Design and Testing of Low Cost Piezoelectric Film Ultrasonic Transducers
Date
1997-01
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Degree Level
Masters
Abstract
Flow measurement using the differential phase technique has shown some promise.
However, there are. certain problems that must be overcome in order for it to prove
viable. These are the inherent ambiguity in phase and the temperature dependence. In theory, these problems can be overcome by using multiple frequencies. This inevitably leads to the necessary use of broadband ultrasonic transducers over the conventional narrowband ones.
A relatively new material that can provide a broadband response, is the piezoelectric
film, polyvinylidene fluoride. The focus of this thesis is to look at the design, construction, and testing of wetted transducers, using this piezoelectric film. The
design stage looks at the theoretical response of a transducer pair, using a general
three port network model. The model provides a means of choosing suitable transducer design parameters.
Construction of the transducers is then performed to confirm the validity of the
design. Several sets of transducers were constructed with different backing materials
having different acoustic properties. The measured responses of each of the sets were
compared to each other and to their models. From this, the final transducer design
was selected, resulting in a broadband wetted ultrasonic transducer, of relatively low
cost.
Finally, the transducers were tested in the differential phase flow measurement
system. The results showed some improvement over the previously used narrowband
transducers. Unfortunately, temperature compensation and the elimination of phase
ambiguity were not attempted, due to certain problems with the flow measurement
system.
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Degree
Master of Science (M.Sc.)
Department
Electrical and Computer Engineering
Program
Electrical Engineering