This paper presents an analysis of a novel, patent pending \cite{MI}, absolute velocity sensor, or geophone. Conventional geophone topologies are discussed and their intrinsic physical limitations, given by the mechanical construction, are shown. Therefore, a new topology with passive magnetic spring is proposed. A unified semi-analytical solution for the magnetic field equations is derived in cylindrical coordinates and used to determine the static response characteristics of the proposed geophone configuration. Furthermore, a prototype is built and measurements are performed and analyzed to obtain the dynamic behavior. A further improvement of the novel geophone is proposed by means of optimization using finite element analysis.

Full text: Modeling of an electromagnetic geophone with passive magnetic spring.pdf