MODEL 7250sys
MULTI-RANGE SYSTEM
USER’S MANUALDIGITAL PRESSURE CONTROLSYSTEM
MODEL 7250sys
USER’S MANUAL

RUSKA INSTRUMENT CORPORATIONGE RUSKA
10311 WESTPARK DR., HOUSTON, TEXAS 77042(713) 975-0547 FAX: (713) 975-6338
e-mail: ruska@ruska.com http://www.Ruska.com

Release: 7250sys-1D01
Revision: A
Date: 02/06/04

WARRANTY
Ruska Instrument Corporation warrants its products to conform to or exceed thespecifications as set forth in its catalogs in use at the time of sale and reserves the right,
at its own discretion, without notice and without making similar changes in articles
previously manufactured, to make changes in materials, designs, finish, or specifications.
Ruska Instrument Corporation warrants products of its own factory against defects ofmaterial or workmanship for a period of one year from date of shipment.
Liability of Ruska Instrument Corporation under this warranty shall be limited toreplacing, free of charge (FOB Houston, Texas), any such parts proving defective within
the period of this warranty, but will not be responsible for transportation charges orconsequential damages.
This warranty is not made for products manufactured by others which are illustrated anddescribed in Ruska catalogs or incorporated in Ruska products in essentially the same
form as supplied by the original manufacturer. However, Ruska Instrument Corporationagrees to use its best efforts to have original suppliers make good their warranties.

-ii-

INTRODUCTION

COPYRIGHT NOTICE
Copyright © 1997 by Ruska Instrument Corporation. All rights reserved. This document
may not be reproduced in part or in whole without the express written consent of Ruska
Instrument Corporation.

DISCLAIMER
No representations or warranties are made with respect to the contents of this user’s
manual. Further, Ruska Instrument Corporation reserves the right to revise this manualand to make changes from time to time in the content hereof without obligation to notify
any person of such revision.

TRADEMARK NOTICE® is a registered trademark of Ruska Instrument Corporation.
Trademarks or tradenames are subject to state and federal laws concerning theirunauthorized use or other infringements. The fact that the product marks or names inthis manual do not bear a trademark symbol DOES NOT mean that the product name ormark is not registered as a trademark or tradename. Any queries concerning theownership or existence of any trademarks or tradenames mentioned in this manual
should be independently confirmed with the manufacturer or distributor of the product.

-iii-

INTRODUCTIONREVISION NOTICERELEASENUMBERREV.

DATE OFRELEASE7250sys-1D01

A

02/06/04

DESCRIPTION

Original release. See DC/RO 24161-iv-

INTRODUCTIONREVISION HISTORYRELEASE 7250sys-1D01
Original release See DC/RO 24161

Revision A (02/06/04)-v-

INTRODUCTION

7250sys – Change Language

Holdmode key for 5 seconds

enter

-vi-

INTRODUCTION

SAFETY SUMMARY
The following are general safety precautions that are not related to any specificprocedures and do not appear elsewhere in this publication. These are recommended
precautions that personnel must understand and apply during equipment operation andmaintenance to ensure safety and health and protection of property.

KEEP AWAY FROM LIVE CIRCUITS
Operating personnel must at all times observe safety regulations. Do not replacecomponents or make adjustments inside the equipment with the voltage supply
connected. Under certain conditions, dangerous potentials may exist when the power
control is in the off position due to charges retained by capacitors. To avoid injuries,
always remove power from, discharge, and ground a circuit before touching it.

DO NOT SERVICE OR ADJUST ALONE
Do not attempt internal service or adjustment unless another person capable of rendering
aid and resuscitation is present.

RESUSCITATION
Personnel working with or near dangerous voltages shall be familiar with modern
methods of resuscitation. Such information may be obtained from your local American
Medical Association.

ELECTRO STATIC DISCHARGE SENSITIVE PARTSCAUTION: Electrostatic discharge sensitive (ESDS) is applied to low power, solid-stateparts which could be damaged or destroyed when exposed to discharges of static
electricity. Maintenance personnel are often not aware that an ESDS part has
been damaged or destroyed because electrostatic discharges at levels less than
4,000 volts cannot be seen, felt, or heard.

COMPRESSED GAS
Use of compressed gas can create an environment of propelled foreign matter. Pressure
system safety precautions apply to all ranges of pressure. Care must be taken during
testing to ensure that all pneumatic connections are properly and tightly made prior toapplying pressure. Personnel must wear eye protection to prevent injury.

PERSONAL PROTECTIVE EQUIPMENT
Wear eye protection approved for the materials and tools being used.

INERT GASES
Operation of pressure equipment may be accompanied by the discharge of inert gases tothe atmosphere. The result is a reduction of oxygen concentration. Therefore, it isstrongly suggested that exhaust gases not be trapped in the work area.

-vii-

INTRODUCTION

TABLE OF CONTENTSWARRANTY ............................................................................................................ -iiCOPYRIGHT NOTICE ............................................................................................ -iiiREVISION NOTICE ................................................................................................ -ivREVISION HISTORY................................................................................................ -vCHANGE LANGUAGE........................................................................................... -viSAFETY SUMMARY ............................................................................................... -viiTABLE OF CONTENTS ..........................................................................................-viii-

SECTION 1.0: GENERAL INFORMATION
1.1
1.2
1.3
1.4

INTRODUCTION...............................................................................1-1
GENERAL INFORMATION ................................................................1-1
FEATURES .........................................................................................1-1
STANDARD EQUIPMENT & OPTIONS ..............................................1-3

SECTION 2.0: THEORY OF OPERATION
2.1
2.2
2.3

2.4

2.5

2.6

INTRODUCTION...............................................................................2-1
POWER SUPPLY.................................................................................2-2
ELECTRONICS MODULE ...................................................................2-2
2.3.1 BACK-PLANE BOARD ................................................................2-2
2.3.2 MICROPROCESSOR BOARD......................................................2-2
2.3.3 DIGITAL CONTROL BOARD ......................................................2-3
2.3.4 IEEE-488 INTERFACE ................................................................2-3
2.3.5 FRONT PANEL ..........................................................................2-3
PNEUMATICS MODULE ....................................................................2-4
2.4.1 MEASURE MODE PNEUMATICS.................................................2-5
2.4.1.1 Reference Port..............................................................2-5
2.4.1.1.1 Barometric Sensor...........................................2-5
2.4.1.1.2 Absolute with Evacuated Reference - Optional ..2-5
2.4.1.2 Test Port ......................................................................2-6
2.4.1.3 Vent Procedure ............................................................2-6
2.4.2 CONTROL MODE PNEUMATICS.............................................2-6
2.4.2.1 Pressure Supply Port .....................................................2-6
2.4.2.2 Vacuum Supply (Exhaust) Port .......................................2-6
2.4.2.3 Pressure Control ..........................................................2-7
CONTROL STRATEGY .......................................................................2-7
2.5.1 INNER VS OUTER LOOPS..........................................................2-7
2.5.2 NORMAL MODE.......................................................................2-7
2.5.3 FAST MODE .............................................................................2-7
2.5.4 ALIGNMENT OF INNER LOOP WITH OUTER LOOP ...................2-8
2.5.5 PID CONTROL..........................................................................2-8
TRANSDUCER MODULE ...................................................................2-9
2.6.1 QUARTZ BOURDON TUBE SENSOR (TRANSDUCER01) ..............2-9
2.6.2 SENSOR BOARD.....................................................................2-10-viii-INTRODUCTION

2.7

2.6.3 LINEARIZATION TERM.............................................................2-10
2.6.4 AUXILIARY SENSORS...............................................................2-11
2.6.4.1 Case Reference Vacuum Sensor - Option ....................2-11
SOFTWARE ...................................................................................2-11
2.7.1 SOFTWARE SAFETY CONTROLS ..............................................2-11
2.7.1.1 Preventing Operator Errors .........................................2-11
2.7.1.2 Pneumatic Errors........................................................2-11
2.7.1.3 Shutoffs .....................................................................2-12
2.7.1.4 Oven Control ............................................................2-12
2.7.1.5 Pressure Reading and Correction ................................2-13

SECTION 3.0: INSTALLATION
3.1
3.2
3.3
3.4
3.5

INTRODUCTION...............................................................................3-1
UNPACKING THE DPC .....................................................................3-1
CAUTIONS .....................................................................................3-2
POWERING UP THE DPC ..................................................................3-2
3.4.1 OBSERVING THE DPC’S FULL SCALE RATING ............................3-2
PNEUMATIC CONNECTIONS...........................................................3-2
3.5.1 PRESSURE SUPPLY PORT............................................................3-2
3.5.2 EXHAUST PORT ........................................................................3-3
3.5.3 TEST PORT................................................................................3-3
3.5.4 REFERENCE PORT .....................................................................3-3
3.5.5 VACUUM SENSOR OPTION ......................................................3-4

SECTION 4.0: LOCAL OPERATION
4.1

4.2
4.3

4.4
4.5

4.6

TUTORIAL .....................................................................................4-3
4.1.1 SELECTING LANGUAGE ...........................................................4-5
4.1.2 SELECTING MODE OF OPERATION ..........................................4-6
4.1.2.1 Simulated Absolute Instruments.....................................4-6
MAIN MENU .....................................................................................4-6
CONTROLLING PRESSURE................................................................4-7
4.3.1 SETTING THE PRESSURE SETPOINT............................................4-7
4.3.2 ENTERING/EXITING CONTROL MODE......................................4-7
4.3.3 ABSOLUTE ZERO OF DEVICE UNDER TEST - OPTION ................4-7
VENT .................................................................................................4-8
STEP | JOG .....................................................................................4-8
4.5.1 STEPPING.................................................................................4-8
4.5.1.1 Setting Step Size...........................................................4-8
4.5.2 JOGGING................................................................................4-8
MENU ...............................................................................................4-8
4.6.1 MENU | SETUP .........................................................................4-9
4.6.1.1 Menu | Setup - Limits ...................................................4-9
4.6.1.1.1 High Limit ....................................................4-10
4.6.1.1.2 Low Limit......................................................4-10
4.6.1.1.3 Auto Vent .....................................................4-10-ix-

INTRODUCTION

4.6.1.1.4 Control Band................................................4-11
4.6.1.1.5 Control ........................................................4-11
4.6.1.1.6 Supply Correction .........................................4-11
4.6.1.1.7 Slew Rate .....................................................4-11
4.6.1.1.8 Slew Limit .....................................................4-11
4.6.1.1.9 Access..........................................................4-12
4.6.1.2 Menu | Setup - User...................................................4-12
4.6.1.2.1 Step Size ......................................................4-12
4.6.1.2.2 Bar Graph Maximum ....................................4-13
4.6.1.2.3 Ready Tolerance ...........................................4-13
4.6.1.2.4 Gas Head Pressure Correction.......................4-13
4.6.1.2.5 Atmosphere..................................................4-13
4.6.1.2.6 Pressure Filter ...............................................4-13
4.6.1.2.7 Changing the Number of Decimals................4-14
4.6.1.2.8 Key Click ......................................................4-14
4.6.1.3 Menu | Setup - Units ..................................................4-14
4.6.1.4 Menu | Setup - Remote ..............................................4-15
4.6.1.4.1 GPIB Address................................................4-16
4.6.1.4.2 Protocol........................................................4-16
4.6.1.4.3 Serial Interface Set-Up...................................4-16
4.6.1.5 Menu | Setup - System ...............................................4-16
4.6.1.5.1 Date | Time..................................................4-16
4.6.1.5.2 Reset ............................................................4-17
4.6.2 MENU | CALIBRATE ................................................................4-17
4.6.2.1 Calibration Password .................................................4-17
4.6.2.2 Zeroing .....................................................................4-18
4.6.3 MENU | PROGRAM - STORING A SEQUENCE IN MEMORY .....4-18
4.6.3.1 Preparing to Program.................................................4-19
4.6.3.2 Entering a New Program ............................................4-20
4.6.3.3 Automatically Generating a Program ..........................4-21
4.6.3.4 Changing the Name of a Program..............................4-22
4.6.3.5 Changing an Existing Program ...................................4-23
4.6.3.6 Changing the Configuration Stored with a Program .....4-24
4.6.3.7 Running a Program ....................................................4-25
4.6.4 MENU | TEST .........................................................................4-25
4.6.4.1 Menu | Test - Sweep Test ...........................................4-26
4.6.4.2 Menu | Test - Self Test................................................4-27
4.6.4.3 Menu | Test - Remote Test ..........................................4-27
4.6.4.4 Menu | Test - Shop 1 .................................................4-27
4.6.4.5 Menu | Test - Control.................................................4-28
4.6.5 MENU | DISPLAY ....................................................................4-28
4.6.5.1 Menu | Display - Temperature....................................4-29
4.6.5.2 Menu | Display - Vacuum...........................................4-29
4.6.5.3 Menu | Display - Blank ..............................................4-29-x-

INTRODUCTION

SECTION 5.0: REMOTE OPERATION
5.1
5.2
5.3
5.4

5.5
5.6

CAPABILITIES ....................................................................................5-1
5.1.1 IEEE-488 ..................................................................................5-1
5.1.2 RS-232 .....................................................................................5-1
REMOTE/LOCAL OPERATION...........................................................5-2
CONFIGURATION ............................................................................5-2
DEVICE MESSAGES ...........................................................................5-3
5.4.1 SCPI COMMAND FORMAT .......................................................5-3
5.4.2 SCPI RESPONSE FORMAT..........................................................5-3
5.4.3 ANSI/IEEE 488.2-1987 COMMAND SUMMARY .........................5-4
5.4.4 SCPI COMMAND SUMMARY.....................................................5-4
5.4.5 EXAMPLE SCPI COMMANDS .....................................................5-9
5.4.6 SCPI STATUS REGISTERS ...........................................................5-9
SERIAL OPERATION ........................................................................5-11
SAMPLE PROGRAMS .......................................................................5-11
5.6.1 SAMPLE PROGRAM 1 - 7252 GPIB (IEEE-488) - CONTROLSPRESSURE TO 20.000%FS .......................................................5-11
5.6.2 SAMPLE PROGRAM 2 - 7252 GPIB (IEEE-488) - ZEROSEQUENCE ............................................................................5-14
5.6.3 SAMPLE PROGRAM 3 - 7252 SERIAL (RS-232) - CONTROLSPRESSURE TO 20.000%FS ......................................................5-17
5.6.4 SAMPLE PROGRAM 4 - QBASIC EXAMPLE FOR 7252 ...............5-21

SECTION 6.0: MAINTENANCE
6.1
6.2
6.3

6.4

INTRODUCTION...............................................................................6-1
OBSERVING THE SOFTWARE VERSION NUMBER............................6-1
PREVENTIVE MAINTENANCE ...........................................................6-1
6.3.1 INITIATING THE DPC'S SELF TEST ..............................................6-1
6.3.2 REMOVING THE DPC'S COVER .................................................6-2
6.3.3 MOISTURE FILTER .....................................................................6-2
6.3.4 PARTICLE FILTERS .....................................................................6-2
6.3.5 VACUUM PUMPS ......................................................................6-2
6.3.6 PROCESSOR BATTERY...............................................................6-3
CALIBRATION ...................................................................................6-3
6.4.1 CALIBRATION INSTRUCTIONS ..................................................6-3
6.4.1.1 Preparation..................................................................6-3
6.4.1.2 Storing the Coefficients.................................................6-6
6.4.2 VACUUM (NEGATIVE GAUGE) CALIBRATIONS ..........................6-7
6.4.3 RPT CALIBRATION - SIMULATED ABSOLUTE ..............................6-8
6.4.4 VACUUM SENSOR CALIBRATION - OPTIONAL CASE
REFERENCE SENSOR.................................................................6-9
6.4.5 EDITING THE CALIBRATION COEFFICIENTS ............................6-10
6.4.6 ZEROING ...............................................................................6-11
6.4.6.1 Gauge and Vacuum (Negative Gauge) Instruments .....6-11
6.4.6.2 Absolute Mode with Evacuated Reference ....................6-12-xi-

INTRODUCTION

6.4.6.3 RPT - Simulated Absolute Instruments ..........................6-13
6.4.6.4 Zero All .....................................................................6-13
6.5 SENSOR PHOTOCELL ZEROING.....................................................6-13
6.6 OPTIMIZING CONTROL..................................................................6-16
6.7 FAN OPERATION............................................................................6-18
6.8 SYSTEM SOFTWARE UPDATE PROCEDURE ....................................6-19
6.9 REPLACEMENT PARTS.....................................................................6-20
6.10 PRESSURE INTENSIFIER - OPTION .................................................6-21

SECTION 7.0: PREPARATION FOR STORAGE & SHIPMENT
7.1
7.2
7.3

DISCONNECTING THE DPC .............................................................7-1
PACKING INSTRUCTIONS ................................................................7-1
SHIPPING INSTRUCTIONS ...............................................................7-2

APPENDIX A: SUMMARY OF SPECIFICATIONS
A.1
A.2

UNCERTAINTY ANALYSIS.................................................................A-1
SPECIFICATIONS ..............................................................................A-6

APPENDIX B: SUMMARY OF ERROR MESSAGES .................................... B-1
LIST OF FIGURESFIGURE 2-1: DPC BLOCK DIAGRAM .......................................................................2-1
FIGURE 2-2: MODEL 7252sys DPC GAUGE PNEUMATICS DIAGRAM .......................2-4
FIGURE 2-3: PRESSURE CONTROL NORMAL MODE ................................................2-8
FIGURE 2-4: PRESSURE CONTROL FAST MODE.......................................................2-9
FIGURE 2-5: SHAFT/MAGNET SECTION................................................................2-10
FIGURE 2-6: PHOTOCELL/LIGHT SPOT .................................................................2-10
FIGURE 4-1: MODEL 7252sys FRONT PANEL ..........................................................4-1
FIGURE 4-2: MENU TREE .....................................................................................4-2
FIGURE 6-4: VACUUM (NEGATIVE GAUGE) CALIBRATION ......................................6-7
FIGURE 6-5: PHOTOCELL LOCATION...................................................................6-15

LIST OF TABLESTABLE 2-1:
TABLE 2-2:
TABLE 3-1:
TABLE 6-1:
TABLE A-1:

CONVERSION FACTORS.....................................................................2-3
MANIFOLD SOLENOID VALVE STATES.................................................2-5
GENERAL SPECIFICATIONS: GENERAL PARAMETERS ............................3-1
ELECTRONICS SELF TEST ....................................................................6-2
PERFORMANCE SPECIFICATIONS........................................................A-6-xii-

INTRODUCTION

SECTION 1.0
GENERAL INFORMATION
1.1 INTRODUCTION
This manual contains operation and routine and preventive maintenance instructions for
the Model 7250sys Digital Pressure Control System (DPC) manufactured by GE
Ruska, Houston, Texas. This section of the manual provides general information about
the DPC and presents its features and options.
1.2 GENERAL INFORMATIONThe GE Ruska Model 7250sys DPC uses force-balanced, fused-quartz Bourdon tube
technology to provide the precise measurement of pressure. During normal operation,
the DPC performs in either Measure mode or Control mode.
In Control mode, the DPC simultaneously measures and controls pressure. Control
mode is commonly used in the calibration and testing of pressure gauges, transducers,pressure switches, and production pressure instruments.
In Measure mode, the DPC measures pressure. Typically, Measure mode applications
are found in research laboratories, wind tunnel testing, power plant testing, and bubbler
tank volume accountancy systems. It is also used to monitor barometric pressures,vacuum systems, and differential pressure devices.
The 7250sys has two full scale pressure ranges and two pressure controllers integrated
into one instrument.
1.3 FEATURES
The following features are available on all Model 7250sys DPC’s.
Multiple Ranges of Fused-Quartz Bourdon Tube Sensor Technology: GE Ruska’sforce-balanced, fused-quartz Bourdon tube sensor makes use of the stability, highelasticity, low hysteresis, and excellent fatigue strength of fused quartz. The 7250sys
integrates multiple ranges into the system. The system automatically switches between
these ranges as it controls pressures, selecting the most accurate sensor to perform apressure measurement.
NIST Traceability: All DPC’s are calibrated using GE Ruska deadweight gauges which
are directly traceable to the National Institute of Standards and Technology (NIST). GE
Ruska is also a NVLAP accredited laboratory and therefore can provide an optional
NVLAP accredited calibration.
Universal Power Supply: The DPC’s universal power supply accepts AC voltages
between 90 and 260 volts, and DC voltages between 100 and 370 volts. To“reconfigure” the DPC for use in another country, the user simply changes the power
cord.
Measure While Control: The DPC simultaneously digitally displays the commanded
pressure, the actual pressure, and the difference between the two. The system integrates

1-1

INTRODUCTION

multiple controllers and automatically switches between these controllers to enhancecontrol performance throughout the range of the system.
Friendly Display: The DPC’s color active matrix TFT display combines a bright, lowglare readout with a wide viewing angle. During normal operation, the measured
pressure is easily visible from a distance of 10 feet (3 meters).
Adjustable Pressure Display: The pressure display may be adjusted to show one
decimal greater than or less than the default resolution.
Ease of Operation: An intuitive, menu-driven interface makes the DPC easy to use.
Frequently used selections such as the units of measure are restored to memory eachtime the DPC powers up.
Easily Programmable: The DPC’s powerful microprocessor provides the basis for smart
electronics. With a few simple keystrokes, the user can set limits on the system pressure,create unique units of measure, program a test sequence, and more.
Modular Design: The sensing element, pneumatics, electronics, and user interface are
separated into modules, making maintenance faster and easier.
Power On Self Test: Upon power-up, the DPC quickly tests its hardware and software.
After the DPC completes this test, the user can select more extensive self-tests for thepneumatics and electronics.
Ease of Calibration: Calibration may be performed either remotely or entirely from thefront panel. No disassembly is required, and there are no potentiometers to tune. On
single sensor units, only a three-point calibration is required to fully characterize theinstrument. On instruments that integrate multiple ranges such as the 7250sys, threecalibration points are required per sensor range.
Automatic Zero Adjust: At the user’s request, the DPC’s software automatically
performs the zero adjustment, with no potentiometers to tune.
Automatic Head Correction: The DPC automatically corrects for head pressure
between the DPC and the device under test (DUT), taking into account the density of thetest gas; e.g., air or nitrogen.
Choice of Medium: Although the DPC is not sensitive to the type of gas used within thesystem, the user can select either instrumentation air or nitrogen, allowing the DPC toautomatically make pressure head corrections.
Choice of Display Units: Standard units include inHg at 0°C and 60°F, kiloPascals,
bars, psi, inH2O at 4°C, 20°C, and 25°C, kilograms per square centimeter, mmHg,
cmHg at 0°C, and cmH2O at 4°C. Altitude and airspeed units include feet, meters, knots,
and kilometers per hour. In addition to these predefined units, four user-defined units
are programmable.
Communications Interface: The DPC includes standard RS-232 serial and IEEE-488
interfaces. The user’s computer communicates with the DPC through the Standard
Commands for Programmable Instruments (SCPI) protocol.

INTRODUCTION

1-2

1.4 STANDARD EQUIPMENT & OPTIONS
A standard DPC includes this manual and a power cord. The components in the system
are mounted in either a table-top cabinet or stand-up roll around cabinet. Although thestandard DPC is fully functional with just these items and the appropriate pressure andvacuum supplies, the following options are also available.
NVLAP Accredited Calibrations - GE Ruska received formal accreditation from the
National Voluntary Laboratory Accreditation Program (NVLAP) which is administrated by
the National Institute of Standards and Technology (NIST). NVLAP has assigned GE
Ruska laboratory code 200491-0 to indicate that our accredited calibration services arein compliance with all relevant requirements of ISO/IEC 17025:1999 and ISO
9002:1994. GE Ruska's calibration laboratory can provide an optional accreditedpressure calibration. The NVLAP calibration certifications are optional and must be
requested at time of order.

1-3

INTRODUCTIONNOTESINTRODUCTION

1-4

SECTION 2.0
THEORY OF OPERATION
2.1 INTRODUCTION
The DPC’s power supply, electronics, pneumatics, and sensor combine to form acomplete, stand–alone, measure and control system. This section of the manual
describes the DPC’s component modules (Figure 2–1) and provides a general discussionof each.
Primary Dual Range Transducer Module A
Reference
Test
SupplyExhaustSection 2.4

Pneumatics
Module A

SENSOR
Section
2.6.1

REF.

