Operation method of interface sensor and interface sensor

Abstract

The invention relates to an operation method of an interface sensor and the interface sensor. The method for operating an interface sensor comprises:-arranging an interface sensor (10) in a container (20) filled with a measuring medium (2) such that the interface sensor (10) is in contact with the measuring medium (2); recording a measured value curve having measured values by means of the interface sensor (10); evaluating the measured value curve by means of the control unit (13), comprising: determining a layer boundary; determining a first settlement parameter; determining a second settlement parameter; -determining a settlement indicator based on a relationship between the first settlement parameter and the second settlement parameter; and outputting the settlement indicator by means of the control unit (13).

Description

Technical Field

[0001] This invention relates to an operation method for an interface sensor, an interface sensor, a settling device, and an automatic control method for the settling device. Background Technology

[0002] For example, interface sensors that emit acoustic or optical signals are used to detect interfaces in containers filled with liquid. To do this, these sensors are immersed in the liquid. The acoustic signals propagate, for example, in the liquid, and are reflected back to the sensor once they strike an interface in the liquid or container composed of, for example, solid particles.

[0003] Such interface sensors are particularly useful in manufacturing processes involving so-called settling or sedimentation. Here, suspended solids are separated from the liquid process medium. The solids in the mixed sample settle to the bottom of the tank, where they are extracted by suction. The liquid medium in the upper tank area is also extracted by suction or transferred via an overflow port to minimize the amount of suspended solids. The deposition rate of solid particles depends on several factors and is a determining factor for the overall capacity of the production process. To accelerate settling, a settling agent or flocculant is added to the medium.

[0004] In order to achieve optimal settling, in many cases the settling agent is over-distributed, which is associated with high costs. Summary of the Invention

[0005] Therefore, one object of the present invention is to provide a method for operating interface sensors that enables reliable and cost-effective monitoring of the settling process.

[0006] According to the present invention, this objective is achieved by the operation method of the interface sensor according to claim 1.

[0007] The operation method according to the present invention includes:

[0008] - The interface sensor is placed in a container filled with the measurement medium, so that the interface sensor is in contact with the measurement medium.

[0009] - Record measurement value curves with measured values ​​using an interface sensor;

[0010] -Evaluate the measurement curve using the control unit, involving:

[0011] Determine the layer boundaries;

[0012] Determine the first settlement parameters;

[0013] Determine the second settlement parameter;

[0014] - Settlement indices are determined based on the relationship between the first and second settlement parameters; and

[0015] - Settlement indicators are output by the control unit.

[0016] The operating method according to the invention enables reliable and cost-effective monitoring of the settling process. Specifically, it allows for early detection of optimized settling. It also enables early detection of suspended solids near the surface. This allows for reliable monitoring of the entire depth of the settling tank. This, in turn, enables cost-effective and environmentally friendly closed-loop control of the settling agent during the settling process.

[0017] According to one embodiment of the present invention, during the evaluation process, the measurement function is determined by curve fitting the measured value curve.

[0018] According to one embodiment of the invention, at least one derivative of the measurement function is used when determining the layer boundary.

[0019] According to another embodiment of the invention, at least a first maximum value of the measurement function and the distance are used when determining the layer boundary.

[0020] According to one embodiment of the invention, at least a first inflection point of the measurement function is used when determining the layer boundary.

[0021] According to one embodiment of the present invention, in determining the first settlement parameter, a first area or a first projected length formed based on the measured value curve is determined.

[0022] In determining the second settlement parameter, the second area or second projected length formed based on the measured value curve is determined.

[0023] According to one embodiment of the present invention, in determining the first settlement parameter, a first inflection point projection or a first maximum projection formed based on a measurement function is determined.

[0024] In determining the second settlement parameter, the second inflection point projection or the second maximum projection is determined based on the measurement function.

[0025] According to one embodiment of the present invention, measurements falling within the exclusion range are ignored in the evaluation of the measurement curve.

