# **ATQASUK METEOROLOGY TOWER USERS MANUAL**

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**TABLE OF CONTENTS**

# SYSTEM MAINTENANCE AND CALIBRATION 

#  Daily Checks 3

#  Monthly Checks 4

#  6-Month Checks 5

#  Annual Checks 6

#  Two-Year Checks and Replacement 7

# 

# AQASUK METEOROLOGY TOWER DAILY PM PROCEDURE 8

# 

# CALIBRATION PROCEDURES FOR THE FD12P PRESENT 

# WEATHER SENSOR 12

# 

# PRESENT WEATHER CHECK SHEET 15

# 

# PRESENT WEATHER SENSOR SET-UP 16

# 

# TEMPERATURE AND RELATIVE HUMIDITY CHECK PROCEDURES 17

# 

# NSA TEMPERATURE SENSOR VERIFICATION 18

# 

# WIND SPEED AND DIRECTION CHECKS AND PROCEDURES 19

# 

# WIND SPEED AND DIRECTION VERIFICATION 20

# 

# CHILLED MIRROR CLEANING & CLAIBRATION 21

# 

# WIRING DIAGRAMS 23

# 

KNOWN ISSUES AND PROBLEMS NOT NOTED ELSEWHERE 27

**SYSTEM CALIBRATION AND MAINTENANCE**

# 

# **[Daily Checks]{.underline}**

The data from the tower should be checked each day during daily
maintenance rounds. Temperature and relative humidity data from both
levels and the CMH should be compared to determine if the data appear
reasonable.

Any discrepancies should be noted on the daily rounds forms. The wind
speed and direction data should be checked to determine if the values
appear reasonable to the current conditions. The barometric and present
weather data should be checked to determine if what is being reported
also appear reasonable. For example, if the present weather sensor is
reporting 100m visibility and heavy snow when it is clear and sunny out,
this indicates a problem with the present weather sensor and should be
noted. The present weather sensor also has an alarm value:

The error or warning from PWS could be any of the following:\
00,\
01,\
02\
10,\
11,\
12,\
20,\
21,\
22

First digit 1 = visibility alarm higher, 2 = visibility alarm lower, 0 =
all ok

Second digit 1 = hardware error, 2 = hardware warning, 0 = all ok.\
\
So when we get a 0, 1 or 2 it is really 00, 01, and 02.\
\
A value of 1 means hardware error and a value of 2 means hardware
warning. Continual values (more than a few hours) of 1, 11 or 21 are of
concern and should be noted on the daily rounds form.

Data from the barometer should be between 800 and 1100 hPa. If the
barometric data is outside of these values then this should be noted on
the daily forms. An RTMC Overview screen has been built which displays
24 hours of data graphed along with text values for the current
readings. The graphs will allow checks of the data to be made to
determine if problems have occurred during the most recent 24 hours.
Long gaps in data, long periods of or many data spikes, and flat line
data (no change in values over extended periods) will be apparent and
should be noted on the form.

##### [Monthly Checks]{.underline}

Once a month the auto balance dial reading should be taken for the CMH.
The auto balance reading is an indication of the contamination on the
surface of the mirror. To obtain a reading, open the control box and
locate the auto balance dial in the upper right hand corner of the
control box. It resembles a typical gym locker dial. The knob has
increments of two and numerals in increments of 10 starting at 0 and
going through 90. The window has numerals of 1 through 10. To take a
reading, use the window value to read the hundreds and the dial to read
the tens and ones. For example, if the window has the numeral 0 and the
dial is on the third division between 0 and 10, then the reading is 6.
If the window has the numeral 1 and the dial is on 60, then the reading
is 160. This value should be recorded once a month on the daily forms.
When the reading reaches or exceeds 500, the mirror will need to be
cleaned and the entire sensor will have to be recalibrated. See CHILLED
MIRROR CLEANING & CALIBRATION on page 21 of this manual or sections
2-3.3 through 2-4.3 of the CMH manual for the procedures to clean and
recalibrate the sensor.