PNEUMATICS

Photo
SensorSENSOR
BOARD
Section
2.6.2

TEST

INNER LOOPSENSOR

Primary Dual Range Transducer Module B
SENSOR
Section
2.6.1

Isolation
Valve

Photo
SensorBarometric
Reference

AC POWERAC
POWER
Section
2.2

POWER
SUPPLY
Section
2.2

BACKPLANEBOARDSENSOR
BOARD
Section
2.6.2

M
O
D
U
L
E

DIGITALCONTROLBOARD A
Section 2.3.3

Section 2.3.1

A

MICROPROCESSOR
BOARD
Section 2.3.2

FRONT
PANEL
Section
2.3.5

RS -232IEEE
CARD
Section
2.3.4

RS-485

Electronic Module A

IEEE-488

Primary Dual Range Transducer Module C
Reference
Test
SupplyExhaust

TEST
PORT

P
R
I
M
A
R
Y

Section 2.4

Pneumatics
Module B

SENSOR
Section
2.6.1

REF.

PNEUMATICS

Photo
SensorTESTINNER LOOPSENSOR

Primary Dual Range Transducer Module D
SENSOR
Section
2.6.1

Isolation
Valve

Photo
Sensor

REFERENCEPORT

AC POWERAC
POWER
Section
2.2

SENSOR
BOARD
Section
2.6.2

POWER
SUPPLY
Section
2.2

BACKPLANE
BOARD
Section 2.3.1

DIGITALCONTROLBOARD B
Section 2.3.3

SENSOR
BOARD
Section
2.6.2

P
R
I
M
A
R
Y
M
O
D
U
L
E
B

Electronic Module B

FIGURE 2-1
DPC BLOCK DIAGRAM
2-1

THEORY OF OPERATIONThe 8 range 7250sys has two pneumatic control and four dual-range primary transducer
modules. A 12 range 7250sys system incorporates a Primary Module C in addition to
the hardware denoted in Figure 2-1. This module would contain the Pneumatic Module
C and the dual-range transducer modules E and F and would be connected into thesystem as the Primary Module B is connected.
2.2 POWER SUPPLYThe DPC’s universal power supply accepts AC voltages from 90 to 260 volts at 47-63 Hz.
and DC voltages from 100 to 370 volts. This quad–output supply produces +5 VDC,+/-12 VDC, and 24 VDC which are distributed to the Control and Backplane Boards.
2.3

ELECTRONICS MODULE

2.3.1 BACK-PLANE BOARD
The Back-plane Board is used to interconnect all of the plug-in electronic boards anddistribute power. The Microprocessor Board, the Digital Control Board, and the IEEE–
488 Interface all plug into the Back-plane Board. The Front Panel communicates with theMicroprocessor Board via cables.
The Sensor Board communicates with theMicroprocessor board through an internal RS-485 serial communication bus.
2.3.2 MICROPROCESSOR BOARD
All of the DPC’s software resides in nonvolatile, programmable, read–only memory(Flash EPROM) on the Microprocessor Board, which plugs directly into the Back-plane
Board. This software contains all of the instructions that operate the DPC, as well as theconversion factors that the DPC uses to translate the internal pressure unit-of measure ofkPa into the units selected by the user. These factors are given in Table 2–1.
Data that is subject to change after the DPC leaves the factory are held in electricallyerasable, programmable, read–only memory (EEPROM). This includes the current unitsof measure, the coefficients from the zeroing process, the current pressure medium,
calibration coefficients, and the conversion factors for the four user–defined units ofmeasure.
When the DPC powers up, its software is loaded into random access memory (RAM), also
on the Microprocessor Board. At the same time, the values stored in EEPROM Board arerestored to memory.
Another important component on the Microprocessor Board is the lithium battery. The
battery continuously updates the DPC’s date and time, even when the unit is powered
down. This battery has a varying life. If the instrument is left on 24 hours a day, it may
last 5 to 10 years. If the instrument is stored, it may only last one year.
The Microprocessor Board also supports the RS–232 serial interface that allows the user’s
computer to communicate with the DPC.

THEORY OF OPERATION

2-2

Symbol

Description

Conversion Factor

InHg

inches of mercury (0 °C)= kPa x 0.2952998

InHg

inches of mercury (60 °F)= kPa x 0.296134

KPa

KiloPascals= kPa x 1.0

Bar

Bars

= kPa x 0.01

Psi

pounds per square inch

= kPa x 0.1450377

cmH20

Centimeters of water (4 °C)= kPa x 10.19744

inH20

inches of water (4 °C)= kPa x 4.014742

kg/cm2

kilograms per square centimeter= kPa x 0.0101972

mmHg

Millimeters of mercury (0 °C)= kPa x 7.500605

cmHg

Centimeters of mercury (0 °C)= kPa x 0.7500605

knots

indicated airspeed

per NASA TN D–822

km/hr

kilometers per hour

= knots x 1.852

Feet

feet of altitude

per MIL–STD–859A

metersmeters of altitude

per MIL–STD–859A

User1

user defined= kPa x user definedUser2

user defined= kPa x user definedPauser defined (Pascals)= kPa x 1000.0hPa

user defined (hectoPascals)= kPa x 10.0

%FS

percent of full scale
UNLESS SPECIFIED OTHERWISE, CONVERSION FACTORS ARE BASED ON ANSI 268–1982.

TABLE 2–1
CONVERSION FACTORS
2.3.3 DIGITAL CONTROL BOARD
The Digital Control Board plugs directly into the Back-plane Board. This board reads ahigh speed silicon strain gauge pressure transducer, PDCR, connected to the pressure
generation point. A digital controller on the board drives two solenoids in thepneumatics section to form a high speed, closed loop controller.
2.3.4 IEEE–488 INTERFACEThe DPC’s IEEE–488 (GPIB) interface card, which plugs directly into the Back-plane
Board, provides the DPC with an IEEE–488 interface. This interface allows the user toautomate the measurement and control processes.
2.3.5 FRONT PANEL
The Front Panel contains the active matrix TFT color display, rotary knob and rubberized
keys used to operate the DPC.

2-3

THEORY OF OPERATION

2.4 PNEUMATICS MODULE
The DPC's Pneumatics Module varies depending on whether the DPC is a Gauge mode,
Absolute mode, or a Simulated Absolute mode instrument. Gauge mode DPC's
reference their measurements to atmospheric pressure, whereas Absolute mode DPC
measurements are made with respect to sealed vacuum. A Simulated Absolute mode
DPC has a barometric sensor in addition to a gauge Bourdon tube sensor. The DPC
adds the barometric reading to the Bourdon tube reading to obtain a Simulated Absolutevalue. It can operate as a Gauge mode instrument if the user selects to not add thereference pressure.
The valves, filters, and transducers that make up the pneumatics module of a Gauge
mode (or Simulated Absolute) DPC are shown in Figures 2-2a. The schematics for theAbsolute mode DPC is shown in Figures 2-2b.
In the sections that follow, the Zero, Isolation, Apply and Release valves are all
24–volt, DC solenoid valves that are either open or closed depending on the DPC’soperational mode. Their behavior is summarized in Table 2–2.
REFERENCE
PORT

TEST
PORT

SUPPLYPRESSURE PORTISOLATION(< 1000 PSI FS)
BAROMETRICREFERENCESENSOR(SIMULATEDABSOLUTEOPTION)EXHAUST
PORT

APPLY

RELEASEZERO

INNER LOOP CONTROL SENSOR
DUAL RANGEPRIMARY SENSOR A

VACUUMSENSOR
OptionVACUUMSENSOR
OptionControl Section

V
ISOLATION

DUAL RANGEPRIMARY SENSOR B

V

FIGURE 2–2
MODEL 7250sys DPC GAUGE PNEUMATICS DIAGRAM
0.36 to 2500 psig (2.5 kPa to 17.2 MPa) Full Scale Ranges
Note, this diagram depicts the components shown in the Primary Module A of
Figure 2-1.

THEORY OF OPERATION

2-4

ValveMeasure Mode

Vent

Control Mode

Zeroing

Test Port Isolation

open

open

open

close

Zero

close

close - open

close

open

Apply

close

close

modulate

close

Releaseclose

open - close

modulate

close

TABLE 2–2
MANIFOLD SOLENOID VALVES STATES
2.4.1 MEASURE MODE PNEUMATICS
Figures 2–2A summarizes the Pneumatics of the DPC.
2.4.1.1 Reference Port
For gauge measurements, the Reference Port is normally left open to atmosphere. This
port can be tied to the reference port of the device under test to assure a common
reference.
The Reference Port is isolated from the Test Port by a solenoid valve that is closed during
the DPC’s Measure and Control modes. When the user commands the DPC to performthe zeroing process, the solenoid automatically opens, and the pressures on the
Reference Port and Test Port become equal.
The Reference Port is protected by a relief valve.
2.4.1.1.1 Barometric Sensor
For Simulated Absolute instruments, the Reference Port is monitored by a precision
barometric sensor (Figure 2-2A). This sensor provides the barometric offset that allows
the gauge mode sensors to function in the absolute mode.
When operating in the simulated absolute mode, the lowest range sensor that the system
can select to operate in the absolute mode must have a full scale pressure range of 14.7
psig (101 kPa).
2.4.1.1.2 Absolute with Evacuated Reference – Optional
An option is available on the 7250sys that will allow a gauge mode instrument to operate
in the absolute mode by evacuating the sensors reference port with an external highcapacity vacuum pump. This option includes a vacuum sensor that is internally tied to thereference port of the pressure channel that is configured with this option. (Note, eachsensor in the system must have a vacuum sensor installed to operate in this mode.) In
gauge mode, the reference port is open to atmosphere. In the absolute mode, a vacuum
pump evacuates the reference port of the sensor. Once a vacuum level of less than 200
mtorr is achieved, the operator can zero the 7250sys. The 7250sys would zero the Ruska
quartz sensor against an internal vacuum sensor measuring this residual vacuum level.
This vacuum sensor continuously monitors and update the pressure reading based on thereference vacuum level.
Following the absolute zero, the channel would operate in the absolute mode. If the
7250sys requires to control sub-atmospheric pressures, then a second vacuum pump
2-5

THEORY OF OPERATION

should be connected to the exhaust port for use in pressure control. It is notrecommended to use one pump connected to both the reference and the exhaust when
operating in absolute mode since the controller could cause an unstable reference
vacuum.
2.4.1.2 Test Port
The Test Port connects the DUT to the Pneumatics Module. The system automaticallyswitches between the various sensor ranges within the system when controlling pressure,selecting the most accurate sensor in the system to monitor the pressure.
A relief valve protects each sensor in the system.
2.4.1.3 Vent Procedure
The vent mode is implemented with a fast multi-step procedure. For gauge instruments,
the DPC controls pressure at the maximum rate towards zero psig. When the primarysensor reads that the pressure is within 1% FS pressure of zero psig, the controller isturned off and the reference zeroing solenoid is opened which vents the remaining test
port pressure to atmosphere. If the DPC is at a sub-atmospheric pressure, then thesystem will control to zero psig, at maximum rate, turn off the controller, and open thezeroing solenoid.
2.4.2

CONTROL MODE PNEUMATICS

2.4.2.1 Pressure Supply Port
The Pressure Supply Port connects the user’s regulated gas supply to the Pneumatics
Module. Please refer to Appendix A for gas specifications and supply pressure limits.
On the 7250sys, there are multiple supply pressure ports, one for each pneumatic control
module. On a standard cart system, a separate regulated pressure supply is connectedto each individual supply pressure ports. On the table-top version of the system, eachcontrol module must be supplied with its individual regulated supply pressure.
2.4.2.2 Vacuum Supply (Exhaust) Port
For many applications, a vacuum pump is not necessary.
The Exhaust Port includes a solenoid valve that is open only when the DPC is controllingpressure.
In Gauge mode, if the DPC will not be used to control pressures at or very nearatmospheric pressure, then the Exhaust Port should simply be left open to atmosphere.
Likewise, in Absolute mode, if the DPC will not be used to control pressures at or below
atmospheric pressure, the same rule would apply. However, if the DPC will be required
to control to atmosphere in Gauge mode or sub-atmospheric pressures in Absolutemode, then a vacuum pump must be connected to the Exhaust Port. Select a vacuum
pump with the test port volumes and system slew rates in consideration. The minimum
requirements are noted in Appendix A. The vacuum pump is an optional accessory in thestandard cart system. When the “absolute mode with evacuated reference“ option is
selected, the system must be configured with two vacuum pumps, one used to control
sub-atmospheric pressures and the second to evacuate the sensor reference ports.
THEORY OF OPERATION

2-6

2.4.2.3 Pressure Control
Pressure control is performed by a dual-loop control system. The inner loop is a digital
loop using a high frequency response silicon strain gauge sensor, a digital controller, andtwo pulse-width modulated solenoids. The two solenoids either add gas to the test port
or remove it. The outer loop provides closed-loop control, based on feedback from thequartz Bourdon tube and an analog output setting which provides the desired set-point
for the inner loop. The 7250sys incorporates multiple controllers into the design andautomatically switches between the controllers to provide the optimum control
performance based on the pressure set point.
2.5

CONTROL STRATEGY

2.5.1 INNER VS. OUTER LOOPS
The inner loop accepts a signal from the outer loop and uses this signal as the pressure
set-point. The inner loop uses a high frequency response strain gauge sensor as its
reference. The frequency response of this transducer allows for high speed modulationof the solenoids. This sensor is aligned to the high accuracy quartz sensor when thesystem is Auto-tuned.
The outer loop is a lower frequency response, analog-digital loop. The outer loop uses acalibrated, forced-balanced sensor. This sensor is used to monitor the pressure of thesystem. The results are used for the displayed pressure. The outer loop is responsible foradjusting the signal sent to the inner loop to compensate for temperature and time drifts
associated with the inner loop sensor.
2.5.2 NORMAL MODE
In the Normal mode, minimizing pressure overshooting takes precedence over control
speed. In the Fast Mode, control speed takes precedence over overshooting the setpoint.
In the Normal mode, the inner loop controls to the set-point using maximum rate until
close to set-point and then slowing down as the set-point is approached to minimize
overshoot. The outer loop continually adjusts the inner loop to compensate fortemperature and drift.
2.5.3 FAST MODE
This mode of operation assumes that the inner loop sensor and the outer loop arealigned. When a new set-point is issued, the outer loop sends a signal that wasdetermined to be equivalent to the desired pressure. When the system detects that thepressure is sufficiently close to the desired set-point, then the outer loop switches to the
PID algorithm.
This control mode results in the highest speed pressure control.

2.5.4

ALIGNMENT OF INNER LOOP WITH OUTER LOOP
2-7

THEORY OF OPERATION

Since the control system of the DPC is based on the alignment between the inner andouter loop sensors, there is a procedure that automatically aligns these sensors. It is
possible that during typical operation the alignment between the inner loop and the outer
loop sensor can become miss-aligned. This can cause control problems such as
overshoot. This can be realigned using the Auto-Tune feature. See the Maintenance
Section (Section 6.0) for details on the Auto-Tune functions of the 7250sys.
2.5.5 PID CONTROLThe outer loop pressure controller is a form of PID control executed every 100
milliseconds (10 times per second). The pressure is controlled to an exponential decay
curve.

V = p * ( S − A) + i * ∫ ( S − A)dt + d *d( S − A)dt

S = Set-point
A = Actual
V = Control Output
p,i,d = Control Coefficientspressure

Figures 2–3 and 2-4 show typical Control mode operation. Pressure in percent of fullscale is plotted versus time to show the change in pressure as the instrument steps fromone control point to the next.

0

10

20

30

40

Time - seconds

FIGURE 2–3
PRESSURE CONTROL NORMAL MODE

THEORY OF OPERATION

2-8

50

60

pressure
0

10

20

30

40

50

60

Time - seconds

FIGURE 2–4
PRESSURE CONTROL FAST MODE
2.6

TRANSDUCER MODULE

2.6.1 QUARTZ BOURDON TUBE SENSOR (TRANSDUCER01)
The quartz Bourdon tube sensor is mounted in a machined aluminum housing. The
sensor consists of a helical quartz tube with a mirror affixed to one end, as shown in
Figure 2-5.
A rigid beam is attached transverse to the axis of the helical tube. Attached to both endsof this beam are electromagnetic coils. Mounted beneath the coils are permanent
magnets. A lamp assembly directs light through a quartz or sapphire window onto themirror affixed to the helical tube, as shown in Figure 2–6. The mirror reflects the lightback through the window and strikes two matching photodiodes. When there is zeropressure differential across the helical tube, the photodiode assembly is mechanicallyadjusted so that the light spot is centered between each photocell. In this “zero position,”the outputs of the two photodiodes provide energy used to maintain the quartz assemblyin its zero position; thus, a force balance is created.
As pressure is applied in the helical tube, the entire apparatus attempts to rotate. This
causes the mirror to move the reflected light spot to shine more on one photodiode thanthe other. The Sensor Board (see Section 2.6.2) then responds by changing the current to
the electromagnetic coils that, through interaction with the permanent magnets, force thehelical tube to return to its zero position. The amount of current required to do this is
proportional to the pressure applied across the helical tube. Thus, the pressure isdetermined by the amount of current required to return the helical tube to its zero
position.
L AB

TE M

SOLU

On Absolute Models, the process is similar, except that the Bourdon tube ispermanently evacuated to less than 0.1 mtorr and sealed at the factory, andthe test pressure is applied to the sensor case. With this configuration, all test
pressures are measured with respect to vacuum.

2-9

THEORY OF OPERATIONODEFIGURE 2–5
SHAFT/MAGNET SECTION

FIGURE 2–6
PHOTOCELL/LIGHT SPOT
2.6.2 SENSOR BOARD
A temperature sensor and the quartz Bourdon tube pressure sensor are monitored by the
Sensor Board. The Sensor board is also used to control and maintain the sensor housing
at 50°C.
2.6.3 LINEARIZATION TERM
As described in the previous section, the relationship between the pressure being
measured and the current required to keep the quartz Bourdon tube in its zero position is
the main principle behind the operation of the DPC’s sensing element.
Ideally this pressure-current relationship would be a linear equation of the form

I = kP,
where I is current, k is a constant of proportionality, and P is pressure. However, due tocertain mechanical characteristics of the helical tube and its supporting structure, thisTHEORY OF OPERATION

2-10

pressure-current relationship is slightly nonlinear. The nonlinear portion of this pressurecurrent relationship closely follows the form of a second order polynomial, or
I = aP 2 + bP + c,
where again P is pressure and a, b, and c are coefficients generated during thecalibration procedure as discussed below.
When the user performs a three-point calibration, the DPC’s software creates the threecoefficients based on the user’s zero, mid-point, and full-scale adjustments. From thenon, the nonlinear term given above is subtracted from the total pressure-current curve toachieve the desired linear pressure-current relationship.
On the 7250sys and 7250sysi, multiple quartz sensor ranges are used in order to provide
the percent of reading specification. In these instruments, a total of three points per
range with one point shared between two ranges is required. Therefore, for the 7250sys,
a 5 point calibration is performed and for the 7250sysi, a 9 point calibration is
performed to fully characterize the Ruska quartz sensors.
2.6.4 AUXILIARY SENSORS
Auxiliary sensors are sensors such as the oven temperature sensor. These are reference
sensors aligned at the factory and are utilized by the firmware.
2.6.4.1 Case Reference Vacuum Sensor - Option
A case reference vacuum sensor is a user selectable option. This option includes avacuum sensor installed into the test port on absolute units and the sensor case reference
port on differential units and can be read directly by the DPC.
On units that have been purchased with the “Absolute Mode with Evacuated Reference”,
this sensor is used to zero the DPC and it is used to continuously monitor the DPC Casereference while operating in the absolute mode.
2.7 SOFTWAREThe DPC is a digital, software-based instrument. The controlling software uses a PID
algorithm and allows for user-definable units and onboard programming. The software
control loop is a digital outer loop with a high-speed inner loop.
2.7.1

SOFTWARE SAFETY CONTROLS

2.7.1.1 Preventing Operator Errors
The operator is required to verify a change to Control mode or Vent mode by pressing
the [Enter] key. Additionally, the control set-point is set to zero on power-up or when anyof the limit errors occur.
2.7.1.2 Pneumatic Errors
The DPC continually monitors the pressure for low, high and slew (rate of change) limits.
When these limits are exceeded, the DPC is returned to Measure mode, shuts off theapply and exhaust control valves, and an error message is generated. Additionally avent limit may be set. The DPC will go to Vent mode when the pressure exceeds this limit.
2.7.1.3 Shut Offs
2-11

THEORY OF OPERATION

Measure mode can be entered at any time by pressing the Measure key on the main
keypad with no further acknowledgment required. The DPC will turn off the controller.
2.7.1.4 Oven Control
The oven temperature is controlled via a pulse-width modulated signal. The time theheater is on can be varied from 0 to 100%. The pulse-width at startup is initialized to theprevious value which was stored in battery-backed CMOS RAM.
The oven control is a PID controller updated approximately every 7 seconds. The sensor
readings are accessed by pressing MENU | DISPLAY | TEMP. The high accuracy quartz
sensor is housed in a temperature controlled oven. There is a 3 hour warm-up timerequired prior to the DPC operating at its optimum precision. The user can verify when
the instrument is thermally stable by viewing the MENU | DISPLAY | TEMP screen andverifying that the temperature is at 50o C for each dual range sensor. In addition to thetemperature, this screen will show the duty cycle of the oven.
When operating the system in either a very cold or hot environment, if the oven in unable
to maintain the temperature of the internal oven, the DPC will generate an Oven
Control Failure error messages. The operator can review the temperature and duty cycleof the oven by pressing the MENU | DISPLAY | TEMP keys. The unit must be have been
warmed up for a minimum of 3 hours prior to determining the condition of the oventemperature control. The temperature of the sensor should be controlled to 50o C. The
Duty Cycle indicates the amount of time (in units of percentage) that the oven control isturned on in order to maintain the oven at the proper set-point of 50o C. A unit that is
operating properly, after it has fully warmed up, should indicate a sensor temperature of
50o C and a duty cycle between 10 to 90%.
If operating the instrument in a very cold environment and the oven duty cycle is at a highpercentage (>90%) you will need to turn the fan off. If you are operating in a warm
environment or when multiple systems are housed in consoles without adequate
ventilation, the system may become too hot and generate the oven control failure error
message. If operating the instrument in a warm environment and the oven duty cycle is
at a low percentage (>10%) you will need to turn the fan on. See Section 6.7 for fan
operation.
When the operator changes the status of the fan, it will remain in that condition until theoperator changes the setting.

THEORY OF OPERATION

2-12

MENU | DISPLY | TEMP- MENU
2.7.1.5 Pressure Reading and Correction
The sensor’s analog output is processed by an analog-to-digital circuit that results in an
output referred to as counts. This output is corrected for the applied effects listed below.
The counts are linearized and the resulting pressure value is corrected for the variationsin head pressure, vacuum, case effect, and oven temperature effects.
The following equations are used by the control algorithm to adjust and correct thepressure signal.
Zero Coefficients
CsH

Zero correction for High FSR (Full-Scale Resistors) Value is in counts(7,381,975 = full scale of current sensor).

CsL

Zero correction for Low FSR. Value is in counts (7,381,975 = full scale of
low FSR)

HsZ

Hardware zero correction. (0 to 4095, center is 2048).

