Electronics > Metrology

DMM does not stabilize when measuring resistance

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What is interesting is that the Metal Foil resistor, at 1kΩ, 0.01% and 0.2ppm/ºC turns out to drift more than I expected - I did not measure the temperature change but it could not have been more than 10ºC worst case, which would mean 1000*0.2e-6*10 = 2mΩ drift, yet it drifted 133mΩ (or 43mΩ if you take initial value and final value and ignore the initial bump in resistance) over 21 minutes.

I saw a similar trend between the short and the Metal Foil resistor - making me think this is more to do with lead resistance than the actual component.  I switched to 4 wire mode and voila:

Delta 1 is for the whole period, if I look at the drift between 4 minutes and 20 minutes I get 0.45mΩ.

Also Z202 max TCR spec is 2.8ppm\K, not 0.2 ppm\K. Don't fall for "typical" specmanship from VPG on these. You cannot expect to have every random resistor meet typical spec. Short term rift of your DMM is also expected to be much bigger than one from resistor itself.

You could ditch the BNC and go to a 4 wire like I show.  Show a picture of  how you connect it.

Last one is 4 wire


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