# **[Six-Month Checks]{.underline}**

# 

#### Present Weather Sensor

The lenses of the present weather sensor need to be cleaned every six
months. Remove any condensed water, ice or snow that may be on the hoods
or lenses. Wipe away any dust from the inner and outer surfaces of the
hoods. Using a clean, lint-free cloth and isopropyl alcohol, moisten the
cloth with alcohol and gently wipe the lenses. Clean the capacitive rain
detector every six months using a soft, lint-free cloth moistened with
mild detergent. The date and time of cleaning should be entered into the
daily rounds forms.

# 

#### Chilled Mirror Hygrometer

The CMH should be cleaned and recalibrated every six months to ensure
proper functioning and that reasonable data is returned from the sensor.
See CHILLED MIRROR CLEANING & CALIBRATION on page 21 of this manual or
sections 2-3.3 through 2-4.3 of the CMH manual for the procedures to
clean and recalibrate the sensor. The date and time of cleaning should
be entered into the daily rounds forms.

#  

# **[Annual Checks]{.underline}**

# 

# [Cup Anemometers and Wind Direction Vanes]{.underline}

# 

The bearings in these sensors need to be checked once a year. These
checks should not be made when the air temperature is below --17.5°C
(0°F). The tower will have to be lowered to access the wind speed and
direction sensors. Carefully remove the cups from the anemometers or the
vane from the wind direction sensors and spin the shafts. They should
spin freely. Slowly turn the shafts with ungloved fingers to sense
anything irregular such as dirt or a flat spot on a bearing or a rubbing
disk. Also inspect the cups and vane for any signs of damage. If any
irregularity is observed, replace the respective anemometer or wind
direction sensor.

# 

# [HMP45D Temperature and Relative Humidity Probes]{.underline}

# 

The filters on the probes need to be checked once a year and replaced if
dirty. These checks should not be made when the air temperature is below
--17.5°C (0°F). The tower will have to be lowered to access the upper
sensor. Remove the air intake from the aspirated radiation shield by
unscrewing it. Remove the protective cover from the probe and inspect
the filter. Replace the filter if it is dirty. Reassemble the probe and
aspirator.

## PTB201 or PTB220 Digital Barometer

Compare the reading of the digital barometer with the reference digital
barometer. Record both readings on the daily forms.

# 

# [FD12P Present Weather Sensor]{.underline}

# 

Check the visibility calibration once a year using the FDA12 calibration
kit. See CALIBRATION PROCEDURES FOR THE FD12P PRESENT WEATHER SENSOR on
page 12 of this manual for the procedures to clean and calibrate the
present weather sensor.

#### **Two-Year Checks and Replacement**

# [Wind Speed and Direction Sensors]{.underline}

# 

Check the calibration of the current cup anemometer and the frequency
measuring portion of the QLI50 Sensor Collectors by using the R. M.
Young Model 18810 Anemometer Drive to spin the anemometer shaft for at
least one minute at the different rpms. Check the calibration of the
current wind vane and decoding portion of the QLI50 Sensor Collector.
Obtain the readings from either the RTMC Overview screen or by directly
connecting to the logger and viewing the Input Location data. Remove and
replace the anemometer and direction sensor. Check the calibration of
the newly replaced sensor. See WIND SPEED AND DIRECTION CHECKS on page
19 of this manual for procedures and page 20 of this manual for the
forms.

# [Temperature and Relative Humidity Sensors]{.underline}

# 

Check the calibration of the current temperature and relative humidity
probes by comparing them to the reference probe. Ensure that there is
proper flow over both the reference and the current probe and that
little or no direct solar radiation influences the reading. Replace the
probes with ones that have a current calibration. Check the calibration
of the newly replaced probes before returning to service. See
TEMPERATURE AND RELATIVE HUMIDITY CHECK PROCEDURES on page 17 of this
manual for procedures and page 18 for the forms.

**ATQASUK METEOROLOGICAL TOWER**

**DAILY PM PROCEDURE**

This document describes the daily PM procedures to be conducted at the
NSA C2 Atqasuk site.

The following items that are not included in the daily rounds forms or
on the LoggerNet RTMC Overview screen are to be verified. Any
discrepancy will be noted in the comments section of any of the Daily
Rounds forms.

