Abstract
In the implementation of any transducer based system, it is desirable that the device characteristics are predicted accurately by a suitable model so that an optimum design of the transducer is realised.The model used in this project was implemented on PSPICE, a widely available, sophisticated circuit analysis program. Mechanical and dielectric losses were introduced to the model using transmission line theory. The model in this study proved to be very useful. Many important characteristics of the transducer were simulated, e.g. electrical and acoustic input impedance, receiver and transmitter response. Matching schemes were easily simulated using the PSPICE program. Electrical matching was done by simply entering the matching network in the circuit description. Acoustic matching was simulated by adding a transmission line of suitable characteristic impedance and time delay between the front face and the load. Pulse echo simulation was done by cascading two transducers circuits.
After design and modelling stages, various ultrasonic probes were constructed. Piezoelectric materials such as ceramics, polymers, copolymers and composite were used to produce a total of 10 transducers using diverse electroactive materials, viz; ceramics (PZT-4), polymer (polyvinylidene fluoride), copolymer of vinylidene fluoride and trifluoroethylene and a polymer/ceramic composite (PIEZEL™), filled with different and appropriate backing materials (i.e. epoxy and tungsten loaded epoxy).
All these ten transducers were characterized in the time and frequency domain using the following equipment; (i) a pulse generator, (ii) 1 mm diameter needle hydrophone, (iii) a digital storage oscilloscope, (iv) a 45 X 70 X 130 cm glass tank with deioniser and (v) a microcomputer. Transformation from the time to the frequency domain was done using a FFT routine. Various acoustic parameters, such as intensities Ispta, I sppa' Isptp and Isata and power W, were determined.
A close agreement between the simulated and the measured data was obtained in all cases. Results showed that broad band ultrasonic transducers can be satisfactorily designed with piezoelectric polymeric sensors and appropriate epoxy-tungsten composite backing.
| Date of Award | Jun 1992 |
|---|---|
| Original language | English |
| Awarding Institution |
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| Sponsors | Universidad Nacional Autónoma de México |
| Supervisor | Dilip Das-Gupta (Supervisor) |
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- Standard