PCM-2 Manual.pdf - Voss Associates

Where:
R bkg = The new computed average background count rate
Raid = The previous computed average background count rate
WF= Weight Factor
R new = The most-recently measured (real) background count rate,
measured in a single count time interval.
Beta Shield Factor
When the instrument is occupied, some detectors are shielded from local radiation
sources which account for part of the observed background. The shield factor is
defined as background while occupied divided by background while unoccupied.
Note: Alpha channel shield factors are always equal to 1.
The following values are displayed, but may not be edited:
Alpha & Beta
Backgrounds
Alpha & Beta
Alarm Levels
Alpha & Beta
RDA Lower Limits
Count Time
The current background count rates for this channel.
Net Count rates (above background) at which this channel will alarm based on the
current backgrounds, RDAs, RDA confidence level, sigma factor, etc.
The minimum RDA values which could be specified for this channel given the the
present backgrounds, count time, confidence and sigma factors.
The shortest count time which this channel can use to detect the specified RDA at
present background levels.
Fixed Count Time Mode
System Parameters
In Fixed Count Time count mode, the confidence factor, sigma factors
and count time are specified when the PCM-2 is set up. In addition,
upper limits for alpha and beta RDAs are entered. If background
count rates are (or become) too high to permit reliable detection of
these activities in the time allowed, the instrument will display a high
background failure message and ceases to perform measurements.
PCM2.MI\N/ REV I\/I\pril 1995
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