Understand high temperature and high pressure thermocouples

The magnitude of the thermoelectric potential of a high-temperature and high-pressure thermocouple is only related to the temperature difference of the thermocouple. If the temperature of the cold end of the thermocouple remains constant, the thermoelectric potential of the thermocouple is only a single value function of the working end temperature Welding two different materials of conductors or semiconductors A and B together to form a closed circuit, when there is a temperature difference between the two attachment points 1 and 2 of conductors A and B, an electromotive force is generated between them, thus forming a current of a certain magnitude in the circuit. This phenomenon is called thermoelectric effect, which is used to work

A high temperature and high pressure thermocouple is a circuit composed of two conductors with different compositions (called high temperature and high pressure thermocouple wires or thermoelectric electrodes) connected at both ends. When the temperatures of the two junction points are different, an electromotive force is generated in the circuit, which is called thermoelectric effect, and this electromotive force is called thermoelectric potential It is using this principle for temperature measurement, where the end directly used to measure the temperature of the medium is called the working end (also known as the measuring end), and the other end is called the cold end (also known as the compensating end); Connect the cold end to the display instrument or matching instrument, and the display instrument will indicate the thermoelectric potential generated by the high temperature and high pressure thermocouple It is actually an energy converter, where high-temperature and high-pressure thermocouples convert thermal energy into electrical energy and measure temperature using the generated thermoelectric potential

The thermoelectric potential of a high-temperature and high-pressure thermocouple is a function of the temperature difference between the two ends of the working end of the thermocouple, rather than the temperature difference between the cold end and the working end of the thermocouple. The choice of atmosphere is suitable for use in strong oxidizing and weak reducing atmospheres. If a protective tube with good airtightness is used, the requirements for the atmosphere are not very strict The selection of durability and thermal responsiveness: Thermocouples with larger wire diameters have better durability, but their response is slower. For thermocouples with larger thermal capacities, their response is slower. When measuring temperatures with large gradients, temperature control is poor under temperature control The selection of high-temperature and high-pressure thermocouples is influenced by the properties and states of the measured objects. The temperature measurement of moving objects, vibrating objects, and high-pressure vessels requires high mechanical strength. In atmospheres with chemical pollution, protective tubes are required. In situations with electrical interference, high insulation is required