[volt-nuts] Bohnenberger electrometer

[Bruce Griffiths]

A method in use 40+ odd years ago for measuring atmospheric electric fields was to use a slotted rotating disk rather than the rotating cylinder.

A matching stationary or counter rotating disk IIRC was used either in front or behind the rotating slotted disk the the sensing disk was behind both.

Bruce.


> 
>     On 17 March 2018 at 07:53 ed breya <eb at telight.com> 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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