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Alchemy2
Canada
89 Posts |
 Posted - 07/26/2014 : 23:47:44
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I recently checked my counter with a Uranium ore sample that is rather "hot"; my counter seems to limit at 3000CPM, and the dosage when peaking over 22uSv/h shows a value of around 9-10uSv/h.
Once the unit is placed back a bit from the sample, the "9" value then goes to ~21, and begins to drop. This suggests to me that the counter or at least the tube is saturating near 20ms pulse time, which means that the max dose rate claimed in the manual must be in error.
Any suggestions? ZLM?
Thanks in advance...
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The more I learn, the more I realize I do not know! |
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| Reply #1
Alchemy2
Canada
89 Posts |
Posted - 07/26/2014 : 23:50:02
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Oh, and I tried resetting again to factory and this still shows up when I use 151 CPM = 1.00uSv/h cal range.
quote:
Originally posted by Alchemy2
I recently checked my counter with a Uranium ore sample that is rather "hot"; my counter seems to limit at 3000CPM, and the dosage when peaking over 22uSv/h shows a value of around 9-10uSv/h.
Once the unit is placed back a bit from the sample, the "9" value then goes to ~21, and begins to drop. This suggests to me that the counter or at least the tube is saturating near 20ms pulse time, which means that the max dose rate claimed in the manual must be in error.
Any suggestions? ZLM?
Thanks in advance...
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The more I learn, the more I realize I do not know! |
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| Reply #2
Alchemy2
Canada
89 Posts |
Posted - 07/27/2014 : 10:54:28
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I Figured it out!
If you set the cal3 point to say, 10usv/h on a CPM reading, the firmware will show a sort of over range display as being out of range.
So, while the default settings are linear at ~200CPM = 1.0uSv/h throughout the ranges, anything over 10uSv/h will get a funny display.
My tube was able to read CPM>3000, so it is the settings of the calibration that affect the displayed readings.
I found that using my dosimeter calibrated to Cs137, that various sources were reading a trend downward in CPM:uSv/h dose equivalent.
At closer to 3000CPM, the relation was closer to 105 vs around 150 for the low counts. Mid ranges (in the 1000CPM values) are about 133 or so, certainly in the 125-135 range.
The non-linearities are subject to proper calibration, though I am curious (ZLM?) whether the unit calculates a weighted average when between two calibration points if their values differ significantly.
Anyway, no worries from a display sense, just extrapolate to larger values >20uSv/h if you plan to measure sources like this.
CPM reads fine, though.
Alchemy2 |
The more I learn, the more I realize I do not know! |
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Does the 4011 tube saturate?
