Frequently Asked Questions about Laser Doppler Vibrometer

A vibrator is a device that applies dynamic forces to an object to induce vibrations. For small structures, an electromagnetic vibrator (also called a dynamic vibrator) is used. This type is what is generally referred to when simply mentioning a vibrator. Electromagnetic vibrators have a wide dynamic range and can individually adjust the frequency, magnitude, and phase of the excitation force, enabling vibrations in the kilohertz range.

One of the precautions when using a vibrator and its greatest drawback 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 structure is. As a result, the influence of noise increases at important resonance points, leading to a decrease in the coherence function, which in turn results in a loss of measurement accuracy and reliability.

Generally, the capacity of the exciter is often overlooked, but if one wishes to measure the resonance point accurately, a smaller exciter should be used as much as possible. Additionally, typical exciters have a fundamental natural frequency of their moving parts above 5 kHz, which serves as the upper limit for the excitation frequency.