A water body turbidity real-time detection system and method

Abstract

The present application relates to water body detection technical field, especially to a kind of water body turbidity real-time detection system and method, including laser emission module, transmitting optical fiber, receiving optical fiber, avalanche photodiode, photoelectric IV amplification conversion module, built-in filter algorithm's main control unit and alarm module.Laser is introduced into water body by transmitting optical fiber, and transmission light is collected by receiving optical fiber and conducted to avalanche photodiode, after photoelectric conversion and voltage amplification, it is sent into main control unit to carry out filtering, quantization operation and turbidity conversion, and automatically alarm when turbidity is over standard.The present application uses optical fiber to realize non-invasive optical path detection, combined with the high sensitivity photoelectric conversion of avalanche photodiode and the filter algorithm of main control unit, realizes high-precision, high anti-interference, maintenance-free turbidity real-time monitoring, solves the problems of high manufacturing cost of existing water body turbidity detection equipment, traditional immersion probe is easy to be corroded and scaled, environmental stray light interference is serious, lack of automatic early warning function and poor measurement accuracy.

Description

Technical Field

[0001] This invention relates to the field of water body detection technology, specifically to a real-time water turbidity detection system and method. More particularly, it is a real-time water turbidity detection system and method based on fiber optic transmission and avalanche photoelectric detection. Background Technology

[0002] Turbidity is one of the core physical indicators for measuring water quality, essentially reflecting the degree to which suspended particulate matter in the water obstructs the passage of light. In many fields such as aquaculture, aquariums, drinking water safety, environmental monitoring, and industrial water treatment, real-time turbidity monitoring is of irreplaceable importance for protecting biological health, ensuring water quality safety, and maintaining stable production processes. With the continuous development of the social economy and the continuous improvement of people's living standards, the aquarium and small-scale aquaculture industries have ushered in a golden age of vigorous development, with more and more families starting to raise ornamental fish or engage in small-scale aquaculture. In these application scenarios, the continuous accumulation of suspended particulate matter, residual feed, fish excrement, and microbial metabolic products in the water will directly lead to a continuous increase in water turbidity, which in turn triggers a series of chain reactions such as water quality deterioration, decreased dissolved oxygen, and the proliferation of harmful substances, ultimately threatening the health and even survival of aquatic organisms. Therefore, establishing a technical means to monitor water turbidity in a long-term, stable, and real-time manner has become an urgent need to ensure the ecological balance and biological health of small aquatic bodies.

[0003] However, the current technological development in the field of water turbidity detection exhibits a clear polarization, making it difficult to meet the actual needs of diverse application scenarios. On the one hand, turbidity detection instruments for industrial production and municipal engineering have formed a relatively complete product system after decades of technological accumulation. Industrial-grade benchtop and handheld turbidity meters generally adopt high-precision optical detection principles. Through precise 90° scattering light path design, high-performance photoelectric detection elements, and complex signal processing algorithms, they can achieve high measurement accuracy and repeatability, and their measurement results strictly comply with international standards such as ISO 7027. Online turbidity analyzers further integrate automatic sampling, continuous monitoring, and remote data transmission functions, and are widely used in large-scale engineering scenarios such as sewage treatment plants, waterworks, and industrial circulating water systems. Although these high-end instruments have significant advantages in terms of accuracy and reliability, their overall structure is large, power consumption is high, the manufacturing cost of core optical components and precision machined parts is extremely high, and operation and maintenance require certain professional technical knowledge. The high price and complex operation of such equipment primarily limit its use to professional laboratory testing and large-scale industrial applications, making it unsuitable for the economic affordability and usage habits of ordinary consumer scenarios such as home aquariums and small-scale aquaculture. On the other hand, integrated multi-parameter water quality monitoring equipment that has emerged in recent years attempts to meet broader application needs by integrating the monitoring functions of multiple sensors such as pH, dissolved oxygen, turbidity, and temperature. While this type of equipment expands the dimensions of water quality monitoring to some extent, its initial design often prioritizes comprehensive functionality, with turbidity detection merely one of many auxiliary functions, lacking in-depth optimization and specialized design for the turbidity measurement principle. This high degree of integration not only leads to a significant price premium for the entire unit but also makes the user interface increasingly complex and raises the maintenance threshold, making it difficult for ordinary users to accurately understand the meaning of various parameters and perform proper equipment maintenance. Furthermore, electromagnetic compatibility issues between sensors in multi-parameter integrated equipment and the varying requirements of different measurement principles on the aquatic environment also objectively affect the long-term stability and data reliability of the turbidity detection channel.

