User Manual

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49
9.4.3 Custom RTDs Library
ThecalibratorcanmeasuretemperaturewithmostRTDs.Butsometimesthereisaneedtosupportnon‐standardRTDs
andStandardPRTs(standardplatinumresistancethermometers).
Thecalibratorallowsyoutoinputthecustomizedvalues,soyoucanmeasuretemperatureusingeverykindofRTDsand
StandardPRTs.
How to create a custom industry RTD?
To get high
 precision, IEC and ASTM standards specify a more complex polynomial that fine‐tunes the
resistance‐temperaturerelationship.Oneformofthatequationisgivenhereasbelow.TheindustryRTDsalsospecify
valuesfortheconstantsR0,A,B,C(TheCconstantisonlyusedfortemperaturelessthan
0℃).




1    

   100


Forexample,forthecommonPt385RTDwith100Ωresistanceat0°C,thevaluesare:


 100Ω
A  3.9083  10


B5.77510


C  4.183  10


How to create a standard PRT?
The Standard Platinum Resistance Thermometer (SPRT) Calibration Laboratory of the NIST ThermometryGroup can
distinguish among the ITS‐90 from the argon triple point (Ar TP, –189.3442 °C) to the silver freezing point (Ag FP,
961.78°C)forthecalibrationofSPRTs.
TheITS‐90definestemperaturethroughasetof
specifiedthermometric fixedpoints, interpolationinstruments, and