Defoaming metering method and structure for water quality equipment

Abstract

The invention discloses a defoaming metering method for water quality equipment and a structure of the defoaming metering method. On one hand, the defoaming metering method for the water quality equipment, provided by the invention, comprises the following steps: S1, driving a water sample or a reagent to forwardly flow into a metering tube along a first path until the liquid level in the metering tube reaches a defoaming liquid level; s2, the liquid level in the metering pipe is driven to repeatedly ascend and descend n times within the preset range of the upper portion and the lower portion of the metering pipe with the defoaming liquid level as the base point, and n is larger than or equal to 2; s3, the water sample or the reagent is driven to reversely flow out of the metering pipe along the first path until the liquid level in the metering pipe reaches a target liquid level, and the height of the target liquid level is lower than that of the defoaming liquid level; and S4, driving the water sample or the reagent in the metering tube to flow out along the second path. On the other hand, the invention further provides a defoaming metering structure for the water quality equipment applying the method. The device has the advantages that bubbles can be reduced, and the metering precision and the testing accuracy are improved.

Description

Technical Field

[0001] The invention relates to the technical field of water quality equipment, in particular to a defoaming metering method and a structure thereof for water quality equipment. Background Art

[0002] In the testing process of water quality monitoring equipment, it is necessary to add several chemical reagents in proportion to a certain volume of water sample, so that the chemical reagents react chemically with the substances to be measured in the water sample, thereby producing measurable chemical reaction products, and then the concentration of the substances to be measured in the original water sample is calculated by measuring the concentration of the chemical reaction products. Therefore, the volume measurement accuracy of the water sample or reagent determines the concentration accuracy of the chemical reaction products, and thus determines the accuracy of the water quality equipment in measuring the concentration of the substances to be measured in the water sample.

[0003] Online water quality monitoring equipment generally uses a metering module for volume measurement. Existing metering modules include Figure 1 As shown, it includes a metering tube 1, a multi-way valve 2, a liquid level sensor 3, and a pump 4, wherein the metering tube 1 is connected to the multi-way valve 2, and different types of liquids and reaction pools (such as digestion cups, etc.) are connected to different valve ports of the multi-way valve 2. When it is necessary to measure the liquid, under the negative pressure suction of the pump 4, the liquid (water sample or reagent) is extracted from the corresponding valve port of the multi-way valve 2 into the metering tube 1. When the liquid level sensor 3 senses that the liquid page in the metering tube 1 reaches a preset horizontal height, the pump 4 stops running and the valve port of the multi-way valve 2 is closed, and the metering module completes a fixed volume of liquid measurement. After the metering module extracts liquid from the corresponding valve port of the multi-way valve 2 to complete the measurement, it transfers the measured liquid to the reaction pool through the valve port of the multi-way valve 2 connected to the reaction pool. After all the liquids participating in the reaction are measured and transferred to the reaction pool, the various liquids participating in the reaction are mixed in the reaction pool, and appropriate conditions (such as temperature, etc.) are applied to make the water sample and the reagent react chemically, thereby obtaining a measurable chemical reaction product. The volume of liquid transferred at one time is the sum of the volume V1 of liquid in the metering tube 1 and the volume V2 of liquid from the metering tube 1 to the corresponding valve port of the multi-way valve 2 .

[0004] Similar metering modules are widely used in water quality equipment, but the metering accuracy of the metering module is more sensitive to bubbles. Suppose a liquid of volume V needs to be measured, but bubbles of volume Va are mixed in the metering tube. After the liquid reaches the target liquid level sensed by the liquid level sensor, the volume of liquid measured by the water sample or reagent is only V-Va, which is lower than the target volume set by the process. This volume deviation will cause a deviation in the concentration of the measured substance after the transfer, and ultimately cause a deviation in the test results. The source of the bubble may be that the air in the side branch cavity of the multi-way valve is extracted when the liquid is pumped out; or when the reagent is extracted, the reagent in the reagent bottle is almost exhausted, and the pipe port is at the critical surface of the reagent and the air. Therefore, the generation of bubbles has a certain randomness, that is, the test situation may be different each time, so the deviation cannot be eliminated by the system error.

