thermocoupleIt is a temperature sensor used to measure temperature, just like a thermistor,But the main difference between it and thermistor is that:
1、 The nature of the signal is that a thermistor itself is a resistor, and changes in temperature cause a positive or negative resistance change in the resistor; Thermocouples, on the other hand, generate changes in induced voltage that are accompanied by temperature fluctuations.
2、 The temperature range detected by the two sensors is different. The thermal resistance generally detects a temperature range of around 0-150 degrees, and the highest measurement range can reach around 600 degrees (of course, negative temperature can be detected). Thermocouples can detect temperatures in the range of 0-1000 degrees Celsius (or even higher), so the former is low-temperature detection and the latter is high-temperature detection.
3、 From a material perspective, thermistor is a metal material that is temperature sensitive, while thermocouple is a bimetallic material. Therefore, these two different metals will generate a potential difference at the two ends of two different metal wires due to temperature changes.
4、 The input modules for thermal resistors and thermocouples corresponding to PLCs are also different. This statement is not a problem, but generally PLCs are directly connected to 4-20mA signals, while thermal resistors and thermocouples are usually connected to PLCs with transmitters. If it's connected to DCS, there won't be a transmitter anymore! Thermistors are RTD signals, while thermocouples are TC signals!
5、 PLCs also have thermal resistance modules and thermocouple modules, which can directly input resistance and thermocouple signals.
6、 Thermocouples come in J, T, N, K, S and other models. Some are more expensive than resistors, while others are cheaper. However, if compensation wires are included, the overall cost of thermocouples is higher. Thermistors are resistance signals, while thermocouples are voltage signals.
7、 The temperature measurement principle of thermal resistance is based on the property of the resistance of the conductor (or semiconductor) changing with temperature. Commonly used are platinum resistance (Pt100, Pt10) and copper resistance Cu50 (negative 50-150 degrees).
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