CN203069223U - Synchronous phase code time difference detection device for ultrasonic flowmeter - Google Patents

Abstract

The utility model discloses a synchronous phase code time difference detection device for an ultrasonic flowmeter. A pair of ultrasonic transducers is adopted as a transmitting and receiving signal probe set and is respectively installed on two sides of a pipeline to be separated by a distance. One measurement period of the synchronous time difference detection method comprises two processes: controlling the two ultrasonic transducers to be simultaneously used as a transmitting end to transmit 13 bit Barker code signals with different frequencies; and controlling the two ultrasonic transducers to stop transmitting the signals and wait for receiving the signals, and utilizing a related processing method to precisely measure and record the time when the first ultrasonic transducer transmits the signals to the second ultrasonic transducer and the time when the second ultrasonic transducer transmits the signals to the first ultrasonic transducer. According to the data, the device combines geometrical information to work out the flow velocity and the quantity of flow.

Description

Phase Encoding Synchronous Time Difference Detection Device for Ultrasonic Flowmeter

technical field

The utility model relates to the ultrasonic flowmeter technology, in particular to a phase encoding synchronous time difference detection device for the ultrasonic flowmeter.

Background technique

Compared with mechanical flowmeters and electromagnetic flowmeters, ultrasonic flowmeters have many advantages: high measurement accuracy, strong adaptability to pipe diameter, non-contact measurement, convenient use and easy digital management, etc. With the development of piezoelectric ceramic technology, electronic technology and high-speed digital signal processing technology, the performance of ultrasonic flowmeter has been greatly improved, and the manufacturing cost has also been greatly reduced. Therefore, ultrasonic flowmeter has been widely used in the industrial field and daily life. widely used.

At present, the time difference method is mostly used in the design of ultrasonic flowmeters for signal detection. The following is a brief introduction to the detection principle of time difference method ultrasonic flowmeters. The working principle of the time-difference ultrasonic flowmeter is shown in Figure 1. It uses a pair of ultrasonic transducers to send and receive ultrasonic waves, and measures the flow velocity of the fluid by measuring the propagation time difference between the forward and reverse flows of the ultrasonic waves in the fluid, and then calculates the flow velocity. An indirect measure of flow.

There are two ultrasonic transducers in attached drawing 1: transducer A and transducer B. The two transducers are respectively installed on both sides of the fluid pipeline and separated by a certain distance. The inner diameter of the pipeline is D, and the ultrasonic wave propagates The path length of the ultrasonic wave is L, the time for ultrasonic waves to propagate forward is t ₁ , and the time for countercurrent propagation is t ₂ , and the angle between the direction of ultrasonic wave propagation and the direction of fluid flow is θ. Due to the fluid flow, the time it takes for the ultrasonic wave to propagate the distance L length is shorter than the time it takes for the upstream flow. The principle of flow velocity measurement can be expressed by the following formula:

$\left\{\begin{array}{c}{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; L</span>}}{\mathrm{<span\; class="notranslate">\; c</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; V</span>}\mathrm{<span\; class="notranslate">\; cos</span>}\mathrm{<span\; class="notranslate">\; \&theta;</span>}}\\ {\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; L</span>}}{\mathrm{<span\; class="notranslate">\; c</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; V</span>}\mathrm{<span\; class="notranslate">\; cos</span>}\mathrm{<span\; class="notranslate">\; \&theta;</span>}}\end{array}\right.<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

Among them: c is the propagation speed of ultrasonic waves in the fluid medium, and V is the flow speed of the target fluid.

The time difference Δt between forward and countercurrent propagation can be obtained by subtracting the two equations in formula (1):

$\mathrm{<span\; class="notranslate">\; \&Delta;t</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; VL</span>}\mathrm{<span\; class="notranslate">\; cos</span>}\mathrm{<span\; class="notranslate">\; \&theta;</span>}}{{\mathrm{<span\; class="notranslate">\; c</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; V</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; cos</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; \&theta;</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

Since the fluid velocity is a very small quantity compared with the propagation velocity of ultrasonic waves in the medium, formula (2) can be simplified as:

$\mathrm{<span\; class="notranslate">\; \&Delta;t</span>}<span\; class="notranslate">\; \&ap;</span>\frac{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; VL</span>}\mathrm{<span\; class="notranslate">\; cos</span>}\mathrm{<span\; class="notranslate">\; \&theta;</span>}}{{\mathrm{<span\; class="notranslate">\; c</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

The flow rate of the fluid is thus obtained as:

$\mathrm{<span\; class="notranslate">\; V</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; c</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; \&Delta;t</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; L</span>}\mathrm{<span\; class="notranslate">\; cos</span>}\mathrm{<span\; class="notranslate">\; \&theta;</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

After measuring the flow velocity, by calculating the cross-sectional area of the pipe, the flow rate in the pipe can be obtained as:

$\mathrm{<span\; class="notranslate">\; Q</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; V</span>}<span\; class="notranslate">\; *</span>\mathrm{<span\; class="notranslate">\; \&pi;</span>}\frac{{\mathrm{<span\; class="notranslate">\; D.</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; )</span>$

Among them: Q is the flow rate, V is the flow rate, and D is the inner diameter of the pipeline.

