Flexible thermocouple extensions illustrated above are constructed using extension wire. They are used as extension cords to provide suitable connections between sensors, jack panels, or instrumentation. Flexible RTD extensions are constructed using stranded copper wire with various insulation material.
Integrity between the sensor tip and the control itself is of the utmost importance... you cannot mix types of sensors (ex. type J and type K) and cannot use plain wire. For more information on system integrity click here.