Chapter 6 Diagnostics/Maintenance
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The F1 – Rate Meter screen displays the detector number in the left-hand column,
with the gross count and count rates in the adjacent columns. The count rates are also
represented on a bar graph that employs a log scale. The initial log scale is from 1
cps to 100 cps. The range is automatically expanded to encompass values measured.
Above the bar graph the Count Time for the previous update, the Dwell Time
remaining for the current update (if Dwell Time > 1 s), and the full-scale setting are
displayed.
This screen includes two active controls for the display refresh. The F1 key forces an
immediate refresh of data. The Dwell Time setting determines the nominal counting
time between automatic screen refreshes. A short dwell time (default =1 s) provides
the most active display, but since statistics are poor, there is more fluctuation of the
readings. A longer dwell time (the maximum is 99 s) allows easier interpretation of
data, since the readings are more stable and there is more time to read the values.
Use F6 to restore the factory default setting (1.0 second). When printing this screen,
set the dwell to a time suitable for your specific printer.
Placing a source in front of a detector will confirm that the detector is responding to
external radiation. This screen is also effective for showing trainees how radiation
affects detectors. Holding a source tight against the center of a detector will result in
the count rate of one detector increasing. Holding the same source farther away from
the detector results in an immediate drop in count rate, but neighbouring detectors
may then see the source and show an increase in their count rates. This
demonstration could be used to explain why the summing of adjacent detectors is
important in radiation detection.
Note that this screen briefly indicates “Ramping HV” while the HV is ramping. This
occurs for normally less than two seconds but can be up to thirty seconds if the High
Voltage on one or more of the boards is not working properly. Use this information
to help troubleshoot detector/preamplifier problems.
For performing geometry, uniformity and similar tests where simultaneous “raw”
count rates are needed from each detector, one can save results to a CSV file by
doing the following:
1. Press F2 to save results or Ctrl+F2 for “Save As…” prompt for file name.
2. Default File name is “RateMeter” and default folder is
“D:\MonitorProgram\DATALOG”.
3. A four-digit number is appended to the file name.
4. The file extension is always CSV.
5. There is a Prompt setting with choices of “None”, “Beep” or “Message”, default
is “Message”.
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