CN109506727B - Ultrasonic flow measurement method and low-power consumption ultrasonic flowmeter - Google Patents
Ultrasonic flow measurement method and low-power consumption ultrasonic flowmeter Download PDFInfo
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- G—PHYSICS
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- 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
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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
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Abstract
The invention discloses an ultrasonic flow measurement method and a low-power consumption ultrasonic flowmeter, wherein the flowmeter comprises an MCU module, and a power management module, an ultrasonic transmitting and receiving module, a temperature and pressure acquisition module, a menu function module, a communication function module and a flow output function module which are respectively connected with the MCU module; the ultrasonic transmitting and receiving module comprises two pairs of ultrasonic transducers, a first analog switch, a four-way ultrasonic driving circuit, a second analog switch, an automatic gain control circuit and a polarity adjusting circuit. The invention has the characteristics of high stability and strong robustness, has strong anti-noise interference capability, can reduce measurement errors, obviously improves the stability and the precision of the measurement of the existing ultrasonic flowmeter, and can reliably, stably and accurately measure the volume flow of the natural gas in the production process of the gas field.
Description
Technical Field
The invention belongs to the technical field of flow detection, and relates to ultrasonic flow measurement, in particular to an ultrasonic flow measurement method and a low-power-consumption ultrasonic flowmeter.
Background
At present, domestic ultrasonic flow meters are more in products and lower in cost, but the overall performance is not high, and foreign ultrasonic flow meters are better in precision, performance and the like, but are high in price, so that a large number of applications in industry are limited.
The ultrasonic flowmeter is mainly used for measuring time by adopting a time difference method, the time is mostly measured based on a threshold zero-crossing comparison or a cross-correlation algorithm, the threshold zero-crossing comparison has higher requirements on stability and consistency of an ultrasonic sensor, ultrasonic echo signals must be stable, but the performance of the ultrasonic sensor in China is not particularly good at present, the performance of the sensor in China is good, but the price is too high and is several times that of the sensor in China. The cross-correlation algorithm is adopted, the flow is in direct proportion to the forward and backward flow time difference, the forward and backward flow propagation time difference is required to be measured with high precision, if the time measurement error is 20ns, the sampling rate of the ADC is required to reach 50MHz, and the ADC with the high sampling rate is not available in the market at present, so that the error of the flow measurement by using the algorithm is large, and the precision is low.
Therefore, the ultrasonic flowmeter and the algorithm thereof which are not particularly good in sensor performance and consistency and high in stability and robustness are designed, and the ultrasonic flowmeter and the algorithm have important practical application values.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide an ultrasonic flow measurement method and a low-power consumption ultrasonic flowmeter.
The aim of the invention is realized by the following technical scheme:
the invention firstly provides an ultrasonic flow measurement method, which measures the flow of a pipeline by ultrasonic signals, and specifically comprises the following steps: the method comprises the steps of taking forward and backward ultrasonic echo signals as input, adopting a cross-correlation and three-parameter fitting sinusoidal algorithm, calculating to obtain the output of the time difference of forward and backward ultrasonic propagation, taking ultrasonic echo in the forward direction and static ultrasonic echo signals under zero flow as input, adopting the cross-correlation and three-parameter fitting sinusoidal algorithm, calculating to obtain the output of the absolute flight time in the forward direction, subtracting the forward and backward flight time difference from the absolute flight time in the forward direction to obtain the absolute flight time in the backward direction, and then adopting the forward and backward ultrasonic signal propagation time difference, the forward absolute flight time, the backward absolute flight time, pipeline parameters and two pairs of ultrasonic transducer installation angle parameters to calculate the flow velocity of fluid, thereby obtaining the volume flow of the fluid.
