Rotary optical encoder sensor has the features of compact size, high accuracy and resolution, no contact loss. One encoder sensor can be used to measure angle displacement and linear position also by the aid of mechanical converting devices.

When the quadrature encoder as a position sensors shaft rotates, there is a corresponding pulse output. The discrimination of the direction of rotation and the increase or decrease of the number of pulses are realized by the rear direction judgment circuit and counter. The starting point of the counting can be setting freely, and the infinite cumulative and measurement of multiple circles can be realized. When the number of pulses is fixed and the resolution needs to be increased, the original pulse number can be multiplied by using two signals of 90° phase difference A and B.