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Elastic Pressure Transducer

Elastic Pressure Transducer. WASEEM ZIA (2007-CHEM-15). Synopsis:. Types Pressure Sensors Summary Functional Uses Merits & Demerits References. Types:. Bellows Bourdon tube Diaphragm. Bellows.

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Elastic Pressure Transducer

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  1. Elastic Pressure Transducer WASEEM ZIA (2007-CHEM-15)

  2. Synopsis: • Types • Pressure Sensors Summary • Functional Uses • Merits & Demerits • References

  3. Types: • Bellows • Bourdon tube • Diaphragm

  4. Bellows The bellows is a one-piece, collapsible, seamless metallic unit that has deep folds formed from very thin-walled tubing.

  5. Bourdon tube The bourdon tube pressure instrument is one of the oldest pressure sensing instruments in use today. The bourdon tube (refer to Figure 3) consists of a thin-walled tube that is flattened diametrically on contrary sides to produce a cross-sectional area elliptical in form, having two long flat sides and two short round sides.

  6. Bourdon tubes are generally are of three types; • C-type • Helical type • Spiral type

  7. Diaphragm Diaphragm elements are made of circular metal discs or flexible elements such as rubber, plastic or leather.

  8. Pressure Sensors Summary In a bellows-type sensor: • System pressure is applied to the internal volume of a bellows and mechanical linkage assembly. • As pressure changes, the bellows and linkage assembly move to cause an electrical signal to be produced or to cause a gauge pointer to move.

  9. Contd… In a bourdon tube-type sensor: • System pressure is applied to the inside of a slightly flattened arc formd tube. As pressure increases, the tube tends to restore to its original round cross-section. This change in cross-section causes the tube to straighten. • Since the tube is permanently fastened at one end, the tip of the tube traces a curve that is the result of the change in angular position with respect to the center. The tip movement can then be used to position a pointer or to develop an electrical signal.

  10. Contd…. In Diaphragm pressure sensor: • They are used to measure gauge pressures over very low ranges. • They may be made up of Metallic diaphragms gauge (brass or bronze) Slack diaphragms gauge (Rubber).

  11. Functional Uses: • Pressure sensors perform the following basic functions: • Indication • Alarm • Control • If a pressure sensor becomes inoperative: • A spare sensor element may be used (if installed). • A local mechanical pressure gauge can be used (if available). • A precision pressure gauge may be installed in the system.

  12. Contd…. • Environmental concerns: • Atmospheric pressure • Ambient temperature • Humidity

  13. Merits & Demerits Merits of Flexible Pressure transducer • Flexible Pressure transducer cost is low. • Flexible Pressure transducer has easy structure • Flexible Pressure transducers have been time tested in application. • Flexible Pressure transducer allows high accuracy, spatially in relation to cost.

  14. Contd…. Demerits of Flexible Pressure transducer • Flexible Pressure transducer has a low spring pitch. • Flexible Pressure transducer is inclined to shock and throb. • Flexible Pressure transducer is inclined to hysteresis.

  15. References • http://controls.engin.umich.edu/wiki/index.php/PressureSensors retrieved at 11/10/2010 • Kirk, Franklin W. and Rimboi, Nicholas R., Instrumentation, Third Edition, American Technical Publishers, ISBN 0-8269-3422-6. • Wightman, E.J., Instrumentation in Process Control, CRC Press, Cleveland, Ohio. • Rhodes, T.J. and Carroll, G.C., Industrial Instruments for Measurement and Control, Second Edition, McGraw-Hill Book Company. • Process Measurement Fundamentals, Volume I, General Physics Corporation, ISBN 0-87683-001-7, 1981 • http://vpmt.com/transducer.htm retrieved at 11/10/2010

  16. THANKS

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