A novel optical dissolved oxygen sensor and a method for detecting dissolved oxygen concentration

Abstract

The present invention belongs to the technical field of optical dissolved oxygen sensors, and particularly relates to a novel optical dissolved oxygen sensor and a method for detecting dissolved oxygen concentration. The sensor includes a front end cover, an optical window, an excitation light LED, an excitation light receiving and detecting unit, a fluorescence receiving and detecting unit, a signal processing module, etc.; the front end cover is recessed with an optical cavity, the optical cavity is covered with an optical window directly above, and an oxygen-sensitive film in direct contact with the water body to be measured is attached to the top surface of the optical window; the excitation light LED emits blue-green light towards the optical window on one side of the optical cavity, so that the oxygen-sensitive film is photo-excited to generate red fluorescence; the excitation light receiving and detecting unit receives the reflected light generated by the excitation light reflected by the optical window on the other side of the optical cavity; the fluorescence receiving and detecting unit receives the red fluorescence directly below the optical cavity. The present invention solves the problem of large power consumption during the operation of the existing optical dissolved oxygen sensor, reduces the drift and error of the sensor output, and makes the measurement of the optical dissolved oxygen sensor more accurate and rapid.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical dissolved oxygen sensors, and particularly relates to a novel optical dissolved oxygen sensor and a method for detecting dissolved oxygen concentration. Background Art

[0002] Dissolved oxygen in seawater is closely related to a variety of marine biogeochemical processes, and is an important research content in marine science and one of the important parameters for marine ecological environment monitoring. Minute changes in dissolved oxygen in seawater can have important impacts on the marine environment, especially on the marine nitrogen cycle and various redox processes. Therefore, accurately and continuously measuring the dissolved oxygen concentration in seawater has important scientific significance. The optical dissolved oxygen sensor based on the fluorescence quenching principle overcomes the deficiencies of traditional dissolved oxygen sensors and has advantages such as accurate measurement, rapidity, and anti-interference. Therefore, the optical method based on the fluorescence quenching principle is the most suitable technology for long-term in-situ detection in the ocean.

[0003] Currently, the optical dissolved oxygen sensors that have emerged in the industry, such as "A Method and Use for Measuring Dissolved Oxygen Based on the Fluorescence Quenching Principle" disclosed in Patent No. CN105136766B and "An Ocean Optical Dissolved Oxygen Sensor" disclosed in Patent No. CN204679422U, both adopt a dual-light-path (one path for excitation light and one path for reference light) setting method. By detecting the phase difference information between the excitation light and the reference light and combining this information with the temperature information self-measured by the sensor, the dissolved oxygen concentration of the water body to be measured is inversely obtained through a detection algorithm. However, the existing optical dissolved oxygen sensors have the following defects:

[0004] 1) It is necessary to set two LEDs for the excitation light and the reference light, and the operation of the two LEDs will result in relatively large power consumption;

[0005] 2) The excitation light LED and the reference light LED emit light successively, and the same photodetector is used to detect the phases of the red fluorescence and the reference light respectively; on the one hand, this makes the measurement period of the optical dissolved oxygen sensor relatively long, and on the other hand, it makes the oxygen-sensitive membrane of the optical dissolved oxygen sensor receive light irradiation for a longer time, increasing the light decomposition effect on the oxygen-sensitive membrane, which will cause a relatively large drift in the output of the optical dissolved oxygen sensor;

[0006] 3) The wavelengths emitted by the excitation light LED and the reference light LED are different, and the differences in LED materials will cause inconsistent aging drift during long-term deployment, which will further cause relatively large errors in the optical dissolved oxygen sensor during long-term testing.

[0007] In addition, for an optical dissolved oxygen sensor, pressure can affect the stability of the excited state of the fluorescent luminescent material itself and also affect the activity of oxygen molecules entering the oxygen-sensitive membrane of the optical dissolved oxygen sensor. Therefore, an optical dissolved oxygen sensor based on the fluorescence quenching method exhibits pressure correlation. When the optical dissolved oxygen sensor is applied in the ocean field, especially during vertical profile measurements, the hydrostatic pressure on the sensor changes, and the pressure correlation of the sensor will cause errors in the output of the sensor at this time. To ensure the accuracy of the data of the optical dissolved oxygen sensor, pressure compensation needs to be performed on the output of the optical dissolved oxygen sensor. However, the existing optical dissolved oxygen sensor itself cannot measure the pressure of its own environment and needs to rely on an external pressure sensor deployed separately outside the optical dissolved oxygen sensor to measure the environmental pressure. Therefore, the existing optical dissolved oxygen sensor cannot directly output the dissolved oxygen concentration of the water body to be measured after pressure compensation, and manual pressure compensation needs to be performed on the output of the optical dissolved oxygen sensor later. Summary of the Invention

[0008] Aiming at the deficiencies in the related art, the present invention provides a novel optical dissolved oxygen sensor and a dissolved oxygen concentration detection method, which are used to at least solve the problems of large power consumption, large drift and error in the output of the existing optical dissolved oxygen sensor during operation, and make the measurement of the optical dissolved oxygen sensor more accurate and rapid.

