[volt-nuts] 34401A Why 10M ohm default i/p resistance?

[John Phillips]

With the 1K ohm per volt you need to know what range you are using. You do
have to know your meter and know how to correct for loading or not loading.
It is not very practical to have a bunch of different input standards 10M
works for a lot of things and is the the standard voltage divider.


On Thu, Apr 10, 2014 at 1:59 PM, Poul-Henning Kamp <phk at phk.freebsd.dk>wrote:

> In message <534704F7.3030101 at toneh.demon.co.uk>, Tony writes:
>
> >Very unlikely I'd have thought - the relay (K104) which selects between
> >the high and low voltage ranges also selects the  I/P resistance. It
> >wouldn't get used any more than the identical relay |(K102) which
> >switches when changing between 10 and 100V ranges.
>
> If you leave your 34401A on 10G input with nothing connected in
> a dry atmosphere, it is going to build up charge and trigger the
> autorange relay.  Anti-wear-out mechanisms are certainly relevant.
>
> A similar mechnism is documented in one of the 3458A manuals.
>
> --
> 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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-- 
John Phillips