CN112649056A - Ultrasonic gas flow measuring method and device - Google Patents

Ultrasonic gas flow measuring method and device Download PDF

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Publication number
CN112649056A
CN112649056A CN201910970010.0A CN201910970010A CN112649056A CN 112649056 A CN112649056 A CN 112649056A CN 201910970010 A CN201910970010 A CN 201910970010A CN 112649056 A CN112649056 A CN 112649056A
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ultrasonic
excitation signal
flow channel
time
time difference
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谢琦
方帅兵
李静
任家顺
汪政伟
李敬宁
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Newcapec Electronics Co Ltd
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Newcapec Electronics Co Ltd
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    • GPHYSICS
    • G01MEASURING; TESTING
    • G01FMEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F1/00Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
    • G01F1/66Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by measuring frequency, phase shift or propagation time of electromagnetic or other waves, e.g. using ultrasonic flowmeters
    • G01F1/667Arrangements of transducers for ultrasonic flowmeters; Circuits for operating ultrasonic flowmeters

Abstract

The invention relates to a method and a device for measuring the flow of ultrasonic gas, belonging to the technical field of fluid flow detection, wherein two ultrasonic transducers which are fixedly arranged on a flow channel and are respectively positioned at the upper and lower streams are adopted for measuring; in a metering period, generating a path of excitation signal, simultaneously sending the path of excitation signal to two ultrasonic transducers through a sending amplifying circuit, and recording the excitation signal; under the action of the excitation signal, the two ultrasonic transducers simultaneously send two paths of ultrasonic signals which are transmitted in opposite directions into the flow channel; and the two paths of ultrasonic signals are received by the opposite ultrasonic transducers; extracting the time difference of opposite transmission of ultrasonic waves according to the excitation signal and the received ultrasonic signals; and calculating the gas flow/flow velocity by using a time difference method according to the time difference of the opposite transmission of the extracted ultrasonic waves. The problems of low detection precision, high energy consumption and low efficiency caused by the existing flow detection by using a time difference method are solved.

Description

Ultrasonic gas flow measuring method and device
Technical Field
The invention relates to a method and a device for measuring the flow of ultrasonic gas, belonging to the technical field of fluid flow detection.
Background
The principle of gas ultrasonic flow measurement utilizes the signal modulation effect of natural gas flow on ultrasonic pulses to obtain flow information by detecting the change of signals. With the improvement of the performance and the reduction of the price of the ultrasonic transducer, the development of computer technology and hydromechanics and the development and application of ultrasonic metering technology in the field of thermotechnical measurement (natural gas meters, water meters, heat meters and the like) are sufficient.
The existing ultrasonic flowmeter has many measuring methods, and a Doppler method, a beam offset method, a time difference method and the like are generally adopted, and the time difference method is most widely applied. The principle of the time difference ultrasonic flowmeter is as follows: the time difference exists when the sound waves propagate in the fluid for the same distance in the forward flow and the backward flow, and the propagation time difference is related to the flow speed of the fluid to be measured, so that the speed of the fluid can be obtained by measuring the time difference.
However, in the conventional measurement method of the time difference method, when performing flow measurement, two times of transmission and reception of ultrasonic signals are generally required to complete a sampling measurement period, and as shown in fig. 1, after the time of the downstream transmission of ultrasonic waves is measured in a measurement period, a corresponding transmission time interval WT needs to pass, and then the time duration used in the upstream transmission process needs to be measured, so that the following problems generally exist in the conventional time difference method:
1) the transducer has longer working time: during the measurement, the ultrasonic signals are required to be transmitted twice in forward flow and reverse flow, and a period of time WT is required to be waited between the two measurements in opposite directions, so that the working time of the transducer is increased, and the power consumption of the system is increased.
2) The two ultrasonic signals have large transmission errors: the forward flow and reverse flow ultrasonic signals are sent at different moments and are influenced by external environments such as environmental temperature, pressure, airflow velocity and the like, and the error influence of the external environments can be accumulated to influence the measurement precision;
therefore, how to design a method and a device for measuring the flow rate of the ultrasonic gas so as to solve the problem caused by adopting the time difference method to detect the flow rate is very important for improving the precision and the efficiency of the existing flow rate detection.
