What is the difference between the thermocouple and thermocouple _ instrument

Thermocouple, thermocouple and both belong to the temperature sensor, and is widely used in agriculture, transportation, science and technology, environmental protection, national defense, culture and education of health and other fields. Although the thermocouple and thermocouple is commonly used in industry temperature detecting element, but both in use process is the following differences. 1, the principle: the size of the thermocouple is through the resistance value to reflect the change in temperature; Thermocouple is through the change of the electromotive force to reflect the changes of temperature. 2, temperature measuring range: thermocouple temperature measurement minus temperature, thermocouple is - large temperature range 70 - 1000 degrees; Thermocouple is not, thermocouple 0 1800 degrees. 3, signal properties: thermocouple itself is the resistance, the change of the temperature, the resistance produce positive or negative resistance changes; The change of the thermocouple, is induced voltage, he along with the change of temperature change. 4, material: thermocouple is a kind of metal material, with a temperature sensitive metal materials; Thermocouple is double metal materials, two different kinds of metals, due to the changes of temperature, in two different electric potential difference at both ends of the wire. 5, PLC corresponding thermocouple and thermocouple input module: general PLC is directly connected to the 4 ~ 20 ma signal, and the thermocouple and thermocouple are generally transmitter to access with a PLC. If access to DCS don't have to use the transmitter! Thermocouple is a sign of RTD, thermocouple is tc signal! 6, thermocouple j, t, n, k, s and other models, there are more expensive than resistance, there are also cheaper than resistance, compensation conductor, but on the comprehensive cost of the thermocouple is high. The application and principle of the thermocouple analysis commonly used in low temperature zone thermocouple is a kind of temperature detector. Its main characteristic is high accuracy, stable performance. Among them is platinum thermal resistance measurement accuracy is high, it is not only widely used in industrial temperature measurement, and is made into standard benchmark instrument. 1. Thermocouple temperature measuring thermocouple temperature measurement principle and the material is based on the metal conductor resistance value increases with the increase of the temperature of the properties for temperature measurement. Thermocouples are mostly made of pure metal materials, the application is a lot of platinum and copper, in addition, now has started using survey, nickel, manganese and rhodium thermocouple materials such as manufacturing. 2. Thermocouple temperature measurement system of thermocouple temperature measurement system in general by thermocouple, connecting wires and display instrument, etc. Must pay attention to the following two points: (1) thermocouple and digital display table index number must be consistent. (2) in order to eliminate the influence of the connection wire resistance change, must use three wire connection. Thermocouple common failure 1, failure phenomenon: display instrument indicates a negative; Possible reasons: the display instrument with thermocouple wiring is wrong or thermocouple have short circuit phenomenon; Processing method: correct wiring, or find out short circuit, reinforced insulation. 2, fault phenomenon: thermocouple table indicating infinity; Possible reasons: thermocouple or loosen the lead wire short circuit or terminal; Methods: the change in resistance or welding and tighten the screw connection, etc. 3, fault phenomenon: display of thermocouple indicated value is lower than the actual value or unstable value; Possible reasons: protecting tube with metal dust, dust, dirt and thermocouple short circuit between terminal; Methods: to remove scrap metal, cleaning dust, water, etc. , find the short circuit point reinforced insulation. 4, failure phenomenon: thermocouple value changes with the temperature relation; Possible reasons: thermocouple wire material corrosion metamorphism; Deal with method: replace thermocouple; Thermocouple common fault has introduced over, when users in the use of thermocouple to the fault can refer to the above article can effectively solve the problem, for the user to reduce unnecessary trouble to improve work efficiency.