Skip to content
ElecDatum

Thermocouple type table J K T E

Type J, K, T and E thermocouples are the four most common types of base metal thermocouples, capable of measuring continuous temperatures from -270 °C / -454 °F to 1100 °C / 2012 °F. Each type uses a different metal combination, giving it a specific temperature range, sensitivity, and corrosion resistance. This page compiles the fundamental properties of these four thermocouples in comparative tables and individual datasheets.

Comparative table of J, K, T, E thermocouples

Section titled “Comparative table of J, K, T, E thermocouples”
Type Composition (positive / negative) Continuous temperature Peak temperature Sensitivity (approx.) Standard tolerance
J Iron / Constantan (Cu‑Ni) -40 °C to 850 °C / -40 °F to 1562 °F 1100 °C / 2012 °F 68 µV/°C ±2,2 °C or ±0,75 %
K Chromel® (Ni‑Cr) / Alumel® (Ni‑Al) -200 °C to 1100 °C / -328 °F to 2012 °F 1300 °C / 2372 °F 41 µV/°C ±2,2 °C or ±0,75 %
T Copper / Constantan (Cu‑Ni) -270 °C to 400 °C / -454 °F to 752 °F 500 °C / 932 °F 45 µV/°C ±1,0 °C or ±0,75 %
E Chromel® (Ni‑Cr) / Constantan (Cu‑Ni) -50 °C to 700 °C / -58 °F to 1292 °F 1000 °C / 1832 °F 50 µV/°C ±1,7 °C or ±0,5 %

Type J thermocouple

Section titled “Type J thermocouple”

Iron and constantan thermocouple with a continuous range from -40 °C / -40 °F to 850 °C / 1562 °F. It has a sensitivity of 68 µV/°C — the highest among base metal types — and a standard tolerance of ±2,2 °C or ±0,75 % (whichever is greater). It is widely used in reducing or inert atmospheres up to 750 °C / 1382 °F, but the iron oxidizes above 550 °C / 1022 °F and should not be exposed to sulfurous environments. Typical applications include heat treatment furnaces, plastic injection, and medium-temperature chemical processes. The special calibration of type J reduces the error by half (±1,1 °C / ±2,0 °F).

Type K thermocouple

Section titled “Type K thermocouple”

Chromel® (Ni‑Cr) and Alumel® (Ni‑Al) combination with a continuous range of -200 °C / -328 °F to 1100 °C / 2012 °F and peak capacity up to 1300 °C / 2372 °F. Its sensitivity is 41 µV/°C, the lowest of the four types, which gives it greater linearity at the cost of lower resolution. It is the most widely used thermocouple thanks to its excellent cost-performance ratio and resistance to oxidation, allowing operation in oxidizing or inert atmospheres. It should be avoided in reducing environments or vacuum at high temperatures, as it suffers preferential corrosion (green rot) between 800 °C / 1472 °F and 1050 °C / 1922 °F. The standard tolerance is ±2,2 °C or ±0,75 %.

Type T thermocouple

Section titled “Type T thermocouple”

Copper and constantan thermocouple capable of measuring from -270 °C / -454 °F (near absolute zero) up to 400 °C / 752 °F in continuous operation, with peaks of 500 °C / 932 °F. It offers a sensitivity of 45 µV/°C and a notably tight tolerance: ±1,0 °C or ±0,75 % (±0,5 °C / ±0,9 °F for special class). It stands out for its excellent linearity and accuracy in cryogenics and sub-zero ranges. Its applications are concentrated in calibration laboratories, climate chambers, food measurements, and tests in moderate oxidizing or reducing atmospheres. The upper limit is set by copper oxidation above 370 °C / 700 °F, so it is not recommended for prolonged high-temperature exposure.

Type E thermocouple

Section titled “Type E thermocouple”

Chromel® (Ni‑Cr) and constantan combination operating continuously up to 700 °C / 1292 °F and reaching peaks of 1000 °C / 1832 °F. With a sensitivity of 50 µV/°C, it ranks among the highest within base metal thermocouples, allowing it to detect temperature changes of tenths of a degree without complex amplification. Its standard tolerance is ±1,7 °C / ±3,0 °F or ±0,5 %. Since it contains no iron, it has good oxidation resistance and can be used in oxidizing, inert, or cryogenic atmospheres. However, in reducing environments it suffers accelerated degradation. It is common in the plastics industry, electric furnaces, and cryogenic applications where high sensitivity is required.

Sensitivity and tolerance

Section titled “Sensitivity and tolerance”
Type Standard temperature range Sensitivity (µV/°C) Standard tolerance Special tolerance
J -40 °C to 850 °C / -40 °F to 1562 °F 68 ±2,2 °C / ±4,0 °F or ±0,75 % ±1,1 °C / ±2,0 °F or ±0,4 %
K -200 °C to 1100 °C / -328 °F to 2012 °F 41 ±2,2 °C / ±4,0 °F or ±0,75 % ±1,1 °C / ±2,0 °F or ±0,4 %
T -270 °C to 400 °C / -454 °F to 752 °F 45 ±1,0 °C / ±1,8 °F or ±0,75 % ±0,5 °C / ±0,9 °F or ±0,4 %
E -50 °C to 700 °C / -58 °F to 1292 °F 50 ±1,7 °C / ±3,0 °F or ±0,5 % ±1,0 °C / ±1,8 °F or ±0,4 %

Color codes according to ANSI and IEC standards

Section titled “Color codes according to ANSI and IEC standards”
Type ANSI MC96.1 (positive / negative / sheath) IEC 60584-3 (positive / negative / sheath)
J White / Red / Black Black / White / Black
K Yellow / Red / Yellow Green / White / Green
T Blue / Red / Blue Brown / White / Brown
E Violet / Red / Violet Violet / White / Violet

Typical applications

Section titled “Typical applications”

Type J thermocouple is chosen for moderate heat processes such as plastic molding, vulcanization, or heat treatments in reducing atmospheres, as long as the temperature does not exceed 750 °C / 1382 °F. Type K dominates in general industry: foundry furnaces, boilers, gas turbines, and industrial HVAC systems, thanks to its wide temperature coverage and low cost. Type T is reserved for high-accuracy measurements in cryogenic and sub-zero ranges, typically in metrology laboratories, frozen food testing, and stability chambers. Finally, type E finds its niche in applications requiring high sensitivity, such as electric furnace control and chemical processes, as well as in cryogenics when a stronger signal than type T is desired.

References

Section titled “References”