Disclosure of Invention
In order to solve the technical problem of large detection error, the invention aims to provide a method and a device for measuring the ultrasonic gas flow.
In order to achieve the purpose, the technical scheme of the invention is as follows: the invention provides an ultrasonic gas flow measuring method, which adopts two ultrasonic transducers which are fixedly arranged on a flow channel and respectively positioned at the upper and the lower reaches to measure; the method comprises the following steps:
two ultrasonic transducers which are fixedly arranged on a flow channel and respectively positioned at the upper and lower streams are adopted for metering; the method comprises the following steps:
1) generating a path of excitation signal in a metering period, simultaneously sending the path of excitation signal to two ultrasonic transducers through a sending amplifying circuit, and recording the excitation signal;
2) under the action of the excitation signal, the two ultrasonic transducers simultaneously send two paths of ultrasonic signals which are transmitted in opposite directions into the flow channel; the two ultrasonic signals are received by the opposite ultrasonic transducers;
3) extracting the time difference of opposite transmission of ultrasonic waves according to the excitation signal and the received ultrasonic signals;
4) and calculating the gas flow/flow velocity by using a time difference method according to the time difference of the opposite transmission of the extracted ultrasonic waves.
The invention generates a path of excitation signal, utilizes a sending amplifying circuit to drive two ultrasonic transducers arranged on the upper and lower streams of a gas pipeline to simultaneously generate two paths of ultrasonic signals transmitted oppositely, simultaneously starts to receive echo signals, controls the switching of the processes of sending and receiving the ultrasonic waves by the transducers through two selector switches, respectively records the time of the corresponding ultrasonic waves passing through the same path in a fluid, and then calculates the gas flow/flow rate according to the corresponding time difference.
The beneficial effect based on the scheme is as follows:
1. two paths of ultrasonic signals are sent at the same time during metering, the environments are equivalent, the influences of conditions such as the ambient temperature and the like are consistent, and the influences of errors can be eliminated by counteracting during calculation; the signals are sent at the same time, the paths are equal, the influence of conditions such as uneven airflow and runners is consistent, the influence of accumulated errors of the airflow and the runners is small, and errors caused by the influence of external conditions are reduced or eliminated fundamentally;
2. the transducer has no special requirement, can be realized by adopting a common transducer, and can transmit and receive signals at one time, thereby reducing the working time and the energy consumption; the flow channel has no special requirement, and the measuring method has strong universality.
3. The method is suitable for two transducers with strong consistency; the use of the change-over switch avoids the direct influence of the transmitting amplifying circuit and the receiving amplifying circuit.
Furthermore, in order to improve the accuracy of calculating the time difference, a cross-correlation method is adopted to extract the time difference of the opposite transmission of the ultrasonic waves in the forward flow direction and the reverse flow direction in the flow channel.
Further, the step of extracting the time difference of the ultrasonic wave transmitted in the forward flow direction and the reverse flow direction in the flow channel in opposite directions by adopting a cross-correlation method comprises the following steps:
the recorded excitation signal includes a transmission time t1, excitation signal sample data x1(x11, x 12.., x1 n);
the downstream ultrasonic transducer receives an ultrasonic signal propagating in the downstream direction, the corresponding sampling data is x2(x21, x22,.., x2m), and a cross-correlation algorithm is utilized
Figure BDA0002231748910000021
Determining the peak value of the signal, thereby determining the sampling time tw corresponding to the peak value signal, and obtaining the time T1 of downstream propagation of the ultrasonic wave in the flow channel, wherein T1 is tw-T1; if the two sequences x1 and x2 are not equal in length, the shorter sequence is supplemented with 0 to form the sequence of equal length, the same principle is as follows.
