Application Rescarch Of Digital Signal Processing In Doppler Ultasonic Flowmeter

The project is a cooperative research between Bland research institute of XI'AN and Department of Electronic Engineering of XI'AN University of Technology. Major work of the project is to improve performance of Doppler flowmeter with digital signal processing and to design a Doppler flowmeter on DSP(digital signal processor). There are six chapters in the paper. The third chapter and the fourth chapter of them are the most important.The first chapter is about the features, application ranges and history of Doppler flowmeter.In the second chapter, the principles of Dopp1er flowmeter and some factors bringing error to measure ware explained briefly.In the third chapter, back wave signal of Doppler was analyzed with theory of random signal processing and source of error for old method were found. A new method of frequency analysis was given. Basing on the method, digital signal processing can be used and more precision of measure can be obtained. At the end of this chapter a Fen Lie Ji FFT program was given by author. It is for calculating signal of power spectra.In the fourth chapter, hardware and software of Doppler flowmeter system on new method were designed and made. They could accomplish amplification,data acquisition and calculation to signal. Hardware includes generating and,amplifying of ultrasonic, mixing, receiving and amplification of signal, data acquisition,memory, RS232 interface, DSP; Software includes subprograms of direct digital frequencysynthesis, subprogram of analog to digital converter, subprogram ofcommunication between PC and DSP and main program.Experiment of measure are described in the fifth chapter. The measure result indicated that the improved Doppler ultrasonic flowmeter was running well. The precision calculation showed that the Doppler ultrasonic flowmeter on DSP had reached the anticipant object. It is better than the old one.End of this paper is summary. Some improvement was given further.