A self-calibration method for an accelerometer having a proof mass separated by a gap from a drive electrode and a sense electrode includes initializing the accelerometer to resonate, applying a first bias voltage to the sense electrode and a second bias voltage to the drive electrode to obtain a first scale factor, measuring a first acceleration over a first time interval, swapping the first bias voltage on the sense electrode with the second bias voltage previously on the drive electrode and the second bias voltage on the drive electrode with the first bias voltage previously on the sense electrode so that a bias voltage on the sense electrode is set to the second bias voltage and a bias voltage on the drive electrode is set to the second bias voltage to obtain a second scale factor, measuring a second acceleration over a second time interval, and calculating a true acceleration.

A MEMS inertial sensor includes a supporting structure and an inertial structure. The inertial structure includes at least one inertial mass, an elastic structure, and a stopper structure. The elastic structure is mechanically coupled to the inertial mass and to the supporting structure so as to enable a movement of the inertial mass in a direction parallel to a first direction, when the supporting structure is subjected to an acceleration parallel to the first direction. The stopper structure is fixed with respect to the supporting structure and includes at least one primary stopper element and one secondary stopper element. If the acceleration exceeds a first threshold value, the inertial mass abuts against the primary stopper element and subsequently rotates about an axis of rotation defined by the primary stopper element. If the acceleration exceeds a second threshold value, rotation of the inertial mass terminates when the inertial mass abuts against the secondary stopper element.

A resonant sensor including a support, a proof body suspended from the support and having a resonant frequency ωa, means for measuring a force including at least one resonator of resonant frequency ω.sub.rn, said force being applied by the proof body, and a mechanical decoupling structure interposed between the proof body and the resonator, said decoupling structure including a decoupling mass, a first connecting element between the decoupling mass and the proof body, a second connecting element between the decoupling mass and the resonator, the decoupling structure having a main vibration mode whose resonant frequency ω.sub.d is such that ωa <ω.sub.d< ω.sub.rn, said decoupling structure forming a mechanical low-pass filter between the proof body and the resonator.

FIG. 1

A microelectromechanical systems (MEMS) accelerometer comprises a compliant spring structure with a first beam, a second beam, and a rigid structure. One end of the first beam and one end of the second beam are coupled to the rigid structure and a proof mass is coupled to another end of the second beam. Further, a spring anchor is coupled to another end of the first beam. In response to the proof mass moving, an extension coupled to the rigid structure moves in an opposite direction to motion of the proof mass to contact the proof mass and stop the movement of the proof mass.

A micromechanical component for a pressure and inertial sensor device. The component includes a substrate having an upper substrate surface; a diaphragm having an inner diaphragm side oriented towards the upper substrate surface and an outer diaphragm side pointing away from the upper substrate surface, the inner diaphragm side bordering on an inner volume, in which a reference pressure is enclosed, and the diaphragm being able to be warped using a pressure difference between a pressure prevailing on its outer diaphragm side and the reference pressure; and a seismic mass situated in the inner volume, a sensor electrode, which projects out on the inner diaphragm side and extends into the inner volume, being displaceable with respect to the substrate due to a warping of the diaphragm. A pressure and inertial sensor device, and a method of manufacturing a micromechanical component for a pressure and inertial sensor device, are also described.

A capacitive accelerometer includes a proof mass, first and second fixed capacitive electrodes, and a DC biasing element arranged to apply a DC voltage (V.sub.B) to the proof mass based on a threshold acceleration value. A first closed loop circuit is arranged to detect a signal resulting from displacement of the proof mass and control the pulse width modulation signal generator to apply the first and second drive signals V.sub.1, V.sub.2 with a variable mark:space ratio. A second closed loop circuit keeps the mark:space ratio constant and to change the magnitude, V.sub.B, of the DC voltage applied to the proof mass by the DC biasing element so as to provide a net electrostatic restoring force on the proof mass for balancing the inertial force of the applied acceleration and maintaining the proof mass at a null position, when the applied acceleration is greater than a threshold acceleration value.

The present invention provides a high-accuracy low-noise MEMS accelerometer by using at least two symmetric out-of-plane proof masses for both out-of-plane and in-plane axes. Movement of the proof masses in one or more in-plane sense axes is measured by comb capacitors with mirrored comb electrodes that minimise cross-axis error from in-plane movement of the proof mass out of the sense axis of the capacitor. The two out-of-plane proof masses rotate in opposite directions, thus maintaining their combined centre of mass at the centre of the accelerometer even as they rotate out of plane.

A physical quantity sensor includes a substrate, a pair of first elements detecting acceleration in a first direction, and a pair of second elements detecting an acceleration in a second direction. The first element portion includes a first movable portion displaceable in the first direction, first and second movable electrode fingers disposed in the first movable portion, first and second fixing electrode fingers disposed to face the first and second movable electrode fingers, and first and second support portions supporting the first and second fixing electrode fingers. The second element includes a second movable portion displaceable in the second direction, third and fourth movable electrode fingers disposed in the second movable portion, third and fourth fixing electrode fingers disposed to face the third and fourth movable electrode fingers, and third and fourth support portions supporting the third and fourth fixing electrode fingers.

A motion sensing system uses high-voltage biasing to achieve high resolution with ultra-low power. The motion sensing system consists of a motion sensor, a readout circuit, and a high-voltage bias circuit to generate the optimized bias voltage for the motion sensor. By using the high-voltage bias, the signal from the motion sensor is raised above the readout circuit's noise floor, eliminating the power-hungry amplifier and signal-chopping used in conventional motion sensing systems. The bias circuit, while producing the programmable bias voltages for the motion sensor, also compensates for the process mismatch raised by the high voltage biases.

An accelerometer comprising: a frame; one or more proof masses suspended from the frame by one or more flexures and movable relative to the frame along a sensing axis; a resonant element assembly, the resonant element assembly comprising a first resonant element and a second resonant element coupled to one another, the first resonant element connected between the one or more proof masses and the frame, the second resonant element connected between the one or more proof masses and the frame, such that movement of the one or more proof masses relative to the frame along the sensing axis results in one of the first and second resonant elements undergoing compression and the other of the first and second resonant elements undergoing tension; and drive circuitry configured to drive the resonant element assembly and a sensing circuit configured to determine a measure of acceleration.