SsZ

Zero corrections scaling factor. Ratio of High FSR to Low FSR. Used only
when Case Effect Coefficient or Oven Temperature Coefficient are nonzero.

s=0 for high range sensor, s=1 for low range sensor.
Range Coefficients
KnF

0=Range Unused
4=Valid High FSR Range
5=Valid Low FSR Range

Kn0, Kn1, Kn2

Calibration constants for range
KK

B = 248n 2 ∗ A2 + 224n1 ∗ A + Kn0
2-13

THEORY OF OPERATION

Where A is the zero corrected counts (7,381,975 = full scale of current
range) and B is the calibrated counts (7,381,975 = full scale of current
sensor)
KnH

Zero corrected counts for upper limit of range. When the zero corrected
counts from the A/D exceed this value the next higher range will be used (ifpossible). (7,381,975 = full scale of current range)

KnL

Zero corrected counts for lower limit of range. When the zero corrected
counts from the A/D are below this value the next lower range will be used
(if possible). (7,381,975 = full scale of current range)n=Range number (1 - 4 for high range sensor, 5 - 8 for low range sensor)

THEORY OF OPERATION

2-14

SECTION 3.0
INSTALLATION
3.1 INTRODUCTION
This section of the manual discusses initial installation for the Model 7250sys DPC.
Installing the DPC involves connecting the supply and test pressure tubing, powering up
the unit, and configuring the system through the front panel.
3.2 UNPACKING THE DPC
Carefully unpack all components, checking for obvious signs of damage. The shipment
contains the following items:
1. Model 7250sys
2. power cord,
3. user’s manual,
4. calibration report,
5. user-specified instrument options.
If necessary, report any shipping damage to the freight agency. Remove all shipping andpacking materials (including the shipping plugs) from all components. If possible, savethe packing materials for future shipping needs.
Finally, install the DPC in a location that meets the requirements listed in Table 3-1. Cart
versions of the system are supplied with leveling feet. Once the cart is rolled into a
desired location, if the cart is to be maintained in the same location, the leveling feetshould be screwed out to secure the cart and level the cart.
NOTE: The DPC should be handled in such a way as to minimize mechanical shocks
or vibration during installation or use. It should be mounted on a rigid bench or ina sturdy 19" rack. Although the zeroing process will compensate for a slightly
unlevel mounting, the DPC should be mounted to within 5° of level.
TABLE 3-1
GENERAL SPECIFICATIONS: GENERAL PARAMETERS
Parameter
Operating Humidity
Storage Humidity
Operating Temperature
Storage Temperature
Electrical PowerPower Consumption
Warm-up Period

Value
5–95%RH, noncondensingnone*
18 – 36°C-20 to 70°C
90–260 VAC
150 W< 3 hrs

Model
all
all
all
all
all
all
all

*If there is any condensation when storing the DPC, it must be thoroughly dried before
power is applied. It is also recommended to connect the reference port to the test port
and evacuating these simultaneously to remove any moisture from the sensor.
3-1

INSTALLATION

3.3 CAUTIONS
The following cautions should be heeded at all times to ensure safe operation of the
DPC.
1. Never operate the DPC with the cover removed. The power supply has internal
voltages near 400 volts.
2. For each channel, never apply more than 120% of the DPC’s channel full scale asa pressure supply. Both pressure supplies must be regulated and meet all of thecriteria stated in Appendix A of this manual.
3. Never apply more than 110% of the DPC’s full scale to the test port of eachchannel. Never try to control while a pressure source is connected to the test port.
4. Do not expose the instrument to thermal and mechanical shock, or vibration. This
may affect performance and require rezeroing.
5. See the safety summary in the introduction.
3.4 POWERING UP THE DPCFirst, plug the power cord supplied with the DPC into the power connector on the DPC’s
back panel.
CAUTION: Grounding for the DPC is provided through the power cord.
Next, plug the power cord into a receptacle rated for any AC voltage between 90 and
260 volts. If a different power cord is necessary for your receptacle, consult Table 1-1 foravailable power cords.
Finally, turn on the DPC by toggling the power switch on the back panel. When the
MEASURE screen appears on the display, the front panel will be fully operational.
3.4.1 OBSERVING THE DPC’S FULL SCALE RATINGThe full scale pressure range of the DPC is noted on a label on the front panel of the
instrument.
3.5 PNEUMATIC CONNECTIONS
The following sections discuss each port. All ports are ¼-inch NPT pipe fittings. See
Figure 3-1. Remove all plastic shipping plugs from the back panel pneumatic ports.
3.5.1 PRESSURE SUPPLY PORT
Each individual control channel internal to the system has its own individual pressure
supply port which must be connected to an independently regulated source of clean, dry
nitrogen or air. Shop air should not be used. Refer to Appendix A for supply port gas
purity and pressure regulation requirements. The integrated cart version of the system
has an integrated regulator panel which supplies the proper pressure to each of thecontrol channels. On these cart systems, a single regulated pressure source supplies theentire cart.

INSTALLATION

3-2

On the table-top version of the system, each control channel will require individual
regulated supply pressures. It is important to assure that each control channel is suppliedwith the proper regulated pressure. Each channel will be labeled with the pressure that itshould be supplied.
Tubing must be of at least 1/8-inch (3-mm) inside diameter and of a sufficient wall
thickness for the pressure. Either stainless steel or copper tubing is acceptable.
3.5.2 EXHAUST PORT
On a cart system, the exhaust port is an port internal to the system. These are ports thatthe controllers vent pressure when in control mode. If the system is purchased with theinternal vacuum supply pump, the control channels that require the vacuum supply pump
to control sub-atmospheric pressures will be connected to this pump.
On the table top systems, the exhaust port may be left open to atmosphere under mostconditions. When controlling pressure below atmospheric pressure, a vacuum pump is
required. Supply vacuum lines must have minimum restrictions. Tubing should have aminimum I.D. of ¼ inch. In small rooms, the exhaust port should be piped outside toprevent an accumulation of nitrogen. It is also very important to install an auto-ventvalve to the vacuum pump. The purpose of the valve is to vent the vacuum toatmosphere when the pump is turned off.
3.5.3 TEST PORTThe device(s) under test is connected to the test port. The DPC controller is designed tooperate within its specification limits into load volumes from 5 to 60 in3 (80 to 1000 cc).
Excessive leaks in the test volume will cause measurement errors in the device under test
and may possibly affect control stability. Tubing connected from the test port to the load
volume should have an internal diameter greater than 1/8 inches (3 mm). Tubing should
be shorter than 15 feet (5 meters) when smaller diameter tubing is used. The 7250sys
automatically switches all of the various pressure range sensors and control channels
internal to the system to the single test port.
3.5.4 REFERENCE PORTThe reference port is open to atmosphere for gauge measurements or it can beconnected to the Reference Port of the Device Under Test.
Instruments with a low full-scale pressure range require special handling to assure theperformance of the instrument. These instruments are very sensitive to atmosphericpressure changes including disturbances in the atmospheric pressure. The reference side
must be very carefully controlled or changes due to wind, air handlers, doors shutting,etc. will cause major variations. The DPC tracks these changes but it may not track inthe same way as the device under test. To control these changes, it is recommended thatthe reference port of all relevant devices be tied to the reference port of the DPC.
The reference port can be sealed from atmosphere in most applications where the test
times are relatively short. This isolates the port from pressure changes in the atmosphereand results in very stable pressure measurement and control.
3-3

INSTALLATION

If the test times are relatively long, in addition to connecting the reference ports together,
they should also be connected to a tank with a volume of 200 cubic inches or better. The
tank should be vented to atmosphere through a small orifice bleeder valve at the otherend of the tank. The entire reference assembly should be shielded from rapid
fluctuations in air temperature and flow. The vent valve should be set experimentally. In
an environment with no temperature change, it would be closed. In an environment withno pressure fluctuations it would be wide open. The heat from the DPC oven and control
valves will cause some temperature variations. Thus the appropriate setting varies but agood compromise can be found. To observe the variations, connect the reference as
discussed and open the test port to the atmosphere. In measure mode, the DPC will
indicate the variations. A good filter may be usable in place of the valve if it provides
approximately the correct restriction of air flow.
One consideration is that if the reference port is completely sealed from atmosphere, itspressure will change due to barometric pressure changes or temperature changes in theenvironment. If the pressure in the reference port becomes lower than the barometricpressure, then a vacuum pump would need to be attached to the exhaust port to allow
the controller to control down close to 0 psig.
For systems that have a barometric reference sensor option, the barometer is tied to thereference port. When operating in the gauge mode, the reference port should beconnected as noted above. When operating in the absolute mode, sealing the reference
port from atmosphere will improve the stability of the DPC.
3.5.5 VACUUM SENSOR OPTION
The DPC is also available with a vacuum sensor option. On DPC ranges that have the
Evacuated Reference Option, the vacuum sensor is used to monitor the vacuum level inthe reference port when the reference port is pulled to a hard vacuum allowing the DPC
to operate in the absolute mode.

INSTALLATION

3-4

SECTION 4.0
LOCAL OPERATIONThis section of the manual describes operation of the DPC using the front panel. The
local interface (front panel) consists of a color TFT display, a rotary knob and a set ofkeys. The display shows the system status and menu options. The keys are grouped
according to function.

7250
7250sys2500 psi

FIGURE 4-1
MODEL 7250sys FRONT PANEL
Numeric Keypad: This includes the number keys, the decimal point [.], and the change
sign key [-]. The [UNITS] key changes between units of measure, [MODE] held down for
5 seconds changes the language. It is also used to change between units of measuresuch as gauge and absolute. [MEASURE] is used to place the system into measuremode. [CLEAR] key will clear the numeric entry field. The [ENTER] key accepts theentered number or confirms a command.
Function Keys: These are the six keys that run vertically beside the display. The labelshown in the display beside each key identifies their function. These functions will change
based on which screen you are operating. For ease of communication, throughout the
manual we refer to these keys as [F1] through [F6]. We consider the top key to be F1
and the bottom F6.
Rotary knob: The rotary knob select a field for editing and are used for small pressurechanges (pressure jog) at the main menu of the single display mode.
CANCEL, PREVIOUS: These keys are used to stop, undo, or exit the current operation.
The [CANCEL] key returns all edited fields on the current entry screen to their originalvalues. It also stops the current program sequence or calibration process. The[PREVIOUS] key exits the current menu and returns to the previous menu.
Figure 4-2 is a menu tree showing the relationship between all the menus in the system.
Refer to it for selections available under the menu. To move to a lower menu, press thefunction key with the correct label. To move towards the main menu, press the[PREVIOUS] key. In the Single channel Main Menu screen, the [F2] key places the unit
in Control mode, [ENTER] must be pressed to actually enter the Control mode.
4-1

LOCAL OPERATION

Control ------------------------------------------------------------h Places the system in Control Mode
Vent ----------------------------------------------------------------h Vents system pressure to atmosphere
Step/Jog ---------------------------------------------------------h Toggle between step and jog mode
Menu ---------------------------------------------------------------h Enter Sub Menus
Setup -------------------------------------------------h Enter Set-up menu
Limits -----------------------------------h Set pressure limits, control band, access code
User -------------------------------------h Set step size, head corr., filter & display digits
Units ------------------------------------h Set User-Defined units of measure
Remote --------------------------------h Set baud, parity, data & stop bits, GPIB address
System ---------------------------------h Set date, time, reset & view software version
Calibrate -------------------------------------------h Enter calibration menu
Zero -------------------------------------h Zero sensor
Calibrate ------------------------------h Perform or edit calibration
Zero ------------------------h Zero sensor from calibration
Calibrate ----------------h Calibrate sensors
Access -------------------h Password to edit calibration coefficients
Sensor --------------------h Select sensor to be calibrated
Zero All --------------------------------h Zero all quartz sensors simultaneously
View -------------------------------------h View sensor coefficients
Sensor ----------------------------------h Select sensor
Program ---------------------------------------------h Enter Program Menu
Run --------------------------------------h Run program test sequence
Delete ----------------------------------h Delete a saved program
Config ----------------------------------h Change the configuration of a program (Limit, etc)
Edit --------------------------------------h Edit program (set-point, tolerance, dwell, etc)
Name ----------------------h Change program name
Test ---------------------------------------------------h Enter test menu
Sweep ----------------------------------h Sweep pressure between points (# cycles)
Self --------------------------------------h Perform self -test
Remote --------------------------------h Display IEEE-488 remote status
Serial 1 -------------------h Display RS-232 serial remote status
Shop1 -----------------------------------h Display solenoid status
Control ---------------------------------h Tune control valve parameters
Display -----------------------------------------------h Display sensor readings
Temp ------------------------------------h Display sensor temperature readings
Vacuum --------------------------------h Display sensor vacuum readings
Blank ------------------------------------h Screen saver

LOCAL OPERATION

4-2

FIGURE 4-2 MENU TREE

4-3

LOCAL OPERATIONThe [F3] key places the unit in Vent mode. This opens the test port to atmosphere andrapidly reduces the pressure, [ENTER] is required to confirm the operation. The [F5] key
places the unit either the stop or the jog mode and the rotary knob is then used to set thecontrol set-point by the correct step or jog amount. To go to one of the menus, press the[F6] key.
4.1 TUTORIAL
To begin the tutorial, first verify that the DPC is powered-up and that the pneumaticconnections have been completed. The DPC should display a screen similar to the one
shown below. (The right hand side of the display should show the options). At power up,
there may be errors relating to the default settings. If an error message is displayed in
red at the bottom of the screen, press [F6], then press [PREVIOUS]. If multiple errors
exist, you will need to press the [F6] key multiple times to clear all of the errors.

MAIN MENU
The double sized numbers in the top center of the display shows the current measured
pressure (0.00 psi gauge). The upper left corner shows the current mode of the DPC(MEASURE, CONTROL or VENT). Below this shows the full scale of the selected pressure
range that the system is operating displayed in current units of measure. The right side of
the screen shows a bar graph displaying the current pressure relative to a userconfigurable full-scale value. Below the pressure is the pressure control set-point, below
this is the difference between the set-point and the actual value. Below this is a numericscratchpad for entering a new set-point value. The highlighted label on the right handside of the screen displays the current assignments of the function keys [F1] through [F6]that are located beside the display.
Step 1. Change the pressure units. The units are changed by selecting the UNITS key
on the keypad.

LOCAL OPERATION

4-4

UNITS - MENU
Step 2. Use the rotary knob located to the right of the display to move the highlight bar
to the desired unit. Note, the highlighted curser initially shows the current unitof measure. When the rotary knob is moved, the current unit remains
highlighted in a gray color, and the new unit is highlighted in a light blue
color.
Step 3. When the unit desired is highlighted, press the [ENTER] key on the far rightside of the front panel, under the numeric keypad. The display will return to
the MAIN screen with the current units.
The second part of this tutorial uses the DPC to generate pressure. The pressure supply
must be connected and the test port must be connected to a closed volume, in
accordance with Section 3.5 of this manual.
Step 4. From the Main Menu, use the numeric keypad to enter the starting pressure.
The pressure is entered in the units set in the previous exercise. As the pressure
is entered, each digit will be displayed in the numeric scratchpad (thehighlighted box in the lower section of the display). If a mistake is made, press
the [CLEAR] key (found in the numeric keypad), and the numeric scratchpad
will be cleared.

MAIN MENU
4-5

LOCAL OPERATION

Step 5. When the entry is correct, press the [ENTER] key. The scratchpad will becleared and the value will appear as the new set-point.
Step 6. Now that the starting pressure is entered, enter Control mode. Press Control(the [F2] key). The CONTROL label will be highlight, and the message “Press
Enter to Confirm” will appear below the scratch pad. Notice that the upper left
corner still shows MEASURE. The DPC stays in Measure mode until the change
is confirmed.
Step 7. Press [ENTER] to confirm the mode change. The upper left corner will change
to CONTROL, and the pressure will start moving towards the set-point.
Step 8. After the pressure is stabilized, assure that the word Step is highlighted in the
Step/Jog (the [F5] key). The Step/Jog (the [F5] key) toggles between Step
and Jog, to switch between these modes, press the function key 5 [F5]. In
addition to using the key-pad to enter a pressure set-point, you can also use
the step function. Using the rotary knob, rotate the knob clock-wise to increase
the set-point, or counter clock-wise to decrease the controller set-point. The
scratchpad will be updated with a new set-point. The step size defaults to 10%
of full scale. This step size is user defined and can be changed in the
Menu|Setup|User menu.

MAIN MENU
Step 9. Press [ENTER] to accept the new set-point. The DPC will move to the new setpoint.
Step 10. Press Measure key which is located in the key-pad. The DPC will change to
Measure mode. No confirmation is necessary to leave Control mode.
4.1.1 SELECTING LANGUAGE
The 7250sys DPC can operate in a variety of different languages. To select a different
language, press and hold the [MODE] key for 5 seconds. The current language will behighlighted. Use the rotary knob to highlight a new language and hit the [ENTER] key toselect that language.
4.1.2

SELECTING MODE OF OPERATIONLOCAL OPERATION

4-6

The 7250sys DPC can operate in gauge or absolute modes.
4.1.2.1 Simulated Absolute Instruments
This 7250sys DPC sensor’s operate in Gauge and Vacuum (Negative Gauge) modes andinclude a barometric reference sensor to monitor the barometric pressure. The
summation of the pressure reading from the measurement sensor in the 7250sys and thepressure reading from the barometric sensor provides for the "simulated absolute"pressure display. To change mode, from the keypad, press Mode, then select either
Absolute [F1] or Gauge [F2]. Alternatively, you can press MENU | MODE to get tothis menu.

MODE - MENU
4.2 MAIN MENUThe Main Menu displays the measured pressure in double-sized numbers. Below thepressure reading is the current unit of measure and mode (Gauge, Differential or
Absolute). The Main Menu can always be reached by repeatedly pressing [PREVIOUS].
The model 7250sys is designed such that all of the commonly used functions areaccessible by a direct key on the key pad or from a top level function key. Less
commonly used set-up type functions are accessible through the menu function key.

MAIN MENU

4-7

LOCAL OPERATIONNOTE – For DPC’s with pressure ranges greater than 100 psi (700 kPa), the supply
pressure port must be plugged or connected to a properly set pressure supply inorder to measure pressure greater than 100 psi (700 kPa).
4.3 CONTROLLING PRESSURE
The Control [F2] function key is used to place the DPC into the Control Mode. A
pressure set-point should be entered into the DPC prior to placing the unit into the control
mode. This is to assure that the operator is aware of the set-point valve prior to entering
into the control mode.
4.3.1 SETTING THE PRESSURE SET-POINT
The pressure set-point is the destination of the pressure control algorithm. It should be
set before entering Control mode. The pressure set-point is set to zero at power-up orwhenever a pressure error occurs.
1. The pressure set-point can be set from the Main Menu
2. Use the numeric keypad to enter the new pressure set-point in the current pressure
units.
3. Press [ENTER] to accept the entry or press [CLEAR] to clear the numericscratchpad.
NOTE: The set-point can also be changed using either the Step or the Jog function.
Please see Section 4.5.
4.3.2

ENTERING/EXITING CONTROL MODE

1. The Control mode is set from the Main Menu. (Press [PREVIOUS] until the Main
Menu appears.)
2. Press CONTROL [F2] to enter Control mode. [ENTER] must be pressed toconfirm entry into Control mode. Note that any entry in the numeric scratchpad
will also be taken as the new pressure set-point. On DPC’s with full scale pressure
ranges less than 1000 psi (6.9 MPa), the DPC controls its internal pressure to thetest port pressure before opening the isolation valve and entering the Control
mode. During this period, the Control mode indicator flashes.
3. Press MEASURE key found in the keypad to exit Control mode. No confirmationis necessary.
4.3.3 ABSOLUTE ZERO OF DEVICE UNDER TEST – OPTION
Some systems are configured with an option that allows the system to pull a hardvacuum on the DUT (Device Under Test) to aid in zeroing the DUT. With thesystem operating in the absolute mode and in control mode, when a set-point of 0
is entered, the system will control down to the lower limit of the controller. The
controller will then be placed in the measure mode. A 3 way valve then switches
to tie the test port of the system directly to the vacuum pump and isolate theremaining section of the system from the test port. This allows the vacuum pump
LOCAL OPERATION

4-8

to pull a hard vacuum to the DUT. A vacuum sensor is tied to this evacuated line
and its reading is displayed on the front panel of the 7250sys controller.
4.4 VENTThe Vent [F3] function is used to rapidly vent the pressure in the system to atmosphere.
This system does not have a designated internal vent valve. Instead, the vent mode is
implemented with a fast multi-step procedure. For gauge instruments, the DPC controls
pressure at the maximum rate towards zero psig. When the primary sensor reads thatthe pressure is within 1% FS pressure of zero psig, the controller is turned off and the zerosolenoid valve that ties the reference port to the test port is opened. This physically vents
the test port to atmosphere. If the DPC is at a sub-atmospheric pressure, then the system
will control to zero psig, at maximum rate, turn off the controller, and open the zeroing
solenoid valve, again venting the test port to atmosphere. This function is not available
on permanent absolute versions of the 7250sys.
4.5 STEP/JOG
This feature is only available when operating in the single channel mode. In addition toentering the pressure set-point through the key-pad, the pressure set-point can bechanged using either the step or the jog functions. The Step function is used primarily
when the operator is taking pressure steps in equal pressure increments. The size of thepressure step is user defined. The Jog function is most often used when calibrating
mechanical gauges such as a dial gauge and the operator wishes to change the pressure
until the mechanical gauge indicates a cardinal point. The operator can then read thehigher resolution DPC to determine the actual pressure value when the mechanicalgauge is indicating a cardinal point. The Step/Jog (the [F5] key) toggles between Step
and Jog, to switch between these modes, press the function key 5 [F5].
4.5.1 STEPPING
Assure that the word Step is highlighted in the Step/Jog (the [F5] key). Using the rotaryknob, rotate the knob clock-wise to increase the set-point, or counter clock-wise to
decrease the controller set-point. The scratchpad will be updated to a new set-point.
The step size defaults to 10% of full scale. Press [ENTER] to accept the new set-point.
4.5.1.1 Setting Step Size
From the Main Menu, press Menu [F6], Setup [F2], and then User [F2]. Using therotary knob, move the cursor to highlight Step Size. Enter the desired step size in thecurrent pressure units and press [ENTER].
4.5.2 JOGGINGAssure that the word Jog is highlighted in the Step/Jog (the [F5] key). From the Main
Menu, the pressure set-point can be modified by rotating the rotary knob clockwise toincrease pressure and counterclockwise to decrease pressure. Each increment ordecrement will change the pressure in the least significant digit. Continually rotating therotary knob, the pressure will continue to change until the rotation is stopped.
4.6 MENU
The menu key is used to access the less commonly accessed configuration type functions.
This accesses the Mode, Setup, Calibration, Program, Test and Display functions.
4-9

LOCAL OPERATION

MENU
4.6.1 MENU | SETUP
Setup is used to configure the system. It includes setting all of the limits, user parameters,
user-defined units of measure, remote interface and system setup. On the 7250sys, theUser and Limits screens are separate for each channel and must be set up independently.
The Units, Remote, and System screens are identical in each channel. Any changes
made in one channel immediate affects the other channel.

MENU | SETUP – MENU
4.6.1.1 Menu | Setup – Limits
The Menu | Setup | Limits menu is used to setup all of the limits in the system. The
pressure limits can be used to protect the device-under-test (DUT) from overpressure. All
limits are defined separately for each channel. Press the [Mode] key to switch between
two pressure channels. The Access code is common and is used for both channels.

LOCAL OPERATION

4-10

MENU | SETUP | LIMITS - MENU
4.6.1.1.1 High Limit – User defined Maximum pressure limit. This is often set just overthe full-scale pressure of the device under test (DUT) in order to protect the DUT. The
DPC will then prevent the pressure from exceeding the high limit. If the user enters avalue greater than the user defined limit, the unit will not accept the value and it will
generate an error code informing the user that they have entered a set-point that isgreater than the high pressure limit. In control mode, if for any reason the pressure
exceeds the user defined limit, it will change into the measure mode and again display
an error message to the operator informing them of the error that occurred.
This value can be edited using the rotary knob to highlight the High Limit. Then enter the
new value using the keypad. This will show up in the scratch pad on the lower portion of
the screen. Press the Enter key and the value for the high limit will be updated to thevalue that was typed into the scratchpad.
4.6.1.1.2 Low Limit – User defined Minimum pressure limit. This is the same as thehigh limit except it is to protect the DUT from low pressure limits.
4.6.1.1.3 Auto Vent – User defined maximum pressure that the DPC can reach prior toventing the test port to atmosphere.
4.6.1.1.4 Control Band – There are two common pressure control approaches that areavailable with the Ruska 7250sys DPC. One of the most common control styles is an
Active controller where the controller remains operative and holds the pressure at acommanded set-point. This allows the system to hold the pressure at a set-point within
the control stability specification (See Appendix A). In addition to possible leaks in asystem, following a pressure step, the pressure in the system changes due to temperatureeffects. When operating an Active control system, the controller continuously monitors
any pressure variances in the system and compensates for these effects to hold thepressure at the set-point. The benefit of the Active control is that it can maintain thepressure at the commanded set-point even when there are slight leaks in the system or
the system is not thermally stable.

