[volt-nuts] Serious problems fluke 731A, 720 and solartron

Will willvolts at gmail.com
Sat Oct 1 08:43:10 UTC 2011

> If i do a calibration on 10 V. It showes 10.000,000 on the display, but if I
> switch the 720 to 1.000,000 Volt the display shows 0.999,980 Volt. If I
> switch the solartron to the 1 V range it reads 1.000,000.x Volt. So the 10 V
> range is not lineair. The stupid thing is, I can get it right. If I use the
> filter while meauring the 1 V in th 10 V range it is correct but then it
> will not read the 10 V correct.  So it looks like there is some noise of
> common mode problem. I have not checked the 1 V range the same way. I will
> do that too.
> Does that ring a bell to someone ?
> Fred PA4TIM

The 7061 input resistance loads the 720A output. 10 Gohm should result
approximately 4ppm error.

IF the 720A is working perfectly, the input resistance of your 7061
(including connection cables) is lower than specified. Could be dust,


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