Analysis of an ultrasonic spatial locating system

Abstract

Describes and analyses an ultrasonic spatial locating system. Based on the transit time of a shock wave produced by a small electric spark, the position of one or more sparks can be determined with respect to a coordinate system. The coordinate system is formed by 3 linear electret microphones arranged orthogonally which detect the arrival of the wave front. A microcomputer is incorporated for system control and for calculating the spatial coordinates (X, Y, Z) from the measured transit times. In addition, the computer can be used to perform certain calibration and performance checks to maintain proper system operation. An analysis of the system indicates that it is possible to locate points within a cube 50 cm on a side with an accuracy of better than ±0.6 mm. The acoustic transit time and the ringing of the microphone determine how many samples per second may be taken. Data rates of about 100 per second are well within the capabilities of the system.