Electromagnetic gauge (UT)

An electromagnetic ultrasonic gauge uses an EMAT (electromagnetic acoustic transducer) to generate and receive ultrasound directly in the steel through a magnetic field and eddy currents, with no liquid couplant and no contact film between probe and surface. That makes it suited to coated, hot, rough, or moving plate where a conventional piezoelectric thickness probe needs gel coupling. In ship survey it serves rapid hull thickness measurement and corrosion mapping, reading wall thickness through paint and at standoff. The tradeoff is lower signal amplitude than piezoelectric UT, so it favors thickness gauging over fine flaw sizing. It is one tool in the close-up survey thickness-measurement campaign.