Visibility Value Is Continuously Too Good; Visibility Constantly Too Low - Vaisala PWD22/52 User Manual

Chapter 7 ___________________________________________________________ Troubleshooting
VAISALA _______________________________________________________________________ 95
Visibility Value is Continuously Too
Good
This can be caused by several reasons. Most probably the light path from
the transmitter to the receiver is disturbed.
1. The lenses may be excessively contaminated. A warning has been
received.
- Clean the lenses (see section Cleaning Lenses and Hoods on
page 82).
2. One of the hoods has been filled with snow, leaves, or something
similar. A warning is generated.
- Clean the hoods (see section Cleaning Lenses and Hoods on
page 82).
3. There is condensation on the lens surfaces. This is a sign of heating
failure.
4. There is an electrical fault in the transmitter or receiver.
- Check the status information with the STA command (see
section STA on page 73).
- Go to section Message Exists but Visibility Value Does Not on
page 94.

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 29.
3. Electrical fault. See items in section Message Exists but Visibility
Value Does Not on page 94.