[volt-nuts] Bohnenberger electrometer

[Hendrik]

Something like this ? https://de.wikipedia.org/wiki/Elektrofeldmeter

(German wikipedia as the english entry is less than stellar. They are 
called field mill.)


Best regards

Hendrik



On 16.03.2018 19:53, ed breya wrote:
> There is another kind of static electric field meter that was commonly 
> used over the past few decades for monitoring charges/voltages in work 
> areas dealing with sensitive semiconductors. It has a small motor 
> spinning a hollow brass cylinder that has a radial hole or slot that 
> alternately shields and exposes a center cylinder inside, which is the 
> pickup electrode. This action causes a small AC signal on the 
> electrode, that can be amplified up to represent the electric field 
> strength from any nearby object. The signal is then rectified and 
> trips a comparator and LED indicator if the level exceeds a certain 
> amount.
>
> I have a couple of these units, but have never experimented with them 
> yet. They don't show any kind of readout or provide a measuring signal 
> - just the LED warning of excessive (unknown trip point) static charge 
> nearby. I figured someday I would modify one up and add a signal 
> output port and a sync output from the motor, allowing a lock-in 
> analyzer to read the result over a wide range, and maybe even be 
> fairly accurate or calibrate-able.
>
> Ed
>
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