Also, by using special elements, normal incidence shear wave or a combination of longitudinalshear wave transducers can be made.

Selection of the proper transducer for a particular application is most important.

Factors including instrument conditions and settings, material properties, and coupling conditions will also impact test results.

Sensitivity is defined as the ability of a transducer to detect small defects in materials.

Resolution is the ability of a transducer to separate signals produced by two reflectors when they are close together either perpendicular to the beam or parallel to the beam.

A transducer that is highly damped helps shorten the reflected pulse allowing the transducer to resolve closely spaced defects.

Transducer device manufacturers can provide focused transducers for improved sensitivity and resolution, and a large selection of polarized ceramic compositions, single crystals, polymers and piezo-composite materials to vary the transducer performance.

Although ultrasound typically starts at 20 KHz, most ultrasonic transducers start at 200 KHz.

Ultrasound, which is similar in nature to audible sound, has far shorter wavelengths and is far more suitable to detect small flaws.

These shorter wavelengths are what make ultrasound and ultrasonic transducers extremely useful for nondestructive testing and measurement of materials.

The active element is a piezoelectric or single crystal material which converts electrical energy to ultrasonic energy.

It will also then receives back ultrasonic energy and converts it to electrical energy.

The electrical energy pulse is generated from an instrument such as a flaw detector.

When the acoustic impedance of the backing material matches that of the piezoelectric crystal, the result is a highly damped transducer with excellent resolution.

By varying the backing material in order to vary the difference in impedance between the backing and the piezoelectric crystal, a transducer will suffer somewhat and resolution may be much higher in signal amplitude or sensitivity.

Wearplates are selected to generally protect against wear and corrosion.

In an immersion-type transducer, the wearplate also serves as an acoustic transformer between the piezoelectric transducer element and water, wedge or delay line.

These zones are called the near field, which is the region directly in front of the transducer, and the far field which is the area beyond N where the sound field pressure gradually drops to zero.

Because of variations of the near field, it may be very difficult to accurately measure and evaluate flaws.

Knowledge of the focal length, beam width and focal zone may be necessary in order to determine whether a particular transducer is appropriate for an application.

This means that a small flaw will reflect a greater portion of the transmitted sound energy.

The length of the focal zone can be calculated with the following equation.

These features include side walls and corners which may cause spurious echoes that could be mistaken for flaws or defects.

Ultrasonic Transducer Manufacturer