Thermocouples

A thermocouple is an electrical device consisting of two dissimilar conductors forming electrical junctions at differing temperatures. A thermocouple produces a temperature-dependent voltage for that gloss of the thermoelectric effect, and this voltage can be interpreted to pretense temperature. Thermocouples are a widely used type of temperature sensor.

Commercial thermocouples are within your means interchangeable, are supplied following plenty connectors, and can comport yourself a broad range of temperatures. In contrast to most supplementary methods of temperature measurement, thermocouples are self powered and require no outside form of excitation. The main limitation subsequent to thermocouples is precision; system errors of less than one degree Celsius (C) can be hard to achieve.

Thermocouples are widely used in science and industry; applications add together temperature measurement for kilns, gas turbine exhaust, diesel engines, and added industrial processes. Thermocouples are furthermore used in homes, offices and businesses as the temperature sensors in thermostats, and in addition to as blaze sensors in safety devices for gas-powered major appliances.

 

The table below describes properties of several different thermocouple types. Within the tolerance columns, T represents the temperature of the hot junction, in degrees Celsius. For example, a thermocouple with a tolerance of ±0.0025×T would have a tolerance of ±2.5 °C at 1000 °C.

Type Temperature range (°C) Tolerance class (°C) Color code
Continuous Short-term One Two IEC[23] BS ANSI
Low High Low High
K 0 +1100 −180 +1300 −40 – 375: ±1.5
375 – 1000: ±0.004×T
−40 – 333: ±2.5
333 – 1200: ±0.0075×T
IEC Type K Thermocouple.svg
BS Type K Thermocouple.svg
MC 96.1 K Thermocouple Grade Color Code.svg
J 0 +750 −180 +800 −40 – 375: ±1.5
375 – 750: ±0.004×T
−40 – 333: ±2.5
333 – 750: ±0.0075×T
IEC Type J Thermocouple.svg
BS Type J Thermocouple.svg
MC 96.1 J Thermocouple Grade Color Code.svg
N 0 +1100 −270 +1300 −40 – 375: ±1.5
375 – 1000: ±0.004×T
−40 – 333: ±2.5
333 – 1200: ±0.0075×T
IEC Type N Thermocouple.svg
BS Type N Thermocouple.svg
MC 96.1 N Thermocouple Grade Color Code.svg
R 0 +1600 −50 +1700 0 – 1100: ±1.0
1100 – 1600: ±0.003×(T − 767)
0 – 600: ±1.5
600 – 1600: ±0.0025×T
BS Type N Thermocouple.svg
BS Type R Thermocouple.svg
Not defined
S 0 +1600 −50 +1750 0 – 1100: ±1.0
1100 – 1600: ±0.003×(T − 767)
0 – 600: ±1.5
600 – 1600: ±0.0025×T
BS Type R Thermocouple.svg
Not defined
B +200 +1700 0 +1820 Not available 600 – 1700: ±0.0025×T No standard No standard Not defined
T −185 +300 −250 +400 −40 – 125: ±0.5
125 – 350: ±0.004×T
−40 – 133: ±1.0
133 – 350: ±0.0075×T
IEC Type T Thermocouple.svg
BS Type T Thermocouple.svg
MC 96.1 T Thermocouple Grade Color Code.svg
E 0 +800 −40 +900 −40 – 375: ±1.5
375 – 800: ±0.004×T
−40 – 333: ±2.5
333 – 900: ±0.0075×T
IEC Type E Thermocouple.svg
BS Type E Thermocouple.svg
MC 96.1 E Thermocouple Grade Color Code.svg
Chromel/AuFe −272 +300 N/A N/A Reproducibility 0.2% of the voltage.
Each sensor needs individual calibration.