CN112964319A - Multi-frequency array ultrasonic flowmeter - Google Patents

Multi-frequency array ultrasonic flowmeter Download PDF

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CN112964319A
CN112964319A CN202110316820.1A CN202110316820A CN112964319A CN 112964319 A CN112964319 A CN 112964319A CN 202110316820 A CN202110316820 A CN 202110316820A CN 112964319 A CN112964319 A CN 112964319A
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transducer
ultrasonic
difference method
wave
time
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CN112964319B (en
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李蕊
李立鹏
刘冰
郭桂梅
杨鹏
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Tianjin University of Commerce
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Tianjin University of Commerce
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
    • G01F1/66—Measuring 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
    • G01F1/667—Arrangements of transducers for ultrasonic flowmeters; Circuits for operating ultrasonic flowmeters
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
    • G01F1/66—Measuring 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
    • G01F1/662—Constructional details

Abstract

The invention discloses a multi-frequency array ultrasonic flowmeter, which comprises a first multi-frequency array ultrasonic transducer and a second multi-frequency array ultrasonic transducer; the two multi-frequency array ultrasonic transducers are respectively and hermetically arranged on the upper side and the lower side of the pipe body of the ultrasonic flowmeter; the ultrasonic flowmeter is characterized in that a transverse flowing medium is arranged in the ultrasonic flowmeter tube body; the two multi-frequency array ultrasonic transducers are centrosymmetric; the multi-frequency array ultrasonic flowmeter comprises a measuring circuit, wherein the measuring circuit comprises a frequency F1 excitation wave generator, a frequency F2 excitation wave generator, a frequency F3 pulse wave generator, a sine modulation wave generator, a first multiplication modulation module, a second multiplication modulation module, a time difference method processing circuit module, a first phase difference method processing circuit module, a second phase difference method processing circuit module and a CPU module; the invention utilizes the multi-frequency array ultrasonic transducer and combines the advantages of a phase difference method and a time difference method, thereby solving the problem of measurement accuracy of the ultrasonic flowmeter on the using site.

Description

Multi-frequency array ultrasonic flowmeter
Technical Field
The invention relates to the technical field of flow measurement, in particular to a multi-frequency array ultrasonic flowmeter.
Background
The medium flow velocity is measured by ultrasonic waves, the method has the advantages of high precision, small pressure loss, convenience in installation and maintenance and the like, and is widely applied to various industries.
At present, methods for measuring the flow rate of a medium by ultrasonic waves generally comprise a time difference method, a phase difference method and the like. The time difference method has the highest measurement resolution and is most commonly applied, and the phase difference method has low measurement accuracy and is less applied.
The time difference method is that two ultrasonic transducers transmit and receive ultrasonic signals mutually, the forward and backward ultrasonic flight time is measured, and then the difference value of the time is calculated to calculate the flow velocity V. The general formula of calculation used is as follows:
Figure BDA0002987909480000011
in the formula: t is tupThe time for the ultrasonic wave to propagate downstream in the fluid is the time required for the transducer B to receive the ultrasonic wave after the ultrasonic wave is transmitted by the transducer A; t is tdownThe time for the ultrasonic wave to propagate in the fluid in a counter-current manner, namely the time for the transducer A to receive the ultrasonic wave after the transducer B transmits the ultrasonic wave; d is the diameter of the pipeline of the ultrasonic flowmeter; phi is the included angle between the sound channel of the ultrasonic transducer and the central axis of the flowmeter.
However, with the above formula, the true time of flight of the ultrasonic wave needs to be accurately measured. In the actual measurement process, in order to prevent the influence of interference signals, a threshold-zero-crossing comparison method is generally adopted to acquire and measure ultrasonic signals, and the measurement resolution and the measurement accuracy of the method are high, but the real flight time of the ultrasonic waves cannot be accurately positioned in the measurement process. Because the introduction of the threshold comparison method in the measurement process can not determine that the actually measured signal waveform is the signal waveform of the period.
In the practical application process, the influence of interference is usually eliminated by methods such as linear regression, direct sound velocity measurement in a standard environment, echo signal measurement and the like. However, these methods cannot directly and accurately measure the flight time of the ultrasonic wave in the field, and when the field is different from the standard environment, the existing ultrasonic flowmeter has a problem that the measurement accuracy is reduced.
The phase difference measurement is that the ultrasonic transducer transmits continuous ultrasonic pulses or ultrasonic pulses with longer period, so that a phase difference is generated between signals received during forward flow and backward flow, the phase difference or a tiny time difference is measured, and the flow velocity of the fluid can be calculated according to a formula.
Figure BDA0002987909480000021
And the flow velocity of the fluid is v, c is the sound velocity of the ultrasonic wave in the fluid, D is the diameter of the pipeline, theta is the included angle between the sound channel of the ultrasonic transducer and the axis of the pipe body, and f is the central frequency of the transducer. In addition to the method of directly measuring the phase difference, there is also a method of measuring the flow velocity of the fluid by measuring the time difference of the modulated wave using the principle of the modulated wave, but in any of the measurement methods, the velocity of sound of the ultrasonic wave in the fluid is affected when the phase difference measurement is used.
Therefore, the time difference method and the phase difference have respective disadvantages, and the flow velocity of the fluid cannot be accurately measured.
Disclosure of Invention
The invention aims to provide a multi-frequency array ultrasonic flowmeter aiming at the technical defects in the prior art.
To this end, the invention provides a multi-frequency array ultrasonic flow meter comprising
A first multi-frequency array ultrasonic transducer and a second multi-frequency array ultrasonic transducer;
the first multi-frequency array ultrasonic transducer and the second multi-frequency array ultrasonic transducer are respectively and hermetically arranged in preset holes on the upper side and the lower side of a pipe body of the ultrasonic flowmeter;
the ultrasonic flowmeter is characterized in that a transverse flowing medium is arranged in the ultrasonic flowmeter tube body;
the first multi-frequency array ultrasonic transducer and the second multi-frequency array ultrasonic transducer are centrosymmetric;
the first multi-frequency array ultrasonic transducer comprises a first main transducer, a second main transducer and a third main transducer;
the second multi-frequency array ultrasonic transducer comprises a first secondary transducer, a second secondary transducer and a third secondary transducer;
the multi-frequency array ultrasonic flowmeter comprises a measuring circuit, wherein the measuring circuit comprises a frequency F1 excitation wave generator, a frequency F2 excitation wave generator, a frequency F3 pulse wave generator, a sine modulation wave generator, a first multiplication modulation module, a second multiplication modulation module, a time difference method processing circuit module, a first phase difference method processing circuit module, a second phase difference method processing circuit module and a CPU module;
the first multiplication modulation module is respectively connected with the second main transducer, the frequency F1 excitation wave generator and the sine modulation wave generator;
the second multiplication modulation module is respectively connected with the third-time transducer, the frequency F2 excitation wave generator and the sine modulation wave generator;
the sinusoidal modulation wave generator is used for generating a sinusoidal modulation wave;
a frequency F1 excitation wave generator and a frequency F2 excitation wave generator, which are respectively used for generating carrier waves;
the first multiplication modulation module is used for executing preset multiplication operation on a sinusoidal modulation wave generated by the sinusoidal modulation wave generator and a carrier wave generated by the frequency F1 excitation wave generator to obtain an excitation waveform of a sinusoidal wave modulation amplitude, namely a continuous amplitude modulation ultrasonic signal with the carrier frequency of F1, and then is used for exciting the second main transducer to realize continuous amplitude modulation wave excitation;
the second main transducer is used as an ultrasonic transmitting transducer and is used for transmitting the continuous amplitude modulation ultrasonic signal with the carrier frequency of F1 to the second secondary transducer as a second ultrasonic transmitting signal;
the second secondary transducer is used as an ultrasonic receiving transducer and used for receiving a continuous amplitude modulation ultrasonic signal with the carrier frequency of F1 transmitted by the second main transducer, and then the continuous amplitude modulation ultrasonic signal is used as a second ultrasonic receiving signal and is output to the second phase difference method processing circuit module;
the second multiplication modulation module is used for executing preset multiplication operation on the sinusoidal modulation wave generated by the sinusoidal modulation wave generator and the carrier wave generated by the frequency F2 excitation wave generator to obtain an excitation waveform of a sinusoidal wave modulation amplitude, namely a continuous amplitude modulation ultrasonic signal with the carrier frequency of F2 is obtained, and then the second multiplication modulation module is used for exciting the third transducer to realize continuous amplitude modulation wave excitation;
the third transducer is used as an ultrasonic transmitting transducer and used for transmitting a continuous amplitude modulation ultrasonic signal with the carrier frequency of F2 to the third main transducer as a first ultrasonic transmitting signal;
the third main transducer is used as an ultrasonic receiving transducer and used for receiving a continuous amplitude modulation ultrasonic signal with the carrier frequency of F2 transmitted by the third transducer, and then the continuous amplitude modulation ultrasonic signal is output to the first phase difference processing circuit module as a first ultrasonic receiving signal;
the frequency F3 pulse wave generator is respectively connected with the first main transducer and the first secondary transducer and is used for alternately exciting the first main transducer and the first secondary transducer through pulse waves;
the time difference method processing circuit module is respectively connected with the first main transducer and the first secondary transducer, and is used for carrying out preset time difference method processing operation on ultrasonic waves output by the first main transducer and the first secondary transducer after excitation and then outputting the ultrasonic waves subjected to the preset time difference processing operation to the CPU module;
the first phase difference method processing circuit module is connected with the third main transducer and used for carrying out preset phase difference method processing operation on a first ultrasonic receiving signal output by the third main transducer and then outputting the first ultrasonic receiving signal to the CPU module;
the second phase difference method processing circuit module is connected with the second transducer and is used for carrying out preset phase difference method processing operation on a second ultrasonic receiving signal output by the second transducer and then outputting the second ultrasonic receiving signal to the CPU module;
and the CPU module is respectively connected with the time difference method processing circuit module, the first phase difference method processing circuit module and the second phase difference method processing circuit module and is used for calculating to obtain the flow velocity of the fluid according to a preset time difference method calculation formula.
