I’ve found this two interesting modules at Marzaglia ham radio flea market (11 May 2019) and bought for 5€.

ZP1210 geiger tube

Each module have soldered two geiger tubes, one per side and a signal conditioning/high voltage generator circuit.

The tubes are ZP1210 made by Valvo during 70’s I think. Valvo company doesn’t still exist but Centronic.co.uk still make this tube. It’s a design original made by Philips and made by various brands under licence.

ZP1210 gamma geiger tube
Lenght: 140mm
Plateau threshold: 400V
Plateau lenght: 100V
Plateau slope: 0.15%/V
Counting rate at 10e-2mGy/h: 110 count/s
Dead time: 200uS
Background shielded: 70 count/s
Dose rate range: 3x10e-4 / 10 mGy/h

The two modules

The onboard circuit seems in working order. I’ve tryied to feed it with  12/24/30V dc and obtained 160V across tubes with 30V input. I don’t know the correct voltage needed by it’s circuit. I don’t know how the circuit output it’s counting pulses. I’m thinking that this two modules are from a steel scrap radiation detection system. They probably are feed with a relatively high voltage like 48Vdc or 70Vdc and the output pulses from the tubes are used to modulate the power supply line. I’m thinking about scrapping the four tubes and as much as possible from the electronics but I’m not a fan of bit tru-hole components from the 70’s. With 5€ I’ve bought 4 very nice geiger tubes with very good characteristics… I’m very happy!

Top circuit

Bottom

Did you have some info about it? There is a mark…