Turning a linear geometry force balance accelerometer to a broad-band seismometer: Design, modelling, and evaluation

In this work we present a prototype broadband seismometer, which is based on a previously designed force-balance accelerometer. The mechanical system has been redesigned to meet the required self-noise levels of the system and the electronic part has been modified to produce velocity output providing the desired sensitivity. The mechanical part has been extensively simulated and adjusted for having the main oscillation mode frequency into the desired recording band and having all other oscillation modes frequencies far outside the used recording band. The electronic part has been carefully designed towards very low electronic noise, which in addition with the mechanical system noise, will result in a total sensor self-noise level, lower the New Low Noise Model (NLNM) in a wide band range. The sensor has been extensively tested and compared against a commercial seismometer, with similar specifications in terms of self-noise. The experiment proved that the new prototype sensor performed equally to the reference unit. The new design offers a simpler sensor at a lower cost.