High performance analog linearization circuit for the Platinum Resistance Thermometer

In the field of resistance thermometry there is a need for an analog circuit that provides an output voltage that is proportional to temperature. Although devices that perform this function have recently become available, their use is limited to applications in which temperatures vary slowly over a narrow temperature range.

The aim of this study is to design, build, and test a circuit that will be suitable for those applications that require performance levels exceeding present capabilities. Particular attention is given to increasing the operating temperature range and the operational speed while maintaining acceptable accuracy. The circuit described is accurate to within ±1.0 deg K of the true temperature over the range of 100.0 deg K to 860.0 deg K and is capable of providing one complete conversion in less than 5.0 microseconds.