MKM 503E-Week3_Nonconventional_ Sensors

MKM 503E-Week3_Nonconventional_ Sensors - MKM 503E- Week3...

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MKM 503E- Week3 Nonconventional Sensors prepared by Assist. Prof. Pinar Boyraz, PhD 1 ITU, 2011
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Outline 2 Piezoelectric sensing Close look at an analog accelerometer LIDAR and IMU ITU, 2011 Non-diagonal terms represent smart materials
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Piezoelectricity-1 3 ITU, 2011 An effect in which energy is converted between mechanical and electrical forms Discovered by 1880s by Curie’s a pressure (piezo >> pressure in Greek) is applied to a polarized crystal, the resulting mechanical deformation results in an electrical charge. Example: piezoelectric microphones Alternatively, when an electrical charge is applied to a polarized crystal, the crystal undergoes a mechanical deformation which can in turn create an acoustical pressure Example: piezoelectric speakers
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Piezoelectricity-2 4 ITU, 2011 Electrets are solids which have a permanent electrical polarization. Electrets are electrical analogs of magnets. The alignment of the internal electric dipoles would result in a charge which would be observable on the surface of the solid. In these structures, each cell of the crystal has an electric dipole, and the cells are oriented such that the electric dipoles are aligned. Again, this results in excess surface charge which attracts free charges from the surrounding atmosphere making the crystal electrically neutral. If a sufficient force is applied to the piezoelectric crystal, a deformation will take place. This deformation disrupts the orientation of the electrical dipoles and creates a situation in which the charge is not completely canceled. This results in a temporary excess of surface charge, which subsequently is manifested as a voltage which is developed across the crystal.
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Piezoelectricity-3 5 ITU, 2011 Piezoelectric linear transducer
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This note was uploaded on 12/04/2011 for the course MECHANICAL 9865325 taught by Professor Ardaç. during the Spring '11 term at Istanbul Bilgi University.

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MKM 503E-Week3_Nonconventional_ Sensors - MKM 503E- Week3...

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