Type K, J, N - The list of thermocouple types is like a alphabet soup. As technology advances and manufacturers offer more options, it may be difficult to track all the different names and classifications. This paper outlines the 11 most common types of industrial thermocouples.
Thermocouple is one of the most commonly used temperature measuring equipment in various industries and applications. These electronic thermometers are made by connecting two wires of different metals together at the measuring point (also called hot junction). Because the electronegativity of the two metals is different, the temperature change at the hot junction will produce a voltage difference at the other end of the wire, which is called the connection point or cold junction. (See this video for more details on what thermocouples are and how they work.)
Type of thermocouple
The difference between a thermocouple and another thermocouple is the metal in its two wires: positive and negative. Because each thermocouple type has different pairs, they are different in temperature limits, process conditions (inert, oxidizing, reducing atmosphere, violent vibration), etc. But how many types of thermocouples are there?
The exact number is not easy to determine. It increases as manufacturers develop new compositions/pairs and standardization organizations recognize them, and decreases as certain thermocouple types fall out of favor and out of date. Then there are thermocouples with different names, but the changes of the same pair are slightly different.
But we can safely say that there are two basic sets of thermocouples. A base metal that uses materials such as iron, nickel, copper, and chromium - a base metal that produces a high thermoelectric voltage when paired. The other group has more expensive precious metals, such as rhodium, platinum, rhenium and tungsten, which are used at higher temperatures.
Thermocouple naming convention
Most thermocouples have only letter names, and the names seem arbitrary. In other words, the letters do not correspond to the chemical symbols of the main metals, and the types are not standardized in alphabetical order. The American National Standards Institute (ANSI) and the ANSI recognized American Society for Testing and Materials (ASTM) list nine major thermocouple types: B, E, J, K, N, R, S, T, and C.
An exception to any designation is thermocouples containing tungsten (its chemical symbol is W) and rhenium. The number after W indicates the rhenium content in the positive electrode. For example, type W5 represents a positive electrode of 95% tungsten and 5% rhenium. If there are no numbers, then the positive electrode has no rhenium. Tungsten thermocouples have maximum temperature limits of all types: up to 4200 ° F (2320 ° C)
Although most thermocouples have only one name, there are more names for these three tungsten types:
W5 or C
Type W3 or D
WR or W or G
Thermocouple type, composition and application
So, how many thermocouple types are there? The quick answer is "at least 11". The most common are K, J, N, E and T, whose base metals are cheaper. This is a quick guide to all types of thermocouples offered by Villian.