Device for measuring water turbidity with optical stabilization

Abstract

This utility model relates to devices for measuring water turbidity in open water bodies and is intended for environmental monitoring, water quality control, assessing suspended particulate matter pollution in water bodies, and for use in hydrology, aquaculture, and water resource management systems. The technical result of the claimed turbidity meter design is improved measurement accuracy.The technical result is achieved in that the device for monitoring water turbidity with optical stabilization contains a controlled light source with a harmonic output signal with a frequency f and additionally four electrical transmission resonant filters tuned to a frequency f, connected to the outputs of the photodetector sections, rectifiers and low-frequency filters are connected to the output of the filters, one output of the rectifier, corresponding to the reference channel, is connected to an automatic gain control device, and the outputs of three other rectifiers are connected to a microcontroller, configured with the possibility of storing measured information and recording turbidity at the level of all channels.

Description

[0001] The utility model relates to devices for measuring water turbidity in open water bodies and is intended for environmental monitoring, water quality control, assessment of water body pollution by suspended particles, as well as for use in hydrology, aquaculture and water resource management systems.

[0002] A known onboard water parameter measuring system (Russian Federation Utility Model Patent No. 96662, IPC GO1N 21 / 01, published March 17, 2010) comprises a submersible module with sensors, a winch for lowering it, an optical radiation generating and receiving unit, and a combined cable-rope with optical fibers and electrical wires, providing communication between the above-water and submersible parts. This device is intended for marine use and allows for water parameter measurements at various depths.

[0003] However, this solution has a number of significant drawbacks that limit its effectiveness for long-term environmental monitoring. The main drawback is the inability to provide continuous, long-term monitoring at a fixed point in the water area to identify water quality trends. The system is mobile and tethered to a vessel, conducting only short-term, point measurements during expeditions, after which the equipment leaves the monitoring area. This prevents the automatic recording of seasonal, daily, and operational changes in indicators, which is critical for analyzing pollution dynamics.

[0004] Furthermore, the device is characterized by its complex and bulky design. The presence of an electromechanical winch, a long, specialized cable, rotating optical connectors, and current collectors makes the system difficult to deploy, operate, and maintain, and it is dependent on a power source and the presence of an operator. This design is not intended for autonomous, year-round operation.

[0005] Another drawback of the analog is the lack of a built-in hardware compensation system for optical source parameter drift. Any changes in luminous flux intensity due to lamp aging, temperature fluctuations, or supply voltage lead to systematic measurement errors that are not corrected in real time.

[0006] The measurements are spotty and asynchronous. Obtaining data at different depths requires time to move the submersible module using a winch, which prevents an instantaneous and synchronous "snapshot" of the entire water column. Furthermore, the submersible module, suspended by a cable, is subject to oscillations due to waves and vibrations from the vessel's machinery, further reducing the accuracy and stability of optical measurements.

[0007] Thus, the known device does not solve the problem of automatic, continuous and highly accurate monitoring of water turbidity with the ability to build dynamic trends and promptly detect changes.

[0008] The closest device to the invention is a device for monitoring water turbidity with automatic optical stabilization and spatial depth resolution (Patent for Utility Model of the Russian Federation No. 243469, IPC G01N21 / 17, published on 15.05.2026), containing a controlled light source, an optical system for forming measuring channels, a photodetector and a signal processing unit, characterized in that it is equipped with a transmitting optical bundle consisting of four fibers, one of which forms a reference channel, and the other three - measuring channels, wherein the reference channel is equipped with a reference optical filter, the spectral characteristics of which correspond to the transmittance of clean water, and the measuring channels are located at different depths in the reservoir; a receiving optical bundle containing a corresponding number of fibers, the input ends of which are installed opposite the output ends of the fibers of the transmitting optical bundle with a fixed gap;and a microcontroller designed with the ability to analyze the reference channel signal and generate a control action on the light source via a feedback circuit to stabilize the optical power, and the photodetector is designed as a linear one with the output ends of all fibers of the receiving optical bundle directed toward it.

[0009] A significant drawback of the prototype is the influence of external background light passing through the water layer and the fiber optic break on the photodetector. This additional background light adds to the information signal and, accordingly, introduces measurement error.

[0010] The technical result of the claimed design of the turbidity meter is an increase in the measurement accuracy.

[0011] The technical result is achieved in that a device for monitoring water turbidity with optical stabilization, containing a controlled light source, an optical system for forming measuring channels, a signal processing unit, a transmitting optical bundle consisting of four fibers, one of which forms a reference channel, and the other three - measuring channels, wherein the reference channel is equipped with a standard optical filter, the spectral characteristics of which correspond to the transmittance of clean water, and the measuring channels are located at different depths in a reservoir, a receiving optical bundle containing an appropriate number of fibers, the input ends of which are installed opposite the output ends of the fibers of the transmitting optical bundle with a fixed gap, a four-section photodetector, to which the output ends of all fibers of the receiving optical bundle are directed, the outputs of the three sections of the photodetector, corresponding to the measuring channels, are connected to a microcontroller,made with the possibility of analyzing the signal of the reference channel and generating a control action on the light source via a feedback circuit for stabilizing the optical power, wherein it contains a controlled light source with a harmonic output signal with a frequency f and additionally four electrical transmission resonant filters tuned to the frequency f, connected to the outputs of the sections of the photodetector, rectifiers and low-frequency filters are connected to the output of the filters, one output of the rectifier, corresponding to the reference channel, is connected to an automatic gain control device, and the outputs of the three other rectifiers are connected to a microcontroller made with the possibility of storing the measured information and recording the turbidity at the level of all channels.

