A Precision Intervalometer for the Remote Acquisition of Ultrasonic Data

An automated intervalometer has been developed which utilizes a signal processing technique which does not depend on the first arrival of the pulse, but generates a cursor from a cross- over feature. The generated cursor gates a high-precision counter which measures and displays the delay and sends BCD data to a microcomputer data acquisition system. The insensitivity of this system to amplitude variations makes it possible to obtain differential time accuracies in the nanosecond range over a 70 db range of signal amplitudes in unattended operation, depending on noise levels and the degree of averaging. The high accuracy with which the ultrasonic velocity can be determined makes it possible to observe small changes in material properties. This technique should have wide application in the evaluation of concrete and steel.