The Critical Importance of Quality in Temperature Sensing Technology

In the realm of industrial temperature measurement, the significance of thermocouples and RTD sensors often goes unnoticed, being mistakenly perceived as simple commodity products. Many buyers, in their pursuit of cost-effectiveness, tend to overlook the crucial factors of quality, reliability, and customer support, assuming all sensors are created equal. However, this oversight can potentially lead to significant problems in the future. When it comes to precise temperature measurement, the choice of sensor manufacturer is a critical decision that should not be underestimated.

While numerous companies produce thermocouples and RTDs, discerning buyers should look beyond the price tag to consider factors like quality, reliability, and customer support. Manufacturers like Duro-Sense stand out from the crowd in this regard. Their focus on excellence and attention to detail can make a crucial difference in your temperature-sensing applications.

Quality-focused manufacturers invest heavily in research, development, and stringent quality control processes. They use superior materials and employ skilled technicians to ensure each sensor meets exacting standards. This commitment to quality translates into sensors that provide more accurate readings, greater longevity, and improved reliability in challenging industrial environments.

Customer service is another area where top-tier manufacturers excel. Companies like Duro-Sense offer extensive technical support, helping customers select suitable sensors for their specific applications. Their experts can guide you through installation, troubleshooting, and maintenance, ensuring you get the most out of your temperature-sensing equipment. This level of support can prove invaluable, especially when dealing with complex or critical temperature measurement tasks.

Furthermore, quality-focused manufacturers often demonstrate a willingness to provide custom solutions. They recognize that off-the-shelf products only sometimes meet the unique needs of every industrial process. Duro-Sense, for example, works closely with customers to design and produce sensors tailored to specific requirements. This flexibility can solve challenging temperature measurement problems that standard sensors simply can't address.

The benefits of choosing a quality-focused manufacturer extend far beyond the initial purchase. While their sensors might carry a higher upfront cost, they often prove more economical in the long run. Higher accuracy reduces errors in production processes, potentially saving significant amounts of money. Greater durability means fewer replacements and less downtime. And the availability of expert support can prevent costly mistakes in sensor selection or installation. This reassurance about the long-term cost-effectiveness of quality sensors can provide peace of mind to the buyers.

In critical applications, the stakes are even higher. Inaccurate temperature readings can lead to product quality issues, energy inefficiency, or even safety hazards. In such cases, the small price difference between a commodity sensor and a high-quality one becomes insignificant compared to the potential costs of failure. This stress on the potential costs of failure can make the audience feel the urgency of investing in quality sensors.

As industries evolve and processes become more sophisticated, the importance of accurate and reliable temperature measurement only grows. Manufacturers prioritizing quality and customer service are better positioned to keep pace with these advancements, continually improving their products to meet emerging needs.

In conclusion, while viewing thermocouples and RTD sensors as interchangeable commodities may be tempting, savvy buyers recognize the value of quality. You invest in more than a sensor by choosing manufacturers like Duro-Sense, who prioritize excellence, customer service, and custom solutions. You gain a partner committed to the success of your temperature measurement applications. In the complex world of industrial processes, that partnership can make all the difference between mediocre results and outstanding performance.

Duro-Sense
310-533-6877
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Duro-Sense, Inc. - Precision in Temperature Sensing Technology

Duro-Sense, Inc. stands as a beacon of excellence and reliability in the intricate world of temperature measurement and control. Established as one of the top providers in the USA, this prestigious company has carved out a significant niche in the market for thermocouples and RTD (Resistance Temperature Detector) temperature assemblies. Their success lies in meticulous materials selection, unmatched craftsmanship, rigorous quality procedures, and widespread acceptance by leading companies across demanding sectors such as aerospace, medical equipment, and industrial process control.

At the heart of Duro-Sense's philosophy lies a commitment to quality that starts with selecting materials. Understanding that the foundation of any superior temperature sensing solution is in the raw materials used, Duro-Sense employs an extensive selection process. This process involves sourcing from only the highest-grade suppliers and conducting extensive testing to ensure that all materials meet their stringent standards. This meticulous approach ensures that every component, from the smallest wire to the housing of the thermocouple itself, contributes to the overall integrity and reliability of the finished product.