4-11

LOCAL OPERATIONThe second approach is to control the pressure in the system to a set-point and then to
shut-off the Active controller. We describe this as a Passive control mode. Following apressure step and the controller becomes passive, the pressure will continue to change inthe system due to thermal effects. However these thermal effects will stabilize over time.
Once the system has thermally stabilized, pressure measurements can be made in thesystem without any “pressure noise” injected into the system as a result of having an
Active controller in the system. The result would be that the controller would not add any
additional uncertainty to the pressure measurement since it would be inactive during themeasurement process. For this method, pressure will not be at a cardinal set-point.
When the Control Off Band and Control On Band are set to zero, the DPC operates in
the Active control mode. Setting a Control On and Off Band, places the DPC in the
Passive control mode.
The Control On and Off Band provides a tolerance around the pressure set-point in thecurrent unit of measurement. The Controller will control the pressure to the commanded
set-point. Once the actual pressure is within the user defined +/- Control Off Band
tolerance, the controller will shut off. The pressure will remain at this level, only changing
by the thermal influences or leaks in the system. The controller will remain off until itreaches the +/- Control On Band limit. The controller will then re-activate and control
the pressure back to the Control Off Band tolerance. This mode of operation removes
any added uncertainty in the measurement system due to the controller since thecontroller is Passive during the high accuracy pressure measurements.
As an example, if a 100 psi (690 kPa) full scale DPC was set-up with the Control Off
Band at 0.001 psi (0.007 kPa) and the Control On Band set to 0.005 psi (0.035 kPa).
This would place the DPC in a Passive control mode. If the DPC was placed into thecontrol mode with a pressure set-point of 10 psi (69 kPa), it would control up to the 10
psi (69 kPa) value. Once it reached a pressure of 9.999 psi (68.993 kPa) the active
control would turn off. Due to the thermal effects caused by pressurizing the system, thepressure will start reducing in the system. Once the pressure reaches 9.995 psi (68.965kPa) the active controller would automatically turn on and control the pressure back to9.999 psi (68.993 kPa) and then turn off. After a few cycles, the system will thermallystabilize and the pressure will hold between the Control On and Control Off Bands.
4.6.1.1.5 Control – The DPC has two control modes of operation, Normal and Fast.
In the Normal mode, minimizing pressure overshooting takes precedence over control
speed. In the Fast Mode, control speed takes precedence over overshooting thecommanded set-point.
4.6.1.1.6 Supply Correction – The control performance of the 7250sys is optimized
when the fully supply pressure is provided to each of the controller ranges in the system.
When inadequate supply pressure is present, the control performance will suffer. When
the Supply Correction function is turned on, the system adjusts the control parameters
to improve the control when it detects insufficient supply pressure.

LOCAL OPERATION

4-12

4.6.1.1.7 Slew Rate – User defined maximum pressure rate of change. The DPC isdesigned to control with minimum overshoot into a wide variety of external volumes at its
highest slew rate. Therefore, in most applications it is recommended that the slew rate
be set at its maximum rate value. This provides the highest speed control without
jeopardizing overshoot or control stability properties. The only application where theoperator may wish to slow down the slew rate (control speed) is in applications where thedevice under test could be damaged by high rate of pressure change. The DPC control
algorithm tries to limit the rate of pressure change to the slew rate.
4.6.1.1.8 Slew Limit – The slew limit is used by the system to assure that the slew rate is
not exceeded. If the slew rate is exceeded, the DPC will change from the control mode to
the measure mode and it will generate an error message to the operator.
4.6.1.1.9 Access – The test access password allows the user to protect access to DPC
configuration and programs. If the test access password is set to any number other thanzero (factory default), it is required before the user is allowed to change the limits, control
parameters or programs.
IMPORTANT: It is recommended that the access password be recorded and filed in asecure location.
4.6.1.2 Menu | Setup – User
The Menu | Setup | User menu is used to setup all of the user specific configurations.
This includes setting the control step size, range of bar-graph, pressure gas head, display
pressure filter, display resolution digits, and audible key click. The step size, bar-graphmax, ready tolerance and gas head are defined separately for each channel. All otherentries are common for both channels.

Menu | Setup | User - Menu
4.6.1.2.1 Step Size - In addition to entering the pressure set-point by the key-pad, thepressure set-point can be changed using the step function. The step function is usedprimarily when the operator is taking pressure steps in equal pressure increments. The
size of the pressure step is user defined. From the Main Menu, press Menu [F6], Setup
4-13

LOCAL OPERATION

[F2], and then User [F2]. Using the rotary knob, move the cursor to highlight Step Size.
Enter the desired step size in the current pressure units and press [ENTER].
4.6.1.2.2 Bar Graph Maximum - The bar graph on the Main Menu screen can bescaled to match the device under test by setting the full scale value of the bar graph.
4.6.1.2.3 Ready Tolerance – A Ready indication is generated when in control modeand the measured pressure is reading within this ready tolerance value. When running
an internal program, the ready indicator is shown when the measured pressure is within
the tolerance stored in the program.
4.6.1.2.4 Gas Head Pressure Correction - The term “head height” refers to thevertical distance between the sensing element in the device under test and the DPC’s
pressure reference plane. Once the user inputs the head height and selects air or
nitrogen, the DPC automatically corrects for head pressure.
1. The Pressure Reference Line on the DPC is defined as the bottom of the color
display where the display and the front panel join. This provides the reference
plane against which the device under test (DUT) pressure is measured.
2. Determine the vertical distance between the DPC Pressure Reference Line and thereference plane of the device under test.
3. Press the Unit key found in the keypad and press in/mm [F1] to select either
inches (in) or millimeters (mm) for the head height entry.
4. The head height is set from the Setup | User | Menu. From the Main Menu(press [PREVIOUS] until the Main Menu appears), press Menu [F6], then Setup[F2], and then User [F2].
5. Press Medium [F3] to select either “Air” or “Nitrogen.” The selected units will behighlighted.
6. Press Position [F4] to select if the position of the Device Under Test is either“Above” or “Below” the 7250sys. The selected units will be highlighted andappear in the Gas Head description.
7. Use the rotary knob to highlight the label “Gas Head.”
8. Use the numeric keypad to enter the height in the selected unit.
9. Press [ENTER] to accept the entry.
4.6.1.2.5 Atmosphere – The nominal barometric pressure value for the location thatthe DPC is utilized should be entered for atmosphere. On gauge mode instruments, thisnumber is used to calculate the density of the test port pressure medium and to correct
for head pressure variances between the reference port of the DPC and the DUT.
4.6.1.2.6 Pressure Filter – is used to adjust the degree to which the front display
pressure value is filtered. A value of four (4), is the default value. As the value increases,
the filtering level increases, however, the display update rate reduces. Typical filter values
would range between 1 to 10. For pressure sensors with full scale ranges of 1 psi (7 kPa)or less, a filter value up to 30 is typically recommended.

LOCAL OPERATION

4-14

4.6.1.2.7 Changing the Number of Decimals – Each unit has a default number ofdecimal places used for pressure display. This may be adjusted up or down by one
decimal place.
1. The decimal digits are set from the Setup | User | Menu. From the Main Menu(press [PREVIOUS] until the Main Menu appears), press Menu [F6], then Setup[F2], and then User [F2].
2. Turn the rotary knob until the label “Display digits” is highlighted.
3. Turn the rotary knob further until the desired number of digits from the default
resolution is highlighted (-1, 0, +1), and then press the [ENTER] key to select.
4.6.1.2.8 Key Click – The DPC can be configured to emit a “clicking” sound each timea key is pressed.
1. The key “click” is set from the Setup | User | Menu. From the Main Menu (press[PREVIOUS] until the Main Menu appears), press Menu [F6], then Setup [F2],and then User [F2].
2. Turn the rotary knob to highlight “Key click” and then highlight either on or off.
3. Press the [ENTER] key to select.
4.6.1.3 Menu | Setup – Units
In addition to the standard units of measure provided by the DPC, four user-defined units
are available. To create a user-defined unit, the user enters a name that is one to ten
characters long and a conversion factor that is a multiple of kiloPascals (kPa).
For example, using the information from table 2-1, the conversion factor for millitorr or
one micron of mercury at 0 °C is calculated as follows.

mTorr = kPa x

1000mTorr
1 Torr1 Torr1mm Hg 0o

x 1mmHg0oC x 0.0193377psi x0.1450377psi
1 kPa

thus the conversion factor simplifies to mTorr = kPa x 7500.6180

MENU | SETUP | UNITS - MENU

4-15

LOCAL OPERATION

1. The pressure units are defined from the Units | Define | Menu. From the Main
Menu (press [PREVIOUS] until the Main Menu appears) press Menu [F6], thenSetup [F2], then Units [F3].
2. Use the rotary knob to highlight the desired user-defined unit, and then select the
Edit Name [F1] function key.
3. The following sequence is used to change the name of the selected unit.

MENU | SETUP | UNITS | EDIT NAME - MENU
a. Use the < [F4] or > [F5] key to highlight the desired character in the matrix.
b. Use the rotary knob to change the character.
c. Repeat steps a and b until the desired name is entered. Press the Clear key tostart over.
d. Press the Done [F6] key when the name change is completed.
4. Use the rotary knob to highlight the desired user-defined unit that has just beenrenamed.
5. Use the numeric keypad to enter the conversion factor and press [ENTER] toaccept.
6. Press [PREVIOUS] three times to return to the Main Menu. The new unit
definition may now be selected using the units key.
4.6.1.4 Menu | Setup – Remote
The Menu | Setup | Remote screen is where the remote communication interface is setup.

LOCAL OPERATION

4-16

MENU | SETUP | REMOTE - MENU
4.6.1.4.1 GPIB Address – Sets the IEEE-488 interface address.
4.6.1.4.2 Protocol – The Protocol defines which protocol should be used by the remoteinterface. The options are Standard Communication for Programmable Instruments(SCPI) which is the only interface available for the 7250sys.
4.6.1.4.3 Serial Interface Set-Up – The operator can set-up the Baud Rate, Data Bits,
Parity, and Stop Bits for the Serial Interface.
4.6.1.5 Menu | Setup – System
The System Menu identifies the Software release version that is being operated in the
DPC. It also stores and allows the operator to edit the Date and Time.

MENU | SETUP | SYSTEM - MENU
4.6.1.5.1 Date/TimeThe DPC’s system clock is continuously updated. If the date or time requires editing, thefollowing applies;

4-17

LOCAL OPERATION

1. The date and time are set from the Setup | System | Menu. From the Main
Menu (press [PREVIOUS] until the Main Menu appears), press Menu [F6], thenSetup [F2], and then System [F5].
2. To set the system date, turn the rotary knob until Date is highlighted. Use thenumeric keypad to enter the current four-digit year, month, and day (yyyymmdd).
All digits must be entered. Press [ENTER] to accept.
3. To set the system time, turn the rotary knob until Time is highlighted. Use thenumeric keypad to enter the current hour, minute, and second (hhmmss). All digits
must be entered. Press [ENTER] to accept.
4.6.1.5.2 Reset
The Reset [F1] command is used to re-boot the DPC.
1. To reset the system, from the Main Menu (press [PREVIOUS] until the Main Menu
appears), press Menu [F6], then Setup [F2], then System [F5], and then Reset[F1].
4.6.2 MENU | CALIBRATEThe Menu | Calibrate command is used to perform the calibrations on all of the sensors
utilized by the DPC. The 7250sys can be completely calibrated using the front panel
interface. It does not require any external computer or software in order to perform a
successful calibration. It also has the capability of being calibrated remotely througheither the RS232 or IEEE-488 interface. The 7250sys will guide the operator through amenu driven calibration procedure identifying the pressures that should be supplied by astandard. Following the calibration procedure, the 7250sys calculates and saves its own
coefficients. The calibration coefficients are date stamped so the user can easily identify
the last time the instrument went through a full calibration, when the coefficients were lastedited or when the DPC was re-zeroed.
The calibration section in the DPC can be password protected to prevent any
unauthorized entry into the calibration section of the system. Please refer to the
Maintenance Section (Section 6.0) of the manual for more detailed information regarding
the calibration of the DPC. The calibration menu is identical for each dual range
sensors. Press the Sensor function key to select the desired dual ranges sensor to becalibrated.
4.6.2.1 Calibration Password
The calibration password allows the user to protect access to DPC calibration constants
and the calibration procedure. If the calibration password is set to any number otherthan zero, it is required before the user is allowed to calibrate the DPC or manuallychange the calibration constants.
IMPORTANT: It is recommended that the access password be recorded and filed in asecure location.

LOCAL OPERATION

4-18

1. The calibration password is set from the Calibration Menu. From the Main
Menu (press [PREVIOUS] until the Main Menu appears), press Menu [F6], thenCalibrate [F3].
2. Press the Access [F4] key. If there is a password in the system other than 0, thenyou must enter the current valid password into the 7250sys before it will allow you
to modify the password.
3. Use the numeric keypad to enter the new calibration password. Setting thecalibration password to zero allows free access to DPC calibration and constants.
Press [ENTER].
4. Press Yes [F4] to acknowledge changing the calibration password. Press No [F5]to reject changing the calibration password.
4.6.2.2 Zeroing
Ruska recommends that the DPC be zeroed once a day to maintain optimal
performance. The zero drift specification is defined in Appendix A under GeneralSpecifications. Refer to Section 6.4.5 for the zeroing procedure. On gauge mode
instruments, the zeroing procedure automatically ties both test and reference ports of theRuska quartz sensor together and performs the zeroing routine.
When operating a system that has the “absolute mode with evacuated reference”, avacuum pump and vacuum sensor is used to zero the instrument. The vacuum sensor isinstalled in a port that is located internally to the DPC very near to the Ruska quartz
sensor. When initiating the zeroing command in the DPC, it will cycle the internal valves
allowing the external vacuum pump to pull a hard vacuum on the Ruska sensor. It is
recommended that the sensor be pulled down to a vacuum of less than 200 mTorr(preferably less than 100 mTorr) in order to obtain a proper zero. The DPC can be
zeroed at higher vacuum levels, however, the uncertainty of vacuum sensors tend toincrease at higher vacuum levels, therefore, the uncertainty in the DPC would also
increase if zeroed at higher vacuum levels. Once the vacuum level is stable, the user
enters the vacuum level as indicated by the vacuum gauge and then the zeroingprocedure completes. Please refer to the Maintenance Section (Section 6.0) of themanual for more detailed information regarding the zeroing procedure of the DPC.
4.6.3 MENU | PROGRAM – STORING A SEQUENCE IN MEMORY
A program can be run on only the one selected channel at a time. Consider an exercisethat requires the DPC to start at 30 psi, increase to 50 psi, then decrease to 20 psi. Test
sequences like this may be stored in the DPC’s memory as a program.
One benefit of storing a sequence in memory is that the user does not have to commandeach pressure separately every time a multipoint test or calibration routine is performed.
Another benefit is that the user can specify a tolerance for each set-point pressure. Oncea tolerance is set, the dwell timer will start counting down instead of waiting until thepressure is at the exact set-point to start the dwell timer. This gives the user a timeadvantage compared to manual mode operation and provides a degree of automation
without the use of an external computer.

4-19

LOCAL OPERATIONThe DPC can store up to 1,000 program steps that may be divided among a maximum of
20 named programs.
The Program menu operates only on the current channel. The other channel will be inmeasure mode while the program is running.
4.6.3.1 Preparing to Program
Before entering a test sequence, consider the items discussed below.
Program Name: Valid program names range from one to eight characters in lengthand can include numbers, upper case letters, and the /, %, and # symbols. For
example, Exer#14 and %FStest are both valid names.
Configuration: Since a program will depend on the current setup of the DPC (thecurrent configuration is stored with the program) the user should set the units, limits,
control parameters, etc., to the desired values before creating a program.
Number of Set-points: Before entering the sequence, the user should determine thenumber of upscale and downscale set-points required to complete the exercise.
Set-point Pressure and Tolerance: Each set-point in the program requires both apressure and a tolerance, in the current units of measure. For example, one set-point
might require a tolerance as low as 0.05 psi (0.35 kPa), whereas another set-point in thesame program could be satisfied with a tolerance as high as 5 psi (0.35 kPa).
Dwell Time: Once the pressure is within the specified tolerance, the DPC starts a timer
that runs for a user-defined number of seconds. This is referred to as dwell time. Aslong as this timer is running, the DPC will remain at the designated set-point unless themax time (see below) elapses. When the dwell time expires, the DPC will proceed to
the next step. Typically the dwell time should be set to a value less than the max time.
Usually dwell time has a value of a few seconds, but a value of 0 can be used to createa pause in the program. When the dwell time is set to zero, the DPC switches tomanual control once it is within the tolerance value of the set-point pressure. The user
must then press a key on the front panel to continue the program.
MaxTime: The max time is the maximum time in seconds, including the dwell time,that the DPC can spend on one step of the program. After the max time elapses, theDPC will automatically proceed to the next set-point in the program, even if the current
set-point has not been achieved. Thus, the max time selection limits the amount of timethat the DPC can spend on any one set-point. Typically the max time should be set to avalue greater than the dwell time. If the max time is set to zero, the DPC will attempt toachieve the set-point indefinitely (i.e. the max time function is disabled).
Mode of Entry: If the upscale portion of the desired pressure step sequence and thedownscale portion of the sequence both have the same highest and lowest set-points andconsist of evenly spaced steps, the <Auto> option can be used to automatically generate
the program. However, if any part of the sequence includes unevenly spaced steps, orthe starting and ending set-points are not the same, each step must be programmed
individually. In the example given at the beginning of Section 4.6.3, each step must be

LOCAL OPERATION

4-20

programmed individually since the starting set-point is 30 psi and the ending set-point is
20 psi.
Detailed instructions for entering these items are given in the sections that follow.
4.6.3.2 Entering a New Program
To program the DPC, use the keys on the front panel to change values on the DPC’s
program editing screen. Instructions for entering each step of a new program areincluded below.
1. Ensure that the units, limits, and control parameters have been set to the desired
values.
2. The program is entered from the Program Menu. From the Main Menu (press[PREVIOUS] until the Main Menu appears), press Menu [F6], then Program[F4].

MENU | PROGRAM - MENU
3. Use the rotary knob to highlight “new.”
4. Press Edit [F4]. Since “new” was highlighted, the DPC will create a new programand give a default name of NAMEnn, where nn is a two digit number. The
program editing screen will appear, displaying the first step.

MENU | PROGRAM | EDIT - MENU
4-21

LOCAL OPERATION

5. Using the numeric keypad, enter the values for Pressure, Tolerance, Dwell time,and Max time, pressing [ENTER] after each value. The rotary knob may be used
to skip fields.
6. At the 0 step, enter the next pressure and the DPC will automatically insert a newpressure step.
7. Repeat steps 5 and 6 until the test sequence is complete. The Tolerance, Dwelltime and Max time will default to the value programmed in the first program
step, and only need to be changed if a different value is desired for a particular
step.
8. It is often suggested that the last point in a calibration program is to vent thepressure to atmosphere. This can be achieved by selecting the VENT function key
as the pressure set point. (Note, you can use the vent as a set-point at any pointin the program. The dwell and max time function with vent just as they would at acontrolled set-point.)
9. When all steps have been entered, press [PREVIOUS] to return to the Named
programs screen. See Section 4.6.3.4 for creating a user-defined program
name.
4.6.3.3 Automatically Generating a Program
For the DPC to automatically generate a program, the user must input the first set-point
pressure, the last set-point pressure, and the number of steps in between, as well as thedwell time, max time and tolerance common to all set-points.
1. Ensure that the units, limits, and control parameters are set to their desired values.
2. The program is entered from the Program Menu. From the Main Menu (press[PREVIOUS] until the Main Menu appears), press Menu [F6], then Program[F4].
3. Use the rotary knob to highlight “new.” If these steps are used on an existing
program, all program steps will be deleted and replaced with the automaticallygenerated program.
4. Press Edit [F4]. Since “new” was highlighted, the DPC will create a new programand give a default name of NAMEnn where nn is a two digit number. The
program editing screen will appear, displaying the first step.
5. Press Auto [F3].

LOCAL OPERATION

4-22

MENU | PROGRAM | EDIT | AUTO - MENU
6. Using the numeric keypad, enter the values for Start, Stop, Tolerance, Dwell
time, Max time, number of pressure Points up, and number of pressure Points
down, pressing [ENTER] after each value. The rotary knob may be used to skip
fields.
7. Press Program [F1]. The program will be generated and the display will show the
first step.
8. Press the Name [F6] key to edit the name of the program. See Section 4.6.3.4
for creating a user-defined program name.
4.6.3.4 Changing the Name of a Program
1. The name of an existing program is changed from the Program Menu. From theMain Menu (press [PREVIOUS] until the Main Menu appears), press Menu [F6],then Program [F4]. In addition to changing the name of an existing program, a
new program may be initiated by selecting “new” and performing the same steps
as outlined to change the name of a program.
2. Use the rotary knob to highlight the current name. (For a new program name,select “new.”)
3. Press Edit [F4]. The program editing screen will appear, displaying the first step.
4. Press Name [F6].

4-23

LOCAL OPERATIONMENU | PROGRAM | EDIT | NAME – MENU
5. Use the < [F4] and > [F5] keys to highlight a character.
6. Turn the rotary knob to select the character from the character set.
7. To correct a mistake, press Clear [F4] and return to step 5.
8. Repeat steps 5 and 6 until the name is complete.
9. Press Done [F6] to store the contents of the scratchpad as the new name of the
program.
4.6.3.5 Changing an Existing Program
Instructions for changing an existing sequence are given below. Both manually andautomatically generated programs may be edited.
1. Programs are changed from the Program Menu. From the Main Menu (press[PREVIOUS] until the Main Menu appears), press Menu [F6], then Program [F4].
2. Use the rotary knob to highlight the name of the program.
3. Press Edit [F4]. The program editing screen will appear as a table showing all of
the steps.

MENU | PROGRAM | EDIT - MENU
4. The rotary knob can be used to move through the program and highlight thevalue you wish to edit. Use the keyboard to enter a new value. This value will
LOCAL OPERATION

4-24

show up in the scratch pad located at the bottom of the window. Press [Enter] toaccept the edited value.
5. To add a step to the program, first move to the step after the new step. For
example, to insert a step between steps 3 and 4, move to step 4. Press Insert[F4].
6. To delete a step in the program, first move to the step to be deleted, then press
Delete [F5].
7. When all changes have been made, press [PREVIOUS] to return to the Named
programs screen. The DPC automatically saves the changes that were made in
the program.
4.6.3.6 Changing the Configuration Stored with a Program
1. Programs are configured from the Program Menu. From the Main Menu (press[PREVIOUS] until the Main Menu appears), press Menu [F6], then Program[F4].
2. Use the rotary knob to highlight the name of the program.
3. Press Config [F3]. The configuration screen will appear.
4. Press Recall [F2]. The DPC will be set to the configuration stored with theprogram.

MENU | PROGRAM | CONFIG - MENU
5. Press [PREVIOUS] until the Main Menu appears.
6. Press Setup [F2], then Limits [F1]. Change the desired parameters using thenormal procedures.
7. Return to the Main Menu by pressing [PREVIOUS] three times.
8. Press Menu [F6], then Program [F4].
9. Use the rotary knob to highlight the name of the program.
10. Press Config [F3], then Save [F1]. The configuration of the DPC will be changed
to the current settings and stored in the program’s configuration.
4.6.3.7 Running a Program
4-25

LOCAL OPERATION

1. Programs are run from the Program Menu. From the Main Menu (press[PREVIOUS] until the Main Menu appears), press Menu [F6], then Program[F4].
2. Use the rotary knob to highlight the name of the program.
3. Press Run [F1]. The program run screen will appear. “Stop” will be highlighted,
showing that the program is not currently running.

MENU | PROGRAM | RUN - MENU
4. Press Run [F2]. The configuration of the DPC stored with the program is restored,
the pressure set-point is set to the pressure value in the first step, and the DPC isplaced in Control mode. “Run” will now be highlighted and the program willproceed through its steps.
5. To pause the program, press Pause [F3]. “Pause” will now be highlighted andthe DPC will continue controlling to the current set-point. The DPC will maintaincontrol of the current set-point until further instructions from the operator. Press
Continue [F4] to resume the program.
6. To stop the program, press Stop [F5]. The program will stop running but the DPC
will continue controlling to the current set-point.
4.6.4 MENU | TESTThe Menu | Test section of the system is used to perform a number of the diagnostic
and tuning functions that are available with the 7250sys.