[0026] According to one embodiment of the present invention, a warning message is issued when the measured value falls within the exclusion range.

[0027] The above objective is also achieved by the settling device according to claim 10.

[0028] The settling device according to the present invention includes:

[0029] - Interface sensor;

[0030] - A container for receiving a measurement medium, wherein an interface sensor is arranged relative to the container such that the interface sensor is suitable for immersion in the measurement medium;

[0031] - A precipitant inlet for introducing precipitant into the measuring medium, wherein the precipitant inlet has an inlet valve connected to the control unit.

[0032] The above objective is also achieved by using the method of controlling the settling device using closed-loop control as described in claim 11.

[0033] The closed-loop control method according to the present invention includes:

[0034] -Provide a settling device according to the present invention;

[0035] - Operate the interface sensor according to the operating method according to the invention;

[0036] - The inlet valve is controlled using open-loop control based on a settling indicator and a threshold by a control unit, so that closed-loop control can be used to control the introduction of the precipitant into the measuring medium. Attached Figure Description

[0037] The invention is explained in more detail below based on the accompanying drawings, in which:

[0038] - Figure 1 : is a schematic diagram of a settling device according to the present invention, which has an interface sensor according to the present invention;

[0039] - Figure 2 :This is a schematic diagram of the measured curves of the settlement process with optimized settlement behavior recorded by the interface sensor;

[0040] - Figure 3 : is derived from curve fitting Figure 1 A schematic diagram of the measurement function determined by the measured value curve;

[0041] - Figure 4 :This is a schematic diagram of the measured value curve of the settlement process with poor settlement behavior recorded by the interface sensor;

[0042] - Figure 5 : This is a schematic diagram of the measured value curves of a settlement process with extreme settlement behavior recorded by an interface sensor. Detailed Implementation

[0043] Figure 1 A sedimentation device 1 according to the invention is shown, which has an interface sensor 10 according to the invention. The sedimentation device 1 is used, for example, in wastewater treatment equipment, drinking water treatment equipment, or metal ore extraction equipment.

[0044] The settling device 1 includes a container 20 for receiving the measuring medium 2. The container 20 is, for example, a secondary sedimentation tank or a so-called "sequencing batch reactor" or another vessel. For example, the container 20 is open at the top. The container 20 is suitable for depositing a sediment layer 3 onto the bottom plate or base of the container 20 through the measuring medium 2. The sediment layer 3 is part of the measuring medium 2 and is produced, for example, by the settling of heavy particles in the measuring medium 2, i.e., the decantation of the measuring medium 2. This settling can be accelerated by a chemical precipitation reaction between the measuring medium 2 and a settling agent or precipitant 30.

[0045] The settling device 1 includes an inlet 21 for the medium to be clarified, an overflow outlet for the clarified medium, and an outlet for the settled material. The inlet 21 can be integrated into the container 20, such as... Figure 1 As shown, or for example, it can be arranged above or inside container 20, for example, by supplying the precipitant 30 to container 20 without contacting the container, such as by using a hose. The precipitant is injected into the inlet of the medium to be clarified via an adjustable device such as a pump or valve, or added directly to the container. Inlet 21 includes an inlet valve 22 for adjusting the amount of precipitant 30 added to the measuring medium 2.

[0046] The interface sensor 10 is preferably an acoustic sensor. However, different sensors that enable the detection of particles in the measurement medium 2 may also be used. For example, the interface sensor 10 is an optical sensor.

[0047] Interface sensor 10 is preferably held by retainer 14 (see Figure 1 The interface sensor 10 is fixedly attached to the container 20, for example, horizontally offset from the container axis. However, the interface sensor 10 can also be movable relative to the container 20, allowing it to be immersed, for example, up to the bottom of the container 20. Immersing the interface sensor 10 in the container 20 is particularly advantageous if it is an optical sensor. If the interface sensor 10 is an acoustic sensor, it is particularly advantageous to fix it to the container 20.

