Chapter 4 Unit Setup
92
8. Use the Page Up/Page Down keys to select each detection zone in turn and
verify that the “Efficiency” is consistent for zones with similar geometry.
Expected differences between efficiencies for foot detectors and body detectors,
for example. Repeat Steps 3 through 6 above for any zone that indicates an
efficiency much different from the others.
9. Repeat Steps 5 through 8 above using a Gamma calibration source to calibrate
all Gamma detectors (#1, #2, #3, #4, #5, #6, #7 and #8).
Following calibration, review the Low Background Rate setting for all detectors on
the (Zone) Settings screen on page 116. Refer to Low Background Rate Setting and
Strategy on page 282.
The calibration results and current efficiencies for all detection zones can be reviewed
using the F3 – Calibration Printout (on page 257) and F4 – Calibration Data
Printout (on page 258) screens.
Note: If all zones have been recently calibrated then the Due For Recalibration date
should be updated on the F4 – Out of Service Causes screen (on page 141),
particularly if the unit is set to go Out of Service for the Due For
Recalibration fault condition.
Factory Default Calibration
If it is not possible to perform a full calibration as described above, it may be
acceptable, though not recommended, to use factory default efficiencies since all
Mirion Technologies (Canberra CA) Ltd. detectors respond within a statistically
tight range of efficiency values. Factory Defaults are based on a large sampling of
detectors calibrated against sources traceable to NIST. These settings can be
recalled by pressing Ctrl+F6 on the F3 – Calibration screen (on page 121). This step
must be repeated for each detection zone. This sets the monitors to a conservative
operational status for use with most types of contamination typically found.
See the appendix, Spare Parts Lists – Standard Models, starting on page 377 for
Factory Default information and see Algorithms appendix on page 270 and
Efficiency Calculation (and Derived Efficiencies) starting on page 291 as well.
Shift + F3 - Calibration Settings
See Section Shift+F3 - Calibration Settings on page 127.
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