Thermocouples are temperature sensors made with two different metal wires joined at one end. When this junction is exposed to heat, it generates a small voltage that correlates with the temperature. Used in various sectors, from aerospace to manufacturing, thermocouples are valued for their simplicity and responsiveness. But what is the limit of their measurement? See which thermocouple has the highest temperature.
Which thermocouple has the highest temperature?
Os thermocouples tungsten-rhenium refractory metal types C (W5%Re/W26%Re) and D (W3%Re/W25%Re), for example, are considered ideal models for working at higher temperatures, and can be used for temperature measurement up to 2300ºC in continuous operation, provided they are not in an oxidizing environment.
In an oxidizing environment, platinum-rhodium noble metal thermocouples, types R, S and B, These are considered the most suitable, with maximum temperature ranges varying between 1400 ºC and 1800 ºC, depending on the construction and protection.
These thermocouples, developed to operate at extremely high temperatures, represent the cutting edge in thermal measurement when it comes to robustness, stability, and performance in extreme conditions. Unlike RTDs, also called resistance thermometers, which can offer good accuracy but suffer from structural limitations, these thermocouples maintain reliability even in thermal ranges where most sensors no longer operate safely.
Models B, R, and S, for example, use platinum-based alloys. Although widely used in industry, the use of these materials causes performance changes over time. Platinum tends to deteriorate at high temperatures, and the sensor may exhibit variable behavior depending on the immersion depth, a typical effect associated with non-homogeneities in the wire.
When the application requires going even further, to truly extreme temperatures, tungsten-rhenium thermocouples are used. types C and DThese are the most suitable. Developed to operate continuously up to approximately 2.300 °C and, for short periods, they can withstand temperatures up to approximately 2750 °C. These sensors perform excellently in atmospheres with hydrogen, inert gases, or in vacuum. However, they have an important limitation: they deteriorate rapidly in the presence of oxygen and, therefore, should not be used in oxidizing environments.
For extreme applications in oxidizing atmospheres, there is also a unique alternative: the Rhodium-iridium thermocouple, one of the most prestigious pieces of equipment. To give you an idea, it is the only one capable of operating at 2000 °C in oxidizing conditions without compromising its integrity. Furthermore, it exhibits high corrosion resistance, excellent precision, and optimal repeatability. It is suitable for sectors that demand extremely rigorous thermal control, such as semiconductor manufacturing.
Already Au/Pt thermocoupleConstructed with 99,999% pure gold and platinum wires, it reaches another level with its stability. According to the Brazilian Society of MetrologySince these metals are stable in the range of 0 to 1000 °C, the result is a highly reliable thermocouple with virtually unchanging behavior.
Higher temperature ranges of thermocouples
Noble metal thermocouples (High temperature)
These types utilize platinum and rhodium alloys, and are essential for ultra-high temperature furnaces and precision calibration.
| Use cases | Composition | temperature range | Application |
| Types | Platinum-10% Rhodium / Platinum | 0°C to 1600°C | Common in semiconductor and glass furnaces. |
| Type R | Platinum-13% Rhodium / Platinum | 0°C to 1600°C | Similar to Type S, but with a slightly different voltage curve. |
| type B | Platinum-30% Rhodium / Platinum-6% Rhodium | 600°C to 1700°C | The most robust of the Platinum/Rhodium group; the high percentage of rhodium allows for higher temperatures. It does not require cold junction compensation below 800°C. |
Extreme temperature thermocouples (Tungsten/Rhenium)
Less common, these types are reserved for higher temperatures, being used in inert atmospheres, vacuum, and hydrogen furnaces.
| Use cases | Composition | temperature range | Application |
| type C | Tungsten-5% Rhenium / Tungsten-26% Rhenium (W5Re/W26Re) | 0°C to 2320°C | The most common of the tungsten thermocouples. Used in extreme applications such as jet engine testing and nuclear reactor testing. |
| Type D | Tungsten-3% Rhenium / Tungsten-25% Rhenium (W3Re/W25Re) | 0°C to 2320°C | As an alternative to Type C, it offers a more linear voltage curve in certain ranges. |
Take advantage and get to know the types of thermocouples more common
How thermocouples withstand high temperatures
A simple, durable design ensures that thermocouples are resistant to vibrations and rapid temperature changes. Because they do not require electrical power, they prevent self-heating and are safe in unstable conditions.
The instruments also react quickly to temperature variations. Their small detection junctions respond in milliseconds, allowing for precise control in high-speed processes.
How do thermocouples work in extreme conditions? Thermocouples utilize... Seebeck effectWhen two different metals are joined and exposed to heat, they generate a voltage that corresponds to the temperature difference between the measuring and reference junctions.
Main components:
- Measuring joint: exposed to a heat source.
- Reference joint: maintained at a known and stable temperature.
- Output voltage: Reflects the temperature difference between the junctions.
Why it works in adverse conditions:
- It has no moving parts and does not require an external power source.
- Resistant to mechanical stress and corrosion.
- Reliable even in environments with electrical noise.
This combination of heat resistance, reliability, and fast response explains why industrial thermocouples outperform many other sensors in extreme environments.
Read also difference between thermocouple and thermistor
Main industrial applications
Thermocouples are essential in industries where extreme heat is part of daily operations. Their wide temperature range and durability make them an indispensable solution in various sectors.
- Power generation
- Iron metallurgy
- Glass industries
- Cement plants
- Various foundries
- Grain storage and transportation
- Boiler and turbine monitoring
- Aerospace
- Heat treatment and metal processing
- Oil & Gas
Choosing the correct thermocouple
When selecting the ideal thermocouple for your process, it is essential to consider several factors. First, it is important to evaluate the chemical resistance of the metal combination used in the thermocouple. In addition, it is necessary to consider the operating temperature range, abrasion resistance, and the practicality of the thermocouple design in relation to its intended use. Finally, the ease of installation of the device at the application site is also crucial.
This is important because the noble metals used in high-temperature measurements by thermocouples are very sensitive to environmental factors. Errors in this measurement can lead to costly losses and affect the usability of the products you manufacture.
In the worst-case scenario, defective products due to incorrect temperature readings can cause major accidents.
Alutal Thermocouples
There are stories built with dedication, precision, and an unwavering passion for what you do, and Alutal's journey since 1994 is one of those. The Brazilian company has become a benchmark in the world of thermometry, especially when it comes to thermocouples.
If you seek precision and reliability in your industrial temperature measurement, Alutal's history proves you've found the right partner. Since 1994, Alutal has established itself as a manufacturer of thermocouples and temperature sensors that is synonymous with excellence in the Brazilian market.
We specialize in industrial thermometry solutions for the steel, heat treatment, automotive, food, and chemical industries.
What makes Alutal a benchmark in thermocouples? It's its unwavering commitment to quality and precision.
- Certified Laboratory: Guarantee that each temperature sensor is rigorously tested and calibrated.
- ISO 9001 Certification: Since 2006, demonstrating quality management and a continuous pursuit of innovation in the development of high-performance thermocouples.
Looking for a reliable thermocouple supplier? Alutal is your choice for temperature sensor manufacturing.
Speak with the leading thermocouple supplier in Brazil and ensure accurate measurement of your industrial temperature.
