PCM-2 Manual.pdf - Voss Associates

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 may be 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.
TIze following values are displayed, but may not be edited:
Alpha & Beta
Backgrounds
Alpha & Beta
Alarm Levels
Alpha & Beta
RDA Levels
The current background count rates for this detector.
Net count rates (above background) at which this detector will alarm based on the
current backgrounds, RDAs, RDA confidence level, sigma factor, etc.
The activity levels which can reliably be detected within the allowed count time
given current background rates and using the specified RDA confidence level and
sigma factor.
Minimum Count Time Mode
System Parameters
In Minimum Count Time mode, the alpha and beta RDAs, confidence
factor, and sigma factors are specified when the PCM-2 is set up. In
addition, a maximum allowable count time is entered. If background
count rates are (or become) too high, it will not be possible to detect
sources of the specified activities (the RDAs) within the specified
maximum count time using the chosen confidence and sigma factors;
when this happens, the instrument will display a high background
failure message and cease to perform measurements until the condition
clears.
PCM2.MANI REV AI April 1995 5-9