output power

level.

Modulation index

adjust

$ Allows operator to adjust percent of AM

modulation based on a 1- kHz, -15-dBm

(600-ohm) audio modulation signal.

Crystal warp adjust

Allows operator to adjust reference crystal

oscillator warp factor to align oscillator

frequency within tolerance limits.

12.3.3 TURN-ON PROCEDURES

The GTA radio is designed for continuous operation and normally remains on at all times, except for

maintenance or repair activities. The GTA radio is normally powered on or powered off when the ACU is

turned on or off. (Chapter 2 describes ACU power-on and power-off.) To turn on the GTA radio manually,

the front panel door of the ACU is opened and the AC PWR switch is pressed; a green LED then illuminates,

showing that ac power has been applied.

12.3.4 TURNOFF PROCEDURES

The GTA radio is normally turned off only for maintenance purposes. When the ACU cabinet is opened and

the AC PWR switch is pressed, the green LED extinguishes, indicating that ac power is no longer being

applied.

12.3.5 GTA RADIO CONFIGURING/OID CONTROL

The following paragraphs describe the manner in which the GTA radio is configured and controlled from

the OID pages. The transmission frequency of the radio cannot be changed in the field unless the site is

licensed for the new frequency.
S100 ASOS Site Technical Manual

12-9/ (12-10 blank)

12.3.5.1 Configuring the GTA Radio - General. The GTA radio must be configured into ASOS via the

REVUE-CONFG-COMMS page in order for the CPU in the ACU to communicate with the GTA radio. The

configuration is accomplished by using the CHANGE function to assign the GTA radio to an available

RS-232 SIO port. When using theCHANGE function, the maintenance technician is prompted to enterserial

communications parameters (1200 baud rate, no parity, 8-bit words, 1 stop bit, and no handshaking). The

connection is hard-wired (lease line if the GTA radio is not installed in the ACU). In addition to these setup

parameters, the maintenance technician must also enter a frequency and power level. The valid frequency

values are from 117.975 to 136.975. Valid power values are from 0 to the maximum power setting of the

specific radio; however, each GTA radio has a unique maximum value (e.g., 180, 220, etc) that could be less

than 255. In any case, the maximum power value for a given radio is 10 watts. Power is not set or adjusted

arbitrarily, but is done using a power meter at the antenna (paragraph 12.5.2.1). The GTA radio has erasable

programmable read only memory (EPROM) so that in the event that the radio loses power, it retains the

configuration data. Configuring the GTA radio in ASOS affects only the RS-232 connection. If the GTA

radio is disabled or deconfigured from the OID, the CPU will not communicate with it even though the GTA

radio continues to broadcast. The only way to stop the GTA radio from transmitting is to turn it off at the

front panel on the radio.

12.3.5.2 Alternative Means of Adjusting Power and Frequency. The maintenance technician may have

to periodically set or adjust power or frequency (preventive maintenance, installation, and troubleshooting).

The GTA radio power and frequency may be adjusted from the COMMS page as described above. Because

an OID may not be in the same location asthe GTA radio, ASOS allows the maintenance technician to make

some adjustments from the LCD display at the radio itself (refer to paragraph 12.3.2.2). When adjustments

to power and frequency are made from the GTA radio, the ACU copies and reads the current setting and

stores it as the final setting. The latest setting is displayed on the COMMS page, whether or not it was

changed from the OID or the GTA radio itself.

12.3.5.3 AOMC Frequency Storage. For each site, the ASOS Operations and MonitoringCenter (AOMC)

stores the GTA radio configuration data, including communications setup (e.g., baud rate, parity, etc) and

the RF frequency. Whenever these parameters are changed in the field (by the OID or from the GTA radio

panel), the current configuration is uploaded to the AOMC. The RF frequency may not be changed unless

the site is licensed for the new frequency. It is available for later download request. The power setting is not

uploaded to the AOMC, because the power setting is variable between radios and is dependent on cable

length and other factors.
S100 ASOS Site Technical Manual

12-11

SECTION IV. THEORY OF OPERATION

12.4.1 INTRODUCTION

This section provides a detailed description of the manner in which the GTA radio interfaces with the ACU

and other components in the cabinet.

12.4.2 SIMPLIFIED BLOCK DIAGRAM

The simplified block diagram (figure 12.4.1) illustrates the basic system components and their functional

relationships. The GTA radio receives serial data for self-test and setup information from an available

RS-232 port (SIO boards 4 through 8). The GTA radio also receives ANALOG VOICE data from the voice

recorder/playback board. The GTA radio amplifies the input voice signal and sends it through its connector

J4 via coaxial cable to ACU I/O panel connector J43. The GTA radio antenna is connected via coaxial cable

W9 to I/O panel connector J43.

12.4.3 DETAILED BLOCK DIAGRAM

This section contains a description and detailed block diagram (figure 12.4.2) of the GTA radio

configuration. Power distribution and control is described using detailed block diagrams of the distribution

of ac voltage to the GTA radio. 

12.4.3.1 SIO Board. The SIO board transmits data from the VMEBUS through its connector P1, processes

the information, then transmits the information from its connector P2 via the RS-232 DATA line to cable

assembly W076 connector P2 to GTA radio pin P1 to jack J5. (Chapter 2, Section IV, provides detailed

information on the SIO board.)

12.4.3.2 Voice Recorder/Playback Board. The voice recorder/playback board receives power interface

logic from the VMEBUS on connector P1 to connector P2. Digitized voice information is supplied from

Voice ProcessorBoard A20.Thisinformation istransmitted via connector P2 to connector P67 ofthe ring/tip

to connector P3 of cable W076 to the GTA radio from connector P1 to jack J5. (Chapter 2, Section IV,

provides additional information on the voice recorder/playback board.)

12.4.3.3 Power Distribution Assembly. The power distribution assembly receives ac power from the

facility main power line and distributes ac power to the GTA radio on jack J1 via cable assembly W79.

12.4.3.4 I/O Panel. The I/O panel is used as the master connection point for all inputs to and outputs from

the ACU. The output signal from connector J4 on the GTA radio is fed via coaxial cable to connector J43

on the I/O panel. Connector J43 also contains a surge suppressor. From connector J43, the signal is fed via

coaxial cable W9 to the antenna.

12.4.4 GTA RADIO SELF-TEST

The GTA radio self-test is performed when the ACU requests data from the radio. The SIO board is

connected to the GTA radio by the RS-232 cable and cable W076. The ACU sends a data request to the SIO

board, which, in turn, sends it to the GTA radio. The GTA radio replies, sending the response back through

the RS-232 cable to the SIO board, which sends the response to the ACU. The ACU then polls the radio

every 15 minutesto verify that allsystems are operating correctly. If there is a problemdetected by the ACU,

a fault is displayed on the OID screen.RADIO ID NUMBER,TRANSMIT FREQUENCY, POWERLEVEL
ASOS Site Technical Manual S100

12-12VME BUS

RS-232

SERIAL I/O BOARDS

4 THRU 8

(OPTIONAL)

VOICE

RECORDER/

PLAYBACK

BOARD

GTA

RADIO

ANTENNA

RS-232 DATA

ANALOG VOICE

Figure 12.4.1. GTA Radio Simplified Block Diagram

SETTING, and MAX POWER SETTING are displays of the values that have already been entered into the

system. The RADIO ID NUMBER is the designator specific to each radio. TRANSMIT FREQUENCY is

the value equal to the command frequency (117.975 to 136.975 in increments of 0.025). The POWER

LEVEL SETTING value is equal to the commanded power level of 0 to the maximum power setting for a

specific radio. MAX POWERSETTING displaysthemaximumpowersetting forthe radio actually installed

in the ACU. The power setting is different for each radio and is between 0 and the maximum power setting

for a specific radio. The POWER SUPPLY STATUS test consists of four individual tests. The +5V test

indicates that the internal measured operating voltage is within 3V and 7V. The +12V test indicates that the

internal measured operating voltage is within 9.6V and 14.4V. The -12V test indicates that the internal

measured operating voltage is within -14.4V and -9.6V, and the -80V test indicatesthat the internal measured

operating voltage is within -96V and -64V. If the test results on the POWER SUPPLY STATUS test are

outside the tolerances, the test fails. The VFWD and VRFD values are digital representations of the forward

and reflected voltages, respectively, as measured by the GTA radio. These digital values may range from 0

to the maximum power setting and do not represent actual voltage values. The ASOS continuous self-test

(CST) performs a comparison calculation of these values. As long as the VRFD value islessthan 75 percent

of the VFWD value, a pass indication is displayed for both the VFWD and VRFD field. If the VRFD value

is greater than or equal to 75 percent of the VFWD value, the test failure indicator (F) is displayed for both

fields. The RADIO RESPONSE test indicates if the ACU is capable of communicating with the GTA radio.
S100 ASOS Site Technical Manual

Figure 12.4.2. GTA Radio, Detailed Block

Diagram

12-13/ (12-14 blank)
S100 ASOS Site Technical Manual

Change 1 12-15

SECTION V. MAINTENANCE

12.5.1 INTRODUCTION

This section provides the preventive and corrective maintenance procedures for the GTA radio. Preventive

maintenance consists of the RF power output check, modulation level check, VSWR at transmitter output check,

and frequency stability check. Corrective maintenance consists of fault isolation using the ASOS GTA radio

maintenance display and removal and replacement of field replaceable units (FRU’s).

12.5.2 PREVENTIVE MAINTENANCE

Preventive maintenance consists of those procedures that are performed on a scheduled basis to maintain the GTA

radio in an operational state. Table 12.5.1 lists the regularly required performance checks necessary to ensure

operation within established tolerances and limits and provides a schedule for their performance.

12.5.2.1 RF Power Output Check. This check (table 12.5.2) is performed at the antenna and is designed to

verify that the RF power output of the GTA radio is the required amount at the antenna. The test equipment is

connected as shown on figure 12.5.1.

12.5.2.2 Modulation Level Check. This check (table 12.5.3 Preferred or 12.5.3 Alternative) ensures a constant

level of modulation. The test equipment is connected as shown on figure 12.5.2.

12.5.2.3 VSWR at Transmitter Output Check. This check (table 12.5.4) ascertains that the VSWR, as

measured at the GTA radio, does not exceed 1.8:1. The test equipment is connected as shown on figure 12.5.3.

12.5.2.4 Frequency Stability Check. This check (table 12.5.5) determines if the transmitter output frequency is

within ±0.0005 percent tolerance. The test equipment is connected as shown on figure 12.5.4.

12.5.2.5 Antenna Cable Insulation Verification. This check (table 12.5.6) performed annually, verifies the

antenna cable insulation integrity. Test equipment is connected as shown in figure 12.5.5.

Table 12.5.1. Periodic Performance Checks

Interval What To Do How To Do It

90 days

RF Power Output Check Table 12.5.2

Modulation Level Check Table 12.5.3

VSWR at Transmitter Output Check Table 12.5.4

Frequency Stability Check Table 12.5.5

Annually Verify Antenna Cable Conductance and Insulation Table 12.5.6

Table 12.5.2. RF Power Output Check

Step Procedure

Tools and Materials Required:

RF power meter w/10-watt, 100-250 MHz element

One N-N test cable

1 At front of GTA radio, press AC PWR switch to remove GTA radio power.

2 At I/O panel on ACU, disconnect antenna cable W9 from connector J43.

3 Connect antenna cable W9 from ACU I/O panel to RF power meter output side.

4 Install 10-watt, 100-250 MHz element into RF power meter. Ensure that arrow points toward antenna.

5 Using N-N test cable, connect RF power meter input to I/O panel J43.
ASOS Site Technical Manual S100

12-16 Change 1

Figure 12.5.1. RF Power Output Check

Table 12.5.2. RF Power Output ChecK -CONT

Step Procedure

6 At front of GTA radio, press AC PWR switch to apply GTA radio power.

7

$

$

$

$

Observe and verify that RF power meter forward power reading is 2.5 ±1 watt plus the insertion loss of the

$ antenna cable. The ‘maximum nominal power’ required at the antenna base is 2.5 ±1 watt however, the

$ power output will be site specific. 

$ Insertion Loss Of The Antenna Cable = {Output Power at TXM (watts) - Output Power at Base of Antenna

$ (watts)}

$

Record power reading. If reading is not within tolerance, perform steps 8 through 12; if reading is correct,

proceed to step 13.

8 At front of GTA radio, press ENB pushbutton twice.

9 Press MOD pushbutton four times to display XMIT power display.

10 If power reading is too low, press up arrow to increase power output, then observe RF power meter to verify

that power reading is within tolerance.

11 If power reading is too high, press down arrow to decrease power output, then observe RF power meter to

verify that power reading is within tolerance.

12 If power reading cannot be corrected to within specified tolerances, remove and replace GTA radio in

accordance with table 12.5.11. 

13 At front of GTA radio, press AC PWR switch to remove GTA radio power.

14 Remove antenna cable W9 from output side of RF power meter.

15 Remove N-N test cable from RF power meter and I/O panel.

16 Connect antenna cable W9 to I/O panel J43.

17 Remove 10-watt, 100-250 MHz element from RF power meter and return it to storage.

18 At front of GTA radio, press AC PWR switch to apply GTA radio power.
S100 ASOS Site Technical Manual

Change 2 12-17

Table 12.5.3. Modulation Level Check (Preferred)

Step Procedure $

Tools and Test Equipment Required: $

 RF power meter, w/RF sampler element $

 Oscilloscope $

 Test cable (BNC-BNC) $

 Two N-N test cables $

 Dummy Load (25 watts, 50 ohms) $

$

NOTE $

This procedure requires firmware VERSION 2.10 or greater. $

1 At front of GTA radio, press AC PWR switch to remove GTA radio power. $

2 Refer to figure 12.5.2 and disconnect antenna cable W9 from J43 connector on I/O panel. Connect RF power $

meter input to connector J43 on I/O panel using N-N test cable. Connect RF power meter output to N-N test $

cable and dummy load. Install RF sampler element into RF power meter. $

3 Connect BNC-BNC test cable from RF sampler to channel 1 input on oscilloscope. $

4 Disconnect ACU harness connector P67 from radio adapter cable W076-P3 to remove the audio signal from $

the carrier. $

5 At GTA radio, press AC PWR switch to apply GTA radio power. $

6 Set oscilloscope time base for 200μ SEC/DIV. Manually adjust oscilloscope so that the carrier amplitude is $

equal to 5 DIV. $

7 Reconnect ACU harness connector P67 to the radio adapter cable W076-P3. $

$

$

$

$

$

8 $

NOTE $

This procedure uses the ACU voice processor board to generate a 1 kHz tone for setting the $

 percent modulation. ASOS generates a tone of 30 seconds duration when the system manager $

 holds the SHIFT key and enters ~TONE. $

$

At the OID, sign on as SYSTEM MANAGER. $

9 Press and hold SHIFT and enter ~TONE. Observe that the oscilloscope displays a 1 kHz tone within 60 $

seconds. If the tone is not displayed, repeat this step. $

10 $

$

$

$

NOTE $

Repeat step 9 if the 1 kHz tone terminates while adjusting percent modulation. $

$

Observe and verify that modulated peaks are at an optimum of 90% ±5%. Modulated peaks should be $

between 22 (88%) and 23 (92%) minor divisions. With peaks set to five major divisions of graticule, there $

are 25 minor divisions, each representing four percent modulation. If readings are not within tolerance, $

perform steps 11 and 12. If readings are within tolerance, proceed to step 13. $

11 Press MOD pushbutton five times. $

12 While observing oscilloscope, press down arrow to decrease percent modulation or up arrow to increase $

percent modulation as required. $

13 At front of GTA radio, press AC PWR switch to remove GTA radio power. $

14 Disconnect BNC-BNC test cable from oscilloscope and RF sampler. $

15 Disconnect N-N test cable from connector J43 to input side of RF power meter. $

16 Reconnect antenna cable W9 to connector J43 on I/O panel. $

17 Disconnect N-N test cable from input side of RF power meter. $

18 Disconnect N-N test cable from output side of RF power meter. $

19 Remove RF sampler from RF power meter and return to storage. $

20 Remove RF terminator from N-N test cable. $

21 At GTA radio, press AC PWR switch to apply GTA radio power. $
ASOS Site Technical Manual S100

12-17.1 (12-17.2 blank) Change 2

Table 12.5.3a. Modulation Level Check (Alternative)

$ Step Procedure

$ Tools and Test Equipment Required:

$ RF power meter, w/RF sampler element

$ Oscilloscope

$ Test cable (BNC-BNC)

$ Two N-N test cables

$ Dummy Load (25 watts, 50 ohms)

$ Audio Test Tone Generator w/ Test Leads (must have pure sine wave 

$ output)

$

$ 1 Inside the back of the ACU, remove the cover from the RJ11 phone jack that feeds audio to the ground to air

$ transmitter.

$ 2 Connect oscilloscope probe to the red and green wires inside the RJ11 phone jack.

$ 3 Measure the peak to peak amplitude of the ASOS voice audio. Should be approximately 2.0 VPP. (If NO

$ signal present, connect the scope ground to the other terminal reversing the connections of the scope probe.)

$ 4 At front of GTA radio, press AC PWR switch to remove GTA radio power.

$ 5 Refer to figure 12.5.2 and disconnect antenna cable W9 fromJ43 connector on I/O panel. Connect RF power

$ meter input to connector J43 on I/O panel using N-N test cable. Connect RF power meter output to N-N test

$ cable and dummy load. Install RF sampler element into RF power meter.

$ 6 Disconnect ACU harness connector P67 from the RJ11 phone jack that feeds audio to the ground to air

$ transmitter to remove audio signal from the carrier.

$ 7 At GTA radio, press AC PWR switch to apply GTA radio power.

$ 8 Connect the ouput of the audio generator to the red and green wires inside the RJ11 phone jack. Make sure

$ the ground of the signal generator and the oscilloscope are connected to the same point.

$ 9 Adjust the audio generator for 1000 Hz at the same Peak to Peak amplitude as measured in step 3 for the

$ ASOS voice audio.

$ 10 Connect BNC-BNC test cable from RF sampler element to channel 1 input on oscilloscope.

$ 11 Turn OFF the audio signal generator.

$ 12 Set oscilloscope time base for 200μ SEC/DIV. Manually adjust the oscilloscope so that the carrier amplitude $ is equal to 5 division.

$ 13 Turn ON the audio signal generator.

$ 14 Set oscilloscope time base for 0.5m SEC/DIV.

$ 15 Observe and verify that modulated peaks are at an optimum of 90% + 5%. If readings are not within

$ tolerance, perform steps 16 and 17. If readings are within tolerance, proceed to step 18.

$ 16 With MOD pushbutton go to MOD Index on LCD display.

$ 17 While observing oscilloscope, use UP and DOWN arrow buttons to set modulation to 90% + 5%.

$

$ ((Peak to Peak) - (Trough to Trough))

$ Percent (%) Modulation = ((Peak to Peak) + (Trough to Trough))

$

$ The easiest way to set modulation: Use an IFR Service Monitor and display percent of modulation, with the

$ Second Function Meter feature, while its receiver is tuned to the GTA radio frequency.

$ 18 At front of GTA radio, press AC PWR switch to remove GTA radio power.

$ 19 Disconnect RF test equipment and cables and reconnect antenna cable.

$ 20 Disconnect audio generator from the RJ11 phone jack and replace the cover to the jack.

$ 21 Reconnect the voice audio to the RJ11 phone jack.

$ 22 Reapply power to the GTA radio.
ASOS Site Technical Manual S100

12-18 Change 1

ACU

SIO

GTA

RADIO

J5

RED

P3

GREEN

W76

CABLE ASSEMBLY

ANT

I/O

PANEL

A9

J43

RED

TONE

GENERATOR

BLACK

RF WATT

TEST CABLE N-N METER TEST CABLE N-N

RF

TERMINATOR

OSCILLOSCOPE

TEST CABLE BNC-BNC

9812502

Figure 12.5.2. Modulation Level Check

Table 12.5.4. VSWR at Transmitter Output Check

Step Procedure

Tools and Materials Required:

Laptop computer with ASOS calibration program installed 

RF power meter w/1-watt 110-160 Mhz element and 

10-watt, 100-250 Mhz element 

N-N test cable 

1 At front of GTA radio, press AC PWR switch to remove GTA radio power.

2 At ACU, disconnect antenna cable W9 from antenna connector J43 on I/O panel.

3 Install a 10-watt, 100-250 MHz element in RF power meter with arrow pointing toward the antenna.

4 Connect RF power meter output to antenna cable W9.

5 Connect RF power meter input to antenna connector J43 on I/O panel with N-N test cable.

6 At front of GTA radio, press AC PWR switch to apply GTA radio power.

7 Using laptop, type ASOS <CR> at the DOS prompt.

8 Type menu item 5 on ASOS menu calibration program and enter forward power value at prompt. Hit return.

9

$ CAUTION

$ Be sure to turn the arrow (2) on the 10 watt, 100-250MHZ element toward the GTA TXM and insure there

$ is < 1 watt of power.

At front of GTA radio, press AC PWR switch to remove GTA radio power.

10 Remove 10-watt, 100-250 MHz element from RF power meter and replace with 1-watt, 110-160 MHz

element.
S100 ASOS Site Technical Manual

12-19

Figure 12.5.3. VSWR at Transmitter Output Check

Table 12.5.4. VSWR at Transmitter Output Check -CONT

Step Procedure

11

CAUTION

To prevent damage to 1-watt, 110-160 MHz element, ensure that arrow is in direction of

GTA radio.

At front of GTA radio, press AC PWR switch to apply GTA radio power.

12 Observe and record reflected power.

13 Enter reflected power at ASOS calibration program prompt.

14 The program calculates VSWR, displays result, and indicates if VSWR is within tolerance.

15 If VSWR is outside of prescribed tolerance, a beep sounds and a warning message is displayed.

16 If reading is not within tolerance, press GTA radio AC PWR switch to remove GTA radio power; then,

troubleshoot radio antenna cable, EMI/EFI filters, or GTA radio.

17 Disconnect N-N test cable from input side of RF power meter and connector J43 on the I/O panel.

18 Connect antenna cable W9 to J43 connector on I/O panel.

19 At front of GTA radio, press AC PWR switch to apply GTA radio power.

20 Remove N-N test cable from output side of RF power meter.

21 Remove 1-watt, 110-160 MHZ element from RF power meter and secure it properly.
ASOS Site Technical Manual S100

12-20 Change 1

Table 12.5.5. Frequency Stability Check

Step Procedure

Tools and Materials Required:

RF power meter w\RF sampler element

Two N-N test cables

BNC-BNC test cable

Frequency counter

Laptop computer w/ASOS program installed

1 At front of GTA radio, press AC PWR switch to remove GTA radio power. Disconnect audio input at cable

W76 connector P67 from connector P3.

2 At ACU, disconnect antenna cable W9 from antenna connector J43 on I/O panel.

3 Install RF sampler element into RF power meter.

4 Using N-N test cable, connect RF power meter input to antenna connector J43 on I/O panel. 

5 Using N-N test cable, connect RF terminator to output side of RF power meter.

6 Connect BNC-BNC test cable to RF sampler element.

7 Connect frequency counter, input C, to BNC-BNC test cable.

8 At front of GTA radio, press AC PWR switch to apply GTA radio power.

9 Observe and verify that frequency count is within 0.0005 percent of assigned frequency using example

provided below. If frequency is not within tolerance, perform steps 10 through 15. If frequency is within

tolerance, proceed to step 16.

$ NOTE

$ Press the Function Key on the Frequency Counter until “Freq C” has been selected.

$

Example: 118.025 MHz x 0.000005 = ±590.125 Hz

Carrier frequency x percentage = tolerance level

Alternate Method:

a. To initializeASOS calibration program, use laptop PCasfollows. At DOS prompt, enter: ASOS,

<ENTER>

b. Choose menu item number 6 to execute GTA frequency tolerance program.

c. Note frequency indicated on frequency counter and enter this value at prompt.

d. The program calculates frequency tolerance and displays upper and lower frequency limits.

10 At GTA radio front panel, press ENB pushbutton twice.

11 Verify that frequency is set to correct setting.

12 Press MOD pushbutton three times to display warp setting.

13 If frequency setting is too high/low, press up/down arrow, respectively, to change warp setting.

14 Verify that frequency level has either increased or decreased to within tolerance.

15 If frequency level cannot be corrected, remove and replace GTA radio in accordance with table 12.5.11.

16 At front of GTA radio, press AC PWR switch to remove GTA radio power.

17 Remove N-N test cable from connector J43 on I/O panel.

18 Connect antenna cable W9 to connector J43 on I/O panel.

19 Remove N-N test cable from input side of RF power meter.

20 Remove BNC-BNC test cable from RF sampler element.

21 Remove RF sampler element from RF power meter and return it to storage.

22 Remove BNC-BNC test cable from frequency counter.

23 At front of GTA radio, press AC PWR switch to apply GTA radio power.
S100 ASOS Site Technical Manual

12-21

Figure 12.5.4. Frequency Stability Check

Table 12.5.6. Coax Cable Conductance and Insulation Check

Step Procedure

Tools and Materials Required:

DMM

Megger

Adapter, N-BNC

Adapter, BNC-Banana

1 At front of GTA radio, press AC PWR switch to remove GTA radio power.

2 At ACU, disconnect antenna cable W9 from antenna connector J43 on I/O panel.

3 Connect N-BNC adapter to W9 RF antenna connector as shown figure 12.5.5.

4 Connect BNC-banana adapter to the N-BNC connector.

5 Connect megger to antenna cable W9 with Banana adapter.

6 Disconnect RF coax connector from the antenna.

7 At the megger, press the trigger button and verify that reading is >50 megohms.

8 Observe and record the reading.

9 Remove megger.

10 Short the shield to the center conductor at the banana adapter.

11 Using the DMM, verify that the center conductor to outer shield, loop resistance at the antenna side of the

cable is #5 ohms.
ASOS Site Technical Manual S100

12-22 Change 1

Figure 12.5.5. Coaxial Cable Insulation and Conductance, Test Setup

12.5.3 CORRECTIVE MAINTENANCE

Corrective maintenance consists of three major tasks: troubleshooting, voice card adjustment, and removal

and replacement of the GTA radio and other FRU's.

12.5.3.1 Troubleshooting. Troubleshooting involves the isolation and removal and replacement of faulty

FRU's. ASOS is equipped with a continuous self-test (CST) program that isolates the majority of faults to

a single FRU. However, due to the system hardware configuration, there will be instances when the

diagnostics can isolate a problem only to the GTA radio. Table 12.5.7 provides corrective maintenance

symptom analysis information for the GTA radio.

12.5.3.1.1 Troubleshoot the GTA Radio RF (Table 12.5.8). When there is a deterioration of the

broadcast signal, it is not normally picked up until an aircraft reports that there is no message or a

deteriorated message on the defined frequency. The technician must first confirm that the radio is powered

on; when that is ascertained, he must verify that the cables are properly connected and the antenna is not

damaged. If the problem is not the antenna or loose cabling, the technician must then perform the RF power

output, frequency, and modulation checks at test points designated by the troubleshooting procedures to

determine the FRU. 
S100 ASOS Site Technical Manual

12-23

12.5.3.1.2 Troubleshoot the GTA Radio RS-232 Data Link (Table 12.5.9). This type of failure is

normally observed as a no-response failure on the GTA radio page of the OID. When there is a

communications problem between the ACU and the radio, the configuration of the radio to the ACU is

checked first on the COMMS page on the OID. If the radio is configured to the ACU incorrectly, the ACU

does not receive data back from the GTA radio. The technician must install the RS-232 tester next to verify

that the data link between the ACU and the SIO board is functioning correctly. If the SIO board is not

operating correctly, it must be removed; if the SIO board is operating correctly, the radio must be removed

and replaced.

12.5.3.1.3 GTA Radio BERT Program. The RS-232 data link can also be tested using the Bit Error Rate

Tester (BERT) program located on the technician's laptop PC in the ASOS directory. Access the BERT

programby typing the phrase ASOS at the command line prompt and selecting itemnumber 2 fromthe menu.

The technician then follows the Bit Error Rate Tester instructions in Chaprer 13, section V.

12.5.3.2 Voice Recorder/Playback Board Check. This check, which adjusts the voice board output, is

performed when the GTA radio has been replaced, when the voice board(s) have been replaced, or when

called out as a part of a troubleshooting procedure.

12.5.3.3 Removal and Installation Procedure. Table 12.5.11 provides the procedure for removing and

installing the GTA radio. Removal and replacement procedures for the CPU, audio, and SIO boards are

provided in Chapter 2, Section V.

Table 12.5.7. Corrective Maintenance Symptom Analysis

Symptom What To Do How To Do It

Loss of broadcast weather voice Troubleshoot GTA radio RF. Paragraph 12.5.3.1.1 and table 12.5.8

GTA radio does not respond to

ACU data test

Troubleshoot GTA RS-232 data link. Paragraph 12.5.3.1.2 and table 12.5.9

Failure of GTA self-test Remove and replace the GTA radio. Table 12.5.11

Table 12.5.8. Loss of Broadcast Weather Voice

Step Test Corrective Action

1 Check that GTA radio has power. If power isturned off, press AC PWR switch to apply

power to the GTA radio.

2 Check cable connections associated with GTA radio.

3 Connect RF power meter to output connector

between connector J43 and cable W9 on I/O panel

and measure RF output power.

Verify that output power is $5 watts. If power is approximately 0 watt or if it is evident

that the radio is not transmitting, proceed to step 4.

If power is less than 5 watts, use ENB, MOD, and

arrow pushbuttons to adjust power. After adjusting

power at I/O panel, perform RF power output check

in accordance with paragraph 12.5.2.1. If power is

within tolerance, proceed to step 6.
ASOS Site Technical Manual S100

12-24 Change 1

Table 12.5.8. Loss of Broadcast Weather Voice -CONT

Step Test Corrective Action

4 Disconnect power meter from connector J43 and

reconnect antenna cable W9.

Connect RF power meter to connector J4 of GTA

Radio 1A10.

Verify that output power is $5 watts.

If poweris present,replace the following components

in sequence and retest system: 

a. Connector J43 filters

b. Antenna cable W51

If power is still not present, proceed to step 5.

5 Turn off GTA radio.

Disconnect adapter cable W076 connector P1 from

GTA radio connector J5.

Verify continuity between pins A and H of cable

W76 connector P1.

If continuity is present, remove and replace GTA

Radio 1A10.

If there is no continuity, remove and replace adapter

cable W076.

6 Perform frequency stability checks in accordance

with table 12.5.5.

Verify that carrier frequency is identical to assigned

frequency.

If carrier frequency is not identical to assigned

frequency, remove and replace GTA radio.

7 Perform modulation level check in accordance with

table 12.5.3. Adjust level as necessary. 

Verify that modulation level is within tolerance. If the modulation level is not within tolerance,

proceed to step 10.

8 Check cable connections at antenna.

9 At antenna, perform RF power output check in

accordance with table 12.5.2.

If power output is correct, remove and replace

antenna.

If power output is incorrect, remove and replace

antenna cable W9.

10 Perform voice recorder/playback board check in

accordance with table 12.5.10.

If the voice is OK, perform the following steps in

sequence:

a. Check cable W076 for continuity.

b. Remove and replace GTA radio.

If the voice is not OK, perform the following stepsin

sequence:

a. Reseat Voice Recorder/Playback

Board A21.

b. Remove and replace the Voice

Recorder/Playback Board A21.
S100 ASOS Site Technical Manual

12-25

Figure 12.5.6. Voice Recorder/Playback Board, Test Setup

Table 12.5.9. GTA Radio Does Not Respond to ACU Data Test

Step Test Corrective Action

1 Check SIO configuration on OID display. If not configured correctly, correct configuration at

OID.

2 If configured correctly, check SIO board self-test

page at the OID; verify that self- test is passing.

If SIO board does not pass self-test, remove and

replace SIO board.

3 Perform RS-232 test.

Connect input side of RS-232 tester to ACU harness

connector DB-25 corresponding to assigned SIO

port.

Connect outputside of RS-232 tester to connector P2

of cable W076.

If transmit line from SIO board is not active, remove

and replace SIO board.

If receive line is not active, check condition of cable

W076. If cable checks out, remove and replace GTA

radio. 

Table 12.5.10. Voice Recorder/Playback Board Check

Step Procedure

Tools and Materials Required:

600-ohm resistor

Oscilloscope

Terminal block, telephone, screw terminal

VME extender board

1 Power off ACU. 

2 Attach 600-ohm load resistor between terminals on telephone jack as shown in figure 12.5.6.

3 Disconnect connector P67 from connector P3.

4 Connect connector P67 to 600-ohm load assembly female jack (42A block).

5

Connect oscilloscope probe across 600-ohmload assembly terminals. Set oscilloscope input to AC at 1V/DIV

and set sweep to 5MS/DIV.

6 Power on ACU and wait for system to initialize.

7

Observe audio on oscilloscope. Verify that amplitude is 2 ±0.2 V p-p. If amplitude is not in tolerance, resistor

R22 on audio board 1A2A21 may be adjusted for 2.0 ±0.2 V p-p. If amplitude cannot be reached, remove

and replace Voice Board 1A2A20.

8 Power off ACU.

9 Disconnect oscilloscope from 600-ohm load assembly terminals.

10 Disconnect 600-ohm load assembly from connector P67.

11 Connect connector P3 to connector P67.

12 Power on ACU.
ASOS Site Technical Manual S100

12-26 Change 1

Table 12.5.11. GTA Radio Removal and Installation

Step Procedure

REMOVAL

Tools required:

 Small flat-tipped screwdriver

CAUTION

Damage to equipment may result if power is not removed prior to removal or installation. Ensure

that the power switch on the GTA radio is set to the off (0) position.

1 At front of GTA radio, press AC PWR switch to remove GTA radio power.

2 Open ACU rear cabinet door.

3 Disconnect ground lug E1.

4 Disconnect antenna connector J4.

5 Disconnect ac power connector J1.

6 Disconnect remote connector J5.

7 Remove four screws located on front of GTA radio that secure GTA radio to cabinet.

8 Slide GTA radio from cabinet until catches are secured.

9 Reaching around both sides of GTA radio, release levers that secure GTA radio to permanent slides

mounted to cabinet.

10 Slowly slide GTA radio from cabinet using both hands and place GTA radio onto suitable work surface.

INSTALLATION

Tools required:

 Small flat-tipped screwdriver

CAUTION

Damage to equipment may result if power is not removed prior to removal or installation. Ensure

that the power switch on the GTA radio is set to the off (0) position.

1 Carefully place GTA radio into slide slots.

2 Slide GTA radio completely back into cabinet so that slide locks engage. (This prevents the GTA radio

from sliding completely out of the ACU cabinet.)

3 Locate and secure four screws that secure GTA radio to ACU cabinet.

4 Open ACU rear cabinet door.

5 Connect ground lug E1.

6 Connect antenna connector J4.

7 Connect ac power connector J1.

8 Connect remote connector J5.

9 Close ACU rear cabinet door.

10 At front of GTA radio, press AC PWR switch to apply GTA radio power.

11 Verify that AC PWR indicator is illuminated.

12 Perform voice recorder/playback board check in accordance with table 12.5.10.

13 Perform RF power output check in accordance with table 12.5.2.

14 Perform modulation level check in accordance with table 12.5.3.

15 Perform VSWR at transmitter output check in accordance with table 12.5.4.

16 Perform frequency stability check in accordance with table 12.5.5.
S100 ASOS Site Technical Manual

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CHAPTER 13

CODEX 3600 SERIES MODEM

SECTION I. DESCRIPTION AND LEADING PARTICULARS

13.1.1 INTRODUCTION

TheCodex 3600 Seriesmodem(figure 13.1.1)supports both point-to-point andmultipoint circuitsfor analog

and digital applications. In the ASOS environment, the 3600 modem interfaces with the Federal Aviation

Administration (FAA) ADAS via the Data Multiplexer Network in both point-to-point and multipoint

circuits. The particular circuit is ASOS site-specific. Typical point-to-point and multipoint circuits are

described in Section IV. 

When operating as an analog leased line device, the 3600 modem can achieve speeds in excess of the

industry standard of 19.2 kbps. This extended rate capability is achieved through a coding/equalization

technique called Trellis Precoding. This extended rate also provides for line testing and transmission speed

adjustment depending on prevailing line conditions, enabling the device to support speeds of 21.6 kbps. A

speed of 24.0 kbps can be achieved under optimum line conditions. In addition to these higher speeds, the

3600 modem offers improved performance at 19.2 kbps. Through its Digital Interface option, the 3600

modem operates at both substrate (2.4, 4.8, 9.6, and 19.2 kbps) and standard rate (56.0 kbps) digital

transmission speeds.

The 3600 modem is a modular system that can be customized with a variety of hardware and software

options to expand in step with communications requirements. These options enable the 3600 modem to be

custom-configured as an analog leased line device or as a digital service unit, both with time division

multiplexing and integrated restoral backup. Different Flex-cartridge operating sets and options can be used

to provide varying levels of control in 3600 Series applications. The Flex-cartridge is removable and can be

replaced with a cartridge containing software updates and configuration changes to accommodate new

communications circuits. In the ASOS environment, one of two Flex-cartridges is used: Premium or

Standard. These cartridges are ASOS site-specific. The Premium Flex-cartridge provides for point-to-point

communications using TURBO PP mode at 19.2 kbps, and the Standard Flex-cartridge provides for

multipoint operation in multipoint-slave (MP-S) mode of operation at 4.8 kbps. It should be noted that

Premium Flex-cartridge mode V.33 is used on some FAA circuits. Table 13.1.1 lists the Codex 3600 Series

operating set characteristics.

13.1.2 PHYSICAL DESCRIPTION

13.1.2.1 General Description. The 3600 modemis Government-furnished equipment (GFE) measuring 3.5

inches high, 17.25 inches wide, and 17.5 inches deep and is installed in position 1A1 above the VME rack

in the acquisition control unit (figure 13.1.2).

The modem is self-operating and, under normal conditions, needs no operator intervention. The front panel

of the device, normally covered with a dress panel (figure 13.1.3), is hinged so that it can be opened to gain

accessto the circuit boards ofthemodemas well as a removable component housing (called a Flex-cartridge)

containing multiple banks of memory devices. The initial Flex-cartridge is factory-installed; however,

software upgrades can be installed by removing and replacing the Flex-cartridge. 
ASOS Site Technical Manual S100

13-2

Figure 13.1.1. Codex Series 3600 Modem

Table 13.1.1. Codex 3600 Series Modem Specifications

Operating

Mode

Data

Rate

(kbps)

Transmit

Carrier

Mode

Point-to-Point/

Multipoint Training

Time

Baud

Rate

(Hz)

Equalization

Recovery

Method

Unique Features

TURBO

PP

24.0

21.6

19.2*

16.8

14.4

12.0

9.6

Constant Point-to-point Normal/

short

3200

2954

2743*

2400

Round robin (3

to 7 sec)

Extended high-speed performance through combination of Trellis Precoding and line probing

V.33 14.4

12.0

Constant Point-to-point 1393 ms 2400 Round robin

(2.6 to 4 sec)

End-to-end compatible

with any CCITT V.33

device (without network

control)

PP/CI 9.6

7.2

4.8

Constant Point-to-point 253 ms 2400 Round robin (1

to 2 sec)

Improved signal constellation (compared to V.29)

V.29 9.6

7.2

4.8

Constant Point-to-point 253 ms 2400 Round robin (1

to 2 sec)

End-to-end compatible

with any CCITT V.29

device (without network

control)

MP-M

(master)

9.6

7.2

4.8

Constant Multipoint 253 ms 2400 None (Retrain

expected with

each outbound

message)

Ability to accept different

inbound rates from slaves

(MIR) MQSB

MP-S

(slave)

4.8 Controlled

(switched)

Multipoint 17 ms 2400* Train on data (2

to 15 sec)

Train on data (TOD)

*ASOS configuration
S100 ASOS Site Technical Manual

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Figure 13.1.2. Codex 3600 Series Modem Location in the ACU

13.1.2.2 System Components. The Codex 3600 Series modem consists of the 3600 modem, including the

circuit boards contained in the 3600 modem enclosure, and the Flex-cartridge. The modem with its

Flex-cartridge and the Flex-cartridge itself are field replaceable units (FRU's). Figure 13.1.4 illustrates the

3600 modem components.
ASOS Site Technical Manual S100

13-4

Figure 13.1.3. Codex 3600 Series Modem Dress Panel

13.1.2.2.1 3600 Series Enclosure. The Codex 3600 Series modem enclosure includes the front panel,

power supply, cooling fan, and backbone slots for all of the cards. The front panel is used to configure the

device and includes light emitting diodes (LED's), touch-sensitive control keys, and an 8-character

alphanumeric display. The rear panel includesthe powerswitch, fuse, power cord, voltage selection jumper,

telephone company connections, hardware interfaces to network control, and data terminal equipment

connections.

13.1.2.2.2 Flex-Cartridge. The Flex-cartridge consists of multiple banks of memory devices packaged in

a component housing. These memory banks contain the associated operating programs that performspecific

functions. The memory size varies, depending on the number of installed software options. The initial

Flex-cartridge is factory-installed. If software upgrades are required, the cartridge is removed and replaced

with the cartridge containing the new software. Each cartridge plugsinto a Flex-cartridge carrier on the front

right side of the processor card. ASOS sites that communicate with ADAS in a point-to-point circuit have

Premium Flex-cartridges, and those communicating in a multipoint circuit have Standard cartridges.

13.1.3 CODEX CONFIGURATIONS

There are two possible configurations of the Codex Modem: Standard (one mode: MP-S) and Premium (two

modes: Turbo PP and V.33). The configuration of a particular CODEX is determined by which of two

Flex-cartridges (Standard or Premium) has been installed in the Codex. The Standard Flex-cartridge is used

when the Codex is connected to ADAS in a multipoint configuration. The Premium Flex-cartridge is used

when the Codex is connected to ADAS in a point-to-point configuration. More information can be learned

about Flex-cartridges and their effect on Codex configurations in section IV. 
S100 ASOS Site Technical Manual

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Figure 13.1.4. Codex 3600 Series Modem Components
S100 ASOS Site Technical Manual

13-7/ (13-8 blank)

SECTION II. INSTALLATION

Installation of the Codex 3600 Series modem is not the responsibility of the ASOS site maintenance

technician; the unit is Government-furnished equipment (GFE). The proceduresfor removing and replacing

the field replaceable units (FRU's) associated with the device are contained in Section V.
S100 ASOS Site Technical Manual

13-9

Figure 13.3.1. Codex 3600 Series Modem Controls and Indicators

SECTION III. OPERATION

13.3.1 INTRODUCTION

The Codex 3600 Series modem is configured and operated through the front panel of the device (figure

13.3.1) or remotely from another 3600 modem. In the ADAS environment, the modem at the ASOS site is

controlled by a 3600 modemat the ADAS network control center. The front panel ofthe remote 3600 modem

at the network control center becomes the logical front panel of the ASOS site modem being controlled.

Network control can be overridden; the procedure for overriding network control to enable local

configuration of the front panel is described in Section V. The device is software-controlled through a

hierarchical menu accessed by pressing the appropriate control keys on the front panel.

13.3.2 CONTROLS AND INDICATORS

Table 13.3.1 identifies the controls and indicators on the front panel of the Codex 3600 Series modem. The

eight control keys, which enable the operator to configure, test, and review the operationalstatus of the 3600

modem, are divided into two groups: menu keys and movement keys. Menu keys enable the operator to

access the software menus (STATUS, TEST, CONFIG, and REMOTE), and the movement keys enable the

operator to move across parameters within menus and make selections. The light emitting diodes (LED's)

on the front panel display conditions relating to data transmission, power, network control, and alarm

conditions. Modem responses to the repeated pressing of the menu keys are displayed on the 8-character

display screen located on the front panel. Figure 13.3.2 illustrates the top level software menu hierarchy of

the Codex 3600 Series modem for each of the main menu categories (i.e., STATUS, TEST, CONFIG, and

REMOTE). 

Table 13.3.1. Codex 3600 Series Modem Controls and Indicators

Control/

Indicator Description Normal Condition

LED's

TXD (green) Transmit data Illuminates when transmitting data.

RXD (green) Receive data Illuminates when receiving data.

RTS (green) Request to send Illuminates when DTE connected to selected port is

requesting to send data to the 3600 modem.

CTS (green) Clear to send Illuminates when 3600 modem indicates that it is

ready to receive data.

DSR (green) Data set ready Illuminates when DTE attached to the 3600 modem

is active but not in a data interruptive mode.
ASOS Site Technical Manual S100

13-10

Table 13.3.1. Codex 3600 Series Modem Controls and Indicators - CONT

Control/

Indicator Description Normal Condition

DSR (green) Data set ready Illuminates when DTE attached to the 3600 modem

is active but not in a data interruptive mode.

DTR (green) Data terminal ready Illuminates when the DTE attached to the 3600

modem is connected and ready to send or receive

data.

DCD (green) Data carrier detect Illuminates when device is receiving an acceptable

signal from the remote device.

TST (red) Test Illuminates when 3600 modem is in test mode.

