Thermocouple temperature sensor is a kind of test, like the thermocouple temperature sensor, thermocouple and thermocouple in the process of use, but there is still a difference between the following four aspects. 1, the difference between the thermocouple and thermocouple signal properties: thermocouple itself is resistance, thermocouple thermometer is according to the principle of wire resistance change with temperature of work; Thermocouple: had two different materials of the conductor or semiconductor welding together, constitute a closed loop, when the conductor when there is a temperature difference between the two contact occurs between the electromotive force, thus forming a certain size of current in circuit, this kind of phenomenon called the thermoelectric effect. Thermocouple is in using this effect to work. 2, two kinds of sensors to detect temperature range: 0 - thermocouple general detection 150 degrees temperature range, high measurement range can be up to 600 degrees, and thermocouple can detect 0 - Temperature range of 1000 c ( Even higher) 。 3, the material cost: thermocouple is a kind of metal material, with a temperature sensitive metal materials, thermocouple is resistance signal, the output is the resistance value ( Ω) , nothing is negative. Commonly used pt100, cu50. The thermocouple is the metal material, both two kinds of different metallic materials, due to the changes of temperature, in two different electric potential difference at both ends of the wire. Can be divided into k, s, e, r, t, n equal degrees, can be used separately in different measurement medium, the temperature measurement range. Thermocouple is a voltage signal, the output is millivolt values ( mv) , have a positive negative. There are also more expensive than resistance, cheaper than resistance, compensation conductor, but on comprehensive cost of the thermocouple is high. 4 and the relationship with PLC, PLC corresponding thermocouple and thermocouple input module is also different, this sentence is no problem, but the general PLC are 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! ( PLC has thermocouple module and thermocouple module, can be directly input resistance and thermocouple signal resistance itself is resistance, thermocouple thermometer is according to the principle of the wire resistance change with temperature.