Process for determining scattered light parameter and measuring device for carrying out process
By combining the measurement of scattered and reflected light signals in the optical sensor, the problem of unclear signal curves in the prior art is solved, and the accurate detection and distinction of liquid turbidity is achieved, and the measurement efficiency and range are improved.
Patent Information
- Application Number
- CN202411660191.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2023-11-27
- Filing Date
- 2024-11-20
- Publication Date
- 2025-05-27
AI Technical Summary
When existing optical sensors measure liquid turbidity, the signal curve is unclear, making it difficult to distinguish between low turbidity and high turbidity, and the turbidity or solid content of the liquid cannot be accurately determined.
The turbidity in the medium is determined by performing optically scattered light measurements using a single measurement channel in the measuring device, combining the scattering and reflected signals of the excitation light. The process includes emitting excitation light into the medium, receiving scattered light, and emitting excitation light towards the surface of the medium to receive reflected light, and ultimately determining the turbidity based on the scattered and reflected light signals.
A clear distinction between low-turbidity and high-turbidity media is achieved, accurately detecting the turbidity and solid content of liquids, reducing the demand for additional measurement equipment, improving economic efficiency, and expanding the measurement range.
Smart Images
Figure CN120043999A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to a process for determining a parameter of scattered light, in particular turbidity, and to a measuring device for carrying out the process. Background Art
[0002] In the following, the problem to be solved is described by way of example based on turbidity measurement. The ISO 7027 standard relating to turbidity measurement in liquids specifies the measurement of low turbidity with Optical sensors for measuring the turbidity of liquids that meet this criterion have the following disadvantage: When the turbidity of the liquid increases, the signal curve is not clear in all media, the scattered light signal initially increases to a maximum value. However, once this limit is exceeded, the signal decreases again, despite the increasing turbidity, because less and less scattered light reaches the sensor's detector due to multiple scattering.
[0003] Due to the ambiguous signal, the measurement cannot distinguish between very low and very high turbidity values and thus cannot clearly determine the turbidity value or solids content of the liquid. For example, a black medium heavily contaminated with particles is wrongly interpreted as a clean, clear liquid.
[0004] Due to international regulations and legal requirements, turbidity measurements according to ISO 7027 are often required and therefore only instruments with Since the individual scattered light signals at different angles are not obtained, additional measuring devices must usually be installed in order to obtain further information about the actual turbidity value or solids content of the medium via additional measured variables. This requires considerable additional costs and installation work for the operator. Summary of the invention
[0005] The invention is based on the use of only one measuring channel (e.g. according to ISO 7027 with ) The purpose of performing optical scattered light measurements is to make it possible to clearly distinguish between media with low turbidity (e.g. clear water) and liquids with very high turbidity (e.g. black wastewater with a high particle content), or to detect the turbidity value and / or the solid content of a liquid.
[0006] This object is achieved by a process for determining a scattered light parameter, in particular turbidity, in a medium by means of a measuring device, in particular a turbidity sensor. Specifically, the process comprises the following steps:
[0007] a) emitting excitation light into a medium, wherein the excitation light is scattered in the medium;
[0008] b) receiving light scattered in the medium;
[0009] c) emitting excitation light into the medium toward a surface of the medium, wherein the excitation light is reflected at the surface of the medium;
[0010] d) receiving light reflected at the surface of the medium; and
[0011] e) Determination of scattered light parameters, in particular turbidity, based on the scattered and reflected light.
[0012] With the solution according to the invention, a clear distinction between a medium with low turbidity and a liquid with very high turbidity or absorption is achieved, since the emitted light of the sensor is reflected permanently in one embodiment, in particular temporarily in one embodiment, at the surface of the medium, and the signal intensity of this reflected light is evaluated. While reflection in clear media leads to a strong measurement signal, the reflected signal is attenuated in strongly absorbing and / or strongly scattering media, since the reflection strikes the detector with full intensity without attenuation, which leads to significantly lower measured values.
[0013] This results in a clear detection of the turbidity or solids content of the medium, although the measurement according to ISO 7027 utilizes only one scattered light signal. This also results in high economic efficiency by saving additional measuring equipment (cost saving, lower installation and maintenance costs). The measuring range can also be extended. Another advantage is that it is easier for the user to select the correct model for calculating the turbidity from the scattered light intensity.
[0014] One embodiment provides that the relative distance between the measuring device and the medium surface is changed between the above-mentioned steps b) and c).
[0015] One embodiment provides that the measuring device is moved towards the medium surface, in particular via a rotational or translational movement.
[0016] One embodiment provides that the medium surface is lowered or raised.
