USER'S GUIDE ____________________________________________________________________
118 __________________________________________________________________ M211187EN-C
Table 21
Warning Messages
WARNINGS
Reasons
WINDOW CONTAMINATED
Window contamination has increased and
caused the window transmission to drop
below 85% either in the transmitter or in
the receiver. The contamination
compensation is still reliable.
BATTERY LOW
Backup battery voltage low (<11 VDC),
limited operation time left
LED AGED
LED aged, required electrical driving power
increased, limited operation time left
Table 22
Indication Messages
INDICATIONS
Reasons
WORKING ON BATTERY
AC (mains) off, hood heaters not
operational
+12V OUTPUT
DISCONNECTED
+12 V output on the interface unit is
disconnected due to a short-circuit in the
output line. This has no effect on the
measurement but warning lights or other
options powered by this output will not
work.
HOOD HEATER FAULT
Hood heater not operational. Hood
temperature has increased less than 2 °C
within 5 minutes since the heater was
turned on by the automatic heater control
circuit.
NOTE: If operated only with battery or DC
power, set the hood heater OFF to prevent
this indication.
DEW HEATER FAULT
Dew heater not operational, no current
runs through the heater when it is on
Optical Contamination and Blocking
Monitoring
Optical contamination and blocking of both the transmitter and the
receiver are continuously monitored. The FS11 sensor monitors
contamination and blocking by measuring window contamination and
backscattered signals. The
CLEAN
command is used to set clean
reference values for the contamination and blocking signals. If the alarm
limit is exceeded in the backscatter measurement, the visibility data is set
as missing (/////) and an alarm is generated.
The transmitter backscatter is measured with an analog circuit using the
transmitter LED as a light source. The transmitter backscatter value is
higher with higher backscatter signals.