Electromagnetic acoustic transducer (emat) technology has revolutionized ultrasonic testing by allowing non-contact sound generation and eliminating the need for liquid couplant. EMAT systems are now widely used in industrial settings for in-line and field inspections, offering advantages such as imperviousness to surface conditions and the ability to generate various wave modes for comprehensive defect detection. Despite limitations in transducer efficiency, advancements in electronics and software continue to enhance EMAT applications in demanding situations.

1. Aerospace Testing
August 2005 Page 1 of 2 Innerspec®
Technologies, Inc.
Electromagnetic Acoustic Transducer (EMAT) systems are no longer limited to laboratory applications.
With the help of new electronics and software they are now widely used in industrial settings and in-
service operations.
Over the last century non-destructive testing has shown tremendous growth. Its ability to provide safe,
volumetric inspection of materials with limited access areas makes Ultrasonic Testing (UT) one of the
fastest growing techniques in NDT. Traditionally ultrasound is generated using piezoelectric crystals and
rely on a liquid couplant to transmit the sound energy into the material. This technology for sound
generation and transition did not change significantly until the advent of non-contact options such as
EMAT.
Electromagnetic Acoustic Transducer (EMAT) technology has been one of the most significant
developments in Ultrasonic Testing in the last 20 years. EMAT is a non-contact technique in which the
sound is induced into the part using magnetic and electrical forces thus eliminating the need for liquid
couplant. EMATs rely on Lorentz Force and magnetostriction to generate the sound and can be used on
most magnetic and electrical conductors including steel, iron, aluminum, copper, brass and most other
metals.
EMATs have all the benefits of traditional ultrasonic testing, but because the sound generation is
generated in the part being inspected, they enjoy some unique advantages.
 Couplant free inspection. EMATs induce the sound in the part therefore liquid couplant is not
necessary. This permits easier probe deployment and more reliable readings, lending itself very
well to automated applications. High temperature and very high speeds are also possible.
 Surface conditions. EMATs are not sensitive to surface conditions. Oxides, oil, water, uneven
surfaces or thin coatings do not pose a problem for EMAT inspection.
 Unique wave modes. EMATs are not limited by the wave transmission properties of the couplant
thus they can generate any type of wave mode including horizontally polarized shear energy (SH).
SH is key to inspecting austenitic welds and other materials with dendritic grain structures such as
stainless steel. Another type of wave that can be easily generated with EMATs is guided or plate
waves (Lamb or SH at 90°)
The main disadvantage of EMAT is the low efficiency of the transducer. EMAT transducers rely on high
currents and very precise electronics to generate and detect the signal. With the advent of more powerful
electronics and software tools that enhance complex signal processing in real-time, the disadvantages are
becoming less relevant.
1. Field Inspection
With the introduction of temate®
TTG-P1 EMATs have entered the portable instrument arena. The
thickness gage uses complex algorithms in real-time for couplant-free thickness measurement. The
instrument is capable of running up to 10 hours on battery and includes an internal memory capable of
storing up to 60 A-Scan screenshots and over 1000 readings.
Other instruments for field inspection include the temate®
Ti-P for plate-wave inspection of Pipelines with
automated scanners.

2. Aerospace Testing
August 2005 Page 2 of 2 Innerspec®
Technologies, Inc.
2. In-line Inspection
EMATs are especially well suited for in-line integration, where the objective is to have automated, real-
time inspection of 100% of the material. Innerspec Technologies has deployed weld and full-volume
inspection for a wide variety of applications.
2.1. Weld Inspection
Shear wave is most commonly used for ultrasonic weld inspection. Conventional Piezoelectric Ultrasonic
Testing uses shear wave with an angle between 30° and 60° from the normal beam and requires rastering
the probe and internal bouncing of the beam for complete weld coverage. EMATs can generate shear
energy at any angle from 0º to 90º and generate plate waves that fill up the cross-section of the material
for complete weld inspection in one shot. This versatility makes EMATs unbeatable for weld inspection in
automated environments.
Full Volumetric Inspection of Plates and Tubes.
Taking advantage of guided waves, EMAT system can perform full volumetric inspection with a limited
number of probes and detect defects in all directions.
3. EMAT, unlimited
Created as a non-contact alternative to piezoelectric transducers, ultrasonic EMAT systems are no longer
limited to laboratories and high-end applications and are widely used for in-line and in-service
applications.
The couplant-free ultrasonic inspection, imperviousness to surface conditions and ability to generate
unique wave modes, such as SH and plate waves, have brought EMATs to the forefront of Ultrasonic
Testing, making it the technique of choice for many demanding applications where speed, reliability and
quality of readings is essential.