CN109506727A - A kind of ultrasonic flow measuring method and low-consumption ultrasonic flow measurement meter - Google Patents
A kind of ultrasonic flow measuring method and low-consumption ultrasonic flow measurement meter Download PDFInfo
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Classifications
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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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- 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 kind of ultrasonic flow measuring method and low-consumption ultrasonic flow measurement meter, which includes MCU module and the power management module being separately connected with MCU module, ultrasonic wave transmitting and receiving module, temperature and pressure acquisition module, menu function module, communication function module and flow output function module；The ultrasonic wave transmitting and receiving module includes two pairs of ultrasonic transducers, the first analog switch, four road ultrasonic drive circuits, the second analog switch, automatic gain control circuit and polarity adjustment circuit.The present invention has the characteristics that stability height and strong robustness, anti-noise jamming ability is strong, can reduce measurement error, it will be apparent that improves the stability and precision of existing ultrasonic flow rate measurement amount, in the production process of gas field, can it is reliable, stablize, accurately natural gas volume flow measured.
Description
Technical field
The invention belongs to flow detection technical fields, are related to measuring ultrasonic wave flow, especially a kind of ultrasonic wave flow measuring
Amount method and low-consumption ultrasonic flow measurement meter.
Background technique
Currently, domestic ultrasonic flowmeter product is more, cost is relatively low, but the ultrasound that overall performance is not high, external
Wave flowmeter precision, in terms of it is relatively good, but it is expensive, limit its a large amount of application in the industry.
The measurement of ultrasonic flowmeter mostly uses time difference method, and the measurement of time is mostly based on threshold value Zero-cross comparator or mutually
Algorithm is closed, threshold value Zero-cross comparator is relatively high for the stability and coherence request of ultrasonic sensor, ultrasonic echo signal
Must stablize, but the performance of ultrasonic sensor domestic at present be not it is especially good, external sensor performance is good, still, valence
Lattice are prohibitively expensive, are several times of state's inner sensor.High-speed ADC, flow and concurrent-countercurrent time difference are needed using cross correlation algorithm
It is directly proportional, to obtain high-precision flow measurement, it is necessary to high-acruracy survey is carried out to concurrent-countercurrent propagation time difference, if the time
Measurement error is 20ns, and the sampling rate of ADC must reach 50MHz, currently on the market without the ADC of so high sampling rate,
So causing the error for carrying out flow measurement using this algorithm can be very big, precision be low.
Therefore, design it is a kind of for sensor performance and consistency be not that especially good and stability is high and strong robustness it is super
Acoustic wave flow meter and its algorithm have important practical application value.
Summary of the invention
It is an object of the invention to overcome the above-mentioned prior art, a kind of ultrasonic flow measuring method and low is provided
Power consumption ultrasonic flowmeter.
The purpose of the present invention is achieved through the following technical solutions:
Present invention firstly provides a kind of ultrasonic flow measuring methods, are measured with ultrasonic signal to pipeline flow,
Specifically: using suitable, counter current ultrasonic wave echo-signal as input, using cross-correlation and three parameter fitting sine curve algorithms, fortune
Obtained output is the time difference of suitable countercurrent direction ultrasonic wave propagation, under the ultrasonic echo and zero delivery of downbeam
Static ultrasound wave echo-signal as input, using cross-correlation and three parameter fitting sine curve algorithms, operation is obtained defeated
Out it is the absolute time of flight of downbeam, suitable, adverse current differential time of flight is subtracted with the absolute time of flight of downbeam and is obtained
The absolute time of flight of countercurrent direction, then using suitable, counter current ultrasonic wave signal propagation time is poor, downbeam absolute flight when
Between, countercurrent direction absolute time of flight and pipe parameter and two pairs of ultrasonic transducer setting angle parameters calculate fluid
Flow velocity, and then obtain the volume flow of fluid.
