How to correctly use thermocouple compensation wires?

How to use thermocouple compensation wires correctly?

People can perceive temperature changes, but if the temperature changes too much, it is very dangerous for people to come into contact with it. Therefore, it is very important if objects can replace people and more accurately perceive temperature. Thermocouples accomplish this task by directly contacting the working environment and transmitting the sensed temperature in real-time.

What is a thermocouple? How is temperature perception achieved?

It consists of two different metals welded together to form a measurement circuit. As long as the temperature of the two welding points is different, an electric potential is generated in the circuit, which is called thermoelectric potential.

To know the actual temperature of the working environment, place one of the welded joints into the working environment and expose the other joint to room temperature. Through the composition and principle of thermocouples, it is known that the generation of thermoelectric potential is related to the temperature difference between the two junctions. Therefore, only when the ambient temperature is zero at room temperature can the temperature in the working environment be truly determined. To address the measurement impact caused by environmental temperature, applying wire compensation method based on on-site conditions is the most convenient and effective approach.

Thermocouple compensation wire compensation method

It should be noted that the compensation wire is not essentially used for compensation, but rather to extend the contact point (cold end) placed in the environment to the secondary instrument. Therefore, the true function of the compensation wire is to extend the cold end to a specific position for processing.

Due to the variety of thermocouple types, each with a corresponding compensation wire, they should not be used randomly, otherwise the display error will be greater. When selecting, pay attention to the correct matching.

According to the principle of thermocouple, its signal is thermoelectric potential, which belongs to analog millivolt signal and is DC. Therefore, the thermocouple wiring is divided into positive and negative poles, and its compensating wire is also divided into positive and negative poles, so it cannot be misconnected during use.

Thermocouple compensation wire

Based on the above, the thermocouple compensation wire must be selected with the correct model, the polarity must not be reversed during connection, and it cannot be mixed with ordinary wires.

How to use compensating wires?

The first step is to choose the type of compensating wire for the thermocouple used, such as using K-type thermocouple compensating wire for the K-type thermocouple.

Step 2 Wiring: Connect the parts as close as possible to the thermocouple terminals to safely introduce the thermoelectric potential into the secondary instrument. Avoid blowing electrical appliances such as fans onto the secondary instrument contacts.

The third step is to compensate for the distance of the wire: try to ensure that the extension distance does not exceed 15m, so as to avoid signal attenuation and strong electrical interference coupling.

Step 4 wiring: Avoid laying strong electrical lines and interference sources.

The fifth step is to compensate for the anti-interference ability of the wire: In order to provide anti-interference capability, shielded compensation wires should be used as much as possible, especially in situations with multiple interference sources. The application of shielded compensation wires is essential, and the shielding layer should also be grounded properly.