[0004] Beyond the two mainstream technical solutions mentioned above, the market also offers a large number of traditional contact sensors and simple photoelectric detection modules designed for low-end applications. These solutions attempt to achieve a rough estimate of turbidity with the lowest possible hardware cost, but their technical approach itself has several inherent and insurmountable flaws. First, regarding sensor structure, traditional immersion turbidity probes require the electrodes or photoelectric sensing components to be directly placed in the water for contact measurement. Probe surfaces exposed to underwater environments for extended periods are highly susceptible to the adhesion of scale, algae, and microbial films. These deposits not only directly obstruct the light path or alter electrode surface characteristics but also accelerate the corrosion and aging of the probe materials, leading to a continuous drift in sensor accuracy. More seriously, the direct immersion of electrical components in water poses safety hazards such as leakage and short circuits, creating potential threats to aquatic life and user safety. Second, in terms of optical detection, existing simple infrared photosensitive modules generally lack standardized optical path packaging designs. The alignment of the optical path between the transmitter and receiver relies on manual adjustment, lacking reliable mechanical positioning and locking structures, resulting in extremely poor repeatability between multiple measurements. Meanwhile, these modules have virtually no effective technical measures to resist interference from stray ambient light. Visible and near-infrared components from indoor lighting and sunlight can be directly projected onto the photosensitive element, causing serious measurement errors after being superimposed on the effective signal. Under different ambient lighting conditions, the measurement results for the same water sample may differ by several times or even more than an order of magnitude, rendering the measurement data completely unusable.

[0005] In summary, existing technologies cannot simultaneously achieve low cost, miniaturization, and high precision. In particular, there is a lack of dedicated turbidity monitoring equipment that can overcome long-term underwater scaling and corrosion, effectively resist environmental stray light interference, and has real-time quantitative measurement and automatic early warning functions. This makes it difficult to meet the actual needs of the aquarium viewing industry and small-scale aquaculture. Summary of the Invention

[0006] To address the problems of high manufacturing cost of water turbidity detection equipment, easy corrosion and scaling of traditional immersion probes, severe interference from ambient light, lack of automatic early warning function, and poor measurement accuracy in existing technologies, this invention provides a real-time water turbidity detection system and method.

[0007] To achieve the above objectives, the present invention employs the following technical solution: This invention provides a real-time water turbidity detection system, comprising: The laser emitting module is used to emit a detection beam; The transmitting optical fiber has its light-incident end coupled to the output end of the laser emitting module, and is used to transmit the detection beam to the water body to be tested; The receiving optical fiber and the transmitting optical fiber are arranged horizontally and coaxially opposite each other in the water body to be tested, and are used to collect the transmitted light beam after passing through the water body to be tested and transmit it out of the water body to be tested. An avalanche photodiode, wherein the photosensitive surface of the avalanche photodiode is arranged opposite to the light-emitting end of the receiving optical fiber, and is used to receive the transmitted light beam and convert the light intensity signal into a photocurrent signal; The photoelectric IV amplification and conversion module, wherein the input terminal of the photoelectric IV amplification and conversion module is electrically connected to the output terminal of the avalanche photodiode, is used to convert the photocurrent signal into a voltage signal and perform primary amplification; The main control unit has a built-in multi-sampling mean filtering and first-order hysteresis exponential smoothing noise reduction algorithm. The main control unit is connected to the photoelectric IV amplification and conversion module for acquiring voltage signals and performing data processing and turbidity conversion. An alarm module, which is electrically connected to the main control unit, is used to issue an alarm signal when the turbidity exceeds the standard.

[0008] Optionally, a voltage divider resistor is provided between the photoelectric IV amplification and conversion module and the main control unit, and the voltage divider resistor is composed of several series resistors.

[0009] Optionally, the laser emitting module is a near-infrared laser.

[0010] Optionally, the transmitting and receiving optical fibers are placed in the water body to be tested via an optical fiber fixing bracket, and the detection ends of the transmitting and receiving optical fibers are arranged horizontally and coaxially facing each other underwater.

[0011] Optionally, both the transmitting and receiving optical fibers are SMA905 standard plastic fiber patch cords with a core diameter of 1mm.

[0012] Optionally, the center-to-center distance between the end faces of the probe of the transmitting optical fiber and the probe of the receiving optical fiber is fixed at 4-6 mm.

[0013] Optionally, it also includes a power module, which is connected to the laser emitting module, the avalanche photodiode, the photoelectric IV amplification and conversion module, the main control unit, and the alarm module.

[0014] Optionally, it also includes an OLED display module, which is connected to the main control unit.

