Re: False alarms on DMC model 90 electronic dosimeters

[Peter Ryge <peter@ancore.com>]

I don't know your particular situation, but could it be electromagnetic noise interfering with the sensitive front end electronics of the sensors?

It reminds me of a situation we had here. A small electrical discharge on our accelerator radiated noise that caused high readings, up to 200 mR/hr, on some survey meters (e.g. Bicron RSO-5, Bicron µREM Meter, Nuclear Research Corp "Snoopy" neutron rem-meter) and not on others (Ludlum 12 neutron rem-meter, Eberline ESP-1). It was diagnosed by wrapping the case of each meter snugly in aluminum foil (with the display exposed) which stopped the effect. Apparently the meter cases themselves were not effective enough as electromagnetic shielding.

If possible, I would try wrapping sensor(s) in aluminum foil and grounding it by pressing against a known ground, e.g. conduit or pipe.

Peter Ryge
Ancore Corporation
peter@ancore.com
www.ancore.com

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