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Old 20th Jun 2018, 1:41 am   #68
G0HZU_JMR
Dekatron
 
Join Date: Sep 2010
Location: Cheltenham, Gloucestershire, UK.
Posts: 3,077
Default Re: Meter Suggestions for Basic Alignment/Calibration

Quote:
Originally Posted by Sinewave View Post
And unless you have it calibrated, if it were to drift by a factor of two, how would you know?
You don't know for sure it hasn't gone out of cal by the time you get it back from the cal house... or it might go out of cal weeks or month later.

The best thing to do is buy several decent DMMs and cross check them now and again if you are worried about accuracy or drift. Where I work I've never seen a single engineer show any interest when a decent DMM comes back from calibration. That would be hundreds of engineers over several decades. But on internet forums there are armies of people who seem obsessed by it.

Last autumn I bought a Keithley 2000 bench DMM at auction for the same cost of a (new) handle/feet kit so I could fit the handle to another meter. I didn't really care if the Keithley 2000 worked because it was worth it for the handle alone and any spares for the other meter. But it did work and it was only out of cal by 1 year. I only checked it once but it agreed with the other Keithley meter within 2 or 3 LSDs. To many hobbyists this LSD error would be a stressful problem that would 'need' addressing but to me it just meant that they were probably both still healthy meters and OK to use.

The meter below probably cost me 1/3rd the cost of even a basic annual calibration on a cheaper meter. Why would I want to calibrate it when it is probably two orders of magnitude better than I will ever need in terms of absolute accuracy and unlikely to drift this much in many years? I expect this meter to fail before it ever needs calibrating for hobby use. Note that it is just connected to a basic 5V supply here to show something on the display. Buy a few cheap/used meters like this and cross check them now and again.
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Regards, Jeremy G0HZU

Last edited by G0HZU_JMR; 20th Jun 2018 at 2:06 am.
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