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" <[email protected]>
To: "'Discussion of precise voltage measurement'" <[email protected]>
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: [email protected] [mailto:[email protected]] On
Behalf Of Joseph Gray
Sent: Sunday, July 28, 2013 5:16 PM
To: [email protected]
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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