Abstract: The present invention provides a gravity gradiometer for measuring components of the gravity gradient tensor. The gravity gradiometer includes at least one sensor mass for movement in response to a gravity gradient and a sensor and actuator unit for generating an electrical signal in response to the movement of the at least one sensor mass and for influencing the movement of the at least one sensor mass. The gravity gradiometer also includes an electronic circuit for simulating an impedance. The electrical circuit is arranged for amplifying the electrical signal received from the sensor and actuator unit and for directing an actuating signal to the sensor and actuator unit. The electronic circuit includes a differential amplifiers having first and second amplifier input terminals and an amplifier output terminal and impedances Z1, Z2, Z3, at least one of the impedances have an imaginary impedance component.

Abstract: A gravity gradiometer is disclosed which has a sensor in the form of bars (41 and 42) which are supported on a mounting (5) which has a first mount section (10) and a second mount section (20). A first flexure web (33) pivotally couples the first and second mount sections about a first axis. The second mount has a first part (25), a second part (26) and a third part (27). The parts (25 and 26) are connected by a second flexure web (37) and the parts (26 and 27) are connected by a third flexure web (35). The bars (41 and 42) are located in housings (45 and 47) and form a monolithic structure with the housings (45 and 47) respectively. The housings (45 and 47) are connected to opposite sides of the second mount section 20. The bars (41 and 42) are connected to their respective housings by flexure webs (59). Transducers (71) are located in proximity to the bars for detecting movement of the bars to in turn enable the gravitational gradient tensor to be measured.

Abstract: A gravity gradiometer is disclosed which has a sensor in the form of bars (41 and 42) which are supported on a mounting (5) which has a first mount section (10) and a second mount section (20). A first flexure web (33) pivotally couples the first and second mount sections about a first axis. The second mount has a first part (25), a second part (26) and a third part (27). The parts (25 and 26) are connected by a second flexure web (37) and the parts (26 and 27) are connected by a third flexure web (35). The bars (41 and 42) are located in housings (45 and 47) and form a monolithic structure with the housings (45 and 47) respectively. The housings (45 and 47) are connected to opposite sides of the second mount section 20. The bars (41 and 42) are connected to their respective housings by flexure webs (59). Transducers (71) are located in proximity to the bars for detecting movement of the bars to in turn enable the gravitational gradient tensor to be measured.

Abstract: A gravity gradiometer is disclosed which has a sensor in the form of bars (41 and 42) which are supported on a mounting (5) which has a first mount section (10) and a second mount section (20). A first flexure web (33) pivotally couples the first and second mount sections about a first axis. The second mount has a first part (25), a second part (26) and a third part (27). The parts (25 and 26) are connected by a second flexure web (37) and the parts (26 and 27) are connected by a third flexure web (35). The bars (41 and 42) are located in housings (45 and 47) and form a monolithic structure with the housings (45 and 47) respectively. The housings (45 and 47) are connected to opposite sides of the second mount section 20. The bars (41 and 42) are connected to their respective housings by flexure webs (59). Transducers (71) are located in proximity to the bars for detecting movement of the bars to in turn enable the gravitational gradient tensor to be measured.

Abstract: The present invention provides a method of tuning properties of a gravity gradiometer for measuring components of the gravity gradient tensor. The gravity gradiometer comprises a pair of first and second transversely arranged sensor masses that are arranged for movement about an axis and relative to each other in response to a gravity gradient. The gravity gradiometer further comprises first and second capacitors for sensing and influencing the movement of the first and second sensor masses. The method comprising applying a bias voltage to at least one of the capacitors for generating an electrostatic force which acts on one of the sensor masses and thereby influences the movement of that sensor mass.

Abstract: The present invention provides a method of tuning properties of a gravity gradiometer for measuring components of the gravity gradient tensor. The gravity gradiometer comprises a pair of first and second transversely arranged sensor masses that are arranged for movement about an axis and relative to each other in response to a gravity gradient. The gravity gradiometer further comprises first and second capacitors for sensing and influencing the movement of the first and second sensor masses. The method comprising applying a bias voltage to at least one of the capacitors for generating an electrostatic force which acts on one of the sensor masses and thereby influences the movement of that sensor mass.