Status Indicators

RSQ (green) Receive signal quality Indicates that the 3600 modem is detecting a good

signal quality. Flashing LED indicates marginal

signal quality.

FLBK (yellow) Fallback Indicates that the 3600 modem is operating at a rate

lower than that configured at the MAX RTE

parameter. 

NC (green) Network control Indicates that the 3600 modem is under the control

of a network management system or a remote front

panel (LED remains ON). Flashes when a message

is received from a remote source.

ALM (red) Alarm Indicates device failure.

DIAL (red) Restoral operation Indicates that the 3600 modem is operating over a

restoral connection. Flashes when 3600 modem is

dialing.

PWR (green) Power Indicates that the power supply is operational and

that 3600 modem is receiving ac power.

Software Menu Keys

STATUS STATUS menu access Used to access the STATUS menu.

TEST TEST menu access Used to access the TEST menu.

CONFIG CONFIGURATION menu Used to access the CONFIG menu.

REMOTE REMOTE menu access Used to access the REMOTE menu.

Movement Keys

Used to move through the different

selections of the selected menu area or

through a series of lead parameters.

Used to move through a series of parameters

within a category.

ADV# Used to increment digits for numeric entry.

This key advances the flashing digit in the

numerical display.

ENTER Used to store a selection or numerical entry

in nonvolatile memory. The selection blinks

after it is entered correctly.

Alphanumeric Display Screen

LED Used with the control keys to display

various menu selections, error messages,

and system responses during testing and

troubleshooting. When not being used, the

alphanumeric display displays the specified

transmission speed of the 3600 modem.
S100 ASOS Site Technical Manual

13-11

Figure 13.3.2. Top Level Software Menu

Figure 13.3.3. STATUS Menu - Top Level

13.3.2.1 STATUS Menu. Pressing the STATUS key (figure 13.3.3) enables the operator to access the

STATUSmenu and examine themenu categories.The categoriesthat are accessed and the figuresillustrating

the parameters that can be displayed within those categories are identified as follows:

Category Figure No.

GENERAL* 13.3.4

DIAGNOS* 13.3.5

CQMS* 13.3.6

PRT SEL* 13.3.7
ASOS Site Technical Manual S100

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Figure 13.3.4. STATUS Menu - GENERAL* Category
S100 ASOS Site Technical Manual

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Figure 13.3.5. STATUS Menu - DIAGNOS* Category
ASOS Site Technical Manual S100

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Figure 13.3.6. STATUS Menu - CQMS* Category
S100 ASOS Site Technical Manual

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Figure 13.3.7. STATUS Menu - PRT SEL* Category

Figure 13.3.8. TEST Menu - Top Level

Figure 13.3.9. TEST Menu - SELF* Category

13.3.2.2 TEST Menu. Pressing the TEST key (figure 13.3.8) enablesthe operator to accessthe TEST menu

and examine the menu categories. The only test category that the ASOS site technician needsto accessisthe

SELF* category, the parameters of which are illustrated on figure 13.3.9.

13.3.2.3 CONFIG Menu. Pressing the CONFIG key (figure 13.3.10) enables the operator to access the

CONFIGmenu and examine themenu categories. The categoriesthat are accessed and the figuresillustrating

the parameters that can be displayed within those categories are identified as follows:

Category Figure No.

DEVICE* 13.3.11

ANALOG* 13.3.12

PORTS* 13.3.13

NWK CTL* 13.3.14
ASOS Site Technical Manual S100

13-16

Figure 13.3.10. CONFIG Menu - Top Level

13.3.2.4 REMOTE Menu. The REMOTE menu is used by the ASOS site technician only to disable and

enable remote control when configuring or testing the modem locally. Pressing the REMOTE key (figure

13.3.15) enablesthe operatorto accesstheREMOTEmenu and examine themenu categories. The categories

that are accessed and the figures illustrating the parameters that can be displayed within those categories are

identified as follows:

Category Figure No.

MISC* 13.3.16

13.3.3 TURN-ON PROCEDURES

The Codex 3600 Series modemreceives ac power fromacquisition control unit (ACU) input. Modem power

is ON when both the ACU power is ON and the modem power switch is ON.

13.3.4 TURNOFF PROCEDURES

The Codex 3600 Series modem ac power is OFF when the ACU AC power is OFF regardless of the position

of the modem power switch. The modem is turned OFF separately by setting the power switch on the rear

of the modem to OFF (position 1).

13.3.5 NORMAL OPERATION

The Codex 3600 Series modem isself-operating. A front dress cover isinstalled over the modem front panel

concealing the display screen, all control keys, and all LED's with the exception of the ALM, DIAL, and

PWR LED's. The modem is normally under network control.

13.3.6 MONITORING AND VERIFYING CODEX 3600 SERIES MODEM AT OPERATOR

INTERFACE DEVICE

The only indication of a possible malfunction of the modem provided at the operator interface device (OID)

is a MODEM HAS LOST POLL FROM ADAS message sent to the SYSLOG. The ASOS central processing

unit (CPU) does not check any self-teststatus on the modem. The operator can only verify the pass/failstatus

of the SIO board to which the modem is assigned by using the OID, accessing the maintenance page for the

SIO boards, and ensuring that no F or C flags are set (SIO/port is assigned as ADAS for the Codex 3600

Series modem).
S100 ASOS Site Technical Manual

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Figure 13.3.11. CONFIG Menu - DEVICE* Category

13.3.7 MONITORING AND VERIFYING CODEX 3600 SERIES MODEM BY VISUAL

INSPECTION 

The operation of the Codex 3600 Series modem can also be monitored by observing that the DCD LED on

the front panel is illuminated, the ALM LED is extinguished, and the PWR indicator is illuminated. The

NC LED on the front panel will also be lit on the modem currently being addressed. 
ASOS Site Technical Manual S100

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Figure 13.3.12. CONFIG Menu - ANALOG* Category (Sheet 1 of 2)
S100 ASOS Site Technical Manual

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Figure 13.3.12. CONFIG Menu - ANALOG* Category (Sheet 2)
ASOS Site Technical Manual S100

13-20

Figure 13.3.13. CONFIG Menu - PORTS* Category
S100 ASOS Site Technical Manual

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Figure 13.3.14. CONFIG Menu - NWK CTL* Category
ASOS Site Technical Manual S100

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Figure 13.3.15. REMOTE Menu - Top Level

Figure 13.3.16. REMOTE Menu - MISC* Category
S100 ASOS Site Technical Manual

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Figure 13.4.1. ADAS Network Topology

SECTION IV. THEORY OF OPERATION

13.4.1 INTRODUCTION

The Codex 3600 Series modem configured for ASOS operation is operated in one of two circuits:

point-to-point or multipoint. The circuit varies from site to site. The ASOS point-to-point circuit uses a

PremiumFlex-cartridge and TURBO PP operating mode at a maximum transmission rate of 19.2 kbps or the

V.33 operating mode at 14.4 kbps or 12 kbps. The ASOS multipoint circuit uses a Standard Flex-cartridge

and multipoint-slave (MP-S) operating mode at a maximum transmission rate of 4.8 kbps. In either a

point-to-point or multipoint circuit, ASOS responds to data requests (polls) from the Federal Aviation

Administration (FAA) ADAS communications network with requisite data. Figure 13.4.1 illustrates the

topology of the ADAS network.

The Codex 3600 Series modem is transparent to ASOS. In either operating circuit, the local modem front

panel can be controlled locally orfroma remote 3600modemon the ADAS network. The modemis normally

under network control. The following chart summarizes the ASOS circuits and operating modes.

Circuit Operating Mode Max Transmission Rate Flex-Cartridge 

(ASOS Site -Specific) 

Point-to-point

TURBO PP 19.2 kbps Premium

V.33 14.4 kbps Premium

V.33 12.0 kbps Premium

Multipoint MP-S 9.6 kbps Standard

Figure 13.4.2 illustrates the ASOS/ADAS point-to-point and multipoint connections.

13.4.2 TURBO POINT-TO-POINT AND V.33 COMMUNICATIONS

The Codex 3600 Series modem configured for ASOS with a Premium Flex-cartridge uses the TURBO PP

operatingmode and a transmission speed of 19.2 kbps, enabling communications at a high performance level

under a variety of operating conditions. TURBO PP supports transmission rates from 9.6 kbps to 24.0 kbps.

A line probing feature automatically adjusts the carrier frequency and the baud rate of the modem to extract

maximum performance from the communications line. To withstand high degrees of distortion at the

transmission band edges, the TURBO PP operating mode uses a Codex proprietary technique called Trellis

Precoding. The TURBO PP operating mode also uses an adaptive rate capability using the line probing

feature with an adaptive rate system (ARS). Upon power up, line probing determines the highest possible

data rate that current line conditions can support. Line probing then instructs the modem to run at that rate.

The modem continually monitors its received error rate. As line conditions improve or deteriorate, the

modem adjusts its speed and transmission band to provide the optimum throughput. The Codex 3600 Series

modem uses a process called point-to-point training to initialize and synchronize point-to-point devices

before transmission can begin. During training, the modem sends a predetermined training sequence.
ASOS Site Technical Manual S100

13-24

Figure 13.4.2. ASOS/ADAS Point-to-Point and Multipoint Connections

Knowing how the training sequence should appear, the receiving device can recognize how specific line

conditions have distorted the training pattern and compensate for the distortion using a technique known as

equalization. Equalization is the reduction of the effects of attenuation or time delay or both on the various

frequencies in the transmission band. The FAA may also utilize PP V.33 mode to improve reliability and

HDLC recovery attempts in some circuits.
S100 ASOS Site Technical Manual

13-25/ (13-26 blank)

13.4.3 MULTIPOINT-SLAVE (MP-S) OPERATING MODE

TheCodex 3600 Seriesmodemconfigured for ASOS with a Standard Flex-cartridge usesthe MP-S operating

mode and a transmission speed of 9.6 kbps. The MP-S mode enables leased line operations at 4.8 kbps over

unconditioned analog transmission lines. This mode of operation is used in a standard multipoint polling

circuit. In the ASOS environment, the ASOS sites operating in the MP-S mode are slaves and the master

3600 modem is at an ADAS site. The MP-S mode enables asymmetrical operation so that the outbound rate

can be configured differently from the inbound rate. In addition, the inbound rate from each slave is

separately selectable using the mixed inbound rates (MIR) feature. The outbound direction uses a 253-ms

training sequence, which enables the 3600 modem slaves to learn all significant channel characteristics. In

the inbound direction, the master receiver has a very short training sequence (17 ms), which improvesspeed

in responding to polls. Throughput in multipoint application is increased with training on data (TOD). TOD

eliminates data-disruptive retrains by enabling slave devices to equalize on the data being transmitted. The

elimination of retraining improves throughput and reduces response time in a multipoint circuit. Codex

modems at ASOS sites are configured for 4.8 kbps.
S100 ASOS Site Technical Manual

13-27

SECTION V. MAINTENANCE

13.5.1 INTRODUCTION

This section contains the preventive and corrective maintenance procedures for the Codex 3600 Series

modem. Preventive maintenance consists of periodic visual inspections for physical damage and cleaning

the device with a clean cloth to remove dust. The Codex 3600 Series modem and its Flex-cartridge are field

replaceable units (FRU's). The Flex-cartridge may be replaced to correct a defective cartridge, or a new

Flex-cartridge may be installed to provide software updates. The Codex 3600 Series modem is a low

maintenance item.

13.5.2 PREVENTIVE MAINTENANCE

13.5.2.1 Routine Inspection and Cleaning. The Codex 3600 Series modem isinspected and cleaned every

90 days in the same manner as other components of the acquisition control unit (ACU) (Chapter 2, Section

V). Cleaning of the Codex 3600 Series modem outer case is required to prevent dust and debris buildup on

the unit. The front dress panel must be properly secured (figure 13.1.3). The modem must not be removed

from its rack for inspection and cleaning.

13.5.3 CORRECTIVE MAINTENANCE

13.5.3.1 Corrective Maintenance Philosophy. The first indication that the operator may observe of a

possible modem problem is that ASOS has not received a request for data (poll) from ADAS in a

predetermined period of time (5 minutes in ACU S/W version 2.0 and 6 minutes in ACU S/W version 2.2);

in this case, ASOS writes a message to the SYSLOG to this effect. This does not mean that the modem is

malfunctioning. The ADAS network operation may be causing a suspension of polling. If polling is not

resumed, the ASOS site technician notifies the cognizant ADAS network personnel that ASOS is not

receiving the ADAS poll. The modem can then be checked via the network and, if possible, the problem

corrected. If the problem cannot be corrected, the cognizant ADAS personnel can advise the ASOS site

technician of the action to be taken. The Codex 3600 Series modem with its Flex-cartridge is an FRU. After

coordinating with cognizant ADAS personnel, the ASOS site technician may be asked to check the modem

locally; in this case, the technician may perform the troubleshooting procedures described in paragraph

13.5.3.3. In coordination with ADAS network management, the ASOS site technician may be asked to

performmaintenance proceduresfortheCodex 3600 Series modem, which requiresthe use oftheBERT (Bit

Error Rate Tester) software package and the technicians laptop computer. 

13.5.3.2 Bit Error Rate Tester. The BERT is a software program resident in the ASOS directory of the

technician's laptop computer. The BERT is used to perform error rate tests of the Codex modem. The BERT

can count the number of bit errors, calculate the percentage of error-free seconds and sync lost seconds, and

sync lost occurrences. The BERT transmits and receives RS-232 compatible signals. The device generates

5 pseudorandom repeating sequences from 63 to 32,767 bits in length and generates FOX messages (i.e.,

quick brown fox).

13.5.3.3 CODEX 3600 Series Modem Troubleshooting. Troubleshooting of the modem is performed in

coordination with cognizant ADAS network personnel for the purpose of isolating the modem as the source

of a problem. In this case, the procedures described in this paragraph are performed to isolate the modem as

the cause of the problem. A three-step approach is used. First, the quick check procedures (table 13.5.1) are

performed. If no problemisfound, menu-driven testsfromthe local front panel (Signal Quality Test and Self

Test) are performed in accordance with the procedures described in tables 13.5.2 and 13.5.3, respectively.
ASOS Site Technical Manual S100

13-28

Third, if the modem passes its menu-driven tests and the problem persists, the BERT Test (table 13.5.4) is

performed when installing a newmodem. If any problemisfound asresult of any test and the problemcannot

be corrected or if after all tests have been conducted, the problem persists, the modem is replaced in

accordance with the procedure described in table 13.5.5. The testing procedures used in troubleshooting the

Codex 3600 Series modem are summarized as follows:

Test Procedure Table Reference

Quick Check 13.5.1

Signal Quality Test 13.5.2

Self Test 13.5.3

BERT Test 13.5.4

13.5.4 REMOVAL AND INSTALLATION PROCEDURES

13.5.4.1 General. The table references for the removal and installation procedures for the modem and

Flex-cartridge are as follows:

Removal/Installation

Unit To Be Replaced Table Reference 

Codex 3600 Series Modem 13.5.5

Flex-cartridge 13.5.6

13.5.4.2 Codex 3600 Series Modem Removal and Installation. The removal and installation procedures

for the Codex 3600 Series modem provided in table 13.5.5 include instructions for configuring the

replacement modem (described in table 13.5.7) and for the use of the pocket BERT for testing the

replacement modem (described in table 13.5.4).

Table 13.5.1. Codex 3600 Series Modem Quick Checks

 Problem Cause Solution

Cabling problems exist This occurs when operating over restoral

lines or if a new piece of equipment has

recently been added to network.

Check all cable connections and electrical

outlets.

TST LED is ON Local or remote device may be running a

diagnostic test.

Clear test in progress by pressing NO

LOOP, or ENTER? and CLT TST*

category.

The device continuously

retrains.

Slaves are not turned on or are

disconnected.

Power on slave and verify processing.

Receive level is too high. Lower transmit level at Master or increase

carrier detect threshold.

CD threshold is too high. Lower carrier detect threshold through CD

THR: parameter located under LS ANGL+

lead parameters. Restart and monitor

operation.

Blind time istoo short. Reconfigure round robin blind time through

LS STP: parameter located under ANLG +

lead parameter.
S100 ASOS Site Technical Manual

Change 1 13-29

Table 13.5.1. Codex 3600 Series Modem Quick Checks -CONT

 Problem Cause Solution

Improper configuration

(refer to table 13.5.7).

Improper configuration has been entered. Review CONFIG menu to ensure correct

selections as shown in table 13.5.7 and

change any nondefault parameters as

necessary.

Device has no power. DC inhibitswitch is in STANDBY position. Place dc inhibit switch in ON position.

TESTING is displayed

continuously on front

panel.

Poor handling during shipment. Reseat cards, including Flex-cartridge and

turn device OFF, then ON.

Check DIAGNOS* category for possible

failures.

ALM LED is ON. Check DIAGNOS* category for possible

failures.

Table 13.5.2. Codex 3600 Series Modem Signal Quality Test

Step Procedure

1 Observe RSQ LED on front panel. 

a. RSQ ON reflects good signal.

b. RSQ flashing reflects marginal signal quality.

c. RSQ OFF reflects poor signal quality.

2

NOTE

When RSQ remains off for any length of time, it may indicate that the device is

operating at a data rate that is too high for current line conditions. The ASOS

maintenance technician can confirm that a problem exists in the telephone lines by

checking the signal-to-noise (SNR) ratio and error probability (ERP) in the CQMS*

category of the STATUS menu (figure 13.3.3). In order to configure or test the modem

from its own front panel, the ASOS maintenance technician mustfirst remove the device

from network control by using the REMOTE menu, the MISC* category, and the

OVERIDE parameter (figure 13.3.16). The following steps assume that the technician

has properly logged onto the modem using his password.

Press REMOTE key on front panel four times. MISC* is displayed.

3 Press down arrow. OVERIDE is displayed.

4 Press right arrow. ENABLE is displayed.

5 Press <ENTER>. The ENABLE indicator flashes, indicating that network control has been overridden. 

6 Press STATUS key on front panel three times. CQMS* is displayed.

7 Press down arrow twice. SNR=XXX is displayed, where XXX equals the SNR in decibels. The SNR is

measured after it has passed through the receiver's equalizer. It is not the SNR of the telephone line, as the

equalizer reduces the effects of certain types of channel distortion.

8 Press down arrow once. ERP=XXX is displayed where XXX equals the probability of error in percent.

Error probability, which acts as a confirmation of line deterioration, increases as the amount of distortion

increases. The ASOS maintenance technician evaluates the ERP as follows:

a. 0 to 30% = Good

b. 31 to 70% = Fair

c. 71 to 99% = Marginal

100% triggers the RSQ indicator to turn off, indicating that the unit cannot pass data.
ASOS Site Technical Manual S100

13-30 Change 1

Table 13.5.2. Codex 3600 Series Modem Signal Quality Test -CONT

Step Procedure

NOTE

The ASOS maintenance technician must disable OVERIDE in order to restore network control

by performing the following steps.

9 Press REMOTE key on front panel. MISC* is displayed.

10 Press down arrow. OVERIDE is displayed.

11 Press right arrow. ENABLE is displayed.

12 Press right arrow. DISABLE is displayed

13 Press <ENTER>. The DISABLE indicator flashes, indicating that network control has been restored (i.e.,

OVERRIDE of network control has been disabled). The NC LED on the front panel is illuminated.

Table 13.5.3. Codex 3600 Series Modem Self-Test

Step Procedure

NOTE

Review the TEST menu on figure 13.3.8. If power has been turned off to the modem, the password

may have to be reentered in order to accessthe test menu. When the TEST menu key is pressed and

if the modem asksfor a password, reenter password using the right arrow key and enter 5215. When

the display shows WELCOME, complete the following steps. During the self-test, the device

disconnects itself from network control, generates test patterns through the internal circuitry, and

displays the test results on the front panel.

1 Press TEST key five times to display SELF*. SELF* is displayed.

2 Press down arrow. START is displayed.

3 Press <ENTER>. TESTING is displayed. The modem performs an internal loopback test. When complete,

PASSED or FAILED is displayed. If FAILED is displayed, replace modem. If PASSED is displayed, inform

ADAS network manager that modem has passed self-test.

Table 13.5.4. BERT Test

Step Procedure

NOTE

The technician's laptop computer, the BERT software program, and this procedure are used to test

the modem. The Serial BERT (Async) software program should already be loaded onto the

technician's laptop; if not, it should be installed using the instructions contained in the

documentation accompanying the BERT software package.

1 Place modem power switch at rear of unit to OFF (position 0).

2 Connect laptop (with FRONTLINE Serial BERT Async) to modem as shown on figure 13.5.1.

a. Connect serial port on laptop to Port 1 on modem.

b. Plug an RJ-11 connector with pin 1 looped to pin 3 and pin 2 looped to pin 4 into

connector J8 on the I/O panel of the ACU.

3 Configure the BERT as follows:

a. Pattern = 2047

b. Block size = 10k

c. Test length = 5 minutes

d. Insert errors = 0 seconds

e. Parity = None
S100 ASOS Site Technical Manual

13-31

CODEX MODEM

PORT 1

LAPTOP/BERT

TESTER COM 1

LEASE

LINE

ACU A9

I/O PANEL

J8 TEST

CABLE

1

TEST 2

CABLE 3

4

(Y)

(G)

(R)

(B)

MAKE FROM MODULAR FLAT

CABLE WITH RJ-11

CONNECTOR & TINNED ENDS

9713501

Figure 13.5.1. BERT Test Setup

Table 13.5.4. BERT Test -CONT

Step Procedure

f. Word length = 8

g. Stop BITS = 1

h. Baud RATE = 2400 (for premium, 1200 for standard) $

I. Port = COM1:

j. Full duplex

k. Flow Cntl = None

l. Code = ASCII

m. Sliding user message = No

4 At rear of modem, apply power by setting modem rocker power switch to ON (position 1).

5 Verify thatmodemcompletes power-on diagnostics and its ALM indicatoris extinguished. If necessary, refer

to table 13.5.7 to configure modem.

5.1 On modem front panel configure the modem as follows: $

a. Press CONFIG until DEVICE* is displayed. Press down arrow until LOAD DEF is $

displayed. Press ENTER. $

b. Press CONFIG until ANALOG* is displayed. Press down arrow until SELECT> is $

displayed. Press right arrow until LS ANGL + is displayed. Press down arrow until TX $

LVL: is displayed. Press right arrow until -13 DBM is displayed. Press ENTER. $

c. Press CONFIG until ANALOG* is displayed. Press down arrow until SELECT> is $

displayed. Pressright arrow until DTE + is displayed. Press down arrow until MUX MOD: $

is displayed. Press right arrow until M is displayed. Press ENTER. $

d. PressCONFIG until PORTS* is displayed. Press down arrowuntil SELECT>is displayed. $

Press right arrow until PORT1 + (or proper port) is displayed. Press down arrow until $

DATA/CL: is displayed. Press right arrow until ASYNC 8D is displayed. Press ENTER. $

Proceed with BERT test. $

6 Execute the BERT "RUN" command and verify that modem is in synch (DCD indicator on front panel is

illuminated and not blinking). Verify that BERT statusis "IN LOCK". Clear BERT display of any errors and

allow system to run for approximately 5 minutes. The system must run without any errors. If an ERROR

occurs, replace modem, reconfigure new modem, and repeat BERT test.

7 Remove laptop serial connection from modem.

8 IftheBERT test hasfailed, replace modemin accordance with removal and installation procedures described

in table 13.5.5.
ASOS Site Technical Manual S100

13-32

Table 13.5.5. Codex 3600 Series Modem Removal and Installation

Step Procedure

REMOVAL

Tools Required:

None 

1 If ACU is a Class I system, turn facility power to ACU OFF. If ACU is a Class II system, set UPS POWER

SWITCH on UPS (1A4) to OFF.

2 Place modem power switch at rear of unit to OFF (position 0).

3 Disconnect all cables and power cord from rear panel of modem.

4 Loosen restraining strap holding modem in place.

5 Slide modem out of ACU rack.

INSTALLATION

Tools Required:

None

1 If ACU is a Class I system, turn facility power to ACU OFF. If ACU is a Class II system, set UPS POWER

SWITCH on UPS (1A4) to OFF.

2 Slide modem into ACU rack in position 1A1 onto brackets.

3 Secure modemin place by running strap (62828-90341-3) through 1-inch slot in angle brackets and fastening

strap over modem.

4 Run modem power cord behind brackets to peripheral cable assembly (W79) and plug into empty socket.

5 If ACU is a Class I system, turn facility power to ACU ON. If ACU is a Class II system, set UPS POWER

SWITCH on UPS (1A4) to ON. 

6 Place modem power switch at rear of unit to ON (position 1).

7 Verify that modem completes power-on diagnostics by observing that ALM indicator on front panel is not

illuminated.

8 Using procedure described in table 13.5.7, configure modem, then perform the following steps.

9 At rear of modem, remove power by setting modem rocker power switch to OFF (position 0).

10 If ACU is a Class I system, turn facility power to ACU OFF. If ACU is a Class II system, set UPS POWER

switch on UPS (1A4) to OFF. 

11 Locate cable from SIO board used for modem being replaced and connect cable to DTE PORT 1 connector

on rear panel of modem being installed.

12 Connect RJ-45 connector end of phone cable (62828-42045-10) to LEASE port on rear panel of modem

being installed.

13 Install RJ-11 connector end of phone cable (62828-42045-10) installed in step 12 to phone filter on ACU I/O

panel at connector J8.

14 If ACU is a Class I system, turn facility power to ACU ON. If ACU is a Class II system, set UPS POWER

switch on UPS (1A4) to ON.

15 At rear of modem, apply power by setting modem power rocker switch to ON (position 1).

16 Verify power up by performing the following steps:

a. After WAITING indication extinguishes on alphanumeric display and transmission rate

(9.6 for a Standard modem and 19.2 for a Premium modem) appears, press STATUS key.

b. Press STATUS key again. DIAGNOS* appears.

c. Using down arrow, drop to PASSED. If PASSED is displayed, perform the following

steps. If FAILURE is displayed, notify ADAS cognizant personnel.
S100 ASOS Site Technical Manual

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Table 13.5.5. Codex 3600 Series Modem Removal and Installation - CONT

Step Procedure

NOTE

The ASOS maintenance technician must disable OVERIDE in order to restore network control by

performing the following steps.

17 Press REMOTE key on front panel. MISC* is displayed.

18 Press down arrow. OVERIDE is displayed.

19 Press right arrow. ENABLE is displayed.

20 Press right arrow. DISABLE is displayed.

21 Press <ENTER>. The DISABLE indicator flashes, indicating that network control has been restored (i.e.,

OVERRIDE of network control has been disabled). The NC LED on the front panel is illuminated.

Table 13.5.6. Flex-Cartridge Removal and Installation

Step Procedure

REMOVAL

Tools Required:

None

NOTE

The 3600 modem is shipped from Codex with the Flex-cartridge installed.

1 Open front panel.

2

CAUTION

Ensure that the dc inhibit switch is in STANDBY position prior to removing the flex

cartridge. Failure to comply could result in equipment damage.

Place dc inhibit switch in STANDBY position (refer to figure 13.5.2) to disable dc power. This allows

removal of the cartridge without disconnecting the modem.

3 Firmly grasp left and right sides or top and bottom of Flex-cartridge and pull it from its rear connector (refer

to figure 13.5.3). Hold processor card in place during this step to prevent processor card from becoming

dislodged.

INSTALLATION

Tools Required:

None 

CAUTION

Ensure that the dc inhibit switch is in STANDBY position prior to removing the flex cartridge.

Failure to comply could result in equipment damage.

1 Align new Flex-cartridge with left and right guides and firmly slide cartridge into place until it engages rear

connectors.

2 Place dc inhibit switch in ON position.

3 Close front panel.
ASOS Site Technical Manual S100

13-34

Figure 13.5.2. Disabling DC Power Through the DC Inhibit Switch

Figure 13.5.3. Removing and Installing the Flex-Cartridge
S100 ASOS Site Technical Manual

13-35

Table 13.5.7. Configuring the Codex 3600 Series Modem

Step Procedure

NOTE

Review the menu hierarchy described in Section III before configuring the modem in accordance

with the following steps. Use the menu hierarchy as a guide in configuring the modem. 

There are two configuration setups for the Codex modem: Standard (multipoint) and Premium

(point-to-point). Follow the strapping instructions for the particular Flex-cartridge (Standard or

Premium) in the Codex modem.

STANDARD MODEM

1 Apply power to the modem and turn power on.

2 Press REMOTE. ENTR PSW is displayed. Enter 5215 as the password. To enter the password:

a. Press right arrow. The left-most digit now flashes, indicating that it may be changed. 

b. Press ADV# key to change value of current digit until correct value is displayed.

c. Press the right arrow to advance to the next digit. 

d. Continue performing steps b and c until all four digits (5215) have been entered.

e. Press ENTER when correct password is displayed. WELCOME displays on the LED

screen. 

3 Press REMOTE four times or until MISC* is displayed. Press the down arrow once or until OVERIDE: is

displayed. Press the right arrow twice or until ENABLE is displayed. Press ENTER.

4 Press CONFIG once or until DEVICE* is displayed. If ENTRPSW is displayed, enter 5215 asin step 2. Use

the down arrow to sequence through the following selections. Verify/set :

LOAD DEF: Press ENTER to signify yes. Press down arrow.

MODE: Press right arrow until 3600 is displayed, then press ENTER. Press down arrow.

MAX RTE: Press right arrow until 4.8 is displayed, then press ENTER. Press down arrow.

PORT/CH: Press right arrow, use ADV# and right arrow to input 12345678. Press ENTER.

5 Press CONFIG twice or until ANALOG * is displayed. Press the down arrow once, SELECT > is displayed.

Press the right arrow once or until LS ANLG+ is displayed. Use the down arrow to sequence through the

following selections. Verify/set :

OP MODE: Press right arrow until MP-S is displayed. Press ENTER. Press down arrow.

RATE_0: Press right arrow until 4.8 is displayed. Press ENTER. Press down arrow.

TX LEVEL: Press right arrow until -13 DBM is displayed. Press ENTER.

6 Press CONFIG until ANALOG * is displayed. Pressthe down arrow once, SELECT > is displayed. Pressthe

right arrow three times or until DTE + is displayed. Use the down arrow to sequence through the following

selections. Verify/set :

MUX MODE: Press right arrow until B is displayed. Press ENTER. Press down arrow.

TIMING: Press right arrow until LOOPBACK is displayed. Press ENTER. Press down

arrow.

SPD CTL: Press right arrow until REMOTE is displayed. Press ENTER
ASOS Site Technical Manual S100

13-36

Table 13.5.7. Configuring the Codex 3600 Series Modem - CONT

Step Procedure

7 Press CONFIG until PORTS* is displayed. Press the down arrow once, SELECT > is displayed. Press the

right arrow until PORT 1 + is displayed. Use the down arrow to sequence through the following selections.

Verify/set :

DATA CL: Press right arrow until SYNC EXT is displayed. Press ENTER. Press down

arrow.

P1 STP1: Pressright arrowonce. Use right arrowand ADV# keys to display 00000000.

Press ENTER. Press down arrow.

P1 STP2: Press right arrow once. Use right arrow and ADV# keys to display 00000010.

Press ENTER.

8 Press CONFIG until NWK CTL* is displayed. Use down arrow to sequence through the following selections.

Verify/set :

ADDRESS: Use right arrow and ADV# keys to display default address. Press ENTER. Press

down arrow.

NC STP1: Press right arrow once. Use right arrow and ADV# keys to display 00000000.

Press ENTER.

9 Press REMOTE until MISC* is displayed. Use the down arrow to sequence display to OVERIDE. Pressright

arrow until DISABLE is displayed. Press ENTER. Codex is now configured.

PREMIUM MODEM

1 Apply power to the modem and turn power on.

2 Press REMOTE. ENTR PSW is displayed. Enter 5215 as the password. To enter the password:

a. Press right arrow. The left-most digit now flashes, indicating that it may be changed. 

b. Press ADV# key to change value of current digit until the correct value is displayed.

c. Press right arrow to advance to next digit. 

d. Continue performing steps b. and c. until all four digits (5215) have been entered.

e. Press ENTER when correct password is displayed. WELCOME displays on LED screen.

3 Press REMOTE four times or until MISC* is displayed. Press the down arrow once or until OVERIDE: is

displayed. Press the right arrow twice or until ENABLE is displayed. Press ENTER.

4 Press CONFIG until DEVICE * is displayed. If ENTR PSW is displayed, enter 5215 as in step 2. Use the

down arrow to sequence through the following selections. Verify/set :

LOAD DEF: Press ENTER to signify yes. Press down arrow.

MODE: Press right arrow until 3600 is displayed, then press ENTER. Press down arrow.

MAX RTE: Press right arrow until 19.2 is displayed, then press ENTER. Press down arrow.

PORT/CH: Press right arrow, use ADV# and right arrow to input 12345678. Press ENTER.

5 Press CONFIG twice or until ANALOG * is displayed. Press the down arrow once, SELECT > is displayed.

Press the right arrow until LS ANLG+ is displayed. Use the down arrow to sequence through the following

selections. Verify/set :

OP MODE: Press right arrow until TURBO is displayed. Press ENTER. Press down arrow.

RATE_0: Press right arrow until 19.2 is displayed. Press ENTER. Press down arrow.

TX LEVEL: Press right arrow until -13 DBM is displayed. Press ENTER.
S100 ASOS Site Technical Manual

Table 13.5.7. Configuring the Codex 3600 Series Modem - CONT

Step Procedure

13-37/ (13-38 blank)

6 Press CONFIG until ANALOG* is displayed. Press the down arrow once, SELECT > is displayed. Press the

right arrow until DTE + is displayed. Use the down arrow to sequence through the following selections.

Verify/set :

MUX MODE: Press right arrow until UDM1 is displayed. Press ENTER. Press down arrow.

TIMING: Press right arrow until LOOPBACK is displayed. Press ENTER. Press down

arrow.

SPD CTL: Press right arrow until REMOTE is displayed. Press ENTER

7 Press CONFIG until PORTS* is displayed. Press the down arrow once, SELECT > is displayed. Press the

right arrow until PORT 1 + is displayed. Use the down arrow to sequence through the following selections.

Verify/set :

DATA CL: Press right arrow until SYNC EXT is displayed. Press ENTER. Press down

arrow.

P1 STP1: Press right arrow once. Use right arrow and ADV# keys to display 00001000.

Press ENTER. Press down arrow.

P1 STP2: Press right arrow once. Use right arrow and ADV# keys to display 00000010.

Press ENTER.

8 Press CONFIG until NWK CTL* is displayed. Use the down arrow to sequence through the following

selections. Verify/set :

ADDRESS: Use right arrow and ADV# keys to display default address. Press ENTER. Press

down arrow. 

NC STP1: Press right arrow once. Use right arrow and ADV# keys to display 00000000.

Press ENTER.

9 Press REMOTE until MISC * is displayed. Use down arrow to sequence display to OVERIDE. Press right

arrow until DISABLE is displayed. Press ENTER. Codex is now configured.
S100 ASOS Site Technical Manual

14-1

CHAPTER 14

SINGLE-CABINET ASOS (SCA) AND ASSOCIATED EQUIPMENT

SECTION I. DESCRIPTION AND LEADING PARTICULARS

14.1.1 INTRODUCTION

The single-cabinet ASOS (SCA) contains both the Acquisition Control Unit (ACU) and data collection

package (DCP) within one cabinet and is designed for outdoorinstallation. The same peripherals and sensors

are used on the SCA as on the standard ASOS. This chapter documents the SCA cabinet and associated

equipment. The table of contents is referenced for the chapters containing sensors and optional equipment

used by both the SCA and the standard ASOS.

14.1.2 SITE DESCRIPTION

A typical SCA site, figure 14.1.1, has the SCA cabinet (with ACU and DCP equipment) located outdoors.

The single-cabinet ASOS configuration need not be located at an airfield: any clear site with 115 Vac, 1N,

and telephone service will suffice. 

NOTE

The SCA discussed in this chapter is different from the standard ASOS Class I reduced

capability configuration. The SCA contains both the ACU and DCP in an equipment cabinet

designed for outdoor use. The ASOS Class I reduced capability configuration uses the

standard indoor ACU equipment cabinet (which requires shelter) and contains internal

(local) DCP interface for sensors located close to the shelter. Chapter 2 is referenced for

ASOS Class I reduced capability configuration.

14.1.3 PURPOSE OF CHAPTER

This chapter serves as the primary source of technical information for site maintenance personnel engaged

in maintaining the SCA. SCA theory presented in this chapter is similar to the theory for the standard ASOS

discussed in Chapter 1. Information provided in this chapter enables maintenance personnel to quickly

remedy any problem and restore the SCA to service. This chapter must be used with other chapters in this

ASOS Site Maintenance Manual (STM) and other publications listed in paragraph 14.1.5.

14.1.4 SCOPE OF CHAPTER

This chapter provides all information neg15

cessary for SCA on-site maintenance support. Included are preventive maintenance instructions, operation,

fault isolation, and removal/installation of field replaceable units (FRU’s). For information on sensor

subsystems, the respective chapters ofthis Site TechnicalManual(STM) are referenced.Chapter 14 includes

five sections as described in the following paragraphs.

14.1.4.1 Section I, Description and Leading Particulars. This section provides an overview of the

system/subsystem and should be used to gain a general understanding of the SCA configuration or to obtain

physical descriptions and location information.
ASOS Site Technical Manual S100

14-2 Change 1

Figure 14.1.1. Typical ASOS Site, Single-Cabinet Configuration

L

14.1.4.2 Section II, Installation. Section II assumes that the SCA FRU’s were previously installed by the

factory installation team and that all mounting hardware and electrical wiring is in place.

14.1.4.3 Section III, Operation. Section III provides procedures for sequencing power, initializing,

determining operational status, and operating the SCA. This information enables maintenance personnel to

effectively use the SCA, but does not repeat information contained in Chapter 1, Section III which applies

generally to SCA sites as well as for standard ASOS sites. Standard operating procedures (SOP's) are

provided in the ASOS Software Users Manual. 
S100 ASOS Site Technical Manual

Change 1 14-3

14.1.4.4 Section IV, Theory of Operation. Section IV provides detailed SCA theory of operation and

contains basic and detailed block diagrams.

14.1.4.5 Section V, Maintenance. Section V provides SCA corrective and preventive maintenance

procedures for cleaning and inspection, adjustment, calibration, troubleshooting using resident diagnostic

firmware, and failed FRU removal/replacement. The SCA partslists are located after the last

chapter in volume II . SCA sites may also include up to three remote DCP's and associated

sensors. Section 14.5 should be used as a troubleshooting guide or when performing SCA scheduled or

corrective maintenance.

14.1.5 RELATED PUBLICATIONS

In addition to this chapter, the SCA site issupported by the other chapters of ASOS Technical Manual(STM)

S100, in addition to the following manuals:

! ASOS Software User's Manual - Provides detailed information on ASOS operation and

ASOS OID displays.

! ASOS Ready Reference Guide - Contains ASOS operator reference information.

! Link MC70 User's Guide - Provides OID vendor support information.

! Panasonic dotmatrix printermodelKX-P3123Operating InstructionsManual - Provides dot

matrix printer vendor support information.

! UDS 2440 Installation and Operation - Provides model 2440 stand-alone telephone modem

vendor support documentation.

! UDS V.3225 Installation and Operation - Provides model V.3225 stand-alone telephone

modem vendor support documentation.

! UDS V.3400 Installation and Operation - Provides vendor support documentation for the

model V.3400 stand-alone telephone modems.

14.1.6 SCA FUNCTIONAL DESCRIPTION

As shown in the basic block diagram (figure 14.1.2), the typical SCA consists of a central cabinet, sensors

that gather weather information, and modems that communicate with user facilities. Optional peripherals may

include a laptop computer (not supplied) that allows data access and equipment control during maintenance

activities. An optional, standard FAA handset allows voice messages to be appended to the computerized

observation message to convey special information for pilots (e.g., Notice to Airmen Messages (NOTAM’s)).

Other optional terminal equipment available forthe standard ASOS is also available forthe SCA.Regardless

of configuration type, all ASOS sites contain at least three major units: ACU or SCA, sensors, and

peripherals. The SCA and standard ASOS ACU cabinet may be supplemented by up to three (optional)

DCP’s at sites where remote data collection is required.

The SCA can accommodate a ground-to-air (GTA) radio and a Codex Modem. A weatherproof auxiliary $

box (aux box) is provided to accommodate either or both of these units plus a second (optional)

uninterruptible power supply (UPS) unit. When required, the aux box will be installed with the SCA.

SCA ASOS sites differ in the quantity of each component type included in the configuration but all sites
ASOS Site Technical Manual S100

14-4 Change 1

L

L

Figure 14.1.2. Single-Cabinet ASOS, Basic Block Diagram

include only one SCA cabinet. The SCA site may include any of the standard or optional equipment items

listed in the partslist.Chapter 3 containsinformation on DCP’s. Each sensor performs a specialized function

in gathering local raw surface weather data. At a minimum, the typical ASOS site has sensors to collect

pressure, temperature/dewpoint, wind, and precipitation data. At the typical SCA site, the SCA houses all

on-site equipment and the pressure sensors. Sensors, other than the pressure sensors, are mounted external

to the SCA.

The entire SCA is designed to operate outdoors. Data and phone lines may be routed to an airport terminal

(or other building) where one operator interface device (OID) and/or one video display unit (VDU) may be

located (but not more than 100 feet from the SCA). Sensors are either polled by the SCA or automatically

transfer data to the SCA for incorporation into the ASOS data processing scheme. Up to 13 local sensors (in

addition to the pressure sensors) can be connected directly to the SCA. At sites where an optional DCP is

$ installed, up to 16 additional sensors may be added per DCP.
S100 ASOS Site Technical Manual

Change 1 14-5

14.1.7 SCA CONFIGURATION

Each SCA is configured to meet specific site-peculiar requirements. The established site configuration can

be reviewed by accessing the site configuration screens via an operator interface device (OID), laptop

personal computer (PC), or remote terminal. This site maintenance manual provides maintenance

documentation for all assemblies and subassembliesincluded in the ASOS but does not relate to any specific

configuration. The technician should consult the configuration pages and site specific documentation to

determine sensor configuration, sensor pad configuration, assigned peripherals, facility power, and signal

cable routing.

SCA sites can be equipped with a wide variety of equipment, depending upon operational requirements and

customer options. To accommodate site requirements, core equipment complements have been established

to which sensorsubsystems, peripheral equipment, and options can be added by selecting kits. These kits are

a collection of assemblies and parts needed to install those assemblies. Shelters are not required for any SCA

configuration. Core single-cabinet systems are designated as follows:

S1 - Class I SCA, for small airports. SCA core equipment complement includes power $

delay relay, two pressure sensors, precipitation identification, cloud height, $

visibility, rain gauge, temperature/dewpoint, and wind sensors. May have the aux $

box if site includes codex modem or GTA Radio. $

S2 - ClassII SCA, forspecial nonairportsites. SCA includes UPS with power delay and $

UPS bypass, may have up to three DCP’s (each with a UPS), and may have the aux $

box (and an additional UPS). S2 SCA includes three pressure sensors, wind,

temperature/dewpoint, visibility, cloud height, precipitation ID,rain gauge sensors.

An OID is also standard equipment at S2 sites.

SR - Class I SCA with reduced capability (no optical sensors), includes power delay $

relay, two pressure sensors, rain gauge, temperature/dewpoint, and wind sensors. $

14.1.8 SCA PHYSICAL DESCRIPTION

The SCA houses and interconnects the FRU’s which are identified on figure 14.1.3 and in table 14.1.1. The

SCA partslist (located after the last chapter in volume II) contains part number

information.

14.1.8.1 Mounting Plate Assembly 7A1A1. Most of the SCA electronic assemblies are located on

Mounting Plate Assembly 7A1A1. The mounting plate is secured on studs against the inside back surface

of the SCA. The following FRU’s are mounted on Mounting Plate Assembly 7A1A1:

14.1.8.1.1 VME Rack 7A1A1A2 Description. The VME rack assembly, shown in figure 14.1.4, contains

2 rows of 96-pin connector sockets on the backplane for up to 21 printed circuit card assemblies (CCA’s).

Reference designators for each card are located on a marker strip at the top-front of the rack. The top row

of connectors are for the 32-bit VME data bus, while the lower row providesinterconnections and operating

voltages. Three exhaust fans are mounted beneath the rack to force cooling air upward, between, and around

installed CCA’s.