LOCAL OPERATION

4-26

MENU | TEST - MENU
4.6.4.1 Menu | Test – Sweep Test
The sweep function can be used to automatically exercise the elastic sensing element of
the device under test prior to performing a calibration. For the DPC to perform thesweep test, input the high and low set-point pressures, the pressure control tolerance, thedwell time at set-point, and the number of cycles to perform.
1. Ensure that the units, limits, and control parameters are set to their desired values.
2. The sweep test is entered from the Sweep Test Menu. From the Main Menu, (press[PREVIOUS] until the Main Menu appears), press Menu [F6], then Test [F5], andthen Sweep [F2].
3. Enter the high and low pressure points, the control tolerance, dwell time, and thenumber of cycles.

MENU | TEST | SWEEP – MENU
4. Press Run [F2] to initiate the test.
5. To pause the program, press Pause [F3]. Pause will now be highlighted and the
DPC will continue controlling to the current set-point. The DPC will maintaincontrol of the current set-point until further instructions from the user. Press
Continue [F4] to resume the program.
4-27

LOCAL OPERATION

6. To stop the program, press Stop [F5]. The program will stop running but the DPC
will continue controlling to the current set-point.
4.6.4.2 Menu | Test – Self Test
The DPC can perform electrical and pneumatic self test to assist in trouble shooting
potential problems. Please refer to the Maintenance – Section 6.0 for more details.
NOTE: In order to perform a pneumatic self test, the supply port must be connected toa properly set supply pressure and the test port not open to atmosphere. For
absolute units, a vacuum supply must also be connected to the exhaust port.
4.6.4.3 Menu | Test – Remote Test
The Menu | Test | Remote section of the system is used to perform a number of thediagnostic functions on the remote interface. It can be used to display the transmitted
and received messages that are sent across the interface. This can be a powerful tool toassist in identifying the source of communication problems.
The Menu | Test | Remote menu displays information from the IEEE-488 interface.
Pressing the Serial 1 [F2] or Serial 2 [F3] keys will display information from the serial
ports.

MENU | TEST | REMOTE – GPIB MENU
4.6.4.4 Menu | Test – Shop1
The Menu | Test | Shop1 menu of the system is used to display the current status of thevarious valve positions in the system. This menu is primarily used for diagnostics and will
be discussed further in the Maintenance Section 6.0.

LOCAL OPERATION

4-28

MENU | TEST | SHOP1 – MENU
4.6.4.5 Menu | Test – Control
The Menu | Test | Control menu of the system is used to tune the controller. On new
instruments, the controller is tuned at the factory and therefore, the user should not needto access or make any adjustments to the controller using this menu. This menu is user
accessible in order to provide a means to set-up the controller when control valves are
replaced or to perform maintenance on the controller. This menu is primarily used for
diagnostics and repair and will be discussed further in the Maintenance Section 6.0.

MENU | TEST | CONTROLLER – MENU
4.6.5 MENU | DISPLAY
The Menu | Display is used to conveniently monitor most of the sensor output
parameters. It is primarily used for troubleshooting.
This display screen shows all
available sensor readings from both channels.

4-29

LOCAL OPERATIONMENU | DISPLAY – MENU
4.6.5.1 Menu | Display – Temperature
The Menu | Display | Temp is used to monitor the temperature of each dual range
sensor. It is primarily used to assist in determining when the sensors in the system arethermally stabilized.
4.6.5.2 Menu | Display – Vacuum
The Menu | Display | Vac is used to monitor the vacuum sensors each dual range
sensor that are supplied with the “absolute with evacuated reference” option. It is
primarily used for troubleshooting.
4.6.5.3 Menu | Display - Blank
This is used as a screen saver in the 7250sys.

LOCAL OPERATION

4-30

THIS PAGE INTENTIONALLY LEFT BLANK

4-31

LOCAL OPERATIONSECTION 5.0
REMOTE OPERATION
5.1 CAPABILITIESThe DPC can be operated remotely by a computer. Two interfaces are supported: IEEE488 and RS-232. Both interfaces support SCPI (Standard Commands for Programmable
Instruments). The IEEE-488 interface additionally supports emulation of a Ruska Single
Channel Interface Panel (Models 6005-701 and 6005-761). The IEEE-488 interface
conforms to the following standards:
ANSI/IEEE Std 488.1-1987 IEEE Standard Digital Interface for Programmable
Instrumentation
ANSI/IEEE Std 488.2-1987 IEEE
Standard
Codes,
Formats,
Protocols,andCommonCommands
SCPI 1991.0
Standard Commands for Programmable Instruments
5.1.1 IEEE-488
The following identification codes define the interface capabilities of the DPC.
Identification codes are described in the IEEE-488 standard.
SH1
AH1
T5
L3
SR1
RL1
PP0
DC1
DT0
C0

Source Handshake, Complete Capability
Acceptor Handshake, Complete Capability
TalkerListener
Service Request, Complete Capability
Remote-Local, Complete Capability
Parallel Poll, No Capability
Device Clear, Complete Capability
Device Trigger, No Capability
Controller, No Capability

The IEEE-488 interface is installed next to the processor board. The interface is identified
by the IEEE-488 standard connector on the back panel of the unit.
NOTE: Do not change any jumpers or switch settings on the IEEE-488 interface board.
The IEEE-488 address is set by the MENU/SETUP/REMOTE screen.
5.1.2 RS-232
The RS-232 interface supports standard serial operation from a computer to a single
DPC. RS-232 supports the IEEE-488.2 and SCPI commands. The DPC allows thefollowing port setups:
Baud Rate:
Data Bits:
Parity:Stop Bits
Handshaking

1200, 2400, 9600, or 19200
7 or 8
Even, Odd, or None
1 or 2
XON/XOFF
5-1

REMOTE OPERATIONThe RS-232 connection is a DB-9P connector found on the back panel of the DPC. It is
located on the processor board. The following pins are used; all other pins are reserved.
Pin #
2
3
5
7

Direction
In
Out
——
Out

SignalRXD Receive DataTXD Transmit Data
GND Ground
RTS Request to Send

5.2 REMOTE/LOCAL OPERATION
In Local mode, the DPC is operated manually through the front panel. Section 4.0
covers local operation. The DPC always powers up in the Local mode. In Remote mode,
the DPC is operated by a computer connected to an interface. Most functions that can be
performed in Local mode can also be performed remotely.
Remote mode does not automatically disable local operation. The remote interface may
be active while local operations are being done. In cases where full remote control isrequired, the following methods may be used.
1. Issue a Local Lockout (LLO) interface message via the IEEE-488 interface. The
DPC will disable the local keyboard until the Go To Local (GTL) interface message
is received or the REN (Remote Enable) line is unasserted. This method cannot be
used on the serial interface.
2. Issue the SCPI command “SYSTEM:KLOCK ON” to lock the local keyboard. The
DPC will disable the local keyboard until the command “SYSTEM:KLOCK OFF” isreceived.
3. Issue the SCPI command “DISPLAY:ENABLE OFF” or “DISPLAY:TEXT <string>.”
These commands will disable the local display in addition to locking the keyboard.
The command “DISPLAY:ENABLE ON” will restore the local display and keyboard
operation.
Local operation may also be restored by turning the DPC off and back on.
5.3 CONFIGURATIONThe remote interface must be configured before it is connected. The remote interface isconfigured using the local interface. The parameters needed vary with the interface used.
IEEE-488
RS-232

Address, Protocol
Baud Rate, Data Bits, Parity, Stop Bits

To configure the remote interface:
1. The remote interface is configured from the Setup | Remote | Menu. From theMain Menu (press [PREVIOUS] until the Main Menu appears), press Menu [F6],then Setup [F2], and finally Remote [F4].
2. Use the rotary knob to highlight the desired parameter.
3. Use the numeric keypad to enter the address; use the rotary knob to change theother parameters. The [ENTER] key must be pressed after entering the address.
REMOTE OPERATION

5-2

4. Repeat steps 2 and 3 to set all parameters needed.
5.4

DEVICE MESSAGES

5.4.1 SCPI COMMAND FORMATSCPI mnemonics have two forms: long and short. The short form is all in capital letters.
The long form is the entire mnemonic. Commands may use either the short form or theentire long form. No other forms are accepted. SCPI ignores case: uppercase andlowercase are equivalent.
A SCPI command is made by following the command tree as presented in the commandsummary. Each level adds a mnemonic to the command separated by colons (:).
Mnemonics enclosed in square brackets are optional and may be omitted.
Some mnemonics are followed by an optional numeric suffix.
defaults to 1.

If omitted, the suffix

Multiple commands may be placed in a single message separated by semicolons (;).
Each command starts at the same level of tree where the last command stopped, unlessthe command starts with a colon. The first command in a message and any commands
starting with a colon start at the root of the command tree. IEEE 488.2 commands may
occur between SCPI commands without affecting the tree level.
Command parameters are separated from the command name by one or more spaces.
Multiple parameters are separated by commas (,). SCPI accepts numeric parameterswith optional sign, decimal point, and exponent. OFF is equivalent to zero and ON isequivalent to one. Floating point numbers are rounded to the nearest integer forcommands accepting integer values only.
A message is terminated by a line feed (hexadecimal 0A). Carriage returns, tabs, andother control characters are ignored.
5.4.2 SCPI RESPONSE FORMAT
Most values can be queried by appending a question mark (?) to a command and not
specifying any parameters. Commands ending with a question mark (?) in the commandsummary cannot be set only queried. Multiple values from a single command areseparated by commas. Responses from different commands in the same message are
separated by semicolons (;). The response message is terminated by a line feed(hexadecimal 0A).
Integer responses are returned as one or more digits. Boolean values (ON and OFF
values) are always returned as numbers, with zero for OFF and one for ON. Floating
point values are returned in the format “+d.ddddddddE+dd.”

5-3

REMOTE OPERATION

5.4.3 ANSI/IEEE 488.2-1987 COMMAND SUMMARY
*CLS
*ESE?
*ESE
<number>
*ESR?
*IDN?
*OPC?
*OPC
*RST
*SRE?
*SRE
<number>
*STB?
*TST?
*WAI

Clear Status
Event Status Enable Query
Event Status Enable
Event Status Register
Identification
Operation Complete Query (Returns 1)
Operation Complete
Reset
Service Request Enable Query
Service Request Enable
Status Byte Query
Self-Test Query
Wait (No operation)

5.4.4 SCPI COMMAND SUMMARY
The current value associated with a SCPI command may be read by appending aquestion mark to the command. For example CALC:LIM:UPP? will return the current
upper pressure limit.
MEASure[:PRESsure]?
:SLEW?
:PRESsure2?
:PRESsure12?
:PRESsure22?
:PRESsure32?
:PRESsure42?
:PRESsure52?
:PRESsure3?
:PRESsure4?
:PRESsure14?
:PRESsure24?
:PRESsure5?
:PRESsure15?
:PRESsure25?
:PRESsure35?
:PRESsure45?
:PRESsure55?
:VACuum?
:VACuum11?
:VACuum21?
:VACuum31?
:VACuum41?
:VACuum51?
:TEMPerature?
:TEMPerature11?
REMOTE OPERATION

Main Pressure
Main Slew Rate
Sensor A Case Reference
Sensor B Case Reference
Sensor C Case Reference
Sensor D Case Reference
Sensor E Case Reference
Sensor F Case Reference
Sensor RPT
Controller A PDCR
Controller B PDCR
Controller C PDCR
Sensor A
Sensor B
Sensor C
Sensor D
Sensor E
Sensor F
Sensor A Vacuum
Sensor B Vacuum
Sensor C Vacuum
Sensor D Vacuum
Sensor E Vacuum
Sensor F Vacuum
Sensor A Gas Temperature
Sensor B Gas Temperature
5-4

:TEMPerature21?
:TEMPerature31?
:TEMPerature41?
:TEMPerature51?
:TEMPerature2?
:TEMPerature12?
:TEMPerature22?
:TEMPerature32?
:TEMPerature42?
:TEMPerature52?

Sensor C Gas Temperature
Sensor D Gas Temperature
Sensor E Gas Temperature
Sensor F Gas Temperature
Sensor A Oven Temperature
Sensor B Oven Temperature
Sensor C Oven Temperature
Sensor D Oven Temperature
Sensor E Oven Temperature
Sensor F Oven Temperature

CALCulate[:PRESsure]:TARE:VALUE <number>:STATe ON|OFF:LIMit:LOWer <number>:SLEW <number>:UPPer <number>:VENT <number>get/set tare value
set tare state using current press.
low pressure limit
slew rate limit
high pressure limit
auto-vent limit

CALibration:MODE?
:MODE <number>calibration edit enabled?
request calibration edit

The next section of calibration commands arevalid for the following main sensors::PRESsure5?
Sensor A:PRESsure15?
Sensor B:PRESsure25?
Sensor C:PRESsure35?
Sensor D:PRESsure45?
Sensor E:PRESsure55?
Sensor F:VALue<n> <number>:DATA:POINts?
:VALue<n>?
:VALue<n> <number>:CALibration:VALue<n>?
:POINts?
:DATE?
:TIME?
:ZERO:DATE?
:TIME?

Perform calibration point
return number of calibration constants
returns label,value (C0,0.123)
sets calibration constantreturn nominal calibration point
return number of calibration points
last calibration datelast calibration time
last zero datelast zero time
5-5

REMOTE OPERATION

:VALue <number>:INITiate:INITiate?
:RUN
:STOP

sets vacuum value (microns/mtorr)
enter zero calibration mode
returns status for cal, press, temp, refstart zero calibrationabort zero calibration

The next section of calibration commands arevalid for the following auxliary sensors::PRESsure2?
Sensor A Case Reference:PRESsure12?
Sensor B Case Reference:PRESsure22?
Sensor C Case Reference:PRESsure32?
Sensor D Case Reference:PRESsure42?
Sensor E Case Reference:PRESsure52?
Sensor F Case Reference:PRESsure3?
Sensor RPT:PRESsure4?
Controller A PDCR:PRESsure14?
Controller B PDCR:PRESsure24?
Controller C PDCR
:VACuum?
Sensor A Vacuum:VACuum11?
Sensor B Vacuum:VACuum21?
Sensor C Vacuum:VACuum31?
Sensor D Vacuum:VACuum41?
Sensor E Vacuum:VACuum51?
Sensor F Vacuum:TEMPerature?
Sensor A Gas Temperature:TEMPerature11?
Sensor B Gas Temperature:TEMPerature21?
Sensor C Gas Temperature:TEMPerature31?
Sensor D Gas Temperature:TEMPerature41?
Sensor E Gas Temperature:TEMPerature51?
Sensor F Gas Temperature:TEMPerature2?
Sensor A Oven Temperature:TEMPerature12?
Sensor B Oven Temperature:TEMPerature22?
Sensor C Oven Temperature:TEMPerature32?
Sensor D Oven Temperature:TEMPerature42?
Sensor E Oven Temperature:TEMPerature52?
Sensor F Oven Temperature:VALue<n> <number>:DATA:POINts?
:VALue<n>?
:VALue<n> <number>:CALibration:VALue<n>?
:POINts?
:ZERO <number>

REMOTE OPERATION

Perform calibration point
return number of calibration constants
returns label,value (C0,0.123)
sets calibration constantreturn nominal calibration point
return number of calibration points
Zero sensor

5-6

DISP
:ENABle ON|OFF|1|0:TEXT "<text>"[:PRESsure]:BGRaph <number>turns front panel display on/off
display message on front panelbar graph maximum

OUTPut[:PRESsure]:STATe ON|OFF|1|0:MODE MEASure|CONTrol|VENT

off=MEASure, on=CONTrol
sets mode

PROGram:CATalog?
returns list of defined programs[SELected]:DEFine <program block><step,press,toler,dwell,max>press1,toler1,dwell1,max1,press2,toler2,dwell2,max2,...
:DELete[:SELected]
deletes current program:ALL
deletes all programs:NAME <program name>select current program:STATe RUN|PAUSe|STOP|CONTinue change program state:CONFigure:RECallload program configuration:SAVE
save current configuration into program
SENSE[:PRESSure][:RESolution] <number>sets pressure display resolution:AUTO ONCE
returns to default resolution:MODE ABSolute|DIFFerential|GAUGE|TARE:RANGE[:UPPer]?
full scale value in units (calibrated)[:UPPer] <number>set 7610 triple range:LOWer?
returns low cal point:LIST?
list installed sensor ranges:CONTrol?
list installed controller ranges:REFerence[:HEIGht] <number>gas head height:MEDium N2|AIR
gas head medium[SOURCE][:PRESsure][:LEVel][:IMMediate][:AMPLitude] <number>:MODE FIXed|LIST:TOLerance <number>:SLEW <number>pressure control setpoint
set control mode
specifies output tolerance
set slew rate
5-7

REMOTE OPERATION

:CONTrol <number>:ON <number>:OFF <number>:OVERshoot ON|OFF|1|0

control band
set control mode 1=FAST/0=NORMAL:LIST:PRESsure <number> [,<number>]:POINts?
:DWELl <number> [,<number>]:POINts?
:TOLerance <number> [,<number>]:POINts?
:DIRection UP|DOWN:COUNt <number>
STATus:OPERation[:EVENT]?
:CONDition?
:ENABle <number>:QUEStionable[:EVENT]?
:CONDition?
:ENABle:PRESetset list of pressure values
number of points defined
specifies dwell times
number of dwell times
specifies tolerances
number of tolerances
direction to go through list
number of times to go through list

read/clear operation event register
read operation condition registerset operation enable mask
read/clear questionable event register
read questionable condition register
set questionable enable mask
clear enable masks

SYSTem:BEEPer <freq>,<length>:DATE <year>,<month>,<day>:ERRor?

<Freq> ignored
system datereturns <error#,"descr;info"> or 0,"No
Error":KLOCk ON|OFF|1|0
keyboard lock
:TIME <hour>,<minute>,<sec>system time
:VERSion?
SCPI protocol version (returns 1991.0):LANGuage "COMP"|"6000"|"SCPI"|"510"
set interface emulation:PRESetreset pressure control:COMMunicate:SERial:RECeive:TRANsmit:BAUD <number>:PARITY EVEN|ODD|NONE:BITS 7|8
:SBITs 1|2:GPIB:ADDRess <number>TEST
REMOTE OPERATION

5-8

:ELECtronic?
:PNEumatic:PNEumatic?
:STOP

Run Elec Self-Test & Return Result
Start Pneu Self-Test
Get Pneu Test Results
Abort Pneu, Volume, or Leak

UNIT
:DEFine<n> <name>,<number>Create Unit
:LENGth EX|PE|T|G|MA|K|M|U|N|P|F|A M|FT|IN set length units[:PRESsure] <name>set pressure units:TEMPerature C|CEL|F|FAR|K
set temperature units:LENGth <name>set length units (head height)

5.4.5 EXAMPLE SCPI COMMANDS
To request the current pressure reading, all of the following commands are equivalent::MEASURE:PRESSURE?
:measure:pressure?
:MeAsUrE:pReSsUrE?
:meas:pres?
:measure?
:meas?
MEAS?

To set the control pressure setpoint to 50, all of the following commands are equivalent:
SOURCE:PRESSURE:LEVEL:IMMEDIATE:AMPLITUDE 50
SOUR:PRES:LEV:IMM:AMPL 50.0
PRESSURE +50
PRES 50

To zero the unit via the remote interface use the following sequence:
CAL:ZERO:INIT
CAL:ZERO:INIT?
CAL:ZERO:RUN
STAT:OPER:COND?

Enter Zero Mode
Read Status (Mode, Pressure, Temperature, Reference)and Wait Until Stable.
Start Zero Adjust Sequence
Wait Until Complete (Bit 0 = 0)

5.4.6 SCPI STATUS REGISTERS
Three type of status registers are available: Condition, Event, and Enable.
Condition registers always show the current status of the instrument. Bits may turn on
and back off between reads. The status read is the status of instrument at the moment of
the read. Condition registers include:
*STB?
*ESR?
STAT:OPER:COND?
STAT:QUES:COND?

Status Byte Register
Standard Event Status Register
Operation Status Condition Register
Questionable status Condition Register

5-9

REMOTE OPERATIONEvent registers do not show the current state but flag the bits in the condition registers thathave changed since the last time the event register was read. When an event register isread it is reset to zero.
STAT:OPER:EVENT?
STAT:QUES:EVENT?

Operation Status Event Register
Questionable Status Event Register

Enable registers are set by the user to create summary bits. If the user sets a bit in theenable register, when the instrument sets the corresponding bit in the event register asummary bit in the Status Byte Register is set.
*ESE
STAT:OPER:ENAB
STAT:QUES:ENAB
The Service Request Enable Register (*SRE) is used to generate service requests on theIEEE-488 bus. If a user sets a bit in this register, when the instruments sets thecorresponding bit in the Status Byte Register (*STB) a service request is generated.
*SRE
Status Byte Register (STB), Service Request Enable Register (SRE)
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0

Operation status summary. Set when an event enabled in OPER:ENABLE occurs.
Service request. Set when an event enabled in SRE occurs. (This bit is not used in SRE.)
EBS - Event status bit. Set when an event enabled in ESE occurs.
MAV - Message available. Set when a response is ready to be sent.
Questionable status summary. Set when an event enabled in QUES:ENABLE occurs.
Error/event queue not empty.
Reserved. 0.
Reserved. 0.

Standard Event Status Register (ESR), Standard Event Status Enable Register (ESE)
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0

Power-on. Set at power-up.
Reserved 0.
Command error. Error in command syntax.
Execution error. Error in command execution.
Device dependent error. Device error independent of commands.
Query error. Output queue empty when request received.
Reserved. 0.
Operation complete. Set for *OPC command.

Operation Status (OPER:EVENT, OPER:CONDITION, OPER:ENABLE)
Bit 0
Bit 1
Bit 2
Bit 3
Bit 4
Bit 5
Bit 7
Bit 8
Bit 9

Calibrating. Currently performing a calibration.
Settling. Control setpoint has not been reached. Pressure tolerance set by
SOUR:PRES:TOL
Reserved. 0.
Reserved. 0.
Measuring. The instrument is actively measuring.
Reserved. 0.
Reserved. 0.
Self-test in progress.
Reserved.

REMOTE OPERATION

5-10

Bit 10
Bit 11
Bit 12
Bit 13
Bit 14
Bit 15Reserved. 0.
Reserved. 0.
Reserved. 0.
Reserved. 0.
Program running.
Reserved. 0.

Questionable Status (QUES:EVENT, QUES:CONDITION, QUES:ENABLE)
Bit 0 Supply voltage questionable.
Bit 1 Reserved. 0.
Bit 2 Time is questionable. Set when the clock has not been set.
Bit 3. Temperature is questionable. Sets when oven temperature is not within range.
Bit 4 Reserved. 0.
Bit 5 Reserved. 0.
Bit 6 Reserved. 0.
Bit 7 Calibration is questionable. Set when the unit has not been calibrated.
Bit 8 Pressure is questionable. Set when the pressure is overranged.
Bit 9 Reserved. 0.
Bit 10 Reserved. 0.
Bit 11 Reserved. 0.
Bit 12 Reserved. 0.
Bit 13 Reserved. 0.
Bit 14 Command warning. Set whenever a command ignores a parameter.
Bit 15 Reserved. 0.