Craftsmanship at Duro-Sense is another pillar of its success. Here, the fusion of traditional skills and modern innovation takes center stage. Skilled artisans with years of experience work in tandem with cutting-edge manufacturing techniques to create products that are not only precise but also durable. Every thermocouple and RTD temperature assembly that leaves the Duro-Sense facility is a testament to the company's dedication to precision engineering and quality. This unique blend of craftsmanship and contemporary technology sets Duro-Sense apart in a crowded market.

Moreover, its rigorous quality procedures show the company's commitment to excellence. Duro-Sense does not merely aim to meet industry standards; it strives to exceed them. Every product undergoes exhaustive tests to ensure flawless performance under even extreme conditions. This relentless pursuit of quality means that Duro-Sense products are not just reliable but consistently outstanding. This commitment has earned the company certifications and the trust and loyalty of customers across various industries.

The acceptance of Duro-Sense's thermocouples and RTD assemblies by leading companies in aerospace, medical equipment, and industrial process control speaks volumes about its quality and reliability. These industries, known for their uncompromising standards and rigorous demands, trust Duro-Sense for their temperature sensing needs. Duro-Sense earns its trust by consistently delivering high-quality, reliable, and accurate temperature-sensing solutions that perform under the most challenging conditions.

Duro-Sense, Inc. has established itself as a temperature measurement and control leader. The company consistently delivers products that set the standard for reliability and precision through its meticulous materials selection, unparalleled craftsmanship, and rigorous quality procedures. The widespread acceptance of Duro-Sense's products by industry leaders across aerospace, medical equipment, and industrial process control is a testament to their unmatched quality and performance. In the demanding world of temperature sensing, Duro-Sense, Inc. is not just a provider but a trusted partner in precision and reliability.

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The History of Modern Industrial Thermocouples

In temperature measurement, few tools have been as pivotal as the thermocouple. A simple yet ingenious device, the thermocouple has been central to the industrial age, contributing significantly to advancements in various sectors, from metallurgy to food processing.

Origins: The Seebeck Effect

The story of the thermocouple begins in 1821 with a German physicist, Thomas Johann Seebeck. While conducting experiments, Seebeck discovered that when two different metals are joined, and one end of the junction is heated, while at the same time, the other is kept at a cooler temperature, and a small voltage is produced. This phenomenon became known as the 'Seebeck Effect'. It laid the foundation for developing the thermocouple, where the voltage generated correlates to the temperature difference.

Early Adaptations

Throughout the 19th century, scientists and engineers began to recognize the utility of the Seebeck Effect for temperature measurements. One of the first to do so was Leopoldo Nobili in the 1820s. He created a galvanometer to measure the voltage produced by thermocouples, thus converting them into practical temperature measurement devices.

The Birth of Modern Thermocouples

As we recognize it, the modern industrial thermocouple began to take shape in the early 20th century. Industries, particularly those involved in high-temperature processes like steel manufacturing and glass blowing, require precise and reliable temperature measurements. As a result, there was a drive to standardize thermocouple materials and calibrations. By the mid-20th century, standardized thermocouples made of specific alloys, such as Type K (chromel-alumel) and Type J (iron-constantan), became widely accepted.

Refinements and Innovations

Thermocouples underwent significant improvements with the advent of the electronic age in the latter half of the 20th century. An important development was cold junction compensation, which allowed for more accurate readings.

Digital technologies also revolutionized thermocouple readings. Before this, analog instruments, like the potentiometer, were used. With the rise of digital electronics, it became easier to interface thermocouples with computers, leading to automated temperature monitoring and control in industrial applications.

Modern Applications

Today, thermocouples are ubiquitous in the industrial landscape. They are employed in myriad applications, including:

• Power Generation: Thermocouples monitor the temperature in nuclear reactors, ensuring safe operations.
• Aerospace: They monitor temperatures in aircraft engines and space vehicles.
• Medical: Thermocouples ensure that medical equipment, like autoclaves, maintains the necessary temperatures.
• Food Processing: Ensuring food is cooked or stored at the correct temperature is essential for safety and quality, and thermocouples play a pivotal role here.