1.  Verify operation of the computer by checking the time and making
    sure it is correct and changing. This can be done by use of the
    computer's task bar or any of the LoggerNet RTMC screens that have a
    date and time display.

2.  Verify that LoggerNet is running. Verifying that the LoggerNet task
    bar is up and available or verifying the RTMC screens are live and
    updating can do this.

The below images have circles and numerals on them. The numerals located
on the Daily Rounds form have a corresponding numeral on the RTMC
Overview screen. These corresponding numerals on the RTMC highlight
where information is found to answer the questions on the Daily Rounds
form. The corresponding numerals work for all portions of the Daily
Rounds form except for the Ground Visual Checks and the Monthly CMH
Autobalance Reading sections. The Ground Visual Checks are accomplished
by visually checking the tower, and physically opening the CMH and
reading the values off the dial accomplish the Autobalance Reading (see
MONTHLY CHECKS on page four of this manual for Autobalance reading
procedures).

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**CALIBRATION PROCEDURES FOR THE**

**FD12P PRESENT WEATHER SENSOR**

1.  Remove the current serial line from the Control Unit (note the
    colors of the wires and to what terminal they are connected) and
    connect another serial cable to the terminals.

2.  Start HyperTerminal.

3.  Set CAPS LOCK ON (PWS commands are all capitals)

4.  In HyperTerminal go to FILE\>Properties

    a.  Under "CONNECT TO" tab Connect using: COM 1

    b.  Under "CONFIGURE" button:

        i.  Bits = 1200

        ii. Data Bits = 7

        iii. Parity = even

        iv. Stop bits = 1

        v.  Flow Control = none

    c.  Under "SETTINGS" tab

        i.  Terminal keys: on

        ii. Emulation: ANSI

        iii. Back Scroll Buffer Lines: 500

        iv. Terminal Settings: underline and blink

    d.  Under "ASCII SETUP" button

        i.  Under Sending:

            1.  Echo Typed Characters Locally: no

            2.  Line Delay: 0

            3.  Character Delay: 0

        ii. Under Receiving:

            1.  Append Line Feeds: yes

            2.  Wrap Lines: yes

5.  Connect (using file\>connect, call\>call, or phone icon) to the
    present weather sensor. Name the file PWSCALxx/xx/xx where the x's
    stand for month, date, and year.

6.  Clean the PWS transmitter windows with the spray and soft cloths in
    the Visibility Calibrator Set FDA 12. Allow the windows to dry for
    about 5 minutes.

7.  Hit return a few times to get a prompt.

8.  Type OPEN \^C (\^ indicates control key) then hit ENTER

9.  Type CLEAN then hit ENTER

10. Record the Transmitter and Receiver settings

11. Insert the Black Blocking plate tightly into the right shield of the
    sensor (small disk toward the inside of shield, plate handle hanging
    down)

12. Type CHEC then hit ENTER

13. Wait until the reading stabilizes around a small range of values
    (about 5 minutes or so, usually)

14. Record the value. The actual value should be less than +/- 0.1 Hz.

15. Hit ESC key to end the check.

16. Install the opaque calibration plates. See installation instructions
    in the calibration case. The mounting clamp is on the sensor
    horizontal tube. The plates are labeled "Right" and "Left". Be
    careful with them, they are glass. Do not get fingerprints on them.
    Clean them with the cloth and spray if necessary.

17. Type CHEC then hit ENTER

18. Wait for readings to stabilize around a small range of values
    (usually about 5 minutes or so)

19. Record the value (should be +/- 39 Hz of the calibration plate value
    1287 Hz).

20. If values do not fall in this range, move the mounting clamp up or
    down slightly. This step may take some time as the mounting clamp
    allows for quite a bit of play.

21. Hit ESC to end the check.

22. Type CAL 1287 then hit ENTER.

23. Type CHEC then hit ENTER.

24. Write down the "scaled frequency average"

25. Hit ESC to end check.

26. Type TCAL then hit ENTER.

27. Record the TS (third value)

28. Type CLOSE then hit ENTER.

29. Disconnect and close out HyperTerminal, you should save the entire
    session and email the .TRM session to the mentor for recording.

30. Remove serial connector from the back of the PC and the Control Unit
    terminals and reconnect the serial cable that goes to the SDM_SI04
    located in the Met Logger Enclosure.

