June 5, 1997

Program converts temperature from RTD sensor

Robert Ruehle, Relco Products, Denver, CO

A 100V, platinum resistance-temperature-detector (RTD) sensor provides an accurate means of obtaining temperature readings. Platinum sensors have a nonlinear resistance-vs-temperature characteristic; therefore, for accurate measurements, you must calibrate the sensor and use a table of resistance vs temperature. The program in Listing 1 gives the calibration data in the table for a 167.482V sensor, according to the ITS-90 reference curve. The executable PC program plattemp.exe searches the table for the two resistances adjacent to the measured sensor resistance and then interpolates between them to obtain the desired temperature. The computer displays the two calibration temperatures (Figure 1). Click here to download the files from DI-SIG, #2040. (DI #2040)

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