Pipe absolute liquid level measuring device

Abstract

The application provides a pipeline absolute liquid level measuring device, comprising: an ultrasonic probe, an ultrasonic liquid level measuring circuit, a GPS-RTK module and a CPU control circuit, the CPU control circuit is electrically connected with the ultrasonic liquid level measuring circuit and the GPS-RTK module respectively, and the ultrasonic probe is electrically connected with the ultrasonic liquid level measuring circuit; the ultrasonic liquid level measuring circuit comprises an ultrasonic transmitting circuit and an ultrasonic echo receiving circuit, the transmitting power of the ultrasonic probe is adjusted through the ultrasonic transmitting circuit according to the measuring distance, and the ultrasonic echo receiving circuit carries out digital processing on ultrasonic echo data; the GPS-RTK module obtains the ground elevation value of a measuring point; the CPU control circuit calculates relative liquid level height data according to the digital ultrasonic echo data, and obtains the absolute height data of the liquid level by subtracting the relative liquid level height data from the ground elevation value. The application combines ultrasonic liquid level measurement and high-precision GPS-RTK elevation data to quickly obtain the absolute liquid level height data of the pipeline liquid surface relative to the altitude.

Description

Technical Field

[0001] This invention relates to the technical field of liquid level measurement, and more specifically, to a device for measuring the absolute liquid level of a pipeline. Background Technology

[0002] With the acceleration of urbanization, the construction of municipal public infrastructure has developed rapidly, and the management and safe operation of facilities have become increasingly complex. Maintaining the safe operation of cities has become an important task for city managers. At present, due to the relatively backward management methods, lack of complete facility information and effective safety monitoring and early warning mechanisms, many accidents and dangers cannot be detected and dealt with in advance, posing hidden dangers to people's normal life and the safe operation of the city.

[0003] Currently, the common method for measuring the liquid level in underground pipe networks is to install measuring devices at manhole openings. However, this method only measures the relative height of the liquid level at that specific manhole opening, i.e., the distance from the liquid level to the manhole. Since numerous manholes are installed in urban underground pipe networks, and the location and depth of each manhole vary, the data obtained from each manhole are inconsistent, causing inconvenience for monitoring and managing the liquid level of the entire underground pipe network. Therefore, a measuring device capable of reflecting the absolute water level of the underground pipe network is needed. Summary of the Invention

[0004] In view of the deficiencies in the prior art, the purpose of this invention is to provide a pipeline absolute liquid level measuring device.

[0005] According to the present invention, a pipeline absolute liquid level measuring device includes: an ultrasonic probe, an ultrasonic liquid level measuring circuit, a GPS-RTK module, and a CPU control circuit. The CPU control circuit is electrically connected to the ultrasonic liquid level measuring circuit and the GPS-RTK module, respectively, and the ultrasonic probe is electrically connected to the ultrasonic liquid level measuring circuit.

[0006] The ultrasonic liquid level measurement circuit includes an ultrasonic transmitting circuit and an ultrasonic echo receiving circuit. The transmitting power of the ultrasonic probe is adjusted by the ultrasonic transmitting circuit according to the measurement distance, and the ultrasonic echo receiving circuit performs digital processing on the ultrasonic echo data.

[0007] The GPS-RTK module acquires the ground elevation value of the measurement point;

[0008] The CPU control circuit calculates the relative liquid level height data based on the digitized ultrasonic echo data, and subtracts the relative liquid level height data from the ground elevation value to obtain the absolute liquid level height data.

[0009] Preferably, the ground elevation value is obtained by subtracting the fixed distance from the measurement point to the GPS-RTK module from the altitude of the GPS-RTK module acquisition device.

[0010] Preferably, the ultrasonic transmitting circuit includes a DAC programmable voltage signal, a programmable boost power supply, an ultrasonic power driving circuit, a DDS ultrasonic signal generating circuit, and a gated logic signal generating circuit;

[0011] The DAC programmable voltage signal is electrically connected to the CPU control circuit and the programmable boost power supply, respectively. The programmable boost power supply is electrically connected to the ultrasonic power drive circuit. The DDS ultrasonic signal generation circuit is electrically connected to the CPU control circuit and the gated logic signal generation circuit, respectively. The gated logic signal generation circuit is electrically connected to the ultrasonic power drive circuit.

[0012] Preferably, the DAC programmable voltage signal generates a voltage scanning signal from low to high according to the instructions of the CPU control circuit, the programmable boost power supply generates a voltage signal of corresponding amplitude according to the voltage scanning signal and sends it to the ultrasonic power drive circuit, and the ultrasonic power drive circuit adjusts the transmission power of the ultrasonic probe according to the voltage signal.

[0013] Preferably, the ultrasonic echo receiving circuit includes an AD conversion circuit, a narrowband bandpass filter circuit, and a pre-differential amplifier circuit;

[0014] The AD conversion circuit is electrically connected to the CPU control circuit and the narrowband bandpass filter circuit, respectively. The pre-differential amplifier circuit is electrically connected to the narrowband bandpass filter circuit and the pre-differential amplifier circuit is electrically connected to the ultrasonic probe.