Conclusion

The modern industrial thermocouple is a testament to how a simple scientific discovery can revolutionize industries. From its humble beginnings with the discovery of the Seebeck Effect to its indispensable role in modern industries, the thermocouple remains a pinnacle of temperature measurement, illustrating the harmonious blend of science, engineering, and practical application.

Duro-Sense
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The Thermoelectric Phenomenon: The Working Principle of Thermocouples

Thermocouples, the stalwarts of temperature measurement, find extensive use across many industries, from HVAC to metallurgy, owing to their versatility, robustness, and the wide range of temperatures they can measure. These devices, invented in the early 19th century, operate on the thermoelectric or Seebeck effect. This article provides a comprehensive view of thermocouples' underlying principles and workings.

Principles of Thermocouples

Thermocouples work on the principle of the Seebeck effect, discovered by the German physicist Thomas Johann Seebeck in 1821. The Seebeck effect stipulates that when two different metallic wires are connected and exposed to a temperature differential, an electromotive force (EMF) or voltage generates at the junction. The magnitude of this EMF is directly proportional to the temperature difference between the two junctions of the wires.

The materials used in the wires, known as thermoelements, are chosen for their specific Seebeck coefficient, a parameter representing the voltage generated per unit temperature. Different combinations of materials give rise to different types of thermocouples, each suited to different temperature ranges and environments, such as Type K (Chromel-Alumel), Type J (Iron-Constantan), Type T (Copper-Constantan), and so on.

How Thermocouples Work

A fundamental thermocouple consists of two dissimilar metal wires joined at one end, forming a junction. This junction gets exposed to the temperature that needs to be measured, known as the measurement or hot junction. The other ends of the wires connect to a device that can read the EMF generated; this is called the reference or cold junction.

An EMF occurs when the measurement junction experiences a different temperature than the reference junction. This EMF is then translated into a temperature reading using the specific Seebeck coefficient for the materials involved. This principle is simple but powerful enough to measure a broad spectrum of temperatures from cryogenic to thousands of degrees Celsius.

It's important to note that the reference junction at a known, stable temperature or its temperature is otherwise measured because the EMF generated is proportional to the temperature difference between the two junctions, not the absolute temperature at the measurement junction. If the temperature at the reference junction changes, it will affect the EMF and, thus, the temperature reading at the measurement junction.

For instance, modern digital thermocouple meters often incorporate a separate temperature sensor at the reference junction. This sensor compensates for changes in the reference junction temperature, allowing the meter to calculate and display the absolute temperature at the measurement junction.

The versatility, durability, and broad temperature range of thermocouples are due to the fundamental principles of the Seebeck effect and the variety of thermoelements available. Although the principles underpinning their operation are nearly two centuries old, thermocouples remain one of the most widely used temperature sensors in today's high-tech world. Translating tiny EMFs into temperature readings is indispensable in various industrial, scientific, and domestic applications.

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Head Mount Thermocouple and RTD Transmitters

A head mount transmitter is a device used in temperature sensing systems that converts the signal generated by a thermocouple or a Resistance Temperature Detector (RTD) into a standardized output signal, typically 4-20 mA or a digital protocol like HART or Foundation Fieldbus. The transmitter is usually installed in a connection head, which is mounted directly on the temperature sensor assembly, hence the term "head mount."

Thermocouples and RTDs are commonly used temperature sensors. Thermocouples work on the principle of the Seebeck effect, where a voltage generates due to the temperature difference between two dissimilar metals. On the other hand, RTDs work on the principle that the electrical resistance of material changes with temperature.

The value provided by a head mount transmitter in temperature sensing includes:

1. Signal conditioning: The raw signal from the temperature sensor (mV for thermocouples or Ohms for RTDs) can be weak and susceptible to noise, interference, and degradation over long distances. The transmitter amplifies and conditions the signal, ensuring a more robust and reliable transmission.
2. Linearization: The relationship between temperature and the sensor output (voltage or resistance) may not be linear. The transmitter linearizes the signal, providing a more accurate representation of the measured temperature.
3. Standardization: By converting the sensor output into a standardized signal, such as 4-20 mA, the transmitter allows easier integration with other process control equipment, like controllers, recorders, and display units.
4. Temperature compensation: The transmitter can compensate for temperature-related errors that may occur in the sensor, such as cold junction compensation in thermocouples, ensuring higher accuracy in the measurement.
5. Digital communication: Some transmitters have digital communication capabilities, allowing for remote configuration, calibration, and diagnostics, as well as providing additional information, such as sensor health and status.

