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An incremental rotary encoder is a type of electromechanical device that converts the angular motion or position of a rotary shaft into analog or digital code that represents that motion or position. It can be used for motor speed and position feedback applications that include a servo control loop and for light- to heavy-duty industrial applications.
An incremental rotary encoder is also known as a quadrature encoder.
An incremental rotary encoder provides great speed and distance feedback. It is simpler than the other type of rotary encoder, the absolute rotary encoder, and features fewer sensors, making it less expensive with fewer points of failure. However, an incremental encoder can only provide motion change information, as it can only provide cyclical outputs when the shaft with the encoder is rotated, so a reference device is required in order to calculate the motion.
The sensor used in an incremental rotary encoder can be either mechanical or optical. The mechanical type requires a process called "debouncing," which is a way to make the output cleaner, smoother and more consistent as opposed to fluctuating or "bouncing." This type of rotary encoder is usually used as a digital potentiometer in some equipment and consumer devices such as the dial of a radio or car stereo or the motion sensor in a ball-type mouse. But because of the mechanical nature of its sensor, the speeds that it can handle are limited. The best feature, however, of the mechanical type is its low cost, and despite having only two sensors, its resolution is not affected at all. There are incremental encoders that have up to 10,000 or more counts per revolution. The optical type of incremental encoders is used for applications that run at higher speeds or that require a higher level of precision.
The two sensors of the incremental encoder allow it to determine the direction of the rotation since the two sensors are 90 degrees out of phase in terms of the generated waveforms (quadrature outputs), so the resulting values in each sensor together determine whether the motion is clockwise or counterclockwise.