[0015] Preferably, the digital processing involves amplifying the ultrasonic echo signal using the pre-amplifier differential amplifier circuit, filtering the amplified ultrasonic echo signal using the narrowband bandpass filter circuit, and converting the ultrasonic echo signal into a digital signal using the AD conversion circuit.

[0016] Preferably, the ultrasonic power drive circuit includes an H-bridge drive circuit and an isolation diode. The H-bridge drive circuit is electrically connected to the positive and negative terminals of the ultrasonic probe, and the isolation diode is connected in series between the H-bridge drive circuit and the positive and negative terminals of the ultrasonic probe.

[0017] The positive terminal of the H-bridge drive circuit is connected to a programmable boost power supply, and the negative terminal of the H-bridge drive circuit is grounded. When the ultrasonic probe switches from the transmitting state to the receiving state, it is grounded through the negative terminal of the H-bridge drive circuit.

[0018] Preferably, the H-bridge drive circuit includes MOSFETs Q1, Q2, Q3, and Q4;

[0019] The MOS transistors Q1 and Q2 are connected in series. The drain of the MOS transistor Q1 is connected to a programmable boost power supply, and the source of the MOS transistor Q2 is grounded. The source of the MOS transistor Q1 and the drain of the MOS transistor Q2 are electrically connected to the positive / negative terminal of the ultrasonic probe S1 through an isolation diode.

[0020] The MOS transistors Q3 and Q4 are connected in series. The drain of the MOS transistor Q3 is connected to the programmable boost power supply, and the source of the MOS transistor Q4 is grounded. The source of the MOS transistor Q3 and the drain of the MOS transistor Q4 are electrically connected to the negative / positive terminal of the ultrasonic probe S1 through an isolation diode.

[0021] When the ultrasonic probe S1 finishes emitting a pulse, the MOS transistors Q2 and Q4 are turned on, and the positive and negative terminals of the ultrasonic probe S1 are grounded through the isolation diode.

[0022] The gates of MOSFETs Q1, Q2, Q3, and Q4 are electrically connected to the gate logic signal generation circuit via an H-bridge controller.

[0023] Preferably, a pre-receiving circuit is provided between the ultrasonic probe and the pre-differential amplifier circuit;

[0024] The front-end receiving circuit includes an RC circuit and a clamping diode D3, as well as capacitors C1 and C2, resistors R1 and R2.

[0025] The capacitor C1 is connected in series with the resistor R1, and the other end of the capacitor C1 is connected to the positive / negative terminal of the ultrasonic probe;

[0026] The capacitor C2 and the resistor R2 are connected in series, and the other end of the capacitor C2 is connected to the negative / positive terminal of the ultrasonic probe;

[0027] The two ends of the clamping diode D3 are electrically connected to the other ends of the resistor R1 and the other ends of the resistor R2, respectively.

[0028] The other end of resistor R1 and the other end of resistor R2 are electrically connected to the pre-differential amplifier circuit.

[0029] Preferably, the method for adjusting the transmission power of the ultrasonic probe includes:

[0030] Step S1: Receive and demodulate the ultrasonic echo, generate digital quantized waveform data, and determine whether the waveform amplitude is within the effective recognition range;

[0031] Step S2: For waveform amplitudes less than the effective recognition range, increase the transmission power of the ultrasonic probe and proceed to step S1; for waveform amplitudes greater than the effective recognition range, decrease the transmission power of the ultrasonic probe and proceed to step S1; for waveform amplitudes within the effective recognition range, use the transmission power for measurement.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] 1. This invention combines ultrasonic level measurement with high-precision GPS-RTK elevation data, which can not only quickly obtain multiple measurement results in one measurement, including the relative liquid level height from the wellhead to the water surface downhole, but also simultaneously measure the vertical elevation data of the wellhead ground and calculate the absolute liquid level height data of the downhole liquid surface relative to the altitude or geoid, thus ignoring the influence of ground elevation undulations.

[0034] 2. This invention can analyze and compare data from multiple points within a region by measuring the absolute liquid level data of the pipeline, quickly determine the dredging status of the underground pipe network, and quickly locate the location of the blockage in the faulty pipeline.

[0035] 3. This invention adopts a single-probe transmit / receive switching control method, which perfectly solves the mutual conflict and influence between transmitting high voltage and receiving weak signals.

[0036] 4. The ultrasonic transmission power in this invention employs automatic power control technology, effectively resolving the contradiction between a large measurement range and a small blind zone. Throughout the measurement process, the blind zone distance is dynamically adjusted to an optimal state. This method extends the minimum measurement limit at short distances without affecting the measurement limit at long distances, significantly improving the measurement effect at close range.

[0037] Other beneficial effects of the present invention will be explained in detail through the introduction of specific technical features and technical solutions in specific embodiments. Those skilled in the art should be able to understand the beneficial technical effects brought about by these technical features and technical solutions through the introduction of these technical features and technical solutions. Attached Figure Description

[0038] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0039] Figure 1 This is a schematic diagram of the absolute liquid level measurement system for pipelines according to the present invention;

[0040] Figure 2 This is a flowchart of the pipeline absolute liquid level measurement method of the present invention;

[0041] Figure 3 This is a circuit topology diagram of the absolute liquid level measuring device for pipelines according to the present invention;

[0042] Figure 4 This is a schematic diagram of the echo demodulation principle in the absolute liquid level measuring device for pipelines of the present invention.