A head mount transmitter is essential in temperature sensing systems, providing signal conditioning, linearization, standardization, temperature compensation, and digital communication capabilities. It improves the temperature measurement system's accuracy, reliability, and performance.

Duro-Sense Corp.

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Shorter Lead Times Make Happier Customers

Customer satisfaction and loyalty can be closely tied to how quickly customers receive their orders. In terms of supply chain, lead time is a big part of any successful business. Reducing lead times as much as possible is vital to a company’s success.

Manufacturing lead time is the total time required to manufacture an item. From an operational standpoint, One should be aware that there are many different types of lead times:

• Material lead time is the amount of time it takes a customer to place an order with a supplier and receive it; from when the order was confirmed to when they have it on hand.
• Pre-production lead time is the amount of time required for the supplier to create a work order. This is sometimes called planning time. It primarily takes the form of paperwork.
• Production or Factory lead time is the actual amount of time the supplier needs to manufacture the product.
• Post-production lead time is the time required for a customer to receive an item from dock to inventory. Depending on the product, it could entail anything from inspection to quarantine time.
• Fixed lead time refers to a part of production or factory lead time that is not dependent on the order quantity.
• Variable lead time, is the part of production or factory lead time that is dependent on the order quantity.
• Cumulative lead time is the term used to describe the entire amount of time required, from order confirmation to the delivery of the product. It is the aggregate of material lead time and production or factory lead time

Accurately forecasting and reducing lead time is a vital element of any manufacturing operation. The need for a timely and accurate response to inquiries, on-time order completion, and the ability to respond quickly in an emergency must be at the core of a manufacturer’s ideals. They are keys to maintaining customer satisfaction, a competitive advantage, and a definitive reputation in the marketplace.

Duro-Sense has spent years researching, analyzing and implementing methods and procedures to continually improve our ability to work efficiently in pre-production and production, and to enable us to respond quickly and seamlessly to a customer’s requirements and unexpected emergencies.

Strategies including:

• Supply chain re-evaluation
• Domestic material sourcing
• Warehouse reorganization
• Creative inventory control
• Re-training and cross-training personnel
• Improved information flow and accuracy

This approach, has given us the ability to have more efficient and streamlined production and customer interaction, which leads to faster response time and shorter lead times. Duro-Sense has moved to the forefront of on-time delivery and the ability to seamlessly adapt to any urgent customer need.

Customers don’t like waiting. Production lead time can be the critical component in the success of your business. Like a bad movie, or a dull and tedious speech, shorter is always better. Choosing the right manufacturer is essential when trying to calculate lead time. After over four decades in manufacturing, Duro-Sense has developed valuable strategies regarding the most effective ways to reduce lead times without compromising quality. Let us prove it to you.

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Fast Selection Criteria between Thermocouples and RTDs

Both RTD and thermocouple probes monitor temperature, but which one is right for your application?

What temperature range are you trying to monitor?

Generally, if the temperature is above a hundred and fifty degrees Celsius, a thermocouple would be used. For anything below a hundred and fifty degrees Celsius, choose an RTD.

What is the required sensor accuracy? 

RTDs provide more accurate readings with repeatable results. Choose RTDs when temperature accuracy and repeatability are critical. 

What is the purchase budget?

Thermocouples can be up to three times less expensive than RTD sensors, making thermocouples the right choice when purchasing large quantities or requirements on tight budgets.

Use these three criteria to narrow down your selection process. There are many other differences between thermocouples and RTDs you need to understand before selection and application.

Always consult a temperature sensor application expert before installing or specifying a thermocouple or RTD where failure can cause harm or personal injury.

Temperature Sensors Used for Power Generation

In an electrical generating plant, most temperature measurements are performed with RTDs (resistance temperature detectors) and thermocouples (T/Cs). 

