Sea Technology

FEB 2017

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

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Page 10 of 72

10 st / February 2017 The Test Environment High hydrostatic loads found in underwater applications require sensors strong enough to survive the loading condi- tions, yet have a functional full-scale measurement range in the milli-g or milli-psi often found in dynamic pressure measurements. Piezoelectric sensors have a wide dynamic range and are AC coupled devices, thus ignoring any ambi- ent or static pressure. For example, this property provides these sensors with the unique ability to monitor low-level dynamic pressures while being subjected to a high static background pressure level. When inserted in the hull of a vessel, the pressure sensors on the hull surface act as water micro- phones. Sensors Configurations, Designs Pressure sensors and accel- erometers are available in many variations. Two key features for S hip vibration and unsteady pressures must be measured and identified, including onboard equipment, water flow across the hull or control surface, cavitation of the screw and other sources. Sensors designed for these mea- surements all require some degree of protection for their intended use near or under water. This article discusses cable attachment methods, waterproofing of cable and sensors and pressure testing of underwater cables that are used with piezoelectric accelerometers and pressure sen- sors to render them suitable for measurement in underwa- ter environments. Design Parameters for Underwater Cables, Sensors Considerations for Cables, Sensors, Accelerometers at Depth By Bob Metz (Photo Credit: John F. Williams) (Left) Typical open-tunnel water test of a ship hull. (Right) Underwater blast test setup.

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