Vibration is a mechanical movement around an equilibrium point. In other words, it is a mechanical phenomenon where a dynamic external force is applied onto structures or floors, causing the oscillation motion that repeats itself after an interval of time. Among the sources of vibration, the low frequency vibration is not perceptible during daily activities, and adversely affect vibration-sensitive metrology tools in the fields of semiconductor, display, electron microscopy, life sciences and photonics.
Classification of Vbiration
Periodic noise is defined as the known magnitude of the excitation acting on a vibratory system at any given time. It is generally caused by rotating machinery. Random noise is caused by unpredictable excitation such as wind velocity, road roughness, foot and vehicular traffic, and ground motion during various activities.
Measurement Unit of Vibration
Vibration can be measured in units of displacement, velocity and acceleration. The shape and frequency of the vibration are the same regardless of which of the three measurement units, used to express vibration, except for the difference in the phase.