What are the different types of thermocouples?

Different types of metals serve as conductors in thermocouples based on typical temperature ranges, environmental conditions, and accuracy requirements of each application. These types include base metal thermocouples (Type K, Type J, Type T, Type E, and Type N) and noble metal thermocouples (Types R, S, and B and Type C).

What are common configurations of thermocouples?

The most common designs of thermocouples include probe style, bead style, bayonet style, and surface style.

Thermocouples - ARi Industries, Inc.

THERMOCOUPLES

When precision temperature measurement is critical to operations, choosing the right thermocouple is the difference between ongoing equipment performance and costly downtime. At ARi Industries, we manufacture thermocouple sensors that are suitable for demanding applications, harsh environments, and reliable, long-term use.

Learn more about different types of thermocouples, common applications for them across industries, and what sets ARi Industries apart.

What is a Thermocouple?
Thermocouple Applications
Why Choose ARi Industries for Thermocouples?

What is a Thermocouple?

Thermocouples are temperature sensors that are made by joining two dissimilar metal conductors at both ends, called junctions. One end of the system, called the “hot junction,” touches the object or material being measured, and the other, the “cold junction,” is connected to a measuring or monitoring device.

When the temperature at one junction end is different from that at the other, the thermal energy causes electrons to move from the hot side to the cold side, generating a very low level of DC voltage (i.e. the Seebeck effect), measured in millivolts (mV). The voltage occurs predictably and is also proportional to the temperature difference between the hot and cold points in the system. As a result, the voltage can be referenced on standardized charts to reliably gauge temperatures.

Types of Thermocouples

Different types of metals serve as conductors in thermocouples based on typical temperature ranges, environmental conditions, and accuracy requirements of each application. ARi Industries manufactures the following types, and can customize them to your application.

Base metal thermocouples: These are cost-effective and suitable for most low-to moderate-temperature applications.

Options include:

Type K. Made with Chromel-Alumel conductors, these are general use thermocouples for -200° C to 1,250° C conditions.
Type J. Made with Iron-Constantan conductors, these are widely used in plastic injection molding, extrusion, and other applications between 0° C and 750° C.
Type T. These low-temperature thermocouples are made with Copper-Constantan conductors for medical cold storage, cryogenic, lab, and HVAC applications between -200° C and 350° C.
Type E. These Chromel-Constantan are used for low temperature and cryogenic applications operating between -270° C and 0° C.
Type N. Made with oxidation-resistant Nicrosil/Nisil conductors, these are used in high-temperature applications up to 1,300° C.

Noble metal thermocouples: High temperature applications above 1,300 °C often require conductors made with noble metals.

Types R, S, and B. These are all made with Platinum-Rhodium conductors. Types R and S maintain accuracy to 1,600° C, and B can be used up to 1,800° C.
Type C. This type is made with Tungsten-Rhenium conductors and is commonly used in vacuum environments with extremely high temperatures up to 2,300° C. These can be manufactured with specialty sheath materials, including molybdenum, tantalum, and tungsten.

Common Thermocouple Configurations

Thermocouples come in a variety of configurations, which is why they can be used in so many types of applications. The most common designs include:

Probe Style

The junction is enclosed in a sheath that protects the conductors from moisture, chemicals, dirt, and other physical damage. This design makes it safe to insert the thermocouple into a liquid, gas, penetrable solid, or a container like a tank or enclosure to monitor temperatures quickly.

Bead Style

This basic style has an exposed junction that takes extremely fast measurements; however, without a protective covering, bead thermocouples cannot be used with corrosive or other damaging materials. They are generally small and well-suited to applications with small or confined space.

Bayonet Style

These feature a twist-to-lock fitting for simple and secure installation and removal. Most also include a spring-loaded mechanism that holds the thermocouple in contact with the liquid or surface being monitored, and some include a fitting to hold it at a specified depth, such as for applications involving liquids.

Surface Style

Designed specifically for measuring surface temperatures on equipment or structures, these low-profile thermocouples are generally made from thin conductors and include a mechanism for holding the junction against the surface (e.g., adhesive backing, clamp, magnet, fasteners).

