Vaisala LM21 - Page 36

User's Guide ________________________________________________________
36 _____________________________________________________ M210283en-A
2. Check that the assembly of the hoods and optics is free
of water condensation and ice or snow deposits.
3. Wipe the dust from the inner and outer surface of the
hood.
NOTE
Do not use any sharp tools to remove ice or snow from the
hood, especially from its heated surface. This can easily
break the heating foil. Do not try to insert any tools under
the foil, because the foil glue may then fail to hold the foil
on the hood surface. It is essential, that the foil is firmly
attached to the hood surface, otherwise the heat transfer
from the foil piece to the hood is impaired resulting in a
burned foil.
4. After the optical surfaces are properly cleaned, check
that the WINDOW CONT value of Background
Luminance Sensor in the status message is close to
zero.
NOTE
The window must be dry before checking the WINDOW
CONT values.
5. If the WINDOW CONT value is not close to zero, give
the command CALIBRATE WINDOW_CLEAN
BL_SENSOR (if the maintenance terminal is
connected to the FS11 maintenance line), or the
command CALIBRATE WINDOW_CLEAN (if the
maintenance terminal is connected to the LM21
maintenance line in an FD12P or MITRAS
installation). These commands have no parameters and
they are used to set the clean reference for the
contamination control.