Further, the time difference for acquiring the forward and backward ultrasonic wave propagation is specifically:
collecting echo signals in the forward and backward directions, performing cross-correlation operation on the two collected signals, and taking the first L points, the maximum point and the last L points of the cross-correlation operation corresponding to the abscissa T to form an input signal in a three-parameter fitting sinusoidal algorithm, wherein L is a natural number; the frequency omega of the sinusoidal curve to be fitted is the excitation frequency of the ultrasonic transducer, and then the abscissa i corresponding to the maximum point of the fitted curve is obtained through a three-parameter fitting curve algorithm, wherein (T-L+i)/Fs is the calculated time difference of ultrasonic wave propagation in the forward and backward directions, and F is the calculated time difference of ultrasonic wave propagation in the forward and backward directions s Is the sampling frequency of the signal.
Further, the acquiring the forward-flow direction absolute flight time specifically includes:
firstly, storing static ultrasonic echo signals under zero flow in the forward flow direction, storing the static signals in an EEPROM (electrically erasable programmable read-Only memory), performing cross-correlation operation on the static echo signals in the forward flow direction and the collected ultrasonic echo signals in the forward flow direction, taking the first L points, the maximum point and the last L points of the cross-correlation operation corresponding to the abscissa T to form an input signal in a three-parameter fitting sinusoidal algorithm, wherein L is a natural number, the frequency omega of the sinusoidal curve to be fitted is the excitation frequency of an ultrasonic transducer, obtaining the abscissa i corresponding to the maximum point of the fitted curve through the three-parameter fitting curve algorithm, and taking (T-L+i)/Fs as the absolute flight time in the forward flow direction, wherein F is calculated s Is the sampling frequency of the signal.
Further, the method for measuring three important parameters of forward and backward time differences, forward absolute flight time and backward absolute flight time based on the ultrasonic time difference method and the flow measurement algorithm specifically comprises the following steps:
step 1): knowing the frequency of the ultrasonic transducer omega, which is the frequency of the sinusoidal curve to be fitted, the length of the acquired signal n, the sampling frequency of the signal F s 。
Step 2): collecting two paths of signals, namely x (n) and y (n), wherein x (n) is an ultrasonic echo signal in the forward flow direction, y (n) is an ultrasonic echo signal in the reverse flow direction, and n is the signal length;
step 3): zero padding before the signal x (N), zero padding after the signal y (N), the length of the sequence after zero padding is N, and the length of N is required to be 2 r R is a natural number, and the signals after zero padding are x '(n) and y' (n);
step 4): performing Fast Fourier Transform (FFT) on x '(n) and y' (n) respectively to obtain signals x (k) and y (k);
step 5): obtaining the conjugate of x (k) as x (k);
step 6): multiplying x (k) by y (k) to obtain a signal ofR xy (k)；
Step 7): for R xy (k) Performing inverse Fourier transform (IFFT) to obtain cross-correlation signal R xy (τ)；
Step 8): for R xy (tau) peak search to find the cross-correlation signal R xy The abscissa corresponding to the (τ) maximum point is denoted T.
Step 9): taking the cross-correlation signal R xy Maximum point (T, R) xy (T)) the ordinate of the first L points, the maximum point and the last L points constitutes the signal y,y is the discrete sequence to be fitted;
step 10): a matrix M is constructed which is then used to construct,
step 11): calculation of
Step 12): the fitted sinusoidal expression is:
wherein,
step 13): let ωi + θ=0, the abscissa corresponding to the maximum point of the fitted sinusoidal curve is i,
step 14): the forward and reverse flow time difference is deltat, deltat= (T-L+i)/Fs;
step 15): collecting two paths of signals, namely x (n) and y (n), wherein x (n) is an ultrasonic echo signal in the forward flow direction, y (n) is a stored static ultrasonic echo signal in the forward flow direction under zero flow, and n is the signal length;
step 16): repeating the steps 3) to 13), wherein the propagation time in the forward direction is t up ，t up ＝(T-L+i)/Fs；
Step 17): counter-current travel time t dn ，t dn ＝t up -Δt；
Step 18): according to the flow calculation formulaAnd obtaining the flow to be finally measured, wherein D is the diameter of the pipeline, and theta is the included angle between the connecting line of the ultrasonic transducer and the axis of the measuring pipeline.
