Capacitive Balancing
Closed loop MEMS accelerometers maintain proof mass position using voltage induced electric fields. Electrostatic restoring force counteracts external inertial acceleration by pulling the suspended mass back toward its nominal zero position. Feedback control loops adjust electrode voltages dynamically based on displacement error signals.
Maintaining constant proof mass location expands operating linearity and prevents mechanical stop contact.
Voltage Scaling
Applied feedback voltage generates an attractive force proportional to the square of the potential difference between drive plates. Control algorithms calculate required corrective voltages to neutralize applied inertial loads. Linearized control schemes convert squared voltage outputs into proportional acceleration measurements.
Feedback loop gain establishes the dynamic range and bandwidth of the closed loop sensor.
Ambient Interference
Temperature variations alter electrode gap dimensions through thermal expansion of package structures. Dimension shifts change capacitance values, altering generated restoring forces for a given control voltage. Dielectric charge accumulation on cavity surfaces distorts internal electric fields over prolonged operation.
Charge buildup shifts zero acceleration voltage baselines, creating offset errors in measured acceleration values.
Final Acceptance
Automated test systems calibrate feedback loop response by applying reference acceleration inputs on tilt tables. Verification routines measure voltage output linearity and scale factor accuracy across operational g ranges. Inspection protocols confirm electrostatic force balancing operates within stability limits over the full operating temperature range.
