What are Encoders? | Incremental vs Absolute Encoder

What are Encoders?

An encoder is an electro-mechanical device that converts motion into electrical feedback signal, read by a controlling device, such as PLC or Encoder Interface Module, to measure changes in position, speed, count, direction, and linear distance.

Encoders are essential components in high-speed, high-volume industrial applications. There are mainly two different types of encoders are available: a linear encoder and a rotary encoder. A linear encoder measures a linear path while a rotary encoder measures a rotational motion.

Another important term by that encoders is categorized by its output: “Incremental Encoder” and “Absolute Encoder”.


Where Encoders are used?

Encoders have become essential components for different applications in many industries. Now you have a question after what are encoders? that where it is used?

Such as Assembly Machines, Packaging, Printers, CNC Machines, Robotics, Labelling Machines, Medical Equipments, Textiles, Drilling Machines, Motor Feedback, Dynamic Weighing Machines, etc.

The above-mentioned examples where encoders are used to measure position, velocity, distance, etc.


Encoder Types

There are mainly two types of encoders as per their application: Absolute and Incremental. However depends on their physical construction the encoder are further categorized such as,

  • Magnetic
  • Mechanical
  • Optical
  • Capacitive

But in these, all “Optical” encoders are most widely used in the industry.


Encoder Working Principle

The below graphic shows an example of an incremental optical type encoder.

what are encoders

As we can see that there is an LED(Light Source), Disk(Must contained Opaque sectioned line with equally spaced to determine movement), Sensor(To detect light must be called as a photodetector), electronics board to determine and calculate pulses.

When the encoder start rotating, a light from the LED passes through the transparent glass disk to the photodetector. This produces a pulse signal like when there is a light it gives ON signal and when there is no light it gives OFF signal. This produces a pulse signal, ON, and OFF.

The output of the incremental encoder is pulses per revolution which are used to determine the speed as well as to keep track of the position.


What is the main difference between “Incremental” and “Absolute” encoder?

The construction of incremental and absolute encoders is almost the same. The difference is absolute encoder uses a disk that has unique bit patterns instead of a disk with evenly spaced lines.

what are encoders

The output signal of the absolute encoder is in digital bits which corresponds to a unique position. This bit configuration is unique for each position. So, the Absolute encoder provides both the indication that the position has changed and an indication of the absolute position of the encoder.


I hope you like this article about What are Encoders? Absolute Encoder vs Incremental Encoder. Do you have any questions or feedback? Please feel free to comment down below. You will also find some helpful articles about PLC below:

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