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Motion Sensors Displacement, velocity and acceleration

Motion Sensors Displacement, velocity and acceleration. Dimensional measurement. Micrometers. Vernier caliper. One complete revolution = 0.5 mm (usually) With 50 divisions, each division movement corresponds to 0.01 mm

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Motion Sensors Displacement, velocity and acceleration

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  1. Motion Sensors Displacement, velocity and acceleration

  2. Dimensional measurement Micrometers Vernier caliper • One complete revolution = 0.5 mm (usually) • With 50 divisions, each division movement corresponds to 0.01 mm • If user can control every one-fifth of a division, a resolution of 0.002 mm is possible

  3. Height & depth measurement Gauge blocks Dial gauge: typical resolution 0.01 mm Height & depth gauges

  4. Resistive potentiometer Rotary potentiometer (a) circular; (b) helical Linear potentiometer Types: wire-wound, carbon-film and plastic-film (according to resistance element)

  5. Linear Variable Differential Transformer (LVDT) • Inductive displacement sensor. • Transformer with 1 primary & 2 secondary coils, connected in series opposition • Output voltage (difference between induced voltages)is proportional to core displacement • Zero reading when core is centered Primary Secondary Rotary differential transformer

  6. Eddy current sensor • Inductive displacement sensor. • Coil is excited at high frequency (typically 1 MHz) • This induces eddy current in the target • Eddy current alters the inductance of the probe coil • This change can be translated into a voltage proportional to the air gap

  7. Piezoelectric transducers • A piezoelectric material generates charge when deformed • Induced charge leaks away with time • Piezoelectric transducers are not suitable for static or slowly-varying dispalcements

  8. Optical encoders (incremental) • Measure instantaneous angular position of a shaft • Output is in the form of pulses to be counted

  9. Optical encoders (coded-disc) • Output is in the form binary numbers to give absolute measure of shaft position Float encoder

  10. Other rotational motion sensors • Gyroscopes • Tachometers • Mechanical flyball Gyroscope Photoelectric tachometer Mechanical flyball

  11. Vibration Measurement

  12. Energy Harvesting Source: J.K. Ward and S. Behrens, “Adaptive learning algorithms for vibration energy harvesting”, Smart Materials & Structures 17 (2008) 035025 1-9.

  13. Vibration-based Energy Harvesting Source: B.P. Mann and N.D.Sims, “Energy harvesting from the nonlinear oscillations of magentic levitation”, Journal of Sound and Vibration (2008) in press.

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