Digital integrated mass vortex-shedding meter

Abstract

The invention discloses a digital integrated mass vortex-shedding meter, which comprises a meter body, a sensor, amplifiers, output circuits and a display device. The digital integrated mass vortex-shedding meter is characterized in that: 1, amplitude-frequency characteristic identification technology is adopted to identify Fourier spectrum according to an amplitude-frequency characteristic model to further improve the lower limit of measurement capacity; 2, linear correction technology is adopted to calculate flow in sections and inversely calculate frequency output with the flow to improve accuracy; 3, a compound sensor is adopted to integrally measure temperature and pressure to provide data for steam state identification and mass flow calculation; 4, steam state identification technology is adopted to judge a steam state and calculate density with the temperature and the pressure; and 5, on the basis of improving volume flow measurement and the steam state identification, integrated mass flow measurement is realized by flow compensation technology. In an actual measurement process, the digital integrated mass vortex-shedding meter completely eliminates the shortcomings of the poor resistance to shock, low disturbance resisting capacity, large measurement dead zone, poor linearity and the like of the conventional vortex-shedding meter and can greatly reduce measurement starting flow velocity and simultaneously improve the radio of measuring range and accuracy.

Description

technical field [0001] The invention belongs to the technical field of flow measurement, and in particular relates to digital signal processing of a vortex flowmeter, integrated temperature and pressure measurement, steam state identification and derivation-type mass flow measurement technology. Background technique [0002] The vortex flowmeter is a flow meter designed based on the Karman vortex principle. There is a resistance element (vortex generator) installed in the instrument. When the fluid reaches a certain flow rate and flows through the resistance element, two rows of vortices (vortex street) appearing alternately and arranged neatly will be stably generated downstream of it. The frequency of the vortex is between Within a certain Reynolds number range, it is proportional to the flow velocity of the fluid. Accordingly, by detecting the vortex frequency and knowing the cross-sectional area of ​​the pipe, the volumetric flow rate of the fluid can be obtained. [0...

AI Technical Summary

Problems solved by technology

[0004] 1) The lower limit measurement ability is low

Since it works on the principle of vibration, the sensor signal will inevitably contain vibration and electromagnetic interference signals; the effective signal amplitude is zero when the flow rate is zero, and the existence of electromagnetic and vibration interference signals makes the signal-to-noise ratio = 0, resulting in non-return to zero; and The effective signal amplitude has a square relationship with the flow velocity. When the flow is small, the effective signal amplitude decreases squarely, and the signal-to-noise ratio is less than 1, which makes it difficult to measure small flow.

[0005] (2) Poor linearity

The usual density correction method to measure mass flow requires additional installation of pressure and temperature instruments, which has many links and high cost and is inconvenient to implement

[0007] (4) For water vapor measurement, there is no state recognition function

Compared with water and gas, steam is a precious secondary energy source. It should have more accurate measurement accuracy, but affected by the three-variable problem, there are generally larger errors than water and gas measurement; vortex flowmeters are used for steam measurement important means, in particular should address the

[0008] Chinese patent application 200410019008.9 proposes a "low power consumption digital vortex flowmeter", which uses a combination of a microcontroller MCU and a DSP (digital signal processor) and an embedded relaxation notch algorithm for digital signal processing, and strives to solve Problems such as power consumption and lower limit measurement and poor shock resistance

One type of technology is achieved by simultaneously measuring frequency and amplitude through piezoelectric sensors or differential capacitance sensors; the other type is achieved by measuring differential pressure and frequency before and after the vortex generator; actual experience, accurate measurement of frequency, amplitude and differential pressure of sensors It is difficult to measure mass flow accurately without solving the key problem of frequency measurement; and there is currently a lack of mass flow standard devices, making calibration difficult; so these products are actually rare

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