To qualify a new generation of high-resolution strong-motion recording equipment, Terrascience Systems Ltd. initiated development of a precise linear shaker for automated verification and calibration of seismic instrumentation. Current electromagnetic (EM) and hydraulic shakers are unable to generate signals of high purity at very low frequencies; this poses a problem in qualification of the seismic instrumentation. In addition to their nonlinearity and static friction, most shaker systems today cannot be optimally adjusted at different loads and movement profiles. This introduces signal distortion, thus reducing the accuracy of important instrument parameters measured at different frequencies: dynamic range, linearity, flatness of the...

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