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.
Resonance Frequency: 4.6 Khz +/- 0.5 Khz
Resonance Impedance: 200 Ohms
Capacitance: 20nF +/- 30% at 1 Khz
Operating Temperature -20...+70 C
Storage Temperature -30...+80 C