Compact and accurate digital thermometer based on Anderson's loop and Pt-100 sensor

A simple and practical digital thermometer with an accuracy better than 0.1 degreesC over a near-room-temperature (from - 10 degreesC to 50 degreesC) measurement range has been developed. The instrument is compact and battery operated and provides for both digital and analog outputs. A four-lead platinum thermal sensor, driven by a constant current loop, allows fur accurate temperature readings with high immunity to the contact resistances and to their variations. A low-noise electronics allows for temperature measurements with a 1 mK resolution. By experimentally characterizing the non-linearity of the adopted Pt-100 sensor, a suitable readout correction table has been calculated in order to compensate for the sensor non-linear behavior. This compensating procedure allows for a wider (from - 50 degreesC to + 200 degreesC) and higher accuracy (similar to 0.05 degreesC) measurement range. The ultimate accuracy was essentially limited by the accuracy of the temperature standard used for calibration. (C) 2001 Published by Elsevier Science Ltd.