Options for Collecting Temperature Data

Thermocouples themselves do not provide a temperature reading directly and must be connected to a device that gathers and converts voltage information into a temperature value. Common options include:

Handheld Digital Thermometer

These are portable devices that can be used to check temperatures at various points in a system. They are useful for spot checking in applications with high or quickly fluctuating temperatures, and may include different types of interchangeable probes for use with different types of media (e.g., liquids, solid surfaces).

Data Loggers

These collect voltage and corresponding temperature data over a period of time. They are often used for tracking in extremely high or low temperatures that need to stay within a narrow range, during process validation, for mapping temperature patterns in an area like a large room or facility, or for remote monitoring.

Transmitters

These convert the weak mV signal generated by the thermocouple into a stronger one so it can be transmitted over a longer distance for remote monitoring. The data is sent to a central computer or other device via wireless connection with text or other messaging and can provide periodic updates as well as alerts when the temperature is out of acceptable parameters (many also include data logging functionality). Transmitters can also help shield the thermocouple itself from electromagnetic interference (EMI) generated by industrial equipment, which improves accuracy. These devices allow for remote monitoring and responsive adjustments to equipment or processes as needed.

Thermocouple Applications

Thermocouples support critical temperature measurement and monitoring in equipment and processes across multiple industries, including:

Aerospace and Defense

Jet engines and avionics system monitoring require sensors that can maintain calibration under high G-force vibration and rapid thermal cycling

Nuclear Energy

Thermocouples for monitoring reactor temperatures must meet regulatory standards and remain viable over the long-term in high-radiation environments

Semiconductor Manufacturing

CVD reactors and epitaxial growth systems rely on precise thermal control to prevent wafer damage and ensure yields

Fusion Energy Research

Experimental reactors operate at extreme temperatures where conventional sensors fail. Our tungsten-rhenium sensors provide accurate data in these pioneering applications

Vacuum Furnaces

Brazing and sintering processes require tight temperature control within furnaces for consistency and part quality

Cold Storage

These allow for precise monitoring in walk-in freezers for food, storage lockers for medicines and vaccines, and cryogenic storage facilities

Food Processing

Thermocouples provide reliable temperature monitoring and control in cooking and baking applications including deep frying, pasteurization, freezing, and fermentation

HVAC Systems

Thermocouples are used in pilot flame sensors, and in ductwork and exhaust components

Automotive Engines

Critical temperatures in exhaust systems, cylinder heads, engines, and brake systems are monitored with thermocouples

Why Choose ARi Industries for Thermocouples?

Established in 1952, we have decades of experience developing and building high-reliability thermal monitoring solutions, and we understand the challenges of reliable temperature monitoring and management. Our in-house engineering team can assist with material selection, optimal sensor placement, and industry-specific compliance.

There are several advantages to choosing ARi Industries for standard and custom thermocouples, including:

We specialize in customized thermal solutions for a range of operating conditions and critical applications. Because we are one of only two US manufacturers of (MI) cable, we control every step of production in-house from raw materials to the finished thermocouple.

Our proprietary AerOpak^® MI cable technology delivers:

Extended Temperature Capability: Conductor material combinations support measurements from cryogenic levels to 2,320 °C.
Atmospheric Compatibility: Sensors can be engineered for oxidizing, reducing, inert, and vacuum environments.
Mechanical Durability: MI cable features bendable sheaths and vibration-resistant construction for complex installations.

We are ISO 9001:2015-certified for quality management and stand behind the materials, calibration, and production of our products. We also provide installation, maintenance, and repair services, as well as training. When properly used and maintained, our thermocouples are accurate, reliable tools with a long service life.

All calibrations reference National Institute of Standards and Technology (NIST) standards.
Thermocouples are manufactured to AMS2750 and AST E230 standards.
As a vertically-integrated, US-based manufacturer with many common configurations in stock, we can provide lead times as short as six weeks for sensors customized to your requirements.