Date: Fri Oct 2 16:48:01 2009

Author: George Herold

Subject: Re: Electroscope v. Voltmeter


Yup, I find that it is nearly imppossible to make anything with
capacitance less than 1 pF. (OK I'm talking about human sized things
and not little etched pieces of silicon.) I've been working on
electronics for noise fundamentals where every bit of C is a loss in
bandwidth. Add a trace on the PCB... 1pF, and a terminal block now it's
2 pF, add a switch... Now it's 3-4 pF...

George H.

-----Original Message-----
From: [] On
Behalf Of Bernard Cleyet
Sent: Friday, October 02, 2009 3:41 PM
Subject: Re: [tap-l] Electroscope v. Voltmeter

Yes, I wasn't thinking.

Apropos the cap. of connecting wires: (Cliff)

I found isolated banana plugged wire to have ~ 4 pF /meter. More

Cap. (pF) = 0.13 + 7.1*x - 3.1*x^2 R = 0.996 wires 0.16 => 0.98 m

Data Precision #938 cap. meter. I held it up away from my body for the
long wires; readings were constant.

bc living room physicist.

On 2009, Sep 30, , at 06:04, George Herold wrote:

> Chuck it is going to be the capacitance between the leaves and the
> rest of the universe, not between one leaf and the other. (They are
> shorted together after all.) But as the leaves move apart one might
> expect that the C will increase... The effective 'area' looks a bit
> bigger.
> George
> -----Original Message-----
> From: [mailto:tap-l-]
> On Behalf Of chuck britton
> Sent: Tuesday, September 29, 2009 8:08 PM
> To:
> Subject: Re: [tap-l] Electroscope v. Voltmeter
> But if the leaves more to any appreciable degree (or radian ;-) , then

> C is no longer constant.
> right?
> ----- Original Message -----
> From: "Wolfgang Rueckner"
> Subject: Re: [tap-l] Electroscope v. Voltmeter
> Q = CV. The electroscope has some capacitance. Q and V are linearly
> related, with C being the proportionality constant. -- Wolfgang