Rotary encoder

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Rotary encoders translate the mechanical rotational motion of an object such as a motor shaft into an electronic signal. Optical rotary encoders measure rotation by shining a LED light through a disc with markings onto an optical sensor to detect motion. Magnetic rotary encoders use a similar principle but measure motion as a magnetized wheel turns and is detected by a magnetic sensor. 

Incremental rotary encoders output a stream of ubiquitous pulses over 360 degrees of rotation, hence the term pulses per revolution of PPR. Incremental rotary encoders can have one channel output (A), two channel output (AB, known as quadrature) as well as an optional index channel (Z).

Absolute rotary encoders output a unique digital word or bit for each position over 360 degrees of rotation. This digital word must be communicated in the same language as the controlling system with options including parallel, serial, field bus and ethernet based communication protocols.

Rotary encoders should be used in any application that requires precision motion control. While a power can be supplied to a motor to make it turn, to control exactly how fast it actually turns  requires real time feedback so that the controlling device can increase or decrease power to achieve a consistent motor speed or shaft position. Rotary encoders are therefore indispensable in precision motion control applications including servo motor feedback, robotics, factory automation and more.