Accurate distance amplitude compensation

In a system for ultrasonic pulse echo testing having means for applying ultrasonic pulses to a workpiece, transducer means for converting ultrasonic pulse echoes reflected from said workpiece into reflected electrical pulses, a receiver for receiving said reflected electrical pulses, and means for displaying electrical signals, the improvement comprising:

• means for generating a voltage function having a characteristic curve which is adjusted to conform to the amplitudes of electrical pulses corresponding to ultrasonic pulse echoes reflected from equal sized discontinuities at varying depths within a testpiece;
• control signal generator means for receiving and modifying said voltage function, in accordance with a predetermined relationship, into a control signal having a value which, when applied to said receiver, will vary the gain of said receiver to attenuate and substantially equalize reflected electrical pulses representative of pulse echoes returned from equal sized discontinuities in said testpiece;
• and
• means for selectively applying said control signal to said receiver for varying the gain of said receiver, whereby the attenuated amplitudes of reflected electrical pulses representative of pulse echoes from workpiece subsequently tested are proportional to the size of corresponding reflecting discontinuities within said workpieces, and are substantially independent of the depth of said discontinuities within said workpieces.

A method of ultrasonic pulse echo testing of workpieces for discontinuities using a system including means for applying ultrasonic pulses to said workpieces, means for transducing pulse echoes reflected from said discontinuities into electrical pulses, and a receiver for receiving said electrical pulses,

• the steps of said method comprising:
• applying ultrasonic pulses to a testpiece having a plurality of equal sized discontinuities defined at various depths therein;
• generating a voltage function which is adjusted to conform to the amplitudes of electrical pulses corresponding to ultrasonic pulse echoes from said equal sized discontinuities within said testpiece;
• modifying said voltage function, in accordance with a predetermined relationship, into a control signal of a value which, when applied to said receiver, will vary the gain of said receiver to attenuate and equalize said electrical pulses at a predetermined value;
• and
• applying said control signal to said receiver to vary the gain of said receiver, whereby the amplitudes of electrical pulses corresponding to discontinuities within workpieces being tested are a function of the size of said discontinuities, and are substantially independent of the depth of said discontinuities within said workpieces.