Patent ID: 8159904

Claim:
A broadband weak-motion seismometer comprising: a frame, a mass, a suspension means for movably connecting the mass to the frame, a sensing transducer for measuring displacement of the mass with respect to the frame and for generating a sensing transducer output signal, which is a function of said displacement, a forcing transducer for applying a feedback force in a predetermined direction to the mass, and a control circuit for receiving the sensing transducer output signal and for generating a forcing transducer input signal that includes a self-noise component; the forcing transducer input signal being processed by the forcing transducer to apply the feedback force so as to maintain the mass at rest with respect to the frame; the feedback force being sufficient to counterbalance a constant acceleration of the frame of at least 0.2 m/s 2 in the predetermined direction of the feedback force, wherein the self-noise component of the forcing transducer input signal, when processed by the forcing transducer, produces variable acceleration of the mass with spectral density less than −150 dB with respect to 1 m 2 /s 3 at 0.01 Hz.