RTD's are sensors that produce a measurable change in electrical resistance, while thermocouples have a change in mV signal in response to temperature change. 

RTD's consist of a thin conductor (nickel, platinum, copper) wrapped around a glass or ceramic bobbin, placed into a protective sheath, and backfilled with an electrically inert material but thermally conductive. 

Power plants use 100-ohm platinum, 100-ohm nickel, 120-ohm nickel, and 10-ohm copper RTDs. Though offering excellent accuracy and long-term reliability, RTDs are vulnerable to mechanical shock and vibration in a generating plant. They are more costly than thermocouples and are generally limited to about 1110 ° F. A very appealing feature for RTDs is their electrical noise immunity, a significant advantage over thermocouples. Finally, inexpensive instrument wire is all that is required to connect the RTD to the measuring instrumentation. 

A thermocouple consists of two wires made of dissimilar alloys, joined at both ends. One junction is coined the "hot junction," the other is the "cold junction" (or reference junction). When the hot junction experiences temperature change, a voltage is produced proportional to the temperature difference between hot and cold junctions. 

T/Cs are made of various alloy combinations and "calibrations" for different temperature ranges. Type J, K and N are the most common thermocouples for power generation applications below 1800 ° F; R and S types are common for applications above 1800 ° F. Besides the evident higher temperature capacity, thermocouples have a quicker response and greater endurance to shock and vibration. However, thermocouples are more susceptible to conducted and radiated electrical noise due to the minute signals generated. Another problem with thermocouples is their deterioration over time when used at high temperatures, hence being less stable than RTDs. One final concern is running an expensive thermocouple extension wire of the same type as the sensor-measuring instrument thermocouple.

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Plastics Industry Thermocouple Catalog

Plastics industry thermocouples are designed as an economical solution for the plastics molding and forming industry, and have many other general uses as well.  Their design typically includes a bayonet connection which is ideal for spring loaded sensing of injection mold equipment. They typically are constructed with the "hollow-tube" design for economy and ease of manufacturing. Most common applications are plastic extruders, injection molding machines, and rubber industry presses.

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Duro-Sense Corporation designs and manufactures the finest quality thermocouples, RTDs, and custom temperature assemblies used in a wide variety of industries including aerospace, medical, power generation, food and beverage, pulp & paper, chemical processing, plastics, pharmaceutical, and life science. Duro-Sense products are known throughout these industries for their quality and reliability.

From simple wire and tube assemblies for the plastics industry, to mineral insulated and multipoint thermocouples, to custom sensors for specific applications, Duro-Sense can design, manufacture, and deliver solutions to virtually any temperature related application.

Engine Compressor Thermocouples Provide the Reliability Needed for Offshore Use

Offshore oil and gas platforms require an uninterrupted source of electricity to power a wide variety of specialized equipment used to drill for oil. Pumps, valve operators, critical communications, turntables, motors, and safety systems are just a subset of the drilling and production ecosystem requiring a reliable source of power. Just as critical is the large amounts of electrical power required for the habitation. Electrical generators provide the power for comfort heating, cooling, desalination of water, food preparation, and even waste processing. The power requirements of an offshore platform is not unlike that of a small town.

The most common source of power for these offshore rigs are diesel powered generators. While diesel is still the most common, alternative fuels such as gas, heavy oil, and steam turbines are being produced for offshore platform use. Major turbine manufacturers continue to develop technologies that efficiently use one, or a combination, of these fuels. Additionally, increased savings and efficiencies are being realized through adopting waste heat recovery systems. These recovery systems assist by reusing and recycling energy from exhaust gases of turbines and generators.

Conditions on offshore platforms are harsh. Equipment and components must provide stable
operation and, by design, reduce the need for frequent maintenance and overhaul.  A specialized temperature sensor, referred to as an "engine compressor thermocouple" is used on platform generator turbines. These are specially designed, heavy-duty temperature sensors used for measuring the exhaust gases from engines, turbines and compressors. These sensors are time-tested and built to withstand the harsh mechanical and environmental conditions subjected by offshore, marine conditions.

For more information about offshore platform compressor thermocouples contact Duro-Sense. You can reach them by phone by calling 310-533-6877 or visit their web site at https://duro-sense.com.

