Rotary Encoder Types Explained

A rotary encoder is a precision device that converts the angular position of a rotating shaft into an electrical signal. It plays a crucial role in numerous industries, including metal, automation, manufacturing, robotics, and aerospace, by providing real-time data on position, speed, and direction. Modern motion control systems would lack the feedback necessary for accuracy without rotary encoders. Rotary encoders are designed to deliver detailed movement information to control systems. This helps machines execute tasks with greater precision and repeatability. These devices ensure smooth operations from conveyor belts in factories to robotic joints. They form a foundational element in closed-loop feedback systems, improving safety and performance.

What is a Rotary Encoder

A rotary encoder is an electromechanical sensor that tracks the rotation of a shaft and converts it into digital or analog signals. It translates rotary motion into real-time position or movement data that machines can understand and respond to. Rotary encoders can measure rotation continuously or in defined steps, depending on their type. They often work alongside controllers or PLCs to fine-tune motor behavior. They ensure accurate, consistent performance in industrial automation or consumer electronics. These encoders may be contactless or mechanical, and the signal generated depends on the internal sensing mechanism. They are typically installed at motor shafts, drive rollers, or rotating platforms to ensure real-time feedback during operation.

Types of Rotary Encoder

Rotary encoders are broadly categorized based on two primary parameters. These are: Output Type – Which output does the encoder provide (absolute or incremental). Sensing Technology – The method of detecting shaft rotation (optical or magnetic). Understanding these classifications helps engineers and designers select the right rotary encoder for their application, depending on factors like accuracy, cost, environment, and complexity.

Based on Output Type

1. Absolute Encoder

An absolute encoder provides a unique digital code for each shaft position. The output reflects the exact angular location at any given moment. Even if the system loses power, the encoder retains the position, allowing seamless operation without reinitialization. Absolute encoders work using a disk divided into sectors, each marked with a binary or Gray code. As the disk rotates, sensors read these patterns and output a position value. Some advanced absolute encoders use multi-turn mechanisms that track multiple revolutions. These encoders are highly valuable in applications that require fault tolerance and zero recalibration, such as Roller positioning in Rolling Mills, robotic arms, and automated cranes. Their ability to instantly provide position feedback improves safety and system readiness. There are two main subtypes: Single-turn Absolute Encoder: Measures position within one complete revolution of the shaft. Multi-turn Absolute Encoder: Measures the position of multiple rotations of the shaft.

2. Incremental Encoder

An incremental encoder generates pulses as the shaft rotates. These pulses represent movement rather than absolute position. Systems using incremental encoders require a reference or “homing” process after startup, as no position data is retained when power is lost. The encoder disc typically has evenly spaced lines or slots. As the encoder turns, a light or magnetic sensor detects transitions between transparent and opaque areas, generating pulses. These are counted and processed to determine speed, and direction. Incremental encoders are favored for their simplicity and cost-efficiency. They are commonly found in applications like CNC machines, elevators, printers, and basic motor feedback loops. Despite needing external counters or controllers, they offer high resolution and fast response times.

Based on Technology

Optical Rotary Encoder

An optical rotary encoder operates using a disk with transparent and opaque segments. A light source, usually an LED, shines through the disk, and a photodetector senses the presence or absence of light. The pattern on the disk corresponds to shaft position, creating precise digital output signals. Optical encoders offer excellent resolution and accuracy, making them ideal for applications requiring fine control. However, they are sensitive to dust, vibration, and moisture, which can interfere with the light path and affect reliability. Protective housings are often used in industrial settings to prevent contamination. These encoders are available in both absolute and incremental configurations. Due to their high precision, they are used in the metal industry, robotics, aerospace instruments, automated test equipment, and scientific measuring devices. Optical encoders also support high-speed operations due to their fast signal response.

One drawback is their relative fragility compared to other types. Since they rely on optical clarity, any misalignment or obstruction can lead to errors in output. Therefore, they are best used in clean or controlled environments.

Magnetic Rotary Encoder

A magnetic rotary encoder uses magnetic fields to determine position. It typically involves a rotating pulse disc or pulse wheel attached to the shaft and a stationary magnetic sensor, scanning Head (often a Hall-effect sensor) to detect changes in magnetic flux. The signal output is interpreted as rotational position or movement. Unlike optical encoders, magnetic encoders are not affected by dust, oil, or vibration, making them ideal for rugged environments. They are often coated with carbon fibre, vulcanization, or special stainless steel against harsh conditions and require less maintenance over time. Magnetic encoders are available as both absolute and incremental types. They are widely used in the metal industry, automotive steering systems, motor drives, factory automation, and outdoor robotics. These encoders can operate in high-temperature zones and resist shocks and mechanical wear. Although magnetic encoders generally offer slightly lower resolution compared to optical ones, they make up for it with durability and reliability. Their use in demanding industrial conditions is skyrocketing due to improved sensor designs and processing algorithms.

Summary

Rotary encoders are critical for systems that require accurate motion control, feedback, and position tracking. With multiple configurations and technologies available, they can be tailored to suit various needs, from simple motor feedback to advanced robotic systems. Choosing the correct type depends on whether absolute or incremental output is needed, and whether optical or magnetic technology is more appropriate for the environment. Speed, resolution, and environmental conditions also influence the decision. When selecting a rotary encoder, it is vital to assess the operating conditions, desired accuracy, and system compatibility. Understanding the difference between encoder types helps avoid system errors, reduces maintenance, and improves performance across automation projects.

Why Choose Manglam Electricals?

Manglam Electricals offers a wide range of high-quality rotary encoders for industrial and automation applications. Their products are built with precision and durability in mind. Whether you require an absolute encoder, incremental encoder, or shaft encoder, Manglam Electricals provides solutions that meet demanding technical standards. Their rotary encoders are tested rigorously for performance and long-term reliability. They offer both optical encoder and magnetic encoder models, which are suitable for different industrial environments. With responsive support and robust inventory, Manglam Electricals is a trusted name in motion sensing solutions.