The Design Of Virtual Instrument Based On USB Interface

With the development of modern instrument and computer technology, the virtual instruments are introduced to measurements. The virtual instrument is an important application in the field of CAT. Compared to traditional instrument, virtual instruments have the advantage of price, flexibility and so on. We expect that virtual instrument will be applied more and more, and the technology used in virtual instrument will be updated continually. The research on virtual instrument will also be deeper and deeper. Currently virtual instrument is still a hot topic in electronics and information technology.A virtual instrument Based on USB Interface is designed and developed in the dissertation. The design includes two parts: hardware and software. The hardware is about the design for circuit of data collection, and the software includes the design of the firmware of MCU and the application program. The circuit of data collection has a buffer of 64K. Its main ICs are the devices with high speed and high quality. The circuit can change sample speed in real time, so it greatly increases sample range for period signal. The USB device is applied in the interface circuit, so that the circuit has a feature of high speed and wide band. The application software for VI can be runed to display the waveform of time domain and frequency domain. The software gives a friendly interface and makes operation easily. The algorism for frequency domain use FFT to realize. Through the interface between VC++ and MATLAB, wavelet de-noising function of MATLAB is called for the algorism for de-noising. The experiment for the virtual instrument has been performed. The final result shows that the method of wavelet de-noising is very helpful for the filtering of signal noise. Finally, the parameter setups for wavelet de-noising function are analyzed in the thesis, and the different results with different parameters have been compared each other for the final conclusions.