Precision Thermocouples and RTDs for the Most Demanding Applications

Duro-Sense Corporation provides the highest quality thermocouples and RTDs to the aerospace, aviation, offshore drilling, medical, R&D, power generation, alternative energy, process control,  primary metals, high-tech and OEM industries.

Contact Duro-Sense by calling 310-533-6877 or visit their web site at https://duro-sense.com.

What Kind of Thermocouple Should I Use?

What kind of thermocouple should I use? Depends on several variables related to the system to be tracked, such as its media / process environment compatibility, the frequency and precision of the necessary measurements, and the regulatory climate in your sector.

Temperature measurement in many industries, from refining to pharmaceuticals to aerospace, is a key parameter in manufacturing and processing operations. Precise temperature monitoring helps to ensure safe, efficient and optimal results.

A thermocouple is invariably the measuring tool of choice for applications above 1400° F, but the selection of the ideal industrial thermocouple also requires knowledge of the process where the device will be used.

INTERFACE WITH PROCESS

First, consider whether the thermocouple is itself in direct contact with the process media or whether it is incorporated into a thermocouple assembly that includes a thermowell. Thermowells are metal, glass, or ceramic tubes that protect the thermocouple against corrosive, fast-flowing or highly hot process media. About 75% of heavy industry thermocouples use thermowell assemblies; these industries include refining, petrochemical, the pulp and paper industry, and power generation.

JUNCTION

The thermocouple junction design depends on the applications requirements for response speed and the likelihood of electrical noise being conducted through the process. A thermocouple has three variations of sensing tip (or junction): Exposed junction, where the exposed wire tips and welded bead have no covering or protection; Grounded junction, where the welded bead is in physical contact with the thermocouple's sheath; Ungrounded junction, where the tip is inside the thermocouple sheath, but is electrical (and somewhat thermally) insulated from the sheath (no sheath contact).

MATERIAL SELECTION

Material selection is the second criteria to choose. A vast majority of industrial thermocouples are made from stainless steel, but specialized alloys such as Inconel 600, Hastelloy X, Monel,  and other unique metals are required in certain applications.

MOUNTING

Next, you have to consider the mounting arrangement. You need to determine whether a more traditional industrial thermocouple/well/head design is required, or if some sort of flexible or remote thermocouple sensor is required for use in a hard to access area.

TYPE

Last, you have to decide the "type" of industrial thermocouple you need. In the case of thermocouples, "type" refers to the composition of metal wires in the instrument whose physical properties respond to changes in temperature. Different metal compositions have different temperature ranges and other properties that make them suitable for use in special applications, or inappropriate for use.

• Type J thermocouples use iron for the positive leg and copper-nickel (constantin) alloys for the negative leg. They may be used unprotected where there is an oxygen-deficient atmosphere, but a thermowell is recommended for cleanliness and generally longer life. Because the iron (positive leg) wire oxidizes rapidly at temperatures over 1000 deg.F, manufacturers recommend using larger gauge wires to extend the life of the thermocouple when temperatures approach the maximum operating temperature.
• Type K thermocouples use chromium-nickel alloys for the positive leg and copper alloys for the negative leg. They are reliable and relatively accurate over a wide temperature range. It is a good practice to protect Type K thermocouples with a suitable ceramic tube, especially in reducing atmospheres. In oxidizing atmospheres, such as electric arc furnaces, tube protection may not be necessary as long as other conditions are suitable; however, manufacturers still recommend protection for cleanliness and prevention of mechanical damage. Type K thermocouples generally outlast Type J, because the iron wire in a Type J thermocouple oxidizes rapidly at higher temperatures.
• Type N thermocouples use nickel alloys for both the positive and negative legs to achieve operation at higher temperatures, especially where sulfur compounds are present. They provide better resistance to oxidation, leading to longer service life overall.
• Type T thermocouples use copper for the positive leg and copper-nickel alloys for the negative leg. They can be used in either oxidizing or reducing atmospheres, but, again, manufacturers recommend the use of thermowells. These are good stable thermocouples for lower temperatures.
• Types S, R, and B thermocouples use noble metals for the leg wires and are able to perform at higher temperatures than the common Types J and K. They are, however, easily contaminated, and reducing atmospheres are particularly detrimental to their accuracy. Manufacturers of such thermocouples recommend gas-tight ceramic tubes, secondary porcelain protective tubes, and a silicon carbide or metal outer protective tube depending on service locations.

