This associates the vibration signals to the rotational speed and its harmonics. There are many speed-related frequency components of interest that relate to specific potential failure modes, and therefore it is considered as a typical condition monitoring function, especially for variable speed machines. Typical speed components that are monitored include the first harmonic (running speed) for unbalance, first three harmonics for misalignment, tooth meshing/blade passing frequency, motor frequencies, sub-synchronous instabilities, etc. These speed related frequency components can be isolated for analysis by timeaveraging (non-speed related vibration is averaged out). Order analysis of a frequency spectrum during transient speeds is called variable speed analysis.