What is the calculation correction method for thermocouples

Due to the fact that the temperature thermoelectric potential curve (thermocouple calibration table) of a thermocouple is obtained while maintaining the cold end temperature at O ℃, and the instrument used in conjunction with it is calibrated based on this relationship curve, although compensation wires are used to extend the cold end of the thermocouple to a constant temperature, as long as the cold end temperature is not O ℃, the instrument's indicated value must be corrected.
If the hot end temperature of the thermocouple is T and the cold end temperature is Tn instead of 0 ℃, the output potential of the thermocouple is measured as E (T, Tn). According to the intermediate temperature law E (T, O ℃)=E (T, Tn)+E (Tn, O ℃), the thermoelectric potential at the hot end temperature T and the cold end temperature O ℃ can be calculated, and then the hot end temperature T can be obtained from the calibration table. It should be noted that due to the nonlinearity of the thermocouple temperature potential curve, the addition mentioned above is the addition of thermoelectric potential, not simply temperature addition.
For example, using a nickel chromium nickel silicon thermocouple for temperature measurement, the cold end temperature Tn of the thermocouple is 30 ℃, and the thermoelectric potential E (T, Tn) measured at 30 ℃ is 40.347 mV. According to the calibration table, the thermoelectric potential E (Tn, 0 ℃) at 30 ℃ for the hot end and 0 ℃ for the cold end is 1 203 mV, then E (T, O)=E (T, Tn)+E (T, O)=(40.347+1.203) mV=41.55mV. Similarly, according to the calibration table, T=1010 ℃.
Thermocouples are sensors that measure temperature based on the thermoelectric effect and are commonly used temperature measuring components in temperature measuring instruments. The appearance of various thermocouples often varies greatly due to their needs, but their basic structures are roughly the same. They are usually composed of main parts such as hot electrodes, insulation sleeves, and junction boxes, and are usually used in conjunction with display instruments, recording instruments, and electronic regulators.
The basic principle of thermocouple temperature measurement is that two conductors with different compositions form a closed circuit. When there is a temperature gradient at both ends, current will flow through the circuit, and there will be an electromotive force - thermoelectric force - between the two ends, which is called the Seebeck effect. Two homogeneous conductors with different compositions are thermoelectric electrodes, with the higher temperature end as the working end and the lower temperature end as the free end, which is usually at a constant temperature. Create a thermocouple calibration table based on the functional relationship between thermoelectric potential and temperature; The calibration table is obtained under the condition of a free end temperature of 0 ℃, and different thermocouples have different calibration tables.
The thermoelectric properties of a thermocouple refer to the phenomenon of a potential difference occurring at the contact surface between two metals at a certain temperature.
1. The size of the thermocouple circuit properties is only related to the properties of the material and the temperature at both ends, and is dependent on the length and thickness of the thermocouple
Details are irrelevant.
2. Only conductors with two different properties can form a thermocouple; When the temperature at both ends of the thermocouple is different
Generate thermoelectric potential.
3. After the material is determined, the magnitude of the thermoelectric potential is only related to the temperature at both ends of the thermocouple.