[0043] Figure 5 This is a waveform diagram of the input signal before the addition of random noise in this invention.

[0044] Figure 6 This is a waveform diagram of the input signal after processing with superimposed random noise in this invention;

[0045] Figure 7 This is a structural diagram of the ultrasonic power drive circuit in this invention;

[0046] Figure 8 This is an equivalent circuit diagram of the ultrasonic power drive circuit during state switching in this invention;

[0047] Figure 9 This is a circuit diagram of the ultrasonic power driving circuit in this invention;

[0048] Figure 10 This is a schematic diagram of the original blind zone of the ultrasonic probe in this invention;

[0049] Figure 11 This is a schematic diagram of the blind zone after superimposed interference from the manhole cover in the ultrasonic blind zone of this invention;

[0050] Figure 12 This is a comparison diagram of the ultrasonic blind zone in this invention;

[0051] Figure 13 This is a flowchart of the probe blind zone correction process in this invention;

[0052] Figure 14 This is a flowchart of the ultrasonic probe output power adjustment method in this invention;

[0053] Figure 15 This is a flowchart of the liquid level measurement process in this invention;

[0054] Figure 16 This is a schematic diagram illustrating the measurement effects of different manhole heights in this invention;

[0055] Figure 17 This is a schematic diagram of the absolute liquid level measuring device for pipelines in this invention.

[0056] Explanation of reference numerals in the attached figures:

[0057] 1 ultrasonic probe, 8 measuring instruments

[0058] Ultrasonic liquid level measurement circuit 2, manhole cover small hole 9

[0059] GPS-RTK module 3 Blind zone waveform 10

[0060] Communication module 4, initial ranging starting position 11

[0061] Power supply circuit 5 Target reflected wave 12

[0062] CPU control circuit 6 Blind zone waveform after superimposing manhole cover 13

[0063] Fixed bracket 7, distance measurement starting position 14 after calibration Detailed Implementation

[0064] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0065] This invention discloses a pipeline absolute liquid level measuring device, with reference to Figure 1 As shown, the system includes: an ultrasonic probe 1, an ultrasonic liquid level measurement circuit 2, a GPS-RTK module 3, a communication module 4, a power supply circuit 5, and a CPU control circuit 6. The control module is electrically connected to the ultrasonic probe 1, the GPS-RTK module 3, and the communication module 4. The ultrasonic probe 1 acquires the relative liquid level height data from the measurement point. The GPS-RTK module 3 acquires the ground elevation value of the measurement point, obtained by subtracting a fixed distance from the GPS-RTK module 3 to the altitude of the device acquired by the GPS-RTK module 3. The control module subtracts the relative liquid level height data from the ground elevation value of the measurement point to obtain the absolute liquid level height data, and uploads this absolute height data to the server via the communication module 4. The power supply circuit 5 provides power to the other modules.

[0066] By providing absolute liquid level data to big data systems to build predictive models, key parameters can be identified from evolutionary patterns for quantitative control. This allows for the prediction of pipeline siltation and defects, enabling proactive maintenance and transforming traditional passive maintenance into proactive operation and maintenance, thus achieving systematic and intelligent pipeline operation and maintenance.

[0067] In a preferred embodiment, the GPS-RTK module 3 collects high-precision RTK coordinates, altitude, and Earth ellipsoid height data of the measurement point where the module is located in real time. The control module binds the absolute height data of the liquid level and the positioning data, and uploads the positioning data and absolute height data to the server through the communication module.

[0068] Reference Figure 2 As shown, the steps for measuring the absolute liquid level in a pipeline are as follows:

[0069] Step 1: Start the GPS-RTK module 3 and enter the satellite search mode. At the same time, place the ultrasonic probe 1 at the measurement point directly above the liquid level and wait for the GPS-RTK module 3 to enter the centimeter accuracy mode.

[0070] Step 2: The control module parses the data from GPS-RTK module 3 to obtain the positioning data and altitude data from GPS-RTK module 3;

[0071] Step 3: The control module subtracts the fixed distance from the liquid level measurement point to the GPS-RTK module 3 from the acquired altitude data to obtain the ground elevation value of the liquid level measurement point;

[0072] Step 4: Start ultrasonic probe 1 to obtain the relative liquid level height data from the measurement point to the liquid surface. Subtract the relative liquid level height data from the ground elevation value of the measurement point to obtain the absolute liquid level height data.

[0073] Step 5: Periodically collect absolute liquid level data, and the control module uploads the absolute liquid level data and positioning data to the server.

[0074] Step 6: The big data platform can subscribe to IoT data, and based on the results of multi-point measurements and historical data analysis, it can determine the blockage and defects of underground pipe networks, issue timely warnings and carry out maintenance in advance, realize the systematization and intelligence of pipeline operation and maintenance, and transform traditional passive maintenance into proactive operation and maintenance.