31. Wait a few minutes to see if the PWS data shows up on the Met
    program.

32. If the data does not show up after a minimum of 10 minutes, it may
    be necessary to clean the lenses again. Follow steps 1 through 9
    again. Although you may use the original saved HyperTerminal
    session.

33. Type CLOSE then hit ENTER.

34. Follow steps 29 -- 31 again to reconnect PWS to collector system.

If data does not show up after a few minutes, contact the mentor.

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**PRESENT WEATHER CHECK SHEET**

Tested by:\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_
Date:\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

Time began:\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ Time
ended:\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

General Weather Conditions:

# [Clean]{.underline}

Transmitter[:\_\_\_\_\_\_\_\_\_\_\_\_]{.underline}

Receiver[:\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_]{.underline}

# [Block Plate Check]{.underline}

## Scaled Frequency Average:\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

# [Calibration Plate Check]{.underline}

## Scaled Frequency Average:\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

### Is Calibration required? Yes/No

If so, CAL final
value:[\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_]{.underline}

# [TCAL Check]{.underline}

## TS value (last value on right):\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

## 

## CMH Temperature:\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

2m T/RH
Temperature[:\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_]{.underline}

Is reported one-minute visibility value reasonable? Yes/No

**PRESENT WEATHER SENSOR**

**SET-UP**

1.  Remove the current serial line from the Control Unit (note the
    colors of the wires and to what terminal they are connected) and
    connect another serial cable to the terminals.

> 2\. Start HyperTerminal.

3.  Set CAPS LOCK ON (PWS commands are all capitals)

4.  In HyperTerminal go to FILE\>Properties

    a.  Under "CONNECT TO" tab Connect using: COM 1

    b.  Under "CONFIGURE" button:

        i.  Bits = 1200 (unless first time then 300)

        ii. Data Bits = 7

        iii. Parity = even

        iv. Stop bits = 1

        v.  Flow Control = none

    c.  Under "SETTINGS" tab

        i.  Terminal keys: on

        ii. Emulation: ANSI

        iii. Back Scroll Buffer Lines: 500

        iv. Terminal Settings: underline and blink

    d.  Under "ASCII SETUP" button

        i.  Under Sending:

            1.  Echo Typed Characters Locally: no

            2.  Line Delay: 0

            3.  Character Delay: 0

        ii. Under Receiving:

            1.  Append Line Feeds: yes

            2.  Wrap Lines: yes

5.  Connect (using file\>connect, call\>call, or phone icon) to the
    present weather sensor. Name the file PWSCALxx/xx/xx where the x's
    stand for month, date, and year.

6.  Type OPEN\^C then hit ENTER.

7.  Type AMES 2 then hit ENTER.

8.  Type BAUD 1200 then hit ENTER. Only do this step if baud is not
    1200.

9.  Type CLOSE then hit ENTER.

10. Before typing CLOSE you can enter in other maintenance commands to
    check operation of the PWS:

    a.  STA -- returns result of built-in test.

    b.  PAR -- returns current system parameters.

\*\*\*MUST TYPE CLOSE AT END OR PWS WILL NOT RESPOND TO REGULAR COMMANDS
FOR DATA.

**Temperature and Relative Humidity**

**Check Procedures**

This check requires two people. One person outside taking readings using
the VTP6 Field Calibration probe and one person inside collecting
readings from the installed sensors using the RTMC programs or by
directly connecting to the logger and viewing the raw input data.
Two-way radios will need to be used to communicate information.

1.  Lower tower to access the T/RH probes at both the 2m and 5m levels.

2.  Place the VTP6 Field Calibration probe outside in the ambient air
    and turn it on. Do not place in direct sunlight; try to find a
    shaded area for it to equilibrate to ambient temperatures.

3.  Rotate the aspirator units so the intake points toward the ground,
    this will prevent any solar influence to the probe.

4.  Once the VTP6 has equilibrated (this may take some time), place the
    probe into the opening of the aspirator intake as close to the T/RH
    probe as possible without allowing any contact. View the temperature
    and RH on the VTP6 readout. When values become stable, take the
    reading and transmit the data to the person inside for comparison
    and recording.

