Thermocouples work on the principle of comparative measurements.A thermocouple is composed of two metal conductors of different materials, which are connected at the measurement point. Depending on the material combination, they generate levels of thermoelectric voltage.
Different material combinations give different levels and of voltage, making them suitable for different temperature ranges.
The most common thermocouples are type K, J, L and S.
To make an informed choice between Type K and Type S thermocouples, it is crucial to thoroughly understand the specifications of both types.
Here are detailed specifications for both thermocouples.
Type K offers several advantages that make it suitable for a variety of applications.
Type K thermocouples have an extended temperature range, from -200°C to +1350°C, which makes them suitable for both low and high temperature measurements.
Type K has high accuracy, with a thermal sensitivity of up to 41 μV/°C.This makes them reliable for precision temperature measurements.
Type K thermocouples have reasonably good resistance to corrosion, making them suitable for use in a variety of environments, including chemical and industrial applications.
They are cost-effective and offer excellent performance for the price, making them a popular choice in various industries.
Type K thermocouples have a fast response time, which is essential for processes that require immediate temperature measurements.
Type S offers specific advantages that make it suitable for demanding applications.
Type S is designed for extremely high temperature measurements, up to 1600°C. This makes them suitable for applications in industrial furnaces, melting processes and other high-temperature applications.
Type S offers impressive accuracy even at these extreme temperatures, with a sensitivity of about 10 μV/°C.
Type S consists of precious metals. With a ceramic sheath, it is highly resistant to corrosion, ensuring longer life even in demanding conditions.
Type S remains stable and reliable over extended periods of time, making them suitable for continuous temperature measurements.
Type S is suitable for a variety of environments, including oxidizing, inert and vacuum environments, making them versatile.
Although type K has many advantages, there are also some disadvantages to consider.
Type K can be sensitive to contamination. Exposure to contaminants, such as sulfur-containing gases, can reduce measurement accuracy.
At temperatures below freezing, the accuracy of Type K thermocouples can be reduced. For low-temperature applications, other thermocouples may be more suitable.
Although type K thermocouples are generally resistant to oxidation, they may have limited life at very high temperatures in oxidative atmospheres.
Type K thermocouples are magnetic, which means they can be affected by magnetic fields. In some applications, this can be a disadvantage.
Galvanic corrosion can occur on contact with other metals, especially in humid environments. Oxygen deficiency can lead to insufficient Ni-oxidation (green discoloration). This can affect the life of the thermocouple.
At very high temperatures, Type K thermocouples may be less stable compared to some other thermocouple types.
Although type S has many advantages, there are also some disadvantages to consider.
Type S thermocouples are often considered more expensive compared to some other thermocouple types. Platinum and rhodium are precious metals with a higher cost.
Type S thermocouples are less suitable for applications in which low temperatures must be measured. For low-temperature applications, other thermocouples may be more suitable.
Unprotected thermocouples should not be used in continuous operation above 1500 °C.
Platinum poisons, such as Silicon, Aluminum, Sulfur and Phosphorus can affect service life.
Specification
Type K
Type S
Material
Chromel and Alumel
Platinum and Rhodium
Measuring range
-200°C to +1350°C
0 to 1600°C
Accuracy
to 41 μV/°C
Ongeveer 10 μV/°C
Lifetime
Standard
Long
Corrosion
Resistance
Moderate Excellent
Response time
Fast
Fast
Type K thermocouples are widely used in various industrial applications, including melting furnaces, heat treatment processes, HVAC systems and food processing.
Type S thermocouples are often used in situations where high temperatures and extreme precision are required, such as in the aerospace, metallurgy, petrochemical, and scientific research industries.
Type S thermocouples are also ideal for use in processes where temperature measurements are critical for product quality and safety, such as in the pharmaceutical and biotechnology industries.
In addition, we find them in laboratory environments where accurate temperature measurements are essential for research and development.
Now that you are familiar with the specifications and applications of Type K and Type S thermocouples, you may want to know which thermocouple is best suited for your specific needs. Choosing the right thermocouple is critical to obtaining accurate temperature readings and ensuring the performance and safety of your processes.
Here are some considerations to help you decide which thermocouple is best for your application.
Consider the temperature requirements of your process.
If you need to measure temperatures up to 1200°C, Type K may be the best choice.
For even higher temperatures up to 1600°C, type S is appropriate.
If your application requires high precision, type S with its highly accurate measurements is a good choice, but type K offer good accuracy for many applications.
If your process environment is corrosive, or if the thermocouple is exposed to wear, Type S with its better corrosion resistance and longer life may be preferred.
Consider the industry and application in which you work.
The cost aspect is important. Type K thermocouples tend to be more affordable than Type S.
Check whether the necessary accessories, such as measuring instruments and compensation cables, are available for the selected type of thermocouple.
Consider the norms and standards applicable in your industry.Ensure that the selected thermocouple meets the required standards.
It is essential to thoroughly evaluate your specific needs and the environment in which the thermocouple will be used before making a choice. You can also consult with our temperature measurement experts to determine the best thermocouple for your application.
By choosing the right thermocouple, you can make accurate temperature measurements and ensure that your processes run smoothly, contributing to product quality and safety.
In this article, we have highlighted the differences between Type K and Type S thermocouples, discussing both specifications and applications. Both thermocouples have their unique advantages and disadvantages and are suitable for different industrial environments.
Understanding these differences is essential to choosing the right thermocouple for your specific application.
My name is Saskia van der Laan and I have been working at JUMO for quite some time, combining my professional skills with my passion for writing. Always with the aim of using written text to translate technology into practice and to inform and inspire the reader. In my spare time, I like to do sports and enjoy a long walk with the dog.