How to connect the three wires of the thermocouple

1. Definition of Thermocouples
A thermocouple is a sensor used to measure temperature and is a paired thermistor composed of two different metal wires. It uses the thermoelectric effect to measure temperature, and when the temperature of two metal wires is different, an electromotive force is generated.
2. Working principle of thermocouples
The working principle of a thermocouple is based on the thermoelectric effect, which means that when two different metal materials come into contact, if the temperature at the two contact points is different, an electromotive force will be generated. This electromotive force is proportional to the temperature difference.
3. Wiring method for thermocouples
Thermocouples are generally composed of two different metal wires, one of which is called the "hot end" and the other is called the "cold end". The wiring methods for thermocouples mainly include single wire method, double wire method, and three wire method.
Connect the hot end to the ground terminal of the measuring instrument, while the cold end is not connected. This method is suitable for measuring relative temperature, but it may result in significant errors.
Connect the hot and cold ends to the two input ports on the measuring instrument, respectively. This method can reduce errors and improve measurement accuracy.
Connect the hot and cold ends to the two input ports on the measuring instrument, and at the same time, connect a compensation wire between the hot and cold ends to the compensation port of the measuring instrument. This method can further reduce errors and improve measurement accuracy, especially suitable for long-distance transmission.
4. Application fields of thermocouples
Thermocouples are widely used in industrial control and laboratory measurements, especially in temperature measurement under high temperatures and harsh environments. It is commonly used in fields such as boilers, furnace temperature control, and high-temperature molten metal temperature measurement.
5. Advantages and disadvantages of thermocouples
Capable of measuring in high temperature environments.
Strong corrosion resistance, suitable for harsh process conditions.
The measurement range is wide and can reach several thousand degrees Celsius.
Poor linearity and relatively low measurement.
Low sensitivity and slow response to temperature.
Compared to other temperature sensors, it is more complex and expensive.
6. Precautions for the use of thermocouples
When using thermocouples, the following points should be noted:
The protective tube for thermocouples should be made of suitable materials to resist corrosion and high temperatures.
The connection of the circuit should be firm and reliable to avoid loosening or disconnection.
Avoid close contact between thermocouples and high-power equipment or electromagnetic interference sources to avoid affecting measurements.
Regularly calibrate and maintain thermocouples to ensure measurement accuracy.
Thermocouples are a commonly used temperature sensor that uses the thermoelectric effect to measure temperature. When using thermocouples, different wiring methods can be selected as needed to improve measurement accuracy. Thermocouples are widely used in industrial control and laboratory measurement, and have good temperature measurement performance in high temperature and harsh environments.