An accelerometer closed loop control system comprising: a capacitive accelerometer comprising a proof mass moveable relative to first and second fixed capacitor electrodes; a PWM generator to generate in-phase and anti-phase PWM drive signals with an adjustable mark/space ratio, wherein said drive signals are applied to the first and second electrodes such that they are charged alternately; an output signal detector to detect a pick-off signal from the accelerometer representing a displacement of the proof mass from a null position to provide an error signal, wherein the null position is the position of the proof mass relative to the fixed electrodes when no acceleration is applied; a PWM servo operating in closed loop to vary the mark/space ratio of said PWM drive signals in response to the error signal so that mechanical inertial forces are balanced by electrostatic forces.

A sensing structure for an accelerometer includes a support and a proof mass mounted thereto by flexible legs. The proof mass has moveable electrode fingers perpendicular to the sensing direction and at least four fixed capacitor electrodes, with fixed capacitor electrode fingers perpendicular to the sensing direction. The fixed capacitor electrode fingers interdigitate with the movable electrode fingers and the proof mass is mounted to the support by an anchor on a centre line of the proof mass. The proof mass has an outer frame surrounding the fixed capacitor electrodes and the flexible legs extend laterally inwardly from the proof mass to the anchor. The fixed capacitor electrodes comprise two inner electrodes, one on each side of the proof mass centre line, and two outer electrodes, one on each side of the proof mass centre line.

A resonant mechanical structure, such as one for use in a torsional oscillator MEMS accelerometer that includes a mounting substrate and a reference mass configured to move within a reference mass plane, the resonant mechanical structure being connected to the mounting structure and the reference mass, and the resonant mechanical structure including a body, a center of mass, and an aperture, wherein the aperture is surrounded and defined by the body, and wherein the body includes a first mass portion and a second mass portion that are configured to oscillate about an oscillation axis located within the reference mass plane, wherein the center of mass is located on the oscillation axis, and wherein a movement of the reference mass within the reference mass plane varies a moment of inertia of the body while the center of mass of the body remains located on the oscillation axis.

An accelerometer sensor having electrodes forming capacitors of capacitance that vary as a function of distances between the electrodes, a control unit being arranged to perform an operation of measuring the capacitances and a control operation that comprises selectively: a fine control stage in which a first voltage is applied between one of the stationary electrodes and the movable electrode, while the other stationary electrode is at the same potential as the movable electrode; and an extended control stage in which a second voltage is applied between one of the stationary electrodes and the movable electrode, the other stationary electrode being at the same potential as the movable electrode, and the second voltage being greater in absolute value than the first voltage. A method using such a sensor.

A MEMS sensor comprising preloaded suspension springs and a method for mechanically preloading suspension springs of a MEMS sensor are described. The MEMS sensor comprises a MEMS support structure; a plurality of suspension springs connected to said support structure; and, a proof mass flexibly suspended by said suspension springs; wherein at least one of said suspension springs is mechanically preloaded with a compressive force for reducing the natural frequency of said proof mass.

A micro-mechanical electrical systems (MEMS) type accelerometer for measuring vibration and movement employs a closed loop measurement mode. The accelerometer comprises at least one capacitive section configured as a sensing section and at least one capacitive section configured as an actuator section. In embodiments of the accelerometer capacitor plates are arranged in a bilateral structure in both the sensing and actuator sections. This structure combined with the capacitive feedback provided by the closed loop operation and other features of the device allow for a much larger sensing range in addition to other advantages over presently available MEMS accelerometers.

A moisture detector includes a sensor chip and a moisture determining unit. The sensor chip includes a humidity detector having a detection surface on which to measure humidity, and also includes a heater heating the detection surface, and the moisture determining unit is configured to, after causing the heater to start heating, determine whether moisture is present on the detection surface based on a difference in changes in the humidity measured by the humidity detector.

A method for closed loop operation of a capacitive accelerometer uses a single current source (62) and a single current sink (64) to apply an in-phase drive signal V.sub.1 to a first set of fixed capacitive electrode fingers and a corresponding anti-phase drive signal V.sub.2 to a second set of fixed capacitive electrode fingers. This provides a net electrostatic restoring force on the proof mass for balancing the inertial force of the applied acceleration and maintains the proof mass at a null position.

Provided is a sensor apparatus including: a normal operation unit including a first sensor and a storage device; an external environment detection unit including a second sensor; a power supply switch unit configured to control supply of electric power to the normal operation unit; and a power supply configured to supply the electric power to the normal operation unit via the power supply switch unit. In the sensor apparatus, in an operational mode, the normal operation unit records data measured by the first sensor into the storage device, and, in a non-operational mode, when a measured value obtained by the second sensor satisfies a predetermined condition, the external environment detection unit controls the power supply switch unit so that the power supply switch unit supplies the electric power to the normal operation unit, and the normal operation unit records the data measured by the first sensor into the storage device.

A microelectromechanical system (MEMS) sensor includes a MEMS layer that includes fixed and movable electrodes. In response to an in-plane linear acceleration, the movable electrodes move with respect to the fixed electrodes, and acceleration is determined based on the resulting change in capacitance. A plurality of auxiliary electrodes are located on a substrate of the MEMS sensor and below the MEMS layer, such that a capacitance between the MEMS layer and the auxiliary loads changes in response to an out-of-plane movement of the MEMS layer or a portion thereof. The MEMS sensor compensates for the acceleration value based on the capacitance sensed by the auxiliary electrodes.