dc surface voltmer eev #247

[michi42]

Hi,
i rememered eev #247 at 7:40 dave plays around with a "voltmeter"

i wonder how this thing works.

It's from alpha-labs afaik.

I thougt it would be impossible to mesaure electrostatic field strength without using a rotary voltmeter.
Second principle that comes in mind is force applied by the e-field to a charged probe.

But this seems to work differently. Do they use a charge amplifier like in piezo sensors?