The encoder is a signal sensor, which transmits the running state of the motor to the motor controller in real time to realize the motor speed regulation, start and stop. An encoder is a precise measuring device that combines machinery and electronics to encode or convert signals or data for communication, transmission, and storage of signal data. According to different features, the encoder is classfied as follows:
The coded disc and the yardstick: the encoder which converts the linear displacement to the electrical signal is called the yardstick, and the angular displacement is converted to the telecommunication code disc.
The incremental encoder: information such as position, angle, and number of cycles is provided, and the rate of separation is defined in terms of the number of pulses per cycle.
The absolute rotary encoder: position, angle, and number of cycles are provided in angular increment giving a unique encoding.
Hybrid absolute rotary encoder: the hybrid absolute rotary encoder outputs two sets of information: one set of information is used to detect the position of the magnetic pole with absolute information function, and the another group is exactly the same as the output information of the incremental encoder.
The difference between incremental encoder and absolute rotary encoder: the incremental encoder converts the displacement into periodic electrical signals, which are then converted into counting pulses, the number of pluses indicating the magnitude of the displacement. In an absolute rotary encoder, each position corresponds to a certain digital code, representing values related only to the starting and terminating positions of the measurement, but not to the intermediate process of the measurement. When an incremental encoder is used, the position is determined by the number of pluses caculated from the zero mark, while the position of the absolute rotary encoder is determined by the reading of the output code. The output code reading for each position is uniquen in a lap; therefore, when the power is off, the absolute rotary encoder is not separated from the actual position. If the power is switched on again, the position reading is still current and valid.