5.  Unscrew the intake tube to gain access to the sensor. The
    measurement head of the HMP-45D's is removable so that rewiring is
    not necessary. Grasp the sensor body and pull downwards. Do not
    grasp by the filter as it can pull off and damage the sensors. Once
    the sensor is removed, make note of the S/N number and transmit it
    to the person inside.

6.  If not already done, make note of and transmit the S/N of the
    recently calibrated probe to be installed to the person inside.

7.  Place the new sensor into the main body of the sensor. Replace the
    intake tube by screwing it back into the aspirator unit. Wait about
    5 minutes or so for the new sensor to equilibrate to being in the
    aspirator unit. Do not allow the VTP6 to sit in the sunlight during
    this time.

8.  Once the new sensor has equilibrated, repeat step 4 with the new
    sensor installed.

9.  If readings do not agree, allow a longer period of time for the new
    sensor to equilibrate and ensure the VTP6 is kept in a shaded area
    during this additional time.

10. If readings still do not agree, replace the sensor with another
    recently calibrated probe. If none are available, leave the new
    probe installed and contact the mentor.

11. Repeat all steps above for both the 2m and 5m levels.

12. The VTP6 requires a 9-volt battery; if problems are occurring with
    the VTP6 try replacing the battery, if problems continue, contact
    the mentor.

> **NSA**

**TEMPERATURE SENSOR VERIFICATION**

# Tested by: Date:\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

### Time began\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ Time ended\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

LOCATION:\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ LEVEL: \_\_\_\_\_M

## TEMPERATURE

**[VTP6]{.underline} [OLD HMP-45D]{.underline}**

\_\_\_\_\_\_\_\_\_ \_\_\_\_\_\_\_\_\_\_\_\_\_\_

**[NEW HMP-45D]{.underline}**

\_\_\_\_\_\_\_\_\_ \_\_\_\_\_\_\_\_\_\_\_\_\_\_

Do the readings from the HMP-45D's agree within +/- .5 deg C of the
VTP6?

Yes / No

Comments:\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

## RELATIVE HUMIDITY

**[VTP6]{.underline} [OLD HMP-45D]{.underline}**

\_\_\_\_\_\_\_\_\_\_ \_\_\_\_\_\_\_\_\_\_\_\_\_\_

**[NEW HMP-45D]{.underline}**

\_\_\_\_\_\_\_\_\_\_ \_\_\_\_\_\_\_\_\_\_\_\_\_\_

Do the readings from the HMP-45D's agree within +/- 3% of the VTP6?

Yes / No

Comments:\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

S/N old HMP-45D:\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

S/N new HMP-45D:\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

**WIND SPEED AND DIRECTION**

**CHECKS AND PROCEDURES**

This check requires two people. One person outside taking readings using
the RM YOUNG RPM Generator and one person inside collecting readings
from the installed sensors using the RTMC programs or by directly
connecting to the logger and viewing the raw input data. Two-way radios
will need to be used to communicate information.

1.  Lower the tower to access the wind speed and direction sensors.

2.  Grasp the wind speed sensor shaft and cups to determine if the
    heater is working (only works when ambient temperatures are below 32
    F). Grasp the shaft of the wind direction sensor to determine if the
    heater is working.

3.  Remove the cups from the anemometer and install the RPM Generator.
    Start the generator and using the buttons with arrows, change the
    RPM's to each of the required settings. Let the RPM generator
    stabilize at each setting and allow it to run at least 2-minutes
    before taking the reading inside.

4.  Once all RPM readings have been taken, remove the wind speed sensor
    and install the new one. Follow step 3 above to take RPM readings
    for the new sensor. Transmit the S/N of both the old and new sensor
    if not already done.

5.  Re-install the cups and if temperatures are low enough, grasp the
    shaft and cups to determine if the heater is working for the newly
    installed sensors.

6.  If it is too windy to firmly hold the wind vane steady, remove it
    before checking the direction values.

7.  Hold the vane or the shaft steady along the four quadrants (N, S,
    E, W) and wait at least 2-minutes before taking a reading for each
    quadrant.

