By Somesh Kumar Malhotra LecturerECE DepttUIETCSJM University Peizoelectric transducer are converter of mechanical energy into electrical energy and are based on the direct peizoelectric ID: 1031359
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1. Peizo-electric TransducerBy:Somesh Kumar MalhotraLecturer,ECE Deptt.,UIET,CSJM University
2. Peizoelectric transducer are converter of mechanical energy into electrical energy and are based on the direct peizoelectric effect observed in a certain nonmetallic and insulating dielectric compounds.Electrical charges is developed on the surface of the crystal ,when they are under mechanical strain due to application of stress.Due to there mechanical rigidity they are treated as near ideal transducer for measurement of force thereby pressure, acceleration, torque, strain and amplitude of vibrations. Peizo-electric Transducer
3. They owe their popularity to thereSmall sizeHigh natural frequencyLinearityHigh sensitivityWide measuring range andPolarity sensitivityCommonly used materials are stable enough for all the application at temperature upto 200 degree C.Peizo-electric Transducer
4. The curie brother discovered the direct peizo-electric effect in certain solid crystalline dielectric substance such as quartz under mechanical stress, the crystaline is strained and the consequent charge developed is proportional to strain.Quartz is silicon di-oxide and is available as a natural substance.Peizo-electric Phenomena
5. The atoms are arranged in the crystal as shown in fig.,forming a hexagon in the plane of paper while the optical axis (z axis) is perpendicular to xy plane.Peizo-electric Phenomena
6. Peizo-electric Phenomena
7. Peizo-electric Phenomena
8. Peizo-electric Phenomena
9. Peizo-electric Phenomena
10. Peizo-electric Phenomena
11. Peizo-electric Phenomena
12. Peizo-electric Phenomena
13. Peizo-electric Phenomena
14. Peizo-electric Phenomena
15. Peizo-electric MaterialThe material exhibiting the peizoelectric phenomena are divided into two groupsNaturalQuartzRochelle saltTourmalinSyntheticAmmonium dihydrogen phosphate (ADP)Lithium sulphate (LS)Dipotassium tartarate (DKT)
16. It is the most stable material and artificially grown quartz is normally preferred as it is purer than natural quartz.Its d coefficient and relative permitivity remain unaffected by the temperature.Only the volume resistivity falls sharply at higher temperature beyond 100 degree C. Quartz
17. TourmalinTourmalin is the only material exhibiting large senstivity in the volume expander mode related to z axis.Its useful temperature range is large (upto 1000 degree C)
18. Rochelle SaltRochelle salt is the material that is being produced on industrial scale for producing gramaphone pickups and crystal microphone.It has the highest relative permitivity among the natural group.
19. ADP and LSADP crystal posses the lowest resistivity which is temperature dependent with temperature compensation, they are used in acceleration and pressure transducersLithium sulphate is highly sensitive when used in VE mode.
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21. Peizoelectric Force TransducerPeizo-electric crystals or element primarily responds to force input and possess all the desired characterisitics of an ideal force transducers.To increase the charge sensitivity, more than one element can be used to form a transducer system and such combination are known as bimorphs or multimorphs (or peizopile) depending on whether they are of two element or more.The series and parallel connected bimorphs are shown in figure.
22. Peizoelectric Force transducer
23. Bender type bimorphs of all the peizoelectic materials can be made from single elements of either thickness expander mode or length expander mode.A twister bimorphs shown in the figure , with the force applied at A, while the remaining three corner B,C and D are held rigidly.These are made up face shear element of ADP and Rochelle salt connected together to form the three point twister with the diagonal on the top surface expanding under forces.Peizoelectric Force Transducer
24. If the force corner can be subjected to concentrated forces as shown in four pt twister, the expanding diagonals will be perpendicular to each other as opposite side of Bimorphs.Peizoelectric Force Transducer
25. Peizoelectric Force Transducer
26. Peizoelectric Strain Transducer
27. Peizoelectric Torque Transducer
28. Peizolelectric Pressure Transducer
29. Large pressure variation occurring at frequencies upto 20 KHz in internal combustion engine are measured by using multimorphs (peizopile) of quartz elements as shown in fig.The net force F1 to which peizopile respond is given byPeizolelectric Pressure Transducer
30. Peizolelectric Pressure Transducer