Methods for the Linearisation of the Transfer Function of Thermoresistive Transducers

The article describes digital and analogue methods for linearising the conversion function of thermoresistive transducers, with a detailed analysis of analogue methods. Analogue methods for linearising bridge circuits and measurement circuits based on passing a reference current through a resistance temperature detector (RTD) are considered. Linearisation of bridge circuits is based on the formation of the compensating supply voltage of the bridge circuit, which depends on the change in the measured temperature. When using the measurement method based on passing a reference current through an RTD, nonlinearity compensation is achieved by changing the conversion coefficient of the measuring signal or passing an additional current through the RTD, which linearly depends on the value of the RTD’s voltage change (measured temperature value). When passing an additional compensation current through the RTD, the nonlinearity error is not grater than 0.1°C in the range of 0…800°C, and the schematic diagram of the measuring transducer contains a minimum number of elements, which allows to increase its reliability. In general, the choice of a linearisation method depends on the requirements for accuracy, operation rate and resource limitations of the measuring system.