Ceilometer CT25K
CT25K-U059en-2.1 User’s Guide
105
8.4.3 Compensation adjustments
Internal crosstalk compensation must be adjusted after a transmitter, a
receiver or an optics monitor has been replaced or if the compensation fiber
has been replaced. Adjustment should be done in clear weather conditions or
indoors using the Optical termination hood (CT25184).
After the command set has been opened using the password ADVANCED
give the following commands:
1. To interrupt autoadjustments give the command
STOP↵
Then give the following commands:
SET DATA_ACQ AUTOADJ OFF↵
SET PORT TIMEOUT 20↵
which set the autoadjustments off and the timeout of the dialog to 20
minutes.
2. Give values for fine and coarse compensation as follows:
SET DATA_ACQ COMP COARSE 13↵
SET DATA_ACQ COMP FINE 125↵
3. Wait until a few measurement cycles have been completed. To monitor
the quality of the compensation give the command
SET OPER_MODE COMP_MONIT↵
which gives you a graphical output as shown in Figure 8-4.
In case the graph differs from the graph shown in Figure 8-4, you have to
adjust the Compensation light level manually. This is done via Screw B
(Compensation light level adjustment) on the receiver CTR21 using a 1.5
mm hexagon key (See Figure 8-3). Later revisions of the receiver have a
locking nut on screw B; if so, loosen it first. Turn the screw either
clockwise or anticlockwise to optimize the form of the graph. If the peak
of the graph broadens, change the direction.
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