A filter is a device that allows through only the desirable part of a signal, rejecting the unwanted part. Unwanted signals can seriously degrade the performance of a mechatronic system.
External disturbances, error components in excitations, and noise generated internally within system components and instrumentation are such spurious signals, which may be removed by a filter.
As well, a filter is capable of shaping a signal in a desired manner.
(a) Illustration of a ground loop, (b) Device isolation to eliminate ground loops