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An Introduction to Non-Contact Vibration Measurement
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An Introduction to Non-Contact Vibration Measurement


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Learn about the technique that is continuing to revolutionize the measurement of structural vibration and shock. The webinar will cover its widespread application to aerospace, automotive, civil, …

Learn about the technique that is continuing to revolutionize the measurement of structural vibration and shock. The webinar will cover its widespread application to aerospace, automotive, civil, biological, medical and micro- structures.

Topics Include:
- Concept and theory of Laser Doppler Vibrometry
- Product types – scanning and non-scanning
- Example applications including modal analysis, dynamics characterization, production quality testing and FEM validation

Published in: Technology, Business

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  • 1. Laser Vibrometry: An Introduction to Non-contact Vibration Measurement #1
  • 2. Vibration is EverywhereAutomobilesAirplanesHome AppliancesData Storage and SemiconductorMicrostructures, MEMS andNanotechnologyEntertainmentLife Sciences(Biology, Medical)Production Testing& Quality ControlUltrasonicsOptical Industry &TelecommunicationsDefense equipmentCivil Structures
  • 3. The TechnologyPoint & shootEye-safe visible laser probeDetects Doppler shiftAnalogous to acoustic Doppler effectHigh-precision laser interferometerDecodes information to give both displacementand velocity signalsEasy-to-use data acquisition & softwareprocessingHardware and software for full-field scanning
  • 4. What does Laser VibrometryProvide? Time History Impulse Response Vibrometers convert changes in the laser Frequencyfrequency to a voltage output proportional Response to instantaneous velocity ODS and modalChanges in optical phase are converted to analysis signals proportional to displacement
  • 5. What is Laser DopplerVibrometry? PDV-100 Portable Digital Vibrometer Laser Doppler Vibrometry is a non-contact, "point and shoot" technology that directly measures the vibration of a test object using the Doppler effect. For car moving at velocity V, Analogy: Acoustic Doppler Effect the observer hears the frequency fD = c/(λ -V/f). λ Sound emitted from c stationary car has frequency f = c/λ v c: velocity of the sound wave Emitted Observed frequency f frequency fD λ: emitted wavelength For a vibrometer: Δ fD α V f: emitted frequency Δ fD = 2V/λ
  • 6. The Heterodyne Interferometer Measurement Beam f0 f0 ± f D Bragg cell Reflected Beam He-Ne Laser <1mw (633nm) x(t) v(t) f0 + 40 MHz Photo-detector Frequency Modulated signal 40 MHz ± fD Δ fD = 2V/λ
  • 7. Signal DemodulationPhoto-detector system FM Doppler signal Controller Voltage ~ Velocity AM electrical signal FFT Spectrum Voltage ~ Displacement
  • 8. Many Vibrometer Types Single Point 3 Axis Differential 3 Axis Scanning Multi Point Scanning Long Range
  • 9. Why Laser Vibrometry?Polytec’s non-contact laser vibrometers are revolutionizing dynamic testing in all kinds of applications because of their: Higher accuracy Cost and time savings Wider range of operation and applications
  • 10. What are the Benefits of Laser DopplerVibrometry? Higher accuracy – no mass or stiffness added Delicate, lightly damped structures frequency and temperature independent fine spatial resolution Down to <1µm Small structures Measurements closer to edges digital decoding Achieves sub-pm displacement resolution!!
  • 11. What are the Benefits of Laser DopplerVibrometry?Cost and time savings – point and shoot Target almost anything quickly and easily Easier set-up, nothing to attach, close or far laser may be moved around with ease or scanned (PSV/MSA) for rapid full-field data Amplitude and phase spectra at up to >250k points Data for modal analysis Only one transducer to calibrate, connect No cables over the structure to secure or fail No phase-matching issues RoboVib is the ultimate solution
