Rapid sump level measurement method and system

Abstract

The application provides a kind of fast inspection well liquid level measuring method and system, comprising: probe blind area correction step: in the power range of ultrasonic ranging sensor, adjust ultrasonic emission power step by step, the last data less than threshold in echo data is regarded as blind area critical point, the blind area critical point of ultrasonic ranging sensor under different emission power is measured and stored;The ultrasonic ranging sensor is located at the small hole of well lid;Liquid level measuring step: according to the emission power selected when measuring, the corresponding blind area critical point is obtained, the blind area critical point is regarded as the starting point of ranging, and the liquid level height is calculated according to the transmission time of ultrasonic at blind area critical point and liquid surface.By the method of the application, the liquid level height under well can be directly measured through various inspection well covers with holes without opening the well cover, which greatly shortens the time and manpower of measurement operation, and also improves the safety of road operation of workers.

Description

Technical Field

[0001] This invention relates to the technical field of liquid level measurement, specifically to a rapid manhole liquid level measurement method and system. Background Technology

[0002] Currently, there are a large number of underground drainage pipe networks in cities, such as sewage pipe networks and rainwater pipe networks. These underground pipe networks have a manhole every certain distance (e.g., 50 meters). Due to the harsh conditions inside the manholes and the varying water levels, it is difficult to install water level sensors to monitor the water level inside the manholes.

[0003] Chinese patent document CN112729480A discloses an "Integrated Device for Detecting Water Levels in Manholes in a Pipeline". For ease of installation, maintenance, and communication, the main unit is typically installed at the manhole opening. A water level sensor is connected to the lowest water level sensor below the main unit via a water level sensor cable. The water level sensor needs to be submerged in water, indicating that it is a contact-type pressure water level sensor. This presents the following problem: In order to detect the lowest water level, the contact-type pressure water level sensor must be placed at the lowest point of the water level. However, the lowest point of the drainage pipe will inevitably have silt that can clog the water level sensor, which limits the practicality of this technology.

[0004] Conventional ultrasonic liquid level detection equipment can usually only measure data within an open distance. Therefore, the common method is to open the manhole cover and use an ultrasonic ranging device to measure the liquid level at the manhole opening. However, this measurement method is labor-intensive, time-consuming, and not suitable for routine inspection of manholes.

[0005] In my country, conventional rainwater well manhole covers usually have two small holes for opening. If a probe is inserted through these holes, the thickness of the manhole cover will increase the echo time at close range, leading to misinterpretation, data corruption, or instability. Summary of the Invention

[0006] In view of the deficiencies in the existing technology, the purpose of this invention is to provide a rapid manhole liquid level measurement method and system.

[0007] A rapid manhole liquid level measurement method according to the present invention includes:

[0008] Probe blind zone correction steps: Adjust the ultrasonic transmission power step by step within the power range of the ultrasonic ranging sensor, and take the last data point in the echo data that is less than the threshold as the blind zone critical point. Measure the blind zone critical points of the ultrasonic ranging sensor under different transmission powers and store them; the ultrasonic ranging sensor is located at the small hole of the manhole cover.

[0009] Liquid level measurement steps: Based on the selected transmission power during measurement, obtain the corresponding blind zone critical point. The blind zone critical point serves as the ranging starting point. Calculate the liquid level height based on the ultrasonic transmission time between the blind zone critical point and the liquid surface.

[0010] Preferably, the probe blind zone correction step includes:

[0011] Step S1: Place the ultrasonic ranging sensor at the small hole in the manhole cover and set the transmission power of the ultrasonic ranging sensor to the lowest setting;

[0012] Step S2: 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.

[0013] Step S3: 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 position of the data and save it.

[0014] Step S4: Increase the transmission power of the ultrasonic ranging sensor by one level, repeat steps S2-S3 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.

[0015] Preferably, the liquid level measurement step includes:

[0016] Step A1: Pass the ultrasonic ranging sensor through the small hole in the manhole cover and emit an ultrasonic pulse. Immediately after the emission is completed, switch to receiving mode, receive and digitally quantize the echo data for the set duration.

[0017] Step A2: Obtain the critical point of the dead zone under this transmit power as the effective start time for calculating the echo time. Clear the echo data before the effective start time point to zero, and demodulate the updated echo data to obtain the peak position.

[0018] Step A3: 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 A1. If the peak value is greater than the preset value, measure the liquid level based on the peak position.

