Frequently Asked Questions about Laser Doppler Vibrometer

A vibrator is a device that generates vibrations by applying a dynamic force to an object. Electromagnetic vibrators (also called electrodynamic vibrators) are used to excite small structures. When people simply refer to a vibrator, they are usually referring to this type. Electromagnetic vibrators have a wide dynamic range, and the frequency, magnitude, and phase of the excitation force can be individually adjusted, allowing for excitation at several kHz.

One of the main drawbacks of using a vibration exciter is the phenomenon where the excitation force decreases sharply at the resonance point of the object. This phenomenon becomes more pronounced the lighter and less damped the object is. This phenomenon increases the influence of noise at important resonance points, reduces the coherence function, and leads to a loss of measurement accuracy and reliability.

While the capacitance of a vibrator is often overlooked, to accurately measure the resonance point, the smallest possible vibrator should be used. Note that in typical vibrators, the fundamental natural frequency of the moving part itself is above 5 kHz (this represents the upper limit of the excitation frequency).