14.1.8.1.2 Circuit Breaker Panel 7A1A1A3 Description. The circuit breaker panel is located below the

VME rack. The panel contains 22 single-pole magnetic circuit breakers and a DB-25F connectorsocket (J1)

for connecting the primary OID. At most SCA sites, the only OID will be the technicians laptop PC. An

optional DB-25 to telco adapter (PN 62828-90197-1) is available for RS-232 interface to the PC via 4-

conductor telephone cable.
ASOS Site Technical Manual S100

14-6 Change 1

Figure 14.1.3. SCA Cabinet 7A1, Interior View

L

L

L

L

Table 14.1.1. SCA (7A1) Major Components

Ref Des Description Ref Des Description

7A1A1 Mounting Plate Assembly 7A1A1A9,A10 User Modems #1, #2 (Optional)

$ 7A1A1A2 VME Rack Assembly 7A1A1A11 Optional Modem

$ 7A1A1A3 Circuit Breaker Panel 7A1A1A12 Optional Modem

$ 7A1A1A4 AC Power Distribution Assembly 7A1A1A13 Power Reset Assembly

7A1A1A5 RF Modem Shelf (Optional) 7A1A1HR2 Heater, Battery (Optional)

7A1A5A1,A2 RF Modem #1, #2 (Optional) 7A1A2 Battery Box Assembly (Optional)

7A1A1A5S1 RF Modem Switch (Optional) 7A1A3 Faraday Box

7A1A1A6 UPS (Optional) 7A1A4 Power Supply Mounting Plate

$ 7A1A1A7 Pressure Shelf Assembly 7A1A5,A6 Optional Modem

7A1A1A8 Power Outlet Strip
S100 ASOS Site Technical Manual

Change 2 14-7

Figure 14.1.4. VME Rack 7A1A1A2, Front View

14.1.8.1.3 AC Power Distribution Assembly 7A1A1A4 Description. The AC power distribution

assembly is mounted vertically at the center of the cabinet. The assembly contains 27 rail-mounted terminal

blocks. Each terminal block has four screw-swaged wire terminals to provide connections for 115 VAC,

neutral, and ground wires.

14.1.8.1.4 RF Modem Shelf 7A1A1A5 Description. The rf modem shelf (optional) is located above the

ac power distribution assembly in the center of the cabinet. The rf modem shelf provides mounts and

interconnections for up to two rf modems (optional) and RF Switch 7A1A1A5S1. The rf modem provides

the communications link between the SCA and DCP’s when the site configuration includes DCP’s. The

second rf modem and rf switch provide a redundant communications link between the SCA and DCP in the

event that the primary rf modem fails.

$

$

$
ASOS Site Technical Manual S100

14-8 Change 2

$ NOTE

$

$ When a Motorola modem (62828-90315-XX) fails and spare Motorola modems are not

$ available, a Johnson Data modem (62828-40506-X), an adapter cable (62828-42110-10),

$ and a SMAM-to-BNCF adapter must be ordered to replace the failing modem. Kit part

$ number 62828-40378-xx can be ordered the first time that the Johnson Data modem is

$ installed in the SCA. 

$

$ The original equipment SCA rf modem shelf must be replaced with rf modem shelf 62828-

$ 40322-20 to support mounting both the Motorola and Johnson Data modems(Motorola and

$ Johnson Data modems can coexist within the SCA). 

$

$ The adapter cable and SMAM-to-BNCF adapter must be removed if a Johnson Data modem

$ fails and a Motorola modem is installed.

14.1.8.1.4A Uninterruptible Power Supply 7A1A1A6 Description. A UPS is included in the Class II

SCA to provide a backup ac power source for the SCA and up to nine sensors. If more than nine sensors are

$ associated with a ClassII SCA, a secondary UPS isinstalled in an optional auxiliary box. Either Deltek UPS

$ 62828-90338-10 or Deltek UPS 62828-90338-20 may be installed.

14.1.8.1.5 Pressure Mounting Assembly 7A1A1A7 Description. The pressure mounting assembly is

located above the rf modem shelf. The assembly provides mounts and interconnections for three identical

pressure sensor assemblies(7A1A1A7A1, A2, and A3) asshown on figure 14.1.5. Temperature sensor board

(7A1A1A7A4) is mounted on the front of the pressure sensor shelf. Plastic vent tubes from each sensor are

joined under the pressure shelf to a tube cross and then routed to the pressure port at the top of the cabinet.

14.1.8.1.6 Power Outlet Strip 7A1A1A8 Description. The outlet strip is mounted below the UPS, on the

bottom left side of the cabinet. The outlet strip is rated at 15 amperes, continuous, and provides connection

for up to five ac power plugs (with grounding pins)

14.1.8.1.7 User Modems 7A1A1A9, A10 Description. The user modems are located at the top of the

cabinet, next to the VME rack. User modems operate asstand-alone 2400, 9600, or 28800 baud modemsthat

connect to dedicated lines. User 1 Modem 7A1A1A9 is supplied with each system and is used to connect to

the AOMC. Optional User 2 Modem 7A1A1A10 provides an additional dedicated line connection to the

SCA.
S100 ASOS Site Technical Manual

Change 2 14-8.1/ (14-8.2 blank)

Figure 14.1.5. Pressure Sensor Shelf 7A1A1A7, Front View
S100 ASOS Site Technical Manual

Change 1 14-9

L

Figure 14.1.6. Faraday Box A3, Panel Views

L

L

14.1.8.1.8 Optional Modems 7A1A1A11, A12 Description.The optionalmodems are located in the upper

left corner of the cabinet. The optional modems can be 2400, 9600 or 28800 baud. The optional modems are $

used to connect to AFOS, OID’s, VDU’s, printer, or telco.

14.1.8.1.9 Power Reset Assembly 7A1A1A13 Description. PowerReset Assembly 7A1A1A13 islocated $

to the left of the ac power distribution assembly. The power reset assembly contains a Time Delay Relay $

7A1A1A13K1 (Class I and Class II), Digital I/O Module 7A1A1A13K2 (Class II only), and Power Relay $

7A1A1A13K3 (Class II only). The time delay relay ensures that the SCA resets properly after power is $

interrupted by delaying power application approximately three seconds. The digital I/O module and power $

relay provide the Class II SCA with UPS bypass capabilities. $

14.1.8.2 Faraday Box 7A1A3 Description. The Faraday box is located in the lower right corner of the

cabinet, beneath the circuit breaker panel.All SCA externalsignal and powerlines passthrough flex conduits

in the bottomof the FaradayBox to prevent rain water fromentering the cabinet. Fiber optic cablesthat enter

the Faraday Box connect to fiber optic modems located on the top of the Faraday box. The Faraday box also

contains two columns of track-mounted terminal blocks on the back side of the hinged front cover that

terminate external power and signal lines. The Faraday box has an internal cable assembly that connects the

terminalsto connectors mounted on the top or leftside surfaces of the box asshown on figure 14.1.6. Mating $

connectors are part of SCA wiring harness 7A1W106. Dependent upon the site specific SCA equipment

configuration, blank cover plates are used in place of connectors not used by the SCA.
ASOS Site Technical Manual S100

14-10

Figure 14.1.7. Power Supply Assembly A4, Front View

14.1.8.3 Power SupplyMounting Plate 7A1A4.The powersupplymounting plate (figure 14.1.7)ismounted against the SCA right side interior and supplies all dc operating voltages (-12V, +12V, and +5V) for the

other assemblies in the SCA. Each of two 12V supplies output both -12V and +12V, while the two 5V

supplies output positive voltage only. Supply outputs are paired by OR diodes, so that loss of either supply

of a pair can not affect the operating voltage. The power supply mounting plate also includes DC Power

Distribution Assembly 7A1A4A1, which distributes all dc operating voltages and protectsthe power supply

inputs with 3.15A fuses on the 5V supply inputs and 2.5A fuses on the 12V supply inputs.

14.1.8.4 Modems 7A1A5, A6Description.These optional, additionalmodems are located in the lowerright

corner of the cabinet. The type and use of these modems are established for each site by the customer.
S100 ASOS Site Technical Manual

Change 1 14-11

Figure 14.1.8. Auxiliary Box 7A2, Interior View

14.1.8.5 Optional Solar Shield. A solar shield kit (P/N 62828-40409-10) is available for SCA sites $

that experience intense solar load and high temperatures. $

$

14.1.9 AUXILIARY BOX PHYSICAL DESCRIPTION

14.1.9.1 Enclosure. The auxiliary box (figure 14.1.8 and table 14.1.2) is a weather-resistant enclosure that

measures approximately 42 inches in width and 36 inches high, exclusive of mounting tabs. 

14.1.9.2 Auxiliary Box Standard Equipment. Supplied as standard equipment in Auxiliary Box 7A2 are

AC Power Distribution Strip 7A2A1A4, Modem Mounting Shelf 7A2A1A5 (without the modems), and

Heater Strip 7A2A1HR1. All other equipment components to be installed in the aux box are customer- $

ordered options, delivered as separate kits. $
ASOS Site Technical Manual S100

14-12 Change 2

Table 14.1.2. Auxiliary Box (7A2) Major Components

Ref Des Description Ref Des Description

7A2A1 Mounting Plate Assembly 7A2A1A5K1, K2,

S1-S3

Heater control circuit

7A2A1A1 Codex Modem (Optional) 7A2A1A6 UPS (Optional)

7A2A1A2 UPS Bypass Assembly (Optional) 7A2A1HR1 Heater, Battery

7A2A1A3 GTA Radio (Optional) 7A2A1HR2 Heater, Battery (Optional)

7A2A1A4 Power Outlet Strip 7A2A2 Battery Box Assembly (Optional)

7A2A1A5 Modem Shelf 7A2W108 Wiring Harness

14.1.9.2.1 Mounting Plate Assembly 7A2A1. Most of the aux box assemblies are located on Mounting

Plate Assembly 7A2A1. The mounting plate is secured on studs against the inside back surface of the aux

box. The following FRU’s are mounted on Mounting Plate Assembly 7A2A1.

14.1.9.2.2 Power Outlet Strip 7A2A1A4 Description. The outlet strip is mounted in the upper right

corner of the cabinet. The outlet strip is rated at 15 amperes, continuous, and provides connection for five

ac power plugs (with grounding pins) including the GTA radio and Codex modem.

14.1.9.2.3 Modem Shelf 7A2A1A5 Description. The modem shelf (optional) in the top center of the

cabinet. The modem shelf provides mounts and interconnections for up to two additional modems (optional

future expansion). The shelf also mounts the aux box heater control circuitry.

14.1.9.3 Auxiliary Box Optional Equipment. Available optional kits are:

! Codex Modem Kit 7A2A1A1

! Auxiliary UPS Kit, including UPS 7A2A1A6 and Battery Box 7A2A2

! GTA Radio Kit, including GTA Radio 7A2A1A3

$ 14.1.10 ALTERNATIVE GTA RADIO ANTENNA MOUNTING KIT

$

$ Atsome SCA combined sites where interference between the GTA radio and the installed sensorsis possible,

$ an alternative GTA Radio Mounting Kit (Part Number 62828-40507-10) isinstalled. This antenna is a unity

$ gain omnidirectional antenna that is precision field-tuned to the GTA frequency. The antenna is mounted

$ near the top of the wind tower. The type and height of the antenna prevents radio frequency interference

$ from the GTA radio with the operation of the present weather sensor.
S100 ASOS Site Technical Manual

Change 1 14-13

Figure 14.2.1. SCA Solar Shield (Optional) $

SECTION II. INSTALLATION

14.2.1 INTRODUCTION

Single-cabinet ASOS (SCA) installation is not the responsibility of the site technician. Information

concerning installation, removal, and replacement of various field replaceable units (FRU’s) and sensors is

provided in the respective chapter of this ASOS Site Technical Manual (STM).

14.2.2 SOLAR SHIELD (OPTIONAL) $

$

An optional solar shield kit (P/N 62828-40409-10) can be added to those SCA installations that endure $

intense solar load and high temperatures. Sites to receive the shields are as directed in letter ASOS-II-97- $

0243 dated April 1, 1997. $
ASOS Site Technical Manual S100

14-14 Change 2

Figure 14.2.2. Alternative GTA Radio Antenna Kit

$ 14.2.3 ALTERNATIVE GTA RADIO ANTENNA KIT

$

$ Some SCA sites with GTA radios may experience radio frequency interference to the Present Weather

$ sensor. When the GTA is transmitting, the transmit frequency may cause interference in the LEDWI and

$ create false LEDWI outputs (such as showing “rain” on a clear day). At these sites, it may be necessary to

$ install Field Modification Kit FMK 114B. This kit (part number 62828-40507-10) replaces the present GTA

$ radio antenna mounted on the DCP/SCA supportstructure with a ground plane antenna mounted nearthe top

$ of the wind tower. The antenna cable is re-routed from the auxilliary box through underground conduit to

$ the wind tower location.

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$ 
S100 ASOS Site Technical Manual

Change 2 14-15

SECTION III. OPERATION

14.3.1 INTRODUCTION

During system maintenance, the single-cabinet ASOS (SCA) is controlled and monitored from a laptop

personal computer (PC) connected to the primary OID connector located at the right side of Circuit Breaker

Assembly 7A1A1A3. The laptop PC functions as the technician’s operator interface device (OID).

Dependent upon the site specific configuration, one or more OID devices may be installed. From the laptop

PC, the technician can:

! Access diagnostic program displays that are an integral part of the system

! Change system configuration

! Change output port assignments, parameters, and message formats

! Change communications port characteristics

! Enable and disable communications ports

! Select pulse or tone telephone dialing mode

! Request 2-hour archive of 5-minute observations

! Enable sensors and/or sensor report processing

! Change selected site constants such as date, time, latitude, longitude, and elevation

! Make system log entries

! Reset the system

By using an optional handset in conjunction with the laptop, the technician also can record, play back, and

control automated voice messages. Functions available to a user depend on how the user signs onto the

system. At the SCA site, the only user might be the technician. As with the standard ASOS, however, four

levels of users may sign onto the system: observers, air traffic controllers (ATC’s), system managers, and

technicians. Additionally, unsigned users also have certain limited capabilities on the system. Some functions

are available to more than one type of user. For example, the technician and system manager have the same

maintenance capabilities under the MAINT (maintenance)function. The ASOS ReadyReference Guide and

Software User's Manual identify the functions granted to each type of user. Thissection provides control and

indicator information for the OID and printer, descriptions of all maintenance pages, and detailed system

maintenance operating procedures. Additional information on the other ASOS screens and operating

procedures are provided in the ASOS Ready Reference Guide and Software User's Manual.

14.3.2 CONTROLS AND INDICATORS

All controls and indicatorsin the cabinet are considered to bemaintenance-related.Only certified technicians

are permitted to open the cabinet. Sensor subsystem controls and indicators are listed and illustrated in the

respective chapters of this ASOS Site Technical Manual (STM).

14.3.2.1 Circuit Breaker Panel 7A1A1A3, Controls and Indicators. Circuit breakers and their functions

are illustrated on figure 14.3.1 and described in table 14.3.1.

14.3.2.2 VME Rack 7A1A1A2, Controls and Indicators. VME CCA controls and indicators and their

functions are illustrated on figure 14.3.2 and described in table 14.3.2. 

14.3.2.2ARFModems.RFdatamodems provide communications between the SCA and DCP cabinets. Only $

the Johnson Data rf modem (62828-40506-X) has controls and indicators as shown on figure 14.3.3 and $

described in table 14.3.3. $

$
ASOS Site Technical Manual S100

14-16 Change 2

Figure 14.3.1. Circuit Breaker Panel 7A1A1A3, Controls

14.3.2.3 Operator Interface Device (OID), Controls and Indicators. The OID controls and indicators are

described in Chapter 1, Section III.

14.3.2.4 Auxiliary Box 7A2, Controls and Indicators. The aux box does not contain controls or indicators

but may contain a GTA radio or Codex Modem. Chapter 12 Section 3 contains GTA radio controls and

indicators and Chapter 13 Section 3 contains Codex modem controls and indicators.

Table 14.3.1. Circuit Breaker Panel 7A1A1A3 Controls and Indicators

Ref Des Placard Type Function

CB1 ELEC/HTR 1E Circuit Breaker CHI

CB2 ELEC/HTR 1H Circuit Breaker CHI HTR

CB3 ELEC/HTR 2E Circuit Breaker FZR (TS1)

CB4 ELEC/HTR 2H Circuit Breaker FZR HTR (TS HTR1)

CB5 ELEC/HTR 3E Circuit Breaker PWI

CB6 ELEC/HTR 3H Circuit Breaker PWI HTR

CB7 ELEC/HTR 4E Circuit Breaker SPARE

CB8 ELEC/HTR 4H Circuit Breaker TB HTR

CB9 ELEC 5E Circuit Breaker WIND

CB10 ELEC 6E Circuit Breaker TEMP/DEWPOINT

CB11 ELEC 7E Circuit Breaker VIS

CB12 ELEC 8E Circuit Breaker SPARE

CB13 ELEC/HTR 9E Circuit Breaker TS1

CB14 ELEC/HTR 9H Circuit Breaker TS HTR1

CB15 ELEC/HTR 10E Circuit Breaker SPARE

CB16 ELEC/HTR 10H Circuit Breaker SPARE

CB17 ELEC/HTR 11E Circuit Breaker SPARE

CB18 ELEC/HTR 11H Circuit Breaker SPARE

CB19 ELEC/HTR 12E Circuit Breaker SPARE

CB20 ELEC/HTR 13E Circuit Breaker SPARE

CB21 UPS 1 Circuit Breaker AC MAIN

CB22 UPS 2 Circuit Breaker AC to Aux UPS

1 CB13 and CB14 are used for TS if site configuration includes FZR .
S100 ASOS Site Technical Manual

14-17

Figure 14.3.2. VME CCA’s, Controls and Indicators

Table 14.3.2. VME Rack 7A1A1A2 Controls and Indicators

Ref Des Placard Type Function

A1,A2 (CPU #1, #2) FAIL LED (r) Self-test fail

PASS LED (gn) Self-test pass (FAIL and PASS both light during self-test)

HALT LED (amb) CPU halted

ABORT Push switch Do not use. If inadvertently pressed, then press RESET.

Resets CPU and VME bus.

A3 (Memory) B1 LED (gn) Bank #1 memory addressed

B2 LED (gn) Bank #2 memory addressed

B3 LED (gn) Bank #3 memory addressed

LOW BATT LED (r) Memory board backup battery low, replace board

A20 (Voice CPU) ALARM LED Audio CPU failure

RESET Push switch Resets audio CPU only

A21 (Voice Audio Bd) ALARM LED No audio output for 30 to 60 seconds
ASOS Site Technical Manual S100

14-18 Change 2

Figure 14.3.3. Johnson Data RF Modem Controls and Indicators

$$ Table 14.3.3. Johnson Data RF Modem Controls and Indicators

$ Index

$ Control/

Indicator Description

$ 1 SMA Connector RF output (requires SMAM-to-BNCF adapter)

$ 2 HDB-15 Connector High density 15 pin female power/communications connector (requires

$ adapter cable 62828-42110-10)

$ 3 RX LED (Yellow) Illuminates when receiving data

$ 4 TX LED (Red) Illuminates when transmitting data

$ 5 PWR LED (Green)

$ (Flashing)

Illuminates when power is applied

Illuminates when setup mode is active

14.3.3 MAINTENANCE DISPLAY PAGES

Using either the OID or a laptop PC, the ASOS technician accesses maintenance display pages to monitor

the ASOS continuous self-test (CST) program, which runs during normal system operation. The hierarchy

of maintenance display pages and the page presentations are illustrated in Chapter 1, Section III.

14.3.4 OPERATING PROCEDURES

Chapter 1, Section III contains operating procedures.
S100 ASOS Site Technical Manual

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SECTION IV. THEORY OF OPERATION

14.4.1 INTRODUCTION

This section describes, at system level, the single-cabinet ASOS (SCA). Information on common subassemblies that are also used at multicabinet ASOS sites is provided in respective chapters of this STM. Each

ASOS is configured to meet the specific requirements of a given site. To configure an SCA system, a site

survey must first be made in which the following factors must be considered:

! If the site is at an airport, appropriately locate sensor groups by considering runway patterns

and lengths

! Mapping areas of frequent meteorological discontinuity

! Locating backup sensor group(s) for optimum system reliability

! Identifying the most suitable location for the SCA

! Identifying required sensors

! Measuring distances from planned sensor group(s) to SCA and from SCA to the air traffic

controller (ATC) or operations area

! Assessing commercial power availability and reliability

! Specifying the number and types of usersthat need to accesssystemdata and controlsystem

functions. (Typically, the maintenance technician will be the only local user at singlecabinet ASOS sites; however, some sites could have other local users. The technician can

control and monitor the system from a laptop PC when the PC data cable is connected to

SCA P19.)

NOTE

SCA is used herein as an acronym for the single-cabinet ASOS to

distinguish the SCA cabinet from the standard ASOS ACU cabinet.

14.4.2 SCA BLOCK DIAGRAM

The typical SCA houses all equipment (except externalsensors)required forstand-alone, automatic,surface

weather data acquisition,reporting, and archiving. At ClassIIsites, an auxiliary box (aux box)is added when

needed to house certain optional equipment. At Class I sites and reduced-capability sites, the aux box is an

optional add-on.

As shown on the simplified block diagram (figure 14.4.1) the SCA receives sensor data, processes data in

accordance with programmed instructions (algorithms) suitable for each sensor type, outputs data to

peripheral devices and users, and archives data in internal memory. The SCA also contains a speech

processor which digitizes English words that have been humanly vocalized and recorded. Digitized words

(rather than phonemes, i.e., phonetic sounds, as in most synthesizers) are then syntactically assembled in

accordance with current weather observation data to convey routine meteorological reports (METAR’s), or

special meteorological reports (SPECI’s) for transmission over telephone lines or radio. The SCA mounts

all data processing boards in 21-slot VME Rack 7A1A1A2. 

NOTE

In the following paragraphs, reference designators for VME circuit card

assemblies (CCA’s) are abbreviated to identify only the CCA number

within the VME rack.
ASOS Site Technical Manual S100

14-20 Change 1Figure 14.4.1. SCA Simplified Block Diagram
S100 ASOS Site Technical Manual

Change 1 14-21

Figure 14.4.2. CPU, Simplified Block Diagram

14.4.2.1 CPU CCA’s A1 and A2. The SCA containstwo CPU’s and other data processingCCA’sin a VME

rack. The VME rack printed-wiring backplane contains 2 rows of board connectors: one for the 32-bit VME

data bus, and one for interconnections and operating voltages. The two CPU CCA’s are similar and provide

redundancy. One CPU CCA serves as the primary processor while the second CPU CCA isin standby. Each

CPU monitors the other processor. If the primary processor fails a self-test, it is automatically switched

offline and the backup CPU assumes the role of primary.

Two pushbuttons (RESET and ABORT) are mounted on the front frame of the CPU CCA: these switches

are not used in the field. ABORT halts program execution without resetting the CPU. In the event that

ABORT isinadvertently pressed, press RESET to reset the CPU’s and activate SYSRESET which resets all

other VME boards. Resetting the CPU does not affect DRAM contents.

The following paragraphs describe the CPU functional block diagram (figure 14.4.2). Each CPU CCA

contains: 

! A 68010 series microprocessor running at 10 MHZ

! EPROM

! Dynamic random access memory (DRAM)

! Two RS-232 ports

! A 16-bit timer

During system operation one CPU CCA is the primary CPU that performs all processing and I/O functions

while the other CPU functions in standby. Initially CPU #1 is the primary CPU.

The CPU CCA consists of nine functional areas:system resource function, two dual universal asynchronous

receiver-transmitters (UART’s), timer, RS-232 transmitter-receiver, CPU clock, microprocessor, interrupt
ASOS Site Technical Manual S100

14-22

logic, VME interface logic, address buffer and decoder, and memory. The system resource function on the

primary CPU provides system clock, system reset, bus arbitration, bus timer and functions as the VME bus

controller. The corresponding system resource function on the secondary CPU is not used unlessit becomes

the online CPU.

The dual UART’s and timer provides two RS-232 serial communication channels, a timer, and two I/O and

control ports. The RS-232 driver and receiver logic interfaces UART channels A and B to external devices

via connector J1 on the CPU by providing standard transmit and receive lines. (CPU’s #1 and #2 each

provide two additional UART channelsthat are not presently used.)CPU #1 is connected asthe primaryCPU

with a loopback jumper installed between channel B transmit and receive lines (JK1 pins 14 and 16). When

power is applied both CPU’s issue a message from their respective UART channel B. CPU #1 immediately

receives this message via the loopback jumper installed on the CCA front panel connector JK1. Both CPU’s

examine their receive lines and CPU #1 detects that it has received the loopback signal and assumes the role

of the online CPU. Conversely, when CPU #2 detectsthat it has not received the loopback signal, it assumes

the role of the standby CPU. The standby CPU continuously monitors CPU status by examining a location

on the memory board where a tally count is stored. The online CPU updates this count on a periodic basis.

Failure to update the count indicates a CPU failure which causes the standby CPU to become the primary

CPU. The CPU operatesfrom an internally generated 10 MHZ clock to execute ASOS operational firmware

in the memory board EPROM’s. Interrupt logic monitors the dedicated interrupt lines and informs the CPU

when an interrupt line is active. The interrupts are prioritized and processed on a first-come,first-serve basis.

VME interface logic provides standard address, data, and control signals for system bus communication.

The address buffer-decoder addresses all devices for microprocessor read/write operations. CPU onboard

memory consists of 128K bytes of EPROM and 512K bytes of DRAM. Refresh circuitry for the DRAM is

not disabled during a RESET; therefore, the CPU may be reset without affecting memory contents.

The SCA continuous self-test (CST) checks CPU status once per minute; results are displayed on the CPU

page of the OID. The CST checks the following areas of both CPU’s:

! DRAM

! EPROM

! BUS ERRORS

! SERIAL PORTs #1 and #2 LOOPBACK

! SERIAL PORTs #1 and #2 XMIT ERRORS

For the online CPU, test pass/fail status is displayed for each functional areas. The backup CPU test status

is displayed for the overall board. The technician can manually run the CPU test from the CPU page at any

time. A “T” status is displayed for each test category until the test is rerun during the next CST cycle. After

each cycle, test status is updated and displayed, and the fail count (if applicable) is incremented. 

The DRAM test is based on an alternating pattern of addressingmemory locations. Data output to the DRAM

are read back and evaluated, and the test status is then displayed. The EPROM test is based on a checksum.

The checksumis compared to the last byte in the EPROM, the result is evaluated, and teststatusis displayed.

The BUS ERRORS test is based on a memory write to a specific address; contents of the addressed memory

location are evaluated, and test status is displayed. SERIAL PORT #1 and #2 LOOPBACK tests ensure that

the CPU can communicate with its internal UART. The CPU reads the UART interrupt vector register and

checks for bus errors.

Test status is displayed as "P" (pass) if no bus errors occur. For SERIAL PORTs #1 and #2 XMIT ERRORS

test, the CPU reads the contents of the status register for the corresponding port. This register contains

information on transmission errors detected by the UART during RS-232 communications. Specifically, the

CPU checksthe statusregister for parity errors, framing errors, and overrun errorsthat might have occurred.
S100 ASOS Site Technical Manual

14-23

Ifsuch errors occur for three consecutive CST cycles, an "F" (fail) is displayed for teststatus; otherwise, test

status is "P" (pass). 

14.4.2.2 Memory Board A3. As shown on the memory board block diagram (figure 14.4.3), the VME-110

memory board contains three memory banks. Each bank is independently configured via jumpers to specify

VME address/memory chip size, device speed, device pinout, and backup power. The following paragraphs

provide a detailed block diagram description of the memory board. (Digitized voice input is stored in Voice

Audio Board A21.) The memory board includes nine functional areas: banks 1, 2, and 3 memory devices;

VME/bank address decode and control; battery backup; data buffer; bus cycle control; address buffer and

decode logic; and systemreal-time clock. The first bank contains up to 4 megabytes of EPROM which stores

the operational software program run by the CPU.

Bank 1 also stores data collection package (DCP) software load that is transferred to the DCP in the event

that a DCP loses its program load and requires initialization. Banks 2 and 3 contain up to 2 megabytes of

static random access memory (SRAM). SRAM provides storage for ASOS weather archives. Address and

control signals used to address memory locations are generated by the VME/bank address decode and

control. The memory boards are configured with a battery backup to provide an alternate power source in

the event of a power loss.

The data buffer, bus cycle control, and address buffer and decoder provide standard address, data, and control

signals for system bus communication. The real-time clock maintains clock calendar timing, which is accessed by the CPU upon initialization. When initialized, the CPU maintains a real-time clock via software.

The SCA CST checksstatus of the memory board once per minute. CST results are displayed on the memory

page of the operator interface device (OID). CST performs an EPROM test and an SRAM test. The

technician can manually run the memory test from the memory page at any time. "T" status is displayed for

each test category until the test is run again during the next CST cycle. After the cycle, the latest test status

is displayed and the fail count (if applicable) is incremented. 

The EPROM test is based on a checksum, which is compared to the last byte in the EPROM. The result is

evaluated and the teststatusis displayed. The SRAM test ensuresthat theCPU can read data fromthe SRAM

on the memory board without encountering bus errors.

14.4.2.3 SerialI/O (SIO) Boards A5 through A11. Seven serial I/O (SIO) boards communicate with other

equipment. SIO #1, A5, communicatesin RS-422 format, while the remaining six boards all use the RS-232

format.The SIO boards communicate with theCPUon a character-by-character basis.TheCPUmust process

interrupts on each and every transmitted and received character. The detailed block diagramofthe SIO board

(figure 14.4.4) is described in the following paragraphs.

The SIOboard consists ofsix functional areas: two serial communication controllers (SCC’s), interrupt logic,

data buffer, bus cycle control, and address buffer and decode logic. The SCC’s provide a variety of

communication modes. Upon power up, the CPU initializes the SCC’s to the proper communication modes.

Interrupts are generated via the interrupt logic. An interrupt could signify that a received character is

available, that the transmit buffer is empty, or that an external status change has occurred.
ASOS Site Technical Manual S100

14-24

Figure 14.4.3. Memory Board, Functional Block Diagram

Figure 14.4.4. SIO Board, Functional Block Diagram
S100 ASOS Site Technical Manual

Change 1 14-25

The data buffer, bus cycle control, and address buffer and decoder logic provide standard address, data, and

control signals for system bus communication.

The four ports of SIO boards 1 through 3 are factory assigned to specific devices. Their ports are dedicated

to these devices via corresponding connectors on the SCA main wiring harness. Although these ports can

be reassigned via the SCA serial communications page of the OID, the technician should not reassign them;

assigning these ports to other field replaceable units (FRU’s) would invalidate their corresponding harness

markers. Table 14.4.1 identifies each port of the SIO boards and lists the corresponding harness connector

and device to which it is connected.

Unlike SIO boards 1 through 3, SIO boards 4 through 8 are installed only asrequired depending upon sensor

complement. Most systems will not have all 8 SIO boards installed. The ports of SIO boards 4 through 8 are

not factory assigned to specific devices. Rather, these ports are assigned to various devices during the initial

configuration of the system. This assignment is made via the SCA serial communications page of the OID.

Table 14.4.1 identifies the ports of SIO boards 4 through 8 and identifies the W106 connector that $

corresponds to each. The devices attached to the connectors correspond to the device assigned to that port

by the SCA serial communications page. Figure 14.4.5 identifies pin-to-pin wiring with signal function

between each of the SIO boards and their respective connectors.

Table 14.4.1. SIO Port Assignments

SIO Data Format Ref Des Interface Function

1-1 RS-422 7A1A1A2A5 P59 FAA

1-2 RS-422 7A1A1A2A5 P60 FAA

1-3 RS-422 7A1A1A2A5 P61 FAA

1-4 RS-422 7A1A1A2A5 P62 FAA

2-1 RS-232 7A1A1A2A6 P13 RF Modem #1

2-2 RS-232 7A1A1A2A6 P14 Pressure #1

2-3 RS-232 7A1A1A2A6 P15 User #1 (A1A9)

2-4 RS-232 7A1A1A2A6 Voice

3-1 RS-232 7A1A1A2A7 P16 RF Modem #2

3-2 RS-232 7A1A1A2A7 P17 Pressure #2

3-3 RS-232 7A1A1A2A7 P18 User #2 (A1A10)

3-4 RS-232 7A1A1A2A7 A1A3J1 Primary OID

4-1 RS-232 7A1A1A2A8 P20 (UPS)

4-2 RS-232 7A1A1A2A8 P21 Pressure #3

4-3 RS-232 7A1A1A2A8 P22 *

4-4 RS-232 7A1A1A2A8 P23 *

5-1 (IAW sensor) P1M/W A3A1J1 Sensor #1

5-2 (IAW sensor) P2 M/WA3A2J1 Sensor #2

5-3 (IAW sensor) P3 M/WA3J1 Sensor #3

5-4 (IAW sensor) P4 M/W A4J1 Sensor #4

6-1 (IAW sensor) P5 M/W A5J1 Sensor #5

6-2 (IAW sensor) P6 M/W A6J1 Sensor #6

6-3 (IAW sensor) P7 M/W A7J1 Sensor #7

6-4 (Not used) P8 M/W A3A8J1 *Sensor #8
ASOS Site Technical Manual S100

14-26

Figure 14.4.5. A/D Board, Functional Block Diagram

Table 14.4.1. SIO Port Assignments -CONT

SIO Data Format Ref Des Interface Function

7-1 RS-232 P24

7-2 RS-232 P25

7-3 RS-232 P26

7-4 RS-232 P27

* Customer Option

The SCA CST checks the status of the SIO boards once per minute. CST results are displayed on the SCA

SIO display pages of the OID (one page for each SIO board). The CST performs the LOOPBACK test and

XMIT ERRORS test on each of the four ports of an SIO board. The technician can manually run the SIO test

from an SIO page at any time. "T" statusis displayed for both test categories until the test isrun again during

the next CST cycle. After the cycle, the latest test status is displayed and the fail count (if applicable) is

incremented. 

For the LOOPBACK test, the CPU reads an interrupt vector register on the SIO board to ensure that it can

communicate with the SIO port. For the XMIT ERRORS test, the CPU reads the contents of the SCC status

register for the corresponding port. Thisregister containsinformation on transmission errors detected by the

SCC during RS-232 communications. Specifically, the CPU checks the status register for parity errors,

framing errors, and overrun errorsthat may have occurred. For both LOOPBACK and XMIT ERRORS tests,

CST status is displayed as either P (pass), F (fail), or D (degraded). A status of D is displayed if five or more

errors have been detected and the port is currently passing the test. At 0600 LST each day, the number of

accumulated failures is summarized in the system (maintenance) log.

14.4.2.4 A/D Board A13. The A/D board, shown functionally on figure 14.4.5, monitors power supply

outputs and quantifies them to provide digital measurements for data processing. From voltage divider

networks on the VME resistor board, the A/D board receives dc voltage samples and convertsthemto digital

values to be read by the CPU via the VME bus.
S100 ASOS Site Technical Manual

Change 1 14-27

Figure 14.4.6. DIO Board, Function Block Diagram

14.4.2.5 VME Resistor Board A14. The VME resistor board mounts discrete resistors used by the other

VME CCA’s for pull-ups, loads, and voltage dividers and a precision voltage source for the A/D board. $

14.4.2.6 DIO Board A15. The digital I/O (DIO) board, shown functionally on figure 14.4.6, provides address buffer and control, data buffer, timing and interrupt control, two dual I/O data port integrated circuits

(IC’s) (#1 and #2), and four data transceiver IC’s. The DIO board has an input bit that selects SCA mode of

operation (APCSEL).

The DIO board communicates with the CPU via the address buffer and decoder, data buffer, and timing and

interrupt control logic. Two dual I/O port IC’s provide a total of four ports (designated A1, B1, A2, and B2),

each of which communicates with external devices via a dedicated data transceiver IC. Configured as an

input-only port, A1 is used by the CPU to input a watchdog timer signal from the Voice Processor Board

A20, status bits for the dc power supplies (via the VME Resistor Board A14), and the UPS bypass circuit. $

Port B1 is configured as an output-only port. This port is used by the CPU to output control signals to the $

voice recorder/playback board, the rf modem switch (or line driver relay), and the UPS bypass circuit. (Two $

additional ports on the DIO board, A2 and B2, are not used in the SCA.) Notice that the SCA CST does not

check status of the DIO board.

14.4.2.7 Digitized Voice Processor System. As shown in figure 14.4.7, the digitized voice processor

subsystem includes Voice Processor Board A20 and Voice Audio Board A21. These two boards operate together as a system and are tested together. Both boards are connected to the VME bus for power and system

reset purposes, but they do not communicate with the CPU via the VME bus. The CPU/voice system

communication is accomplished via the RS-232 link between SIO board #2 and the voice processor board.

Digital voice processing consists of three operations:

! Recording an operator-generated addendum up to 90-seconds long

! Using a stored vocabulary of voiced words to assemble a verbal report in accordance with

current ASOS data

! Producing an output message consisting of the verbal report plus the addendum.
ASOS Site Technical Manual S100

14-28

Figure 14.4.7. Digitized Voice Processor, Functional Block Diagram

14.4.2.7.1 Voice Processor Board A20. The voice processor board contains a Z80XXX series (Z80

thousand series)microprocessor and the necessaryDRAMto execute the firmware stored in onboard erasable

programmable read only memory (EPROM). These instructions reconstruct digitized human voice, create

voice reports, and receive operator-generated digitized audio from the voice audio board. The voice processor

board communicates with the VME bus directly for power and system reset but indirectly via SIO board #2

for system communication. The following paragraphs provide a detailed block diagram description of the

voice processor board. The voice processor board consists of nine functional areas: system reset/power

interface, DRAM, EPROM vocabulary, CPU, audio board interface, timing and control logic, serial

communications controller, RS-232 driver and receiver logic, and watchdog timer and alarm. Upon receipt

of a system reset signal from the VME bus, when the RESET pushbutton (on the front of the CCA) is

pressed, or when power is applied, the system reset/power interface logic generates an internal reset. This

internal reset disables message broadcast until a play message string isreceived fromthe CPU via SIO board

2. The VME bus interface for power and ground requirements is also provided by the system reset/power

interface. DRAM provides 1 megabyte of memory for message/file storage: this is the memory area where

digitized voicemessagesfromthe FAAhandset are stored.Thesemessages are appended to the automatically

generated observation messages. The EPROM vocabulary consists of 512 kilobytes of EPROM for voice

files.
S100 ASOS Site Technical Manual

Change 1 14-29

Voice ProcessorBoard A20 executesthe operationalsoftware to execute newmessage strings and to monitor

the eight telephone lines. Interface between Voice Processor Board A20 and Voice Audio Board A21 is $

provided by 50-pin connectors on the front of the boards and a ribbon cable. Timing and interface signals

required by the CPU and peripherals are provided by the timing and control logic section of Voice Processor

Board A20. The serial communications controller providestheRS-232 serial communication channel, while

the RS-232 driver and receiver logic section provides the standard RS-232 receive and transmit lines. The

watchdog timer and alarm provides an alarm signal to the primary CPU (via Digital I/O Board A15)

whenever a CPU software or hardware failure occurs.

14.4.2.7.2 Voice Audio Board A21. Voice Audio Board A21 receives digitized voice from Voice

Processor Board A20 and converts it into audio. Audio is output as a weather data message for dial-in

weather requests and is broadcast by a ground-to-air (GTA) radio transmitter for aviation use. In addition,

the voice audio board receives voice audio fromthe FAA handset, quantifiesit, and transmits digitized audio

to Voice Processor Board A20 for message processing. The following paragraphs provide a detailed block

diagram description of Voice Audio Board A21which consists of six functional areas: CPU board interface,

power interface logic, radio transmitter output logic, record and playback logic, telephone line output logic,

and audio alarm output logic.

Pinouts for the output of the voice audio board (XA21-P2) are provided in table 14.4.2. The signal

mnemonics and pins associated with row A and row C of XA21-P2 are listed with the associated plug

connector. For example, the RING signal of the FAA handset line can be monitored at pin 20 of XA21-P2

or pin 2 of plug 46 (P46). The CPU board interface provides the communication path to the voice processor $

board via the 50-pin connector on the front of the board. The VME bus interface for power and ground

requirements is provided by the power interface logic. Radio transmitter output logic and record and

playback logic digitize audio input and synthesize digitized voice words to form audio clauses or sentences.

Interface circuits to the telephone outputs and line output peripherals are provided by the telephone line

output logic section. The audio alarm output logic section drives an audio ALARM indicator. One of the

audio line outputs is continually monitored by the alarm circuit. A loss of audio for a predetermined period

causes the indicator on Voice Audio Board A21 to illuminate. Chapter 12 provides information on GTA

radio pin-to-pin connections.

Table 14.4.2. Digitized Audio Connections

Function I/O Conn VME Rack 7A1A1A2- Signal Mnemonic

Call-in Line #1, ring P43-2 XA21P2-A32 L1-RING

Call-in Line #1, tip P43-3 XA21P2-C32 L1-TIP

Call-in Line #2, ring P44-2 XA21P2-A31 L2-RING

Call-in Line #2, tip P44-3 XA21P2-C31 L2-TIP

FAA Radio, ring P45-2 XA21P2-A24 FAA RADIO RING

FAA Radio, tip P45-3 XA21P2-C24 FAA RADIO TIP

NOTAM Record, ring P46-2 XA21P2-A20 NOTAM RECORD RING

NOTAM Record, tip P46-3 XA21P2-C20 NOTAM RECORD TIP

14.4.2.7.3 Digital Voice Processing System Self-Tests. The SCA CST checks the status of the digital

voice processing system once per minute. CST results are displayed on the voice page of the OID. The CST

performs four tests on the voice processing system: CPU, AUDIO OUTPUT, AUDIO STATUS, and

TIMEOUT. At any time, the technician can manually run the voice processing test from the VOICE page.

A "T" status is displayed for the four test categories until the test is run again during the next CST cycle.

After the cycle, the latest test status is displayed and the fail count (if applicable) is incremented. The CPU

test checks operational status of the voice processor board. The TIMEOUT test checks operational status of
ASOS Site Technical Manual S100

14-30 Change 1

the watchdog timer. The AUDIO OUTPUT and AUDIO STATUS tests check operation of the voice audio

board and indirectly test the voice processor board. The AUDIO OUTPUT test is based on an internal audio

test that checks audio circuitry. The AUDIO STATUS test is based upon a monitored audio line. The status

of each of these tests is evaluated and test status is displayed.

14.4.2.8 Pressure Sensor Shelf 7A1A1A7. Pressure sensor shelf 7A1A1A7 mounts either two or three

$ identical atmospheric pressure sensors. Cable W106 provides the electrical connections to the sensors as

$ shown on figure 14.4.8. Plastic vent tubesfromeach sensor are joined under the pressure shelfto a tube cross

$ and then routed to the pressure port at the top of the cabinet. Because the SCA is installed outdoors, a

$ temperature sensor board (7A1A1A7A4) is mounted on the front of the pressure sensor shelf to monitor

internal cabinet temperature. The board sends an analog temperature signal to the processor via A/D Board

A2A13 to be used in the pressure algorithms. 

14.4.3 AC POWER DISTRIBUTION

AC power service entrance into the SCA is through a stuffing tube in the bottom of Faraday Box A3;

termination isto terminal blocks A3A17 and A3A18, which are mounted on the back side of the hinged front

$ cover. AC power is routed to Power Reset Assembly A1A13 (figure 14.4.8A) which delays power

$ application for three seconds before distributing the power to SCA assemblies (Class Isystems) or the UPS

$ bypass circuit (Class II systems). The Class II SCA UPS bypass circuit consists of a power relay (which

$ routes site power or UPS output to SCA assemblies) and a digital I/O module (which provides ASOS

$ operational software with UPS bypass monitoring and control). 

As shown on figure 14.4.9, Faraday box connectors J1, J2, and J3 apply power to the main SCA cable

$ harness W106. J1 supplies power through main circuit breaker A1A3CB1 (via the UPS bypass circuit in

$ ClassIIsystems).Connector A3J3 provides heater power for primary sensors(sensors 1-4). Connector A3J9

$ provides cabinet heater power. Connector A3J10 provides heater power for the aux box. AC power for aux

box componentsis provided through short conduitsfromFaradayBox 7A1A3. The aux box isinstalled with

most Class II single-cabinet systems, but is an available option on Class I and reduced capability systems.

A secondary UPS, 7A2A1A6, is an option for installation in the aux box.

$ 14.4.3.1 Power Reset Assembly A1A13. Power from the power distribution assembly is routed to Power

$ Reset Assembly A1A13 Time Delay Relay K1 (figure 14.4.9 sheet 4) which provides a three second delay

$ before distributing the power to the SCA assemblies (Class I systems) or UPS bypass circuit (Class II

$ systems). The three second delay enables the pressure sensors and rf modems to reset after power is

$ interrupted. In Class IIsystems, the UPS bypass circuit consists of Digital I/O Module K2 and Power Relay

$ K3. Power from Time Delay Relay K1 is applied to Power Relay K3 normal closed contacts and to UPS

$ A1A6. Power to Power Relay K3 normally closed contactsisrouted to the AC Power Distribution Assembly

$ where it is distributed to the SCA assemblies. UPS output power isrouted to Power Relay K3 normally open

$ contacts.

