1. 1 Motion Sensors Displacement, velocity and acceleration

2. 2 Dimensional measurement 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 Micrometers Vernier caliper

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

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

5. 5 Primary Secondary 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 Rotary differential transformer

6. 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. 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. 8 Optical encoders (incremental) Measure instantaneous angular position of a shaft Output is in the form of pulses to be counted

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

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

11. 11 Vibration Measurement

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16. 16 Energy Harvesting Source: J.K. Ward and S. Behrens, “Adaptive learning algorithms for vibration energy harvesting”, Smart Materials & Structures 17 (2008) 035025 1-9.

17. 17 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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