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 2.GQ Geiger Muller Counter
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Discopotato

Australia
3 Posts
Posted - 05/05/2025 :  02:54:49  Show Profile  Reply with Quote
Hi everyone
I recently just bought a GMC-600 but when I trst against a uranium glass bowl I have the responds very well to black light the max reading im getting is 36cpm
I don't know, I no expert at all but shouldn't I be seeing atleast 500cpm on something like this?
Reply #1

ullix

Germany
1196 Posts
Posted - 05/05/2025 :  04:06:33  Show Profile  Reply with Quote
36 CPM is barely background, and could well be just electronic noise with a broken Geiger tube.

Can you try some other stuff as readio-source? Potassium, e.g. If you are unfamiliar, I suggest my article "Potty-Training" as a primer.
https://sourceforge.net/projects/geigerlog/files/Articles/
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Reply #2

Discopotato

Australia
3 Posts
Posted - 05/07/2025 :  13:31:09  Show Profile  Reply with Quote
So in the mean time i pulled the back cover of the gieger counter and put in a plastic snap lock bag and the readings came up to roughly 80-90cpm but the ticks are not a consistent tone. Is that normal?
I did have a quick read of the article you directed me too
Also what is the best setting to use for fast estimate, dynamic?
Edited by - Discopotato on 05/07/2025 13:37:22
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Reply #3

ullix

Germany
1196 Posts
Posted - 05/09/2025 :  02:50:53  Show Profile  Reply with Quote
What radioactive source did you use? How was the counter place in your room? CPM80-90 would be a lot for just background.

The sequence of clicks is a random distribution. To be more prceise: a Poisson distribution. Google for it, and/or use GeigerLog to see it yourself.

The "Fast Estimate" is the worst feature of the GMC counters I can think of. I urge erveryone to switch it OFF by setting it to 60 sec.
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Reply #4

ihab17

Italy
220 Posts
Posted - 05/09/2025 :  12:02:10  Show Profile  Reply with Quote
Either you do not have a real Uranium sample, or your device is broken (in case you were using it the right way). Can you post a short video somewhere to see what and how are you using it?
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Reply #5

Discopotato

Australia
3 Posts
Posted - 05/10/2025 :  03:24:21  Show Profile  Reply with Quote
The uranium source i used was a glass bowl i bought, advertised as uranium glass.
The counter back plate was removed and placed in a snap lock sandwich bag and than placed inside the bowl on my loungeroom table
For reference the background here is around 24cpm and 80-90 in the bowl
If i have the back plate on i get around 36cpm for memory.
Edited by - Discopotato on 05/10/2025 03:25:26
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