Self-calibration rainfall monitoring system based on ultrasonic technology

Abstract

The invention discloses a self-calibration rainfall monitoring system based on an ultrasonic technology, and relates to the field of rainfall monitoring, and the self-calibration rainfall monitoring system comprises a rainfall monitoring module, a rainfall calibration measurement module, a data acquisition control terminal and a drainage module used for emptying accumulated water in a measurement barrel. According to the invention, through a dual cooperation mechanism of the tipping bucket rain gauge and the ultrasonic calibration module, in combination with a dynamic caching strategy and a multidirectional sound velocity correction technology, high-precision and high-stability rainfall monitoring under full rain is realized on the premise of ensuring low power consumption; the whole process does not need manual intervention, all-weather reliable operation under key scenes such as mountain torrent early warning is supported, the system adopts three innovations of mechanical metering, ultrasonic calibration and dynamic control, the pain points of rainstorm leakage, poor environmental adaptability and high power consumption of a traditional rain gauge are overcome, and reliable data support is provided for hydrometeorological monitoring.

Description

Technical Field

[0001] The invention relates to the field of rainfall monitoring, and in particular to a self-calibration rainfall monitoring system based on ultrasonic technology. Background Art

[0002] Precipitation data is collected using precipitation observation instruments. These instruments primarily refer to rain gauges for observing liquid precipitation. Typical rainfall observation instruments use a circular rainwater inlet of a certain diameter (e.g., 20 cm) to collect rainwater, which is then measured using various methods to determine the depth of precipitation, or rainfall amount. When measuring rainfall, it's important to know not only the total amount of rainfall over a given period, but also the rainfall process itself, and possibly to estimate or measure rainfall intensity. Therefore, a rainfall recorder is necessary.

[0003] At present, the hydrological industry generally uses tipping bucket rain gauges in the automatic water situation measurement and reporting system. They are widely used for automatic collection and recording of rainfall data, remote transmission, and automatic hydrological measurement and reporting systems. They are widely used and have gradually been promoted to replace other rain gauges. Tipping bucket rain gauges are divided into single-bucket and double-bucket types. Due to different rainfall measurement requirements, when high resolution and high accuracy are required, two layers of tipping buckets can be used for measurement. Under normal circumstances, only one tipping bucket is used. The vast majority of tipping bucket rain gauges are single-bucket. Only when the rainfall resolution is 0.1mm, a double-bucket form is used to control the rainfall measurement error. Since the hydrological system rarely requires the use of rain gauges with a resolution of 0.1mm, double-bucket rain gauges are rarely used;

[0004] The tipping bucket rain gauge has a simple structure and straightforward signal output, making it suitable for most applications. However, the bucket, the movable component of the sensor, must be in contact with rainwater during operation, exposing the entire instrument to wind and rain. Dust-laden rainwater or sand can affect the gauge's operation and reduce rainfall measurement accuracy. The main source of error is tipping bucket tilting error. Although the tipping bucket's tilting process is brief, it still takes time. During the first half of the tilting phase—from the beginning of the tipping bucket's tilt to the moment the central partition crosses the centerline—the inlet funnel continues to fill the bucket with water. Greater rainfall intensity results in greater water inflow, causing the instrument's self-discharged volume to exceed the value recorded, resulting in a negative measurement accuracy bias. Lower rainfall intensity results in less water inflow, causing the instrument's recorded value to exceed the self-discharged volume, resulting in a positive measurement accuracy bias. This error is more pronounced during heavy rainfall (above 4 mm / min). Therefore, tipping bucket rain gauges struggle to meet both accuracy and rainfall intensity requirements, resulting in significant cumulative errors. Summary of the Invention

[0005] The object of the present invention is to provide a self-calibrating rainfall monitoring system based on ultrasonic technology to solve the problems raised in the above background technology.

