[volt-nuts] nA advice

[Rob Klein]

50V across 5GOhm is 10nA. Put a standard multimeter's 10MOhm input in 
series and
you have 10mV per nA reading. Anything below 100mV is pass.


My 2 eurocents.

Rob Klein

Op 13-11-2015 om 17:15 schreef Andrea Baldoni:
> Hello!
>
> I would like to measure insulation resistance of some defective load cells.
> The measurement should be done with no more than 50V and the full scale
> reading should be >=5Gohm. Accuracy of +-10% is enough (in fact it could
> suffice just to check if it's >=5Gohm or not).
>
> I have not been able to find a ready made instrument that could do this within
> a reasonable price (100 EUR); the normal insulation resistance testers go much
> high with the probing voltage (on the purpose, but this also lighten much the
> requirements on the sensitivity of the meter).
>
> It could be as simple as a led indicator "pass/fail", but at this point, why
> not to build a good frontend for a multimeter, so it could be much more useful?
>
> There are many way to do this and also many ready circuits (like the
> null detector in the mini metrology lab by Conrad Hoffmann) or in the AoE,
> but instead of making it from scratch, someone knows if there is something
> already made (or a kit)?
>
> Best regards
> Andrea Baldoni
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