Further, the above time difference for obtaining suitable, the countercurrent direction ultrasonic wave and propagating specifically:
Suitable, countercurrent direction echo-signal is acquired, computing cross-correlation is carried out to collected two paths of signals, cross-correlation is taken to transport
Preceding L point, maximum of points and the rear L point that maximum of points corresponds to abscissa T after calculation constitute three parameter fitting sine curves and calculate
Input signal in method, wherein L is natural number；The sinusoidal frequencies omega to be fitted is the excitation frequency of ultrasonic transducer
Rate, the then maximum of points corresponding abscissa i of the curve after three parameter curve fit algorithms are fitted, (T-L+i)/
Fs is the time difference that suitable, the countercurrent direction ultrasonic wave being calculated are propagated, wherein FsFor the sample frequency of signal.
Further, the above acquisition downbeam absolute time of flight specifically:
The static ultrasound wave echo-signal under downbeam zero delivery is stored first, and every flowmeter need to only store primary quiet
State signal, is stored in EEPROM, then by downbeam static state echo-signal and collected downbeam ultrasonic echo
Signal carries out computing cross-correlation, and maximum of points after computing cross-correlation is taken to correspond to preceding L point, maximum of points, the Yi Jihou of abscissa T
L point constitutes the input signal in three parameter fitting sine curve algorithms, and L is natural number, the sinusoidal frequency to be fitted
ω is the driving frequency of ultrasonic transducer, then the maximum value of the curve after three parameter curve fit algorithms are fitted
The corresponding abscissa i of point, (T-L+i)/Fs is the downbeam absolute time of flight being calculated, wherein FsFor the sampling of signal
Frequency.
Further, above suitable, the adverse current time difference based on ultrasonic wave time difference method, downbeam absolute time of flight, and
The measurement of three important parameters of countercurrent direction absolute time of flight and flow measurement algorithm steps are specific as follows:
Step 1): the frequency of known ultrasonic transducer is ω, which is the sinusoidal frequency to be fitted, acquisition
Signal length be n, the sample frequency of signal is Fs。
Step 2): acquisition two paths of signals, respectively x (n) and y (n), x (n) are the ultrasonic echo signal of downbeam, y
It (n) is the ultrasonic echo signal of countercurrent direction, n is signal length；
Step 3): the zero padding before signal x (n), in the zero padding of the back signal y (n), the sequence length after zero padding is N, N's
Length need to be 2r, r is natural number, and the signal after zero padding is x ' (n) and y ' (n)；
Step 4): Fast Fourier Transform (FFT) (FFT) is carried out to x ' (n) and y ' (n) respectively, obtains signal x (k) and y (k)；
Step 5): the conjugation for seeking x (k) is x* (k)；
Step 6): x* (k) is multiplied with y (k), and obtained signal is Rxy(k)；
Step 7): to Rxy(k) inverse Fourier transform (IFFT) is carried out, obtains cross-correlated signal Rxy(τ)；
Step 8): to Rxy(τ) carries out peak value searching, finds cross-correlated signal RxyThe corresponding abscissa of (τ) maximum of points,
It is denoted as T.
Step 9): cross-correlated signal R is takenxy(τ) maximum of points (T, Rxy(T)) L point, maximum of points and rear L are a before
The ordinate of point constitutes signal y,Y is the discrete series to be fitted；
Step 10): structural matrix M,
Step 11): it calculates
Step 12): the sine curve expression formula of fitting are as follows:
Wherein,
Step 13): enabling θ=0 ω i+, and the corresponding abscissa of sinusoidal maximum of points being fitted is i,
Step 14): suitable, the adverse current time difference is Δ t, Δ t=(T-L+i)/Fs；
Step 15): acquisition two paths of signals, respectively x (n) and y (n), x (n) are the ultrasonic echo signal of downbeam,
Y (n) is the static ultrasound wave echo-signal under the downbeam zero delivery of storage, and n is signal length；
Step 16): it repeats step 3) and arrives step 13), the propagation time of downbeam is tup, tup=(T-L+i)/Fs；
Step 17): the adverse current reversed propagation time is tdn, tdn=tup-Δt；
Step 18): according to flow rate calculation formulaObtain the flow finally to be measured, wherein D is
Pipe diameter, θ are the line of ultrasonic transducer and the angle of measurement conduit axis.
