[volt-nuts] Reference Calibration Options - Solartron 7081andFluke 731B and 335A

Charles P. Steinmetz charles_steinmetz at lavabit.com
Sat Sep 10 08:15:17 UTC 2011


Greg wrote:

>(Wish I had a 732B, but those are pricey indeed!)

A number of cal types I know think the performance of the 732A is 
actually better than the 732B.  I have not played with the B myself, 
so I cannot comment from personal experience.

>The Solartron 7081 is spec'd +/- 4.3ppm at 10Vdc/year (2nd year), so based
>on published specs the 7081 uncertainty at 10Vdc is almost 7x better than
>the 731B (spec'd 30ppm/year).

Perhaps, but the actual expected stability of a properly operating 
731B (particularly one that has been operating 24/7 for several years 
or more) is significantly better than the specified performance of a 
7081 (or 3458A), and in addition its drift can be characterized 
reasonably accurately and subtracted (not so much with meters, with 
their several different error mechanisms).

>Not having personal experience with the 7081, I can't offer anything
>anecdotal about it. ...So I must rely on what actual owners (of the 7081)
>have experienced. (Have you read anything from any actual users claiming
>that their 7081 did *not* meet the 4.3ppm/year spec at 10Vdc?

I designed some process control systems that were used by a number of 
clients, which, due to systems integration requirements, used 
off-the-shelf DMMs to monitor DC process variables (6 to 24 per 
system).  I specified 3458As, and several clients used 7081s 
instead.  Those clients all had problems that were traced to the 
accuracy of the 7081s, and changing to 3458As cured the problems.  As 
far as I know, no time was spent characterizing the 7081s that were 
pulled, but they were all brand new and there was no reason to 
believe they were not operating nominally.

Best regards,

Charles









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