The sound frequency used in these is usually in the range of one hundred kilohertz to fifty megahertz that is way above the normal human hearing range of twenty thousand hertz. Sound generated at these frequencies has a shorter wavelength that can reflect small surfaces and enable it to detect the defects inside solid materials such as metal and plastic.
These devices use Piezo or ferroelectric material as an active element to detect flaws by converting the excitation pulse (electrical energy) generated from the flaw detector into ultrasonic energy. The transducer’s performance is enhanced with the use of materials such as Piezo polymers and composites that are capable of producing different wave modes, by cutting the ceramics in different forms. These devices contain a backing component made from high density material to absorb the energy radiated from the active element’s back face, and control the vibration of the transducer. They also contain a wear plate made from corrosion resistant material such as steel order to protect the transducer element from the environment of testing.
The operations of these devices are based on the principles of piezoelectric effect or magneto restrictive effect for producing ultrasonic sound. Ultrasonic frequencies used in these devices are produced by combining the output of an electronic oscillator to a thin wafer or piezoelectric material like lead zirconate titanate.
Ultrasonic transducers are better than electronic sensors as they can be used in measuring and detecting object distances and detecting small objects from a long distance. They are also resistant to dust, dirt, moisture, and are not affected by external disturbances such as vibration, infrared radiation, ambient noise, and EMI radiation.