The invention also provides a low-power consumption ultrasonic flowmeter based on the ultrasonic flow measurement method: the system comprises an MCU module, a power management module, an ultrasonic transmitting and receiving module, a temperature and pressure acquisition module, a menu function module, a communication function module and a flow output function module, wherein the power management module, the ultrasonic transmitting and receiving module, the temperature and pressure acquisition module, the menu function module, the communication function module and the flow output function module are respectively connected with the MCU module; the ultrasonic transmitting and receiving module comprises two pairs of ultrasonic transducers, a first analog switch, a four-way ultrasonic driving circuit, a second analog switch, an automatic gain control circuit and a polarity adjusting circuit; wherein, two pairs of ultrasonic transducers are arranged on the measuring pipeline in an x shape; the first analog switch realizes a channel for transmitting a four-way selection excitation signal to the ultrasonic transducer, and the four-way ultrasonic driving circuit increases the voltage of the excitation signal to drive the ultrasonic transducer by the excitation signal, so that the ultrasonic transducer resonates and generates an ultrasonic emission signal; the second analog switch is a four-out gating ultrasonic transducer receiving signal; the automatic gain control circuit amplifies echo signals received by the ultrasonic transducer; the polarity adjusting circuit adjusts the echo signals and is used for the ADC inside the MCU module to collect.
Further, the included angle between the connecting line of each pair of ultrasonic transducers and the axis of the measuring pipeline is 45 degrees.
Furthermore, the MCU module is an STM32L476RG low-power consumption chip; the automatic gain control circuit amplifies echo signals received by the ultrasonic transducer, the amplitude is controlled to be +/-3.3V, and the amplification factor is automatically adjusted according to the current signal amplitude; the polarity adjusting circuit adjusts the echo signal to be between 0 and 2.5V so as to collect ADC in STM32L476RG chip.
Further, the temperature and pressure acquisition module comprises a temperature sensor, a temperature amplification circuit, a pressure sensor, a pressure amplification circuit and a 24-bit Sigma-Delta ADC; the temperature amplifying circuit amplifies a signal of the temperature sensor; the pressure amplifying circuit amplifies a signal of the pressure sensor; the 24-bit Sigma-Delta ADC is used for collecting temperature and pressure signals, and the collected temperature and pressure signals are used for temperature and pressure measurement and also used for calculating the working condition flow to standard condition flow.
Further, the menu function module comprises keys and liquid crystal, wherein the keys are used for checking and setting parameters, the liquid crystal is used for displaying the content of key operation, and the keys and the liquid crystal are combined to realize menu functions and realize man-machine interaction; the communication function module comprises RS485 communication and NB-IOT wireless communication, wherein the RS485 communication adopts MODBUS communication protocol; the wireless communication adopts an NB-IOT module, a built-in SIM card, and the wireless communication has a networking function, so that the meter is networked, and remote meter reading is realized.
Further, the flow output functional module comprises pulse output and constant current source output, wherein the pulse output is used for metering, and the constant current source output is used for transmitting and outputting the flow in a standard current signal mode.
Compared with the prior art, the invention has the following beneficial effects:
the invention can accurately measure the time difference of ultrasonic wave propagation in the forward and backward directions and the absolute flight time in the forward and backward directions, has the characteristics of high stability and strong robustness, is little affected by external interference, and can obviously improve the stability and the accuracy of the measurement of the traditional ultrasonic flowmeter.
Furthermore, the NB-IOT wireless communication module is added in the low-power consumption ultrasonic flowmeter, and the SIM card is arranged in the low-power consumption ultrasonic flowmeter, so that the low-power consumption ultrasonic flowmeter has a networking function and can realize remote meter reading.
Drawings
Fig. 1 is a block diagram of the structure of the present invention.
Wherein: the intelligent control system comprises a power management module 1, an ultrasonic wave transmitting and receiving module 2, a temperature and pressure acquisition module 3, an MCU4, a menu function module 5, a communication function module 6 and a flow output function module 7.