Abstract: A gravity gradiometer is disclosed which comprises a pair of sensor masses arranged in housings. Transducers are provided for measuring movement of the sensor masses in response to the gravity gradient tensor. The masses are supported for movement by a flexure web between the mass and a support and a stop comprises a pair of abutment services defined by a cut prevent movement of the sensor masses beyond the elastic limit of the flexure web.

Abstract: A gradiometer is disclosed which has a pair of sensor bars 41, 43 supported in housings 45, 47. Transducers 71 are located adjacent the bars 41, 43 to detect movement of the bars in response to the gravity gradient tensor. At least one of the transducers 71 comprises a first coil 510 and a second coil 516 arranged in parallel and a switch 362 for proportioning current between the coils 510 and 516 so as to create a virtual coil at a position D between the coils 510 and 516.

Abstract: A gravity gradiometer and method for forming a pivot flexure web for a gradiometer is disclosed. The gradiometer has measurement bars 41, 43 supported in housings 45 and 47 and transducers 71 for measuring movement of the bars to provide an indication of the gravity gradient tensor. The bars 41, 43 are mounted on flexure webs. The webs are formed in separate elements to the housing and bars.

Abstract: A heat switch 570 is disclosed as well as a gradiometer having the heat switch. The heat switch is formed from a non-magnetic material such as a semi-conducting material. The semi-conducting material may be provided by way of a Hall effect device. The heat switches are arranged in the gradiometer on a circuit board 856. The circuit board 850 has conducting strips 856 which are connected to conducting strips on a sensor 71 by bridges 852. The heat switch 570 is connected on the opposite side of the circuit board 850 to the strips 856 and processing circuitry 859. A copper substrate 865 is provided on the same side of the circuit board as the heat switch 570 to conduct heat away from the heat switch 570 when the heat switch is closed.

Abstract: A gravity gradiometer is disclosed which has a sensor in the form of bars (41 and 42) which are supported on a mounting (5) which has a first mount section (10) and a second mount section (20). A first flexure web (33) pivotally couples the first and second mount sections about a first axis. The second mount has a first part (25), a second part (26) and a third part (27). The parts (25 and 26) are connected by a second flexure web (37) and the parts (26 and 27) are connected by a third flexure web (35). The bars (41 and 42) are located in housings (45 and 47) and form a monolithic structure with the housings (45 and 47) respectively. The housings (45 and 47) are connected to opposite sides of the second mount section 20. The bars (41 and 42) are connected to their respective housings by flexure webs (59). Transducers (71) are located in proximity to the bars for detecting movement of the bars to in turn enable the gravitational gradient tensor to be measured.

Abstract: The present invention provides a method of tuning properties of a gravity gradiometer for measuring components of the gravity gradient tensor. The gravity gradiometer comprises a pair of first and second transversely arranged sensor masses that are arranged for movement about an axis and relative to each other in response to a gravity gradient. The gravity gradiometer further comprises first and second capacitors for sensing and influencing the movement of the first and second sensor masses. The method comprising applying a bias voltage to at least one of the capacitors for generating an electrostatic force which acts on one of the sensor masses and thereby influences the movement of that sensor mass.

Abstract: The present invention provides a gravity gradiometer for measuring components of the gravity gradient tensor. The gravity gradiometer comprises a housing and a gimballed support structure with at least one actuator. The gravity gradiometer further comprises at least one sensor mass arranged for movement in response to a gravity gradient. The gravity gradiometer also comprises a transducer that is arranged so that the movement of the at least one sensor mass relative to a portion of the transducer generates a transducer signal. Further, the gravity gradiometer comprises an electrical feedback loop arranged to direct an electrical signal to the actuator of the external support structure. The gravity gradiometer is arranged so that an influence of an external angular acceleration on the rotation of the housing is reduced by the actuator when the transducer generates a transducer signal effected by the external angular acceleration on the gravity gradiometer.

