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 2.GQ Geiger Muller Counter
 "CPM" appears to be counting ?
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esp

United Kingdom
4 Posts

Posted - 02/12/2020 :  08:19:18  Show Profile  Reply with Quote
I am considering purchasing the GMC-600+
In the following YT vid, the presenter holds the GMC-600 (ordinaire and plus versions) over low and high emitter specimens. I notice that during these times, the readings (CPM, uSv/h, mR/h) do not settle down. Indeed when plotted, they appear to be linearly increasing, as if it is the count itself rather than the count rate that is being displayed. Please what is the explanation for this?
Reply #1

EmfDev

1243 Posts

Posted - 02/12/2020 :  10:25:51  Show Profile  Reply with Quote
Hi esp could you please include the link to the youtube video? The CPM should start to increase and stable after 1 minute. But the current firmware should be able to become stable faster.
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Reply #2

esp

United Kingdom
4 Posts

Posted - 02/12/2020 :  15:15:55  Show Profile  Reply with Quote
Oops, I forgot the video link:
https://www.youtube.com/watch?v=BgrvhhY8rqE&t=104

I had expected the reading to fluctuate around some mean value right from the start, the amount of fluctuation decreasing with time, as the size of the count (and integration period) increased, but staying with the same mean.
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Reply #3

esp

United Kingdom
4 Posts

Posted - 02/12/2020 :  15:19:45  Show Profile  Reply with Quote
What is the integration period BTW? Is it one minute? Can it be varied (e.g. for very low background measurements)? Is it a sliding integration window after the first integration period has passed? And leading up to that first period, does the CPM value actually show just the count? I am trying to understand correctly. Many thanks.
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Reply #4

Damien68

France
241 Posts

Posted - 02/13/2020 :  04:33:15  Show Profile  Reply with Quote
I think the integration time is configurable,
now there is also a dynamic estimation mode: if the counter detects an abnormally high cps, it can reconstruct an estimate in fast mode (over 1 or a few seconds i don't know), which is very practical if you want to have a quick alarm faster than integrating over a minute for example but then requires verification / confirmation.

Mastery is acquired by studying, with it everything becomes simple

Edited by - Damien68 on 02/13/2020 04:34:47
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Reply #5

EmfDev

1243 Posts

Posted - 02/13/2020 :  10:09:35  Show Profile  Reply with Quote
There is a menu to change it in User Options->Fast Estimate time. The default is dynamic which means as Damien68 mentioned, if it detects a significant change in CPS, then it will estimate the CPM after few seconds and as CPS becomes stable the estimation becomes more accurate till 1 minute.
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Reply #6

esp

United Kingdom
4 Posts

Posted - 02/13/2020 :  11:17:18  Show Profile  Reply with Quote
Thank you!
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