[0015] Optionally, the main control unit is an ESP32 microcontroller with a built-in 12-bit ADC; the alarm module is a buzzer.

[0016] The present invention also provides a method for real-time water turbidity detection using the above-mentioned real-time water turbidity detection system, comprising: The sensor level under clean water conditions is collected as the reference voltage; A detection beam is emitted using a laser emitting module. The beam passes through the optical detection area of ​​the water body to be tested via an emitting optical fiber. Suspended particles in the water body scatter and absorb the detection beam, and the remaining transmitted beam is collected by the receiving optical fiber and transmitted back to the photosensitive surface of the avalanche photodiode. The avalanche photodiode generates avalanche gain under high voltage bias to convert the optical signal into photocurrent. The primary voltage is amplified by the photoelectric IV amplification and conversion module, and after range adaptation, the analog voltage signal is output and sent to the main control unit. The main control unit uses a built-in filtering algorithm to remove noise, obtains a stable real-time voltage value, and calculates the change in the real-time voltage value relative to the reference voltage. The voltage-turbidity mathematical model in the main control unit is used to convert the change in voltage value relative to the reference voltage into a turbidity value, and compare it with the preset safety warning threshold in real time; if the turbidity value exceeds the preset safety warning threshold, the alarm module is driven to issue an alarm signal.

[0017] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a real-time water turbidity detection system. The system comprises core components such as a laser emitting module, transmitting optical fiber, receiving optical fiber, avalanche photodiode, photoelectric IV amplification and conversion module, a main control unit with a built-in specific filtering algorithm, and an alarm module. The system uses the transmitting and receiving optical fibers to import and export optical signals. All electrical components, including the laser emitting module, avalanche photodiode, and main control unit, are located outside the water body, with only the detection end of the optical fiber submerged. The optical fiber itself is a completely dielectric material, avoiding any metal electrodes or electrical components entering the water, thus physically avoiding problems such as electrode corrosion, scaling, and potential drift, achieving non-invasive detection. The system uses optical fiber as the optical signal transmission medium. The numerical aperture characteristics of the optical fiber itself constitute a natural physical space filter, effectively filtering out lateral stray light. By horizontally and coaxially aligning the transmitting and receiving optical fibers, a directional transmission optical path is constructed, ensuring that only optical signals propagating along the fiber axis are effectively received, while stray light from other directions is difficult to couple into the receiving fiber. This further isolates the system from interference from indoor lighting and ambient natural light, enabling the system to maintain stable measurement performance even under strong ambient light conditions. The system utilizes an avalanche photodiode, a semiconductor photodetector with internal current gain. When a high reverse bias voltage is applied to the PN junction, photogenerated carriers in the depletion layer gain sufficient kinetic energy to collide with the crystal lattice and ionize, generating new electron-hole pairs. This leads to a chain avalanche multiplication effect, resulting in significant internal current gain. Therefore, even the slight changes in transmitted light caused by trace suspended impurities in low-turbidity water can be amplified into a detectable electrical signal through avalanche gain. Consequently, compared to traditional detection devices, it offers higher detection sensitivity in the low-turbidity range. The alarm module automatically issues an alarm signal when turbidity exceeds the standard, avoiding hysteresis. This system has a simple structure and fills the technological gap in dedicated intelligent turbidity monitoring equipment for specific scenarios such as small water bodies and household aquariums.

[0018] By setting a voltage divider resistor consisting of several series resistors between the photoelectric IV amplification and conversion module and the main control unit, the amplified analog voltage signal can be linearly compressed to the safe sampling range of the main control unit's ADC. This protects the main control unit pins from damage by excessive voltage while ensuring the linear integrity of the photoelectric signal, making the signal conditioning link more complete.

[0019] Using a near-infrared laser as the light source, its emission spectrum is located in the infrared band, effectively avoiding the 400-760nm visible light range and isolating spectral interference from indoor lighting and ambient natural light. At the same time, infrared light does not cause visual damage to aquatic organisms, making it perfectly suited for aquatic keeping scenarios.

[0020] By using fiber optic mounting brackets to keep the probe ends of the transmitting and receiving optical fibers horizontally, coaxially, and facing each other underwater, the accuracy and repeatability of the optical path alignment are ensured, guaranteeing consistency between multiple measurements.

[0021] The SMA905 standard plastic fiber optic patch cord with a 1mm core diameter is used. This model has an industrial standard interface and has the advantages of low cost, reliable connection and convenient assembly, which helps to reduce system manufacturing costs and simplify assembly process.

