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4 wire thermistor measurement on a 2701

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daveatfernie
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Joined: September 2nd, 2016, 3:07 am
Country: United Kingdom

4 wire thermistor measurement on a 2701

Post by daveatfernie » September 2nd, 2016, 3:50 am

Good morning,

We're using a 4 wire thermistor measurement to provide a temperature reading. The condensed specifications for the 2701 states the following:

When using the 4 wire resistance setting that the accuracy over a year (for a 10k thermistor) is 0.01% +0.0006% with a test current of 100uA and the resolution is 10mOhms.
When using the 2701 in Thermistor mode, the specification however states that the resolution is 0.01DegreesC (equivalent to the same as the resistance measurement) but with an accuracy for a year of 0.08 Degrees C.
I believe that this equates to a better range over the year if we measure as a resistance measurement rather than as a thermistor and calculate the temperature from the known thermistor characteristics? Will this provide a more stable reading over the year or have I misunderstood the figures?

Kind regards

David

Andrea C
Keithley Applications
Keithley Applications
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Joined: October 15th, 2010, 10:35 am
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Re: 4 wire thermistor measurement on a 2701

Post by Andrea C » November 2nd, 2016, 8:00 am

The overall thermistor specs are for a span of temperatures which would cause different ohms measure ranges to be used (not just 10KΩ range). It also includes the computation of the temperature from the Steinhart Hart equation for certain assumed coefficients.

If your expected temperatures will result in always using the 10KΩ range, then I agree, you could use the ohms measure specs for that range and compute the temperature yourself from the reported ohms values.

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