RTD Temperature Sensors: Precise Measurement Through Metal Resistance

RTD (Resistance Temperature Detector) sensors deliver precise and repeatable temperature readings by capitalizing on a predictable relationship between temperature and electrical resistance. Engineers typically use platinum as the sensing element because it remains stable over wide temperature ranges and offers high accuracy. Other metals, such as nickel and copper, also appear in RTDs, but platinum dominates critical applications that demand reliable performance.

An RTD consists of a wire coil or thin film of the chosen metal housed in a protective sheath that shields the sensor from harsh environmental conditions. As the sensor’s temperature rises, the metal’s resistance increases. Monitoring equipment then measures this change in resistance and converts the data into a temperature reading. This active principle underpins the RTD’s reputation for accuracy and repeatability in industrial and laboratory settings.

Engineers often favor RTDs in situations that involve narrow tolerance for temperature fluctuations. Semiconductor fabrication plants, pharmaceutical laboratories, and food processing facilities rely on RTDs to maintain strict process control. In these environments, temperature excursions of just a few degrees can compromise product quality or risk safety. RTDs enable a proactive response to potential issues by providing timely data about process temperatures.

Instrument manufacturers integrate RTDs into control loops alongside transmitters and data acquisition systems. The transmitter injects a small current into the RTD element, measures the resulting voltage drop, and calculates the corresponding temperature. This active approach ensures minimal sensor self-heating, which could distort readings. Engineers often calibrate RTDs to accommodate specific measurement ranges or environmental conditions, thus guaranteeing reliable data when environmental stressors threaten accuracy.

Field technicians appreciate the robustness of RTDs in industrial processes. Many RTD assemblies include protective stainless-steel thermowells or special coatings that shield the sensor from corrosive chemicals and abrasive particles. This protection extends the RTD’s service life and reduces maintenance costs for facilities that must avoid downtime. RTDs endure extreme weather conditions in outdoor applications and still report consistent measurements.

Designers integrate RTD temperature sensors into advanced systems, including programmable logic controllers (PLCs) and distributed control systems (DCS). These systems coordinate multiple sensors to maintain precise conditions in large manufacturing operations—automation engineers program alarm thresholds to trigger safety measures or shut down processes when temperatures approach critical limits. RTDs excel in these roles because they provide trustworthy data and withstand harsh operating environments.

Overall, RTDs are a vital resource for anyone requiring accurate temperature readings over a broad range of conditions. Many industries trust them for their ability to deliver reproducible and stable measurements. By leveraging the predictable change in metal resistance, RTDs empower engineers, technicians, and researchers to uphold product quality, ensure safety, and optimize operational efficiency.

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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.

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The Future of Temperature Sensors in Manufacturing: Innovations in RTDs and Thermocouples

Over the next five years, manufacturing will witness significant advancements in temperature sensing technologies, particularly in resistance temperature detectors (RTDs) and thermocouples. These advancements will be driven by material science, wireless networking, and artificial intelligence breakthroughs, revolutionizing how temperature is monitored and controlled in manufacturing processes.

Material Science Innovations:

Material science will play a crucial role in enhancing the performance and durability of RTDs and thermocouples. Researchers are developing novel materials with higher temperature stability, improved accuracy, and faster response times. For instance, using graphene-based materials in RTDs has shown promising results, offering exceptional thermal sensitivity and conductivity. Similarly, advancements in ceramic materials for thermocouples will enable them to withstand even harsher industrial environments while maintaining accuracy.

Wireless Networking Integration:

Integrating wireless networking technologies like the Industrial Internet of Things (IIoT) and 5G will transform how temperature sensors are deployed and managed in manufacturing settings. Wireless RTDs and thermocouples will become increasingly prevalent, eliminating the need for extensive wiring and enabling real-time data transmission. This will significantly simplify installation, reduce maintenance costs, and improve the flexibility of temperature monitoring systems. Furthermore, the low latency and high bandwidth of 5G networks will enable faster data processing and more responsive control systems.