Detailed Description
The invention firstly provides an ultrasonic flow measurement method which comprises the following steps: the method uses the arithmetic processing capability of the MCU module, takes ultrasonic signals as objects to measure flow, and mainly obtains stable and high-precision forward and backward time differences and absolute flight time in forward and backward directions, and the algorithm specifically comprises the following steps of: the method comprises the steps of taking forward and backward ultrasonic echo signals as input, adopting a cross-correlation and three-parameter fitting sinusoidal algorithm, calculating to obtain the output of the time difference of forward and backward ultrasonic propagation, taking ultrasonic echo in the forward direction and static ultrasonic echo signals under zero flow as input, adopting the cross-correlation and three-parameter fitting sinusoidal algorithm, calculating to obtain the output of the absolute flight time in the forward direction, subtracting the forward and backward flight time difference from the absolute flight time in the forward direction to obtain the absolute flight time in the backward direction, and then adopting the forward and backward ultrasonic signal propagation time difference, the forward absolute flight time, the backward absolute flight time, pipeline parameters and two pairs of ultrasonic transducer installation angle parameters to calculate the flow velocity of fluid, thereby obtaining the volume flow of the fluid.
In the invention, the time difference for acquiring the ultrasonic wave propagation in the forward and backward directions is specifically as follows:
the method comprises the steps of acquiring echo signals in the forward and backward directions, performing cross-correlation operation on the acquired two paths of signals, taking the first L points, the maximum points and the last L points of the maximum points corresponding to the abscissa T after the cross-correlation operation to form an input signal in a three-parameter fitting sinusoidal algorithm, wherein L is a natural number, the frequency omega of a sinusoidal curve to be fitted is the excitation frequency of an ultrasonic transducer, and then obtaining the abscissa i corresponding to the maximum points of the fitted curve through a three-parameter fitting curve algorithm, wherein (T-L+i)/Fs is the calculated time difference of ultrasonic wave propagation in the forward and backward directions.
In the invention, the acquisition of the forward-flow direction absolute flight time is specifically as follows:
firstly, storing static ultrasonic echo signals under zero flow in the forward flow direction, storing the static signals in an EEPROM (electrically erasable programmable read-Only memory), performing cross-correlation operation on the static echo signals in the forward flow direction and the collected ultrasonic echo signals in the forward flow direction, taking the first L points, the maximum point and the last L points of the cross-correlation operation, which correspond to the abscissa T, to form an input signal in a three-parameter fitting sinusoidal algorithm, wherein L is a natural number, the frequency omega of the sinusoidal curve to be fitted is the excitation frequency of an ultrasonic transducer, and then obtaining the abscissa i corresponding to the maximum point of the fitted curve through the three-parameter fitting curve algorithm, and (T-L+i)/Fs is absolute flight time in the forward flow direction, which is obtained through calculation.
Further, based on the forward and backward time difference of the ultrasonic time difference method, the measurement of three important parameters of the forward direction absolute flight time and the backward direction absolute flight time and the flow measurement algorithm specifically comprises the following steps:
step 1): knowing the frequency of the ultrasonic transducer omega, which is the frequency of the sinusoidal curve to be fitted, the length of the acquired signal n, the sampling frequency of the signal F s 。
Step 2): collecting two paths of signals, namely x (n) and y (n), wherein x (n) is an ultrasonic echo signal in the forward flow direction, y (n) is an ultrasonic echo signal in the reverse flow direction, and n is the signal length;
step 3): zero padding before the signal x (N), zero padding after the signal y (N), the length of the sequence after zero padding is N, and the length of N is required to be 2 r R is a natural number, and the signals after zero padding are x '(n) and y' (n);
step 4): performing Fast Fourier Transform (FFT) on x '(n) and y' (n) respectively to obtain signals x (k) and y (k);
step 5): obtaining the conjugate of x (k) as x (k);
step 6): multiplying x (k) by y (k) to obtain a signal R xy (k)；
Step 7): for R xy (k) Performing inverse Fourier transform (IFFT) to obtain cross-correlation signal R xy (τ)；
Step 8): for R xy (tau) peak search to find the cross-correlation signal R xy The abscissa corresponding to the (τ) maximum point is denoted T.