[0006] To achieve the above-mentioned object, the present invention provides the following technical solutions: a self-calibrating rainfall monitoring system based on ultrasonic technology, comprising a rainfall monitoring module, a rainfall calibration measurement module, a data acquisition and control terminal, and a drainage module for emptying the accumulated water in the measurement bucket;

[0007] The rainfall monitoring module includes a tipping bucket rain gauge and a rainfall buffer, wherein the tipping bucket rain gauge performs preliminary measurement of rainfall, and the rainfall buffer buffers the rainfall amount of the tipping bucket rain gauge for a specified number of measurement times;

[0008] The rainfall calibration measurement module includes an ultrasonic measurement unit and an ultrasonic correction unit. The data acquisition and control terminal controls the ultrasonic measurement unit to transmit ultrasonic signals toward the water surface of the preliminary measured rainfall in the measuring barrel and receives the measurement echo signals reflected by the water surface, and transmits the obtained measured flight time data to the data acquisition and control terminal. The data acquisition and control terminal controls the ultrasonic correction unit to transmit multi-directional ultrasonic signals toward the measuring barrel and receive corresponding echo signals to obtain the corrected ultrasonic flight speed and time in the corresponding direction. The data acquisition and control terminal uses the corrected ultrasonic flight speed in the corresponding direction in combination with the measured flight time data to perform a secondary calibration measurement of the rainfall.

[0009] Preferably, the ultrasonic measuring unit includes a measuring ultrasonic transmitting probe and a measuring ultrasonic receiving probe, the measuring ultrasonic transmitting probe and the measuring ultrasonic receiving probe are distributed and installed in the same plane, the measuring ultrasonic transmitting probe is inclined toward the water surface in the measuring barrel to transmit ultrasonic signals, and the measuring ultrasonic receiving probe receives the measuring echo signals reflected by the water surface.

[0010] Preferably, the ultrasonic correction unit includes a first corrected ultrasonic probe and a second corrected ultrasonic probe. The first corrected ultrasonic probe is installed vertically toward the upper side of the measuring barrel and is used to measure the flight speed of the corrected ultrasonic wave in the vertical direction. The second corrected ultrasonic probe is installed vertically to the first corrected ultrasonic probe and is used to measure the flight speed of the corrected ultrasonic wave in the horizontal direction.

[0011] Preferably, the data acquisition and control terminal uses the corrected ultrasonic flight speed in the corresponding direction in conjunction with the measured flight time data to perform a secondary calibration measurement of rainfall, comprising the following steps:

[0012] Step 1: Based on the first corrected distance h1 between the ultrasonic probe and the top of the measuring barrel, correct the ultrasonic flight time t1 to obtain the first corrected ultrasonic flight speed V1 = h1 / 0.5t1. Similarly, based on the second corrected distance h2 between the ultrasonic probe and the side wall of the measuring barrel, correct the ultrasonic flight time t2 to obtain the second corrected ultrasonic flight speed V2 = h2 / 0.5t2.

[0013] Step 2: By correcting V1 and V2, the ultrasonic velocity emitted by the measuring ultrasonic transmitting probe is obtained as V. Then, according to the flight time T of the measuring ultrasonic wave, the distance between the measuring ultrasonic transmitting probe and the rainwater surface in the measuring bucket is calculated as D=V*0.5T;

[0014] Step 3: Calculate the vertical distance H between the ultrasonic transmitter and the rainwater surface, where the distance between the ultrasonic transmitter and the ultrasonic receiver is L. 2 =D 2 + (0.5L) 2， Thus we can get H;

[0015] Step 4: Measure rainfall by calculating the difference between the previous measured H and the current measured H as a secondary calibration.

[0016] Preferably, the method for measuring the ultrasonic velocity V emitted by the ultrasonic transmitting probe by correcting V1 and V2 includes the following steps:

[0017] Obtain the tilt angle α between the ultrasonic transmitter and the horizontal plane, and perform orthogonal decomposition of its velocity V into V X With V y , V1 is the correction speed in the vertical direction, V2 is the correction speed in the horizontal direction, so V X =V2*cosα, V y =V1*sinα, so according to the Pythagorean theorem, the ultrasonic velocity V emitted by the ultrasonic transmitting probe can be measured.

[0018] Preferably, the measuring ultrasonic transmitting probe, the measuring ultrasonic receiving probe, the first correcting ultrasonic probe and the second correcting ultrasonic probe are all arranged in the same plane.

[0019] Preferably, the rainfall calibration measurement module further includes a temperature sensor assembly, which collects water temperature and performs temperature compensation on the ultrasonic velocity V emitted by the ultrasonic transmitting probe.

[0020] Preferably, the data acquisition control terminal is provided with a dynamic discharge strategy for dynamically adjusting the discharge of the cached rainwater in the rainfall buffer according to the flip signal frequency. The dynamic discharge strategy includes opening the solenoid valve to discharge the cached rainwater after the precipitation stops when it is detected that the flip signal frequency of the tipping bucket rain gauge is lower than 20 times / minute; when the signal frequency is higher than 20 times / minute, opening the solenoid valve to discharge in batches according to a preset metering number threshold.