[0005] There are two states of bubbles: one is bubbles that exist above the liquid surface due to tension; the other is bubbles that exist in the connecting capillary tube. In order to allow a larger volume of liquid to be measured at one time, the measuring glass tube in the metering module generally has a larger diameter. In order to reduce tube wall residue, the pipes connecting the metering tube and the multi-way valve, as well as the pipes connecting the multi-way valve to each reagent bottle and water sample, generally have a smaller diameter. The presence of bubbles above the liquid surface can easily cause the liquid level sensor to misjudge the liquid level, thereby affecting the measurement accuracy; the presence of bubbles in the capillary tube will cause the volume of the measured liquid to be smaller than the target volume due to the volume of the bubbles, affecting the measurement accuracy. Since the second type of bubbles exists inside the pipeline and is surrounded by liquid, it is difficult to eliminate.

[0006] How to solve the above problems has become a technical problem that needs to be solved urgently. Summary of the invention

[0007] The first object of the present invention is to provide a defoaming metering method for water quality equipment that can reduce bubbles and improve metering accuracy.

[0008] The second purpose of the present invention is to provide a defoaming metering structure for water quality equipment using the above method, which can effectively eliminate bubbles that may exist in the liquid before extracting water samples or reagents for chemical reactions, thereby avoiding the influence of bubbles on the test results.

[0009] To achieve the above object, the present invention adopts the following technical solutions:

[0010] On the one hand, the present invention provides a defoaming metering method for water quality equipment, which comprises the following steps:

[0011] S1, driving the water sample or reagent to flow into the metering tube in a positive direction along the first path until the liquid level in the metering tube reaches the defoaming liquid level;

[0012] S2, driving the liquid level in the metering tube to rise and fall repeatedly n times within a preset range above and below the defoaming liquid level with the defoaming liquid level as the base point, where n ≥ 2;

[0013] S3, driving the water sample or reagent to flow out of the metering tube in the reverse direction along the first path until the liquid level in the metering tube reaches a target liquid level, and the height of the target liquid level is lower than the height of the defoaming liquid level;

[0014] S4. Drive the water sample or reagent in the metering tube to flow out to the outside along the second path.

[0015] Furthermore, the metering tube is connected to a multi-way valve. In steps S1 to S3, the valve port corresponding to the first path on the multi-way valve is opened and the valve port corresponding to the second path is closed. In step S4, the valve port corresponding to the first path on the multi-way valve is closed and the valve port corresponding to the second path is opened to achieve switching between the first path and the second path.

[0016] Furthermore, in steps S1 to S3, the liquid level in the metering tube is monitored in real time by a liquid level sensor.

[0017] Furthermore, in steps S1 to S4, the water sample or reagent is driven to flow by a pump.

[0018] Furthermore, when the liquid level in the metering tube is at the defoaming liquid level, the liquid volume V1+V3 in the metering tube is greater than the liquid volume V1+V2 to be flowed out of the outside through the second path, wherein V1 represents the liquid volume in the metering tube when it is at the target liquid level, V2 represents the liquid volume in the pipeline from the valve port of the multi-way valve corresponding to the second path to the metering tube, and V3 represents the liquid volume between the target liquid level and the defoaming liquid level in the metering tube.

[0019] Furthermore, the height difference between the defoaming liquid level and the target liquid level is

[0020]

[0021] In the formula, d1 is the inner diameter of the metering tube, d2 is the inner diameter of the pipe connecting the metering tube and the multi-way valve, d3 is the inner diameter of the internal liquid flow channel of the multi-way valve, l2 is the length of the pipe connecting the metering tube and the multi-way valve, and l3 is the length of the internal liquid flow channel between the common port of the multi-way valve and the valve port corresponding to the second path on the multi-way valve.

[0022] On the other hand, the present invention also provides a defoaming metering structure for water quality equipment, including a first path and a second path, one end of each of the first path and the second path is connected to a metering tube, the metering tube is provided with a liquid level sensor capable of monitoring the liquid levels at at least two different heights in the metering tube, and also includes a pump assembly for providing power to drive the water sample or reagent to flow in both directions along the first path and drive the water sample or reagent to flow out of the second path to the outside, the pump assembly and the liquid level sensor are both electrically connected to a controller.

[0023] Furthermore, it also includes a multi-way valve and a common pipeline, wherein the two ends of the common pipeline are respectively connected to the lower end of the metering tube and the common port of the multi-way valve, one of the valve ports of the multi-way valve is a liquid outlet port and at least another valve port on the multi-way valve is a liquid inlet port, when the metering tube, the common pipeline, the multi-way valve, and the liquid inlet port are connected in sequence, a first path is formed, and when the metering tube, the common pipeline, the multi-way valve, and the liquid outlet port are connected in sequence, a second path is formed.

[0024] Furthermore, the pump assembly includes a pump tube, one end of which is connected to the upper end of the metering tube and the other end of which is connected to the atmosphere, and a pump capable of forward and reverse rotation is provided on the pump tube, and the pump is electrically connected to a controller.