Artificial Intelligence-Driven Analytics:

Artificial intelligence (AI) will revolutionize how temperature data is analyzed and utilized in manufacturing processes. Machine learning algorithms will process temperature data collected by RTDs and thermocouples, identifying patterns, anomalies, and potential issues in real-time. Predictive AI-powered maintenance models will anticipate temperature-related equipment failures, allowing for proactive maintenance and minimizing downtime. Additionally, AI-driven optimization algorithms continuously adjust process parameters based on temperature data, ensuring optimal performance and energy efficiency.

Self-Calibrating and Self-Healing Sensors:

The next generation of RTDs and thermocouples will incorporate self-calibrating and self-healing capabilities. Advances in sensor design and materials will enable these devices to automatically calibrate themselves, eliminating the need for frequent manual calibration. Furthermore, self-healing mechanisms will allow the sensors to detect and recover from minor damage or degradation, extending their lifespan and reducing maintenance requirements.

Miniaturization and Integration:

Miniaturization of temperature sensors will continue progressing, enabling the development of compact and highly integrated sensing solutions. Micro-electromechanical systems (MEMS) technology will be leveraged to create miniaturized RTDs and thermocouples seamlessly integrated into various manufacturing equipment and processes. This miniaturization will allow for more precise temperature measurements in confined spaces and enable the deployment of dense sensor networks for comprehensive temperature monitoring.

Conclusion:

The future of temperature sensors in manufacturing industries looks promising, with RTDs and thermocouples set to undergo significant advancements over the next five years. Material science innovations will enhance performance and durability, while wireless networking integration will streamline deployment and data transmission. AI-driven analytics will unlock new insights and optimization opportunities, and self-calibrating and self-healing capabilities will reduce maintenance requirements. Miniaturization and integration will enable more precise and comprehensive temperature monitoring. These advancements will ultimately improve manufacturing industries' process control, efficiency, and product quality.

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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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Looking for High Accuracy in Temperature Measurement?

Industrial temperature measurement is a critical aspect of many processes, including manufacturing, processing, and energy production. The choice of temperature sensor is vital to ensure accuracy, reliability, and durability. Several types of temperature sensors are available, including Resistance Temperature Detectors (RTDs), Thermocouples, Thermistors, and Infrared Sensors. Each sensor type has its unique strengths and weaknesses. However, after a thorough analysis, RTDs generally offer the highest level of accuracy in industrial settings.

RTDs (Resistance Temperature Detectors) are temperature sensors that use the predictable increase or decrease in electrical resistance of some materials with rising or falling temperatures. The most common RTD type is platinum (Pt100 or Pt1000) due to its stability, repeatability, and nearly linear temperature-resistance relationship. RTDs have a typical accuracy within ±0.1°C, making them among the most accurate temperature sensors available.

Thermocouples are a type of temperature sensor made from two dissimilar metals joined together at one end, and changes in temperature cause a small voltage, which can be measured and interpreted. While they are robust and can handle extreme temperatures, their accuracy is lower than that of RTDs, generally within ±0.5°C to ±2°C.

Thermistors are temperature-sensitive resistors, typically made from ceramic or polymer. While they can offer high accuracy, they have a non-linear response and a limited temperature range, making them less suitable for broad industrial applications.

Infrared sensors measure temperature by capturing the infrared energy emitted by an object. They are non-contact sensors, which can be advantageous in certain situations, but they also require a clear line of sight and can be affected by dust, fog, or other environmental factors.

RTDs are the primary choice for high-accuracy industrial temperature sensing for several reasons:

1. Their accuracy is superior to most other types, typically within ±0.1°C.
2. They exhibit good long-term stability, making them reliable over the lifespan of many industrial processes.
3. Platinum RTDs are highly repeatable and have a nearly linear temperature-resistance relationship, making them easy to interpret and integrate into control systems.

However, it's important to note that the choice of the sensor should ultimately depend on the specifics of the application, including the temperature range, required accuracy, environmental conditions, and budget. Thermocouples, for instance, might be more suitable for high-temperature applications, and infrared sensors may be necessary when a non-contact measurement is required.

In conclusion, RTDs are recommended for a broad range of industrial applications requiring high accuracy, stability, and repeatability. Nevertheless, a careful evaluation of the specific requirements of each application should always be carried out before making a final decision.

