- The maximum distance from the equilibrium position that occurs in periodic motion.
- Peak amplitude
- The difference between the maximum excursion and the equilibrium point.
- Peak-to-peak amplitude
- The difference between the maximum positive and maximum negative points of excursion.
- RMS amplitude
- The standard deviation of all values.
In the measurement of the vibration of an object it is common to use the following:
- displacement - Peak to Peak
- velocity - Peak
- acceleration - RMS