5.5 SERIAL OPERATIONThe RS-232 port accepts the same SCPI commands as the IEEE-488 port. The
commands can be terminated by a carriage return (hexadecimal 0D) or a line feed(hexadecimal 0A). The responses are always terminated by a carriage return followed bya line feed.
The serial port also supports XON/XOFF. When the XOFF (hexadecimal 13) command isreceived, the DPC will stop transmitting. Transmission is restarted when the XON(hexadecimal 11) command is received.
When only one unit is attached, the Control-C (hexadecimal 03) command will clear thetransmit and receive buffers and disable addressing. When addressing is disabled, theunit will respond to commands without being addressed.
5.6

SAMPLE PROGRAMS

5.6.1

SAMPLE PROGRAM 1 - 7252 GPIB (IEEE-488)- CONTROLS PRESSURE TO
20.000 %FS/*--------------------------------------------------------------------*//*
Sample Program 1 - 7252 GPIB (IEEE-488)
*/
/*
*/
/*
Controls pressure to 20.000 %FS*//*--------------------------------------------------------------------*/#include <stdio.h>#include <stdlib.h>#include <string.h>#include <conio.h>
5-11

REMOTE OPERATION

#include "decl.h"/*--------------------------------------------------------------------*/
int
device;charbuffer[256];
double pressure;int
status;/* GPIB Device descriptor *//* buffer for input/output strings *//* Pressure read from unit *//* Status register from unit */int
check_errors (void);
void
write_7000 (char *s);void
request_7000 (char *s);/*--------------------------------------------------------------------*/
void main (void){char *p;/*---------------------------*//* Initialize GPIB Interface *//*---------------------------*/
device = ibdev (0,/* First GPIB Board */4,/* GPIB Address of 7010 */NO_SAD,/* No secondary addressing */T1s,/* 1 Second Timeout */0,/* No automatic EOI for transmit */REOS+LF);/* Terminate read on Line Feed */if (ibsta & ERR)
{ printf ("GPIB Driver not installed.\n");return;}/*-----------------------------------------------------------*//* Initialize 7252 Interface
*/
/*
*/
/*
UNIT %FS
Set units to percent of full scale *//*PRES 20.0
Set control setpoint to 20 %FS*//*
PRES:TOL 0.001
Set control tolerance to 0.001 %FS *//*OUTP:MODE CONTROL Enter control mode*//*-----------------------------------------------------------*/
write_7000 ("UNIT %FS;:PRES 20.0;TOL 0.001;:OUTP:MODE CONTROL\n");if (check_errors ( )){ ibonl (device, 0);
return;}/*-------------------------------------------------*//* Read pressure status until setpoint is reached. */
/*
*/
/*
MEAS?
Read pressure*//*
STAT:OPER:COND?
Read status setpoint*//*-------------------------------------------------*/
while (!kbhit ( )){ request_7000 ("MEAS?;:STAT:OPER:COND?\n");pressure = strtod (buffer, &p);status= atoi (++p);
if (check_errors ( ))REMOTE OPERATION

5-12

continue;}

if (status & 0x10)
printf ("Pressure = %9.3lf\n", pressure);if ((status & 2) == 0)
break;/*-------------------------------------------*//* Reset 7252 to Measure mode
*/
/*
*/
/*
OUTP:MODE MEASURE Enter Measure mode *//*-------------------------------------------*/
write_7000 ("OUTP:MODE MEASURE\n");check_errors ( );}/*----------------------*//* Reset GPIB Interface *//*----------------------*/
ibonl (device, 0);/*--------------------------------------------------------------------*//* check_errors : display all GPIB and 7252 error messages*//*
return TRUE if any errors were found*//*--------------------------------------------------------------------*/
int check_errors (void){
unsigned char status7;
int retval;/*---------------------------------*//* Check for GPIB Interface Errors *//*---------------------------------*/
if (ibsta & ERR)
{ printf ("GPIB Status=%4X Error=%d\n");return 1;}/*-----------------------*//* Check for 7252 Errors *//*-----------------------*/
retval = 0;
while (!kbhit ( )){ ibrsp (device, &status7);
if ((status7 & 4) == 0)
break;
retval = 1;
request_7000 ("SYST:ERR?\n");printf (buffer);}
return retval;/* Serial poll *//* Check error bit *//* Get error message */}/*--------------------------------------------------------------------*//* write_7000 : write a command to the 7250*//*--------------------------------------------------------------------*/
void write_7000 (char *s){
ibwrt (device, s, strlen (s));
5-13

REMOTE OPERATION

}/*--------------------------------------------------------------------*//* request_7000 : write a query command and read the response*//*--------------------------------------------------------------------*/
void request_7000 (char *s){
ibwrt (device, s, strlen (s));
ibrd (device, buffer, sizeof (buffer));}/*--------------------------------------------------------------------*/

5.6.2 SAMPLE PROGRAM 2 - 7252 GPIB (IEEE-488)- ZERO SEQUENCE/*--------------------------------------------------------------------*//*
Sample Program 2 - 7252 GPIB (IEEE-488)
*/
/*
*/
/*
Zero Sequence*//*--------------------------------------------------------------------*/#include <stdio.h>#include <stdlib.h>#include <string.h>#include <conio.h>#include "decl.h"/*--------------------------------------------------------------------*/
int
device;charbuffer[256];
double pressure;int
status;/* GPIB Device descriptor *//* buffer for input/output strings *//* Pressure read from unit *//* Status register from unit */int
check_errors (void);
int
zero (void);
void
write_7000 (char *s);void
request_7000 (char *s);/*--------------------------------------------------------------------*/
void main (void){char *p;/*---------------------------*//* Initialize GPIB Interface *//*---------------------------*/
device = ibdev (0,/* First GPIB Board */4,/* GPIB Address of 7252 */NO_SAD,/* No secondary addressing */T1s,/* 1 Second Timeout */0,/* No automatic EOI for transmit */REOS+LF);/* Terminate read on Line Feed */if (ibsta & ERR)
{ cprintf ("GPIB Driver not installed.\n");return;}/*-----------*//* Zero 7010 *//*-----------*/
if (!zero ( ))REMOTE OPERATION

5-14

}

{ ibonl (device, 0);
return;}/*----------------------*//* Reset GPIB Interface *//*----------------------*/
ibonl (device, 0);/*--------------------------------------------------------------------*//* Zero : perform zero adjust of 7252*//*--------------------------------------------------------------------*/
int zero (void){
int cstat, pstat, tstat, rstat;clrscr ( );cprintf ("Zeroing");
gotoxy (1, 5); cprintf ("Pressure Reading");
gotoxy (1, 6); cprintf ("Sensor Temperature");gotoxy (1, 7); cprintf ("Reference Pressure");/*-------------------*//* Enter Zero Mode*//*
CAL:ZERO:INIT *//*-------------------*/
write_7000 ("CAL:ZERO:INIT\n");/*-------------------------------------------------*//* Wait for calibration values to be within limits *//*CAL:ZERO:INIT?
*//*-------------------------------------------------*/
do{ if (kbhit ( )){ getch ( );break;}
request_7000 ("CAL:ZERO:INIT?\n");sscanf (buffer, "%d,%d,%d,%d", &cstat, &pstat, &tstat, &rstat);if (check_errors ( ))return 0;
gotoxy (20, 5);
if (pstat == 0)
cprintf ("Stable");else if (pstat < 0) cprintf ("Out of Range");
else if (pstat > 0) cprintf ("Unstable (%2d seconds)", pstat);gotoxy (20, 6);
if (tstat == 0)
cprintf ("Stable");else if (tstat < 0) cprintf ("Out of Range");else if (tstat > 0) cprintf ("Unstable (%2d minutes)", tstat);gotoxy (20, 7);
if (rstat == 0)
cprintf ("Stable");else if (rstat < 0) cprintf ("Out of Range");else if (rstat > 0) cprintf ("Unstable (%2d seconds)", rstat);
5-15

REMOTE OPERATION

}while (pstat != 0 || tstat != 0 || rstat != 0);/*-------------------*//* Start Zero Adjust *//*CAL:ZERO:RUN *//*-------------------*/
write_7000 ("CAL:ZERO:RUN\n");/*---------------------------*//* Wait for zero to complete *//*STAT:OPER:COND?
*//*---------------------------*/
do{ request_7000 ("STAT:OPER:COND?\n");sscanf (buffer, "%d", &status);
if (check_errors ( ))return 0;
gotoxy (1, 9);cprintf ("Zeroing");}
while ((status & 1) != 0);}

gotoxy (1, 9);cprintf ("Zero Complete");return 1;/*--------------------------------------------------------------------*//* check_errors : display all GPIB and 7252 error messages*//*
return TRUE if any errors were found*//*--------------------------------------------------------------------*/
int check_errors (void){
unsigned char status7;
int retval;/*---------------------------------*//* Check for GPIB Interface Errors *//*---------------------------------*/
if (ibsta & ERR)
{ cprintf ("GPIB Status=%4X Error=%d\r\n", ibsta, iberr);
return 1;}/*-----------------------*//* Check for 7252 Errors *//*-----------------------*/
retval = 0;
while (!kbhit ( )){ ibrsp (device, &status7);
if ((status7 & 4) == 0)
break;
retval = 1;
request_7000 ("SYST:ERR?\n");cprintf (buffer);
REMOTE OPERATION/* Serial poll *//* Check error bit *//* Get error message */
5-16

}

}
return retval;/*--------------------------------------------------------------------*//* write_7000 : write a command to the 7250*//*--------------------------------------------------------------------*/
void write_7000 (char *s){
ibwrt (device, s, strlen (s));}/*--------------------------------------------------------------------*//* request_7000 : write a query command and read the response*//*--------------------------------------------------------------------*/
void request_7000 (char *s){
ibwrt (device, s, strlen (s));
ibrd (device, buffer, sizeof (buffer));}/*--------------------------------------------------------------------*/

5.6.3

SAMPLE PROGRAM 3 - 7252 SERIAL(RS-232)- CONTROLS PRESSURE TO
20.000 %FS/*--------------------------------------------------------------------*//*
Sample Program 3 - 7252 Serial (RS-232)
*/
/*
*/
/*
Controls pressure to 20.000 %FS*//*--------------------------------------------------------------------*/#include <stdio.h>#include <stdlib.h>#include <conio.h>#include <dos.h>#include <time.h>#define TRUE 1#define FALSE 0#define TIMEOUT (CLK_TCK * 5)#define XON 0x11
#define XOFF 0x13
#define CLEAR 0x03
#define DLE 0x10
#define QUEUE_SIZE 1024/* 5 second timeout */charbuffer[QUEUE_SIZE];
double pressure;int
status;/* buffer for input/output strings *//* Pressure read from unit *//* Status register from unit */int address;
int portbase;int intnum;
volatile int transmit_enabled = TRUE;
char inqueue[QUEUE_SIZE];
int inq_in;
int inq_out;
void interrupt (*old_vector) ( );intcheck_errors (void);
5-17

REMOTE OPERATION

void serial_initialize (void);void write_7000_serial (char *s);void serial_close (void);
int request_7000_serial (char *s);void serial_write (char ch);/*--------------------------------------------------------------------*/
void main (void){char *p;/*-----------------------------*//* Initialize Serial Interface *//*-----------------------------*/
address = 4;
serial_initialize ( );/*-----------------------------------------------------------*//* Initialize 7252 Interface
*/
/*
*/
/*
UNIT %FS
Set units to percent of full scale *//*PRES 20.0
Set control setpoint to 20 %FS*//*
PRES:TOL 0.001
Set control tolerance to 0.001 %FS *//*OUTP:MODE CONTROL Enter control mode*//*-----------------------------------------------------------*/
write_7000_serial ("UNIT %FS;:PRES 20.0;TOL 0.001;:OUTP:MODE CONTROL\n");if (check_errors ( )){ serial_close ( );return;}/*-------------------------------------------------*//* Read pressure status until setpoint is reached. */
/*
*/
/*
MEAS?
Read pressure*//*
STAT:OPER:COND?
Read status setpoint*//*-------------------------------------------------*/
while (!kbhit ( )){ if (!request_7000_serial ("MEAS?;:STAT:OPER:COND?\n")){ printf ("Timeout\n");continue;}pressure = strtod (buffer, &p);status= atoi (++p);
if (check_errors ( ))continue;}

if (status & 0x10)
printf ("Pressure = %9.3lf\n", pressure);if ((status & 2) == 0)
break;/*-------------------------------------------*//* Reset 7252 to Measure mode
*/
/*
*/
/*
OUTP:MODE MEASURE Enter Measure mode */REMOTE OPERATION

5-18

/*-------------------------------------------*/
write_7000_serial ("OUTP:MODE MEASURE\n");check_errors ( );}/*------------------------*//* Reset Serial Interface *//*------------------------*/
serial_close ( );/*--------------------------------------------------------------------*//* check_errors : display all 7252 error messages*//*
return TRUE if any errors were found*//*--------------------------------------------------------------------*/
int check_errors (void){
unsigned char status7;
int retval;*//*-----------------------*//* Check for 7252 Errors *//*-----------------------*/
retval = 0;
while (!kbhit ( )){ if (!request_7000_serial ("*STB?\n")){ printf ("Timeout\n");return TRUE;}
status7 = atoi (buffer);if ((status7 & 4) == 0)
break;
retval = 1;
request_7000_serial ("SYST:ERR?\n");/* Check error bit *//* Get error message

printf (buffer);}
return retval;}/*--------------------------------------------------------------------*//* serial_int : receive interrupt for serial port*//*--------------------------------------------------------------------*/
void interrupt serial_int ( ){char ch;if ((inportb (portbase + 2) & 0x07) == 0x04){ ch = inportb (portbase);if (ch == XON)
transmit_enabled = TRUE;
else if (ch == XOFF)
transmit_enabled = FALSE;
else{ inqueue[inq_in++] = ch;if (inq_in == QUEUE_SIZE)
inq_in = 0;}}
outportb (0x20, 0x20);}/*--------------------------------------------------------------------*/
5-19

REMOTE OPERATION

/* serial_initialize : initialize serial port*//*--------------------------------------------------------------------*/
void serial_initialize ( ){char msg[10];int divisor;
unsigned v;
portbase = 0x3F8;
intnum= 4;
outportb (portbase + 3, 0x80);
outportb (portbase + 1, 0);
outportb (portbase,
0x0C);
outportb (portbase + 3, 3);/* COM1 = 0x3F8, COM2 = 0x2F8 *//* COM1 = 4,
COM2 = 3*/

old_vector = getvect (intnum + 8);
setvect (intnum + 8, serial_int);/* Save old interrupt vector *//* Set new interrupt vector */v = inportb (0x21);
v &= ~(1 << intnum);
outportb (0x21, v);/* Enable interrupt */outportb (portbase + 1, 0x01);
outportb (portbase + 4, 0x0B);/* Enable receive interrupt *//* Enable Interrupt, DTR, RTS *//* 9600 Baud *//* 8 Databits, No Parity, 1 Stopbit */serial_write (CLEAR);}/*--------------------------------------------------------------------*//* serial_close : turn off serial receive interrupt*//*--------------------------------------------------------------------*/
void serial_close ( ){unsigned v;
outportb (portbase + 1, 0);
outportb (portbase + 4, 0);v = inportb (0x21);
v |= 1 << intnum;
outportb (0x21, v);
setvect (intnum + 8, old_vector);}/*--------------------------------------------------------------------*//* serial_write : write a single character to serial port*//*--------------------------------------------------------------------*/
void serial_write (char ch){
while (!transmit_enabled);
while ((inportb (portbase + 5) & 0x20) == 0);
outportb (portbase, ch);}/*--------------------------------------------------------------------*//* write_7000_serial : write a string to the correct 7252*//*--------------------------------------------------------------------*/
void write_7000_serial (char *s){
if (address == -1)
serial_write (CLEAR);/* Disable Addressing */REMOTE OPERATION

5-20

else
{ serial_write (DLE);
serial_write (address + 0x20);}
while (*s)
serial_write (*s++);/* Enable Addressing *//* Address *//* Write string */}/*--------------------------------------------------------------------*//* request_7000_serial : write a commmand and read the response*//*--------------------------------------------------------------------*/
int request_7000_serial (char *s){
int i;
char ch;clock_t start, current;
write_7000_serial (s);/* Write Command */i = 0;
while (i < QUEUE_SIZE - 1)
{ start = clock ( );while (inq_in == inq_out)/* Wait for a character */{ current = clock ( );if (current < start)
current += CLK_TCK * 86400;
if (current - start > TIMEOUT)/* Check for timeout */{ buffer[i] = 0;
return FALSE;}}
ch = inqueue[inq_out++];/* Put character in buffer */if (inq_out == QUEUE_SIZE)
inq_out = 0;
if (ch == 0x0A)/* Line Feed? - End of response */{ buffer[i] = 0;
return TRUE;}
else
buffer[i++] = ch;}buffer[QUEUE_SIZE - 1] = 0;/* Buffer full */return FALSE;}/*--------------------------------------------------------------------*/

5.6.4

SAMPLE PROGRAM 4 - QBASIC EXAMPLE FOR 7252

REM $INCLUDE: 'C:\GPIB-PC\QBDECL.BAS'DIM READING AS STRING*30
CALL IBDEV(0,4,0,12,1,&H40A,R7010%)
CALL IBCLR(R7010%)
CALL IBWRT(R7010%,"MEAS?" + chr$(&H0A))
CALL IBRD(R7010%,READING$)
PRINT READING$CALL IBONL(R7010%,0)END

Note: EOM & EOS are linefeed

5-21

REMOTE OPERATIONTHIS PAGE INTENTIONALLY LEFT BLANKREMOTE OPERATION

5-22

SECTION 6.0
MAINTENANCE
6.1 INTRODUCTION
Very little maintenance is required for the DPC. This section of the manual discusses
suggested maintenance procedures.
6.2 OBSERVING THE SOFTWARE VERSION NUMBER
Follow the steps below to observe the DPC’s software version number.
1. If necessary, press [PREVIOUS] several times to return the display to the Main
Menu.
2. Select MENU | SETUP | SYSTEM. The software version number will appear on
the screen.
3. Press [PREVIOUS] to return to the previous screen.
6.3 PREVENTIVE MAINTENANCE
Although the DPC is designed to be nearly maintenance free, occasional preventive
maintenance is required to keep the DPC’s performance optimal.
6.3.1 INITIATING THE DPC’S SELF TESTTo test the DPC’s hardware and software follow the steps below.
1. If necessary, press [PREVIOUS] several times to return the display to the Main
Menu then press the MODE key to select the channel main menu.
2. Select MENU | TEST | SELF

MENU | TEST | SELF - MENU
3.

Press ELECTRICAL [F1]. The electronics self test will run and display the results.

The electronics test runs eight sets of tests on various parts of the electronic modules.
Table 6-1 describes these tests and the possible actions needed if a test fails. The
pneumatics test runs nine tests on the pneumatics module. Table 6-2 describes these tests
and the possible actions needed if a test fails.
6-1

MAINTENANCETABLE 6-1
ELECTRONICS SELF TEST
Test

Description

Processor
Clock
Timer
EEPROM
Oven

Tests the processor chip
Tests the real time clock
Tests the 10 ms interval timer
Tests the nonvolatile memory
Tests operation of the sensor oven

Action on failure
Replace processor board.
Replace processor board.
Replace processor board.
Replace processor board.
Replace sensor assy.
Allow oven to warm up.

RIC Part #7215-586-3
7215-586-3
7215-586-3
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Contact Ruska

6.3.2 REMOVING THE DPC’S COVER
The DPC should be kept clean and completely assembled at all times. Operating the
DPC without its cover affects the DPC’s thermal gradients and therefore may reduce
precision. If it becomes necessary to remove the DPC’s cover, follow the instructions
below.
CAUTION: The DPC should only be opened by qualified electrical/mechanical service
technicians. Lethal voltages are present and exposed in the power supply anddisplay.
1. Turn off the DPC and disconnect the power cord from the DPC.
2. Locate and unscrew the four screws that secure the cover to the back panel.
3. Place your hands near the middle of the cover and slide the cover towards the
DPC’s back panel.
4. Lift up on the cover. With the cover removed, use typical electronic cleaning tools
to remove any accumulated dust from inside the instrument.
5. Replace the cover before resuming operation.
6.3.3 MOISTURE FILTER
The Bourdon tube sensor is hydroscopic. An external desiccant filter prevents introductionof moisture and is strongly recommended for high humidity areas. The filter should be
replaced annually. The moisture filter is used with the reference port only (absolute only
instruments do not need a moisture filter).
6.3.4 PARTICLE FILTERS
Refer to Appendix A for air supply quality requirements. During normal operation, theDPC transfers gas both into and out of the device under test (DUT). When necessary, theuser is expected to use and maintain an in-line disposable particle filter to protect the
DPC’s pneumatics from any contamination that may exist in the DUT.
6.3.5 VACUUM PUMPS
Periodic checks of the user’s vacuum pumps for oil levels. It is very highly recommended
that a power-down vacuum venting valve is installed onto the vacuum pumps to ensure
minimal chances of oil contamination from the vacuum sources. These are normallyopen solenoid valves that are powered through the vacuum pump power switch. When
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the vacuum pump is turned on, the solenoid valve is energized and closes allowing thepump to operate normally. When the pump is turned off, power is removed from thesolenoid and the vacuum is vented to atmosphere. Periodic changing of vacuum pump
oil as recommended by the vacuum pump manufacturer should also be done.
6.3.6 PROCESSOR BATTERY
The processor board uses a lithium battery to maintain time and date information. Thisbattery has a varying life. If the instrument is left on 24 hours a day, it may last 5 to 10
years. If the instrument is stored, it may only last one year. Annual replacement isrecommended. To replace the battery:
1. Turn off power and remove the instrument cover. (See Section 6.3.2.)
2. Remove the processor card by removing the screw and the bracket that locks thedisplay cable in place and gently rock the card upward.
3. Holding the processor card, remove the battery (the round silver object), by
carefully pulling on the battery.
4. Plug in a new battery (RIC # 4-725).
5. Reinstall the processor card, the bracket that locks the display cable in place andthe screw. Replace the instrument cover.
6. The time and date may have to be re-entered. See Section 4.6.1.5.
6.4 CALIBRATION
To keep the DPC operating within its specified precision, the calibration proceduredescribed below should be performed once every year. If a higher level of overall
performance is desired, the user can calibrate more frequently.
NOTE: The calibration procedure automatically generates coefficients that are stored
in memory on the DPC’s. If these constants are “lost” for any reason, thecalibration procedure must be performed, regardless of the last calibration date.
If the calibration coefficients have been recorded, they may be restored to the DPC
at any time by “editing the coefficients” (Section 6.4.3).
6.4.1 CALIBRATION INSTRUCTIONS
To calibrate the DPC, the user connects a calibration standard such as the Ruska
Instrument Model 2465 (or 2470 for high pressure ranges) Gas Piston Gauge to the
DPC’s test port, then follows the multi-step calibration procedure on the DPC’s display.
The standard DPC requires a positive pressure calibration. A vacuum (negative gauge)
option is available and requires special calibration per Section 6.4.2. No disassembly isrequired and there are no potentiometers to tune.
NOTE: The uncertainty of the final calibration must include the uncertainty of thepressure standard being used.
6.4.1.1

Preparation

1. Verify that the DPC’s Reference Port is open to atmosphere for gauge calibrations
and that the calibration standard is connected to the Test Port.
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2. For DPC’s with pressure ranges greater than 100 psi (690 kPa) verify that the
supply pressure port is plugged, or a supply pressure is connected to the supply
port and adjusted to 110% of the full scale of the DPC.
3. Verify that the DPC has been at stable environmental temperature and that eachsensor’s oven temperature (MENU | DISPLAY | TEMPERATURE) are stable to 50
degree Celsius. The typical warm up time is 3 hours.
4. Verify that the DPC is in Measure mode (Section 4.0).
5. If desired, change the DPC’s units of measure (Section 4.0) to match those of thecalibration standard.
6. Set the gas head to 0. Select MENU | SETUP | USER.
7. To access the calibration screen, select MENU | CALIBRATE | CALIBRATE.

8. When you first enter the Calibrate menu, the top left hand side of the display will
indicate which sensor is being the viewed. The sensors coefficients are then shown
below the sensor label. On the 7250sys, there are multiple dual range primarypressure sensors. The first sensor that is shown is the primary measuring sensor A.
This is indicated by the word A Primary displayed in the top of the display. To
cycle through the various sensors that exist in the system, you would press the
Sensor [F6] function key. Assure that you are in the screen that is labeled A
Primary (or the desired range) depending on which channel is being calibrated.
9. To begin the calibration process, press the Calibrate [F2] button. If thecalibration access code is enabled, enter it at the prompt. The first calibration
screen will appear.
NOTE: To exit the calibration procedure before the calibration coefficients have beenchanged, press [CANCEL] any time during the procedure. Canceling restores all
previous calibration values.
Step 1
1.1 The first step automatically performs the sensor zeroing routing.