[0019] Preferably, 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 to the target object. Therefore, the distance from the ultrasonic ranging sensor to the liquid level is... V is the speed of ultrasound in air.

[0020] Preferably, the probe blind zone correction step is performed when the ultrasonic ranging sensor is used for the first time or when it is replaced.

[0021] A rapid manhole liquid level measurement system according to the present invention includes:

[0022] The probe blind zone correction module adjusts the ultrasonic transmission power step by step within the power range of the ultrasonic ranging sensor, and takes the last data point in the echo data that is less than the threshold as the blind zone critical point. The blind zone critical points of the ultrasonic ranging sensor under different transmission powers are measured and stored; the ultrasonic ranging sensor is located at the small hole of the manhole cover.

[0023] Liquid level measurement module: Based on the selected transmission power during measurement, the corresponding blind zone critical point is obtained. The blind zone critical point serves as the ranging starting point, and the liquid level height is calculated based on the transmission time of ultrasound between the blind zone critical point and the liquid surface.

[0024] Preferably, the probe blind zone correction module includes:

[0025] Module M1: Set the ultrasonic ranging sensor at the small hole in the manhole cover and set the ultrasonic ranging sensor's transmission power to the lowest setting;

[0026] Module M2: It emits ultrasonic pulses through an ultrasonic ranging sensor, receives the echoes within a specified time at that power, and performs continuous digital quantization into digital data of the echo amplitude.

[0027] Module M3: Compares each point in the echo data with a threshold, takes the last data point in the set of echo data that is less than the threshold as the blind zone critical point under the transmit power, records the location of the data and saves it;

[0028] Module M4: Increase the transmission power of the ultrasonic ranging sensor by one level, repeat the process from module M2 to module M3 until the blind zone critical point corresponding to the maximum transmission power is recorded, then reset the ultrasonic ranging sensor power to zero and end the calibration.

[0029] Preferably, the liquid level measurement module includes:

[0030] Module A1: Passes the ultrasonic ranging sensor through the small hole in the manhole cover and emits an ultrasonic pulse. After the emission ends, it immediately switches to receiving mode to receive and digitally quantize the echo data for the set duration.

[0031] Module A2: Obtain the critical point of the dead zone under this transmit power as the effective start time for calculating the echo time, clear the echo data before the effective start time point to zero, and demodulate the updated echo data to obtain the peak position;

[0032] Module A3: 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 A1. If the peak value is greater than the preset value, measure the liquid level based on the peak position.

[0033] Preferably, 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 to the target object. Therefore, the distance from the ultrasonic ranging sensor to the liquid level is... V is the speed of ultrasound in air.

[0034] Preferably, the probe blind zone correction module is executed when the ultrasonic ranging sensor is used for the first time or when it is replaced.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] 1. The method of this invention allows for direct measurement of the underground liquid level through various perforated manhole covers without opening the manhole cover. A single operator can complete a measurement in no more than 10 seconds. This significantly reduces the time and manpower required for measurement operations and improves the safety of workers on the road.

[0037] 2. The method of this invention can also make the instrument adaptable to various ultrasonic probes of different specifications and models. Since the blind zone time of probes of different manufacturers, models and powers varies greatly, when the instrument is replaced with a probe of a different model, the blind zone parameters of the current probe can be obtained through the probe automatic scanning function and saved in the instrument memory. This makes the instrument almost perfectly match any probe of the same frequency.

[0038] 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

[0039] 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:

[0040] Figure 1 This is a flowchart of the probe blind zone correction process in the rapid manhole liquid level measurement method disclosed in this invention;

[0041] Figure 2 This is a flowchart of the rapid manhole liquid level measurement method disclosed in this invention;

[0042] Figure 3 This is a topology diagram of the rapid manhole liquid level measurement circuit disclosed in this invention;

[0043] Figure 4 This is a schematic diagram of the rapid manhole liquid level measurement device disclosed in this invention;

[0044] Figure 5 This is a schematic diagram of the original blind zone of the ultrasonic probe in this invention.

[0045] Figure 6 This is a schematic diagram of the blind zone after superimposed interference from the manhole cover in the ultrasonic blind zone of this invention;

[0046] Figure 7 This is a comparison diagram of the ultrasonic blind zone in this invention.