The upstream ultrasonic transducer receives a signal propagating in the countercurrent direction, and the corresponding sampling data is x3(x31, x 32).X3m), using a cross-correlation algorithm
Figure BDA0002231748910000031
Determining the peak value of the signal, thereby determining the sampling time tw 'corresponding to the peak value signal, and obtaining the time T2 of downstream propagation of the ultrasonic wave in the flow channel, wherein T2 is tw' -T1;
and calculating the difference delta T as T2-T1 according to the time for the ultrasonic waves to be transmitted in the forward and backward directions in the flow channel.
Further, the two ultrasonic transducer arrangement forms comprise an I type, a Z type or a V type.
The invention also provides an ultrasonic gas flow metering device, which comprises an MCU, a first ultrasonic transducer, a second ultrasonic transducer, a first change-over switch, a second change-over switch, a transmitting amplification circuit, a first receiving amplification circuit and a second receiving amplification circuit, wherein the first ultrasonic transducer, the second ultrasonic transducer, the first change-over switch and the second change-over switch are fixedly arranged on a flow channel and are respectively positioned at the upper stream and the lower stream; the first switch is used for connecting the first ultrasonic transducer to a transmitting amplification circuit or a first receiving amplification circuit; the second change-over switch is used for connecting the second ultrasonic transducer to the transmitting amplifying circuit or the second receiving amplifying circuit; the MCU executes the computer program to implement the following method:
in a metering period, the MCU generates a path of excitation signal, simultaneously sends the path of excitation signal to the two ultrasonic transducers through a sending amplifying circuit, and records the excitation signal;
under the action of an excitation signal, two ultrasonic transducers simultaneously send two paths of ultrasonic signals which are transmitted in opposite directions into the flow channel, and the two paths of ultrasonic signals are simultaneously received by the opposite ultrasonic transducers;
the MCU acquires ultrasonic signals received by the two ultrasonic transducers by controlling the analog switch, and extracts the time difference of opposite transmission of ultrasonic waves according to the excitation signals and the received ultrasonic signals;
and the MCU calculates the gas flow/flow velocity by using a time difference method according to the time difference of the opposite transmission of the extracted ultrasonic waves.
The invention uses two ultrasonic transducers arranged on the upper and lower parts of the gas pipeline to simultaneously generate two ultrasonic signals transmitted oppositely, and simultaneously starts to receive the ultrasonic signals transmitted by the opposite transducers, respectively records the time of the corresponding ultrasonic waves passing through the same path in the fluid, and then calculates the gas flow according to the corresponding time difference. Two paths of ultrasonic signals are sent at the same time, the influence of conditions such as ambient temperature and the like is consistent, and the influence of errors can be eliminated by offsetting during calculation; the signals are sent at the same time, the paths are equal, the influence of conditions such as uneven airflow and runners is consistent, the influence of accumulated errors of the airflow and the runners is small, and errors caused by the influence of external conditions are reduced or eliminated fundamentally; in addition, the ultrasonic gas flow measuring method has no special requirements on the transducer, and can be realized by using a common transducer, signals are transmitted and received at one time, so that the working time is reduced, and the energy consumption is reduced; the flow channel has no special requirement, and the measuring method has strong universality; moreover, the method is suitable for two transducers with strong consistency; the use of the change-over switch avoids the direct influence of the transmitting amplifying circuit and the receiving amplifying circuit.
Furthermore, in order to improve the accuracy of calculating the time difference, the MCU adopts a cross-correlation method to extract the time difference of the opposite transmission of the ultrasonic waves in the forward flow direction and the reverse flow direction in the flow channel.
