What is an encoder
The encoder is a rotary transducer, which by means of an electrical signal serves to indicate the angular position of an axis, speed, and acceleration of the rotor of a motor.

How does an encoder work?
An encoder is basically made up of a disk connected to a rotating shaft. The disk is made of glass or plastic and is “coded” with some transparent and other opaque parts that block the passage of light emitted by the light source (typically infrared emitters). In most cases, these blocked (coded) areas are arranged radially.

As the axis rotates, the infrared emitter emits light that is received by the optical sensor (or photo-transistor) generating the digital pulses as light crosses through the disc or is blocked in different sections of it. This produces a sequence that can be used to control the turning radius, the direction of movement, and even speed.


Encoder types
A classification of the encoders according to the type of information on the position they generate would be:

As its name implies, it is an encoder that determines the position angle by means of making incremental counts.

This means that the incremental encoder provides a strategic position from where the count will always start. The current encoder position is incremental when compared to the last position recorded by the sensor.

Incremental encoders are a type of optical encoder and in this type of encoder, each position is completely unique. Inside the incremental encoders are the
Quadrature encoders
It corresponds to a type of incremental encoder that uses two optical sensors positioned with a 1⁄4 slot offset from each other, generating two digital pulse signals offset by 90º or quadrature. These output signals are commonly called A and B. Through them it is possible to supply data on the position, speed and direction of rotation of the axis. If the reference signal is included, it is called the I (index).

Usually, if signal A overtakes signal B (signal A takes the logical value “1” before signal B, for example), it is established that the axis is rotating clockwise, while if B overtakes A, the sense will be counterclockwise.

It is based on the information provided to determine the absolute position in the sequence. An absolute encoder offers a unique grip for each position.

They are divided into two groups: single-turn encoders and absolute multi-turn encoders and are small in size to allow easier integration.

absolute encoder

They divide a mechanical revolution into a certain number of measurement steps. After a complete revolution, the measurement values are repeated. The maximum number of steps is 8,192.

Not only do they record angular positions, they also count revolutions (up to a maximum of 4,096). The signals are emitted either through an SSI interface or a CAN or Profibus type bus system.