Thermal Mass Flow Meters: Sensor Design is Key to Stability, Accuracy, and In-Situ Validation скачать в хорошем качестве

Thermal Mass Flow Meters: Sensor Design is Key to Stability, Accuracy, and In-Situ Validation

The type of thermal sensor design used in thermal mass flow meters can have a significant impact on the stability, accuracy and in-situ validation of the application. Watch the video to learn the similarities and differences in so-called “wet” organic sensors and “dry” non-organic sensor design and how innovation has yielded a patented breakthrough all-metal, no-drift thermal sensor design called DrySense™. Sierra has backed quality claims to be the only company in the industry to offer a lifetime warranty on its DrySense™ sensor. Find out more about QuadraTherm Thermal Mass Flow Meters: http://www.sierrainstruments.com/libr... The DrySense™ sensor has been in use on all Sierra thermal mass flow meters since its invention in 1999 and in 2009 was named the bestselling thermal meter in North America by Flow Research, Inc. of Boston, MA. VISIT SierraInstruments.com for more information: http://www.sierrainstruments.com/ SUBSCRIBE for other helpful Videos & news: http://www.youtube.com/subscription_c... CONNECT with Sierra! LinkedIn ►   / sierra-instruments   Facebook ►   / sierrainstruments   Google+ ► http://plus.google.com/+Sierrainstrum... Twitter ►   / sierraflow   [Video Summary] Industrial thermal mass flow meters comprise a family of instruments for precision measurement of total mass flow rate of gases in the pipes and ducts. Standard accuracy is 1.0% of full-scale flow, but recent innovation, as with Sierra's four-sensor QuadraTherm thermal meter, has pushed accuracy to 0.5% of reading, rivaling that of Coriolis meters. In addition to accuracy, thermal flow meters have become extremely popular due to high turn-down, up to 1000:1, giving the ability to measure very low flows up to very high flows with the same instrument. Since they are rugged and reliable, have no moving parts, are easy to insert via hot tap, have negligible pressure drop, and offer an economical solution to large-diameter pipes and ducts, thermal technology has been rapidly adopted over the last decade. Today, thermal mass flow technology is widely used in a broad range of industrial process control applications spread across global industries. Dr. John George Olin, founder of Sierra Instruments, saw the rapidly growing need for a truly industrial thermal hot-wire anemometer. To make a thermal flow sensor truly industrial strength, Dr. Olin pioneered the innovation of an all-metal clad thermal sensor in the early 1980s, winding platinum wire around a ceramic mandrel and placing it inside a metal sheath called a thermo well. The problem was that the air gaps between the thermo well and the platinum-wound mandrel needed to be filled to assure stable heat transfer. This was the key to assuring an accurate and stable thermal mass flow meter. Sierra never stopped improving the technology, knowing that wet sensor drift problems must be solved. After all, by its very principle of operation, a thermal sensor is heated and cooled over time, expanding and contracting the cement inside the sensor, making it crack, settle and shift from its original state. In 1999, Dr. Olin patented a breakthrough thermal sensor design. Like other thermal mass flow sensors, it was made of a platinum resistance temperature detector wire wound around a ceramic mandrel, but this is where the similarities ended. Through a proprietary, highly controlled manufacturing process, a metal sheet is tightly formed on the mandrel and wire assembly to be in such intimate contact that no air gaps exist and no organic filler cements are needed. In contrast to wet sensor design, this innovative cement-free sensor is known as a dry sensor and is patented as DrySense. All materials used to make the DrySense sensor were selected such that their coefficients of thermal expansion are approximately the same. The added benefit is that they expand and contract at the same rate, further assuring rock-solid stability. The DrySense sensor has been in use on all Sierra thermal meters since its invention in 1999. In 2009, it was named the best-selling thermal meter in North America by Flow Research Incorporated of Boston, Massachusetts. So, when evaluating thermal mass flow meters for in-situ calibration validation capability, be aware that sensor drift will create false positives, reducing the reliability of the validation. Sierra's DrySense, all-metal, no drift sensor has a big advantage during in-situ calibration validation. With Sierra's all-metal DrySense velocity sensor, you have the mechanical design confidence that there will be no drift and that in-situ calibration validation is, indeed, actually valid. For accurate and repeatable gas mass flow measurement down to the last molecule, choose thermal mass flow technology.