The application of thermocouples in the conductive slip ring industry

Thermocouples are commonly used temperature measuring components in temperature measuring instruments. When two conductors with different compositions are connected at both ends to form a circuit, thermal current will be generated in the circuit when the temperature of the two junction thermocouples is different. If there is a temperature difference between the working end and the reference end of the thermocouple, the display instrument will indicate the temperature value corresponding to the thermoelectric potential generated by the thermocouple. The thermoelectric heat of a thermocouple will increase with the temperature of the measuring end, and its size is only related to the thermocouple material and the temperature at both ends, regardless of the length and diameter of the thermoelectric electrode. The appearance of various thermocouples is often very different due to needs, but their basic structure is generally the same. They are usually composed of main parts such as thermal electrodes, insulated protective tubes, and junction boxes, and are usually used in conjunction with display instruments, recording instruments, and electronic regulators.
To choose a suitable conductive slip ring, it is necessary to first determine the type of temperature measurement system. The commonly used temperature measurement systems are thermal resistance type and thermocouple type. The following is an analysis of the differences between the two temperature measurement systems:
Thermocouples are one of the commonly used temperature detection components in industry. The working principle of thermocouples is based on the Seeback effect, which means that two conductors with different compositions are connected to form a circuit at both ends. If the temperature of the two connection ends is different, a physical phenomenon of thermal current is generated in the circuit. Its advantages are:
① High measurement accuracy. Due to the direct contact between the thermocouple and the measured object, it is not affected by the intermediate medium.
② Wide measurement range. Common thermocouples can measure continuously from -50 to+1600 ℃, while some special thermocouples can measure temperatures as low as -269 ℃ (such as gold iron nickel chromium) and up to+2800 ℃ (such as tungsten rhenium).
③ Simple construction and convenient use. Thermocouples are usually composed of two different types of metal wires, and are not limited by size or beginning. They have a protective sleeve on the outside, making them very convenient to use.
1. Types and structure formation of thermocouples
(1) The types of thermocouples commonly used can be divided into two categories: standard thermocouples and non-standard thermocouples. The standard thermocouple referred to is a thermocouple that has a national standard that specifies the relationship between its thermoelectric potential and temperature, allowable errors, and a unified standard graduation table. It has accompanying display instruments available for selection. Non standardized thermocouples are not as good as standardized thermocouples in terms of usage range or magnitude, and generally do not have a unified graduation table. They are mainly used for measurement in certain special occasions. Since January 1, 1988, standardized thermocouples and thermal resistors have been produced in accordance with IEC international standards in China, and seven standardized thermocouples, S, B, E, K, R, J, and T, have been designated as the unified design type thermocouples in China.
(2) In order to ensure the reliable and stable operation of thermocouples, the structural requirements for thermocouples are as follows:
① The welding of the two thermoelectric electrodes that make up the thermocouple must be firm;
② The two thermoelectric electrodes should be well insulated from each other to prevent short circuits;
③ The connection between the compensating wire and the free end of the thermocouple should be convenient and reliable;
④ The protective sleeve should ensure sufficient isolation between the thermoelectric electrode and harmful media.