What factors affect the accuracy of thermocouple cold junction temperature compensation?

The accuracy of the cold-end temperature compensation of thermocouples is affected by many factors, as follows:
Environmental factors
Temperature fluctuations: The ambient temperature of the cold end is unstable and fluctuates greatly, which will cause inaccurate cold-end temperature measurement and thus affect the accuracy of compensation. For example, if the cold end is close to a heat source, an air-conditioning outlet, or is in a well-ventilated but frequently changing location, the cold-end temperature may fluctuate.
Electromagnetic interference: If there is a strong electromagnetic field near the cold end, it may interfere with the signal transmission of the thermocouple and the measurement of the cold-end temperature sensor, resulting in measurement errors and affecting the compensation accuracy. For example, in some industrial sites, there is strong electromagnetic interference around large motors, transformers and other equipment.
Equipment factors
Cold-end temperature sensor accuracy: The accuracy of the cold-end temperature sensor directly determines the accuracy of the cold-end temperature measurement. If the sensor itself has a large error, the cold-end temperature compensation based on the measured value will also be inaccurate. For example, using a thermistor with low accuracy as a cold-end temperature sensor may not accurately measure the actual temperature of the cold end.
Compensation wire characteristics: The material, length, and laying method of the compensation wire will affect the compensation effect. If the compensation wire does not match the thermocouple, or the wire is too long or damaged during the laying process, it may cause signal transmission distortion and inaccurate cold end temperature compensation.
Measuring instrument accuracy: The instrument used to measure the thermoelectric potential and cold end temperature of the thermocouple is not accurate enough, which will cause errors in the measurement results, thereby affecting the accuracy of cold end temperature compensation. For example, the resolution of the instrument is not high enough to accurately measure small changes in thermoelectric potential.
Installation and maintenance factors
Improper installation position: The installation position of the cold end temperature sensor is unreasonable, such as not being close to the cold end of the thermocouple, or being installed in an area with uneven temperature, which will make the measured cold end temperature unable to truly reflect the actual temperature of the cold end of the thermocouple, resulting in compensation errors.
Poor connection: The connection points between the thermocouple and the compensation wire, and the compensation wire and the measuring instrument are poorly contacted, which will generate additional contact resistance, resulting in inaccurate thermoelectric potential measurement and affecting the cold end temperature compensation effect. For example, loose connection points and oxidation may increase contact resistance.
Failure to calibrate and maintain regularly: If thermocouples, cold-end temperature sensors, and measuring instruments are not calibrated and maintained regularly, the performance of the equipment may decline over time, and the measurement error may gradually increase, thus affecting the accuracy of cold-end temperature compensation.