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Laser-Based Displacement Transducers

Laser-Based Displacement Transducers. Joe Wilkey CEE 398. Overview. Types of Laser-Based Displacement Transducers Operation Specifications Applications Advantages/Disadvantages Additional Information and References. Types of Laser-Based Displacement Transducers. Optical Triangulation.

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Laser-Based Displacement Transducers

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  1. Laser-Based Displacement Transducers Joe Wilkey CEE 398

  2. Overview • Types of Laser-Based Displacement Transducers • Operation • Specifications • Applications • Advantages/Disadvantages • Additional Information and References

  3. Types of Laser-Based Displacement Transducers Optical Triangulation

  4. Operation (Optical Triangulation) • Laser shines onto surface of material which reflects to receiver • Location of reflected beam allows calculation of reflection angle and consequently distance can be calculated

  5. Specifications • Ranges: 0.5 – 400 mm • Frequency Limits: 10 kHz, 25 kHz, 500 kHz • Resolution: 0.5 – 600 μm • Typically Class 3B laser used with wavelength of 675 nm

  6. Applications (Optical Triangulation) Flaw Detection

  7. Applications (Optical Triangulation) Displacement or Vibration Amplitude

  8. Types of Laser-Based Displacement Transducers D Type Fiber Optic

  9. Operation (D Type Fiber Optic) • D Type Fiber Optic sensors directly detect motion of target using intensity of reflected light

  10. Operation (D Type Fiber Optic) • D Type Fiber Optic sensors directly detect motion of target • Output voltage follows general curve as shown • Slopes of “near side” and “far side” portion of curve given for each unique sensor

  11. Specifications • Ranges: 20 μm – 7 mm • Frequency Limit: 200 kHz+ • Resolutions: up to 0.002 μm

  12. Applications • Measuring small displacements in axis of sensor including: • Vibration (including ultra-sonic vibration) • Simple Displacement Measurements for solids or fluids • Displacement or Vibration in mechanisms

  13. Types of Laser-Based Displacement Transducers RC Type Fiber Optic

  14. Operation (RC Type Fiber Optic) • RC Type Fiber Optic sensors also directly detect motion of target

  15. Operation (RC Type Fiber Optic) • RC Type Fiber Optic sensors also directly detect motion of target • Output voltage follows general curve as shown • Only one output voltage for each position, so no “near” and “far” side slopes

  16. Specifications • Ranges: 50 μm – 2.5 mm • Frequency Limit: 200 kHz+ • Resolutions: up to 0.01 μm

  17. Applications • Measuring small displacements in axis of sensor • Also measures rotation and movement past sensor including: • Thermal Growth • Deformation Studies • Bearing/Rotor Dynamics

  18. Advantages Gives accurate measurements regardless of reflectivity of object being measured Relatively long range (up to 400 mm) Faster sampling rate Disadvantages Rather bulky, can only measure exterior parts Low resolution (0.5 μm) Accuracy may be affected by surrounding conditions Advantages/Disadvantages (Optical Triangulation)

  19. Advantages Small and sturdy, can take measurements in mechanisms, fluids, extreme pressures and extreme temperatures Fiber optic principle allows measurements to be taken in magnetic/electric fields Extremely high resolutions give more accurate measurements Disadvantages Only measures distance in direction of laser beam Surfaces with high, changing, or low reflectivity affect readings Range only goes to 7 mm One output voltage corresponds to two different displacements Advantages/Disadvantages (D Type Fiber Optic)

  20. Advantages Gives accurate measurements regardless of reflectivity of object being measured, even if reflectivity of object changes Offers same versatility as D Type sensor Only one displacement value for each output voltage Measures rotations and transverse displacements as well as “axial” displacements Disadvantages Range less than 2.5 mm Resolution 5x lower than that of D Type Advantages/Disadvantages (RC Type Fiber Optic)

  21. Advantages Very accurate non-contact measurement device Easier to transport, set-up, and operate than video systems Use of multiple sensors increases number of applications (thickness measurements, etc.) Disadvantages Do not use “targets” like camera system, so must ensure system is in line with point of interest and perpendicular to sensor Some limited in use (i.e. can only be used in “axial direction”) Advantages/Disadvantages (General)

  22. References/Additional Info • http://www.sensors-uk-transducers-instruments.com/ • http://www.scantron-net.co.uk/laserdistance.htm

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