Qinetiq Limited

David O King

Kevin Michael Brunson

Mark Edward McNie

David J Combes

David James Hamilton

A magnetic field sensor device () is described that comprises an oscillatory member () and current control means (). The current control means () is arranged to pass an alternating current (AC) along at least first () and second () current paths provided through the oscillatory member () and is arranged to provide magnetic gradiometer mode operation (i.e. to measure magnetic field gradient) in which current flow through the first current path () is in substantially the opposite direction to current flow through the second current path (). The current control means () can also prove magnetometer mode operation (i.e. to measure magnetic field strength). The magnetic field sensor () may be used in a compass.

Combined magnetic field gradient and magnetic field strength sensor

An electronic safety and arming unit comprises a micro electromechanical system (MEMS) shutter device. The shutter () is suspended by thin lightweight arms and hinges, all formed by silicon processing of SOI substrates and includes holding latches for holding the shutter () in the closed position. The holding latches may be released by an electrothermal actuator. The shutter () separates an initiator section from an explosive train () of munitions such as shells, thereby providing safety until the shell is fired and away from its start point. After firing, the shutter () is opened ready for the main explosive to be detonated by the initiator (). The shutter () may be suspended by a compliant displacement multiplier and may include an electrothermal actuator such as an electrically heatable bent beam. Heating of the beam causes movement of a shutter blade from a shut condition covering a firing aperture to an open condition. Alternatively the shutter () may operate by inertial centrifugal forces generated by a spinning munition. The shutter () may include latches for retaining the shutter in its open position.

Electronic safety and arming unit

A resonant magnetometer comprises a substrate having a member and circuitry for passing an alternating current (AC) through the member. The magnetometer is characterized in that a driver is also provided to impart a magnetic field independent oscillatory force to the member. Disclosed is a micro-electro mechanical systems (MEMS) implementation of a magnetometer.

Resonant magnetometer device

A micro-electromechanical system (MEMS) comprises a substrate incorporating an oscillatory ring, forcing electrodes for driving the ring into resonance, and sensing electrodes providing an electrical output signal dependent on oscillation of the ring as a result of such forcing and any externally applied force. A positive feedback circuit is provided for feeding back a signal dependent on the output signal of the sensing electrodes to the forcing electrodes in order to sustain oscillation of the ring. The use of positive feedback to drive the forcing electrodes in order to sustain oscillation of the ring is highly advantageous in such an application since it produces a system which exhibits very low phase noise of a magnitude considerably less than the phase noise experienced in use of a phase-lock loop circuit to sustain oscillation.

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Malvern, United Kingdom

David O King