Composite probe apparatus

摘要

A composite probe apparatus exhibiting a high performance and a high efficiency in detecting internal defects of a steel pipe or a steel plate, coupled with offering a stable sensitivity and covering a wide range for flaw detection. A plurality of reception oscillators PR1 to PR4 are disposed in a zigzag fashion in both sides of a transmission oscillator PT. The length l T of the transmission oscillator PT is determined such that a near sound field is established over the entire measuring range, while the width WT of the transmission oscillator PT is determined such that a far sound field takes place over the entire measuring range. The transmission and reception oscillators are constructed with a common piezoelectric plate an electrode of which undergoes division.