A microcomputer-based instrument for applications in platinum resistance thermometry

Abstract

Platinum resistance thermometers are widely used in temperature measurements not only for calibration purposes but also in industrial applications. A new automatic instrument is described which can determine the actual value of the resistance of a platinum resistance thermometer in less than 0.52 s with a resolution of 8 PPM. The self-heating index can also be determined and the instrument is able to multiplex up to eight different platinum resistances. The temperature is calculated by using the interpolation formulae defined by the International Practical Temperature Scale of 1968 (IPTS-68).