Skip to content
Close
en
de
Contact us
en
de
Contact us
4 min read

What is a rotary encoder and how does it work?

Roger Zingg Jul 9, 2025 8:30:00 AM
rotary encoder
What is a rotary encoder and how does it work?
6:46
Rotary encoders, also known as angle sensors, angle encoders or encoders, are indispensable
components in industrial automation, mechanical engineering and many other technical applications. They enable the precise measurement of rotary movements and positions. Machines can thus be efficiently controlled and monitored.
What is a rotary encoder?
A rotary encoder is a sensor that converts the rotary movement of an axis into an electrical signal. This signal can be used by control systems to precisely record the position, speed or direction of a movement, position, speed or direction of a movement. Rotary encoders are crucial for automated systems in many applications. They enable precise and reliable acquisition of movement data.

 

Areas of application for rotary encoders:

  • Industrial automation: Position control of robots, machine control
  • Vehicle technology: Steering angle detection, engine control, pedal position
  • Medical technology: Precision control in diagnostic devices, surgical robots
  • Renewable energies: Speed and blade angle monitoring of wind turbines

How does a rotary encoder work?

Rotary encoders typically consist of three components:

  • The measuring body can consist of a magnetic encoder or an encoder disk, for example, and is connected to the rotating axis of the machine.
  • The sensor system detects the movement and converts it into an electrical signal.
  • The electronic interface transmits the signals to a controller or a display.

The function of rotary encoders is based on various measuring principles, which are divided into two main categories:

Incremental encoders

Functionality:

An incremental encoder generates a certain number of pulses per revolution. By counting these pulses, the speed or relative position can be determined.

Advantages:

  • High resolution possible
  • Simple design and cost efficiency
  • Ideally suited for speed detection

Disadvantages:

  • No absolute value (position is lost in the event of a power failure)

Application example:

  • In CNC machines for detecting the speed of a spindle

Absolute rotary encoder

Functionality:

Absolute encoders measure the exact angular position of an axis and output this as a digital value. They are available in singleturn (measures position in one revolution) or multiturn (measures position and number of revolutions)versions.

Advantages:

  • Saves position even after a power failure
  • Direct angle measurement possible
  • Greater safety thanks to exact position data

Disadvantages:

  • More complex and more expensive than incremental encoders

Application example:

  • In robot arms to maintain the exact position of each joint even after a restart.

There are also two fundamental differences in the mechanical design of rotary encoders:

Rotary encoders with integral bearing

  • This type of encoder has its own bearing-mounted axis to which the measuring scale is attached.

 

Advantages:

  • The dimensional scale is precisely guided, the encoder can be precisely calibrated by the manufacturer
  • Simple installation in the customer application
  • The measuring scale and sensor system form a complete unit

Disadvantages:

❌ Limitation of the permissible rotation speed (depending on the bearing)

❌ Use of couplings required so that no forces are transferred to the sensor bearings

❌ Relatively high overall height due to the integrated bearing

Bearingless encoders

With these rotary encoders, the measuring scale, for example the magnetic encoder, rotates freely. It is not connected to the actual sensor unit.


Advantages:

  • No wear
  • No mechanical limitation of the rotational speed
  • No couplings required
  • Flat design

Disadvantages:

❌ The measuring scale must be aligned with the sensor unit (within certain tolerances: x-y-z, eccentricity and tilt).
❌ The accuracy is lower than that of a rotary encoder with integral bearing.
❌ Depending on the sensor technology, the installation space must be protected against contamination.

 

Rotary encoder technologies

Different sensor technologies are used depending on the measuring principle:
  • Optical rotary encoders: The movement is detectedusing a light source and a coded disk - precise, but sensitive to dust and dirt.
  • Magnetic encoders work with Hall sensors or magnetoresistive sensors - more robust than optical variants, ideal for harsh environments and compact in design.
  • Inductive encoders are based on electromagnetic induction - insensitive to magnetic interference fields.
  • Capacitive encoders use electric fields for measurement - robust and durable, but complex in design.

Which technology is the best?

The choice of technology depends entirely on the application. Optical encoders are ideal for high-precision applications, while magnetic and inductive variants are preferredfor use in harsh environments.

Selection criteria for the right encoder

When choosing an encoder for a specific application, there are several factors to consider
must be considered:

  • Resolution - How many distinguishable positions per revolution are required?
  • Ambient conditions - Temperature, humidity, dust exposure
  • Measuring accuracy - Is relative or absolute position detection required?
  • Installation conditions - How much space is available? How should the encoder and the measuring scale be mounted?
  • Interface and protocols - Compatibility with existing control systems (e.g.
    CANopen, IO-Link, SSI, SPI, SENT, analog)

Tip: Contelec offers a wide range of customized encoder solutions - absolute
measuring and incremental, magnetic and inductive, singleturn and multiturn.

Why Contelec?

Contelec stands for high-precision encoder solutions that are based on state-of-the-art, continuously developed sensor technologies:

  • Customized solutions from prototype to series production
  • Highest precision: Swiss-made sensor technology for industrial applications
  • Flexibility and individualization: Customizable encoders for specific requirements
  • Reliability and durability: Developed for demanding applications

Whether highly precise angle measurement or a robust encoder solution for extreme conditions - Contelec offers the optimum solution for every application.

Conclusion: Encoders as key components for modern control systems
Encoders are essential components for the precise control of machines and processes. Whether incremental or absolute, inductive or magnetic - the right choice of sensor depends on the requirements of the application.

With customized solutions and innovative technology, Contelec offers the perfect encoder technology for all individual requirements.
Roger Zingg
Roger Zingg has been Managing Director of Contelec AG, a company based in Biel, Switzerland, which specializes in the development and production of angle sensors, since 1989. Under his leadership, Contelec has established itself as a leading provider of sensor solutions used in various industries such as agricultural engineering, medical technology and the energy sector. With over 35 years of experience in the sensor industry and a strong commitment to sporting activities, Roger Zingg embodies a balance between professional success and personal passion. Translated with DeepL.com (free version)

RELATED ARTICLES