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Frequency modulation wave marking method for time-difference process ultrasonic flowmeter

A technology of frequency modulation and marking method, which is applied in fluid velocity measurement, flow/mass flow measurement, liquid/fluid solid measurement, etc. It can solve the problem of unstable signal waveform amplitude and achieve the effect of avoiding harsh requirements and reducing requirements.

Inactive Publication Date: 2008-04-16
ZHEJIANG SCI-TECH UNIV
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  • Abstract
  • Description
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Problems solved by technology

[0004] The main problem to be solved by the present invention is the time difference measurement problem caused by the unstable signal waveform amplitude in the time difference method gas ultrasonic flowmeter flow detection

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  • Frequency modulation wave marking method for time-difference process ultrasonic flowmeter
  • Frequency modulation wave marking method for time-difference process ultrasonic flowmeter

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Embodiment Construction

[0019] The invention proposes to superimpose a frequency change on the working center frequency of the transducer, use the frequency change correlation characteristics of the transmitted and received signals to mark the arrival time of the waveform, and measure the transit time between the transmission and reception of ultrasonic waves. Since the main mark in the correlation operation is the frequency change, it is not sensitive to the amplitude change of the waveform signal, which can significantly reduce the requirements for the signal-to-noise ratio.

[0020] The implementation steps are as follows:

[0021] (1) As shown in Figure 2, a high-speed processor is used to generate a transmission signal with a frequency of f(t)+Δf(t), where f(t) is the resonance frequency of the transducer, and Δf(t) is a predefined frequency change. This process is equivalent to performing a frequency modulation on the transmitted signal. The transmitted and received waveforms obtained by this m...

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Abstract

The present invention relates to a frequency modulation waveform marking method of time difference method ultrasonic flowmeter, and is used to measure the transmitting time of an ultrasonic signal in the fluid medium, thereby measuring the flow speed and the flow capacity of medium. The method provided by the invention has the following procedures: (1) frequency variation is overlaid on transducer operating frequency to form an emitting signal; (2) the emitting signal carries the information of flow speed when the fluid medium transmits; (3) signals are collected on a receiving transducer terminal; the frequency variation signals are demodulated and have related calculation with the original frequency variation signals in the procedure one; (4) according to the related function peak value, the signal transmitting time is calculated to gain the flow speed and the flow capacity. The frequency variation provided by the invention can be achieved through overlaying frequency deviation on transducer resonance central frequency; the frequency after overlaid is in the operation bandwidth of the transducer; the invention has the advantages of having no interference by signal amplitude fluctuation and flow and of achieving the signal transmitting time with high measuring precision.

Description

technical field [0001] The invention belongs to the category of time-difference ultrasonic flowmeters, in particular to a frequency modulation waveform marking method for ultrasonic flowmeters. Background technique [0002] Compared with traditional flowmeters, ultrasonic flowmeters have no moving parts, no pressure loss, good traceability, and cost is not sensitive to caliber changes. Therefore, ultrasonic flowmeters have obvious local advantages in flow measurement of medium and large pipe diameters. Promote faster. Due to the serious attenuation of ultrasonic signals in gas and the low acoustic transmittance of gas and ultrasonic transducers, there are still many problems in gas flow measurement, and it is generally difficult to achieve the measurement accuracy in liquid measurement. [0003] The main accuracy interference factors of the time difference method ultrasonic flowmeter include: (1) The ultrasonic waveform is severely attenuated during the gas transmission pro...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01F1/66G01P5/24
Inventor 鲍敏沈卫平
Owner ZHEJIANG SCI-TECH UNIV
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