Encoder Function And Classification
An encoder is a device that compiles or converts a signal or data into a form that can be used for communication, transmission, and storage. The encoder converts an angular displacement or a linear displacement into an electrical signal, the former being called a code wheel and the latter being called a code ruler. According to the readout mode, the encoder can be divided into contact type and non-contact type; according to the working principle, the encoder can be divided into two types: incremental type and absolute type. The incremental encoder converts the displacement into a periodic electrical signal, which is then converted into a counting pulse, and the number of pulses is used to represent the magnitude of the displacement. Each position of the absolute encoder corresponds to a certain digital code, so its indication is only related to the start and end positions of the measurement, regardless of the intermediate process of the measurement.
First, the classification of the encoder
According to the detection principle, the encoder can be divided into optical, magnetic, inductive and capacitive. According to its calibration method and signal output form, it can be divided into three types: incremental, absolute and hybrid.
1.1 Incremental encoder The incremental encoder directly outputs three sets of square wave pulse A, B and Z phases by photoelectric conversion principle; the phase difference between A and B pulses is 90 degrees, so that the rotation direction can be easily determined. The Z phase is one pulse per revolution and is used for reference point positioning. Its advantage is that the principle structure is simple, the average mechanical life can be more than tens of thousands of hours, the anti-interference ability is strong, the reliability is high, and it is suitable for long-distance transmission. The disadvantage is that the position information of the shaft rotation cannot be output.
1.2. Absolute encoder The absolute encoder is a direct output digital sensor. There are several concentric discs in the radial direction of its circular encoder. Each lane has a transparent and opaque sector. The sector tree of the adjacent code channel is doubled, and the number of code channels on the code disc is the number of digits of its binary digit. On one side of the disc is a light source, and the other side has a photosensitive element corresponding to each code channel. When the disk is in different positions, each photosensitive element converts a corresponding level signal according to whether it is illuminated or not, and forms a binary number. The feature of this type of encoder is that it does not require a counter, and a fixed digital code corresponding to the position can be read at any position of the rotary shaft. Obviously, do you have to say N? At present, there are 16 absolute encoder products in China.
1.3. Hybrid absolute encoder Hybrid absolute encoder, which outputs two sets of information, one set of information is used to detect the magnetic pole position with information function; the other set is completely the same as the output information of the incremental encoder.