A thermocouple consists of two (or more) dissimilar metals joined on one side. These 2 wires produce a voltage relative to the temperature of the application the thermocouple is used in. When temperature increases, the voltage becomes stronger. This voltage can thereafter be interpreted as temperature.
The original method to measure temperature is to combine two dissimilar alloys (thermocouple wire) together at the sensing end by welding. When properly joined, a thermo-electric current is produced that can be read to determine temperature (Seebeck effect). Sometimes this method of temperature measurement is still the most cost-effective method. Typically, the thermocouple wire will be insulated with ceramic beads and placed in a stainless steel, kanthal or Inconel tube.
That highly depends on the type of thermocouple wire you choose. Below you can find an overview of the temperature ranges per thermocouple type. When choosing a mineral insulated thermocouple, one should also look at the properties of the sheath materials and the sheath diameter.
|Thermocouple type||Useful application range|
|E||-270 .. +900°C|
|J||-210°C .. +760°C|
|K||-270°C .. +1260°C|
|N||-270°C .. +1260°C|
|R||-50°C .. +1480°C|
|S||-50°C .. +1480°C|
|B||0°C .. +1700°C|
|T||-270°C .. +370°C|
See this page for the advantages and limitations of a thermocouple.
The most common thermocouple junction is a type K (NiCr-Ni) junction. This type of thermocouple junction has the widest temperature range of all thermocouple types. Furthermore, type K thermocouples tend to be cost-efficient, accurate and reliable.
In the 1960’s, the type N (NiCroSil-NiSil) thermocouple was developed. This thermocouple type had a positive effect on short range ordering. The type N and type K thermocouples share the same accuracy and temperature range, but type N thermocouples tend to be more stable.
No there is not. These three words are commonly used to describe the same themperature sensor using thermocouple wires.