Development Of Piezoelectric Transducer Admittance Circle Measuring Instrument Base On Arm7

Piezoelectric transducer is a key component of acoustic logging apparatus for transmitting and receiving acoustic signals. In Well Logging, piezoelectric transducers are usually used in pairs. Experiments showed that only when the pair of piezoelectric transducers had the same resonant frequency and band width, the received waveforms are highly consistent under the same conditions. Generally speaking, a great number of practices have confirmed that whether Well Logging transducers are consistent or not directly determine a successful logging.Based on actual demand, the new generation of digital piezoelectric transducer admittance circle measurement system, which is based on the ARM controller and high-speed ADC, is designed and aimed to measure the characteristic parameters of the transducer, which are essential to select transducers of a good consistency.The idea of the hardware part: firstly, the microcontroller LPC2146 controls signal generator AD9850, which is using DDS technology, to generate sinusoidal signal under desired frequency. Secondly, the high-speed ADC ADS2806 converts the sinusoidal signals on the two-way. Thirdly, the microcontroller completes conversion data collection and USB transmission. Finally, the collected data are processed in the PC in order to obtain the curves, which indicate the relationship between admittance and frequency of the transducer, and ultimately determine the characteristic parameters.The software part of the system includes the measurement software and data processing program. Measurement software is realized with C + + language to achieve the initialization of test data, data collection, data transmission and preservation. Data processing program is completed with MATLAB, using three different methods: digital correlation, fast Fourier transform and sine curve fitting parameters to achieve data processing and obtain the characteristic parameters of the transducer.Comparison experimental results show that: compared with analogous admittance circle measuring instrument, the new system has the advantages of wide measuring range, high accuracy, good stability and flexibility. Compared with expensive foreign impedance analyzer, the new system has the well-targeted and inexpensive advantages. For existing digital admittance circle measurement system, the new system has a wider measuring range, better testing accurate and lower cost.