VDD PC-Based Digital Vibrometer - Features

New measurements for data storage, micro-electro-mechanical structures (MEMS) and hearing dynamics push a traditional analog LDV beyond its resolution limits. Polytec offers a choice of either the stand-alone VDD-E-600 Digital Front-End or a DD-600 equipped OFV-5000 Vibrometer Controller with analog and digital  capability. The VDD PC-Based Digital Vibrometer utilizes 5 MSa/s, a multi-channel data acquisition and the VibSoft-VDD comprehensive software package for data processing.

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The sophisticated design of Polytec’s Digital Vibrometers opens the door to many new possibilities. One of the most significant advantages of the digital LDV is the extremely low  noise floor and the exceptional sub-picometer displacement resolution on mirror-like surfaces. Digital LDVs are best-suited when extreme accuracy is desired. With a maximum velocity of 810 mm/s and a 2 MHz bandwidth, a wide range of applications can be addressed.

In addition, a digital LDV is an excellent choice when signals are expected to be saved, processed or exported to sophisticated signal processing software. The VibSoft-VDD Software package is cost effective, as it already includes a spectrum analyzer, an arbitrary waveform generator and a data acquisition system.

• Ultra-precise vibration measurements for data storage, MEMS, hearing dynamics or calibration applications
• True DC capabilities for switches and stages
• 2 MHz bandwidth and cutting edge, sub-picometer resolution
• Outstanding linearity, accuracy and dynamic range
• Excellent stability, insensitive to drift and ageing effects (all digital)
• Upgrade any OFV-5000 based vibrometer system by adding a DD-600 Decoder Module
• Stand-alone VDD-E-600 Digital Front-End, can be used with any OFV Series Sensor
• Comprehensive VibSoft-VDD Software for data acquisition, processing and export, with open software interface (PolyFileAccess)
• Optional integrated arbitrary waveform generator
• Optional upgrade for precision MEMS displacement measurements using the MSV-400 Microscope Scanning Vibrometer and the MSA-400 Micro System Analyzer
  

Front-Ends

The vibrometer signal from the sensor head can go to one of two basic configurations – the stand-alone, digital-only VDD-E-600 Front-End or, for the greatest flexibility, the DD-600
Digital Decoder board installed in the OFV-5000 Vibrometer Controller omplemented by a VDD-Z-011 Junction Box. This configuration enables both digital and analog demodulation, which is preferred by data storage and MEMS applications.

The output from the front-end passes to the data management and acquisition system where the displacement, velocity and acceleration can be calculated and displayed. A  reference channel input is available for acquiring additional signals for phase and frequency response function (FRF) measurements. The output from an internal arbitrary waveform generator is also available and can be used to drive the device under test.
 

Sensor Heads

Polytec offers five vibrometer sensor heads – the Dual Fiber OFV-552 Interferometer, the Single Fiber OFV-551 Interferometer, the OFV-534 Compact Sensor Head with optional video camera or the standard OFV-505 and OFV-503 Sensor Heads. Both the OFV-551 and OFV-552 are coupled to microscope based fixtures (MSV-050, MSV-100) for head Media, MEMS or inner ear dynamic testing.

The output signal from the vibrometer sensor head contains information about the velocity (signal frequency) and displacement (signal phase) of the test object. The VDD decodes the phase of the signal to measure the dynamic displacement of the test object. In the VDD system a quadrature demodulator generates the sine and cosine components of the sensor signal. They are digitized by a high sampling rate ADC board inside the data management system. These two signals can be represented as a rotating vector whose phase is directly related to the displacement of the test object and the laser wavelength. By numerically decoding the phase with an arctan function, high displacement accuracy and resolution is achieved. Velocity and acceleration data are available through VibSoft-VDD Software by differentiation of the displacement signal.

To learn more about digital vibrometry, please read our tutorial PDF “Basics of Digital Vibrometry” on our Vibrometer University pages.

The VibSoft-VDD Software package manages the data acquisition, signal decoding, arbitrary waveform generator and data display. Measurements can be presented in both time and frequency domains. Included with the software are an extensive number of functions including FRF, auto power spectra, cross power spectra, coherence and phase.

• Controls acquisition, signal processing, display and export of all data
• Calculates of FRFs, coherence and other signal properties
• Applies digital high, low and band pass filters; User can load custom ASCII format filters
• Differentiates and integrates in time and frequency domain
• Averages the input signal in the time domain
• Calculates FFT with 12,800 lines of resolution
• Controls integrated arbitrary waveform generator with common and user defined excitation waveforms
• Program automatic test routines and interface with other software using Visual Basic scripting (VBS)
• Export data in ASCII format, Universal file UFF, direct data access to binary data using Poly File Access software and optional binary ME’Scope interface
• Access all settings of the OFV-5000 Controller via RS-232 interface
• Access live video images of the test object and laser beam position when using a sensor head equipped with an internal video camera, or an MSV-050/100 Microscope Adapter