The La Coste Suspension--Principles and Practice

Abstract

For 35 years the La Coste suspension has been used in gravimeters and vertical component seismometers, yet its precise design and best adjustment have been handicapped by limited knowledge of the forces which combine to produce a stable instrument. The present analysis gives quantitative relations which merit consideration in design, and provides a rational step-by-step basis for obtaining the best possible adjustment of any instrument using the La Coste principle. The magnitude and effect of spurious forces such as may be caused by magnetic impurities or faulty construction is discussed briefly. The special case of the inclined boom seismometer is covered in a discussion of the symmetrical triaxial instrument invented by the author.

The sensitivity and dynamic range of inertial seismographs

“…ral periods in excess of 20 s require great care in design, installation, and mechanical adjustment with seismometers having masses on the order of 10 kg. Hinge alignment, adjustment of La Coste suspension where employed, and nonlinear diamagnetic and paramagnetic effects of plastic coil forms and wire coatings all contribute to instabilities, as noted by Melton [1971]. On the other hand, manufacturing experience (largely unpublished) in connection with seismometers having masses of 1 or 2 kg has shown that all such related long-period problems are increased appreciably.…”

Earthquake seismograph development: A modern history—Part 1

“…These instruments were put in service late in 1962. The problems with these instruments resulted in publication of the Melton [1971 ] paper on the LaCoste sus pension.…”