FAQs
What is thermocouple cable?
Thermocouple cable is used to connect a thermocouple sensor to a measuring instrument while preserving the correct thermoelectric signal. To maintain accuracy, the conductors must produce the same EMF characteristics as the thermocouple type being used.
What is thermocouple extension wire?
Thermocouple extension wire is designed to extend a thermocouple signal from the sensor head to the measuring instrument. It uses alloys that are matched to the thermocouple type but is intended for use over a limited temperature range, typically where the cable remains near ambient temperature.
What is the difference between thermocouple grade and extension grade wire?
Thermocouple grade wire is manufactured from the same alloys as the thermocouple sensor and is accurate over the full temperature range of the thermocouple type.
Extension grade wire uses matched extension alloys with looser tolerances and is intended for lower-temperature environments between the sensor and the instrument.
Thermocouple grade wire may be used anywhere in the circuit, while extension grade wire should not be exposed to elevated temperatures. See our Thermocouple Extension Wire Explained page for more details.
What does KX, JX, or TX mean?
The “X” suffix indicates extension grade wire. For example:
KX = Type K extension grade
JX = Type J extension grade
Thermocouple grade wire does not use the “X” designation.
Is thermocouple polarity important?
Yes. Thermocouple cables are polarity sensitive, and reversing the conductors will cause incorrect temperature readings. ANSI color coding is used to identify positive and negative conductors.
Are thermocouple cables interchangeable between types?
No. Thermocouple and extension cables must always match the thermocouple type. Using the wrong cable type will result in measurement errors.
What insulation types are available for thermocouple cable?
Common insulation materials include PVC, PTFE/PFA, fiberglass, and ceramic fiber. The correct insulation depends on temperature, chemical exposure, flexibility, and environmental conditions.