[0009] The present invention provides a novel optical dissolved oxygen sensor, which includes a cylinder body, a watertight connector and a front end cover assembly respectively connected to both ends of the cylinder body. The front end cover assembly specifically includes:

[0010] A front end cover, one end of which is a connection end sealed to the cylinder body, and the other end is a test end. A light cavity is recessed in the test end; a first channel and a second channel obliquely penetrating the front end cover are respectively communicated with the left and right sides of the light cavity. The axes of the first channel and the second channel are symmetrically arranged with respect to the axis of the light cavity; a third channel penetrating the front end cover is communicated directly below the light cavity, and the axial direction of the third channel is consistent with the axial direction of the light cavity;

[0011] A light window, which is installed in the test end and covers directly above the light cavity. An oxygen-sensitive membrane is attached to the top surface of the light window, and the top surface of the oxygen-sensitive membrane is in direct contact with the water body to be measured;

[0012] An excitation light LED, which is installed in the first channel and is used to emit blue-green excitation light towards the light window, so that the oxygen-sensitive membrane is excited by the excitation light to generate red fluorescence;

[0013] An excitation light receiving and detecting unit, which is installed in the second channel and is used to receive the reflected light generated by the excitation light being reflected by the light window;

[0014] A fluorescence receiving and detecting unit, which is installed in the third channel and is used to receive the red fluorescence;

[0015] The novel optical dissolved oxygen sensor further includes a signal processing module, and the signal processing module is communicatively connected to the excitation light LED, the excitation light receiving detection unit, and the fluorescence receiving detection unit.

[0016] In the above technical solution, by arranging the excitation light receiving detection unit on the reflection light path of the excitation light, the technical effect of using the reflection light of the excitation light LED to replace the reference light of the existing optical dissolved oxygen sensor is achieved; thus, through the setting of a single LED, i.e., the excitation light LED, and the setting of two receiving detection units, i.e., the excitation light receiving detection unit and the fluorescence receiving detection unit, the excitation light LED only needs to emit light once, and the optical dissolved oxygen sensor can synchronously detect the phases of the reflection light and fluorescence generated by the excitation light LED; therefore, the present technical solution solves the problem of high power consumption caused by the use of two LEDs in the existing optical dissolved oxygen sensor, breaks through the conventional practice of the existing optical dissolved oxygen sensor using two LEDs to emit light successively and detecting the phases of red fluorescence and reference light step by step through the same photodetector, and also solves the problems of long measurement period and long light receiving time of the oxygen-sensitive film in the existing optical dissolved oxygen sensor, significantly reduces the light decomposition effect of the oxygen-sensitive film, better reduces the drift and error of the output of the optical dissolved oxygen sensor, and further makes the measurement of the optical dissolved oxygen sensor more accurate and rapid.

[0017] In some embodiments, the excitation light receiving detection unit specifically includes an excitation light receiving narrowband filter and a first photodetector communicatively connected to the signal processing module; the excitation light receiving narrowband filter is installed at one end of the second channel close to the optical cavity for filtering other light except the excitation light; the first photodetector is installed below the excitation light receiving narrowband filter to detect the signal of the reflection light.

[0018] In some embodiments, the fluorescence receiving detection unit specifically includes a fluorescence receiving narrowband filter and a second photodetector communicatively connected to the signal processing module; the fluorescence receiving narrowband filter is installed at one end of the third channel close to the optical cavity for filtering other light except the red fluorescence; the second photodetector is installed below the fluorescence receiving narrowband filter to detect the signal of the red fluorescence.

[0019] In some embodiments, the optical cavity, the optical window, and the oxygen-sensitive film are all inclined relative to the cylinder body, and the inclination angle is 30 - 60 degrees.

[0020] In some embodiments, the front end cover assembly further includes a temperature sensor, and the temperature sensor protrudes from the test end and is in direct contact with the water body to be measured to measure the temperature of the water body to be measured; the temperature sensor is communicatively connected to the signal processing module.

[0021] In some of these embodiments, the front end cover assembly further includes a pressure sensor, which protrudes from the test end and is in direct contact with the water body to be measured to measure the pressure of the water body to be measured; the pressure sensor is communicatively connected to the signal processing module.

