[volt-nuts] nA advice

[Todd Micallef]

Do you have a high Z input dmm on the 10V range? Perhaps you can characterize its impedance  with another high value resistor of known value and then connect the UUT to the meter and measure its drop across the input with a test voltage.

Todd

Sent from my iPad

> On Nov 13, 2015, at 11:15, Andrea Baldoni <erm191ba3 at ermione.com> wrote:
> 
> 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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