What is meant by the _ of thermocouple instrument

Thermocouple can bend, high pressure resistance, heat fast response time and strong and durable many advantages, such as it and industrial prefabricated thermocouple, as measure temperature sensor, at the same time, also can be used as a prefabricated thermocouple temperature components. Electric conductor is to use two different ingredients of welded together, two end temperature is not at the same time, there will be a thermoelectric potential generated in the circuit, thus the potential galvanic couple is determined by measuring the electric potential to measure the temperature of a thermal original, it is a kind of converter, it can make temperature signals into electrical signals and then displayed by the display instrument. Thermocouple measuring temperature is the basic principle of thermoelectric effect, will be connected to the metal conductor fore and aft of the two different ingredients into a closed loop, such as the temperature of the two contact, can produce thermoelectric emf in the loop, form the thermal current, this is called the thermoelectric effect. Thermocouple is one end will be two different kinds of metal material welding, welding, called at the end of the measuring end not welding is called a reference at the end of the end, the reference side when use constant in a certain temperature (usually Such as 00 c) When to measure the heating, thermoelectric potential is at the junction produced. Such as reference end temperature constant, the size and direction of thermoelectric potential only with the characteristics of two kinds of metal material and measure the temperature, and has nothing to do with potential galvanic fine and length. When measuring the temperature change, the potential potential changes, and the temperature and a fixed function relationship between thermoelectric potential, take advantage of this relationship can measure the temperature. The application principle of thermocouple thermocouple is one of the industry commonly used temperature detecting element. Its advantage is high accuracy of measurement. Because of thermocouple direct contact with the object being measured, not affected by intermediate medium. Wide measuring 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. 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. 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. ( 2) The structure of thermocouple in order to keep the thermocouple is reliable, steady work, requirements for its structure composition of the thermocouple as follows two 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. Installation dimensions should try to choose metric [5 China standard] Such as thread: 12 x1. 5、16 x1。 5、20 x1。 5,27X2,33X2mm. Flange 95, 105, 115 mm in diameter. 3, the thermocouple cold end temperature compensation due to the thermocouple materials are generally more expensive ( Especially when using your metal) And temperature measuring points are far away the distance to the instrument, in order to save thermocouple materials, reduce cost, usually adopt the compensating conductor (of the cold junction of the thermocouple The free end) Reaches to the relatively stable control indoor temperature and connected to the meter terminals. It must be pointed out that the role of the thermocouple compensation wire only extend thermal electrode, make moves to the control room of the cold junction of the thermocouple meter terminal, it itself does not eliminate the cold end temperature change on the influence of temperature, no compensation. So, still need other correction method is used to compensate the cold end temperature t0 indicates influence on measuring temperature 0 ℃. Generally display and control instrument has automatic temperature compensation system, do not need to worry about. Instrument must pay attention to when using thermocouple compensating conductor model is suitable, the polarity can't wrong, compensation conductor should be connected to the thermocouple is generally not more than 100 ℃, the temperature here is important to note that many reproduced the technical data on the network speak: compensation conductor should be connected to the thermocouple is generally not more than 100 ℃, the temperature in fact, this is wrong! Special working conditions, can choose thermocouple extension, namely the conductor material and thermocouple electrode material consistent wire connection, such as: KX nickel chrome - Nickel silicon compensation conductor; The EX nickel chrome - Constantan thermocouple cable; JX iron - Constantan thermocouple cable; TX copper - Compensation conductor of copper nickel deposit is not the problem, according to the law of the middle of the thermocouple conductor, the compensating conductor temperature is not restricted. And some thermocouple such as: B dividing platinum rhodium - 30 Platinum rhodium 6, the thermocouple compensation conductor, in 400 degrees without accuracy using ordinary double core copper wire. There are two kinds of structure of the thermocouple, regular and type. Ordinary thermocouples generally by the hot electrode, insulation tube, to protect casing and junction box parts, such as the type of thermocouple is the thermocouple wire, insulation material and metal protective casing combination after assembly, after stretching processing from a combination of a solid.