Re : Re: 4 wire resistance readings are sometimes negative

[K C]

Hi,

You talked about a 2% accuracy of the FS in your test document. This doesn't really make sense. You can easily take a Fluke multimeter to meet this spec. but it will not do for your measurement.

What do you really need for accuracy ? Did you check this with your instrument ?

[ChrisR.]

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@nitad54448 wrote:

The solution is to take care of thermoelectric coefficient, better voltmeter or alternating the sense of the current to get rid of the thermoelectric contribution (or use AC measurement ?).

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I just want to point out that that is exactly what the 4072 does when you enable offset-compensated ohms. It takes readings with the current source alternately enabled and disabled and subtracts the two different readings. That should take care of thermoelectric problems with the connections. There can still be calibration imperfections and noise, however.

Chris

[nitad54448]

hi

i don't know what 4072 is or does, but canceling the thermoelectric effect you don't need to enable and then disable the current source, you need to apply a current then apply the opposite one.

N