Encoder is a sensor class, mainly used to detect mechanical movement speed, position, angle, distance, or counting, in addition to applications in industrial machinery, many of the motor control servo motors, BLDC motors need to be equipped with encoders for motor controllers as a phase change, speed and position of the detection, so the scope of application is quite wide.
According to the detection principle, encoders can be divided into optical, magnetic, inductive, and capacitive. According to its scale method and signal output form, divided into the incremental encoder and absolute encoder. Optical encoder is the use of the grating diffraction principle to realize the displacement digital conversion, from the '50s began to be used in machine tools and computing instruments, because of its simple structure, high metrological accuracy, long service life, and other advantages, at home and abroad to be attached importance to and promote, in precision positioning, speed, length, acceleration, vibration and other aspects of a wide range of applications.
Contact encoder ---- adopts brush output, the brush contacts the conductive area or insulating area to indicate whether the state of the code is "1" or "0".
Non-contact encoder ---- accepts the sensitive element as a light-sensitive element or magnetic element, the use of light-sensitive element with light-transparent and light-impermeable area to indicate the state of the code is "1" or "0".
The incremental encoder ---- converts the displacement into a periodic electrical signal, which is then converted into counting pulses, and the number of pulses indicates the size of the displacement. When the rotary axis rotates, there is a corresponding pulse output, and its counting starting point is set arbitrarily; so that unlimited accumulation and measurement of multiple turns can be realized.
Absolute encoders ---- are sensors that output digital quantities directly and are commonly used in motor positioning or speed measurement systems. Since each of its angular positions corresponds to a unique digital code, its indicated value is only related to the start and end positions of the measurement, not to the intermediate process of the measurement.
The rotary incremental encoder ---- outputs pulse when it rotates and its position is known through the counting device, which relies on the internal memory of the counting device to remember the position when the encoder is not moving or when there is a power failure.
Multi-turn absolute encoder ---- uses the principle of the clock and watch gear machinery, when the center code disk rotates, through the gear drive another set of code disks (or multiple sets of gears, multiple sets of code disks), on the basis of a single-turn encoding and then increase the number of turns of encoding, in order to expand the measurement range of the encoder, the code is determined by the mechanical position, and the code is unique and not repeated in each position, without the need for memory.