Chapter 4 Unit Setup
90
− Set High Voltage Levels – The factory default high voltage for Gamma
detectors is 650 V but this is not necessarily the “optimum” voltage
setting. The settings should be reviewed and adjusted if required using
the F1 – Optimize Gamma HV screens on page 82.
Following any High Voltage or discrimination level(s) adjustment a new
background count should be collected for at least the Background Average
Period (default = 300 s). This can be accomplished conveniently using to the
F12 – Background Trend Graph on page 212), which is accessed from the
F2 – Test Menu. Remember to remove all radioactive sources from the area
and vacate the monitor (to prevent self shielding) during the background
collection.
2. Edit the Calibration Source List (if necessary).
The calibration procedure requires that the certificate data for the calibration
source(s) used be entered in the built-in Calibration Source List. This
information is usually entered only once for each of the sources that could
potentially be used for calibration. The source data are entered and edited using
the F9 – Edit Calibration Source List screen on page 137.
3. Open the Calibration Setup screen (see the Shift+F3 – Calibration Setup
screen on page 127).
Choose settings to change as required.
4. Set Group and/or Global Settings Values (optional).
Review and update settings for Calibration Source in the F5 – Group screen
(on page 127) and/or Shift+F5 – Global Settings screen (on page 131). Select
appropriate calibration sources for Gamma calibration.
5. Open the Calibration screen (see the F3 – Calibration screen on page 121).
6. Perform Background Collection (optional).
This step can be skipped if the monitor, including all the detectors, has been in
operation in its present location sufficiently long to collect a reasonable
background value or if the background average was updated at Step 1 above.
Remove all sources from the area and vacate the monitor during the
background collection.
Press Ctrl+F2 = Initialize All Background. This performs the Initialize
Background routine, which updates the Average Background Rate for all
detection zones. “Please Wait Initializing Background” is displayed during this
time. The result for the currently selected zone appears in the Current Bkg
Rate text box.
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