The present invention also proposes a kind of based on the low-consumption ultrasonic flow measurement of above-mentioned ultrasonic flow measuring method: including
MCU module and the power management module being separately connected with MCU module, ultrasonic wave transmitting and receiving module, temperature and pressure acquisition
Module, menu function module, communication function module and flow output function module；The ultrasonic wave transmitting and receiving module includes two
To ultrasonic transducer, the first analog switch, four road ultrasonic drive circuits, the second analog switch, automatic gain control circuit
And polarity adjustment circuit；Wherein, two pairs of ultrasonic transducers are mounted on measurement pipeline in x type；First analog switch realizes four
A gating pumping signal is selected to be sent to the channel of ultrasonic transducer, four road ultrasonic drive circuits add the voltage of pumping signal
Greatly, so that pumping signal is driven ultrasonic transducer, so that ultrasonic transducer be made to resonate, generate ultrasonic wave and emit signal；Second
Analog switch be four select a gating ultrasonic transducer receive signal；Automatic gain control circuit receives ultrasonic transducer
Echo-signal amplify；Polarity adjustment circuit adjustment echo-signal is simultaneously acquired for MCU module inside ADC.
Further, the angle of the line of above each pair of ultrasonic transducer and measurement conduit axis is 45o.
Further, above-mentioned MCU module is STM32L476RG low-power chip；The automatic gain control circuit will be ultrasonic
The echo-signal that wave transducer receives amplifies, and amplitude is controlled in ± 3.3V, and amplification factor is according to current signal magnitude
Adjust automatically；The polarity adjustment circuit is by echo-signal adjustment between 0~2.5V, in STM32L476RG chip
Portion ADC is acquired.
Further, above-mentioned temperature and pressure acquisition module include temperature sensor, temperature amplifying circuit, pressure sensor,
Pressure amplifying circuit and 24 Sigma-Delta ADC；Wherein, the temperature amplifying circuit carries out the signal of temperature sensor
Amplification；Pressure amplifying circuit amplifies the signal of pressure sensor；24 Sigma-Delta ADC are to temperature and pressure
Force signal is acquired, and collected temperature and pressure signal is used for temperature and pressure measurement, operating condition flow is also used for and turns mark
Condition flow rate calculation.
Further, above-mentioned menu function module includes key and liquid crystal, and parameter, liquid crystal display key are checked and be arranged to key
The content of operation, key and liquid crystal are implemented in combination with menu function, realize human-computer interaction；The communication function module includes RS485
Communication and NB-IOT wireless communication, RS485 communication use MODBUS communication protocol；Wireless communication uses NB-IOT module, built-in
SIM card has network savvy, instrument is made to network, and realizes remote meter reading.
Further, above-mentioned flow output function module includes pulse output and constant-current source output, and pulse is exported for measuring,
Constant-current source output is that flow is carried out to pick-up output in the form of the current signal of standard.
Compared with prior art, the invention has the following advantages:
The present invention can accurately measure the time difference that suitable, countercurrent direction ultrasonic wave is propagated and downbeam and adverse current side
To absolute time of flight, and have the characteristics that stability height and strong robustness, influenced by external interference it is small, can be apparent
Improve the stability and precision of existing ultrasonic flow rate measurement amount.
Further, NB-IOT wireless communication module, built-in SIM be joined in low-consumption ultrasonic flow measurement meter of the invention
Card has network savvy, remote meter reading may be implemented.
Detailed description of the invention
Fig. 1 is structural block diagram of the invention.
