Sending and receiving one somatotype non-contact ultrasonic toransujiyu - sa

摘要

PURPOSE:To realize a small and light transmission-reception integrated type non-contact ultrasonic transducer requiring neither magnet nor electromagnet, by combining a bias-free EMAT (electromagnetic-acoustic transducer) and an ESAT (electro-static- acoustic transducer). CONSTITUTION:A coil 2 is provided on an end face of a bakelite cylinder 1 and a conductive cylinder 3 is provided inscribing the inside of the cylinder 1. A bakelite column with flat electrodes 5 and 5' for ESAT on the end face thereof is provided inside the cylinder 3. To form the flat electrodes 5 and 5', a disc made of PbTiO3 6 yet to be polarized as ferrodielectric material is divided in two and silver is sputtered on the top surfaces thereof. When a large current (I) flows through the coil 2, an induced eddy current runs over the surface of an object to be inspected and with interaction thereof, a longitudinal ultrasonic wave with the frequency doubling the large current I is excited in the metal object being inspected. When a DC bias voltage of + or - hundreds of V is applied to the ESAT electrodes 5 and 5' for reception, an electric charge equivalent to Q=CV is generated between the electrodes and the metal object being inspected. As a longitudinal ultrasonic wave arrives, an electrostatic capacitance varies between the electrodes and the metal object being inspected to generate a high frequency voltage.