With the advancement of science and technology, the automation level of control systems is increasingly high, and the precision requirements for detection components are also rising. As a sensor for detecting mechanical movement, an encoder can not only detect rotational speed but also measure distance, position, angular displacement, and count. As a "multi-functional" detection component, encoders have been widely used in transmission control systems. ### How Many Types of Encoders Are There? An encoder is a sensor that converts the linear displacement or rotational angle of mechanical equipment into electrical signals. According to different detection methods, it can be divided into linear and rotary types. Among them, rotary encoders can be divided into incremental encoders and absolute encoders based on different signal principles. An incremental encoder converts displacement into periodic electrical signals, which are then converted into counting pulses, with the number of pulses indicating the magnitude of displacement. Each position of an absolute encoder corresponds to a unique digital code. 1. Classification by the engraving method of the code disc: (There are many classification methods for encoders now; only the commonly used ones are mentioned here) (1) **Absolute encoder**: Its circular code disc has several concentric code tracks along the radial direction. Each track consists of alternating light-transmitting and light-opaque sectors. The number of sectors in adjacent code tracks is in a double relationship. The number of code tracks on the code disc equals the number of bits of its binary code. On one side of the code disc is a light source, and on the other side, there is a photosensitive element corresponding to each code track. When the code disc is in different positions, each photosensitive element converts into a corresponding level signal based on whether it is illuminated, forming a binary number. (2) **Principle of incremental encoder**: The rotating shaft emits a pulse signal after rotating a specified unit angle (some emit sine signals, which are then subdivided to generate higher pulses). It usually has three-phase outputs: A, B, and C. Phases A and B are pulse outputs with a mutual delay of 4 cycles, and the direction of rotation can be determined based on the delay relationship. By using the rising and falling edges of phases A and B, 2x or 4x frequency multiplication processing can be performed. Phase Z is a single-circle pulse, i.e., one pulse is emitted per circle. 2. Classification by the mechanical installation form of the encoder: (1) **Shafted type**: It can be further divided into clamping flange type, synchronous flange type, servo mounting type, etc. (2) **Hollow shaft type**: It can be further divided into semi-hollow type, fully hollow type, large-caliber type, etc. 3. Application scenarios of encoders: Encoders are mainly used in CNC machine tools and mechanical accessories, robots, automatic assembly machines, automatic production lines, elevators, textile machinery, sewing machinery, packaging machinery (for length fixing), printing machinery (for synchronization), woodworking machinery, plastic machinery (for quantity fixing), rubber and plastic machinery, plotters, goniometers,疗养 equipment, radars, etc. ### Detailed Explanation of Encoder Models A: "RE" is the general code for encoders. The prefix varies according to manufacturers' naming rules; for example, "RE" used by Linji is derived from the initials of "rotary encoder". B: Key dimension of the appearance: "11" indicates that the dimension of a certain surface is approximately 11mm. C: "03" refers to a thin base with a switch; other examples include "00" (thick base without a switch) and "01" (thick base with a switch). D: Code for the shape of the shaft sleeve: "I" represents a 3.5mm length non-threaded shaft sleeve; other specifications include 7mm, 5mm, 10mm, with or without threads, etc. E: Bracket code: "C" bracket indicates a plug-in installation method, with a bracket foot width of 2.0mm and a total span of 13.2mm; other types include those with a width of 2.5mm, a span of 12.9mm, and SMD bracket feet. F: Indicates whether the bottom cover has positioning posts: "1" means no posts; "2" means two positioning posts; "3" means two large positioning posts, etc. G: Terminal pin type: "H01" represents vertical plug-in pins; other parameters include "V01" and others related to the number, shape, and span of terminal pins. H: Internal serial number: The information is indicated in the brackets following it. I: Number of pulses: Represents the pulse information of the product. Different types of encoders have different pulse counts, such as 9, 12, 15, 20, 24 pulses, etc. J: Direction of pulse output: Indicates whether pulses are output via forward or reverse rotation; "P" represents clockwise rotation, and "T" represents counterclockwise rotation. K: Number of positioning points: Represents the number of positioning points (i.e., gear feel) per rotation. The number of positioning points and pulses must be in a 1:1 or 2:1 ratio. L: Shape of the shaft core: "A" represents a D-shaped half-shaft; "K" represents a plum blossom-toothed knurled shaft, etc. M: Material of the shaft core: "A" represents aluminum alloy; "B" represents zinc alloy; "C" represents copper; "D" represents stainless steel; "L" represents plastic, etc. N: "15" indicates the actual installation height, i.e., the height from the PCB to the top. O: "F" indicates the opening direction of the shaft core, which generally only applies to A-shaft D-shaped half-shafts. P: "7" indicates the length of the operating part of the shaft core; "N" and "Q" can be selected according to specific actual requirements. **Note**: Encoder model codes usually consist of a string of letters and numbers. Different manufacturers may adopt different coding methods. To identify the encoder model, check the marking or label on the encoder itself, which is usually found near the housing or bottom. In addition, you can refer to the encoder's product manual or specification sheet, which details the model, specifications, and characteristics. If you have further questions, contact the encoder manufacturer or supplier, who can provide more detailed information and assistance. ### Encoder Selection The selection of encoders for converter systems should consider the following parameters: - **Encoder type**: Incremental encoders are generally used for closed-loop control with frequency converters, while absolute encoders are used for measuring displacement distance. A single-turn absolute encoder is selected for the converter tilting angle, and a multi-turn absolute encoder is selected for the oxygen lance height due to its wide measurement range. - **Output signal type**: Encoders have output forms such as open-collector output, voltage output, line driver output, and push-pull output. They also have bus interfaces like Profinet and Profibus for connection to PLC networks. Encoder polarities include unipolar and bipolar; bipolar signals are connected to A+A- and B+B-. Bipolar uses shielded twisted-pair cables, with better anti-interference ability and longer transmission distance than unipolar. The incremental encoder in the converter system uses a push-pull output interface with bipolar differential output signals, and the absolute encoder uses a Profibus-DP bus interface. - **Signal voltage level**: Encoders have voltage levels such as DC24V, DC12V, and DC5V. The converter system uses DC24V because it has strong anti-interference ability, long transmission distance, and easy access to power. - **Maximum output frequency**: Confirm parameters such as maximum output frequency, resolution, and number of bits according to the application scenario and process requirements of the encoder. The converter incremental encoder is selected with 1024 PR per circle, and the multi-turn absolute encoder is selected with 8192 circles. - **Installation method and external dimensions**: Consider requirements such as installation space, mechanical strength, appearance specifications, and mechanical life. The converter system uses flexible couplings to solve the eccentricity problem in connection. In summary, selecting a suitable encoder model requires comprehensive consideration of factors such as resolution, precision, output signal type, power requirements, installation method, protection level, interface type, and special functions. By understanding these specifications, you can better select an encoder model suitable for your application. Article sources: Kaidi, Science and Technology Innovation, Wangcai Motor and Electronic Control