1. 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

2. 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

3. 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

4. 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

5. 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