Wherein: 1 is power management module, and 2 be ultrasonic wave sending/receiving module, and 3 be temperature and pressure acquisition module, and 4 are
MCU, 5 be menu function module, and 6 be communication function module, and 7 be flow output function module.
Specific embodiment
Present invention firstly provides a kind of ultrasonic flow measuring methods: this method is the calculation process energy with MCU module
Power measures flow as object using ultrasonic signal, and the measurement of ultrasonic flow is most important to be able to obtain surely
The absolute time of flight of suitable, adverse current time difference fixed and with high accuracy and downbeam and countercurrent direction, to obtain three times
Parameter, the algorithm specifically: sinusoidal using cross-correlation and three parameter fittings using suitable, counter current ultrasonic wave echo-signal as input
Curved line arithmetic, the output that operation obtains is the time difference of suitable countercurrent direction ultrasonic wave propagation, with the ultrasonic echo of downbeam
With the static ultrasound wave echo-signal under zero delivery as input, using cross-correlation and three parameter fitting sine curve algorithms, fortune
Obtained output is the absolute time of flight of downbeam, subtracts suitable, adverse current with the absolute time of flight of downbeam and flies
Time difference obtains the absolute time of flight of countercurrent direction, then using suitable, counter current ultrasonic wave signal propagation time is poor, downbeam
Absolute time of flight, countercurrent direction absolute time of flight and pipe parameter and two pairs of ultrasonic transducer setting angle parameters
The flow velocity of fluid is calculated, and then obtains the volume flow of fluid.
In the present invention, the time difference that suitable, countercurrent direction ultrasonic wave is propagated is obtained specifically:
By acquiring suitable, countercurrent direction echo-signal, computing cross-correlation is carried out to collected two paths of signals, is taken mutually
It is sinusoidal bent that preceding L point, maximum of points and the rear L point that maximum of points corresponds to abscissa T after the operation of pass constitute three parameter fittings
Input signal in line algorithm, L are natural numbers, and the sinusoidal frequencies omega to be fitted is the excitation frequency of ultrasonic transducer
Rate, the then maximum of points corresponding abscissa i of the curve after three parameter curve fit algorithms are fitted, (T-L+i)/
Fs is the time difference that suitable, the countercurrent direction ultrasonic wave being calculated are propagated.
In the present invention, downbeam absolute time of flight is obtained specifically:
The static ultrasound wave echo-signal under downbeam zero delivery is stored first, and every flowmeter need to only store primary quiet
State signal, is stored in EEPROM, then by downbeam static state echo-signal and collected downbeam ultrasonic echo
Signal carries out computing cross-correlation, and maximum of points after computing cross-correlation is taken to correspond to preceding L point, maximum of points, the Yi Jihou of abscissa T
L point constitutes the input signal in three parameter fitting sine curve algorithms, and L is natural number, the sinusoidal frequency to be fitted
ω is the driving frequency of ultrasonic transducer, then the maximum value of the curve after three parameter curve fit algorithms are fitted
The corresponding abscissa i of point, (T-L+i)/Fs is the downbeam absolute time of flight being calculated.
Further, suitable, adverse current time difference based on ultrasonic wave time difference method, downbeam absolute time of flight, and adverse current
The measurement of three important parameters of direction absolute time of flight and flow measurement algorithm steps are specific as follows:
Step 1): the frequency of known ultrasonic transducer is ω, which is the sinusoidal frequency to be fitted, acquisition
Signal length be n, the sample frequency of signal is Fs。
Step 2): acquisition two paths of signals, respectively x (n) and y (n), x (n) are the ultrasonic echo signal of downbeam, y
It (n) is the ultrasonic echo signal of countercurrent direction, n is signal length；
Step 3): the zero padding before signal x (n), in the zero padding of the back signal y (n), the sequence length after zero padding is N, N's
Length need to be 2r, r is natural number, and the signal after zero padding is x ' (n) and y ' (n)；
Step 4): Fast Fourier Transform (FFT) (FFT) is carried out to x ' (n) and y ' (n) respectively, obtains signal x (k) and y (k)；
Step 5): the conjugation for seeking x (k) is x* (k)；
Step 6): x* (k) is multiplied with y (k), and obtained signal is Rxy(k)；
Step 7): to Rxy(k) inverse Fourier transform (IFFT) is carried out, obtains cross-correlated signal Rxy(τ)；
Step 8): to Rxy(τ) carries out peak value searching, finds cross-correlated signal RxyThe corresponding abscissa of (τ) maximum of points,
It is denoted as T.
