In industrial installations where the recorder and control instruments are located remotely from the thermocouples, compensating cable or extension Cable must be used between the thermocouple and instrument to reduce costs.
Extension cables use the actual thermocouple materials. This is achieved by using cheaper insulations, wider tolerance alloys and thinner conductors. They are produced in multi-stranded forms for ease of installation. Calibration: NX , KX , EX , JX , TX
Compensating cables use completely different alloys that happen to exhibit very similar thermo-electric properties up to a limited temperature (usually 250 °C ).