Abstract: The present invention provides a gravity gradiometer which comprises at least one sensor mass suspended by a coupling which enables movement of the at least one sensor mass about an axis in response to a gravity gradient. Further, the gravity gradiometer comprises at least one transducer for generating an electrical signal in response to the movement of the at least one sensor mass relative to a component of the transducer and for influencing the movement of the at least one sensor mass. The gravity gradiometer also comprises electrical circuitry for receiving the electrical signal from the at least one transducer and for directing an actuating signal to the at least one transducer so that in use the at least one transducer functions as sensor and actuator.

Abstract: A gravity gradiometer is disclosed which has sensor masses in the forms of bars 41 and 43 arranged orthogonal to one another and transducers for providing an output signal indicative of movement of the bars in response to changes in the gravity gradient tensor. The transducers are formed from thin film structure having a first layer forming a fine pitch coil 510 and a second layer forming a coarse pitch coil 511. The layers are separated by an insulating layer. The coarse pitch coil 511 forms a transformer for stepping up the current flowing through the fine pitch coil 510 and the coarse pitch coil 511 supplies current to a SQUID device 367.

Abstract: A gravity gradiometer is disclosed which has a pair of sensor bars 41, 42 mounted in housings 43 and 45. Transducers 71 are located adjacent the bars for measuring movement of the bars in response to the gravity gradient tensor. Signals from the transducers are supplied to a SQUID device 367 for processing the signals. A connector is supplied for connecting the circuitry to external equipment which comprises a container 560 having a feed through filter 564, a three terminal cap 565, a relay 566 and an output terminal. The output terminal is connected to further RF attenuation which comprises a second connector 5b having parallel inductors and resistors.

Abstract: The present invention provides a gravity gradiometer for measuring components of the gravity gradient tensor. The gravity gradiometer comprises at least one sensor mass for movement in response to a gravity gradient. The gravity gradiometer also comprises a pivotal coupling enabling the movement of the at least one sensor mass about an axis. Further, the gravity gradiometer comprises a plurality of capacitors. Each capacitor has first and second capacitor elements positioned opposite each other so that a gap is defined between respective first and second capacitor elements. The capacitors are arranged so that movement of the at least one sensor mass results in a change in the gap between respective first and second capacitor elements. At least one of the capacitor elements has at least two separate capacitor portions arranged so that separate voltages can be applied to the capacitor portions.

Abstract: The present invention provides a gravity gradiometer for measuring components of the gravity gradient tensor. The gravity gradiometer comprises at least one sensor mass for movement in response to a gravity gradient and a pivotal coupling enabling the movement of the at least one sensor mass about an axis. Further, the gravity gradiometer comprises a constant charge capacitor that is arranged so that the movement of the at least one sensor mass generates a change in a voltage across the constant charge capacitor.

Abstract: A gravity gradiometer is disclosed which has a sensor in the form of bars (41 and 42) which are supported on a mounting (5) which has a first mount section (10) and a second mount section (20). A first flexure web (33) pivotally couples the first and second mount sections about a first axis. The second mount has a first part (25), a second part (26) and a third part (27). The parts (25 and 26) are connected by a second flexure web (37) and the parts (26 and 27) are connected by a third flexure web (35). The bars (41 and 42) are located in housings (45 and 47) and form a monolithic structure with the housings (45 and 47) respectively. The housings (45 and 47) are connected to opposite sides of the second mount section 20. The bars (41 and 42) are connected to their respective housings by flexure webs (59). Transducers (71) are located in proximity to the bars for detecting movement of the bars to in turn enable the gravitational gradient tensor to be measured.

Abstract: A gravity gradiometer is disclosed which has a sensor in the form of bars (41 and 42) which are supported on a mounting (5) which has a first mount section (10) and a second mount section (20). A first flexure web (33) pivotally couples the first and second mount sections about a first axis. The second mount has a first part (25), a second part (26) and a third part (27). The parts (25 and 26) are connected by a second flexure web (37) and the parts (26 and 27) are connected by a third flexure web (35). The bars (41 and 42) are located in housings (45 and 47) and form a monolithic structure with the housings (45 and 47) respectively. The housings (45 and 47) are connected to opposite sides of the second mount section 20. The bars (41 and 42) are connected to their respective housings by flexure webs (59). Transducers (71) are located in proximity to the bars for detecting movement of the bars to in turn enable the gravitational gradient tensor to be measured.