Influence of parasitic electromotive force in Industrial Platinum Resistance Thermometer

Industrial Platinum Resistance Thermometer (IPRT) is a temperature sensor makes use of relationship between resistances of a platinum sensing element and temperatures. IPRT is widely used in industry, research and developing fields due to its high reliability. In precision measurements, AC bridges or high resolution digital instruments which can reverse the polarity of measurement current are used to eliminate parasitic electromagnetic-force (EMF) produced at somewhere in a metal-sheath of IPRT. On the other hand, low-cost digital instruments which cannot reverse the polarity are using in some applications. It should be noted that the readout temperatures from such instruments may be affected by parasitic EMF depending on measurement conditions. In some cases, the magnitude of temperature affected by parasitic EMF may be beyond calibration uncertainty. This problem has not been focused in the past. The results of measurements using 10 IPRTs are reported.