what is a rotary encoder and how does it work?

Introduction: Rotary Encoder

Rotary encoders are position sensors used for determining the angular position of a rotating shaft. They convert the angular position or motion of a rotating shaft axle into analog or digital output signals. There are two main types of rotary encoders- absolute encoder and incremental encoders. The different types of rotary encoders, its working principle, and applications are discussed below:

Absolute Encoder

Absolute encoders provide speed and positional information by offering output in the form of a digital word or bit, relative to motion. They maintain position information even when the power is removed from the encoder. The position of encoder is instantly available on applying power. An absolute encoder has multiple code rings with various binary weights. This provides data word with the absolute position of the encoder within one revolution. This type of absolute encoder is also known as a parallel encoder.

Incremental Encoder

Incremental encoders work by reading the changes in angular displacement instead of reading an absolute angle of the encoded shaft. An incremental encoder will immediately report any changes in position. They are suitable for applications that require accurate reporting of position changes. Increment encoders do not track the absolute position. They may need to be moved to a fixed reference point to commence the position measurement. A rotary incremental encoder has two signals A and B, which issue square waves when the encoder shaft rotates.

How Rotary Encoders Work?

A rotary encoder has a disk with evenly spaced contact zones. These contact zones are connected to a common point and two other separate contact points. Once the disk starts rotating, the two contact points will touch the common pin. This will cause two square wave output signals to be generated. These square waves will be displaced at 90-degrees out of phase from each other.  Either of these signals can be used to determine the rotated position. However, if you want to count the rotation direction too, then both the signals need to be considered simultaneously.

Applications of Rotary Encoders

Rotary encoders are used in applications that need monitoring and control of mechanical systems. Such applications need the feedback of position, velocity, distance, etc. Rotary encoders are widely used in assembly machines, packaging, printers, testing machines, CNC machines, labeling machines, robotics, drilling machines, etc. They are highly reliable and accurate and help to provide high-quality feedback cost-effectively. Rotary encoders can be integrated into existing applications and have a compact size.