Accelerometers

A method for controlling closed loop operation of a capacitive accelerometer 100 comprises applying first in-phase and anti-phase PWM drive signals 302, 304, respectively, to a first pair of fixed capacitive electrodes 106a, 108b and applying second in-phase and anti-phase PWM drive signals 306, 308, respectively, to a second pair of fixed capacitive electrodes 108a, 106b. A displacement of a proof mass 102 relative to fixed capacitive electrodes 106a, 108b, 108a, 106b is sensed by measuring a pickoff signal from the proof mass 102 and adjusting the mark-space ratio of the first and/or second PWM drive signals 302, 304, 306, 308 to provide a restoring force on the proof mass 102 that balances an applied acceleration and maintains the proof mass 102 at a null position. The first and second PWM drive signals 302, 304, 306, 308 applied to the first and second pairs of fixed capacitive electrodes 106a, 108b, 108a, 106b are offset in time from one another by an offset period.