27mm Piezo Electric Sensor (Piezo Buzzer Ceramic Plate)

A piezoelectric sensor/element is a device that uses the piezoelectric effect, it is basically a device which converts voltage to vibration and vibration to voltage. It normally comes in handy to measure knock (knock  sensor) or vibration (vibration sensor).

Now a days it is also used extensively in power generation projects e.g. Foot Step Power Generation.