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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.
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:
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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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:
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.
Duro-Sense Corporation
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Only a few of the approximately 300 different temperature measuring thermocouples defined and tested have achieved mass acceptance because they exhibit more desirable electrical and physical characteristics. Resultantly, these eight preferred thermocouple types are the most widely used in industrial, commercial, medical, and aerospace applications.
* temperature range as per NIST Table I: Thermocouple Types Definitions.
Certain combinations of alloys, such as Type J and K, have become popular as industry standards. Cost, availability, melting point, chemical properties, stability, and output are all drivers for thermocouple application. Different types of thermocouples are best suited for different uses/applications. Thermocouple selection also depends on the temperature range and accuracy needed. Other selection criteria include the chemical inertness of the thermocouple material and whether it is magnetic or not.
For more information about thermocouples, contact Duro-Sense by calling 310-533-6877 or visiting https://duro-sense.com.
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
Base-metal thermocouples, ANSI standard Types J, K, T, E, have innate thermoelectric instability related to time or temperature-dependent instabilities in many of their chemical, physical, and electronic properties.
When a thermocouple is used to measure the temperature of a particular environment, it can be expected that the measured voltage does not change if the temperature of that environment remains constant. Actually, the voltage can change over time, even though the temperature of the environment remains constant: this phenomenon is called DRIFT. Drift is a source of error in thermocouple measurement.
Drift occurs because of metallurgical changes in the conductors during the operation of the thermocouple. Because these changes are time dependent, the voltage change from the expected value, called drift, is also time dependent. An example of drift is shown below, in Figure 10, for a 1.5mm bare wire Type ‘K’ thermocouple exposed at 500ºC. The change in voltage is reported as a function of the exposure time.
Metallurgically, drift can be distinguished in the following:
Some examples of surface modifications can be identified below:
In relation to bulk modifications, the following phenomena can occur:
Duro-Sense Corporation
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References
{1} R.E. Bentley, “Long-term drift in mineral-insulated Nicrosil-sheath type K thermocouple”. Sensor and Actuators A, 24(1990) 21-26
Robert J. Collier Trophy |
Providing power to a broad range of sophisticated equipment on offshore oil and gas platforms requires a large amount of uninterrupted electricity. Pumps, valve operators, essential communications, turntables, engines, and safety devices are just a subset of the environment of drilling and processing that needs a reliable power source. A large amount of electrical power, not unlike a small town, is required. Electric generators provide comfort heating, cooling, water desalination, food storage, and even waste processing.
On offshore platforms, conditions are harsh. Equipment and components must be robust to function correctly and decrease the need for regular maintenance.
Temperature is one of the compressor's most critical measurement parameters and its accuracy can directly affect compressor efficiency. Analysis reveals that errors in temperature calculation account for over 80% of efficiency errors. More aspects of compressor temperature measurement and improved methods of temperature measurement are required. Thermocouples are used to measure inter-stage gas compressor temperature and outlet gas temperature.
A specialized temperature sensor known as an 'engine-compressor thermocouple' measures temperature in these applications. These are heavy-duty, specially built temperature sensors that monitor a variety of parameters including exhaust gases and lubricant temperatures. Such sensors are time-tested and designed to withstand the harsh mechanical and environmental conditions of offshore marine conditions. The thermocouple's prime requirement is to be robust enough to withstand a high vibration and corrosive environment and still be accurate and fast responding.
The engine-compressor thermocouple provides oil and gas platform technicians with precise measurements, excellent accuracy, and rapid response times. These thermocouples are also easily checked for calibration, removed, and replaced if necessary.
Duro-Sense Corporation
310-533-6877
https://duro-sense.com
3-wire configuration |
2-wire configuration |
3rd wire used to cancel wire error |
Meter reading 2 common wires |
Diagram of a thermocouple circuit. |
Typical sheathed thermocouple. |