an introduction to non-contact vibration measurement
DESCRIPTION
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 validationTRANSCRIPT
AutomobilesAirplanesHome AppliancesData Storage and SemiconductorMicrostructures, MEMS and NanotechnologyEntertainmentLife Sciences (Biology, Medical)Production Testing & Quality Control UltrasonicsOptical Industry & Telecommunications Defense equipmentCivil Structures
Vibration is Everywhere
The TechnologyPoint & shootEye-safe visible laser probeDetects Doppler shiftAnalogous to acoustic Doppler effectHigh-precision laser interferometerDecodes information to give both displacement and velocity signalsEasy-to-use data acquisition & software processingHardware and software for full-field scanning
TimeHistory
Impulse Response
Frequency Response
Vibrometers convert changes in the laser frequency to a voltage output proportional
to instantaneous velocityChanges in optical phase are converted to
signals proportional to displacement
ODS and modal analysis
What does Laser Vibrometry Provide?
Laser Doppler Vibrometry is a non-contact, "point and shoot" technology that directly measures the vibration of a test object using the Doppler effect.
Emitted frequency f
vObserved frequency fD
c: velocity of the sound waveλ: emitted wavelength
f: emitted frequency
Analogy: Acoustic Doppler EffectFor car moving at velocity V, the observer hears the frequency fD = c/(λ -V/f).
Sound emitted from stationary car has frequency f = c/λ
What is Laser Doppler Vibrometry? PDV-100 Portable Digital
Vibrometer
c
λ
For a vibrometer: Δ fD α VΔ fD = 2V/λ
Frequency Modulated signal
40 MHz ± fD
Bragg cellf0 ± fD
f0
f0 + 40 MHz
He-Ne Laser<1mw (633nm)
x(t)v(t)
Photo-detector
The Heterodyne Interferometer
Measurement Beam
Reflected Beam
Δ fD = 2V/λ
Signal Demodulation
Voltage ~Velocity
Voltage ~ Displacement
FM Doppler signal
AM electrical signal
Controller
Photo-detector system
FFT Spectrum
Single Point
Multi Point Scanning
3 Axis
Differential 3 AxisScanning
Many Vibrometer Types
Long Range
Why Laser Vibrometry?
Polytec’s non-contact laser vibrometers are revolutionizing dynamic testing in all kinds of applications because of their:
Higher accuracyCost and time savingsWider range of operation and applications
Higher accuracy –no mass or stiffness added
Delicate, lightly damped structuresfrequency and temperature independentfine spatial resolution
Down to <1µmSmall structuresMeasurements closer to edges
digital decodingAchieves sub-pm displacement resolution!!
What are the Benefits of Laser Doppler Vibrometry?
What are the Benefits of Laser Doppler Vibrometry?Cost and time savings –
point and shootTarget almost anything quickly and easilyEasier 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 pointsData for modal analysis Only one transducer to calibrate, connectNo cables over the structure to secure or failNo phase-matching issuesRoboVib is the ultimate solution
What are the Benefits of Laser Doppler Vibrometry?
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)
What are the Benefits of Laser Doppler Vibrometry?
Wider range of operation and applications – Part 2 of 3
submergedthrough windowsdelicate
What are the Benefits of Laser Doppler Vibrometry?
Wider range of operation and applications – Part 3 of 3
long range rotating inaccessible microscopic
All Kinds of ApplicationsSame technology packaged for different applications:
Macro-Structures
Micro-Structures
SmallStructures
Measure on macro- and micro-structures Example - OFV-534 with integrated video and illumination for sensor positioning and sample viewingTailored solutions for:
Research, production, industrial and in-the-field environmentsUltrasonic and high amplitude applications
Single Point Measurement
VibraLight
Resonance Testing of Disk-drive components
OFV-534 sensor head
Objective lens
Controller
Disk-drive
Vertical test stand
Applications Example
VibSoft
Differential Measurement
Example: HSV-2000
Engine valve-train testing:
- relative movement between two surfaces
- removes background vibration of engine block
- 12 kHz valve bounce revealed
Car engine
Two optical sensor heads
Beam steering probes
Rotational MeasurementRLV-5500 - Rotational vibrometer measures pure angular motion –independent of shape or any lateral vibrations
Measured outputs:1. DC rpm value2. Angular velocity signal3. Angular displacement
Example applications:Order tracking analysisCrankshaftsPropshafts
RotVib Features
Two interferometers
Measures angular velocity and displacement from -8,000 to +20,000 RPM
Eliminates down-time associated with contact methods
d = 7.5mm or 24mm
3-D Single Point Vibrometry
Integrates 3 independent vibrometers
Simultaneous measurement of all axes of motion at a single point
Vx, Vy & Vz
Full Field - Traditional Approach Using Contact TransducersMass loading
Damping and stiffness errors
Time consumingCoarse spatial resolutionLimited working environmentsComplicated cablingCumbersome correlation of coordinates to FEM geometryTransducer re-calibration (book keeping)Limited bandwidth
LDV Controller
Data ManagementSystem
Video
LDVSensor
ScanningMirrors
ScanElectronics
Stitched data
Sensor Head Test Object
Test Object
Up to 250,000 points scannedEasy-to-use software for data acquisition, display &
manipulationAnimated data visualizationEfficient interfaces for modal analysis or FEM
validationGeometry file imported or measuredInternal waveform generator
Scanning Vibrometry (PSV)
3-D Scanning MeasurementDeflection Shape
Full 3-D vibration response over measurement surface (>2,500 points)Integrated data stitching provides complete coverage with single systemPrecise data for modal analysis and model verification
Correlation with accelerometer data out-of-plane
Micro System AnalyzerMSA-500 - Powerful all-in-one measurement workstation for 3-D static and dynamic characterization of MEMS and MOEMS microstructures
Characterization of out-of-plane vibrations by scanning vibrometry
PLUS:
Measurement of in-plane motion and vibration by stroboscopic video microscopy
Determination of surface topography by white light interferometry
Three
Measurement
Technologies
One
Integrated
Package
Customer Support
Five Territory Sales Offices
Software Maintenance Contracts
Three Application Engineering Support Facilities
Engineering Services and Rentals
On-site Training
Training and Technical Seminars
Two Service Centers
Hardware Maintenance and Calibration Programs
Engineering Services and Rental Program
Advanced non-contact vibration measurements available for every budget
Measurements using Polytec’s latest, non-contact measurement technologyApplication engineers to operate the measurement system to its fullest potentialRental of any of Polytec‘s productsConvenience of testing at the customer’s facility or in a Polytec labComplete measurement data for further processingShort-notice, critical measurementsOccasional measurementsExtended evaluation prior to purchaseBudget Flexibility