$

$ After power is applied to the SCA assemblies, ASOS operational software monitors the bypass status of

$ Power Relay K3 via Digital I/O Module K2 and Digital I/O Board A1A2XA15. When UPS A1A6 status is

$ good, Power Relay 7A1A1A13K3 is energized (via Digital I/O Board A1A2XA15 and Digital I/O Module

$ A1A13K2) which enables UPS output power to be distributed to the SCA assemblies. During turn on and

$ when the UPS status is bad, the power relay is deenergized allowing site power to be applied directly to the

$ SCA assemblies.
S100 ASOS Site Technical Manual

Change 1 14-31Figure 14.4.8. Pressure Sensor Shelf, Functional Diagram
ASOS Site Technical Manual S100

14-32 Change 1

Figure 14.4.8A. SCA Power Reset Assembly
S100 ASOS Site Technical Manual

Change 2 14-32.1 $

Figure 14.4.9. AC Power Distribution Diagram (Sheet 1 of 4)
ASOS Site Technical Manual S100

$ 14-32.2 Change 2Figure 14.4.9. AC Power Distribution Diagram (Sheet 2)
S100 ASOS Site Technical Manual

Change 1 14-33Figure 14.4.9. AC Power Distribution Diagram (Sheet 3)
ASOS Site Technical Manual S100

14-34 Change 1

Figure 14.4.9. AC Power Distribution Diagram (Sheet 4)
S100 ASOS Site Technical Manual

Change 1 14-35

Figure 14.4.10. SCA Cabinet, Heater Control Circuit

14.4.4 SCA CABINET HEATERS

Because the SCA must operate out-of-doors in all climatic conditions, electrical heaters are included to

ensure accurate,reliable operation in cold weather. Asshown on figure 14.4.10,separate heaters aremounted

on the 7A1A1 mounting assembly, with cabinet heater 7A1A1HR1 behind Circuit Breaker Panel 7A1A1A3,

and battery heater 7A1A1HR2 at bottomleft of Mounting Panel 7A1A1. These heaters operate from115 vac

which is applied through solid-state relays 7A1A1K1 and 7A1A1K2. The relays are controlled by three

thermostatic switches,which also aremounted on 7A1A1 behind the circuit breaker extrusion. Cabinet heater

7A1A1HR1 includes two 325-Watt heating elements(metalstrips), while 7A1A1HR2 is a 350-Watt silicon

strip. When ambient temperature in the cabinet falls to 60°F, thermostatic switch 7A1A1S1 closes to apply

+5V to 7A1A1S2 and 7A1A1S3. If the temperature falls to 50°F, S3 closes to energize relay 7A1A1K2 and $

7A1A1S2 closesto energize relay 7A1A1K1.Relay 7A1A1K2 contactsthen applies 115 vac powerto heater $

7A1A1HR2 and one element of cabinet heater 7A1A1HR1. Relay 7A1A1K2 contacts apply 115 vac to the $

other half of cabinet heater 7A1A1HR1. At 70°F S2 and S3 open to deenrgize relays K1 and K2. At 80°F, $

S1 opens to ensure removal of all heating power. $
ASOS Site Technical Manual S100

14-36

Figure 14.4.11. Auxiliary Box, Heater Control Circuit

14.4.5 AUXILIARY BOX CABINET HEATERS

The Aux box cabinet heater control circuit is shown in figure 4.4.11, and is similar to that in the SCA.

.

14.4.6 DC POWER DISTRIBUTION AND MONITORING

Figure 14.4.12 illustrates dc power distribution within the SCA. DCpowerforthe SCA is provided by paired

power supplies located in DC Power Supply Plate Assembly A4. These power supplies receive ac input

$ power from UPS output (or bypass circuit) to provide +5 vdc, +12 vdc, and -12 vdc. Paired outputs are

OR’ed together by diodes to ensure that one supply continues to provide power if the other fails and that the

failed supply is isolated from the output line. AC input power to each of the four supplies is separately fused

on DC Distribution Assembly A4A1, with 3.15A fuses F1 and F2 protecting PS1 and PS2, respectively,

while 2.5A fuses F3 and F4 protect PS3 and PS4, respectively. The wiring harness for Power Supply

Mounting Assembly A4 is designated W024.

Powersupply output voltages are distributed fromPower Distribution Assembly 7A1A1A4,shown on figure

14.4.13. There they are distributed by cable harness W024 (part of Power Supply Mounting Assembly A4)

$ and wire harness W106, which interconnects the assemblies on Mounting Panel 7A1A1. To accommodate

monitoring by systemsoftware, powersupply outputs are connected to VME ResistorBoard 7A1A1A2A14,

which applies voltage samplesto the A/D board for access. DC power applied to the rf modems is monitored

in the same manner.
S100 ASOS Site Technical Manual

Figure 14.4.12. DC Power Distribution 

Diagram (Sheet 1 of 2)

Change 2 14-37/ (14-38 blank)
S100 ASOS Site Technical Manual

14-39Figure 14.4.12. DC Power Distribution Diagram (Sheet 2)
ASOS Site Technical Manual S100

14-40 Change 1

Figure 14.4.13. DC Power Distribution Assembly

14.4.7 SENSORS

$ The complement of sensors includes the pressure sensors that are mounted in the SCA and up to 13

additionalsensors. Sensors are customer-selected to accommodate site requirements. Fiberoptic Transducer

$ Modules 7A1A3A1 through 7A1A3A13, located in the Faraday box, interconnect up to 13 sensors. These

transducers are paired with identical transducers in the respective sensor cabinets. Each pair communicates

inRS-232 format via fiberoptic cables. The SCA fiberoptic transducer modules connect through SIO Boards

#5, #6, and #8 (A9, A10, and A12), each interfacing up to four modems.

The sensor complement installed at any particular site reflect requirements of that site as determined by the

customer. Some sites may be provided with more than one type ofsensor. Cloud height and visibility sensors

are often duplicated at a site, with a maximumofthree each possible. Usually, each touchdown zone is provided with cloud height and visibility sensors to ensure that current ceiling and visibility conditions at that

specific runway are reported accurately.

14.4.8 PERIPHERALS

Peripheral devices are not supplied as standard equipment with the SCA. Any laptop PC can be connected

to serve as an OID for maintenance purposes. The maintenance technician uses a laptop PC to check ASOS

system status, to reconfigure the system, and to run on-demand diagnostic tests on specific elements of the

system. Optionally, an OID and/or a video display unit (VDU) could be installed in an adjacent building,

provided that it is within 200 feet of the SCA. All other outputs from ASOS are via direct connection

(hardwire) or telephone modems. A modem also interfaces with the NWS Automation of Field Operations

& Services (AFOS) system.
S100 ASOS Site Technical Manual

Change 1 14-41/ (14-42 blank)

A digitized voice output is routed via phone modems to dial-in users (or via the GTA radio) to provide local

weather and pressure data to pilots at or near the airport. The GTA radio continuously transmits current local

meteorological observations on assigned VHF comm frequencies to pilots.

The FAA handset enables air traffic control specialists to append a NOTAM onto the digitized voice output

forthe local weather observation message. The printer provides hard copy data output of weathersummaries,

routine METAR’s, SPECI’s, and log messages. Log messages identify system status. The system maintenance log providesthe technician with the maintenance history of the systemand providesthe results of each

self-test performed on the system. If an SCA unit fails self-test, the log records the source of failure.

14.4.9 MODEMS

Three categories ofmodems provide I/Ointerfaces: phone line, dedicated line (forstand-alonemodems), and

rf. Table 14.4.3 lists the complement of standard and optional modems available in the SCA. All sites are

equipped with data communication for one user via stand-alonemodem. Asecond user can be accommodated

by an additional (optional) 2400 baud or 28800 baud stand-alone modem. 

14.4.9.1 Telephone Modems. The SCA contains up to six telephone modems which provide

communications to external devices over leased lines or public, switched-telephone networks. All data

transfers are underthe control ofthe SIO boardsthat communicate with data terminal equipment(DTE) ports

of those modems which use RS-232 protocol. The telephone modems operate in a 2-wire, full-duplex mode.

These modems operate at data rates of 2400, 9600, or 28800 baud.

Modems available for the single-cabinet ASOS are listed in table 14.4.3. These additional modems can be

installed, as required, to provide the connections to AFOS phone, proximity user OID, ADAS, or other user

requirements.

14.4.9.2 RF Modems. The rf modems are used by the SCA for intercabinet communications at sites

equipped with DCP’s. The rf modems operate in the UHF range through an omnidirectional antenna or Yagi $

antenna (used in conjunction with 3 dB, 6 dB, 10 dB, 20dB, or 30 dB attenuators at sites where co-channel $

interference exists). A second, redundant, rf modem can be added, together with RF Switch 7A1A1A5S1. $

The rf switch (DPST coaxial relay) is installed at all sites where two rf modems are used. The rf switch

connects the active rf modem to the antenna. The rf switch is controlled by the CPU via DIO board A15.

When the CPU senses a failure in the rf modem communications link, it writes a selection word to the DIO

board to toggle the switch. The CPU communicates with modem RF #1 through SIO board #2 and with RF

#2 through SIO board #3. 

Table 14.4.3. Modem Complement

Ref Des Modem # Category Function/Type CAGE Model/PN

7A1A1A5A1* RF #1 RF DCP Communications 90315-10 or -20

7A1A1A5A2* RF #2 RF DCP Communications 90315-10 or -20

7A1A1A9 User #1 Stand-alone User #1, 2400 Baud 97384 90051-1

7A1A1A10* User #2 Stand-alone User #2, 2400 Baud or

28800 Baud 97384 90051-1 or

90431-1

7A1A1A11* #3 Telephone line 2400 or 9600 Baud 97384 90050-1, 90051-1

7A1A1A12* #4 Telephone line 2400 or 9600 Baud 97384 90050-1, 90051-1

7A1A5* #5 (Optional category & use.) $

7A1A6* #6 (Optional category & use.) $

7A2A1A1* Stand-alone Codex Modem 97384 90362-10 or -20

* Optional
S100 ASOS Site Technical Manual

14-43

WARNING

SECTION V. SCA MAINTENANCE

Before attempting to service any ASOS equipment, the technician must

perform the following:

Upon arrival at an airport, notify airport security and gain access to the

system by following local procedures.

Adhere to all airport traffic regulations. 

Before crossing any runway, radio the tower (ground control) and request

clearance.

Proceed only after obtaining clearance from ground control and only after

illuminating the caution light mounted atop the vehicle.

14.5.1 GENERAL

Thissection contains corrective and preventive maintenance proceduresforthe single-cabinet ASOS (SCA).

Preventive maintenance proceduresidentify quarterly and semiannual tasksrequired to keep the SCAin peak

operating condition.Corrective maintenance proceduresinclude those for performing systemdiagnostic test,

fault isolation, and removing and installing field replaceable units (FRU’s). The system diagnostic test runs

continuously and automatically and prints a system operational status message after each self-test cycle. If

self-test detects a failure, the suspected FRU is identified in the system maintenance log by reference

designator. The technician's first step in restoring system operability is to replace the identified FRU. The

corrective maintenance table in this section is used if the system does not automatically identify an FRU.

14.5.1.1 Tools and Test Equipment. Tools and test equipment required to perform maintenance on the

systemare listed in Chapter 1, Section V. These are preferred items that the technician should have available

to perform maintenance on the system. If the specific item listed in the table is not available, an equivalent

item may be substituted. Specific tools required for removal and installation of each FRU are specified in

each procedure.

14.5.1.2 Consumable Materials List. Consumables needed to maintain the SCA are the same as for the

standard multicabinet ASOS listed in Chapter 1, Section V. Although the Source column lists a

recommended source for some consumable items, the technician may substitute equivalent products.

14.5.1.3 Maintenance Action Recording and Documentation. Whenever a maintenance technician

performs maintenance tasks, all actions must be documented in the system maintenance log. For the purpose

of entering unit or assembly identification numbers the procedure in table 14.5.1 is performed.
ASOS Site Technical Manual S100

14-44 Change 1

Table 14.5.1. Maintenance Documentation Procedures

Step Procedure

1 Sign onto system as TECH.

2 Press MAINT key. Observe that maintenance display screen is displayed.

3 Press ACT key and observe that maintenance action screen is displayed.

4 Press START to store a maintenance action message in system maintenance log (SYSLOG) page in

preparation for maintenance action which is to follow.

5 Select required maintenance action, categorized as either preventive maintenance, corrective maintenance,

calibration, or field modification kit installation.

6 Upon completion ofrequired maintenance task,select appropriate maintenance page (PREVT,CORR, CAL,

or FMK).

7 Enter appropriate identification numbers and exit screen.

8 From 1-minute screen, select REVUE followed by SYSLOG. Enter any additional maintenance data or

messages into SYSLOG and verify that all maintenance actions performed have been entered in SYSLOG.

9 Sign off of ASOS.

14.5.2 PREVENTIVE MAINTENANCE

ASOS preventive maintenance is performed at two intervals: 90 days and semiannually. Chapter 1 contains

general information about preventive maintenance of ASOS systems and equipment. SCA preventive

maintenance tasks consist of visual inspection procedures (table 14.5.2), SCA facilities maintenance (table

14.5.3), and cleaning (table 14.5.4).

14.5.2.1 Desiccant. A desiccant dryer is installed in the center of the SCA cabinet, in the air line leading

fromthe pressure sensorsto the pressure sensing port. The desiccant is a silica gel (i.e., a drying agent). The

gel is a consumable item in powdered form that is contained and if necessary, replaced in the bowl unit of

the dryer. Before handling the desiccant, the Material Safety Data Sheet (MSDS) for Davidson Blue Indicating Gel issued by W.R. Grace & Co., P.O. Box 2117, Baltimore, MD 21203 (telephone: 410-659-9000) or

the current supplier should be obtained from the supervisor and read. The gel should be replaced with new

desiccant when necessary in accordance with table 14.5.2A.

Table 14.5.2. Visual Inspection Procedures

Step Procedure

1 With power applied, ensure that fan (on rear of UPS), and muffin fans (on bottom of VME card rack) are

operating correctly.

2 With power applied, at wind sensor tower, cover light sensor on tower light control box and ensure that

clearance lights (at top of tower) illuminate.

3 Remove power from system, inspect interior of all cabinets for signs of pinched or chafed wiring, loose

hardware, and proper connector mating.

4 With power off, check outside of all enclosures for signs of corrosion.

5 With power off, atsensor pad, ensure that all hardware securing sensorsto pad istight. Check each mounting

column for visual signs of wear or corrosion. Ensure that there are no cracks in columns.

$ 6 Inspect desiccant in desiccant dryer (Dryer, figure 14.1.3). If indicated by color, remove and replace

$ desiccant (refer to table 14.5.2A).

NOTE

After performing visual inspection procedure, reapply power to the systemand wait until the system

initializes and successfully completes its diagnostic check before leaving the area.
S100 ASOS Site Technical Manual

Change 2 14-44.1/ (14-44.2 blank) $

Table 14.5.2A. Desiccant Replacement Procedure $

Step Procedure

Tools and material required:

Hand-held vacuum cleaner

Mild detergent and water

Lint-free cloth(s).

CAUTION

Before handling the desiccant, the Material SafetyData Sheet(MSDS)for DavidsonBlue Indicating

Gel issued byW.R. Grace & Co., P.O. Box 2117, Baltimore, MD 21203 (telephone: 410-659-9000)

or the current supplier should be obtained from the supervisor and read. 

NOTE

Wring out cloth before washing screens.

1 At SCA cabinet, loosen dryer clamp ring, slide off metal bowl guard, and unscrew bowl from top housing.

2 Pour out used desiccant into plastic bag and seal bag for proper disposal.

3 Open new container and refill bowl,shaking or tapping bowl to settle desiccant to 1/2 inch from top of bowl.

CAUTION

Do not install the bowl without installing the metal bowl guard.

4 Replace bowl, bowl guard, and clamp ring onto unit. Ensure that clamp ring is securely in place.
S100 ASOS Site Technical Manual

14-45

WARNING

Table 14.5.3. Facilities Maintenance Checklist

Item Task Period

Towers and pedestals Inspect for corrosion Semiannually

Fasteners Paint Semiannually, Yearly

Foundations Inspect condition Yearly

Fencing Inspect condition

Paint

Yearly

Yearly

Signage Inspect condition

Paint

Yearly

Yearly

Lightning protection system Inspect condition Semiannually

Roads and walkways Inspect condition:

Snow removal:

Yearly

Quarterly (in season)

Land Inspect ground cover:

Inspect grass height:

Snow removal:

Yearly

Quarterly (in season)

Quarterly (in season)

Electrical equipment & cables Inspect condition:

Check operation:

Semiannually

Quarterly

Table 14.5.4. Cleaning Procedure

Step Procedure

Tools and material required:

Hand-held vacuum cleaner

Mild detergent and water

Lint-free cloth(s).

Ensure that power has been removed from any peripheral device before cleaning that device.

NOTE

Wring out cloth before washing screens.

1 Using soft cloth dampened with mixture of mild detergent and water, cleanCRT display screens and external

cases of peripheral devices. Using lint-free cloth, dry screens and cases.

2 Using small hand-held vacuum cleaner, remove dust from OID keyboard and printer.

14.5.3 CORRECTIVE MAINTENANCE

Correctivemaintenance involves isolation, removal, and replacement of faulty FRU’s. The ASOS is equipped

with an automatic self-test program designed to isolate most faults to a single FRU; however, due to system

hardware configuration, there will be instances when the diagnostics can only isolate to a group of FRU’s,

such as a sensor or an I/O channel. The troubleshooting approach for these two types of conditions is very

different. When the FRU is specifically identified, the technician need only replace the faulty unit.

14.5.3.1 Warmup and Initialization. To ensure proper operation of the system, the technician must allow

the SCA to automatically initialize after application of primary power and then verify that the continuous

self-test diagnostics run without failure. Table 14.5.5 provides corrective maintenance symptom analysis

information.
ASOS Site Technical Manual S100

14-46

14.5.3.1.1 System Diagnostics. System diagnostics run continuously in the background. The diagnostics

complete a check ofthe entire systemevery 7 minutes. Test data received fromthe diagnostic programis displayed on the technician interface display screens. Error messages are also entered into the system log and

printed on the printer.

14.5.3.1.2 Preliminary Troubleshooting Checks. When the diagnostics program identifies two or more

FRU’s asthe trouble source, the technician must isolate the failed FRU. Using Section IV theory of operation

and associated drawings as references, the following two basic procedures are performed:

a. Check connectorsto ensure that all boards, cables, and connectors are present and correctly

connected.

b. Check AC and DC power. 

Although ASOS monitors all critical power supply voltages in the SCA, sensors, and DCP’s, failure of a

power supply could result in loss of communications between circuits powered by that supply and the rest

of the system. Power supplies are tested by both visual inspection and electrical checks. Before measuring

voltages, the technician should visually inspect the area of the suspected FRU for obvious signs of power

supply failure. During thisinspection, the technician should pay particular attention to circuit breakers, panel

lights, and light emitting diodes (LED’s) to ensure that they are functioning normally then use a digital

multimeter (DMM) to check voltages at fuses and power supply output terminals. In most cases, these tests

will isolate the faulty FRU. 

Table 14.5.5. Symptom Analysis

Symptom What To Do How To Do It

SCA system is completely dead. Check ac and dc power. Refer to SCA ac/dc power distribution diagram (figure 14.4.9 and

14.4.12) and use DMM to verify

voltages.

Problem with UPS. Check UPS operation. Refer Chapter 2, Section V.

SCA computer does not initialize. Check VME card rack. Refer Chapter 2, Section V.

SCA heaters do not work. Check heater circuit. Refer Chapter 2, Section V.

Loss of SCA communications. Check communications links. Refer Chapter 2, Section V.

SIO CCA failure or communications

loss with a peripheral or user.

Check SIO boards. Refer Chapter 2, Section V.

WIND SENSOR does not respond. 1. Check fiberoptic modules. 

2. Troubleshoot sensor.

Refer to paragraph 14.5.3.2.

Refer Chapter 4, Section V.

TEMPERATURE/DEWPOINT

SENSOR does not respond.

1. Check fiberoptic modules.

2. Troubleshoot sensor.

Refer to paragraph 14.5.3.2.

Refer to Chapter 5, Section V.

VISIBILITY SENSOR does not

respond. 

1. Check fiberoptic modules.

2. Troubleshoot sensor.

Refer to paragraph 14.5.3.2.

Refer to Chapter 6, Section V.

PRESENT WEATHER SENSOR

does not respond.

1. Check fiberoptic modules.

2. Troubleshoot sensor.

Refer to paragraph 14.5.3.2.

Refer to Chapter 7, Section V.

PRESSURE SENSORS

 All 3 incorrect.

 1 or 2 incorrect.

 1 sensor does not respond.

Clean pressure port.

Replace sensor(s).

Troubleshoot sensor.

Refer to Chapter 8, Section V.

Refer to Chapter 8, Section V.

Refer to Chapter 8, Section V.

CEILOMETER does not respond. 1. Check fiberoptic modules.

2. Troubleshoot sensor.

Refer to paragraph 14.5.3.2.

Refer to Chapter 9, Section V.

TIPPING BUCKET does not report

rain accumulation.

Test the rain gauge. Refer to Chapter 10, Section V.
S100 ASOS Site Technical Manual

Change 1 14-47

14.5.3.2 Fiberoptic Module Test. The SCA communicates with sensors via fiberoptic data links. Each

fiberoptic link is made up of a fiberoptic module in the SCA, a corresponding module in the sensor, and two

fiberoptic cables linking the two modules. These modules are optoelectric transducers that convert RS-232

serial digital data in electric media to optical media and vice versa. The model H083 temperature/ dewpoint

sensor operates in simplex mode where data is periodically sent to the SCA. Communications mode for the

rain gauge sensor is half-duplex, but it does not communicate inRS-232 or any other digital format: it merely

sends an optical pulse over the inbound link each time the rain bucket tips. All other sensors use full-duplex

communication mode, where simultaneous unidirectional messages pass over the paired fiberoptic links. 

In full-duplex communication mode, each link of the fiberoptic pair is unidirectional. In half-duplex RS-232

communication, the SCA pollsthe sensor via one link, then the sensor responds with the requested data over

the other link. In simplex communication, the links are redundant, with time-shared bidirectional message

transfer over each link. Fiberoptic links are not tested automatically: they must be tested with an RS-232 test

tool as directed in table 14.5.6 for the half-duplex link and table 14.5.7 for the HO-83 link.

Table 14.5.6. Fiberoptic Link Testing - Half-Duplex Link

Step Procedure

1 At OID, accesssensor configuration page. Determine assigned SIO port.Referto SIO port assignments(table

14.4.1) and identify corresponding fiberoptic module.

2 Connect RS-232 test tool in line with fiberoptic module.

3 Using RS-232 test tool, verify periodic activity on TxD pin. If pin is active, proceed to step 4; if inactive,

problem is in SIO board.

4 Using RS-232 test tool, verify activity on RxD pin in response to TxD signals. If TxD and RxD pins both are

active, problem is in SIO board. If RxD pin is inactive, proceed to step 5.

5 Remove RS-232 test tool from fiberoptic module and reconnect DB-9 connector to module.

6 At failing sensor, connect RS-232 test tool in line with sensor fiberoptic module (between fiberoptic module

and corresponding DB-9 connector from cabinet harness).

7 Verify periodic activity on TxD signal on RS-232 test tool. If signal is active, continue with step 8. If signal

is not active, proceed to step 9.

8 Using RS-232 test tool, verify RxD pin activity in response to TxD signals. If no activity on RxD signal,

problem is sensor serial data interface circuits. If both TxD and RxD pins are active, proceed to step 9.

9 Remove RS-232 test tool from sensor fiberoptic module and reconnect DB-9 connector to module. One at

a time, remove and replace following units and retest system until problem is corrected:

a. Fiberoptic module in SCA (or DCP)

b. Fiberoptic module in sensor

c. If TxD signal was missing (step 7), replace transmit fiberoptic cable between DCP (or

SCA) and sensor (transmit cable is farthest from DB-9 connector on fiberoptic module)

10 If all signals were active through step 9, replace receive fiberoptic cable between DCP (or SCA) and sensor

(receive cable is nearest to DB-9 connector on fiberoptic module).

Table 14.5.7. Fiberoptic Link Testing - HO83 Link

Step Procedure

1 At HO83 sensor, connect RS-232 test tool in line with sensor fiberoptic module (between fiberoptic module

and corresponding DB-9 connector from cabinet harness).

2 Verify periodic activity of RxD signal on RS-232 test tool. If RxD is active, proceed to step 3; if RxD is

inactive, problem is in HO83 sensor serial data interface.

3 Remove RS-232 test tool from HO83 fiberoptic module and reconnect DB-9 connector to module.
ASOS Site Technical Manual S100

14-48 Change 2

Table 14.5.7. Fiberoptic Link Testing - HO83 Link -CONT

Step Procedure

4 At OID, access sensor configuration page. If HO83 sensor is associated with a remote DCP, determine

sensor’s assigned SIO port. Refer to list of Port Assignments for DCP SIO Boards (table 3.4.1) and identify

corresponding fiberoptic module. If HO83 sensor is associated with SCA, refer to SIO Port Assignments

(table 14.4.1) and identify corresponding fiberoptic module.

5 At DCP (or SCA), connect RS-232 test tool in line with fiberoptic module for HO83 sensor (between

fiberoptic module and corresponding DB-9 connector from cabinet harness).

6 Verify periodic activity of RxD pin on RS-232 test tool. If RxD is active, problem is in SIO board. If RxD

is inactive, proceed with step 7.

7 Remove RS-232 test tool from fiberoptic module and reconnect DB-9 connector to module. One at a time,

remove and replace following units and retest system until problem is corrected:

a. Fiberoptic module in cabinet.

b. Fiberoptic module in sensor.

c. Receive fiberoptic cable.

14.5.3.3 Modem Setup. SCA modems must be set up after installation by configuring the SCA serial

communications. Additionally, stand-alone modems connecting remote peripherals to the SCA by leased line

must be set up manually. The following paragraphs describe setting up the SCA modems and stand-alone

modems.

14.5.3.3.1 Setting Up SCA Modems. SCA modems are configured via the SCA serial communications

page after installation. From this page, the modem is assigned a function, assigned to an SIO port, assigned

a baud rate, and specified for leased line operation. The baud rate for the model 2440 modem is 2400 for

OID’s, VDU’s, and printers. The baud rate is 9600 for the model V.3225 modem and 28800 for the model

V.3400 modem. After the modem is installed and configured on the SCA serial communications page, the

SCA program automatically programs the modem for operation. No other action is required on the part of

the technician.

14.5.3.3.2 Setting Up Stand-Alone (S/A) Modems. After the S/A modem is installed at the peripheral

end, it must be manually programmed to operate in leased line mode with the correct parameters. The LCD

display and the YES and NO pushbutton switches on the front panel of the modem (same as standard ASOS

rack-mounted modems) are used to program the modem. The modem LCD displays main menus,submenus,

and configuration optionsto the technician. The YES/NO pushbuttons are used to sequence through themain

menus and submenus and to select appropriate options. The Installation and Operation Manual for the standalone modem provides detailed information on all menus,submenus, and options available with the modem.

$ Refer to Paragraph 2.5.5.2 for model 2440, V.3225, and V.3400 stand-alone modem settings.

These tables address only the settings that must be checked or changed by the technician. They do not

address options that are automatically set by the factory or are not required for ASOS operation. The menu

and option titles that appear on the LCD display vary from site-to-site, depending on modem firmware.

$ 14.5.3.3.3 Setting Up Johnson Data RF Modem. Johnson Data rf modem frequencies are assigned

$ and setup at the depot. Order rf modem part number 62828-40506-1 for 410.075 MHz or 62828-40506-2 for

$ 410.950 MHz.

14.5.3.4 FRU and Subassemblies Removal and Installation. Removal and installation procedures for most

FRU’s and subassemblies are the same as those for the standard ASOS system, which are listed in Chapter

2, Section V. Those procedures that are unique to the SCA configuration are given in the following

paragraphs.
S100 ASOS Site Technical Manual

Change 1 14-49

Figure 14.5.1. VME CCA Locations $

14.5.3.4.1 Removal and Replacement of VME7A1A1A2 CCA’s. Typical assignment ofCCA’sto VME

slots is shown on figure 14.5.1, but an SCA for any particular site could be equipped with additional,

optional, CCA’S depending upon site requirements. Procedures for circuit card removal and installation is

the same as given for the standard ASOS in Chapter 2, Section V. Each CCA has a board puller lever located

at the top and bottom which forcibly extracts the CCA from the slot and backplane connectors.

14.5.3.4.2 Removal and Replacement ofMemoryBoard 7A1A1A2A3.Before removingMemoryBoard

7A1A1A2A3, blank panel 7A1A1A2A4 must be removed to gain access to Memory Board 7A1A1A2A3.

14.5.3.4.3 Removal and Replacement of SCA UPS 7A1A1A6. The following tables remove UPS

7A1A1A6 (table 14.5.8), install UPS 7A1A1A6 (table 14.5.9, and set the UPS DIP switches(table 14.5.10).

Table 14.5.8. UPS 7A1A1A6 Removal Procedure

Step Procedure

1 Set ASOS facility power breaker OFF and tag breaker.

2 Raise SCA cover and set support arms.

3 At Circuit Breaker Panel 7A1A1A3, set UPS CB1 OFF; then set UPS switch (on 7A1A6 control panel, on

bottom) to OFF.

4 On Circuit Breaker Panel 7A1A1A3, set all other circuit breakers OFF.

5 Prior to disconnecting UPS, record UPS connections to ensure correct connection upon installation.

6 Disconnect battery power connectorfromUPS, and disconnect ac power cord with yellowpendant connector

from cabinet harness connector W106P36.

7 Disconnect yellow UPS ac output plug, W106P37, from UPS bottom panel, then disconnect remaining ac

plugs from UPS bottom panel receptacles.

8 Disconnect RS-232 connector W106P20.

9 Loosen UPS strap.

10 Lift UPS out of the SCA.
ASOS Site Technical Manual S100

14-50 Change 2

Figure 14.5.2. VME CCA Connector Pin Assignment

Table 14.5.9. UPS 7A1A1A6 Installation Procedure

Step Procedure

1 Ensure that ASOS facility power breaker is OFF and breaker is tagged.

2 With SCA cover raised, check that all wires and cables are clear of UPS mounting shelf.

3 Lift UPS into place on mounting shelf.

4 Fasten UPS mounting strap.

5 Connect RS-232 connector W106P20.

6 Connect UPS outputs as recorded per table 14.5.8 step 5.

$ 7

$ Referto table 14.5.10 and setUPSDIP switches(Deltek UPS 62828-90338-10 only: Deltek 62828-90338-20

$ does not have dip switches).

$ Table 14.5.10. UPS DIP Switch Setup (Deltek UPS 62828-90338-10 Only)

Sw Set to Position Position Functions Alternate Position Functions

1 1 & 2 OFF

1 OFF, 2 ON

120 V input

127 V input

2 1 & 2 ON

2 OFF, 1 ON

120 V input w/ext range

110 V input w/ext range

3 OFF Enable Site Warning Alarm Disable Site Warning Alarm
S100 ASOS Site Technical Manual

Change 2 14-51

Figure 14.5.3. Faraday Box Assembly A3, Parts Location Diagram

Table 14.5.10. UPS DIP Switch Setup (Deltek UPS 62828-90338-10 Only) -CONT $

Sw Set to Position Position Functions Alternate Position Functions

4 OFF Backup time .2 minutes 4 6ON, backup time .5 minutes

5 OFF Enable <5% load auto shutdown 5 6ON disables <5% load auto shutdown

6 OFF (Not used.)

7 OFF Baud rate=1200 7 -ON Baud rate =9600

8 OFF 60 Hz input select 8 -OFF = 50 Hz (Not used.)

14.5.3.4.4 Removal and Installation of Faraday Box 7A1A3 Subassemblies. Figure 14.5.3 identifies

connectors and subassemblies of FaradayBoxAssembly 7A1A3. The fiberoptic modules are socket-mounted

on top of the box. Table 14.5.11 describes Faraday box internal wiring and terminals.

Table 14.5.11. Faraday Box Access Procedure

Step Procedure

1 Ensure that ASOS facility power breaker is OFF and breaker is tagged.

2 At SCA Circuit Breaker Panel 7A1A1A3, set all circuit breakers OFF.

3 Set UPS power switch OFF.

4 At Faraday Box 7A1A3 front cover, remove perimeter screws and remove front cover.
ASOS Site Technical Manual S100

14-52 Change 2

$ 14.5.3.4.5 Removal and Installation of Alternative GTA Antenna. At SCA sites where the

$ alternative GTA antenna (ground plane antenna mounted on the wind tower) isinstalled, use the procedures

$ in table 14.5.12 for replacement of the antenna.

$

$$ Table 14.5.12. Removal and Installation of Alternative GTA Antenna

$ Step Procedure

$ REMOVAL

$ Tools required:

$ #1 Flat blade screwdriver

$ #1 Phillips screwdriver

$ #2 Phillips screwdriver

$ 3/8" socket wrench

$ Hacksaw

$ Tape measure

$ 1 At auxilliary box, remove power from GTA radio.

$ 2 Using the procedures in table 4.5.8, lower the wind tower to gain access to the antenna.

$ 3

$

Remove the weather shield from the antenna cable connection and disconnect the antenna cable from the

bottom of the antenna. Retain the NF/NF cable adapter.

$ 4 Loosen the terminal lug that holds the ground wire. Remove the ground wire from the antenna.

$ 5

$

Refer to figure 14.5.4, remove the two 1" pipe straps that secure the antenna pipe to the mounting bracket.

$ Remove the antenna from the bracket.

$ INSTALLATION

$

$

$

$

$

$ 1

$

$

$ CAUTION

$ The aternative antenna must be field tuned for the operating frequency assigned to the

$ GTA radio. DO NOT cut the antenna elements unless the assigned operating frequency

$ is known.

$

$ Refer to figure 14.5.6 and table 14.5.13 to determine the proper lengths to cut the antenna ground plane

$ radials and antenna radiating element . Using a hacksaw, cut the radials and radiating element to the proper

$ lengths for the assigned frequency.

$ 2

$

$

$ Using the removed antenna as a model; assemble the new antenna, attaching the terminal lug under the nut

$ of one of the u-bolts that secure the ground plane radials. Arrange so that the antenna grounding wire can

$ go into the barrel of the terminal lug.

$ 3

$

$ Loosely fasten the antenna support pipe to the mounting bracket using the 1" pipe straps. Adjust so that the

$ antenna axis is parallel to the wind tower axis at a distance of 17" to 19" from the tower.

$ 4

$

Refer to figure 14.5.5. Orient the antenna so the radials are at a 45 degree angle with the wind tower.

Tighten the two pipe straps to secure the antenna in this position.

$ 5

$

$ Connect the antenna cable to the bottom of the antenna using the NM connector and NF/NF adapter. Cover

$ the connectors using the weather shield provided on the antenna terminal extension.

$ 6 Fasten the antenna grounding wire in the terminal lug barrel.

$ 7 Using the procedures in table 4.5.8, raise the tower.

$ 8 In the auxilliary box, apply power to the GTA radio.

$ 9 Refer to chapter 12. Verify proper operation of GTA radio.

$
S100 ASOS Site Technical Manual

Change 2 14-53

Figure 14.5.5. Orienting Antenna Radials with Wind Tower

Figure 14.5.4. Alternative Antenna Installation

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$
ASOS Site Technical Manual S100

14-54 Change 2

Figure 14.5.6. Ground Plane Radials and Radiating Element

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$

$$ Table 14.5.13. Length of Radiating Element and Ground Plane Radials

$

$ GTA

$ FREQ (MHZ)

$

$ RADIATING

$ ELEMENT

$ GROUND

$ PLANE

$ RADIALS

$

$ GTA

$ FREQ (MHZ)

$

$ RADIATING

$ ELEMENT

$ GROUND

$ PLANE

$ RADIALS

$ 118 22-3/16" 33-1/2" 128 20-15/32" 30-31/32"

$ 119 22-1/32" 33-7/32" 129 20-5/16" 30-23/32"

$ 120 21-27/32" 32-15/16" 130 20-5/32" 30-1/2"

$ 121 21-11/16" 32-11/16" 131 20-1/32" 30-1/4"

$ 122 21-17/32" 32-7/16" 132 19-7/8" 30-1/16"

$ 123 21-7/32" 32-5/32" 133 19-3/4" 29-7/8"

$ 124 21-1/16" 31-7/8" 134 19-19/32" 29-21/32"

$ 125 20-29/32" 31-11/16" 135 19-7/16" 29-7/16"

$ 126 20-3/4" 31-7/16" 136 19-5/16" 29-1/4"

$ 127 20-19/32" 31-7/32" 137 19-5/32" 29-1/32"

$
S100 ASOS Site Technical Manual

15-1

CHAPTER 15

PORT SHARING DEVICE

SECTION I. DESCRIPTION AND LEADING PARTICULARS

15.1.1 INTRODUCTION

The port sharing device (PSD) is a software task executing within the acquisition control unit (ACU) that

enables the single port on the remote terminal to AFOS (RTA) to communicate with both ASOS and the

auxiliary backup terminal (ABT). The PSD performs the communications management functions necessary

for forwarding messages between the RTA and ABT and between the RTA and ASOS. In order to provide

the buffering necessary to support PSD functions, an additional memory board has been installed in the ACU

at those installations where the PSD has been implemented.

15.1.2 PHYSICAL DESCRIPTION

PSD functions are performed as a task in the ASOS software. Figure 15.1.1 illustrates the communications

paths between the PSD, ASOS, RTA, and ABT. An additional memory board isrequired for PSD operation.

Figure 15.1.2 illustrates the position of the memory board in location A4 of the ACU card rack assembly.

Two leased line modems will also be installed in cases where the RTA and the ABT are remote from the

ACU (i.e., more than 100 feet). The RTA and ABT are co-located in all cases so that these devices will both

be remote or both local. A detailed diagram illustrating the pin-to-pin connection between the ACU Serial

I/O (SIO) boards and connectors on the RTA and ABT is provided in Section IV.

15.1.3 FUNCTIONAL DESCRIPTION

The PSD handles message traffic between the RTA and ABT and between ASOS and the RTA. The

following general categories of message-types handled by the PSD are as follows:

a. ASOS/RTA messages

b. ABT to RTA data requests

c. ABT to RTA status messages

d. RTA to ABT data replies

e. RTA to ABT unsolicited messages

The PSD acknowledges each message (i.e., requests, replies, or status messages) received from either the

ABT or the RTA; however, messages received from ASOS are not acknowledged. The communications

procedures utilized by the PSD to handle message traffic is described in detail in Section IV. The use of the

DIAG function to monitor PSD communications is described in Section V.
ASOS Site Technical Manual S100

15-2

Figure 15.1.1. PSD Communications

Figure 15.1.2. PSD Memory Board Location
S100 ASOS Site Technical Manual

15-3/ (15-4 blank)

SECTION II. INSTALLATION

Installation instructionsfor the PSD are not applicable to this Chapter; however, installation instructionsfor

the hardwired PSD are contained in ASOS Field Modification Kit (FMK) No. 057-1, AAI Systems

Management, Inc., February 24, 1994, and for the leased line PSD in ASOS Field Modification Kit (FMK)

No. 057-2, AAI Systems Management, Inc., February 24, 1994. Instructions for installation of the memory

board associated with the PSD are provided in Chapter 3. The following documents provide technical

information on the RTA and ABT (Volume 2 refers to the RTA and Volume 4 to the ABT):

a. AFOS Handbook 2, Operator's Handbook, Volume 4, Remote Terminals to AFOS (RTA),

Auxiliary/Backup Terminal, 3rd Edition, U.S. Department of Commerce, National Oceanic

and Atmospheric Administration, July 1989

b. AFOS Handbook 2, Operator's Handbook, Volume 2, Remote Terminals to AFOS, Part 1

SynchronousRemoteTerminalstoAFOS,U.S.Department ofCommerce, National Oceanic

and Atmospheric Administration, July 1986
S100 ASOS Site Technical Manual

15-5/ (15-6 blank)

SECTION III. OPERATION

15.3.1 INTRODUCTION

The operation of the PSD is transparent to the user. Message management by the PSD, including

acknowledgment and retransmission, occurs automatically with no operator intervention. The PSD also

creates necessary queues to process the message traffic.

15.3.2 CONTROLS AND INDICATORS

The operator has no direct interface with or control over the PSD. All operator functions associated with the

PSD, including configuring the RTA and ABT, viewing the PSD memory board self-test status, and using

the PSD DIAG function are performed using the operator interface device (OID) display pages. The memory

board in location A4 isthe only newhardware component associated with PSD operation. Thememory board

is identical to the memory board installed in the DCP. The indicators on the memory board, which, when

illuminated, indicate when the ASOS ACU is accessing bank 1 or bank 2, are illustrated in Chapter 2,

Section III and are as described in Chapter 3, Section III.
S100 ASOS Site Technical Manual

15-7

SECTION IV. THEORY OF OPERATION

15.4.1 PSD FUNCTIONAL DESCRIPTION

The PSD is an intelligent software (firmware) device that manages RTA/ABT and ASOS/RTA

communications.Themessagessent and received to/fromthese units consist of hourly observations, specials,

and SHEF’s. The PSD uses asynchronous protocol and providesfor bidirectional product transmissions and

specific request/reply capability. The PSD also enables the ABT to receive spontaneous asynchronous

routing products from the RTA. The following paragraphs describe the PSD traffic management scheme as

well as the physical connections within the ACU and the pin-to-pin connections between the SIO board in

the ACU and the connectors on the RTA and ABT, respectively. The PSD, acting as a transparent

communications management task on the ACU, maintains the same protocols for RTA/ABT communications

as if the RTA and ABT were connected directly to each other. The following paragraphs also describe the

way in which the PSD manages ASOS/ RTA and RTA/ABT message traffic. The PSD DIAG function is

utilized to monitor PSD messages (paragraph 15.5.3.2.3).

15.4.1.1 PSD Message Traffic Management. The message traffic between the PSD and ASOS, RTA, and

ABT follows a particular sequence that depends on the origin of the message. The PSD acknowledges

messagesreceived from the RTA and ABT; however, messagesreceived fromASOS are not acknowledged.

The sequence of messages traveling over the PSD link is illustrated on figure 15.4.1 and described in the

following paragraphs. Examples of message traffic are provided in Section V, following

paragraph 15.5.3.2.5.

15.4.1.1.1 ASOS/RTA Communications. ASOS sends status messages, (e.g., METAR’s and SHEF’s) to

theRTA via the PSD. The RTA acknowledgesthe receipt of messagesfromthe PSD. After 2 minutes, ASOS

sends a request to the RTA via the PSD for a copy of the last message sent. The RTA responds to the PSD

with an acknowledgment. The RTA subsequently sends the message copy to the PSD and the PSD

acknowledges receipt. The PSD then sends the copy to ASOS. ASOS compares the last message sent with

the copy received and, if they are equal, treats the situation as an acknowledgment. ASOS does not

acknowledge receipt of the copy to the PSD. When the PSD is communicating with the RTA (e.g., urgent

specials), the PSD is also able to handle ABT to RTA communications, including multiple ABT to RTA

requests and RTA to ABT replies. The PSD also handles ASOS/RTA communications when the ABT is

disconnected or otherwise unavailable. 

15.4.1.1.2 RTA/ABT Communications. All RTA/ABT communications are via the PSD and are grouped

into the following generic message-types:

a. ABT to RTA data requests

b. RTA to ABT replies

c. RTA unsolicited messages to the ABT

d. ABT to RTA unsolicited messages

When the PSD receives a data request from the ABT, the PSD forwards the request to the RTA,

acknowledges receipt to the ABT, and receives an acknowledgment from the RTA. When the PSD receives

a reply from the RTA, the PSD forwards the reply to the ABT, acknowledges receipt to the RTA, and
ASOS Site Technical Manual S100

15-8

Figure 15.4.1. PSD Message Traffic

receives an acknowledgment from the ABT. When the PSD receives an unsolicited message (i.e., not in

response to an ASOS or ABT request) from the RTA, the PSD forwards the message to the ABT,

acknowledges the message from the RTA, and receives an acknowledgment from the ABT. When the PSD

receives an unsolicited message from the ABT (i.e., not in response to an ASOS or RTA request), the PSD

forwards the message to the RTA, acknowledges the message to the ABT, and receives an acknowledgment

from the RTA. The order in which the PSD retransmits and acknowledges messages may be affected by the

instantaneous volume of message traffic (including ASOS/RTA traffic). In order to maintain uninterrupted

communications, particularly when handling long messages, the PSD maintainssufficient queues(normally

64 KB, which is four times the maximum product size for each port). If either the RTA or the ABT rejects

products (indicated by a negative acknowledgment), the PSD continues to transmit the product until it is

acknowledged or until the PSD buffer is 80 percent exhausted, at which time the PSD on a first in first out

(FIFO) basis attemptsto transmit the next product for the port. Thisroutine permitsthe PSD to accommodate

the ABT off or disconnected condition without relying on control signals from the ABT. The PSD shares

transmissions to the RTA between ASOS and the ABT on a reciprocal basis. At the end of each block

transmission (including the acknowledgment), the other user(either ABT or ASOS) has an equal opportunity

to send. The PSD accomplishes the ASOS RTA port sharing via a FIFO store-and-forward queue to which

products received from ASOS or the ABT are appended. The PSD, RTA, and ABT retransmit

unacknowledged messages at approximately 5-second intervals.
S100 ASOS Site Technical Manual

15-9

Figure 15.4.2. PSD Hardware Connectivity Within the ACU

15.4.1.1.3 PSD Connectivity. Figure 15.4.2 illustrates the physical connection of the ACU components

used to accomplish the PSD function. Figure 15.4.3 illustrates the end-to-end connection between the SIO

board pins in the ACU and the pins on the RTA and ABT connectors. The port/pin assignments of SIO 

boards 4 through 8 are also identified in Chapter 2, Section IV. The particular physical connection between

the RTA and/or ABT and the PSD depends on whether the RTA and ABT are remote from the ACU. If the

RTA and ABT are remote from the ACU, the connection to each unit is via a leased line with the appropriate

modem installed in the ACU modem rack. The PSD is transparent to the RTA or ABT and processes

RTA/ABT messagesin either direction using the same signals on the same pins asif the RTA and ABT were

communicating directly. The PSD communicates with the RTA and ABT using RS-232C level signaling,

which terminatesin 25-pinD-type connectors.TheRTAandABTare equippedwithmodularTelco adapters,

however, so that the units are connected to the ACU using 8-wire telephone cables with Telco adapters.

