How do you measure vibration?

Vibration is measured in terms of displacement, velocity and acceleration. Vibration is defined as to and fro motion of an object from its equilibrium or means position as shown in the following figure. The distance travelled by an object between the mean position and the extreme position is called displacement and similarly, the distance travelled between the extreme left and extreme right position (with respect to the following figure) is called peak displacement. The velocity of an object is zero at its extreme positions and maximum at the mean position. Since velocity is changing with respect to the position, average velocity or Root Mean Squared (RMS) velocity is preferred. Sometimes peak velocity is also used. Since an object changes the direction of motion at its extreme positions, the acceleration is maximum at the extreme positions and zero at the mean position. Since acceleration also changes with respect to the position of an object, average acceleration or Root Mean Squared (RMS) acceleration is preferred.

Figure: Spring mass sytem