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Old 15th May 2018, 8:33 pm   #2
G4_Pete's Avatar
Join Date: Feb 2014
Location: Southampton, Hampshire, UK.
Posts: 330
Default Re: Very high input resistance voltmeter

Another trick I have used is to put one side of the meter on a variable power supply and wind up the low impedance side to approach the measured voltage. The meter then becomes a null detector with impedance approaching infinity at balance.
You always have to be mindful that attaching wires to a high impedance point is like attaching a pick up areal so capacitor filters at the point of measuring if not inherent in the circuit might also be needed. But with your 100 meg that effect is reduced significantly.
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