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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.

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Thermocouples and RTDs: Understanding Their Uses in Industrial Temperature Sensing

Various industrial applications widely use thermocouples and RTDs for temperature measurement. The choice of which to use depends on the application's specific requirements. Here are some industrial applications where one may be better suited than the other:

Industrial Applications where Thermocouples are better suited:

• High-temperature measurements: Thermocouples can measure temperatures ranging from -270°C to 2700°C and are more suitable for high-temperature measurements than RTDs.
• Quick response: Thermocouples have a faster response time than RTDs and are suitable for measuring fast-changing temperature processes.
• Harsh environments: Thermocouples can withstand harsh environments, such as high-pressure environments, corrosive or abrasive materials, and vibration, making them more suitable for applications where the temperature probe becomes exposed to such environments.
• Low cost: Thermocouples are relatively inexpensive compared to RTDs, making them a preferred choice in cost-sensitive applications.

Industrial Applications where RTDs are better suited:

• High accuracy: RTDs have higher accuracy than thermocouples and are, therefore, more suitable for applications that require precise temperature measurements.
• Stable and repeatable: RTDs are stable over time and offer repeatable measurements, making them a better choice for applications where process control is critical.
• Wide temperature range: Although RTDs have a lower temperature range than thermocouples, they can still measure temperatures as low as -200°C, making them more suitable for low-temperature applications.
• Longer lifespan: RTDs have a longer lifespan than thermocouples and are a better choice for applications where longevity is critical.

Examples of industrial applications for thermocouples:

• Steel industry: For measuring temperature in furnaces and blast furnaces.
• Petrochemical industry: For measuring temperature in pipelines, storage tanks, and reactors.
• Power generation: For measuring temperature in turbines and boilers.
• Glass industry: For measuring temperature in glass furnaces.

Examples of industrial applications for RTDs:

• Pharmaceutical industry: For measuring temperature in bioreactors and other critical process equipment.
• Food industry: For measuring temperature in food processing equipment.
• Aerospace industry: For measuring temperature in aircraft engines and other high-precision applications.
• Laboratory and research applications: For measuring temperature in calibration and testing equipment.

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What's The Difference Between Thermocouples and RTDs?

Thermocouples and resistance temperature detectors (RTDs) are both types of temperature sensors that are used to measure the temperature of a system. While they both operate on the same basic principle of using a physical property to determine temperature, they differ in the specific way they do this and the accuracy and precision of their measurements.

A thermocouple is a type of temperature sensor that is made up of two different metals that are joined together at one end. When a temperature difference is applied to the other end of the thermocouple, a small electrical voltage is generated. This voltage is proportional to the temperature difference, and can be measured and used to determine the temperature of the system. Thermocouples are relatively simple and inexpensive, but they are not very accurate or precise and are only capable of measuring a limited range of temperatures.

On the other hand, a resistance temperature detector (RTD) is a type of temperature sensor that uses the principle of electrical resistance to measure temperature. RTDs consist of a coil of fine wire that is wrapped around a core material, typically made of a metal with a high electrical resistance such as platinum, nickel, or copper. When the temperature of the RTD changes, the electrical resistance of the wire also changes, and this change can be measured and used to determine the temperature of the system. RTDs are generally more accurate and precise than thermocouples, and can be used to measure a wider range of temperatures. However, they are also more complex and expensive than thermocouples.

In summary, the key differences between thermocouples and RTDs are the way they measure temperature, the accuracy and precision of their measurements, and the range of temperatures they can measure. Thermocouples use the voltage generated by two different metals to measure temperature, while RTDs use the change in electrical resistance of a wire to measure temperature. Thermocouples are relatively simple and inexpensive, but not very accurate or precise, while RTDs are more complex and expensive, but can provide more accurate and precise measurements over a wider range of temperatures.

For expert guidance specifying or applying thermocouples or RTD's in your application, contact:

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Wire-wound and Thin Film Resistance Temperature Detectors

The wire-wound platinum resistance thermometer was patented in 1924 and has since become the most popular device for measuring laboratory and industrial process temperatures. RTDs provide high accuracy, long-term stability, repeatability, and integration with electronic controls. As the temperature rises, so does electrical resistance in a very predictable manner. PRTs measure all sorts of processes, from industry to laboratory work. Additionally, the platinum resistance sensor has a linear resistance vs. temperature relationship over a wide operating range of -196°C to 850°C. 