[0025] Further, the pump is a peristaltic pump.

[0026] Due to the adoption of the above method and structure, the present invention has the following beneficial effects:

[0027] In the method of the present invention, after driving the water sample or reagent into the metering tube along the first path, the liquid level in the metering tube is repeatedly raised and lowered within a preset range near the defoaming liquid level, so that the bubbles can be repeatedly rubbed against the wall of the metering tube, increasing the probability of bubble rupture, thereby achieving the defoaming effect, reducing bubbles, and improving the accuracy of metering. In the structure of the present invention, the water sample or reagent is driven to flow in both directions along the first path multiple times through the pump assembly, so that the liquid level in the metering tube can be repeatedly raised and lowered, and the bubbles can be repeatedly rubbed against the wall of the metering tube and ruptured, which can effectively eliminate the bubbles that may exist in the liquid, so that the volume of the water sample or reagent that finally flows out from the second path for chemical reaction is closer to the predetermined target volume, thereby avoiding the influence of bubbles on the test results and improving the accuracy of water quality monitoring.

[0028] The present invention will become more apparent from the following description taken in conjunction with the accompanying drawings, which are used to illustrate embodiments of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0030] Figure 1 It is a structural schematic diagram of an existing metering module;

[0031] Figure 2 It is a schematic diagram of the overall structure of the present invention. DETAILED DESCRIPTION

[0032] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] Embodiment 1

[0034] Please refer to Figure 2 The defoaming metering method for water quality equipment provided in this embodiment comprises the following steps:

[0035] S1, driving the water sample or reagent to flow into the metering tube 1 along the first path in a positive direction until the liquid level in the metering tube 1 reaches the defoaming liquid level;

[0036] S2, driving the liquid level in the metering tube 1 to rise and fall repeatedly n times within a preset range above and below the defoaming liquid level, wherein n≥2; the preset range may be a range from the target liquid level to the top of the metering tube 1;

[0037] S3, driving the water sample or reagent to flow out of the metering tube 1 in the reverse direction along the first path until the liquid level in the metering tube 1 reaches a target liquid level, and the height of the target liquid level is lower than the height of the defoaming liquid level;

[0038] S4, driving the water sample or reagent in the metering tube 1 to flow out to the outside along the second path for chemical reaction.

[0039] When the water sample or reagent flows into the metering tube 1 along the first path in a positive direction to the defoaming liquid level, there are the most bubbles and the measurement accuracy is the worst. By driving the water sample or reagent to flow back and forth between the metering tube 1 and the first path, the liquid level in the metering tube 1 is repeatedly raised and lowered within a preset range near the defoaming liquid level. The bubbles will repeatedly rub against the wall surface of the metering tube 1, which can increase the probability of bubble bursting, thereby achieving the defoaming effect. After the liquid level in the metering tube 1 is lowered to the target liquid level, the water sample or reagent in the metering tube 1 is driven to flow out along the second path, which can effectively cut off part of the water sample or reagent from the end away from the metering tube 1 from the first path, and avoid the new bubbles introduced into the first path in step S2 from also flowing out through the second path for chemical reaction, thereby greatly reducing the bubbles in the metering tube 1, and the larger the value of n, the better the defoaming effect; until when step S3 is finished, the liquid level in the metering tube 1 is at the target liquid level, at this time most of the bubbles in the liquid are eliminated, and the volume of the water sample or reagent in the metering tube 1 is close to the volume of pure liquid without bubbles, thereby improving the measurement accuracy.

[0040] In this embodiment, the metering tube 1 is connected to a multi-way valve 2, which has at least three valve ports, one of which is connected to the metering tube 1 and the other two correspond to the first path and the second path, respectively; in steps S1 to S3, the valve port corresponding to the first path on the multi-way valve 2 is opened and the valve port corresponding to the second path is closed, and in step S4, the valve port corresponding to the first path on the multi-way valve 2 is closed and the valve port corresponding to the second path is opened to achieve switching between the first path and the second path.

[0041] In some preferred embodiments, the valve ports corresponding to the first path and the valve ports corresponding to the second path on the multi-way valve 2 are both valve ports with valves, so that the on-off of the first path and the second path can be controlled separately as needed.

[0042] In some optional embodiments, by respectively providing valves on the first path and the second path, the on-off of the first path and the second path can also be controlled.

[0043] In this embodiment, in steps S1 to S3 , the liquid level in the metering tube 1 is monitored in real time by the liquid level sensor 3 .

