Process and apparatus for activating a time gate in the ultrasonic testing of materials using the impulse-echo system

An apparatus for activating a time gate in an ultrasonic testing device for inspection of a test body utilizing pulse reflection techniques, comprising:

• a first test head for applying ultrasonic pulses originating therefrom to a surface of the test body at normal incidence to said surface and receiving pulses reflected from said surface;
• means for detecting the pulses reflected from said surface relating to said first test head and for evaluating an entry echo from the pulses;
• a second test head for applying ultrasonic pulses originating therefrom into the test body at oblique incidence to said surface and receiving pulses reflected from at least one error in the test body;
• means for firmly connecting the first test head and the second test head and for moving the first test head and the second test head relative to the test body:
• means for controlling the first test head and the second test head to emit pulses cyclically and at given intervals;
• means for detecting the pulses reflected from the at least one error in the test body including the time gate, so that only those pulses reflected from at least one error in the test body are further processed which are in the time gate;
• and
• means for establishing a sliding chronological mean value of the entry echoes of several ultrasonic pulses originating from the first test head and utilizing the sliding chronological mean value obtained in each instance to activate the time gate.