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Registered Member #96
Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4059
Hi all.
Does anyone have some of those "block" type 3 wire HV modules originally used on GM counters, etc? I think they got used in a lot of insulation testers as well as they are very reliable if not ever overloaded.
The ones I have are about 4-800V out at 0.1mA (100uA) it seems, good enough for most purposes as long as a 10M resistor is added in series. The ones with 3 pins on a black insulated block are also suitable.
Need 12 total, have 6 maybe 7 if the damaged one (bad insulation) can be patched up somehow. A few spares would be useful in case one or two go bad.
My alternate option is to make some, they are not that hard as HV853's are good for +130/-90V and can be obtained for very little $ then driven in antiphase to get the 270V needed for at least an APD. Some GM tubes will work somewhat on a voltage this low and in fact the "tiny" ones only ever needed 330V to begin with. Adding a GM counter to my laptop(s) and phones is on my projects list.
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
I use a miniature PCB-type mains isolating transformer - 230:230 - followed by a voltage doubler using small AC rated mains filter capacitors. This will motor along 24/7 delivering around 600V at up to a hundred microamps or so without ever getting warm. Clearly, if I tried to get more current out of it the volts would sag badly because of the low capacitances (100nF) but the power disspitation of GM tubes is very low even at high counting rates.
You could make one using slightly larger capacitors and power all your GM tubes from one HT source. Why make work for yourself?
And no forgetting to put a fuse in the mains input line!
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
My home in 146 miles from the centre of Gurnsey. The bearing is approximately North East. This course goes just north of Cherbourg Peninsula, so all but the very beginning and the very end of the journey is made over the sea.
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HV modules for cosmic ray detector(s)