[0075] Reference Figure 3 As shown, the ultrasonic liquid level measurement circuit 2 includes an ultrasonic transmitting circuit and an ultrasonic echo receiving circuit. The transmitting power of the ultrasonic probe 1 is adjusted by the ultrasonic transmitting circuit according to the measurement distance, and the ultrasonic echo receiving circuit performs digital processing on the ultrasonic echo data.

[0076] The ultrasonic transmitting circuit includes a DAC programmable voltage signal, a programmable boost power supply, an ultrasonic power drive circuit, a DDS ultrasonic signal generation circuit, and a gated logic signal generation circuit. The DAC programmable voltage signal is electrically connected to the CPU control circuit 6 and the programmable boost power supply, respectively. The programmable boost power supply is electrically connected to the ultrasonic power drive circuit. The DDS ultrasonic signal generation circuit is electrically connected to the CPU control circuit 6 and the gated logic signal generation circuit, respectively. The gated logic signal generation circuit is electrically connected to the ultrasonic power drive circuit.

[0077] The DAC programmable voltage signal generates a voltage scanning signal from low to high according to the instructions of the CPU control circuit 6. The programmable boost power supply generates a voltage signal of corresponding amplitude to the ultrasonic power drive circuit according to the voltage scanning signal. The ultrasonic power drive circuit adjusts the transmission power of the ultrasonic probe 1 according to the voltage signal.

[0078] The ultrasonic echo receiving circuit includes an AD conversion circuit, a narrowband bandpass filter circuit, and a pre-differential amplifier circuit. The AD conversion circuit is electrically connected to the CPU control circuit 6 and the narrowband bandpass filter circuit, respectively. The pre-differential amplifier circuit is electrically connected to the narrowband bandpass filter circuit and the ultrasonic probe 1.

[0079] The digital processing involves amplifying the ultrasonic echo signal using the pre-amplifier differential amplifier circuit, filtering the amplified ultrasonic echo signal using the narrowband bandpass filter circuit, and converting the ultrasonic echo signal into a digital signal using the AD conversion circuit.

[0080] Because the ultrasonic probe 1 is connected via a long cable, it is easily coupled with various electromagnetic noises in the environment. The pre-amplifier stage has the greatest impact on the signal-to-noise ratio of the entire receiving system. Differential amplifier circuits have a higher common-mode rejection ratio than ordinary single-ended amplifier circuits, which can minimize noise coupling in complex electromagnetic environments. Therefore, this invention uses a high-speed instrumentation amplifier circuit as the pre-amplifier. The subsequent stage uses a narrowband Butterworth bandpass filter to further amplify the signal amplified by the pre-amplifier stage, significantly boosting the useful signal and attenuating the useless signal, further improving the signal-to-noise ratio and providing a reliable signal to the subsequent AD conversion circuit.

[0081] Echo demodulation also employs digital correlation detection. Correlation detection only identifies and amplifies the frequency components of interest, while attenuating unrelated noise or interference frequencies. This allows for the extraction of effective signal components from strong interference. The principle is explained in [link to documentation]. Figure 4 A reference signal with the same frequency as the transmitted waveform is generated locally. This reference signal is multiplied point by point with the input signal in a multiplier. The product is then integrated in an integrator, and the integrated data is averaged in a divider. The result after correlation operations only amplifies frequency components that are the same frequency as or correlated with the reference signal. Uncorrelated noise is attenuated during continuous integration and averaging.

[0082] The algorithm was tested using a VC++ program written on a host computer, and the results are verified as follows. Figure 5 It is the input signal before processing with added random noise. Figure 6 This is the processed waveform, which shows that it greatly attenuates irrelevant noise and amplifies only the useful signal, significantly improving the signal-to-noise ratio. Subsequent identification only requires the software to perform a maximum value search on the demodulated signal and calculate the echo distance based on the location of the maximum value.

[0083] This device employs a single ultrasonic probe for time-division multiplexing of ultrasonic pulse transmission and reception, offering advantages such as low hardware cost, high integration, and simple deployment. Since the ultrasonic probe typically has a parasitic capacitance of several thousand pF, if it immediately switches to receiving mode after transmitting a pulse, the high-voltage charge on the probe requires a long time to discharge. During this period, residual charge on the probe will be superimposed on the input of the differential amplifier in a mixed manner of common-mode and differential-mode. To address potential interference during state transitions of the single ultrasonic probe, the ultrasonic power drive circuit in this device incorporates charge blocking.

[0084] Reference Figure 7 As shown, the ultrasonic power drive circuit includes an H-bridge drive circuit and an isolation diode. The H-bridge drive circuit is electrically connected to the positive and negative terminals of the ultrasonic probe 1. The ultrasonic probe 1 is as follows: Figure 7 As shown in S1, the isolation diode is connected in series between the H-bridge drive circuit and the positive and negative terminals of the ultrasonic probe 1; the positive terminal of the H-bridge drive circuit is connected to the programmable boost power supply, the negative terminal of the H-bridge drive circuit is grounded, and the ultrasonic probe 1 is grounded through the negative terminal of the H-bridge drive circuit when switching from the transmitting state to the receiving state.

