Signal processing method and system of vortex street flowmeter

Abstract

The related signal processing method with vortex shedding flowmeter dynamic adjusts the amplitude-frequency characteristics break over point Z of filter amplifier to control the dynamic range of signal pulse amplitude and eliminate high-frequency interference noise and inhibit low-frequency swing noise. This invention can work well on 4-20mA low-consumption two-wire system.

Description

technical field [0001] The invention relates to a signal processing method and system of a vortex flowmeter. Background technique [0002] The vortex flowmeter uses the principle of the Kalman vortex street in fluid mechanics, and according to the characteristic that the frequency of the sensor output signal is proportional to the flow velocity within a certain range of flow velocity, the frequency of the sensor output signal is used to measure the fluid flow velocity. Theoretically, the direct correspondence between the signal frequency and the flow velocity has a range of 100:1. But at the same time, the frequency amplitude of the output signal of the general stress sensor is proportional to the square of the signal frequency value, that is, the pulsation amplitude of the output signal of the sensor is relatively large when the flow rate is slightly high, and the corresponding frequency measurement is relatively easy. When it is low, the pulsation amplitude of the signal ...

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Problems solved by technology

But at the same time, the frequency amplitude of the output signal of the general stress sensor is proportional to the square of the signal frequency value, that is, the pulsation amplitude of the output signal of the sensor is relatively large when the flow rate is slightly high, and the corresponding frequency measurement is relatively easy. When it is low, the pulsation amplitude of the signal will be greatly reduced, and the noise such as high-frequency interference and low-frequency swing in the signal makes it very difficult to detect the vortex frequency in the signal

[0003] At present, there are mainly four signal processing methods for vortex flowmeters: one is a simple signal processing method and system that does not pursue low flow rate measurement, and mainly uses a fixed filter and a window comparator with a fixed threshold to capture the signal frequency; It adopts an adjustable band-pass filter method with tracking vortex street frequency to improve the processing level of low flow rate signals. This method mainly includes US patents 5372046, 5429001 and 5576497. Since the center frequency of the band-pass filter has to be Adjust to the vicinity of the current vortex street frequency to be found, so the contradiction between the correctness, rapidity and technical complexity of the tracking all make the realization difficult; the third is to use the digital spectrum analysis method to estimate the signal frequency of low amplitude, which is The first method has Chinese patent 99101209.7, etc., but there is a technical problem that the resolution and real-time performance of digital spectrum analysis are difficult to balance; the fourth is to use the second and third methods combined, such as U.S. Patent US6480812B1, U.S. Patent US6212975B1 and European Patent 645258, etc., mainly use spectrum analysis to find the frequency to be tracked, and then use a band-pass filter to improve the resolution of frequency detection. This type of method uses technical complexity to improve the accuracy of frequency tracking in the second method

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