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

Abstract

The invention provides a working frequency detection and tuning method and device for an ultrasonic water meter, and the method comprises the steps: obtaining the echo signal data of the ultrasonic water meter, the echo signal data at least comprises the time TZn of each wave negative rotation positive zero crossing point, the actual period time TCn, the initial frequency FCn of a transducer, and the real-time working frequency FSn of the transducer; based on the echo signal data, whether the ultrasonic water meter is in a working frequency deviation state or not is judged; when the ultrasonic water meter is in the working frequency deviation state, the ultrasonic water meter is controlled to correct the working frequency of the transducer through a tuning matching circuit according to the difference between the real-time working frequency FSn and the initial frequency FCn of the transducer. The working frequency of the transducer is acquired and judged on line, and the frequency deviation is corrected on line, so that the problem that the measured value of the water meter is higher or lower than the actual flow due to different degrees of aging of the transducer in the use process of the ultrasonic water meter is solved.

Description

Technical Field

[0001] The invention belongs to the technical field of ultrasonic water meters, and in particular relates to a working frequency detection and tuning method and device for an ultrasonic water meter. Background Art

[0002] As the core of the ultrasonic water meter's measurement function, the ultrasonic transducer can realize the mutual conversion of electrical and acoustic signals of specific frequencies. The water flow rate is calculated by the time difference between the electric and acoustic signals sent and received by a pair of transducers, and the purpose of water metering is achieved by combining the cross-sectional area of ​​the pipe section. However, as time goes by and the use environment changes, the frequency of the transducer shifts, causing the transducer performance to deteriorate, which will lead to reduced measurement accuracy and stability of the water meter, and even mismeasurement in static water conditions and discrepancies between the measurement value and the actual flow rate. Usually, the only way to deal with this is to replace the water meter on site or make adjustments and corrections. However, these methods will not only affect the user experience, but may also lead to inaccurate measurement, while also increasing maintenance costs. Summary of the invention

[0003] In order to solve the above problems in the prior art, the present invention provides a method for detecting and tuning the working frequency of an ultrasonic water meter, the method comprising: 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 working frequency deviation state, the real-time working frequency F of the transducer is Sn With the initial frequency F Cn The difference is used to control the ultrasonic water meter to correct the operating frequency of the transducer through a tuning matching circuit.

[0004] On the basis of the above scheme, the step of obtaining the echo signal data of the ultrasonic water meter includes: 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.

[0005] Based on the above solution, judging whether the ultrasonic water meter is in a working 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; Based on the above scheme, the operating frequency offset state also includes determining the direction of the frequency offset and determining the 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.

[0006] Based on the above solution, the tuning and matching circuit includes: 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.

[0007] The present invention also provides an ultrasonic water meter, comprising an UP transducer, a DOWN transducer, a TDC metering chip and a tuning and matching circuit. The ultrasonic water meter uses the method provided by the above scheme to perform working frequency detection and tuning.

[0008] Compared with the prior art, the present invention has the following beneficial effects: by online acquisition and judgment of the working frequency of the transducer and adjusting the value of the capacitor or inductor in the circuit to correct the frequency deviation of the transducer, the problem of different degrees of aging of the transducer of the ultrasonic water meter during use, which causes the water meter measurement value to be higher or lower than the actual flow rate, is solved. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 This is a schematic diagram of the measurement principle of an ultrasonic water meter; Figure 2 This is the equivalent circuit diagram of the measurement principle of the ultrasonic water meter; Figure 3 is a flow chart of the detection and tuning method of the present invention; Figure 4 A detection and tuning flow chart of an embodiment of the present invention; Figure 5 This is a schematic diagram of the echo received by the metering chip; Figure 6 is a schematic diagram of a tuning and matching circuit; Figure 7 is a tuning flow chart of an embodiment of the present invention; Figure 8 A tuning and matching circuit according to an embodiment of the present invention; Fig. 9 A comparison diagram of frequency ratio curves in one embodiment of the present invention; DETAILED DESCRIPTION The invention is further described below in conjunction with specific embodiments.

[0010] like Figure 1 As shown in the figure, the ultrasonic water meter contains an upstream (UP) transducer and a downstream (DOWN) transducer. The excitation end (TX) and the receiving end (RX) of the TDC (Time-to-Digital Converter) metering module are connected to the transducers respectively. The excitation end of the metering module sends 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 signal and propagates through the water flow. The DOWN transducer receives the acoustic signal and converts it into an electrical signal. After passing through the pull-up bias voltage and power amplifier inside the TDC metering chip, the signal reaches the receiving end of the TDC metering chip.

[0011] According to the excitation Fs from the metering chip, both UP and DOWN transducers can be regarded as equivalent circuits composed of resistors, capacitors and inductors with a resonant frequency of about Fs, such as Figure 2As shown, the equivalent circuit of the UP transducer is UL1, UC1, UR1 connected in series and then connected in parallel with UC0, and the equivalent circuit of the DOWN transducer is DL1, DC1, DR1 connected in series and then connected in parallel with DC0. Therefore, the transducer has two resonant frequencies: the series resonant frequency and the parallel resonant frequency. The values ​​of its resistance, capacitance and inductance will change with the use time and use environment, causing the resonant frequency of the transducer itself to shift.

