Vaisala PWD22 - Page 107

Appendix A __________________________________________________ Internal Monitoring Values
VAISALA ______________________________________________________________________ 105
APPENDIX A
INTERNAL MONITORING VALUES
Typical values come from factory testing and may change within the
given Min/Max limits. Fault limits give hints for troubleshooting.
Table 24 STA Message Values
Status Message
Typical
Min. / Max.
Fault
Description
Action
AMBL
Ambient light
-0 V
-9 V / +3 V
> 3 V
'RECEIVER
ERROR'
Preamplifier is
not working.
Change
PWC22/52.
< -9 V
'RECEIVER
SATURATED'
The sun is
shining directly or
from reflecting
surface such as
snow, to the
receiver.
Check the
orientation of
PWD22/52
OFFSET
Measurement
signal offset. The
lowest frequency
for measurement
signal
140Hz...
150Hz
80 Hz /
170 Hz
< 80 Hz
>170 Hz
'OFFSET
ERROR'
Drifting may be
caused by other
disturbing
optical sensors
nearby or other
interference
problems.
1) Check
other parts of
STA
message.
2) If offset
does not
remain stable,
change the
control unit
PWC22/52.
REC. BACKSCATTER
Measurement
signal from the
receiver
contamination
control circuit.
'CHANGE' value
is the instant
signal difference
to clean value.
Rec.backscatter
change (Instant
backscatter
minus clean
backscatter) >
alarm limit
'BACKSCATTER
HIGH'
Rising value can
be caused by
contamination of
receiver optics,
snow inside the
receiver hood,
spider net in front
of the hood etc.
Check the
contamination
limits also.
Clean the
outside of
optical
surfaces and
remove
possible
disturbances
from optical
path.