Low natural frequency vibration isolator or seismograph

Abstract

This passive vibration isolator, or stable table, attenuates horizontal displacements as well as tilt due to bending of the floor under shifting loads. It has a transmissiblity of 0.1 for horizontal displacements at a frequency that can be as low as 0.1 Hz. Higher frequencies are attenuated as 1/f 2. The stable platform floats on a simple air bearing that rests on a pair of I beams supported on the concrete beams of the building. A weak horizontal restoring force is exerted on the platform by two light vertical springs. The device can also be used as a two‐dimensional seismograph, or as a sensitive tilt meter.