PURPOSE: To make the maximum values of defects of less then the effective width of a probe quantitative by detecting the maximum inclination values of the loci of the ultrasonic echo signals of fixed time intervals.
CONSTITUTION: The detect echo signals corresponding to scanning through a probe 3 from a rolling steel material, etc. T extracted at every fixed time interval in a gate circuit 6 are applied to a signal processing circuit 7 and a differential comparator 8. When the echo height reaches a peak, the circuit 7 generates a timing signal, thereby controlling a peak holding circuit 9. Then, the differences in the echo height peak values at the previous extracting and the extracting of this time corresponding to the inclination of the echo height loci compared in the circuit 8 are held in the circuit 9. The held values are converted to defect lengths in a conversion circuit 10, and the maximum defect length signals are generated from an output circuit 11. With this constitution, the maximum values of the defects below the effective width of the probe are made quantitative, and the maximum lengths of the defects extending to adjacent scanning areas are surely made quantitative.
MIYAWAKI HIROKI
KATOU MASAO
