[volt-nuts] What really gets calibrated?

[Didier Juges]

The big difference is that nowadays, adjustment is done in software without moving parts. There is no wear out involved in doing frequent adjustment and through the software you can record by how much each setting was adjusted.

These were the main reasons for not adjusting an instrument that was in spec when going to the cal lab.


Didier KO4BB

Orin Eman <orin.eman at gmail.com> wrote:
>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.
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