NOTE

The PSD programs CTS and DTR HI on its ABT connector so that transmissions for the

ABT are not interrupted.
ASOS Site Technical Manual S100

15-10

Figure 15.4.3. RTA and ABT to PSD Physical Connections
S100 ASOS Site Technical Manual

15-11

SECTION V. MAINTENANCE

15.5.1 INTRODUCTION

The PSD is an ASOS software task executing on the ACU. There are no preventive maintenance procedures

for the PSD; therefore, the PSD is not maintained in the same manner as a hardware component. The only

hardware component directly associated with the PSD is a memory board used for message queuing. In cases

where the RTA and/or ABT is connected to the ACU via leased line modems, however, the operation of the

modem(s) may need to be verified. PSD maintenance consists of verifying that the software functions of the

PSD are properly performed. Because these functions require the proper operation and functioning of the

memory board, RTA, ABT, and modems, the maintenance philosophy of the PSD is to isolate a potential

fault to these components and/or to the connectivity between them. The proper operation of those

components located within the ACU that could affect PSD functions is verified using the same standard

self-test features of ASOS, as would be used to test the operation of any ASOS component, regardless of

whether the PSD was installed. The following paragraphs describe the corrective maintenance procedures

thatshould be used to monitor, verify, and, if necessary, restore and maintain performance of PSD functions.

15.5.2 PREVENTIVE MAINTENANCE

There are no preventive maintenance procedures for the PSD.

15.5.3 CORRECTIVE MAINTENANCE

15.5.3.1 General. Because the PSD is a transparent function in the communication path between ASOS and

the RTA and between the RTA and ABT, the cause of any inability to communicate can be attributed to the

PSD, ASOS, RTA, or ABT or where the RTA and/or ABT are in close proximity to the ACU, in the cables

connecting the unitsto the ACU. The process of corrective maintenance begins with the isolation of the PSD

as the cause of the problem. If possible, the RTA and ABT should be connected directly together and the

technician should attempt to perform the function that is exhibiting the symptom of the problem. If the

problem continuesto exist, the PSD is not at fault. If the problem is in ASOS/RTA communications, and the

RTA or ABT, including cables, is not at fault, the following procedures are performed to isolate and correct

the problem.

15.5.3.2 PSD Troubleshooting.

15.5.3.2.1 Determining SIO Board Assignments of the PSD. When performing corrective maintenance

on the PSD, the first task of the maintenance technician is to determine the SIO board assignments of the

PSD as described in the following paragraphs. The SIO boards for the PSD are assigned at installation time;

in order to properly diagnose a fault condition, however, the particular SIO boards assigned to the PSD must

be determined as follows:

a. On OID with the 1-minute display displayed, enter REVUE-SITE-CONFG-COMMS. This

sequence displays the COMMS page on the OID.

b. Locate "RTA" and "ABT" in the function column of the COMMS page.

c. Record the SIO board assignments of the RTA and ABT and verify that both are enabled

and configured with the proper COMM values.
ASOS Site Technical Manual S100

15-12

NOTE

If a leased line arrangement is used between the ACU and/or the RTA and ABT, modems

are indicated in the COMMS page.

15.5.3.2.2 Verifying ASOS Operating Condition. The operating condition of each component should be

determined using the maintenance menus as described in Chapter 2, paragraph 2.5.3. If a component failure

is indicated, the component is removed and replaced in accordance with the procedures contained in

Chapter 2, paragraph 2.5.4. If replacement of any component is necessary, the componentshould be retested

to ensure proper operation. When it is established that there are no failures indicated on ASOS, the PSD

should be tested using the DIAG function of the PSD as described in the following paragraph.

15.5.3.2.3 Using the PSD Diagnostic (DIAG) Function. The PSD DIAG function is available if there is

a printer or video display unit (VDU) configured in the system. The feature is used to display or print all

messages between the ASOS and the RTA or ABT. To use the PSD DIAG feature, the following steps must

be performed:

a. On OID with 1-minute display displayed, enter REVUE-SITE-CONFG-COMMS. This

sequence displays the COMMS page on the OID.

b. Move cursor to printer, VDU, or spare SIO port to be used to print or display messages. 

c. Press CHANG and set up port as follows:

NOTE

Entries are shown in bold.

FUNCTION PSD DIAG

STATUS ENABLED HANDSHAKE NONE

BAUD RATE 9600* CONNECTION HARDWIRE**

PARITY SELECT NONE

BITS/CHAR 8

STOP BITS 1

*Baud rate of connected device

**Will indicate leased if modems are used.

d. Press EXIT. The PSD DIAG feature is now ready to display or print messages being handled

by the PSD.

NOTE

When PSD corrective maintenance is complete, configure the SIO port for its original

assignment.

15.5.3.2.4 PSD Hardware Connectivity Within the ACU. The ACU hardware signaling scheme,

including the site-specific SIO boards that have been assigned to the PSD, are described and illustrated in

Chapter 2, Section IV. Figure 15.4.2 illustrates the PSD hardware connectivity within the ACU.

15.5.3.2.5 Monitoring PSD Message Traffic. The following examples illustrate typical PSD message

traffic that appears on the display or printer used as the PSD DIAG monitoring device.
S100 ASOS Site Technical Manual

15-13

EXAMPLE 1. ASOS/RTA MESSAGES

00:01:12 Received No Special Product Id: DENSAODEN from ASOS

00:01:13 Transmitting No Special Product Id: DENSAODEN to RTA

00:01:15 Received Positive Acknowledgment from RTA

00:53:13 Received Request for Product Id. DENSAODEN from ASOS

00:54:00 Transmitting Request For Product Id. DENSAODEN to RTA

00:54:01 Received Positive Acknowledgment from RTA

00:54:03 Received Reply to Request For Product Id. DENSAODEN from RTA

00:54:04 Transmitting Reply to Request For Product Id. DENSAODEN to ASOS 

00:54:12 Transmitting Positive Acknowledgment to RTA

NOTE

As shown above, the PSD does not acknowledge messages received from ASOS.

EXAMPLE 2. ABT TO RTA STATUS MESSAGES

00:01:12 Received No Special Product Id. DENSAODEN from ABT

00:01:13 Transmitting No Special Product Id. DENSAODEN to RTA

00:01:14 Transmitting Positive Acknowledgment to ABT

00:01:15 Received Positive Acknowledgment from RTA

EXAMPLE 3. ABT TO RTA DATA REQUESTS

00:01:12 Received Request For Product Id. DENSAO4LJ from ABT

00:01:13 Transmitting Request For Product Id. DENSAO4LJ to RTA

00:01:14 Transmitting Positive Acknowledgment to ABT

00:01:15 Received Positive Acknowledgment from RTA

EXAMPLE 4. RTA TO ABT DATA REPLIES

00:01:12 Received Reply to Product Id. DENSAO4LJ from RTA

00:01:13 Transmitting Reply to Product Id. DENSAO4LJ to ABT

00:01:14 Transmitting Positive Acknowledgment to RTA

00:01:14 Received Positive Acknowledgment from ABT

EXAMPLE 5. RTA TO ABT UNSOLICITED MESSAGES

00:01:12 Received No Special Product Id: DENSAOAKO from RTA

00:01:13 Transmitting No Special Product Id: DENSAOAKO to ABT

00:01:15 Transmitting Positive Acknowledgment to RTA

00:01:17 Received Positive Acknowledgment from ABT

In practice, the messages shown in the examples do not follow one another directly. The device connected

to the PSD DIAG port actually logs transmissions to and from the PSD in time order. The PSD manages

messages concurrently to and from ASOS, the RTA, and the ABT. The log, therefore, reflectsthe time order

of all transmissions. For example, there may be some intervening transmissions between a request for a

particular product and the reply to the product requested. Multiple transmissions not acknowledged are also

shown on the transmission log.
ASOS Site Technical Manual S100

15-14

WARNING

15.5.4 FIELD REPLACEABLE UNIT (FRU) REMOVAL AND REPLACEMENT

Severe injury or death may result if power is not removed from the equipment prior to

maintenance activities. Ensure that the output power switch is set to the zero (0) (OFF)

position and that facility power is removed from the ACU.

15.5.4.1 PSD Memory Removal and Replacement. The only unique hardware item in the ACU that

supports the PSD is the memory board installed in location 1A2A4. This board is identical to the memory

board installed in the DCP in location A2A3. The corrective maintenance procedures for the two boards are

identical and are described in Chapter 2, Section V.

15.5.4.2 Modem Removal and Replacement. One or two modems may be installed to support remote

connection of the RTA and ABT. The locations and operating status of the modems can be determined by

accessing the COMMS page. Removal and replacement procedures for the modem(s) are described in

Chapter 2, Section V.
S100 ASOS Site Technical Manual

Change 1 16-1

Figure 16.1.1. Thunderstorm Sensor

CHAPTER 16

THUNDERSTORM SENSOR

SECTION I. DESCRIPTION AND LEADING PARAMETERS

16.1.1 INTRODUCTION

The ASOS thunderstorm sensor is a model TSS-924 electrooptical short-range thunderstorm detector manufactured by

Global Atmospherics, Inc. of Tucson, Arizona. The sensor

detects and differentiates between cloud-to-ground (CG) and

cloud lightning discharges. The sensor provides a range estimate

for CG lightning discharges from thunderstorms that occur

within approximately thirty miles. The sensor indicates the

count and range of CG discharges in three range categories of

0-5, 5-10, and 10-30 miles.

The sensor communicates with the data collection package

(DCP), or Single Cabinet ASOS (SCA) via a fiberoptic serial

data link. The DCP or SCA polls the sensor once every 60

seconds, and the sensor responds with the current flash count

and sensor status. The DCP, in turn, passes the data to the

acquisition control unit (ACU). When the ACU receives a flash

count indicating lightning, the ACU issues a SPECI with a

thunderstorm onset message. In addition to flash count data, the

thunderstorm sensor provides built-in test (BIT) results that are

interpreted by the ASOS continuous self-test (CST) to detect

sensor failures.

16.1.2 PHYSICAL DESCRIPTION

The thunderstorm sensor (figure 16.1.1) consists of a main

enclosure installed on amounting pole. Themounting pole itself

is a part of the supporting structure for the sensor and does not

have a reference designator. The main enclosure contains all

sensorfield replaceable units(FRU’s), which include an electrooptical antenna assembly, power and communications module

(power/comm module), an electronics module, and a fiberoptic

module.

The antenna assembly supplies signals to the electronics module, the electronics module interprets and

processes these signals, and the power/comm module provides power for the sensor and communications

with the outside world. The main enclosure is a specially designed, weather-proof box with a hinged and

gasket-sealed door held closed with two stainlesssteel fasteners. When closed, the box is air-tight and watertight. The main enclosure contains the electronics module and the power/comm module. The electronics

module contains the analog board and the processor board. The power/comm module consists of the

power/comm board, the fiberoptic modem, and the heater, all of which are mounted on a special mounting

plate. 
ASOS Site Technical Manual S100

16-2 Change 1

16.1.3 THUNDERSTORM SENSOR CONFIGURATIONS

There is only one configuration of the thunderstorm sensor; the TSS 924.

Table 16.1.1. Operational specifications

OPERATIONAL SPECIFICATIONS

Detection 

Efficiency

Thunderstorm

detection

100% for thunderstorms within 10 miles with 3 or more cloud-to-ground

discharges

Cloud-to-ground

flashes

Approximately 90% for flashes within 0-10 miles

False Lightning Reports None. False lightning reports do not occur for properly installed and properly

maintained sensors

Thunderstorm Range Resolution

(user selections available)

0-5, 5-10, 10-30 miles

0-5, 5-10, 10-30 nautical miles

0-8, 8-16, 16-50 kilometers

 Sensing Transducers Wideband electric field change meter describing local thunderstorm conditions

 Sensor Output Serial ASCII alphanumeric message describing local thunderstorm conditions

(automatic one-minute intervals or polled)

ELECTRICAL SPECIFICATIONS

115 VAC Power Option 90-120 VAC, 50/60 Hz, 6 Watts maximum without heater, 80 Watts maximum

with heater

230 VAC Power Option 180-250 VAC, 50/60 Hz, 6 Watts maximum without heater, 80 Watts maximum with

heater

12 VDC Power Option 11.5-16.5 VDC available on special request

ELECTRICAL SPECIFICATIONS

Communications line Metallic or fiberoptic cable

Data type Serial ASCII

Data transfer 9600 baud

Parity None

Data bits 8

Stop bits 1

ENVIRONMENTAL SPECIFICATIONS

Maximum wind load 120 knots, 222 kilometers/hour (standard mast mount)

Humidity 0-100% (Stainless steel NEMA 4X enclosure provides complete protection

against corrosion and severe weather.)

Temperature -40° to +60° C (with heater)

ELECTRICAL SPECIFICATIONS

Ground mount Standard mast (3-inch (~7.6 cm) inside diameter schedule 80 aluminum pipe,

4 feet (1.2 m) tall)

Mast mount Mast-mounting brackets, outside diameter 4.5 inches (11.43 cm)

Maximum height 9.8 feet (3 m) maximum recommended

SENSOR DIMENSIONS

Height 32.5 in (82.5 cm)

Width 11.0 in (27.9 cm)

Depth 8.0 in (20.3 cm)

Weight 28.0 lbs (12.6 kg)
S100 ASOS Site Technical Manual

Change 1 16-3

WARNING

SECTION II. INSTALLATION

16.2.1 INTRODUCTION

To install the thunderstorm sensor, the mounting pole is installed, the main enclosure is installed on the

mounting pole, the sensor is assembled, and electrical connections are made. Following installation, the

sensor must be configured. Refer to table 16.2.1 and figures 16.2.1 through 16.2.3 for installation and

table 16.2.2 to configure the sensor. After installation, refer to instructions contained in Section V for

inspecting the sensor. 

Table 16.2.1. Thunderstorm Installation Procedure

Step Procedure

Tools and Materials Required:

Two 15/16-inch wrenches

7/16-inch wrench and torque driver

11/32-inch wrench

Large flat-tipped screwdriver

Large pliers (12 inch, 2-1/4 inch capacity, curved jaw)

7/16-inch hex key wrench and torque driver

Cable ties

Death or severe injury may result if power is not removed from sensor prior to maintenance

activities. Ensure that circuit breakers supplying power to sensor are set to off (right) position. 

NOTE

DCP Thunderstorm sensor installation requires prior or concurrent ECP E96SM05F189 (DCP

Power Expansion) installation. ECP E96SM05F192 (ACU/SCA Firmware Version 2.45 and DCP

Firmware Version 1.80) is also required.

1 At DCP (SCA), open equipment cabinet door, set UPS power switch to 0 (OFF) on CLASS II systems only,

and turn off UPS POWER circuit breaker A1A3A1 (DCP) or A1A3CB21/CB22 (SCA).

2 Open DCP (SCA) Power Distribution Panel and turn off DCP (SCA) power. This removes all DCP (SCA)

and sensor power.

3 Open DCP (SCA) Faraday box to access sensor power wiring and fiberoptic modems.

4 For the DCP, insert circuit breaker module (62828-40155-100) into A1A3A2 position. For the SCA, install

1⁄2A breaker (62828-90037-6) in A1A1A3CB13 and 1A breaker (62828-90037-1) in A1A1A3CB14, using

screws (MS51957-27), lock washers(AA55610-136), and flat washers(MS15795-805) supplied. For SCA,

connect wires (W106) to circuit breaker terminals as marked.

5 Remove blank cover from A3A1(DCP) or A3A8 (SCA) (on Faraday Box) position and save gasket.

6 Install fiberoptic modem (62828-90006-1) and gasket in position A1 (DCP) or A8 (SCA) using screws

(62828-90075-1) and washers (62828-90174-1).

7 Locate SIO connector in harness marked M/WA3A1J1 (DCP) or P8 M/W A3A8J1 (SCA). Attach connector

to fiberoptic modem installed in position A1 (DCP) or A8 (SCA) and tighten connector screws.

8 Remove protective plug from 3/4" hole on bottom of DCP (SCA). If Line Drivers are installed, a conduit

outlet tee (62828-90257-1, 62828-90258-1, 62828-90259-1) must be installed at DCP (SCA) end of conduit

running to wind sensor using a conduit hub (62828-90426-1) and close nipple (MS51953-97), with conduit

adapters(62828-90260-1)to connect tee to hub and liquidtight conduit connectors. Note locations of existing

wire and cable terminations to wind sensor for reconnection after tee installation (when used).

9 Install connector(62828-62828-90097-1) and O Ring gasket(62828-90293-1).Route fiberoptic cable, power

wiring, and flex conduit through hole on bottom of DCP (SCA). Secure flex conduit to connector.
ASOS Site Technical Manual S100

16-4 Change 1

Table 16.2.1. Thunderstorm Installation Procedure -CONT

Step Procedure

10 Connect fiberoptic cable to fiberoptic modem installed in Step 6. Ensure that RX and TX are properly

connected.

11 Connect sensor power wires as follows. Strip insulation back 1⁄4inch from wire ends.

Wire DCP Terminal SCA Terminal

M16878/1BJE0 (black) A17-3 A17-11

M16878/1BJE9 (white) A18-3 A18-11

M16878/1BJE5 (green) A17-GND A17-GND

M16878/1BJE2 (red) A17-19 A17-23

M16878/1BJE4 (yellow) A18-19 A18-23

12 In SCA (only), connect jumpers as follows. Strip insulation back 1⁄4inch from wire ends.

Wire From To

M16878/1BJE0 (Black) A1A4-5B A1A4-8B

M16878/1BJE0 (Black) A1A4-12C A1A4-14C

M16878/1BJE9 (White) A1A4-17A A1A4-20A

13 At top of left DCP (SCA) mounting pole, remove end cap.

14 Install pipe extension (62828-40418-1) using pipe coupler (MS39233-11).

15 Reinstall pipe cap on top of extension.

16 Using hardware supplied with sensor, install thunderstormsensormounting brackets on sensor(figure 16.2.1)

and mount sensor on pole extension .

17 Remove retaining nut from end of flex conduit and install gasket P/N 62828-90097-1 on conduit. Route

fiberoptic cable, power wiring, and flex conduit through entry hole on sensor. Secure flex conduit to sensor

using retaining nut removed at beginning of this step.

18 At thunderstorm sensor, open main enclosure door.

19 Remove plastic seal protecting liquid-tight coupler at top of enclosure. Loosen large hexagonal nut at top of

enclosure several turns. Do not completely unscrew large hexagonal nut. 

CAUTION

To avoid breaking glass diffuser at end of antenna, do not remove protective rubber tubing

on antenna until sensor is mounted.

20 Arrange antenna cable to hang freely from bottom of antenna housing. Carefully feed connector end of cable

into liquid-tight coupler and pull cable through to inside of enclosure and guide antenna end into opening in

liquid-tight coupler.While holding antenna perpendicularto top of enclosure,slowly and gently push antenna

into liquid-tight coupler until fully seated as shown in figure 16.2.2.

21

CAUTION

Failure to properly tighten liquid-tight coupler nut will result in moisture damage.

Hand tighten hex nut on liquid-tight coupler.

22 Route antenna cable under clamps and connect to electronics module J104 as shown in figure 16.2.3.

23 Connect spade lug to ground terminal located below antenna mounting coupler.

24 Connect sensor power wires as follows. Strip insulation and install lug (62828-90132-11) on wire.

Wire Terminal

M16878/1BJE0 (Black) TB1-1

M16878/1BJE9 (White) TB1-2

M16878/1BJE5 (Green) TB1-3

M16878/1BJE2 (Red) TB1-4

M16878/1BJE4 (Yellow) TB1-5

25 Connect fiberoptic cable to fiberoptic modem in sensor making sure RX and TX are installed properly.
S100 ASOS Site Technical Manual

Table 16.2.1. Thunderstorm Installation Procedure -CONT

Step Procedure

Change 1 16-5

Figure 16.2.1. Thunderstorm Sensor Top and Bottom Mounting Brackets Assembly

26 Install lug (62828-90253-1) on 10 ga.solid wire (QQW343S10S1B). Connect wire to ground stud on sensor

using hardware supplied with sensor. Connect other end of ground wire to systemground wire running across

bottom of DCP (SCA) using split bolt connector (62828-90254-1).

27 Secure flex conduit and ground wire to DCP (SCA) pole using cable ties (62828-90256-1) as required.

28

NOTE

Performthisstep only when all actionsrequiring accessto the interior ofthe sensor enclosure

are complete.

The desiccant bag must be removed from airtight outer packaging (DO NOT open the desiccant bag

containing desiccant granules) and flattened by shaking and patting to evenly distribute its contents so that

it may be placed on top of electronics module. Ensure that desiccant bag does not interfere with door or other

internal assemblies. Turn sensor ON using switch S1 inside enclosure; close and secure sensor door. Remove

protective rubber tubing on antenna.

29 At DCP (SCA), close Faraday box and secure using original hardware.

30 Set thunderstorm sensor circuit breakers A1A3A2 (DCP) or A1A3CB13/CB14 (SCA) to "ON".

31 At DCP Turn UPS "OUTPUT POWER" A1A3A1 to "ON". Set UPS power switch to 1 (ON) CLASS II

SYSTEMS ONLY. (At SCA turn UPS#1 “OUTPUT POWER” A1A3CB21 to “ON”.)

32 Turn ON DCP (SCA) Power Circuit Breaker in Power Distribution Panel. Close and secure Power

Distribution Panel Door. Power is now restored to DCP (SCA) and all sensors. Secure all doors.
ASOS Site Technical Manual S100

16-6 Change 1

Antenna assembly

Liquid-tight coupler

Push antenna

into coupler

until fully seated

as shown

TSI003A

Figure 16.2.2. Thunderstorm Sensor Antenna Seating

TSI007A

Antenna ground strap

Attach ground faston to

ground clip on coupler nut

Route antenna cable under

wire clips as shown

Attach antenna cable

connector to J104

Antenna cable

Figure 16.2.3. Thunderstorm Sensor Antenna Cable Routing
S100 ASOS Site Technical Manual

Change 1 16-7

SECTION III. OPERATION

16.3.1 INTRODUCTION

Automatic thunderstorm sensor operation is controlled by the acquisition control unit (ACU) via the data

collection package (DCP) or the single cabinet ASOS (SCA). This section provides turn-on and turnoff

procedures and information on operation, checkout, and diagnostic testing of the sensor.

16.3.2 CONTROLS AND INDICATORS

The thunderstorm sensor contains maintenance controls and indicators on the power/comm module and

electronics module. Descriptions of the test data displayed as part of the system diagnostic test program are

provided in Chapter 1. The thunderstorm sensor controls/indicators are illustrated on figures 16.3.1 and

16.3.2 and described in tables 16.3.1 through 16.3.4.

16.3.3 TURN-ON PROCEDURES

The thunderstorm sensor is designed for continuous operation and normally remains on at all times, except

for maintenance or repair. The sensor turn-on procedures are provided in table 16.3.5.

16.3.4 CHECKOUT PROCEDURES

The ACU via the DCP (or the SCA) continuously monitors the thunderstorm sensor diagnostic output for

failure indications. If the ACU (SCA) detects a failure, it flags the sensor off-line and enters the appropriate

message in the system log. The technician can review the sensor's test data via thunderstorm sensor screen

on the OID. For most failures, the diagnostic identifies the faulty field replaceable unit (FRU). If the

diagnostic fails to indicate the faulty FRU, the troubleshooting procedures provided in Section V of this

chapter should be performed.

The sensor should be powered up only after complete assembly and checkout of all electrical power and

communications connections. If the sensor has been disassembled for any reason before the first power-up,

then all electrical connections must be remade and checked. Refer to figure 16.3.1 and table 16.3.1 for

power/comm module indicators.

16.3.5 RUNNING DIAGNOSTICS

The ASOS contains diagnostic pages for the thunderstorm sensor. The diagnostic test can be performed by

using an on-demand diagnostic test as explained in Chapter 1.

16.3.6 NORMAL OPERATING PROCEDURES

The thunderstorm sensor is in continuous operation under the control of the DCP (SCA). The thunderstorm

indications are displayed in the PRESENT WX field on the 1-minute display at the OID.

16.3.7 TURNOFF PROCEDURES

The thunderstorm sensorshould be turned off for maintenance purposes only using the procedures provided

in table 16.3.6.
ASOS Site Technical Manual S100

16-8 Change 1

Figure 16.3.1. Power/Comm Module Controls and Indicators

Table 16.3.1. Power/Comm Module Controls and Indicators

Indicator Description

CR1-CR4 Transient suppressors (MOV’s)

F1 1/4A +12V supply fuse

F2 1A heater fuse

S1 Power switch

S2 Reset switch

S3 Data input select switch (ASOS default is UP, DB9)

LED1 LED indicator that illuminates when 12V is present

LED2 RXD active LED indicator that illuminates when RS-422 data is received from DCP (SCA)

LED3 TXD active LED indicator that illuminates when RS-422 data is transmitted to DCP (SCA)

LP1 Neon lamp status indicator that illuminates when switch S1 is ON, fuse F1 is good, and power is

applied to the 12V power supply

LP2 Neon lamp status indicator that illuminates when switch S1 is ON, fuse F2 is good, and power is

applied to heater circuit

LP3 Neon lamp status indicator that illuminates when power/comm module temperature is less than 32°F

(0°C)
S100 ASOS Site Technical Manual

Change 1 16-9

Figure 16.3.2. Analog Board and Processor Board Indicators
ASOS Site Technical Manual S100

16-10 Change 1

Table 16.3.2. Analog Board and Processor Board Controls and Indicators

Indicator Description

ANALOG BOARD INDICATORS

10VOK LED indicator illuminated when 10V level is OK

12VOK LED indicator illuminated when 12V level is OK

5VOK LED indicator illuminated when 5V level is OK

12VHI LED indicator illuminated when 12V level is high

PROCESSOR BOARD INDICATORS

RXD LED indicator illuminated when processor board receives data from the data/comm board

TXD LED indicator illuminated when processor board transmits data from the data/comm board

FLS LED indicator flashes when lightning is detected

RUN LED indicator illuminated during normal CPU activity

OVR LED indicator illuminated when there is activity on the overrange signal

OPT LED indicator illuminated when optical activity is detected

ENA LED indicator illuminated when electrical activity that enables flash identification is detected

Table 16.3.3. Processor Board Switch Bank 101 Settings

Switch Bank 1 Positions 1 - 8 Output Modes

Pos1 UP VT100 terminal (ASOS required setting)

Pos2 UP One-minute message (ASOS required setting)

Pos3 UP Reserved, always leave up (ASOS required setting)

Pos4 UP Flash message output (ASOS required setting)

Pos5 UP Simulator command set enabled (ASOS required setting)

Pos6 DOWN Host command set enabled (ASOS required setting)

Pos7 UP 24-hour history message not cleared (ASOS required setting)

Pos8 UP Reserved, always leave up (ASOS required setting)

Table 16.3.4. Processor Board Switch Bank 100 Settings

Positions 1 2 3 Diagnostic Test

UP UP UP Normal operation (ASOS required setting)

UP UP DN Self-test @ 1sec

UP DN UP Echo test

UP DN DN Watchdog timeout test

DN UP UP Switch test

DN UP DN Type test

DN DN UP Reserved

DN DN DN Reserved

Position 4 (not defined)

UP (ASOS required setting)

Positions 5-6 Units of Measure

UP UP Miles (ASOS required setting)

UP DN Nautical miles

DN UP Kilometers

DN DN Miles

Positions 7- 8 Flash Aging Interval

UP UP 15 minutes (ASOS required setting)

UP DN 10 minutes

DN UP 5 minutes

DN DN 30 minutes
S100 ASOS Site Technical Manual

Change 1 16-11/ (16-12 blank)

Table 16.3.5. Thunderstorm Sensor Turn-On Procedures

Step Procedure

Tools required:

 No. 2 Phillips screwdriver

1 At DCP (SCA) equipment cabinet, set thunderstorm sensor circuit breaker module to off (right) position.

2 At thunderstorm sensor, use No. 2 Phillips screwdriver to loosen two captive bolts securing hinged sensor

access door and open door. 

3 At power/comm board, set S1 power switch to ON (up) position.

4 Using No. 2 Phillips screwdriver, close and secure thunderstorm sensor access door.

5 At DCP (SCA), set thunderstorm sensor circuit breakers on circuit breaker module to on (left) position.

Table 16.3.6. Thunderstorm Sensor Turnoff Procedures

Step Procedure

Tools required:

 No. 2 Phillips screwdriver

1 At DCP (SCA) equipment cabinet, set thunderstorm sensor circuit breaker module to off (right) position.

2 At thunderstorm sensor, use No. 2 Phillips screwdriver to loosen two captive bolts securing hinged sensor

access door and open door. 

3 At power/comm board, set S1 power switch to OFF (down) position.

4 Using No. 2 Phillips screwdriver, close and secure thunderstorm sensor access door.
S100 ASOS Site Technical Manual

Change 1 16-13

SECTION IV. THEORY OF OPERATION

16.4.1 PRINCIPLES OF OPERATION

The thunderstormsensor(figure 16.4.1) consists ofthreemajor components contained in themain enclosure:

! Antenna assembly

! Power/Comm module

! Electronics module 

The main enclosure is a specially designed, weather-proof box with a hinged and gasket-sealed door held

closed with two stainless steel fasteners. When closed, the box is air-tight and water-tight. The main

enclosure contains the electronics module and the power/communications module (power/comm module).

The electronics module contains the analog board and the processor board. The power/comm module

contains the power/comm board, heater, and fiberoptic modem. 

The antenna assembly suppliessignalsto the electronics module which interprets and processes these signals.

The power/comm module provides power for the sensor and communications with the outside world. 

16.4.2 SIMPLIFIED BLOCK DIAGRAM DESCRIPTION

A functional block diagram of the thunderstorm sensor is shown in figure 16.4.2. The thunderstorm sensor

consists of an electro-optical antenna assembly, power/comm module , and an electronics module. The

antenna assembly detectsthe electric field signal generated by lightning discharges while the antenna optical

sensor detects the associated flash. These two inputs are processed in the electronics module analog board.

The main functions of the analog board are:

! Separate noise and lightning signals 

! Determine if lightning is “cloud to cloud” or “cloud to ground”

! Estimate range of “cloud to ground” lightning 

After these functions are performed, the analog signal isrouted to the processor board. The analog board and

the processor board are the main components of the electronics module. The processor board performs both

analog and digital functions. The analog signals from the analog board are shaped and converted to digital

format required by the processor board’s microprocessor circuitry. The following functions are performed

by the processor board:

! Convert lightning data into message format for transmission to the ACU, DCP, or SCA

! Store lightning and self-test data and include into reports

! Fiberoptic modem data input/output (I/O) handling

! Microprocessor housekeeping functions 

The processor board sends data to the power/commmodule, where the data is converted to theRS-232 format

and sent to the fiberoptic modem. The power/comm module also provides 12-volt power for the sensor and

processes data communications with the DCP (SCA). Each field replaceable unit (FRU) is easily replaced

and interchangeable with other thunderstorm sensors.
ASOS Site Technical Manual S100

16-14 Change 1

Figure 16.4.1. Thunderstorm Sensor Modules
S100 ASOS Site Technical Manual

Change 1 16-15

ANTENNA MODULE

'E' FIELD ANTENNA

OPTICAL SENSOR

ELECTRIC FIELD

OPTICAL SIGNAL

ANALOG SIGNAL

PROCESSOR

DATA

PROCESSOR

ELECTRONICS MODULE

POWER

SUPPLY

DATA COMM

INTERFACE

POWER/COMM MODULE

FIBER OPTIC

MODEM

FIBER OPTIC

CABLES

ELECTRONICS ENCLOSURE

EXTERNAL POWER

NEX075

Figure 16.4.2. Functional Block Diagram

16.4.2.1 Power and Power Supplies. Power is supplied to all circuitry by a linear, 12 VDC power supply.

AC power is brought on to the power/comm module where it is fused, switched, over-voltage limited, and

filtered before being passed to the power supply. The regulated 12 VDC output is supplied to the circuitry

where additional regulation to other power supply voltages is performed. The power/comm module also

manages the power for the heater. Power is supplied to the heater by a separate AC circuit on the

power/comm module that is switched in common with the main circuit power. AC for the heater is passed

through a full-wave rectifier,filtered, current limited, and supplied to a heating element through a thermostat

mounted to the power/comm module. Inrush current limiters are used in the heater circuit to slow the turn-on

transient of the heater.

16.4.2.2 Communications. The power/comm module also handles data communications to the outside

world. TTL level transmit and receive data signals are converted to RS-232 levels on the power/comm

module. RS-232 level data lines are passed to the fiberoptic modem.

16.4.2.3 Self-tests. Given a healthy sensor in a normal sensor site, failed self-tests are rare. An occasional

failed self-test does not necessarily indicate a defective unit.Occasionally, a self-testfails because of external

interference. 

The self-test exercises the majority of the circuitry in the sensor. Every 30 minutes and upon command from

a host computer or terminal, the sensor injects simulated lightning signals into the electric field channel and

simultaneously injects a simulated lightning light pulse into the optical sensor. These signals are acted upon

by circuitry on the analog board and processor board in the electronics module and a self-test result is

generated. The processor board keeps track of a bit that indicatesthat the signal in process is from a self-test

and not from natural lightning.
ASOS Site Technical Manual S100

16-16 Change 1

The sensor reports that a self-test has failed only after successive failed self-tests, not on a single failed selftest (which can occur in normal sites with a healthy sensor due to transient, external noise interference).

When the sensor fails a single self-test, it repeats the self-test four times. The self-test result reported is the

majority value of the results of the five self-tests. After the sensor reports a failed self-test, it does not

continue to report lightning.

If the sensor is unable to perform a self-test, it tries four more times (as with a failed self-test). If

unsuccessful after five attempts, the sensor reports a failed self-test and puts the sensor in the DOWN state.

Due to an approximate 2-second time-out, the total delay from the time a self-test is requested until a

response is received may be 10-14 seconds if a self-test cannot be performed on all five attempts. In the

DOWN state, the sensor will attempt to do a self-test once each minute. After the sensor reports a failed selftest, it does not continue to report lightning.

16.4.2.4 Lightning Categories. The sensor detects two types of lightning: cloud-to-cloud and cloud-toground (CG) lightning. CG lightning is further categorized according to its range. As set at the factory, CG

lightning within zero to five miles of the sensor is categorized as Overhead, lightning within five to ten miles

is categorized as Near, and lightning within ten to thirty miles is categorized as Distant.

16.4.2.5 Processing Strokes and Flashes. A CG lightning discharge is actually made up of one or more

individual discharges occurring in rapid succession. The totalCG discharge is called a flash. Each individual

discharge within a flash is called a stroke.

The sensor detects individual lightning strokes. The sensor groups stroke messages into flashes. All stroke

messages received within one second of the first stroke message are considered to be part of a single flash.

A flash counter is increased by one for each flash detected, regardless of the number of stroke messagesthat

were received within one second of the first stroke of the flash.

The sensor reports the range of a flash as the range of the nearest stroke in that flash. Signals from different

CG discharges that occur at nearly the same time may occasionally be grouped together and counted as one

flash. Cloud discharges that occur during the one-second period for flash grouping are not considered part

of the CG discharge.

The algorithm used in the sensor for processing bursts of lightning stroke data was designed to identify and

classify lightning in much the same way that a diligent, omniscient human lightning observer would.

16.4.2.6 Signal Processing. The sensor antenna responds to changes in the electric field and to optical

impulses. The electronics module inside the sensor processes both of these signals in order to determine if

they were caused by lightning. If so, the signals are further processed to determine whether their source was

a cloud or a CG discharge. If the signals were caused by CG lightning, additional processing determines the

approximate range and polarity of the lightning.

All of the functions listed above are provided by fast, low-power analog signal processing circuitry on the

analog board and pulse-shape logic on the processor board.

The data about each stroke of each lightning flash is supplied to the microcontroller portion of the processor

board where the following functions are performed:

 ! Stroke data messages are sorted into sensible flash counts.

 ! Flash counts are aged.

 ! All data I/O is handled.

 ! Housekeeping functions (self-test, error counting, and history accounting) are performed.
S100 ASOS Site Technical Manual

Change 1 16-17

16.4.3 COMMAND DESCRIPTION

16.4.3.1 Host Mode. The thunderstorm sensor host mode uses two-way (duplex) communications with a

laptop computer connected to the sensor (refer to Section V). Host mode is enabled when switch 6 of SW101

is Down. Table 16.4.1 shows the requests or commands that a host computer can send to the sensor. These

requests are made by sending a single, upper-case, ASCII character to the sensor. The Host mode commands

are further described in the following paragraphs.

Table 16.4.1. Host Command Set

ASCII Character Function

A Send a present Weather Message

B Send a Status message

C Perform a Self-Test

D Perform a Reset

E Perform a Type Test

F Send system Run Time

G Send Version Message

16.4.3.2 Send Present Weather Message. When the host computer issues the ASCII character A to the

sensor in the Host mode, the sensorsends a present weather message with flash count and statusinformation

as shown in table 16.4.2.

Table 16.4.2. Response to Command A: Present Weather Message

Byte Description Value 

1 Overhead flash counts label O

2-6 Overhead flash counts 0-29999

7 Near flash counts label N

8-12 Near flash counts 0-29999

13 Distant flash counts label D

14-18 Distant flash counts 0-29999

19 Cloud flash counts label C

20-24 Cloud flash counts 0-29999

25 Total flash counts label T

26-30 Total flash counts 0-29999

31 Self-test results: P = passed

F = failed

? = no self-test performed

P F ?

32-33 Status byte (see section 5.2.5.3.1) 00-FF

34 Hex radix delimiter H

35 Carriage return <CR>

36 Line feed <LF>

C Format String "O%5uN%5uD%5uC%5uT%5u%c%2xH\n"

Example: O 7N 1D 2C 2T 12PC6H<CR><LF>

16.4.3.3 Send Status Message. By sending the ASCII character B, the host may request from the sensor a

status message that consists of accumulated status, flash, and stroke counts. The accumulated counts are

strictly for diagnostic purposes as they do not reflect the current storm counts, but rather the history of

lightning counts and housekeeping information. The history accumulates during a cycle of the sensor*s

internal clock. When the sensor is powered up or reset, the internal clock isstarted; the clock rolls over every

24 hours. The status message counts are cleared (set to zero) at power-up, reset, and normally at rollover of
ASOS Site Technical Manual S100

16-18 Change 1

the 24-hour clock. The status message format is described in table 16.4.3.

If switch 7 on SW101 is Down, the status message is not cleared at clock rollover; counts will accumulate

until the sensor is reset or powered up.

Table 16.4.3. Response to Command B: Status Message

Line Byte Description Value 

1 1 Overhead flashes label O

2-6 Overhead flashes 0-29999

7 Near flashes label N

8-12 Near flashes 0-29999

13 Distant flashes label D

14-18 Distant flashes 0-29999

19 Cloud flashes label C

20-24 Cloud flashes 0-29999

25 Total flashes label T

26-30 Total flashes 0-29999

31 Carriage return <CR>

32 Line feed <LF>

2 33 Overhead strokes label o

34-38 Overhead strokes 0-29999

39 Near strokes label n

40-44 Near strokes 0-29999

45 Distant strokes label d

46-50 Distant strokes 0-29999

51 Cloud strokes label c

52-56 Cloud strokes 0-2999

57 Total strokes label t

58-62 Total strokes 0-29999

63 Carriage return <CR>

64 Line feed <LF>

3 65 Passed self-tests label p

66-70 Passed self-tests 0-29999

71 Failed self-tests label f

72-76 Failed self-tests 0-29999

77 Lost real strokes label l

78-82 Lost real strokes 0-29999

83 Lost simulated strokes label l

84-88 Lost simulated strokes 0-29999

89 Total of row label t

90-94 Total of row 0-29999

95 Carriage return <CR>

96 Line feed <LF>

C Format String: "O%5uN%5uD%5uC%5uT%5u\n"

"o%5un%5ud%5uc%5ut%5u\n"

"p%5uf%5ul%5ul%5ut%5u\n"

Example: O 7N 1D 2C 2T 12<CR><LF>

o 35n 1d 7c 2t 45<CR><LF>

p 16f 0l 0l 0t 16<CR><LF>
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Change 1 16-19

16.4.3.4 Perform Self-test. The sensor performs a self-test every 30 minutes; the status byte in the Present

Weather message indicates the results of the most recent self-test. The host computer may initiate a self-test

at any time by sending the ASCII character C to the sensor. The results of the self-test are described in

table 16.4.4.

Table 16.4.4. Response to Command C: Self-test Message

Byte Description Value 

1 Self-test result P = passed

F = failed

? = no self-test performed

P F ?

2-3 Status byte (see section 5.2.5.3.1) 00-FF

4 Hex radix delimiter H

5 Carriage return <CR>

6 Line feed <LF>

C Format String: "%c%2xH\n"

Example: PC6H<CR><LF>

Self-test commands that are issued too frequently may interfere with the reception of natural lightning

signals. If a natural lightning signal is “in process” at the time that a self-test command is issued, the sensor

completes the processing of the natural lightning signal.

The self-test may fail during a thunderstorm because of high levels of background noise. Therefore,self-test

results should be ignored during thunderstorms until all lightning counts have aged out of the count fields.

The host computer must monitor and make decisions about the status byte that is shown in the present

weather message.

16.4.3.4.1 Self-test Status Byte. The eight-bit status byte gives information about the state of the

electronics and power supplies in the sensor. The status byte, contained in the response to the ASCII

character C, can be scanned for diagnostic information about the sensor as shown in table 16.4.5. 

Table 16.4.5. Self-test Status Byte

7 6 5 4 3 2 1 0 Bit

0: Input voltage greater than approximately 11V

1: Input voltage less than approximately 11V, analog board shutdown

0: Input voltage greater than approximately 13V

1: Input voltage less than approximately 13V

0: Sensor is in reset mode

1: Sensor is running

0: Sensor is ready for lightning

1: A stroke is being processed

0: 5V supply OK

1: 5V supply low

0: 10V supply OK

1: 10V supply low

1: Always 1

1: Always 1
ASOS Site Technical Manual S100

16-20 Change 1

16.4.3.5 Perform Reset. Turning power on and off resets the sensor. As an alternative, the host computer

may issue a reset command (the ASCII character D) to cause the sensor to reset (CPU and hardware).

Because this command resetsthe sensor, no serial response isissued fromthe sensor. Otherthan for EPROM

program storage and DIP switches for option selection, there is no nonvolatile memory in the sensor.

16.4.3.6 Perform Type Test. A type test has been included in the Host mode command set to allow

troubleshooting of communications links. The type test is initiated by sending the ASCII character E to the

sensor. The type test output is shown in table 16.4.6.

Table 16.4.6. Response to Command E: Type Test Output

Byte Description Value 

1-37 Test string ABCDEFGHIJKLMNOPQRSTUVWXYZ O123456789

38 Carriage return <CR>

39 Line feed <LF>

C Format String: "ABCDEFGHIJKLMNOPQRSTUVWXYZ 0123456789\n"

Example: ABCDEFGHIJKLMNOPQRSTUVWXYZ 0123456789<CR><LF>

16.4.3.7 Send System Run Time. The sensor has a system clock which indicates the length of time the

sensor firmware has been running. The system clock message, described in table 16.4.7, is sent when the

ASCII character F is sent to the sensor by the host.