[0048] The interface sensor 10, which is designed as an acoustic sensor, is described first in the following text.

[0049] The interface sensor 10 includes a sound transmitter 11, a sound detector 12, and a control unit 13. The sound transmitter 11 and the sound detector 12 can also be implemented in a common unit, i.e., implemented as transceivers 11 and 12. In this case, the transceivers 11 and 12 thus function as both a sound transmitter and a sound detector. If the sound transmitter 11 or sound detector 12 is mentioned below, it always also means transceiver. Of course, all embodiments can also be implemented using transceivers.

[0050] Sound transmitter 11 and sound detector 12 are connected to control unit 13. Similarly, inlet valve 22 is connected to control unit 13 for control by control unit 13. Interface sensor 10 is fixedly arranged relative to the bottom of the container. However, interface sensor 10 can also be movable relative to container 20, as interface sensor 10 is suitable for determining the bottom distance BA and water level distance WA.

[0051] According to another embodiment (not shown), the interface sensor 10 can also be arranged to float or be freely immersed in the measuring medium 2.

[0052] The sound transmitter 11 is adapted to generate at least one sound signal. The sound detector 12 is adapted to detect at least one signal response initiated by the first sound signal.

[0053] Control unit 13 is adapted to determine a measurement curve MK with a measurement value Mi from a signal response.

[0054] The control unit 13 may also be equipped with a communication module, such as a wireless or wired communication module. Therefore, the control unit 13 is suitable for outputting information to the user or the inlet valve 22.

[0055] The operation method of interface sensor 10 will be discussed in detail below.

[0056] This operating method involves placing the interface sensor 10 in a container 20 filled with the measurement medium 2, such that the interface sensor 10 is in contact with the measurement medium 2. For example... Figure 1 As shown, the interface sensor 10 is preferably partially immersed in the measurement medium 2.

[0057] The interface sensor 10 then records a measurement curve MK with measured values ​​Mi (where I = {1, 2, 3, ...}). For this purpose, the sound transmitter 11 emits a sound signal, which is then detected by the sound detector 12. The control unit 13 determines the measurement curve MK from the detected sound signal. The measurement curve MK consists of measured values ​​Mi, which on the vertical axis represents, for example, the amplitude of the detected sound signal, i.e., the echo amplitude E, and on the horizontal axis represents, for example, the depth D of the detected sound signal. Therefore, it is possible to see how many particles are in the measurement medium 2 and at what depth. Depth D0 is the position of the sound transmitter 11 and the sound detector 12 in the measurement medium 2.

[0058] Next, the control unit 13 evaluates the measured value curve MK. This evaluation process specifically involves determining the layer boundary SG, determining the first settlement parameter S1 based on the measured value Mi above the layer boundary SG, and determining the second settlement parameter S2 based on the measured value Mi below the layer boundary SG.

[0059] Use the measured value Mi directly from the measured value curve MK (see Figure 2 and Figure 5 Alternatively, the measurement function MF can be used to evaluate the measured curve MK. The measurement function MF represents the fitted curve of the measured curve MK, that is, the mathematical approximation of the measured curve MK (see...). Figure 3 and Figure 4 ).

[0060] First, describe the evaluation of the measured curve MK without curve fitting, such as... Figure 2 As shown in the image.

[0061] In determining the layer boundary SG, the first maximum value H1 of the measured value curve MK is first determined, i.e., the measured value Mi with the highest echo amplitude E. Then, the depth of this first maximum value H1 is recorded. Next, the layer boundary SG is set at a depth X0 above the depth of the first maximum value H1. Therefore, the layer boundary SG is further away from the tank bottom plate than the first maximum value H1. The distance X0 is stored in the control unit 13 and depends, for example, on the expected number of particles in the measuring medium 2. The distance X0 is based, for example, on an empirical value. For example, the distance X0 is several decimeters.

[0062] In determining the first settlement parameter S1, the region of the measured value curve MK above the layer boundary SG, that is, further away from the bottom plate of the tank than the layer boundary SG, is considered.

