Fluke Biomedical 942A-200L-M4 - Manual (Page 51)

Operation
Alarms
3
3-11
WARN Alarm
The WARN alarm condition is “true” when the display CPM rate is greater than or equal to the WARN
alarm set point and "false" for all other conditions.
The standard logic for the WARN alarm is fail-safe, manual reset.
When the WARN alarm is tripped, the amber WARN alarm indicator begins flashing, the bargraph goes to
amber, the WARN alarm relay coil de-energizes. When the alarm is acknowledged, the WARN alarm
indicator goes steady on. The auxiliary output on the UDR can be used to drive a remote alarm/alarm
indicator.
RANGE Alarms (UNDERRANGE, OVERRANGE and ANTI-JAM)
The underrange condition is “true” when the CPM rate is below the underrange setpoint and “false” for all
other conditions. The RANGE indicator illuminates, the bargraph is off, and the display reads 0.00 CPM
when the underrange condition is true. The Alarm, Warn, and Fail relays are not affected by the
underrange alarm. The underrange alarm is factory set to 10 cpm.
The overrange is true when the CPM rate is greater than or equal to the overrange set point or the
detector is sending an output pulse greater than the UDR electronic Anti-Jam circuit threshold. The
condition is false when neither of the above conditions is true.
When the OVERRANGE alarm is tripped, WARN and HIGH alarm logic is tripped, the red RANGE
indicator illuminates steady on, the bargraph illuminates red, and the display reads EEEEE.
The OVERRANGE alarm must be reset by pressing the acknowledge pushbutton when the overrange
condition is false (i.e. radiation level returns to a value below the overrange setpoint). The OVERRANGE
alarm will not reset automatically, at a later time, after the acknowledge pushbutton is pressed as it does
for the HIGH and WARN alarms.
If auto reset is selected for HIGH and WARN alarms, these will reset automatically, but the overrange
display will remain until the acknowledge pushbutton is pressed. In addition, if the detector output is
above the electronic anti-jam circuit threshold, the anti-jam circuit will be activated, opening the anti-jam
fuse on the UDR. This causes the fail relay to change state and the detector high voltage to turn off,
indicating a non-operational mode. To return to normal operation, the ambient radiation must be reduced,
the UDR AC power cycled ON/OFF and the anti-jam fuse replaced.
FAIL Alarms
Several equipment failure conditions are monitored which produce a FAIL alarm and in some cases an
error message. The fail condition is “true” whenever any equipment failure is detected and “false” when
no equipment failures are detected. When a fail condition occurs, other than power failure, the red FAIL
alarm indicator illuminates and the fail relay coil de-energizes.
The FAIL alarm logic is always fail-safe, auto reset.
The following are the fail alarms included in the 942A-200-M4 and 942A-200L-M5 UDR:
1. NO COUNT Failure
2. POWER Failure
3. MPU Failure (hardware)
4. Anti-Jam Trip