[volt-nuts] What really gets calibrated?

[Orin Eman]

On Mon, Jul 29, 2013 at 12:25 AM, David Kirkby <david.kirkby at onetel.net>wrote:

> On 28 July 2013 23:15, Joseph Gray <jgray at zianet.com> wrote:
> > I recently had it explained to me that "calibration" is really just
> > checking a piece of gear against a known standard, to see if it meets the
> > manufacturers specification. If it is outside specified values, then it
> > gets "adjusted", not "calibrated".
>
>
> I think it depends somewhat on who cals it, and under what conditions
> are stated.
>
> I think if something is specified with an uncertainty of 10%, and is
> found to be 9.9% off, then I feel it should be adjusted as it is close
> to the limits of being acceptable, even though it is within spec.
>
> Certainly with Agilent, you will pay more for the cal if you want both
> "before" and "after" data.
>


Here is what Agilent say about the new 3446xA DMMS:

"Adjustment is Recommended

Whatever calibration interval you select, Agilent Technologies recommends
that complete re-adjustment should
always be performed at the calibration interval. This ensures that the
instrument will remain within specifications for
the next calibration interval and provides the best long-term stability.
Performance data measured during performance
verification tests does not mean that the instrument will remain within
these limits unless the adjustments are
performed. Use the calibration count to verify that all adjustments have
been performed. "

This is however, a closed box calibration where the calibration process
stores correction constants in non-volatile memory.  There are no concerns
about flaky trimpots etc..

Orin.