Electronics > Metrology

Precise and accurate measurement of high value resistors

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stevebyan:
As an example, let’s say I want to restore an old HP-410B VTVM. It has two 50 Megohm 1% resistors in its input voltage divider. I need to measure them to within 0.33% or even better to within 0.1% in order to determine whether they are within tolerance or if instead they must be replaced. What instruments can I use to make this measurement? The only choices I know of are the Guildline 9520 Teraohmmeter and its successors, the General Radio 1666 DC Resistance Bridge, and the Guildline 9920 Current Comparator Bridge and its successors.

I’m particularly interested in instruments that are affordable by a hobbyist. Are there other possibilities? I’d like to cover up to a couple hundred Megohms with 0.1% accuracy.

jbb:
I could be horribly mistaken, but would a Source Measure Unit (SMU) work? They can apply a pretty high test voltage in combination with a sensitive current range.

Kleinstein:
The high value resistors are used in the higher voltage ranges. It should be enough to check if these range work OK and thus the divider. This is testing the resistor ratio for the divider, but this may be even better than just a resistor measurement.

stevebyan:
So I then need an electrometer, something with an input impedance of 5 Gohms or more, with 0.1% accuracy, right? So a Fluke differential voltmeter, I guess.

Edit: looks like my HP 3456A could do it if I stick to less than 10 Volts input.

Wallace Gasiewicz:
Is it more important that the 50 Meg Ohm resistors be entirely accurate or more important that they are the same value?   
Do you have equipment to measure One Meg?

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