[0085] The H-bridge drive circuit includes MOSFETs Q1, Q2, Q3, and Q4; MOSFETs Q1 and Q2 are connected in series, the drain of MOSFET Q1 is connected to a programmable boost power supply, the source of MOSFET Q2 is grounded, and the source of MOSFET Q1 and the drain of MOSFET Q2 are electrically connected to the positive / negative terminal of the ultrasonic probe 1S1 through an isolation diode.

[0086] The MOS transistors Q3 and Q4 are connected in series. The drain of the MOS transistor Q3 is connected to a programmable boost power supply, and the source of the MOS transistor Q4 is grounded. The source of the MOS transistor Q3 and the drain of the MOS transistor Q4 are electrically connected to the negative / positive terminal of the ultrasonic probe 1S1 through an isolation diode.

[0087] When the ultrasonic probe 1S1 finishes emitting a pulse, the MOS transistors Q2 and Q4 are turned on, and the positive and negative terminals of the ultrasonic probe 1S1 are grounded through an isolation diode; the gates of the MOS transistors Q1, Q2, Q3, and Q4 are electrically connected to the gate logic signal generation circuit through an H-bridge controller.

[0088] A pre-receiving circuit is provided between the ultrasonic probe 1 and the pre-differential amplifier circuit; the pre-receiving circuit includes an RC circuit and a clamping diode D3, as well as capacitors C1 and C2, resistors R1 and R2.

[0089] The capacitor C1 is connected in series with the resistor R1, and the other end of the capacitor C1 is connected to the positive / negative terminal of the ultrasound probe 1; the capacitor C2 is connected in series with the resistor R2, and the other end of the capacitor C2 is connected to the negative / positive terminal of the ultrasound probe 1; the two ends of the clamping diode D3 are electrically connected to the other ends of the resistor R1 and the other ends of the resistor R2, respectively; the other ends of the resistor R1 and the other ends of the resistor R2 are electrically connected to the pre-differential amplifier circuit.

[0090] When transmitting an ultrasonic pulse, the ultrasonic probe 1S11 is driven by pulse power through Q1, Q2, Q3, Q4 of the H-bridge drive circuit and isolation diodes D1 and D2, exciting it to transmit ultrasonic pulse waves. When receiving the echo, the echo signal sensed by the probe is coupled to the differential amplifier U1 for differential amplification through the high-impedance RC network of C1, C2, R1, R2 and the clamping circuit of D3. When the ultrasonic probe 1S1 finishes transmitting the pulse, the two low-side MOSFETs Q2 and Q4 of the H-bridge drive circuit are immediately forced to conduct, as shown in the equivalent diagram below. Figure 8 The residual charge on the ultrasonic probe 1S1 is rapidly discharged to ground through MOSFETs Q2 and Q4. In this way, the residual high voltage on the ultrasonic probe 1S1 is rapidly discharged through isolation diodes D1 and D2. Since the isolation diodes have a forward voltage drop of several hundred millivolts, this voltage drop plays a good role in isolating the echo signal. For weak echo signals in the range of μV or several mV, the amplitude is much lower than the forward voltage drop of D1 and D2. Therefore, D1 and D2 are high impedance to the echo signal and cannot be attenuated by short-circuiting Q2 and Q4. This perfectly achieves seamless switching between single probe transmission and reception.

[0091] Reference Figure 9 As shown, the H-bridge controller uses the IR2101STRPBF chip. H-bridge controller U2 is connected to the gates of MOSFETs Q1 and Q2, and H-bridge controller U3 is connected to the gates of MOSFETs Q3 and Q4. The HIN and LIN ports of the H-bridge controller are electrically connected to the gate logic signal generation circuit to obtain control signals. The VCC port of the H-bridge controller is connected to VCC, and the COM port of the H-bridge controller is grounded. A capacitor is connected in series between the VCC port and the COM port. The HO port of the H-bridge controller is connected to the gate of MOSFET Q1. Bootstrap diodes D4 and D5 are connected between the VB port and the VCC port of the H-bridge controller, with the anode of the bootstrap diode connected to the VCC port. The VS port of the H-bridge controller is connected to the source of MOSFET Q1. Bootstrap capacitors C3 and C4 are connected in series between the VB port and the VS port. The LO port of the H-bridge controller is connected to the gate of MOSFET Q2.

[0092] The TTL timing control signal from the control unit provides control signals to the H-bridge controllers U1 and U2 through the four input terminals H1, H2, L1, and L2. The output level of the H-bridge controller is passed through the bootstrap diode and bootstrap capacitor to obtain the drive level of the high-side MOS transistor of the H-bridge, thereby realizing level matching and driving of the drive bridge composed of MOS transistors.

[0093] After the ultrasonic pulse is emitted, the control unit provides a high level to L1 and L2 and a low level to H1 and H2, which turns on the two low-side MOSFETs Q2 and Q4 and turns off the high-side MOSFETs Q1 and Q3. In this way, the residual charge on the ultrasonic probe 1S1S1 is discharged instantaneously by Q2 and Q4, achieving the effect of forced blanking.

