Fluke Biomedical 945A - Manual (Page 33)

RANGE Alarm
The underrange condition is "true" when the dose rate is below the underrange setpoint and "false" for all
other conditions. The RANGE indicator illuminates, the analog output is set to zero, and the display
reads 0.00 mR/h when the underrange condition is true. The bargraph will operate normally.
The underrange condition clears automatically when the detector output returns within the normal range.
There is no relay contact associated with the underrange alarm.
The overrange is true when the dose rate is greater than or equal to the overrange set point or the
preamplifier is sending an overrange status to the UDR. The condition is false when neither of the above
conditions is true.
When the OVER RANGE alarm is active; WARN and HIGH alarms are true, the red RANGE indicator
illuminates, the bargraph illuminates red, the analog output reads full scale, and the display reads
EEEEE. The default overrange setpoint is 1.00E7 mR/h.
Once the radiation value is less than the setpoints, the overrange condition may be manually reset to
return to normal operation. There is no relay contact associated with the overrange alarm.
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 946A-200 UDR:
1. LOW SIGNAL Failure
2. AUTO ZERO Failure
3. HIGH VOLTAGE Failure
4. LOOP Failure (communications)
5. POWER Failure
6. MPU Failure (hardware) in either detector or UDR
Low Signal Failure
If the dose rate reported to the UDR by the preamplifier is zero for five minutes, a low signal failure is
detected. A low signal alarm usually indicates a failure in the electrometer since normal leakage currents
will result in a non-zero dose rate. The UDR display may read zero for five minutes or more without a low
signal fail alarm. In this case, the preamplifier is reporting a dose rate that is below the underrange
setpoint value. The low signal failure alarm can be disabled by removing jumper JP3-4 from the UDR
main board. Error code E0011 will be displayed under the fail conditions given.
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