The Observatory Superconducting Gravimeter OSG-050 has been installed at the Pecný station in February 2007. The OSG-050 was manufactured by GWR Instruments, Inc (http://www.gwrinstruments.com). The sensor of the meter is an spherical test mass levitated in an ultra-stable magnetic field generated by persistent currents in two niobium coils that are superconducting below a temperature of 9.3 K. Small changes in gravity produce large displacements of the test mass that are easily detected in the capacitive displacement transducer that surrounds the mass. During operation, the position of the sphere is held close to its null position by a feedback circuit which applies a magnetic force through a separate feedback coil.S ince the force from feedback coil is linear with current, measuring the current through the feedback coil provides a linear measurement of the force of gravity. The measurement is thus relative and need a calibration.
The SG is the world’s most sensitive gravimeter with the sensitivity of 1 nano-Gal .