[0094] To simplify the measurement process, the ultrasonic probe 1 in this device is placed directly at the small hole 9 in the manhole cover during measurement, and the measurement is performed through the hole. However, this increases the echo time of the probe at close range due to the thickness of the manhole cover, leading to misinterpretation and causing data errors or instability. Therefore, it is necessary to first address the impact of the small hole on the blind zone of ultrasonic ranging.

[0095] After ultrasonic probe 1 emits an ultrasonic pulse, due to the "tailing" characteristic of its mechanical vibration, a damped oscillation will occur for a certain period after the driving pulse ends. This damped oscillation, once received by the receiving circuit, will affect the echo recognition in near-field detection. Therefore, ultrasonic detection always has a "blind zone," such as... Figure 10 As shown in waveform 10 in the middle blind zone, after a period of oscillation, it gradually decays to zero. The effective recognition range of the probe begins at this position, which is the original ranging starting position 11.

[0096] When it is necessary to measure the liquid level through the small hole 9 in the well cover, the small hole 9 and the relatively thick thickness of the well cover will cause near-field reflection of the ultrasonic waves radiated by the ultrasonic probe 1. The reflected wave, combined with the waveform 10 in the blind zone, will produce a result similar to... Figure 11 Waveform 13 of the blind zone after overlaying the manhole cover, from Figure 11 As can be seen, the position where the blind zone waveform 13 decays to zero after the manhole cover is superimposed will be extended backward compared to the original ranging starting position 11. Therefore, in order to measure the liquid level normally through the manhole cover, this working condition must be recalibrated to obtain the calibrated ranging starting position 14, so that the result can be measured reliably and stably.

[0097] Figure 12 The data compares the blind zone data collected by the ultrasonic probe 1 under two conditions: without and with manhole covers. It can be seen that the blind zone distance increases after the manhole cover is added.

[0098] Probe blind zone correction steps: Adjust the ultrasonic transmission power step by step within the power range of the ultrasonic ranging sensor, take the last data in the echo data that is less than the threshold as the blind zone critical point, measure the blind zone critical point of the ultrasonic ranging sensor under different transmission powers, and store it; the ultrasonic ranging sensor is located at the small hole 9 of the manhole cover.

[0099] Specifically, refer to Figure 13 As shown, the blind spot correction process is as follows:

[0100] Step A1: Set the ultrasonic ranging sensor at the small hole 9 on the manhole cover and set the transmission power of the ultrasonic ranging sensor to the lowest setting;

[0101] Step A2: The ultrasonic ranging sensor emits an ultrasonic pulse, receives the echo within a specified time at that power, and performs continuous digital quantization to convert the echo amplitude into digital data.

[0102] Step A3: Compare the echo data point by point with the threshold, and take the last data point in the echo data set that is less than the threshold as the blind zone critical point under the transmission power. Record the location of the data and save it.

[0103] Step A4: Increase the transmission power of the ultrasonic ranging sensor by one level, repeat steps A2-A3 until the blind zone critical point corresponding to the maximum transmission power is recorded, then reduce the power of the ultrasonic ranging sensor to zero and end the calibration.

[0104] During the calibration process, the ultrasonic probe 1 is placed close to the small hole 9 in the manhole cover, with the hole facing an open area or the sky. A calibration command is sent to the device, and the device automatically emits ultrasonic signals with continuously increasing power, starting from the minimum ultrasonic transmission power and increasing to the maximum power. Simultaneously, it continuously samples and receives echoes, recording the blind zone critical point of the echoes in the device's memory as a reference value for future measurements. Subsequent measurements can then be performed by finding the corresponding blind zone distance based on the current ultrasonic transmission power, thus avoiding interference from reflected noise caused by the manhole cover and accurately measuring the liquid level. The probe blind zone calibration step is performed when the ultrasonic ranging sensor is used for the first time or when it is replaced.

[0105] After completing the blind zone correction within the full output power range of the ultrasonic probe 1, the CPU control circuit 6 will automatically select the ultrasonic transmission power during measurement. Based on the selected transmission power, the corresponding blind zone critical point is obtained. The blind zone critical point is used as the ranging starting point, and the liquid level height is calculated based on the transmission time of the ultrasonic wave at the blind zone critical point and the liquid surface.

[0106] Reference Figure 14 As shown, the method for adjusting the transmission power of the ultrasonic probe 1 includes:

[0107] Step S0: Adjust the transmission power of ultrasonic probe 1 to emit ultrasonic pulses. During measurement, the initial test power can be set to the minimum value, and the optimal measurement power can be obtained by gradually increasing the ultrasonic power. Alternatively, the initial test power can be set to the maximum value, or any value in the middle of the ultrasonic power range, depending on the actual distance to be measured.

[0108] Step S1: Receive and demodulate the ultrasonic echo, generate digital quantized waveform data, and determine whether the waveform amplitude is within the effective recognition range;

[0109] Step S2: For waveform amplitudes less than the effective recognition range, increase the transmission power of the ultrasonic probe 1 and proceed to step S1; for waveform amplitudes greater than the effective recognition range, decrease the transmission power of the ultrasonic probe 1 and proceed to step S1; for waveform amplitudes within the effective recognition range, use the transmission power for measurement.

