Thermocouple Wire Construction

Thermocouple Wire

Insulated thermocouple wire is single pair wire that can be made into a thermocouple. Thermocouple wire is made from two dissimilar metals conductors that are joined (welded) together at the sensing end. Different metal wires are used for the various types of thermocouple types (J, K, T, E, etc). These dissimilar metals produce a millivolt electrical signal at the cold junction that is proportional to the change in temperature at the sensing end. Thermocouple wire has two grades; standard and Special Limits of Error. Special Limits of Error wire is made of the same metals as standard wire, but uses a higher grade with increased accuracy and higher expense than standard thermocouple wire.

Insulation varies from low temp (Nylon, FEP Teflon, TFE Teflon, PFA Teflon, Kapton) to high temp (fiberglass, Hi-Temp fiberglass, Refrasil, Ceramic Fiber).


Nylon
Suggested operating range:
-85°F to 250°F (-65°C to 121°C)

Nylon provides high tensile, impact and flexural resistance.  It has excellent resistance to abrasion and is unaffected by most alkalis, oil, grease, dilute mineral acids and most organic acids.  It is inert to most organic solvents including hydraulic fluid and aviation oil. The individual conductors and outer jacket are extruded.


Fluorinated Ethylene Propylene (FEP)
Suggested operating range:
-90°F to 400°F (-67°C to 204°C)

Also available: 
FEP Twisted Singles (No Outer Jacket)
Shielded FEP

FEP retains useful strength and flexibility over broad ranges of environmental temperature or thermal aging. FEP is flame retardant and non-propagating in fire conditions. It is moisture and chemical resistant and accepted for use around food and pharmaceuticals. The individual conductors and outer jacket are extruded.


Perfluoroalkoxy (PFA)
Suggested operating range:
-328°F to 500°F (-200°C to 260°C)

Flame retardant PFA provides flexibility and toughness with stress crack resistance, resistance to weather, non-aging characteristics and a low coefficient of friction.  PFA also provides outstanding electrical characteristics, as well as resistance to virtually all chemicals.  The individual conductors and outer jacket are extruded.


Tetrafluoroethylene (TFE)
Suggested operating range:
-328°F to 500°F (-200°C to 260°C)

TFE is flame retardant (passes IEEE 383 & VW-1 flame tests) and has excellent solvent and abrasion resistance.  TFE is unaffected by long term exposure to virtually all chemicals and solder iron temperatures. The individual conductors and outer jacket are insulated with TFE Tape.


Polymide Tape (Kapton)
Suggested operating range:
-400°F to 600°F (-240°C to 315°C)

Kapton is extremely tough.  It has excellent abrasion, impact and cut through resistance, very high resistance to oxidative degradation, weathering, and all chemicals except strong bases.  Kapton also offers high dielectric strength and insulation resistance.  Kapton does not support combustion; even at extremely high temperatures, it decomposes slowly without visible burning.  It is also resistant to radiation. The individual conductors and outer jacket are insulated with Kapton Tape.


Fiberglass
Suggested maximum operating temperature:
900°F (482°C) continuous
1000°F (538°C) single exposure
{Impregnation maintained to 400°F (200°C)}

Fiberglass insulation, with the special binder impregnation, offers good moisture and chemical resistance, as well as good abrasion resistance.  Typical applications include aerospace, foundries, heat treating, plastics industry and a wide variety of other uses.


Hi-Temp Fiberglass
Suggested maximum operating temperature:
1300°F (704°C) continuous
1600°F (871°C) single exposure
{Impregnation maintained to 400°F (200°C)}

Also available: 
Twisted Singles (No Outer Jacket)

Hi-Temp fiberglass is used in applications where standard fiberglass won’t stand up.  With the special binder impregnation, Hi-Temp fiberglass offers good moisture and chemical resistance, as well as good abrasion resistance.


Vitreous Silica Fiber (Refrasil)
Suggested maximum operating temperature:
1600°F (  871°C) continuous
2000°F (1093°C) single exposure

Vitreous Silica Fiber is designed to be used at very high temperature.  However, since no saturant is used, it is not recommended for use in abrasive applications without an additional metal covering.  Vitreous Silica Fiber is  typically used under conditions where beaded ceramic or sheathed thermocouples were previously necessary.


Ceramic Fiber
Suggested maximum operating temperature:
2200°F (1204°C) continuous
2400°F (1316°C) single exposure

Ceramic Fiber is flexible and offers good abrasion and chemical resistance. It is supplied white, without saturant or colored tracers.  Because the insulation retains it’s overall product integrity at elevated temperatures, serviceability is increased while reducing maintenance and replacement costs.

Email the Expert

Please fill in the form and our highly skilled staff will reply. The required fields are marked with an *.
*Name 
*Email 
Phone 
*Company 
City 
Country 
*Message 
  * Required Field