Step 9): taking the cross-correlation signal R xy Maximum point (T, R) xy (T)) the ordinate of the first L points, the maximum point and the last L points constitutes the signal y,y is the discrete sequence to be fitted;
step 10): a matrix M is constructed which is then used to construct,
step 11): calculation of
Step 12): the fitted sinusoidal expression is:
wherein,
step 13): let ωi + θ=0, the abscissa corresponding to the maximum point of the fitted sinusoidal curve is i,
step 14): the forward and reverse flow time difference is deltat, deltat= (T-L+i)/Fs;
step 15): collecting two paths of signals, namely x (n) and y (n), wherein x (n) is an ultrasonic echo signal in the forward flow direction, y (n) is a stored static ultrasonic echo signal in the forward flow direction under zero flow, and n is the signal length;
step 16): repeating the steps 3) to 13), wherein the propagation time in the forward direction is t up ，t up ＝(T-L+i)/Fs；
Step 17): counter-current travel time t dn ，t dn ＝t up -Δt；
Step 18): according to the flow calculation formulaAnd obtaining the flow to be finally measured, wherein D is the diameter of the pipeline, and theta is the included angle between the connecting line of the ultrasonic transducer and the axis of the measuring pipeline.
The time measurement algorithm in the invention is suitable for any application field with two paths of input signals for measuring time.
Based on the above-mentioned ultrasonic flow measurement method, the invention also provides a low-power consumption ultrasonic flow meter, and the low-power consumption ultrasonic flow meter is described in further detail below with reference to the accompanying drawings:
the low-power consumption ultrasonic flowmeter of the invention is shown in figure 1, and comprises a power management module 1, an ultrasonic transmitting and receiving module 2, a temperature and pressure acquisition module 3, an MCU4, a menu function module 5, a communication function module 6 and a flow output function module 7.
The power management module realizes low-power consumption measurement of the ultrasonic flowmeter, the MCU adopts an STM32L476RG low-power consumption chip, a plurality of low-power consumption modes are arranged in the chip, the CPU can work in different low-power consumption modes according to tasks to be processed, meanwhile, the power supply of an external circuit module is controlled through an I/O pin of the CPU, when the CPU works, the module is powered, and when the CPU does not work, the module is powered off. The power consumption of the whole ultrasonic flowmeter is reduced through power management, and the service life of the battery is prolonged.
The ultrasonic transmitting and receiving module is connected with the MCU, the ultrasonic excitation signal is output through the MCU, the analog switch 1 realizes that the 4-to-1 control gating excitation signal is transmitted to which ultrasonic transducer, and the 4-way ultrasonic driving circuit is used for increasing the voltage of the excitation signal, so that the energy of the excitation signal can drive the ultrasonic transducer, thereby enabling the ultrasonic transducer to resonate and generating an ultrasonic transmitting signal; the control of the transmission and reception of the ultrasonic wave is that the ultrasonic transducer 1 transmits a signal, the ultrasonic transducer 3 receives an echo signal, the signal is a one-channel forward direction echo signal, the ultrasonic transducer 3 transmits a signal, the ultrasonic transducer 1 receives an echo signal, the signal is a one-channel backward direction echo signal, the ultrasonic transducer 2 transmits a signal, the ultrasonic transducer 4 receives an echo signal, the signal is a two-channel forward direction echo signal, the ultrasonic transducer 4 transmits a signal, and the ultrasonic transducer 2 receives an echo signal, the signal is a two-channel backward direction echo signal. The analog switch 2 realizes the 4-to-1 control and gates which ultrasonic transducer receives the signal, the forward and backward echo signals of the first and second channels are controlled to be within +/-3.3V by an automatic gain control circuit, and then the echo signals are adjusted to be between 0 and 2.5V by a polarity adjustment circuit.
