Thermocouple sensors are widely used in industry as contact temperature measuring devices. This is because the thermocouple has the characteristics of stable performance, large temperature measurement range, long-distance transmission of signals, and simple structure and convenient use. In order to help you understand, this article will summarize the relevant knowledge of thermocouple sensors.

A thermocouple sensor can be defined as a temperature sensor used to measure the temperature of a specific point in the form of EMF or current. The sensor comprises two different wires, which are connected together at a junction. The temperature can be measured at the junction, and the temperature change of the metal wire will stimulate the voltage. Thermocouples can directly convert heat energy into electrical signals and output DC voltage signals, making it easy to display, record and transmit.

Advantages and disadvantages of thermocouple sensors

The sensitivity is relatively low, it is easily affected by environmental interference signals, and it is also easily affected by the temperature drift of the preamplifier, so it is not suitable for measuring small temperature changes. Since the sensitivity of the thermocouple temperature sensor is independent of the thickness of the material, the temperature sensor can also be made of very fine materials. Also because the metal material used to make the thermocouple has good ductility, this fine temperature measuring element has a very high response speed and can measure the rapid change of the process.

Thermocouple Sensor Applications

Thermocouple sensors are varied, a variety of sensors are commonly used in a modern thermocouple sensor shape is very small, so that it is more widely used in various fields of production practice, but also for our lives to provide a myriad of convenience and function.

The difference between thermocouple sensor and thermal resistance sensor

1. The nature of the signal: the thermal resistance itself is a resistance, and the thermal resistance thermometer works according to the principle that the resistance of the metal wire changes with temperature. Thermocouple: two wires or semiconductors of different materials are welded together to form a closed loop. When there is a temperature difference between the two contacts of the wire, electromotive force is generated between the two, thus forming a certain amount of current in the loop. This phenomenon is called thermoelectric effect. Thermocouples use this effect to work.

The temperature range detected by the two sensors: the thermal resistance generally detects the temperature range of 0-150 degrees, and the maximum measurement range can reach about 600 degrees, while the thermocouple can detect the temperature range of 0-1000 degrees (or even higher).

3. Material cost: Thermal resistance is a kind of metal material with temperature sensitive change. Thermal resistance is a resistance signal, and its output is resistance value (Ω) without positive and negative electrodes. Commonly used Pt100, Cu50.. Thermocoupler is a bimetallic material, which is two different metal materials. Due to the change of temperature, a potential difference is generated at both ends of two different metal wires. It can be divided into K, S, E, R, T, N type and other indexing numbers, which can be used in different measuring media and temperature measuring ranges. Thermocouple is a voltage signal, the output is millivolt value (mV), there are positive and negative. Some are more expensive than resistance and some are cheaper than resistance, but if compensation wires are included, the comprehensive cost of thermocouples is high.

4. Relationship with PLC: The input modules of thermal resistance and thermocouple corresponding to PLC are also different. This sentence is no problem, but generally PLC is directly connected to 4 ~ 20ma signals, while thermal resistance and thermocouple are generally connected to PLC with transmitters. If you connect to DCS, you don't have to use a transmitter. The thermal resistance is the RTD signal, and the thermocouple is the TC signal! (PLC also has thermal resistance module and thermocouple module, which can directly input resistance and thermocouple signals.