[0017] One embodiment provides that the incident angle of the excitation light into the medium is designed so that total reflection occurs at the surface of the medium.
[0018] One embodiment provides that the above-mentioned steps c) and d) are performed less frequently than steps a) and b).
[0019] The object is also achieved by a measuring device for performing the above process, which is particularly a turbidity sensor, comprising: at least one light source, which emits excitation light into the medium and toward the surface of the medium; at least one photodiode, which receives light scattered in the medium and light reflected at the surface of the medium and converts it into an electrical signal; and a data processing unit, which determines scattered light parameters, particularly turbidity, based on the electrical signal.
[0020] One embodiment provides that the measuring device comprises one or more floating bodies which hold the measuring device at a defined but variable distance from the surface of the medium, wherein the floating bodies are arranged outside the measuring device.
[0021] One embodiment provides that the measuring device comprises at least one buoyancy chamber which holds the measuring device at a defined but variable distance from the surface of the medium, wherein the buoyancy chamber is arranged in the measuring device.
[0022] One embodiment provides that the measuring device comprises a basin with an inflow and an outflow for the medium, wherein the light source and the photodiode are arranged in the basin or outside the basin.
[0023] One embodiment provides that the measuring device comprises a basin with at least one inflow and a plurality of outflows for the medium, wherein the light source and the photodiode are arranged in the basin or outside the basin. BRIEF DESCRIPTION OF THE DRAWINGS
[0024] This is explained in more detail with reference to the following figures.
[0025] Figure 1 An apparatus for measuring scattered light having an optical path is generally shown.
[0026] Figure 2a / Figure 2b Shown are the scattered light intensities measured at different turbidities according to the prior art (a) and by means of the claimed measuring device or process (b).
[0027] Figure 3a to Figure 3d Reflection at the medium surface in a less turbid medium (b, d) and a more turbid medium (a, c) is shown, wherein the device is arranged further away (a, b) or closer (c, d) to the medium surface.
[0028] Figures 4a to 4d Reflection at the medium surface in a less turbid medium (b, d) and a more turbid medium (a, c) is shown, wherein the device is arranged further away (a, b) or closer (c, d) to the medium surface.
[0029] Figure 5a / Figure 5b Symbolically shows the movement of the sensor or the change of the medium surface.
[0030] Figures 6a to 6c An embodiment for varying the distance of the device from the surface of the medium is shown.
[0031] Figure 7 The claimed measuring device is shown in one embodiment.
[0032] Figure 8 The claimed measuring device is shown in one embodiment.
[0033] Fig. 9 The claimed measuring device is shown in one embodiment.
[0034] In the drawings, identical features are marked with identical reference numerals. DETAILED DESCRIPTION
[0035] Any light that strikes the particles suspended in the liquid is scattered. The intensity of this scattered light is used as a direct measure for the determination of turbidity in optical turbidity measurements. Different measuring angles are used for different applications - partly due to national legal regulations. For example, Diffused light is used for drinking water applications, etc. Brewing is usually used in to In the measurement of sludge, most of the scattered light angles are used. (For example, ) of the backscatter angle. The "FNU" unit ( ) is often used as a reference measurement or turbidity value.
[0036] Typically, turbidity sensors based on scattered light measurement can be represented symbolically as Figure 1 From the light source 2, excitation light 8 (see broad arrow) is radiated into the measuring chamber through a window 7 which is transparent to the excitation light 8. There, the light is scattered by the particles in the medium 3 to form a beam at the measuring angle. (Here is ) is measured at an exemplary scattered point P under the medium 3 and converted into "scattered light 19" (dashed vertical line). In reality, the scattering is not a single line (ray) as shown but a blurred volume. Likewise, the scattering does not occur at a single point P but at all particles in the medium 3.
[0037] The light reaches the receiver 4 via the window 7, which is transparent for the scattered light 6 (only a single window can be used), for example via one or more apertures or lenses. The light intensity reaching the receiver 4 is a measure of the turbidity. The light path from the light source 2 into the medium 3 through the window 7, to the scattering point P, through the medium 3 and to the receiver 4 through the window 7 is generally referred to as the "optical path 20" (dashed line). As mentioned above, in reality the scattering does not result in only a single line (ray), but a blur volume. Therefore, the "optical path 20" covers the entire blur volume.
