Low Cost Signal Conditioning Technique for RTD Measurement.

RTD sensor resistances and temperature coefficients are relatively small. Lead wires with a total resistance as low as 10 Ω and relatively high temperature coefficients can change the data acquisition system’s calibration. The lead wire’s resistance change over temperature can add to or subtract from the RTD sensor’s output and produce appreciable errors in temperature measurement. Three-wire RTD measurement technique using a current source is widely used in industries for the measurement of RTD résistance. The benefit of 3 wire RTD connection over the 4 wire RTD is one less lead wire. However, this connection assumes that the two current-carrying wires have the same resistance. Novel approach for the measurement of RTD resistance through 3-wire cancellation using software techniques with constant voltage source (instead of current source) is proposed and implemented successfully.