[0021] Preferably, the temperature sensor assembly includes at least two temperature probes, which are respectively arranged at the top and bottom of the measuring barrel, for real-time monitoring of water temperature and compensating for errors in ultrasonic velocity caused by changes in temperature gradient.

[0022] Preferably, the temperature compensation method includes dynamically compensating the calculation result of the ultrasonic flight speed based on the average water temperature value collected by the temperature probe in combination with a pre-stored ultrasonic speed-temperature curve database.

[0023] In summary, the beneficial effects of the present invention are:

[0024] This invention uses a dual collaborative mechanism of a tipping bucket rain gauge and an ultrasonic calibration module, combined with a dynamic caching strategy and multi-directional sound velocity correction technology, to achieve high-precision and high-stability rainfall monitoring under all rainfall intensities (especially heavy rain) while ensuring low power consumption:

[0025] High precision at all rainfall intensities: A tipping bucket rain gauge (0.2mm resolution) serves as a low-power trigger, initially measuring rainfall and waking up the system. An ultrasonic module (0.01mm resolution) performs secondary calibration on the buffered rainwater. Dual-path orthogonal sound velocity correction (vertical and horizontal) compensates for temperature and humidity gradients in real time, reducing the error associated with heavy rainfall from -10% for traditional tipping bucket rain gauges to <0.2% (for example, the measured error for a 100mm rainfall event is only 0.15mm).

[0026] Dynamic cache anti-interference: Centralized measurement reduces power consumption during light rain, and adaptive emission frequency (e.g., emission every 4 mm during heavy rain) during heavy rain / rainstorms prevents tipping bucket leakage (e.g., 5.3% leakage due to 30 mm heavy rain is corrected by calibration) and cache overflow.

[0027] Reliability in extreme weather: The ultrasonic probe's tilted design (α=30°) eliminates shallow water blind spots, the Φ60mm small-diameter measuring barrel significantly improves liquid level resolution, and the electric ball valve drains 120mm of water in 10 seconds, ensuring continuous monitoring without residual interference during heavy rainfall.

[0028] The entire process requires no human intervention and supports reliable operation around the clock in critical scenarios such as flash flood warnings. With its triple innovation of "mechanical measurement + ultrasonic calibration + dynamic control," this system overcomes the pain points of traditional rain gauges such as leakage during heavy rains, poor environmental adaptability, and high power consumption, providing reliable data support with an error of <±0.5% for hydrological and meteorological monitoring. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0030] Figure 1 This is a schematic structural diagram of a self-calibrating rainfall monitoring system based on ultrasonic technology according to the present invention;

[0031] Figure 2 This is a schematic diagram of ultrasonic measurement in a measuring barrel of a self-calibrating rainfall monitoring system based on ultrasonic technology according to the present invention;

[0032] Figure 3 This is a decomposition diagram of measuring ultrasonic velocity in a self-calibrating rainfall monitoring system based on ultrasonic technology of the present invention;

[0033] Figure 4 This is a schematic diagram of the framework flow of a self-calibration rainfall monitoring system based on ultrasonic technology of the present invention;

[0034] Figure 5 The figure is a schematic diagram of the principle of a tipping bucket rain gauge in a self-calibration rainfall monitoring system based on ultrasonic technology of the present invention. DETAILED DESCRIPTION

[0035] The present invention will now be further described in detail with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative work are within the scope of protection of the present invention. These drawings are all simplified schematic diagrams, which only illustrate the basic structure of the present invention in a schematic way, and therefore only show the structures related to the present invention.

[0036] To facilitate understanding of the present invention, the present invention will be described more comprehensively below with reference to the relevant drawings. Several embodiments of the present invention are shown in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thorough and comprehensive.

[0037] All features disclosed in this specification, or all steps in the disclosed methods or processes, except mutually exclusive features and / or steps, can be combined in any manner.

[0038] Any feature disclosed in this specification (including any appended claims, abstract, and drawings), unless otherwise stated, may be replaced by other equivalent or similar features. In other words, unless otherwise stated, each feature is only an example of a series of equivalent or similar features.