[0022] By limiting the center-to-center distance between the end faces of the transmitting fiber detector and the receiving fiber detector to 4-6 mm, a transmission detection area with a fixed optical path is constructed. This ensures sufficient optical detection path length so that suspended particles can fully scatter and absorb the light beam, while avoiding excessive attenuation of transmitted light due to excessive spacing, which would prevent effective detection. This achieves an optimized balance between detection sensitivity and signal strength.

[0023] The power supply module is configured to provide unified power to the laser emission module, avalanche photodiode, photoelectric IV amplifier conversion module, main control unit, and alarm module, ensuring a stable operating voltage supply for all modules in the system.

[0024] An OLED display module is connected to the main control unit to display monitoring data in real time, enabling users to intuitively obtain key parameters such as current water turbidity, reference voltage, and real-time voltage, thereby improving the human-machine interaction experience and ease of use of the equipment.

[0025] The system uses an ESP32 microcontroller as the main control unit, whose built-in 12-bit ADC can provide high sampling accuracy; it uses a buzzer as the alarm module, which is low in cost, responds quickly, and has a clear warning effect, effectively attracting the user's attention when the turbidity exceeds the standard.

[0026] This invention also provides a method for real-time detection of water turbidity using the aforementioned system. By acquiring the sensor level under clean water conditions as a reference voltage, and using the current clean water state as a reference for zeroing calibration, it effectively eliminates systematic offsets caused by factors such as device aging, temperature changes, and slight contamination of the fiber optic end face, ensuring the accuracy and reliability of long-term monitoring. The detection beam passes through the water body via the transmitting fiber and is collected and transmitted back by the receiving fiber. Throughout the detection process, there are no electrical components or metal electrodes inside the water body; only the fiber optic end face contacts the water, ensuring the safety of the detection process and avoiding the safety hazards caused by electrical components entering the water in traditional electrode-type sensors. Utilizing an avalanche photodiode under high-voltage bias to generate avalanche gain converts the optical signal into a photocurrent, amplifying the weak transmitted light signal hundreds of times, ensuring effective detection of weak transmitted light in highly turbid water and avoiding detection failure. The system utilizes a built-in filtering algorithm in the main control unit to remove noise and obtain stable real-time voltage values. A voltage-turbidity mathematical model is then used to convert voltage changes into turbidity values. The original voltage signal undergoes a standardized processing chain of filtering, denoising, quantization, and model conversion to achieve a precise mapping from physical signal to turbidity value, ensuring the accuracy and repeatability of the detection results and completely eliminating reliance on manual judgment. Finally, by comparing the turbidity value with a preset safety warning threshold in real time, if the threshold is exceeded, the alarm module is activated to issue an alarm signal. This automatically alerts users at the first sign of excessive turbidity, avoiding alarm lag. The method is simple, reliable, and easy to operate, better meeting the practical needs of the aquarium and small-scale aquaculture industries. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the structure of a real-time water turbidity detection system according to the present invention.

[0028] Figure 2 This is a flowchart of the real-time water turbidity detection method of the present invention.

[0029] Among them, 1-laser emitting module, 2-emitting optical fiber, 3-optical fiber fixing bracket, 4-receiving optical fiber, 5-avalanche photodiode, 6-photoelectric IV amplification and conversion module, 7-voltage divider resistor, 8-main control unit, 9-alarm module, 10-OLED display module, 11-power supply module, 12-universal board. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0031] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0032] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0033] In the description of the embodiments of the present invention, it should be noted that if terms such as "upper," "lower," "horizontal," or "inner" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of the invention is in use, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. Furthermore, terms such as "first" and "second" are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0034] Furthermore, the use of the term "horizontal" does not imply that the component must be absolutely horizontal, but rather that it can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0035] In the description of the embodiments of the present invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in the present invention according to the specific circumstances.

[0036] The present invention will be further described in detail below with reference to specific embodiments. These descriptions are for explanation purposes only and are not intended to limit the scope of the invention.

