Method and device for detecting and tuning operating frequency of ultrasonic water meter

Abstract

The present invention provides a method and device for detecting and tuning the operating frequency of an ultrasonic water meter. The method includes obtaining echo signal data of the ultrasonic water meter, and the echo signal data at least includes the time T when each wave changes from negative to positive through zero crossing Zn , the actual cycle time T Cn , the initial frequency F of the transducer Cn and the real-time operating frequency F of the transducer Sn ; based on the echo signal data, determining whether the ultrasonic water meter is in a state of operating frequency deviation; when the ultrasonic water meter is in a state of operating frequency deviation, according to the difference between the real-time operating frequency F Sn of the transducer and the initial frequency F Cn , controlling the ultrasonic water meter to correct the operating frequency of the transducer through a tuning matching circuit. By online collecting and judging the operating frequency of the transducer and online correcting the frequency deviation, the problem that the metering value of the ultrasonic water meter is higher or lower than the actual flow rate due to different degrees of aging of the transducer during use is solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of ultrasonic water meters, and particularly relates to a method and device for detecting and tuning the operating frequency of an ultrasonic water meter. Background Art

[0002] As the core of the metering function of an ultrasonic water meter, an ultrasonic transducer can realize the mutual conversion of electrical and acoustic signals of a specific frequency, and calculate the water flow velocity through the time difference between the transmission and reception of electrical signals by a pair of transducers. Combining with the cross-sectional area of the pipe section, the purpose of water metering is achieved. However, with the passage of time and the change of the use environment, the frequency of the transducer shifts, resulting in a decline in the performance of the transducer, which will lead to a reduction in the metering accuracy and stability of the water meter, and even mis-metering in the static water state and the situation where the metering value does not match the actual flow rate. Usually, only the methods of on-site water meter replacement or adjustment and correction can be adopted. However, these methods not only affect the user experience, but may also lead to inaccurate metering, and at the same time increase the maintenance cost. Summary of the Invention

[0003] In order to solve the problems existing in the above-mentioned prior art, the present invention provides a method for detecting and tuning the operating frequency of an ultrasonic water meter, and the method includes:

[0004] Obtain the echo signal data of the ultrasonic water meter, where the echo signal data at least includes the time T when each wave changes from negative to positive through the zero point Zn , the actual cycle time T Cn , the initial frequency F of the transducer Cn and the real-time operating frequency F of the transducer Sn ;

[0005] Based on the echo signal data, determine whether the ultrasonic water meter is in a state of operating frequency deviation;

[0006] When the ultrasonic water meter is in a state of operating frequency deviation, according to the difference between the real-time operating frequency F of the transducer Sn and the initial frequency F Cn , control the ultrasonic water meter to correct the operating frequency of the transducer through a tuning matching circuit.

[0007] On the basis of the above solution, the step of obtaining the echo signal data of the ultrasonic water meter includes:

[0008] Step S1, the metering chip receives the echo signal of the transducer, and collects the time when the wave changes from negative to positive after FHL, denoted as T Z1 , T Z2 , …, T Zn ;

[0009] Step S2: Calculate the actual cycle time T of each echo based on the time points collected in Step S1 Cn = T Zn+1 - T Zn ;

[0010] Step S3: Obtain the working frequency F of each echo based on the actual cycle time calculated in Step S2 n , where F n = 1 / T Cn ;

[0011] Step S4: Record the initial frequency F of each echo at the time of factory shipment cn = F n1 ; Detect the real-time frequency F of each echo during use Sn = F n2 ; where F n1 is the initial frequency of the transducer, and F n2 is the real-time frequency after the transducer works.

[0012] Based on the above solution, determining whether the ultrasonic water meter is in a working frequency offset state includes:

[0013] Determine whether the working frequency of the transducer has shifted. When ABS(F Sn - F Cn ) > F limit , it is determined that the working frequency has shifted, where F limit is the offset threshold;

[0014] Based on the above solution, the working frequency offset state further includes determining the direction of the frequency offset and determining the frequency correction method according to this direction. If F Sn - F Cn > F limit , it is a positive offset; if F Sn - F Cn < F limit , it is a negative offset.

[0015] Based on the above solution, the tuning matching circuit includes:

[0016] Adjustable inductors, fixed capacitors or adjustable capacitors connected in series or in parallel with the transmitting path of the UP transducer;

[0017] Adjustable inductors, fixed capacitors or adjustable capacitors connected in series or in parallel with the receiving path of the DOWN transducer;

[0018] The tuning matching circuit realizes online calibration of the working frequency of the transducer by adjusting the value of the series adjustable inductor or adjustable capacitor in real time.