Table 16.4.7. Response to Command F: System Run Time Message

Byte Description Value 

1 Days label D

2-4 Days 0-999

5 Hours label H

6-7 Hours 0-24

8 Minutes label M

9-10 Minutes 0-59

11 Seconds label S

12-13 Seconds 0-59

14 Carriage return <CR>

15 Line feed <LF>

C Format String: "D%3uH%2uM%2uS%2U\n"

Example: D 0H 1M26S 6<CR><LF>

16.4.4 DIAGNOSTIC TESTS

Using SW100, the user may select diagnostic tests, units of measure for ground discharge range estimates,

and the aging interval. The switch settings in SW100 for diagnostic tests are shown in table 16.4.8. The

diagnostic tests are further described in the following paragraphs. Once a diagnostic has been entered, the

only way to exit the diagnostic is to change the switches and reset the sensor. 
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Change 1 16-21/ (16-22 blank)

Table 16.4.8. SW100 Switches 1-3: Diagnostic Tests

SW100

1 2 3 Diagnostic Test

Up Up Up Normal operation

Up Up Down Self-test @ 1 per second

Up Down Up Echo test

Up Down Down Watchdog timer test

Down Up Up Switch test

Down Up Down Type test

Down Down Up Reserved

Down Down Down Reserved

16.4.4.1 Self-test. The self-test diagnostic (switch 1 Up,switch 2 Up, and switch 3 Down on SW100) causes

a self-test to occur once persecond. Self-testresults are transmitted (in hex) every second, one result perline.

Note that there are certain sensor failure modes that prevent it from performing a self-test.

16.4.4.2 Echo Test. The echo test (switch 1 Up, switch 2 Down, and switch 3 Up on SW100) continuously

polls the receiver of the serial port for input from the attached terminal or computer. In the echo test, every

character sent to the sensor is sent back (retransmitted or “echoed”) to the terminal, and carriage returns are

expanded to a carriage return/line feed. Since there are no spaces inserted between echoed characters, what

is typed is what is echoed. The echo test may be useful for troubleshooting problems with data

communications links.

16.4.4.3 WatchdogTimerTest.To prevent theCPUfromremaining in a hung-up or non-running condition,

a timer (referred to as the watchdog timer) is implemented in the hardware to periodically issue a reset to the

CPU. The watchdog timer test (switch 1 Up, switch 2 Down, and switch 3 Down on SW100) puts the CPU

into an idle state that allows the watchdog timer to reset it. Failure of this test implicates the watchdog timer

function of the CPU on the processor board.

16.4.4.4 Switch Test. The switch test (switch 1 Down, switch 2 Up, and switch 3 Up on SW100)

continuously reads each of the switches in SW101 and SW100 and displays their values in hex each time

they change. This test also causes the status byte to be read and output.

16.4.4.5 Type Test. The type test (switch 1 Down, switch 2 Up, and switch 3 Down on SW100) causes a

continuousstring of alphanumeric charactersto be sent out the serial port. The type test is usefulfor checking

out communications links between the sensor and the host computer, data terminal, or data collection

platform. Because there is no delay inserted between transmissions, slow computers may experience

buffering problems with this test.
S100 ASOS Site Technical Manual

Change 1 16-23

SECTION V. MAINTENANCE

16.5.1 INTRODUCTION

This section provides preventive and corrective maintenance procedures for the thunderstorm sensor.

Preventive maintenance consists of sensor inspection, cleaning (if necessary), and desiccant replacement.

Corrective maintenance consists of fault isolation using the ASOS thunderstorm screen and removing and

replacing sensor field replaceable units (FRUs) or removing and replacing the sensor.

16.5.2 PREVENTIVE MAINTENANCE

The thunderstormsensorisinspected and cleaned every 90 days. Sensor desiccant isreplaced annually.Table

16.5.1 provides the procedure for sensor inspection, cleaning, and desiccant replacement.

16.5.3 CORRECTIVE MAINTENANCE

Thunderstorm sensor corrective maintenance consists of troubleshooting failures and sensor FRU removal

and replacement. The technician can review the sensor's test data via Thunderstorm sensor Screen on the

OID. For most failures, the diagnostic identifies the faulty field replaceable unit (FRU). The technician can

also communicate with the sensor directly by connecting a laptop computer to the sensor. 

16.5.3.1 Using the Laptop Computer With the Thunderstorm Sensor. In order to communicate with the

sensor, the maintenance technician must use the laptop computer. Table 16.5.2 providesthe procedure to set

up the laptop computer to communicate with the sensor. Section IV, paragraph 16.4.3 provides detailed

descriptions of individual sensor commands.

16.5.3.2 Troubleshooting. The OID Thunderstorm sensor maintenance screen is the primary

troubleshooting tool. Although diagnostic commands can be issued directly from the laptop computer, these

commands provide no additional information other than what is displayed on the OID. Table 16.5.3 provides

a summary of troubleshooting actions for different failure indications. Remove and replace the sensor when

fault isolation identifies the antenna or electronics module as the source of the failure.

16.5.4 CALIBRATION.

There are no procedures for calibrating the thunderstorm sensor. The sensor must be returned to the

authorized repair facility for calibration

16.5.5 FRU REMOVAL AND INSTALLATION

The thunderstorm sensor consists of an electronics enclosure and three FRUs; Antenna module, electronics

module, and power/comm module. Removal and installation proceduresidentified on the following chart by

table number are provided to facilitate safe and efficient removal of sensor FRU’s. 

Unit to be replaced Table

Antenna Module 16.5.4

Electronics Module 16.5.5

Power/Comm Module 16.5.6

Fiberoptic Module 16.5.7
ASOS Site Technical Manual S100

16-24 Change 1

WARNING

WARNING

Table 16.5.1. Thunderstorm Sensor Inspection and Cleaning

Step Procedure

Tools and Materials Required:

1" Wrench

Soft cotton cloth

Large flat-tipped screwdriver

No. 2 Phillips screwdriver

Death or severe injury may result if power is not removed from sensor prior to maintenance

activities. Ensure that circuit breakers (located inside DCP or SCA equipment cabinet) supplying

power to sensor are set to off (right) position.

1 Set circuit breakers on thunderstorm sensor circuit breaker module inside DCP (SCA) equipment cabinet to

off (right) position. The thunderstorm sensor circuit breaker module is labeled.

2 At thunderstorm sensor, ensure that ground wires and connections are short, direct, and electrically

continuous. Grasp wire near ground clamps and pullslowly and firmly to verify attachment.Repeat on ground

rod end of wire. If connection isloose, tighten it using appropriate tools. Ensure that all grounding hardware

and ground connections are free of corrosion. Replace grounding hardware thatshows any signs of corrosion.

3 Inspect two sensor enclosure lid hold-down clamps. Verify that each is securely in place on edge of lid.

Inspect all enclosure-to-mast mounting hardware for corrosion and replace weakened fasteners. Tighten any

loose mounting hardware screws.

4 Wipe dust off optical sensor at tip of antenna with a damp, soft cloth.

5 Inspect all electronic components in sensor enclosure and electronics module that are easily visible. Check

for cracked, discolored, charred, or broken components and for darkening of the printed circuit boards,

especially under components mounted directly on a board.

6 Verify that transient suppressors (MOVs) on power line (CR1, CR2. CR3. and CR4 in figure 16.3.1) on

power/comm module are not damaged. Burn marks, cracking, and/or external carbon are evidence of failure.

Slight damage to these devicesis cumulative as they shunt brief transients to ground. A prolonged surge will

blow power input circuit fuse. Eventually, transientsuppressorslose heat dissipation and recovery properties

and will fail (short) and open the fuse after shunting a transient.

7 If desiccant has not been replaced for a year, replace desiccant, and properly reseal enclosure. New desiccant

bag must be removed from airtight outer packaging (DO NOT open desiccant bag containing desiccant

granules) and flattened by shaking and patting to evenly distribute contents and place on top ofthe electronics

module. Ensure that desiccant bag does not interfere with door or other internal assemblies. 

Table 16.5.2. Using the Laptop Computer With the Thunderstorm Sensor

Step Procedure

INITIAL SETUP PROCEDURE

Tools Required:

Laptop computer with PROCOMM Plus installed

Laptop interface (Y-shaped) cable

Laptop null cable

Large flat-tipped screwdriver

No. 1 Phillips screwdriver

No. 2 Phillips screwdriver

Death or severe injury may result if power is not removed from sensor prior to maintenance activities.

Ensure that circuit breakers(located insideDCP or SCAequipment cabinet)supplying powerto sensor

are set to off (right) position.

1 At DCP (SCA) equipment cabinet, set thunderstorm sensor circuit breaker module to off (right) position.
S100 ASOS Site Technical Manual

Change 1 16-25

Table 16.5.2. Using the Laptop Computer With the Thunderstorm Sensor -CONT

Step Procedure

2 Using No. 2 Phillipsscrewdriver, loosen two captive boltssecuring hinged sensor access door and open door.

3 Using No. 1 Phillips screwdriver, disconnect DB-9 connector J4 from power/comm P4.

4 Using laptop computer null cable and interface (Y-shaped) cable, connect RS-232C (COM1) port of laptop

computer to DB-9 connector removed from fiberoptic module. 

5 Turn on laptop computer and initialize PROCOMM Plus program. After program initializes, press any key

to enter terminal mode (blank) screen.

6 Using ALT-S command (setup facility), set up the following terminal options:

a. Terminal emulation: VT220

b. Duplex: FULL

c. Soft flow control (XON/XOFF): OFF

d. Hard flow control (CTS/RTS): OFF

e. Line wrap: OFF

f. Screen scroll: ON

g. CR translation: CR

h. BS translation: NON-DESTRUCTIVE

i. Break length (milliseconds): 035

j. Enquiry: OFF

k. EGA/VGA true underline: OFF

l. Terminal width: 80

m. ANSI 7 or 8 bit commands: 8 BIT

7 Press ESC key to exit to terminal mode (blank) screen.

8 Using ALT-P command (line/port option), set current settings as follows:

a. Baud rate: 9600

b. Parity: NONE

c. Data bits: 8

d. Stop bits: 1

e. Port: COM1

9 Press ESC key to exit to terminal mode (blank) screen

10 Set laptop computer CAPS LOCK to ON.

11 Set circuit breakers on thunderstorm sensor circuit breaker module inside DCP (SCA) equipment cabinet to

on (left) position

12

NOTE

Bad,spurious, erroneous, or false data may be transmitted from sensor when power isturned

on or off. Ignore all data transmissions from sensor that occur at power on or power off.

The thunderstorm sensor is now available for legal commands from the laptop computer. Refer to

paragraph 16.4.3 for detailed descriptions of sensor commands and for specific restrictions on their use. 

TEARDOWN

1 At laptop computer, press ALT-X (exit) to exit PROCOMM Plus.

2 Turn off laptop computer.

3 At DCP (SCA), set thunderstorm sensor circuit breakers on circuit breaker module to off (right) position.

4 Disconnect cables between laptop computer and thunderstorm sensor. 

5 Using No. 1 Phillips screwdriver, connect DB-9 connector J4 to power/comm P4.

6 Using No. 2 Phillips screwdriver, close and secure thunderstorm sensor access door.

7 At DCP (SCA), set thunderstorm sensor circuit breakers on circuit breaker module to on (left) position.
ASOS Site Technical Manual S100

16-26 Change 1

Table 16.5.3. Thunderstorm Sensor Troubleshooting

Symptom What to Do

Sensor does not respond

(communications failure)

If TXD LED (figure 16.3.1) and RXD LED on electronics module processor board are

not active, electronics module is bad. Replace sensor.

If the TXD LED and RXD LED on power/comm module are not active, but the TXD

LED and RXD LED on the processor board in the electronics module are active, the

power/comm module is bad or the DC cable is bad. Replace the power/comm module

first; if the TXD LED and RXD LED are still not active, replace the DC cable.

If both sets of LEDs are active, the fiberoptic modem or cable is bad. Replace fiberoptic

modem or cable.

Electronics module Processor Board Enable signal

(ENA LED, figure 16.3.1)

shows unusual activity

(e.g., the ENA LED is lit

when there is no lightning

activity or is not lit when

there is lightning activity)

Disconnect antenna to see if abnormal enable signal activity is internally caused or

externally caused.If activity persists when antenna is disconnected, cause isinternal, and

electronics module is bad. Replace sensor.

If the activity does not persist when antenna is disconnected, cause is external (external

electric field problem), and site must be changed or fixed. Change or fix site.

Fuse failure Indicates a power supply or a transient suppression circuit problem. Replace

power/comm module.

Lightning is not detected

but self-tests are passed

Check optical sensor for opaque covering such as dirt, mud, bird droppings, etc.

Clean optical sensor.

Electronics module Processor Board Opticalsignal

(OPT LED (figure 16.3.1)

shows unusual activity

(e.g., the OPT LED is lit

when there is no lightning

activity or is not lit when

there is lightning activity)

Place a cover over optical sensor. If activity stops, problem is external. If activity

persists, cause is probably internal or may be an external electric field problem. An

external electric field problemusually causes unusual activity on the enable signal(ENA

LED) on electronics module processor board as well. Replace sensor or change/fix site.

Electronics Module Processor board RUN LED

(figure 16.3.1) blinks or is

not lit but power supplies

are OK

Indicates an electronics module problem. Replace sensor.

Self-test failure 

(failed self-test result)

Indicates an electronics module problem. Replace sensor.

Self-test failure

(no self-test performed)

Indicates an Antenna Module or electronics module problem. Replace sensor.

Voltage failure (5 VDC or

10 VDC)

Indicates an electronics module problem. Replace sensor.

Voltage failure (12 VDC

measures below 11 VDC or

above 13 VDC)

Indicates a power supply problem if input voltage is OK. Replace power/comm module

if input AC power is OK; otherwise, determine cause of AC failure.
S100 ASOS Site Technical Manual

Change 1 16-27

WARNING

WARNING

Table 16.5.4. Electro-optical Antenna Removal and Installation

Step Procedure

REMOVAL

Tools Required:

No. 2 Phillips screwdriver

Death or severe injury may result if power is not removed from sensor prior to maintenance activities.

Ensure that circuit breakers(located insideDCP or SCAequipment cabinet)supplying powerto sensor

are set to off (right) position.

1 At DCP (SCA) equipment cabinet, set thunderstorm sensor circuit breaker module to off (right) position.

2 At thunderstorm sensor, use No. 2 Phillips screwdriver to loosen two captive bolts securing hinged sensor

access door and open door. 

3 Disconnect plug P104 from electronics module J104.

4 Disconnect ground spade lug from bottom of coupler.

5 Loosen hex nut on liquid tight coupler.

6 Remove antenna from enclosure.

INSTALLATION

Tools Required:

No. 2 Phillips screwdriver

Death or severe injury may result if power is not removed from sensor prior to maintenance activities.

Ensure that circuit breakers (located inside DCP or SCA equipment cabinet) supplying power to sensor

are set to off (right) position.

1 At thunderstormsensor, arrange antenna cable to hang freely frombottomof antenna housing. Carefully feed

connector end of cable into liquid-tight coupler and pull cable through to inside of enclosure and guide

antenna end into opening in liquid-tight coupler. While holding antenna perpendicular to top of enclosure,

slowly and gently push antenna into liquid-tight coupler until fully seated as shown in figure 16.2.2.

2

CAUTION

Failure to properly tighten the nut on the liquid-tight coupler will result in moisture damage

to the sensor.

Hand tighten hex nut on liquid-tight coupler.

3 Route antenna cable under clamps and connect J104 to electronics module P104 as shown in figure 16.2.3.

4 Connect spade lug to ground terminal located below the antenna mounting coupler.

6 Using No. 2 Phillips screwdriver, close and secure thunderstorm sensor access door.

7 At DCP (SCA), set thunderstorm sensor circuit breakers on circuit breaker module to on (left) position.
ASOS Site Technical Manual S100

16-28 Change 1

WARNING

WARNING

Table 16.5.5. Electronics Module Removal and Installation

Step Procedure

REMOVAL

Tools Required:

No. 2 Phillips screwdriver

Death or severe injury may result if power is not removed from sensor prior to maintenance activities.

Ensure that circuit breakers(located insideDCP or SCAequipment cabinet) supplying power to sensor

are set to off (right) position.

1 At DCP (SCA) equipment cabinet, set thunderstorm sensor circuit breaker module to off (right) position.

2 At thunderstorm sensor, use No. 2 Phillips screwdriver to loosen two captive bolts securing hinged sensor

access door and open door. 

3 Remove J103 and J104 from electronics module connectors P103 and P104.

4 Disconnect electronics module chassis ground strap from spade lug near door hinge.

5 Slide clamps at top of electronics module securing module to front cover and remove module.

INSTALLATION

Tools Required:

No. 2 Phillips screwdriver

Death or severe injury may result if power is not removed from sensor prior to maintenance activities.

Ensure that circuit breakers(located insideDCP or SCAequipment cabinet)supplying powerto sensor

are set to off (right) position.

1 At thunderstorm sensor, position electronics module on front cover and slide top clamps to secure module.

2 Connect electronics module chassis ground strap to spade lug near door hinge.

3 Route antenna cable under clamps as shown in figure 16.2.3.

4 Connect J103 and J104 to electronic module connectors P103 and P104.

5 Using No. 2 Phillips screwdriver, close and secure thunderstorm sensor access door.

6 At DCP (SCA), set thunderstorm sensor circuit breakers on circuit breaker module to on (left) position.
S100 ASOS Site Technical Manual

Change 1 16-29

WARNING

WARNING

Table 16.5.6. Power/Comm Board Removal and Installation

Step Procedure

REMOVAL

Tools Required:

Large flat-tipped screwdriver

No. 2 Phillips screwdriver

Death or severe injury may result if power is not removed from sensor prior to maintenance activities.

Ensure that circuit breakers(located insideDCP or SCAequipment cabinet)supplying powerto sensor

are set to off (right) position.

1 At DCP (SCA) equipment cabinet, set thunderstorm sensor circuit breaker module to off (right) position.

2 At thunderstorm sensor, use No. 2 Phillips screwdriver to loosen two captive bolts securing hinged sensor

access door and open door. 

3 At power/comm board, loosen four thumb screws securing plexiglassshield over powerstrip P1 and remove

shield.

4 Tag and disconnect five 115V ac power connectors from P1.

5 Disconnect cables J4, J3, and J2 from connectors P4, P3, and P2.

6 At power/commmodule, using ccw rotation, remove two fiberoptic cables from bottom of fiberoptic module.

Install plastic protective covers over board connectors.

7 Loosen four captive screws and remove power/comm board from power/comm module.

INSTALLATION

Tools Required:

Large flat-tipped screwdriver

No. 2 Phillips screwdriver

Death or severe injury may result if power is not removed from sensor prior to maintenance activities.

Ensure that circuit breakers(located inside DCP or SCA equipment cabinet) supplying power to sensor

are set to off (right) position.

1 At thunderstormsensor, position power/commboard on power/commmodule and tighten four captive screws

securing board to module.

2 Connect cables J4, J3, and J2 to connectors P4, P3, and P2.

3 Connect five 115V ac power connectors to P1.

4 Position plexiglass shield over power strip P1 and secure by tightening four thumb screws.

5 Remove any protective covers from fiberoptic connectors and install the receive (RX) and transmit (TX)

connectors on fiberopticmodule.RXcablemates with fiberoptic connector nearest DB-9 electrical connector.

6 Using No. 2 Phillips screwdriver, close and secure thunderstorm sensor access door.

7 At DCP (SCA), set thunderstorm sensor circuit breakers on circuit breaker module to on (left) position.
ASOS Site Technical Manual S100

16-30 Change 1

WARNING

WARNING

Table 16.5.7. Fiberoptic Module Removal and Installation

Step Procedure

REMOVAL

Tools and Materials Required:

Flat-tipped screwdriver 

 Small flat-tipped screwdriver

 No. 1 Phillips screwdriver

 No. 2 Phillips screwdriver

Death or severe injury may result if power is not removed from sensor prior to maintenance activities.

Ensure that circuit breakers(located insideDCP or SCA equipment cabinet) supplying power to sensor

are set to off (right) position.

1 At DCP (SCA) equipment cabinet, set thunderstorm sensor circuit breaker module to off (right) position.

2 At thunderstorm sensor, use No. 2 Phillips screwdriver to loosen two captive bolts securing hinged sensor

access door and open door. 

3 At power/commmodule, using ccw rotation, remove two fiberoptic cables from bottom of fiberoptic module.

Install plastic protective covers over board connectors.

4 Using No. 1 Phillipsscrewdriver, remove screws securing fiberoptic module mounting plate to power/comm

module.

5 Using small flat-tipped screwdriver, loosen two retaining screws on DB-9 connector located on top of

fiberoptic module. Remove DB-9 connector.

6 Using No. 1 Phillips screwdriver, remove screws securing fiberoptic module to mounting plate. Remove

fiberoptic module.

INSTALLATION

Tools and Materials Required:

 Flat-tipped screwdriver

 Small flat-tipped screwdriver

 No. 1 Phillips screwdriver

 No. 2 Phillips screwdriver

Death or severe injury may result if power is not removed from sensor prior to maintenance activities.

Ensure that circuit breakers (located in DCP) supplying power to sensor are set to off (right) position.

1 Position fiberoptic module and gaskets on mounting plate. Using No. 1 Phillips screwdriver, install screws

and lockwashers securing fiberoptic module to mounting plate.

2 Install signal cable removed in removal step 5 to DB-9 connector on fiberoptic module and using small

flat-tipped screwdriver, tighten two retaining screws.

4 Using No. 1 Phillips screwdriver, secure fiberoptic module mounting plate to power/comm module.

3 Remove any protective covers from fiberoptic connectors and install the receive (RX) and transmit (TX)

connectors on fiberoptic module. RX cable mates with fiberoptic connector nearest DB-9 electrical connector.

4 Using No. 2 Phillips screwdriver, close and secure thunderstorm sensor access door.

5 At DCP (SCA), set thunderstorm sensor circuit breakers on circuit breaker module to on (left) position.
S100 ASOS Site Technical Manual

17-1

CHAPTER 17

MAINTENANCE DRAWINGS

17.1 INTRODUCTION

This chapter describes the use of ASOS oversize maintenance drawings, including detailed block

diagrams, power distribution diagrams, and cabling interconnect diagrams. These drawings are provided

with and support the theory of operation provided in Sections IV of the previous chapters. The drawings

are intended to aid in the understanding of ASOS system operation and to assist maintenance personnel

in the troubleshooting and repair of affected assemblies.

17.2 DRAWING FORMAT

Explanations of the symbology and referencing methods used in the maintenance drawings are provided

to facilitate their use. Simplified block diagrams show a basic level operating relationship of individual

assemblies and are straightforward in presentation. The basic processing depicted in the simplified block

diagrams is expanded upon and presented in detailed block diagrams. The detailed block diagrams depict

specific signal and data processing by using certain drawing conventions to simplify the circuitry and

assemblies involved. This simplification provides an easier means to understand the more complex

circuit operations. The drawing format and conventions used for the detailed block diagrams are depicted

in a sample provided as figure 1. This sample shows typical applications of the drawing conventions,

each of which is described in following paragraphs. All pin-to-pin wiring is shown on the detailed block

diagrams, including circuit board, panel, assembly, and cable pin numbers. Mnemonics are used to

identify particular signal paths. The mnemonics are derived from engineering source data and typically

indicate the purpose or function of the signal.

17.2.1 Unit Assembly Identification (1, Figure 1). The top left corner of the illustration contains the

assembly name of the top level unit. The unit reference designator is also included following the unit

name. The assembly level is indicated through the use of dashed generation lines, with the top level

represented by a solid line.

17.2.2 Subunit Assembly Identification (2). The subunit assemblies are identified by the same method

as the unit assemblies. The assembly name and reference designator are located in the top left corner of

the depicted assembly. The number of dashes in the subunit assembly generation lines represents the

assembly level. For example, the first subunit level uses a single-dash line, second subunit level uses a

two-dash line, etc.

17.2.3 Circuit Board Assembly Identification (3, Figure 1). The top left corner of the illustrated box

contains the circuit board assembly name and reference designator. For rack-mounted circuit boards, the

reference designator depicts the physical location of the board in the card rack. For example, the

reference designator A6 indicates that the board is located in the sixth card slot of the card rack.

17.2.4 Functional Representation of Circuitry (4). Circuit elements or groups of circuit elements in a

particular assembly are represented by boxes or simplified logic symbols. These representations do not

suggest the quantity, complexity, or physical appearance of the circuit elements. They do, however,

depict the operational function of the circuitry. When circuitry is functionally represented by a

rectangular box, the box is assigned a name that identifies the purpose or function performed by the

associated circuitry. Signals that interact with the functional boxes and symbols are assigned names to

further identify their purpose or function. Arrowheads are used on signal paths to depict the flow of data
ASOS Site Technical Manual S100

17-2

through the circuitry. The purpose of the functional diagrams is to describe the basic signal and data flow

through the various functional areas. Therefore, no effort is made to depict the critical timing

relationships essential to the operation of the circuitry.

17.2.5 Intrafunctional Referencing (5). When signal connections cannot be shown in their entirety

because a circuit is depicted on more than one sheet, a reference letter is assigned to the signal line. This

letter matches a letter on a following sheet and locates the continuation of the signal path. At the source,

the letter follows the signal line; at the destination, the letter precedes the signal line.

17.2.6 Bundled Signals (6). For ease of routing, both internally and externally to circuit board

assemblies, multiple signal lines are often bundled into a single representative line. These bundled

signals are then separated as necessary to connect their interface points.

17.2.7 Cable/Connector Identification (7). The drawings depict all interfunctional equipment cabling.

The cable number and its connector designations are identified adjacent to the associated

cable/connector. In instances where only a portion of a particular cable or assembly is shown, the

designation P/O (to indicate part of) is used.

17.2.8 Signal Names (8). The signal mnemonics used at the input and output connections of the

electronics assemblies are the same signal names used in the engineering source data. The signal

mnemonics are generally an abbreviation of the signal's function. In addition, as in the case of address

and data bus signals, numbers may be incorporated into the mnemonic. These numbers are used to

indicate bit position, or bit weight, of that signal with respect to the associated signals. In this convention,

the lower the number, the lower the bit weight. For example, the signal MDAT0 represents the least

significant bit, while MDAT15 represents the most significant bit. The active state of a signal or voltage

level may also be indicated by the mnemonic. This is typically indicated by a + or - sign in the signal

name.

17.2.9 Supplementary Names (9, Figure 1). Occasionally, a given signal or group of signals performs

one or more particular functions with a circuit. The mnemonic for the signal may also not readily indicate

the particular function. For these reasons, supplemental names or mnemonics are assigned to signals

internal to the circuit assembly. In instances where the supplemental name and the actual signal name

appear together, the supplemental name is contained within parentheses.

17.2.10 Connector Pin Numbers (10). Signals applied to circuit board or cable connectors have the pin

designation identified. These pin identifications may consist of either letters or numbers and reflect the

identification markings on the physical cable or connector.

17.2.11 Interfunctional Referencing (11). The signal interfacing with other functional areas of the

system is shown by references to the titles of those areas. In these instances, the associated area is

identified by both name and figure number when possible. For signals that interface with equipment other

than ASOS equipment, only a general name of the associated area is referenced.
S100 ASOS Site Technical Manual

Figure 1. ASOS Drawing Format and

Conventions

17-3/(17-4 blank)
S100 ASOS Site Technical Manual

18-1

CHAPTER 18 $

STANDARD ASOS PARTS LIST

18.1 INTRODUCTION $

$

This parts list provides a listing of field replaceable units (FRU’s) and related items used to maintain ASOS $

systeminstallations at the organizational level of maintenance by field service technicians. This partslist has $

been modified from previous versions of the ASOS Site Technical Manual in order to present a clearer $

description of each item while reducing unnecessary clutter. The All the items in this list can also be found $

in the NWS Engineering Handbook No.1. $

$

NOTE $

This parts list is subject to change but is current as of August 25, 2000. Refer to EHB-1 $

for continuing updates. $

$

18.2 DESCRIPTION OF PARTS LIST $

$

The ASOS parts list provides a list of items located within the major assemblies of the ASOS $

installations. Each item is identified by its National Stock Number (NSN), Agency Stock Number $

(ASN), and description. The entire list as a whole is sorted by the ASN column. $

$

18.2.1 Agency Stock Number (ASN). This column identifies the unique number assigned by the NWS $

to identify equipment, components, supplies, etc. $

$

18.2.2 National Stock Number (NSN). This column identifies the unique identifier assigned to each $

stock item. It is normally a federally asigned number comprised of a Federal Supply Class (FSC), North $

Atlantic Treaty Organization (NATO) code, and a sequential number cataloged in the Federal Supply $

Cataloging System. $

$

18.2.3 Description. This column is used to provide some description of each item. $

$

18.3 SOFTWARE VERSION COMPATIBILITIES $

$

Before replacing any CPU, Memory, or Voice cards, consult the following table for compatibility $

between the software versions (example: to upgrade the ACU memory to version 2.6, you must also $

upgrade the ACU CPU to 1.81, the ACU Voice card to 4.0, and the the DCP CPU to 1.90). $

$

Table 18.1 Software Compatibilities $

ACU/SCA $

MEMORY

ACU/SCA

CPU $

ACU/SCA

VOICE

DCP 

CPU

2.4 1.81 3.0 1.70 $

2.42 1.81 3.0 N/A $

2.49 1.81 3.0 1.80 $

2.6 1.81 4.0 1.90 $
ASOS Site Technical Manual S100

18-2 Change 2

ASN NSN Description

S100-1-1 6660-01-390-2144 ACU cabinet

S100-10-1 5895-01-368-4615 2440 Modem

S100-10-2 5895-01-368-4614 V.3225 Modem

S100-10-3 5920-01-438-3444 AC Wall Mount, RJ-11 Surge Protector

S100-10-4 5895-01-462-1911 Stand Alone 28.8 High Speed Modem

S100-102A1 5975-01-452-0552 Electrical Equipment Cabinet

S100-11-1 5895-01-390-2666 OID Keyboard

S100-11-1A 7025-01-451-6477 OID Keyboard

S100-11-2 7025-01-424-0696 OID Monitor

S100-12 7025-01-368-4592 Panasonic Printer, Model KX-P1180I

S100-12-2 7025-01-411-9533 Panasonic Printer, Model KX-P3123

S100-1A1-1 5895-01-364-6861 CODEX Modem

S100-1A1-2 5895-01-364-6864 Premium CODEX Modem

S100-1A10 5820-01-369-1352 GTA Radio Transmitter, VHF Model CM-200VT

S100-1A1A1-1 5895-01-411-9983 CODEX Flex Cartridge

S100-1A1A1-2 5895-AS-200-0067 Premium CODEX Flex Cartridge

S100-1A2-T 5985-01-462-7521 VME Terminator

S100-1A2A1 5998-01-368-8655 CPU Board

S100-1A2A1-U29 5962-AS-200-0155 ACU CPU EPROM, Revision 1.81

S100-1A2A11 5975-01-472-8456 VME Front Panel with Handle

S100-1A2A13-1 5998-01-390-2153 A/D Converter Board, Model XVME590/1

S100-1A2A14 5905-01-431-8054 VME Resistor Board

S100-1A2A15-1 5998-01-390-2151 Digital I/O Board

S100-1A2A16 5998-01-368-8654 Graphics Counter

S100-1A2A20 5998-01-390-2148 Voice Processor, VR-9800

S100-1A2A20-U11A 7025-AS-000-0160 Voice Processor EPROM, Revision 3.0

S100-1A2A20-U11B NWS9-81-410-0002 Voice Processor EPROM, Revision 4.0

S100-1A2A3 5998-01-368-8651 ACU Memory Board, XVME-110/1

S100-1A2A3-U8B NWS9-61-140-0002 ACU Memory EPROMs, Revision 2.40

S100-1A2A3-U8D NWS9-81-410-0004 ACU Memory EPROMs, Revision 2.60

S100-1A2A5 5998-01-368-8653 Serial I/O Board, RS422

S100-1A2A6-1 5998-01-368-8652 Serial I/O Board, RS232

S100-1A2MP2 5340-01-472-7674 Line Driver Mounting Plate
S100 ASOS Site Technical Manual

Change 2 18-3

S100-1A2MP3 5340-01-472-7676 Line Driver Mounting Plate

S100-1A3 5895-01-358-4452 ACU Modem Rack Assembly

S100-1A3A1 5895-01-368-8662 Rack Mount 2440 Modem

S100-1A3A1-2 5895-01-308-2794 Rack Mount V.3225 Modem

S100-1A3A1-3 5895-01-445-3519 Rack Mount 28.8 Modem (High Speed)

S100-1A3A13 5998-01-368-8657 ACU Rack Mount Line Driver

S100-1A3PS1 6130-01-299-2561 ACU Modem Rack Power Supply

S100-1A3XA1 5935-01-389-8232 Rack Mount Modem Adapter; 1 DB25, 1 RJ-45

S100-1A3XA2 5895-01-450-8660 Rack Mount Modem Adapter: 1 DB25, 2 RJ-25

S100-1A4A1 5998-AS-000-0015 UPS Status Panel Board, SOLA

S100-1A4A1-2 6130-01-411-5252 UPS Power Supply, DELTEC

S100-1A4A1MP3 5975-01-411-9547 UPS Mounting Strap, DELTEC

S100-1A4A2-1 5998-01-369-4730 UPS RS232 Interface Board, SOLA

S100-1A4A3 5915-01-389-3012 UPS 1.5 KVA Filter Board, SOLA

S100-1A4A4 5998-01-368-4595 UPS 1.5 KVA Inverter Board, SOLA

S100-1A4CB1 5925-01-389-6136 UPS 20 Amp Circuit Breaker, SOLA

S100-1A4F1 5920-00-998-2231 UPS Fuse, SOLA

S100-1A4S1 5895-01-411-9538 UPS Power Switch, SOLA

S100-1A4T1 5950-AS-000-0014 UPS 1.5 KVA Transformer, SOLA

S100-1A5 6130-01-454-5212 DC Power Supply Enclosure

S100-1A5B2 4140-01-407-3985 5 Bladed Axial Tube Fan (Power Supply Fan)

S100-1A5PS1 6130-01-368-8643 DC Power Supply

S100-1A6-MP2 4930-01-451-6809 Static Pressure Vent

S100-1A6A1 6685-01-368-4611 Setra Model 470 Pressure Sensor

S100-1A6A1-1 6685-01-424-0671 Setra Model 470-T Pressure Sensor

S100-1A6A1-2 6110-01-423-1328 External Threshold Detector

S100-1A6A4-3 5895-01-381-0769 RF Modem, 410.075 MHz (Motorola)

S100-1A6A4-4 5895-01-381-0771 RF Modem, 410.950 MHz (Motorola)

S100-1A6A4-5 NWS9-81-880-0007 RF Modem, 410.075 MHz (Johnson Data)

S100-1A6A4-6 NWS9-81-880-0008 RF Modem, 410.950 MHz (Johnson Data)

S100-1A6A6 5895-01-449-8433 LD1/LD2 Switching Board

S100-1A6MP1 4330-AS-200-0140 Pressure Vent Kit

S100-1A6MP10 4720-00-818-3478 Pressure Vent Tubing

S100-1A6MP12 5340-01-277-5032 ACU Mounting Bracket, 4" Long
ASOS Site Technical Manual S100

18-4 Change 2

S100-1A6MP13 5340-01-242-5172 ACU Mounting Bracket, 8.5" Long

S100-1A6MP14 5340-01-389-1343 Chassis Slide; 24" long closed, 49"long opened

S100-1A6MP7 4730-00-834-7434 Cross Tube Fitting

S100-1A6MP9 4730-01-286-8840 Insert Tube Fitting

S100-1A6S1 5895-01-411-5106 RF Modem Switch

S100-1A6W1 5995-01-389-2451 ACU RF Modem 1 Cable Assembly

S100-1A6W2 5995-01-389-2470 ACU RF Modem 2 Cable Assembly

S100-1A6W26 5995-01-389-2439 Pressure Sensor Cable Assembly

S100-1A7A12-1 5940-01-390-2561 Terminal Block

S100-1A7A12-20 5940-01-390-2558 Ground Terminal Block

S100-1A7A12MP3 5340-01-389-9815 Din Rail End Clamp

S100-1A7A12MP4 6150-01-389-8917 Conductor Bus

S100-1A7A12MP8 5340-01-389-1349 End Plate

S100-1A7A1MP7 5340-01-390-5846 Din Rail

S100-1A7K1 5945-01-451-6807 ACU Solid-State Time Delay Module

S100-1A8A1-1 6160-01-406-7503 ACU UPS 5-Battery Box, SOLA

S100-1A8A1-2 6160-01-411-4536 ACU UPS 4-Battery Box, DELTEC

S100-1A8BT1 6140-01-389-6178 Battery

S100-1A9-W1 NWS9-60-180-0001 Fiber Optic Cable Assembly, 175'

S100-1A9A1-1 5935-01-426-3801 RJ-11/RS232 Adapter

S100-1A9A5 6110-01-389-2467 Video Surge Protector

S100-1A9A6MP2 5999-01-396-5464 EMI Gasket

S100-1A9A6MP3 5330-01-432-9937 EMI Gasket

S100-1A9J1 5935-01-399-2558 RJ-11 EMI Surge Connector

S100-1A9J22 5935-01-399-2554 EMI Surge Adapter (RS232 DB25 Connector)

S100-1A9J39 5920-01-445-3521 RF Surge Detector

S100-1A9J40 5915-01-389-3113 UPS Output Filter

S100-1A9J41 5915-01-389-3004 AC Line Filter

S100-1A9J9-12 NWS9-93-510-0021 Module Adapter

S100-1A9MP18 4730-00-011-2969 Tube Nipple

S100-1A9W1 5995-01-459-5548 Power Strip Cable Assembly with ACU Power Plug

S100-1A9W12 5995-01-407-8410 ACU RF SW Out Cable Assembly

S100-1ACU-UPS NWS9-93-510-0018 ACU UPS Bypass Kit Assembly

S100-1A9W77 5995-01-446-9779 ACU Adapter Cable
S100 ASOS Site Technical Manual

Change 2 18-5

S100-1B1 4140-01-114-9097 ACU Blower

S100-1E1 5985-01-389-1785 ACU/DCP Antenna Assembly

S100-1E1MP1 5340-01-436-8776 Antenna Mounting Bracket

S100-1E2 5985-01-050-7522 GTA Radio Antenna, Omnidirectional, 50 Ohm 

S100-1E3 5985-01-146-0911 YAGI Antenna

S100-1E3W1 5915-01-440-9260 Band Pass Filter

S100-1MP038 5340-01-389-1338 Blank Cover

S100-1MP039 5340-01-390-1179 Fiber Optic Module Blank Cover

S100-1MP040 5340-01-389-1306 DB25 Blank Cover

S100-1MP16 5310-00-531-1580 Lockwasher, 0.195 X 0.25

S100-1MP17 5305-01-411-9536 Roundhead Screw, 0.31" Long

S100-1W1 5995-01-444-3711 3 Conductor AC Cable

S100-1W11 5995-01-436-8770 Local Sensor Cable Assembly

S100-1W6P1 5935-01-343-8839 Electrical Plug Connector

S100-1W6P2 5935-01-381-8081 Electrical Power Plug

S100-1W72 5995-01-389-2014 TELCO Modem Cable

S100-2-1 5975-01-369-5862 DCP Cabinet, Class I

S100-2-2 5975-01-440-9261 DCP Cabinet, Class 2

S100-2-2MP1 5330-01-457-1202 DCP Gasket, Top

S100-2-2MP2 5330-01-457-1205 DCP Gasket, Bottom

S100-2-2MP3 5330-01-457-1206 DCP Gasket, Side

S100-2-3 5975-01-449-8412 DCP Cabinet, Class2, New Backplate with DELTEC UPS

S100-2-4 5975-01-449-8410 DCP Cabinet, Class 1, with DELTEC UPS

S100-2-OMNI-KIT NWS9-93-510-0019 Omni Antenna Kit

S100-2-UPS-KIT NWS9-93-510-0020 DCP UPS Bypass Kit Assembly

S100-2A131 1290-TM-000-0007 HO83 Sun Shield

S100-2A1A2A1 5998-01-368-8658 CPU Board, with Firmware Revision 1.90

S100-2A1A2A10 5905-01-431-8056 VME Resistor Board

S100-2A1A2A1U29 NWS9-71-550-0001 DCP Firmware Revision 1.80

S100-2A1A2A1U29A NWS9-81-410-0003 DCP Firmware Revision 1.90

S100-2A1A2A3 5998-01-368-4601 XVME-100/02 Memory Board

S100-2A1A2MP01 5998-01-411-7109 VME Back Plane

S100-2A1A2MP10 5340-01-389-1351 Circuit Card Rack Hinge

S100-2A1A2MP6 4140-00-100-4563 Fan Guard
ASOS Site Technical Manual S100

18-6 Change 2

S100-2A1A3A1 5925-01-389-2981 Circuit Breaker Module, Primary

S100-2A1A3A2 5925-01-406-4090 Circuit Breaker Module, Ceilometer

S100-2A1A3A3-1 5925-01-406-4093 Circuit Breaker Module, Freezing Rain Sensor

S100-2A1A3A3CB1 5925-01-432-0547 Circuit Breaker, 0.5 Amp

S100-2A1A3A4 5998-01-368-8649 Circuit Breaker Module, Present Weather Sensor (LEDWI)

S100-2A1A3A5 5998-01-369-4727 Circuit Breaker Module, Tipping Bucket

S100-2A1A3A5CB1 5925-01-462-2209 Circuit Breaker, 6 Amp

S100-2A1A3A6 5998-01-368-4594 Circuit Breaker Module, Wind Sensor

S100-2A1A3A7 5925-01-390-2150 Circuit Breaker Module, Temperature/Dewpoint Sensor

S100-2A1A3A8 5998-01-368-8648 Circuit Breaker Module, Visibility Sensor

S100-2A1A3A9 5925-01-441-7595 Circuit Breaker Module, Thunderstorm Sensor

S100-2A1A3CB9 5925-01-468-3322 Circuit Breaker, 1 Amp

S100-2A1A3MP3-2 5305-00-429-4414 Captive Screw

S100-2A1A3MP4 9510-01-389-6496 Retention Bar

S100-2A1A3MP4-2 5305-00-140-2379 Captive Screw

S100-2A1A4MP7 5340-01-390-5848 Power Distribution Rail

S100-2A1A5A1-1 5895-01-411-9529 Stand Alone Line Driver

S100-2A1B1 4140-01-388-9742 Fan

S100-2A1HR1 4540-01-245-4803 Heater Element

S100-2A1HR2 4540-01-411-8854 Battery Box Heater Pad

S100-2A1K1 5945-01-104-7652 DCP Solid-State Time Delay Relay

S100-2A1MP-1 5340-01-349-5543 Latch

S100-2A1MP-2 5340-01-387-0854 Over-Center Latch

S100-2A1MP59 4010-01-389-4199 Circuit Breaker Panel Lanyard Restraint

S100-2A1S1 5930-01-332-1095 Thermal Switch, 60/40

S100-2A1S2 5930-01-391-2510 Thermal Switch, 70/50

S100-2A1S3 5930-01-391-2511 Thermal Switch, 80/60

S100-2A2A1 6160-01-406-7502 5-Battery Box, SOLA

S100-2A2A1-1 6160-01-411-5230 4-Battery Box, DELTEC

S100-2A2A1A1 6160-AS-200-0111 Battery Box Lid, SOLA

S100-2A2MP12 4730-01-412-0007 Polypropylene Nozzle, Battery Box

S100-2A2MP13 4010-01-411-8857 Battery Box Lanyard

S100-2A3A1-1 6030-01-411-8853 Fiber Optic Modem

S100-2A3A17-10 5940-01-390-2559 Power Distribution Block
S100 ASOS Site Technical Manual

Change 2 18-7

S100-2A3A17MP1 5940-01-389-1644 Terminal Block End Cap

S100-2A3A17MP6 6150-01-389-8905 ACU Power Distribution Mounting Rail, 9.69 X 0.22 X 9.25

S100-2A3MP1 5999-01-389-9559 EMI Gasket, DB-9 Connector

S100-2A3MP2 5999-01-389-9496 EMI Gasket, Power Plug Connector

S100-2A3MP3 5999-01-389-9578 EMI Gasket, Fiber Optic Module Connectors

S100-2A3MP4 5999-01-389-9562 EMI Gasket, TELCO Connector

S100-2A3MP9 5999-01-388-8552 EMI Gasket, Antenna Connector

S100-2A3W10 5995-01-389-3539 DCP Faraday Box Cable Assembly

S100-2A3W42 5995-01-389-2473 DCP Antenna Cable Assembly

S100-2A4A1-1 5920-01-432-2743 Fuse Plug Terminal Block

S100-2A4A1F1 5920-01-431-9363 Fast Blow Fuse, 2.5 Amp, 250 V, 5 X 20 mm

S100-2A4A1F2 5920-01-431-9364 Fast Blow Fuse, 3.15 Amp, 250 V, 5 X 20 mm

S100-2A4A1MP3 5920-01-389-4077 Fuse Plug

S100-2A4A1MP7 5340-01-390-5844 DCP Power Distribution Mounting Rail, 7.5 X 0.25 X 11.0