8.  Remove the wind direction sensor and install the new one. Follow
    step 7 above to take the readings for the new sensor. Transmit the
    serial numbers of both the old and new sensors if not already done.

9.  Re-install the wind vane and if the temperatures are low enough
    grasp the shaft to determine if the heater is working.

10. Once all sensors have been replaced and verified to be working
    correctly, the tower may be raised back into the vertical position.

**WIND SENSOR VERIFICATION**

# Tested by: Date:

Time began\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ Time
ended\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_­

###### LOCATION\_\_\_\_\_\_\_\_\_\_\_\_\_ LEVEL\_\_\_\_\_\_M WIND SPEED CHECKS 

S/N Old Sensor:\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ S/N New
Sensor\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

[RPM]{.underline} [Calculated speed m/s]{.underline} [Measured
speed]{.underline}

Old sensor New sensor

200 4.67 -- 4.81 m/s \_\_\_\_\_\_\_\_\_ \_\_\_\_\_\_\_\_\_\_

300 7.00 -- 7.10 m/s \_\_\_\_\_\_\_\_\_ \_\_\_\_\_\_\_\_\_\_

400 9.33 -- 9.38 m/s \_\_\_\_\_\_\_\_\_ \_\_\_\_\_\_\_\_\_\_

500 11.67 +/- 0.2 m/s \_\_\_\_\_\_\_\_\_ \_\_\_\_\_\_\_\_\_\_

Are values acceptable for new sensor: Yes / No

\_\_\_\_\_\_**M WIND DIRECTION CHECKS** (accuracy +/- 5 deg, resolution
1.0 deg**)**

[Quadrant]{.underline} [Measured Value]{.underline}

> Old sensor New Sensor S/N Old Sensor

\_\_\_\_\_\_\_ \_\_\_\_\_\_\_\_\_ \_\_\_\_\_\_\_\_\_
\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

\_\_\_\_\_\_\_ \_\_\_\_\_\_\_\_\_ \_\_\_\_\_\_\_\_\_ S/N New Sensor

\_\_\_\_\_\_\_ \_\_\_\_\_\_\_\_\_ \_\_\_\_\_\_\_\_\_
\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

\_\_\_\_\_\_\_ \_\_\_\_\_\_\_\_\_ \_\_\_\_\_\_\_\_\_

Are values acceptable for new sensor: Yes / No

**Chilled Mirror Cleaning & Calibration**

It is best to do the recalibration and cleaning in an indoor
environment. Stable temperatures and dew points are needed. If the unit
is outdoors or in an environment where temperature and dew point is
fluctuating during the recalibration, the settling time of the unit will
take much longer.

Items needed: Fluke meter able to read 0 -- 5 V DC, distilled water,
lacquer thinner, isopropyl alcohol, cotton swabs.

1.  Remove CMH unit from the tower and take inside the GW or back to the
    duplex.

2.  Leave power disconnected from unit at this time.

3.  Turn Auto balance dial to 000 so that 0 is read in the "window" and
    0 is set to the mark below the window.

4.  Remove mirror assembly from the sensor housing assembly (white
    mushroom).

    a.  Remove retaining screw from side of housing assembly.

    b.  Grab sensor (from the bottom) by the handle and pull assembly
        out, you may want to disconnect the sensor data cable. The unit
        connects through two banana connectors and slides in and out of
        assembly only one way.

5.  Once unit is removed, you can begin the cleaning of the mirror.
    Begin by taking a clean cotton swab and distilled water, thoroughly
    wet mirror surface using a moistened swab. Once mirror is wet, wash
    with a gentle circular motion.

6.  Wipe the surface with a clean dry swab until dry and all loosened
    material is removed.

7.  Repeat steps 4 and 5 until the cleaning has no further effect, i.e.
    dry swab is clean after drying sequence.

8.  Repeat steps 4 & 5 using lacquer thinner.

9.  Continue lacquer thinner cleaning until it has no further effect.

10. Repeat steps 4 & 5 using Isopropyl Alcohol.

11. Continue alcohol cleaning until it has no further effect.

12. NEVER use soap or any other detergent to wash mirror.

13. Re-install mirror assembly into the sensor housing assembly. Ensure
    the banana connectors line up before seating mirror assembly.
    Tighten retaining screw and ensure the grounding cable is connected
    between the assembly cap and retaining screw.

