Chapter 6 _______________________________________________________________ Maintenance
VAISALA _______________________________________________________________________ 173
The calibration procedure checks two points: a zero scatter signal and a
very high scatter signal. The zero signal is obtained using the zero plugs
and the high signal using the opaque glass scatter plates.
The visibility corresponding to the opaque glass calibrator signal is
approximately 3 to 4 meters. If the calibrator is used in precipitation, the
error will be proportional to the area of the scatter plates that is covered
with droplets. Make sure that this area is negligible compared to the total
area.
NOTE
Before the check and calibration, clean the windows and check the
condition of the calibrator glass plates cleaning them also if needed.
NOTE
Avoid scratching the glass plates since scratches will have a negative
affect on the results of t
he calibration.
FSM102 Calibration Check Procedure
The calibration check procedure is performed as follows:
1. Clean the windows following the instructions in section Cleaning
FSM102 Windows on page 169 and check the condition of the
calibrator glass plates, cleaning them also, if necessary.
2. In order to block the light path, install the zero plugs on both
receiver and transmitter optics (see Figure 47 below).
0201-076
Figure 47 Installing Zero Plugs
3. Give the OPEN command and go to the advanced level by giving
the command LEVEL 1.
4. Give the CALIBRATE CHECK command. The value produced
by the check command must be within the range of ±0.0001. If it is
not, there may be a hardware error.
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