Existing transit-time ultrasonic flowmeters usually use the following two methods when performing transit-time detection:

Method 1: Using a pair of ultrasonic transducer A and transducer B (as shown in Figure 1), the detection process is as follows:

1) Ultrasonic transducer A is used as the transmitting end, and transducer B is used as the receiving end. Control transducer A to transmit signals, and then detect the signals received by transducer B to obtain the time t for ultrasonic waves to propagate downstream in the fluid ₁ ;

2) Ultrasonic transducer B is used as the transmitting end, and transducer A is used as the receiving end. Control transducer B to transmit signals, and then detect the signals received by transducer A, and obtain the time t ₂ of ultrasonic waves propagating upstream in the fluid ;

3) Calculate the time difference Δt=t ₂ -t ₁ between the forward and reverse propagation of ultrasonic waves.

Method 2: Use two pairs of ultrasonic transducers A and B, transducer C and transducer D (as shown in Figure 2), the detection process is as follows:

1) Ultrasonic transducer A is used as the transmitting end, and transducer B is used as the receiving end. Control transducer A to transmit signals, and then detect the signals received by transducer B to obtain the time t for ultrasonic waves to propagate downstream in the fluid ₁ ; at the same time, the ultrasonic transducer C is used as the transmitting end, and the transducer D is used as the receiving end, and the transducer C is controlled to transmit the signal, and then the signal received by the transducer D is detected to obtain the time t for the ultrasonic wave to propagate upstream in the fluid ₂ ;

2) Calculate the time difference Δt=t ₂ -t ₁ between the upstream propagation time and the downstream propagation time.

Considering the actual application situation, the shortcomings of the two existing time difference detection methods are analyzed from three aspects: measurement accuracy, power consumption and manufacturing cost:

Method 1 to measure a time difference value requires ultrasonic waves to travel back and forth in the target fluid. If the flow velocity of the target fluid is uneven and changes frequently, then the time difference value obtained by method 1 measurement is not real-time. Therefore, The real-time performance of the calculated flow rate is not high, and the accuracy of the final calculated flow rate is not high.

Method 2 uses two pairs of ultrasonic transducers for measurement. Although this can shorten the time for measuring a time difference value, it increases the complexity of the control and detection circuits, and also increases the power consumption of the entire flowmeter. Power consumption is also an important indicator that must be considered in the design in practical applications.

In practical applications, manufacturing cost is also an important criterion to measure the quality of a design. Method 2 uses two pairs of transducers, and the complexity of the control and detection circuits is high. While increasing power consumption, it also increases manufacturing costs.

Contents of the invention

The purpose of this utility model is to provide a phase encoding synchronous time difference detection device for ultrasonic flowmeters. The main problem to be solved is how to make the time difference method ultrasonic flowmeter meet the problems of high measurement accuracy and low power consumption at the same time.

The technical scheme that the utility model solves its technical problem adopts is:

The utility model proposes a phase encoding synchronous time difference detection device for an ultrasonic flowmeter, comprising: a first ultrasonic transducer, a second ultrasonic transducer, a first correlator, a second correlator, a first display, The second display, the code generator; the first ultrasonic transducer and the second ultrasonic transducer are fixed on both sides of the fluid pipeline wall by bolts and staggered from each other, the inner diameter of the pipeline is D, and the path length of ultrasonic propagation is L (L>D), the angle between the direction of ultrasonic propagation and the flow direction of the fluid is θ (0°<θ<90°), the first ultrasonic transducer is connected to the first correlator, and the second ultrasonic transducer is connected to The second correlator is connected, the first correlator is connected with the first display, the second correlator is connected with the second display, and the code generator is respectively connected with the first ultrasonic transducer, the second ultrasonic transducer, the first correlator, The second correlator is connected.

The first ultrasonic transducer and the second ultrasonic transducer are identical ultrasonic transducers; the first correlator and the second correlator are two identical correlators; the display and the display are two identical displays .

