Mobile plate accelerometer with electrostatic feedback motor

Slaved mobile plate accelerometer using variations of capacitance to detect the movement of a mass, comprising:

• at least one pair of fixed electrodes rigidly attached to an armature, and
• at least one mobile electrode suspended by springs from the armature, between the two fixed electrodes of said pair of fixed electrodes, to form two capacitors, said mobile electrode being adapted to move between the fixed electrodes of each pair of fixed electrodes, due to the effect of the acceleration, so causing a variation of the capacitance of each capacitor,
• characterized in that
• said accelerometer includes an electronic circuit for adjusting the electrostatic stiffness of at least one combination of a fixed electrode and a mobile electrode and comprising a control system for detecting the variation of the capacitance of each capacitor by applying two voltages (+Vm,−Vm) symmetrical about ground, and reacting by applying a feedback voltage between each mobile electrode and the fixed electrode facing said mobile electrode, in that
• the springs have a stiffness chosen intentionally to place the mechanical resonant frequency beyond the lop frequency of the band of interest, and in that
• the circuit for adjusting the electrostatic stiffness is adapted to return the apparent resonant frequency into the band of interest.