Will having a junction box in the middle of the compensation wire affect the measurements?
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To save on cables, considering the use of junction boxes with compensating cables at both the front and back of these boxes, could the materials inside the junction boxes affect the measurement results? It seems that according to the intermediate conductor law, as long as the temperature of the junction box material is the same on both the front and back, there should be no effect. Is this explanation reasonable? Are there any relevant examples or related junction box products?
The intermediate connector of the compensation wire theoretically has no impact on the measurement； In fact, when the joints of the compensation wires become damp or corroded, it may affect the measurements (when damp or corroded, chemical reactions similar to those in a galvanic cell occur at the joints, and this is a factor that is not taken into account in thermocouple theory) ； Therefore, construction codes do not permit joints in the compensating wires, while design codes allow the use of junction boxes; the purpose of this is to standardize the joints, facilitate inspection and maintenance, and provide a record for reference. A small number of connections can use electric explosion-proof junction boxes; explosion-proof gland fittings should be used at the points where cables enter, and the connections should be made in areas of the cable tray where there is no water ； If the quantity is large, it’s best to guide the wires to the appropriate location in the junction box.
It depends on how precise you are with this temperature value. It’s very difficult to achieve exactly the same resistance at the two connection points, especially after oxidation. If it really has to be added, proper work must be done: use soldering, and then apply glue.