Data Sheet: Thermocouple Grade Alloys

Learn more about each nickel speciality alloy

  • Thermocouple Extension And Compensation Alloys

Thermocouple Extension & Compensation Alloys: Wire \ Strip \ Ribbon

JLC produces a wide range of alloys that are used to manufacture thermocouples, extension and compensating wires/cables. Thermocouples are formed by joining two dissimilar alloys that will produce a thermal EMF when the junctions are at different temperatures. Different grades of thermocouple alloys are used depending upon the temperature being measured.

Thermocouples are connected to the temperature indicating instruments by using the leads made of same material. These leads which have the same EMF output as the thermocouple are called Extension Leads. Use of extension leads avoids lead junction error. However, for economic reasons, cheaper alloys having similar EMF output over a limited temperature range (generally 200 °C) are often used. These leads are called Compensating Leads.

JLC offers a full range of materials for Extension/Compensating leads. The different grades of these materials and the EMF tolerance for these grades over a required temperature range are shown in this data sheet.

Forms of Supply

Cold Drawn, Annealed.
Oxidized wire surface is also available for applications where corrosive atmosphere is present.


JLC range of thermocouple alloys meets the specification of ASTM E 230 and ANSI MC 96.1.

JLC can also manufacture thermocouple alloys to conform to any of the following specifications: IS, IEC, DIN, BS, NF, UNI, ENI, JIS, ENEL, or GOST.

Special tolerances and properties can be made available upon customer request.

Extension/Compensation Alloy Specifications

Thermocouple Extension or
Compensation Alloy
Composition American Specification (ANSI MC 96.1)
EMF At Temp Tolerance
mV °C Standard Special
KPX (NiCr) 4.095 100.0 ± 2.2°C
KNX (NiAl) 8.137 200.0
K Cu-CuNi44
Cu 4.095 100.0 ± 2.2°C
CuNi44 - -
K Fe-CuNi43 (W)
Fe 4.095 100.0 ± 2.5°C
CuNi43Mn2 8.137 200.0
EPX (NiCr) 6.317 100.0 ± 1.7°C
ENX (CuNi44) 13.419 200.0
TPX (Cu) - - ± 1°C
± 0.5°C
TNX (CuNi44) 4.277 100.0
JPX (Fe) 5.268 100.0 ± 2.2°C
± 1°C
JNX (CuNi44) 10.777 200.0
S / R Cu-CuNi3
(SX) (RX)
Cu 0.645 100.0 ± 0.057 mV
From 0°-200°C
CuNi3 1.440 200.0
NPX (NiCr) 2.774 100.0 ± 2.2°C
NNX (NiSi) 5.912 200.0

*Type VX, KCA, KCB are not included in ANSI

Standard & Special grades

The EMF tolerance of standard grade of alloys is according to the table presented on the previous page. JLC's special grades offer closer tolerances (½ and ¼ of standard grades) for applications where higher accuracy is needed.

Nominal Physical, Electrical & Mechanical Properties (at room temperature for annealed wire)

Alloy Density Electrical Resistivity
at 20°C
Temp Coeff of Resistance Thermal Linear
Expansion Coeff.
b/w 20-95°C
Thermal Conductivity
g/cm³ µΩ-cm Value Temp range 10-6/K W/m K
KPX 8.72 70.6 300 20-100 °C 17.0 19.2
KNX 8.60 29.2 1900 20-100 °C 17.0 29.7
Cu Ni44 8.90 49.0 60 20-100 °C 14.0 21.4
Cu Ni43 8.90 52.0 100 20-100 °C 15.0 21.0
SX / RX 8.91 12.0 1500 20-100 °C 16.0 -
Fe 7.86 13-14 5000 20-100 °C 11.7 66.2
NPX 8.53 100.0 90 20-100 °C 17.0 13.0
NNX 8.58 36.5 680 20-100 °C 17.0 27.0


JLC thermocouple grades are calibrated over the temperature range according to international specifications. All JLC grades are individually calibrated versus NBS Pt 67. Each coil/spool is tested for EMF and value of deviation from the standard EMF at different temperatures is shown on the labels attached to each coil/spool. All JLC thermocouple materials are made confirming to EMF/temperature requirements for thermocouples as per NBS monograph 125. Alternatively, calibration is also performed as per ASTM E220 comparison technique.

Size Range

JLC thermocouple materials are available in different sizes (mm/AWG/SWG) or resistance based upon customer's requirement.

Form Dia (mm) AWG
Wire 0.142-8.255 0-35

Strips and ribbons are also available in various sizes upon request.

Final Inspection & Testing

Each spool/coil of JLC thermocouple, extension and compensating alloy is calibrated according to specifications given above. JLC thermocouple alloys are fully tested for homogeneity of chemical composition, physical, and thermoelectric properties. This includes the testing of electrical resistivity (loop resistance), which is an important property of thermocouple alloys.

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Related Links


Nickel Alloys

Standard Nickel Grades:

Nickel-Manganese Alloys:

Nickel-Copper Alloys:

Welding Alloys Heating & Resistance

Nickel-Chromium Alloys:

Iron-Chrome-Aluminum Alloys

Nickel Chrome Iron Alloys Low Resistance & Shunt Alloys

Cu-Ni Low Resistance Alloys:

Cu-Mn-Ni Alloys:

Lamp Components & Alloys Thermocouple Alloys

Thermocouple Grade Alloys:

Extension and Compensating Grade Alloys:

Automotive Alloys

Alloys for Earth and Central Electrodes:

  • NiSi
  • NiCr15Fe
  • NiCr5SiMn
  • NiCr2SiMn
  • NiSi1Al1Y
Soft Magnetic Alloys

Temperature Compensating Alloys:

  • Ni30Fe
  • Ni31Fe
  • Ni32Fe

High Permeability Alloys:

  • SMA 50 (Ni50Fe)
Controlled Expansion Alloys
Dumet Wires
Clad Wires
  • Copper-Clad FeNi42
  • Copper-Clad FeNi60
  • Iron-Clad Nickel
  • Nickel-Clad Iron