For more information about industrial thermocouples, contact Duro-Sense Corporation. Call them at 310-533-6877 or visit their web site at https://duro-sense.com.

Duro-Sense Corporation: Celebrating Our 40th Year in Business

Duro-Sense designs and manufactures temperature sensors and assemblies used in power generation, plastics production, semiconductor processing, environmental control, packaging, aerospace, medical equipment, foodservice equipment and a myriad of other industries. Duro-Sense partners with customers to optimize their temperature sensing processes, thereby assisting in improving their customers efficiency and profitability.

Since 1979, Duro-Sense has grown exponentially in product capability and market experience. The company today continues to succeed by operating under a simple core value – providing customers with superior products, meticulously engineered for their individual requirements.

Duro-Sense: A Long History of Solving Tough Temperature Sensing Problems

With engineering, design, and support resources available at their headquarters in Southern California, Duro-Sense delivers value-added temperature sensing solutions that improve operations and increase profitability for customers in the power generation, alternative energy, plastics, medical, gas & oil, chemical, refining, mining, agricultural, food service, pharmaceutical, and aerospace industries.

Duro-Sense offers their customers products and services designed to provide outstanding value and cost savings throughout the customer's equipment life span. By integrating the highest quality standards, state-of-the-art machinery, and decades of application experience, Duro-Sense assists customers through:

• Improved product quality
• Optimize asset uptime and performance 
• Lower total cost of operation and maintenance
• Increase equipment reliability
• Improve plant and personnel safety

ENGINEERING AND TECHNICAL SERVICES

Technical Analysis — Duro-Sense can identify temperature sensor operational issues that may be constraining output or elevating operating costs, and then recommend laser-focused solutions.

Reliability and Efficiency Services — Duro-Sense lends their decades of hands-on experience to offer practical temperature sensing solutions that improve the performance, efficiency, and reliability of your process control equipment - all while lowering your total cost of ownership.

Loop Design, Integration and Engineering Support — Duro-Sense engineers engage with their customers, providing support for grassroots project planning, system design, or project management requirements.

Equipment Life Cycle Optimization — Through a combination of assessments and technology, Duro-Sense experts help customers benchmark operational performance, define key metrics, and implement precise sensor solutions to achieve long-term operational goals.

Intelligent Product Design — By employing an array of sophisticated products, services, and software that collects, examines and understands data, Duro-Sense helps customers use predictive analytics to take action and improve asset reliability and reduce downtime.

Have a challenging temperature sensing requirement? Call Duro-Sense.

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Quick Comparison of Temperature Sensors

Thermocouples are commonly used because of their simplicity, reliability, and relative low cost. They are self-powered and eliminate the need for a separate sensor power supply. Thermocouples are quite durable when selected for a given application appropriately. Thermocouples can also be used for applications with high temperatures.

Resistance temperature detectors (RTDs) are attractive alternatives to thermocouples when the output is desired to be highly accurate, stable and linear (i.e. just how close the calibration curve looks a straight line). The superior linearity of relative temperature resistance enables simpler signal processing devices for RTDs than thermocouples.

Thermistors are similar to RTD because they're a resistance measurement device, but thermistors use a very cheap polymer or ceramic material as the element in lieu of the use of pure metal.

For more information on any type of industrial or OEM temperature sensor, contact Duro-Sense by calling 310-533-6877 or by visiting https://duro-sense.com.