[0047] Explanation of reference numerals in the attached figures:

[0048] Ultrasonic probe 1, initial ranging starting position 6

[0049] Fixed support 2 Target reflected wave 7

[0050] Measuring instrument 3: Waveform of the blind zone after overlaying the manhole cover 8

[0051] Manhole cover hole 4, starting position for distance measurement after calibration 9

[0052] Blind zone waveform 5 Detailed Implementation

[0053] 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.

[0054] This invention provides a rapid method for measuring manhole liquid level, comprising:

[0055] Probe blind zone correction steps: Adjust the ultrasonic transmission power step by step within the power range of the ultrasonic ranging sensor, and take the last data point in the echo data that is less than the threshold as the blind zone critical point. Measure the blind zone critical points of the ultrasonic ranging sensor under different transmission powers and store them; the ultrasonic ranging sensor is located at the small hole of the manhole cover.

[0056] Liquid level measurement steps: Based on the selected transmission power during measurement, obtain the corresponding blind zone critical point. The blind zone critical point serves as the ranging starting point. Calculate the liquid level height based on the ultrasonic transmission time between the blind zone critical point and the liquid surface.

[0057] In this embodiment, the ultrasonic ranging sensor can be an ultrasonic probe. During the calibration process, the ultrasonic probe is placed close to the small hole 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 blind zone reference value for future measurements. Subsequent measurements only require finding the corresponding blind zone distance based on the current ultrasonic transmission power to correctly avoid the reflection noise interference caused by the manhole cover and measure the liquid level normally. The probe blind zone calibration step is performed when the ultrasonic ranging sensor is used for the first time or when it is replaced.

[0058] In a preferred embodiment, refer to Figure 1 As shown, the probe blind zone correction step includes:

[0059] Step S1: Place the ultrasonic ranging sensor at the small hole in the manhole cover and set the transmission power of the ultrasonic ranging sensor to the lowest setting;

[0060] Step S2: 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.

[0061] Step S3: 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 position of the data and save it.

[0062] Step S4: Increase the transmission power of the ultrasonic ranging sensor by one level, repeat steps S2-S3 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.

[0063] The ultrasonic measurement circuit employs automatic power control (APC) technology to ensure that the ultrasonic sensor's measurement range meets the requirements of a large range while minimizing the measurement blind zone. At the same time, the output power of the ultrasonic pulse is continuously adjustable from zero to its maximum value.

[0064] In a preferred embodiment, referring to the figure, the liquid level measurement step includes:

[0065] Step A1: Pass the ultrasonic ranging sensor through the small hole 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.

[0066] Step A2: Obtain the critical point of the blind 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 to zero, and demodulate the updated echo data to obtain the peak position. The peak position is the echo reflected from the target position. When measuring the liquid surface, the target position is the liquid surface.

[0067] Step A3: 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 A1. If the peak value is greater than the preset value, measure the liquid level based on the peak position.

[0068] 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 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.

[0069] The present invention also provides a rapid manhole liquid level measurement system, which can be implemented by executing the process steps of the rapid manhole liquid level measurement method. That is, those skilled in the art can understand the rapid manhole liquid level measurement method as a preferred embodiment of the rapid manhole liquid level measurement system.

[0070] This invention also discloses a rapid manhole liquid level measurement system, comprising:

[0071] The probe blind zone correction module adjusts the ultrasonic transmission power step by step within the power range of the ultrasonic ranging sensor, and takes the last data point in the echo data that is less than the threshold as the blind zone critical point. The blind zone critical points of the ultrasonic ranging sensor under different transmission powers are measured and stored; the ultrasonic ranging sensor is located at the small hole of the manhole cover.

[0072] Liquid level measurement module: Based on the selected transmission power during measurement, the corresponding blind zone critical point is obtained. The blind zone critical point serves as the ranging starting point, and the liquid level height is calculated based on the transmission time of ultrasound between the blind zone critical point and the liquid surface.

[0073] The probe blind zone correction module is executed when the ultrasonic ranging sensor is used for the first time or when it is replaced.

[0074] In a preferred embodiment, the probe blind zone correction module includes:

[0075] Module M1: Set the ultrasonic ranging sensor at the small hole in the manhole cover and set the ultrasonic ranging sensor's transmission power to the lowest setting;

[0076] Module M2: It emits ultrasonic pulses through an ultrasonic ranging sensor, receives the echoes within a specified time at that power, and performs continuous digital quantization into digital data of the echo amplitude.

