SAM 950 Berkeley Nucleonics Corporation 49 of 62
Figure 5.15. Attaching photo procedure
AUTO CALIBRATION AND STABILIZATION
The auto calibration and stabilization feature adjusts the calibration parameters of the system to correct for
any drift caused by environmental changes (generally ambient temperature).
Auto calibration is automatically executed when the SAM 950 is powered up (refer to figure 2.45). If user
determines to cancel the auto calibration, it can be stop by touch ‘Cancel’ button. The auto stabilization is
executed every 3 minutes unless the unit is in alarm status.
When auto calibration and stabilization is executed the system automatically adjusts its gain using radiation
generated by the K-40 radionuclide found in natural potassium. The 1.4 MeV peak from the K-40 nuclide
present in naturally occurring potassium is utilized. A calibration source is not needed. KCl powder is
already securely installed if it is desired to achieve stabilization in a shorter time, as might be in the rare case
of a location where there are unnaturally low levels of potassium. The stopping criteria for this automatic
feature are the integrated counts in the K-40 peak. The stopping criteria for this automatic feature is the
integrated counts in the K-40 peak. The value for the integrated counts is defined in the setup configuration.
Typically 5,000 counts are recommended in order to ensure that the stabilization K-40 peak is well defined.
Supplemental Potassium Chloride (KCL) salt can be used to assist the stabilization if necessary.
If drift of more than ± 6% between the stabilized peak and the original peak (Cs-137 calibration peak)
occurs then re-calibration using a Cs-137 source is required.
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