[0044] In some preferred embodiments, the liquid level sensor 3 is a point liquid level sensor, such as a photoelectric liquid level sensor. By respectively setting two photoelectric liquid level sensors at the target liquid level and the defoaming liquid level, it is possible to monitor whether the liquid level in the metering tube 1 reaches the target liquid level and the defoaming liquid level.

[0045] In some optional embodiments, the liquid level sensor 3 is a continuous liquid level sensor, such as a float liquid level sensor, an ultrasonic liquid level sensor, etc.

[0046] In this embodiment, in steps S1 to S4 , the water sample or reagent is driven to flow by the pump 4 .

[0047] In some preferred embodiments, there is one pump 4 and the pump 4 is a reversible bidirectional pump, and the pump 4 is connected to the upper end of the metering tube 1 through a pipeline; when the pump 4 rotates forward, negative pressure is generated, and in step S1, the water sample or reagent can be sucked to the defoaming liquid level of the metering tube 1 along the first path, and in step S2, the liquid level in the metering tube 1 can be raised to above the defoaming liquid level; when the pump 4 reverses, the external pressure is sucked into the metering tube 1 and acts on the liquid surface, and in step S2, the liquid level in the metering tube 1 can be pressed down to below the defoaming liquid level and the bubbles formed on the liquid surface due to tension can be crushed, and in step S3, the liquid level in the metering tube 1 can be lowered to the target liquid level, and in step S4, the water sample or reagent can be driven to flow out of the outside along the second path; and in step S2, through multiple forward and reverse rotations of the pump 4, the liquid surface can be repeatedly pushed and pulled, so that the bubbles and the wall of the metering tube 1 are repeatedly rubbed, thereby increasing the probability of bubble rupture. In addition, in step S1, the pump 4 is set to a high speed, and the water sample or reagent is rushed into the metering tube 1 along the first path. The bubbles in the water sample or reagent will obtain a large initial kinetic energy when entering the metering tube 1. Combined with the effect of buoyancy, they can float from the liquid to the surface of the liquid and burst.

[0048] In some optional embodiments, there are two pumps 4, which are installed on the first path and the second path respectively, and at least the pump 4 installed on the first path is a bidirectional pump that can rotate forward and reverse.

[0049] After the bubbles are broken, the gas rises and is discharged to the outside through the top of the metering tube 1, that is, the farther the distance between the position of the bubbles in the water sample or reagent and the liquid surface of the metering tube 1 is, the lower the probability of being eliminated. Therefore, in this embodiment, when the liquid level in the metering tube 1 is at the defoaming liquid level, the liquid volume V1+V3 in the metering tube 1 is greater than the liquid volume V1+V2 to be discharged to the outside through the second path, wherein V1 represents the liquid volume in the metering tube 1 when it is at the target liquid level, V2 represents the liquid volume in the pipeline from the valve port of the multi-way valve 2 corresponding to the second path to the metering tube 1, and V3 represents the liquid volume between the target liquid level and the defoaming liquid level in the metering tube 1. That is, V3>V2, so that when the liquid level in the metering tube 1 drops from the defoaming liquid level to the target liquid level, the water sample or reagent originally in the pipeline between the metering container and the multi-way valve 2 will flow back into the container for storing water samples or reagents along the first path, and the bubbles in this part of the water sample or reagent will also flow back into the container for storing water samples or reagents, which can prevent part of the water sample or reagent far away from the liquid surface of the metering tube 1 and the bubbles therein from flowing out to the outside along the second path in step S4 for chemical reaction, thereby further improving the accuracy of water quality monitoring.

[0050] The liquid volume can be calculated by measuring the inner diameter and length of each component in advance, or by extracting the liquid when the defoaming liquid level and the target liquid level are reached to the outside and measuring it with a volume measuring tool such as a measuring cylinder, or by calculating it by weighing the weight change. The above methods are all existing technologies and will not be repeated here.

[0051] In some optional embodiments, the height difference between the defoaming liquid level and the target liquid level is

[0052]

[0053] In the formula, d1 is the inner diameter of the metering tube 1, d2 is the inner diameter of the pipe connecting the metering tube 1 and the multi-way valve 2, d3 is the inner diameter of the internal liquid flow channel of the multi-way valve 2, l2 is the length of the pipe connecting the metering tube 1 and the multi-way valve 2, and l3 is the length of the internal liquid flow channel between the common port of the multi-way valve 2 and the valve port corresponding to the second path on the multi-way valve 2.

[0054] because Thereby, there is enough liquid level height difference to transfer the liquid with bubbles in the pipeline connected to the metering tube 1 into the metering tube 1, so that the liquid floats to the liquid surface and the bubbles are broken by friction.