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1.2 Wait until the zero procedure finishes. This may take several minutes. When
the DPC completes step 1, the calibration screen will appear.
Step 2
2.1
To begin step 2, use the calibration standard to apply the various pressuresthat will be requested by the 7250sys. There will be 5 primary calibration
points per dual range sensor. The number of pressure points required tocalibrate the DPC will increase if the range is set up with the a vacuum(negative gauge) option. The screen will display a table noting thefollowing information;
Step – The pressure step in the calibration sequence
Apply – The pressure that the standard is to generate to the DPC.
Tolerance – The tolerance about the apply value that can be generated by
the standard and still accepted by the DPC.
Actual – The actual pressure value that was generated by the standard when
the point was accepted.
Adj. %FS – Depicts the amount that the DPC corrected its output to align tothe standard. This is used as a trouble-shooting tool. If one point has asignificantly higher adjustment required than other points in the calibration,
this may indicate that there was an error in that specific calibration point.
The operator can re-check this pressure point prior to completing andaccepting the full calibration.
2.2 The Step 1, actual value will be highlight. This is your first pressure point in
the calibration procedure.
NOTE: If the DPC has the Vacuum (Negative Gauge Option) or the Barometricreference, the first two points in the procedure will show the negative pressuresthat should be generated to calibrate the sensor in the negative gauge direction.
You are not required to perform both the negative and the positive gauge
calibrations every time the unit is calibrated. If you want to calibrate only the
positive pressures, using the rotary knob move the highlighted curser down to thefirst positive pressure step and generate all of the positive pressures in theprocedure. When you are complete with the positive points, hit the Done key, theunit will maintain the older coefficients for the negative gauge portion of thesensor and calculate new coefficients for the positive gauge ranges. Conversely,
you can calibrate just the negative gauge section if desired. However, you mustcomplete all of the positive or negative gauge steps in the procedure to complete
a valid calibration.
2.3 Using your calibration standard, generate the pressure shown in the Applycolumn. When the measured pressure stabilizes, use the DPC’s numeric
keypad to enter the actual pressure applied by the calibration standard andthen press ENTER. Do not enter the measured pressure reported by the
DPC. If necessary, use the [CLEAR] key to correct a mistake in the edit field.
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If the actual pressure applied is within the indicated tolerance, the unit will
accept that point and the highlighted curser will automatically scroll down to
the next calibration step.
NOTE: If the actual pressure is outside of the tolerance for the requested mid-point
pressure, Error —222 Data out of range will occur. Acknowledge this error by
selecting OK [F6], then re-enter the actual pressure, repeating step 2.1 ifnecessary.
Step 3
3.1 Generate the next pressure calibration point requested by the DPC. Apply
this pressure using calibration standard and follow the instructions in Step
2.3, entering the actual pressure applied.
3.2 Repeat this procedure until all of the calibration steps are complete. Review
the Adj. %FS field to see if one point has a significantly higher adjustment
required than other points in the calibration. This may indicate that there
was an error in that specific calibration point. The operator can re-check thispressure point prior to completing and accepting the full calibration. To reenter a point, use the rotary knob and move the highlighted curser to theactual pressure values in the step in question. Generate the requested applypressure using the standard and enter then new actual value when stabilized.
6.4.1.2 Storing the Coefficients
Step 4
4.1 Calibration is complete. To exit the calibration procedure without storing thecalibration coefficients in memory, press [CANCEL]. To store the calibration
coefficients in memory, select the Done [F1] key and the DPC will calculate
all of its new coefficients.
NOTE: In additional to saving the calibration coefficients to the DPC's memory, theuser is advised to separately record the calibration coefficients and store this"backup" in a safe place.
Step 5
5.1 Press [PREVIOUS] to return to the Main Menu.
5.2 Once the calibration procedure is complete, the user should verify several
pressure readings against the pressure standard. If there are variances
beyond the stated precision, then an error was probably made in generating
one of the calibration pressures, and the calibration procedure should be
repeated.
Since the system is a multi sensor system, it is important to assure that you
are reading from the proper system when performing the verification. One
method to achieve this is;
1. From the main screen, VENT the system pressure.
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2. Press the MODE key,
3. Press the SENSOR key to toggle between all of the ranges in the system.
It will start at range A and then switch to B, C and so on. Please note that
all of the sensors in the system are dual scale sensors. With the systempressure vented, the lower scale of the dual sensor range will be selected.
As pressure is then applied to this sensor, the sensor will automaticallyswitch from the low to the high scale of the sensor when the pressure
exceeds the low scale pressure range. The selected range will be
displayed to the left hand side of the screen in the current unit of measure
followed by its range letter designator. For example, if range A is a
2500/1250 psi scale sensor and you are operating in units of psi, therange would be displayed as 1250.0 A. Pressing the SENSOR key again,
it would then display 300.0 B (if Range B in the system is a 600/300 psi
scale sensor). Assure that the sensor range that you want to verify isselected.
4. Generate pressures to verify the calibration of the dual scale sensor.
6.4.2
VACUUM (NEGATIVE GAUGE) CALIBRATIONS
Vacuum mode is an available option. The following configuration should be used whencalibrating in the Vacuum mode.

FIGURE 6-4
VACUUM (Negative Gauge) CALIBRATION

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To calibrate in Vacuum mode with the configuration shown in Figure 6-4, the following
actions should be taken. The system pressure and vacuum inlet valve should remainclosed. The bottom side of the piston must be open (vented) to atmosphere andconnected to the reference port of the DUT. The test port of the DUT must be connectedto the bell jar with a cutoff valve to isolate it from the DUT. Additionally, there must be acutoff valve located between the Vacuum pump and the bell jar.
Close the Cut-off valve to isolate the DUT test port from the bell jar. Open the Vacuum
Pump Valve to pull a hard vacuum on the bell jar to seal the bell jar and to float themasses. Once the masses have risen in response to evacuation of the bell jar, close thereference vacuum pump cutoff valve. Use the metering valve on the bell jar to adjust(vent) the bell jar vacuum towards atmosphere until the masses begin to float. Close themetering valve as soon as the masses begin to float. Open the bell jar cutoff valve to thetest port of the DUT, close the exhaust (Vent) valve, and use the pressure adjuster
handwheel to adjust float position of the deadweight gauge to float the piston at midfloat position.
6.4.3 RPT CALIBRATION - SIMULATED ABSOLUTE
A span correction can be applied to the RPT (barometric) sensor. This correction is doneusing the DPC software and can be performed without removing the RPT from the DPC
chassis.
1. Place the DPC in Measure mode. Remove all pressure sources from the system.
2. Connect a pressure standard to the Reference Port of the DPC. Note, on the
7250sys, there are two reference ports. Typically the RPT is connected to the top
reference port. However, this can vary based on the configuration of the 7250sys.
If the barometric sensor does not react when changing the pressure in the top
reference port, try the lower reference port.
3. If desired, change the DPC’s units of measure (see Section 4) to match those of thecalibration standard.
4. To access the Calibration screen, from the Main Menu, select MENU |CALIBRATE | CALIBRATE.
5. Select the atmospheric sensor by pressing the Sensor [F6] key until the words
Atmospheric Sensor is displayed above the calibration coefficients.
6. To begin the calibration process, press CALIBRATE. If the calibration access codeis enabled, enter it at the prompt. The first Calibration screen will appear.
7. You will use the calibration standard to apply the various pressures that will be
requested by the 7250sys. The screen will display a table noting the following
information;a. Step –the pressure step in the calibration sequence.
b. Apply – The pressure that the standard is to generate to the DPC.
c. Actual – The actual pressure value that was generated by the standard when
the point was accepted.
8. The Actual value will be highlighted. This is your first pressure point in thecalibration procedure. This calibration requires the generation of two pressures
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within the range of 700 to 1100 mbar absolute. The selected pressures should bespaced as far apart as possible within the allowable range.
9. Generate the first pressure. Enter the actual value of the applied pressure
generated by the standard and press [ENTER].
10. Generate the second pressure. Enter the actual value of the applied pressure
generated by the standard and press [ENTER].
11. The RPT sensor is now linearly compensated. Once the calibration procedure iscomplete, the user should verify several pressure readings against the pressure
standard. If there are variances beyond the stated precision, then an error wasprobably made in generating one of the calibration pressures, and the calibration
procedure should be repeated.
12. Remove the pressure source from the Reference Port.
6.4.4 VACUUM SENSOR CALIBRATION – OPTIONAL CASE REFERENCE SENSOR
A span correction can be applied to the vacuum sensor. This correction is done using the
DPC software and can be performed without removing the vacuum sensor from the DPC
chassis.
1. Place the DPC in Measure mode. Remove all pressure sources from the system.
2. The Vacuum sensors are located inside the black sensor oven assembly.
Connect a pressure standard physically as close to the vacuum sensor as
possible. You may wish to remove the top cover of the instrument and connect
directly to the pressure ports going into the quartz sensor oven assembly. Note,on the 7250sys each sensor will have its own independent vacuum sensor.
3. If desired, change the DPC’s units of measure (see Section 4) to match those of
the calibration standard.
4. To access the Calibration screen, from the Main Menu, select MENU |CALIBRATE | CALIBRATE.
5. Select the atmospheric sensor by pressing the Sensor [F6] key until the words
Vacuum Sensor A (or B, etc) is displayed above the calibration coefficients.
6. To begin the calibration process, press CALIBRATE. If the calibration accesscode is enabled, enter it at the prompt. The first Calibration screen will appear.
7. You will use the calibration standard to apply the two vacuum points on thevacuum sensor.
8. The Actual value will be highlighted. This is your first pressure point in thecalibration procedure. This calibration requires the generation of two pressures
within the range of 50 to 350 mtorr absolute. The selected pressures should bespaced as far apart as possible within the allowable range.
9. Generate the first pressure. Enter the actual value of the applied pressure
generated by the standard and press [ENTER].
10. Generate the second pressure. Enter the actual value of the applied pressure
generated by the standard and press [ENTER].

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11. The Vacuum sensor is now linearly compensated. Once the calibration
procedure is complete, the user should verify several pressure readings against
the pressure standard. If there are variances beyond the stated precision, thenan error was probably made in generating one of the calibration pressures, andthe calibration procedure should be repeated.
12. If the instrument is fitted with two vacuum sensor, calibrate the second vacuum
sensor.
13. Remove the vacuum standard from the instrument.
14. Reinstall the cover onto the 7250sys.
6.4.5 EDITING THE CALIBRATION COEFFICIENTS
If the DPC’s memory is erased but the calibration coefficients are known, the user can
restore the coefficients to the DPC by following the directions below.
CAUTION: Never randomly adjust the calibration coefficients.
Only qualified
personnel with valid backup data should be allowed to edit the coefficients. If the
backup coefficients are questionable, perform the calibration procedure in its
entirety.
1. Verify that the DPC is in Measure mode (Section 4.0).
2. Enter the Calibration screen by selecting MENU | CALIBRATE.
3. When you first enter the Calibration menu, the top line of the display will indicate
which sensor is being the viewed. The sensors coefficients are then shown below
the sensor label. The first sensor that is shown is the primary measuring sensor.
This is indicated by the word Primary displayed in the top of the display. To cycle
through the various sensors that exist in the system, you would press the Sensor[F6] function key. The two common sensors that would be calibrated would be
the Ruska sensor which would be labeled as Primary and if the unit has theoptional Barometric Reference sensor, this would be labeled as AtmosphericSensor.
4. To edit the calibration coefficients, press the EDIT button. If the calibration accesscode is enabled, enter it at the prompt. The first calibration screen will appear.
NOTE: To exit the calibration procedure before the calibration coefficients have beenchanged, press [CANCEL] any time during the procedure. Canceling restores all
previous calibration values.
5. Use the rotary knob to highlight the coefficient to be edited. The terms arecoefficients of a linear regression analysis.
6. Use the numeric keypad and the [ENTER] key to enter a new value. To correct a
mistake in the edit field, use the [CLEAR] key.
7. Repeat steps 4 and 5 until all coefficients are correct.

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NOTE: In addition to saving the calibration coefficients to the DPC’s memory,
separately record the calibration coefficients and store this “backup” in a safe
place.
8. To exit the editing procedure without storing the calibration coefficients in memory,press [CANCEL]. To store the calibration coefficients in memory, select DONE
[F6].
9. Press [PREVIOUS] to return to the Main Menu.
Once the calibration coefficients are input, the user should record several pressure
readings. If there are any variances beyond the stated precision at these points, then thecalibration procedure should be performed.
6.4.6 ZEROING
The zeroing procedure is performed to correct for system zero shift and does not requirea full calibration. The most important requirement for performing a valid zeroingprocedure is to guarantee that there is not a pressure differential between the sensor’s
test port and case reference.
If during the zeroing procedure, the message “Mechanical Zeroing Needed” appears,
the sensor photocell may need to be zeroed. See Section 6.5 for more information.
The zeroing screen presents several pieces of information.
The screen will display the current status of the pressure sensor Stability and Temperature.
If any of the above are unstable, then the system will delay until stability is achieved.
Pressing OK [F6] will bypass this wait period.
NOTE: Bypassing this wait period can have a negative effect on the zeroingprocedure.
6.4.6.1 Gauge and Vacuum (Negative Gauge) Instruments
1. Verify that the Reference Port is open to atmosphere.
2. Enter the Calibration screen by selecting MENU | CALIBRATION.
3. Select Zero [F1]. Do NOT press the Calibrate button.

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4. Do not disturb the instrument while zeroing is in process.
5. Wait for the zeroing procedure to finish.

6. Press [PREVIOUS] to return to the Main Menu.
6.4.6.2 Absolute Mode with Evacuated Reference
A vacuum pump must be connected to the reference port.
A vacuum gauge should be installed for measuring the case reference pressure. Thisgauge should be installed internal to the Ruska quartz sensor oven assembly.
1. Select the desired pressure units using the UNITS key. You can change both theunit of measure that the DPC is displaying Pressure and the unit of measure for thevacuum sensor. It is not required to have the DPC displaying pressure in the same
unit of measure as the vacuum sensor. To change the unit of measure for the
Vacuum sensor, press the UNIT key and then the Vacuum [F2] key.
2. Enter the Calibration screen by selecting MENU | CALIBRATE.
3. Select which sensor range is to be zeroed.
4. Select Zero [F1]. Do NOT press the Calibrate button. When initiating the zeroingcommand in the DPC, it will cycle the internal valves allowing the external vacuum
pump to pull a hard vacuum on the Ruska sensor. It is recommend that the sensor
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be pulled down to a vacuum of less than 200 mTorr (preferably less than 100
mTorr) in order to obtain a proper zero. The DPC can be zeroed at higher
vacuum levels, however, the uncertainty of vacuum sensors tend to increase at
higher vacuum levels, therefore, the uncertainty in the DPC would also increase if
zeroed at higher vacuum levels.
5. Wait for the vacuum level on the test port to stabilize.
6. The vacuum level as read by the vacuum gauge will be displayed, once stable andat an acceptable level, press OK [F6].
7. Do not disturb the instrument while zeroing is in process.
8. Wait for the zeroing procedure to finish.
9. Press [PREVIOUS] to return to the Main Menu.
6.4.6.3 RPT - Simulated Absolute Instruments
Simulated absolute DPC’s contain two sensors that require periodic zeroing. The primarysensor is zeroed according to the instructions in Section 6.4.5.1 or 6.4.5.2. The
barometric sensor is zeroed according to the following instructions.
1. Verify that the Reference Port is open to atmosphere.
2. Enter the Calibration screen by selecting MENU | CALIBRATE.
3. Select the Atmospheric Sensor by pressing the Sensor [F6] key until the words
Atmospheric Sensor is displayed above the calibration coefficients.
4. To begin the zeroing process, press ZERO. If the calibration access code isenabled, enter it at the prompt. The zeroing screen will appear.
NOTE: The next step requires the use of a properly calibrated standard. This zeroingprocess does contribute directly to the overall accuracy of the system, since thepressure applied to the sensor is a non-zero differential pressure.
5. Enter the current barometric pressure. Press [ENTER].
6.4.6.4 ZERO ALL
All of the primary dual range sensor can be zeroed in the system at one time.
1. Verify that the Reference Port is open to atmosphere.
2. Enter the Calibration screen by selecting MENU | CALIBRATION.
3. Select Zero All [F3]. Do NOT press the Calibrate button.
4. Do not disturb the instrument while zeroing is in process.
5. Wait for the zeroing procedure to finish.
6. Press [PREVIOUS] to return to the Main Menu.
6.5 SENSOR PHOTOCELL ZEROING
If the error message “Mechanical Zeroing Needed” is displayed, the sensor photocell
must be zeroed. The following steps describe this process. Press the MODE key to selectthe desired channel.
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CAUTION: The DPC should only be opened by qualified electrical/mechanical service
technicians. Lethal voltages are present and exposed in the power supply anddisplay.
1. Identify which dual range sensor requires mechanical zeroing.
2. Remove the DPC’s top cover.
3. Locate and remove the plastic zeroing plug located in the side of the sensor ovenassembly.
4. Enter the Zeroing screen by selecting MENU | CALIBRATE.
5. Select the Primary sensor by pressing the Sensor [F6] key until the words Primaryis displayed above the calibration coefficients.
6. Select Zero [F1]. Do NOT press the Calibrate button.
7. Select the Mechanical Zero [F1] key.

8. Referring to Figure 6-5, slightly loosen the Allen screw on the back of the sensor
bracket, making sure to maintain a snug fit on the screw. Using the T-shaped
Photocell Centering Tool (RIC # 7250sys-111), adjust the photocells by placing
the tool in the hole in the back of the sensor and turning the tool slightly. The
screen will show a number of horizontal lines. The top yellow bar represents thecurrent zero setting. The bottom portion of the bar has a green bar in the centerand two red bars on either end. If the top yellow bar is over the red bar, thenmechanical zeroing is required. If the yellow bar is over the green bar, then no
adjustment is required.

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9. Adjusting the photocell will cause the yellow bar to reduce in width. You want toadjust the photocell until the yellow line is as thin as possible over the green bar.

10. Tighten the Allen screw.
11. Often, when the Allen screw is tightened, the zero will move. Review the width of
the yellow line, again loosen the Allen screw, and now offset the yellow bar thesame width that you observed it moving from tightening the Allen screw, and now
offset it in the opposite direction by this same width.
12. Again, tighten the Allen screw. Now the width of the yellow line should be
minimized.
13. Tap on the bracket with a screwdriver handle to relieve mechanical stress.
Continue to tap on the bracket until the counts stop changing.
14. If the zero moved significantly as a result from tapping the bracket, repeat thisprocedure as necessary.
15. Reinstall plastic zeroing plug.

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16. After the unit has become thermally stabilized, perform a normal instrument
zeroing procedure. Refer to Section 6.4.5.

FIGURE 6-5
PHOTOCELL LOCATION
6.6 OPTIMIZING CONTROLThe performance of the controller may be optimized for certain environments or
performance criteria by adjusting the values available in the Control screen. The Control
screen is available from the Main Menu by pressing Menu [F6], Test [F5], Control [F6].
The 7250sys has multiple control channels integrated into the system. It is important to
identify the range of the channel that requires auto-tuning and it would be recommended
to only tune the channel that requires tuning. When in the Auto-tune screen, pressing the
MODE key on the front panel toggles between the various controllers in the system. The
ranges are identified by the full scale pressure range of the controller. The Control screen
is shown below.

MENU | TEST | CONTROL – MENU
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NOTE: Be sure the Control Band parameter is set to zero (Section 4.6.1.1.3).
If the controller does not control optimally, it would be recommended to first assure thatthe system is free of leaks and is operating within the external volume specifications (seeAppendix A). You should verify that the instrument is fitted with the proper sized pressurelines to minimize flow restrictions (see Section 3.5). Verify that the control band is set as
intended (see Section 4.6.1.1.3). For active control, when testing the controller theControl Band Off and Control Band On values should be set to zero. Finally verify thatthe control is set to Normal to minimum overshoot (see Section 4.6.1.1.4). If the system
continues to control improperly, you can perform the Auto-tune.
There are two options available to the operator.
Full – This fully characterizes the control function of the 7250sys. It automaticallyadjust the control valve biases and aligns the inner loop high control pressure sensor
to the high accuracy quartz sensor. This should be performed any time major
components are replaced in the controller such as the control valves or the highspeed inner loop control sensor. Additionally, if the controller is not functioning
properly, a full Auto-tune can be performed to optimize the control.
Calibrate – This automatically aligns the inner loop high control pressure sensor tothe high accuracy quartz sensor. If in the Normal control mode (as opposed to thefast control mode), the controller overshoots the commanded pressure valve, this
could be an indication that the inner loop control sensor needs to be realigned withthe high accuracy quarts sensor. This is achieved by running the Calibrate Auto-Tunefunction.
NOTE: Prior to performing any Auto-Tune functions in an effort to improve thecontroller performance, confirm that the system is a leak free system and thevolume attached to the test port is within the recommended range (see Appendix
A). Additionally, assure that the system has adequate pressure and vacuum
supply (when required).
To perform these Auto-Tune functions, the instrument must be connected to a pressure
supply with the pressure supply set to the proper supply pressure (please refer to thespecifications in Appendix A). On absolute instruments, a vacuum pump must beconnected to the exhaust port.
Disconnect any device under test from the test port. The test port must be connected to asealed volume of 5 to 15 cubic inches (80 to 240 cc’s).
Use the Rotary knob to select which Auto-Tune procedure is to be performed and thenpress the enter key. The Full performs the complete Auto-Tune sequence. If selected, you
are not required to run any of the other Auto-Tune functions. Press the enter key.
The DPC with go through a sequence of controlling to various pressures andautomatically adjusting the control parameters of the valves. The DPC will display a
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message indicating when it is complete with the Auto-Tune procedure. The time required
to complete the Auto-tune procedure can range anywhere from 15 to 45 minutes.

If any control valves or the high speed inner loop pressure sensor has been replaced, theAuto-Tune should be run to characterize the new hardware.
6.7 FAN OPERATION
The fan in the 7250sys can be turned on or off. It is recommended to keep the fan ON
since this will extend the life of the power supply.
When operating the system in either a very cold or hot environment, if the oven is unable
to maintain the temperature of the internal oven, it will generate error Oven Control
Failure Error messages. The operator can review the temperature and duty cycle of theoven by pressing the MENU | DISPLAY | TEMPERATURE keys. The unit must havebeen warmed up for a minimum of 2 hours prior to determining the condition of theoven temperature control. The temperature of the sensor should be controlled to 50o C.
The Duty cycle indicates the percentage of time that the oven control is turned on in orderto maintain the oven at the proper set-point of 50o C. A unit that is operating properly,
after it has fully warmed up, should indicate a sensor temperature of 50o C and a duty
cycle between 10 to 90%.
If operating the instrument in a very cold environment and the oven duty cycle is at a highpercentage (>90%) you will need to turn the fan off. If you are operating in a warm
environment or when multiple systems are housed in consoles without adequate
ventilation, the system may become too hot and generate the oven control failure error
message. If operating the instrument in a warm environment and the oven duty cycle is
at a low percentage (>10%) you will need to turn the fan on.
When the operator changes the status of the fan, it will default to that condition until it ischanged by the operator.

