Signal processing method with cold junction compensation for thermocouple

Thermocouple is a very popular and effective sensor for temperature measurement. But how to eliminate the interference of the temperature of cold junction is always a problem. A method based on recursive B-spline least-squares is proposed as a solution. The method establishes two models to convert the cold junction temperature to electromotive force (EMF) and the hot junction EMF to temperature respectively. And in the middle of them, the famous law of intermediate temperature is used to translate the measured EMF into the hot junction EMF. B-spline least-squares is adopted because of its great quality of approximation. Recursive approach is used to simplify the operation and make it suitable to be used in MPU. The simulate results show that the method is of high precision and stabilization whose average relative error is only 0.01% and has a powerful ability to reduce the nonlinearity of thermocouples.