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 2.GQ Geiger Muller Counter
 1 mSv/hr! a very hot integrated check source...
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jlp1528

USA
19 Posts

Posted - 07/06/2020 :  11:19:54  Show Profile  Reply with Quote
My Swiss "Landis & Gyr" made EMB3 Geiger counter finally arrived today. The check source inside has to be the hottest integrated check source I've ever seen!
https://i.imgur.com/EQwdYF3.jpg
https://i.imgur.com/lotEwSQ.jpg
The particular unit I found does not have a warning label, but the ones that do indicate an original activity of 10 microCuries of Sr-90, which is quite a lot. Just thought I'd share this impressive (and somewhat scary!) info. Fortunately that little bead does appear to be well shielded (possibly by lead on the side closer to the GM tubes) so it shouldn't pose any hazard so long as the lever to use it is kept in the CLOSED position. Still crazy if you ask me!

Edited by - jlp1528 on 07/06/2020 18:35:43
Reply #1

EmfDev

1243 Posts

Posted - 07/06/2020 :  15:06:32  Show Profile  Reply with Quote
Hi jlp1528, thanks for sharing! Im just not sure is this a calibration source or a geiger counter?
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Reply #2

jlp1528

USA
19 Posts

Posted - 07/06/2020 :  18:47:12  Show Profile  Reply with Quote
I have edited my post for a bit of clarity. This particular model of Geiger counter includes an integrated check source which is moved into position with the lever opposite the scale selection lever on the side of the unit with the battery compartment.

In the pictures you can see the reading on my GMC-600+, and the check source itself - a small metal bead on a swinging arm. I may take some more pictures of the unit itself, as it is a good yet seemingly obscure model - there isn't a lot of pictures nor info online about this particular device.

Despite being an older unit, it takes 2 D batteries. The housing is quite robust; it appears to be designed for some degree of weatherproofing. There is a big O ring on the battery compartment and rubber gaskets under every screw, 4 long and well fitting screws on each side.

The unit itself is still functional and was last calibrated in 1984. There is a flipping door over the "window" to the GM tubes, which acts as a beta shield so either gamma only or beta+gamma readings can be taken. I don't think the lowest range works at the moment, but I may see if I can repair it. It's not a big deal anyway as that range only goes up to 10 mR/hr. The scales are logarithmic, which is different but quite nice in my opinion.

Edited by - jlp1528 on 07/06/2020 18:48:55
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Reply #3

EmfDev

1243 Posts

Posted - 07/07/2020 :  12:06:50  Show Profile  Reply with Quote
That is really interesting! Take good care of it :D What is the minimum radiation it can detect? looks like it is not for background radiation use.
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Reply #4

jlp1528

USA
19 Posts

Posted - 07/07/2020 :  13:52:24  Show Profile  Reply with Quote
There are two very dark reddish brown Geiger tubes inside, one much smaller than the other, and the lowest scale tops out at 10 mR/hr. So it's possible it could be used for background radiation if I can get it to work at that scale. The second scale is 1000 mR/hr, and the third is 100 R/hr. I think it's meant to be similar in range and use case to the Russian DP-5 series, but the design is completely different. The most notable difference is that this EMB3 has everything in the housing, while the DP-5s and Polish DP-75 have external probes. I suppose there are advantages and disadvantages to both, but I personally prefer the fully integrated designs.
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Reply #5

jlp1528

USA
19 Posts

Posted - 07/07/2020 :  14:36:09  Show Profile  Reply with Quote
More pictures and info here:
https://imgur.com/gallery/ZdWXsZT
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Reply #6

EmfDev

1243 Posts

Posted - 07/08/2020 :  09:36:57  Show Profile  Reply with Quote
Wow that looks great! Still checking the dead time issue.
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