Circuit diagram of a thermocouple cold junction temperature compensation

This article will introduce a thermocouple cold-end temperature compensation circuit, which includes a voltage temperature sensor TMP35 and a K-type thermocouple. The working principle of a thermocouple is to generate a potential difference based on the temperature difference between the hot end and the cold end. Since the temperature of the cold end is often not 0°C during actual measurement, the thermocouple needs to be temperature compensated. The thermocouple temperature compensation formula is as follows:

E(t,0)=E(t,t0)+E(t0,0)

Among them, E(t0,0) is the actual measured electromotive force, t represents the hot end temperature, t0 represents the cold end temperature, and 0 represents O℃. In on-site temperature measurement, since the temperature of the cold end of the thermocouple is generally not 0°C, but changes within a certain range, the measured thermoelectric potential is E(t,t0). If you want to measure the thermoelectric potential E(t,0) corresponding to the actual measured temperature, you must compensate for the cold junction not being 0°C. The compensation potential E(t0,0) required, and the compensation potential changes with the cold junction temperature. The changing characteristics must be consistent with the thermoelectric characteristics of the thermocouple for optimal compensation. The figure below is a circuit diagram of a thermocouple cold junction temperature compensation. In the figure, the temperature sensor TMP35 has completed the temperature compensation work very well. The voltage output by the TMP35 is first divided by the resistor and then amplified by the amplifier, which is the E(t0,O) corresponding to the K-type thermocouple.