Founded in 1854, O'Fallon's namesake comes from Colonel John O'Fallon who was a wealthy gentleman from St. Louis. In downtown O'Fallon, a Baltimore and Ohio Railroad railroad depot was built, which helped put O'Fallon on the map.
â¢ Transducers and sensors are physical devices that are used in electrical, electronic and many other types of gadgets and appliances. â¢ Transducers are used to convert one energy type into another while sensors measure energy levels and convert them into electrical signals that can be measured digitally.
This chapter discusses electromagnetic acoustic transducers (EMATs), which produce ultrasonic waves without any coupling medium, in the surface of an electrically conductive material. In Section 2.1 the difference between piezoelectric and electromagnetic generation and reception of ultrasonic waves is described. Section 2.2 presents the mechanisms acting mainly during ultrasound excitation by EMATs, the Lorentz force and magnetostriction.