[0063] For example, determine the first area F1 below the measured curve MK between the first depth D1 and the layer boundary SG. The first depth D1 is defined by the highest measured value Mi, i.e., the measured value Mi farthest from the tank bottom plate (see...). Figure 2 In determining the first area F1, for example, the echo amplitudes of the measured values ​​Mi are summed and multiplied by the difference between the depth of the layer boundary SG and the first depth D1. Therefore, the first area F1 corresponds to the first settlement parameter S1.

[0064] As an alternative, in determining the first settlement parameter S1, the difference between the depth of the layer boundary SG and the first depth D1, i.e., the first projection length L1 of the measured curve MK on the horizontal axis, can also be used as the first settlement parameter S1 (see example). Figure 2 ).

[0065] In determining the second settlement parameter S2, the region of the measured value curve MK below the layer boundary SG, that is, closer to the bottom plate of the tank than the layer boundary SG, is considered.

[0066] For example, determine the second area F2 below the measured curve MK between the layer boundary SG and the second depth D2. The second depth D2 is defined by the lowest measured value Mi, i.e., the measured value Mi closest to the bottom plate of the tank (see...). Figure 2To this end, for example, the echo amplitudes of the measured values ​​Mi are summed and multiplied by the difference between the depth of the layer boundary SG and the second depth D2. Therefore, the second area F2 corresponds to the second settlement parameter S2.

[0067] Alternatively, in determining the second settlement parameter S2, the difference between the depth of the layer boundary SG and the second depth D2, i.e., the second projection length L2 of the measured curve MK on the abscissa, can also be used as the second settlement parameter S2 (see example). Figure 2 ).

[0068] The following describes how to evaluate the measured value curve MK using curve fitting, for example... Figure 3 As shown in the image.

[0069] In evaluating the measured curve MK, it is preferable to first determine the measurement function MF by curve fitting the measured curve MK. For example, curve fitting can be performed by polynomial fitting, least squares method, or spline interpolation. Determining and using the measurement function MF has the advantage that many evaluation steps can be implemented mathematically simply. Figure 3 Shown from Figure 2 A schematic curve fitting of the measured value curve MK. Figure 4 Another measurement function MF is shown, which is created using a curve fit schematically illustrated by the measurement curve MK.

[0070] In determining the layer boundary SG, at least one derivative of the measurement function MF is preferably used.

[0071] For example, in determining the layer boundary SG, the first derivative of the measurement function MF is used to determine at least the first maximum value H1 and the distance X0 (see...). Figure 2 This means that the first maximum value H1 is first determined by differentiating the measurement function MF, and then the layer boundary SG is set at a depth D above the depth of the first maximum value H1 at a distance X0. Therefore, the layer boundary SG is further away from the tank bottom plate than the first maximum value H1. The distance X0 is stored in the control unit 13 and depends, for example, on the expected number of particles in the measurement medium 2. The distance X0 is based, for example, on an empirical value. For example, the distance X0 is a few decimeters.

[0072] As an alternative to the first derivative of the measurement function MF, for example, in the determination of the layer boundary SG, the second derivative of the measurement function MF is used to determine the layer boundary SG. Here, at least the first inflection point W1 of the measurement function MF is determined (see...). Figure 3 If there are two inflection points, the inflection point above the first maximum value H1, that is, further away from the bottom plate of the tank than the first maximum value H1, is used as the layer boundary SG.

[0073] If the measurement function MF has, for example, in Figure 4If the measurement function MF shown has more than two inflection points W1, W2, W3, and W4, then the layer boundary SG at the third inflection point W3 is preferably selected. However, alternative points can also be selected for the layer boundary SG, such as inflection points above the first maximum value H1, i.e., inflection points farther from the tank bottom plate than the first maximum value H1, and even higher inflection points. Another alternative when selecting the layer boundary SG is to select it between the first inflection point W1 and the fourth inflection point W4. In other words, the selection of the layer boundary SG depends on the user. However, the first example above is a very reliable and robust process for selecting the layer boundary SG.

