CLV-3D Compact 3-D Laser Vibrometer - Features

Polytec’s CLV-3D non-contact vibration sensor simultaneously measures all three linear velocity components at a single point on a vibrating structure. The individual vibration components are available as analog outputs. The CLV-3D’s wide dynamic range, excellent bandwidth and low noise enable its use in many advanced applications.

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Convenient Measurements with Zero Mass Loading

Using the CLV-3D, engineers can now make simple, non-contact measurement of all three vibration vector components simultaneously.  Single-axis laser vibrometer users will especially appreciate the convenience of no longer having to make three separate measurements and then manually calculating vx, vy and vz. In addition, users of tri-axial accelerometers will be pleased to finally make 3-axis measurements with no contact and zero mass loading. The small measurement spot diameter of only 80 µm is much smaller than any accelerometer footprint and allows measurement of smaller components.  And, of course, with a bandwidth of 250 kHz, all three components of a high frequency vibration can be accurately measured simultaneously.



  
Key Features

  • Simultaneous measurement of 3 orthogonal vibration velocity components
  • Zero mass loading
  • Geometry calculation module generates true vx, vy and vz analog outputs in real time for velocities up to 1.25 m/s 
  • Two frequency ranges: 0.5 Hz to 50 kHz and 0.5 Hz to 250 kHz
  • High sensitivity requires little or no reflectivity enhancement
  • Three velocity ranges for high resolution
  • Two different stand-off distances available
  • Compact and ruggedized sensor head
  • Optional motorized test stand



  
The CLV-3D System

The system comprises a three-channel CLV Compact Laser Vibrometer Controller unit coupled to a CLV-3D Optical Sensor Head containing three independent CLV optical systems, all focused to the same measurement point approximately 140 mm (or 300 mm) from the front lens.

Optical Sensor

The CLV-3D Optical Head contains the optical components of three independent CLV-700 sensors. Each output laser beam is inclined at a 12° angle (f = 160 mm lens version) with respect to the surface, but from three slightlydifferent directions separated by 120° in the output plane. A 12° angle is small enough to allow the sensors to collect enough back-scattered light to make a high-quality measurement, but still large enough for good sensitivity to the in-plane vibration components. Furthermore, the narrow cone angle allows the beams to pass through small holes or windows in wind tunnels or environmental test chambers. For even narrower cone angle applications, a 310 mm focal length front lens may be fitted in combination with a 310 mm version of the geometry module.

Signal Outputs

The CLV-3D provides separate analog outputs for the vibration velocity along the three laser beams vL, vR and vT. These outputs can be used to calculate the cartesian velocity components vx, vy and vz. For external software calculations, these raw outputs are connected to a three channel data acquisition board and processed by a computer. A better choice is Polytec’s internal geometry calculation module where the Cartesian velocity components vx, vy and vz are provided as three separate, real-time, analog outputs. With a “perfect” surface such as 3M™ Scotchlite™ retro-reflective tape, vx and vy have a noise floor of better than 1 µm/s measured in a 10 Hz resolution bandwidth. Vz is better than 0.5 µm/sec.

Hardware

The controller unit is divided into upper and lower sections.  The lower section contains three CLV laser modules (CLV-810) plus the master power supply module.  The upper section comprises a 3-channel vibrometer signal processor, which generates the three analog velocity outputs vx, vy and vz in addition to the "raw" outputs vL, vR and vT.

Doppler signal demodulation is performed by a combination of three input modules (type CLV-M200) and three velocity decoding modules (type CLV-M020.B for 50 kHz version or CLV-M030.B for 250 kHz version) chosen according to the bandwidth demanded by the application. A range selector knob controls the velocity rangesetting for all three channels. Each input module generates an LED bar proportional to gathered light. 

A single output module conditions the raw Doppler signals from the three laser beams and outputs vL, vR and vT. The single geometry module performs an analog coordinate transform and outputs the true vx, vy and vz components. A switchable 10 Hz high-pass filter is provided for cutting off low-frequency vibrations.



  
Accessories



  




CLV-3D Laser Vibrometer




CLV-3D Vibrometer Controller




CLV-3D Sensor Head




CLV-3D Principle




CLV-Z-018 Motorized Test Stand