Positioning tasks require current and precise position values to monitor or control motion activity. In many applications position sensing is done using rotary encoders, also called shaft encoders or simply encoders. These sensors transform a mechanical angular position of a shaft or axle into an electronic signal that can be processed by a control system.
Incremental Rotary Encoders
Incremental encoders measure angle values by counting a material with a periodic pattern, starting from an arbitrary origin. This measuring method does not inherently render absolute positions for a measured signal. Initial homing to a reference point is therefore inevitable in all positioning tasks, both upon startup of the control system and whenever power to the encoder has been interrupted.
Absolute Rotary Encoders
Absolute rotary encoders are capable of providing unique position values from the moment they are switched on as well as immediately after a power loss. This is accomplished by scanning the position of a coded material. All positions in these systems correspond to a fixed code. Even movements that occur while the system is without power are translated into accurate position values at once when the encoder is powered up again.
Single- and Multi-Turn Rotary Encoders
Single turn encoders are systems that measure absolute positions for one turn of the shaft (up to 360°). After one turn the measuring range is exceeded and loops back to the starting value. However, in many applications several turns of the shaft must be distinguished. In these cases, multi turn encoders will keep track of the angle position of the shaft while also providing code information about the number of turns.