[0019] The present invention also provides an ultrasonic water meter, which includes a UP transducer, a DOWN transducer, a TDC measurement chip, and a tuning and matching circuit. The ultrasonic water meter uses the method provided by the above solution to detect the operating frequency and perform tuning.

[0020] Compared with the prior art, the present invention has the following beneficial effects: By online collecting and judging the operating frequency of the transducer, and adjusting the value of the capacitance or inductance in the circuit to correct the frequency deviation of the transducer, the problem that the measurement value of the ultrasonic water meter is higher or lower than the actual flow rate due to different degrees of aging of the transducer during use is solved. Description of the Drawings

[0021] Figure 1 Schematic diagram of the measurement principle of the ultrasonic water meter;

[0022] Figure 2 Equivalent circuit diagram of the measurement principle of the ultrasonic water meter;

[0023] Figure 3 Flow chart of the detection and tuning method of the present invention;

[0024] Figure 4 Flow chart of the detection and tuning of an embodiment of the present invention;

[0025] Figure 5 Schematic diagram of the echo received by the measurement chip;

[0026] Figure 6 Schematic diagram of the tuning and matching circuit;

[0027] Figure 7 Flow chart of the tuning of an embodiment of the present invention;

[0028] Figure 8 Tuning and matching circuit of an embodiment of the present invention;

[0029] Figure 9 Comparison chart of frequency ratio curves in an embodiment of the present invention; Detailed Embodiments

[0030] The invention will be further described below in conjunction with specific embodiments.

[0031] As Figure 1As shown in the figure, the ultrasonic water meter internally includes an upstream (UP) transducer and a downstream (DOWN) transducer. The excitation terminal (TX) and the receiving terminal (RX) of the TDC (Time-to-Digital Converter) metering module are respectively connected to the transducers. The excitation terminal of the metering module emits a square wave signal with a frequency of Fs. After passing through the impedance matching resistor URs of the UP transducer, the signal is converted into an acoustic wave signal and propagated through the water flow. The DOWN transducer receives the acoustic wave signal and converts it into an electrical signal. This signal reaches the receiving terminal of the TDC metering chip after passing through the pull-up bias voltage and power amplifier inside the TDC metering chip.

[0032] According to the excitation of Fs issued by the metering chip, both the UP and DOWN transducers can be regarded as equivalent circuits composed of resistors, capacitors, and inductors with a resonant frequency of approximately Fs, as Figure 2 shown. The equivalent circuit of the UP transducer is the series connection of UL1, UC1, and UR1 in parallel with UC0, and the DOWN transducer is the series connection of DL1, DC1, and DR1 in parallel with DC0. Therefore, the transducer has two resonant frequencies: the series resonant frequency and the parallel resonant frequency, and the values of its resistance, capacitance, and inductance will change with the usage time and environment, resulting in the shift of the resonant frequency of the transducer itself.

[0033] If the flight time from the UP transducer to emit a signal to the DOWN transducer to receive the signal is t1, the flight time from the DOWN transducer to emit a signal to the UP transducer to receive the signal is t2, and the time difference between the two is Δt, then the ultrasonic water meter can calculate the water consumption according to the time difference Δt, combined with the water flow rate and the cross-sectional area of the pipe section. However, the resonant frequency of the transducer will shift with the change of usage time and environment, resulting in inaccurate time difference Δt, and further causing the problem of flow deviation in the ultrasonic water meter after using for a period of time.

[0034] To solve the above problems, the present invention provides a method for detecting and tuning the working frequency of an ultrasonic water meter. This method can not only monitor the working frequency of the transducer in real time but also automatically perform frequency tuning to ensure that the water meter always works in the best state.

[0035] As Figure 3 and Figure 4 shown, the method for detecting and tuning the working frequency of the present invention includes

[0036] Obtaining the echo signal data of the ultrasonic water meter, where the echo signal data at least includes the time T of each wave from negative to positive zero crossing Zn , the actual cycle time T Cn , the initial frequency F of the transducer Cn and the real-time working frequency F of the transducer Sn ;

[0037] The steps of obtaining the echo signal data of the ultrasonic water meter include:

[0038] Step S1, the metering chip receives the echo signal, and collects the time of each zero crossing from negative to positive after the FHL (First High Level), which are respectively denoted as T z1 , T z2 , …, T Zn ;

[0039] Specifically, when the UP transducer receives the square wave excitation sent by the TDC metering chip, it converts electrical energy into mechanical energy and directly transmits it in water in the form of ultrasonic waves to the DOWN transducer. The DOWN transducer then converts the received mechanical energy back into an electrical signal, which is the so-called echo signal, and this signal is received by the TDC metering chip.

