Parasitic capacitance of SMD resistors and their generated noise

It might get expensive.

Nice stuff. MMBD5004S/1SS398TE85LF is a dual 400v diode in SOT23, which can shorten a C-W multiplier string.

That's a variant of traditional electrostatic voltmeter design with a vane and plates, which typically is done in rotary fashion with a hairspring for return force... and requires jeweled bearings and level adjustment... it's a fiddly nuisance of an instrument, but does pretty well at sorting out kilovolts without many picoamps of leakage. I suspect the weight sensor will respond to every bit of building shake in the wind...

Yow. So many parts just to replace a single vacuum tube rectifier...

And then the long string of low-V resistors...

It'd almost be easier to meter with a field mill (motorized vane changing capacitance-to-electrode, and AC amplification of the resulting current). An interesting variant would be to program a second electrode with some smart PWM and balance the pulses from the known-voltage electrode and the unknown-voltage electrode.

The classical method is the vibrating-reed electrometer.

Cheers

Phil Hobbs

On a sunny day (Wed, 9 Mar 2022 13:35:31 -0500) it happened Phil Hobbs snipped-for-privacy@electrooptical.net wrote in snipped-for-privacy@electrooptical.net:

Thanks, bit of googling found a nice wikipedia article:

That's also a 'do not move near it' solution. I scavenged a head unit from an old Cary 31 vibrating-reed electrometer, and it's got 10lbs of cast iron to keep acoustic input to a minimum; there were selected tubes inside to deal with the microphonic feedback, and anyone who could afford it (circa 1970) was swapping in new sockets and nuvistor tubes, 'cuz microphonics.

"Doctor, doctor, it hurts when I go like this!"

"So don't go like that."

I used to have a handheld electrometer with an analog dial. It looked a bit like an old CdS photographic light meter, and worked fine.

Cheers

Phil Hobbs