Research Of Impedance Automatic Measuring System Based On The Virtual Instrument

With the development of the computer technology,the field of instrumentation begins to change dramatically from traditional instruments and intelligent instruments to virtual instruments.Due to its strong advantages on storage,data display and data analysis,the virtual instruments have gained more attention.Virtual-instrument technology combines the computer and the instrument hardware together using software.It combines the excellent data processing ability of computer with the measurement,and controlling ability of instruments hardware together in this technology.Consequently,not only the cost of the production is reduced,but the instrument performance is also improved.Therefore,the virtual instrument has been widely used.In addition,with the progress of modern science and technology,the measurement of impedance has gradually become the basis of all kinds of electronic products.At present,the impedance measurement technology has been widely used in biomedical science,industrial measurements,power control and other domains.In order to satisfy the measurement requirements of electronic components and their subsidiary parameters in the university laboratory,a kind of impedance measurement system based on virtual instrument is designed in this paper.Based on the combination of virtual instrument technology and traditional hardware,this paper designs and realizes a system to measure the impedance parameters using the volt-ampere method.Utilizing the relationships between the real and the imaginary parts of the voltage vector and the complex impedance,the measurement of the complex impedance can be converted to the measurement quality of the voltage vector.The process can effectively improve the precision of the system.The system consists of two parts: hardware and software.The hardware part is mainly composed of the signal source module designed by FPGA,the conversion module of impedance to voltage vector,the phase sensitive detection module,the A/D conversion module,and the communication module.The design and realization of sinusoidal excitation signal and the reference signal is utilized by FPGA.We separate the real and imaginary parts of the voltage vector by the phase sensitive detection,and filter out the interference by a low pass filter.Then the collected signal is converted to a digital signal by an A/D conversion chip.The data will be transmitted to the computer through a communication bus of the system,and then it will be processed and displayed.The software part realizes the data processing,display and control using the virtual instrument software LabVIEW.And the operation of the instrument is performed by calling dynamic link libraries.