Further, the step of extracting the time difference of the ultrasonic wave transmitted in the forward flow direction and the reverse flow direction in the flow channel in opposite directions by adopting a cross-correlation method comprises the following steps:
the recorded excitation signal includes a transmission time t1, excitation signal sample data x1(x11, x 12.., x1 n);
the downstream ultrasonic transducer receives an ultrasonic signal propagating in the downstream direction, the sampling data is x2(x21, x 22.., x2m), and a cross-correlation algorithm is utilized
Figure BDA0002231748910000041
Determining the peak value of the signal, thereby determining the sampling time tw corresponding to the peak value signal, and obtaining the time T1 of downstream propagation of the ultrasonic wave in the flow channel, wherein T1 is tw-T1;
upstream located ultrasoundThe wave transducer receives a signal propagating in a counter-current direction, the sampling data is x3(x31, x32,.., x3m), and a cross-correlation algorithm is used
Figure BDA0002231748910000042
Determining the peak value of the signal, thereby determining the sampling time tw 'corresponding to the peak value signal, and obtaining the time T2 of downstream propagation of the ultrasonic wave in the flow channel, wherein T2 is tw' -T1;
and calculating the difference delta T as T2-T1 according to the time for the ultrasonic waves to be transmitted in the forward and backward directions in the flow channel.
Further, the two ultrasonic transducer arrangement forms comprise an I type, a Z type or a V type.
Drawings
FIG. 1 is a timing diagram of a conventional time difference measurement;
FIG. 2 is a schematic diagram of a metering device according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of a V-mount for two transducers in an embodiment of the present invention;
FIG. 4 is a schematic diagram of a two transducer type I installation in an embodiment of the present invention;
FIG. 5 is a schematic diagram of a two transducer Z-mount in an embodiment of the present invention;
FIG. 6 is a flow chart of flow measurement in an embodiment of the present invention;
fig. 7 is a timing diagram corresponding to the metering process in the embodiment of the present invention.
Detailed Description
Embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.
Metering device embodiment:
as shown in fig. 2, this embodiment provides an ultrasonic gas flow meter, which includes an MCU, two ultrasonic transducers, namely a transducer a and a transducer B, fixedly installed in a flow channel and located at the upstream and downstream, respectively, and a first switch, a second switch, a first receiving amplifier circuit and a second receiving amplifier circuit, where the MCU is connected to the transmitting amplifier circuit; the first switch connects the transducer A to the transmitting amplifying circuit or the first receiving amplifying circuit; the second change-over switch connects the wave transducer B to the transmitting amplifying circuit or the second receiving amplifying circuit; and after one path of excitation signal generated by the MCU is amplified by the transmitting amplifying circuit, the transducer A and the transducer B are driven to generate ultrasonic signals.
And the MCU respectively samples and receives ultrasonic signals which are received by the two ultrasonic transducers and sent by the opposite transducers in the forward flow and the reverse flow through the first receiving and amplifying circuit and the second receiving and amplifying circuit.
The transmission amplifying circuit described in this embodiment is actually a driving circuit, and functions as a transmission amplifying circuit because it has a certain signal amplifying function; the receiving circuit is actually a sampling circuit, also has a certain amplification function, and is used as a receiving amplification circuit.
The change-over switch can be realized by adopting an analog switch, namely, the analog switch changes the switching state of the internal switch under the control of the MCU. As other embodiments, the form of the switch is not limited to the switch circuit or a dedicated chip, and it falls within the scope of the present invention as long as the controlled switching of the transducer between transmitting and receiving ultrasonic signals can be realized.
The present embodiment also provides a specific arrangement form of the transducer a and the transducer B, that is, by changing the arrangement form of the transducers, the transmission path of the ultrasonic wave in the flow channel is changed, so as to adapt to different metering requirements.
In this embodiment, the transducers a and B are installed in a V shape, and the specific form is as shown in fig. 3, and the transducers a and B are installed on the pipe wall and form an angle θ with the pipe wall, so that the length of the path can be increased, and the error of uneven distribution of the flow velocity cross section can be reduced.
In fig. 3, V is the fluid flow velocity, c is the sound velocity of the ultrasonic wave under the stationary fluid condition, and d is the pipe diameter. The ultrasonic pulse is transmitted from the transducer A to the transducer B in a downstream flow, and the transmission time is T1; the ultrasonic pulse is transmitted in reverse flow from transducer B to transducer a with a transit time T2. Countercurrent and concurrent with a time difference Δ t. Letter after simplificationThe numerical relational expression:
Figure BDA0002231748910000051
and after the flow velocity is obtained, the gas flow is further obtained according to the sectional area of the pipeline.