[0037] Example 1 This invention provides a real-time water turbidity detection system, including a laser emitting module 1 and a power supply module 11. The laser emitting module 1 is used to emit a detection beam. An emitting optical fiber 2 is coupled to the output end of the laser emitting module 1 to transmit the detection beam to the water body to be tested. The detection end of the emitting optical fiber 2 is placed in the water body to be tested, and a receiving optical fiber 4 is arranged opposite to the detection end of the emitting optical fiber 2. The detection end of the receiving optical fiber 4 and the detection end of the emitting optical fiber 2 are arranged horizontally and coaxially opposite each other in the water body to be tested via an optical fiber fixing bracket 3, for collecting the transmitted beam after passing through the water body to be tested and transmitting it out of the water body. An avalanche photodiode 5 is arranged opposite to the light-emitting end of the receiving optical fiber 4, with the photosensitive surface of the avalanche photodiode 5 opposite to the light-emitting end of the receiving optical fiber 4, for receiving... The transmitted light beam converts the light intensity signal into a photocurrent signal; preferably, the fixed distance between the center of the end faces of the receiving optical fiber 4 and the transmitting optical fiber 2 is 4-6mm, more preferably 5mm; the avalanche photodiode 5 is connected to a photoelectric IV amplification and conversion module 6 through a voltage divider resistor 7, which is used to convert the photocurrent signal into a voltage signal and perform primary amplification; the output end of the photoelectric IV amplification and conversion module 6 is connected to a main control unit 8, which has a built-in multi-sampling mean filtering and first-order hysteresis exponential smoothing noise reduction algorithm, used to collect voltage signals and perform data processing and turbidity conversion; the main control unit 8 is connected to an alarm module 9 and an OLED display module 10, the alarm module 9 is used to issue an alarm signal when the turbidity exceeds the standard, and the OLED display module 10 is used to display monitoring data in real time; The main control unit 8 uses an ESP32 microcontroller. The voltage divider resistor 7 is preferably composed of a 1.5kΩ and a 3kΩ low-temperature drift resistor connected in series, linearly compressing the 0~5V analog amplified voltage to the safe sampling range of the ESP32 microcontroller's ADC (0~3.3V), protecting the main control pins while ensuring the linear integrity of the photoelectric signal. The ESP32 microcontroller has embedded multi-sampling mean filtering and first-order hysteresis exponential smoothing noise reduction algorithms. It is pre-calibrated in the 0~175NTU low turbidity range based on the Beer-Lambert law, establishing a voltage-turbidity mathematical model of v=a+bx, where v represents the real-time acquired voltage value (or the stable voltage signal after filtering), x represents the standard water turbidity value to be converted (in NTU, i.e., scattering turbidity unit), and x represents the intercept (regression constant) of the linear regression equation. In a physical sense, it corresponds to the theoretical baseline value of the voltage output by the system when the theoretical turbidity is zero (i.e., pure clear water). This constant is determined by gradient calibration experiments and linear fitting using software (such as Origin) before shipment. b represents the slope (regression coefficient) of the linear regression equation. Physically, it represents the system's sensitivity coefficient, i.e., the change in the system's output voltage signal (in V / NTU) corresponding to a 1 NTU change in water turbidity. This slope reflects the sensitivity of the photoelectric detection link to changes in turbidity, and is also obtained from calibration fitting experiments before shipment. The calibration linear correlation coefficient R... 2 ≥0.9765; The OLED display module 10 is a 1.3-inch display screen, with its SDA communication pin connected to pin 21 of ESP32 and its SCL clock pin connected to pin 22, displaying the reference voltage, real-time detection voltage and turbidity change Delta in real time; The buzzer is an active buzzer, which triggers an automatic sound and light alarm when the change Delta exceeds the user-preset threshold.

[0038] The laser emitting module 1, avalanche photodiode 5, photoelectric IV amplification and conversion module 6, voltage divider resistor 7, main control unit 8, alarm module 9, and OLED display module 10 are all connected to the power supply module 11.

[0039] The voltage divider resistor 7, main control unit 8, alarm module 9 and display module 10 are all integrated and fixed on the universal board 12.

[0040] The connection logic and workflow of each module are as follows: Power module 11 provides the appropriate operating voltage for avalanche photodiode 5, photoelectric IV amplification and conversion module 6, main control unit 8, etc.; Laser emitting module 1 outputs infrared laser, which is transmitted into the water body to be tested through emitting optical fiber 2. The transmitted light is attenuated by the suspended matter in the water body and then transmitted to avalanche photodiode 5 through receiving optical fiber 4; Avalanche photodiode 5 converts the light signal into a weak electrical signal, which is then sent to photoelectric IV amplification and conversion module 6 to complete the primary signal amplification; The amplified analog electrical signal is matched with the input range of main control unit 8 by voltage divider resistor 7 and then connected to main control unit 8; Main control unit 8 samples, filters, and calculates the signal, quantizes the voltage signal into water turbidity data, drives OLED display module 10 to display the value in real time, and compares it with the preset alarm threshold in real time. When the turbidity exceeds the standard, the alarm module 9 is triggered to complete the sound and light warning.