Preferably, the CPU module specifically functions as follows:
the time difference method measurement device comprises a time difference method processing circuit module, a time difference method measurement module and a time difference measurement module, wherein the time difference method processing circuit module is used for receiving ultrasonic waves which are sent by the time difference method processing circuit module and are subjected to preset time difference processing operation, and then the time difference method is used for calculating to obtain a time difference method measurement value of ultrasonic wave flight time; secondly, the time difference between the output signals of the first phase difference processing circuit module and the output signals of the second phase difference processing circuit module and the output signals of the first ultrasonic wave emission excitation signal and the output signals of the second ultrasonic wave emission excitation signal are respectively measured, and a phase difference measured value of the ultrasonic wave flight time is obtained; thirdly, after a time difference method measurement value and a phase difference method measurement value of the ultrasonic flight time are obtained, the forward flight time and the backward flight time of the ultrasonic measured by the time difference method are adjusted according to a preset processing rule, and after adjustment, the flow velocity of the medium is calculated according to the forward flight time and the backward flight time of the ultrasonic measured by the adjusted time difference method and a preset time difference method calculation formula;
the time difference method measurement value of the ultrasonic wave flight time comprises forward flight time and backward flight time of the ultrasonic wave measured by the time difference method;
the phase difference method measurement value of the ultrasonic flight time comprises the forward flight time and the backward flight time of the ultrasonic measured by the phase difference method;
the first ultrasonic emission excitation signal is an excitation signal which is generated by the CPU module and used for driving the third transducer to emit the first ultrasonic emission signal;
the second ultrasonic emission excitation signal is an excitation signal generated by the CPU module and used for driving the second main transducer to emit the second ultrasonic emission signal.
Preferably, for the CPU module, the adjusting of the forward flight time and the backward flight time of the ultrasonic waves measured by the time difference method according to the preset processing rule specifically includes the following operations:
adjusting the forward-travel time and the backward-travel time of the ultrasonic waves measured by the time difference method according to a preset processing rule until the difference value between the forward-travel time of the ultrasonic waves measured by the time difference method and the forward-travel time of the ultrasonic waves measured by the phase difference method is smaller than a pulse wave period T and the difference value between the backward-travel time of the ultrasonic waves measured by the time difference method and the backward-travel time of the ultrasonic waves measured by the phase difference method is smaller than a pulse wave period T, and then calculating to obtain the flow velocity of the medium according to the adjusted forward-travel time and backward-travel time of the ultrasonic waves measured by the time difference method and a preset time difference method calculation formula;
wherein, the pulse wave period T is the period of the pulse wave generated by the pulse wave generator with the frequency F3;
the preset processing rule is as follows:
judging whether the difference value between the ultrasonic forward-travel time measured by the time difference method and the ultrasonic forward-travel time measured by the phase difference method is greater than a pulse wave period T or not, if so, subtracting at least one pulse wave period T from the ultrasonic forward-travel time measured by the time difference method until the difference value between the ultrasonic forward-travel time measured by the time difference method and the ultrasonic forward-travel time measured by the phase difference method is less than one pulse wave period T;
and judging whether the difference between the ultrasonic wave back flight time measured by the time difference method and the ultrasonic wave back flight time measured by the phase difference method is larger than a pulse wave period T or not, if so, subtracting at least one pulse wave period T from the ultrasonic wave back flight time measured by the time difference method until the difference between the ultrasonic wave back flight time measured by the time difference method and the ultrasonic wave back flight time measured by the phase difference method is smaller than one pulse wave period T.
Preferably, the preset multiplication operation performed by the first multiplication modulation module and the second multiplication modulation module, that is, the multiplication modulation, is to control the amplitudes of the carrier wave generated by the frequency F1 excitation wave generator and the carrier wave generated by the frequency F2 excitation wave generator respectively by using the sinusoidal modulation wave generated by the sinusoidal modulation wave generator, so that the amplitudes are changed linearly with the modulation signal, and the method is implemented by: and multiplying the carrier wave and the sine modulation wave by a multiplier circuit, and outputting the multiplied result as an excitation waveform of the sine wave modulation amplitude.
Preferably, the sinusoidal modulation wave is a 100Hz to 1000Hz sinusoidal wave.
Preferably, the first multi-frequency array ultrasonic transducer and the second multi-frequency array ultrasonic transducer have the same shape and structure;
a first multi-frequency array ultrasonic transducer comprising a cylindrical transducer housing;
a first main transducer, a second main transducer and a third main transducer are arranged in the transducer shell;
the first main transducer, the second main transducer and the third main transducer are respectively connected with one end of a transducer lead;
the first main transducer, the second main transducer and the third main transducer are distributed in the inner cavity of the transducer shell at equal intervals along the circumferential direction;
the first main transducer, the second main transducer, and the third main transducer are cylindrical in shape.
Preferably, the first main transducer, the second main transducer and the third main transducer are fixedly connected with the back panel of the transducer housing through a positioning pin respectively.
Preferably, the resonant frequencies of the first main transducer, the second main transducer and the third main transducer are all different.
Preferably, the resonant frequencies of the first main transducer, the second main transducer and the third main transducer are all selected to be between 30kHz and 2MHz, and the difference between any two is greater than 30 kHz;
the first main transducer and the first secondary transducer are in a corresponding group, and the center frequencies are the same;
the second main transducer and the second secondary transducer are in a corresponding group, and the center frequencies are the same;
the third main transducer and the third secondary transducer are in a corresponding group, and the center frequencies are the same.
Preferably, the central axis of the first secondary transducer is located on the same straight line with the central axis of the first primary transducer;
the central axis of the second secondary transducer and the central axis of the second main transducer are positioned on the same straight line;
the central axis of the third secondary transducer is located on the same straight line with the central axis of the third primary transducer.
Compared with the prior art, the technical scheme provided by the invention has the advantages that the design is scientific, the pair of multi-frequency array ultrasonic transducers are excited through the pulse wave and the sine modulation wave, the accurate value and the coarse timing of the flight time of the ultrasonic wave are measured through the time difference method and the phase difference method respectively, and the measurement accuracy of the flow velocity of the fluid is ensured, so that the field applicability problem of the ultrasonic flowmeter is solved, the ultrasonic flowmeter can be applied to more working condition fields, is not influenced by the field environment and interference, and ensures the accuracy of field use.
The multi-frequency array ultrasonic flowmeter provided by the invention has the advantages of high field use accuracy, good stability and wider application.
Drawings
Fig. 1a is a front structural view of a first multi-frequency array ultrasonic transducer in a multi-frequency array ultrasonic flow meter provided by the present invention;
FIG. 1b is a right side view of a first multi-frequency array ultrasonic transducer in a multi-frequency array ultrasonic flow meter according to the present invention;
fig. 2 is a schematic structural diagram of a pipe body of an ultrasonic flowmeter in a multi-frequency array ultrasonic flowmeter provided by the present invention;
fig. 3 is a block diagram of a measuring circuit of a multi-frequency array ultrasonic flowmeter according to the present invention;
FIG. 4 is a schematic diagram of a sine wave modulated excitation waveform in a multi-frequency array ultrasonic flow meter provided by the present invention;
fig. 5 is a flowchart of an operating mode of a multi-frequency array ultrasonic flowmeter according to the present invention.
Detailed Description
In order to make the technical means for realizing the invention easier to understand, the following detailed description of the present application is made in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are merely illustrative of the relevant application and are not limiting of the application. It should be noted that, for convenience of description, only the portions related to the present application are shown in the drawings.
It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present application will be described in detail below with reference to the embodiments with reference to the attached drawings.
