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 2.GQ Geiger Muller Counter
 500+ False readings
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CrocodileDandee

Australia
55 Posts

Posted - 07/14/2020 :  03:38:58  Show Profile  Reply with Quote
I just realized I can bring up my Geiger counter far over 100 CPM just using in a plastic case rubbing the case from outside. Why? Is that why there is not a clear plastic cover for this device available? I turned Tube 1 only on or both, it doesnít matter I can easily just with rubbing the plastic from outside make my Geiger counter getting wild....
P.S.: it happens only where the black tube is.

Edited by - CrocodileDandee on 07/14/2020 05:08:35
Reply #1

Stargazer 40

USA
370 Posts

Posted - 07/14/2020 :  03:59:07  Show Profile  Reply with Quote
The reason the black tube is black is to prevent light from activating the tube. The more sensitive a GM tube is, it is generally more sensitive to other triggering energy. Not sure if you are creating some capacitive effect by rubbing the plastic cover, but that seems likely. So don't. ;-)

Stargazer 40
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Reply #2

CrocodileDandee

Australia
55 Posts

Posted - 07/14/2020 :  04:14:19  Show Profile  Reply with Quote
quote:
Originally posted by Stargazer 40

The reason the black tube is black is to prevent light from activating the tube. The more sensitive a GM tube is, it is generally more sensitive to other triggering energy. Not sure if you are creating some capacitive effect by rubbing the plastic cover, but that seems likely. So don't. ;-)



Thanks for responding. I will have to use it out of the case then. Thatís disappointing, because I tried to find a plastic clear case, which is it turning not into a good idea... I wonder how other users are using theirs when travelling in dusty and bad weather conditions outside...
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Reply #3

Damien68

France
241 Posts

Posted - 07/14/2020 :  04:50:53  Show Profile  Reply with Quote
with certain plastics, rubbing it make electrostatic charge. perhaps this cause discharges passing through the tube and especially cross its current detection circuit.
These discharges can be interpreted as detected particles and increment the cpm counter. we could try the same thing with an "antistatic bag" or "ESD bag".

as said stargazer40, there could be problems of capacitive coupling between the tube cathode and an external reference (like a hand). but the fact of rubbing would have no influence.
but in general cases it is true that is better to avoid putting the tube too close with your hand, especially if you are in an environment with significant electromagnetic radiation because the hand would act in some way 'like an antenna'.

Mastery is acquired by studying, with it everything becomes simple

Edited by - Damien68 on 07/14/2020 05:38:13
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Reply #4

CrocodileDandee

Australia
55 Posts

Posted - 07/14/2020 :  05:09:28  Show Profile  Reply with Quote
quote:
Originally posted by Damien68

with certain plastics, rubbing it make electrostatic charge. this must cause discharges passing through the tube and especially through its current detection circuit.
These discharges must then be interpreted as detected particles and increment the cpm counter. we could try the same thing with an "antistatic bag" or "ESD bag".

as said stargazer40, there could be problems of capacitive coupling between the tube cathode and an external reference (like a hand). but the fact of rubbing would have no influence.
but in general cases it is true that is better to avoid putting the tube too close with your hand, especially if you are in an environment with significant electromagnetic radiation.



Thanks for your response and explanation.
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Reply #5

Damien68

France
241 Posts

Posted - 07/14/2020 :  05:27:17  Show Profile  Reply with Quote
to protect from dust, it is important especially if you go to contaminated areas, you can use a simple ziploc bag

Mastery is acquired by studying, with it everything becomes simple
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Reply #6

EmfDev

1243 Posts

Posted - 07/14/2020 :  09:49:32  Show Profile  Reply with Quote
Rubbing the plastic can generate very high static EF (Electric Field) which can affect the tube voltage.
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Reply #7

CrocodileDandee

Australia
55 Posts

Posted - 07/14/2020 :  19:50:04  Show Profile  Reply with Quote
Many thanks for your explanation. I will try today if I can generate the same electric field in a ziplock bag. It might be a good alternative to use one because then I can just chuck it out after my trip.
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