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# Formulas for Calculating Coefficients for RTD / PRTD Calibration According to ITS-90

T

#### TJOHNY

Hi

According to the ITS-90 reference function for PRTD calibration, Can anyone help me with the formulas for calculating Alpha, Beta, Delta from the temperature V resistance. Also help me to find out the coefficients A, B, A and B from Alpha, Beta and Delta?

Staff member
Re: Coefficients for rtd /prtd calibration

Hello! Welcome to the Cove! Is there some electronic instrument/device you are connecting the probe to that is requesting these coefficients?

#### dwperron

Trusted
Re: Formulas for Calculating Coefficients for RTD / PRTD Calibration According to ITS

Here is a decent document for the Callendar - Van Dusen method of calculating the Alpha, Beta, ands Delta coefficients:

As for the A, B, etc. terms for ITS-90, here is a document with the formula, "How to calibrate an RTD or Platinum Resistance Thermometer (PRT)":

http://us.flukecal.com/literature/a...on/application-notes/how-calibrate-rtd-or-pla

The ITS-90 coefficients are real high level functions, there is software out there for sale (no free programs that I know of) that will do the job for you, such as Tableware from Fluke:

http://us.flukecal.com/products/cal...oftware/9933-tableware-v3-temperature-calibra

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#### TJOHNY

Re: Coefficients for rtd /prtd calibration

Yes, Black Stack Thermometer

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#### yosarian

Re: Formulas for Calculating Coefficients for RTD / PRTD Calibration According to ITS

The only way to calculate the ITS-90 coefficients from CVD coefficients is to generate a set of values of resistance and calculate the coefficients with that. Is a really high level work. Most temperature calibration labs can not do that.

The Black Stack have an option to use CVD in the form of A, B and C. To calculate A, B, C from alpa, beta and delta use:

A=alpha+(alpha*delta/100)
B=-alpha*delta/10000
C=-alpha*Beta/100000000