[0022] In some of these embodiments, the signal processing module has a built-in pressure compensation program to automatically perform pressure compensation on the output of the novel optical dissolved oxygen sensor.

[0023] The present invention also provides a method for detecting dissolved oxygen concentration, which is carried out using the above-mentioned novel optical dissolved oxygen sensor, and includes the following steps:

[0024] Place the novel optical dissolved oxygen sensor in the water body to be measured, and control the excitation light LED to emit blue-green excitation light; the temperature sensor synchronously measures the temperature t of the water body to be measured;

[0025] The excitation light is reflected by the light window to generate reflected light, and the reflected light is received by the excitation light receiving and detecting unit and converted into a reflected light signal; at the same time, the excitation light also passes through the light window to reach the oxygen-sensitive film, and the oxygen-sensitive film is excited by the excitation light to generate red fluorescence, and the red fluorescence is received by the fluorescence receiving and detecting unit and converted into a fluorescence signal;

[0026] The signal processing module performs a difference calculation on the phases of the fluorescence signal and the reflected light signal to obtain a phase delay θ r , and then performs a calculation according to Equation (1) to obtain the uncompensated dissolved oxygen concentration Do of the water body to be measured;

[0027]

[0028] Among them, in Equation (1), C1, C2, C3, C4, C5, C6, and C7 are calibration coefficients based on the novel optical dissolved oxygen sensor itself, and are all constants.

[0029] The above technical solution enables the excitation light LED to emit light only once, and the optical dissolved oxygen sensor can synchronously detect the phases of the reflected light and fluorescence generated by the excitation light LED, and then combine the temperature of the water body to be measured synchronously measured by the temperature sensor to calculate the uncompensated dissolved oxygen concentration of the water body to be measured.

[0030] The present invention also provides a method for detecting dissolved oxygen concentration, which is carried out using the above-mentioned novel optical dissolved oxygen sensor, and includes the following steps:

[0031] Place the novel optical dissolved oxygen sensor in the water body to be measured, and control the excitation light LED to emit blue-green excitation light; the temperature sensor synchronously measures the temperature t of the water body to be measured; the pressure sensor synchronously measures the pressure P of the water body to be measured;

[0032] The excitation light is reflected by the optical window to generate reflected light, which is received by the excitation light receiving and detecting unit and converted into a reflected light signal. At the same time, the excitation light also passes through the optical window to reach the oxygen-sensitive film. The oxygen-sensitive film is excited by the excitation light to generate red fluorescence, which is received by the fluorescence receiving and detecting unit and converted into a fluorescence signal.

[0033] The signal processing module calculates the difference in the phases of the fluorescence signal and the reflected light signal to obtain the phase delay θ. r , and then performs calculations according to Equation (1) to obtain the uncompensated dissolved oxygen concentration Do of the water body to be measured, and then performs calculations according to Equation (2) to obtain the dissolved oxygen concentration Do of the water body to be measured after pressure compensation. pres ;

[0034]

[0035]

[0036] Among them, in Equation (1) and Equation (2),

[0037] C1, C2, C3, C4, C5, C6, C7 are calibration coefficients based on the new optical dissolved oxygen sensor itself and are all constants;

[0038] C press1 is the first pressure compensation coefficient, and its value is 0.00025;

[0039] C press2 is the second pressure compensation coefficient, and its value is 0.0328.

[0040] The above technical solution enables the excitation light LED to emit light only once, and the optical dissolved oxygen sensor can synchronously detect the phases of the reflected light and fluorescence generated by the excitation light LED. Furthermore, combined with the temperature of the water body to be measured synchronously measured by the temperature sensor, the uncompensated dissolved oxygen concentration of the water body to be measured is calculated. On this basis, combined with the pressure of the water body to be measured synchronously measured by the integrated pressure sensor, the dissolved oxygen concentration of the water body to be measured after pressure compensation is calculated, thereby realizing automatic pressure compensation for the output of the optical dissolved oxygen sensor and solving the problem that the existing optical dissolved oxygen sensor needs to deploy a pressure probe separately and requires manual pressure compensation later.

