Ultrasonic inspection of articles

A method of ultrasonically inspecting an article comprising transmitting a succession of ultrasonic pulses into the article;

• for each transmitted pulse, detecting and registering electrically the reflected pulse from the front surface of the article;
• detecting and registering electrically, with a predetermined gain, any reflected pulses indicative of faults or discontinuities within the article;
• detecting and registering electrically, again with a predetermined gain, at least the first reflected pulse from the rear surface of the article;
• monitoring the amplitudes of the registered reflected pulse from the front surface and at least the first reflected pulse from the rear surface of the article;
• continuously controlling gains for succeeding pulses in dependence on the amplitude of the reflected pulse from the front surface of the article;
• and maintaining the amplitude of the detected and registered reflected pulse from the front surface of the article at a predetermined level by means of an automatic gain control system.

Apparatus for ultrasonically inspecting an article comprising means for transmitting a succession of ultrasonic pulses into the article;

• means for each transmitted pulse, for detecting and registering electrically the reflected pulse from the front surface of the article;
• means for detecting and registering electrically, with a predetermined gain, any reflected pulses indicative of faults or discontinuities within the article;
• means for detecting and registering electrically, again with a predetermined gain, at least the first reflected pulse from the rear surface of the article;
• means for monitoring the amplitudes of the registered reflected pulse from the front surface and at least the first reflected pulse from the rear surface of the article;
• means for continuously controlling gains for succeeding pulses in dependence on the amplitude of the reflected pulse from the front surface of the article;
• and an automatic gain control system for maintaining the amplitude of the detected and registered reflected pulse from the front surface of the article at a predetermined level.