Thermocouple and the working principle of thermocouple _ instrument

Thermocouple is one of the industry commonly used temperature detecting element. Its advantages are: (1) high accuracy of measurement. Because of thermocouple direct contact with the object being measured, not affected by intermediate medium. (2) the measurement range. The commonly used thermocouple from - 50 ~ + 1600 ℃ can be continuous measurement, some special thermocouple low measurable to - 271 - + 2800 ℃ as gold iron nickel chromium and tungsten - Rhenium. 3. Simple structure, easy to use. Thermocouple is usually composed of two different kinds of metal wire, but is not limited by the size and the beginning of, outside has protective casing, which are very convenient. Principle 1, the basic principle of thermocouple temperature measurement is to two different material a conductor or semi-conductor welding, form a closed loop. Due to two different metal carries different number of electrons, when two conductor when there is a temperature difference between the two fixation point of high potential to low potential discharge phenomenon occurs, thus formed in the loop current, the bigger the temperature difference, the greater the current, this kind of phenomenon called the thermoelectric effect, also called the seebeck effect. Thermocouple is in using this effect to work. 2, thermocouple type and structure formation ( 1) Thermocouple types commonly used thermocouple could be divided into two types: standard thermocouple and non-standard thermocouple. Standard thermocouple refers to the standard specifies the thermoelectric potential and the relationship between temperature, permissible error, and a unified standard score table of thermocouple, it has with matching display instrument to choose from. Non-standard thermocouple or on the order of magnitude less than the range using standardized thermocouple, generally no unified indexing table, mainly used for the measurement of some special occasions. Standardized thermocouple since January 1, 1988 in our country, the thermocouple and thermocouple were manufactured according to IEC international standard, and specify the S, B, E, K, R, J, T seven standardization thermocouple type thermocouple for our country unified design. Thermocouple temperature measurement principle is based on a conductor or semiconductor resistance changes with the temperature change and this feature to measure temperature and parameters related to the temperature. Thermocouple are mostly made of pure metal materials, the application is a lot of platinum and copper, now have begun to use the materials such as nickel, manganese and rhodium thermocouple. Thermocouple is usually need to get the resistance signal through wire transfer to the computer control device or other secondary instrument. The structure of thermocouple in order to keep the thermocouple is reliable, steady work, the structure of its requirement is as follows: two of thermocouple hot electrode welding must be strong; Two hot electrode should be well insulated between each other, in case of short circuit; Compensation conductor should be connected to the free cod of a thermocouple to be convenient and reliable; Protect casing thermal electrode should ensure sufficient isolation and harmful medium.