[0074] In determining the first settlement parameter S1, the region of the measurement function MF above the layer boundary SG, that is, further away from the bottom plate of the tank than the layer boundary SG, is considered.

[0075] For example, determine the first area F1 below the measurement function MF between the first depth D1 and the layer boundary SG. The first depth D1 is defined by the first point where the measurement function MF intersects with the abscissa (see...). Figure 3 In determining the first area F1, an integral is formed over the measurement function MF from the first depth D1 to the layer boundary SG. Therefore, the first area F1 corresponds to the first settlement parameter S1.

[0076] As an alternative, for example, a first area F1 is determined below the measurement function MF between a first reference value of the measurement function and the layer boundary SG. For example, the first reference value is located at 5% of the maximum amplitude of the measurement function MF relative to the measurement function. That is, the point where the measurement function MF intersects with a line that intersects the measurement function MF is at 5% of the maximum amplitude of the measurement function. Since this line will have at least two intersection points with the measurement function, the first reference value is a left-handed intersection point, i.e., a position close to the surface.

[0077] As an alternative, in determining the first settlement parameter S1, the difference between the depth of the layer boundary SG and the first depth D1, i.e., the first projection length L1 of the measurement function MF on the abscissa, can be used as the first settlement parameter S1 (see...). Figure 3 ).

[0078] As a further alternative, in determining the first settlement parameter S1, the difference between the depth of the first maximum value H1 and the first depth D1, i.e., the first maximum projection HP1 of the measurement function MF on the abscissa, can also be used as the first settlement parameter S1 (see...). Figure 3 ).

[0079] In determining the second settlement parameter S2, the region of the measurement function MF below the layer boundary SG, that is, closer to the bottom plate of the tank than the layer boundary SG, is considered.

[0080] For example, determine the second area F2 below the measurement function MF between the layer boundary SG and the second depth D2. The second depth D2 is defined by the first intersection point between the measurement function MF and the abscissa (see...). Figure 3 When the first area F1 is determined, an integral is formed over the measurement function MF from the layer boundary SG to the first depth D1. Therefore, the second area F2 corresponds to the second settlement parameter S2.

[0081] As an alternative, for example, a second area F2 is determined below the measurement function MF between the layer boundary SG and a second reference value of the measurement function. The second reference value is, for example, 5% of the maximum amplitude of the measurement function MF relative to the measurement function. That is, the point where the measurement function MF intersects with a line that intersects the measurement function MF is at 5% of the maximum amplitude of the measurement function. Since this line has at least two intersection points with the measurement function, the second reference value is the intersection point on the right side of the figure, i.e., near the bottom of the tank.

[0082] As an alternative, in determining the second settlement parameter S2, the difference between the depth of the layer boundary SG and the second depth D2, i.e., the second projection length L2 of the measurement function MF on the abscissa, can also be used as the second settlement parameter S2 (see...). Figure 3 ).

[0083] As a further alternative, in determining the second settlement parameter S2, the difference between the depth of the first maximum value H1 and the second depth D2, i.e., the second maximum projection HP2 of the measurement function MF on the abscissa, can also be used as the second settlement parameter S2 (see...). Figure 3 ).

[0084] In the evaluation of the measured curve MK with or without curve fitting, at least one exclusion range AB may optionally be defined, where the measured values ​​Mi or regions of the measured function MF are not considered. This is in Figure 5 As shown in the diagram. The advantage of this exclusion range AB is that, for example, interference signals caused by obstacles in the tank, such as fixtures or other sensors, are ignored.

[0085] Preferably, a warning message is issued if the measured value Mi falls within the exclusion range AB. The warning message is issued, for example, via the display, speaker, or communication module of the control unit 13. For example, the warning message is issued during or after the evaluation of the measured value curve.

