Can thermocouples use ordinary connectors?

Ordinary connectors, here we refer to the common connectors for transmitting electrical signals or power. The contact parts of this connector use copper alloys because copper and copper alloys have excellent electrical properties. As for thermocouple connectors, we refer to connectors specially made for transmitting thermocouple signals. We found that many people use ordinary connectors casually because they do not understand the working principle of thermocouples or to save costs and simplify the drawings. In fact, this is a very inappropriate practice and has great hidden dangers.

We know that the positive and negative poles of thermocouples are made of special metal materials. The composition ratio of each element in the material is strictly required, and it produces extremely weak electrical signals. In order to ensure accurate signals, thermocouple temperature measuring wires and extension wires must use thermocouple-specific materials or materials with matching characteristics. So why can't ordinary connectors be used to transmit thermocouple signals?

According to the intermediate conductor law, one of the four laws of thermocouples, the third conductor (intermediate conductor) is connected to the original thermocouple circuit. As long as the temperatures at both ends of the intermediate conductor are consistent, the connection of the intermediate conductor has no effect on the temperature measurement results. If the temperatures at both ends of the copper connector we use are inconsistent, measurement errors will be introduced. This temperature difference cannot be taken for granted that it will be small. We have done experiments, using a hot air gun to heat up one end of the copper connector to increase the temperature difference between the two ends of the copper needle. As a result, the thermocouple temperature measurement error is as high as tens or even hundreds of degrees Celsius, while the length of the copper connector is only about 2cm. The impact of inaccurate temperature measurement data can be fatal.

Since the thermocouple temperature measurement principle is closely related to the material, the selection of materials is required, and generally special wires and connectors with specific graduation numbers are used.