[0110] In a preferred embodiment, during ultrasonic measurement, as the output voltage of the programmable boost power supply gradually increases from low to high, the transmission power of the ultrasonic probe 1 gradually increases from zero, and the detection range searches for the target from near to far. When the ultrasonic wave encounters the object being measured, the echo signal reflected is demodulated by the echo receiving and demodulation circuit, and then quantized, calculated, and analyzed by the control unit. If the control unit calculates that the amplitude of the echo signal reaches a reasonable level, the control unit stops further boosting the voltage of the programmable boost power supply, maintains the current voltage amplitude, and starts the ultrasonic time-of-flight calculation program to calculate the measurement result.

[0111] The output voltage step size of the programmable boost power supply is set non-linearly, and the voltage step size is positively correlated with the output voltage value of the programmable boost power supply. At the initial low voltage, because the dead zone has a significant impact on the measurement results, a higher resolution is required, and a smaller step value is selected to increase the voltage subdivision resolution, thereby selecting the optimal transmission power. At high voltage, because the size of the dead zone has a smaller impact on the measurement value, a lower resolution is required, and a higher step value is selected.

[0112] Furthermore, referring to Figure 15 As shown, the liquid level measurement is as follows:

[0113] Step B1: Pass the ultrasonic ranging sensor through the small hole 9 in the manhole cover and emit an ultrasonic pulse. Immediately after the emission is completed, switch to receiving mode, receive and digitally quantize an echo data of about 100ms.

[0114] Step B2: Obtain the critical point of the dead zone under this transmission power as the effective start time for calculating the echo time. Clear the echo data before the effective start time point and demodulate the updated echo data to obtain the peak position.

[0115] Step B3: Determine the peak value. If the peak value is less than the preset value, increase the transmission power of the ultrasonic ranging sensor and return to step B1. If the peak value is greater than the preset value, measure the liquid level based on the peak position.

[0116] In a preferred embodiment, the liquid level measurement is specifically as follows: the time from the effective start time of the ultrasonic pulse to its reflection back to the ultrasonic ranging sensor, plus the blind zone time, is the round-trip flight time t2 of the ultrasonic probe 1 to the target object. Therefore, the distance from the ultrasonic ranging sensor to the liquid level is calculated. V is the speed of ultrasound in air.

[0117] In environments with varying ground elevations, this invention allows for the measurement of liquid levels in vertical pipe shafts, negligibly eliminating the influence of ground elevation differences and yielding accurate absolute liquid level heights. (See also...) Figure 16 As shown, the terrain at well 1 is relatively high. The level gauge measures the elevation H1 of the instrument location and the relative distance D1 from the wellhead to the water surface. The distance from the instrument to ultrasonic probe 1 is fixed at L. Then, the absolute water level values ​​measured at well 1 and well 2 are respectively:

[0118] Absolute liquid level in well 1 = H1 - L - D1;

[0119] Absolute liquid level in well 2 = H2 - L - D2;

[0120] If the two downhole fluid levels are horizontal, the measured absolute fluid level results should be equal, because the difference in elevation between the two locations can be obtained through GPS-RTK and is equal to the difference in relative fluid level measurements. After cancellation, the influence of ground elevation undulations can be ignored.

[0121] The actual product of the pipeline absolute liquid level measuring device disclosed in this invention is shown below. Figure 17 As shown, the device includes a rapid manhole level measurement circuit, a fixed support 7, and a measuring instrument 8. The ultrasonic probe 1 is located at the bottom of the fixed support 7, and the measuring instrument 8 is mounted on the fixed support 7. The ultrasonic transmitting circuit, ultrasonic echo receiving circuit, and CPU control circuit 6 are all housed within the measuring instrument 8. The fixed support 7 can be a tripod, which serves to fix and support the device.

