Optical measuring device for determining measurement variable in water
By arranging an optical measuring device of a light source and a photodiode below the water surface, total reflection is used to improve detection sensitivity, and the problem of difficulty in detecting fluorescent analytes on the neutral surface of the water body is solved, and efficient detection of oil content, microplastics and algae content is achieved.
Patent Information
- Application Number
- CN202411656548.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2023-11-27
- Filing Date
- 2024-11-19
- Publication Date
- 2025-05-27
AI Technical Summary
Existing fluorescent sensors are difficult to detect fluorescent analytes in water and oil droplets on the surface simultaneously, resulting in insensitive and accurate detection.
An optical measuring device is designed, which includes a light source, a photodiode and a data processing unit. By arranging the light source and a photodiode below the water surface, the sensitivity of the measurement system can be improved by total reflection, and fluorescent substances in the liquid volume and on the surface can be detected simultaneously.
More reliable and high sensitivity detection of oil content, microplastic content and algae content in water is achieved, and fluorescent analytes in volume and on the surface are simultaneously detected.
Smart Images
Figure CN120044007A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to an optical measuring device for determining a measurement variable in water, in particular for determining the oil content in water. Background Art
[0002] Water in not only technical systems (e.g., scrubbers for exhaust gas cleaning on ships), but also natural surface water may be contaminated by oil or plastic particles, etc. A well-known method for detecting such contamination is fluorescence measurement. In particular, for example, UV fluorescence can be used to quantitatively determine the content of polycyclic aromatic hydrocarbons. Depending on the pretreatment, the presence of solubilizers or suspended particles, and depending on the turbulence in the liquid, the medium to be measured, especially oil, is distributed throughout the liquid volume or at least partially floats on the surface.
[0003] However, available fluorescence sensors measure in the liquid volume or are guided onto the water surface from above. The fluorescence sensor "CFS51" from the Endress+Hauser Group is suitable for ship exhaust gas cleaning and is installed in a flow-through fitting or immersed in a basin, channel, river or ocean. Other fluorescence sensors can optionally be used for floats for measuring below the water surface or directly on the water surface.
[0004] Therefore, current measurement principles detect analytes in the volume or on the surface, but not both simultaneously. For example, conventional immersion sensors detect fluorescence in the volume, but cannot detect oil droplets floating on the surface. Sensors for surface measurement are less sensitive to substances distributed in the volume. Summary of the Invention
[0005] The present invention is based on the object of detecting fluorescence analytes in water more reliably and with greater sensitivity.
[0006] The object is achieved by an optical measuring device for determining a measurement variable in water, in particular for determining the oil content, microplastic content or algae content in water; the device includes: at least one light source that sends excitation light into the water in the direction of the water surface, wherein the excitation light is converted into fluorescence light in the water and on the water surface; at least one photodiode that receives the fluorescence light from the water and the water surface and converts the fluorescence light into an electrical signal; and a data processing unit that determines the measurement variable based on the electrical signal.
[0007] The claimed device is directed from bottom to top and can be directly arranged below the water surface to detect fluorescence of oil, microplastics or algae in the liquid volume and simultaneously on the surface. In this case, total internal reflection at the liquid surface can be utilized to improve the sensitivity of the measurement system. Therefore, the claimed device describes the possibility of simultaneously detecting fluorescence substances in the liquid volume and on the surface.
[0008] In one embodiment, it is provided that a light source, a photodiode, and a data processing unit are arranged in a housing, and the light source and the photodiode are in optical contact with water via a common or separate optical window in each case.
[0009] In one embodiment, it is provided that the light source and the photodiode are arranged below the water surface.
[0010] In one embodiment, it is provided that the light source and the photodiode are arranged in water.
[0011] In one embodiment, it is provided that the incident angle of the excitation light into the water is such that total internal reflection occurs at the water surface.
[0012] In one embodiment, it is provided that the distances from the light source and the photodiode to the water surface are variable.
[0013] In one embodiment, it is provided that the incident angle of the excitation light and / or the detection angle of the fluorescence light are variable.
[0014] In one embodiment, it is provided that the device includes one or more floating bodies that hold the measuring device at a defined distance from the water surface, wherein the floating bodies are arranged outside the measuring device.
[0015] In one embodiment, it is provided that the measuring device includes at least one swimming bladder that holds the measuring device at a defined distance from the water surface, wherein the swimming bladder is arranged in the measuring device.
[0016] In one embodiment, it is provided that the measuring device includes a barrel having an inlet and an outlet for water, wherein the light source and the photodiode are arranged in the barrel.
[0017] In one embodiment, it is provided that the measuring device includes a barrel having an inlet and an outlet for water, wherein the light source and the photodiode are arranged outside the barrel.
[0018] The object is also achieved by a method that includes the following steps: sending excitation light in the direction of the water surface into the water, wherein the excitation light is converted into fluorescence light in the water and at the water surface; receiving the fluorescence light from the water and the water surface; converting the fluorescence light into an electrical signal; and determining a measurement variable based on the electrical signal.