[0041] Based on the above technical solution, the novel optical dissolved oxygen sensor and the dissolved oxygen concentration detection method in the embodiments of the present invention solve the problem of relatively high power consumption during the operation of the existing optical dissolved oxygen sensor, reduce the drift and error of the sensor output, and make the measurement of the optical dissolved oxygen sensor more accurate and rapid. In addition, through the integrated setting of the pressure sensor, the pressure of the water to be measured can be synchronously measured during the operation of the optical dissolved oxygen sensor, so as to automatically perform pressure compensation on the output of the optical dissolved oxygen sensor, and further enable the novel optical dissolved oxygen sensor to directly output the dissolved oxygen concentration of the water to be measured after pressure compensation. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The drawings described herein are used to provide a further understanding of the present invention, and constitute a part of this application. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings:

[0043] Figure 1 is a three-dimensional structure diagram of the novel optical dissolved oxygen sensor of the present invention;

[0044] Figure 2 is a sectional view of the structure of the novel optical dissolved oxygen sensor of the present invention;

[0045] Figure 3 is Figure 2 the A-A sectional view of;

[0046] Figure 4 is a block diagram of the circuit module of the novel optical dissolved oxygen sensor of the present invention.

[0047] In the figure: 10, cylinder body; 11, analog board; 12, digital board; 13, power supply and interface board; 14, watertight connector; 15, first sealing ring; 20, front end cover assembly; 21, front end cover; 211, optical cavity; 212, first hole; 213, second hole; 214, third hole; 22, optical window; 23, second sealing ring; 24, oxygen-sensitive film; 25, oxygen-sensitive film retaining ring; 26, excitation light LED; 27, LED retaining ring; 28, excitation light receiving and detecting unit; 281, excitation light receiving narrowband filter; 282, first photodetector; 283, first bracket; 284, first retaining ring; 29, fluorescence receiving and detecting unit; 291, fluorescence receiving narrowband filter; 292, second photodetector; 293, second bracket; 294, second retaining ring; 30, temperature sensor; 31, pressure sensor. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0048] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work belong to the scope of protection of the present invention.

[0049] In the description of the present invention, it should be understood that the terms "center", "upper", "lower", "top", "bottom", "inner", "outer", "left", "right", "front", "rear", "vertical", "horizontal", etc. indicate the orientation or positional relationship based on the Figure 3 orientation or positional relationship shown, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention.

[0050] The terms "first", "second", etc. are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first", "second", etc. may explicitly or implicitly include one or more of such features.

[0051] In the description of the present invention, it should be noted that unless otherwise clearly specified and limited, the terms "mounted", "connected", "coupled" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be directly connected, or indirectly connected through an intermediate medium, and it may be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0052] As Figures 1 - 3 shown, the novel optical dissolved oxygen sensor of the present invention includes a cylinder 10 and a watertight connector 14 and a front end cover assembly 20 respectively connected to both ends of the cylinder 10. The front end cover assembly 20 further includes a front end cover 21, an optical window 22, an excitation light LED 26, an excitation light receiving and detecting unit 28, and a fluorescence receiving and detecting unit 29.

[0053] One end of the front end cap 21 is a connection end that is hermetically connected to the cylinder body 10. This connection end extends into the cylinder body 10, and a radial seal is achieved between it and the cylinder body 10 through the first sealing ring 15. The other end of the front end cap 21 is a test end, and a light cavity 211 is recessed in the test end. The left and right sides of the light cavity 211 are respectively communicated with a first hole 212 and a second hole 213 that obliquely penetrate the front end cap 21. The axis of the first hole 212 and the axis of the second hole 213 are symmetrically arranged with respect to the axis of the light cavity 211, and the axes of the first hole 212, the second hole 213, and the axis of the light cavity 211 are coplanar. A third hole 214 that penetrates the front end cap 21 is communicated directly below the light cavity 211, and the axial direction of the third hole 214 is the same as the axial direction of the light cavity 211.

[0054] The optical window 22 is installed inside the test end of the front end cap 21 and covers directly above the light cavity 211; it can be understood that the bottom area of the optical window 22 is larger than the upper opening of the light cavity 211, and a seal is achieved between the bottom surface of the optical window 22 and the front end cap 21 through the second sealing ring 23. An oxygen-sensitive film 24 is attached to the top surface of the optical window 22, and the oxygen-sensitive film 24 is fixed to the front end cap 21 through an oxygen-sensitive film retaining ring 25; the top surface of the oxygen-sensitive film retaining ring 25 is flush with the top surface of the test end of the front end cap 21, and the center of the oxygen-sensitive film retaining ring 25 has a through hole so that the top surface of the oxygen-sensitive film 24 can be in direct contact with the water body to be measured.

