USER'S GUIDE ____________________________________________________________________
86 __________________________________________________________________ M210543EN-F
When calibrating visibility measurement, make sure that visibility is 500
meters or higher. Calibration is not recommended in heavy rain or in
bright sunshine. Bright sunlight on the calibrator plates increases noise in
the scatter measurement and makes the CHEC command output less
stable. However, light rain does not matter.
Calibration Check
The calibration check procedure determines whether or not the unit needs
calibrating. Before performing the calibration check:
- Clean the lenses following the instructions in section Cleaning Lenses
and Hoods on page 84.
- Check the opaque glass plates and clean them if necessary.
To perform the calibration check:
1. Block the light path by placing the blocking plate in the receiver
hood and wait 30 seconds.
2. Give the ZERO command.
PWD22/52 responds as follows:
ZERO SIGNAL: OK
3. Move the blocking plate.
4. Install the calibrator plates on the lens hoods. See Figure 19 on
page 87.
5. Fasten the opaque glass plates to the hoods.
Note the signal value printed on the plates, you will need it during
the following steps.
6. Move away from the optical path and wait 30 seconds.
7. Give the CHEC command.
8. After one minute, read the displayed signal.
9. The signal value must be close to the one printed on the plates. If
the difference is less than 5 %, calibration is correct. If not,
continue with the calibration procedure.
10. Press the ESC key to terminate the CHEC command.
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