Wide bandwidth capacitive acoustic emission sensor with stopband movable electrodes

This paper presents a capacitive acoustic emission sensor with movable electrodes, which operate at stopband. Stopband electrodes cannot be excited by an AE signal, while the substrate vibrates with the signal. The change in the capacitance between the stopband electrodes and substrate is proportional to the amplitude of the AE signal. As bandwidth and sensitivity are not limited by the mechanical properties of the movable electrodes, the sensor features a wide bandwidth.