Types and Applications of Rotary Encoders: Magnetic and Optical

What is a rotary encoder?

A rotary encoder is a sensor that converts rotary motion into an electrical signal. This signal can be digital or analog and is used to determine the position, speed or direction of rotation. There are two main types of rotary encoders, differing in measurement technology: magnetic and optical.

Optical encoders

How do optical encoders work?

Optical encoders operate on the principle of measuring changes in light passing through the encoder disc. This disc contains a pattern in the form of transparent and opaque areas through which light from the LED passes. The light-receiving sensor generates a signal that is then converted into electrical pulses corresponding to the angular position of the shaft.

Types of optical encoders

Optical encoders are divided into:

1. Incremental encoders – generate pulses that determine the change in the position of the shaft. The advantage is the simplicity of the design and lower cost, but in the event of a power loss, the position of the shaft is lost.

2. Absolute encoders – each shaft position has a unique binary code, which allows information about the position to be retained after the power is disconnected.

Applications of optical encoders

Optical encoders are characterized by high precision, which makes them used in applications requiring accurate measurement, such as:

• Robotics – control of the position and movement of robot arms,

• Industrial automation – precise monitoring of speed in drives and production belts,

• CNC machines – control of the position of tools.

Magnetic encoders

How do magnetic encoders work?

Magnetic encoders use magnets and Hall effect sensors to determine the shaft position. There is a magnet on the encoder shaft that creates a magnetic field, which is read by the sensor. Changes in the magnetic field are converted into an electrical signal that provides information about the angular position.

Types of magnetic encoders

Similarly to optical encoders, we distinguish magnetic encoders:

1. Incremental - they measure changes in position by generating pulses.

2. Absolute - each shaft position has a unique value, which eliminates the need to zero after disconnecting the power supply.

Applications of magnetic encoders

Magnetic encoders are more resistant to dust, vibration and moisture, making them suitable for harsh conditions. They are used in:

• Automotive industry - monitoring the position of pedals, steering wheel and shafts,

• Construction machinery - controlling the position of arms and working elements,

• Renewable energy - systems monitoring the rotational speed of wind turbines.

Summary: Which encoder to choose?

The choice between an optical or magnetic encoder depends on the specific requirements of the application:

• Optical encoders are the ideal choice where high precision and a clean working environment are required.

• Magnetic encoders are suitable for harsh environments where resistance to external factors is key.

Rotary encoders, both optical and magnetic, are an essential element of modern automation and robotics systems. Thanks to their versatility, they are used in many industries, providing reliable measurement of position and speed.