Thermocouple compensation wire selection, contact connection

A pair of wires with insulation having the same nominal value as the thermal electromotive force of the matched thermocouple over a range of temperatures (including room temperature), with which they connect the thermocouple to the measuring device in order to compensate for errors arising from temperature variations at the point where they are connected to the thermocouple.

Compensating wire precautions

1. Selection of compensation wire

Compensating wires must be selected correctly according to the type of thermocouple used and the occasion in which it is used. For example, the k-type coupling should be selected k-type coupling compensation wire, according to the use of occasions, select the operating temperature range. Usually kx working temperature for -20 ~ 100 ℃, wide range of -25 ~ 200 ℃. Ordinary level error of ± 2.5 ℃, precision level of ± 1.5 ℃.

2. Contact connection

And thermocouple terminal 2 contacts as close as possible, try to maintain the same temperature of the 2 contacts. The temperature of the connection with the instrument terminal is the same as possible, and where there is a fan in the instrument cabinet, the contact point should be protected so that the fan does not blow directly into the contact point.

3. Length

Because the signal of the thermocouple is very low, microvolt level, if the use of the distance is too long, the signal attenuation and the environment of strong electrical interference coupled, enough to make the thermocouple signal distortion, resulting in inaccurate measurement and control of the temperature, in the control of the temperature fluctuations will be generated in a serious situation.

According to our experience, the length of the thermocouple compensation wire is usually controlled within 15 metres, if it exceeds 15 metres, it is recommended to use a temperature transmitter to transmit the signal. Temperature transmitter is to convert the potential value corresponding to the temperature into DC current transmission, strong anti-interference.

4. Wiring

Compensation wire wiring must be away from power lines and interference sources. In order to avoid crossing the place, but also as far as possible to use the cross way, not parallel.

5. Shielded compensation wire

In order to improve the anti-interference thermocouple connection line, can be used to shield the compensation wire. For the scene of more sources of interference, the effect is better. But must be strictly grounded shielding layer, otherwise the shielding layer not only does not play a shielding role, but enhance the interference.