| Among many flow meters,vortex flowmeter is widely used to measure the flow of various media such as liquids,gases and saturated vapors.The vortex flowmeter is based on the principle of fluid vibration for flow measurement.In practical applications,vortex flowmeters is particularly susceptible to pipeline vibration disturbances.When there is vibration interference on the pipeline,the output signal of the vortex flow sensor includes not only the flow signal but also the pipeline vibration interference signal.If the energy of the pipeline vibration interference is greater than the energy of the flow signal,that is,there is strong pipeline vibration interference on the pipeline,the conventional signal processing algorithm according to the energy dominant principle extracts the frequency of the vibration noise as the frequency of the flow signal,and this means that a measurement error has occurred.The experimental platform of vortex flowmeter against strong vibration interference was built,and a large amount of experimental data about flow signal,vibration interference signal and co-frequency signal(the output signal of the vortex flow sensor when the frequency of the flow signal is the same or similar to the frequency of the vibration disturbance)were collected.The frequency variance and spectral amplitude of the signal are analyzed,at the same time,the influence of the vibration interference on the spectral amplitude of the flow signal is also analyzed.A method of anti-strong pipe vibration of vortex flowmeter combined with frequency variance calculation and amplitude operation is proposed.The method calculates the frequency variance and processes the calculation result of frequency variance,and then performs spectral amplitude calculation.Combining the results of frequency variance and amplitude calculations,the frequency of the flow signal is extracted from the signal containing strong vibration interference.In this way,the frequency information and amplitude information of the signal are fully utilized to estimate the frequency of the flow signal,thereby better eliminating vibration fundamental interference and vibration harmonic interference,and solving the problem of measuring the same frequency signal.A low-power vortex flowmeter system based on MSP430F5418 microcontroller is developed to realize anti-vibration algorithm in real time,and carried out gas calibration experiments and anti-vibration experiments to verify the anti-vibration performance of the algorithm and the accuracy level of the algorithm for normal flow measurement in Chongqing Chuanyi Automation Co.,Ltd.Among them,the results of anti-vibration experiments are summarized as follows:if the frequency of the flow signal and the vibration signal are different,the vortex flowmeter can extremely resist the horizontal vibration interference whose spectral amplitude is 21.2 times of the spectral amplitude of the flow signal or the vertical vibration interference whose spectral amplitude is 18.5 times of the spectral amplitude of the flow signal;if the frequency of the flow signal and the vibration signal are same,the vortex flowmeter can extremely resist the horizontal vibration interference whose spectral amplitude is 1.3 times of the spectral amplitude of the flow signal or the vertical vibration interference whose spectral amplitude is 1.3 times of the spectral amplitude of the flow signal.The results of the gas flow calibration experiment are as follows:the vortex flowmeter developed by us has a measuring turndown ratio 1:10 or more for measuring gas flow and its measurement accuracy reaches the Chinese standard 1.0 level.The power consumption tests are designed to examine the current consumed by the developed signal processing system.The test result is:the current consumed by the system during full load operation is 3.7580 mA,which satisfies the requirement that the two-wire process control instrument needs less than 4 mA for the system current consumption. |
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