An in-situ test calibration system and method are disclosed where a perpetual out-of-band electrostatic force induced excitation is used to dither the proof-mass of a MEMS based accelerometer where the amount of deflection change is proportional to sensitivity changes. The supplier of the accelerometer would exercise the accelerometer in a calibration station to determine initial sensitivity values. After the calibration and before removing the accelerometer from the calibration station, the supplier would start the dither and calibrate the acceleration equivalent force (F.sub.G) to drive voltage transfer function (F.sub.G/V). After installation of the accelerometer into a system or sometime later in the field, any changes in the F.sub.G/V transfer function due to changes in the sensitivity are observable and can be used for re-calibrating the accelerometer.

A MEMS accelerometer includes a suspended spring-mass system that has a frequency response to accelerations experienced over a range of frequencies. The components of the suspended spring-mass system such as the proof masses respond to acceleration in a substantially uniform manner at frequencies that fall within a designed bandwidth for the MEMS accelerometer. Digital compensation circuitry compensates for motion of the proof masses outside of the designed bandwidth, such that the functional bandwidth of the MEMS accelerometer is significantly greater than the designed bandwidth.

A MEMS accelerometer includes proof masses that move in-phase in response to a sensed linear acceleration. Self-test drive circuitry imparts an out-of-phase movement onto the proof masses. The motion of the proof masses in response to the linear acceleration and the self-test movement is sensed as a sense signal on common sense electrodes. Processing circuitry extracts from a linear acceleration signal corresponding to the in-phase movement due to linear acceleration and a self-test signal corresponding to the out-of-phase movement due to the self-test drive signal.

A MEMS accelerometer includes at least one proof mass and two or more drive electrodes associated with each proof mass. Self-test signals are applied to the drive electrodes. The self-test signals have a signal pattern that includes different duty cycles being applied to the drive electrodes simultaneously, which in turn imparts an electrostatic force on the proof mass. The response of the proof mass to the electrostatic force is measured to determine a sensitivity of the MEMS accelerometer.

A MEMS accelerometer includes at least one proof mass and two or more drive electrodes associated with each proof mass. Self-test signals are applied to the drive electrodes. The self-test signals have a signal pattern that includes different duty cycles being applied to the drive electrodes simultaneously, which in turn imparts an electrostatic force on the proof mass. The response of the proof mass to the electrostatic force is measured to determine a sensitivity of the MEMS accelerometer.

A microelectromechanical system (MEMS) accelerometer sensor has a mobile mass and a sensing capacitor. To self-test the sensor, a test signal is applied to the sensing capacitor during a reset phase of a sensing circuit coupled to the sensing capacitor. The test signal is configured to cause an electrostatic force which produces a physical displacement of the mobile mass corresponding to a desired acceleration value. Then, during a read phase of the sensing circuit, a variation in capacitance of sensing capacitor due to the physical displacement of the mobile mass is sensed. This sensed variation in capacitance is converted to a sensed acceleration value. A comparison of the sensed acceleration value to the desired acceleration value provides an indication of an error in operation of the MEMS accelerometer sensor if the sensed acceleration value and desired acceleration value are not substantially equal.

A MEMS accelerometer includes a suspended spring-mass system that has a frequency response to accelerations experienced over a range of frequencies. The components of the suspended spring-mass system such as the proof masses respond to acceleration in a substantially uniform manner at frequencies that fall within a designed bandwidth for the MEMS accelerometer. Digital compensation circuitry compensates for motion of the proof masses outside of the designed bandwidth, such that the functional bandwidth of the MEMS accelerometer is significantly greater than the designed bandwidth.

A method for generating a sensor output from the outputs of first and second sensors is provided. The method comprising receiving the outputs from the first and second sensors; estimating an offset between the outputs of the first and second sensors over a first range of outputs; adjusting the output of the second sensor based on the estimated offset; and generating a sensor output, based on the output of the first sensor, the adjusted output of the second sensor and a blending function that blends the output of the first sensor and the adjusted output of the second sensor.

In a method for open loop operation of a capacitive accelerometer, a first mode of operation comprises electrically measuring a deflection of a proof mass (204) from the null position under an applied acceleration using a pickoff amplifier (206) set to a reference voltage Vcm. A second mode of operation comprises applying electrostatic forces in order to cause the proof mass (204) to deflect from the null position, and electrically measuring the forced deflection so caused. In the second mode of operation the pickoff amplifier (206) has its input (211) switched from Vcm to Vss, using a reference control circuit (209), so that drive amplifiers (210) can apply different voltages Vdd to the proof mass (204) and associated fixed electrodes (202).

An acceleration detecting portion that detects an acceleration in a predetermined direction and an offset detecting portion that detects an offset amount with respect to the acceleration detecting portion are included. The offset detecting portion includes a second semiconductor substrate with a second cavity formed in its interior, a second fixed structure including a second fixed electrode that is supported, in a state of floating with respect to the second cavity, by the second semiconductor substrate, a second movable structure including a second movable electrode that is supported, in a state of floating with respect to the second cavity, by the second semiconductor substrate, and a disabling structure that disables a function of the second movable electrode displacing with respect to the second fixed electrode.