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PT100 4 wire with CR6 , current Vs voltage excitation

smile Sep 9, 2020 10:31 AM

Hi to All,

for the measurement of PT100 4 wire with CR6, with the need for an accuracy of at least one tenth of a degree, are there any advantages or contraindications in using current  versus voltage excitation?



JDavis Sep 9, 2020 10:56 AM

If you use voltage excitation, you need to add an external resistor like a 4WPB100. If you use current excitation, the CR6 uses a fixed reference resistance internal to the CR6. You can get a good measurement either way.

For comparison, you can look at the specification sheet of the CR6 to see the accuracy of resistance measurements and compare that to the accuracy of ratiometric measurements. Note that the resistance measurement accuracy takes into account the accuracy of the internal resistor. For the ratiometric, add in the error of the fixed resistor you plan to use.

smile Sep 10, 2020 10:08 AM

Hi JDavis

many thanks.

Maybe I lack the right technical preparation and I can't make a correct comparison.

Do you know if using a 100 Ohm 0.01% about only 1 PPM reference resistor, which technique gives better results? Current or voltage (ratiometric)? thank you so much


ZooKeeper Sep 14, 2020 10:03 AM

Either will result in less than 0.1 degree uncertainty but the method you suggest with a 0.01% 1PPM resistor should be slightly better than using the current excitation method internal to the datalogger. The tradeoff of course it that it takes an additional set of datalogger inputs.

smile Sep 14, 2020 10:11 AM

Well Many thanks

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