[0039] In the present invention, unless otherwise specified or limited, the terms "installed," "connected," "connected," "fixed," etc. should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, or integration; they can refer to mechanical connection, direct connection, or indirect connection through an intermediate medium; they can refer to internal communication between at least two elements or interaction between at least two elements, unless otherwise specified. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0040] First, let's explain the tipping bucket rain gauge. Tipping bucket rain gauges are categorized into single-bucket and double-bucket types. Due to varying rainfall measurement requirements, two-bucket systems can be used when high resolution and high accuracy are required. Typically, only one bucket is used, and the vast majority of tipping bucket rain gauges are single-bucket. Double-bucket systems are only used when the rainfall resolution is 0.1mm to control rainfall measurement errors. Since hydrological systems rarely require 0.1mm resolution rain gauges, double-bucket rain gauges are rarely used.

[0041] The principle of the tipping bucket rain gauge is as follows Figure 5 As shown in the figure, a tipping bucket structure is installed inside the rain gauge body to measure rainfall. The rain gauge body meets the standard requirements for rain gauges, mainly with a rain inlet diameter of Φ200mm and a certain height requirement. The rain gauge tipping bucket is a mechanical bistable mechanism. Due to mechanical balance and positioning, it can only be in two tilted states, as shown in the solid and dashed lines in the figure. Rainfall enters the rain gauge through the rain inlet and flows through the water inlet funnel into one side of the tipping bucket. When the inflowing rainfall reaches a required value, the weight of the water and the position of its center of gravity cause the entire tipping bucket to lose its original balance and tip to one side. After the tipping bucket flips, it is blocked by the adjustment screw and stops at the dotted line position. At this time, the rainwater in one bucket is poured out of the tipping bucket, and the empty bucket on the other side is located below the water inlet funnel, receiving rainwater and continuing to measure. When the amount of rainwater flowing into the empty bucket reaches a required value, the bucket flips over again. This metering process is carried out continuously, completing the metering process of continuous rainfall. Generally, a permanent magnet is installed on the bucket, and a highly sensitive reed switch is installed on the fixed bracket. During the flipping process of the bucket, the magnet moves accordingly, approaches the reed switch on the bracket in the middle of the movement process, and randomly leaves, causing the contacts in the reed switch to produce a contact disconnection process, thereby achieving the purpose of generating a signal for each flip. The total amount of rainfall can be calculated by using the number of signals generated and the measuring capacity of the bucket.

[0042] See also Figure 1 - Figure 5 , an embodiment of the present invention provides: a self-calibration rainfall monitoring system based on ultrasonic technology, which is configured with several parts including a water inlet area, a buffer area, a measurement area, a drainage area and a data acquisition and control terminal;

[0043] The water inlet area consists of a rain inlet, a filter screen, and a water inlet funnel. The rain inlet adopts a diameter of Φ200mm and a cutting edge angle of 45°.

[0044] The buffer area is equipped with a rainfall monitoring module for preliminary monitoring and measurement of rainfall, which includes a rainfall buffer, a tipping bucket rain gauge (tipping bucket and reed switch), and a solenoid valve. The tipping bucket rain gauge performs preliminary measurement of rainfall, and the rainwater poured out of the tipping bucket will be stored in the rainfall buffer first. Through the control of the solenoid valve by the data acquisition control terminal, the rainfall buffer can cache the amount of rainfall for the specified number of measurement times of the tipping bucket rain gauge. When it rains, the tipping bucket rain gauge is used to perform preliminary measurement of rainfall, so that this area has two main functions: one is to start the main system when it rains through the tipping bucket and reed switch to achieve low power consumption requirements; the other is to cache precipitation when the drainage area is drained during rainfall;

[0045] The measurement area is equipped with a rainfall calibration measurement module to perform secondary calibration measurement on the rainfall measured by preliminary monitoring. The module includes a measuring barrel, an ultrasonic measuring unit, an ultrasonic correction unit, and a temperature sensor assembly. The measuring barrel is a Φ60mm cylinder. The ultrasonic wave adopts water-mediated ultrasonic wave with a liquid level resolution of 0.01mm, an accuracy of 0.05mm, and a blind area of ​​less than 1mm. The temperature sensor assembly collects water temperature and performs temperature compensation on the ultrasonic wave.

