Seismic (inertial or proof) mass is suspended between two plates of Pyrex glass or silicon with a narrow gap between them
Counter plates contain fixed electrodes
Inertial mass constitutes a movable electrode
Movement of the mass due to acceleration of the device will change the capacitance with the two fixed electrodes
This capacitance is used in a capacitive bridge to transduce the displacement into a voltage
Fabrication of bulk micromachined capacitive accelerometer consists of
Silicon wafer etching from the back side or both sides to form the suspension and proof mass
This wafer is anodically bonded to two capping wafers on both sides
Capacitor plates are defined on both sides of the proof mass and are aligned with the capacitor plates on the capping wafers to form two differential capacitors
Size of bulk micromachined accelerometers is typically a few milimeters.
Accelerometer
