Electrostatic Restoration
Active control of a sensor proof mass utilizes capacitive forces to maintain a neutral position against external accelerations. Implementing closed-loop electrostatic feedback allows high-performance accelerometers to operate with minimal physical displacement of the internal structure. This technique counters the input force by applying an equal and opposite electrostatic force.
Feedback Loop
A dedicated application-specific integrated circuit continuously monitors the deflection of the proof mass via sensing electrodes. In systems utilizing closed-loop electrostatic feedback, the controller adjusts the voltage applied to feedback electrodes to drive the displacement back to zero. This continuous correction prevents the mass from moving far from its null position under high acceleration loads.
The dynamic response of the feedback loop determines the frequency response and bandwidth of the sensor.
Sensor Stability
Calibration of the loop parameters occurs during production using precise voltage references. The scale factor depends primarily on the stability of the reference voltage and the geometric alignment of the electrodes. Environmental testing under varying temperatures ensures the feedback loop maintains its stability across the operating range.
Nulling Voltage
The maximum restoring voltage defines the input limit of the system. If the applied acceleration exceeds this threshold, closed-loop electrostatic feedback loses control and the mass contacts the mechanical stops. This event causes output saturation and requires a reset sequence.
