초록 ▼

A method and apparatus is disclosed for calibrating an ultrasonic inspection system having a plurality of transducers (12a, 12b, 12c) coupled by a common amplifier (16) to a distance-amplitude correction (D-AC) circuit comprised of a multiplying digital-to-analog converter (26′) which receives, as a

A method and apparatus is disclosed for calibrating an ultrasonic inspection system having a plurality of transducers (12a, 12b, 12c) coupled by a common amplifier (16) to a distance-amplitude correction (D-AC) circuit comprised of a multiplying digital-to-analog converter (26′) which receives, as a function of the transit time of an ultrasonic signal measured by a clock counter (34), a D-AC correction stored in a look-up table in a random access memory (24′). The D-AC correction function stored in the look-up table for each transducer is the inverse of a return signal response curve determined by measuring the peak amplitude of return signals from calibration holes at known depths in a test block (10) while in a calibrate mode, i.e., with a switch (SW) in a state to bypass the MDAC. An equation of a curve that best fits the peak measurements is then found by a digital computer (20) and used to determine the values of points along a curve superimposed on the response curve, except at near field where the calibration system is provided with truncation for near-field effects. Inverse values of these points are then stored in the look-up table for use as correction factors applied to the amplitudes of return signals during an inspection mode of operation. In that way, all return signals from flaws of the same size are caused to have the same amplitude regardless of depth, without the need for utilizing tedious and time-consuming manual calibration methods.

대표청구항 ▼

Apparatus for calibrating with a test block having holes at known depths, the sensitivity of an ultrasonic system for nondestructive inspection of structural material so that a flaw produces a return signal of the same amplitude independent of its depth in the material, comprising means for receivin

Apparatus for calibrating with a test block having holes at known depths, the sensitivity of an ultrasonic system for nondestructive inspection of structural material so that a flaw produces a return signal of the same amplitude independent of its depth in the material, comprising means for receiving ultrasonic return signals from said calibration holes in said test block of the material with said system in a calibration mode during which no calibrating correction is applied to ultrasonic return signals, means for storing as a function of transit time peak amplitudes of said return signals returned from said calibration holes separately while in said calibration mode, means for determining the equation of a signal amplitude curve as a function of transit time that best fits said peak amplitudes and known depths of said calibration holes, means for determining a set of values from said equation for a number of evenly spaced points over a predetermined range of depths through said test block, and means for applying the reciprocals of said values to ultrasonic return signals from corresponding depths as correction functions to ultrasonic return signals during nondestructive inspection of the structural material.