[0012] In the proposed device for monitoring water turbidity with optical stabilization, the measurement accuracy is increased by introducing modulation of the output radiation source with a harmonic signal with a frequency f and four electrical transmission resonant filters tuned to the frequency f, connected to the outputs of the photodetectors, and rectifiers and low-pass filters are connected to the output of the resonant filters, which eliminates the influence of the background radiation flux on the measurement error and eliminates a wide range of noise from the information signal, which also improves the measurement accuracy.

[0013] The device for monitoring water turbidity with optical stabilization comprises a controlled voltage source 1 of harmonic shape with a frequency f, which powers a lamp with a reflector - a controlled light source 2. Opposite the lamp is the input end of a transmitting bundle consisting of four optical fibers 3, 4, 5, 6. The output end of fiber 3 forms a reference channel and is located above the water surface. An optical filter 7 is installed at its end, the spectral characteristics of which correspond to the transmittance of pure water, which provides a reference signal. Fibers 4, 5, 6 form measuring channels: their output ends are introduced into the reservoir and are located at various depths, evenly distributed vertically: 4 - at the surface, 5 - in the middle thickness, 6 - at the bottom. Opposite each output end of the measuring fibers, maintaining a constant gap (d), the input ends of the fibers of the corresponding receiving bundle 8, 9, 10, 11 are placed.Similarly, the input end of the fiber 8 of the receiving bundle is mounted opposite the reference channel (fiber 3 with optical filter 7). The output ends of all four receiving fibers 8, 9, 10, 11 are fixed in front of a four-section photodetector 12, to which the output ends of all fibers of the receiving bundle are directed. The outputs of the three sections of the photodetector 12, corresponding to the measuring channels, are connected to a microcontroller 13, allowing the storage of measured information, and the signal of the reference channel is connected to a light source control device for stabilizing the emitted optical power. Four identical devices 14, containing a series-connected electrical transmission resonant filter tuned to a frequency f, a rectifier and a low-pass filter, are connected to the outputs of the four sections of the photodetector 12.The low-pass filter output corresponding to the reference channel is connected to automatic gain control unit 15, while the outputs of the other three low-pass filters are connected to microcontroller 13, which contains modem 16 for data transmission. Power for the claimed device is provided by solar battery 17.

[0014] The claimed device for monitoring water turbidity with optical stabilization operates as follows.

[0015] The radiation flux from light source 2 enters the input end of the cable of fibers 3, 4, 5, 6. This flux is focused onto the output end of a bundle of four identical optical fibers 3, 4, 5, 6, which serve as light guides to the measurement points. The reference contour plays a key role in ensuring metrological stability. The radiation flux from fiber 3 enters through reference optical filter 7, optical fiber 8, photodetector 13 with devices 14 containing resonant filters, a rectifier, and a low-pass filter, to automatic gain control device 15.

[0016] Three measuring fibers 4, 5, and 6 deliver a stabilized light flux into the water column at strictly defined depths, forming a vertical profile. The ends of these fibers and the ends of the corresponding receiving fibers 9, 10, and 11 of the second bundle are secured to ensure a precise and constant base distance (optical path d) between them. This distance is analogous to a cuvette containing the monitored liquid. Light emerging from the transmitting fiber diverges and passes through a water layer of thickness d, where it is attenuated. Optical signals passing through different water layers at different depths have different turbidity. The signals are proportional and fed to microcontroller 13, which measures turbidity at different depths, compares the results, and transmits information via modem 16, indicating the water degradation trend.

[0017] When operating a water turbidity monitoring device with optical stabilization, errors may occur in each channel element due to various factors, especially temperature, which negatively impacts the measurement results. An automatic gain control (AGC) is used to compensate for these errors. The total measurement error of the entire optoelectronic path is recorded by the photodetector section of the reference channel, and the signal from this photodetector section, using AGC 15, adjusts the source's radiant flux so that the signal at the output of the photodetector section of the reference channel remains constant. Thus, automatic gain control compensates for the influence of all errors on the water turbidity measurement results in a body of water.

[0018] The use of modulation of the information signal with a harmonic function ensures a reduction in error by eliminating the influence of external factors caused by the influence of the external background light flow passing through the water layer and the break in the optical fiber to the photodetector.

Claims

A device for measuring water turbidity with optical stabilization, comprising a controlled light source, an optical system for forming measuring channels, a signal processing unit, a transmitting optical bundle consisting of four fibers, one of which forms a reference channel, and the other three - measuring channels, wherein the reference channel is equipped with a standard optical filter, the spectral characteristics of which correspond to the transmittance of clean water, and the measuring channels are located at different depths in a reservoir, a receiving optical bundle containing an appropriate number of fibers, the input ends of which are installed opposite the output ends of the fibers of the transmitting optical bundle with a fixed gap, a four-section photodetector, to which the output ends of all fibers of the receiving optical bundle are directed, the outputs of the three sections of the photodetector, corresponding to the measuring channels, are connected to a microcontroller,made with the possibility of analyzing the signal of the reference channel and generating a control action on the light source via a feedback circuit for stabilizing the optical power, characterized in that the output signal of the controlled light source is a harmonic signal with a frequency f and additionally four electrical transmission resonant filters tuned to the frequency f, connected to the outputs of the sections of the photodetector, rectifiers and low-frequency filters are connected to the output of the filters, one output of the rectifier, corresponding to the reference channel, is connected to an automatic gain control device, and the outputs of the three other rectifiers are connected to a microcontroller made with the possibility of storing the measured information and recording the turbidity at the level of all channels.

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