Type T Thermocouple Extension Cable
Conductor specification
TYPE T (Copper vs Constantan) is used or service in oxidizing, inert or reducing atmospheres or
in vacuum. It is highly resistant to corrosion from atmospheric
moisture and condensation and exhibits high stability at low
temperatures. It is the only type with limits of error guaranteed
for cryogenic temperatures.
1. Chemical Composition
| Material | Chemical composition (%) |
| Ni | Cu | Si | Iron | Al |
| TP(Copper) | | 100 | | | |
| TN(Constantan) | 45 | 55 | | | |
2. Physical Properties and Mechnical Properties
Material |
Density(g/cm3) |
Melting point(ºC) |
Tensile Strength(Mpa) |
Volume resistivity(μΩ.cm) |
Elongation rate (%) |
| TP(Copper) | 8.9 | 1084 | >196 | 1.71(20ºC) | >30 |
| TN(Constantan) | 8.8 | 1220 | >390 | 49.0(20ºC) | >25 |
In actual temperature measurement, usually there are long measuring
distance with the measuring device, a thermocouple compensation
wire is generated to compensate the temperature difference caused
by the temperature change between the measuring device and the
thermocouple connecting piece.
The compensation cable has the following advantages: improving
thermocouple temperature measurement line physical properties and
mechanical properties; improving the measurement line flexibility
and making the connection convenient by using multi-strand core or
small-diameter compensation wire; easy to shield external
interference; reducing measuring lines cost.
Thermocouple Cable Grade
A:Extension Grade Cable
Whose wire composition is totally as the same as the thermocouple
wire, remarked by the letter"X"after the thermocouple symbol
number, such as"KX""JX""TX"
B:Compensation Grade Cable
Whose wire composition is different from the thermocouple wire, but
its wire electromotive force (EMF) value is the same as
thermocouple wire only at 0-100ºC or 0-200ºC. It remarked by the
letter"C"after the thermocouple symbol number, such as"KC""JC""TC"
- For cost consideration, when the tested temperature under 200ºC,
compensation grade cable is preferred. But compensation grade cable
will occur enormous tested temperature value deviation if the
tested temperature above 200ºC. The higher the tested temperature,
the greater deviation be.
- For compensation grade cable, the max testing temperature is less
than 200ºC, the bigger the cable, the smaller the signal loss.
- Extension cable and compensation cable comparison:
| Performance | Extension Grade | Compensation Grade |
| Material | Same as thermocouple | Different from thermocouple |
| EMF Value Feature | Same as the thermocouple's at certain temperature range | Same as the thermocouple's |
| Deviation Curve | Nonlinear, varies with temperature | Linear |
| Working Temperature Range | Limited(usual at 100ºC) | Unlimited(depend on insulation material temperature bearing) |
| Line Resistance | Low resistance | High resistance |
| Compensation Contact Interference | Different contactor material may cause interference | None |
| Accuracy | Low | High |
| Price | Low | High(about 1-2 times higher) |
