Incremental Encoder of Encoders Understanding the Working Principles and Incremental Encoder of Encoders
Understanding the Working Principles and Incremental Encoder of Encoders
In the field of industrial control on-site, encoders are frequently used. What is an encoder? And how does it work? In today's article, we will discuss the working principles of encoders and delve into the details of incremental encoders.
An encoder is a sensor that converts distance (linear displacement) and angle (angular displacement) into electrical signals and outputs them. Encoders are commonly used in industrial motion control to measure and provide feedback on the position and status of the object being measured, such as machine tools, robots, motor feedback systems, measurement and control devices, etc.
The components of an optical encoder include a connecting shaft, code disk, light source, output circuit, outer shell, and connecting flange, as shown in the diagram below:
The connecting shaft is connected to the code disk and is linked to the object being measured, such as a motor. As the measured object rotates, the code disk also rotates. The rotation of the code disk causes alternating changes in light and darkness. The photosensitive element at the receiving end detects these changes and converts them into electrical signals for output.
Based on the different structures of the code disk, encoders can be further divided into incremental encoders and absolute encoders. In this article, we will mainly discuss incremental encoders.
Incremental encoders have a code disk divided into equally sized alternating light and dark grids. As the code disk rotates, the receiving end detects changes between light and dark, converting them into electrical signal pulses for external output. By counting the pulses, the magnitude of displacement can be determined, as illustrated in the diagram below:
To distinguish between clockwise and counterclockwise rotation and to detect the zero point, the actual code disk used is more complex than shown in the previous diagram. It typically consists of three parts: A phase, B phase, and Z phase. The A phase and B phase have a phase difference of 1/4 cycle (90 degrees), which can be used to differentiate between clockwise and counterclockwise rotation. The Z phase generates a single pulse per revolution, serving as a reference zero position for the encoder, as illustrated in the diagram below:
The output waveform of the incremental encoder is as shown in the following diagram:
Due to the pulse counting method used, incremental encoders must first locate the reference zero position before measurement, making their measurement results relative. Additionally, data from incremental encoders is lost after power outage.
To overcome the drawbacks of incremental encoders, absolute encoders have emerged. We will introduce the relevant knowledge of absolute encoders in the next article.