Miniaturized Underwater Sensors for the Realization of Conformal Arrays

Abstract

The development of cymbal transducers in India and the primary results obtained are presented in this paper. Commercial software ATILA is used to model Cymbal transducers. Simulation as well as experimental results are presented. The fundamental flexural resonance frequency of the transducers in water is ~20 kHz, for the cymbal with 12.7 mm cap diameter. The simulation studies showed that the resonant frequency can be reduced to ~8 kHz for a 19 mm cap Cymbal where as it reduces to ~3 kHz when the diameter increases to 30 mm. Pure brass caps showed a better performance compared to naval brass. Large d33 values of the order >15000 Pico Coulomb/N has been experimentally measured for the standard cymbals with PZT-5A where as the values are ~7000-9000 Pico Coulomb/N using PZT-4. The standard cymbals with pure brass showed the resonance frequency around 19kHz in water and a TVR value of ~120 dBre 1 muPa/V @ 1 m has been measured at resonance frequency. A receiving sensitivity (RS) of -205 dBre 1 V/muPa has been obtained on single element cymbals. In addition to single elements, a 3times3 array of cymbals have been fabricated and tested using two different water tight encapsulation. A 3times3 array with 3 M epoxy encapsulation gave a TVR value of ~135 dBre 1 muPa/V@ 1 m around 22 kHz for the standard cymbals of 12.7 mm diameter. A nearly flat frequency response is obtained for the array. An operating region of 15-90 kHz has been achieved. The Cymbals with 19 mm diameter using brass caps gave very high d33 values even >30000 Pico Coulomb/N. It resonated around 7 kHz in water while in-air resonance is 9 kHz. Probably this is the highest d33 value reported for a cymbal transducer as on to date. Earlier reports by Newnham et. al did not exceed a value of 15000 for standard cymbals.