Shielded fringe field compression sensors for open ocean applications

Abstract

Fringe field sensors based on piezo dielectrics offer opportunities in under water sensing as they are solid state, incompressible and robust. Questions remain regarding their susceptibility to noise. Specifically, we refer to anomalous outputs when the sensor is brought in close proximity to or just touching a conductive object. One solution involves isolation through a flexible Faraday cage.We have investigated two approaches for such a Faraday cage. One approach utilizes a conductive fabric while the other is based on a carbon filled dielectric. We compared the performance of both shielding approaches regarding noise suppression and their influence on sensitivity. The anomalous effects upon contact with conductive objects leading to inconsistent measurements were overcome. Furthermore, their response to salinity levels and submersion time were investigated and the influence of design parameters on the performance of the sensor determined in a Design of Experiment study. Varied parameters include overall footprint alongside electrode spacing and width. Performing a full factorial design plan enabled us to quantify the relations between the parameters. This investigation improved signal stability in the piezo dielectric fringe field sensors, making it possible to design a broader range of sensory systems able to withstand the harsh marine environment. The sensor will assist fish robots in their exploration of the 'Silent World'.