Piezoresistive+accelerometers

Piezoresistive+accelerometers - Piezoresistive...

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Piezoresistive Accelerometers SEN2MET
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In plane piezoresistive accelerometer for structural monitoring Journal of Aerospace engineering ASCE July 2003 pp. 108-114
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Piezoresistive Accelerometers •First piezoresistive silicon accelerometer prototype developed at Stanford in 1979. •Not successful in mass production and industrial applications until the late 1980s. Single crystalline silicon wafer Piezoresistors formed by selective diffusion Resistor on frame and beam form a half bridge by metallization
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Cantilever beam accelerometers-1 Basic equations for deflection and stress: M(x) is bending moment along beam Should be 2!
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Cantilever beam accelerometers-2 Setting x=a 1 /2 for average resistor position Sensitivity very dependent on beam thickness:
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Cantilever beam accelerometers-3 Conservative value of fracture stress for Si gives a fracture acceleration of 122g. Drop from 1 m can give above 1000g. Over-range protection needed . Maximum deflection at a 2 is 1,65 m m for 1 g acceleration
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Cantilever beam accelerometers-4 Over range protection bumpers placed above and below the centre of the mass
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Cantilever beam accelerometers-5 Stress induced by acceleration along x-axis Stress induced by acceleration along z-axis For most applications acceleration along the beam gives a negligible effect on the device .
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Cantilever beam accelerometers-6 Stress induced on the side edges of beam by acceleration along
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This note was uploaded on 05/30/2011 for the course SEN 2MET taught by Professor Ulrikhanke during the Spring '11 term at VCU.

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Piezoresistive+accelerometers - Piezoresistive...

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