[0012] If the flight time from the UP transducer transmitting signal to the DOWN transducer receiving signal is t1, and the flight time from the DOWN transducer transmitting signal to the UP transducer receiving signal is t2, and the time difference between the two is Δt, then the ultrasonic water meter can calculate the water consumption based on 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 use time and environmental changes, resulting in inaccurate time difference Δt, and then the ultrasonic water meter will have flow deviation after a period of use.

[0013] In order to solve the above problems, the present invention provides a method for detecting and tuning the working frequency of an ultrasonic water meter, which 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.

[0014] like Figure 3 and Figure 4 As shown, the working frequency detection and tuning method of the present invention includes 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 ; The steps of obtaining the echo signal data of the ultrasonic water meter include: Step S1: The metering chip receives the echo signal and collects the time of each negative-to-positive zero-crossing point after FHL (First High Level), which is recorded as T z1 、T z2 ,…,T Zn ; Specifically, when the UP transducer receives the square wave excitation emitted by the TDC metering chip, it converts electrical energy into mechanical energy and transmits it directly to the DOWN transducer in the form of ultrasound in the water. The DOWN transducer converts the received mechanical energy into an electrical energy signal, the so-called echo signal, which is received by the TDC metering chip.

[0015] like Figure 5 As shown, FHL is the first wave high level, T z1is the time when the first negative-to-positive zero crossing occurs, T z2 It is the time of the second negative to positive zero crossing; Based on step S1, step S2 is executed to calculate the actual cycle time T of each echo. Cn =T Zn+1 -T Zn ; By calculating the actual cycle time of each echo, it lays the foundation for further analysis of the operating frequency of the transducer; Based on step S2, step S3 is executed to obtain the operating frequency F of each echo of the transducer after the FHL first wave. n , where F n =1 / T Cn ; Based on the above steps S1-S3, the parameters in step S4 are obtained: the ultrasonic water meter automatically collects and stores the initial frequency F of each echo after the FHL first wave during factory calibration. Cn During use, the frequency of each echo is collected regularly to obtain the real-time frequency F of the echo. Sn .

[0016] Initial frequency F Cn With real-time frequency F Sn The frequency calculation method is the same, but the state is different. The initial frequency is when the ultrasonic water meter just starts working, that is, the frequency has not shifted, and the real-time frequency is after the ultrasonic water meter has been used for a period of time. At this time, the frequency may or may not shift.

[0017] Then, based on the echo signal data, determining whether the ultrasonic water meter is in an operating frequency deviation state; Determining whether the ultrasonic water meter is in a state of operating frequency deviation includes: determining whether the operating frequency of the transducer is offset, when ABS(F Sn -F Cn )>F limit When the operating frequency is judged to have shifted, F limit is the offset threshold; When the ultrasonic water meter is in a working frequency deviation state, the real-time working frequency F of the transducer is Sn With the initial frequency F Cn The ultrasonic water meter is controlled to correct the operating frequency of the transducer through a tuning and matching circuit, and if no offset occurs, the detection is terminated.

[0018] like Figure 6As shown, the tuning and matching circuit includes an adjustable inductor, a fixed capacitor or an adjustable capacitor in parallel or in series, and the tuning and matching circuit is located on the signal path of the UP transducer and the DOWN transducer, and the adjustable inductor, the fixed capacitor and the adjustable capacitor are connected in parallel or in series, and there are switches connected in series with the adjustable inductor, the fixed capacitor and the adjustable capacitor respectively, and the appropriate circuit elements are selected according to the direction of the frequency offset, and the corresponding switches are closed. And for the adjustable capacitors and inductors connected in parallel or in series, the offset of the transducer operating frequency is reduced to the set frequency offset threshold value by real-time adjustment, so as to realize the online calibration of the frequency offset. Therefore, according to the present invention, no matter how the frequency is offset, it can be corrected by the tuning and matching circuit.

[0019] According to one embodiment of the present invention, Figure 7 As shown in the figure, by judging the offset direction of the transducer operating frequency, a suitable tuning and matching circuit is selected. If the real-time frequency is greater than the initial frequency, it is a positive offset, otherwise it is a reverse offset. When F Sn -F Cn >F limit When F Sn -F Cn <F limit When the frequency reverse shift is too large, the series capacitance of the transmitting path is reduced.

[0020] Specifically, Figure 8 As shown, an adjustable capacitor UC is connected in series in the transmitting path. S , connect an adjustable capacitor DC in parallel on the receiving path L When 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.

[0021] 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.

[0022] like Fig. 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. sThe 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. 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.

[0027] Although the above describes the specific implementation methods of the present invention, it is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art on the basis of the technical solution of the present invention without creative work are still within the scope of protection 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 working frequency deviation state, the real-time working frequency F of the transducer is Sn With the initial frequency F Cn The difference is used to control the ultrasonic water meter to correct the operating frequency of the transducer through a tuning matching circuit.

2. The method for detecting and tuning the working frequency of an ultrasonic water meter according to claim 1, characterized in that: 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.

3. 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.

4. The method for detecting and tuning the working frequency of an ultrasonic water meter according to claim 3, 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.

5. 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.

6. 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 5 to perform working frequency detection and tuning.

Images