Patent ID: 6155117
Filing Date: 2000-12-05
Classification: G01N

Abstract:
A method for detecting the location of an edge of a workpiece, comprising:positioning electromagnetic acoustic transducer (EMAT) sensor means at a known location adjacent the workpiece, using the EMAT sensor means to generate an ultrasonic wave along a surface of the workpiece toward the edge, and detecting a reflected ultrasonic wave from the edge;measuring a round trip time-of-flight (TOF) of the ultrasonic wave to propagate from the EMAT sensor means to the edge, be reflected from the edge, and propagate back to the EMAT sensor means; andknowing a velocity of the ultrasonic wave in the workpiece, calculating the distance from the EMAT sensor means to the edge using the TOF and the velocity to determine the location of the edge on the workpiece as a function of the known location of the EMAT sensor means.