[0077] Module M3: Compares each point in the echo data with a threshold, takes the last data point in the set of echo data that is less than the threshold as the blind zone critical point under the transmit power, records the location of the data and saves it;

[0078] Module M4: Increase the transmission power of the ultrasonic ranging sensor by one level, repeat the process from module M2 to module M3 until the blind zone critical point corresponding to the maximum transmission power is recorded, then reset the ultrasonic ranging sensor power to zero and end the calibration.

[0079] In a preferred embodiment, the liquid level measurement module includes:

[0080] Module A1: Passes the ultrasonic ranging sensor through the small hole in the manhole cover and emits an ultrasonic pulse. After the emission ends, it immediately switches to receiving mode to receive and digitally quantize the echo data for the set duration.

[0081] Module A2: Obtain the critical point of the dead zone under this transmit power as the effective start time for calculating the echo time, clear the echo data before the effective start time point to zero, and demodulate the updated echo data to obtain the peak position;

[0082] Module A3: 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 A1. If the peak value is greater than the preset value, measure the liquid level based on the peak position.

[0083] 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, equals the round-trip flight time t2 of the ultrasonic probe to the target object. Therefore, the distance from the ultrasonic ranging sensor to the liquid level is... V is the speed of ultrasound in air.

[0084] This invention also discloses a rapid manhole liquid level measurement circuit. Conventional ultrasonic liquid level detection equipment can typically only measure data within an open distance. If the probe is inserted through a small hole in the manhole cover, the thickness of the manhole cover increases the echo time of the probe at close range, leading to misjudgments and causing data corruption or instability. The device of this invention employs an ultrasonic detection technology that can automatically scan and correct the blind zone distance of the ultrasonic probe 1, enabling rapid liquid level measurement without opening the manhole cover, using a small hole 4 in the manhole cover.

[0085] This invention refers to Figure 3As shown, the system includes: an ultrasonic transmitting circuit, an ultrasonic echo receiving circuit, a CPU control circuit, a memory, and an ultrasonic probe 1. The CPU control circuit is electrically connected to both the ultrasonic transmitting circuit and the ultrasonic echo receiving circuit. The ultrasonic probe 1 is also electrically connected to both the ultrasonic transmitting circuit and the ultrasonic echo receiving circuit. The ultrasonic transmitting circuit includes an ultrasonic power driving circuit, which adjusts the ultrasonic power of the ultrasonic probe 1 according to instructions from the CPU control circuit. The ultrasonic echo receiving circuit receives and calculates the probe blind zone critical point at each power point of the small hole 4 on the manhole cover. The position of the probe blind zone critical point serves as the starting point for ultrasonic ranging. The memory stores the probe blind zone critical points of the ultrasonic probe 1 at each power point of the small hole 4 on the manhole cover. The position of the probe blind zone critical point serves as the starting point for ultrasonic ranging. The CPU control circuit measures the liquid level based on the ultrasonic power and the corresponding probe blind zone critical point.

[0086] The blind zone critical point stored in the memory is obtained using the probe blind zone correction step in the rapid manhole level measurement method.

[0087] The CPU control circuit controls the output power of the ultrasonic probe 1 to gradually increase from zero to full power. The echo receiving circuit synchronously receives and calculates the probe blind zone critical point for each power point. Through this automatic probe scanning correction technology, the ultrasonic probe 1 performs a blind zone boundary scan before measurement. After scanning, the data of the probe blind zone at each power point is saved in memory as the blind zone reference value for future measurements. In future measurements, the corresponding blind zone distance can be found based on the current ultrasonic transmission power to avoid the interference of reflected noise caused by the manhole cover and measure the liquid level normally.

[0088] In a preferred embodiment, before measurement, the same manhole cover or the same hole structure is used to scan the blind zone boundary. After measurement, the probe blind zone critical point is obtained at each power point, and the blind zone data is stored in memory. During measurement, an appropriate ultrasonic transmission power is selected based on the liquid level depth and the acquired ultrasonic wave pattern, and the liquid level height is calculated based on the ultrasonic blind zone corresponding to that ultrasonic transmission power point.

