What is ring encoders?

Ring encoders are devices that use a special ring located outside the body as a scale.


  1. Rotary ring encoder design
  2. Operation principle
  3. Variants of installation
  4. Magmetic and optical versions

Rotary ring encoder design

Ring type encoders are rotary or angular sensors. They use tape in form of a circle, as a scale, which is placed on the measuring object (for example, a pipe flange).

Such devices are able to provide feedback on the position and speed of rotation. That is, their tasks are completely similar to common models of encoders.

Usually ring encoder consists of several main parts:

  1. Ring
  2. Receiver
  3. Electrical interface
  4. Mechanical interface

Ring is a circle which consists of special material tape. It is mounted directly on the measuring detail and make rotation with it. Tape have special marks at certain distance from each other.

Receiver is a device that, with using various methods, determines speed and direction of the marks when they pass a certain point.

Electrical interface allows to process and transfer data to following control systems.

Mechanical interface consist of elements which coupling encoder with measuring object and mounting surfaces.

Operation principle of the ring encoder

Ring sensors can have absolute or incremental principle of work.

Like standard encoders, ring type sensors are divided into two types:

  1. Incremental
  2. Absolute

Operation principle makes changes in the design both receiver and ring.

Ring incremental encoders determine the position relative to a start (also called zero) point. This means that device needs to set a starting point before work. Further counting will be conducted relative to this mark. The tape most often has identical tags at the same distance between them.

Ring absolute encoders can determine absolute position. This means that each mark is unique and defines its specific position. Consequently, the sensor does not require to setting a zero point at the start of operation.

Absolute type ring encoders can be:

  • singleturn
  • multiturn

Single-turn device remembers the indicators only in the range of one turn.

Multi-turn sensors are able to store information about data at several of turns. For this purpose, additional computational disks are installed in the housing.

Ring type encoder installation

The placement of the receiver relative to the ring can also be performed in two ways:

  1. Axially
  2. Radially

In the first case, a special axial ring is used. Receiver is located either above or below the ring. It is important to pay attention that a surface with marks is directed to it. In this case, there is a tight tolerance system for correct operation.

In radial reading, the receiver is located on the side of ring. This gives many accommodation options. It is used radial ring for this purpose.

In both cases, the rotation can be carried out in two directions, if the capabilities of model permit that.

Magnetic and Optical Ring Encoders

Depending on the method of obtaining data, the presented encoders can be:

  • Optical
  • Magnetic

Each category has its own advantages.

Optical ring encoders operate with a signal that is in the form of a pulse. Then beam of light fall into marks on the ring. After that, the signal enters into receiver, where it is already converted to results data. This method is highly accurate, but the work is highly dependent on the state of environment. Since such sensors often have a miniature size, even small particles getting on the ring surface can change results.

Magnetic ring encoders works with magnetic fields. Poles are placed on a ring with a certain step, and receiver interacts with them. This method is quite reliable, since it does not require direct contact of elements.

In conclusion: due to its special design, devices can work with very large diameter parts, while having a miniature size. At the same time, the functionality of the sensors is equal to main encoders.

On our website eltra-encoder.eu you can find the rotary rotary encoder ETMR by Eltra.

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