Abstract: An array of ultrasonic transducer (A) are disposed along a circular arc for examining tubular objects moving therethrough. A calibrating apparatus (B) includes a calibrating cylinder (22) having a plurality of calibrating flaws (24, 26) therein. A rotary positioning device (30) and an axial positioning device (40) adjust the relative spatial relationship of each calibration flaw and transducer. An ultrasonic control instrument (50) produces an echo signal having components corresponding to echoes received from the examined object. A computer (60) includes a gate adjustment control subroutine (66) which selectively separates a preselected component from the echo signal. A pulse amplitude measurement subroutine (64) measures the amplitude of the preselected echo signal component and, first, determines the peak amplitude of the component and, second, compares the amplitude of the component with a preselected standard.

Abstract: A first array (A) of ultrasonic transducers transmits ultrasonic shear waves circumferentially around an examined cylindrical object (110). A second array (B) transmits ultrasonic shear waves axially along the examined object. Triggering pulses from a triggering amplifier (22) are switched by a multiplexer (24) to each individual transducer of the first and second arrays. As one of the transducers assumes the role of a transmitting transducer and transmits an ultrasonic wave, the other transducers of the first and second arrays assume a receiving mode to receive reflected ultrasonic components. A wave travel timer (26) measures the duration for an ultrasonic wave to be transmitted from the transmitting transducer to a defect and for a reflected component to propagate from the defect to the receiving transducer.