Chapter 5 Parameters Definition
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Current Bkg Time/Rate: The rate is the background average rate that will be used to
calculate the net count rate during calibration. It can be updated by pressing F2. The
Bkg Time is the averaging time used to calculate the Bkg Rate; it indicates the quality
of the background average and should be near the Background Average Period
(default is 300 seconds) set in the F2 – Wait Timeouts screen when calibrating.
Discriminator and HV: current Discriminator V and HV settings for zone (for sum
zones this is the average of the detectors making up the sum zone).
Note: If the actual voltage value for the discriminator or the HV used during
calibration does not match the setting shown here, a Calibration Fault will
occur.
Auto Sequence Extra Time: This is to add additional time for specific detector
sections during an Auto Sequence Calibration to give time to get source into position
for particular zones. See Calibration Settings. Range is 0 to 30 s.
Factory Default Efficiency/Derived Efficiency/Manual Calibration/Calibrated:
The Calibration text box indicates the calibration method used and the date/time
when the zone was last calibrated, i.e. whether factory default, (F6 or Ctrl+F6, single
detection zone), derived (F6 or Ctrl+F6, sum zone), manual, or a calibration source
collection (F1). The text box updates when a new calibration is performed using F1,
F6, Ctrl+F6 or manually. There is no date/time associated with factory default or
derived efficiency calibration values.
The remaining line items provide the results and values used for the most recent
calibration, i.e. the zone calibration currently in effect.
Efficiency: The current value (to three significant figures) for zone efficiency, based
on factory default, manual entry or a calibration collection, as indicated on the
preceding line. Calibration Efficiency based on Activity is marked as 4π.
The minimum allowed Efficiency is 1%. Efficiencies below this value will generate
a Calibration Fault and will appear in red showing the last value(s) (see Not
Calibrated in F4 – Out of Service Causes on page 141 and Failure to Return to
Service on page 225).
In certain high background conditions or in other unusual circumstances, it may not
be possible to perform a normal calibration. An efficiency value can be entered
manually to allow the monitor to return to service. Select the Efficiency line item
and use the +/- keys or Ctrl+E to change to the new value. A maximum value of
100% can be entered; however the theoretical maximum is 50%
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if the Alarm
Activity is defined in terms of 4π geometry.
The remaining calibration related line items are blanked out and the text for the
Calibration line item changes to “Manual Calibration” plus the Date and Time.
Pressing F6 restores the factory default calibration. Factory Calibrations also render
the following lines blank. Derived efficiencies (for Factory Calibrations only) show
the derivations but none of the line items below.
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Note that Gamma sum zones, and in particular, Gamma Sum Zone All can be >50%.
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