Sea Technology

MAY 2013

The industry's recognized authority for design, engineering and application of equipment and services in the global ocean community

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Comparing Encapsulation Methods Of Piezoelectric Transducers Oil-Filled Boot Transducers Demonstrate Deepwater Performance By Adam Lipper • Joe Borden A s oceanographic systems evolve, there is a constant evaluation of production methods, driven by the demand for high-quality reliable products that perform well in the harsh ocean environment. In underwater acoustic communications this holds true, especially as telemetry schemes continue to evolve. New developments necessitate the evaluation of technology, both old and new. As manufacturers continue to produce new systems, periodic evaluation of methods improves performance and the value of these systems for the end user. In the piezoelectric transducer feld, the comparison of technology is very important to both reliability and performance, not to mention manufacturability. One aspect of piezoelectric transducers is the encapsulation of the ceramic element, the core of the transducer. Different methods of encapsulation can affect transmit and receive capabilities of the transducer element, with particular advantages and disadvantages. Results of deepwater, openocean testing for the two most prevalent methods are presented here in order to discuss these advantages and disadvantages. Encapsulation Methods The encapsulation methods to be compared are potting in polyurethane and mounting in an oilflled boot. Both methods offer advantages but neither can completely replace the other in all applications. The requirements of differing electronics systems and mechanical designs necessitate both methods in equipment operations. It is not unusual to fnd both methods in the current acoustic communications product offerings of many manufacturers. Assemblies encapsulated in polyurethane are typically extremely reliable, which is desirable for both manufacturers and users. Transducers potted in polyurethane, called potted transducers, tend to be lower in cost and simpler to assemble but are often not economically repairable because of the harsh chemicals needed to remove the polyurethane. Potted transducers are also much simpler designs when compared to oil-flled boot transducers. Pot- (Top) The full range of output source levels measured during controlled-environment testing. The mooring used for offshore testing in Hawaii. May 2013 / st 31

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