Practical Investigation of an Acoustic Encoder

Abstract

In this work a trial has been made to explore the possibility of designing an acoustic speed encoder. In order to realize that a virtual open-end circular air tube was utilized to create a standing wave with a given frequency between an acoustic transmitter and acoustic receiver. A light disk with a finite number of equally spaced apertures is fixed on the rotating shaft of the motor and rotates between the acoustic transmitter and the receiver and periodically chops the standing wave. The chopped signal is acquired by the PC sound card and processed with Lab view signal processing tool. Experiments show acceptable results for common industrial applications, with a maximum percentage error of 3 % compared with a reference, custom designed PLC-based optical encoder.