Step 9): cross-correlated signal R is takenxy(τ) maximum of points (T, Rxy(T)) L point, maximum of points and rear L are a before
The ordinate of point constitutes signal y,Y is the discrete series to be fitted；
Step 10): structural matrix M,
Step 11): it calculates
Step 12): the sine curve expression formula of fitting are as follows:
Wherein,
Step 13): enabling θ=0 ω i+, and the corresponding abscissa of sinusoidal maximum of points being fitted is i,
Step 14): suitable, the adverse current time difference is Δ t, Δ t=(T-L+i)/Fs；
Step 15): acquisition two paths of signals, respectively x (n) and y (n), x (n) are the ultrasonic echo signal of downbeam,
Y (n) is the static ultrasound wave echo-signal under the downbeam zero delivery of storage, and n is signal length；
Step 16): it repeats step 3) and arrives step 13), the propagation time of downbeam is tup, tup=(T-L+i)/Fs；
Step 17): the adverse current reversed propagation time is tdn, tdn=tup-Δt；
Step 18): according to flow rate calculation formulaObtain the flow finally to be measured, wherein D is
Pipe diameter, θ are the line of ultrasonic transducer and the angle of measurement conduit axis.
Time Measurement Algorithm in the present invention is suitable for any application field for carrying out time of measuring with two-way input signal.
Based on above-described ultrasonic flow measuring method, the present invention also proposes a kind of low-consumption ultrasonic flow measurement meter,
Low-consumption ultrasonic flow measurement meter of the invention is described in further detail with reference to the accompanying drawing:
Low-consumption ultrasonic flow measurement meter of the invention is as shown in Figure 1, include power management module 1, ultrasonic wave transmits and receives
Module 2, temperature and pressure acquisition module 3, MCU4, menu function module 5, communication function module 6, flow output function module 7.
Power management module realizes the low-power consumption measurement of ultrasonic flowmeter, and MCU uses STM32L476RG low-power consumption core
Piece, the chip interior have a variety of low-power consumption modes, and CPU can be made to work according to task to be processed in different low-power consumption moulds
Formula, meanwhile, the module is powered, when not when operating by the power supply that the I/O pin of CPU controls external circuit module
When work, to the module power down process.Make entire ultrasonic flowmeter lower power consumption by power management, extends battery and use the longevity
Life.
Ultrasonic wave sending/receiving module is connect with MCU, and by MCU output ultrasonic wave pumping signal, analog switch 1 realizes 4
Select 1 control gating pumping signal that will be sent to which ultrasonic transducer, the effect of 4 road ultrasonic drive circuits is by pumping signal
Voltage increase, so that the energy of pumping signal is driven ultrasonic transducer, so that ultrasonic transducer be made to resonate, generate super
Acoustic emissions signal；The transmitting-receiving control of ultrasonic wave is that ultrasonic transducer 1 sends signal, and ultrasonic transducer 3 receives echo letter
Number, which is a sound channel downbeam echo-signal, and ultrasonic transducer 3 sends signal, and ultrasonic transducer 1 receives echo
Signal, the signal are a sound channel countercurrent direction echo-signal, and ultrasonic transducer 2 sends signal, and ultrasonic transducer 4 is received back
Wave signal, the signal are two sound channel downbeam echo-signals, and ultrasonic transducer 4 sends signal, and ultrasonic transducer 2 receives
Echo-signal, the signal are two sound channel countercurrent direction echo-signals.Analog switch 2 is to realize that 4 select which ultrasonic wave 1 control gates
Energy converter receives signal, and the suitable of one, two sound channels, adverse current echo-signal are controlled signal amplitude by automatic gain control circuit
It is then to adjust echo-signal between 0~2.5V by polarity adjustment circuit in ± 3.3V.
