[volt-nuts] What really gets calibrated?

[Tom Miller]

Hi guys,

The "as found" measurements are most likely useful to determine if gross 
errors were made while the instrument was in use. Say you were using it to 
calibrate DMM multimeters in a production environment, you would like to 
know that a batch of meters went out with defective calibrations.

If you are getting an instrument calibrated for the first time after 
replacing a NVRAM battery, there would not be a need to have that known bad 
data recorded.

Many of the newer instruments require entering a known voltage and telling 
the instrument to record a calibration constant in its NVRAM.

I think that is mostly correct but if not, please feel free to criticize it.


Regards,
Tom

----- Original Message ----- 
From: "J. L. Trantham" <jltran at att.net>
To: "'Discussion of precise voltage measurement'" <volt-nuts at febo.com>
Sent: Sunday, July 28, 2013 6:42 PM
Subject: Re: [volt-nuts] What really gets calibrated?


> Joe,
>
> I agree with your analysis of 'calibration' and 'adjustment'.  However, if 
> a
> piece of equipment was able to meet a higher specification, I would 
> suspect
> the manufacturer would have claimed that.
>
> The benefit of the 'as found' and 'as left' measurements is that it tells
> you not only whether the unit is 'in spec' but also where it is in the
> range.  Might be useful.
>
> All of this, of course, is dependent of the 'quality' of the 'standard' 
> that
> is used to compare with.  That is probably where the price goes up and the
> 'metrolophilosophy' comes in.  In other words, do you trust your 'cal 
> lab'?
>
> Good luck.
>
> Joe
>
> -----Original Message-----
> From: volt-nuts-bounces at febo.com [mailto:volt-nuts-bounces at febo.com] On
> Behalf Of Joseph Gray
> Sent: Sunday, July 28, 2013 5:16 PM
> To: volt-nuts at febo.com
> Subject: [volt-nuts] What really gets calibrated?
>
> 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 can see that on the part of the calibration lab, it is easier and faster
> to simply check that a device meets spec and not have to spend time
> adjusting anything. It should also be less expensive for the customer.
>
> My question is, is just meeting spec good enough? If an instrument is
> capable of exceeding spec, shouldn't it be adjusted to the best standard
> available? In other words, if spec says 2 ppm, but it can be adjusted to 1
> ppm, wouldn't you want to do that?
>
> Joe Gray
> W5JG
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