Evaluating circuit for incremental shaft encoders

摘要

Incremental shaft encoders convert rotational movements into digital electrical signals. For this purpose, a pulse disc which carries a light/dark division is mounted on the transmitter shaft. This data track is scanned by means of photodetectors. The signals are electronically conditioned to form squarewave pulses. Counting of the pulses provides the magnitude of the angle of rotation. The pulse disc also exhibits one defined mark per revolution (zero pulse) which is used as reference point for the angle measurement. To correlate the zero pulse accurately with a particular pulse on the data track both at low and at high rotational speeds, it is proposed to convert the zero pulse by means of a set/reset circuit. This only requires two flip flops, these being set and reset, respectively, by a pulse of the data track. <IMAGE>