[0040] As Figure 5 shown, FHL is the first wave high level, T z1 is the time of the first zero crossing from negative to positive, and T z2 is the time of the second zero crossing from negative to positive;

[0041] Based on step S1, execute step S2 to calculate the actual period time T Cn = T Zn+1 - T Zn ;

[0042] By calculating the actual period time of each echo, it lays a foundation for further analyzing the working frequency of the transducer;

[0043] Based on step S2, execute step S3 to obtain the working frequency F n of each echo after the FHL first wave of the transducer, where F n = 1 / T Cn ;

[0044] Based on the above steps S1 - S3, obtain the parameters in step S4: When the ultrasonic water meter is factory-calibrated, it automatically collects and stores the initial frequency F Cn of each echo after the FHL first wave; During use, the frequency of each echo is regularly collected to obtain the real-time frequency F Sn of the echo.

[0045] The calculation method of the initial frequency F Cn and the real-time frequency F Sn is the same, but the states are different. The initial frequency is when the ultrasonic water meter just starts to work, that is, the frequency has not shifted, while the real-time frequency is after the ultrasonic water meter has been used for some time, and at this time the frequency may or may not shift.

[0046] Then, based on the echo signal data, it is determined whether the ultrasonic water meter is in a working frequency offset state;

[0047] Determining whether the ultrasonic water meter is in a working frequency offset state includes: determining whether the working frequency of the transducer has shifted. When ABS(F Sn -F Cn )>F limit , it is determined that the working frequency has shifted. Here, F limit is the offset threshold;

[0048] When the ultrasonic water meter is in a working frequency offset state, according to the difference between the real-time working frequency F Sn of the transducer and the initial frequency F Cn , the ultrasonic water meter is controlled to correct the working frequency of the transducer through the tuning matching circuit. If there is no shift, the detection ends.

[0049] As Figure 6 shown, the tuning matching circuit includes adjustable inductors, fixed capacitors or adjustable capacitors in parallel or in series. The tuning matching circuit is located on the signal paths of the UP transducer and the DOWN transducer. By connecting adjustable inductors, fixed capacitors, and adjustable capacitors in parallel or in series, and having switches respectively connected in series with the adjustable inductors, fixed capacitors, and adjustable capacitors, and selecting appropriate circuit elements according to the direction of frequency offset and closing the corresponding switches. And for the adjustable capacitors and inductors in parallel or in series, the offset of the working frequency of the transducer is reduced to within the set frequency offset threshold value through real-time adjustment, realizing on-line calibration of frequency offset. Therefore, according to the present invention, no matter how the frequency shifts, it can be corrected through the tuning matching circuit.

[0050] According to an embodiment of the present invention, as Figure 7 shown, by determining the offset direction of the working frequency of the transducer, a suitable tuning matching circuit is selected. It is assumed that when the real-time frequency is greater than the initial frequency, it is a positive offset, and vice versa is a negative offset. When F Sn -F Cn >F limit , the positive offset is too large, and the parallel capacitance of the receiving path is increased; when F Sn -F Cn <F limit , the frequency negative offset is too large, and the series capacitance of the transmitting path is reduced.

[0051] Specifically, as Figure 8 shown, an adjustable capacitor UC S is connected in series on the transmitting path, and an adjustable capacitor DC LWhen the frequency offset exceeds the offset threshold, the capacitance of the adjustable capacitor is adjusted in real time to achieve online calibration of the frequency offset. According to the present invention, fixed capacitors with different capacitances can also be connected in series or in parallel, and the frequency can be corrected by replacing the fixed capacitors.

[0052] According to another embodiment of the present invention, the frequency offset is corrected by adjusting the inductance. Increasing the parallel inductance can correct the forward frequency offset. At the transmitting end, reducing the series inductance can correct the reverse frequency offset.

[0053] like Figure 9 As shown, according to this embodiment, the aged ultrasonic water meter is calibrated, and the initial frequency F of each wave collected by the ultrasonic water meter before leaving the factory is cn , the real-time frequency F of the echo collected after the ultrasonic water meter product has been accelerated aging Sn In order to more accurately reflect the frequency deviation, the collected frequency and the excitation frequency F of the metering chip are respectively s The three curves in the figure are the initial frequency and F of the ultrasonic water meter. s The ratio curve (original curve) of the echo real-time frequency F after accelerated aging Sn With F s The ratio curve (long time curve) and the frequency and F after tuning s From the ratio curve (tuning curve), it can be seen that the tuned curve basically coincides with the original curve, and the frequency offset is corrected, ensuring the measurement accuracy of the water meter.

