Figure 1.16 shows tile basic form of an incremental เอ็นโคดเดอร์ for the measurement of angular displacement of a shaft. It consists of a disc Figure 1.16 Incremental encoder: which rotates along with the shaft. In the form shown, the rotatable disc angular displacement results in has a number of windows through which a beam of light can pass and be pulses being detected, the number detected by a suitable light sensor.