[volt-nuts] Solartron 7081, other meters, and some voltage standards

[Charles P. Steinmetz]

Joe wrote:

>I have been testing my 'new' 7081
>      *   *   *
>I have two Fluke 731B's
>an HP 3478A and an HP 3457A, as well as a
>Fluke 335A
>      *   *   *
>Soooooooo, what, if any, conclusions are reachable?  I am tempted to believe
>that the 'black' face 731B and the 7081 are correct.  What are the odds?

Others have indicated what sort of stability you might expect from 
some of these, assuming that they have not been adjusted (or 
otherwise molested) since their last traceable calibration.  However, 
from what you have said about their provenance, you have no way of 
knowing who's been "calibrating" or adjusting any of these, or when, 
or what standards were used.  So you have no basis for *any* belief 
about which, if any, of them is "correct."

If you are going to have just one of them calibrated by a standards 
lab, you should calibrate the most stable one.  The 731s should be 
the most stable of that bunch.  Ideally, you should ship a 731 "hot" 
(under battery power) to the lab, and the lab should return it hot, 
so that there are no issues with power-cycle hysteresis (note that 
the 731's successor, the 732, which uses the same reference element, 
is only guaranteed to remain in cal if it has been under continuous 
power since calibration).

Best regards,

Charles