2023 Magnetic ring encoders.Encoders are relatively common in motion control products, and rotary encoders are all key components that make up the feedback loop for motion control, including industrial automation equipment and process control, robotics, medical devices, energy, aerospace, and more. As devices that convert mechanical motion into electrical signals, encoders provide engineers with basic data such as position, speed, distance and direction to optimize the performance of the entire system.SourceRare earth magnet-https://www.rare-earthmagnet.com/magnetic-ring-encoders/
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Encoders are measured in two main parts: the moving parts and the static parts. All encoders store position information on the moving parts in different ways, and different storage methods with different reading methods bring about variability in performance and cost: the moving parts of magnetic encoders are magnetic substances, and their carriers can be magnetic materials such as ferrite, neodymium iron boron, samarium cobalt, etc.SourceRare earth magnet-https://www.rare-earthmagnet.com/magnetic-ring-encoders/
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There are three main types of encoders on the market today: optical encoders, magnetic encoders, and capacitive encoders.SourceRare earth magnet-https://www.rare-earthmagnet.com/magnetic-ring-encoders/
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Optical encoders.
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Optical encoders have been a popular choice in the market for motion control applications for many years. It consists of an LED light source (usually infrared) and a photodetector, which is located on each side of the encoder disk. The code plate is made of plastic or glass with a series of light-transmitting and non-light-transmitting lines or slots arranged at intervals. As the disc rotates, the LED light path is blocked by the spaced lines or slots on the disc, resulting in two typical square-wave A and B quadrature pulses that can be used to determine the rotation and speed of the axis.SourceRare earth magnet-https://www.rare-earthmagnet.com/magnetic-ring-encoders/
Despite their wide range of applications, optical encoders have a few drawbacks. In dusty and dirty environments such as industrial applications, contaminants can build up on the code plate and prevent the LED light from being projected to the optical sensor. The reliability and accuracy of optical encoders is greatly affected by the fact that contaminated discs can cause discontinuity or complete loss of the square wave, and LEDs have a limited lifetime and will eventually burn out, leading to encoder failure. In addition, glass or plastic discs are easily damaged by vibration or extreme temperatures, thus limiting the applicability of optical encoders in harsh environment applications; assembling them to motors is not only time consuming, but also poses a greater risk of contamination. Finally, if the optical encoder has a high resolution, it draws more than 100 mA of current, further compromising its use in mobile or battery-powered devices.SourceRare earth magnet-https://www.rare-earthmagnet.com/magnetic-ring-encoders/
Magnetic encoders.
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Magnetic encoders consist of rotating disks with alternating magnetic poles and Hall effect or magnetoresistive sensors that work by detecting changes in the magnetic flux field. Magnetic encoders are robust and can effectively cope with shock and vibration while being unaffected by oil, dirt and moisture. Disadvantages are susceptibility to electromagnetic interference caused by electric motors and a limited operating temperature range. Although several improvements have been made to magnetic encoders, the resolution and accuracy are usually lower than that of optical and capacitive encoders.SourceRare earth magnet-https://www.rare-earthmagnet.com/magnetic-ring-encoders/
A magnetic encoder is similar in construction to an optical encoder, but it utilizes a magnetic field rather than a light beam. Instead of a slotted optical encoder, a magnetic encoder uses a magnetic disk with spaced magnetic poles that rotate on an array of Hall effect sensors or magnetoresistive sensors. Any rotation of the disk causes these sensors to respond, and the resulting signal is transmitted to a signal conditioning front-end circuit to determine the position of the shaft. The advantage of magnetic encoders over optical encoders is that they are more durable, vibration and shock resistant. Furthermore, while optical encoders can lose performance in the presence of contaminants such as dust, dirt and oil, magnetic encoders are unaffected, making them ideal for harsh environment applications. However, electromagnetic interference from motors (especially stepper motors) can have a significant impact on magnetic encoders, and temperature variations can cause position drift. In addition, magnetic encoders have relatively low resolution and accuracy, and in this respect are far inferior to optical and capacitive encoders.SourceRare earth magnet-https://www.rare-earthmagnet.com/magnetic-ring-encoders/
The picture shows our 128-pole magnetic ring encoder.SourceRare earth magnet-https://www.rare-earthmagnet.com/magnetic-ring-encoders/
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Capacitive encoders.
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Capacitive encoders consist of three main parts: the rotor, the fixed transmitter and the fixed receiver. Capacitive sensing uses a strip or line pattern with one pole on the fixed element and the other on the movable element to form a variable capacitor and configured as a receiver/transmitter pair. The rotor is etched with a sinusoidal pattern that generates a special but predictable signal as the motor shaft rotates. This signal is then converted by the encoder's on-board ASIC to calculate the position and direction of rotation of the shaft.SourceRare earth magnet-https://www.rare-earthmagnet.com/magnetic-ring-encoders/
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Comparison of encoder code plates.SourceRare earth magnet-https://www.rare-earthmagnet.com/magnetic-ring-encoders/
Benefits: Capacitive encoders do not suffer from LED burnout, so they tend to last longer than optical encoders. Capacitive encoders have a range of programmable resolutions, while eliminating the need for designers to change encoders every time a new resolution is needed. The digital nature of capacitive encoders also provides key advantages in terms of flexibility and programmability.SourceRare earth magnet-https://www.rare-earthmagnet.com/magnetic-ring-encoders/
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