As another embodiment of this embodiment, in this embodiment, as shown in fig. 4, the transducers a and B may also be mounted by the method I (the transducers are fixedly mounted at two ends of the flow channel measuring portion), and the transducers are mounted on the pipeline by means of connectors.
In the above embodiments, the transducers are installed on the same side of the pipeline, but the method of the present invention is not limited to the above installation manner, the installation manners of the transducer a and the transducer B may be Z-shaped, and the corresponding installation manners are given as in fig. 5, and different installation manners make the paths of the ultrasonic waves propagating in the flow channel different, and the formulas used in the calculation according to the time difference method are different, and the calculation processes corresponding to different installation manners are not described in detail here.
In the present embodiment, several installation modes of the transducer are given, and the above-mentioned several installation modes are mainly direct type, reflective type and parallel type installation modes, and any direct type, reflective type and parallel type installation modes made by those skilled in the art on the basis of the present invention, or installation modes modified from the above-mentioned several installation modes, fall into the protection scope of the present invention.
In this embodiment, a flow of metering by using the metering device is shown in fig. 6, the MCU regularly meters a period, detects whether the metering period is reached, and if so, in one metering period, the MCU drives to generate one path of excitation signal, and sends the two paths of excitation signals to the two ultrasonic transducers through a transmission amplifying circuit, and records the excitation signals;
then, under the action of the excitation signal, the two ultrasonic transducers are driven to simultaneously send out ultrasonic signals, the two ultrasonic transducers simultaneously send two paths of ultrasonic signals which are transmitted in opposite directions into the flow channel, and the two paths of ultrasonic signals are received by the two opposite ultrasonic transducers, so that the ultrasonic signals in the flow channel are simultaneously transmitted along the forward flow direction and the backward flow direction.
And the MCU extracts the time difference of opposite transmission of the ultrasonic waves according to the excitation signal and the received ultrasonic signals. Specifically, the time tw of receiving the forward-flow flight ultrasonic wave signal and the time tw' of receiving the reverse-flow flight ultrasonic wave signal are obtained in a corresponding manner, and then the forward-flow flight time T1 and the reverse-flow flight time T2 are calculated.
Then, the MCU calculates the gas flow rate/flow velocity by the time difference method based on the extracted time difference Δ T between the ultrasonic waves propagating in opposite directions, T2-T1.
In the embodiment, a cross-correlation method is adopted to extract the time difference of the opposite transmission of the ultrasonic waves in the forward flow direction and the reverse flow direction in the flow channel. As other embodiments, other manners capable of extracting the time difference may also be adopted, for example, a threshold method is adopted, and a threshold value is set to extract the time difference, which is a conventional technique in the art and therefore will not be described again.
Specifically, the calculation process of extracting the time difference of the ultrasonic wave transmitted in the flow channel in the opposite direction by using the cross-correlation algorithm includes:
(1) the recorded excitation signal includes a transmission time t1, excitation signal sample data x1(x11, x 12.., x1 n);
(2) the downstream ultrasonic transducer receives an ultrasonic signal propagating in the downstream direction, the sampling data is x2(x21, x 22.., x2m), and a cross-correlation algorithm is utilized
Figure BDA0002231748910000061
Determining the peak value of the signal, thereby determining the sampling time tw corresponding to the peak value signal, and obtaining the time T1 of downstream propagation of the ultrasonic wave in the flow channel, wherein T1 is tw-T1;
(3) the upstream ultrasonic transducer receives the signal propagating in the countercurrent direction, the sampling data is x3(x31, x 32.., x3m), and a cross-correlation algorithm is utilized
Figure BDA0002231748910000062
Determining the peak value of the signal, thereby determining the sampling time t corresponding to the peak signalw 'so as to obtain the time T2 of downstream propagation of the ultrasonic wave in the flow channel, wherein T2 is tw' -T1;
(4) and calculating the difference delta T as T2-T1 according to the time for the ultrasonic waves to be transmitted in the forward and backward directions in the flow channel.
