Electromagnetic ultrasonic thickness probes use EMAT principles to generate and receive ultrasonic waves without couplant. Their technical parameters determine measurement reliability, accuracy, and application range. Key parameters include operating frequency, bandwidth, lift-off, probe size, magnet type, coil design, excitation energy, output impedance, temperature range, and protection class.

Frequency usually ranges from 0.5 MHz to 5 MHz. Lower frequency improves penetration for thick or attenuating materials, while higher frequency improves resolution for thin walls. Bandwidth affects pulse shape and echo separation. Lift-off is the gap between probe and surface; typical values are 1 mm to 5 mm, but optimized designs can work at larger gaps with reduced signal strength.

Measurement range depends on material, frequency, and power. Common EMAT probes measure 1 mm to 100 mm or more in carbon steel. Resolution is often 0.01 mm to 0.1 mm, with accuracy around +/-0.1 mm or +/-(0.5% + 0.05 mm). Repeatability and signal-to-noise ratio are critical for stable readings.

Magnet type, such as permanent or pulsed, and coil geometry influence signal amplitude. Excitation voltage, pulse energy, and impedance matching affect efficiency. Operating temperature may range from -20 deg C to 500 deg C for special high-temperature versions. Housing materials, connectors, cable length, ingress protection, and hazardous-area certification must match the inspection environment. Selecting the correct parameters ensures reliable thickness measurement on coated, hot, rough, or moving steel components.