Using Operational Amplifiers to Realize the Compensation of Thermocouples

Abstract

It was commonly modified a thermocouple transducer artificially and piecewise through the presupposed values in order to compensate its nonlinearity effects on the temperature measurement. In doing so, although it can solve some errors in measurement, the parameters appear to be divergent from one to another for the same group of thermocouple transducers, and hence compensations must be executed for each of them. The work is heavy, the efficiency is low and the effect is poor. Just for those reasons, the designers have been obsessed with such sort of issues, which are sticky ones in front of them as well. Is there a better way to help them out of the present predicament? Yes, The author has found out the relationship among the external temperature, the measured temperature and the thermoelectric potential generated through the thermocouple transducer by comparing a great deal of thermocouple transducers, that is,there is a certain linear relationship existing in a high-order power series function. So we have used high-speed operational amplifiers to compute the high-order power series function and compensate the circuit in order to realize the real-time compensation for thermocouple transducers, which has not only realized the linearity optimization of them, but also got the instantaneous time of temperature measurement. In the end the accuracy of the controlled temperature has greatly increased. The results are satisfying according to the application of temperature-controlled furnaces.