[0038] The claimed measuring device 1 (see FIG. 3- Fig. 9) is also referred to as sensor or turbidity sensor hereinafter. The turbidity sensor 1 is arranged on a container, in particular on a pipe or in a basin or an open channel. This is performed via a fastening device, such as a flange. The turbidity sensor can also be arranged on an immersion or quick-change fitting or the like. The medium 3 to be measured is located in the container; in particular the medium 3 flows through the container. The medium 3 to be measured is mostly liquid - often process and waste water. However, the device is also used for fresh water, in particular drinking water. When used on a container, the turbidity sensor is arranged essentially perpendicular to the longitudinal axis of the container, such as a pipe. The turbidity sensor comprises a housing 5. Stainless steel, plastic or ceramic can be used as material for the device 1, in particular for the housing 5. The materials are selected to ensure that they are suitable for the respective application.
[0039] The device 1 comprises at least one light source 2 and a receiver 4. The light source and the receiver are electrically connected (see Figure 1 The data processing unit 10 is connected to a data processing unit 10 (e.g. a microcontroller) by means of a dashed line in the figure. The data processing unit 10 determines the measured variable to be determined, namely the turbidity, from the electrical signal of the scattered light. The determination of this measured variable is achieved with the aid of a calibration model which combines the measured information about the intensity of the received scattered light and uses this information to determine the turbidity. For example, Figure 2a / Figure 2b The relationship between the measured scattered light intensity and the corresponding turbidity is shown.
[0040] The receiver 4 is designed, for example, as a photodiode, which generates a receiver signal such as a photocurrent or a photovoltage (usually an electrical signal) from the received light.
[0041] A light source 2, typically an LED, emits light towards a medium 3. In this respect, "light" within the meaning of the present application is not limited to the visible range of the electromagnetic spectrum, but should be understood as electromagnetic radiation of any wavelength, in particular in the ultraviolet (UV) and infrared (IR) wavelength ranges. In particular, a wavelength of 860 nm is used. The device may include further optical components in the beam path after the light source, such as filters or one or more lenses (not shown). At the photodiode 4, corresponding components are also arranged on the receiver side.
[0042] exist Figure 2a In this case, the measured scattered light intensity is the same for two different turbidity values, so it is not possible to distinguish between turbid and clear water from a purely measurement point of view (prior art).
[0043] With the claimed measuring device 1 and the corresponding process, a clear distinction between a medium 3 with low turbidity and a medium with very high turbidity or absorption is achieved, since the emitted light 8 of the sensor 1 is temporarily reflected on the surface 6 of the medium 3 and the signal intensity of this reflected light 9 is evaluated. While the reflection in a clear medium leads to a strong measurement signal, the reflected signal is strongly attenuated in an absorbing and / or scattering medium, since the reflection impinges on the detector 4 with full intensity without major attenuation, which leads to significantly lower measured values.
[0044] Since the claimed solution eliminates the ambiguity of the signal curve, the measuring range of the sensor 1 can be significantly increased, since even high turbidities on the descending part of the signal curve can be measured. While with turbidity sensors in the prior art only the measured values of one side of the curve could be used, since the measured scattered light intensity is clearly assigned to one of the two sides of the signal curve, both sides of the curve can be used. On the one hand, this leads to a significantly larger measuring range, and on the other hand, the assignment of the measured scattered light intensity to an incorrect turbidity value is avoided. Figure 2b The left and right hand halves of a "light intensity-turbidity curve" that can be used for scattering are shown. In this way, separate calibration curves can be assigned to the right and left hand sides of the curve, which assign a unique turbidity measurement value to the measured scattered light intensity depending on the known side of the curve. While a medium with low turbidity is evaluated using the left hand side of the curve, a medium with high turbidity values can be detected with the help of the right hand side of the curve.
[0045] Furthermore, the uniqueness of the signal curve simplifies model selection for the user. For example, if the sensor detects a liquid with very high turbidity or absorption (e.g. contaminated black wastewater with a high particle content), the model optimized for measuring clear media (e.g. drinking water) can be pre-empted or actively blocked by the sensor 1 software.
[0046] In order to achieve reflection at the surface of the medium, the sensor 1 must be positioned at least temporarily in such a way that its beam path is directed from below toward the surface 6 of the medium.
[0047] Figure 3 shows that in a less turbid medium ( Figure 3b , Figure 3d ; i.e., right-hand side of Figure 3) and in more turbid media ( Figure 3a , Figure 3c ; i.e., the left-hand side of FIG. 3 ). The measuring device 1 may be arranged further away from the medium surface 6 ( Figure 3a , Figure 3b ; i.e., the upper half of FIG. 3) or closer thereto ( Figure 3c , Figure 3d ; i.e., the lower half of Figure 3). This is also Figures 4a to 4dScale 16 shows the light intensity measured at detector 4. The scattered light cone is also shown in Figures 4a to 4c Shown in.
