A circuit design in piezoelectric vibration measurement system

This paper presents a circuit to measure the output voltage of piezoelectric polyvinylidene fluoride (PVDF) sensor. The PVDF sensor is applied in a vibration test system. With direct piezoelectric effect, the PVDF generates voltage while vibration signal is loaded. When the vibration is week, and the voltage of PVDF is low, then the high output impedance of PVDF makes the voltage pick-up hard, therefore a special voltage pre-amplify circuit is needed. The circuit adopts a JEFT-input Operational Amplifier (OP) with high input impedance and low bias current. Decoupling capacitors are used to smooth the DC power output for OP. Noise suppression measures are taken and band-reject filter is adapted to remove 50Hz power frequency noise. Experiment shows the circuit is stable, and the vibration signal can be accurately analyzed.