Campbell Scientific PWS100 Present Weather Sensor - Manual (Page 104)

Section 10. Troubleshooting
10.2.3 Ice has formed in the end of the hoods
The heaters may not be working. Enter the command mode of the sensor, run
DIAGSET with the following command:
DIAGSET 10 102
Ensure that the laser hood temperature (first value following the 9000 and 0
output) is above zero. If it is not then it is possible that the heaters may not be
active or may need servicing.
To check the settings of the hood heaters use the SETCONFIG command.
Ensure that the fifth value is between 10 and 50 (temperature setting). If this is
set to 0 then the hood heaters are off and should be set between 10 and 50. If
the hood heaters are on but ice is still present set the hood heaters to a higher
temperature. If this does not clear the ice then the hood heaters may have
failed. Contact Campbell Scientific in this instance.
If the heater settings are correct and only some of the hoods are clear and
others not then it is possible that a single heater may have failed. Contact
Campbell Scientific if the problem persists.
10.2.4 The visibility output is clearly in error
Ensure that the sensor is placed in a location free from obstructions which may
cause erroneous scatter into the sensors. Following the installation instructions
in this manual is sufficient.
If the sensor still gives erroneous output then it is possible that the lenses have
become contaminated. Refer to Section 9.2 for cleaning the lenses.
10.2.5 The sensor does not detect particles during a
precipitation event
It is possible that the lenses have become overly contaminated. Refer to
Section 9.2 for cleaning the lenses. If there is no contamination, the laser may
have failed, check with a commercial power meter if available. If there is no
contamination and the laser output is within accepted limits, then hardware
reset the sensor (see Section 6.3.10, Load Factory Defaults).
The PWS100 samples only a small area and in events where
precipitation is falling but with high spatial separation then there
may be periods where no particles fall through the volume but an
observer looking at a larger area observes some particles. NOTE
10.2.6 The sensor detects particles when there are none
present
Although the sensor uses sophisticated processing routines to determine
particle types and eliminate false alarms, under certain conditions the sensor
may report the incidence of particles in the detection volume when an observer
does not. There are possibly several reasons for this. Firstly it should be
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