As shown in fig. 7, which is a timing chart of the measurement in the present embodiment, the measurement method provided in the present embodiment implements a measurement process of simultaneous transmission and reception of transducers, which radically reduces or eliminates errors caused by external conditions, and has a short measurement period and reduced energy consumption. Moreover, no special requirements are required on the transducer, and the process can be realized only by the existing common transducer.
The embodiment of the metering method comprises the following steps:
the embodiment provides an ultrasonic gas flow metering method, which comprises the steps of fixedly installing two ultrasonic transducers which are respectively positioned at the upper and lower streams on a flow channel for metering; the method comprises the following steps:
1) generating a path of excitation signal in a metering period, simultaneously sending the path of excitation signal to two ultrasonic transducers through a sending amplifying circuit, and recording the excitation signal;
2) under the action of the excitation signal, the two ultrasonic transducers simultaneously send two paths of ultrasonic signals which are transmitted in opposite directions into the flow channel; the two paths of ultrasonic signals are simultaneously received by the opposite ultrasonic transducers;
3) extracting the time difference of opposite transmission of ultrasonic waves according to the excitation signal and the received ultrasonic signals;
4) and calculating the gas flow/flow velocity by using a time difference method according to the time difference of the opposite transmission of the extracted ultrasonic waves.
The specific implementation manner of the above steps has been described in detail in the above embodiment of the metering device, and is not described herein again.
The specific embodiments are given above, but the present invention is not limited to the described embodiments. The basic idea of the present invention is to provide the above basic solution, and those skilled in the art can make changes, modifications, substitutions and variations to the embodiments without departing from the principle and spirit of the present invention.

Claims (8)

1. A method for measuring the ultrasonic gas flow adopts two ultrasonic transducers which are fixedly arranged on a flow channel and respectively positioned at the upper and the lower reaches to measure; the method is characterized by comprising the following steps:
1) generating a path of excitation signal in a metering period, simultaneously sending the path of excitation signal to two ultrasonic transducers through a sending amplifying circuit, and recording the excitation signal;
2) under the action of the excitation signal, the two ultrasonic transducers simultaneously send two paths of ultrasonic signals which are transmitted in opposite directions into the flow channel; the two paths of ultrasonic signals are simultaneously received by the opposite ultrasonic transducers;
3) extracting the time difference of opposite transmission of ultrasonic waves according to the excitation signal and the received ultrasonic signals;
4) and calculating the gas flow/flow velocity by using a time difference method according to the time difference of the opposite transmission of the extracted ultrasonic waves.
2. An ultrasonic gas flow metering method according to claim 1, wherein a cross-correlation method is used to extract the time difference of the opposite transmission of ultrasonic waves in the forward and backward directions in the flow channel.
3. An ultrasonic gas flow metering method according to claim 2, wherein the step of extracting the time difference of the opposite transmission of the ultrasonic waves in the forward flow direction and the reverse flow direction in the flow channel by using a cross-correlation method comprises the following steps:
the recorded excitation signal includes a transmission time t1, excitation signal sample data x1(x11, x 12.., x1 n);
the downstream ultrasonic transducer receives an ultrasonic signal propagating in the downstream direction, the corresponding sampling data is x2(x21, x22,.., x2m), and a cross-correlation algorithm is utilized
Figure FDA0002231748900000011
Determining the peak value of the signal, thereby determining the sampling time tw corresponding to the peak value signal, and obtaining the time T1 of downstream propagation of the ultrasonic wave in the flow channel, wherein T1 is tw-T1;
the upstream ultrasonic transducer receives the signal propagating in the countercurrent direction, the corresponding sampling data is x3(x31, x32,.., x3m), and a cross-correlation algorithm is utilized
Figure FDA0002231748900000012
Determining the peak value of the signal, thereby determining the sampling time tw 'corresponding to the peak value signal, and obtaining the time T2 of downstream propagation of the ultrasonic wave in the flow channel, wherein T2 is tw' -T1;
and calculating the difference delta T as T2-T1 according to the time for the ultrasonic waves to be transmitted in the forward and backward directions in the flow channel.
