Thermocouples
A thermocouple is a temperature sensor that generates a voltage signal based on the temperature difference between two different metals or alloys. It consists of two dissimilar metal wires joined together at one end, forming a junction. When this junction is exposed to a temperature gradient, it produces a small voltage (which is known as the measuring junction) that is proportional to the temperature difference.
This phenomenon is known as the Seebeck effect. It occurs because different metals have different electron configurations, resulting in varying electron densities and thermal conductivities. As a result, when the junction is exposed to a temperature difference, an electric current is induced due to the flow of electrons from the hotter metal to the colder metal.
The voltage produced by the thermocouple can be read and measured by data loggers such as voltmeters or a specialised temperature measurement device. By knowing the relationship between the temperature and the voltage output, typically described in a calibration table or equation specific to the type of thermocouple being used, the temperature at the measurement point can be determined.
Types of Thermocouples
There are a wide range of thermocouple types available, each with different characteristics such as temperature range and their robustness. Each thermocouple is defined by a letter referring to the type of materials used, indicating what temperature they are typically usable at (taking other factors into consideration as well). Some thermocouples come with an additional sheath that insulates the wires to prolong their life.
Type J Thermocouple: Type J thermocouples are made of iron and constantan (a copper-nickel alloy). They are cost-effective and suitable for general-purpose temperature measurements in reducing atmospheres up to 760°C.
Type K Thermocouple: Type K thermocouples are the most common type, made of chromel (a nickel-chromium alloy) and alumel (a nickel-aluminium alloy). They offer a wide temperature range (-200°C to 1260°C) while maintaining a relatively affordable price, and are suitable for various applications, including industrial furnaces, ovens, and automotive.
Type T Thermocouple: Type T thermocouples are made of copper and constantan. They are known for their accuracy at lower temperatures (-270°C to 400°C) and are commonly used in cryogenic and refrigeration applications.
Type N Thermocouple: Type N thermocouples are similar to Type K, but with better resistance to high-temperature oxidation.
Type E Thermocouple: Type E thermocouples offer the highest output voltage among common thermocouple types, making it suitable for low-temperature measurements.
Type R and Type S Thermocouples: Type R and S thermocouples are made of platinum and rhodium alloys, offering high accuracy and stability at high temperatures. However, this also makes them more expensive than other thermocouple types.
Thermocouple Materials
Stainless Steel Thermocouple
Stainless steel thermocouples are robust and resistant to corrosion, making them suitable for various industrial applications. Common grades include:
- 310 Stainless Steel: Offers excellent heat resistance and is often used in high-temperature applications.
- 316 Stainless Steel: Provides good corrosion resistance and is suitable for general-purpose use.
- 316L Stainless Steel: A low-carbon version of 316 stainless steel with improved weldability.
Inconel Thermocouple
Inconel thermocouples, made from an alloy of nickel containing chromium and iron, are known for their high-temperature resistance and corrosion resistance, making them suitable for extreme environments. One example is the Inconel 600 thermocouple which offers excellent resistance to oxidation and carburisation at high temperatures.
PFA Thermocouple
PFA thermocouples use a PFA (perfluoroalkoxy alkane) insulation, which offers excellent chemical resistance and can withstand high temperatures. They are often used in harsh environments where other materials might degrade.
What are Thermocouples Used for?
Thermocouples are used for a wide range of domestic and industrial applications in Singapore related to temperature monitoring and control. They are ideal tools for the measurement of high temperatures due to their robustness, reliability, and affordability. Some applications for thermocouples include:
- Industrial Manufacturing: Monitoring temperatures in furnaces, ovens, kilns, and other industrial processes, or as components in PID temperature controllers.
- Food Processing: Ensuring food safety by monitoring temperatures during cooking, baking, and refrigeration.
- Pharmaceutical Industry: Maintaining precise temperatures in pharmaceutical production and storage.
- Automotive: Measuring exhaust gas temperatures in vehicles for emissions control and engine performance optimisation.
- HVAC: Monitoring and controlling temperatures in heating, ventilation, and air conditioning systems.
- Aerospace: Measuring temperatures in aircraft engines and other critical components.
- Scientific Research: Used in laboratories for various temperature measurement applications.
Buy Thermocouples from a Trusted Supplier and Manufacturer in Singapore
RS is a trusted supplier, distributor, and manufacturer of thermocouples in Singapore, delivering units from reputable thermocouple supplier brands such as Omron, Electrotherm, and our own RS PRO line. We also carry a wide range of control and automation gear ranging from proximity sensors to sensor actuator cables to help you carry out your tasks to the most precise measurement.
Order your thermocouples online from RS today and enjoy fast delivery across Singapore, including next-day delivery and self-collection options. For more details on how to place an order, delivery details, and delivery fees, please refer to our Ordering Page and Delivery Page.