USER'S GUIDE ____________________________________________________________________
84 __________________________________________________________________ M210543EN-F
Cleaning
It is important to clean PWD22/52. No specific operations are necessary
before cleaning the sensor and it is possible to use the service terminal
while cleaning. Some erroneous data may, however, be generated. To
minimize this problem, restart PWD22/52 after cleaning by pressing
power OFF/ON.
Cleaning Lenses and Hoods
The lenses of the PWD22/52 transmitter and receiver units must be
relatively clean to get reliable results as dirty lenses give too good
visibility values. Clean the units at least every six months, more often if
the conditions require it (for example, if there are roads nearby).
The hardware alarm field of the data message (2nd character on the
message) indicates when cleaning is needed. See section Message Types
on page 52.
Number 3 = backscatter alarm indicates that the contamination level is
too high and cleaning must be done at once. The measurement values are
not shown in the data message.
Number 4 = backscatter warning indicates that the contamination level
has increased and cleaning must be performed in the near future. The
measurement values are still reliable and are shown in the data message.
To clean PWD22/55 and PWL111 lenses and hoods:
1. Moisten a soft, lint-free cloth with isopropyl alcohol and wipe the
lenses. Be careful not to scratch the lens surfaces.
Confirm that the lens heating works by checking that the lenses dry
after wiping.
2. Check that the hoods and lenses are free of condensed water, or ice
and snow deposits.
3. Wipe the dust from the inner and outer surfaces of the hoods.
4. After the optical surfaces are properly cleaned, give the CLEAN
command.
It is not necessary to give the
CLEAN command after every cleaning.
, give the STA command and check that the Backscatter
value of both the receiver and the transmitter is close to zero
(set to zero by the previous
CLEAN command).
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