[0086] Based on the above variation of the measured value curve MK evaluated by control unit 13, the settlement index SI is determined based on the ratio between the first settlement parameter S1 and the second settlement parameter S2.

[0087] The settling index SI is determined, for example, by the following first formula: SI = S1 / (S1 + S2). In this case, the smaller the settling index SI, the more optimized the settling of particles in the measurement medium 2 will be. Therefore, SI = 0 would be perfect settling.

[0088] Alternatively, the sedimentation index SI can be determined, for example, using the following second formula: SI = S2 / (S1 + S2). In this case, the larger the sedimentation index SI, the more optimized the sedimentation of particles in the measurement medium 2 will be. Therefore, SI = 1 would represent perfect sedimentation.

[0089] Of course, the above formula can be supplemented with further mathematical objects so that the settlement index SI can be used directly or indirectly for regulation with the help of the closed-loop control transfer function. For example, it can also be given as a percentage. The above formula would then be multiplied by, for example, 100. Alternatively, of course, addition / subtraction with fixed values ​​is also possible in order to shift the settlement index SI into the positive / negative range. This then makes, for example, "closed-loop control at zero," i.e., at a specific target value equal to zero as a result of the offset, possible. Alternatively, it is also conceivable to multiply the first settlement parameter S1 or the second settlement parameter S2 by a factor to produce specific weights.

[0090] In other words, depending on the above-described variation used to determine the first settlement parameter S1 or the second settlement parameter S2, the first area F1 and the second area F2 are compared, or the first projected length L1 and the second projected length L2 are compared, or the first maximum projection HP1 and the second maximum projection HP2 are compared.

[0091] The settlement index SI is then output by the control unit 13. This is done, for example, via a display or communication module of the control unit 13.

[0092] As described above, this method can also be applied to interface sensors 10 that are not acoustic sensors. For example, optical sensors or density measurement sensors using vibration electronics can also be used as interface sensors 10. However, when using these sensors, recording the measurement curve MK involves gradually immersing the interface sensor 10 from the surface of the container 20 to the bottom plate into the measurement medium 2. However, a disadvantage of this gradual immersion is that the interface sensor 10 may be exposed to particles and may be damaged or contaminated. Therefore, the advantage of acoustic interface sensors 10 is that they are arranged close to the surface of the measurement medium 2, which typically corresponds to an area in which few and / or only very small particles are disposed, thereby avoiding damage to the interface sensor 10.

[0093] The following describes a method for controlling the settling device 1 using a closed-loop control approach.

[0094] First, the sedimentation device 1 as described above is provided. This means that the sedimentation device 1 is ready for operation, i.e., the container 20 is filled with the measuring medium 2, and the interface sensor 10 is in contact with the measuring medium 2.

[0095] Then operate the interface sensor 10 according to one of the above operating methods.

[0096] Next, the inlet valve 22 is controlled by the control unit 13 based on the sedimentation index SI and a threshold, thereby adjusting the introduction of the precipitant 30 into the measuring medium 2. Specifically, if the sedimentation index SI reports suboptimal sedimentation, the inlet valve 22 will be opened. This would be the case, for example, if the sedimentation index SI is greater than a threshold of 0.5, using the first formula described above. Of course, another threshold, specified by the user and dependent on the particles in the measuring medium 2, can also be set.

[0097] One advantage of using the first projection length L1 and the second projection length L2 is that it is particularly effective at observing the presence of particles near the surface of the measurement medium 2. In this case, for example, a separate warning message can be issued to the user.

