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User's Guide _______________________________________________________________________
102___________________________________________________________________ M210543EN-B
Visibility Constantly Too Low
Usually there is something disturbing the sample volume.
1.
Check the condition of the hoods. If the hoods are twisted,
consult Vaisala.
2.
Try to find a better direction for the receiver/transmitter optics.
See section Selecting Location on page 37.
3.
Electrical fault. See items in section Message Exists but
Visibility Value Does Not on page 101.
PWD22 Reports Precipitation When
There Is None
In temperatures under 0 °C, only the optical measurement is used in
detecting precipitation. In temperatures above 0 °C, the RAINCAP
detection is used in cross-checking the optical detection, and false
detection can only be caused by problems in both measurements.
1.
Check that there are no flashing lights close to PWD22. Flashing
lights may cause PWD22 to detect peaks in the optical signal.
2.
Check that there are no foreign objects in the sample volume.
Tree branches or other moving objects may cause sudden
changes in the scatter signal.
3.
Check that receiver is not facing cars passing by. If the sun
beams are reflected from the passing cars towards the receiver,
this could cause false precipitation reports especially in the
winter. These short sun beam reflections can cause short spikes
to the PWD22 optical signal and they are interpreted as light
snow. This might even happen if there are sharp changes of the
lighting condition of the ground where the receiver is looking at.
If the area where the receiver is looking at is bright and shiny
and passing cars cause shadows to that area, it might be possible
that it will cause similar short spikes to the receiver signal.
4.
If the false detection has occurred in temperatures above 0 °C,
®
RAINCAP
does not function correctly. The RAINCAP
sensing surfaces should be thoroughly cleaned.
®
®
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Table of Contents
Troubleshooting
