Readout System of Piezoelectric Sensor Used for High Speed Weigh in Motion Application

The piezoelectric sensors are the main electronic devices widely used to measure the instantaneous force that is exerted on the sensor surface by vehicle wheels moving at normal speed. This application is typically implemented in High Speed Weigh in Motion system, which has been until today under research studies. The system aims to perform an accurate and reliable axle load measurement of heavy trucks in motion. The piezoelectric sensor produces a voltage when a strain is applied on its surface. In general, the voltage signal is in a pulse form as a deterministic signal, easy to operate, but often it is not so. This problem is due to more signal noise, for the most part, because of either the modest quality of piezoelectric sensor or the inefficiency of sensor signal conditioning stage design. The present paper introduces a newly readout system allowing the processing of the piezoelectric sensor output signal in response of exerted force. The studied system consists on the charge amplifier, which is coupled with a transistor used in decoupled common emitter. This circuitry scheme cancels noise and random effect on sensor signal. The purpose of the present study focuses on the achievement of a reliable and deterministic signal, using a sensor with modest quality. The experiment results show the efficiency of the proposed readout system. Even though more noises affect the piezoelectric sensor output signal, the proposed electric interface provides a deterministic and suitable analog signal offering more possibilities to process with the standard tools of signal processing.