[volt-nuts] Eppley Standard Cell and What Is It?

[gbusg]

P.S. Conrad Hoffman has good info on the topic of Weston saturated and 
un-saturated standard cells.

According to his info, even high resistance input modern DMMs shouldn't be 
used to directly measure the output of Weston standard cells.

See:
http://conradhoffman.com/stdcell.htm

Greg


----- Original Message ----- 
From: "gbusg" <gbusg at comcast.net>
To: <jfor at quikus.com>; "Discussion of precise voltage measurement" 
<volt-nuts at febo.com>
Sent: Wednesday, September 21, 2011 9:58 PM
Subject: Re: [volt-nuts] Eppley Standard Cell and What Is It?


John wrote:
>Some types of cells really do not
>like being inverted. It is designed to work into an open circuit....  ie:
>potentiometric comparison.

>From the Solartron 7081 specs I see its DCV input resistance is >10G ohms 
for 0.1 thru 10 V ranges.

Have any of you Solartron 7081 users looked to see if there are reverse 
switching transients present at its front DCV input jack while in its DCV 
mode?

In the case of the HP 3458A, you can temporarily turn-off Auto-Zero, which, 
I *think* should minimize if not eliminate any possible switching transients 
present at its front DCV input terminals. By comparison I'm not sure how 
this works with the Solartron 7081?

Disclaimer: I've not personally characterized any possible reverse switching 
transients present at the 3458A input terminals. But, in theory I think I'd 
temporarily turn-off Auto-Zero immediately prior to connecting to the 
Eppley.

Admittedly the Eppley was originally designed to work into infinite load 
resistance (potentiometric comparison back in the old days when DCV meter 
input resistance was lower than for the 7081 and 3458A).

Comments?

Greg
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