The method comprises the steps that a signal output by a polarity adjustment module is connected to an MCU, an ADC (analog-digital converter) in the MCU chip is used for collecting echo signals, the collected forward and backward ultrasonic echo signals are used as input, a cross-correlation and three-parameter fitting sinusoidal algorithm is adopted, the calculated output is a time difference of forward and backward ultrasonic propagation, an ultrasonic echo in the forward direction and a static ultrasonic echo signal under zero flow are used as input, the cross-correlation and three-parameter fitting sinusoidal algorithm is adopted, the calculated output is an absolute flight time in the forward direction, the forward and backward flight time difference is subtracted from the absolute flight time in the forward direction to obtain the absolute flight time in the backward direction, and then the flow velocity of fluid is calculated by adopting the forward and backward ultrasonic signal propagation time difference, the forward direction absolute flight time, the backward direction absolute flight time, pipeline parameters and two pairs of ultrasonic transducer installation angle parameters, so that the volume flow of the fluid is obtained.
The temperature sensor is connected with the temperature amplifying circuit, the pressure sensor is connected with the pressure amplifying circuit, the temperature amplifying circuit and the pressure amplifying circuit are connected with the 24-bit Sigma-Delta ADC to collect temperature and pressure, the 24-bit Sigma-Delta ADC can collect temperature and pressure signals with high precision, the collected temperature and pressure signals are used for temperature and pressure measurement, and the collected temperature and pressure signals are also used for calculating the working condition flow to standard condition flow.
The menu function module comprises keys and liquid crystal, the keys are used for checking and setting parameters, the liquid crystal is used for displaying the key operation content, and the keys and the liquid crystal are combined to realize menu functions and human-computer interaction.
The communication function module comprises RS485 communication and NB-IOT wireless communication, wherein the RS485 communication adopts MODBUS communication protocol; the wireless communication adopts an NB-IOT module, a built-in SIM card, and the wireless communication has a networking function, so that the meter is networked, and remote meter reading is realized.
The flow output functional module comprises pulse output and constant current source output, wherein the pulse output is used for metering, and the constant current source output is used for transmitting and outputting the flow in a standard current signal mode.
The ultrasonic flow measurement method and the low-power consumption ultrasonic flow meter have the characteristics of high stability and strong robustness, have strong noise interference resistance, can reduce measurement errors, obviously improve the stability and the accuracy of the measurement of the existing ultrasonic flow meter, and can reliably, stably and accurately measure the volume flow of the natural gas in the production process of a gas field.
Claims (9)
1. An ultrasonic flow measurement method for measuring the flow of a pipeline by ultrasonic signals is characterized in that: the method comprises the steps of taking forward and backward ultrasonic echo signals as input, adopting a cross-correlation and three-parameter fitting sinusoidal algorithm, calculating to obtain the output of time difference of forward and backward ultrasonic propagation, taking ultrasonic echo in the forward direction and static ultrasonic echo signals under zero flow as input, adopting the cross-correlation and three-parameter fitting sinusoidal algorithm, calculating to obtain the output of absolute flight time in the forward direction, subtracting the forward and backward flight time difference from the absolute flight time in the forward direction to obtain the absolute flight time in the backward direction, and then adopting the forward and backward ultrasonic signal propagation time difference, the forward absolute flight time, the backward absolute flight time in the backward direction, pipeline parameters and two pairs of ultrasonic transducer installation angle parameters to calculate the flow velocity of fluid, so as to obtain the volume flow of the fluid;
the method comprises the following steps of measuring three important parameters of forward and backward time differences, forward absolute flight time and backward absolute flight time based on an ultrasonic time difference method and a flow measurement algorithm, wherein the steps are as follows:
step 1): knowing the frequency of the ultrasonic transducer omega, which is the frequency of the sinusoidal curve to be fitted, the length of the acquired signal n, the sampling frequency of the signal F s ；
Step 2): collecting two paths of signals, namely x (n) and y (n), wherein x (n) is an ultrasonic echo signal in the forward flow direction, y (n) is an ultrasonic echo signal in the reverse flow direction, and n is the signal length;
step 3): zero padding before the signal x (N), zero padding after the signal y (N), the length of the sequence after zero padding is N, and the length of N is required to be 2 r R is a natural number, and the signals after zero padding are x '(n) and y' (n);
step 4): performing Fast Fourier Transform (FFT) on x '(n) and y' (n) respectively to obtain signals x (k) and y (k);
step 5): obtaining the conjugate of x (k) as x (k);
step 6): multiplying x (k) by y (k) to obtain a signal R xy (k)；
Step 7): for R xy (k) Performing inverse Fourier transform (IFFT) to obtain cross-correlation signal R xy (τ)；
Step 8): for R xy (tau) peak search to find the cross-correlation signal R xy The abscissa corresponding to the maximum point (τ) is denoted T;
step 9): taking the cross-correlation signal R xy Maximum point (T, R) xy (T)) the ordinate of the first L points, the maximum point and the last L points constitutes the signal y,y is the discrete sequence to be fitted;
step 10): a matrix M is constructed which is then used to construct,
step 11): calculation of
Step 12): the fitted sinusoidal expression is:
wherein,
step 13): let ωi + θ=0, the abscissa corresponding to the maximum point of the fitted sinusoidal curve is i,
step 14): the forward and reverse flow time difference is deltat, deltat= (T-L+i)/Fs;
step 15): collecting two paths of signals, namely x (n) and y (n), wherein x (n) is an ultrasonic echo signal in the forward flow direction, y (n) is a stored static ultrasonic echo signal in the forward flow direction under zero flow, and n is the signal length;
step 16): repeating the steps 3) to 13), wherein the propagation time in the forward direction is t up ，t up ＝(T-L+i)/Fs；
Step 17): counter-current travel time t dn ，t dn ＝t up -Δt；
Step 18): according to the flow calculation formulaAnd obtaining the flow to be finally measured, wherein D is the diameter of the pipeline, and theta is the included angle between the connecting line of the ultrasonic transducer and the axis of the measuring pipeline.
2. The ultrasonic flow measurement method according to claim 1, wherein the time difference for acquiring the forward and backward ultrasonic propagation is specifically:
collecting echo signals in the forward and backward directions, performing cross-correlation operation on the two collected signals, and taking the first L points, the maximum point and the last L points of the cross-correlation operation corresponding to the abscissa T to form an input signal in a three-parameter fitting sinusoidal algorithm, wherein L is a natural number; the frequency omega of the sinusoidal curve to be fitted is the excitation frequency of the ultrasonic transducer, and then the abscissa i corresponding to the maximum point of the fitted curve is obtained through a three-parameter fitting curve algorithm, wherein (T-L+i)/Fs is the calculated time difference of ultrasonic wave propagation in the forward and backward directions, and F is the calculated time difference of ultrasonic wave propagation in the forward and backward directions s Is the sampling frequency of the signal.
3. The ultrasonic flow measurement method according to claim 1, wherein the acquiring of the absolute time of flight in the forward flow direction is specifically:
firstly, storing static ultrasonic echo signals under zero flow in the forward flow direction, storing the static signals in an EEPROM (electrically erasable programmable read-Only memory), performing cross-correlation operation on the static echo signals in the forward flow direction and the collected ultrasonic echo signals in the forward flow direction, taking the first L points, the maximum point and the last L points of the cross-correlation operation corresponding to the abscissa T to form an input signal in a three-parameter fitting sinusoidal algorithm, wherein L is a natural number, the frequency omega of the sinusoidal curve to be fitted is the excitation frequency of an ultrasonic transducer, obtaining the abscissa i corresponding to the maximum point of the fitted curve through the three-parameter fitting curve algorithm, and taking (T-L+i)/Fs as the absolute flight time in the forward flow direction, wherein F is calculated s Is the sampling frequency of the signal.