Wire-wound and thin film sensing elements are the two most common forms of RTD sensing elements. Wire-wound sensing components apply in applications requiring high accuracy and long-term stability. The RTD sensor utilizes platinum wire wrapped around a ceramic core and offers various housings designed to give the optimum heat transfer and contact with the process, regardless of whether it is gas, liquid, or solid.

The thin film RTD sensor style is made by depositing a thin layer of platinum on a ceramic plate, then trimming a path with a laser or other techniques to create a narrow ribbon of platinum with a resistance of 100 ohms at 0°C. After that, the leads are joined and protected with glass. As a result, the sensor is relatively small and available in rectangular shapes in various sizes. They are inexpensive and, if properly packaged, can last for years. Long-term stability and repeatability are not as excellent as with wire wound sensors. 

Each sensor type for industrial applications meets the specifications of ASTM 1137 or IEC 60751. The specifications include an ice point (0°C) resistance and a temperature coefficient. The ice point resistance is calculated in a container using an ice bath made of ice and water. There is a tolerance called "interchangeability" associated with this measurement. Various interchangeability bands have label assignations such as A, B, or C, with A being the strictest and C being less tight.

The temperature coefficient of resistance, or TCR, is the amount of resistance change per degree Celsius change in temperature. The TCR of an industrial grade PRT is 0.00385 ohms/ohm/°C. In other words,  there is an average of 0.385 ohms of resistance per degree C of temperature change between 0°C and 100°C. The coefficients used for lab standards are 0.003925 and 0.003902, but the more widely used standard is now 0.00385 for industrial applications. For an accurate reading, you need to match the temperature coefficient and resistance of your PRT with the input requirements of the instrumentation you are using. Not doing this will result in a significant error.

For expert guidance specifying or applying RTD's in your application, contact:

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Industrial Uses of Resistance Temperature Detectors (RTDs) Explained

Introduction: What is an RTD?

RTDs are sensors that measure the temperature of a material and provide an indication of its resistance to thermal changes.

An RTD is a sensor that measures the temperature of a material and provides an indication of its resistance to thermal changes. RTDs can be manufactured as either a wire or as a thin film on silicon.

The first RTD was developed in 1887 by German inventor Hermann von Helmholtz.

RTDs are typically used in industrial applications such as power plants, refineries, paper mills, and steel mills where they monitor temperatures of process fluids, gases, or equipment surfaces.

RTDs have also been used for years in home appliances like ovens and furnaces to control the temperature inside them.

What is a Typical Industrial Use of RTDs?

RTDs are used in industrial settings to measure the temperature of liquids and gases. This is done by measuring the resistance of a metal element which changes with temperature. RTDs have many applications in industry, such as controlling the temperature of devices, monitoring equipment, and testing for leaks.

Industrial use of RTDs can be found in a wide range of industries. For example, they are used to monitor the temperature of food processing plants and oil refineries. They are also used for quality control purposes in semiconductor manufacturing plants and petrochemical factories.

Other Industrial Uses of Resistance Temperature Detectors

Industrial use of RTDs is extremely common in the manufacturing industry. They are used in industrial processes to measure and control temperature, as well as to detect hot spots and cool spots.

RTDs are also used in many engineering applications such as process control, instrumentation, and automation for a variety of purposes.

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Industry Leading Delivery Times for Thermocouples and RTDs

Customers dislike having to wait. Customer happiness and loyalty are directly related to how soon items are delivered. 

Lead time is a critical component of any effective supply chain. It is vital to a company's success to reduce lead times as much as feasible. Production lead time may be a significant factor in your company's success. Whether it's a poor movie or a dull and tiresome speech, shorter is usually better. Selecting the correct manufacturer is critical when determining the lead time.

Duro-Sense has over four decades of manufacturing experience and has developed essential solutions for reducing lead times without sacrificing quality. Allow us to show you.