The signal that polarity adjusts module output accesses MCU, echo-signal is acquired using ADC inside MCU chip, to collect
Suitable, counter current ultrasonic wave echo-signal as input, after cross-correlation and three parameter fitting sine curve algorithms, operation is obtained
Output be time difference that suitable, countercurrent direction ultrasonic wave is propagated, with the static state under the ultrasonic echo of downbeam and zero delivery
Ultrasonic echo signal is as input, and after cross-correlation and three parameter fitting sine curve algorithms, the output that operation obtains is
The absolute time of flight of downbeam subtracts suitable, adverse current differential time of flight with the absolute time of flight of downbeam and obtains adverse current
The absolute time of flight in direction, then using it is suitable, counter current ultrasonic wave signal propagation time is poor, downbeam absolute time of flight,
Countercurrent direction absolute time of flight and pipe parameter and two pairs of ultrasonic transducer setting angle parameters calculate the stream of fluid
Speed, and then obtain the volume flow of fluid.
Temperature sensor connect temperature amplifying circuit, pressure sensor connect pressure amplifying circuit, temperature amplifying circuit and
Pressure amplifying circuit is connected to 24 Sigma-Delta ADC and carries out temperature and pressure acquisitions, and 24 Sigma-Delta ADC can be with
High precision collecting is carried out to temperature and pressure signal, collected temperature and pressure signal is measured for temperature and pressure, also used
Turn mark condition flow rate calculation in operating condition flow.
Menu function module includes key and liquid crystal, and parameter is checked and be arranged to key, the content of liquid crystal display key operation,
Key and liquid crystal are implemented in combination with menu function, realize human-computer interaction.
Communication function module includes RS485 communication and NB-IOT wireless communication, and RS485 communication uses MODBUS communication protocols
View；Wireless communication uses NB-IOT module, and built-in SIM card has network savvy, instrument is made to network, and realizes remote meter reading.
Flow output function module includes pulse output and constant-current source output, and pulse is exported for measuring, constant-current source output
It is that flow is carried out to pick-up output in the form of the current signal of standard.
Ultrasonic flow measuring method and low-consumption ultrasonic flow measurement meter of the invention has stability high and strong robustness
The characteristics of, anti-noise jamming ability is strong, can reduce measurement error, it will be apparent that improves the stabilization of existing ultrasonic flow rate measurement amount
Property and precision, in the production process of gas field, can it is reliable, stablize, accurately natural gas volume flow measured.
Claims (10)
1. a kind of ultrasonic flow measuring method, measures pipeline flow with ultrasonic signal, it is characterised in that: with it is suitable,
Counter current ultrasonic wave echo-signal is as input, using cross-correlation and three parameter fitting sine curve algorithms, the output that operation obtains
For the time difference that suitable, countercurrent direction ultrasonic wave is propagated, with the static ultrasound wave under the ultrasonic echo of downbeam and zero delivery
Echo-signal is as input, and using cross-correlation and three parameter fitting sine curve algorithms, the output that operation obtains is downbeam
Absolute time of flight, suitable, adverse current differential time of flight is subtracted with the absolute time of flight of downbeam and obtains the exhausted of countercurrent direction
To the flight time, then using suitable, counter current ultrasonic wave signal propagation time is poor, downbeam absolute time of flight, countercurrent direction
Absolute time of flight and pipe parameter and two pairs of ultrasonic transducer setting angle parameters calculate the flow velocity of fluid, in turn
Obtain the volume flow of fluid.