[0122] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. A pipeline absolute liquid level measuring device, characterized in that, include: The ultrasonic probe (1), ultrasonic liquid level measurement circuit (2), GPS-RTK module (3) and CPU control circuit (6) are respectively electrically connected to the ultrasonic liquid level measurement circuit (2) and the GPS-RTK module (3), and the ultrasonic probe (1) is electrically connected to the ultrasonic liquid level measurement circuit (2). The ultrasonic liquid level measurement circuit (2) includes an ultrasonic transmitting circuit and an ultrasonic echo receiving circuit. The transmitting power of the ultrasonic probe (1) is adjusted by the ultrasonic transmitting circuit according to the measurement distance. The ultrasonic echo receiving circuit performs digital processing on the ultrasonic echo data. The GPS-RTK module (3) acquires the ground elevation value of the measurement point; The CPU control circuit (6) calculates the relative liquid level height data based on the digitized ultrasonic echo data, and subtracts the relative liquid level height data from the ground elevation value to obtain the absolute liquid level height data. The ultrasonic transmitting circuit includes a DAC programmable voltage signal, a programmable boost power supply, an ultrasonic power drive circuit, a DDS ultrasonic signal generation circuit, and a gated logic signal generation circuit. The DAC programmable voltage signal is electrically connected to the CPU control circuit (6) and the programmable boost power supply respectively. The programmable boost power supply is electrically connected to the ultrasonic power drive circuit. The DDS ultrasonic signal generation circuit is electrically connected to the CPU control circuit (6) and the gated logic signal generation circuit respectively. The gated logic signal generation circuit is electrically connected to the ultrasonic power drive circuit. The ultrasonic power drive circuit includes an H-bridge drive circuit and an isolation diode. The H-bridge drive circuit is electrically connected to the positive and negative terminals of the ultrasonic probe (1). The isolation diode is connected in series between the H-bridge drive circuit and the positive and negative terminals of the ultrasonic probe (1). The positive terminal of the H-bridge drive circuit is connected to the programmable boost power supply, and the negative terminal of the H-bridge drive circuit is grounded. When the ultrasonic probe (1) switches from the transmitting state to the receiving state, it is grounded through the negative terminal of the H-bridge drive circuit. The H-bridge drive circuit includes MOSFETs Q1, Q2, Q3, and Q4; The MOS transistors Q1 and Q2 are connected in series. The drain of the MOS transistor Q1 is connected to a programmable boost power supply, and the source of the MOS transistor Q2 is grounded. The source of the MOS transistor Q1 and the drain of the MOS transistor Q2 are electrically connected to the positive / negative terminal of the ultrasonic probe (1) S1 through an isolation diode. The MOS transistors Q3 and Q4 are connected in series. The drain of the MOS transistor Q3 is connected to the programmable boost power supply. The source of the MOS transistor Q4 is grounded. The source of the MOS transistor Q3 and the drain of the MOS transistor Q4 are electrically connected to the negative / positive terminal of the ultrasonic probe (1) S1 through an isolation diode. When the ultrasonic probe (1) S1 finishes emitting a pulse, the MOS transistors Q2 and Q4 are turned on, and the positive and negative terminals of the ultrasonic probe (1) S1 are grounded through the isolation diode; The gates of MOSFET Q1, MOSFET Q2, MOSFET Q3, and MOSFET Q4 are electrically connected to the gate logic signal generation circuit via an H-bridge controller. The method for adjusting the emission power of the ultrasonic probe (1) includes: Step S1: Receive and demodulate the ultrasonic echo, generate digital quantized waveform data, and determine whether the waveform amplitude is within the effective recognition range; Step S2: For waveform amplitude less than the effective recognition range, increase the transmission power of the ultrasonic probe (1) and proceed to step S1; for waveform amplitude greater than the effective recognition range, decrease the transmission power of the ultrasonic probe (1) and proceed to step S1; for waveform amplitude within the effective recognition range, use the transmission power for measurement.

2. The pipeline absolute liquid level measuring device according to claim 1, characterized in that, The ground elevation value is obtained by subtracting the fixed distance from the measurement point to the GPS-RTK module (3) from the elevation of the measurement point itself.

3. The pipeline absolute liquid level measuring device according to claim 2, characterized in that, The DAC programmable voltage signal generates a voltage scanning signal from low to high according to the instructions of the CPU control circuit (6). The programmable boost power supply generates a voltage signal of corresponding amplitude to the ultrasonic power drive circuit according to the voltage scanning signal. The ultrasonic power drive circuit adjusts the transmission power of the ultrasonic probe (1) according to the voltage signal.

4. The pipeline absolute liquid level measuring device according to claim 1, characterized in that, The ultrasonic echo receiving circuit includes an AD conversion circuit, a narrowband bandpass filter circuit, and a pre-differential amplifier circuit; The AD conversion circuit is electrically connected to the CPU control circuit (6) and the narrowband bandpass filter circuit respectively. The pre-amplifier circuit is electrically connected to the narrowband bandpass filter circuit and the pre-amplifier circuit is electrically connected to the ultrasonic probe (1).

5. The pipeline absolute liquid level measuring device according to claim 4, characterized in that, The digital processing involves amplifying the ultrasonic echo signal using the pre-amplifier differential amplifier circuit, filtering the amplified ultrasonic echo signal using the narrowband bandpass filter circuit, and converting the ultrasonic echo signal into a digital signal using the AD conversion circuit.

6. The pipeline absolute liquid level measuring device according to claim 4, characterized in that, A pre-receiving circuit is provided between the ultrasonic probe (1) and the pre-differential amplifier circuit; The front-end receiving circuit includes an RC circuit and a clamping diode D3, capacitors C1 and C2, resistors R1 and R2; The capacitor C1 is connected in series with the resistor R1, and the other end of the capacitor C1 is connected to the positive / negative terminal of the ultrasonic probe (1); The capacitor C2 and the resistor R2 are connected in series, and the other end of the capacitor C2 is connected to the negative / positive terminal of the ultrasonic probe (1); The two ends of the clamping diode D3 are electrically connected to the other ends of the resistor R1 and the other ends of the resistor R2, respectively. The other end of resistor R1 and the other end of resistor R2 are electrically connected to the pre-differential amplifier circuit.

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