[0055] The excitation light LED 26 is installed in the first hole 212 through an LED retaining ring 27 and is used to emit blue-green excitation light towards the optical window 22. Further, the excitation light passes through the optical window 22 and reaches the oxygen-sensitive film 24, so that the oxygen-sensitive film 24 is excited by the excitation light to generate red fluorescence; at the same time, the excitation light is also reflected by the optical window 22 to generate reflected light. Since the emission direction of the excitation light is the same as the axial direction of the first hole 212, and the axis of the second hole 213 is symmetrically arranged with respect to the axis of the first hole 212 with respect to the light cavity 211, the reflected light generated by the excitation light being reflected by the optical window 22 will directly enter the second hole 213.

[0056] The excitation light receiving and detecting unit 28 is installed in the second hole 213, that is, the excitation light receiving and detecting unit 28 is located on the emission optical path of the excitation light and is used to receive the reflected light generated by the excitation light being reflected by the optical window 22. The fluorescence receiving and detecting unit 29 is installed in the third hole 214 and is used to receive the red fluorescence generated by the oxygen-sensitive film 24 being excited by the excitation light.

[0057] The new optical dissolved oxygen sensor further includes a signal processing module, and the signal processing module is communicatively connected to the excitation light LED 26, the excitation light receiving and detecting unit 28, and the fluorescence receiving and detecting unit 29. As Figure 4As shown, the signal processing module can be an FPGA-based signal processing module, which is used to control the excitation light LED 26 to emit light, extract the phase information of the reflected light collected by the excitation light receiving and detecting unit 28 and the red fluorescence collected by the fluorescence receiving and detecting unit 29, and then calculate the dissolved oxygen concentration of the water body to be measured, and output the result data through the interface module. It can be understood that the working principle and main functions of the signal processing module are well-known to those skilled in the art and will not be described in detail here.

[0058] The new optical dissolved oxygen sensor further includes a detection circuit board; the detection circuit board further includes an analog board 11, a digital board 12, a power supply and interface board 13, etc. The analog board 11, the digital board 12, and the power supply and interface board 13 are sequentially connected together by bolts and connectors and fixed inside the cylinder 10. The detection circuit board is connected to both the excitation light receiving and detecting unit 28 and the fluorescence receiving and detecting unit 29, and completes signal reception, conditioning, data acquisition, storage and analysis through the analog board 11 and the digital board 12, and powers the optical dissolved oxygen sensor through the power supply and interface board 13.

[0059] In the above-mentioned exemplary embodiment, by arranging the excitation light receiving and detecting unit 28 on the reflection light path of the excitation light, the technical effect of using the reflected light of the excitation light LED 26 to replace the reference light of the existing optical dissolved oxygen sensor is achieved; thus, through the setting of the single LED of the excitation light LED 26 and the two receiving and detecting units of the excitation light receiving and detecting unit 28 and the fluorescence receiving and detecting unit 29, the excitation light LED 26 only needs to emit light once, and the optical dissolved oxygen sensor can realize the synchronous detection of the phases of the reflected light and fluorescence generated by the excitation light LED 26; therefore, the technical solution of the present invention solves the problem of large power consumption caused by the use of dual LEDs in the existing optical dissolved oxygen sensor, breaks through the conventional method of the existing optical dissolved oxygen sensor using dual LEDs to emit light successively and detecting the phases of the red fluorescence and the reference light step by step through the same photodetector, and also solves the problems of long measurement period and long light receiving time of the oxygen-sensitive film 24 in the existing optical dissolved oxygen sensor, significantly reduces the light decomposition effect of the oxygen-sensitive film 24, better reduces the drift and error of the output of the optical dissolved oxygen sensor, and further makes the measurement of the optical dissolved oxygen sensor more accurate and rapid.

[0060] Such as Figure 3As shown, in some embodiments, the excitation light receiving and detecting unit 28 specifically includes an excitation light receiving narrowband filter 281 and a first photodetector 282 communicatively connected to the signal processing module. The excitation light receiving narrowband filter 281 is installed at one end of the second channel 213 close to the optical cavity 211 for filtering out light other than the excitation light, such as filtering out red fluorescence and other stray light. The first photodetector 282 is installed below the excitation light receiving narrowband filter 281 for detecting the signal of the reflected light. Further, one end of the first photodetector 282 is crimped to the bottom surface of the excitation light receiving narrowband filter 281, and the other end is fixed in the second channel 213 through a first retaining ring 284. In some embodiments, the fluorescence receiving and detecting unit 29 specifically includes a fluorescence receiving narrowband filter 291 and a second photodetector 292 communicatively connected to the signal processing module. The fluorescence receiving narrowband filter 291 is installed at one end of the third channel 214 close to the optical cavity 211 for filtering out light other than the red fluorescence, such as filtering out the excitation light and other stray light. The second photodetector 292 is installed below the fluorescence receiving narrowband filter 291 for detecting the signal of the red fluorescence. Further, one end of the second photodetector 292 is crimped to the bottom surface of the fluorescence receiving narrowband filter 291, and the other end is fixed in the third channel 214 through a second retaining ring 294. It should be noted that the first photodetector 282 is separated from the metal front end cover 21 by a first bracket 283, and the second photodetector 292 is separated from the metal front end cover 21 by a second bracket 293 to avoid signal interference. In addition, the first photodetector 282 and the second photodetector 292 can be the same type of photodetector, the first bracket 283 and the second bracket 293 can also be the same type of bracket, and the first retaining ring 284 and the second retaining ring 294 can also be the same type of retaining ring.

