Vaisala FD12P - Manual (Page 138)

User's Guide _______________________________________________________________________
138 _____________________________________________________ M210296en-A
Table 29 Values for Internal Monitoring
Message Typical Min/
Max Fault Description Action
DUTY
Indicates the pulse
ratio in lock-in
amplifier circuit. 1.6 V +1 V/
+2.5 V <1 V
>2.5 V
0.0 V or 5 V
Synchronizing signal
from the receiver to the
transmitter is missing.
The oscillator of the
transmitter is not working.
1.Check condition
and contact of
-flat cable
-connectors
2. Change the
receiver.
1. Change the
transmitter.
AMBL
Ambient light. -0 V -9 V/ +3
V >3 V
<-9 V
Preamplifier is not
working.
The sun is shining
directly or from reflecting
surface (water, window,
etc.) to the receiver.
1. Change the
receiver.
2. Check orientation
of FD12P.
VH
Lens heater. 0.8 V +0.6 V/
+1.2 V <0.2 V No heating current is
flowing. 1. Check that the
jumper X13 (CPU) is
1-2 or 2-3.
OFFSET
The lowest
frequency for
measurement
signal. 130 Hz 120 Hz/
150 Hz <120 Hz
>150 Hz 1. Check other parts
of the STA
message.
2. Change the
receiver.
REC.
BACKSCATTER
Measurement
signal from the
receiver
contamination
control circuit.
Clean value. Rec.
backscatter
CHANGE
(Instant
backscatter -
clean back
scatter >
alarm limit
'BACK-
SCATTER
HIGH'. Alarm that there is
obstruction in the light
path. Rising value can be
caused by -
contamination of receiver
optics - snow inside the
receiver hood - spider net
in front of the hood, etc.
Check also the
contamination limits. Clean outside of
optical surfaces and
remove possible
disturbances from
the optical path.
Rec.
backscatter
CHANGE
(Instant
backscatter -
clean back
scatter >
warning limit
'BACK-
SCATTER
INCREASED'. Warning that there is
small obstruction in the
light path or increased
contamination on the lens
surface. Indication that
optical surface should be
cleaned in the near
future. Clean the optical
surfaces in the near
future. The
measurement values
are still reliable.