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paul

United Kingdom
33 Posts

Posted - 05/25/2019 :  07:48:47  Show Profile  Reply with Quote
I'm curious as to why I am reading such high background levels.
I have a new 600+ with a LND 7317 tube, Rev. is 2.07
I'm staying on the west coast of Scotland at the moment.
You can see the "72" on your map,data is open to read.
My readings seem to be 2 or 3 times higher than most others.
I checked the village and it fluctuates from 30 to 85.
Reply #1

ZLM

1236 Posts

Posted - 05/25/2019 :  21:30:34  Show Profile  Reply with Quote
Different tube should have different CPM reading on same level of radiation. The LND 7317 is a high sensitive tube. The CPM reading should be 2-3 time higher than M4011 tube.


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Reply #2

paul

United Kingdom
33 Posts

Posted - 05/30/2019 :  09:05:13  Show Profile  Reply with Quote
More observations than questions,perhaps the community wish to comment.

I still find my readings in uSv/h ,50% to 100% or more,higher than the
readings of the official EU monitoring sites ,available here -
h**ps://remap.jrc.ec.europa.eu/GammaDoseRates.aspx

The nearest EU reading stations are at least 50 miles away ,North,East
and South over rugged terrain.West is in the Atlantic ocean.
This area is on the edge of a relatively high Radon area,map here -
h**ps://www.ukradon.org/information/ukmaps

My 600+ LND 7317 also seems to be a lot more sensitive than the official
readings on the graphs at the first link,which vary little over time.
My readings vary a lot over time,as my GQ map data shows.
Are the EU official readings to be trusted ?
(Are any officials to be trusted ?)
Online,various commentators express doubt as to the accuracy of
Japanese official readings.
Perhaps the Japanese officials are wishing not to spook the herd.
GQ map readings show surprisingly low readings in Japan,although there
are few counters,and none close to Fukushima prefecture.

I understand,after reading the excellent work of stargazer 40 and ikerrg at
this amazing thread -
https://www.gqelectronicsllc.com/forum/topic.asp?TOPIC_ID=5554
that this is a complex field of research,and no longer expect straight definitive
answers.
It is not even clear exactly what I am measuring.
Background indeed.
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Reply #3

EmfDev

800 Posts

Posted - 05/30/2019 :  12:31:50  Show Profile  Reply with Quote
We don't really know why readings from government or official readings are lower. They're usually lower in most countries compared to readings from the public.
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Reply #4

paul

United Kingdom
33 Posts

Posted - 05/30/2019 :  13:17:24  Show Profile  Reply with Quote
As I said,don't spook the herd.
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Reply #5

ullix

Germany
391 Posts

Posted - 06/04/2019 :  01:21:14  Show Profile  Reply with Quote
@paul:
given what kamilw has found, and what I have basically confirmed, here http://www.gqelectronicsllc.com/forum/topic.asp?TOPIC_ID=7149

can you take a look around your counter and check for any possible sources for interference?

Sources could be: phones, WiFi, router,radio, elevators, air conditioning, microwave ovens, workshop equipment, etc, etc!
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Reply #6

paul

United Kingdom
33 Posts

Posted - 06/04/2019 :  10:17:15  Show Profile  Reply with Quote
Yes,I saw with interest kamilw's post.
And I have discovered under floor wiring that does have
RF spikes on it,which I can see with my EMF390.
So I have put my 600+ on the floor in a space that has no
RF according to the EMF390,and have put it on the Map just now.
First 5 minuets it looks the same,0.200 uSv/h already.
II'l leave it on for a while,lets see.

Edited by - paul on 06/04/2019 15:23:55
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Reply #7

paul

United Kingdom
33 Posts

Posted - 06/04/2019 :  12:00:11  Show Profile  Reply with Quote
That's well over an hour and my readings are the same.
I don't think my device is reacting to stray EMF.
Its in a cold spot,no Voltage,RF,mG,nothing.
I think its working OK.
Just a sensitive tube in a slightly higher Radiation zone I guess.
Glad I bought it.

Edited by - paul on 06/04/2019 12:32:33
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Reply #8

bc10

7 Posts

Posted - 08/14/2019 :  12:48:18  Show Profile  Reply with Quote
If the high reading is not because of your actual environment, is it possible your device is contaminated somehow?

Perhaps cleaning the surface may help? I'd probably prefer to clean the detector's mica window too but I'd be afraid of damaging it.

I just got my GMC 600+ and the first thing I did was tape up the openings of the new device including the detector opening so dust particles can't contaminate it over time when not actively attempting to measure alpha readings.

My background is high too. 50 CPM indoors, but works out to be within range of annual dosage for my area provided the Raw-to-dose conversion factor is correct. Currently my CPM to uSv/h conversion factor is set at 350 from the factory. I don't have a calibration source to test, tune and verify accuracy of the conversion readings though.
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Reply #9

EmfDev

800 Posts

Posted - 08/14/2019 :  13:04:32  Show Profile  Reply with Quote
bc10, you might be blocking the alpha particles by taping your device.
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Reply #10

bc10

7 Posts

Posted - 08/14/2019 :  13:22:07  Show Profile  Reply with Quote
quote:
Originally posted by EmfDev

bc10, you might be blocking the alpha particles by taping your device.

Yeah I know. I am using it for environmental monitoring so it's ok to just detect beta + gamma. I was gonna buy the cheaper GMC500+ but decided to go for the better GMC600+ which detects alpha too and an added bonus.

I'll expose the detector again if there was a desire to measure alpha. Otherwise I like the idea of keeping the internals clean so I can wipe down the surface if need be.

My nightmare scenario is if some dust contaminated the detector over time, which will ramp up the background measurement over time due to the contamination's constant contribution to the CPM.

Edited by - bc10 on 08/14/2019 13:24:21
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Reply #11

EmfDev

800 Posts

Posted - 08/14/2019 :  13:31:57  Show Profile  Reply with Quote
I see, it's good keeping it clean. However if you think the CPM has increased, then you can still change the CPM to uSv/h conversion on the unit.
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Reply #12

paul

United Kingdom
33 Posts

Posted - 08/14/2019 :  13:52:48  Show Profile  Reply with Quote
bc10 (If the high reading is not because of your actual environment)

Actually I think the high reading IS because of the environment.
The Radon map link above shows that I am on the edge of an area of
slightly elevated Radon gas levels.

Contamination is unlikely.
The device is relatively new and is used indoors.
Mainly it is kept in the bag.
I would leave it on more,but I've read that the tubes wear out over time
I would rather keep it for when it may be needed.....
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