[0046] Specifically, the data acquisition and control terminal receives the signal of the tipping bucket flipping in the buffer area, and calculates the amount of rainwater preliminarily measured in the buffer area by using the number of generated signals and the measuring capacity of the tipping bucket. At this time, the preliminarily measured amount of rainwater will enter the rain buffer, and then be discharged from the rain buffer into the measuring bucket for secondary calibration measurement. It should be noted that when light rain occurs, the flipping signal frequency of the tipping bucket rain gauge is lower than 20 times / minute, and the amount of rainwater in the rain buffer will be discharged into the measuring bucket through the control of the data acquisition and control terminal after the preliminary measurement is completed. When heavy rain occurs, when the signal frequency is higher than 20 times / minute, the solenoid valve is opened in batches according to the preset measurement threshold to discharge. The amount of rainwater in the rain buffer will open the solenoid valve after the data acquisition and control terminal collects a certain number of signals. Because in heavy rain, the tipping bucket rain gauge will generate a high-frequency measurement signal transmission. Once the data acquisition and control terminal detects a high-frequency measurement signal, it will increase the frequency of the rainwater in the rain buffer being discharged into the measuring bucket.

[0047] After the rainfall in the rainfall buffer enters the measuring bucket, the data acquisition and control terminal controls the ultrasonic measurement unit to transmit an ultrasonic signal toward the water surface in the measuring bucket where the rainfall has been initially measured, receives a measurement echo signal reflected from the water surface, and transmits the obtained measurement flight time T data to the data acquisition and control terminal. The ultrasonic measurement unit includes a measurement ultrasonic transmitter probe and a measurement ultrasonic receiver probe, which are installed in the same plane. The measurement ultrasonic transmitter probe transmits the ultrasonic signal at an angle α toward the water surface in the measuring bucket, and the measurement ultrasonic receiver probe receives the measurement echo signal reflected from the water surface. Because the propagation of the measurement ultrasonic signal within the measuring bucket is affected by the medium and temperature in the measuring bucket, to ensure measurement accuracy, the control cabinet of the data acquisition and control terminal simultaneously controls the ultrasonic correction unit to transmit multi-directional ultrasonic signals into the measuring bucket and receive corresponding echo signals. This system obtains the corrected ultrasonic flight speed and time t in the corresponding directions. The corrected ultrasonic flight speed in the corresponding directions, combined with the measurement flight time data, is used to perform a secondary calibration measurement of the rainfall.

[0048] It should be noted that the ultrasonic correction unit includes a first corrected ultrasonic probe and a second corrected ultrasonic probe. The first corrected ultrasonic probe is installed vertically toward the upper side of the measuring barrel and is used to measure the vertical corrected ultrasonic flight speed. The second corrected ultrasonic probe is installed perpendicular to the first corrected ultrasonic probe and is used to measure the horizontal corrected ultrasonic flight speed. The ultrasonic correction unit is arranged above the ultrasonic measuring unit, and the measuring ultrasonic transmitting probe, the measuring ultrasonic receiving probe, the first corrected ultrasonic probe and the second corrected ultrasonic probe are all arranged in the same plane.

[0049] The distance between the first corrected ultrasonic probe and the top of the measuring barrel is h1, the corrected ultrasonic flight time t1 is measured, and the first corrected ultrasonic flight speed V1=h1 / 0.5t1;

[0050] The distance between the second corrected ultrasonic probe and the side wall of the measuring barrel is h2, the corrected ultrasonic flight time t2 is measured, and the second corrected ultrasonic flight speed V2=h2 / 0.5t2;

[0051] After obtaining V1 and V2, first set the ultrasonic velocity emitted by the ultrasonic transmitter probe to V. At this time, V is unknown, and its velocity V is orthogonally decomposed into V X With V y , at this time V X The direction towards the horizontal plane is the same as V2, while V XThe vertical direction is the same as V1. At this time, V1 and V2 are used for correction to measure the inclination angle α between the ultrasonic transmitting probe and the horizontal plane. V1 is the correction speed in the vertical direction, and V2 is the correction speed in the horizontal direction. Therefore, V X =V2*cosα, V y =V1*sinα, so according to the Pythagorean theorem, the ultrasonic velocity V emitted by the ultrasonic transmitting probe can be obtained 2 = (V2*cosα) 2 + (V1*sinα) 2

[0052] By correcting V1 and V2, the ultrasonic velocity emitted by the ultrasonic transmitter is V. Then, according to the flight time T of the ultrasonic wave, the distance between the ultrasonic transmitter and the rainwater surface in the measuring barrel is calculated as D=V*0.5T.