The correlator is composed of several identical branches connected in parallel, and each branch is composed of a multiplier and a low-pass filter in series.

The ultrasonic transducer adopts the 200K-75KHz underwater acoustic transducer of Hangzhou Umbrella Automation Technology Co., Ltd., the model is XIHUW-75/200-E.

The beneficial effect that the utility model has is:

Different from the usual time difference detection method, the phase encoding synchronous time difference detection device and method for ultrasonic flowmeters provided by the utility model can reduce the influence of the change of the propagation speed of the ultrasonic wave in the medium, and at the same time use the correlation processing method to measure the ultrasonic flow rate. Flow propagation and countercurrent propagation time can significantly improve the measurement accuracy of ultrasonic flowmeters. Compared with the traditional time difference detection method, the utility model also meets the requirement of low power consumption, and provides a more suitable detection method for the design of the time difference method ultrasonic flowmeter. This method transmits ultrasonic signals of different frequencies, which can effectively avoid the influence of standing waves generated by the mutual propagation of ultrasonic waves on the measurement results.

Description of drawings

Figure 1 is a schematic diagram of the measurement principle of the transit-time ultrasonic flowmeter.

Fig. 2 is a schematic diagram of the measurement principle of the time-of-flight ultrasonic flowmeter realized by using two pairs of ultrasonic transducers.

Fig. 3 is a schematic diagram of the measurement principle of the ultrasonic flowmeter by the phase encoding modulation synchronous time difference detection method.

Fig. 4 is a schematic diagram of related processing principles.

Figure 5 is the autocorrelation function of the 13-bit Barker code.

Figure 6 is the distance autocorrelation function of the display output.

Detailed ways

Combined with Fig. 3, Fig. 4 and Fig. 5, the utility model proposes a phase encoding synchronous time difference detection device for ultrasonic flowmeters, including: a first ultrasonic transducer 1, a second ultrasonic transducer 2, a first A correlator 3, a second correlator 4, a first display 5, a second display 6, a code generator 7; the first ultrasonic transducer 1 and the second ultrasonic transducer 2 are fixed on the wall of the fluid pipeline by bolts The two sides are staggered from each other, the inner diameter of the pipeline is D, the path length of ultrasonic propagation is L (L>D), and the angle between the direction of ultrasonic propagation and the flow direction of the fluid is θ (0°<θ<90°). An ultrasonic transducer 1 is connected with the first correlator 3, the second ultrasonic transducer 2 is connected with the second correlator 4, the first correlator 3 is connected with the first display 5, and the second correlator 4 is connected with the second display 6, and the code generator 7 is connected to the first ultrasonic transducer 1, the second ultrasonic transducer 2, the first correlator 3, and the second correlator 4 respectively.

The first ultrasonic transducer 1 and the second ultrasonic transducer 2 are identical ultrasonic transducers; the first correlator 3 and the second correlator 4 are two identical correlators; the display 5 and the display 6 are Two identical monitors.

The correlator is composed of several identical branches connected in parallel, and each branch is composed of a multiplier and a low-pass filter in series.

The ultrasonic transducer adopts the 200K-75KHz underwater acoustic transducer of Hangzhou Umbrella Automation Technology Co., Ltd., the model is XIHUW-75/200-E.

A phase encoding synchronous time difference detection method for an ultrasonic flowmeter, the steps are as follows:

The first step: the code generator generates 13-bit Barker code signals and different time delays corresponding to 13-bit Barker code signals, and uses different time delays corresponding to 13-bit Barker code signals as different reference signals, and corresponds to Different times; the code generator will generate 13-bit Barker code signals and transmit them to the first ultrasonic transducer 1 and the second ultrasonic transducer 2 respectively, and transmit the reference signal to the first correlator 3 and the second correlator respectively 4.

Step 2: The first ultrasonic transducer 1 and the second ultrasonic transducer 2 simultaneously act as the transmitting code generators at the transmitting end to generate a 13-bit Barker code signal.

Step 3: The first ultrasonic transducer 1 serves as the receiving end to receive the signal transmitted by the second ultrasonic transducer 2 , and the second ultrasonic transducer 2 serves as the receiving end to receive the signal transmitted by the first ultrasonic transducer 1 .

Step 4: In the correlator, when the propagation time of the received 13-bit Barker code signal in the fluid is the same as the delay time of the code generator, the output signal of this branch is the largest, corresponding to the main peak of the distance autocorrelation function, At this time, the delay time corresponding to the branch is the propagation time of the ultrasonic wave in the fluid, and the forward propagation time is marked as t ₁ and the countercurrent propagation time is marked as t ₂ .

