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 GQ Geiger Muller Counter
 [GMC320] 18ÁSv/h on the autobahn??
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Nudnik

40 Posts

Posted - 03/13/2016 :  12:13:06  Show Profile  Reply with Quote
Hi,

today, I took my GMC320 on the road. It was connected to my iphone with the safecast app running. Everything worked as expected. I drove for an hour and arrived at my destination. 5 hours later (meanwhile it started raining), I went back home and noticed that something seemed to be fishy with my setup. The safecast app showed 0,6ÁSv/h which is 5-6 times the regular background radiation I saw before.

I looked at the display of the GMC320 and it showed 0,6ÁSV/h as well.
I activated the speaker to have some audible feedback because I had this kind of phenomenon in the past, when there was noise on the audio line which was falsely detected as pulses. But the ticks sounded 'accordingly' to the numbers


This was strange because ok, the rain could raise background radiation a bit but not to that extent.
As I left the town where that happened, the numbers went down to reasonable 0,15ÁSv/h which is even more strange because this was kind of an indication that the system is working ok and that there really was such a high bg. radiation.

But it became even more strange. 1/2 hour later on the autobahn the numbers suddenly increased to unbelieveable 18Ásv/h. The ticking noise from the speaker sounded like when I hold the GMC to a piece of uranium ore.

I couldn't stop the car and investigate the location because I was on the autobahn. I checked the signal shape on the scope of the app for noise. Everything looked like it should. Still, both the iphopne app and the GMC320 showed 18ÁSv/h.

I disconnected the audio cable from the GMC and it kept ticking like hell and still showed world war 3 numbers.

This lasted for roughly 2km and then the numbers and the ticking sound dropped back to normal. I have absolutely no idea what the counter caused to freak out.

Could it have been the connection between iphone and GMC? Why didn't it stop after disconneting the cable?

A software issue?

A hardware defect?

Some sort of avalanche effect caused by ...???

A speed traps radar, interfering with GMC electronics?

Illegal transport of radioactive material? (just kidding)

Any ideas?

Your feedback is highly appreciated!


Edited by - Nudnik on 03/14/2016 12:00:08
Reply #1

Distelzombie

Germany
141 Posts

Posted - 03/14/2016 :  15:03:03  Show Profile  Reply with Quote
Electromagnetic fields can create false clicks. I documented? this by lighting a fluorescent bulb with a Tesla coil in the vicinity of the tube and it went bananas.
I tried the same setup but this time I built a faraday cage and put the GMC insider. This got rid of any electric interference.
My cage was built using a kitchen sieve and aluminum foil wrapped around a piece of cardboard.

Try this the next time you drive around there.

:)

GMC-300E+ V4.20 with sbt-11 alpha tube
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Reply #2

Nudnik

40 Posts

Posted - 03/15/2016 :  08:25:12  Show Profile  Reply with Quote
Yes, there seems to be an emc issue with the GMC320. Today I entered my car and took the counter out of my pocket and it showed above 4ÁSv/h for no reason. Maybe caused by an electrostatic discharge when I touched the cars body. However the level dropped down to normal and I could not induce the behavior a second time.

Maybe ZLM can shed some light on this?
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Reply #3

ZLM

1024 Posts

Posted - 03/15/2016 :  22:50:28  Show Profile  Reply with Quote
I think the problem comes from the tube.

If the tube is about to fail, then the main symptom is the unstable clicking. Sometimes the clicking will go very high, but it return to normal later.
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Reply #4

Nudnik

40 Posts

Posted - 03/16/2016 :  03:44:03  Show Profile  Reply with Quote
Thanks for that information. The tube is not very old. I bought my GMC320 just last year, but I'll observe that further and maybe replace the tube with an SB20.


Edited by - Nudnik on 03/16/2016 03:44:30
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Reply #5

Distelzombie

Germany
141 Posts

Posted - 03/17/2016 :  04:05:46  Show Profile  Reply with Quote
Old or not is not determined by time. A tube gets old by clicks. That's why you can use found tube from chernobyl with no problem.

GMC-300E+ V4.20 with sbt-11 alpha tube
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Reply #6

Nudnik

40 Posts

Posted - 03/18/2016 :  02:34:49  Show Profile  Reply with Quote
Well, lets consider a ~one year old tube running for one year in 0.75nSv/h background radiation as not old in terms of time and in terms of counts.

Edited by - Nudnik on 03/18/2016 02:37:58
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Reply #7

ZLM

1024 Posts

Posted - 03/25/2016 :  11:28:10  Show Profile  Reply with Quote
For the tube, most likely it should last around average 50,000,000 clicks, about 2 years if it runs 24/7.
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