[0048] The light source 4 emits excitation light 8 into the medium 3 to be measured, for example into water, wherein the excitation light 8 is scattered in the medium. The scattered light 9 is received by the photodiode 4 and converted into an electrical signal. Figure 3a , Figure 3c and Figure 4a , Figure 4c In turbid media with a large number of particles, relatively high scattering occurs, as can be seen symbolically in . In less turbid media, see Figure 3b , Figure 3c and Figure 4b , Figure 4c , less scattering occurs.
[0049] In addition to the scattering in the medium 3, the emitted light 8 is reflected at the medium surface 6. If the measuring device 1 is arranged closer to the medium surface 6, more light can be reflected, see Figure 3c , Figure 3d and Figure 4c , Figure 4d The scattered light 9 is received by the photodiode 4 and converted into an electrical signal.
[0050] As a function of the distance of the measuring device 1 from the surface 6, more reflections or scattering occur.
[0051] The sensor 1 can then be moved as a movable measuring device towards the surface 6 (see Figure 5a ; indicated by a vertical arrow above the measuring device 1) or by mounting the sensor 1 in a fixed position and lowering or raising the liquid level ( Figure 5b ; indicated by a vertical arrow above the surface 6) to achieve temporary reflection. In addition to translational movement, rotational movement is also possible (this is in Figure 5a or a combination of rotational and translational motion).
[0052] For example, an increase or decrease in the liquid level can be achieved by arranging different outlets 15 at different heights in the basin, fitting or channel, which are opened or closed to change the level. Figure 6a To automate the process, the outlet can be automatically controlled via a solenoid valve and a higher-level control system.
[0053] Figure 6b and Figure 6cAn embodiment is shown with a basin 13 having an inflow 14 and an outflow 15 for the medium 3. Here, the device is measured from bottom to top toward the medium surface 6. The distance d between the device 1 and the surface can be adjusted by means of the inflow 14 when the discharge 15 is closed. Figure 6b An embodiment is shown in which the light source 2 and the photodiode 4 (in the housing 5 ) are arranged in a pot 13 . Figure 6c An embodiment is shown in which these are arranged outside the pot 13. The optical window 7 is then part of the pot 13.
[0054] The relative distance between the measuring device 1 and the medium surface 6 can be varied so that the measurement of the scattered light in the medium (particularly below ) and the measurement of the reflection at the surface. This can be achieved by moving the measuring device 1 towards the medium surface 6 (in particular via a rotational or translational movement). Alternatively, the medium surface 6 can be lowered or raised. Examples are shown in the drawings.
[0055] The light source 2 also emits excitation light 8 into the medium toward the medium surface 6 (upward), wherein the excitation light 8 is reflected at the medium surface 6. This reflected light (reference numeral 9) is detected by the photodiode 4 and converted into an electrical signal.
[0056] As mentioned, the light source 2 and the photodiode 4 are connected to a data processing unit 10 (e.g. a microcontroller), which determines the measured variable to be determined, namely the turbidity, from the electrical signals of the scattered and reflected light. The determination of this measured variable is achieved with the aid of a calibration model, which combines the measured information on the received intensity and uses this information to confirm the turbidity. The reflected light is used to check the measurement or to resolve ambiguities using scattered light.
[0057] During the detection of reflections, the light source 2 emits the excitation light 8 substantially against gravity (even though gravity has no effect of course). "Below" within the meaning of this text is at the bottom of the medium, while "above" is at the surface. The light source 2 is at an angle The excitation light 8 is emitted from below to the medium surface 6. The reflected light 9 is at an angle The light source 2 and the photodiode 4 are therefore arranged below the medium surface 6. Figure 7 Shown in.
[0058] If the angle and / or angle is chosen to be small enough that total reflection at the medium surface 6 directs part or all of the excitation light out of the way, which increases the measured signal strength and, if applicable, leads to easier differentiation between the left-hand and right-hand sides of the curve of the scattered light signal, see Figure 2b .
[0059] The reception of reflected light 9 can occur less frequently than the reception of scattered light 19. For this purpose, the measuring device 1 is only occasionally moved about once a minute, once an hour or once a day for checking the measured value in a way that the signal is emitted towards the medium surface 6. Alternatively, and as mentioned above, the surface 6 (or level) of the medium 3 can also be changed. The operation can also be started manually. Similarly, if the turbidity value is below or exceeds a certain threshold value (in particular to avoid or resolve ambiguity), the "emission towards the surface 6" operation can be started.
[0060] In one embodiment of the measuring device 1, the distance d from the light source 2 and the photodiode 4 to the medium surface 6 is variable (see above and Figures 6a to 6c ). As a result, it is possible to "switch" between the measurement of scattering and reflection. Similarly, the incident angle Or detection angle Can be variable. It does not refer to the angle at which turbidity is determined. Used to check whether the confirmed turbidity is reasonable.
