Selection and precautions of compensation wire
1. Selection of compensation wire
The compensation wire must be selected correctly according to the type of thermocouple used and the occasion of use. For example, k-type couple should choose k-type compensation wire, and then choose the operating temperature range according to the application.
2. Connect the contacts
Make the two contacts of the thermocouple terminal as close as possible, and then keep the temperature of the two contacts similar. Keep the temperature at the connection of the instrument terminal as consistent as possible. Where there is a fan in the instrument cabinet, the contact should be protected. Do not let the fan blow directly onto the contact, otherwise it will cause unnecessary trouble.
3. Use length
Because the signal of the thermocouple is very low, in the microvolt level, if the use distance is too long, the signal will be attenuated and coupled due to the lengthening of the length and the interference from the strong electricity in the environment. This level is sufficient to cause the signal distortion of the thermocouple, causing Measuring and controlling the temperature is not accurate, and temperature fluctuations will occur when the control is severe.
According to our experience, it is usually better to control the length of thermocouple compensation wire within 15 meters. If it exceeds 15 meters, it is recommended to use a temperature transmitter to transmit the signal. The temperature transmitter converts the potential value corresponding to the temperature into a direct current for transmission, which has strong anti-interference.
4. Wiring position
Compensation wire wiring must be far away from power lines and interference sources. Where crossing is unavoidable, the crossing method should be adopted as much as possible instead of parallel.
5. Shielding compensation wire
In order to improve the anti-interference of the thermocouple connecting wire, shielded compensation wire can be used. For occasions with many on-site interference sources, the effect is better. However, the shielding layer must be strictly grounded, otherwise the shielding layer will not only not play a shielding role, but will increase interference.