  • 12. What are the Benefits of Laser DopplerVibrometry? Wider range of operation and applications – Part 1 of 3 wide frequency range (DC – 1,200 MHz) large amplitude (to 30 m/s) hot (no surface temperature limit)
  • 13. What are the Benefits of Laser DopplerVibrometry? Wider range of operation and applications – Part 2 of 3 submerged through windows delicate
  • 14. What are the Benefits of Laser DopplerVibrometry? Wider range of operation and applications – Part 3 of 3 long range rotating inaccessible microscopic
  • 15. All Kinds of ApplicationsSame technology packagedfor different applications: Small Structures Macro-Structures Micro-Structures
  • 16. Single Point MeasurementMeasure on macro- and micro-structuresExample - OFV-534 with integrated videoand illumination for sensor positioningand sample viewingTailored solutions for: Research, production, industrial and in-the-field environments Ultrasonic and high amplitude applications VibraLight
  • 17. Applications Example Resonance Testing of Disk-drive components OFV-534 Vertical test sensor head stand Controller Objective lens Disk-drive VibSoft
  • 18. Differential Measurement Car engine Two optical sensor heads Example: HSV-2000 Engine valve-train testing: Beam steering probes- relative movement between two surfaces- removes background vibration of engine block- 12 kHz valve bounce revealed
  • 19. Rotational MeasurementRLV-5500 - Rotational vibrometermeasures pure angular motion –independent of shape or anylateral vibrationsMeasured outputs:1. DC rpm value2. Angular velocity signal3. Angular displacementExample applications: Order tracking analysis Crankshafts Propshafts
  • 20. RotVib FeaturesTwo interferometers d = 7.5mm or 24mmMeasures angular velocity and displacement from-8,000 to +20,000 RPMEliminates down-time associated with contactmethods
  • 21. 3-D Single Point Vibrometry Integrates 3 independent vibrometers Simultaneous measurement of all axes of motion at a single point V x , V y & Vz
  • 22. Full Field - Traditional Approach UsingContact TransducersMass loading Damping and stiffness errorsTime consumingCoarse spatial resolutionLimited workingenvironmentsComplicated cablingCumbersome correlation ofcoordinates to FEM geometryTransducer re-calibration(book keeping)Limited bandwidth
  • 23. Scanning Vibrometry (PSV) Test Object Sensor Head Test Object Scan Video Electronics LDV Scanning Sensor Mirrors LDV Data Management Controller System Up to 250,000 points scanned Easy-to-use software for data acquisition, display &manipulation Animated data visualization Efficient interfaces for modal analysis or FEM Stitched datavalidation Geometry file imported or measured Internal waveform generator
  • 24. 3-D Scanning MeasurementDeflection Shape Correlation with accelerometer data out-of-plane Full 3-D vibration response over measurement surface (>2,500 points) Integrated data stitching provides complete coverage with single system Precise data for modal analysis and model verification
  • 25. RoboVibCAE workflow
  • 26. Micro System AnalyzerMSA-500 - Powerful all-in-one Threemeasurement workstation for3-D static and dynamic Measurementcharacterization of MEMS andMOEMS microstructures TechnologiesCharacterization ofout-of-plane vibrationsby scanning vibrometryPLUS:Measurement ofin-plane motion andvibration by stroboscopic videomicroscopy OneDetermination of surfacetopography by white light Integratedinterferometry Package
  • 27. Customer SupportFive Territory Sales OfficesSoftware Maintenance ContractsThree Application Engineering Support FacilitiesEngineering Services and RentalsOn-site TrainingTraining and Technical SeminarsTwo Service CentersHardware Maintenance and Calibration Programs
  • 28. Engineering Services and Rental Program Advanced non-contact vibration measurements available for every budget Measurements using Polytec’s latest, non-contact measurement technology Application engineers to operate the measurement system to its fullest potential Rental of any of Polytec‘s products Convenience of testing at the customer’s facility or in a Polytec lab Complete measurement data for further processing Short-notice, critical measurements Occasional measurements Extended evaluation prior to purchase Budget Flexibility