A Pro and Con Comparison of Thermocouples and RTDs

Thermocouple Advantages 

• Inexpensive
• Wide temperature range
• Various types, sizes and application methods
• Remote read back
• Read back electronics can be simple
• Usable in virtually any environment

Thermocouple Disadvantages

• Requires cold junction compensation
• Slow response time
• Not as accurate as many other devices without good CJC and calibration
• Susceptible to noise
• Connection cable/wire is expensive compared to copper conductors
• Cable/wire length is limited

RTD Advantages

• More linear than thermocouples
• Cold junction not an issue
• Special cable/wire not needed
• Cable/wire length can be much longer than TC’s
• Better noise immunity
• More stable over time than thermocouples
• Remote read back
• Usable in virtually any environment

RTD Disadvantages

• More expensive than thermocouples
• More delicate than thermocouples unless encased
• Not as wide of temperature range as thermocouples
• Requires more conductors per device
• Read back electronics more complex

Theory of Thermocouple Operation

• A thermocouple is a simple temperature measurement device consisting of a junction of two dissimilar metals.
• Contrary to popular belief, the voltage measured (and converted to a temperature) is not a function of the junction alone. Rather it is the temperature difference (or gradient) between the junction (or hot), end and the reference (or cold), end.
• A thermocouple circuit whose junction and reference are the same temperature will measure no temperature (0V).
• If this were not true, we could create a self-sustaining voltage generator using a thermocouple, a resistive load and an oven, that would require energy only at start-up.

The temperature equation for the simplest of thermocouple circuits shown above is:

T = T_junc – T_ref

Where T is the desired measurement, T_junc is the hot junction temperature and T_ref is the reference

temperature, or cold end.

For simplicity’s sake, we use T, T_junc and T_ref here, but in reality these are voltages that are later converted to a temperature.

Cold Junctions

The temperature equation for this diagram is:

T = T_junc – T_cj1 – T_cj2

A fundamental problem when using thermocouples is the fact the when connected to a measurement device (voltmeter or TC meter), a third metal is introduced (the connecting terminals), and two more thermocouple junctions are created. These adversely affect the temperature being measured. The new, (and unwanted), junctions are referred to as “cold junctions” and need some type of “cold junction compensation” in order to make accurate measurements.

In addition to the added variables in the previous equation, the temperature of the cold junctions

(reference end), is still not known. The following rule helps things out a bit:

• If both TC connections to the meter are of the same metal or alloy, they cancel each other and have no affect on the measurement, as long both connections are at the same temperature (which can be assumed).

Since the definition of a thermocouple states that it must be of dissimilar metals, a second thermocouple must be introduced to the circuit to achieve this. This was the first of what is commonly called “cold junction compensation”

By adding a second series thermocouple suspended in an ice bath, the cold junctions at the meter are of identical metals and cancel each other. In addition, the temperature of the ice bath is known to be 0 Deg. C and becomes the reference end of the thermocouple.

The temperature equation is now simplified and once again becomes:

T = T_junc – T_ref

While the ice bath reference junction eliminates errors, it is clearly impractical for most, if not all applications.  Fortunately, all of today’s thermocouple read back options (meters, chart recorders, PLCs, etc.), come equipped with cold junction compensation, usually a thermistor and associated circuitry and software. By taking the cold junction worries out of the picture, the thermocouple remains one of the simplest, most robust and widely used temperature measurement devices around.

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Thermocouples

Diagram of a thermocouple circuit.

A thermocouple is a temperature measurement sensor. Thermocouples are made of two different metal wires, joined to form a junction at one end. The connection is placed on the surface or in the measured environment. As the temperature changes, the two different metals start to deform and cause resistance changes. A thermocouple naturally outputs a millivolt signal, so that the change in voltage can be measured as the resistance changes. Thermocouples are desirable because they are extremely low cost, easy to use and can provide precise measurements.

Typical sheathed thermocouple.

Thermocouples are produced in a variety of styles, such as sheathed, washer type, bayonet,  mineral insulated, hollow tube, food piercing, bare wire thermocouples or even thermocouple made from thermocouple wire only.

Because of their wide range of models and technical specifications, it is extremely important to understand their basic structure, functionality and range in order to better determine the right thermocouple type and material for an application.

Operating Principle

When two wires consisting of different metals are connected at both ends and one end is heated, a continuous current flows through the thermoelectric circuit. If this circuit is broken in the center, the net open circuit voltage (Seebeck Effect) depends on the temperature of the junction and the composition of the two metals. This means that a voltage is produced when the connection of the two metals is heated or cooled that can be correlated to the temperature.

Contact Duro-Sense Corporation with any questions about applying industrial and commercial thermocouples.

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