
The instrument is based on the principal of a spring mounted coil which moves within a magnetic field. The geophone’s coil remains stationary due to its inertia and the case moves in relation generating a voltage as the coil windings move through the magnetic field. Compared to active (powered) sensors a geophone offers the advantage of extreme low noise having only Brownian motion noise. The bandwidth of a geophone is generally defined from its natural frequency to the spurious frequencies which are unwanted parasitic resonances present in all geophones and caused by the sideward motion of the coil.
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