Features: The rotary encoders can count the output pulse times by rotating positively and negatively. This counting method have no limitations, can be resets and return to the initial state if it matching the encoders key (will count from 0) Working principle: Incremental encoders is a type of rotating sensors that transforms the rotation displacement into digital pulses signal. These pulses is used to control angulars displacement. In the encoders, the angulars displacement transformation adopts the principle of photoelectric scanning. The reading system is base on the rotation of the radials dividing plate of the alternative light window and the lightfree window, and will be exposed to light source at the same time. The light will reflect the images of plates on the surfaces of the receiver. The receiver is covered by a diffraction grid and have the same window width as plate. The function of the receiver is to detect the rotation change of the light plate and then transform the light change into electrical change. Increase the low level signal to high level and generate a square pulse without any interferences. This process requires a circuit to solve it. The reading system generally adopts a method, that is, it compares two different signal that have the same waveforms but the phase difference is 180 degrees to improve the quality and stability of the output signal. The reading is formed base on the difference between two signal, thus eliminating interferences. Specifications: Component:Plastic Size:Approx.23.4x23.4mm/0.92x0.92inch Option Type:1pc,3pcs; Operating voltages:5V Number of pulse a circle:20 Package Includes: Package A 1pc Rotary encoders Module Package B 3pcs Rotary encoders Module note: Please allow 1-10mm errors due to manual measurement. Due to the differences between different monitors, the picture may not reflect the actual item color.