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The Philpott · 17th Aug 2018, 11:25 am

I had a similar attack of 'why isn't it working perfectly' on an avominor based low resistance ohmmeter. Repeatability of reading and repeatability of zeroing was not as it should be and it turned out to be a combination of 3 factors, bad continuity from the adaptor block used to make the AA cell fit, a little bit of static from the acrylic i used as a replacement for the cracked glass, and finally the movement showing it's age.

I replaced these parts, using a substitute movement scavenged from a contemporary avominor which i had confidently (and wrongly) calculated to be of the same sensitivity....All had to come apart again as the movement is unique to this particular meter and somewhat more sensitive than the 2mA standard article. More like 1 or 1.25mA...

Eventually... i got away with it. The glass seemed to improve the repeatability of readings so i shan't be using plastic again for this purpose! Twice i had to walk away from the job to avoid damaging anything through rushing..

17th Aug 2018, 11:25 am	#20
The Philpott Dekatron Join Date: Aug 2016 Location: Colchester, Essex, UK. Posts: 4,105	Re: Fluke 70 Series LCD Blotch Dilemma I had a similar attack of 'why isn't it working perfectly' on an avominor based low resistance ohmmeter. Repeatability of reading and repeatability of zeroing was not as it should be and it turned out to be a combination of 3 factors, bad continuity from the adaptor block used to make the AA cell fit, a little bit of static from the acrylic i used as a replacement for the cracked glass, and finally the movement showing it's age. I replaced these parts, using a substitute movement scavenged from a contemporary avominor which i had confidently (and wrongly) calculated to be of the same sensitivity....All had to come apart again as the movement is unique to this particular meter and somewhat more sensitive than the 2mA standard article. More like 1 or 1.25mA... Eventually... i got away with it. The glass seemed to improve the repeatability of readings so i shan't be using plastic again for this purpose! Twice i had to walk away from the job to avoid damaging anything through rushing..