4. An ultrasonic gas flow metering method according to claim 1, wherein the two ultrasonic transducer arrangements are of the type I, Z or V.
5. An ultrasonic gas flow metering device is characterized by comprising an MCU (microprogrammed control unit), a first ultrasonic transducer, a second ultrasonic transducer, a first change-over switch, a second change-over switch, a transmitting amplification circuit, a first receiving amplification circuit and a second receiving amplification circuit, wherein the first ultrasonic transducer, the second ultrasonic transducer, the first change-over switch and the second change-over switch are fixedly arranged on a flow channel and are respectively positioned at the upper and lower streams; the first switch is used for connecting the first ultrasonic transducer to a transmitting amplification circuit or a first receiving amplification circuit; the second change-over switch is used for connecting the second ultrasonic transducer to the transmitting amplifying circuit or the second receiving amplifying circuit; the MCU executes the computer program to implement the following method:
in a metering period, the MCU generates a path of excitation signal, simultaneously sends the path of excitation signal to the two ultrasonic transducers through a sending amplifying circuit, and records the excitation signal;
under the action of an excitation signal, two ultrasonic transducers simultaneously send two paths of ultrasonic signals which are transmitted in opposite directions into the flow channel, and the two paths of ultrasonic signals are simultaneously received by the opposite ultrasonic transducers;
the MCU acquires ultrasonic signals received by the two ultrasonic transducers by controlling the analog switch, and extracts the time difference of opposite transmission of ultrasonic waves according to the excitation signals and the received ultrasonic signals;
and the MCU calculates the gas flow/flow velocity by using a time difference method according to the time difference of the opposite transmission of the extracted ultrasonic waves.
6. An ultrasonic gas flow meter according to claim 5, wherein the MCU uses a cross correlation method to extract the time difference of the opposite transmission of ultrasonic waves in the forward and backward directions in the flow channel.
7. An ultrasonic gas flow meter according to claim 6, wherein the step of extracting the time difference of the ultrasonic waves transmitted in the flow channel in the forward and backward directions in the opposite direction by using the cross-correlation method comprises:
the recorded excitation signal includes a transmission time t1, excitation signal sample data x1(x11, x 12.., x1 n);
the downstream ultrasonic transducer receives an ultrasonic signal propagating in the downstream direction, the sampling data is x2(x21, x 22.., x2m), and a cross-correlation algorithm is utilized
Figure FDA0002231748900000021
Determining the peak value of the signal, thereby determining the sampling time tw corresponding to the peak value signal, and obtaining the time T1 of downstream propagation of the ultrasonic wave in the flow channel, wherein T1 is tw-T1;
the upstream ultrasonic transducer receives the signal propagating in the countercurrent direction, the sampling data is x3(x31, x 32.., x3m), and a cross-correlation algorithm is utilized
Figure FDA0002231748900000022
Determining the peak value of the signal, thereby determining the sampling time tw' corresponding to the peak value signal, and obtaining the time T2 when the ultrasonic wave propagates in the flow channel, wherein T2 is the timetw’-t1;
And calculating the difference delta T as T2-T1 according to the time for the ultrasonic waves to be transmitted in the forward and backward directions in the flow channel.
8. An ultrasonic gas flow metering device according to claim 6, wherein the two ultrasonic transducer mounting forms comprise an I-type, a Z-type or a V-type.
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CN113340363A (en) * 2021-06-09 2021-09-03 河北大学 High-precision wide-range ultrasonic flow measurement device and measurement method
CN113916719A (en) * 2021-10-12 2022-01-11 北京航空航天大学 Fluid density and flow rate online synchronous detection system and detection method
CN114814284A (en) * 2022-04-21 2022-07-29 上海理工大学 Method and device for measuring cascade flow field by reflection-type mounted ultrasonic array
CN114814284B (en) * 2022-04-21 2023-11-07 上海理工大学 Method and device for measuring cascade flow field by using reflectively-installed ultrasonic array

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