[0061] Combined with Figure 4 As shown, the second photodetector 292 and the first photodetector 282 respectively detect the red fluorescence signal and the emission light signal of the excitation light. Both first perform IV conversion, then are amplified through band-pass filtering in multiple stages, and then the data is given to the FPGA-based signal processing module through AD conversion.

[0062] Such as Figure 1 、 Figure 2 As shown, in some embodiments, the optical cavity 211, the optical window 22, and the oxygen-sensitive film 24 are all inclined relative to the cylinder body 10, and the inclination angle is 30 - 60 degrees; that is, the end face of the test end of the front end cover 21 forms an inclination angle of 30 - 60 degrees relative to the axis of the cylinder body 10. This inclined setting protects the oxygen-sensitive film 24 on the one hand, and on the other hand, can quickly drain the water on the surface of the oxygen-sensitive film 24 when the optical dissolved oxygen sensor emerges from the water surface, and further drift correction can be performed on the measurement data of the optical dissolved oxygen sensor in the air environment.

[0063] As Figure 1 , Figure 3 shown, in some embodiments, the front end cap assembly 20 further includes a temperature sensor 30. The temperature sensor 30 protrudes from the test end and is in direct contact with the water body to be measured, so as to measure the temperature of the water body to be measured; further, the temperature sensor 30 is disposed near the oxygen-sensitive film 24 to more accurately measure the temperature of the water body to be measured near the oxygen-sensitive film 24. The temperature sensor 30 is communicatively connected to the signal processing module; as Figure 4 shown, the signal detected by the temperature sensor 30 is given to the FPGA-based signal processing module after signal conditioning and AD conversion. This illustrative embodiment realizes the integrated setting of the temperature sensor 30 on the optical dissolved oxygen sensor and the data transmission of the temperature of the water body to be measured.

[0064] As Figure 1 , Figure 2 shown, in some embodiments, the front end cap assembly 20 further includes a pressure sensor 31. The pressure sensor 31 protrudes from the test end and is in direct contact with the water body to be measured; compared with the existing method of separately deploying the pressure sensor 31 for the optical dissolved oxygen sensor, this embodiment can more accurately measure the pressure of the water body to be measured at the test end of the optical dissolved oxygen sensor. The pressure sensor 31 is communicatively connected to the signal processing module; as Figure 4 shown, the signal detected by the pressure sensor 31 is given to the FPGA-based signal processing module after signal conditioning and AD conversion. This illustrative embodiment realizes the integrated setting of the pressure sensor 31 on the optical dissolved oxygen sensor and the data transmission of the pressure of the water body to be measured.

[0065] In some embodiments, the signal processing module is built with a pressure compensation program to automatically perform pressure compensation on the output of the new optical dissolved oxygen sensor. This illustrative embodiment enables the optical dissolved oxygen sensor to directly output the dissolved oxygen concentration of the water body to be measured after pressure compensation.

[0066] Combined with Figures 1 - 4 shown, the present invention also provides a method for detecting the dissolved oxygen concentration of a water body to be measured using the above new optical dissolved oxygen sensor, which will be described in detail below.

[0067] Embodiment 1:

[0068] The present invention provides a method for detecting the dissolved oxygen concentration, which is carried out using the above new optical dissolved oxygen sensor, and includes the following steps:

[0069] Place the new optical dissolved oxygen sensor in the water body to be measured, and control the excitation light LED 26 to emit blue-green excitation light; the temperature sensor 30 synchronously measures the temperature t of the water body to be measured;

[0070] The excitation light is reflected by the optical window 22 to generate reflected light, and the reflected light is received by the excitation light receiving and detecting unit 28 and converted into a reflected light signal; at the same time, the excitation light also passes through the optical window 22 to reach the oxygen-sensitive film 24, and the oxygen-sensitive film 24 is excited by the excitation light to generate red fluorescence, and the red fluorescence is received by the fluorescence receiving and detecting unit 29 and converted into a fluorescence signal;

[0071] The signal processing module uses the digital orthogonal lock-in amplification algorithm to extract the phase information of the collected red fluorescence and the reflected light of the excitation light, and calculates the difference between the phases of the fluorescence signal and the reflected light signal to obtain the phase delay θ r , and then referring to the phase-temperature-dissolved oxygen concentration inversion method, the calculation is carried out according to Equation (1) to obtain the uncompensated dissolved oxygen concentration Do of the water body to be measured;

[0072]

[0073] Among them, in Equation (1), C1, C2, C3, C4, C5, C6, and C7 are calibration coefficients based on the new optical dissolved oxygen sensor itself, and are all constants.

