Replacing transmitter module

2.5-mm Allen key
Calculator
Laptop
Maintenance cable

Make sure that you have the replacement spare part available.

The transmitter emits invisible laser radiation, which is harmful to the eye if viewed at a short distance. Never remove the transmitter module from its normal position without first switching off the AC (mains) power and disconnecting the transmitter cable from the device control module.

When the transmitter is contained in the enclosure, the laser class is 1M, the transmitter is safe to the eye if magnifying instruments are not used.

When the transmitter is removed from the optics unit, the laser class is 3B, the laser is hazardous to the eye.

WARNING Do not remove the transmitter module CLT611 from its normal position without first switching off the AC (mains) power.

WARNING Do not look at the transmitter module CLT611 of the ceilometer from the beam direction when the transmitter is powered.

Replacing the transmitter includes adjusting the clean window reference and the calibration scalar.

Set the new clean window reference for a clean and dry window, in clear weather, and ideally with the termination hood placed on top of the device. The clean window calibration ensures that the window condition diagnostics respond appropriately to dirt accumulation.

CL61 is amplitude calibrated in manufacturing, which means that the attenuated backscatter (ABS) profiles it measures are in SI units of m⁻¹*sr⁻¹. This is important so that the ABS profiles from different CL61s are comparable.

Establish a maintenance connection to the device.
Change the user level.
```
level 2
```
Get the factory laser power value, p1, of the old transmitter.
```
get clt.factory.laserpower
```
Write down the value p1 in Table 1.

Keep the value for later use. The value is needed to adjust the calibration scalar after the transmitter replacement, as well as if the transmitter is replaced again, if the device control module is replaced, and after factory reset.
Switch off AC (mains) power.

WARNING To make sure that there is no AC (mains) power available for the system, disconnect the AC (mains) cable (AC in).

1

AC (mains) power switch

2

AC (mains) power cable connector AC in
Open the measurement unit door.
Disconnect the cable from the side panel.

1

Cable

2

Ring
Loosen the ring by hand with the help of an Allen key and remove the transmitter module.

To use the Allen key as a lever, insert it in a hole on the ring.

Turn counterclockwise to remove the transmitter.

1

Ring

2

Slots for Allen key

3

Allen key
Attach the replacement transmitter module and attach the ring.

Make sure that the guide pin is aligned with the groove in the transmitter module. Use an Allen key to tighten.

1

Groove for guide pin
Connect the cable.
Connect the power.
Change the user level.
```
level 2
```
Adjust the laser reference.
```
mode adjustlaserref
```
Type Y to continue.
Reset the device.
```
reset
```
Establish a maintenance connection to the device.
Change the user level.
```
level 2
```
When the device has been running for 5 minutes, set a new clean window reference.
```
mode adjustcleanwindow
```
Type Y to continue.

Setting the new reference takes a couple of minutes. Wait for the message that this was successful.
Get the factory laser power value, p2, of the new transmitter.
```
get clt.factory.laserpower
```
Write down the value p2 in Table 1.
Get the calibration scalar, c1, that the instrument currently uses.
```
get clo.field.cloudfactor
```
Write down the value c1 in Table 1.

If you have modified the cloud calibration factor and want to discard the change and restore the factory value, get the calibration scalar.
```
get clo.factory.cloudfactor
```
If you have not modified the value, the factory and field values are the same.

Calculate the values for r and c2 and add them in the following table.

Calculate the adjustment ratio, r:

r = \frac{p 1}{p 2}

Calculate the adjusted calibration scalar, c2:

c 2 = r \times c 1

Table 1. Values for calculating adjusted calibration scalar
Parameter	Value	Description
Date:
p1		Factory laser power value of the old transmitter
p2		Factory laser power value of the new transmitter
r		Adjustment ratio for the transmitter power
c1		Previous calibration scalar
c2		New adjusted calibration scalar

Set the instrument to use the adjusted calibration scalar c2.
```
set clo.field.cloudfactor <c2>
```
For example:
```
set clo.field.cloudfactor 0.6134534
```
Verify that the adjusted calibration scalar is correct.
```
get clo.field.cloudfactor
```

Replacing transmitter module - CL61

CL61 User Guide