[0019] Furthermore, the object is achieved by using the measuring device as described above to determine the oil content in water.
[0020] Furthermore, the object is achieved by using the measuring device as described above to determine the microplastic content.
[0021] Furthermore, the object is achieved by using the measuring device as described above to determine the algae content. Description of the Drawings
[0022] This will be explained in more detail with reference to the following drawings.
[0023] Figure 1 An overview of the claimed measuring device is shown.
[0024] Figure 2 The claimed measuring device in an embodiment is shown.
[0025] Figure 3 The claimed measuring device in an embodiment is shown.
[0026] Figure 4a / Figure 4b Each shows the claimed measuring device in an embodiment.
[0027] In the drawings, the same features are labeled with the same reference numerals. Detailed Description
[0028] The claimed measuring device as a whole has the reference numeral 1 and is shown in Figure 1 .
[0029] The measuring device 1 includes a light source 2, a photodiode 4, and a data processing unit 10. The measuring device 1 is also referred to hereinafter as a "sensor".
[0030] The sensor is a fluorescence sensor. For measuring fluorescence, a medium (in this case water) is typically irradiated with short-wavelength excitation light 8, and the longer-wavelength fluorescence light generated by the medium is detected.
[0031] The light source 2 radiates the excitation light 8 into the medium 3 to be measured, i.e., water, where the excitation light 8 is converted by the water 3 into fluorescence light 9. The fluorescence light 9 is received by the photodiode 4, for example via intensity, decay curve, or phase, and is converted into an electrical signal.
[0032] The light source 2 is, for example, a UV light source that emits light with a wavelength of 200 - 400 nm. The light source 2 is, for example, designed as a UV flash lamp. The light source 2 can also be configured as an LED. The UV flash lamp emits light from UV to IR within the spectral range. Depending on the application, the light source 2 is designed accordingly. For an application of determining the algae content, the light source 2 emits within the UV / VIS range (200 - 800 nm). The device also includes other optical components in the beam path after the light source, such as a filter that only transmits the desired wavelength of the fluorescence emission of the analyte to be measured, or one or more lenses. The flash lamp then emits only the desired excitation wavelength together with the filter. At the photodiode 4, corresponding components are also arranged on the receiver side.
[0033] The light source 2 and the photodiode 4 are connected to a data processing unit 10, such as a microcontroller, which uses electrical signals to determine a measurement variable to be determined, such as the proportion of microplastics in the oil content, water or algae content in water. A calibration model is used to determine this measurement variable, which, for example, determines the concentration from the fluorescence intensity.
[0034] The light source 2, the photodiode 4 and the data processing unit 10 are arranged in a common housing 5, wherein, in each case, the light source 2 and the photodiode 4 are in optical contact with the water 3 via a common or separate optical window 7.
[0035] In order to be sensitive to the analyte both in the water body 3 and at the surface 6, both the excitation light 8 and the fluorescence light 9 are sent or received at an angle or from below towards the water surface 6. Depending on the exact arrangement, the ratio between the sensitivity at the surface and in the volume can be adjusted. The light source 2 thus sends light through the medium 3 towards the water surface 6. The excitation light 8 is converted into fluorescence light 9 not only in the water 3 but also on its surface 6. The light source 2 emits the excitation light 8 substantially opposite to the direction of gravity (although this of course has no effect). Thus, in the sense of this document, the "bottom" is at the bottom of the water, while the "top" is at the surface.
[0036] The light source 2 and the photodiode 4 are thus arranged below the water surface 6.
[0037] Figures 1 - 3 and Figure 4b shows an embodiment in which the light source 2 and the photodiode 4 (together with the data processing unit 10 and the housing 5) are arranged in the water 3.
[0038] Since fluorescence light is usually emitted in all spatial directions, the optical paths of the excitation light 8 and the fluorescence light 9 can in principle be at any angle to each other.
[0039] If the angles of detection and / or the angle are chosen to be suitably small, total internal reflection at the water surface 6 causes significantly more of the volume to be excited or detected, which significantly increases the sensitivity of the system. The exact value of the critical angle at which total internal reflection occurs depends on the wavelength. It is approximately 42° in the UV range.
[0040] In one embodiment of the measuring device 1, the distance d from the light source 2 and the photodiode 4 to the water surface 6 is variable. The optimal distance depends on various parameters, such as the size of the measuring device and the angle of the beam path. In one embodiment, the distance d varies in the centimeter range, for example 1 - 10 cm. In one embodiment, the distance d varies from a few millimeters to a few centimeters, approximately 10 cm. Distances up to 1 meter are possible.
[0041] The measuring device 1 may also be equipped with an (automatically) movable detector to determine the distribution of the analyte between the surface and the volume. Similarly, the angle of incidence or the angle of reflection may be variable.
