[volt-nuts] Calibration of voltage standards

Chuck Harris cfharris at erols.com
Wed Feb 11 02:36:47 EST 2015

To do a comparison of the sort you are asking about, the
sensitivity of the null meter is much more important than
its ultimate accuracy.

So, neither of your meters is really the right meter to
use for this task.  What you want is called a null meter,
and is generally sensitive to the microvolt region.

-Chuck Harris

Ken Peek wrote:
> Hi Group,
> I have heard of a few different ways to measure one 10V voltage standard
> against another 10V voltage standard.
> Assume we have two 10V voltage standards.  One is calibrated, the other
> not only needs to be calibrated, but probably adjusted.  For the sake of
> simplicity, let's say the two standards are Fluke 732B's.
> I *think* the best way is to connect the two units' (-) terminals
> together, then connect a calibrated meter in between the (+) terminals,
> and measure the difference.  I have also heard that to remove thermal
> EMFs, you should use a low-thermal-EMF DPDT switch or a low-thermal-EMF
> relay to reverse the connections on the DMM, so you can take the reading
> forward and reversed, then split the difference.  There is the
> possibility to introduce thermal-EMF errors from the switch/relay as
> well, so I'm wondering if this is a good idea.  This sort of makes sense
> to me, but I'm not a metrologist, so I would like to hear what others in
> this group think about this.
> So, just what is the proper way to accomplish this task?
> BTW-- I have an Agilent 34420A and an HP 3458A, which would be the
> better instrument for this task?
> Best Regards,
> Ken Peek
> =============================
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