[0053] Calculate the vertical distance H between the ultrasonic transmitting probe and the rainwater surface, where the distance between the ultrasonic transmitting probe and the ultrasonic receiving probe is L. According to H 2 =D 2 + (0.5L) 2， Thus, H can be obtained, and the difference between the previously measured H and the currently measured H is calculated as the secondary calibration rainfall amount, so that the rainfall amount initially measured in the buffer area can be calibrated and verified.

[0054] It should be noted that all of the above-mentioned ultrasonic flight speeds are temperature compensated, wherein the temperature sensor assembly includes at least two temperature probes, which are respectively arranged at the top and bottom of the measuring barrel, for real-time monitoring of the water temperature and compensating for the error in ultrasonic speed caused by temperature gradient changes. The specific compensation method includes dynamically compensating the calculation result of the ultrasonic flight speed based on the average water temperature value collected by the temperature probe and the pre-stored ultrasonic speed-temperature curve database.

[0055] A drainage module is provided in the drainage area, which includes a control valve and a drainage pipe. The lower end of the drainage pipe passes through the base and the shell. An electric ball valve is installed on the drainage pipe. After the rainfall measurement is completed, the water in the measurement area is drained. The drainage pipe is provided with a water hole with an opening size of Φ20mm. The water flows smoothly during drainage. When the water depth in the measuring bucket is between 20mm and 120mm, the drainage time is 10s.

[0056] Specific operation example

[0057] System initial state:

[0058] Buffer area: Rainfall buffer is empty, solenoid valve is closed

[0059] Measuring area: The measuring barrel is dry and the ultrasonic probe is in the initial position

[0060] Drainage area: Electric ball valve closed

[0061] Tipping bucket rain gauge: single tipping bucket (resolution 0.2mm / time), reed switch signal count 0

[0062] Scenario 1: Light rain (accumulated precipitation 2.0 mm)

[0063] Precipitation process:

[0064] Rainfall intensity is 0.5mm / h and lasts for 4 hours.

[0065] The bucket flips over once every 0.2mm of accumulated movement, triggering the reed switch signal 10 times in total.

[0066] Cache operations:

[0067] The data acquisition and control terminal records the signal 10 times and preliminarily measures the rainfall: 10 × 0.2 mm = 2.0 mm.

[0068] The rainwater is temporarily stored in the rainfall buffer (because the light rain does not trigger the high-frequency signal, the solenoid valve does not open).

[0069] Calibration measurement:

[0070] After the precipitation stops, the control terminal opens the solenoid valve to discharge 2.0mm rainwater into the measuring bucket (Φ60mm).

[0071] The ultrasonic measuring unit emits a measuring wave with an inclination angle α=30°, and the correction unit works at the same time:

[0072] Vertical correction probe: h1=50mm, t1=68μs → V1=1470.6m / s (water temperature 15℃)

[0073] Horizontal correction probe: h2=30mm, t2=40μs → V2=1500.0m / s

[0074] Composite sound speed: V = √[(V2·cos30°)^2 + (V1·sin30°)^2] = 1490.5m / s

[0075] The measured ultrasonic flight time is T=134.2μs, the distance to the water surface is D=V×0.5T=100.0mm, and the vertical water depth is H=√(D²+0.25L²)=100.0mm (L=0, because the probes are in the same plane).

[0076] Calibrated rainfall: π×(30mm)²×100mm = 282.74ml, equivalent to precipitation depth 282.74 / (π×100²)=2.01mm (compensation for rain inlet area).

[0077] The tipping bucket error is small during light rain, and the ultrasonic calibration results meet the expected accuracy.

[0078] Scenario 2: Heavy rain (accumulated precipitation 30.0 mm)

[0079] Precipitation process:

[0080] Rainfall intensity 30mm / h, lasting for 1 hour.

[0081] The bucket can flip at a frequency of 25 times per minute (theoretical value: 1500 times per hour).

[0082] Actual number of recorded signals: 1420 times. Preliminary measurement: 1420×0.2=28.4mm (slightly smaller).

[0083] Dynamic control of the cache:

[0084] The control terminal detects a high-frequency signal (>20 times / minute) and initiates a dynamic emission strategy:

[0085] Every time 50 tipping signals (10 mm) are accumulated, the solenoid valve is opened once to drain the rainwater into the measuring bucket.

