METHODS FOR CLOSED LOOP OPERATION OF CAPACITIVE ACCELEROMETERS, AND CAPACITIVE ACCELEROMETERS

摘要

To provide methods for closed loop operation of capacitive accelerometers.SOLUTION: A capacitive accelerometer includes a proof mass, first and second fixed capacitive electrodes, and a DC biasing element arranged to apply a DC voltage of magnitude VB 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 a pulse width modulation signal generator to apply first and second drive signals V1, V2 with a variable mark:space ratio. A second closed loop circuit keeps the mark:space ratio constant, and is arranged to change the magnitude VB 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.SELECTED DRAWING: Figure 6