Do you really know how to use KX compensating wires?

KX compensation wire is usually composed of compensation wire alloy wire, insulation layer, sheath and shielding layer. A pair of wires with insulation layer that have the same nominal value of thermoelectric electromotive force as the matched thermocouple within a certain temperature range (including room temperature) are used to connect the thermocouple and the measuring device to compensate for the error caused by the temperature change at the connection between them and the thermocouple. How to correctly select and use thermocouple compensation wires is crucial. Do you really know how to use thermocouple compensation wires?

1. Using thermocouple compensation wires over long distances will introduce measurement errors due to signal attenuation and interference

The potential value generated when thermocouples measure temperature is an mV signal. Due to the increase in the length of the compensation wire, signal attenuation and on-site magnetic and electric interference coupling occur, causing the temperature display value of the instrument or DCS system to fluctuate.

Processing method:

1. If the compensation wire needs to be laid over a long distance, the wire diameter of the compensation wire should not be less than Φ1.5mm2 to reduce the attenuation of the mV signal.

2. Use shielded compensation wires and ground the shielding layer according to the specifications (the shielding layer must be grounded at one end of the compensation wire, and the grounding must be incorporated into the instrument signal grounding network. It is forbidden to incorporate the grounding into the factory electrical grounding network) to avoid measurement errors caused by incorrect grounding of the shielding layer.

3. Use a temperature transmitter to convert the local thermocouple signal into a 4-20mA signal transmission to improve the signal's anti-interference ability.

2. The temperature at the connection point between the thermocouple and the compensation wire exceeds the specified range of use

The operating temperature of ordinary thermocouple compensation wires is 0-100℃; the operating temperature of high-temperature resistant compensation wires is 0-200℃. For example, R-type thermocouple compensation wire Rc and S-type thermocouple compensation wire Sc are both compensation compensation wires. They have low accuracy among all types of compensation wires. The error is small when used in an environment of 0-60℃, and there is a large negative error when used in an environment of 0-150℃.

Correct method: The ambient temperature of general compensation thermocouple compensation wires does not exceed 100℃, and the high-temperature thermocouple compensation wire can reach 200℃.