ULTRASONIC MEASUREMENT WITHOUT COUPLING LIQUID.

If the test object itself is part of the ultrasonic transducer, the otherwise customary coupling liquid can be dispensed with in the ultrasonic measurement of wall thicknesses. A measuring instrument developed for checking the wall thicknesses (3 to 30 mm) of steel pipes with outside diameters of 25 to 180 mm operates on the basis of this electrodynamic ultrasonic transduction. Both lamination defects and local changes in wall thickness can be detected.