It should be noted that in the description of the present application, the terms of direction or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. are based on the directions or positional relationships shown in the drawings, which are merely for convenience of description, and do not indicate or imply that the device or element must have a specific orientation, be constructed and operated in a specific orientation, and thus, should not be construed as limiting the present application.
In addition, it should be noted that, in the description of the present application, unless otherwise explicitly specified and limited, the term "mounted" and the like should be interpreted broadly, and may be, for example, either fixedly mounted or detachably mounted.
The specific meaning of the above terms in the present application can be understood by those skilled in the art as the case may be.
Referring to fig. 1 to 5, the present invention provides a multi-frequency array ultrasonic flowmeter, including a first multi-frequency array ultrasonic transducer 100 and a second multi-frequency array ultrasonic transducer 200;
the first multi-frequency array ultrasonic transducer 100 and the second multi-frequency array ultrasonic transducer 200 are respectively and hermetically installed in preset openings at the upper side and the lower side of an ultrasonic flowmeter tube body 1;
the ultrasonic flowmeter comprises an ultrasonic flowmeter body 1, a flow sensor and a flow control device, wherein a medium flowing transversely is arranged in the ultrasonic flowmeter body 1;
wherein, the first multi-frequency array ultrasonic transducer 100 and the second multi-frequency array ultrasonic transducer 200 are centrosymmetric;
the first multi-frequency array ultrasonic transducer 100 comprises a first main transducer 101, a second main transducer 102 and a third main transducer 103;
a second multi-frequency array ultrasonic transducer 200 comprising a first secondary transducer 201, a second secondary transducer 202 and a third secondary transducer 203;
the multi-frequency array ultrasonic flowmeter comprises a measuring circuit, wherein the measuring circuit comprises a frequency F1 excitation wave generator, a frequency F2 excitation wave generator, a frequency F3 pulse wave generator, a sine modulation wave generator, a first multiplication modulation module, a second multiplication modulation module, a time difference method processing circuit module, a first phase difference method processing circuit module, a second phase difference method processing circuit module and a CPU module;
the first multiplication modulation module is respectively connected with the second main transducer 102, the frequency F1 excitation wave generator and the sine modulation wave generator;
the second multiplication modulation module is respectively connected with the third-time transducer 203, the frequency F2 excitation wave generator and the sine modulation wave generator;
the sinusoidal modulation wave generator is used for generating a sinusoidal modulation wave;
a frequency F1 excitation wave generator and a frequency F2 excitation wave generator, which are respectively used for generating carrier waves;
the first multiplication modulation module is used for executing preset multiplication operation on a sinusoidal modulation wave generated by the sinusoidal modulation wave generator and a carrier wave generated by the frequency F1 excitation wave generator to obtain an excitation waveform of a sinusoidal wave modulation amplitude, namely obtaining a continuous amplitude modulation ultrasonic signal with a carrier frequency of F1 and then exciting the second main transducer 102, namely realizing continuous amplitude modulation wave excitation;
a second main transducer 102 serving as an ultrasonic transmitting transducer for transmitting a continuous amplitude-modulated ultrasonic signal having a carrier frequency of F1 as a second ultrasonic transmitting signal to a second sub-transducer 202;
the second secondary transducer 202, as an ultrasonic receiving transducer, is configured to receive a continuous amplitude modulation ultrasonic signal with a carrier frequency of F1, which is transmitted by the second main transducer 102, and then output the continuous amplitude modulation ultrasonic signal as a second ultrasonic receiving signal to the second phase difference processing circuit module;
the second multiplication modulation module is used for executing preset multiplication operation on the sinusoidal modulation wave generated by the sinusoidal modulation wave generator and the carrier wave generated by the frequency F2 excitation wave generator to obtain an excitation waveform of a sinusoidal wave modulation amplitude, namely a continuous amplitude modulation ultrasonic signal with the carrier frequency of F2 is obtained, and then the second multiplication modulation module is used for exciting the third transducer 203, namely continuous amplitude modulation wave excitation is realized;
a third sub-transducer 203 serving as an ultrasonic transmission transducer for transmitting a continuous amplitude-modulated ultrasonic signal having a carrier frequency of F2 as a first ultrasonic transmission signal to the third main transducer 103;
the third main transducer 103 is used as an ultrasonic receiving transducer for receiving a continuous amplitude modulation ultrasonic signal with a carrier frequency of F2 transmitted by the third sub-transducer 203, and then outputting the continuous amplitude modulation ultrasonic signal as a first ultrasonic receiving signal (also an excitation waveform with a sine wave modulation amplitude) to the first phase difference processing circuit module;
wherein, the frequency F3 pulse wave generator is respectively connected with the first main transducer 101 and the first secondary transducer 201, and is used for alternately exciting the first main transducer 101 and the first secondary transducer 201 by pulse waves;
the time difference processing circuit module is respectively connected with the first main transducer 101 and the first secondary transducer 201, and is used for performing preset time difference processing operation on ultrasonic waves output by the first main transducer 101 and the first secondary transducer 201 after excitation, and then outputting the ultrasonic waves subjected to the preset time difference processing operation to the CPU module;
the first phase difference processing circuit module is connected to the third main transducer 103, and is configured to perform a preset phase difference processing operation on a first ultrasonic receiving signal (i.e., a continuous amplitude modulation ultrasonic signal with a carrier frequency of F2, that is, an excitation waveform of a sine wave modulation amplitude, which is a continuous amplitude modulation ultrasonic signal with a carrier frequency of F2) output by the third main transducer 103, because an ultrasonic transmitting transducer corresponding to the third main transducer 103 is the third main transducer 203, and a transmitting signal of the ultrasonic transmitting transducer is a signal after sine wave modulation, the ultrasonic receiving signal is also a signal after sine wave modulation), and then output the signal to the CPU module;
similarly, the second phase difference processing circuit module is connected to the second secondary transducer 202, and is configured to perform a preset phase difference processing operation on a second ultrasonic received signal (i.e., a continuous amplitude modulation ultrasonic signal with a carrier frequency of F1) output by the second secondary transducer 202, and then output the signal to the CPU module;
the CPU module is respectively connected with the time difference method processing circuit module, the first phase difference method processing circuit module and the second phase difference method processing circuit module, and has the functions of: the ultrasonic wave processing circuit module is used for receiving ultrasonic waves which are sent by the time difference processing circuit module and are subjected to preset time difference processing operation, and then calculating by using a time difference method to obtain a time difference method measured value of ultrasonic wave flight time (the measured value comprises forward flight time and backward flight time of the ultrasonic waves measured by the time difference method); secondly, the phase difference measuring circuit is used for measuring the time difference between the output signals (specifically pulse square waves) of the first phase difference processing circuit module and the output signals of the second phase difference processing circuit module and the time difference between the output signals and the first ultrasonic wave emission excitation signal and the time difference between the output signals and the second ultrasonic wave emission excitation signal respectively to obtain the phase difference measuring value of the ultrasonic wave flight time (the measuring value comprises the forward flight time and the backward flight time of the ultrasonic wave measured by the phase difference method); thirdly, after the time difference method measurement value and the phase difference method measurement value of the ultrasonic wave flight time are obtained, the forward flight time and the backward flight time of the ultrasonic wave measured by the time difference method are adjusted according to a preset processing rule, and after the adjustment, the flow velocity of the medium (namely the flow velocity of the fluid) is calculated according to the forward flight time and the backward flight time of the ultrasonic wave measured by the adjusted time difference method and a preset time difference method calculation formula.
The first ultrasonic emission excitation signal is an excitation signal generated by the CPU module and used for driving the third transducer 203 to emit the first ultrasonic emission signal, that is, a frequency F2 excitation wave;
the second ultrasonic transmission excitation signal is an excitation signal generated by the CPU module and used for driving the second main transducer 102 to transmit the second ultrasonic transmission signal, that is, a frequency F1 excitation wave;
it should be noted that the ultrasonic emission excitation signal, that is, the excitation signal for driving the ultrasonic emission by the CPU module, is an excitation wave with frequency F1 and an excitation wave with frequency F2, the second main transducer 102 and the third sub-transducer 203 are excited by the two excitation waves, respectively, and the ultrasonic signal with the same frequency as the excitation wave, that is, the first ultrasonic emission signal emitted by the third sub-transducer 203 and the second ultrasonic emission signal emitted by the second main transducer 102, are generated by the electro-acoustic conversion characteristics of the transducers.
For the present invention, regarding the calculation time difference, the time difference between the second main transducer 102 and the second secondary transducer 202 is the starting time of the output signal (specifically, pulse square wave) of the processing circuit module by using the first phase difference method, minus the starting time of the first ultrasonic transmission excitation signal generated by the CPU module driving the transmission of the first ultrasonic transmission signal; the time difference between the third transducer 203 and the third main transducer 103 is the starting time of the output signal (specifically, pulse square wave) of the processing circuit module by using the second phase difference method, minus the starting time of the ultrasonic emission excitation signal generated by the CPU module driving the second ultrasonic emission signal.
