Thermocouples are essential instruments for measuring temperature in industrial processes. Simple in design but extremely reliable, these sensors convert the difference in electrical potential between two different metals into temperature values. It is because of this precision and durability that they have become one of the most widely used technologies in sectors such as steel, oil and gas, automotive, chemical, and even scientific research.
However, there is not just one model: each type of thermocouple has specific characteristics that make it more suitable for certain uses.
Knowing these differences is essential to ensure performance and safety in large-scale operations.
What are the types of Thermocouples?
While all thermocouples operate on the same basic scientific principles, differences in their materials, construction, and ultimately their operating temperature ranges create different types of thermocouples. These different types of thermocouples are identified by a letter, such as "Type K thermocouple."
The table below shows the differences between each piece of equipment.
| Type | Composition | Temperature Range | Features |
|---|---|---|---|
| K | Nickel-Chromium / Nickel-Aluminum | -200°C to 1.260°C | Versatile, resistant to oxidation, most used in industry |
| J | Iron / Copper-Nickel | -40°C to 750°C | Economical, used in old systems, unstable in humid environments |
| T | Copper / Copper-Nickel | -200°C to 350°C | High accuracy at low temperatures, good in humid environments |
| E | Nickel-Chromium / Copper-Nickel | -200°C to 900°C | High sensitivity, suitable for rapid variations |
| N | Nickel-Chromium-Silicon / Nickel-Silicon-Magnesium | -200°C to 1.300°C | Greater stability and resistance to oxidation, evolution of type K |
| S | Platinum-Rhodium / Platinum | -50°C to 1.480°C | High precision, used in calibration and glass and ceramic industries |
| R | Platinum-Rhodium / Platinum | -50°C to 1.760°C | Stable at high temperatures, applied to semiconductors and precious metals |
| B | Platinum-Rhodium / Platinum-Rhodium | 0°C to 1.820°C | Extremely resistant, used in ovens and high temperature processes |
Below, see details of the main types of thermocouples used on the market.
Type K thermocouple
The K-type thermocouple is by far the most popular in industrial settings. Made from a nickel-chromium and nickel-aluminum combination, it withstands temperatures ranging from -200°C to 1.260°C. Its wide measurement range makes it the most versatile sensor, suitable for a variety of processes.
Robustness and cost-effectiveness also explain the preference for Type K. It resists oxidation well in oxidizing or neutral environments, which increases its service life. Because of these characteristics, it is widely used in chemical industries, the oil and gas sector, and also in power generation processes. It is no coincidence that Type K is considered the standard in many factories.
Type J Thermocouple
Composed of iron and copper-nickel, the Type J thermocouple operates at temperatures from -40°C to 750°C. Its strength lies in its stability in reducing and vacuum environments. However, it has lower oxidation resistance, requiring additional care in humid or oxygen-rich atmospheres.
Despite this limitation, Type J is widely used in older equipment, as many systems were designed for this standard. Furthermore, it's an economical option for measurements in intermediate temperature ranges.
Type T Thermocouple
Among the most accurate low-temperature models, the T-type thermocouple is made of copper and copper-nickel. It operates in a range of -200°C to 350°C, making it highly reliable in laboratories and cryogenic applications.
Another advantage is stability in humid environments, as copper offers good corrosion resistance. This makes the T-type an ally in sectors that require strict control at low temperatures, such as the food industry, pharmaceuticals, and refrigeration processes.
Type E Thermocouple
The Type E thermocouple is made of nickel-chromium and copper-nickel. Its distinguishing feature is its ability to offer the highest electrical output coefficient of all common models, resulting in greater sensitivity. It operates at temperatures ranging from -200°C to 900°C.
Due to its precision, it's recommended for measurements where small variations need to be detected quickly. Furthermore, it's highly efficient in oxidizing environments. It's widely used in research, materials testing, and in industries that work with controlled heating processes.
Type N Thermocouple
Developed as an evolution of the K-type, the N type thermocouple It is made of nickel-chromium-silicon and nickel-silicon-magnesium. It can withstand temperatures from -200°C to 1.300°C, offering superior oxidation resistance and greater long-term stability.
This robustness makes it ideal for power generation industries, such as thermal power plants, as well as processes that require reliability under critical conditions. With less degradation at high temperatures, type N tends to gradually replace type K in some more demanding applications.
Type S thermocouple
Type S is composed of platinum-rhodium and pure platinum, noble materials that ensure high precision. Its operating range ranges from -50°C to 1.480°C. It is one of the most reliable and stable models, although it is also more expensive.
Because of these characteristics, type S is widely used in laboratories and industries that require maximum accuracy, such as glass, metallurgy, and ceramics. Furthermore, it is frequently used as a reference in calibration of other thermocouples.
Type R Thermocouple
Similar to the S-type thermocouple, the R-type thermocouple is made of platinum-rhodium in varying proportions. It offers similar performance, with a temperature range of -50°C to 1.760°C, but even greater stability at high temperatures. It is also expensive due to the use of noble metals.
In practice, type R is used in melting and processing precious metals, as well as in semiconductor manufacturing. Its durability makes it worth the investment in sectors where precision is essential.
Type B Thermocouple
The Type B thermocouple is one of the most durable, made of high-grade platinum-rhodium alloy. Its measurement range is from 0°C to 1.820°C, making it ideal for extreme applications.
Widely used in the glass industry, high-temperature furnaces, and metal refining processes, Type B is virtually oxidation-free, ensuring reliability even under harsh conditions. It's a preferred choice in production environments where there's no margin for error.
What is the best type of temperature sensor?
When it comes to temperature measurement in industrial processes, a common question arises: after all, what is the best thermocouple? The answer, however, is not so simple. The "best" model will depend directly on the application in which it will be used.
In some cases, the priority is measurement accuracy. In others, the most important factor is response speed—how quickly the sensor reacts to changes in the environment. In more complex situations, the challenge may lie in the equipment's resistance to corrosive environments, acids, or aggressive gases.
Want to better understand how to choose the ideal thermocouple for your process? Watch the full video and see in practice how each type of sensor works and in which situations it is most effective.
Alutal is a national and international reference in thermocouples
Alutal is recognized in the market for its excellence in manufacturing temperature sensors and instrumentation solutions. Present for decades in major Brazilian industrial projects, the company has also gained a foothold in the international market, exporting reliable technology to several countries. This expansion reflects our high quality standards, combined with continuous investment in innovation and operational safety.
Discover complete solutions for your industry by visiting the official website: www.alutal.com.br.