MAINTENANCE

6-18

MENU | TEST| SHOP 1 – MENU
To turn the fan on or off, press Menu [F6] from the Main Menu, then Test [F5], thenShop1 [F5].
Use the rotary knob to highlight either fan Off or On. Press [ENTER] to select.
6.8

SYSTEM SOFTWARE UPDATE PROCEDURE

NOTE: Calibration and other stored constants are not affected by program updates.
The update procedure requires a PC connected to the RS-232 port on the 7XXX. (9-pin to
9-pin, null modem cable minimum pinout 2-3, 3-2, 5-5).
1. When appropriate, Ruska can e-mail the latest version of the software for
upgrading instruments. The e-mail will have a zip file attached contains two files
UPDATE7.EXE and <version>.IMG. Unzip these files into a directory on the PC.
2. Set the 7XXX to 9600 baud, 8 databits, no parity, 1 stopbit.
3. Run the program Update7.
4. Follow the prompts to select the communications port and the image file.
5. When the upgrade is finished, Update7 running on the PC and the 7XXX shouldboth display Complete.
6.8.1 Model 7250sys Controller Software Upgrade
In addition to the main code, the 7250sys include code for the pressure controller. The
controller software version can be viewed by pressing the MENU | TEST | REMOTE |SERIAL2 keys. The controller software version is displayed next to ‘Ctrl’. This code canbe upgraded through the RS-232 port on most units. Press the MENU | TEST |CONTROL key and check for ‘Download Yes’.
If ‘Download
No’ is displayed the chip must be replaced to upgrade software. If‘Download’ is not displayed upgrade the main software to 7250sys-1R17 or higher first.
(The digit in front of the R increases with revision levels and the last two digits will
increment upwards as the revision level increases, e.g. 0R99 is older code than 1R01
which is older than 1R08, etc.)
6-19

MAINTENANCE

1. Connect a PC to the RS-232 port on the 7XXX using a null modem cable.
2. The zip file labeled 7250sys Control|XRXX contains files UPDATE7.EXE and<version>.IMG. Unzip these files into a directory.
3. Set the 7XXX to 9600 baud, 8 databits, no parity, 1 stopbit.
4. Run the program Update7.
5. Follow the prompts to select the communications port and the image file.
6. Update7 should display Complete.
Note, when updating the controller code, the 7250sys will display various error
messages. This is expected. The front display will freeze on the 7250sys when thecontroller code is being downloaded. It will operate properly once the download iscomplete. Finally, the main software only reads the software versions on power-up. So,
following the controller code upgrade, pressing the MENU | TEST | REMOTE |SERIAL2 keys will only show the new revision level of the controller code after power iscycled on the 7250sys.
6.9 REPLACEMENT PARTS
The following is a list of the common replacement parts used in the Model 7250sys DPC.
Valve
Identification

Supply Pressure
Vent
Test Port
Reference Port

MAINTENANCE

Low Pressure Manifold
Maximum Full Scale
Pressure Range < 1000 psi(6895 kPa)
Valve Body
88-1074
88-1074
88-1076
88-1076

Valve Coil
88-1081
88-1081
88-1078
88-1078

6-20

High Pressure Manifold
Maximum Full Scale
Pressure Range 1000 – 2500
psi
(6.9 – 20.7 MPa)
Valve Body
Valve Coil
88-1054
88-1055
88-1054
88-1055
7250sys-109
88-1055

Part Number
7250sys-109
88-1055
11-763
11-7647000-70
7000-717250sys-111
62-29323-9067250sys-100-005
7215-PCA-KEY

Description
7250sysxi isolation manifold valve body7250sysxi isolation manifold valve coil
TFT Display
Display Inverter Electronic Board
Sensor LED Lamp Assembly
Sensor Photocell
Photocell Adjustment Tool
Power Supply
Fan
Rotary Encoder
Front Panel Keyboard Electronic Card

6.10 PRESSURE INTENSIFIER - OPTION
Some systems have an integrated pressure intensifier option installed. These systems
require a nominal shop “Air” supply of 100 psi. A clean dry nitrogen pressure supply isconnected to the high pressure “Gas” supply port on the rear panel of the system. This
supply fills the accumulator in the system and then supplies the various regulators in the
cart system which ultimately supply each individual control channel in the system. The
system can operate directly from the high pressure supply. Additionally, as long as aminimum supply pressure of 500 psi is available, the intensifier can boost theaccumulator pressure which supplies the system. Turning the “Driver Air” valve clockwise
to the on position, turns the intensifier on. The regulator directly below the Drive Air valve
is used to adjust the maximum pressure that the intensifier boost the pressure to theaccumulator. All of the regulators in the system are preset at the factory.

6-21

MAINTENANCE

THIS PAGE INTENTIONALLY LEFT BLANK

MAINTENANCE

6-22

SECTION 7.0
PREPARATION FOR STORAGE & SHIPMENT
NOTE: The procedures given in sections 7.1 through 7.3 must be strictly adhered to inorder to prevent damage to the instrument. Failure to follow these procedures will
likely result in damage to the DPC during shipment. This damage is not coveredby the carrier’s insurance.
7.1

DISCONNECTING THE DPC

1. Relieve all pneumatic pressure from the DPC.
2. Turn the DPC power switch to the off position.
3. Disconnect the power cable from the DPC power receptacle.
4. Disconnect all pneumatic lines from the DPC’s back panel.
5. Plug all ports.
7.2 PACKING INSTRUCTIONS
To prevent shipping and handling damage to the instrument, adhere to and strictly follow
the instructions below.
If shipping a cart system, within USA, it is recommended to ship either via air freight orelectronic van ride.
If the primary measurement and control components are removed from the system andreturned to Ruska, the governing discipline in ensuring a damage-free shipment is toensure that the possibility of handling shocks to the DPC is minimized and/or prevented
during transit. Ruska accomplishes this task by cradling the DPC within two foam cradles
that are encapsulated within a double-walled, corrugated box. The DPC is restrained
and supported, but still has resilience. The materials used in the packaging operation
are foams that have a minimum impact rating of not less than N-95.
If polyfoam or rubber foam other than that used in the original packaging is to be used,
cut it into strips so that it will not present a large rigid surface to the DPC.
Ruska has found that corrugated cardboard boxes provide the best packaging exterior.
The box must have an impact rating of 275 lb and be of double-walled construction.
This type of box will sustain most types of damages incurred during the shipping andhandling process, but ensures that the contents remain intact and damage-free. The
foam cradle ensures that a minimum of 3 inches of foam separates the inner surface ofthe box and any portion of the DPC. Wood or metal boxes do not absorb shock
when dropped and therefore are not recommended.
The DPC must be prepared for shipment in the following manner:
1. Ruska Instrument has an RMA procedure in place. Please contact the Customer
Service Center to obtain an RMA number prior to returning any equipment to
Ruska. Have the following information available when contacting Ruska:
a. the part number,
7-1

STORAGE & SHIPMENT

b. the serial number,c. the purchase order number,d. the billing and ship to address, ande. the buyer’s name and telephone number.
This information plus the RMA number must be attached to the unit when it isshipped to Ruska Instrument. There will be a minimal charge for inspection
and/or evaluation of returned goods.
2. Enclose the DPC in plastic or any good water barrier material. Antistatic material
is recommended.
3. For shipping the individual controller components, use a double-walled
corrugated carton with a 275-lb rating. The recommended carton size is 25 1/2 x
19 1/2 x 12 3/8 inches
4. Insert one foam cradle from the original shipment onto the floor of the box. (Theoriginal foam cradles are of the same type of construction and are completelyinterchangeable.) If the foam cradles are not available, cover the bottom andsides with no less than 3 inches of N–95 foam strips. Arrange the strips in theconfiguration illustrated in figure 7-1.
5. Before sealing the carton, include the following:a. Statement of the problem or service needed. Be specific. Include the nameand telephone number of a knowledgeable technician for consultation.
b. The part number, serial number, return address, and purchase order number.
6. Seal the carton using gummed tape.
7. Address the carton to:
RUSKA INSTRUMENT CORPORATION
10311 WESTPARK DRIVE
HOUSTON, TX 77042
USA
8. Label the carton with the following labels: THIS SIDE UP, HANDLE WITH CARE,
DO NOT DROP, and FRAGILE. (If the original Ruska shipping carton is utilized forthis shipment, the above markings are preprinted on the carton.)
7.3 SHIPPING INSTRUCTIONS
Ruska recommends using air freight for transportation. Surface transportation subjects
the shipment to more frequent handling and much more intense shock. In most cases, if
surface transportation is the mode of transport employed, handling damage is likely.
Again, it is essential that the procedures mentioned in sections 7.1 through 7.3 be strictly
adhered to in order to prevent any shipping and handling damage to the instrument.

STORAGE & SHIPMENT

7-2

APPENDIX ASUMMARY OF SPECIFICATIONS
A.1 UNCERTAINTY ANALYSIS
To perform an Uncertainty Analysis on a measurement device, you must be able toidentify all of the parameters that influence the measurement. You must be able toquantify the magnitude of the potential error source and combine these into an overall
uncertainty statement.
To determine the expanded uncertainty on any manufacturers pressure Transfer Standard(TS), you must identify the following four primary influences;
1.) Performance specifications of the TS
2.) Long term Stability of TS
3.) Uncertainty of the standard used to calibrate the TS4.) Environmental or installation influences that could cause errors in the TS
A.1.1 PERFORMANCE SPECIFICATIONS are the short-term measurement properties ofthe device. These traditionally include linearity, hysteresis, and repeatability properties of
the transfer standard. There often is considerable confusion with the performance
specification because different manufacturers use different terms to describe theperformance characteristics of their instruments. The two most common terms used are“Accuracy” and “Precision”. In both cases, as a minimum the manufacturers define theseterms to be the combined effects of linearity, hysteresis and repeatability. Since the
manufacturer defined the terms they used, this should not be a problem. However, it iscommon that the users definition of these terms differ from the manufacturers andtherefore cause considerable confusion. For instance, the user may believe that the term
“Accuracy” includes all sources of uncertainty. This would include items 1 through 4
listed above which would be an all encompassing specification. The manufacturer may
define “Accuracy” as the performance specification which consist only of item 1 above.
The result would be that the instrument would not be capable of meeting the users
application because it would not meet the users definition of “Accuracy”.
A.1.2 LONG TERM STABILITY defines how the instrument drifts with time. This
specification can be utilized to define the calibration interval for the standard. Somemanufacturers will provide more than one stability specification for their instrument basedon different calibration time intervals. It is important to understand that you should notarbitrarily vary the manufacturers stability specification based on time without knowing
the characteristics of their device. Some manufacturers identify that their stability
specification is proportional with time. Therefore, if the calibration interval were reducedin half, the magnitude of the stability specification would also be halved. This can be a
powerful tool when you are trying to improve the measurement performance of astandard. By reducing the calibration interval, the expanded uncertainty would also
reduce. On the other hand, some manufacturers do not claim that their stability
specification is proportional with time. This would be the case for instance if the
instrument naturally drifted in a sinusoidal fashion. This would suggest that the sensor
A-1

APPENDIX A

could drift to its maximum stability limit at any time and therefore, reducing thecalibration interval would not improve the expanded uncertainty of the device.
A.1.3 SHORT TERM STABILITY relates to the zero drift characteristics of the instrument.
This generally is classified as short term drift since the instrument can be re-zeroed
without performing a full calibration as required to correct for long term span drifts. The
magnitude of zero drift can be assessed based on the length of time between re-zeroing
the instrument.
A.1.4 UNCERTAINTY OF THE STANDARD used to calibrate the transfer standard. This is
the expanded uncertainty of the calibration standard that was used by the manufacturer
to calibrate the digital transfer standard. This should be the expanded uncertainty of thecalibration standard and include all sources of uncertainty that would influence thecalibration standard including the uncertainty from the National Standards Laboratorythat the standard is traceable.
It should also be noted that when the instrument is re-calibrated, the uncertainty of thedevice is influenced by the uncertainty of the calibration standard that will be used toperform the re-calibration. Therefore, the uncertainty analysis should be evaluatedfollowing each re-calibration. If the instrument is re-calibrated using a different
calibration service provider than the manufacturer, the uncertainty of the standard thatthe calibration service provider used to perform the calibration would need to be
substituted for the manufacturers calibration uncertainty that was used in the original
uncertainty analysis.
A.1.5 ENVIRONMENTAL OR INSTALLATION INFLUENCES that could cause errors in thetransfer standard. This includes influences such as ambient temperature, line pressure,head pressure, time response, and controller effects. (It may include other influences thatare very specific to one manufacturers instrument.) It is recommended that the intended
application is reviewed to assure that the environmental does not impact the instruments
performance, or that the impact from the environment is accounted for in the uncertainty
analysis. For instance, if an instrument has a 0.001%FS per degree Celsius temperatureeffect from a calibrated temperature of 20 degrees Celsius, and the instrument is to be
used in an environment where the temperature will vary from 15 to 25 degree Celsius,then a +/- 0.005% of full scale uncertainty should be included in the uncertainty analysis
for ambient temperature effects.
A.1.6 COMBINING THE UNCERTAINTY COMPONENTS INTO AN EXPANDEDUNCERTAINTY STATEMENT
Once all of the uncertainty components are identified, they can be combined into an
overall Expanded Uncertainty Statement for the instrument. The vast majority of themeasurement community has adopted a statistical approach to uncertainty analysis suchas the International Organization for Standards (ISO) Guild to the Expression ofUncertainty in Measurement. This statistical approach combines all of the uncertainty
components in quadrature (RSS).
In this approach, it is important to define the level of confidence that all of the uncertainty
components are defined. For instance, all of the uncertainty specifications that GE Ruska
APPENDIX A

A-2

publishes are at the 2 sigma level which would be at a 95% confidence level. Somemanufacturers may state their uncertainty at different confidence level and therefore, you
would need to be able to convert from one to the other in order to compare the two
devices. For instance, if a manufacturer states that they have an uncertainty of 0.005%
FS and that the uncertainty is expressed at the 1 sigma level, then it would be doubled toexpress it at the 2 sigma level (i.e. it would be an 0.01% FS device at a 2 sigma or 95%
confidence level.)
The following two tables are uncertainty analysis examples for a 7250sys based on athree month and a yearly calibration.
Uncertainty Analysis – 3 Month Calibration Interval
Ruska Model 7250sys
A. Performance – (Linearity, Hysteresis, Repeatability
and Temperature)
B. Stability – (3 months)

Uncertainty(2 sigma)
0.003% of Each Range
0.0019% of Reading per 90 days

C. Calibration Standard – (Ruska 2470 or 2465 DWG)

0.0011% of Reading

D. Environmental –Temperature (Included in A. above)

0.000% of Reading

Head Pressure

0.001% of Reading

Control – (in Passive Control Mode)

0.000% of Controller Range

2 sigma Expanded Uncertainty (RSS)

Uncertainty Analysis – One Year Calibration Interval
Ruska Model 7250sys
A. Performance – (Linearity, Hysteresis, Repeatability
and Temperature)
B. Stability – (1 year)

0.003% of Range RSS with
0.0022% of Reading per 3 months

Uncertainty(2 sigma)
0.003% of Each Range
0.0075% of Reading / year

C. Calibration Standard – (Ruska 2470 or 2465 DWG)

0.0011% of Reading

D. Environmental –Temperature (Included in A. above)

0.000% of Reading

Head Pressure

0.001% of Reading

Control – (in Passive Control Mode)

0.000% of Controller Range

2 sigma Expanded Uncertainty (RSS)A-3

0.003% of Full Scale RSS with
0.0076% of Reading per year
APPENDIX A

A.1.7 ABSOLUTE MODE
With the 7250sys, there are 2 methods of operating the system in the absolute mode.
These are by adding a Barometric Reference Sensor to the system to monitor thebarometric pressure and add this value to the gauge reference quartz sensor. Or thesecond is to evacuate the reference port of the Ruska quartz sensor and then monitor the
residual vacuum in the reference port and correcting for this residual vacuum.
In either case, the expanded uncertainty of the system must account for the potential
uncertainty of whichever sensor is used in the system to allow it to operate in the absolutemode. Therefore, the uncertainty of one of these sensors would be combined RSS (RootSum Squared) with the expanded uncertainty of the system.
A.1.7.1 Barometric Reference Sensor – Option
The two sigma expanded uncertainty of the barometric reference sensor is estimated tobe less than or equal to 0.002 psi (13.8 Pa) per year. This uncertainty component should
be combined RSS with the primary sensor uncertainty when operating in the absolutemode with a barometric reference sensor.
A.1.7.2 Evacuated Reference – Option
The two sigma expanded uncertainty of the vacuum sensor used to monitor the reference
pressure is estimated to be less than or equal to 10 mtorr (1.33 Pa) per year. This
uncertainty component should be combined RSS with the primary sensor uncertainty
when operating in the absolute mode with a evacuated reference vacuum sensor.
A.1.8 CONTROLLER SPECIFICATION - When the system is in control mode, the control
noise is defined as how close the controller can maintain the control pressure to thecommanded set-point. In the active control mode, the 7250sys has a control noise
specification of 0.001% of each controller range. On an 8 range system, there are twocontrol ranges. One has a full-scale range equal to the full-scale of sensor Range A.
The other has a full scale range equal to the full scale range of the sensor range C. On
a 12 range system, there are three controller ranges equal to the full-scale of ranges A,
C and E.
In the Passive control mode, since the controller shuts off when it reaches a user-definedband about the commanded set-point, the uncertainty of the pressure measurement in
not influenced by the controller.
A.1.9 TWO SIGMA EXPANDED UNCERTAINTY OF THE 7250sys
Since the 7250sys automatically switches between multiple sensors selecting the highest
performance sensor to monitor the pressure, there are two ways to express theuncertainty of the system. One method results in the highest performance values that canbe assigned to the system. However, this uncertainty statement is more difficult to express
since it must be expressed for each sensor range in both “Percent of Range” and “Percent
of Reading” terms. Because of the “Percent of Range” components associated with eachsensor, the uncertainty of a sensor increases as a percent of reading as the pressure
decreases. However, as the pressure decreases, the system switches to a lower range
sensor resulting in the uncertainty improving. This process repeats throughout the ranges
APPENDIX A

A-4

of the system. The graph below depicts an example of a typical 1000 psi full scale, 8
range system maintained on a 1 year calibration cycle. The uncertainty of each sensor isplotted resulting in the saw tooth pattern shown.
The second method is to describe the uncertainty as a Percent of Reading. In thisexample, from 3.5 psi to 1000 psi, the system maintains an uncertainty level better than
0.01% of Reading as indicated by the horizontal line shown on the graph. Below 3.5 psi,the maximum uncertainty of the lowest range sensor in the system is 0.00035 psi. So,
the two sigma uncertainty for the system could be expressed as “0.01% of Reading or
0.00035 psi whichever is greater per year”. This significantly simplifies the uncertainty
statement for the system. However, this method actually downgrades the system
performance of the system since it is defining the uncertainty in a worst-case scenario.
Either method is appropriate. It is recommended to select a method that best meets an
individuals requirement.

1000 psi Full Scale - 8 Range System
Two Sigma Uncertainty per year
0.0110%0.01% of Reading

0.0105%

Uncertainty (%)

0.0100%0.0095%0.0090%0.0085%0.0080%0.0075%
1

10

100

1000

Pressure (psi)

A-5

APPENDIX A

A.2

SPECIFICATIONSGENERAL SPECIFICATIONS
Available Pressure Range:
Display:
Display Resolution:
Electrical Power:
Operating Temperature:
Storage Temperature:
Humidity:
Nominal Control Volume:
Standard Pressure Units:
Pneumatic Ports:
Relief Valves:
Supply Pressure:

Minimum; 0 to 1000 (0 to 70 bar)
Maximum; 0 to 2500 psi (0 to 170 bar)
6.4 inch, TFT Active Matrix Color
User-selectable up to 1:1,000,000
90–260 VAC, 47 - 63 Hz (50-400 Hz for i/xi models), 150 W
18–36°C–20–70°C
5–95% relative humidity, non-condensing
5–60 in3 (80–1000 cc’s)
inHg at 0°C and 60°F, kPa, bar, psi, inH2O at 4oC, 20, and 25°C, kg/cm2, mmHg at 0°C, cmHg at 0°C, and cmH2O at 4°C
1/4-inch NPT female
Test Port: 120% of Maximum Scaled Quartz Sensor Range
Reference: 10 Psig (where applicable)
115%FS for units greater than 100 psi of each channel
100%FS plus 15 psi for units less than or equal to 100 psi foreach channel.

PERFORMANCETABLE A-1
PERFORMANCE SPECIFICATIONS: 7250sys
Pressure Range
Mode
Precision2
Stability
Over 3 Months:
Over 1 Year:
Zero Drift4
Control Stability
Control Low Limits3
Slew Rate5< 5 psi(< 0.34bar)

5–2500 psi(0.34–172 bar)Gauge

0.004% of Each Range

0.003% of Each Range

0.0019% RDG/ 3 months
0.0075% RDG/year<0.004% of Range / 24hrs
Active Control Mode - 0.001% of Controller Range
Passive Control Mode -0.000% of Controller Range
0 psig0.15 psia<20 Seconds

2

Precision is defined as the combined effect of linearity, repeatability, and hysteresis throughout theoperating temperature range. Some manufacturers use the word “Accuracy” in place of “Precision”,
however the meaning is identical.
3
Requires vacuum pump to control 0 psig, or the vent mode can be used to obtain 0 psig.
4
Zero drift typically improves with sensor age.
5
Defined as 10% FS increments into a 15 cubic inch volume
APPENDIX A

A-6

GAS SPECIFICATIONS
Pressure Source Medium:

Clean Dry Air or Nitrogen*Pressure Source Particle Size Contamination:≤50 microns

Pressure Source Max. Moisture Content:-50 °C dew point

Pressure Source Max. Hydrocarbon Content:

30 ppmVACUUM REQUIREMENTS
Supply Vacuum:

50 liters per minute (minimum) with auto vent feature(absolute units only)

Bypass Supply Vacuum Valve for High Pressure Gauge work

* Industrial grade nitrogen, 99.5% pure

A-7

APPENDIX ATHIS PAGE INTENTIONALLY LEFT BLANKAPPENDIX A

A-8

APPENDIX B
SUMMARY OF ERROR MESSAGES
Negative error numbers are from the Standard Commands for Programmable Instruments(Version 1991.0).
Value

Description and Corrective Action

0
-103
-104
-109
-110
-113
-114
-221

No Error.
Invalid Separator. Check punctuation in the SCPI command.
Data Type. The type of parameter data is incorrect.
Missing Parameter. No valid parameter was found for the SCPI command.
Command Header. The command name is not valid.
Command Unknown. The command specified does not exist.
Header Suffix. The numeric suffix for the command name is out of range.
Settings Conflict. The command could not be executed due to the current state of
the DPC. Some commands cannot be executed while a program, self-test, or
calibration is in progress.
Out of Range. The value is not within the valid range. For pressures check highand low limits.
Cannot create program. Program memory is full.
Illegal Program Name. The name specified is not valid or does not exist.
Program Currently Running. The command cannot be executed while a programis running.
Program Syntax Error. The syntax of the program definition is not correct.

-222
-281
-282
-284
-285

-330

Program Runtime Error. An error occurred while running the program. Usually
the setpoint is out of range.
Calibration Data Lost. The calibration data has been lost and the unit must berecalibrated.
Configuration Data Lost. The configuration data has been lost. Check allparameters to be sure they are correct.
Self-Test Failed. Check the display for the test that failed.

-350

Queue Overflow. The error queue was full and messages were lost.

-400

Query Error. A read request was received when there was nothing to read.

500

Controller Malfunction. Internal control failure.

501

High Limit Exceeded. The pressure was greater than the high limit.

502

Low Limit Exceeded. The pressure was less that the low limit.

503

Slew limit Exceeded. The pressure changed faster than the slew limit allowed.

521

Pressure Overrange. The pressure reading is outside the range of the DPC.

531

Oven Temp Overrange. Either the transistor that drives the heater for the quartz
Bourdon tube sensor (section 2) or the oven temperature sensor itself ismalfunctioning. To observe the oven temperature, select OK then select
MENU/DISP. Check the transistor and sensor for malfunction, requesting service

-286
-313
-315

B-1

APPENDIX B

(section 7) if necessary.
533

Case Pressure Overrange. Select OK, then reduce the pressure at the casereference port to 30 psia or lower.

538

Automatic Vent – Pressure exceeded the Auto-Vent limit

540

Mechanical Zeroing Needed. The zero point of the quartz Bourdon sensor isbeyond the range of the compensation circuit. The zero is adjusted by thesoftware but should be manually adjusted for complete accuracy.

542

Oven Control Failure. The temperature controller is unable to keep the sensor at
the proper temperature.

545

Sensor Communication Error. Unable to Communicate with 7215xi Sensor

546

Sensor Calibration Lost. The 7215xi sensor has lost its calibration and must berecalibrated.

600

Factory Data Lost. Internal factory constants have been lost. Contact Ruska for
more information.

601

Calibration Mode. The Calibrate button must be pressed before SCPI calibrationcommands can be executed.

707

Pressure Too High800

Solenoid Over-Temperature. The control solenoids have over-heated. Wait until
they have cooled before entering Control mode.

801

Error reading Barometric RPT Pressure Sensor

802

Control Sensor out of range

803

Controller Communication Error

804

Autotune Failed

APPENDIX B

B-2