[0041] The detailed parameters and space installation instructions for each functional module are as follows: The laser emitting module 1 uses an 850nm near-infrared laser emitter. This wavelength can avoid interference from visible light in the environment, such as indoor fluorescent lights and natural light, and will not cause visual damage to organisms in the water being tested. It is fixed to one side of the optical path area of ​​the light-shielding base, and the light outlet is coaxially connected to the end face of the transmitting fiber 2 and locked in place by a snap-fit ​​structure. Both the transmitting fiber 2 and the receiving fiber 4 use 1mm core diameter SMA905 standard plastic fiber optic patch cords, which form a physical filtering structure based on the numerical aperture characteristics of the fiber to filter out lateral stray light in a 360° range.

[0042] The fiber optic mounting bracket 3 is made of rigid engineering plastic and features fine-tuning and locking functions. In actual deployment, the fiber optic mounting bracket 3 is placed underwater in the water body to be tested, i.e., a submerged probe, to securely hold the underwater probe ends of the transmitting fiber 2 and the receiving fiber 4. The two fiber probe ends are adjusted to a horizontal, coaxial, and aligned position, and the center-to-center distance between the end faces is strictly controlled to a fixed optical path of 5mm. By tightening the locking screws of the fiber optic mounting bracket 3, the consistency of optical path alignment is ensured in multiple measurements.

[0043] The photosensitive surface of the avalanche photodiode 5 is precisely aligned with the light-emitting end face of the receiving optical fiber 4. It is provided with a stable 10V DC bias voltage by an independent bias module, allowing it to operate within the optimal avalanche gain range and amplify weak transmitted light signals in high-turbidity scenes by hundreds of times. The photoelectric IV amplification and conversion module 6 is located in the circuit area, and its input is connected to the output of the avalanche photodiode 5 via a shielded wire.

[0044] Voltage divider resistor 7 is constructed using 1.5kΩ and 3kΩ resistors to form a 1:2 voltage divider network, which is directly soldered onto the universal board 12. Since the avalanche photodiode 5 and the amplifier module output voltage range is 0~5V, exceeding the microcontroller's safe input range of 0~3.3V, the intermediate node of the voltage divider is used as the signal output terminal and connected to the ADC sampling pin (pin 34) of the main control unit 8.

[0045] The main control unit 8 has a built-in 12-bit high-precision ADC, soldered and integrated in the center of the multi-board 12. The OLED display module 10 uses a 1.3-inch SH1106 screen, adopts I2C communication, and is fixed on the outside of the multi-board 12; its SDA pin is connected to pin 21 of the main control unit 8, and its SCL pin is connected to pin 22. The alarm module 9 is a low-level triggered active buzzer, arranged in the reserved sound holes at the corner of the multi-board 12, and its control pin is connected to pin 27 of the main control unit 8. Its power supply shares a common ground with the main control module. The power supply module 11 includes an adjustable DC power supply, a voltage regulator module, and a bias module, outputting multiple clean voltages of 10V, 5V, and 3.3V to meet the needs of digital and analog circuits.

[0046] Usage steps: Power-on initialization: When the power module 11 is turned on, the laser emitting module 1, avalanche photodiode 5, ESP32 microcontroller 8 and peripherals are powered on and self-tested in sequence. The system automatically performs clean water baseline calibration, using the collected voltage under clean water conditions as the reference BASE value. Optical path transmission detection: Laser emitting module 1 continuously emits 850nm infrared laser. The laser is injected into the water body to be tested in the fish tank through the emitting optical fiber 2. The suspended impurities in the water body scatter and absorb the incident laser. The optical power decreases as the turbidity of the water increases. The receiving optical fiber 4 collects the remaining transmitted beam and conducts it to the photosensitive surface of the avalanche photodiode 5. Photoelectric signal conversion and amplification: Avalanche photodiode 5 converts the transmitted light signal into a weak current signal, which is then amplified by photoelectric IV amplification and conversion module 6 and sent to voltage divider resistor 7 to complete the range adaptation. Main control data processing: The ESP32 microcontroller's built-in ADC collects the voltage data after voltage division, removes sampling noise by combining multi-sampling averaging with exponential smoothing algorithm, calls the pre-stored voltage-turbidity linear calibration formula to convert the real-time turbidity, and synchronously calculates the change in the current voltage relative to the baseline, Delta. Real-time data visualization: The OLED display module 10 refreshes four parameters in real time: BASE reference voltage, real-time sampling voltage, Delta change, and converted water turbidity. Threshold discrimination and closed-loop logic: The ESP32 microcontroller 8 compares the measured Delta with the system's preset alarm threshold. If Delta exceeds the set limit, the microcontroller immediately drives the buzzer 9 to sound and trigger an over-limit alarm. If it does not exceed the limit, the system automatically returns to step 2 and enters the continuous loop monitoring state.

