A Guide to the Design and Application of Active Low Pass Filters for Use in a Low Level Data Acquisition System.

Filters are used in data acquisition systems to reduce the effects of series mode noise and aliasing errors. Active filters are more effective than passive filters for reducing the interaction between input channels and a multiplexer. Active filters can produce any frequency response required but introduce additional noise, drift and offsets to the system unless special care is taken in the choice of components. Two methods of filtering differential signals, and a method of producing a switchable frequency range filter are described.