| Measurement about the impedance parameters of ultrasonic transducer is an important content in the transducer measurement. There are two main methods to measure the impedance characteristic parameters of transducer:transmission line method and the admittance circle diagram. Measuring transducer impedance characteristic by admittance circle diagram will be very accuracy. Therefore, currently, this method is applied in most of the ultrasonic transducer impedance analyzer in science research and engineering field. But this impedance analyzer is very expensive, so it is difficult to be widely used.This paper discusses the advantages of various transducer parameters measurement method. Basing on virtual instrument to design ultrasonic transducer impedance analyzer, it researches mainly in the following aspects:(1) Discuss the application of phase detecting technology in the transducer measurement, according to the measuring standards made by country, improve the methods of voltage and current signals of phase detection in the traditional admittance circle diagram, design signal usually used the frequency range that transducer works to acquire circuit, and measure the phase by using the virtual instrument technology to construct relevant analysis and improve accuracy.(2) Research the method of controlling instrument,use the signal generator and digital oscilloscope and other common laboratory equipments as the major hardware of ultrasonic transducer impedance analyzer, by Lab VIEW software programming, control sweeping signal output from signal generator and the signal acquisition of digital oscilloscope, and compose signal generator and receiver system of impedance analyzer.(3) Research the calculated methods about measuring transducer impedance by traditional admittance circle diagram, propose the method of eliminating random noise when system is designed, eliminate the influence to the calculated results of the system ineffective signal by cubic spline fitting method.(4) This paper designed the software platform about ultrasonic transducer impedance analyzer, developed the module of system controlling signal generator, oscilloscope data acquisition module, signal filtering module, phase detection module, data calculation and processing module and data storage module.After the measurement and structural comparison, it shows that the ultrasonic transducer impedance analyzer which is designed based on Virtual Instrument has the following merits: (1) By comparing with the measurement of commercial products impedance analysis, the admittance circle diagram of measuring impedance designed in the paper has the same level accuracy.(2) Using the virtual instrument technology to design system, makes up the complex line connections, using common laboratory instrument to construct system reduces the costs of system and the application range.(3) Introducing the high-precision correlated analysis method of measuring the phase to the system, solves well the shortcomings that there are large errors in traditional phase detection. |
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