[volt-nuts] Cropico DO4A Digital Ohmmeter

gandalfg8 at aol.com gandalfg8 at aol.com
Mon Apr 30 05:45:09 EDT 2018

-----Original Message-----

From: Dr. David Kirkby <drkirkby at kirkbymicrowave.co.uk>
To: gandalfg8 <gandalfg8 at aol.com>; Discussion of precise voltage measurement <volt-nuts at febo.com>
Sent: Sun, 29 Apr 2018 22:18
Subject: Re: [volt-nuts] Cropico DO4A Digital Ohmmeter

I see this is a low-resistance (10 u ohm resolution) ohmmeter. Have you any
idea how you are going to check the calibration? I just bought a Simpson
444, which has 1 u ohm resolution. I have not got it yet, but are wondering
how I am going to check the calibration.

0.005% resistors are available from Farnell in a fairly limited number of
values, but certainty not in the range of values needed for a milli/micro
ohm meter.



Whoops, whilst checking the calibration is one thing, actual self calibration on the DO4A is perhaps not looking quite so straightforward, it's an automated calibration process that requires six set resistor values of 4mohm, 40 mohm, etc up to 4Kohm, and a quick check online doesn't show high tolerance versions of these values exactly falling out of the woodwork!

Nigel, GM8PZR
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