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A blog providing information about industrial temperature measurement, specifically in the areas of temperature sensors. The posts will contain educational information about thermocouples, RTDs, and other common types of temperature sensors. The application of these sensors will focus on aerospace, aircraft, research and development, medical, chemical, plastics processing, and power generation industries. For more, visit Duro-Sense.com or call 310-533-6877.
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.
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.
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.
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.
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.
Today, thermocouples are ubiquitous in the industrial landscape. They are employed in myriad applications, including:
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.
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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:
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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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:
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:
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.
Duro-Sense Corporation
310-533-6877
https://duro-sense.com
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.
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.
Duro-Sense Corporation
310-533-6877
https://duro-sense.com
Diagram of a thermocouple circuit. |
Typical sheathed thermocouple. |