Analyze the characteristics and applications of various rotary encoders2021

There are many types of rotary encoders. According to the materials and principles, there are photoelectric encoders, magnetic encoders, incremental encoders, and absolute encoders. When choosing a rotary encoder, we should make the correct one according to our own needs. s Choice.

Do customers choose to use a photoelectric encoder or a magnetic encoder? Some of the most important characteristics of the encoder should first be considered. In addition to successfully implementing professional applications, customers and friends should also consider whether to choose an incremental encoder or an absolute encoder? Even if the same sensing mechanism is used, the performance of the two rotary encoders is quite different. In order to achieve a successful application system, the customer should understand all the characteristics of the two encoders and make the right choice. Incremental encoders need to use additional electronic equipment for pulse counting, pulse and data conversion to achieve speed or motion data, and absolute encoders can generate digital signals to identify absolute positions. All in all, simple applications of incremental encoders are usually more suitable for low performance, while absolute encoders are the best choice for critical applications-these complex applications with higher speed and position control requirements. The output type depends on the specific application. When a mobile incremental encoder, the encoder is proportional to the shaft speed (rotary encoder) or moving distance (linear encoder) to generate a binary pulse stream. The optical encoder placed between the LED light source and a specific style of light sensor or linear encoder replaces the generated analog signal with an alternative to conduct or block the beam; then an additional circuit (usually onboard ASIC) converts the analog signal into a square wave . Magnetoelectric encoders can be operated with various mechanisms, but it rotates the magnetic field, causing voltage pulses or resistance changes, which can be converted into pulses. The biggest disadvantage of an incremental encoder is that when the system is powered down (for example, temporarily power off), it will not track any incremental changes in the encoder output. Therefore, in order to provide accurate position data, the incremental encoder must return to the initial position when starting. For applications such as conveyors that are closed every night and restarted every morning, the return of the incremental encoder to the initial position will not affect the application. However, in the application of automobile assembly manipulator, if the welding seat is powered off, the incremental encoder returns to the initial position, which will seriously damage the product and the manipulator. Absolute encoders are ideal for high-reliability applications. For incremental encoders, absolute encoders do not output pulses, but output digital signals to indicate the position of the encoder, and the position of the encoder is the static absolute coordinate of the reference point. Therefore, when the power is cut off, the absolute encoder can still maintain its absolute position record. After restarting, the system can resume movement immediately without returning to the initial position. As mentioned above, absolute encoders are used in critical safety issues, and returning to the initial position of the encoder is not allowed, such as CNC machine tools with high performance. In addition, this kind of encoder or returning to the original position will greatly increase the ideal application time or application cost. For example, when the power is cut off for DNA sequencing for multiple days, the system needs to be restarted reliably without damaging the results of carefully cultured samples or affecting the analysis. .