S100-2A4CR1 5961-AS-000-0063 MBR3535 Diode

S100-2A4CR3 5961-01-016-8485 Motorola Semiconductor

S100-2A4PS1 6130-01-186-4853 +5V Power Supply

S100-2A4PS3 6130-01-390-2201 +12V Power Supply

S100-2A5A1W3 5995-01-407-8411 Class II DCP RF Modem 1 Cable Assembly

S100-2A5A2W4 5995-01-397-6345 Class II DCP RF Modem 2 Cable Assembly

S100-2A5S1W13 5995-01-407-8412 DCP RF SW OUT Cable Assembly

S100-2A6 5975-01-411-7106 AC Junction Box

S100-2A6S1 6210-01-411-8882 Photo Control

S100-2A6XS1 5935-00-232-2576 Receptacle Connector

S100-2A8DS-1 6210-00-223-8477 Hughey & Phillips Obstruction Light

S100-2A8DS1MP1 6210-01-329-2448 UNR-ROHN Lens

S100-2A8DS2 6240-00-842-2887 Incandescent Lamp, C-9, 8000 hours, 120 V, 114 W, 0.950 Amp

S100-2A8MP1-1 5365-01-389-4249 Wind Tower Shim

S100-2A8MP1-2 5920-01-462-7524 Lightning Rod, 72"

S100-2A8MT1A1 6660-01-375-5146 Wind Sensor Enclosure Assembly

S100-2A8MT1A1A1MP1 5330-01-411-3937 Fiber Optic Modem Gasket

S100-2A8MT1A1A1MP2 5330-01-411-3928 Fiber Optic Module Gasket

S100-2A8MT1A1A2-1 5998-01-432-3079 Mod 2 Wind Transmitter Processor Controller Card, Firmware 4.0

S100-2A8MT1A1A2-U7A 5962-01-436-0441 Wind Sensor EPROM, Revision 4.0, Chip U7
ASOS Site Technical Manual S100

18-8 Change 2

S100-2A8MT1A1PS1 6130-01-368-4591 Wind Sensor Power Supply, 5 VDC, 500 mA

S100-2A8MT1A2A1-1 6660-01-411-9548 Mod 2 Wind Speed Transmitter Bottle

S100-2A8MT1A2A2 5895-01-432-3075 Cup Assembly, Small Skirt

S100-2A8MT1A2A2-1 6660-01-424-0664 Cup Assembly, Large Skirt

S100-2A8MT1A2MP1 5310-01-411-5242 Decorative Nut Sleeve

S100-2A8MT1A2MP2 5305-01-389-5960 Setscrew

S100-2A8MT1A2MP3 5310-01-411-9543 Flatwasher, 1" OD

S100-2A8MT1A3A1-1 6660-01-411-9545 Mod 2 Wind Direction Transmitter Bottle

S100-2A8MT1A3A2 6660-01-390-7357 Vane Assembly, Small Skirt

S100-2A8MT1A3A2-1 5985-01-431-9010 Vane Assembly, Large Skirt

S100-2A8MT1A4 5975-01-370-3054 Crossarm Assembly

S100-2A8MT1MP1 5340-01-444-3709 Wind Tower Rain Shield

S100-2A8MT1W1 5995-01-411-9485 Wind System Retrofit Cable Assembly

S100-2A8XDS1 6210-00-060-7321 Obstruction Light Assembly for mounting on 1" pipe

S100-2A8MTKIT01 NWS9-93-510-0003 Mounting Kit

S100-2A9 8145-01-461-8118 Auxiliary Box Assembly (AUX BOX)

S100-2DS1 5980-01-018-6273 Optoelectronic Display

S100-2MP037 4010-01-411-5239 Lanyard

S100-2MP038 4010-01-424-0685 Lanyard, 16" X 0.25 OD

S100-2MP1 5975-01-412-0013 Electronics Equipment Mounting Frame with 2 switches

S100-2MP2 NWS9-80-930-0002 Black Keeper for the DCP

S100-2MT1-1 6660-01-375-4809 Ceilometer with Pole

S100-2MT1-2 NWS0-00-750-0001 Refurbished Ceilometer with Solar Protection Package

S100-2MT1A1 5998-01-420-6855 Data Processor Board, Firmware 2.46

S100-2MT1A2 5998-01-248-3596 Unregulated Power Supply

S100-2MT1A5 5998-01-248-3598 Light Monitor

S100-2MT1A6 5998-01-248-3593 Receiver

S100-2MT1A6-2 5998-01-406-3915 Receiver Filter Board, 30 Degree

S100-2MT1A7 5998-01-248-3594 Transmitter

S100-2MT1B1 4120-01-249-1431 Window Conditioner

S100-2MT1B1MP1 6515-93-000-0019 Ceilometer Adhesive Strips

S100-2MT1HR1 5999-01-352-6561 Heater Foils

S100-2MT1J1 5935-01-115-0215 Ceilometer AC Connector Accessory

S100-2MT1J4 5935-00-403-7661 Ceilometer RS232 Connector Accessory
S100 ASOS Site Technical Manual

Change 2 18-9

S100-2MT1K1 6660-01-248-5525 Solar Shutter Option

S100-2MT1MP1 5895-01-450-8657 Ceilometer GFE Hinge Kit

S100-2MT1MP2 5999-01-411-9537 Ceilometer Snow Radiation Shield

S100-2MT1MP3 5985-01-472-8399 Stainless Steel Ceilometer Pedestal

S100-2MT1MS1 6660-01-367-7677 Tropical Filter

S100-2MT1MS2 6660-01-367-1036 Tropical Filter/Block Conversion Kit

S100-2MT1PS1 6130-01-390-2202 Power Supply Assembly

S100-2MT1R1 4520-01-250-0151 Temperature Control Heater (2 required per unit)

S100-2MT1SP1 6625-01-352-6579 Equipment Cover

S100-2MT1T1 5950-01-248-8454 Temperature Control Transformer

S100-2MT1TE1 4320-01-349-7982 Ceilometer Diffuser

S100-2MT1TE2 6660-01-331-4152 Optical Coupling Fixture, CTX-16

S100-2MT1TS1 5905-01-248-5495 Temperature Sensor

S100-2MT1W1 5999-01-352-6589 Main Harness

S100-2MT1W10 6145-01-352-6458 Receiver HI-V Cable

S100-2MT1W11 6145-01-352-6459 Transmitter HI-V Cable

S100-2MT1W18 6020-01-389-6053 Fiber Optic Cable Assembly, 19'

S100-2MT1W2 5999-01-352-6590 Window Conditioner Harness

S100-2MT1W3 6150-01-248-5474 Output Harness

S100-2MT1W5 5995-01-352-7328 Light Monitor Cable

S100-2MT1W6 6145-01-352-6455 Receiver LO-V Cable

S100-2MT1W7 6145-01-352-6456 Transmitter LO-V Cable

S100-2MT1W8 5995-01-352-6541 Receiver Signal Cable

S100-2MT1W9 6145-01-352-6457 Transmitter Control Cable

S100-2MT2 6660-01-368-4828 Present Weather Sensor (LEDWI)

S100-2MT2A1 5975-01-390-2213 Electronics Enclosure

S100-2MT2A1A1A1 5998-01-375-4810 Transmitter Card

S100-2MT2A1A1A3 5998-01-368-4596 Microprocessor Card, Firmware 3.64

S100-2MT2A1A1A3-U11 5962-01-411-9987 LEDWI Firmware Revision 3.64, Chip U-11

S100-2MT2A1A1A6 5998-01-368-4598 Signal Processing Card II

S100-2MT2A1A1A7 5998-01-368-4597 Signal Processing Card I

S100-2MT2A1A1A8 5998-01-375-4811 AGC Receiver Card

S100-2MT2A1A2 5975-01-368-4581 AC Switchbox

S100-2MT2A1PS1 6130-01-369-4723 Hood Heater Power Supply
ASOS Site Technical Manual S100

18-10 Change 2

S100-2MT2A1PS2 6130-01-369-4725 Analog Power Supply

S100-2MT2A1PS3 6130-01-369-4724 Digital Power Supply

S100-2MT2A2 6660-01-368-4825 Sensor Head

S100-2MT2A2A1A3 4540-01-412-0006 Heater Bar

S100-2MT2MS1 8010-01-442-8269 Insecta Paint, 16 oz.

S100-2MT2MS2 8010-01-442-8265 Insecta Paint, 128 oz.

S100-2MT3-1 6660-01-441-1830 Freezing Rain Sensor

S100-2MT3A2 NWS9-93-510-0006 Spool Installation Kit

S100-2MT3MP1-2 4710-01-448-6236 Aluminum Mounting Pole

S100-2MT3MP1-3 5340-01-457-7048 Vinyl Protective Cap, 1" X 0.75"

S100-2MT3MP1-4 NWS9-82-050-0001 Freezing Rain Sensor Hardware Kit

S100-2MT4-MP1-KIT nws9-93-510-0005 Mounting Kit

S100-2MT4A1A1-1 6660-01-412-2335 Dewpoint Sensor, 1088

S100-2MT4A1A1-2 6660-01-437-8888 Dewpoint Sensor, 1088 (slightly different components than in -1)

S100-2MT4A1A1MP1 6660-01-228-1210 Neoprene O-Ring, 0.25" ID, HO83

S100-2MT4A1A2 5999-01-411-7107 Aspirator Housing Assembly, 1088

S100-2MT4A1A2B1 4140-01-304-4728 Pabst Fan

S100-2MT4A1A2W1 5995-01-455-1723 Fan Adapter Wire

S100-2MT4A1R7 6625-01-423-1323 Auto Balance Module

S100-2MT4A2 4940-01-436-8772 Electronics Enclosure, 1088

S100-2MT4A2-1 4940-01-436-6222 Electronics Enclosure, 1063

S100-2MT4A2A1-1 5998-01-375-4812 Transmit Logic Card, 1088

S100-2MT4A2A1-2 5998-01-369-4728 Transmit Logic Card, Firmware B91A and F91, R1063

S100-2MT4A2A3 6130-01-208-5925 5 V DC Power Supply, 1063

S100-2MT4A2A4 6130-01-205-6975 Auxiliary Power Supply, 1063

S100-2MT4MP1 5305-01-432-2746 Stainless Steel Enclosure Screw, 5/8" long

S100-2MT4MP2 5340-01-464-9134 Insect Skirt

S100-2MT4W21 6015-01-390-0234 Fiber Optic Cable Assembly, 26.5'

S100-2MT5A1 5975-01-375-4808 Visibility Sensor Electronics Emclosure

S100-2MT5A1A1 5998-01-368-4599 Processor Board with Firmware 040

S100-2MT5A1A1-U2A NWS9-72-660-0001 Visibility EPROM, Revision 039

S100-2MT5A1A1-U2B NWS9-92-290-0001 Visibility EPROM, Revision 040

S100-2MT5A1A3A1 5998-01-368-4608 24 V Regulator Board

S100-2MT5A1A3A1F1 5920-00-284-7134 Slow-Blow Fuse, 32 V, 15 Amp
S100 ASOS Site Technical Manual

Change 2 18-11

S100-2MT5A1A3A1XF1 5920-01-391-4658 Fuse Carrier

S100-2MT5A1PS1 6130-01-390-2211 5 V Electronics Power Supply

S100-2MT5A2 5340-01-368-4827 Crossarm Assembly with End Caps

S100-2MT5A2A3 6660-01-369-5858 Optical Transmitter

S100-2MT5A2A3A2 5340-01-389-1359 Cap

S100-2MT5A2A4 6660-01-369-5857 Optical Detector

S100-2MT5A2MP1 5310-01-448-6234 Master Seal Washer

S100-2MT5A5 6695-01-368-4826 Day/Night Sensor

S100-2MT5MP36 5999-01-391-2515 Hinge Plate Assembly

S100-2MT5MP36-1 5315-01-424-0665 Quick Release Pin

S100-2MT6-1B1 6135-01-471-7325 3.6 V Lithium Battery

S100-2MT6-2 6660-01-441-1826 Heated Tipping Rain Gauge

S100-2MT6-S1 6685-01-445-3517 Thermostat

S100-2MT6A2A1-1 5975-01-436-8774 Frame Assembly with a Reed Switch

S100-2MT6A2A1-OLD 6660-AS-200-0135 Frame Assembly

S100-2MT6A2A2A1 6025-01-369-7460 Fiber Optic Transmitter

S100-2MT6A3MP1 5975-01-432-3074 Windscreen Panel, 47.5" X 17"

S100-2MT6FMK01 6685-01-445-3518 Heated Tipping Bucket Thermostat

S100-2MT6MP3 6660-01-390-9548 Rain Shield Assembly

S100-2MT6MP4 NWS9-90-570-0001 Aluminum Connector

S100-2MT7 6350-01-441-7596 Thunderstorm Sensor (Single-Site Lightning Detection Sensor)

S100-2RF-KIT NWS9-93-510-0022 RF Surge Suppressor Kit

S100-2T240/480 5950-01-411-9542 Transformer, 3KVA, 120-240V or 480V

S100-2T480-2 5950-00-635-7414 Transformer, 5KVA, 240-480V

S100-2T600-1 5950-01-411-9541 Transformer, 3KVA, 120-600V

S100-2T600-2 5950-01-411-9540 Transformer, 5KVA, 120-600V

S100-2W25 5995-01-411-9522 RF Cable Assembly

S100-2W27 5995-01-472-8410 DCP CPU 1 Cable Assembly

S100-2W28 5995-01-389-2441 DCP CPU 2 Cable Assembly

S100-2W35-2 6020-01-411-9493 Fiber Optic Cable Assembly, 75'

S100-3A3J1 4130-01-472-7515 Blank Cover

S100-41 7025-01-368-8646 Video Display Unit

S100-4A3J11 NWS9-93-510-0008 Telephone Jack Assembly

S100-4MT1KIT 6660-AS-200-0119 Ceilometer Backup Kit
ASOS Site Technical Manual S100

18-12 Change 2

S100-5 5805-01-389-9541 FAA Handset

S100-6 6660-01-368-4829 Observer Notification Device

S100-6-1 6240-01-412-0012 Special Festoon Lamp Bulb, 12V, 10W

S100-6PS1 6130-01-389-5888 Tamura AC to DC Power Supply

S100-7 NWS9-82-300-0001 Single Cabinet Assembly ASOS

S100-7-1A2A14 5905-01-465-6027 VME Resistor Board

S100-7A1-1 5998-01-451-6812 Temperature Sensing Board Assembly

S100-7A1-DES 6850-01-358-5837 Activated Desiccant

S100-7A1-LABEL 7530-01-451-0144 Single Cabinet Assembly Label

S100-7A1-MP1 4440-01-451-6813 Desiccant Dryer

S100-81 6660-01-369-5856 Controller Video Display Unit

S100-AN565AC8H8 5305-00-582-9466 Setscrew, MIL Spec AN565AC8H8

S100-F/O-10 6020-01-451-6481 Fiber Optic Cable Assembly, 10'

S100-F/O-100 6020-01-451-6787 Fiber Optic Cable Assembly, 100'

S100-F/O-110 6020-01-451-6788 Fiber Optic Cable Assembly, 110'

S100-F/O-180 6020-01-451-6789 Fiber Optic Cable Assembly, 180'

S100-F/O-20 6020-01-451-6490 Fiber Optic Cable Assembly, 20'

S100-F/O-240 6020-01-451-6790 Fiber Optic Cable Assembly, 240'

S100-F/O-30 6020-01-451-6492 Fiber Optic Cable Assembly, 30'

S100-F/O-300 6020-01-451-6791 Fiber Optic Cable Assembly, 300'

S100-F/O-40 6020-01-451-6493 Fiber Optic Cable Assembly, 40'

S100-F/O-50 6020-01-451-6781 Fiber Optic Cable Assembly, 50'

S100-F/O-60 6020-01-451-6782 Fiber Optic Cable Assembly, 60'

S100-F/O-70 6020-01-451-6783 Fiber Optic Cable Assembly, 70'

S100-F/O-80 6020-01-451-6785 Fiber Optic Cable Assembly, 80'

S100-F/O-90 6020-01-451-6786 Fiber Optic Cable Assembly, 90'

S100-FMK-039 5340-AS-200-0117 Brass Adapter

S100-FMK-048-1 5995-01-411-9523 Cable Adapter for FMK048

S100-FMK-090 5895-01-450-8658 Thunderstorm Sensor Kit

S100-FMK-50 NWS9-81-410-0001 Voice EPROM Revision 4.0

S100-FMK-60 5915-01-436-0446 Wind System Filter

S100-FMK028-038 3431-AS-200-0087 Battery Box Lid

S100-FMK028-LABEL 7530-AS-200-0088 Label

S100-FMK040 NWS9-80-060-0001 D-ATIS VDU Port Kit
S100 ASOS Site Technical Manual

Change 2 18-13

S100-FMK048 5895-AS-200-0070 V.3225 9600 Baud Modem

S100-FMK049B NWS9-61-080-0001 Tipping Bucket Funnel Extension and Label

S100-FMK059 NWS9-60-170-0004 ACU Memory Upgrade

S100-FMK077C 5945-01-451-6814 Class I SCA Solid-State Time Delay Relay Kit

S100-FMK098 5895-01-450-8659 DCP Power Upgrade Kit

S100-FMK102 NWS9-81-400-0002 Temperature Probe Board Upgrade Kit

S100-FMK109 5895-01-451-2987 SCA Vent Kit

S100-FMK109CLII NWS9-73-380-0010 Third Pressure Sensor Adapter, SCA

S100-FMK70 NWS0-00-870-0001 GTA Radio Aux Box Installation Kit

S100-FMK95ACU 5945-01-451-6804 Class II ACU UPS Bypass Kit

S100-FMK95DCP 5945-01-451-6805 Class II DCP UPS Bypass Kit

S100-FMK95SCA 5945-01-451-6806 Class II SCA UPS Bypass Kit

S100-H083-BX 5330-AS-200-0072 Packing Box for the HO83 Transmitter/Aspirator

S100-MS25281-R10 5340-00-989-3032 Cable Bundle Loop Clamp, 5/8" Diameter

S100-MS25281-R16 5340-00-807-1065 Cable Bundle Loop Clamp, 1.00" Diameter

S100-MS25281-R5 5340-00-721-5315 Cable Bundle Loop Clamp, 5/16" Diameter

S100-TE300 6625-01-354-3026 RS232 Communication Signal Polarity Test Box

S100-TE301 6625-01-354-3025 Torque Watch Gauge

S100-TE303 6605-01-196-6971 Magnetic Compas

S100-TE304 6640-01-383-1098 Beaker

S100-TE305 6625-01-354-3015 Visibility Sensor Calibration Kit

S100-TE305-1 6110-AS-200-0079 Molex Connection Jumper for the Visibility Calibration Kit

S100-TE305-2 6625-01-440-1773 Portable Light Source for the Visibility Sensor

S100-TE307 5995-01-366-6300 “Y” Interface Laptop Cable

S100-TE308 6625-01-354-3017 Present Weather Sensor Field Tester

S100-TE309 5995-01-366-6278 Nulling Interface Cable

S100-TE315 6685-00-840-6317 Aspirated Psychrometer, Battery Operated 

S100-TE316 5180-01-412-0008 Solar Noon Alignment Kit

S100-TE318 7030-01-436-7410 SerialBERT® Bit Error Rate Testing Software by Frontline®

S100-TE318-1 7030-AS-200-0158 ASOS Calibration Software, Version 2.03

S100-TE318-2 7030-01-462-1909 ProComm Plus® Version 4.7, CD-ROM

S100-TE320 6625-00-978-6012 Directional RF Wattmeter, Type N Connectors

S100-TE320-1 5985-01-432-2240 50 Ohm RF Terminator, 25 W, Type N Connector

S100-TE320-2 6625-00-949-5382 10 W Element, 100-250 MHz
ASOS Site Technical Manual S100

18-14 Change 2

S100-TE320-3 6625-00-497-2912 5 W Element, 200-500 MHz

S100-TE320-4 6625-01-080-5452 Directional Coupler Detecting Element

S100-TE321 5995-01-432-2245 Wind Speed Test Cable

S100-TE323-1 7035-01-412-0004 T1910 Laptop Carrying Case

S100-TE327 3010-00-857-2090 Flexible Coupling Shaft

S100-TE329 6685-AS-200-0138 Wind Skirt Concentricity Tester Gauge

S100-TE330 7035-01-412-0005 HP Carrying Case

S100-TE331 NWS9-82-530-0001 Computer Carrying Case, Heated

S100-TE335 6625-01-432-2346 1 Watt Element, 110-160 MHz

S100-TE350 6625-01-411-9539 Tone Test Set

S100-TE351 5935-01-412-0009 Surface Mounted RJ-11 Jack

S100-TE352 5935-01-411-5249 N-Plug to BNC Adapter

S100-TE353 5935-01-411-5250 BNC to Binding Post Plug

S100-TE356 6625-01-411-9530 Biddle Merger

S100-TE357 6625-01-411-5232 Audio Generator, 20-150 Hz

S100-TE360 4940-01-454-2259 Heat Enclosure for the DCP Sensors

S100-TE361 4520-01-454-5204 Heat Mounting Assembly

S100-TE362-1 6760-01-457-0844 A/C Adapter

S100-TE401 7035-01-412-0002 Carrying Case

S100-TE401-1 6625-01-360-3380 Frequency Counter, 120-160 MHz

S100-TE402 5340-01-411-9980 Front Cover

S100-TE403 6625-01-411-9532 Digitizing Oscilloscope, 200 MHz, 2 Channel

S100-W43 5995-01-472-8423 Line Driver Cable Assembly, 84" Long

S100-W44 5998-01-472-8429 Line Driver Cable Assembly, 84" Long

S100-W45 5995-01-472-8436 Line Driver Cable Assembly, 48" Long

S100-W46 5995-01-472-8438 Line Driver Cable Assembly, 24" Long

S100-W47 5995-01-472-8444 Line Driver Cable Assembly, 24" Long

S100-W48 5995-01-472-8447 Line Driver Cable Assembly, 24" Long

S100-W49 5995-01-472-8451 Line Driver Cable Assembly, 24" Long

S100-W78 5995-01-411-9515 UPS Adapter Cable Assembly

S100-W85 5995-01-472-7503 Audio Adjust Ribbon Cable
S100 ASOS Site Technical Manual

INDEX

Subject Paragraph, Figure, Table

Index 1

A

ACQUISITION CONTROL UNIT (ACU) ............................................. 1.4.2

A/D Board and VME Resistor Board ........................................... 2.4.3.2.7

AC Distribution ............................................................ 2.4.3.9.1

AC Distribution for Power Supply Assembly 62828-40265-10 ................ 2.4.3.9.3, F2.4.13

AC Distribution for Power Supply Assembly 62828-40124-10 ................ 2.4.3.9.2, F2.4.12

ACU AND PERIPHERALS OVERVIEW .......................................... 2.4.1

Cabinet Cleaning ....................................................... 2.5.2.3, T2.5.3

Cabinet. ....................................................... 2.1.2.2, F2.1.2, T2.1.1

CPU AND SIO BOARD JUMPER CONFIGURATIONS .............................. 2.5.8

ACU/DCP Communication ................................................... 2.4.2.2.6

ACU/DCP Communication System Checks ........................................ 2.5.3.4

Power and Signal Monitoring ............................................ 2.4.3.8, F2.4.11

Serial Communications ........................................................ 2.5.7.1

ACU Tie-Down ............................................................ 2.1.2.2.1

Air Filter Cleaning ..................................................... 2.5.2.1, T2.5.2

Airline Displays ............................................................. 2.1.2.10

Analog to Digital (A/D) and VME Resistor Boards ................................ 2.4.2.2.2

Battery Box 1A8 ............................................................. F2.1.8

Card Rack Assembly 1A2 ................. F2.1.3, 2.3.2.5, F2.3.3, T2.3.1, 2.4.3.2, F2.4.2, F2.4.3

Card Rack Assembly Fault Isolation Procedures .................................... T2.5.8

Central Processing Units (CPU's) ...................................... 2.4.2.1.1, 2.4.3.2.1

Check/Clean Batteries ......................................................... 2.5.2.5

Check Memory Board LOW BATT Indicator ...................................... 2.5.2.4

Class I and Class II Systems .................................................... 2.1.2.1

Codex Modem ............................................................... 2.3.2.9

CONFIGURATIONS .......................................................... 2.1.3

Controller Video Display (CVD) ................................... 2.1.2.3, 2.3.2.3, F2.3.2

CONTROLS AND INDICATORS ................................................ 2.3.2

CORRECTIVE MAINTENANCE .......................................... 2.5.3, T2.5.4

Data Input/Output ............................................................ 2.4.2.2

Data Processing .............................................................. 2.4.2.1

DC Power Distribution ............................................... 2.4.3.9.4, F2.4.14

DC Power Supply Enclosure 1A5 .......................................... F2.1.6, 2.3.2.8

DETAILED BLOCK DIAGRAM DESCRIPTION ............................. 2.4.3, F2.4.1

Diagnostics ................................................................. 2.5.3.6

Digital I/O Board ................................................... 2.4.2.2.3, 2.4.3.2.6

Digital Voice Processing ..................................................... 2.4.2.2.4

Digital Voice Processor System ........................................... 2.4.3.3, F2.4.5

Display Screen Cleaning ....................................................... 2.5.2.2

Earthquake Mounting Installation ................................................ F2.5.1

FAA Handset ................................................................ 2.1.2.5

I/O Panel Assembly 1A9 ....................................................... F2.1.9

LAPTOP COMPUTER AS PRIMARY OID .................................. 2.3.4, T2.3.9

Line Driver Communications ................................................. 2.5.3.4.2

Line Drivers ......................................................... 2.4.3.4.3, F2.4.7

Local Sensor Fiberoptic Modems .......................................... 2.4.3.6, F2.4.9

Memory Board ..................................................... 2.4.2.1.2, 2.4.3.2.2
ASOS Site Technical Manual S100

INDEX

Subject Paragraph, Figure, Table

Index 2 Change 2

A -CONT

ACQUISITION CONTROL UNIT (ACU) -CONT

Modem AC Power Rack 1A3 ................................ F2.1.4, 2.3.2.6, F2.3.4, T2.3.2

Modem Communications ................................................ 2.4.3.4, F2.4.6

Observer Notification Device (OND) ...................................... 2.1.2.8, 2.3.2.4

Observer Notification Device and Peripheral Power .......................... 2.4.3.7, F2.4.10

OPERATIONAL PROCEDURES ................................................ 2.3.3

Operator Interface Device (OID) ................................... 2.1.2.6, 2.3.2.1, F2.3.1, 

Orienting DB-25 Adapters ..................................................... 2.5.4.2

PHYSICAL DESCRIPTION ............................................... 2.1.2, F2.1.1

Port Assignments for SIO's 1 Through 3 ........................................... T2.4.1

Power Distribution and Control .......................................... 2.4.2.3, 2.4.3.9

$ Power Supply Assembly 1A4 ........ F2.1.5, 2.3.2.7, F2.3.5, F2.3.6, F2.3.7, T2.3.3, T2.3.4, T2.3.5

$ Power Supply Assembly 62828-40265-10 DIP Switch Configurations ................... T2.3.4

Power Up and Power Down Procedures .............................. 2.3.3.1, T2.3.6, T2.3.7

Pressure Sensors ....................................................... 2.4.3.5, F2.4.8

PREVENTIVE MAINTENANCE .......................................... 2.5.2, T2.5.1

Printer .............................................................. 2.1.2.4, 2.3.2.2

Refresh OID ................................................................. 2.3.3.3

REMOVAL AND INSTALLATION

ACU Tie-Down ............................................................. T2.5.32

REMOVAL AND INSTALLATION PROCEDURES ................................. 2.5.4

Battery Box and Battery ............................................ T2.5.30

Blower .......................................................... T2.5.29

DC Power Supply Fan Connector Board ................................ T2.5.28

DC Power Supply ................................................. T2.5.27

Modem/Line Driver Rack Power Supply ............................... T2.5.14

Modem/Line Driver Rack Circuit Board ................................ T2.5.18

Power Supply Assembly Transformer .................................. T2.5.20

Power Supply Assembly Filter Board .................................. T2.5.19

Power Supply Assembly OUTPUT POWER Switch ...................... T2.5.25

Power Supply Assembly Fuse ........................................ T2.5.21

Power Supply Assembly RS-232 Board ................................ T2.5.22

Power Supply Assembly Inverter Board ................................ T2.5.23

Power Supply Assembly Status Panel .................................. T2.5.24

Power Supply Assembly Circuit Breaker ............................... T2.5.26

$ RF Modem ....................................................... T2.5.15

RF Switch ....................................................... T2.5.16

Uninterruptible Power Supply ........................................ T2.5.31

VME Card Rack Circuit Board ....................................... T2.5.17

RF Antenna ................................................................. 2.1.2.7

RF Communications ........................................................ 2.5.3.4.1

RF Communication Checkout Class I ............................................ T2.5.11

RF Communication Checkout Class II ........................................... T2.5.10

RF Communication Checkout Class I ............................................ T2.5.13

RF Communication Checkout Class II ........................................... T2.5.12

RF Failure Symptoms ......................................................... T2.5.9

$ RF Modems ......................................................... 2.4.3.4.2, F2.4.7
S100 ASOS Site Technical Manual

INDEX

Subject Paragraph, Figure, Table

Change 2 Index 3

A -CONT

ACQUISITION CONTROL UNIT (ACU) -CONT

RF/Pressure Mounting Shelf 1A6 ................................................ F2.1.7

Serial I/O (SIO) Board ......................................... 2.4.2.2.1, 2.4.3.2.3, F2.4.4

Serial I/O Board Checks ....................................................... 2.5.3.5

Setting Up ACU Rack-Mounted Modems .......................................... 2.5.5.1

Setting Up Stand Alone Modems ......................................... 2.5.5.2, T2.5.33

SETTING UP A DOT MATRIX PRINTER .................... 2.5.7, T2.5.35, T2.5.36, T2.5.37

SETTING UP LEASED LINE MODEMS .......................................... 2.5.5

SETTING UP LINE DRIVER MODEMS ................................... 2.5.6, T2.5.34

SIMPLIFIED BLOCK DIAGRAM DESCRIPTION .................................. 2.4.2

Site ID and AOMC Phone Number ......................................... 2.3.3.2, T2.3.8

Telephone Modems ................................................... 2.4.3.4.1, F2.4.6

Telephone Modems ......................................................... 2.4.2.2.7

Testing the Digital Voice Processing System ..................................... 2.4.3.3.3

Upper Cabinet Removal ....................................................... F2.5.2

UPS (62828-40124-10) Pre-Service and Post-Service Procedures ...................... T2.5.6

UPS Checks ................................................................. 2.5.3.2

UPS Fault Isolation (62828-40124-10) ............................................ T2.5.5

UPS Fault Isolation (62828-90338-10 or 62828-xxxxx-xx) ............................ T2.5.7 $

Video Board .............................................................. 2.4.3.2.5

Video Controller Board ...................................................... 2.4.2.2.5

Video Display Unit (VDU) ..................................................... 2.1.2.9

VME Card Rack Check ........................................................ 2.5.3.3

Voice Processor and Voice Recorder/Playback Boards ............................. 2.4.3.2.4

Voice Processor Board ...................................................... 2.4.3.3.1

Voice Recorder/Playback Board ............................................... 2.4.3.3.2

AOMC Interface to ACTS ....................................................... 1.4.6.4.1

ASOS/AOMC Interface ........................................................... 1.4.6.1

ASOS OPERATION AND MONITORING CENTER (AOMC) ............................ 1.4.6

ASOS Site Specific Data .......................................................... 1.4.6.3

ASOS Synchronization Sequence ................................................. 1.4.6.4.2

ASOS SYSTEM DESCRIPTION ........................................ 1.1.4, F1.1.1, F1.4.1

ASOS Time Synchronization ....................................................... 1.4.6.4

ASOS Trouble Monitoring ........................................................ 1.4.6.2

ASOS Users .................................................................... T1.1.1
ASOS Site Technical Manual S100

INDEX

Subject Paragraph, Figure, Table

Index 4 Change 2

C

CEILOMETER

Alarm Limits (ALIM) Command Display .......................................... F9.3.6

ASSEMBLY ................................................................. 9.2.2

Automatic Mode and Maintenance Mode. ......................................... 9.3.6.3

Blower Control (BLOW) Command Display ...................................... F9.3.12

Calibration. ........................................................... 9.5.2.4, T9.5.3

Clean Snow Radiation Shield. ............................................. 9.5.2.5, T9.5.4

Cleaning and Inspection ....................................................... T9.5.2

Cleaning and Window Conditioner Checks. ........................................ 9.5.2.3

Cloud Detection Missing. ...................................................... 9.5.3.4

Command Descriptions. ....................................................... 9.3.6.4

Configurations ......................................................... 9.1.2.3, T9.1.2

CONTROLS AND INDICATORS .................................... 9.3.2, F9.3.1, T9.3.1

CORRECTIVE MAINTENANCE ................................................ 9.5.3

Data Message Contains Alarm. .................................................. 9.5.3.2

Data Tables (TAB) Command Display ........................................... F9.3.16

DETAILED BLOCK DIAGRAM DESCRIPTION ............................. 9.4.3, F9.4.4

$ Device Scale Calibration Check Procedure ....................................... T9.5.3a

Digital Message No. 2 ................................................... 9.3.5.2, F9.3.3

Digital Message No. 3 ................................................... 9.3.5.3, F9.3.4

DIRECT DIALOGUE COMMANDS .............................................. 9.3.6

Fault Symptoms. ............................................................. 9.5.3.1

Fiberoptic Module. ........................................................... 9.4.3.9

Frequency Control (FREQ) Command Display ..................................... F9.3.9

General Hardware Alarm Messages .............................................. T9.5.6

Graphic Output (GRAP) Command Display ....................................... F9.3.17

Hardware Alarm. ........................................................... 9.5.3.2.1

Heater Control (HEAT) Command Display ....................................... F9.3.11

Help Message (HELP) Command Display ........................................ F9.3.14

High Voltage Power Supply. .................................................... 9.4.3.7

I/O Connector Board Voltage Test Points ......................................... T9.5.20

I/O Connector Board. ........................................................ 9.4.3.10

Initialization Error Messages ................................................... T9.5.7

INSTALLING THE CEILOMETER ............................ 9.2.3, F9.2.1, F9.2.2, T9.2.1

Internal Monitoring ......................................................... 9.4.2.2.4

Internal Temperature Control. ................................................ 9.4.2.2.3

Laser Control (LASE) Command Display ......................................... F9.3.7

Laser Power Low Alarm. .................................................... 9.5.3.2.3

Laser Transmission/Reception Cycle ............................................. F9.4.1

Light Monitor Board Voltage Test Points ......................................... T9.2.22

Light Monitor Board. ......................................................... 9.4.3.5

Line Open and Line Closed. .................................................... 9.3.6.2

Measurement (MEAS) Command Display ........................................ F9.3.15

Measurement Circuit ........................................................ 9.4.2.2.1

Monitored Power Test Points Fuses and Loads ..................................... T9.5.9

Noise (NOIS) Command Display ............................................... F9.3.19

NORMAL OPERATION ....................................................... 9.3.5

Offset Calibration. ................................................... 9.5.4.12, T9.5.35
S100 ASOS Site Technical Manual

INDEX

Subject Paragraph, Figure, Table

Index 5

C -CONT

CEILOMETER -CONT

Output Interfaces. ......................................................... 9.4.2.2.2

Parameter (PAR) Command Display ............................................ F9.3.18

Parameters .................................................................. T9.3.4

PHYSICAL DESCRIPTION ............................................... 9.1.2, F9.1.1

Power Supply General Troubleshooting Procedure ................................. T9.5.10

Power Supply Monitored Voltage Levels .......................................... T9.5.8

Power Supply Section ....................................................... 9.4.2.2.5

PREVENTIVE MAINTENANCE .......................................... 9.5.2, T9.5.1

Principles of Operation. ........................................................ 9.4.2.1

Processor Board Operating Voltage Checkpoints ................................... T9.5.15

Processor Board. ............................................................. 9.4.3.2

Received Signal Sampling Noise Cancellation ...................................... F9.4.2

Receiver Board Voltage Test Points ............................................. T9.5.25

Receiver Board. ............................................................. 9.4.3.4

Receiver Gain Control (GAIN) Command Display ................................. F9.3.10

Removal and Installation

Equipment Cabinet Cover ........................................... T9.5.14

I/O Connector Board ............................................... T9.5.21

Snow Radiation Shield .................................... 9.5.4.10.3, T9.5.33

Processor Board ................................................... T9.5.16

Solar Shutter Driver ................................................ T9.5.23

Unregulated Power Supply Board ..................................... T9.5.19

Fiberoptic Module. ......................................... 9.5.4.13, T9.5.36

Routine Inspection. ........................................................... 9.5.2.2

RS-232C Interface Nonoperational. .............................................. 9.5.3.3

Sequence Control (SEQ) Command Display ....................................... F9.3.8

SIMPLIFIED BLOCK DIAGRAM DESCRIPTION ............................ 9.4.2, F9.4.3

Snow Radiation Shield Option. ................................................ 9.4.2.2.8

Solar Shutter Control (SHUT) Command Display .................................. F9.3.13

Solar Shutter Option ........................................................ 9.4.2.2.7

Specifications ............................................................... T9.1.1

Startup Message. ....................................................... 9.3.5.1, F9.3.2

Status (STA) Command Display ................................................. F9.3.5

Superfluous Detection. ........................................................ 9.5.3.5

Supply Voltage Alarm. ...................................................... 9.5.3.2.2

System Components .................................................... 9.1.2.2, F9.1.2

Temperature Alarm References ................................................ T9.5.11

Temperature Alarm With High Temperature ...................................... T9.5.12

Temperature Alarm With Reasonable Temperatures ................................ T9.5.13

Temperature Alarm. ........................................................ 9.5.3.2.4

Transmitter Board Voltage Test Points ........................................... T9.5.27

Transmitter Board. ........................................................... 9.4.3.3

Troubleshooting ............................................................. T9.5.5

TURN-ON PROCEDURES ............................................... 9.3.3, T9.3.2

TURNOFF PROCEDURES ............................................... 9.3.4, T9.3.3

Unregulated Power Supply Board. ............................................... 9.4.3.8
ASOS Site Technical Manual S100

INDEX

Subject Paragraph, Figure, Table

Index 6

C -CONT

CEILOMETER -CONT

Unregulated Power Supply Voltage Limits ........................................ T9.5.17

Unregulated Power Supply Voltage Test Points and Loads ........................... T9.5.18

VERIFICATION AND REPLACEMENT PROCEDURES ............................. 9.5.4

Cabinet Heaters R1 and R2. .................................... 9.5.4.9, T9.5.31

External Air Temperature Sensor TS1. .......................... 9.5.4.10, T9.5.32

High Voltage Power Supply PS1 ................................ 9.5.4.7, T9.5.29

I/O Connector Board A3. ............................................. 9.5.4.3

Light Monitor Board A5 ...................................... 9.5.4.4, T9.5.24

Temperature Compensation Transformer T1. ...................... 9.5.4.8, T9.5.30

Transmitter Board A7. ........................................ 9.5.4.6, T9.5.28

Unregulated Power Supply Board A2 ................................... 9.5.4.2

Window Conditioner. ....................................... 9.5.4.11, T9.5.34

Processor Board A1 ................................................. 9.5.4.1

Receiver Board A6 ........................................... 9.5.4.5, T9.5.26

Window Conditioner. ......................................................... 9.4.3.6

Cleaning ................................................................. 1.5.3.3, T1.5.7

CODEX SERIES 3600 MODEM

Bit Error Rate Tester .......................................... 13.5.3.2, F13.5.1, T13.5.4

CONFIG Menu ..................................................... 13.3.2.3, F13.3.10

CONFIGURATIONS ......................................................... 13.1.3

Configuring the Codex 3600 Series Modem ....................................... T13.5.7

CONTROLS AND INDICATORS ................................. 13.3.2, F13.3.1, T13.3.1

Corrective Maintenance Philosophy ............................................. 13.5.3.1

CORRECTIVE MAINTENANCE ............................................... 13.5.3

Enclosure ................................................................ 13.1.2.2.1

Flex-Cartridge ............................................................ 13.1.2.2.2

Flex-Cartridge Removal and Installation ......................................... T13.5.6

Modem Troubleshooting ...................................................... 13.5.3.3

MONITORING AND VERIFYING MODEM AT OPERATOR INTERFACE DEVICE .... 13.3.6

MONITORING AND VERIFYING MODEM BY VISUAL INSPECTION .............. 13.3.7

MULTIPOINT-SLAVE (MP-S) OPERATING MODE ............................... 13.4.3

NORMAL OPERATION ...................................................... 13.3.5

PHYSICAL DESCRIPTION ............................... 13.1.2, F13.1.1, F13.1.2, F13.1.3

PREVENTIVE MAINTENANCE ............................................... 13.5.2

Quick Checks ............................................................... T13.5.1

REMOTE Menu .................................................... 13.3.2.4, F13.3.15

Removal and Installation ............................................... 13.5.4.2, T13.5.5

REMOVAL AND INSTALLATION PROCEDURES ......................... 13.5.4, F13.5.3

Routine Inspection and Cleaning ............................................... 13.5.2.1

Self-Test .................................................................. T13.5.3

Signal Quality Test .......................................................... T13.5.2

Specifications .............................................................. T13.1.1

STATUS Menu ...................................................... 13.3.2.1, F13.3.3

System Components .................................................. 13.1.2.2, F13.1.4
S100 ASOS Site Technical Manual

INDEX

Subject Paragraph, Figure, Table

Change 1 Index 7

C -CONT

CODEX SERIES 3600 MODEM -CONT

TEST Menu ......................................................... 13.3.2.2, F13.3.8

THEORY OF OPERATION ...................................... 13.4.1, F13.4.1, F13.4.2

TURBO POINT-TO-POINT AND V.33 COMMUNICATIONS ........................ 13.4.2

TURN-ON PROCEDURES .................................................... 13.3.3

TURNOFF PROCEDURES .................................................... 13.3.4

Combined Zone Pedestal Locational ................................................. F1.5.1 $

Configuring the OID ..................................................... 1.3.10.1, T1.3.22 $

Configuring the Remote Terminals ................................................. 1.3.10.2

Consumable Materials List ........................................................ T1.5.2

Corrective Maintenance Symptom Analysis ........................................... T1.5.8

CORRECTIVE MAINTENANCE ................................................... 1.5.4

Corrosion Removal and Prevention, Steel Surfaces ..................................... 1.5.3.4

D

DATA COLLECTION PACKAGE (DCP) ............................................. 1.4.4

A/D Boards, Digital I/O Board, and VME Resistor Board ........................... 3.4.3.2.4

AC Distribution - General .............................................. 3.4.3.6.1, F3.4.9

AC Junction Box ....................................................... 3.1.3.2, F3.1.8

Analog to Digital (A/D) and VME Resistor Boards ................................ 3.4.2.3.3

Auxiliary DCP Equipment Cabinet (Optional) ...................................... 3.1.2.2

BASIC BLOCK DIAGRAM DESCRIPTION ....................................... 3.4.2

Cabinet Cleaning ....................................................... 3.5.2.1, T3.5.2

Card Rack Assembly .............................................. 3.4.3.2, F3.4.3, F3.4.4

Card Rack Assembly A1A2 ...................................... 3.1.3.1.1, 3.3.2.2, F3.1.4

Card Rack Assembly Fault Isolation Procedures .................................... T3.5.7

Central Processing Units (CPU's) .............................................. 3.4.3.2.1

Check/Clean Batteries ......................................................... 3.5.2.2

Circuit Breaker Rack 1A1A3 ........................ 3.1.3.1.2, 3.3.2.3, F3.1.5, T3.1.1, T3.3.1

Class I and Class II Systems .................................................... 3.1.2.1

CONFIGURATIONS .......................................................... 3.1.4

CONTROLS AND INDICATORS .......................................... 3.3.2, F3.3.1

Corrective Maintenance Symptom Analysis ........................................ T3.5.3

CORRECTIVE MAINTENANCE ................................................ 3.5.3

CPU AND SIO (RS-232) BOARD JUMPER CONFIGURATIONS ...................... 3.5.5

CPU Boards ............................................................... 3.4.2.2.1

Data Processing .............................................................. 3.4.2.2

DC Power Distribution ............................................... 3.4.3.6.2, F3.4.10

DCP/ACU Communication ................................................... 3.4.2.3.1

DDS/MR64 Stand Alone Line Driver Setup ....................................... T3.5.32

DETAILED BLOCK DIAGRAM DESCRIPTION ....................... 3.4.3, F3.4.1, F3.4.2
ASOS Site Technical Manual S100

INDEX

Subject Paragraph, Figure, Table

Index 8 Change 2

D -CONT

DATA COLLECTION PACKAGE (DCP) -CONT

Diagnostics ................................................................. 3.5.3.6

Digital I/O Board ........................................................... 3.4.2.3.4

Equipment Cabinet Heater Troubleshooting ........................................ 3.5.3.5

Equipment Cabinet, Unit 2, 3, or 4 .................................. 3.1.3.1, F3.1.3, T3.1.1

Faraday Box A3 ...................................................... 3.1.3.1.5, F3.1.7

Fiberoptic Modules ..................................................... 3.4.3.4, F3.4.6

Heaters ................................................................... 3.1.3.1.4

Input/Output ................................................................ 3.4.2.3

Line Drivers ............................................................... 3.4.3.3.2

