PCM-2 Manual.pdf - Voss Associates

System Parameters - Min Count Time Mod
ALPHA RDA (DPM):
5000
BETA RDA (DPM): 25000
ALPHA SENSITIVITY: 0.050
BETA SENSITIVITY: 0.10
RDA CONFIDENCE: 95%
MAX COUNT TIME (SEC): 60
SIGMA FACTOR: 4.00
BACKGROUND SIGMA FACTOR: 4.00
ALPHA SUM ZONE ALARM (DPM): 1400
BETA SUM ZONE ALARM (DPM): 7000
ALPHA SUM CH ALARM (DPM): 5000
BETA SUM CH ALARM (DPM): 30000
~calCulated Values
II COUNT TIME (SEC): 1.00
FALSE ALARM RATE (%): 0.16
J
Alpha & Beta RDAs
Alpha & Beta
Sensitivities
RDA Confidence
Max Count Time
Sigma Factor
Background
Sigma Factor
These are the Reliably Detectable Activities used to compute alarm setpoints for
the alpha and beta channels. Values entered here will be copied to all detector
channels. Individual detectors may later be changed.
A ratio above and below the mean of background counts beyond which a single
detector's background is determined to be indicative of a detector failure. The
default value is 0.5, meaning that a detector with more than twice or less than half
as many counts as the system average is considered suspect. Note that because
the size, location and orientation of a detector affects its background counts, each
detector has a Geometry Factor which is used to compensate for these variables.
This is the probability of detecting contamination of the specified RDA. Possible
values are 50 %, 75 %, 90 %, 95 %, 99 %, and 99.9 %. Refer to the manual section
on statistical algorithms for a detailed discussion of this parameter.
The longest acceptable count time which the PCM-2 may use for measurements.
If increases in background levels require a measurement time exceeding this
value, a high background alarm condition occurs.
A multiplier of the average background count rate standard deviation which
influences the false alarm rate. Refer to the section on statistical algorithms.
If a background update count differs from the computed average background rate
by this many standard deviations, the new rate will immediately replace the old.
If the detector(s) on which this occurs alarmed on the last measurement, they are
assumed to be contaminated.
5-10
P"M?MAr--I/ Rpv Ail\pril 1995