4. A low-power consumption ultrasonic flowmeter based on the ultrasonic flow measurement method according to any one of claims 1-3, characterized by comprising an MCU module (4), and a power management module (1), an ultrasonic transmitting and receiving module (2), a temperature and pressure acquisition module (3), a menu function module (5), a communication function module (6) and a flow output function module (7) which are respectively connected with the MCU module (4);
the ultrasonic transmitting and receiving module (2) comprises two pairs of ultrasonic transducers, a first analog switch, a four-way ultrasonic driving circuit, a second analog switch, an automatic gain control circuit and a polarity adjustment circuit; wherein, two pairs of ultrasonic transducers are arranged on the measuring pipeline in an x shape; the first analog switch realizes a channel for transmitting a four-way selection excitation signal to the ultrasonic transducer, and the four-way ultrasonic driving circuit increases the voltage of the excitation signal to drive the ultrasonic transducer by the excitation signal, so that the ultrasonic transducer resonates and generates an ultrasonic emission signal; the second analog switch is a four-out gating ultrasonic transducer receiving signal; the automatic gain control circuit amplifies echo signals received by the ultrasonic transducer; the polarity adjusting circuit adjusts the echo signals and is used for the acquisition of an internal ADC of the MCU module (4).
5. The low power ultrasonic flow meter of claim 4, wherein the line connecting each pair of ultrasonic transducers is at an angle of 45 ° to the axis of the measurement conduit.
6. The low-power consumption ultrasonic flowmeter of claim 4, wherein the MCU module (4) is an STM32L476RG low-power consumption chip; the automatic gain control circuit amplifies echo signals received by the ultrasonic transducer, the amplitude is controlled to be +/-3.3V, and the amplification factor is automatically adjusted according to the current signal amplitude; the polarity adjusting circuit adjusts the echo signal to be between 0 and 2.5V so as to collect ADC in STM32L476RG chip.
7. The low power consumption ultrasonic flow meter according to claim 4, wherein the temperature and pressure acquisition module (3) comprises a temperature sensor, a temperature amplification circuit, a pressure sensor, a pressure amplification circuit and a 24 bit Sigma-Delta ADC; the temperature amplifying circuit amplifies a signal of the temperature sensor; the pressure amplifying circuit amplifies a signal of the pressure sensor; the 24-bit Sigma-Delta ADC is used for collecting temperature and pressure signals, and the collected temperature and pressure signals are used for temperature and pressure measurement and also used for calculating the working condition flow to standard condition flow.
8. The low-power consumption ultrasonic flowmeter according to claim 4, wherein said menu function module (5) comprises keys and liquid crystal, wherein the keys view and set parameters, the liquid crystal displays the content of key operation, and the combination of keys and liquid crystal realizes menu functions to realize man-machine interaction; the communication function module (6) comprises RS485 communication and NB-IOT wireless communication, and the RS485 communication adopts a MODBUS communication protocol; the wireless communication adopts an NB-IOT module, a built-in SIM card, and the wireless communication has a networking function, so that the meter is networked, and remote meter reading is realized.
9. The low power consumption ultrasonic flow meter according to claim 4, wherein the flow output functional module (7) comprises a pulse output for metering and a constant current source output for transmitting the flow in the form of a standard current signal.
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| FR3098599B1 (en) * | 2019-07-12 | 2021-08-06 | Sagemcom Energy & Telecom Sas | Method of measuring the speed of a fluid |
| CN110631958B (en) * | 2019-09-09 | 2024-04-16 | 西安安森智能仪器股份有限公司 | Gas-liquid two-phase flow parameter measurement method |
| CN110646042A (en) * | 2019-10-16 | 2020-01-03 | 上海交通大学 | Cross-correlation interpolation method for calculating flight time difference of low-power-consumption ultrasonic flowmeter |
| CN111220222B (en) * | 2020-02-27 | 2020-11-24 | 成都千嘉科技有限公司 | Measuring algorithm for flow of ultrasonic gas meter |
| CN112362119B (en) * | 2020-11-02 | 2023-07-14 | 深圳市汇顶科技股份有限公司 | Ultrasonic flowmeter |
| CN113588022A (en) * | 2021-07-22 | 2021-11-02 | 山东力创科技股份有限公司 | Household three-meter low-power-consumption ultrasonic metering chip and low-power-consumption control method |
| CN114152298B (en) * | 2021-11-26 | 2024-05-17 | 浙江威星智能仪表股份有限公司 | Method for ultrasonic metering flight time sampling |
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