In the invention, the first multi-frequency array ultrasonic transducer 100 is positioned at the upstream of the flow, the second multi-frequency array ultrasonic transducer 200 is positioned at the downstream of the flow, and the time difference measured by a phase difference method is transmitted by the second main transducer 102 and received by the second secondary transducer 202, namely the forward flight time of the ultrasonic wave; the time difference measured by the phase difference method used for transmitting by the third transducer 203 and receiving by the first main transducer 103 is the ultrasonic wave reverse flight time.
In the invention, for a CPU module, the forward flight time and the backward flight time of ultrasonic waves measured by a time difference method are adjusted according to a preset processing rule, and the method specifically comprises the following operations:
adjusting the forward-travel time and the backward-travel time of the ultrasonic waves measured by the time difference method according to a preset processing rule until the difference value between the forward-travel time of the ultrasonic waves measured by the time difference method and the forward-travel time of the ultrasonic waves measured by the phase difference method is smaller than a pulse wave period T and the difference value between the backward-travel time of the ultrasonic waves measured by the time difference method and the backward-travel time of the ultrasonic waves measured by the phase difference method is smaller than a pulse wave period T, and then calculating to obtain the flow velocity of the medium (namely the flow velocity of the fluid) according to the adjusted forward-travel time and backward-travel time of the ultrasonic waves measured by the time difference method and a preset time difference method calculation formula;
here, the pulse wave period T is the period of the pulse wave generated by the pulse wave generator having the frequency F3.
The preset processing rule is as follows:
judging whether the difference value between the ultrasonic forward-travel time measured by the time difference method and the ultrasonic forward-travel time measured by the phase difference method is greater than a pulse wave period T or not, if so, subtracting at least one pulse wave period T from the ultrasonic forward-travel time measured by the time difference method until the difference value between the ultrasonic forward-travel time measured by the time difference method and the ultrasonic forward-travel time measured by the phase difference method is less than one pulse wave period T;
and judging whether the difference between the ultrasonic wave back flight time measured by the time difference method and the ultrasonic wave back flight time measured by the phase difference method is larger than a pulse wave period T or not, if so, subtracting at least one pulse wave period T from the ultrasonic wave back flight time measured by the time difference method until the difference between the ultrasonic wave back flight time measured by the time difference method and the ultrasonic wave back flight time measured by the phase difference method is smaller than one pulse wave period T.
In the present invention, it should be noted that the preset multiplication operation performed by the first multiplication modulation module and the second multiplication modulation module, that is, the multiplication modulation, uses the modulation signal (that is, the sine modulation wave generated by the sine modulation wave generator) to respectively control the amplitude of the carrier wave generated by the frequency F1 excitation wave generator or the amplitude of the carrier wave generated by the frequency F2 excitation wave generator, so that the carrier waves linearly change with the modulation signal, and the implementation method is as follows: and multiplying the carrier wave and the sine modulation wave by a multiplier circuit, and outputting the multiplied result as an excitation waveform of the sine wave modulation amplitude.
In a specific implementation, the multiplication modulation may be implemented by using an analog multiplier chip, such as an analog multiplier chip of MC 1496.
In the invention, the waveforms generated by the F1 excitation wave generator and the frequency F2 excitation wave generator are used as carriers, and the two waveforms are respectively modulated by the waveform generated by the sine modulation wave generator to obtain the carriers with two frequencies modulated by sine waves, namely, the frequency F1 excitation wave and the frequency F2 excitation wave are respectively obtained.
The multiplication modulation technology is widely applied in the radio field, and in the invention, because the ultrasonic transducer can only pass signals with fixed excitation frequency, amplitude modulation operation can be realized by adopting the multiplication modulation technology. The ultrasonic transmitting transducer (including the second main transducer 102 and the third secondary transducer 203) is excited by a waveform modulated by a sine wave, a modulated common-frequency signal can be received at a corresponding ultrasonic receiving transducer end (namely the third main transducer 103 and the second secondary transducer 202), a signal with the same frequency of the sine modulated wave can be demodulated after being processed by a demodulation circuit, the phase difference between the demodulated signal and the exciting signal can be measured by a time measuring circuit, and the phase difference is in direct proportion to the flow velocity of a fluid, namely the phase difference method ultrasonic flowmeter measuring principle. The carrier frequency is far greater than the modulated wave signal, so the demodulation circuit is realized by adopting a low-pass filter circuit, and the high-frequency carrier signal is filtered by low-pass filtering, so the modulated wave signal can be obtained.
In the invention, the center frequencies of the second main transducer 102 and the second secondary transducer 202 are the same, and the center frequencies of the third main transducer 103 and the third secondary transducer 203 are the same, but the center frequencies of the second main transducer 102 and the second secondary transducer 202 are different from the center frequencies of the third main transducer 103 and the third secondary transducer 203, and the frequency of the frequency F2 excitation wave is different from the frequency of the frequency F1 excitation wave, so that ultrasonic signals generated by the excitation of the modulation waveforms respectively using two frequencies (namely, the frequencies F1 and F2) as carriers are transmitted and received at the same time without mutual interference, and the two signals can be synchronously measured to synchronously measure the time difference (equal to the signal phase difference) of the two signals, thereby obtaining the forward and reverse flight time of the ultrasonic waves.
The concept of the forward and backward flight time of the ultrasonic wave is as follows: the ultrasonic wave flight time in the direction with the included angle between the ultrasonic wave propagation direction and the fluid flow velocity smaller than 90 degrees; in contrast, the flyback is the ultrasonic flight time in the direction where the ultrasonic wave propagation direction is at an angle of more than 90 degrees to the fluid flow rate.
In the invention, the first multi-frequency array ultrasonic transducer 100 is located at the upstream, the second multi-frequency array ultrasonic transducer 200 is located at the downstream, the first main transducer 101 and the second main transducer 102 transmit ultrasonic signals, the first secondary transducer 201 and the second secondary transducer 202 receive the ultrasonic signals, and the one-to-one corresponding time difference value is the forward flight time of the ultrasonic wave; the first transducer 201 and the third transducer 203 emit ultrasonic signals, and the first main transducer 101 and the third main transducer 103 receive the ultrasonic signals, and the one-to-one corresponding time difference between the ultrasonic signals is the ultrasonic reverse flight time.
It should be noted that: the first main transducer 101 and the first secondary transducer 201 can alternately transmit ultrasonic signals and receive the ultrasonic signals for time difference measurement;
the second main transducer 102, the second secondary transducer 202, the third main transducer 103 and the third secondary transducer 203 are measured by a phase difference method, and continuous ultrasonic excitation signals are adopted, and pulse excitation ultrasonic signals are not alternately transmitted, so that the second main transducer 102 and the third secondary transducer 203 only transmit ultrasonic signals, and the second secondary transducer 202 and the third main transducer 103 only receive the ultrasonic signals. The first main transducer 101 transmits an ultrasonic signal, the first secondary transducer 201 receives the ultrasonic signal, and the group of transducers obtain a group of time difference values; the second primary transducer 102 transmits, the second secondary transducer 202 receives, and the set of transducers obtains a set of time difference values, both sets being ultrasonic forward flight time; the first secondary transducer 201 emits an ultrasonic signal, the first primary transducer 101 receives the ultrasonic signal, and the group of transducers obtain a group of time difference values; the third transducer 203 transmits and the third main transducer 103 receives, and this set of transducers gets a set of time difference values, both sets being the ultrasonic reverse flight time.
The time difference value obtained by the first main transducer 101 and the second main transducer 102 is measured by a time difference method, and the measured flight time of the ultrasonic wave comprises the error of the cycle multiple; the second main transducer 102, the second secondary transducer 202, the third secondary transducer 203 and the second main transducer 103 are measured by a phase difference method, the measured ultrasonic waves have no cycle multiple error during flight, but have the problems of low measurement precision and more accurate flow velocity measurement result by combining the two methods if the error caused by the sound velocity is directly calculated by using a phase difference formula.
Similarly, first primary transducer 101 has the same center frequency as first secondary transducer 201, but has a different center frequency from the other transducers. The center frequencies of the three pairs of transducers are different, so that when the phase difference method processing module and the time difference method processing module perform signal processing, the mutual influence between signals can be avoided only by simple band-pass filtering operation.
Because the first multi-frequency array ultrasonic transducer 100 (including the first main transducer 101, the second main transducer 102 and the third main transducer 103) and the second multi-frequency array ultrasonic transducer 200 (including the first secondary transducer 201, the second secondary transducer 202 and the third secondary transducer 203) are combined, the flight time of the forward and backward travel of the ultrasonic wave is the flight time between the two sets of ultrasonic transducers, which is also the flight time between 101 and 201, and thus the flight time (coarse value) of the forward and backward travel of the ultrasonic wave between the transducers is obtained.