[0089] In a preferred embodiment, the ultrasonic transmitting circuit includes a DAC programmable voltage signal, a programmable boost power supply, a DDS ultrasonic signal generating circuit, and a gated logic signal generating circuit; the DAC programmable voltage signal is electrically connected to the CPU control circuit and the programmable boost power supply, the programmable boost power supply is electrically connected to the ultrasonic power driving circuit, the DDS ultrasonic signal generating circuit is electrically connected to the CPU control circuit and the gated logic signal generating circuit, and the gated logic signal generating circuit is electrically connected to the ultrasonic power driving circuit.

[0090] 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. The ultrasonic power drive circuit adjusts the transmitting power of the ultrasonic probe 1 according to the voltage signal. The transmitting power of the ultrasonic probe 1 gradually increases from zero, and the detection range searches for targets from near to far. 5. The ultrasonic measurement circuit adopts automatic power control (APC) technology to ensure that the measurement range of the ultrasonic sensor meets the requirements of a large range while minimizing the measurement blind zone as much as possible. At the same time, the output power of the ultrasonic pulse is continuously adjustable from zero to the maximum value.

[0091] In a preferred embodiment, 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 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 1.

[0092] The pre-amplifier circuit amplifies the ultrasonic echo signal, the narrowband bandpass filter circuit filters the amplified ultrasonic echo signal, and the AD conversion circuit converts the ultrasonic echo signal into a digital signal.

[0093] During measurement, the ultrasonic transmitting circuit gradually increases the transmitting power from zero until the CPU calculates that the amplitude of the echo signal reaches a reasonable level. Then, the CPU control circuit sends a command to the DAC programmable voltage signal circuit to stop the voltage scanning, so that the programmable boost power supply maintains the current voltage amplitude. The CPU searches for the corresponding blind zone critical point in memory based on the current transmitting power as the starting point for calculating the ultrasonic flight time, and starts the ultrasonic flight time calculation program to calculate the measurement result. This avoids the additional noise interference caused by the manhole cover.

[0094] This invention also discloses a rapid manhole liquid level measuring device, referring to... Figure 4 As shown, the device includes a rapid manhole level measurement circuit, a fixed support 2, and a measuring instrument 3. The ultrasonic probe 1 is located at the bottom of the fixed support 2, and the measuring instrument 3 is mounted on the fixed support 2. The ultrasonic transmitting circuit, the ultrasonic echo receiving circuit, and the CPU control circuit are all located in the measuring instrument 3. The fixed support 2 can be a tripod, which serves to fix and support the device.

[0095] In a preferred embodiment, the ultrasonic probe 1 is replaceable, and the blind zone critical point of the replaced ultrasonic probe 1 is recalibrated. Different models and manufacturers of ultrasonic probes 1 have different blind zone distances. Before the instrument is used for the first time, a blind zone self-scan of the ultrasonic probe 1 needs to be performed, recording the blind zone parameters under various driving powers into the instrument's memory for later retrieval during measurement. For example, under a certain driving power, the echo obtained by the ultrasonic probe 1 is as follows... Figure 3 As shown, after ultrasonic probe 1 emits an ultrasonic pulse, due to the "tailing" characteristic of the mechanical vibration of ultrasonic probe 1, a certain period of damped oscillation will occur after the driving pulse ends. This damped oscillation, once received by the receiving circuit, will affect the echo recognition of near-field detection. Therefore, ultrasonic detection always has a "blind zone," just as... Figure 5 As shown in waveform 5 in the mid-blind zone, after a period of oscillation, it gradually decays to zero. This point, exactly at zero, marks the beginning of the probe's effective recognition range, which is the initial ranging starting position 6. This period continues until the target's reflected wave 7 appears. This time, plus the previously known blind zone time, equals the round-trip flight time t2 of the ultrasonic probe 1 to the target object. Therefore, the distance from the probe to the target object... V represents the speed of ultrasound in air, approximately 340 meters per second.

[0096] When it is necessary to measure the liquid level through the small hole 4 in the well cover, the small hole 4 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 5 in the blind zone, will produce a result similar to... Figure 4 Waveform 8 of the blind zone after overlaying the manhole cover, from Figure 6 As can be seen, the position where the blind zone waveform 8 decays to zero after the manhole cover is superimposed will be extended backward compared to the original ranging starting position 6. 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 9, so that the result can be measured reliably and stably.

