[volt-nuts] Voltage standards, Fluke 730A v.s. 731B

WB6BNQ wb6bnq at cox.net
Sun Aug 19 12:55:04 UTC 2012


Chris,

While the hp-3456 is a nice meter, I own one, it is not a replacement for a 731.  The
hp-3456 is called a transfer standard for only a very limited period of time (i.e., 24
hours or less).  Whereas the 731 will  hold its position (value) far longer (i.e., many
months if not longer).

Bill....WB6BNQ

Christopher Brown wrote:

> On 8/19/12 2:40 AM, WB6BNQ wrote:
> > Chris,
> >
> > Otherwise, if you are just looking for a working voltage standard then go for a
> > 731B and have it calibrated by a responsible credited LAB.  You can possibly save
> > calibration costs if you specify that you are only concerned with the 10 volt
> > output.  The other output taps are only good if no current is drawn from them by
> > using a proper null detector, specifically the Fluke 845.  The 10 volt output has
> > a low output impedance providing the ability to handle some small amount of
> > loading, such as the nominal 10 Meg Ohm input on good DMM's with very minor error
> > due to the loading.
> >
> > Bill....WB6BNQ
>
> On that front, please check my understanding.
>
> As I understand it, the 3456A is itself rated as a transfer standard
> with a nominal input impedance in the .1, 1 and 10 VDC ranges of 10Gohm
> and with due care (controlled environment, proper test leads, everything
> clean and free of potentially conductive residue degrading isolation,
> etc...) suitable for direct connection to a standard such as a 730A or
> 731B for calibration of said standard.  Also usable (in a pinch and only
> below 11VDC) in place of a NULL detector.
>
> Am I off kilter here?
>
> Thanks,
> Chris
> WL7CLA
>
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