Thermocouple Extention & Compensating Cable


Nowadays, Thermocouple are being widely used in very industrial field from chemical, petrochemical, metal, ceramic, glass and electronic to aerospace, althought it is theoretically ideal to have thermocouple connected directly to instrument, long distance between them often makes the cost prihibitive and causes some troubles in the circuit. Therefore, it is desirable to use extention or compensating cables that have some or similar EMF caracterististies to those of thermocouple, it is also nessesary to change insulation cover materials according to the operating conditions.

Sokindo have a large stock of various cables tolerance to JIS C 1610 - 1981, ANSI MC 961 - 1982, DIN 43714, BS 1843 to meet your requipment. Insulation materials from PC, PTFE, FEP, Glass Fibre & Silicon Rubber. Single or stannded conductor according to AWG.


Twin, single conductor, having a temperature / e.m.f.relationship to the appropriate standard over the complete temperature range.


Twin, standed conductor for connection between measuring thermocouple and instrument (or external reference junction), ofthe same materials as the thermocouple, and having the same e.m.f. / temperature characteristics over a temperature range limited bu insulation material.


Twin, single or standed conductor for connection between measuring thermocouple and instrument (or external reference junction), of defferent composition from the thermocouple material, but having similar e.m.f. / temperature characteristic over a limited temperature range.




The choice is mainly determined by application (e.g. Termination considerations and internal diameter of associated sheath). Generally, single strand  wires  are  used fot hot junctions, and multi-stand for extentions of the thermocouple loop resistance, an important consideration with long cable runs.

Ordinary copper wires should never be used, as the error will equal to the difference in temperature between yhe connecting point of the thermocouple and the instrument (or external reference junction).

Extension or compensating wire or cable must be employed, and it is essential that the same polarity is maintained. If the polarity is reversed, the error is equal to twice the temperature difference between the connecting point of the thermocouple and the instrument (or external reference junction).

For maximum accuracy extension cables should be used, and the terminals and connectors should be of thermocouple materials to maintain continuity.



No B & S (AWG) No B & S (AWG)
Inches mm Inches mm
0 0.3249 8.25 23 0.0226 0.574
1 0.2893 7.35 24 0.0201 0.511
2 0.2576 6.54 25 0.0179 0.455
3 0.2294 5.83 26 0.0179 0.404
4 0.2043 5.19 27 0.0142 0.361
5 0.1819 4.62 28 0.0126 0.320
6 0.1620 4.11 29 0.0113 0.287
7 0.1443 3.67 30 0.0100 0.254
8 0.1285 3.26 31 0.0089 0.226
9 0.1144 2.91 32 0.0080 0.203
10 0.1019 2.59 33 0.0071 0.180
11 0.0907 2.30 34 0.0056 0.160
12 0.0808 2.05 35 0.0056 0.142
13 0.0720 1.83 36 0.0050 0.127
14 0.0641 1.63 37 0.0045 0.114
15 0.0571 1.45 38 0.0040 0.102
16 0.0508 1.29 39 0.0035 0.089
17 0.0453 1.15 40 0.0031 0.079
18 0.0403 1.02 41 0.0028 0.071
19 0.0359 0.912 42 0.0025 0.064
20 0.0320 0.813 43 0.0022 0.056
21 0.0285 0.724 44 0.0020 0.051
22 0.0253 0.643 45 0.0018 0.046


PVC Sheath:

PVC insulation sheath has been widely used as a good substitute for insulator. At Sokindo, PVC is used as an insulating material of standard compensating cables for general use.
Recommended Temperature Range: -20 ~ 90°C

Glass Fiber Sheath:

Glass fiber is known as traditional high temperature  insulaton material because it has excellent incombustibility, heat resistance, electric insulation, and chemical stability.
Although single glass fiber is not hygroscopic, bundled cover are somewhat hygroscopic. So, silicon or other resin is impregnated and boked over them to prevent moisture absorbtion.
Recommended Temperature Range: 0 ~ 150°C

Silicon Rubber Sheath:

Silicon rubber has been widely used as an excellent insulation material with less deterioration physical properties even under hostile conditions. It has almost same electric properties as natural rubber and no serious change and voltage with standing value occur over recommended temperature range. It has also good resistance to  chemicals (except for cocentated Alkalis), oils and grease, outdoor and ozone environments.
Recommended Temperature Range: -25 ~ +180°C

Teflon* (fluoric resin PTFE, FEP) Cover:

Teflon is the best insulation material among organic materials in respect of heat resistance, chemical resistance, electrical insulation, high frequency resistance, weather resistance, etc. High mechanical strength and, especially, high pressure resistance over wider range of operating temperature.
Recommended Temperature Range: -25 ~ +200°C
*Teflon is the registered trade mark by Dupont, U.S.A.

Metal Sheathed Compacted Mineral Insulation:

The insulation materials is fine grain MgO which is similar insulant to SMIFLEX Metal Sheathed Thermocuoples, Inorganic ceramic powder insulation tightly hold extension or compensating wires inside the Metal Sheath, composing perfectly integral constructions. This Ml. Extension or Compensating cable can withstand fire or high temperature, corrosion and mechanical shock and is approved as the only non=inflamabl safety cable. Available in all calibarations with varios metal sheath such as Copper, Cupro-Nickel, Stainless Steels, etc. Cable Size 1.6 mm - 8.0 mm O.D. Temperature Range: 20 - 270°C, but the cable withstands highs temperatures up to 900°C. Recommended for wiring at has hazardous location without conduit tube.