In the invention, the first phase difference method processing circuit module and the second phase difference method processing circuit module respectively transmit the demodulated signals (namely the signals processed by the preset phase difference method processing operation) to the CPU for time measurement, thereby obtaining the flight time (rough value) of the forward and backward strokes of the ultrasonic waves between the transducers.
It should be noted that, for the present invention, the time difference processing circuit module includes a signal switching circuit, a signal filtering circuit, a signal amplifying circuit, a threshold-zero crossing comparison detection circuit and a time measuring circuit, and the preset time difference processing operation is adopted, specifically as follows;
firstly, a signal switching circuit adopts an analog electronic switch to alternately receive and process the receiving signals of a first main transducer 101 and a first secondary transducer 201, namely when the first main transducer 101 excites and transmits ultrasonic waves, the receiving signals of the first secondary transducer 201 are switched and processed; when the first transducer 201 excites the transmission ultrasonic wave, the received signal of the first main transducer 101 is switched.
The signal filtering circuit is respectively connected with the signal switching circuit and the signal amplifying circuit, and is used for performing band-pass filtering processing on a receiving signal of the signal switching circuit (namely, the receiving signal of the first main transducer 101 or the first secondary transducer 201 received by the signal switching circuit), eliminating interference of other transducers on the signal, and then performing signal amplification through the signal amplifying circuit;
and the signal amplifying circuit is connected with the threshold-zero-crossing comparison circuit and is used for sending the amplified signal to the threshold-zero-crossing comparison circuit for wave detection, and after the signal is processed by the threshold-zero-crossing comparison circuit, the output of the threshold-zero-crossing comparison circuit is pulse square waves which are sent to the time measuring circuit.
And the time measuring circuit is respectively connected with the threshold-zero-crossing comparison circuit and a CPU module (such as the CPU module shown in figure 1) and is used for processing the pulse square waves output by the threshold-zero-crossing comparison circuit to obtain a signal time value and sending the signal time value to the CPU module through SPI communication.
For the invention, in the concrete implementation, the common measurement chips of the time measurement circuit part are TDC-GP21, TDC-GP22 and the like. Therefore, the CPU measures the forward and backward flight time of the ultrasonic waves in the time difference method measurement, and the time is measured by a time measuring part (a special precise time digital converter chip, commonly used TDC-GP21 and TDC-GP22) in a time difference method processing circuit module, so that the precision and the resolution are very high and can reach 2 ps. The measured time of flight of the ultrasonic wave in this part, although the accuracy and resolution are high, includes the delay error of the ultrasonic detection period (the delay occurs in the zero-crossing comparison), so the error needs to be eliminated before use. Because the delay error of the ultrasonic detection period is a multiple of the ultrasonic excitation waveform period, and the frequency of the time difference method excitation waveform is F3, the time difference method module subtracts the multiple of the excitation waveform period from the ultrasonic flight time obtained until the difference between the time difference method module and the phase difference method measurement result is less than the excitation waveform period, and the real forward and reverse flight time of the ultrasonic can be obtained. And then the CPU calculates the fluid flow rate according to a time difference calculation formula.
It should be noted that the principle of the equation of the time difference method is that, due to the fluid flow, the ultrasonic wave is influenced by the fluid flow, the component along the fluid flow direction increases, and the component opposite to the fluid flow direction decreases, so the backward flight time of the ultrasonic wave is longer than the forward flight time of the ultrasonic wave, and the relationship between the ultrasonic wave and the fluid flow rate conforms to the following equation. By using the formula, after the forward and backward flight time of the ultrasonic wave is accurately measured, the flow velocity of the fluid can be calculated according to the following time difference calculation formula because the diameter D of the pipeline and the included angle between the sound channel and the central axis are fixed values.
Figure BDA0002987909480000151
In the formula: t is tupThe time for the ultrasonic wave to propagate downstream in the fluid is the time required for the transducer B to receive the ultrasonic wave after the ultrasonic wave is transmitted by the transducer A; t is tdownThe time for the ultrasonic wave to propagate in the fluid in a counter-current manner, namely the time for the transducer A to receive the ultrasonic wave after the transducer B transmits the ultrasonic wave; d is the diameter of the pipeline of the ultrasonic flowmeter; phi is the included angle between the sound channel of the ultrasonic transducer and the central axis of the flowmeter.
In the present invention, it should be noted that the two phase difference processing circuit modules (including the first phase difference processing circuit module and the second phase difference processing circuit module) respectively include a band-pass filter circuit, a signal amplification circuit, a low-pass filter circuit, a threshold-zero-crossing comparison circuit, and other circuits; the processing method (namely the preset phase difference method processing operation) is as follows:
firstly, an ultrasonic receiving signal passes through a band-pass filter circuit to filter interference signals brought by other transducers, then the processed signal is amplified through a signal amplifying circuit, then a low-pass filter circuit is used for filtering a carrier signal to realize demodulation operation, and a modulated wave signal can be obtained. And finally, the pulse square wave signal is sent to a CPU module, and the difference value is made between the pulse square wave signal and the starting moment of the ultrasonic wave emission excitation signal controlled by the CPU module, so that the flight time of the ultrasonic wave can be measured. Based on the principle, the CPU module receives the pulse square wave signals processed by the first phase difference method processing module and the second phase difference method processing module, and respectively measures the time difference between the two pulse square wave signals and the ultrasonic emission signal to obtain the flight time of the clockwise and anticlockwise ultrasonic.
It should be noted that the ultrasonic emission excitation signal controlled by the CPU module, that is, the excitation signal used by the CPU module to drive the ultrasonic emission, that is, the frequency F1 excitation wave and the frequency F2 excitation wave, respectively excite the second main transducer 102 and the third transducer 203, and the ultrasonic signals having the same frequency as the excitation wave, that is, the first ultrasonic emission signal emitted by the third transducer 203 and the second ultrasonic emission signal emitted by the second main transducer 102, are generated by the electro-acoustic conversion characteristics of the transducers.
Calculating the time difference, wherein the time difference between the second main transducer 102 and the second secondary transducer 202 is obtained by subtracting the starting time of the ultrasonic emission excitation signal generated by the CPU module for driving and emitting the first ultrasonic emission signal from the starting time of the output signal (specifically, pulse square wave) of the first phase difference processing circuit module; the time difference between the third secondary transducer 203 and the third main transducer 103 is the starting time of the output signal (specifically, pulse square wave) of the processing circuit module by using the second phase difference method minus the starting time of the ultrasonic emission excitation signal generated by the CPU module for driving and emitting the second ultrasonic emission signal.
It should be noted that, because the output waveform of the phase difference processing circuit module is a square wave at the arrival time of the modulated wave, and the frequency of the modulated wave is low, and the accuracy of direct measurement by the CPU module is low, the forward and backward flight times of the ultrasonic waves measured by the phase difference method are only used as coarse timing.
In the invention, in the phase difference method measurement, the second main transducer 102 and the third sub-transducer 203 are ultrasonic transmitting transducers which are respectively excited by a first multiplication modulation module and a second multiplication modulation module;
the ultrasonic receiving transducer corresponding to the second main transducer 102 is the second sub-transducer 202, and the ultrasonic receiving transducer corresponding to the third sub-transducer 203 is the third main transducer 103;
the third main transducer 103 and the second secondary transducer 202 are ultrasonic receiving transducers, and are respectively connected to the first phase difference processing module and the second phase difference processing module for processing received signals. Then the processed received signal is sent to a CPU module to measure the forward flight time and the backward flight time of the ultrasonic wave, and the coarse timing of the forward flight time and the backward flight time of the ultrasonic wave is obtained.
It should be noted that, in terms of the specific implementation of the present invention, since the time difference method cannot accurately determine the waveform of the period, the forward flight time and the backward flight time of the ultrasonic waves obtained by measurement thereof contain an error of the whole period time, and the coarse timing obtained by measurement by the phase difference method can be used for comparing with the time measured by the time difference method to eliminate the error of the whole period time.
In the present invention, fig. 4 is a schematic diagram of a sine wave modulated excitation waveform in a multi-frequency array ultrasonic flow meter provided by the present invention. Referring to fig. 4, the sine-modulated wave is generated by a sine-modulated wave generator, and the carrier waves are generated by a frequency F1 excitation wave generator and a frequency F2 excitation wave generator, respectively. The modulation wave and the carrier wave are modulated by a multiplication modulation module to obtain a sine wave modulated excitation waveform.
In particular, the sine modulation wave is a sine wave from 100Hz to 1000 Hz.
In the invention, the time difference processing circuit module comprises signal switching, signal filtering, signal amplification and a threshold value-zero-crossing comparison detection circuit and a time measurement circuit.
In a specific implementation aspect of the present invention, the first phase difference processing circuit module and the second phase difference processing circuit module each include a band-pass filter, a signal amplifier, a low-pass filter, a zero-cross comparison, and the like.
In the present invention, in a specific implementation, the first multi-frequency array ultrasonic transducer 100 and the second multi-frequency array ultrasonic transducer 200 have the same shape and structure.
