Thermocouple cold junction temperature, also known as cold junction reference temperature, cold junction temperature, or reference temperature. As a thermocouple itself, it is a reaction temperatureThe millivolt value generated by a faulty component is only related to the temperature difference between the cold and hot ends. If one end is at 100 ℃ and the other end is at 20 ℃, then the thermocouple itself produces a millimeter waveThe voltage value only corresponds to 80 ℃. When used for temperature measurement, such as measuring an object at 100 ℃ in an environment of 20 ℃, and obtaining millivolt values corresponding to 80 ℃, onlyTo determine the temperature of the object being measured, an environmental temperature of 20 ℃ must be added. This 20 ℃ (ambient temperature) is the reference temperature for the cold end. The vast majority of temperature measuring instruments are capable ofAutomatic detection of cold junction temperature and automatic addition is called automatic cold junction compensation. But when he was on the school schedule, he became redundant, so he had to close himself on the scheduleDynamic cold end compensation or manual correction.

The thermoelectric potential of a thermocouple is related to the material of the thermoelectric electrode and the temperature of the two junctions. The graduation table of the thermocouple and the thermometer calibrated according to the graduation table are both based on the condition that the reference temperature of the thermocouple is equal to 0 ℃. Therefore, we must follow this condition when using them. If the reference temperature tn is not equal to 0 ℃, even if the measured temperature t remains constant, the thermoelectric potential E (t, tn) will also change with the variation of the reference temperature tn.

For example, we insert a nickel chromium nickel silicon thermocouple into a tubular electric furnace at 600 ℃ when the reference temperature of the thermocouple is 0 ℃; Its output thermoelectric potential is 24.91 millivolts; If the reference temperature is 30 ℃, the thermoelectric potential output by the thermocouple drops to 23.74 millivolts, which is the measurement error introduced when the reference temperature is not equal to 0 ℃. If the reference temperature changes, the introduced measurement error will be a variable. It can be seen that when the reference temperature is not equal to 0 ℃, it has a significant impact on the accuracy of the measured temperature.

When using thermocouples for temperature measurement, it is difficult to keep the reference temperature at 0 ℃, and it is generally only necessary for precise measurements in the laboratory. In typical engineering measurements, the reference temperature is mostly in the room temperature or fluctuating temperature range. At this point, in order to measure the actual temperature, measures such as correction or compensation must be taken.