Patent ID: 7823448

Claim:
A gravity gradiometer for measuring components of the gravitational gradient tensor, comprising: a sensor mass; a mount supporting the sensor mass for movement about three orthogonal axes; and a plurality of actuators to act between a body part of the gradiometer and the mount to move the mount about the three orthogonal axes to stabilize the mount during use of the gradiometer, wherein each actuator comprises: a first part for coupling to one of the mount and the body part; a moveable member for connection to the other of the mount and the body part; at least one coil carried by one of the first part and the moveable member so that when the coil receives a signal, the moveable member is moved relative to the first part to, in turn, move the mount relative to the body part; and a lead extending into the actuator for supplying a signal to the coil, wherein the actuator has an elongate passage through which the lead extends into the actuator to the coil for minimizing leakage of magnetic flux from the actuator.