Abstract
This paper describes the design, construction, and calibration of a horizontal-component seismic pickup developed particularly for measurements of the kinematic errors of machine tools such as the non-uniformity of the feed motions of slides. The pickup described in this paper consists of a inverted pendulum, an eddy-current damping device, a differential transformer, and a coil-magnet assembly for the fine adjustment of the position of seismic mass, and has the following characteristics; size 75×65×100 mm : weight 1 kg : natural frequency 0.5 Hz : fraction of critical damping 0.55 : minimum measurable displacement ±0.03 μm.It is shown that the sensitivity for rotational vibration can be made small compared with that for linear vibration by minimizing the distance between the center of gravity of the seismic mass and the center of rotation of the pendulum. The 2nd resonant frequency of the inverted pendulum, which determines the higher limit of frequency range, can be shifted as far as 215 Hz by the use of a cross-spring pivot in place of a conventional leaf-spring suspension.
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