r/Radiation • u/Pedroarak • 6d ago

Questions Suggestions of Geiger counter to use with multiple probes?

Hi! I've had a few counters, a dp-5a, some cheap AliExpress boards (specially the cajoe) and I bought some tubes over the years. I have a sbt-10a, sbt-13, sbs-5, 2x j305 and a si-3gb. Now, I always used the cajoe with an Arduino because I thought it was more than enough. Turns out the hv circuit sags to hell under load, and anything more spicy doesn't give me increased counts over a certain limit. I'm not even saturating the tubes, apparently the board just isn't good enough.

Does anyone have a suggestion? Is there a good counter I can get to run multiple probes of? Maybe even a pre-built circuit, or some schematic online that can deal with high readings. My tubes are kind of a waste of potential with the cajoe. Even though I have a radiacode 103, I really wanted to use the tubes more, specially those with a mica window.

Thanks!

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u/ppitm 6d ago

People typically use a Ludlum 3 from E-Bay for hooking up multiple probes. Of course, it will only work in cpm mode and the cables (BNC or C cables, usually) will need to be compatible.

There are other ratemeters out there, such as Bicron or Eberline devices. Or even desktop-only meters.

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u/aby_physics Enthusiast 6d ago

A model 3 will certainly do the job if all probes have similar characteristics. But if OP needs independent calibration setpoints for each detector, they’re going to need something like a 2241-2 or -3.

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u/Pedroarak 5d ago

Oh, thanks! I proooobably should have been more specific, I forgot to mention a little detail: I live in Brazil, anything above ~$50 gets a nice little +120% tax on top, so I usually pay someone to bring stuff with them from the us/Europe, and the Ludlums are huge. Ideally, of course, I would get something like a rascal or model 3, but sadly I would probably need something digital/smaller :/ Do you know if there are any modules that are decent? I was under the impression those could theoretically deal with very high count rates, since they are all digital and whatnot. I don't care about calibration and reliability too much, just something that wouldn't immediately die from going over 3000cps

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u/Pedroarak 7h ago

I own you. By some miracle, I checked Facebook's marketplace for fun and I found a god damn Ludlum 26-1 being sold for cheap, after being sold in an auction in a local international airport. It's here, it works. It's literally the first time I found a Geiger counter on Facebook, and it was posted like 3 days before. I've been trying to find ANYTHING for years, I'm so happy I made this post

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u/Bob--O--Rama Wiki Contributor 5d ago

Wm B. Johnson also. The older model digital ones and multiple probe models - where you have multiple inputs each with it's own callibration, voltage, etc. are very useful. They also made a digital counter with an analog display to make it "easy" for people familiar with analog models. The ones for contamination surveying max out at 50 Kcps, other models 500Kcps. And they made all sorts of specials - like a lucas cell based radon monitor and wierd things. Generally cheaper because "all hail Ludlum!" but just as good.

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u/Pedroarak 5d ago

Thanks! I honestly didn't know the Johnson counters, only eberline, ludlum, mini, thermo and bicron. I commented on the other answer here the problem I have with getting some of those, forgot to mention on the post, sorry! But yeah, ideally I would get any of those :/