Next, a specific shape and structure design of the multi-frequency array ultrasonic transducer is described by taking the first multi-frequency array ultrasonic transducer 100 as an example.
In the present invention, as shown in fig. 1, a first multi-frequency array ultrasonic transducer 100 includes a cylindrical transducer housing 2;
inside the transducer housing 2, a first main transducer 101, a second main transducer 102, and a third main transducer 103 are mounted;
note that, the transducer housing 2 protects the first main transducer 101, the second main transducer 102, and the third main transducer 103;
the first main transducer 101, the second main transducer 102 and the third main transducer 103 are respectively connected with one end of a transducer lead 4;
it should be noted that the other end of the transducer lead 4 is used for connecting to other preset circuit modules, and is used for other circuits to drive and collect signals, for example, as shown in fig. 3;
the first main transducer 101, the second main transducer 102 and the third main transducer 103 are distributed in the inner cavity of the transducer shell 2 at equal intervals along the circumferential direction;
first main transducer 101, second main transducer 102, and third main transducer 103 are cylindrical in shape.
In a specific implementation, the first main transducer 101, the second main transducer 102 and the third main transducer 103 are respectively and fixedly connected with the back panel of the transducer housing 2 through a positioning pin 2.
It should be noted that the positioning pins 2 are used to position the first main transducer 101, the second main transducer 102, and the third main transducer 103, so as to ensure that the 3 sets of transducers that are opposite to each other can be aligned one to one.
It should be noted that, for the three transducers of the first multi-frequency array ultrasonic transducer 100, the first main transducer 101 is used to implement time difference measurement, and is excited by using a pulse wave; second main transducer 102 and third main transducer 103 are used to implement phase difference measurements, excited with a continuous amplitude modulated wave modulated by a sine wave.
In a specific implementation, the resonant frequencies of the first main transducer 101, the second main transducer 102, and the third main transducer 103 are all different.
In a specific implementation, the resonant frequencies of first main transducer 101, second main transducer 102 and third main transducer 103 are generally selected to be between 30kHz and 2MHz, and the difference between any two is greater than 30kHz, so as to facilitate detection by a subsequent processing circuit.
Similarly, it should be noted that, for the second multi-frequency array ultrasonic transducer 200, there is the same shape and structure as the first multi-frequency array ultrasonic transducer 100, and the first sub-transducer 201, the second sub-transducer 202 and the third sub-transducer 203 thereof also have the same shape and structure design and resonance frequency requirements as the first main transducer 101, the second main transducer 102 and the third main transducer 103.
In the specific implementation, fig. 2 is a structural diagram of the pipe body of the ultrasonic flow meter, a hole is formed in the pipe body of the ultrasonic flow meter, the hole is used for installing the multi-frequency array ultrasonic transducer, and when the hole is formed, the hole-forming position of the positioning pin is required to ensure that three transducers inside a pair of multi-frequency array ultrasonic transducers (i.e., the second multi-frequency array ultrasonic transducer 200 and the first multi-frequency array ultrasonic transducer 100) are correspondingly installed on a straight line.
That is, the central axis of first secondary transducer 201 is located on the same straight line as the central axis of first main transducer 101;
the central axis of the second secondary transducer 202 is located on the same straight line as the central axis of the second primary transducer 102;
the center axis of the third secondary transducer 203 is located on the same straight line as the center axis of the third main transducer 103.
In the present invention, it should be noted that, for the first multi-frequency array ultrasonic transducer 100 and the second multi-frequency array ultrasonic transducer 200, the first main transducer 101, the second main transducer 102, and the third main transducer 103 employ ultrasonic transducers with three different center frequencies, and at the same time, the first secondary transducer 201, the second secondary transducer 202, and the third secondary transducer 203 also employ ultrasonic transducers with three different center frequencies.
In order to avoid mutual interference of the center frequencies of the transducers, the difference between the center frequencies (i.e., resonant frequencies) of the first multi-frequency array ultrasonic transducer 100 and the second multi-frequency array ultrasonic transducer 200 is greater than 30 kHz.
In a specific implementation, the first primary transducer 101 and the first secondary transducer 201 are a corresponding group, and have the same model and the same center frequency. The second primary transducer 102 and the second secondary transducer 202 are in a corresponding group, and have the same model and the same center frequency. The third main transducer 103 and the third secondary transducer 203 are a corresponding group, and adopt the same model and have the same center frequency. The model of each group can be selected arbitrarily. The DYA-200-01H, DYA-125-02A, DYA-49-08FB ultrasonic transducer of Dayu electronic in Fuzhou can be adopted.
In the concrete implementation, three types of ultrasonic transducers are packaged together, namely three ultrasonic transducers of a main transducer 101, a second main transducer 102 and a third main transducer 103 are packaged into a first multi-frequency array ultrasonic transducer 100, and a first secondary transducer 201, a second secondary transducer 202 and a third secondary transducer 203 are packaged into a second multi-frequency array ultrasonic transducer 200, so that after the three transducers are combined together, the direct distances of the three transducers, namely the sound paths of ultrasonic wave propagation are the same, the propagation paths are the same, the time used by the three transducers during forward flow propagation and backward flow propagation is the same, the time can be roughly timed by using a phase difference method and accurately timed by using a time difference method, the problem that the flight time of the ultrasonic wave caused by threshold value-zero crossing comparison measured by the time difference method contains fixed period errors is solved, and the problem that the phase difference method is influenced by the speed of the ultrasonic wave is avoided, meanwhile, the center frequencies of the three ultrasonic transducers are different, and when the ultrasonic transducer is used, the mutual interference among the transducers can be eliminated through a band-pass filtering method.
In the invention, the CPU module controls each module to work, and the signals processed by the time difference method and the signals processed by the phase difference method are operated.
In particular, referring to fig. 5, for the multi-frequency array ultrasonic flow meter provided by the present invention, the specifically adopted operation mode includes the following steps:
first, initialize all modules (i.e., the individual modules shown in FIG. 3);
secondly, respectively generating sine wave modulated excitation waveforms for exciting the second main transducer 102 and the third sub-transducer 203 by exciting a sine modulation wave generated by the sine modulation wave generator and a carrier generated by the frequency F1 excitation wave generator, and exciting a sine modulation wave generated by the sine modulation wave generator and a carrier generated by the frequency F2 excitation wave generator;
thirdly, exciting the pulse wave generated by the pulse wave generator with the frequency F3 and alternately exciting the first main transducer 101 and the first secondary transducer 201 with the pulse wave;
fourthly, judging whether preset timing time (for example, 1 second) is reached, if not, performing the fifth step, if so, calculating ultrasonic forward-travel and backward-travel flight coarse timing (forward-travel timing, namely ultrasonic flight time in the direction that the included angle between the ultrasonic propagation direction and the fluid flow velocity is less than 90 degrees; conversely, backward-travel timing, namely ultrasonic flight time in the direction that the included angle between the ultrasonic propagation direction and the fluid flow velocity is greater than 90 degrees) by a phase difference method, and respectively recording the ultrasonic forward-travel and backward-travel coarse timing as t1 and t 2;
it should be noted that, because the measurement principle of the phase difference method needs to demodulate a signal, measure the phase difference between a received modulated wave and an excited modulated wave, and needs to measure the zero-crossing waveform of the modulated wave, rather than immediately measure the received signal, if the signal is immediately measured, the zero-crossing waveform cannot be measured, and the phase difference cannot be accurately measured, the measurement is performed with a preset timing time, such as 1 second, in the algorithm, and the timing time must exceed a complete modulated wave period. The phase difference method measurement method is that a signal obtained by amplifying and filtering an excitation modulation wave passes through a threshold-zero crossing comparison circuit to obtain a pulse square wave, and the signal is used as an initial point to start timing; the signal after the received signal is amplified and filtered is processed by a threshold value-zero crossing comparison circuit to obtain a pulse square wave, the pulse square wave is used as a stop signal to stop timing, and the recorded time is the phase difference time value of the excitation signal and the received signal.
