ELECTROMAGNETIC ULTRASONIC MEASURING INSTRUMENT

摘要

PURPOSE:To measure the wall thickness and thickness of a tubular body whose sectional shape is not round with high precision by arranging a doughnut-shaped good conductor disk rotatably between opposite magnetic poles of an iron core so that a steel pipe is surrounded. CONSTITUTION:Ring-shaped bearings 47 and 48 are fitted to magnetic pole parts of the iron core 13 and gears 45 and 46 made of doughnut-shaped good conductors are fitted thereto rotatably. A transmitting and receiving coil 11 is arranged between the gears 45 and 46 radially to the steel pipe 1 while suspended on the iron core. While coils 14 and 15 are excited to generate magnetic flux, the gears 45 and 46 are rotated at a high speed to flow an eddy current to surfaces of the gears 45 and 46, and the main magnetic flux between main magnetic poles N and S is repelled to nearby the surface of the steel pipe 1 through the operation of the secondary magnetic field established with the eddy current, thereby converging the magnetic flux. Consequently, the wall thickness and thickness of the steel pipe 1 are measured precisely in a high magnetic field even if the sectional shape is not round.