Ultrasonic wave sonde for subterranean investigation - is applicable in small boreholes giving high quality emission and detection

摘要

A sonde for ultrasonic detection which can be raised and lowered in a verticla pit shaft has an elongated housing presenting a longitudinal axis. Inside the housing there is an assembly for emitting and an assembly for receiving acoustic waves. The active parts of both the emitting and the receiving assemblies consist of >=1 washer of piezo-electrical material, the active face of which is perpendicular to the longitudinal axis of the housing, and is aligned to the active face of a mirror for reflecting acoustic waves. Each assembly is formed by a piezo-electrical washer fixed by its active face to a first mass of metal which is fixed in its turn to the housing of the sonde. The mirror is fixed to the first mass of metal, and a second mass of metal is fixed to the non-active face of the washer. The sonde is used in boreholes of small dia. and is designed to emit waves with a frequency of ten to several times ten kHz. A single frequency is emitted and the power can be adjusted by grouping the ceramic piezo-electrical elements under precompression.