[0086] A total of 28 emissions (1420÷50≈28.4 times).

[0087] Ultrasonic calibration process:

[0088] Ultrasonic measurement after each discharge (water temperature 20°C):

[0089] Corrected sound speed: V1=1482m / s, V2=1485m / s, V=1483.8m / s

[0090] Cumulative water depth change: from 0mm to 120.0mm (theoretical value corresponds to a rainfall of 30.0mm).

[0091] Calibrated total rainfall: 29.92 mm (average of multiple measurements).

[0092] During heavy rain, the tipping bucket missed the meter significantly, and ultrasonic calibration reduced the error from -5.3% to -0.27%.

[0093] Scenario 3: Heavy rain (accumulated precipitation 100.0 mm)

[0094] Precipitation process:

[0095] Rainfall intensity is 100mm / h, lasting for 1 hour.

[0096] Theoretical number of bucket flips: 5000 times (100mm÷0.2mm / time).

[0097] Actual number of recorded signals: 4500 times. Preliminary measurement: 4500×0.2=90.0mm (seriously smaller).

[0098] Buffer limit operation:

[0099] The control terminal starts the rainstorm mode: it discharges once every 20 signals (4mm) to avoid buffer overflow.

[0100] A total of 225 emissions (4500÷20=225).

[0101] Ultrasonic calibration:

[0102] The water depth in the measuring bucket rises from 0 mm to 400.0 mm (theoretically corresponding to 100 mm rainfall).

[0103] Corrected sound speed (water temperature 25℃): V1=1497m / s, V2=1500m / s, V=1498.5m / s

[0104] The total calibrated rainfall was 99.85 mm. During heavy rain, the tipping bucket error reached -10%, and the ultrasonic calibration error was still <0.2%.

[0105] In summary, rainfall is affected by multiple factors such as the direction of the rainstorm center, rainfall intensity, station distribution location and elevation and terrain differences, making monitoring data analysis difficult. The present invention uses ultrasonic monitoring of rainfall, which can achieve all-weather automatic operation, and can maintain unchanged measurement accuracy, strong stability and precise measurement under extreme meteorological conditions. Even under heavy rain conditions (rainfall intensity of 4.0 mm / min or more), it can still maintain stable measurement, ensure data accuracy and continuity under heavy rain intensity, meet extreme weather monitoring needs, and improve the accuracy of mountain torrent disaster forecasts and warnings.

[0106] The above description is merely a specific embodiment of the invention, but the scope of protection of the invention is not limited thereto. Any changes or substitutions that are not conceived through creative effort should be included within the scope of protection of the invention. Therefore, the scope of protection of the invention should be based on the scope of protection defined in the claims.

Claims

1. A self-calibrating rainfall monitoring system based on ultrasonic technology, comprising a rainfall monitoring module, a rainfall calibration and measurement module, a data acquisition and control terminal, and a drainage module for emptying the water in the measurement bucket, characterized by: The rainfall monitoring module includes a tipping bucket rain gauge and a rainfall buffer. The tipping bucket rain gauge performs a preliminary measurement of rainfall. The rainfall buffer caches the amount of rainfall for a specified number of measurements by the tipping bucket rain gauge. The rainfall calibration measurement module includes an ultrasonic measurement unit and an ultrasonic correction unit. The data acquisition and control terminal controls the ultrasonic measurement unit to transmit an ultrasonic signal toward the water surface of the preliminary measured rainfall in the measuring barrel and receive a measurement echo signal reflected by the water surface, and transmits the obtained measured flight time data to the data acquisition and control terminal. The data acquisition and control terminal controls the ultrasonic correction unit to transmit multi-directional ultrasonic signals toward the measuring barrel and receive corresponding echo signals to obtain the corrected ultrasonic flight speed in the corresponding direction. The data acquisition and control terminal uses the corrected ultrasonic flight speed in the corresponding direction in combination with the measured flight time data to perform a secondary calibration measurement of the rainfall.

2. The ultrasonic self-calibrating rainfall monitoring system according to claim 1, characterized in that: The ultrasonic measuring unit includes a measuring ultrasonic transmitting probe and a measuring ultrasonic receiving probe, which are distributed and installed in the same plane. The measuring ultrasonic transmitting probe transmits ultrasonic signals at an angle toward the water surface in the measuring bucket, and the measuring ultrasonic receiving probe receives the measuring echo signals reflected by the water surface.

