Laser Doppler VibrometerParameter: Vibration

Vibration is mechanical movement where oscillation occurs at an equilibrium point

Two types of vibrationo Free Vibration

o Forced Vibration

Instrument is necessary to measure the level of vibrationo Accelerometer

Figure 1: Vibration of two plane

BACK

Accelerometero Mounted directly onto machine

Laser Doppler Vibrometero Advanced interference technology

o Precise measurement

o Capable of measuring both small and large objects

Laser Doppler Vibrometero Utilizes Laser Doppler Technique

Introduce by L.E Drain in 1975 for measuring the speed wind

o Apply laser on the subject for measurement

o Analyzing different waveform to give the measurement of vibration.

o Different types of Laser Vibrometer for different purposes.

Sensing Element: Laser Beam

EM wave emits to the vibrate object.

This beam is the sensor where the beam splitter acts as the transducero convert the beam into detectable signal by comparing the frequency of

the signals.

Beam Splitter

In beam splitter 1, the laser light is split into two. o Reference beam.

o Measure beam.

The laser light incident to the surface of the test subject will be reflected.

The two reference beam and measure beam will undergo superposition and direct to photo detector.

Filter and Electronic

Controller

To amplify the current from the photo detector.

To filter away the high frequency noise and ensure that the Doppler frequency is always lower than the

carrier frequency.

In mixing stage, the carrier signal is shifted to an intermediate frequency (10.7 Mhz)

To converts the frequency to voltage by using an averaged-time, pulse technique that gives a linear conversion.

To view the output of the operator and stored value.

The output signal can be viewed on several intrument.

Function to measure vibration

displacement and velocity.

With digital high speed processing provides precise and high resolution

data enormously fast.

Compare to conventional analog decoder solutions used for vibration

measurement.

Overcome the LDVs limitation and enhance their performances.

For example advanced the signal decoding and improvement on the signal to noise ratio.

Scanning Laser Doppler Vibrometer(SLDV)

3-D vibrometer

Differential vibrometer

Figure 2: Different Types of Laser Doppler Vibrometer

In scientific, industrial and medical fields.

For example, in biological has eardrum diagnostics

For example, in automotive has structural dynamics, brake diagnostics and quantification of noise, vibration and harshness.

Video from and it is with sound

https://www.youtube.com/watch?v=o0qkmG_S4QY

1. http://en.wikipedia.org/wiki/Laser_Doppler_vibrometer

2. http://www.sciencedirect.com/science/article/pii/S088832700

5002220

3. http://www.polytec.com/us/solutions/vibration-

measurement/basic-principles-of-vibrometry/

4. http://d2s.ec-lyon.fr/Donnees/EquipEssai/Bp1896.pdf

5. http://www.metrolaserinc.com/Literature/MetroLaserSB-

LDVpaper.pdf

6. http://www.ti.com/analog/docs/litabsmultiplefilelist.tsp?literat

ureNumber=sloa033a&docCategoryId=1&familyId=1483

7. http://www.polytec.com/fileadmin/user_uploads/Applications

/Data_Storage/Documents/LM_TP_Idema_JP_2005_E.pdf

8. http://www.metrolaserinc.com/Vibromet500_FAQ.htm