It should be noted that the phase difference method part is controlled by timing, the common timing time is 1s, when the timing time arrives, the signals output by the phase difference method processing circuit module received from the second transducer 202 and the third transducer 103 are sent to the CPU module, the time difference between the excitation signal (i.e. the excitation signal used by the CPU module to drive the ultrasonic wave to emit, i.e. the frequency F1 excitation wave and the frequency F2 excitation wave) and the output signal (i.e. the output waveform) of the two phase difference method processing circuits (the first phase difference method processing circuit and the second phase difference method processing circuit) is measured and respectively used as the ultrasonic forward-travel and backward-travel coarse timing (i.e. the ultrasonic forward-travel and backward-travel flight times measured by the phase difference method), and the time difference is respectively measured as t1 and t 2;
a fifth step of judging whether the first main transducer 101 and the first secondary transducer 201 receive an ultrasonic receiving signal (a pulse wave, i.e. a pulse wave generated by the pulse wave generator with the frequency F3), if the ultrasonic receiving signal is not received, performing a sixth step, if the ultrasonic receiving signal is received (because of a time difference method, the ultrasonic transducer needs to be excited in a single pulse or small pulse mode, and the corresponding ultrasonic receiving signal is also a waveform of single pulse or small pulse attenuation oscillation), calculating the forward flight time and the reverse flight time of the ultrasonic wave by a time difference method (the time difference method measuring module directly measures the ultrasonic receiving signal, the time difference method measuring module is a time difference method processing circuit module, and unlike a phase difference method which measures a modulated wave, the measuring resolution and the measuring accuracy of the ultrasonic forward flight time and the reverse flight time measured by the time difference method are higher), denoted t3 and t4, respectively;
the control of the time difference method part judges whether an ultrasonic receiving signal is received or not, and when the ultrasonic receiving signal is received, the forward flight time and the backward flight time of the ultrasonic are measured by the time difference method and are respectively counted as t3 and t 4;
and sixthly, after T3 and T4 are recorded, the pulse wave period is T, whether T3-T1 is smaller than the time difference method ultrasonic wave emission signal period T or not is judged, if yes, the seventh step is carried out, otherwise, the T3 is subtracted from the T, whether T3-T1 is smaller than the time difference method ultrasonic wave emission signal period T or not is continuously judged, and the seventh step is carried out until the time difference method ultrasonic wave emission signal period T is smaller.
And seventhly, judging whether T4-T2 is smaller than the pulse wave period T or not, if so, subtracting T from T4 until the difference between T4 and T2 is smaller than the pulse wave period T.
And eighthly, calculating to obtain the flow velocity v of the fluid according to a time difference method calculation formula, judging whether the timing time is reached again, and measuring the next period.
It should be noted that, for the present invention, after receiving the time difference signal, the measured time is adjusted according to the coarse timing time T1 and T2 of the phase difference method, and whether the difference between T3 and T1 is less than a pulse wave period is determined, if the difference is greater than the pulse wave period T, the difference between T3 and T1 is subtracted by the pulse wave period until the difference between T3 and T1 is less than the pulse wave period T; similarly, whether the difference value between T4 and T2 is smaller than a pulse wave period is judged, if the difference value is larger than the pulse wave period T, the pulse wave period T is subtracted from T4 until the difference value between T4 and T2 is smaller than the pulse wave period T; and calculating the flow velocity v of the fluid according to the adjusted t3 and t4 by a time difference calculation formula.
That is, with the present invention, according to a preset processing rule, the clockwise time T3 and the counterclockwise time T4 of the ultrasonic wave measured by the time difference method are adjusted until the difference between the clockwise time T3 of the ultrasonic wave measured by the time difference method and the clockwise time T1 of the ultrasonic wave measured by the time difference method is less than one pulse wave period T, and until the difference between the counterclockwise time T4 of the ultrasonic wave measured by the time difference method and the counterclockwise time T2 of the ultrasonic wave measured by the phase difference method is less than one pulse wave period T, and then the flow velocity of the medium (i.e., the flow velocity of the fluid) is calculated and obtained according to the adjusted clockwise and counterclockwise time of the ultrasonic wave measured by the time difference method and a preset time difference method calculation formula;
wherein, the pulse wave period T is the period of the pulse wave generated by the pulse wave generator with the frequency F3;
in particular, the preset processing rule is as follows:
judging whether the difference value between the ultrasonic forward-travel flight time T3 measured by the time difference method and the ultrasonic forward-travel time T1 measured by the phase difference method is greater than a pulse wave period T or not, if so, subtracting at least one pulse wave period T from the ultrasonic forward-travel flight time T3 measured by the time difference method until the difference value between the ultrasonic forward-travel flight time measured by the time difference method and the ultrasonic forward-travel time measured by the phase difference method is less than one pulse wave period T;
and judging whether the difference value T2 between the ultrasonic wave back flight time T4 measured by the time difference method and the ultrasonic wave back flight time measured by the phase difference method is larger than a pulse wave period T or not, if so, subtracting at least one pulse wave period T from the ultrasonic wave back flight time T4 measured by the time difference method until the difference value between the ultrasonic wave back flight time measured by the time difference method and the ultrasonic wave back flight time measured by the phase difference method is smaller than one pulse wave period T.
It should be noted that, for solving the problem that the actual flight time of the ultrasonic wave cannot be accurately measured on the application site when the flow velocity is measured by the ultrasonic wave, the invention provides a multi-frequency array ultrasonic flowmeter, which utilizes a multi-frequency array ultrasonic transducer to combine the advantages of a phase difference method and a time difference method to solve the problem of the measurement accuracy of the ultrasonic flowmeter on the application site.
According to the invention, the flow velocity of the fluid (namely the medium) is calculated by measuring the phase difference of two ultrasonic transducers and measuring the time difference of one ultrasonic transducer.
Based on the above discussion, the multi-frequency array ultrasonic flowmeter of the invention respectively uses 3 groups of ultrasonic transducers, two groups are used for measuring by a phase difference method, and one group is used for measuring by a time difference method; the phase difference method is used for coarse timing to determine the specific period measured by the time difference method, and the time difference method is adopted for accurate timing measurement after the corresponding period number is subtracted. The application of the invention can eliminate the zero point error of the time difference method, ensure the measurement accuracy, has simple and strong practicability, and can be widely applied to the field of ultrasonic flow measurement.
In summary, compared with the prior art, the multi-frequency array ultrasonic flowmeter provided by the invention has a scientific design, the pair of multi-frequency array ultrasonic transducers are excited by the pulse wave and the sine modulation wave, the accurate value and the coarse timing of the flight time of the ultrasonic wave are measured by the time difference method and the phase difference method respectively, and the measurement accuracy of the fluid flow velocity is ensured, so that the field applicability problem of the ultrasonic flowmeter is solved, the ultrasonic flowmeter can be applied to more working condition fields, is not influenced by the field environment and interference, and ensures the accuracy of field use.
The multi-frequency array ultrasonic flowmeter provided by the invention has the advantages of high field use accuracy, good stability and wider application.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.

Claims (10)

1. A multi-frequency array ultrasonic flowmeter is characterized by comprising
A first multi-frequency array ultrasonic transducer (100) and a second multi-frequency array ultrasonic transducer (200);
the ultrasonic flowmeter comprises a first multi-frequency array ultrasonic transducer (100) and a second multi-frequency array ultrasonic transducer (200), wherein the first multi-frequency array ultrasonic transducer and the second multi-frequency array ultrasonic transducer are respectively and hermetically arranged in preset holes on the upper side and the lower side of an ultrasonic flowmeter tube body (1);
the ultrasonic flowmeter comprises an ultrasonic flowmeter tube body (1) and a flow control device, wherein a medium flowing transversely is arranged in the ultrasonic flowmeter tube body (1);
the first multi-frequency array ultrasonic transducer (100) and the second multi-frequency array ultrasonic transducer (200) are centrosymmetric;
wherein the first multi-frequency array ultrasonic transducer (100) comprises a first main transducer (101), a second main transducer (102) and a third main transducer (103);
a second multi-frequency array ultrasonic transducer (200) comprising a first secondary transducer (201), a second secondary transducer (202), and a third secondary transducer (203);
the multi-frequency array ultrasonic flowmeter comprises a measuring circuit, wherein the measuring circuit comprises a frequency F1 excitation wave generator, a frequency F2 excitation wave generator, a frequency F3 pulse wave generator, a sine modulation wave generator, a first multiplication modulation module, a second multiplication modulation module, a time difference method processing circuit module, a first phase difference method processing circuit module, a second phase difference method processing circuit module and a CPU module;
the first multiplication modulation module is respectively connected with the second main transducer (102), the frequency F1 excitation wave generator and the sine modulation wave generator;
the second multiplication modulation module is respectively connected with the third-time transducer (203), the frequency F2 excitation wave generator and the sine modulation wave generator;
the sinusoidal modulation wave generator is used for generating a sinusoidal modulation wave;
a frequency F1 excitation wave generator and a frequency F2 excitation wave generator, which are respectively used for generating carrier waves;
the first multiplication modulation module is used for executing preset multiplication operation on a sinusoidal modulation wave generated by the sinusoidal modulation wave generator and a carrier wave generated by the frequency F1 excitation wave generator to obtain an excitation waveform of a sinusoidal wave modulation amplitude, namely a continuous amplitude modulation ultrasonic signal with the carrier frequency of F1, and then is used for exciting the second main transducer (102), namely continuous amplitude modulation wave excitation is realized;
a second main transducer (102) serving as an ultrasonic transmitting transducer for transmitting a continuous amplitude-modulated ultrasonic signal having a carrier frequency of F1 as a second ultrasonic transmitting signal to a second sub-transducer (202);
the second secondary transducer (202) is used as an ultrasonic receiving transducer and is used for receiving a continuous amplitude modulation ultrasonic signal with the carrier frequency of F1 transmitted by the second main transducer (102), and then the continuous amplitude modulation ultrasonic signal is used as a second ultrasonic receiving signal and is output to the second phase difference method processing circuit module;
the second multiplication modulation module is used for executing preset multiplication operation on the sinusoidal modulation wave generated by the sinusoidal modulation wave generator and the carrier wave generated by the frequency F2 excitation wave generator to obtain an excitation waveform of a sinusoidal wave modulation amplitude, namely a continuous amplitude modulation ultrasonic signal with the carrier frequency of F2, and then is used for exciting the third transducer (203), namely continuous amplitude modulation wave excitation is realized;
a third secondary transducer (203) serving as an ultrasonic transmission transducer for transmitting a continuous amplitude-modulated ultrasonic signal having a carrier frequency of F2 as a first ultrasonic transmission signal to the third main transducer (103);
the third main transducer (103) is used as an ultrasonic receiving transducer and is used for receiving a continuous amplitude modulation ultrasonic signal with the carrier frequency of F2 transmitted by the third sub-transducer (203), and then outputting the continuous amplitude modulation ultrasonic signal as a first ultrasonic receiving signal to the first phase difference processing circuit module;
wherein, the frequency F3 pulse wave generator is respectively connected with the first main transducer (101) and the first secondary transducer (201) and is used for alternately exciting the first main transducer (101) and the first secondary transducer (201) through pulse waves;
the time difference method processing circuit module is respectively connected with the first main transducer (101) and the first secondary transducer (201), and is used for carrying out preset time difference method processing operation on ultrasonic waves output by the first main transducer (101) and the first secondary transducer (201) after excitation, and then outputting the ultrasonic waves subjected to the preset time difference processing operation to the CPU module;
the first phase difference method processing circuit module is connected with the third main transducer (103) and is used for carrying out preset phase difference method processing operation on a first ultrasonic receiving signal output by the third main transducer (103) and then outputting the first ultrasonic receiving signal to the CPU module;
the second phase difference method processing circuit module is connected with the second secondary transducer (202) and is used for carrying out preset phase difference method processing operation on a second ultrasonic receiving signal output by the second secondary transducer (202) and then outputting the second ultrasonic receiving signal to the CPU module;
and the CPU module is respectively connected with the time difference method processing circuit module, the first phase difference method processing circuit module and the second phase difference method processing circuit module and is used for calculating to obtain the flow velocity of the fluid according to a preset time difference method calculation formula.