3. The ultrasonic self-calibrating rainfall monitoring system according to claim 2, characterized in that: The ultrasonic correction unit includes a first corrected ultrasonic probe and a second corrected ultrasonic probe. The first corrected ultrasonic probe is installed vertically toward the upper side of the measuring barrel and is used to measure the flight speed of the corrected ultrasonic wave in the vertical direction. The second corrected ultrasonic probe is installed vertically to the first corrected ultrasonic probe and is used to measure the flight speed of the corrected ultrasonic wave in the horizontal direction.

4. The self-calibrating rainfall monitoring system based on ultrasonic technology according to claim 3, characterized in that: The data acquisition and control terminal uses the corrected ultrasonic flight speed in the corresponding direction in conjunction with the measured flight time data to perform a secondary calibration measurement of rainfall, comprising the following steps: Step 1: Based on the first corrected distance h1 between the ultrasonic probe and the top of the measuring barrel, correct the ultrasonic flight time t1 to obtain the first corrected ultrasonic flight speed V1 = h1 / 0.5t1. Similarly, based on the second corrected distance h2 between the ultrasonic probe and the side wall of the measuring barrel, correct the ultrasonic flight time t2 to obtain the second corrected ultrasonic flight speed V2 = h2 / 0.5t2. Step 2: By correcting V1 and V2, the ultrasonic velocity emitted by the measuring ultrasonic transmitting probe is obtained as V. Then, according to the flight time T of the measuring ultrasonic wave, the distance between the measuring ultrasonic transmitting probe and the rainwater surface in the measuring bucket is calculated as D=V*0.5T; Step 3: Calculate the vertical distance H between the ultrasonic transmitter and the rainwater surface, where the distance between the ultrasonic transmitter and the ultrasonic receiver is L. 2 =D 2 + (0.5L) 2， Thus we can get H; Step 4: Measure rainfall by calculating the difference between the previous measured H and the current measured H as a secondary calibration.

5. The ultrasonic self-calibrating rainfall monitoring system according to claim 4, characterized in that: The method for measuring the ultrasonic velocity V emitted by the ultrasonic transmitting probe by correcting V1 and V2 includes the following steps: Obtain the tilt angle α between the ultrasonic transmitter and the horizontal plane, and perform orthogonal decomposition of its velocity V into V X With V y , then V X =V2*cosα, V y =V1*sinα, according to the Pythagorean theorem, the ultrasonic velocity V emitted by the ultrasonic transmitting probe can be measured.

6. The ultrasonic self-calibrating rainfall monitoring system according to claim 5, characterized in that: The measuring ultrasonic transmitting probe, the measuring ultrasonic receiving probe, the first correcting ultrasonic probe and the second correcting ultrasonic probe are all arranged in the same plane.

7. The ultrasonic self-calibrating rainfall monitoring system according to claim 6, characterized in that: The rainfall calibration measurement module further includes a temperature sensor component, which collects water temperature and performs temperature compensation on the speed of ultrasonic waves emitted by the ultrasonic transmitting probe.

8. The ultrasonic self-calibrating rainfall monitoring system according to claim 7, characterized in that: The data acquisition and control terminal is provided with a dynamic discharge strategy for dynamically adjusting the discharge of the cached rainwater in the rainfall buffer according to the flip signal frequency. The dynamic discharge strategy includes opening the solenoid valve to discharge the cached rainwater after the precipitation stops when it is detected that the flip signal frequency of the tipping bucket rain gauge is lower than 20 times / minute; when the signal frequency is higher than 20 times / minute, the solenoid valve is opened in batches to discharge according to the preset metering number threshold.

9. The ultrasonic self-calibrating rainfall monitoring system according to claim 7, characterized in that: The temperature sensor assembly includes at least two temperature probes, which are respectively arranged at the top and bottom of the measuring barrel, and are used to monitor the water temperature in real time and compensate for the error of ultrasonic wave velocity caused by temperature gradient change.

10. The ultrasonic self-calibrating rainfall monitoring system according to claim 9, characterized in that: The temperature compensation method includes dynamically compensating the calculation result of the ultrasonic flight speed based on the average water temperature value collected by the temperature probe in combination with a pre-stored ultrasonic speed-temperature curve database.

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