Encoders for simultaneous sensing of position and speed in electrical drives with digital control

Speed and position sensors for servo drives still are an issue not yet completely understood. There is a swapping of expressions like "accuracy" and "resolution" amongst engineers when talking about encoders-these words, however, do describe different characteristics and should not be mixed up. The introduction of digital control made these issues much more important for servo drive applications than before. This paper presents some general explanation of the items mentioned above as well as different encoder technologies available today and their characteristics-especially with respect to digitally controlled servo drives.