[0047] Based on the aforementioned hardware, a Bluetooth communication submodule can be added. This Bluetooth communication submodule is electrically connected to the reserved serial port pin of the ESP32 microcontroller 8, forming an advanced monitoring device. In addition to basic monitoring functions, it adds features such as remote data viewing via a mobile app, cloud storage of historical turbidity data, and over-limit mobile pop-up alerts, catering to advanced, intelligent aquarium users.

[0048] See Figure 2 The present invention also provides a method for real-time water turbidity detection using the above-mentioned real-time water turbidity detection system, comprising: S1: Collect the sensor level under clean water conditions as the reference voltage; S2: The detection beam is emitted by the laser emitting module 1 and passes through the optical detection area of ​​the water body to be tested via the emitting optical fiber 2. The suspended particles in the water body scatter and absorb the detection beam, so that the remaining transmitted beam is collected by the receiving optical fiber 4 and transmitted back to the photosensitive surface of the avalanche photodiode 5. S3: The avalanche photodiode 5 generates avalanche gain under high voltage bias, converts the optical signal into photocurrent, completes primary voltage amplification through the photoelectric IV amplification and conversion module 6, and outputs an analog voltage signal after range adaptation to the main control unit 8. S4: Use the built-in filtering algorithm of the main control unit 8 to remove noise, obtain a stable real-time voltage value, and calculate the change of the real-time voltage value relative to the reference voltage. S5: The voltage-turbidity mathematical model in the main control unit 8 is used to convert the change in voltage value relative to the reference voltage into a turbidity value, and compare it with the preset safety warning threshold in real time; if the turbidity value exceeds the preset safety warning threshold, the alarm module 9 is driven to issue an alarm signal.

[0049] In summary, this invention provides a real-time water turbidity detection system and method. All digital circuits, photoelectric chips, and laser components in this system do not contact the water; only the fiber optic end enters the water. The fiber optic mounting bracket 3, placed directly at the bottom of the aquarium, ensures stable detection, fundamentally avoiding the scaling, corrosion, and potential drift defects caused by long-term immersion in water in traditional electrode-type sensors, thus significantly extending the equipment's lifespan. The dual anti-stray light design, combining an 850nm near-infrared light source with fiber optic spatial filtering, completely isolates the spectral interference from indoor lighting and ambient natural light. Unlike ordinary visible light photosensitive modules, this system maintains extremely high measurement stability even near windows or in strong indoor lighting environments; furthermore, the infrared band has no bio-phototoxicity, making it perfectly suited for aquarium keeping. Leveraging the avalanche multiplication gain of the aforementioned avalanche photodiode 5, weak light signals can be physically amplified by hundreds of times. Even minute changes in suspended impurities in low-turbidity water can trigger a significant voltage response (measured voltage changes exceeding 100mV under high-turbidity conditions). Furthermore, within the standard measurement range of 0~175 NTU, the linear fitting coefficient R²=0.9765, demonstrating measurement accuracy and long-term stability far exceeding traditional, simplified civilian photosensitive solutions. Thanks to the ingenious optical path design and standardized electronic component selection, the hardware material cost of the entire core sensing and computing system is extremely low, possessing significant advantages for industrialization. The system automatically captures a baseline and completes adaptive calibration upon power-up, completely eliminating the need for manual calibration by professionals. Combined with real-time numerical visualization and automatic alarm functions for exceeding limits, it replaces the traditional subjective estimation mode relying on human eyes, greatly reducing the user's learning curve. The core controller and interactive peripherals of the system are highly integrated on the universal board 12. The modular wiring greatly suppresses electromagnetic interference, and the overall structure is compact and small, making it extremely easy to deploy and install in various small water containers without taking up extra aquaculture space.

[0050] Therefore, this system employs transmissive fiber optic sensing technology, combined with an avalanche photodiode 5 and a photoelectric IV amplification and conversion module 6, to convert weak light signals into measurable voltage signals. It achieves high-precision detection within the standard aquarium turbidity range of 0-175 NTU, exhibiting excellent linear response. This intelligent detection system boasts advantages such as high safety from non-electric immersion, strong environmental adaptability, simple structure, low cost, and convenient installation. It overcomes the current bottlenecks in home aquarium water quality monitoring and small-scale aquaculture, which include large errors in manual judgment, high costs of professional equipment, and the susceptibility to corrosion and leakage of traditional probes. It has enormous application potential in home aquariums and small aquarium shops.

