Fluke Biomedical 956A-201-M2 - Manual (Page 36)

3-10
The WARN alarm is normally inhibited in Check Source mode. By removing jumper JP3-5, the HIGH and
WARN alarms may be enabled in Check Source mode.
The firmware will not accept a Warn setpoint that is higher than the High setpoint. ON the 956A-201-M2
Error Code E0004 will be displayed.
RANGE Alarms
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 Alarm, Warn,
and Fail relays are not affected by the underrange alarm.
The underrange condition clears automatically when the detector output returns within the normal range.
There is no relay associated with the UNDERRANGE alarm.
The OVERRANGE is true when the dose rate is greater than or equal to the overrange setpoint or the
Model 897A preamplifier is sending an output pulse greater than the detector preamplifier Anti-Jam circuit
setpoint. The condition is false when neither of the conditions are true.
When the OVERRANGE 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 OVERRANGE alarm setpoint is operator adjustable.
In addition to the display of EEEEE when in Overrange, the
mR/h engineering units will be displayed if the HIGH or WARN
front panel set point display pushbuttons have been accessed.
IF desired, the mR/h units display may be cleared by either
pressing the ENTER push button, or cycling the UDR power
OFF/ON. The mR/h unit’s display, however, does not affect the
operation of the Overrange function.
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 of the UDR, the anti-jam
circuit will be activated, opening the anti- jam fuse on the UDR. This causes the Fail LED to turn on, the
Fail relay to change state, and the detector High Voltage power supply to turn off indicating a non-
operational mode. After the anti-jam condition has cleared, to return to normal operation, the 956A UDR
must be powered off, the anti-jam fuse replaced, and the power turned back on.
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.
NOTE