{"id":13099,"date":"2020-04-22T14:54:33","date_gmt":"2020-04-22T19:54:33","guid":{"rendered":"https:\/\/blog.wika.com\/us\/\/?p=13099&post_date=20200415111654"},"modified":"2026-02-02T10:34:07","modified_gmt":"2026-02-02T15:34:07","slug":"how-many-thermocouples-types-are-there-and-what-makes-each-one-different","status":"publish","type":"post","link":"https:\/\/blog.wika.com\/us\/knowhow\/how-many-thermocouples-types-are-there-and-what-makes-each-one-different\/","title":{"rendered":"How Many Thermocouples Types Are There, and What Makes Each One Different?"},"content":{"rendered":"

Type K, Type J, Type N \u2013 the list of thermocouple types seems like an alphabet soup. And as technology improves and manufacturers come up with more options, it can be hard to keep track of all the various names and classifications. This article outlines the 11 most common types of industrial thermocouples.<\/strong><\/p>\n

Thermocouples <\/a>are one of the most common devices used across industries and applications to measure temperature. These electrical thermometers are made of two wires of dissimilar metals joined together at the measuring point, also known as the hot junction. Due to the two metals\u2019 differences in electronegativity, changes in temperature at the hot junction generate a voltage difference at the other end of the wires, called the connection point or cold junction. (See this video <\/a>for more details about what thermocouples are and how they work.)<\/p>\n

Types of Thermocouples<\/span><\/h2>\n

What differentiates one thermocouple from another is the metals in its two wires: the positive leg and the negative leg. Because each thermocouple type has a different pairing, they differ in temperature limits, process conditions (inert, oxidizing, reducing atmospheres, heavy vibration), and so on. But just how many types of thermocouples are there?<\/p>\n

The exact number is not easy to pin down. It increases as manufacturers develop novel compositions\/pairings and as standardizing organizations recognize them, and decreases as certain thermocouple types fall out of favor and become obsolete. Then there are the thermocouples with different names but only slightly different variations of the same pairings.<\/p>\n

But what we can safely say is that there are two basic groups of thermocouples. One uses materials like iron, nickel, copper, and chromium \u2013 base metals that produce high thermoelectric voltages when paired.\u00a0The other group has more expensive noble metals, such as rhodium, platinum, rhenium, and tungsten, and are used at much higher temperatures.<\/span><\/p>\n

Thermocouple Naming Conventions<\/span><\/h2>\n

Most thermocouples have just letter names, and the designations appear to be arbitrary. In other words, the letters do not correspond to the dominant metal\u2019s chemical symbol, nor were the types standardized in alphabetical order. The American National Standards Institute (ANSI) and the ANSI-accredited American Society for Testing and Materials (ASTM) lists nine main thermocouple types<\/a>: B, E, J, K, N, R, S, T, and C.<\/p>\n

The one exception to the arbitrary designations are thermocouples that contain tungsten, whose chemical symbol is W, and rhenium. The number that follows the W states how much rhenium is in the positive leg. For example, Type W5 means the positive leg is 95% tungsten and 5% rhenium. If there\u2019s no a number, there\u2019s no rhenium in the positive leg. Tungsten thermocouples have the highest temperature limit of all types: up to 4,200\u00b0F (2,320\u00b0C)<\/p>\n

While most thermocouples have one name, these three tungsten types have more:<\/p>\n