[0042] In Figure 2 - Figure 4, only the differences or additions with respect to Figure 1 are marked with reference numerals.
[0043] Figure 2 An embodiment is shown with two floating bodies 11 arranged outside the measuring device 1. It is also possible to use only one. The floating bodies 11 are connected to the device 1 by a net and hold the latter at a defined distance underwater.
[0044] Figure 3 An embodiment is shown with a swimming bladder 12 arranged in the housing 5. This also holds the device 1 at a defined distance below the water surface 6. In one embodiment, the swimming bladder can be filled with air or water so that the device 1 is movable.
[0045] In both cases, the ability of the measuring device 1 to move continuously relative to the surface 6 ensures that the depth distribution of the analyte concentration can be determined.
[0046] Figure 4a And 4b An embodiment is shown with a tub 13 having an inlet 14 and an outlet 15 for water 3. Also here, the device measures from the bottom to the top in the direction of the water surface 6. The distance d from the device 1 to the surface can be adjusted by the inlet 14. Figure 4a An embodiment is shown in which the light source 2 and the photodiode 4 (in the housing 5) are arranged in the tub 13. Figure 4b An embodiment is shown in which these are arranged outside the tub 13. The optical window 7 is then part of the tub 13.
[0047] In one embodiment, the measuring device 1 is attached to a cord, rope, cable, etc. and can be manually or automatically raised and lowered in the water 3 in order to change the distance to the water surface 6.
[0048] List of reference numerals
[0049] 1 Measuring device
[0050] 2 Light source
[0051] 3 Water
[0052] 4 Photodiode
[0053] 5 Housing
[0054] 6 Water surface
[0055] 7 Optical window
[0056] 8 Excitation light
[0057] 9 Fluorescent light
[0058] 10 Data processing unit
[0059] 11 Floating body
[0060] 12 Swimming airbag
[0061] 13 Bucket
[0062] 14 Inlet
[0063] 15 Outlet
[0064] d Distance from 1 to 6
[0065] Incident angle of the excitation light to 6
[0066] Reflection angle of the excitation light to 6
Claims
1. An optical measuring device (1) for determining a measured variable in water (3), in particular for determining the oil content or the microplastic content in water, comprising: at least one light source (2) which emits excitation light (8) into the water (3) in the direction of the water surface (6), wherein the excitation light (8) is converted into fluorescent light (9) in the water (3) and on the water surface (6); - at least one photodiode (4) which receives fluorescent light (9) from the water (3) and from the water surface (6) and converts the fluorescent light into an electrical signal; and - a data processing unit (10) which determines a measured value from the electrical signal.
2. The measuring device (1) according to claim 1, in, The light source (2), the photodiode (4) and the data processing unit (10) are arranged in a housing (5), and the light source (2) and the photodiode (4) are in optical contact with the water (3) in each case via a common or separate optical window (7).
3. The measuring device (1) according to claim 1 or 2, in, The light source (2) and the photodiode (4) are arranged below the water surface (6).
4. The measuring device (1) according to any one of the preceding claims, in, The light source (2) and the photodiode (4) are arranged in the water (3).
5. The measuring device (1) according to any one of the preceding claims, in, The incident angle of the excitation light (8) into the water (3) causes total reflection to occur at the water surface (6).
6. The measuring device (1) according to any one of the preceding claims, in, The distance from the light source (2) and the photodiode (4) to the water surface (6) can be varied.
7. The measuring device (1) according to any one of the preceding claims, in, The incident angle ( ) and / or the detection angle ( ) is capable of change.
8. The measuring device (1) according to any one of the preceding claims, It comprises one or more floating bodies (11) which hold the measuring device (1) at a defined distance (d) from the water surface (6), wherein: The floating body (11) is arranged outside the measuring device (1).
9. The measuring device (1) according to any one of the preceding claims, It comprises at least one swimming bladder (12) for holding the measuring device (1) at a defined distance (d) from the water surface (6), wherein: The swim bladder is arranged in the measuring device (1).
10. The measuring device (1) according to any one of the preceding claims, comprising a bucket (13) having an inlet (14) and an outlet (15) for said water (3), in, The light source (2) and the photodiode (4) are arranged in the barrel (13).
11. The measuring device (1) according to any one of the preceding claims, comprising a bucket (13) having an inlet (14) and an outlet (15) for said water (3), in, The light source (2) and the photodiode (4) are arranged outside the barrel (13).
12. A method for determining a measured variable in water (3), The following steps are involved: - sending excitation light (8) into the water (3) in the direction of the water surface (6), wherein the excitation light (8) is converted into fluorescent light (9) in the water (3) and at the water surface (6); - receiving the fluorescent light (9) from the water (3) and the water surface (6); - converting the fluorescent light (9) into an electrical signal; and - determining said measured variable from said electrical signal.
13. Use of a measuring device (1) according to any one of claims 1 to 12 for determining the oil content, microplastic content or algae content in water.