[0054] The present invention also provides an ultrasonic water meter, comprising an UP transducer, a DOWN transducer and a TDC metering chip, and the working frequency of the transducer is detected and tuned using the working frequency detection and tuning method of the ultrasonic water meter provided above.

[0055] Specifically, the ultrasonic water meter also includes adjustable inductance, fixed capacitance and adjustable capacitance. The operating frequency is tuned by connecting the adjustable capacitance or inductance in parallel or in series. When adjusting, the matching circuit is changed by closing the switch connected in series with the adjustable inductance, fixed capacitance or adjustable capacitance, and the inductance or capacitance is adjusted in real time to realize the correction of the frequency of the ultrasonic water meter.

[0056] In summary, through the working frequency detection and tuning method of the ultrasonic water meter provided by the present invention, the working frequency of the transducer in the ultrasonic water meter can be monitored and automatically tuned in real time, ensuring that the water meter maintains high precision and stability during long-term use, which not only improves the reliability of the water meter but also extends its service life.

[0057] The above are only the preferred embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

[0058] Although the specific implementation manners of the present invention are described above, it is not a limitation on the protection scope of the present invention. Those skilled in the art should understand that, based on the technical solution of the present invention, various modifications or deformations that can be made by those skilled in the art without creative efforts are still within the protection scope of the present invention.

Claims

1. A method for detecting and tuning the working frequency of an ultrasonic water meter, characterized in that: The method comprises: Acquire the echo signal data of the ultrasonic water meter, wherein the echo signal data at least includes the time T of each wave turning from negative to positive and crossing the zero point Zn , actual cycle time T Cn , initial frequency F of the transducer Cn and the real-time operating frequency F of the transducer Sn ; Based on the echo signal data, determining whether the ultrasonic water meter is in an operating frequency deviation state; When the ultrasonic water meter is in a state of operating frequency deviation, the real-time operating frequency F of the transducer is Sn With the initial frequency F Cn The difference between the values ​​of the abovementioned two parameters is used to control the ultrasonic water meter to correct the operating frequency of the transducer through a tuning matching circuit; The steps of obtaining the echo signal data of the ultrasonic water meter include: Step S1, the metering chip receives the transducer echo signal and collects the time when the negative turns positive and crosses the zero point after FHL, which is recorded as T Z1 , T Z2 ,…,T Zn ; Step S2, based on the time points collected in step S1, calculate the actual cycle time T of each echo Cn =T Zn+1 -T Zn ; Step S3, based on the actual cycle time calculated in step S2, obtain the operating frequency F of each echo n , where F n =1 / T Cn ; Step S4, record the initial frequency F of each echo at the factory Cn =F n1 ; Detect the real-time frequency F of each echo during use Sn =F n2 Among them, F n1 is the initial frequency of the transducer, F n2 It is the real-time frequency after the transducer works.

2. The method for detecting and tuning the working frequency of an ultrasonic water meter according to claim 1, characterized in that: Determining whether the ultrasonic water meter is in an operating frequency deviation state includes: Determine whether the transducer operating frequency is offset. Sn -F Cn ) > F limit When the operating frequency is judged to have shifted, F limit is the offset threshold.

3. The method for detecting and tuning the working frequency of an ultrasonic water meter according to claim 2, characterized in that: The operating frequency offset state also includes determining the direction of the frequency offset and determining a frequency correction method according to the direction. Sn -F Cn > F limit , then it is a positive offset; if F Sn -F Cn < F limit , it is a reverse offset.

4. The method for detecting and tuning the working frequency of an ultrasonic water meter according to claim 1, characterized in that: The tuning and matching circuit comprises: An adjustable inductor, fixed capacitor or adjustable capacitor connected in series or in parallel with the transmitting path of the UP transducer; An adjustable inductor, fixed capacitor or adjustable capacitor connected in series or in parallel with the receiving path of the DOWN transducer; The tuning and matching circuit achieves online calibration of the operating frequency of the transducer by adjusting the value of the series adjustable inductor or the adjustable capacitor in real time.

5. An ultrasonic water meter, characterized in that: The ultrasonic water meter comprises an UP transducer, a DOWN transducer, a TDC metering chip and a tuning and matching circuit. The ultrasonic water meter uses the method described in any one of claims 1 to 4 to perform working frequency detection and tuning.

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