Dosimeter Charger

May 02, 2004 7 Replies
C

I've got an old pen-type dosimeter, and I've been googling for hours trying to find charging/calibrating details.



As far as I have found, the charge voltage is (apparently) around 200 volts, and is basically an electrostatic charge.



So if I rectify and smooth the mains (UK 240V) and apply it to a high value (1M or more) pot, with a 10M resistor from the wiper connected to the dosimeter charging pin, and the neutral to the body of the dosimeter, will it work?



(Disclaimer - I've worked in electronics for 35 years, and I am not about to be electrocuted now. I just can't find enough parameter information.)



TIA Chris



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A

Yup, I think the basic principle is to "zero" it by charging to a set voltage.

-A

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C

Sounds about right - I have a hand-cranked charger for them in a box somewhere. If memory serves, it generates about 200V AC then rectifies and current-limits it. Nice little thing! Voltage regulation wasn't much to write home about (non-existent?), so it should work OK with rectified mains.

Rick.

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P

The Web site for surplustuff.com shows quite a bit of radiological equipment for sale, including some dosimeter manuals. It sounds like the site proprietor has first-hand experience operating and repairing this gear as well. Maybe an email will get your question answered.

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Paul Hirose To reply by email delete INVALID from address.
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P

Where I work, I don't think there is any attempt to zero the dosimeters - they are just reset to some low reading periodically. When someone signs out a dosimeter, he records the current reading, then records the reading when he returns it - the difference is the dose he received.

Peter Bennett VE7CEI email: peterbb4 (at) interchange.ubc.ca GPS and NMEA info and programs: http://vancouver-webpages.com/peter/index.html Newsgroup new user info: http://vancouver-webpages.com/nnq
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H

Right, it's roughly 200-250 volts.

A while back I unwisely purchased 100 dosimeter readout/chargers. If you want one, I'd gladly mail it to you for $10 (US).

Harry C.

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T

Just a folow-on to what has been said so far... Your mains voltage is

240 volts RMS, after rectifying and filtering it will almost be at the peak voltage which is 1.414 times the RMS voltage - about 340 volts. This might be too much for the dosimeter.
Tony Newman Springfield, OR USA
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C

I found this schematic inside my CD V-750 dosimeter charger. It's old, but FWIW, here it is.

If God hadn't intended us to eat animals, He wouldn't have made them out of MEAT! - John Cleese

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