Step 5: Calculate the time difference Δt=t ₂ -t ₁ between forward and backward propagation of ultrasonic waves.

Step 6: Using the time difference Δt calculated in step 5, according to formula (4), the flow velocity V of the measured fluid can be calculated.

Step 7: Using the flow velocity V of the measured fluid obtained in step 6, the fluid flow Q can be calculated according to the formula (5).

Embodiment: set the inner diameter of the fluid pipeline to be tested to be 3m, the path length of ultrasonic wave propagation to be 5m, the included angle between the direction of propagation of ultrasonic wave and the flow direction of fluid to be 36.87°, and the propagation speed of ultrasonic wave in the fluid to be 1600m/s, code The 13-bit Barker code signal sequence generated by the generator is [11111-1-111-11-11], and the different delays for generating the 13-bit Barker code reference signal at the same time are 2500μs, 2501μs, 2502μs, ..., 3500μs.

The first step: install the first ultrasonic transducer 1 and the second ultrasonic transducer 2 on both sides of the pipeline wall and stagger each other; the code generator 7 generates a 13-bit Barker code signal and a 13-bit Barker code signal Corresponding different time delays, the different time delays corresponding to the 13-bit Barker code signal are used as different reference signals, and correspond to different times; the code generator 7 will generate 13 Barker code signals and deliver them to the first The ultrasonic transducer 1 and the second ultrasonic transducer 2, and transmit the reference signal to the first correlator 3 and the second correlator 4 respectively;

The second step: the first ultrasonic transducer 1 and the second ultrasonic transducer 2 simultaneously serve as the transmitting code generator at the transmitting end to generate a 13-bit Barker code signal;

The third step: the first ultrasonic transducer 1 receives the signal transmitted by the second ultrasonic transducer 2 as the receiving end, and the second ultrasonic transducer 2 receives the signal transmitted by the first ultrasonic transducer 1 as the receiving end;

Step 4: In the first correlator 3, the reference signal with a time delay of 3156 μs outputs the peak value of the maximum distance autocorrelation function, so it is measured that the transmission signal of the second ultrasonic transducer 2 reaches the first ultrasonic transducer 1 The propagation time is 3156 μs, that is, the countercurrent propagation time _t2 is 3156 μs; in the second correlator 4, the reference signal with a time delay of 3094 μs outputs the peak value of the maximum distance autocorrelation function, so the emission of the first ultrasonic transducer 1 is measured The propagation time for the signal to reach the second ultrasonic transducer 2 is 3094 μs, that is, the downstream propagation time t ₁ is 3094 ts. The distance autocorrelation function output by the display is shown in FIG. 6 .

Step 5: Calculate the time difference Δt between the forward and backward propagation of the ultrasonic wave to be 62μs.

Step 6: According to the formula (4), the flow velocity V of the measured fluid can be calculated as 19.84m/s.

Step 7: According to the formula (5), the fluid flow Q can be calculated as 140.2406m ³ /s.

Claims (3)

1. device for detecting difference when the phase encoding for ultrasonic flow meter is synchronous, comprise: first ultrasonic transducer (1), second ultrasonic transducer (2), first correlator (3), second correlator (4), first display (5), second display (6), sign indicating number generator (7), it is characterized in that: first ultrasonic transducer (1) and second ultrasonic transducer (2), also stagger mutually by the both sides that are bolted to the fluid line tube wall, the interior diameter of pipeline is D, the path that ultrasound wave is propagated is L, and L＞D, the direction that ultrasound wave is propagated and the flow direction angle of fluid are θ, 0 °＜θ＜90 ° wherein, first ultrasonic transducer (1) is connected with first correlator (3), second ultrasonic transducer (2) is connected with second correlator (4), first correlator (3) is connected with first display (5), second correlator (4) is connected with second display (6), the sign indicating number generator (7) respectively with first ultrasonic transducer (1), second ultrasonic transducer (2), first correlator (3), second correlator (4) connects.

2. device for detecting difference when a kind of phase encoding for ultrasonic flow meter according to claim 1 is synchronous is characterized in that: first ultrasonic transducer (1) and second ultrasonic transducer (2) are identical ultrasonic transducer; First correlator (3) and second correlator (4) are two identical correlators; Display (5) and display (6) are two identical displays.

3. device for detecting difference when a kind of phase encoding for ultrasonic flow meter according to claim 1 is synchronous is characterized in that: correlator is composed in parallel by some identical branch roads, and every multiplier of route and a low-pass filter are composed in series.

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