Two-parameters Approximation Curve for NTC Resistors

Damir Ilić, Josip Butorac, Luka Ferković

Abstract

The table data for R-T dependence of NTC resistors (NTCRs), which have resistance RN = 10000 Ω at a temperature of 25 °C and limits of error ±0,2 °C in the range (0 to 70) °C [1-4], are analysed. The determination of two approximation curves is described: a three-parameters (abbreviated as AC1) and a two-parameters (AC2). These curves are compared with the three-parameters Steinhart-Hart equation (S&H) by using the table data of resistance for different NTCRs and calculating the following for all of them: unknown parameters by the least-squares method, approximated temperature using determined parameters, and the difference to the table data of temperature. The obtained results are presented, which show a very good agreement of curves, with their mutual differences within a few millikelvin, and the differences to the table data within ±15 mK for the range (0 to 70) °C. Therefore, presented two-parameters approximation curve AC2 can be very convenient for the use with some NTCRs for the calculation of unknown temperature from the measured resistance.

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IMEKO TC

TC4 - Measurement of Electrical Quantities

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