[0098] List of reference numerals in the attached figures

[0099] 1. Settling equipment

[0100] 2. Measuring medium

[0101] 3. Settlement layer

[0102] 10 Interface Sensors

[0103] 11 Sound transmitter

[0104] 12 Sound detectors

[0105] 13 Control Unit

[0106] 14 Retainer

[0107] 20 containers

[0108] 21. Precipitator Inlet

[0109] 22 Inlet Valve

[0110] 30 Precipitator

[0111] AB Exclusion Scope

[0112] BA base plate distance

[0113] D1 First Depth

[0114] D2 Second Depth

[0115] F1 First Area

[0116] F2 Second Area

[0117] H1 First maximum value

[0118] HP1 First Maximum Projection

[0119] HP2 Second Largest Projection

[0120] L1 First projection length

[0121] L2 Second Projection Length

[0122] MK measurement curve

[0123] Mi measurement value

[0124] MF measurement function

[0125] SG layer boundary

[0126] S1 First Settlement Parameter

[0127] S2 Second Settlement Parameter

[0128] SI Settlement Index

[0129] WA water level distance

[0130] W1 First Turning Point

[0131] W2 Second Turning Point

[0132] W3 Third Inflection Point

[0133] W4 Fourth Inflection Point

[0134] WP1 First Inflection Point Projection

[0135] WP2 Second Inflection Point Projection

[0136] X0 Distance

Claims

1. A method of operating an interface sensor (10), comprising: - arranging an interface sensor (10) in a container (20) filled with a measuring medium (2) such that the interface sensor (10) is in contact with the measuring medium (2); - recording a measurement curve (MK) with measurement values (Mi) using the interface sensor (10); - evaluating the measurement curve (MK) using the control unit (13), comprising: o determining a layer boundary (SG); o determining a first settling parameter (SI); o determining a second settling parameter (S2); - determining a settling indicator (SI) based on a relationship between the first settling parameter (SI) and the second settling parameter (S2); - outputting the settling indicator (SI) by means of the control unit (13).

2. The operating method of claim 1, wherein, During the evaluation process, a measurement function (MF) is determined by curve fitting the measurement curve (MK).

3. The operating method of claim 2, wherein, At least one derivative of the measurement function (MF) is used in the determination of the layer boundary (SG).

4. The operating method of claim 3, wherein, At least a first maximum (HI) and a distance (X0) of the measurement function (MF) are used in the determination of the layer boundary (SG).

5. The operating method of claim 3, wherein, At least a first inflection point (WI) of the measurement function (MF) is used in the determination of the layer boundary (SG).

6. The method of operation according to any of the preceding claims, wherein, In the determination of the first settling parameter (SI), a first area (Fl) or a first projection length (LI) formed on the basis of the measurement curve (MK) is determined, wherein in the determination of the second settling parameter (S2), a second area (F2) or a second projection length (L2) formed on the basis of the measurement curve (MK) is determined.

7. The method of operation according to any one of claims 2 to 5, wherein, In the determination of the first settling parameter (SI), a first inflection point projection (WP1) or a first maximum projection (HP1) formed on the basis of the measurement function (MF) is determined, wherein in the determination of the second settling parameter (S2), a second inflection point projection (WP2) or a second maximum projection (HP2) formed on the basis of the measurement function (MF) is determined.

8. The method of operation according to any of the preceding claims, wherein, In the evaluation of the measurement curve (MK), measurement values (Mi) falling within an exclusion range (AB) are ignored.

9. The operating method of claim 8, wherein, When a measurement value (Mi) falls within the exclusion range (AB), a warning message is issued.

10. A settling device (1), comprising: - an interface sensor (10); - a container (20) for receiving a measuring medium (2), wherein the interface sensor (10) is arranged relative to the container (20) such that the interface sensor (10) is suitable for being immersed in the measuring medium (2); - a precipitant inlet (21) for introducing a precipitant (30) into the measuring medium (2), wherein the precipitant inlet (21) has an inlet valve (22) connected to the control unit (13).

11. A closed-loop control method of a settling device (1), comprising: - providing a settling device (1) according to claim 10; - operating an interface sensor (10) according to any one of claims 1 to 9; and - operating a precipitant inlet (21) according to claim 10. - controlling, by means of the control unit (13), the inlet valve (22) on the basis of the sedimentation indicator (SI) and a threshold value, such that the introduction of the precipitant (30) into the measuring medium (2) is adjusted.

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