An electromechanical device called a rotary encoder is fastened to a motor/shaft assembly to precisely record the rotating shaft’s location, speed, and acceleration. The rotary encoder, also known as the shaft encoder, uses rotating mechanical displacements to sense the angular location and velocity of the rotary shaft and produces digital output signals in response.

Different Types of Rotating Encoders 

Rotating encoders come in two primary varieties: 

  • Incremental 
  • Absolute

Relative position changes are reported via incremental rotary encoders. Upon first starting or following a power outage, motion-controlled devices that employ incremental rotary encoders must be “homed in.” 

Hall effect sensors also make use of particular encoders for smooth functioning.

When absolute rotary encoders are powered on, they can report position data immediately, even if there was a power outage during the last usage. Since the absolute (beginning) position is always known, no calibration is required. Additionally, there are three primary categories of rotary encoder technologies:


Optical rotary encoders consist of a photosensor, a spinning disk with apertures resembling slots, and an LED light source. Light pulses are produced as the disc rotates with the shaft, and an electrical circuit converts these pulses into digital square waveforms.

  • Mechanisms: Centric copper rings and contact brushes are used by mechanical rotary encoders, also known as conductive encoders, to produce a positionally encoded conduction that an electronic circuit can read. 
  • Magnetism: A revolving wheel with several magnetic poles around it is the feature of magnetic rotary encoders. A circuit that detects changes in the magnetic field and transforms feedback into a digital output signal is passed by while the wheel revolves. 
  • High-performance incremental optical rotary encoders that are perfect for a wide range of markets and uses are designed and produced by Quantum Devices.

Rotary Encoders Use 

  • Different mechanical systems are monitored and/or controlled using rotary encoders. For instance, conveyor belt direction and speed are managed using rotary encoders in industrial automation. 
  • Rotary encoders are also employed in servo motor feedback, multiple-axis motion control, and speed control. In textile machinery, material handling equipment, and packaging/labeling machines, rotary encoders are mounted directly to the motor shaft.
  • Applications for rotary encoders are also found in dosing pumps, flying simulators, and AGVs, among many other devices. Application-specific encoders are offered by Quantum Devices in collaboration with OEM equipment manufacturers; free samples are provided for projects that meet the requirements. 

Factors to Consider while Selecting a Rotating Encoder 

  • Size

The size and type of shaft are the most important factors to take into account when choosing a rotary encoder, assuming that your application calls for an absolute or incremental rotary encoder.

  • Dimensions 

The system’s space requirements, where your rotary encoder will be integrated, must be known. Important measures consist of: 

  • Diameter of the housing 
  • Profile of housing (height) 
  • The diameter of the shaft or bore 
  • Shaft style 

Depending on the type of incoming shaft in your application, rotary encoders might have a solid or hollow shaft. To guarantee correct alignment, the appropriate fittings and mounting configuration must be selected.

  • Environment

After defining the mechanical parameters of your rotary encoder, you must take the operating environment into account. You may lessen the effects of dust, vibration, severe temperatures, moisture, and other impurities by selecting a rotary encoder that is made to work in harsh environments. 


The smallest unit of measurement that an encoder can detect is referred to as resolution. The resolution of rotary encoders is measured in pulses per revolution (PPR). Not every application needs the same degree of positional accuracy, and the encoder’s controller’s maximum input frequency plays a role as well. Visit our page on selecting a rotary encoder’s resolution for further information.

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