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The difference of working principle and application between thermocouple and thermal resistance

2022-02-26 15:11:57
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Thermocouple is a temperature sensor, and thermal resistance are the same temperature sensor, but thermocouple and thermal resistance in the process of use, there are still the following four aspects.


1, the nature of the signal: the thermal resistance itself is resistance, thermal resistance thermometer is based on the principle of wire resistance with temperature change; And thermocouple: is the two different data wire or semiconductor welding together, forming a closed loop, when there is a temperature difference between the two contacts of the wire, electromotive force will occur between the two, so in the loop to form a certain size of the current, this phenomenon is called thermoelectric effect. Thermocouples operate using this effect.


2, two kinds of sensor detection temperature scale: thermal resistance is generally detected 0-150 degrees temperature scale, high measurement scale can reach about 600 degrees, and thermocouple can detect 0-1000 degrees temperature scale (or even higher).


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3, data cost: thermal resistance is a kind of metal data, metal data with temperature sensitive changes, thermal resistance is resistance signal, its output is resistance value (ω), no positive and negative poles. Commonly used are Pt100, Cu50. The thermal coupling is bimetallic data, that is, two different metal data, because of the temperature change, at the two ends of the different metal wire potential difference. Can be divided into K, S, E, R, T, N type isometric number, can be used in different measurement medium, temperature measurement scale. A thermocouple is a voltage signal that outputs millivolts (mV) with positive and negative poles. There are more expensive than resistance, there are cheaper than resistance, but the compensation wire, the comprehensive cost of the thermocouple is high.


4, and THE relationship with PLC: PLC corresponding thermal resistance and thermocouple input module is not the same, this sentence is no problem, but the general PLC are directly access to 4 ~ 20MA signal, and the thermal resistance and thermocouple are generally with a transmitter to access PLC. If you plug into a DCS, you don't need a transmitter. Thermal resistance is RTD signal, thermocouple is TC signal! PLC also has thermal resistance module and thermocouple module, can directly input resistance and coupling signal.



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Company: Zhejiang Chunhui Instrument Co., LTD

Address: 101 Mingyue Road, Shangyu District, Shaoxing City, Zhejiang Province