[0097] Figure 7 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] 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 rapid method for measuring manhole liquid level, characterized in that, include: Probe blind zone correction steps: Adjust the ultrasonic transmission power step by step within the power range of the ultrasonic ranging sensor, and take the last data point in the echo data that is less than the threshold as the blind zone critical point. Measure the blind zone critical points of the ultrasonic ranging sensor under different transmission powers and store them; the ultrasonic ranging sensor is located at the small hole of the manhole cover. Liquid level measurement steps: Based on the selected transmission power during measurement, obtain the corresponding blind zone critical point. The blind zone critical point serves as the ranging starting point. Calculate the liquid level height based on the ultrasonic transmission time between the blind zone critical point and the liquid surface. The probe blind zone correction step includes: Step S1: Place the ultrasonic ranging sensor at the small hole in the manhole cover and set the transmission power of the ultrasonic ranging sensor to the lowest setting; Step S2: 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. Step S3: 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 position of the data and save it. Step S4: Increase the transmission power of the ultrasonic ranging sensor by one level, repeat steps S2-S3 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. The liquid level measurement steps include: Step A1: Pass the ultrasonic ranging sensor through the small hole in the manhole cover and emit an ultrasonic pulse. Immediately after the emission is completed, switch to receiving mode, receive and digitally quantize the echo data for the set duration. Step A2: Obtain the critical point of the dead zone under this transmit power as the effective start time for calculating the echo time. Clear the echo data before the effective start time point to zero, and demodulate the updated echo data to obtain the peak position. Step A3: 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 A1. If the peak value is greater than the preset value, measure the liquid level based on the peak position.

2. The rapid manhole liquid level measurement method according to claim 1, characterized in that, 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, equals the round-trip flight time t2 of the ultrasonic probe to the target object. Therefore, the distance D from the ultrasonic ranging sensor to the liquid level is D = ×V, where V is the speed of ultrasound in air.

3. The rapid manhole liquid level measurement method according to claim 1, characterized in that, The probe blind zone correction step is performed when the ultrasonic ranging sensor is used for the first time or when it is replaced.

4. A rapid manhole liquid level measurement system, characterized in that, include: The probe blind zone correction module adjusts the ultrasonic transmission power step by step within the power range of the ultrasonic ranging sensor, and takes the last data point in the echo data that is less than the threshold as the blind zone critical point. The blind zone critical points of the ultrasonic ranging sensor under different transmission powers are measured and stored; the ultrasonic ranging sensor is located at the small hole of the manhole cover. Liquid level measurement module: Based on the selected transmission power during measurement, the corresponding blind zone critical point is obtained. The blind zone critical point serves as the ranging starting point, and the liquid level height is calculated based on the ultrasonic transmission time between the blind zone critical point and the liquid surface. The probe blind zone correction module includes: Module M1: Set the ultrasonic ranging sensor at the small hole in the manhole cover and set the ultrasonic ranging sensor's transmission power to the lowest setting; Module M2: It emits ultrasonic pulses through an ultrasonic ranging sensor, receives the echoes within a specified time at that power, and performs continuous digital quantization into digital data of the echo amplitude. Module M3: Compares each point in the echo data with a threshold, takes the last data point in the set of echo data that is less than the threshold as the blind zone critical point under the transmit power, records the location of the data and saves it; Module M4: Increase the transmission power of the ultrasonic ranging sensor by one level, repeat the process from module M2 to module M3 until the blind zone critical point corresponding to the maximum transmission power is recorded, then reset the ultrasonic ranging sensor power to zero and end the calibration. The liquid level measurement module includes: Module A1: Passes the ultrasonic ranging sensor through the small hole in the manhole cover and emits an ultrasonic pulse. After the emission ends, it immediately switches to receiving mode to receive and digitally quantize the echo data for the set duration. Module A2: Obtain the critical point of the dead zone under this transmit power as the effective start time for calculating the echo time, clear the echo data before the effective start time point to zero, and demodulate the updated echo data to obtain the peak position; Module A3: 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 A1. If the peak value is greater than the preset value, measure the liquid level based on the peak position.

5. The rapid manhole liquid level measurement system according to claim 4, characterized in that, 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, equals the round-trip flight time t2 of the ultrasonic probe to the target object. Therefore, the distance D from the ultrasonic ranging sensor to the liquid level is D = ×V, where V is the speed of ultrasound in air.

6. The rapid manhole liquid level measurement system according to claim 4, characterized in that, The probe blind zone correction module is executed when the ultrasonic ranging sensor is used for the first time or when it is replaced.

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