Precision analogue lineariser for thermocouples

An analogue fourth-order polynomial curve fitting circuit has been designed using only two precision squarers to linearise the thermocouple voltages of standard thermocouples. Typical design data and performance of the circuit are illustrated for the Type K thermocouple. This circuit can also be used to linearise the outputs of other types of transducers and simulate nonlinear variations with temperature of physical quantities such as the absolute thermoelectric power of chromel and alumel.