Thermocouples

Wondering what a thermocouple is? Thermocouples — or thermal couples — 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. This voltage, also known as the measuring junction, is proportional to the temperature difference. You can read more about these sensors in our Thermocouples Guide.

How Thermocouples Work

The generation of a voltage in a thermocouple due to the temperature difference between its two junctions is known as the Seebeck effect. It occurs because different metals have different electron configurations, resulting in varying electron densities and thermal conductivities. Consequently, when the junction experiences a temperature difference, an electric current is generated as electrons flow from the hotter metal towards the colder one.

The voltage produced by the thermocouple can be read and measured by a voltmeter or a specialised temperature measurement device. The relationship between temperature and voltage output for a given thermocouple is typically described in a calibration table or equation. By referencing this information specific to the type of thermocouple in use, the temperature at the measurement point can be accurately determined.

Types of Thermocouples

There are a wide range of thermocouple types available, including specialised options like flat thermocouples, each with different characteristics such as temperature ranges based on their robustness. Each thermocouple is defined by a letter, with common thermocouple types including Type J, Type K, Type L and Type T.

The letters used to designate thermocouple types, such as J, K, L, and T, correspond to the specific materials used in their construction. This material composition directly influences the temperature range within which a thermocouple can operate effectively. To further enhance their lifespan, some thermocouples are equipped with an additional sheath that provides insulation and protection to the internal wires.

The robustness, reliability and affordability of thermocouples make them a preferred choice for temperature monitoring and control across various industries, especially for high-temperature measurements:

Type J

Type J thermocouples, composed of iron and constantan, are characterised by a wide temperature range — from approximately 0°C to 816°C — and good sensitivity. Their suitability for general-purpose applications in oxidising or inert atmospheres makes them a common choice in industries like plastic processing, food processing and heat treatment.

Type K

Crafted from chromel and alumel, Type K thermocouples stand out for their broad temperature range and exceptional resistance to oxidation. A popular choice at RS NZ, their versatility makes them ideal for a variety of industrial settings, including furnaces, ovens and power generation facilities.

Type L

Composed of chromel and constantan, Type L thermocouples are well-suited for high-temperature measurements in oxidising or inert environments. Their notable stability and oxidation resistance make them a preferred choice in demanding industries like aerospace, automotive and petrochemicals.

Type T

Type T thermocouples, constructed from copper and constantan, are recognised for their high accuracy and stability at low temperatures. This characteristic makes them invaluable in cryogenic applications, refrigeration systems and scientific research.

Applications of Thermal Couples

Thermocouples, often integrated into thermocouple probes for convenient and precise measurements, are essential temperature sensors utilised in a wide array of applications, from everyday devices to critical industrial processes:

• Thermostats: Precisely control temperature in heating and cooling systems, optimising comfort and energy usage.
• Hospital Equipment: Safeguard patient health and medical equipment sterility through accurate temperature monitoring.
• Thermometers: Deliver precise temperature readings across diverse settings, from laboratories to kitchens.
• Vehicle Diagnostics: Enhance performance and identify potential problems by monitoring engine and exhaust temperatures.
• Boilers and Heating: Maintain optimal temperature control and oversight in both industrial and residential heating systems.
• Sensors: Enable accurate temperature measurement in diverse industrial processes, including manufacturing and chemical processing.
• Oven Safety Features: Prevent overheating and ensure safe operation in ovens and other cooking appliances.
• Food Thermometers: Ensure food safety by precisely measuring internal temperatures during cooking and storage.

Find the Right Thermocouple for Your Needs

If you are in need of thermocouples, RS NZ is a dependable provider of high-quality industrial components from reputable brands like Electrotherm and Correge, providing other temperature-related products like thermal pads and heating elements too.

With next-day delivery options available, you can get your project up and running in no time. Do not compromise on accuracy and reliability — order your thermocouples from RS NZ today!

Ordering and Delivery Information for NZ

Acquiring thermocouples — and other temperature-related equipment like digital thermometers and thermal fuses — from RS NZ is simple. Browse our catalogue, add items to your cart, and checkout securely. Once done, you will receive your order confirmation and delivery details via email, which can be used to track your package.

RS NZ offers fast and reliable delivery across New Zealand, with flexible options to suit your needs. To find out more, visit our Delivery Information page, or contact our customer support team.