A thermocouple is the junction of 2 dissimilar metals, for this reason we use connectors made of the same 2 metals of the thermocouple. The wire connecting the thernocouples is also of the same 2 metals. For example, in the case of copper constantan thermocouples one conductor is copper, and all connections are copper, the other conductor is constantan, so the wire is constantan as well as all of the connections.
In the case you describe, each place where the wrong metal is used creates a thermocouple. So in a sense you have added 4 additional thermocouples in series, the output of thermocouples in series is equal to the difference in temperatre between the elements. Thus if we assume the primary thermocouple is at 400 degrees C abd the remaining thermocouples are at 25 degrees c then the output would roughly correspond to 300 degrees C. I say roughly due to the questionable quality of the accidental thermociuples.
This principle was put to use many years ago by a furnace manufacturer that used a center zone thermocouple and an end zone thermocouple in inverse series. the output of those 2 t/c's was used to control the power to the end zone.
This was very effective in allowing the end zone to follow the center zone temp, buy outputting only the difference in temperatures to the end zone controller.
Hope this helps,
Mark Perry
electrical engineer and furnace design consultant
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