On Mon, 27 May 2002, Jim wrote:

>I've been searching via Google for a simple static
>E-field measuring accessory that I might add to
>a weather station for measuring static electric
>fields as those created by convective thunderstorms.
>
>So far, I've run across 'Field Mills' projects
>
>http://www.izzy.net/~jc/FieldMill/FieldMill.html

Build the field mill and calibrate it using a plate held at 1000V (I
assume you have some anode supply somewhere). I once built a similar
device following a physics textbook and it works fine iff the space is
well clear between it and the target. This means mounting it on a pole.
You can use a thin 'radome' (plastic bag or balloon). The 1000V was
applied to a zinc tabletop in my case, held at a measured distance from
the mill can. I used a beverage can and a walkman motor (smaller unit than
theirs). The electronics used TL074+CD4066, readout was DVM. My electrodes
were of different shape (only 2 blades -- i.e. 2 strips of metal, one
spinning, one fixed).

Peter

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