Protean Instrument Corporation
123
Concepts MPC
900
Calibrated
Conversion
Factors
In order to report accumulated counts in terms of activity, several conversion factors
must be determined and applied. Determination of these conversion factors constitutes
the instrument calibration.
Once determined, conversion factors must be revalidated on a routine basis to insure
instrument stability. This is accomplished (usually daily) by collecting counts from a
standard and comparing the results to those obtained during the calibration. If these
results repeat within statistical expectations, the instrument is stable and the calibration
conversion factors are valid.
The
Control
Chart
Revalidation procedures are called control checks. Control checks are usually plotted
on a chart representing a control mean and the standard deviations of the control mean.
This chart is referred to as a control chart. Several control charts are usually
maintained (e.g., one for an alpha standard, one for a beta standard, and one for
background).