Research of eddy current sensors applied to displacement-based vector hydrophones

This paper provides insights into the principle of eddy current sensors applied to displacement-based vector hydrophones by both theoretical and experimental analyses. These displacement-based vector hydrophones provide excellent performances at the Ultra-Low Frequency. First, theoretical calculations are presented to demonstrate the feasibility of the eddy current sensors for measurements of underwater acoustic signals. Theoretical models are then established to calculate the transduction constants of eddy current sensors with the flat, spherical, and cylindrical conductive materials, respectively. The influence of the axial offset of eddy current sensors on the transduction constant is analyzed by finite element models lastly. The theoretical models are further validated by comparison with experimental results. The experiment results show that, when the radii of the spherical and cylindrical conductive materials are greater than eight times the coil radius, the spherical and cylindrical conductive materials are equivalent to the flat conductive material. Moreover, the axial tolerable offset between the conductive material and the coil is proportional to the radius of the spherical or cylindrical conductive material.