[0061] exist Figure 8 and Fig. 9 In the drawings, only the differences or additions to the previous drawings are marked with reference numerals. Figure 8 and 9 An embodiment for varying the distance from the sensor 1 to the surface 6 is shown.
[0062] Figure 8 An embodiment is shown with two floating bodies 11 arranged outside the measuring device 1. It is possible to use only one. The floating body 11 is connected to the device 1 via a connection and holds it at a defined but possibly variable distance below the medium.
[0063] Fig. 9 An embodiment is shown with a buoyancy chamber 12 arranged in the housing 5. This also keeps the device 1 at a defined (but potentially variable) distance below the medium surface 6. In one embodiment, the buoyancy chamber can be filled with air, water or medium so that the device 1 can be moved.
[0064] In both cases, the continuous mobility of the measuring device 1 relative to the surface 6 ensures that the depth profile of the turbidity can be determined.
[0065] In one embodiment, the measuring device 1 is attached to a harness, rope, cable or the like and can be raised and lowered manually or automatically in the medium 3 in order to vary the distance to the medium surface 6 .
[0066] Reference numerals list
[0067] 1. Measuring device
[0068] 2 Light Source
[0069] 3 Medium
[0070] 4 Photodiode
[0071] 5 Housing
[0072] 6 Medium surface
[0073] 7 Optical Window
[0074] 8 Excitation light
[0075] 9 Reflected Light
[0076] 10 Data processing unit
[0077] 11 Floating body
[0078] 12 Buoyancy Chamber
[0079] 13 basin
[0080] 14 Inflow
[0081] 15 Outflow / Export
[0082] 16 Scale
[0083] 19 Scattered Light
[0084] 20 Optical Path
[0085] d The distance from 1 to 6
[0086] The incident angle of the excitation light is 6
[0087] Reflection angle of excitation light at 6
[0088] P Scattering Point
Claims
1. A process for determining a scattered light parameter, in particular turbidity, in a medium by means of a measuring device (1), in particular a turbidity sensor, comprising the following steps: a) emitting excitation light (8) into the medium (3), wherein the excitation light (8) is scattered in the medium (3); b) receiving light scattered in the medium (3); c) emitting excitation light (8) into the medium (3) toward the medium surface (6), wherein the excitation light (8) is reflected at the medium surface (6); d) receiving light (9) reflected from the medium surface (6); and e) determining the scattered light parameter, in particular the turbidity, based on the scattered light and the reflected light (9).
2. The process according to claim 1, in, The relative distance between the measuring device (1) and the medium surface (6) is changed between steps b) and c).
3. The process according to claim 2, in, The measuring device (1) is moved towards the medium surface (6), in particular via a rotational or translational movement.
4. The process according to claim 2 or 3, in, The medium surface (6) is lowered or raised.
5. A process according to any one of claims 2 to 4, in, The incident angle ( ) is designed so that total reflection occurs at the medium surface (6).
6. The process according to any one of the preceding claims, in, Steps c) and d) are performed less frequently than steps a) and b).
7. A measuring device (1), in particular a turbidity sensor, for carrying out a process according to any of the preceding claims, the measuring device (1) being used for determining a scattered light parameter, in particular the turbidity, in a medium (3), the measuring device (1) comprising: - at least one light source, which emits excitation light (8) into the medium (3) and towards the medium surface (6); - at least one photodiode, which receives light scattered in the medium (3) and light reflected at the surface (6) of the medium and converts it into an electrical signal; as well as A data processing unit (10) for determining the scattered light parameter, in particular the turbidity, from the electrical signal.
8. The measuring device (1) according to the preceding claim, The measuring device (1) comprises one or more floating bodies (11) which hold the measuring device (1) at a defined but variable distance (d) from the medium surface (6), wherein: The floating body (11) is arranged outside the measuring device (1).
9. The measuring device (1) according to claim 7 or 8, The invention comprises at least one buoyancy chamber (12) which holds the measuring device (1) at a defined but variable distance (d) from the medium surface (6), wherein: The buoyancy chamber is arranged in the measuring device (1).
10. The measuring device (1) according to any one of the preceding claims, comprising a basin (13) with an inflow (14) and an outflow (15) for the medium (3), in, The light source (2) and the photodiode (4) are arranged in the pot (13) or outside the pot (13).
11. The measuring device (1) according to any one of the preceding claims, comprising a basin (13) having at least one inflow (14) and a plurality of outflows (15) for the medium (3), in, The light source (2) and the photodiode (4) are arranged in the pot (13) or outside the pot (13).