misc radiation measurement stuff

Herfurth Minicont contamination monitor

Herfurth Minicont proportional chamber contamination monitor, build 1979.
This device has a typical null-rate of 4-5 counts per second, the tiles in the bathroom generate 10 cps
The meter shows impulses per second. Left switch: battery/alpha+beta/alpha selector, right switch turns of the clicking sound.
Power push button not visible, build into the black handle.
Gas valve, screw-in battery cover and gas release valve at the front
top view

The gas tank, it runs with lighter gas, 85% Butane, 15% Propane
gas tank

The open wire hamber normally covered by metallized foil. Note the tiny wire held by a teflon frame.

Fixing the foil using a sheet cut out of a mylar helium-balloon, conducting side inside. The original foil is thinner.
fixing the foil

High voltage PCB, and the Schematic for the High voltage PCB, this generates 3.7kV for alpha+beta and 2.7kV for alpha detection
high voltage PCB

Analyzer PCB
analyzer PCB