Thermocouple sensors consist of the wires often called thermoelements, insulation, sheath, end seal and a means of connection (extension wires, connectors, etc.). The wires are connected together on one end to form the “measuring” or “hot” junction.
The sensor must be connected to a read-out device that compensates for the reference temperature. If a thermocouple readout is used then it will contain the needed circuitry. If a millivolt meter is used, then either a properly prepared ice bath or some other cold junction compensation is needed.