What Is a Rotary Encoder? Complete Guide for Engineers

Rotary encoders are essential components in modern automation, robotics, and motion control systems. But what is a rotary encoder, exactly? Whether you're an engineer designing complex machinery or simply exploring industrial control systems, understanding rotary encoders is crucial for precision motion feedback and positioning accuracy.

In this comprehensive guide, we’ll explore:

• What rotary encoders are and how they work

• Types of rotary encoders: Incremental vs Absolute

• Real-world use cases and industries that rely on them

• Diagrams to help you visualise encoder function

• How to choose the right rotary encoder for your application

🤔 What Is a Rotary Encoder?

A rotary encoder is an electro-mechanical device that converts the angular position or motion of a shaft into a digital or analog signal. It is commonly used in applications requiring precise motion control, such as CNC machinery, robotics, industrial automation, and motor feedback systems.

At its core, a rotary encoder measures rotation, direction, and sometimes position or speed, depending on the encoder type.

🔧 How Does a Rotary Encoder Work?

A rotary encoder typically consists of:

• A rotating disk (optical, magnetic, or mechanical)

• A sensor or reader head

• Signal processing electronics

As the shaft rotates, the disk interrupts or modulates a signal, which is then translated into digital pulses or absolute values.

🖼️ Diagram: Basic Structure of a Rotary Encoder

📊 Types of Rotary Encoders

Rotary encoders come in two main types: Incremental and Absolute. Each has distinct advantages and applications.

🔁 1. Incremental Rotary Encoders

Incremental encoders produce a series of pulses as the shaft rotates. Each pulse represents a movement step. They don’t retain positional data when power is lost—only relative position is tracked.

Key Features:

• Simple and cost-effective

• Outputs pulses (A, B, sometimes Z)

• Direction determined by phase difference

• Requires a homing process after power loss

Common Applications:

• Conveyor belt speed control

• Stepper motor feedback

• 3D printers and hobbyist robotics

Diagram: Incremental Encoder Signal

🔒 2. Absolute Rotary Encoders

Absolute encoders provide a unique digital code for each shaft position. This means the encoder "remembers" its position even after a power cycle—no homing is required.

Key Features:

• High accuracy and reliability

• Outputs unique binary or Gray code

• Supports single-turn and multi-turn tracking

• More complex and expensive

Common Applications:

• Industrial robots

• Medical imaging devices

• Aerospace systems

• Wind turbines and heavy machinery

Diagram: Absolute Encoder Code Disk

🧰 Use Cases: Where Are Rotary Encoders Used?

Rotary encoders are found across numerous industries and machines. Here are some real-world examples:

🚗 Automotive

• Electronic throttle control

• Steering wheel position sensors

• Adaptive headlights

🏭 Industrial Automation

• Robotics arm joints

• Conveyor belt feedback

• Servo motor positioning

🖨️ Office & Consumer Electronics

• Printers (paper feed tracking)

• Digital volume knobs (audio systems)

🧠 Medical Technology

• Surgical robots

• MRI and CT scanner precision controls

🌬️ Renewable Energy

• Wind turbine yaw and pitch control

• Solar tracking systems

🧠 Choosing the Right Rotary Encoder

When selecting a rotary encoder, engineers should consider:

Factor	Incremental Encoder	Absolute Encoder
Cost	Lower	Higher
Position Retention	No	Yes
Signal Output	Pulses	Digital code
Complexity	Simple	Complex
Applications	Speed/direction	Precise position control

Other key specs to consider:

• Resolution (PPR or CPR)

• Output type (TTL, HTL, Analog, etc.)

• Mounting options (shaft, hollow, through bore)

• Environmental protection (IP ratings)

🔍 Need Help Selecting a Rotary Encoder?

At Encoders UK, we specialise in supplying and repairing rotary encoders from all major manufacturers including Heidenhain, Baumer, Hengstler, Sick, TR, and more.

Whether you need help identifying an obsolete part, sourcing a custom encoder, or urgent encoder repair, our team of encoder specialists is here to support you.

👉 Browse Rotary Encoders or Contact Us for expert advice.

✅ Summary: What Is a Rotary Encoder?

To recap:

• A rotary encoder converts shaft rotation into electrical signals.

• Two main types: Incremental (relative) and Absolute (exact).

• Used in automation, robotics, automotive, and energy industries.

• Choosing the right encoder involves understanding your application’s precision and feedback requirements.

Whether you're upgrading your automation system or replacing a legacy encoder, understanding what is a rotary encoder helps ensure reliable and efficient motion control.

Ready to find the perfect encoder solution?Visit Encoders UK — the UK's trusted name in encoder supply and repair.