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Laser Doppler Vibrometer

Laser Doppler Vibrometer Working Principle

Our laser Doppler Vibrometer system measures vibrational displacement according to the heterodyne interferometer principle, which generates a high-frequency carrier signal at the photo detector with the aid of a acousto-optic frequency modulator (AOM). The beam of a helium neon laser is pointed at the vibrating object and scattered back from it. The velocity or displacement of a vibrating object generates a frequency or phase modulation due to the Doppler effect. The object beam is thereby subjected to a small frequency shift which is described as the Doppler frequency fD. The Doppler frequency is a function of the velocity component v in the direction of the object beam according to

fD = 2 * v/λ,

where λ is the laser wavelength. The AOM also generates an optical frequency shift fB in the reference beam (40MHz). After superimposed the measurement and the reference beam, an electrical signal is generated at the photo-detector with the instantaneous frequency

fc(t) =  fn+fD(t) = fn + 2  * v/λ

This is a carrier frequency signal with the central frequency fB, which is frequency modulated with the signed Doppler frequency. Through frequency demodulation the velocity can be decoded. In PNV-RD-AVD1 demodulation of the Doppler signal is purely based on a digital process. In contrast to the conventional vibrometers which use analogy, this means that the measurement accuracy is virtually independent of aging and environmental influences. State of-art FPGA technology makes it possible to realize excellent measurement system characteristics, despite the compact design and minimal energy consumption.



Single-Point Laser Doppler Vibrometer

● Mesurement distance 0.2m - 5m

● 1 LDV head, direct connection to computer, no control box 

● Frequence measurement range 0.1hz to 5Mhz

● Resolution Velocity displacement 1pm

Multi-Point Laser Doppler Vibrometer

● Mesurement distance 0.2m - 5m

● 2/4/8 LDV head, With multi point control box 

● Frequence measurement range 0.1hz to 5Mhz

● Resolution Velocity displacement 5pm

Long Distance Laser Doppler Vibrometer

● Mesurement distance 20m - 200m

● 1 LDV head, with control box

● Frequence measurement range 0.1hz to 250Khz

● Resolution Velocity displacement 10pm



Single and Multi-Point Laser Doppler Vibrometer 

Product Brochure: Single-point Laser Doppler | Multi-point Laser Doppler 

SpecificationsSingle-point Laser Doppler Vibrometer Multi-point Laser Doppler Vibrometer 
Measurement point12,  4 , 8
LaserHe-Ne Laser (wavelength at 632.8nm, Class II,Eye-safe)He-Ne Laser (wavelength at 632.8nm, Class II,Eye safe)
Standoff distance0.2m - 5m (adjustable focal length, up to 30m with retro-reflective surfaces)

0.2m - 5m (adjustable focal length, up to 20m with

retro-reflective surfaces)

Spot size of laser20µm - 500µm20µm - 500 µm
OutputAcceleration, velocity or displacement (selected from software)Velocity or displacement (selection from software)
Frequency measurement range0.1Hz - 250kHz (Analog);
Up to 5MHz (Digital)
0.1Hz - 250kHz
Velocity measurement rangeAdjustable based on resolution, from 10mm/s to 2m/sAdjustable based on resolution, from 10mm/s to 2m/s
ResolutionVelocity Displacement: 1pmVelocity Displacement: 5pm
Demodulation systemFPGA digital decoding system (real time output)FPGA digital decoding system (real time output)
Interface of controlSoftware controlSoftware control
Data outputDigital output(USB3.0 interface)
Analog output (SMA interface)
Digital output(USB2.0 interface)
Analog output (BNC interface)
Mounting hole on systemM4, M6,1/4"-20M4, M6,1/4"-20
Software

Windows-based interface for display analyze and save

measurement data

Windows-based interface for display analyze and 

save measurement data

Power supply110V-240V, 50Hz-60Hz110V-240V, 50Hz-60Hz
Size of sensing head300mm (L) x 62mm (W) x 120mm (H)300mm (L) x 60mm (W) x 120mm (H)
Trigger interfaceTTL Signal, SMA interfaceTTL Signal, BNC interface
Synchronization among channelsNA20ns
Cable length head to systemNA2m


Long Distance Laser Doppler Vibrometer 

Product Brochure: Long-distance Laser Doppler

SpecificationsLong distance Laser Doppler VibrometerCustom Design
Measurement point1
LaserNarrow linewidth laser group   (eye safe)
Standoff distance20m - 200m on diffused surface Up to 500m on retro- reflective surface
Spot size of laser10mm at 200m
Aperture size4"
Aiming methodThrough laptop monitor
FocusingAutofocus (Bluetooth control)
Velocity measurement rangeAdjustable based on resolution, From 100mm/s to 3m/sUp to 10m/s
Frequency measurement range0.1Hz - 250kHz
Demodulation systemFPGA digital decoding system (real time output)
Interface of controlSoftware control
ResolutionVelocity Displacement: 10pm
Mounting hole of sensing head1/4"-20, 3/8"-16Custom design
Data outputDigital output(USB2.0 interface)
Analog output (BNC interface)

Power supply24V DC-power supply (included)
SoftwareWindows-based interface for  display analyze and save measurement dataOptional laptop with SSD



Laser Head Layout

1, Digital output interface (USB3.0, connect to computer for digital data output)
2, Analog output interface (SMA interface, +/-10V, connect to oscilloscope or data acquisition devices)
3, Trigger interface(SMA interface,5V TTL signal)
4, Power interface (15V/5A DC)
5, Signal strength indicator


Software Interface

(1) Start/stop switch button:
(2) Time-domain waveform display window:
(3) Waveform display window color mode switch:
(4) Time axis display setting: Rotate this knob will adjust the time axis display range from 200ns/DIV to 100ms/DIV (2ms to 1s for the whole time-domain waveform)
(5) Frequency range selector:
(6) Frequency-domain X-axis(Frequency) display setting: 
(7) FFT window and resolution setting:
FFT window: This software has 5 windows (Rectangular, Hamming, Hann, Flattop and Blackman) to select, 
FFT resolution: The frequency resolution of frequency-domain spectrum can be select in this drop-down list, 
(8) Measurement range setting:
(9) Frequency-domain waveform display window:


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Local Same Day Service

-Singapore Main office:  Call us at +65 6996 0391 Office Hours: 9am - 6pm (+8GMT)
-China Shanghai Main office:Call us at +86 1500085 3620. Office Hours: 9am - 6pm (+8GMT)
For Other Internation sales office  
click here.


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