Non-Contact EMAT Transduction A current, I, in a wire near a metal surface induces an equal and opposite eddy current, Ie in the surface of the metal. N S When the eddy current occurs in a magnetic field a force is created in the metallic surface. F = I x B This force can generate elastic waves, ie. ultrasonic Guided Waves I F B Ie Sonic Sensors of EMAT Ultrasonics Inc. SLO CA USA

Sonic Sensors of EMAT Ultrasonics Inc. SLO CA USA EMATs are Versatile Surface Waves: Rayleigh Wave Surface SH waves Angle Beam waves: SH or SV Through Thickness Shear Waves Through Thickness “L” Waves SH SV L S Sonic Sensors of EMAT Ultrasonics Inc. SLO CA USA

EMAT are Exceptional for Guided Waves SHn Shear Horizontal Often called Plate Waves Sensitive to Plate Thickness There are many different kinds of Plate Waves These depend on the displacement through the plate thickness EMATs are great for SH waves Propagation Sn Symmetric Propagation An Anti-symmetric Propagation Sonic Sensors of EMAT Ultrasonics Inc. SLO CA USA

EMATs offer Superior Control of Guided Waves There are MANY guided waves to possible in a single thickness plate Isolating a single mode can be very difficult with a piezo transducer EMATs isolate guided waves easily! EMAT defines the wavelength Choose the frequency at the defined EMAT wavelength, and only one mode generated and detected. M120 EMAT only generates and receives these modes in a 3/8 inch thick plate Sonic Sensors of EMAT Ultrasonics Inc. SLO CA USA

Sonic Sensors of EMAT Ultrasonics Inc. SLO CA USA Automated Analysis Example: Sizing of defects in Pipe Girth Weld Length Depth NDE Indication (sized between accept & reject curves) Upstream Side of Weld Downstream Side of Weld Sonic Sensors of EMAT Ultrasonics Inc. SLO CA USA