When Watlow thermocouple sensors measure a device or material’s temperature, the open side is exposed to heat, creating a thermoelectric circuit through the wires. The circuit cannot flow freely because the wires are not joined at both ends, though, so electricity escapes through the broken end.
The voltage that the thermocouple releases, which is called its electromotive force, reflects the medium’s temperature, which is calculated through an equation. A higher EMF reading reflects a higher temperature.
Depending on the type of junction your thermocouple sensors have, you may not be able to see the wires. With grounded and ungrounded junctions, the wires are inside the sheath. Grounded wires are welded to their sheaths, while ungrounded ones are insulated from the sheath. Wires with exposed junctions are outside their sheaths, exposing them to corrosion but also allowing them to read temperatures more quickly.