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

A simple and practical digital thermometer with an accuracy better than 0.1/spl deg/C over a near-room-temperature (from -10/spl deg/C to 50/spl deg/C) 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 for 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-linearity. This compensating procedure allows for a wider (from -50/spl deg/C to +200/spl deg/C) and higher accuracy (/spl sim/0.05/spl deg/C) measurement range. The accuracy, up to now, is essentially limited by the accuracy of the temperature standard used for calibration.