In this blog post, we will tell you all about thermocouples. In a nutshell, a thermocouple is a thermoelectric device that uses a sensor to measures temperature. It consists of two dissimilar metal wires. They are joined together at one end. When heating or cooling this junction of metals, a voltage is released. This is called the Seebeck effect, but you will learn more about that when reading the rest of this blogpost. To determine the exact temperature, a thermocouple reference table is needed. These specific tables tell you the material properties of a certain pressure or temperature.
The Seebeck effect
We can’t write a blogpost about thermocouples without going deeper into the Seebeck effect. In the year 1821, Mr. Thomas Johann Seebeck discovered that a device made out of two dissimilar metals, with junctions that have different temperatures would result in deviation of a compass. Compasses contain a magnet and that’s why Mr. Seebeck concluded that this junction caused magnetism. It didn’t take him a lot of time before he realized that the deflection of the magnet was caused by an electrical current. Like explained before, the temperature differences result in an electric voltage at the junction point. This voltage is proportional to the temperature difference between the two dissimilar metals. This proportionality constant is known as the Seebeck coefficient.
Types of thermocouples
Different situations ask for different devices. Also when it comes to thermocouples. That’s why an overall distinction is made between two types of thermocouples. Read about them below:
- Base metal thermocouples. Under this subheading, thermocouples type J, K, T & E are found. Base metal thermocouples are the most common.
- Type J thermocouples consist of iron and constantan. It has a slightly restricted range of -40˚c to 750˚c.
- Type K thermocouples consist of chrome and luminal. This type is most common since it’s general purposed and not expensive. It’s range is -200˚c to 1350˚c.
- Type T thermocouples consist of copper and constantan. It’s very resistant from corrosion and it’s stable when used in sub-zero temperatures. The range of a type T thermocouple is -200˚c to 350˚c.
- Type E thermocouples consist of chrome and constantan. It’s not very sensitive when it comes to corrosion.
- Noble metal thermocouples. Here you can find thermocouples type R, S & B. Noble metal thermocouples are used in high temperature applications. These thermocouples are made of platinum or a rhodium alloy for each conductor. They are very stable, but are less sensitive in measuring. Type R & S can measure up to 1480˚c.
Thermocouples are meant to suit your needs perfectly. That’s why thermocouples don’t just divide themselves in different types. They also differ in operation and form. Read about these differences below:
- Beaded wire thermocouples.
- Thermocouple probes.
- Surface probes.
- Wireless thermocouples.
All four different sorts speak for itself and are quite obvious. Still, we understand that this much freedom of choice raised many questions as well. That’s where our experts come in handy. Tell us all about your needs and we can give you advice about which thermocouple to select.