Spectrum From The Regression Model Is Estimated In The Flow Measurement Applications

Flow is an important parameter in industrial control and production. People designed diversified flowmeters to measure flow accurately. Because vortex flowmeter has no movable mechanical parts, the output signal of it is a frequency signal that is proportional to flow signal, and it has less pressure loss, wider measurement range, it is used widely. But, due to the work principle of vortex flowmeter, vortex flowmeter is sensitive to all kind of extraneous disturbances. These disturbances reduce measurement accuracy and make locale measurement accuracy greatly lower than the accuracy that is calibrated in laboratory. The traditional signal processing methods that amplify, filter, rectify signal and count, which are used in vortex flowmeter now, has shortage in extracting real flow signal from noise. The methods that restrict measurement range or don't measure small flow have to be adopted. This article is to develop autoregressive(AR) model spectrum estimation based on the theory of digital signal processing to analyze, process flow signal, to get the frequency of flow signal and then convert it to flow value. At last, the flow value is compared with the result that is gained by using count method. The methods and developing status of flow measurement and physical parameter of fluid, the principle of vortex flowmeter, the theory of AR model spectrum estimation are described at the beginning of the thesis. The author develops a flow measurement system comprising the signal processing circuit and measurement software to measure flow and do qualitative and quantitative to measurement results that gain by count method and AR model spectrum estimation method. The article approaches the following points:(1) Research of flow sensor theory, sorts, history. The principle, structure and measurement circuit of vortex flowmeter are mainly discussed in the article.(2) Research of AR model spectrum estimation theory. According to the theory, the method that processes and analyzes flow signal and calculates the frequency of it and converts the frequency to flow is brought forward.(3) Flow measurement system based on vortex flowmeter. The author designs a circuit that attenuates and shapes the output signal of flowmeter. Interrupt mode is used for acquiring the processed signal in the measurement software. The signal is processed and converted to flow in the software. Finally, the flow is showed on the screen of computer and is stored in computer files.(4) Count method and AR model spectrum estimation method are adopted respectively to experiment. Validated by the experiments, AR model spectrum estimation method is a good way to process flow signal and the results of it is more accuracy than the results that gain by count method.