[0074] In the above-mentioned schematic Example 1, the excitation light LED 26 only needs to emit light once, and the optical dissolved oxygen sensor can realize the synchronous detection of the phases of the reflected light and fluorescence generated by the excitation light LED 26, and then combined with the temperature of the water body to be measured synchronously measured by the temperature sensor 30, the uncompensated dissolved oxygen concentration of the water body to be measured is calculated.

[0075] Example 2:

[0076] The present invention also provides a method for detecting the dissolved oxygen concentration. On the basis of Example 1, the following steps are further included:

[0077] While the temperature sensor 30 measures the temperature t of the water body to be measured, the pressure sensor 31 also synchronously measures the pressure P of the water body to be measured;

[0078] On the basis of the uncompensated dissolved oxygen concentration Do of the water body to be measured obtained in Example 1, referring to the pressure compensation method, the calculation is carried out according to Equation (2) to obtain the pressure-compensated dissolved oxygen concentration Do of the water body to be measured pres ;

[0079]

[0080] Among them, in Equation (2), C press1 is the first pressure compensation coefficient, and its value is 0.00025; C press2 is the second pressure compensation coefficient, and its value is 0.0328.

[0081] Based on the first exemplary embodiment, the second exemplary embodiment calculates the dissolved oxygen concentration of the water body to be measured after pressure compensation by combining with the pressure of the water body to be measured synchronously measured by the integrated pressure sensor 31, thereby realizing automatic pressure compensation for the output of the optical dissolved oxygen sensor and solving the problem that the existing optical dissolved oxygen sensor cannot measure the pressure of the water body to be measured by itself, another pressure probe needs to be deployed and manual compensation needs to be carried out later.

[0082] In summary, the novel optical dissolved oxygen sensor and the dissolved oxygen concentration detection method of the present invention solve the problem of high power consumption when the existing optical dissolved oxygen sensor works, reduce the drift and error of the sensor output, and make the measurement of the optical dissolved oxygen sensor more accurate and rapid; in addition, through the integrated setting of the pressure sensor, the pressure of the water body to be measured can be synchronously measured when the optical dissolved oxygen sensor works, realizing automatic pressure compensation for the output of the optical dissolved oxygen sensor, and further enabling the novel optical dissolved oxygen sensor to directly output the dissolved oxygen concentration of the water body to be measured after pressure compensation.

[0083] Finally, it should be noted that the embodiments in this specification are described in a progressive manner, and the key point of each embodiment is to illustrate the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other.

[0084] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them; although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the specific implementation manners of the present invention can still be modified or some technical features can be equivalently replaced; without departing from the spirit of the technical solutions of the present invention, they should all be covered within the scope of the technical solutions claimed by the present invention.

Claims

1. A novel optical dissolved oxygen sensor, comprising a cylinder body, a watertight connector and a front end cover assembly respectively connected to two ends of the cylinder body, characterized in that, The front end cover assembly specifically includes: A front end cover, one end of which is a connection end sealed to the cylinder body, and the other end is a test end. A light cavity is recessed in the test end. A first channel and a second channel obliquely penetrating the front end cover are respectively communicated with the left and right sides of the light cavity. The axis of the first channel and the axis of the second channel are symmetrically arranged with respect to the axis of the light cavity, and the axis of the first channel, the axis of the second channel and the axis of the light cavity are coplanar. A third channel penetrating the front end cover is communicated directly below the light cavity, and the axial direction of the third channel is consistent with the axial direction of the light cavity. A light window is installed in the test end and covers directly above the light cavity. An oxygen-sensitive film is attached to the top surface of the light window, and the top surface of the oxygen-sensitive film is in direct contact with the water body to be measured. An excitation light LED is installed in the first channel and is used to emit blue-green excitation light toward the light window, so that the oxygen-sensitive film is excited by the excitation light to generate red fluorescence. At the same time, the excitation light is also reflected by the light window to generate reflected light and is injected into the second channel. An excitation light receiving and detecting unit is installed in the second channel and is used to receive the reflected light generated by the reflection of the excitation light by the light window. A fluorescence receiving and detecting unit is installed in the third channel and is used to receive the red fluorescence. A temperature sensor protrudes from the test end and is in direct contact with the water body to be measured to measure the temperature of the water body to be measured. A pressure sensor protrudes from the test end and is in direct contact with the water body to be measured to measure the pressure of the water body to be measured. The novel optical dissolved oxygen sensor further includes a signal processing module, and the signal processing module is communicatively connected to the excitation light LED, the excitation light receiving and detecting unit, the fluorescence receiving and detecting unit, the temperature sensor, and the pressure sensor.