2. ultrasonic flow measuring method according to claim 1, which is characterized in that obtain the suitable, countercurrent direction and surpass
The time difference of Acoustic Wave Propagation specifically:
Suitable, countercurrent direction echo-signal is acquired, computing cross-correlation is carried out to collected two paths of signals, after taking computing cross-correlation
Preceding L point, maximum of points and the rear L point that maximum of points corresponds to abscissa T are constituted in three parameter fitting sine curve algorithms
Input signal, wherein L is natural number；The sinusoidal frequencies omega to be fitted is the driving frequency of ultrasonic transducer, so
The maximum of points corresponding abscissa i, (T-L+i)/Fs of the curve after three parameter curve fit algorithms are fitted are afterwards
The time difference that suitable, the countercurrent direction ultrasonic wave being calculated is propagated, wherein FsFor the sample frequency of signal.
3. ultrasonic flow measuring method according to claim 1, which is characterized in that when obtaining the absolute flight of downbeam
Between specifically:
The static ultrasound wave echo-signal under downbeam zero delivery is stored first, and every flowmeter need to only store primary static letter
Number, it is stored in EEPROM, then by downbeam static state echo-signal and collected downbeam ultrasonic echo signal
Computing cross-correlation is carried out, takes that maximum of points after computing cross-correlation correspond to the preceding L point of abscissa T, maximum of points and L is a afterwards
Point constitutes the input signal in three parameter fitting sine curve algorithms, and L is natural number, and the sinusoidal frequencies omega to be fitted is
The driving frequency of ultrasonic transducer, the then maximum of points pair of the curve after three parameter curve fit algorithms are fitted
The abscissa i answered, (T-L+i)/Fs are the downbeam absolute time of flight being calculated, wherein FsFor the sampling frequency of signal
Rate.
4. ultrasonic flow measuring method according to claim 1, which is characterized in that based on ultrasonic wave time difference method it is suitable,
The adverse current time difference, the measurements of three important parameters of downbeam absolute time of flight and countercurrent direction absolute time of flight with
And flow measurement algorithm steps are specific as follows:
Step 1): the frequency of known ultrasonic transducer is ω, which is the sinusoidal frequency to be fitted, the letter of acquisition
Number length is n, and the sample frequency of signal is Fs。
Step 2): acquisition two paths of signals, respectively x (n) and y (n), x (n) are the ultrasonic echo signal of downbeam, y (n)
For the ultrasonic echo signal of countercurrent direction, n is signal length；
Step 3): the zero padding before signal x (n), in the zero padding of the back signal y (n), the sequence length after zero padding is N, the length of N
It need to be 2r, r is natural number, and the signal after zero padding is x ' (n) and y ' (n)；
Step 4): Fast Fourier Transform (FFT) (FFT) is carried out to x ' (n) and y ' (n) respectively, obtains signal x (k) and y (k)；
Step 5): the conjugation for seeking x (k) is x* (k)；
Step 6): x* (k) is multiplied with y (k), and obtained signal is Rxy(k)；
Step 7): to Rxy(k) inverse Fourier transform (IFFT) is carried out, obtains cross-correlated signal Rxy(τ)；
Step 8): to Rxy(τ) carries out peak value searching, finds cross-correlated signal RxyThe corresponding abscissa of (τ) maximum of points, is denoted as T.
Step 9): cross-correlated signal R is takenxy(τ) maximum of points (T, Rxy(T)) L point before, maximum of points and rear L point are indulged
Coordinate constitutes signal y,Y is the discrete series to be fitted；
Step 10): structural matrix M,
Step 11): it calculates
Step 12): the sine curve expression formula of fitting are as follows:
Wherein,
Step 13): enabling θ=0 ω i+, and the corresponding abscissa of sinusoidal maximum of points being fitted is i,
Step 14): suitable, the adverse current time difference is Δ t, Δ t=(T-L+i)/Fs；
Step 15): acquisition two paths of signals, respectively x (n) and y (n), x (n) are the ultrasonic echo signal of downbeam, y (n)
For the static ultrasound wave echo-signal under the downbeam zero delivery of storage, n is signal length；
Step 16): it repeats step 3) and arrives step 13), the propagation time of downbeam is tup, tup=(T-L+i)/Fs；
Step 17): the adverse current reversed propagation time is tdn, tdn=tup-Δt；
Step 18): according to flow rate calculation formulaObtain the flow finally to be measured, wherein D is that pipeline is straight
Diameter, θ are the line of ultrasonic transducer and the angle of measurement conduit axis.
