What is an Encoder and How are They Used in Industrial Machinery?

An encoder is a sensing device that provides feedback in motion control systems across nearly every industry.       

These devices provide precise motion feedback, making them essential components in automation, robotics, and manufacturing equipment.

You’ll find encoders used in applications such as:

• Cut-to-length systems

• Conveyors and material handling

• Robotics and AGVs

• Packaging and labeling machines

• Plotters and printers

• Sorting, filling, and imaging systems

While they’re often hidden from view—typically mounted to motors or shafts—encoders are vital for controlling and monitoring motion accurately and efficiently.

How Encoders Work in Motion Control Systems

Encoders convert mechanical motion into electrical signals that can be read by a control device such as a PLC (Programmable Logic Controller) or counter. These signals provide real-time feedback on key parameters, including:

• Position

• Speed

• Direction

• Count or rotation

This feedback allows the control system to make decisions and send commands that drive precise movement—for example, stopping a conveyor at a specific location or adjusting motor speed based on load.

Encoders use different types of technologies to create a signal, including: mechanical, magnetic, resistive and optical – optical being the most common. In optical sensing, the encoder provides feedback based on the interruption of light.

The graphic outlines the basic construction of an incremental rotary encoder using optical technology. A beam of light emitted from an LED passes through the Code Disk, which is patterned with opaque lines (much like the spokes on a bike wheel). As the encoder shaft rotates, the light beam from the LED is interrupted by the opaque lines on the Code Disk before being picked up by the Photodetector Assembly. This produces a pulse signal: light = on; no light = off. The signal is sent to the counter or controller, which will then send the signal to produce the desired function.

What's the difference between absolute and incremental encoders?

Both incremental and absolute rotary encoders are electromechanical devices that provide motion feedback about a rotating shaft. 

Encoders may produce either incremental or absolute signals. Incremental signals do not indicate specific position, only that the position has changed. Absolute encoders, on the other hand, use a different “word” for each position, meaning that an absolute encoder provides both the indication that the position has changed and an indication of the absolute position of the encoder.

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