14. Reconnect the sensor data cable to the main housing unit.

15. Apply AC power to the unit.

16. Turn the Mode Selector Switch to HEAT, and leave on for one-minute.
    This will ensure a dry mirror after following the cleaning steps
    above. Turn mode Selector Switch to OPR position after one-minute
    time period is up.

17. Remove AC power.

18. Connect a digital voltmeter set to read 0 -- 5 V DC to the transmit
    logic board. Connect the positive lead to the left side of R3
    (junction of R8, R3, and C2) on the transmit logic board and the
    negative lead to ground.

19. Reapply AC power.

20. THE FOLLOWING STEPS MUST BE DONE WITH A COMPLETELY DRY MIRROR. TO
    INSURE A DRY MIRROR CHECK THAT THE DEW POINT IS ABOVE THE AMBIENT
    AIR TEMPERATURE BY TOGGLING THE MONITOR SELECTOR SWITCH BETWEEN Ta
    and Td AND PUSHING THE MONITOR DISPLAY SWITCH TO READ THE VALUES.
    NEED TO KEEP Td ABOVE Td. THE FOLLOWING ADJUSTMENTS **MUST NOT** BE
    MADE WHILE HEATING THE MIRROR. YOU **MUST** MONITOR THE Td, AND HEAT
    AS NECESARRY. MAKE MEASUREMENTS AND ADJUSTMENTS **IN BETWEEN**
    HEATING CYCLES. SELECTOR SWITCH SHOULD BE IN **OPR** POSITION WHEN
    MAKING ADJUSTMENTS

21. Turn the Sd gain adjustment (R21) clockwise until the Sd LED (CR5)
    just goes on. This is the threshold level. The voltmeter should read
    approximately 4.9 Volts.

22. Adjust the Si gain adjustment (R22) Clockwise until the Si LED (CR9)
    goes on then let system stabilize then turn the Si gain adjustment
    Counterclockwise until the Si LED (CR9) just goes off.

23. Turn the MODE SELECTOR switch to 0, check the Ta and Td readings by
    depressing the display switch for both. If necessary, adjust the TA0
    and TD0 trimpots to achieve 32.0 with a +/- 0.1 accuracy.

24. Turn the MODE SELECTOR switch to 50, check the Ta and Td readings by
    depressing the display switch for both. If necessary, adjust the TA+
    and TD+ trimpots to achieve 22.0 with a +/- 0.1 accuracy.

25. Adjust the FAN FAIL trimpot counterclockwise until the FAN FAIL LED
    comes on. Turn the trimpot slowly clockwise until the LED just goes
    off, then one full turn clockwise. Verify operation of the FAN FAIL
    LED by blocking the aspirator intake. Within 30 seconds the light
    should come on, and after removal of blockage the LED should
    extinguish within 30 seconds.

**WIRING DIAGRAMS**

![](media/image6.jpeg){width="5.991666666666666in" height="5.3125in"}

![](media/image7.jpeg){width="5.996527777777778in" height="4.78125in"}

![](media/image8.jpeg){width="5.995833333333334in"
height="5.565972222222222in"}

![](media/image9.jpeg){width="5.998611111111111in"
height="8.026388888888889in"}

**KNOWN ISSUES/PROBLEMS NOT NOTED ELSEWHERE**

1\. The CMH does not accomplish a self-test at temperatures below 0^o^
C/ -17^o^ F. This prevents a measure of the amount of contamination on
the mirror. As long as 6-month calibration procedures are accomplished,
problems with a dirty mirror should be alleviated.

2\. The connections on the CR23X datalogger are pinch-type connections.
Tightening of the connection is accomplished through a small screw.
Fluctuations in temperature cause the expansion and contraction of the
metal, which can cause a loosening of the connector. Periodically the
connections should be checked and/or tightened to insure a good
connection.

3\. Oxidation on contacts of the logger enclosure thermostats prevents
the heater/thermostat from working correctly. Periodically the
thermostat should be cycled on and off to arc the oxidation off of the
contacts to insure proper operation.