Method and apparatus for measuring true discontinuities in members of varying thickness by compensating for the effect of thickness on such measurements

Claim 1

IN APPARATUS RESPONSIVE TO THE TRUE MAGNITUDE OF DISCONTINUITIES IN MEMBERS BEING INSPECTED, THE COMBINATION OF MEANS FOR ESTABLISHING IN SAID MEMBER FIXED INSPECTION CONDITIONS, FIRST MEANS FOR MAGNETICALLY INSPECTING A SELECTED PORTION OF SAID MEMBER TO PROVIDE A DETECTED FIRST SIGNAL WHICH IS A FUNCTION OF THE MAGNITUDE OF DISCONTINUITIES IN SAID PORTION BEING INSPECTED, AND WHICH IS UNAVOIDABLY ALSO A FUNCTION OF THE THICKNESS OF SAID PORTION BEING INSPECTED; SECOND MEANS FOR MEASURING THE THICKNESS OF SAID PORTION BEING INSPECTED BY SAID FIRST MEANS TO PROVIDE A SECOND SIGNAL, SAID SECOND SIGNAL BEING A FUNCTION OF SAID THICKNESS; AND CIRCUIT MEANS RESPONSIVE TO SAID FIRST AND SECOND SIGNALS TO PROVIDE AN INDICATION IN ACCORDANCE WITH THE TRUE DISCONTINUITY MAGNITUDE, SAID CIRCUIT MEANS BEING OPERATIVE TO UTILIZE SAID SECOND SIGNAL REPRESENTATIVE OF THICKNESS TO COMPENSATE SAID FIRST SIGNAL FOR THE EFFECT OF THICKNESS TO THEREBY PROVIDE SAID INDICATION OF THICKCORDANCE WITH THE TRUE DISCONTINUITY MAGNITUDE.