Memory Board ..................................................... 3.4.2.2.2, 3.4.3.2.2

OPERATIONAL PROCEDURES ................................................ 3.3.3

OVERVIEW ................................................................. 3.4.1

PHYSICAL DESCRIPTION ......................................... 3.1.3, F3.1.1, F3.1.2

Port Assignments for DCP SIO Boards ............................................ T3.4.1

Power and Signal Monitoring ............................................. 3.4.3.5, F3.4.7

Power Distribution and Control .................................... 3.4.2.4, 3.4.3.6, F3.4.8

Power Down Procedure ........................................................ T3.3.3

Power Up Procedure .......................................................... T3.3.2

PREVENTIVE MAINTENANCE .......................................... 3.5.2, T3.5.1

REMOVAL AND INSTALLATION 

Battery Box and Battery ............................................ T3.5.17

DC Power Supply (+5 and ±12 VDC) .................................. T3.5.18

Fan ............................................................. T3.5.28

Fiberoptic Module ................................................. T3.5.22

Heater HR1 ...................................................... T3.5.25

Heater HR2 ...................................................... T3.5.26

Power Control Module A1A3A1A2-A8 and A9-A18 ...................... T3.5.23

Power Supply Assembly Diodes A4CR1 Through A4CR6 .................. T3.5.30

Primary and Secondary Circuit Breakers A1A3A1CB1 and A10CB1 ......... T3.5.29

RF Antenna ...................................................... T3.5.21

$ RF Modem ....................................................... T3.5.19

RF Switch ....................................................... T3.5.20

Solid State Relay .................................................. T3.5.24

Thermostat Switch ................................................. T3.5.27

UPS ............................................................ T3.5.31

UPS 1.5 KVA Inverter Board ........................................ T3.5.13

UPS Fan ......................................................... T3.5.14

UPS Filter Board ................................................... T3.5.9

UPS Fuse ........................................................ T3.5.11

UPS OUTPUT POWER Switch ...................................... T3.5.16

UPS RS-232 Interface Board ......................................... T3.5.12

UPS Status Panel Board ............................................. T3.5.15

UPS Transformer .................................................. T3.5.10

VME Card Rack Circuit Board ........................................ T3.5.8

RF Antenna ................................................................. 3.1.3.3

$ RF Modem Communications ............................................. 3.4.3.3, F3.4.5
S100 ASOS Site Technical Manual

INDEX

Subject Paragraph, Figure, Table

Change 2 Index 9

D -CONT

DATA COLLECTION PACKAGE (DCP) -CONT

RF Modem Rack ........................................................... 3.4.3.3.1 $

Serial I/O (SIO) Boards .............................................. 3.4.2.3.2, 3.4.3.2.3

Serial I/O Board Checks ....................................................... 3.5.3.4

Uninterruptible Power Supply (UPS) ..................................... 3.1.3.1.3, F3.1.6

UPS (62828-90057) Pre-Service and Post-Service Procedures ......................... T3.5.5

UPS Checks ................................................................. 3.5.3.2

UPS Fault Isolation (62828-90057) .............................................. T3.5.4

UPS Fault Isolation (62828-90338-10 or 62828-xxxxx-xx) ............................ T3.5.6 $

UPS Status Panel ............................................................. 3.3.2.1

USING LAPTOP COMPUTER AS DCP OID ................................. 3.3.4, T3.3.4

VME Card Rack Check ........................................................ 3.5.3.3

DCP DOWNLOAD ....................................................... 1.3.11, T1.3.24

Deconfiguring and Reconfiguring Sensors to a Remote DCP ...................... 1.3.10.3, T1.3.23

DIAGNOSTICS ........................................................... 1.3.8, T1.3.20

F

Facilities Maintenance Checklist .................................................... T1.5.6

Fiberoptic Cables ............................................................... T1.5.11

Fiberoptic Cable Replacement ..................................................... T1.5.12

Fiberoptic Link Testing - Half-Duplex Link ........................................... T1.5.9

Fiberoptic Link Testing - HO83 Link ............................................... T1.5.10

Fiberoptic Module Test ........................................................... 1.5.4.3

File Upload and Download ...................................................... 1.4.6.3.1

FREEZING RAIN SENSOR

Calibration. ......................................................... 11.5.3.3, T11.5.5

COMMAND DESCRIPTION ............................................ 11.4.3, F11.4.3

Communications Link. ....................................................... 11.4.2.2

CONFIGURATIONS ......................................................... 11.1.3

CONTROLS AND INDICATORS ............................................... 11.3.2

CORRECTIVE MAINTENANCE ............................................... 11.5.3

Depot Level Electronics Processor Board Removal and Installation .................... T11.5.7

Depot Level Probe Assembly Removal and Installation .............................. T11.5.8

Depot Level Probe Assembly Heater Troubleshooting ............................... T11.5.4

Electrical Input Requirements. ................................................. 11.4.2.1

Electronics Enclosure Removal and Installation .................................... T11.5.6

Electronics Processor Board. ............................................ 11.1.2.2, F11.1.2

Fiberoptic Module Removal and Installation ...................................... T11.5.9

Fiberoptic Module. .......................................................... 11.1.2.3
ASOS Site Technical Manual S100

INDEX

Subject Paragraph, Figure, Table

Index 10 Change 2

F -CONT

FREEZING RAIN SENSOR -CONT

Freezing Rain Sensor Inspection and Cleaning ..................................... T11.5.1

Heat Sink. ................................................................. 11.4.1.3

Heater Control. ............................................................. 11.4.2.5

Heaters. ................................................................... 11.4.1.2

INSTALLATION .............................................. 11.2.1, F11.2.1, T11.2.1

Microcontroller ............................................................. 11.4.2.3

Model 0872C2 Ground Fault Check ............................................. 11.5.2.1

NORMAL OPERATION ...................................................... 11.3.4

PHYSICAL DESCRIPTION ............................................. 11.1.2, F11.1.1

POWER OFF ................................................................ 11.3.5

POWER-ON ................................................................ 11.3.3

PREVENTIVE MAINTENANCE ............................................... 11.5.2

PRINCIPLES OF OPERATION ................................................. 11.4.1

Probe Assembly ...................................................... 11.4.1.1, F11.4.1

Probe Assembly and Heat Sink. ................................................ 11.1.2.1

REMOVAL AND INSTALLATION ............................................. 11.5.4

SIMPLIFIED BLOCK DIAGRAM DESCRIPTION .......................... 11.4.2, F11.4.2

Troubleshooting. ..................................................... 11.5.3.2, T11.5.3

Using the Laptop Computer With the Freezing Rain Sensor ................... 11.5.3.1, T11.5.2

Watchdog Timer/Reset Power Monitor .......................................... 11.4.2.4

G

GTA RADIO

Alternative Means of Adjusting Power and Frequency .............................. 12.3.5.2

Antenna Cable Insulation Verification ............................ 12.5.2.5, F12.5.5, T12.5.6

AOMC Frequency Storage .................................................... 12.3.5.3

BERT Program ........................................................... 12.5.3.1.3

Configuring the GTA Radio - General ........................................... 12.3.5.1

CONFIGURING/OID CONTROL ............................................... 12.3.5

CONTROLS AND INDICATORS .......................... 12.3.2, F12.3.1, F12.3.2, T12.3.1

CORRECTIVE MAINTENANCE ........................................ 12.5.3, T12.5.7

DETAILED BLOCK DIAGRAM ......................................... 12.4.3, F12.4.2

Display/Control Modes (Panels) ............................................... , T12.3.2

Frequency Stability Check ..................................... 12.5.2.4, F12.5.4, T12.5.5

I/O Panel .................................................................. 12.4.3.4

$ Modulation Level Check (Preferred) ............................. 12.5.2.2, F12.5.2, T12.5.3

$ Modulation Level Check (Alternative) .......................................... T12.5.3a

PHYSICAL DESCRIPTION ............................................. 12.1.2, F12.1.1

Power Distribution Assembly .................................................. 12.4.3.3

PREVENTIVE MAINTENANCE ........................................ 12.5.2, T12.5.1

Removal and Installation Procedure ..................................... 12.5.3.3, T12.5.11

RF Power Output Check ....................................... 12.5.2.1, F12.5.1, T12.5.2

SELF-TEST ................................................................. 12.4.4

SIMPLIFIED BLOCK DIAGRAM ........................................ 12.4.2, F12.4.1

SIO Board ................................................................. 12.4.3.1
S100 ASOS Site Technical Manual

INDEX

Subject Paragraph, Figure, Table

Index 11

G -CONT

GTA RADIO -CONT

Troubleshoot the GTA Radio RS-232 Data Link .......................... 12.5.3.1.2, T12.5.9

Troubleshoot the GTA Radio RF ...................................... 12.5.3.1.1, T12.5.8

Troubleshooting ............................................................ 12.5.3.1

TURN-ON PROCEDURES .................................................... 12.3.3

TURNOFF PROCEDURES .................................................... 12.3.4

Voice Recorder/Playback Board Check .......................... 12.5.3.2, F12.5.6, T12.5.10

Voice Recorder/Playback Board ................................................ 12.4.3.2

VSWR at Transmitter Output Check ............................. 12.5.2.3, F12.5.3, T12.5.4

L

LIQUID PRECIPITATION ACCUMULATION SENSOR (See Tipping Bucket Rain Gauge)

M

Maintenance Action Sequence ...................................................... T1.5.3

MAINTENANCE ACTION RECORDING AND DOCUMENTATION ...................... 1.5.2

O

OPERATOR INTERFACE DEVICE (OID) CONTROLS AND INDICATORS .......... 1.3.2, F1.3.1

P

PERIPHERALS .................................................................. 1.4.3

PORT SHARING DEVICE (PSD)

ASOS/RTA Communications ................................................ 15.4.1.1.1

Connectivity ............................................... 15.4.1.1.3, F15.4.2, F15.4.3

CONTROLS AND INDICATORS ............................................... 15.3.2

CORRECTIVE MAINTENANCE ............................................... 15.5.3

Determining SIO Board Assignments of the PSD ................................. 15.5.3.2.1

FUNCTIONAL DESCRIPTION ................................................. 15.4.1

FUNCTIONAL DESCRIPTION ................................................. 15.1.3

Hardware Connectivity Within the ACU ....................................... 15.5.3.2.4

Message Traffic Management ........................................... 15.4.1.1, F15.4.1

Monitoring PSD Message Traffic ............................................. 15.5.3.2.5

PHYSICAL DESCRIPTION ............................................. 15.1.2, F15.1.1

PREVENTIVE MAINTENANCE ............................................... 15.5.2
ASOS Site Technical Manual S100

INDEX

Subject Paragraph, Figure, Table

Index 12

P -CONT

PORT SHARING DEVICE (PSD) -CONT

REMOVAL AND REPLACEMENT ............................................. 15.5.4

Modem .......................................................... 15.5.4.2

PSD Memory .............................................. 15.5.4.1, F15.1.2

RTA/ABT Communications ................................................. 15.4.1.1.2

Troubleshooting ............................................................ 15.5.3.2

Using the PSD Diagnostic (DIAG) Function .................................... 15.5.3.2.3

Verifying ASOS Operating Condition ......................................... 15.5.3.2.2

PRESENT WEATHER SENSOR

ASSEMBLY ............................................... 7.2.2, F7.2.1, F7.2.2, T7.2.1

Calibration ............................................................ 7.5.2.3, T7.5.2

Checking Lens and Hood Heaters .......................................... 7.5.2.1, T7.5.1

Cleaning Transmitter and Receiver Lenses ......................................... 7.5.2.2

CONFIGURATIONS .......................................................... 7.1.3

CORRECTIVE MAINTENANCE ................................................ 7.5.3

DETAILED BLOCK DIAGRAM DESCRIPTION ............................. 7.4.3, F7.4.3

Fiberoptic Module (2MT2A1A2A1) .............................................. 7.4.3.9

Field Description ............................................................. 7.4.4.4

Frame Assembly ............................................................. 7.1.2.2

Hex - Binary Nibble Conversion Chart ............................................ T7.4.1

INSTALLING THE PRESENT WEATHER SENSOR ................................ 7.2.3

Main Electrical Enclosure Assembly ............................................. 7.1.2.3

Microprocessor Board (2MT2A1A1A3) ........................................... 7.4.3.8

PHYSICAL DESCRIPTION ......................................... 7.1.2, F7.1.1, F7.1.2

POLL/FRAME FORMATS ..................................................... 7.4.4

Power Distribution .................................................... 7.4.3.10, F7.4.4

Power Supply Test ............................................................ T7.5.5

PREVENTIVE MAINTENANCE ................................................ 7.5.2

Principles of Operation .................................................. 7.4.2.1, F7.4.1

Receiver AGC Board (2MT2A1A1A8) ........................................... 7.4.3.5

Receiver Head (Part of Frame Assembly 2MT2A2) .................................. 7.4.3.4

REMOVAL AND INSTALLATION .............................................. 7.5.4

Frame Head Assembly ......................................... 7.5.4.1, T7.5.6

Analog Power Supply ......................................... 7.5.4.3, T7.5.8

Card Rack Assembly ......................................... 7.5.4.8, T7.5.13

Circuit Board ............................................... 7.5.4.5, T7.5.10

Digital Power Supply .......................................... 7.5.4.4, T7.5.9

Fiberoptic Module ........................................... 7.5.4.6, T7.5.11

Heater Power Supply .......................................... 7.5.4.2, T7.5.7

Heater Bar Assembly ......................................... 7.5.4.7, T7.5.12

Main Electrical Enclosure ..................................... 7.5.4.9, T7.5.14

Signal Processor Board No. 2 (2MT2A1A1A6) ..................................... 7.4.3.7

Signal Processor Board No. 1 (2MT2A1A1A7) ..................................... 7.4.3.6

SIMPLIFIED BLOCK DIAGRAM DESCRIPTION ............................ 7.4.2, F7.4.2

Spider Paint Application Procedure ................................. 7.5.2.4, F7.5.1, T7.5.3

Status Field Encoding ............................................ 7.4.4.5, F7.4.5, T7.4.2
S100 ASOS Site Technical Manual

INDEX

Subject Paragraph, Figure, Table

Index 13

P -CONT

PRESENT WEATHER SENSOR -CONT

Transmitter Board (2MT2A1A1A1) .............................................. 7.4.3.2

Transmitter Head (Part of Frame Assembly 2MT2A2) ............................... 7.4.3.3

Troubleshooting ............................................................. T7.5.4

Type A - Routine Data Poll ..................................................... 7.4.4.1

Type B - Simulated Data Poll ................................................... 7.4.4.2

Type C - Full Raw Data Poll .................................................... 7.4.4.3

PRESSURE SENSOR

Class I System Pressure Sensors ................................................. 8.1.3.1

Class II System Pressure Sensors ................................................ 8.1.3.2

Cleaning and Inspection ....................................................... 8.5.2.2

CLEARING PRESSURE SENSOR DATA QUALITY FAILURES ................ 8.5.6, T8.5.5

CONFIGURATIONS .......................................................... 8.1.3

CORRECTIVE MAINTENANCE ................................................ 8.5.3

Effect of Data Quality Failures on Altimeter Report ................................. 8.5.6.1

Model 470T Extended Range Pressure Sensor ...................................... 8.1.3.3

NORMAL OPERATION ....................................................... 8.3.4

PHYSICAL DESCRIPTION ............................................... 8.1.2, F8.1.1

PREVENTIVE MAINTENANCE .......................................... 8.5.2, T8.5.1

REMOVAL AND INSTALLATION ........................................ 8.5.4, T8.5.3

REPORT PROCESSING PROCEDURES .................................... 8.5.5, T8.5.4

SIMPLIFIED BLOCK DIAGRAM DESCRIPTION ............................ 8.4.2, F8.4.1

Single Cabinet ASOS Pressure Sensor ............................................ 8.1.3.4

Troubleshooting ............................................................. 8.5.3.2

TURN-ON PROCEDURES ..................................................... 8.3.2

TURNOFF PROCEDURES ..................................................... 8.3.3

Use of the Portable Pressure Standard .......................................... 8.5.2.3.1

Verifying Accuracy of Pressure Sensor Data ................................. 8.5.2.3, T8.5.2

PREVENTIVE MAINTENANCE (PM) ......................................... 1.5.3, T1.5.4

PRINTER CONTROLS AND INDICATORS .......................................... 1.3.3

R

RECONFIGURING THE SYSTEM ................................................. 1.3.10

Refurbishment of Painted Aluminum Surfaces ......................................... 1.5.3.5

REMOTE MAINTENANCE MONITORING ......................................... 1.3.14

ASCII Terminal Mode ........................................................ 1.3.14.4

Direct Command Mode ................................................ 1.3.14.2, T1.3.27

Monochrome Monitor Mode ................................................... 1.3.14.3

Remote OID Mode .......................................................... 1.3.14.1
ASOS Site Technical Manual S100

INDEX

Subject Paragraph, Figure, Table

Index 14 Change 1

S

$ Sensor Codes .................................................................. T1.3.29

SINGLE CABINET ASOS (SCA) .......................................... F14.1.1, T14.1.1

A/D Board A13 ...................................................... 14.4.2.4, F14.4.5

AC Power Distribution Assembly 7A1A1A4 Description .......................... 14.1.8.1.3

AC POWER DISTRIBUTION ........................................... 14.4.3, F14.4.9

Auxiliary Box 7A2, Controls and Indicators ....................................... 14.3.2.4

Auxiliary Box Optional Equipment ............................................. 14.1.9.3

Auxiliary Box Standard Equipment ...................................... 14.1.9.2, F14.1.8

AUXILIARY BOX CABINET HEATERS ................................ 14.4.5, F14.4.11

AUXILIARY BOX PHYSICAL DESCRIPTION ............................ 14.1.9, T14.1.2

BLOCK DIAGRAM ................................................... 14.4.2, F14.4.1

CABINET HEATERS ................................................. 14.4.4, F14.4.10

Circuit Breaker Panel 7A1A1A3 Description .................................... 14.1.8.1.2

Circuit Breaker Panel 7A1A1A3, Controls and Indicators ............. 14.3.2.1, F14.3.1, T14.3.1

Cleaning Procedure .......................................................... T14.5.4

CONFIGURATION .......................................................... 14.1.7

Consumable Materials List .................................................... 14.5.1.2

CONTROLS AND INDICATORS ............................................... 14.3.2

CORRECTIVE MAINTENANCE ............................................... 14.5.3

CPU CCA’s A1 and A2 ................................................ 14.4.2.1, F14.4.2

DC POWER DISTRIBUTION AND MONITORING ................ 14.4.6, F14.4.12, F14.4.13

Digital Voice Processing System Self-Tests ..................................... 14.4.2.7.3

Digitized Audio Connections .................................................. T14.4.2

Digitized Voice Processor System ....................................... 14.4.2.7, F14.4.7

DIO Board A15 ...................................................... 14.4.2.6, F14.4.6

Enclosure .................................................................. 14.1.9.1

Facilities Maintenance Checklist ............................................... T14.5.3

Faraday Box 7A1A3 Description ........................................ 14.1.8.2, F14.1.6

Faraday Box Access Procedure ................................................ T14.5.11

Fiberoptic Link Testing - Half-Duplex Link ....................................... T14.5.6

Fiberoptic Link Testing - HO83 Link ............................................ T14.5.7

Fiberoptic Module Test ....................................................... 14.5.3.2

FRU and Subassemblies Removal and Installation .................................. 14.5.3.4

FUNCTIONAL DESCRIPTION .......................................... 14.1.6, F14.1.2

Maintenance Action Recording and Documentation ......................... 14.5.1.3, T14.5.1

MAINTENANCE DISPLAY PAGES ............................................ 14.3.3

Memory Board A3 .................................................... 14.4.2.2, F14.4.3

Modem Setup .............................................................. 14.5.3.3

Modems 7A1A5, A6 Description ............................................... 14.1.8.4

MODEMS ........................................................... 14.4.9, T14.4.3

Mounting Plate Assembly 7A1A1 ............................................... 14.1.8.1

Mounting Plate Assembly 7A2A1 ............................................. 14.1.9.2.1

OPERATING PROCEDURES .................................................. 14.3.4

Operator Interface Device (OID), Controls and Indicators ............................ 14.3.2.3

Optional Modems 7A1A1A11, A12 Description ................................. 14.1.8.1.8

PERIPHERALS .............................................................. 14.4.8
S100 ASOS Site Technical Manual

INDEX

Subject Paragraph, Figure, Table

Change 2 Index 15

S -CONT

SINGLE CABINET ASOS (SCA) -CONT

PHYSICAL DESCRIPTION ............................................. 14.1.8, F14.1.3

Power Outlet Strip 7A1A1A8 Description ...................................... 14.1.8.1.6

Power Outlet Strip 7A2A1A4 Description ...................................... 14.1.9.2.2

Power Supply Mounting Plate 7A1A4 .................................... 14.1.8.3, F14.1.7

Preliminary Troubleshooting Checks .......................................... 14.5.3.1.2

Pressure Mounting Assembly 7A1A1A7 Description ...................... 14.1.8.1.5, F14.1.5

Pressure Sensor Shelf 7A1A1A7 ........................................ 14.4.2.8, F14.4.8

PREVENTIVE MAINTENANCE ............................................... 14.5.2

RELATED PUBLICATIONS ................................................... 14.1.5

Removal and Installation of Faraday Box 7A1A3 Subassemblies .................... 14.5.3.4.4

Removal and Replacement of SCA UPS 7A1A1A6 ............................... 14.5.3.4.3

Removal and Replacement of VME 7A1A1A2 CCA’s ............................ 14.5.3.4.1

Removal and Replacement of Memory Board 7A1A1A2A3 ........................ 14.5.3.4.2

RF Modem Shelf 7A1A1A5 Description ....................................... 14.1.8.1.4 $

RF Modem Shelf 7A2A1A5 Description ....................................... 14.1.9.2.3 $

RF Modems ................................................................ 14.4.9.2 $

SENSORS .................................................................. 14.4.7

Serial I/O (SIO) Boards A5 through A11 .................................. 14.4.2.3, F14.4.4

Setting Up SCA Modems ................................................... 14.5.3.3.1

Setting Up Stand-Alone (S/A) Modems ........................................ 14.5.3.3.2

SIO Port Assignments ........................................................ T14.4.1

SITE DESCRIPTION ......................................................... 14.1.2

Symptom Analysis ........................................................... T14.5.5

System Diagnostics ........................................................ 14.5.3.1.1

Telephone Modems .......................................................... 14.4.9.1

Tools and Test Equipment ..................................................... 14.5.1.1

UPS 7A1A1A6 Installation Procedure ........................................... T14.5.9

UPS 7A1A1A6 Removal Procedure ............................................. T14.5.8

UPS DIP Switch Setup (Deltek UPS 62828-90338-10 Only) ......................... T14.5.10 $

User Modems 7A1A1A9, A10 Description ..................................... 14.1.8.1.7

Visual Inspection Procedures .................................................. T14.5.2

VME Rack 7A1A1A2, Controls and Indicators ..................... 14.3.2.2, F14.3.2, T14.3.2

VME Rack 7A1A1A2 Description ....................... 14.1.8.1.1, F14.1.4, F14.5.1, F14.5.3

VME Resistor Board A14 ..................................................... 14.4.2.5

Voice Audio Board A21 .................................................... 14.4.2.7.2

Voice Processor Board A20 ................................................. 14.4.2.7.1

Warmup and Initialization ..................................................... 14.5.3.1

SCREENS, CONFIGURATION ............................................. 1.3.16, F1.3.41

Hardware Configuration Screen ......................................... 1.3.16.1, F1.3.42

Sensor Configuration Screen ............................................ 1.3.16.2, F1.3.43

Sensor-Algorithm Configuration Screen ................................... 1.3.16.3, F1.3.44

Define Configuration Screen ............................................ 1.3.16.4, F1.3.45

ACU Serial Communications Screen ..................................... 1.3.16.5, F1.3.46

External Communications Screen ........................................ 1.3.16.6, F1.3.47
ASOS Site Technical Manual S100

INDEX

Subject Paragraph, Figure, Table

Index 16 Change 1

S -CONT

SCREENS, MAINTENANCE 

$ A/D Screen Description. ................................................ 1.3.4.12, F1.3.9

$ ACU/DCP Communications Status Screen ................................. 1.3.4.36, F1.3.34

$ ACU Modem Screen .................................................. 1.3.4.15, F1.3.12

$ ACU Power Screen ................................................... 1.3.4.16, F1.3.13

$ ACU Status Screen ..................................................... 1.3.4.7, F1.3.4

$ ACU UPS Screen ............................................. 1.3.4.17, F1.3.14, T1.3.9

$ ACU VME Cards Screen ................................................ 1.3.4.8, F1.3.5

$ ADAS Summary Screen ............................................... 1.3.4.38, F1.3.36

$ Calibration Maintenance Action Screen ................................... 1.3.4.43, F1.3.38

$ Ceilometer and Ceilometer Sensor Dialogue Screens .......... 1.3.4.23, F1.3.20, F1.3.21, T1.3.13

$ Corrective Maintenance Action Screen .................................... 1.3.4.21, F1.3.38

$ CPU Screen .................................................... 1.3.4.9, F1.3.6, T1.3.4

$ DCP #1, #2, #3 Power Screen ........................................... 1.3.4.21, F1.3.18

$ DCP UPS Screen ............................................. 1.3.4.22, F1.3.19, T1.3.12

$ DCP VME Cards Screen Description. .................................... 1.3.4.20, F1.3.17

DESCRIPTIONS ............................................ 1.3.4, F1.3.2, F1.3.3, T1.3.2

$ Field Modification Kit Action Screen ..................................... F1.3.40, 1.3.4.44

$ Freezing Rain Screen .................................................. 1.3.4.24, F1.3.22

$ Frozen Precipitation Screen ............................................ 1.3.4.31, F1.3.29

$ Graphics Screen ............................................... 1.3.4.13, F1.3.10, T1.3.7

$ GTA Radio Screen ........................................... 1.3.4.18, F1.3.15, T1.3.10

$ Keypad ............................................................... 1.3.4.2, F1.3.1

$ Maintenance Action Screen ............................................ 1.3.4.40, F1.3.38

Maintenance Action Selection .................................................. 1.3.4.6

$ Memory Screen .................................................. 1.3.4.10, F1.3.7, T1.5

$ Present Weather Sensor Screen .................................. 1.3.4.25, F1.3.23, T1.3.14

$ Pressure Sensor Screen. ............................................... 1.3.4.35, F1.3.33

$ Preventive Maintenance Action Screen ................................... 1.3.4.41, F1.3.39

$ Processor Status Screen ................................................ 1.3.4.39, F1.3.37

$ Remote DCP Status Screen Description ........................... 1.3.4.19, F1.3.16, T1.3.11

Sensor Data Quality, Report Process, and Sensor Response Fields ...................... 1.3.4.4

$ Serial I/O Screen ............................................... 1.3.4.11, F1.3.8, T1.3.6

$ Snow Depth Screen ................................................... 1.3.4.32, F1.3.30

Status Indicator Fields ......................................................... 1.3.4.3

$ Sunshine Screen ..................................................... 1.3.4.33, F1.3.31

$ Temperature/Dewpoint (Model 1088) Screen ....................... 1.3.4.27, F1.3.25, T1.3.16

$ Temperature/Dewpoint (Model H083) Screen .............................. 1.3.4.28, F1.3.26

$ Thunderstorm Screen ........................................................ F1.3.32

$ Tipping Bucket Sensor Screen .......................................... 1.3.4.30, F1.3.28

Trend Screen ........................................................ 1.3.4.37, F1.3.35

$ Visibility Sensor Screen ....................................... 1.3.4.29, F1.3.27, T1.3.17

$ Voice Screen ................................................. 1.3.4.14, F1.3.11, T1.3.8

$ Wind Speed and Direction Sensor Screen .......................... 1.3.4.26, F1.3.24, T1.3.15

SCREENS, SITE ................................................................ 1.3.17

$ Site Criteria Screen ................................................... 1.3.17.5, F1.3.55

$ Site Normals Screen .................................................. 1.3.17.3, F1.3.53

$ Site Physical Screen .................................................. 1.3.17.1, F1.3.48
S100 ASOS Site Technical Manual

INDEX

Subject Paragraph, Figure, Table

Change 1 Index 17

S -CONT

SCREENS, SITE -CONT

Site Pressure Screen .................................................. 1.3.17.4, F1.3.54 $

Site Version AOMC Screen ............................................ 1.3.17.2, F1.3.52 $

Site Version Screen ................................................... 1.3.17.2, F1.3.49 $

Site Version SW Screen ............................................... 1.3.17.2, F1.3.50 $

Sensor Data Quality Algorithm Checks ............................................... T1.3.1

SENSOR POWER, MONITORING/CONTROLLING FROM THE OID .............. 1.3.9, T1.3.21 $

SENSORS ...................................................................... 1.4.5

System Diagnostics .............................................................. 1.5.4.2

SYSTEM CONFIGURATIONS ..................................................... 1.1.5

SYSTEM MAINTENANCE LOG ENTERING DATA .......................... 1.3.13, T1.3.27 $

SYSTEM MAINTENANCE LOG REVIEWING/PRINTING ............... 1.3.12, T1.3.25, T1.3.26 $

SYSTEM POWER OFF PROCEDURES ............................................. 1.3.15

SYSTEM POWER ON PROCEDURES ............................................... 1.3.5

SYSTEM SIGN-ON ........................................................ 1.3.6, T1.3.18 $

SYSTEM SIGN OFF ....................................................... 1.3.7, T1.3.19 $

SYSTEM SPECIFICATIONS ................................................. 1.1.7, T1.1.2

T

TEMPERATURE/DEWPOINT SENSOR ............................................ F5.1.1

+5 Volt Power Supply 2MT4A2A3 ............................................ 5.1.2.5.3

Aspirator 2MT4A1 .............................................. 5.1.2.4, 5.4.3.2, F5.1.2

Aspirator Cleaning and Inspection ......................................... 5.5.2.2, T5.5.2

Autobalance Module 2MT4A2A5 ............................................. 5.1.2.5.5

Auxiliary Power Supply 2MT4A2A4 ........................................... 5.1.2.5.4

Calibration .................................................... 5.5.2.7, T5.5.9, T5.5.11

Calibrator Assembly 2MT4A2A2 .............................................. 5.1.2.5.2

CHECKOUT PROCEDURES ................................................... 5.3.4

CONFIGURATIONS .......................................................... 5.1.3

CONTROLS AND INDICATORS .................................... 5.3.2, F5.3.1, T5.3.1

CORRECTIVE MAINTENANCE ................................................ 5.5.3

DC Power Supply Check ................................................. 5.5.2.6, T5.5.8

DETAILED BLOCK DIAGRAM DESCRIPTION ................. 5.4.3, F5.4.1, F5.4.2, F5.4.3

Fan Fail Monitoring Circuit Test and Adjustment (Model 1088 Only) ............. 5.5.2.5, T5.5.7
ASOS Site Technical Manual S100

INDEX

Subject Paragraph, Figure, Table

Index 18 Change 1

T -CONT

TEMPERATURE/DEWPOINT SENSOR -CONT

Fiberoptic Module 2MT4A2A6 ............................................... 5.1.2.5.6

FRU’s Common to -30 and -40 Configurations ..................................... 5.1.3.1

FRU’s Unique to Each Configuration ............................................. 5.1.3.2

INSTALLATION ........................................... 5.2.2, F5.2.1, T5.2.1, T5.2.2

MEASUREMENT SYSTEM CONCEPTS ......................................... 5.4.2

Model 1088 Checkout ......................................................... 5.3.4.2

Model H083R Checkout ....................................................... 5.3.4.1

NORMAL OPERATING PROCEDURES .......................................... 5.3.6

Optical Loop Adjustment ......................................... 5.5.2.3, T5.5.3, T5.5.4

Physical Components ......................................................... 5.1.2.2

PHYSICAL DESCRIPTION ..................................................... 5.1.2

PREVENTIVE MAINTENANCE .......................................... 5.5.2, T5.5.1

Principles of Operation ........................................................ 5.1.2.3

Removal and Installation

Autobalance Module ......................................... 5.5.3.6, T5.5.16

Aspirator Housing ........................................... 5.5.3.4, T5.5.14

Dewpoint Sensor Assembly .................................... 5.5.3.3, T5.5.13

Fiberoptic Module ........................................... 5.5.3.8, T5.5.19

Power Supplies ..................................... 5.5.3.7, T5.5.17, T5.5.18

Transmit Logic Board ........................................ 5.5.3.5, T5.5.15

RUNNING DIAGNOSTICS ..................................................... 5.3.5

“T” Commands for Model 1088 Checkout ....................................... , T5.5.10

Temperature/Dewpoint Sensor Turnoff Procedures ................................. , T5.3.3

Transmit Logic Board 2MT4A2A1 ............................................. 5.1.2.5.1

Transmitter 2MT4A2 ............................................ 5.1.2.5, 5.4.3.3, F5.1.3

Troubleshooting Procedures ............................................. 5.5.3.1, T5.5.12

TURN-ON PROCEDURES ............................................... 5.3.3, T5.3.2

TURNOFF PROCEDURES ..................................................... 5.3.7

Verify ASOS Temperature and Dewpoint Readings .................... 5.5.2.4, T5.5.5, T5.5.6

$ THUNDERSTORM SENSOR

$ CALIBRATION ............................................................. 16.5.4

$ CHECKOUT PROCEDURES .................................................. 16.3.4

$ COMMAND DESCRIPTION ................................................... 16.4.3

$ Host Mode ................................................ 16.4.3.1, T16.4.1

$ Perform Self-test ........................................... 16.4.3.4, T16.4.4

$ Self-test Status Bytes ............................... 16.4.3.4.1, T16.4.5

$ Perform Type Test .......................................... 16.4.3.6, T16.4.6

$ Send Present Weather Message ................................ 16.4.3.2, T16.4.2

$ Send Status Message ........................................ 16.4.3.3, T16.4.3

$ Send System Run Time ...................................... 16.4.3.7, T16.4.7

$ CONTROLS AND INDICATORS ..... 16.3.2, F16.3.1, F16.3.2, T16.3.1, T16.3.2, T16.3.3,T16.3.4

$ CORRECTIVE MAINTENANCE ............................................... 16.5.3

$ Troubleshooting ............................................ 16.5.3.2, T16.5.3

$ Using Laptop Computer With Thunderstorm Sensor ............... 16.5.3.1, T16.5.2
S100 ASOS Site Technical Manual

INDEX

Subject Paragraph, Figure, Table

Change 1 Index 19

T -CONT

THUNDERSTORM SENSOR -CONT $

DIAGNOSTIC TESTS ................................................. 16.4.4, T16.4.8 $

Echo Test ........................................................ 16.4.4.2 $

Self-test ......................................................... 16.4.4.1 $

Switch Test ...................................................... 16.4.4.4 $

Type Test ........................................................ 16.4.4.5 $

Watchdog Timer Test .............................................. 16.4.4.3 $

FRU REMOVAL AND INSTALLATION ............ 16.5.5, T16.5.4, T16.5.5, T16.5.6, T16.5.7 $

INSTALLATION ................................ 16.2.1, F16.2.1, F16.2.2, F16.2.3, T16.2.1 $

NORMAL OPERATING PROCEDURES ......................................... 16.3.6 $

PHYSICAL DESCRIPTION ............................................. 16.1.2, F16.1.1 $

PREVENTIVE MAINTENANCE ........................................ 16.5.2, T16.5.1 $

PRINCIPLES OF OPERATION .......................................... 16.4.1, F16.4.1 $

RUNNING DIAGNOSTICS .................................................... 16.3.5 $

SIMPLIFIED BLOCK DIAGRAM DESCRIPTION .......................... 16.4.2, F16.4.2 $

Communications .................................................. 16.4.2.2 $

Lightning Categories ............................................... 16.4.2.4 $

Power and Power Supplies .......................................... 16.4.2.1 $

Processing Strokes and Flashes ....................................... 16.4.2.5 $

Self-tests ......................................................... 16.4.2.3 $

Signal Processing .................................................. 16.4.2.6 $

THUNDERSTORM SENSOR CONFIGURATIONS ......................... 16.1.3, T16.1.1 $

TURN-ON PROCEDURES ............................................. 16.3.3, T16.3.5 $

TURNOFF PROCEDURES ............................................. 16.3.7, T16.3.6 $

$

TIPPING BUCKET RAIN GAUGE (TBRG)

CONFIGURATIONS ......................................................... 10.1.3

CORRECTIVE MAINTENANCE ............................................... 10.5.3

DESCRIPTION OF OPERATION ........................................ 10.4.2, F10.4.1

Fault Isolation .............................................................. T10.5.2

Fiberoptic Transmitter Removal and Installation. ............................ 10.5.3.5, T10.5.5

Inspection and Calibration Check ............................................... T10.5.1

INSTALLATION .............................................. 10.2.2, F10.2.1, T10.2.1

PHYSICAL DESCRIPTION ............................................. 10.1.2, F10.1.1

PREVENTIVE MAINTENANCE ............................................... 10.5.2

Removal and Installation. ............................................ 10.5.3.3, T T10.5.3

Switch Removal and Installation. ........................................ 10.5.3.4, T10.5.4

Testing. ................................................................... 10.5.3.2

Tools and Test Equipment ......................................................... T1.5.1

U

Upload/Download Sequence ..................................................... 1.4.6.3.2
ASOS Site Technical Manual S100

INDEX

Subject Paragraph, Figure, Table

Index 20 Change 1

V

VISIBILITY SENSOR

AC and DC Power Troubleshooting .............................................. 6.5.3.2

AC Power Checks ........................................................... , T6.5.5

Accuracy .................................................................. , T6.1.1

ASSEMBLY ................................................................. 6.2.2

Basic Block Diagram Description ................................................ 6.4.2.2

CABLES .............................................................. 6.2.3, T6.2.4

Cabling .................................................................... 6.1.2.3

Calibration ............................................................ 6.5.2.2, T6.5.3

Calibration Data Sheet ....................................................... , F6.5.1

Cleaning and Inspection ...................................................... , T6.5.2

COMMAND DESCRIPTION .................................................... 6.4.4

Configurations ............................................................... 6.1.3.1

CONTROLS AND INDICATORS ................................................ 6.3.2

CORRECTIVE MAINTENANCE ................................................ 6.5.3

Crossarm ................................................................... 6.2.2.5

Crossarm Support ...................................................... 6.2.2.4, F6.2.2

Crossarm/Support .......................................................... 6.1.2.1.1

Day/Night Assembly .................................................. 6.1.2.1.4, 6.4.3.3

Day/Night Sensor ............................................... 6.2.2.6, F6.2.3, T6.2.3

DC Power Checks ........................................................... , T6.5.4

DETAILED BLOCK DIAGRAM DESCRIPTION ............................. 6.4.3, F6.4.2

DIAGNOSTICS ............................................................... 6.5.4

Electronics Enclosure .............................. 6.1.2.2.1, F6.1.2, 6.2.2.3, F6.2.1, T6.2.2

Enclosure Support .............................................. 6.1.2.2.2, 6.2.2.2, T6.2.1

Fiberoptic Module ............................................................ 6.4.3.5

Heater ..................................................................... 6.5.3.3

Heater Troubleshooting ....................................................... , T6.5.6

Hinge Plate Assembly ......................................................... 6.2.2.1

Lower Section ............................................................... 6.1.2.2

NORMAL OPERATION ....................................................... 6.3.4

PHYSICAL DESCRIPTION ............................................... 6.1.2, F6.1.1

Power Distribution ..................................................... 6.4.3.6, F6.4.3

PREVENTIVE MAINTENANCE .......................................... 6.5.2, T6.5.1

Principles of Operation ........................................................ 6.4.2.1

Processor Board .............................................................. 6.4.3.4

Receiver Assembly ........................................................... 6.4.3.2

Receiver Assembly ......................................................... 6.1.2.1.3

REMOVAL AND INSTALLATION .............................................. 6.5.5

Crossarm Assembly .......................................... 6.5.5.7, T6.5.13

Day/Night Assembly ......................................... 6.5.5.4, T6.5.10

Electronics Enclosure. ........................................ 6.5.5.8, T6.5.14

Electronics Power Supply ..................................... 6.5.5.5, T6.5.11

Fiberoptic Module ........................................... 6.5.5.6, T6.5.12

Processor Board .............................................. 6.5.5.3, T6.5.9

Receiver Assembly ........................................... 6.5.5.1, T6.5.7

Regulator Board ............................................. 6.5.5.9, T6.5.15
S100 ASOS Site Technical Manual

INDEX

Subject Paragraph, Figure, Table

Change 1 Index 21

V -CONT

VISIBILITY SENSOR -CONT

Transmitter Assembly ......................................... 6.5.5.2, T6.5.8

SIMPLIFIED BLOCK DIAGRAM DESCRIPTION ............................ 6.4.2, F6.4.1

SPECIFICATIONS ............................................................ 6.1.3

Transmitter Assembly ......................................................... 6.4.3.1

Transmitter Assembly ....................................................... 6.1.2.1.2

TURN-ON PROCEDURES ..................................................... 6.3.3

TURNOFF PROCEDURES ..................................................... 6.3.5

Upper Section ............................................................... 6.1.2.1

Visual Inspection .......................................................... 1.5.3.2, T1.5.5

W

WIND SENSOR

ASSEMBLY ................................................................. 4.2.2

BLOCK DIAGRAM DESCRIPTION ........................................ 4.4.3, F4.4.2

Checking Wind Direction and Speed Data ................................... 4.5.2.4, T4.5.5

Cleaning and Lubrication ...................................................... 4.5.2.6

CONFIGURATIONS .......................................................... 4.1.3

CORRECTIVE MAINTENANCE ................................................ 4.5.3

Crossarm Assembly ........................................................... 4.1.3.3

Data Processing Board ........................................................ 4.4.3.3

Davis Pelorus Instrument ...................................................... F4.5.4

Davis Pelorus Instrument Wind Direction Sensor Alignment Procedure .......... 4.5.2.5.2, T4.5.4

Diagnostics ................................................................. 4.5.3.1

Electronics Enclosure ......................................................... 4.1.3.4

Fiberoptic Module ............................................................ 4.4.3.4

Installing Crossarm Support on Tower ............................... 4.2.2.2, F4.2.2, T4.2.2

Julian Calendar ............................................................. , F4.5.2

Lowering and Raising the Wind Tower ..................................... 4.5.3.3, T4.5.8

Mechanical Operation Inspection .......................................... 4.5.2.3, T4.5.2

Mounting Wind Sensor Electronics Enclosure ......................... 4.2.2.1, F4.2.1, T4.2.1

Obstruction Lights ...................................................... 4.4.3.6, F4.4.3

Obstruction Lights Check ...................................................... 4.5.2.2

PHYSICAL DESCRIPTION ............................................... 4.1.2, F4.1.1

PREVENTIVE MAINTENANCE .......................................... 4.5.2, T4.5.1

Removal and Installation ....................................................... 4.5.3.4

Crossarm Assembly ......................................... 4.5.3.10, T4.5.16

Cup Assembly and Vane Assembly .................................... T4.5.10

Fiberoptic Module ........................................... 4.5.3.6, T4.5.12

Power Supply ............................................... 4.5.3.5, T4.5.11

Processor Board ............................................. 4.5.3.7, T4.5.13

Wind Tower Signal Cable W1 ........................................ T4.5.15

Wind Direction and Wind Speed Sensors ................................ T4.5.9
ASOS Site Technical Manual S100

INDEX

Subject Paragraph, Figure, Table

Index 22 Change 1

W -CONT

WIND SENSOR -CONT

Wind Tower Signal Cable W1 ......................................... 4.5.3.9

Wind Sensor Electronics Enclosure ............................. 4.5.3.8, T4.5.14

Routine Inspection ............................................................ 4.5.2.1

Solar Noon Wind Direction Sensor Alignment Procedure ..................... 4.5.2.5.1, T4.5.3

Starting Torque Bearing Test ........................................... 4.5.3.11, T4.5.17

System Physical Components ................................................... 4.1.2.2

Temperature ................................................................. 4.4.2.2

Troubleshooting ............................................................. 4.5.3.2

True North Alignment ........................................................ , F4.5.5

Wind Alignment Procedures ................................................... , F4.5.3

Wind Direction Sensor ................................................. 4.1.3.2, 4.4.3.2

Wind Direction Sensor Alignment Tool .......................................... , F4.5.1

Wind Direction Sensor Alignment Procedure ....................................... 4.5.2.5

Wind Direction Transducer ................................................... 4.1.3.2.1

Wind Direction Vane Assembly ............................................... 4.1.3.2.2

Wind Sensor AC and DC Power Supply Checks .................................... T4.5.7

Wind Sensor Power Distribution ................................................. 4.4.3.5

Wind Sensor Troubleshooting ................................................... T4.5.6

Wind Speed and Direction ..................................................... 4.4.2.1

Wind Speed Cup Assembly ................................................... 4.1.3.1.2

Wind Speed Sensor .................................................... 4.1.3.1, 4.4.3.1

Wind Speed Transducer ..................................................... 4.1.3.1.1

WIND SENSOR SENSING TECHNIQUES .................................. 4.4.2, F4.4.1