Low cost broadband ultrasonic transducers

The design of a broadband wetted transducer involves stacking a piezoelectric device in layers of adhesives, electrodes and protective coatings. The frequency response of the transducer is heavily influenced by the electrodes, adhesives and protective coatings. A relatively new piezoelectric material, polyvinylidene fluoride, has a very flat linear phase response over a broad frequency band. This paper suggests specific materials for the backing and protective coating to maintain a flat response. Results of modeling, construction, and testing of transducers are reported. The transducer is designed to be used in a water flow meter.