A Linear Thermocouple Temperature Meter Based on Inverse Reference Function

A linear thermocouple temperature meter based on the inverse reference function is presented, whose hardware consists of AD590M, multiplexer, standard resistor, amplifier, AD converter, digital display and so on. The software comprises an applied program and a thermal electromotive force-temperature reference table calculated by the inverse reference function. The AD590M is used as a current source in addition to cold junction compensation. A temperature measuring-calculating model is built according to the structure of data acquisition hardware. Under the control of a single chip processor, the system samples the value of cold junction compensation, thermal electromotive force of thermocouple, standard milli-voltage signal, zero signal etc and calculates the highly accurate value of the thermal electromotive force according to the temperature measuring-calculating model. Then the temperature is obtained by looking up the thermal electromotive force-temperature reference table with the value of thermal electromotive force. Between the tow temperature points of the reference table the temperature is calculated by linear interpolation methods accurate to 0.1°C. The test error is about ±1°C in -100°C~1372°C without considering the error of thermocouple when using the K type thermocouple.