2. The novel optical dissolved oxygen sensor according to claim 1, characterized in that, The excitation light receiving and detecting unit specifically includes an excitation light receiving narrowband filter and a first photodetector communicatively connected to the signal processing module. The excitation light receiving narrowband filter is installed at one end of the second channel close to the light cavity and is used to filter other light except the excitation light. The first photodetector is installed below the excitation light receiving narrowband filter to detect the signal of the reflected light.

3. The novel optical dissolved oxygen sensor according to claim 1, characterized in that, The fluorescence receiving and detecting unit specifically includes a fluorescence receiving narrowband filter and a second photodetector communicatively connected to the signal processing module. The fluorescence receiving narrowband filter is installed at one end of the third channel close to the light cavity and is used to filter other light except the red fluorescence. The second photodetector is installed below the fluorescence receiving narrowband filter to detect the signal of the red fluorescence.

4. The novel optical dissolved oxygen sensor according to claim 1, characterized in that, The light cavity, the light window and the oxygen-sensitive film are all inclined with respect to the cylinder body, and the inclination angle is 30-60 degrees.

5. The novel optical dissolved oxygen sensor according to claim 1, characterized in that, The signal processing module has a built-in pressure compensation program to automatically perform pressure compensation on the output of the novel optical dissolved oxygen sensor.

6. A method for detecting dissolved oxygen concentration, characterized in that, Using the novel optical dissolved oxygen sensor according to any one of claims 1-4, includes the following steps: Place the novel optical dissolved oxygen sensor in the water body to be measured, and control the excitation light LED to emit blue-green excitation light; the temperature sensor synchronously measures the temperature t of the water body to be measured; The excitation light is reflected by the light window to generate reflected light, and the reflected light is received by the excitation light receiving and detecting unit and converted into a reflected light signal; at the same time, the excitation light also passes through the light window to reach the oxygen-sensitive membrane, and the oxygen-sensitive membrane is excited by the excitation light to generate red fluorescence, and the red fluorescence is received by the fluorescence receiving and detecting unit and converted into a fluorescence signal; The signal processing module calculates the difference in the phases of the fluorescence signal and the reflected light signal to obtain a phase delay θ r , and then performs a solution according to Equation (1) to obtain the dissolved oxygen concentration Do of the water body to be measured without compensation; Among them, in formula (1), C1, C2, C3, C4, C5, C6, and C7 are calibration coefficients based on the novel optical dissolved oxygen sensor itself and are all constants.

7. A method for detecting dissolved oxygen concentration, characterized in that, It is carried out by using the novel optical dissolved oxygen sensor as described in claim 5, and includes the following steps: Place the novel optical dissolved oxygen sensor in the water body to be measured, and control the excitation light LED to emit blue-green excitation light; the temperature sensor synchronously measures the temperature t of the water body to be measured; the pressure sensor synchronously measures the pressure P of the water body to be measured; The excitation light is reflected by the light window to generate reflected light, and the reflected light is received by the excitation light receiving and detecting unit and converted into a reflected light signal; at the same time, the excitation light also passes through the light window to reach the oxygen-sensitive membrane, and the oxygen-sensitive membrane is excited by the excitation light to generate red fluorescence, and the red fluorescence is received by the fluorescence receiving and detecting unit and converted into a fluorescence signal; The signal processing module calculates the difference in the phases of the fluorescence signal and the reflected light signal to obtain a phase delay θ r , and then performs calculations according to Equation (1) to obtain the dissolved oxygen concentration Do of the water body to be measured without compensation. Then, calculations are performed according to Equation (2) to obtain the dissolved oxygen concentration Do of the water body to be measured after pressure compensation pres ; Among them, in formula (1) and formula (2), C1, C2, C3, C4, C5, C6, and C7 are calibration coefficients based on the novel optical dissolved oxygen sensor itself and are all constants; C press1 is the first pressure compensation coefficient, and its value is 0.00025; C press2 is the second pressure compensation coefficient, and its value is 0.0328.

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