A capacitance detection circuit inhibits noise. The capacitance detection circuit detects a change in capacitance between a pair of electrodes of a physical quantity sensor, with these electrodes generating the change in capacitance in response to a change in physical quantity. The capacitance detection circuit has a carrier signal generating circuit that supplies a carrier signal to one of the electrodes, an operational amplifier that has an inverting input terminal to which the other one of the electrodes is input, a dummy capacity that is connected in parallel to the pair of electrodes, and a carrier signal conditioning circuit that inverts a phase of a carrier signal supplied from the carrier signal generating circuit to the dummy capacity and adjusts a gain to inhibit the dummy capacity.

A micro-electromechanical (MEMS) apparatus includes a substrate, two first anchors, a frame, and two elastic members. The substrate is provided with a reference point thereon. The frame surrounds the two first anchors, and each of the elastic members connects the corresponding first anchor and the frame. Each of the first anchors is disposed near the center of the MEMS apparatus to decrease an effect caused by warpage of the substrate. The MEMS apparatus can be applied to an MEMS sensor having a rotatable mass, such as a three-axis accelerometer or a magnetometer, to improve process yield, reliability, and measurement accuracy.

A producing method for a diaphragm-type resonant MEMS device includes forming a first silicon oxide film, forming a second silicon oxide film, forming a lower electrode, forming a piezoelectric film, forming an upper electrode, laminating the first silicon oxide film, the second silicon oxide film, the lower electrode, the piezoelectric film, and the upper electrode in this order on a first surface of a silicon substrate, and etching the opposite side surface of the first surface of the silicon substrate by deep reactive ion etching to form a diaphragm structure, in which the proportion R.sub.2 of the film thickness t.sub.2 of the second silicon oxide film with respect to the sum of the film thickness t.sub.1 of the first silicon oxide film and the film thickness t.sub.2 of the second silicon oxide film satisfies the following condition:
0.10 mt.sub.12.00 m; and
R.sub.20.70.

An acceleration sensor includes: a moving electrode extending in at least one of a first direction and a second direction perpendicular to the first direction, and including a plurality of planar patterns connected with each other; and an opposing electrode forming a capacitance with the moving electrode, wherein the plurality of planar patterns include: a first frame pattern; a first anchor pattern fixing the moving electrode to a surrounding structure; a first spring pattern connecting the first frame pattern and the first anchor pattern and having a stretching direction of the first direction; a second spring pattern connecting the first frame pattern and the first anchor pattern and having a stretching direction of the second direction; a wing pattern; and a third spring pattern connecting the first frame pattern and the wing pattern and having a stretching direction of a third direction perpendicular to the first and second directions.

A capacitance detection circuit has at least a carrier signal generating circuit that supplies a carrier signal to one of a movable or a fixed electrode of a sensor, an operational amplifier with one of the movable or fixed electrode as an input and ground as another input, and a printed circuit board on which the physical quantity sensor, the carrier signal generating circuit, and the operational amplifier are mounted. An insulation-secured area on the printed circuit board is configured as a moisture absorption reduction area, including at least an electrode connection part of the physical quantity sensor, an input-side connection part of the operational amplifier, and a connection part connected to the input side of the operational amplifier out of connection parts of input-side circuit components connected between the electrode connection part and the input-side connection part.

A seismic sensor comprises a central mass having three principal axes and disposed within a frame. A plurality of transducers is mechanically coupled between the frame and the central mass. The transducers are arranged in pairs, with the transducers in each pair being coupled to opposing sides of the central mass, as defined along each of the three principal axes. Electronics can be provided to combine signals of the transducers in each pair to generate output characterizing acceleration and rotation of the frame.

A seismic sensor system includes a seismic sensor suspended in an acoustic medium, which is disposed between first and second sensor housings. The acoustic medium can be selected to preferentially transmit pressure wave energy, based on the acoustic impedance of the surrounding water column or other seismic medium. The acoustic medium can also be selected to preferentially dissipate or otherwise reduce the transmitted shear wave energy. The second housing can similarly be configured to dissipate shear wave energy, while transmitting pressure wave energy in the form of acoustic waves that propagate through the acoustic medium to the seismic sensor.

A micro-electro-mechanical system (MEMS) motion sensor is provided that includes a MEMS wafer having a frame structure, a plurality of proof masses suspended to the frame structure, movable in three dimensions, and enclosed in one or more cavities. The MEMS sensor includes top and bottom cap wafers bonded to the MEMS wafer and top and bottom electrodes provided in the top and bottom cap wafers, forming capacitors with the plurality of proof masses, and being together configured to detect motions of the plurality of proof masses. The MEMS sensor further includes first electrical contacts provided on the top cap wafer and electrically connected to the top electrodes, and a second electrical contacts provided on the top cap wafer and electrically connected to the bottom electrodes by way of vertically extending insulated conducting pathways. A method for measuring acceleration and angular rate along three mutually orthogonal axes is also provided.

An acceleration sensor can ensure rigidity of its movable electrode despite a large number of through-holes formed in the movable electrode. The acceleration sensor has an SOI substrate in which a silicon oxide layer is formed on a silicon support layer and an active silicon layer is formed on the silicon oxide layer, wherein the active silicon layer of the SOI substrate has a movable electrode supported by elastic beams and configured with a weight, and also has fixed electrodes disposed in a fixed manner around the movable electrode to face the movable electrode, and wherein through-holes penetrating in a Z-axis direction are formed over the entire surface on the inner side of an outer circumference to which the elastic beams of the movable electrode are connected.

A microelectromechanical accelerometer is provided that includes one or more proof masses. The accelerometer also includes four sets of stator combs that form a set of four measurement capacitors together with rotor combs. Some rotor combs have a positive offset in a direction in the device plane in relation to stator, while others have a negative offset. Some rotor combs have a negative offset in a direction perpendicular to the device plane in relation to stator combs. Moreover, some stator combs have a negative offset in the direction perpendicular to the device plane in relation to rotor combs.