Thermocouples: Types and Uses

Thermocouples are sensors used to measure temperatures. These devices consist of different metals to form two wire legs forming a junction. Manufacturers weld together these two wire legs to make sure the connection is stable. Thermocouple junctions are used to check for changes in temperatures. There are different types of thermocouples available in the market, and these models have distinct characteristics and features.

The Types of Thermocouples

The manufacturing of a thermocouple requires producers to classify units with distinct color codes. Manufacturers classify these codes in either ANSI/ASTM E230 OR IEC60584. The thermocouples, their calibrations, and their color designations (in ANSI/ASTM E320) are:

• Type K: Yellow (+) / Red (-)
• Type T: Blue (+) / Red (-)
• Type N: Orange (+) / Red (-)
• Type S: Black (+) / Red (-)
• Type C: N/A
• Type J: White (+) / Red (-)
• Type E: Purple (+) / Red (-)
• Type R: Black (+) / Red (-)
• Type B: Black (+) / Red (-)

Conversely, here are the thermocouples once more and their calibrations, but with their IEC 60584 color designations:

• Type K: Green (+) / White (-)
• Type T: Brown (+) / White (-)
• Type N: Rose (+) / White (-)
• Type S: Orange (+) / White (-)
• Type C: N/A
• Type J: Black (+) / White (-)
• Type E: Purple (+) / White (-)
• Type R: Orange (+) / White (-)
• Type B: Orange (+) / White (-)

Thermocouple Temperature Range

Aside from the color codes, thermocouple types have specific melting points and continuous maximum temperatures. For example, the thermocouple Type B with a platinum 30% rhodium (+) composition may have a temperature range of 2,500 to 3,100 degrees Fahrenheit. Conversely, a platinum 6% rhodium (-) composition of the same thermocouple type may yield a similar temperature range.

Another example is a thermocouple type E with a chromel (+) composition. For this model, you may use it for handling temperature ranges of 200 to 1,650 degrees Fahrenheit. Still, consider the environment before using specific thermocouple types.

Uses of Thermocouples

Different thermocouple types may have diverse uses. Hospital thermometers, automotive technologies, and machines handling renewable energies might use thermocouples to help users detect changes in temperatures. Here are a few thermocouple types and their uses:

• Type J

This thermocouple type may have an iron and Constantan leg. Various organizations in different industries find this model to be helpful in several operations. For example, it may be useful in reducing, oxidizing, and vacuuming atmospheres. Type J models may have durable constructions. Thus, these units may not require sensitive handling when installing them in other machines or industrial environments.

• Type K

This thermocouple has a Chromel and Alumel composition for its wire legs. Consider using this type to oxidize or inert atmospheres with temperatures of up to 2,300 Fahrenheit. Companies may use this thermocouple model thanks to its relatively accurate and stable readings even at high temperatures.

• Type N

Type N thermocouples may be akin to better Type K models. This type has a Nicrosil and Nisil composition for its wire legs. It also has a similar temperature range as the Type K. However, type N models might have better resistance than its type K counterparts thanks to its temperature cycling features. Furthermore, its hysteresis and green rot allow type N models to be more cost-effective units than type Ks.

• Type T

A copper and Constantan composition reside in the wire legs of type T thermocouples. Like the type J models, type Ts help users reduce, oxidize, vacuum, and inert atmospheres. Still, this thermocouple class has excellent resistance against corrosion in several atmospheres. It may also offer high-stability readings at sub-zero temperatures.

• Type E

For this thermocouple, it has one Chromel and one Constantan leg. Like the type T thermocouple, it may also be resistant to corrosion in various atmospheres. However, there’s one characteristic that may put type E thermocouples better than other models: Type Es may have the highest EMF per degree in comparison with different thermocouple types. Nonetheless, it might not be resistant to sulfurous environments.

• Type C

Environments that have sweltering temperatures may use type C thermocouples. This model has a tungsten and rhenium composition for its wire legs. Organizations may use this thermocouple type in extremely high-temperature environments of up to 4,200 degrees Fahrenheit. While it can withstand high temperatures, this thermocouple may have a brittle construction. Proceed with caution when handling it as one false move might break the device.

Conclusion

Always consider the right thermocouple type when you want to read temperatures accurately in specific environments. For instance, consider the right thermocouple when reading temperature levels in automotive technologies and their hot engines. These devices may also activate gas shut-off modules aside from reading temperatures. Take time in researching the right model for the job to avoid complications.

Salman Zafar

Salman Zafar is the CEO of BioEnergy Consult, and an international consultant, advisor and trainer with expertise in waste management, biomass energy, waste-to-energy, environment protection and resource conservation. His geographical areas of focus include Asia, Africa and the Middle East. Salman has successfully accomplished a wide range of projects in the areas of biogas technology, biomass energy, waste-to-energy, recycling and waste management. Salman has participated in numerous national and international conferences all over the world. He is a prolific environmental journalist, and has authored more than 300 articles in reputed journals, magazines and websites. In addition, he is proactively engaged in creating mass awareness on renewable energy, waste management and environmental sustainability through his blogs and portals. Salman can be reached at salman@bioenergyconsult.com or salman@cleantechloops.com.

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