Duro-Sense 100 OHM Platinum RTD Temperature Sensors

RTDs (Resistance Temperature Detectors) are temperature detecting devices that vary their resistance value when surrounding temperature changes. RTD sensing elements use well-known materials that change resistance in a predictable and repeatable manner. Their popularity and general use are outcomes of the RTD's predictability and stability. 

The most common type and material of RTD is the 100-ohm platinum sensor. Its use is ubiquitous in the laboratory and industrial process applications going back many decades. The precision, reproducibility, and stability of 100-ohm platinum RTDs (PT100) are well known. 

For the most part, resistance temperature detectors (RTDs) fall into two main categories. Thin-film elements are one form of RTD, and wire-wound elements are the other. Each type provides advantages in certain situations and purposes. The more common design, wire-wound, is a length of tightly coiled wire wrapped around a ceramic or glass bobbin. Because the wire and wrapping are delicate, it is usually enclosed in an encased metallic tube to protect them from stress and vibration. 

The 100-ohm platinum RTD provides accurate temperature readings with excellent stability and repeatability. They are also very resistant to electrical noise, making them ideal for temperature monitoring in industrial facilities near motors, generators, and high voltage equipment. 

The American and European (known as the DIN or IEC standard) 100-ohm platinum RTD standards are the same, with the IEC standard considered the default for PT100. According to the IEC751 standard, the RTD must have:

•  The electrical resistance of 100.00 O at 0°C 
• A TCR (temperature coefficient of resistance) of 0.00385 O/O/°C between 0 and 100°C. 

Because resistance is used to measure temperature in 100-ohm platinum RTDs, the lead wires, connections, and measurement devices contribute extra resistance, requiring external compensation to offset the error. A solution is found by inserting a third or fourth lead wire inversely proportional to the external resistances.

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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.

100-Ohm Platinum RTD Temperature Sensors

RTDs (short for Resistance Temperature Detectors) are temperature sensing devices that change resistance value as its temperature changes. The most popular RTD is the 100-ohm platinum sensor, used for many years to measure temperature in laboratory and industrial process applications. 100-ohm platinum RTDs (PT100) have a reputation for accuracy, repeatability, and stability.

Most RTD element designs include a length of finely coiled wire wound around a ceramic or glass bobbin. The inherent system is fragile, so it is typically placed inside a sheathed metallic tube to protect from shock and vibration. RTD sensing elements are made from a material with a very predictable and repeatable change in resistance. This predictability and stability is the basis for its widespread application.

The 100-ohm platinum RTD provides accurate temperature readings with reasonable accuracy, excellent stability, and repeatability. They are also significantly immune to generated electrical noise, and as such, they are well suited for temperature measurement in industrial plants, near motors, generators, and high voltage equipment.

There are two 100-ohm platinum RTD standards, the American and the European (known as the DIN or IEC standard), with the IEC standard considered the default for PT100. The IEC751 standard requires the RTD to have an electrical resistance of 100.00 O at 0°C and a TCR (temperature coefficient of resistance) of 0.00385 O/O/°C between 0 and 100°C.

Because 100-ohm platinum RTDs use resistance to measure temperature, the lead wires, connectors, and measuring devices introduce additional resistance. These must be compensated for by configuring the RTD circuit to null out these outside resistances by incorporating a third or fourth lead wire to offset the introduced error.

For more information about 100-ohm platinum RTD temperature sensors, contact Duro-Sense Corporation. Call them at 310-533-6877 or visit their website at https://duro-sense.com.

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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Resistance Temperature Detector (RTD) Catalog

Resistance Temperature Detectors (RTD’s) operate under the principle that the electrical resistance of certain metals increases or decreases in a repeatable and predictable manner with a temperature change. RTD’s may have a lower temperature range than some thermocouples and a slower response time, however, they are more stable and repeatable over long periods of time. RTD’s higher signal output makes them easier to interface with computers and data loggers and reduces the effects of radio frequency interference. RTD’s are used in the plastic processing industry, environmental test chambers, motor windings, pumps and bearings, ovens, kilns, waste treatment and the pulp and paper industry, as well as many other applications.

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Full Duro-Sense Product Catalog Now Available

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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.