[volt-nuts] Small capacitance

[Pete Lancashire]

Might want to take a look a the manual for the GR 1621A and 1622A
bridges, and the 10 pF air cap standard.

-pete

On Fri, Jan 13, 2012 at 8:48 AM, Poul-Henning Kamp <phk at phk.freebsd.dk> wrote:
> In message <E7EAFDAE-17F8-48DC-AC7B-F8E42CB367D0 at gmail.com>, Fred Schneider wri
> tes:
>
>>so I need a sturdy standard capacitance. Any suggestions, something
>>using air will be best I think but two metal plates should be
>>straight and mounted solid opposite.
>
> I think a major part of your uncertainty is stray fields:  parallel
> plates have them all over the place.
>
> I read somewhere that "real metrologists" use a particular design
> for which the theoretical value has an analytical solution.
>
> I can't remember the geometry which was described, but using circular
> symmetry is a pretty good bet, and coaxial would make even more
> sense, because the electrical field is mostly contained.
>
> Found it, where else but at BIPM:
>        http://www.bipm.org/en/scientific/elec/calc_capacitor/
>
> And here's a good slide-set:
>        http://www.metas.ch/LesHouches/downloads/talks/24_Bachmair.pdf
>
> --
> Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
> phk at FreeBSD.ORG         | TCP/IP since RFC 956
> FreeBSD committer       | BSD since 4.3-tahoe
> Never attribute to malice what can adequately be explained by incompetence.
>
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