Ratiometric digital position encoder of potentiometer cursor - uses MOS integrated circuit current sources and counter synchronised to supply waveform

摘要

The encoder has a fixed resistance, from which a reference current is obtained, and a potentiometer in series with a parallel array of current generators. Eahc generator can be switched into circuit with the potentiometer to provide a current which has a predetermined ratio w.r.t that of the other current generators and the reference current. The outputs of the current generators are controlled by the reference current to follow any fluctuations in the latter. An encoder circuit is connected to a switch to successively connect each crrent generator. A differential amplifier determines the sign of the magnitudes of the voltage drops at the terminals of the fixed resistance to give either a stop or start signal to a counting circuit. The output of the encoder is taken from the counting circuit. The system is used in the central of machine tools.