Research On Accuracy Of Digital Piezoelectric Transducer Admittance Circle Measurement System

There are a lot of kinds of acoustic logging instruments. And their common characteristic is measuring acoustic velocity and amplitude through sending and receiving sound waves. The piezoelectric transducer is the key component of the logging instrument ,it is used in pairs most of the time. Experiments show that, the received waveform shape will be basical same when the launch transducer and receive transducer have the same electronic characteristics. Therefore, it is necessary to get the electrical parameters of the piezoelectric transducer before using it.There are many ways to get the electrical parameters. The paper designed a new type of digital admittance circle measuring instrument according to the impedance characteristics of transducer that the conductances and susceptances near the resonant frequency of the piezoelectric transducer form a circle. The measuring instrument can accurately obtain the electrical parameters of the transducer.The hardware part contains controller, ADC, sine signal generator, digital potentiometer. The sine signal generator and digital potentiometer are managed by the controller,they are used to produce a given sine signals and resistance ; Sine signal is collected by the ADC.The software of the measurement system consisting of two parts: The hypogynous machine sets the frequency control words of sine signal generator and digital potentiometer , ADC acquisition frequency size through receiving the given relevant information from PC machine by the USB; save the signal sampled data of both sides of the piezoelectric transducer through the FIQ interrupt; transmitt the acquisition data to PC machine through the USB. The PC machine draws the user interface to set the start and stop frequency, frequency step, variable step size and other information; process the sampled data gathering from the hypogynous machine by using digital correlation method and other data processing methods; realize real-time drawing, data preservation and other functions at last.The experimental results show that: Using different measurement resistance, the admittance circle measurement effect is different ; Using different methods of data processing method, the admittance circle measurement effect is also different.