[0051] The above description is merely a preferred embodiment of the present invention and is not intended to limit the technical solution of the present invention in any way. Those skilled in the art should understand that, without departing from the spirit and principles of the present invention, the technical solution can be modified and replaced in several simple ways, and these modifications and replacements are all within the scope of protection covered by the claims.

Claims

1. A real-time water turbidity detection system, characterized in that, include: Laser emitting module (1), used to emit a detection beam; The transmitting fiber (2) is coupled to the output end of the laser emitting module (1) to transmit the detection beam to the water body to be tested. The receiving optical fiber (4) and the transmitting optical fiber (2) are arranged horizontally and coaxially opposite each other in the water body to be tested, and are used to collect the transmitted light beam after passing through the water body to be tested and transmit it out of the water body to be tested. Avalanche photodiode (5), wherein the photosensitive surface of the avalanche photodiode (5) is arranged opposite to the light-emitting end of the receiving optical fiber (4), and is used to receive the transmitted light beam and convert the light intensity signal into a photocurrent signal; The input terminal of the photoelectric IV amplification and conversion module (6) is electrically connected to the output terminal of the avalanche photodiode (5) to convert the photocurrent signal into a voltage signal and perform primary amplification. The main control unit (8) has a built-in multi-sampling mean filtering and first-order hysteresis exponential smoothing noise reduction algorithm. The main control unit (8) is connected to the photoelectric IV amplification and conversion module (6) for collecting voltage signals and performing data processing and turbidity conversion. An alarm module (9) is electrically connected to the main control unit (8) and is used to issue an alarm signal when the turbidity exceeds the standard.

2. The real-time water turbidity detection system according to claim 1, characterized in that, A voltage divider resistor (7) is provided between the photoelectric IV amplification and conversion module (6) and the main control unit (8), and the voltage divider resistor (7) is composed of several series resistors.

3. The real-time water turbidity detection system according to claim 1, characterized in that, The laser emitting module (1) is a near-infrared laser.

4. The real-time water turbidity detection system according to claim 1, characterized in that, The transmitting optical fiber (2) and the receiving optical fiber (4) are placed in the water body to be tested through the optical fiber fixing bracket (3), and the detection ends of the transmitting optical fiber (2) and the receiving optical fiber (4) are arranged horizontally and coaxially facing each other underwater.

5. The real-time water turbidity detection system according to claim 1, characterized in that, Both the transmitting fiber (2) and the receiving fiber (4) are made of SMA905 standard plastic fiber patch cord with a core diameter of 1 mm.

6. The real-time water turbidity detection system according to claim 1, characterized in that, The center distance between the detection end of the transmitting optical fiber (2) and the detection end of the receiving optical fiber (4) is fixed at 4-6 mm.

7. The real-time water turbidity detection system according to claim 1, characterized in that, It also includes a power module (11), which is connected to a laser emitting module (1), an avalanche photodiode (5), a photoelectric IV amplification and conversion module (6), a main control unit (8), and an alarm module (9).

8. The real-time water turbidity detection system according to claim 1, characterized in that, It also includes an OLED display module (10), which is connected to the main control unit (8).

9. The real-time water turbidity detection system according to claim 1, characterized in that, The main control unit (8) is an ESP32 microcontroller with a built-in 12-bit ADC; the alarm module (9) is a buzzer.

10. A method for real-time water turbidity detection using the real-time water turbidity detection system according to any one of claims 1-9, characterized in that, include: The sensor level under clean water conditions is collected as the reference voltage; The detection beam is emitted by the laser emission module (1) and passes through the optical detection area of ​​the water body to be tested via the emission fiber (2). The suspended particles in the water body scatter and absorb the detection beam, so that the remaining transmitted beam is collected by the receiving fiber (4) and transmitted back to the photosensitive surface of the avalanche photodiode (5). Using an avalanche photodiode (5) to generate avalanche gain under high voltage bias, the optical signal is converted into photocurrent. The primary voltage is amplified by the photoelectric IV amplification and conversion module (6), and after range adaptation, the analog voltage signal is output and sent to the main control unit (8). The filtering algorithm built into the main control unit (8) is used to remove noise, obtain a stable real-time voltage value, and calculate the change of the real-time voltage value relative to the reference voltage. The voltage-turbidity mathematical model in the main control unit (8) is used to convert the change of voltage value relative to the reference voltage into turbidity value, and compare it with the preset safety warning threshold in real time; if the turbidity value exceeds the preset safety warning threshold, the alarm module (9) is driven to issue an alarm signal.

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