An electromagnetic ultrasonic thickness probe, also called an EMAT thickness probe, measures material thickness without a liquid couplant. Its core is an electromagnetic acoustic transducer that generates and receives ultrasonic waves directly in a conductive or ferromagnetic specimen. The probe usually contains a permanent magnet, a coil, and sometimes a high-frequency power stage. When a pulsed current at ultrasonic frequency flows through the coil, it creates a dynamic magnetic field. In a conductive material, this field induces eddy currents near the surface. The static magnetic field from the magnet interacts with these eddy currents, producing a Lorentz force. This force vibrates the material lattice and launches an ultrasonic wave. In ferromagnetic materials, magnetostriction can also contribute to wave generation. For thickness measurement, the probe is placed near the surface with a small air gap, or liftoff. The generated ultrasonic wave travels through the material until it reaches the back wall. Part of the wave reflects and returns to the probe. The same EMAT coil detects the returning wave: surface motion changes the magnetic field, inducing a voltage in the coil. The instrument records the time of flight between the initial pulse and the first back-wall echo. Thickness is calculated by d = v x t / 2, where d is thickness, v is the ultrasonic velocity in the material, and t is the round-trip time. Because EMAT does not need couplant, it can work on rough, hot, or moving surfaces. However, its signal efficiency is lower than piezoelectric probes, so signal processing and probe design are critical. Liftoff, material conductivity, permeability, and magnetic field strength influence performance. With proper calibration and filtering, electromagnetic ultrasonic thickness probes provide reliable non-contact wall thickness readings for pipelines, tanks, plates, and high-temperature components.