The most significant part of an ultrasonic test is an ultrasonic transducer. For any ultrasonic application, the selection of the correct transducer is the most vital step. A number of factors that affect the results are the material properties, the instrument and conditions used for coupling and settings.
Depending on the particular application it is required for; the transducer can be selected accordingly according to its sensitivity and resolution. The ability of the transducer to detect the small defects is called its sensitivity whereas the separation to of the two signals produced by the two reflectors when close and either perpendicular or parallel to the beam is called the resolution. A highly damped transducer allows resolving defects that are closely spaced only by helping to shorten the reflected pulse.
The maker of this device can also make transducers that are focused for improved resolution and sensitivity, a large selection of polarized ceramic compositions, polymers, piezo composite materials and ceramic compositions so that the performance of the transducer can be altered according to the requirement.
An ultrasound is a sound which is above the level of human hearing range. Although most of the transducers produce ultrasounds that have a frequency above 200 KHz, the ultrasounds begin at only 20 KHz. These sounds are like ordinary sound-waves but have a wavelength which is a lot shorter. This key feature makes these waves more suitable for detecting small flaws.
In fact, it is these short wavelengths that make the ultrasound transducers tremendously useful in the testing, detection, inspection and measurement of different materials.