5. it is a kind of based on the low-consumption ultrasonic flow measurement of ultrasonic flow measuring method described in claim 1-4 any one,
It is characterised in that it includes MCU module (4) and the power management module (1) being separately connected with MCU module (4), ultrasonic wave transmitting
Receiving module (2), temperature and pressure acquisition module (3), menu function module (5), communication function module (6) and flow output work
It can module (7)；
The ultrasonic wave transmitting and receiving module (2) includes two pairs of ultrasonic transducers, the first analog switch, the driving of four road ultrasonic waves
Circuit, the second analog switch, automatic gain control circuit and polarity adjustment circuit；Wherein, two pairs of ultrasonic transducers are pacified in x type
On measurement pipeline；First analog switch realizes that four select a gating pumping signal to be sent to the channels of ultrasonic transducer, four
Road ultrasonic drive circuit increases the voltage of pumping signal, so that pumping signal is driven ultrasonic transducer, to make ultrasonic wave
Transducer resonant generates ultrasonic wave and emits signal；Second analog switch be four select a gating ultrasonic transducer receive signal；From
The echo-signal that dynamic gain control circuit receives ultrasonic transducer amplifies；Polarity adjustment circuit adjusts echo-signal
And it is acquired for the internal ADC of MCU module (4).
6. low-consumption ultrasonic flow measurement meter according to claim 5, which is characterized in that the line of each pair of ultrasonic transducer
Angle with measurement conduit axis is 45o.
7. low-consumption ultrasonic flow measurement meter according to claim 5, which is characterized in that the MCU module (4) is
STM32L476RG low-power chip；The echo-signal that the automatic gain control circuit receives ultrasonic transducer carries out
Amplification, amplitude are controlled in ± 3.3V, and amplification factor is according to current signal magnitude adjust automatically；The polarity adjustment circuit be by
Echo-signal adjusts between 0~2.5V, so that STM32L476RG chip interior ADC is acquired.
8. low-consumption ultrasonic flow measurement meter according to claim 5, which is characterized in that the temperature and pressure acquisition module
It (3) include temperature sensor, temperature amplifying circuit, pressure sensor, pressure amplifying circuit and 24 Sigma-Delta ADC；
Wherein, the temperature amplifying circuit amplifies the signal of temperature sensor；Letter of the pressure amplifying circuit to pressure sensor
It number amplifies；24 Sigma-Delta ADC are acquired temperature and pressure signal, by collected temperature and pressure
Force signal is measured for temperature and pressure, is also used for operating condition flow and is turned mark condition flow rate calculation.
9. low-consumption ultrasonic flow measurement meter according to claim 5, which is characterized in that menu function module (5) packet
Key and liquid crystal are included, parameter is checked and be arranged to key, and the content of liquid crystal display key operation, key and liquid crystal are implemented in combination with menu
Function realizes human-computer interaction；The communication function module (6) includes RS485 communication and NB-IOT wireless communication, RS485 communication
Using MODBUS communication protocol；Wireless communication uses NB-IOT module, and built-in SIM card has network savvy, instrument is made to network,
Realize remote meter reading.
10. low-consumption ultrasonic flow measurement meter according to claim 5, which is characterized in that the flow output function module
It (7) include pulse output and constant-current source output, pulse is exported for measuring, and constant-current source output is to believe flow with the electric current of standard
Number form carries out pick-up output.
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