2. The multi-frequency array ultrasonic flow meter of claim 1, wherein the CPU module functions as follows:
the time difference method measurement device comprises a time difference method processing circuit module, a time difference method measurement module and a time difference measurement module, wherein the time difference method processing circuit module is used for receiving ultrasonic waves which are sent by the time difference method processing circuit module and are subjected to preset time difference processing operation, and then the time difference method is used for calculating to obtain a time difference method measurement value of ultrasonic wave flight time; secondly, the time difference between the output signals of the first phase difference processing circuit module and the output signals of the second phase difference processing circuit module and the output signals of the first ultrasonic wave emission excitation signal and the output signals of the second ultrasonic wave emission excitation signal are respectively measured, and a phase difference measured value of the ultrasonic wave flight time is obtained; thirdly, after a time difference method measurement value and a phase difference method measurement value of the ultrasonic flight time are obtained, the forward flight time and the backward flight time of the ultrasonic measured by the time difference method are adjusted according to a preset processing rule, and after adjustment, the flow velocity of the medium is calculated according to the forward flight time and the backward flight time of the ultrasonic measured by the adjusted time difference method and a preset time difference method calculation formula;
the time difference method measurement value of the ultrasonic wave flight time comprises forward flight time and backward flight time of the ultrasonic wave measured by the time difference method;
the phase difference method measurement value of the ultrasonic flight time comprises the forward flight time and the backward flight time of the ultrasonic measured by the phase difference method;
the first ultrasonic emission excitation signal is an excitation signal which is generated by the CPU module and used for driving the third transducer (203) to emit the first ultrasonic emission signal;
the second ultrasonic emission excitation signal is an excitation signal generated by the CPU module and used for driving the second main transducer (102) to emit the second ultrasonic emission signal.
3. The multi-frequency array ultrasonic flow meter of claim 2, wherein the adjusting of the forward and backward flight times of the time-of-flight ultrasonic waves measured according to the predetermined processing rules for the CPU module comprises the following operations:
adjusting the forward-travel time and the backward-travel time of the ultrasonic waves measured by the time difference method according to a preset processing rule until the difference value between the forward-travel time of the ultrasonic waves measured by the time difference method and the forward-travel time of the ultrasonic waves measured by the phase difference method is smaller than a pulse wave period T and the difference value between the backward-travel time of the ultrasonic waves measured by the time difference method and the backward-travel time of the ultrasonic waves measured by the phase difference method is smaller than a pulse wave period T, and then calculating to obtain the flow velocity of the medium according to the adjusted forward-travel time and backward-travel time of the ultrasonic waves measured by the time difference method and a preset time difference method calculation formula;
wherein, the pulse wave period T is the period of the pulse wave generated by the pulse wave generator with the frequency F3;
the preset processing rule is as follows:
judging whether the difference value between the ultrasonic forward-travel time measured by the time difference method and the ultrasonic forward-travel time measured by the phase difference method is greater than a pulse wave period T or not, if so, subtracting at least one pulse wave period T from the ultrasonic forward-travel time measured by the time difference method until the difference value between the ultrasonic forward-travel time measured by the time difference method and the ultrasonic forward-travel time measured by the phase difference method is less than one pulse wave period T;
and judging whether the difference between the ultrasonic wave back flight time measured by the time difference method and the ultrasonic wave back flight time measured by the phase difference method is larger than a pulse wave period T or not, if so, subtracting at least one pulse wave period T from the ultrasonic wave back flight time measured by the time difference method until the difference between the ultrasonic wave back flight time measured by the time difference method and the ultrasonic wave back flight time measured by the phase difference method is smaller than one pulse wave period T.
4. The multi-frequency array ultrasonic flow meter of claim 1, wherein the predetermined multiplication operations performed by the first multiplicative modulation module and the second multiplicative modulation module are multiplicative modulations, and wherein the amplitudes of the carrier generated by the frequency F1 excitation wave generator and the carrier generated by the frequency F2 excitation wave generator are controlled to vary linearly with the modulation signal by: and multiplying the carrier wave and the sine modulation wave by a multiplier circuit, and outputting the multiplied result as an excitation waveform of the sine wave modulation amplitude.
5. The multi-frequency array ultrasonic flow meter of claim 1, wherein the sine modulated wave is a 100Hz to 1000Hz sine wave.
6. The multi-frequency array ultrasonic flow meter of claim 1, wherein the first multi-frequency array ultrasonic transducer (100) and the second multi-frequency array ultrasonic transducer (200) are identically configured;
a first multi-frequency array ultrasonic transducer (100) comprising a cylindrical transducer housing (2);
a first main transducer (101), a second main transducer (102) and a third main transducer (103) are arranged in the transducer shell (2);
the first main transducer (101), the second main transducer (102) and the third main transducer (103) are respectively connected with one end of a transducer lead (4);
the first main transducer (101), the second main transducer (102) and the third main transducer (103) are distributed in the inner cavity of the transducer shell (2) at equal intervals along the circumferential direction;
the first main transducer (101), the second main transducer (102), and the third main transducer (103) are cylindrical in shape.
7. The multi-frequency array ultrasonic flow meter of claim 6, wherein the first primary transducer (101), the second primary transducer (102) and the third primary transducer (103) are each fixedly attached to the back side panel of the transducer housing (2) by a locating pin (2).
8. The multi-frequency array ultrasonic flow meter of claim 4, wherein the resonant frequencies of the first primary transducer (101), the second primary transducer (102), and the third primary transducer (103) are all non-uniform.
9. The multi-frequency array ultrasonic flow meter of claim 6, wherein the resonant frequencies of the first main transducer (101), the second main transducer (102), and the third main transducer (103) are each selected to be between 30kHz and 2MHz, and the difference between any two is greater than 30 kHz;
the first main transducer (101) and the first secondary transducer (201) are in a corresponding group, and the center frequencies are the same;
the second main transducer (102) and the second secondary transducer (202) are in a corresponding group, and the center frequencies are the same;
the third main transducer (103) and the third secondary transducer (203) are in a corresponding group, and the center frequencies are the same.
10. The multi-frequency array ultrasonic flow meter of claim 6, wherein the central axis of the first secondary transducer (201) is collinear with the central axis of the first primary transducer (101);
the central axis of the second secondary transducer (202) is positioned on the same straight line with the central axis of the second main transducer (102);
the central axis of the third secondary transducer (203) is aligned with the central axis of the third main transducer (103).
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