Abstract: A capacitive accelerometer including: at least one additional fixed capacitor electrode with a plurality of additional fixed capacitive electrode fingers extending along the sensing direction. The proof mass comprises a plurality of moveable capacitive electrode fingers extending from the proof mass along the sensing direction and arranged to interdigitate with the plurality of additional fixed capacitive electrode fingers of the at least one additional fixed capacitor electrode. A means is provided for applying a voltage to the at least one additional fixed capacitor electrode to apply an electrostatic force to the plurality of moveable capacitive electrode fingers that acts to pull the proof mass towards the at least one further fixed capacitor electrode and thereby reduces the lateral spacings between the movable capacitive electrode fingers of the proof mass and the first and second sets of fixed capacitive electrode fingers that provide electrostatic forces for sensing purposes.

Abstract: An accelerometer comprises a support (12), a proof mass (14) supported for movement relative to the support (12) by a plurality of mounting legs (16), a plurality of fixed capacitor fingers associated with the support (12) and a plurality of movable capacitor fingers associated with the proof mass (14), the fixed capacitor fingers being interdigitated with the movable capacitor fingers, the mounting legs (16) being of serpentine shape, each mounting leg (16) comprising at least a first generally straight section (16a), a second generally straight section (16a), and an end section (16b) of generally U-shaped form interconnecting the first and second generally straight sections (16a), wherein the thickness Te of the end section (16b) is greater than the thickness Tc of a central part (16c) of both of the first and second generally straight sections (16a).

Abstract: An accelerometer open loop control system comprising a variable capacitance accelerometer having a proof mass movable between fixed capacitor plates, drive signals applied to the capacitor plates, a charge amplifier amplifying an accelerometer output signal representing applied acceleration, and an autoranging facility for monitoring the output signal, and for adjusting the drive signals in dependence on the output signal in order to restrict the amplitude of the accelerometer output signal, thus maintaining sensitivity of the accelerometer while permitting response to a wide range of g values. Corrections are applied by means of look up tables to compensate for inaccuracies arising from movement of the proof mass and temperature variations.

Abstract: An accelerometer comprises a support (12), a proof mass (14) supported for movement relative to the support (12) by a plurality of mounting legs (16), a plurality of fixed capacitor fingers associated with the support (12) and a plurality of movable capacitor fingers associated with the proof mass (14), the fixed capacitor fingers being interdigitated with the movable capacitor fingers, the mounting legs (16) being of serpentine shape, each mounting leg (16) comprising at least a first generally straight section (16a), a second generally straight section (16a), and an end section (16b) of generally U-shaped form interconnecting the first and second generally straight sections (16a), wherein the thickness Te of the end section (16b) is greater than the thickness Tc of a central part (16c) of both of the first and second generally straight sections (16a).

Abstract: An accelerometer comprises a support, a first mass element and a second mass element, the mass elements being rigidly interconnected to form a unitary movable proof mass, the support being located at least in part between the first and second mass elements, a plurality of mounting legs securing the mass elements to the support member, at least two groups of movable capacitor fingers provided on the first mass element and interdigitated with corresponding groups of fixed capacitor fingers associated with the support, and at least two groups of movable capacitor fmgers provided on the second mass element and interdigitated with corresponding groups of fixed capacitor fingers associated with the support.

Abstract: An accelerometer open loop control system comprising a variable capacitance accelerometer having a proof mass movable between fixed capacitor plates, drive signals applied to the capacitor plates, a charge amplifier amplifying an accelerometer output signal representing applied acceleration, and an autoranging facility for monitoring the output signal, and for adjusting the drive signals in dependence on the output signal in order to restrict the amplitude of the accelerometer output signal, thus maintaining sensitivity of the accelerometer while permitting response to a wide range of g values. Corrections are applied by means of look up tables to compensate for inaccuracies arising from movement of the proof mass and temperature variations.

Abstract: The accelerometer has a base (2), an outer planar ring-like support frame (17) fixedly bonded to the base (2), and an inner planar ring-like support frame (18) flexibly suspended within the outer frame (17) by mounts (19) connecting the inner frame (18) to the outer frame (17) so that the inner frame (18) is spaced from the base (2), co-planar with the outer support frame (17) so as to provide flexible suspension for the inner support frame (18) reducing compressive and/or tensile forces on mounting legs (4) flexibly mounting a proof mass (3) in the inner support frame (18).

Abstract: A method of calibrating bias drift with operating temperature over an operating temperature range for a vibrating structure gyroscope having a substantially planar, substantially ring shaped silicon vibrating structure (1), primary drive means (7) for putting and maintaining the vibrating structure (1) in carrier mode resonance, and secondary drive means (9) for nulling response mode motion of the vibrating structure is described. The secondary drive means (9) includes means to separate a detected response mode motion signal into a real component induced by applied rotation of the vibrating structure gyroscope and a quadrature component which is an error term indicative of error mismatch between carrier mode resonance frequency and response mode resonance frequency.

Abstract: An accelerometer having a plate-like proof mass (1), flexible mounting legs (2) each co-planar with the proof mass (1), a ring-like support (3), in which the proof mass (1) is moveably mounted, with each mounting leg (2) being connected at one end to the proof mass (1) and connected at another end to the support (3) and with the mounting legs (2) extending substantially perpendicularly to the sensing direction, a plurality of interdigitated capacitor fingers mounted, in a gaseous medium, in the ring-like support (3) for sensing linear movement of, and for providing gaseous medium squeeze damping for the proof mass (1) in the sensing direction, with the fingers, proof mass (1), mounting legs (2) and support (3) being co-planar and formed from a single plate of mono-crystalline silicon, which fingers comprise fixed first, second, third and fourth arrays (5, 6, 7, 8) of laterally spaced fingers extending substantially perpendicularly to the sensing direction and away from the support (3) towards to the proof mas

Abstract: A modulated fibre Bragg grating strain gauge assembly for absolute gauging of strain including at least one sensor element (1) in the form of a length of optical fibre containing, along part its length, means for partially reflecting light (1a), means for generating and passing a beam of light (2a) with a spectral feature less than 0.

Abstract: A fiber optic interferometric strain gauge assembly includes a sensor element (1) in the form of a length of single mode optical fiber whose ends (1a) and (1b) have a peak reflectivity not exceeding 10%. This reflectivity is provided either by semi-transparent coating on the fiber ends or by the establishment of Bragg gratings within the fiber length. A laser source (2) provides a beam which is coupled into the element (1) as one arm of an interferometer. The light reflected in the interferometer whose intensity varies depending upon the degree of strain applied to the element (1) is detected and separated out into samples corresponding to the frequency of the laser source and to twice the frequency of the laser source with the two values being processed to provide both the magnitude of strain and the direction of strain in the element (1).

Abstract: To overcome Kerr effect induced gyro bias in a ring resonator optical gyro, the intensities of the beams travelling in opposite directions around the ring have to be very accurately matched. To achieve this a ring resonator gyro includes a first optical coupler (6), the coupling ratio of which is variable and which divides light from a laser (1) into a first and a second component of generally equal intensity, a second optical coupler (8) which transmits a predetermined proportion of the first component to one input of the ring resonator (15) for transmission around the ring resonator (15) in one sense, and a third optical coupler (9), the coupling ratio of which is variable to couple a variable proportion of the second component to the other input of the ring resonator (15) for transmission around the ring resonator (15) in the opposite sense.