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Registered Member #95
Joined: Thu Feb 09 2006, 04:57PM
Location: Norway
Posts: 1308
Your opinion strengthens my suspicion, Suliaman. I set the tube voltage to 420 and listened for 2 minutes, and I heard a total of 3 pops. About right I guess. The lack of sensitivity bothers me though, if it's made for high radiation environments will the x-rays still excite the tube? And to think I could have bought a 1r/hr tube instead... Not that I will be relying on the counter for protection, everything will be encased in lead/steel shielding, but it would be nice to know if x-rays are even being generated.
Registered Member #99
Joined: Thu Feb 09 2006, 06:10PM
Location: florida, usa
Posts: 637
Uzzors wrote ...
Your opinion strengthens my suspicion, Suliaman. I set the tube voltage to 420 and listened for 2 minutes, and I heard a total of 3 pops. About right I guess. The lack of sensitivity bothers me though, if it's made for high radiation environments will the x-rays still excite the tube? And to think I could have bought a 1r/hr tube instead... Not that I will be relying on the counter for protection, everything will be encased in lead/steel shielding, but it would be nice to know if x-rays are even being generated.
You need to find a GM tube with MUCH more sensitivity for xrays. 1r/hr is still way too high. Get a CDV700 off of ebay. It will go to 50mR/Hr. Chest xrays are like 10mR... Matt
Registered Member #95
Joined: Thu Feb 09 2006, 04:57PM
Location: Norway
Posts: 1308
So much for that then, at least I'll know where to find safe shelter when WW3 breaks out. If I really need the GM-counter for the x-ray machine I'll buy a more sensitive tube. I've found SBM-20 tubes on ebay for 17 USD, their range is 40 - 400 mR/hr, which should suffice. Thanks for the help everyone.
Registered Member #151
Joined: Sun Feb 12 2006, 02:53PM
Location: Poland
Posts: 153
Uzzors wrote ... If I really need the GM-counter for the x-ray machine I'll buy a more sensitive tube. I've found SBM-20 tubes on ebay for 17 USD, their range is 40 - 400 mR/hr, which should suffice.
Remember that radiation from x-ray tube can easily overload this GM tube. Then it becomes sth like short-circuit and the counter stops, just like there was no radiation!
Registered Member #530
Joined: Sat Feb 17 2007, 07:56AM
Location: Victoria BC, Canada
Posts: 178
I know of several US based dealers who sell reconditioned -remade civil defense counters. Sure you could build one, but for $100 USD you can get one that is all remade. My brother owns a CDV-700 that has been altered to 100mr/hr and has a pancake probe that does alpha-beta-gamma and XRAYS. Also it comes with a scintillator kit and a digital CPM meter built in :) all for $200. You can't beat that kind of pricing.
Registered Member #95
Joined: Thu Feb 09 2006, 04:57PM
Location: Norway
Posts: 1308
I finished my mini Geiger counter last weekend, but without any known radiative sources it's hard to test. The circuit works anyway, so I'll see how the tube works when I build my x-ray machine. (if it works) I bought a small SBM 21 which has a range of 40 to 400 mRh, so if there are any x-rays present it should sense them. A buzzer and an ultra bright LED are activated when the GM tube is ionized.
In the end it would have been cheaper just to just buy a finished Geiger counter like Sulaiman did.
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Making a Geiger-Müller Counter
If I really need the GM-counter for the x-ray machine I'll buy a more sensitive tube. I've found SBM-20 tubes on ebay for 17 USD, their range is 40 - 400 mR/hr, which should suffice. Thanks for the help everyone.
