Measurement Principle

The physical principle of EMAT is to produce a guided wave through the combination of Lorentz Force and Magnetostriction.
To generate the wave a coil is placed on a pipeline within a magnetic field and a current pulse is sent through the coil. As a result, forces are created within the pipe wall. If the pulses are short enough, an acoustic wave will develop from the associated forces within the boundary created by the pipe wall (see Figures).
A receiver works in the reverse of the sender whereby an acoustic wave will interact with the EMAT and produce a measurable current pulse.