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Charlotte Stonestreet
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THE PRESSURE TRANSDUCER PACKAGE
25 October 2012
The combined benefits of advanced sensor deposition methods and innovations in electronic technology make the modern pressure transducer an increasingly powerful package, says Mike Powers, product marketing director for Gems Sensors and Controls
Pressure transducers, which detect movement in a pressure diaphragm and convert the information into electrical signals, have proven to be highly effective in protecting and maximising engineering systems in a variety of process conditions. To appreciate how pressure transducers achieve such levels of accuracy, we must consider the innovative and precisely controlled methods employed to construct sensor elements and electronics packages.
ADVANCED TECHNOLOGIES
The sensitive pressure-sensing mechanisms of today’s pressure transducers are constructed via the advanced strain gauge technologies of sputtered thin film and chemical vapour deposition (CVD).
Sputtered thin film technology involves bombarding a solid target material with energised particles, causing it to release atoms that, in turn, are used to form a thin film.
The sputtered thin film process produces a sensitive, robust diaphragm that is suitable for direct contact with almost all liquids, oils and gases. CVD is also highly effective in the manufacture of strain gauge sensors; CVD sensors are produced on wafers in large batches, using polysilicon deposited on a stainless steel substrate, with the strain gauge patterns being chemically milled. Sensors produced via CVD and sputtered thin film technology offer the potential to deliver high levels of accuracy and this potential is fully tapped when combined with modern electronics packages.
Recently, the electronic packages that have been supplied with pressure transducers have enabled sensors to be tuned to the specific requirements of many applications and also customised, allowing end-users to cut costs when complex control is not required. These electronics packages incorporate advanced ASIC (application specific integrated circuits) technology. As well as enabling enhanced performance and increased functionality, the introduction of ASIC, combined with improvements in volume manufacturing techniques, has slashed the typical transducer unit cost, resulting in a component that can offer the same level of performance as that provided by an earlier design for approximately 10% the cost.
CONSTRUCTION COMBO
The combination of these sensor constructions and sophisticated electronics packages results in pressure transducers that can respond to changes in pressure of 1msec or less, offer accuracy with almost zero drift over time and an operating life in excess of 100 million cycles. Not only that, these pressure transducers can provide the exceptionally high degree of accuracy in aggressive environments. For example, Gems Sensors & Controls 3300 series pressure transducers are capable of operating over a temperature range of -40°C to +125°C, with stainless steel wetted parts that are capable of resisting harsh chemicals, while a strong and corrosion-resistant structure with low hysteresis and creep high is generated by the temperature vacuum brazing of the stainless steel components during sensor production.
The robustness of these transducers, which can resist shocks, vibration and corrosion, coupled with high repeatability and sensitivity, has enabled their use across many industries, from the clean room environments of medical markets to the contam - inated atmospheres of off-highway construction vehicles. The wide range of specifications available, coupled with the reduced cost, is allowing operators across many industries in businesses large and small to capitalise on the benefits of these pressure transducers.
The new methods of constructing sensor elements and electronics packages have considerably enhanced the performance and functionality of pressure transducers and established these devices as increasingly common components in modern engineering systems.
