Patent ID: 7559149

Claim:
A gravity gradiometer for measuring components of the gravity gradient tensor, the gravity gradiometer comprising: a pair of transversally arranged sensor masses for movement in response to a gravity gradient; a pivotal coupling enabling the movement of the sensor masses about an axis; and constant charge capacitors, each constant charge capacitor arranged so that each sensor mass is associated with a plurality of the constant charge capacitors in a manner such that movement of the sensor masses generates changes in voltages applied to the constant charge capacitors, each constant charge capacitor comprising first and second capacitor elements, the first capacitor elements being coupled to one of the sensor masses and the second capacitor elements being held in positions relative to which the one of the sensor masses in use moves so that a gap is defined between respective first and second capacitor elements; wherein the sensor masses, the pivotal coupling, and the constant charge capacitor form a part of a gravity gradient sensor element and the gravity gradiometer further comprises a support structure arranged to rotate the gravity gradient sensor element about an axis whereby a local change in gravity gradient resulting from the rotation generates an oscillating movement of the sensor masses.