[0055] In some preferred embodiments, the pump 4, the liquid level sensor 3, and the valve are all connected to a master control module, thereby realizing the automation of defoaming metering;

[0056] In some optional embodiments, the pump 4, the liquid level sensor 3, and the valve are all provided with independent processing modules, and each independent processing module is connected with each other in a wireless or wired manner, thereby realizing the automation of defoaming metering.

[0057] When the present embodiment is in use, the valve port corresponding to the first path on the multi-way valve 2 is opened and the valve port corresponding to the second path is closed, the pump 4 runs at a relatively high speed to generate a negative pressure in the metering tube 1, and the water sample or reagent in the external container is sucked into the metering tube 1 from the first path until the liquid level sensor 3 detects that the liquid level of the metering tube 1 reaches the defoaming liquid level, the pump 4 rotates forward and reversely for many times, so that the liquid level in the metering tube 1 repeatedly rises and falls near the defoaming liquid level, so that the bubbles are rubbed and broken by the wall surface of the metering tube 1, and float from the liquid to above the liquid surface under the action of buoyancy and are discharged to the outside, when the liquid level in the metering tube 1 repeatedly rises and falls near the defoaming liquid level for a preset number of times, the pump 4 reverses to lower the liquid level in the metering tube 1 from the defoaming liquid level to the target liquid level, then, the valve port corresponding to the first path on the multi-way valve 2 is closed and the valve port corresponding to the second path is opened, and the water sample or reagent flows out to the outside along the second path to wait for a chemical reaction.

[0058] Embodiment 2

[0059] Please refer to Figure 2This embodiment is a defoaming metering structure for water quality equipment using the method provided by the present invention, including a first path and a second path, one end of each of the first path and the second path is connected to a metering tube 1, and the metering tube 1 is provided with a liquid level sensor 3 capable of monitoring at least two liquid levels at different heights in the metering tube 1, and also includes a pump assembly for providing power to drive the water sample or reagent to flow in both directions along the first path and drive the water sample or reagent to flow out of the outside from the second path, and the pump assembly and the liquid level sensor 3 are both electrically connected to a controller.

[0060] In some preferred embodiments, the liquid level sensor 3 includes two photoelectric liquid level sensors. By respectively arranging the two photoelectric liquid level sensors at the target liquid level and the defoaming liquid level, the liquid levels at two different heights in the metering tube 1 can be monitored.

[0061] When in use, the controller starts the pump assembly, the pump assembly runs and generates negative pressure in the metering tube 1 to suck the water sample or reagent, so that the water sample or reagent flows into the metering tube 1 along the first path until the liquid level in the metering tube 1 reaches the defoaming liquid level, and then controls the pump assembly to rotate forward and reverse multiple times to drive the water sample or reagent to flow in both directions along the first path, so that the liquid level in the metering tube 1 repeatedly rises and falls near the defoaming liquid level, so that the bubbles can be rubbed and broken by the wall of the metering tube 1, and float from the liquid to above the liquid surface under the action of buoyancy and be discharged to the outside, and, when the liquid level in the metering tube 1 repeatedly rises and falls near the defoaming liquid level for a preset number of times, the pump assembly reverses to lower the liquid level in the metering tube 1 from the defoaming liquid level to the target liquid level, and then the pump assembly provides power to drive the water sample or reagent to flow out of the outside from the second path to wait for a chemical reaction.

[0062] In this embodiment, a multi-way valve 2 and a common pipeline 5 are also included, wherein the two ends of the common pipeline 5 are respectively connected to the lower end of the metering tube 1 and the common port of the multi-way valve 2, one of the valve ports of the multi-way valve 2 is a liquid outlet port 202 and at least another valve port on the multi-way valve 2 is a liquid inlet port 201. When the metering tube 1, the common pipeline 5, the multi-way valve 2, and the liquid inlet port 201 are connected in sequence, a first path is formed, and when the metering tube 1, the common pipeline 5, the multi-way valve 2, and the liquid outlet port 202 are connected in sequence, a second path is formed, so that the water sample or reagent in the liquid outlet port 202 from the target liquid level of the metering tube 1 can be discharged to the outside to carry out a chemical reaction.

[0063] In some preferred embodiments, there are multiple liquid inlet ports 201, which are respectively used to allow different water samples or reagents to enter the first path.

[0064] In some preferred embodiments, the liquid inlet port 201 and the liquid outlet port 202 are both valve ports with valves, and the valves are electrically connected to the controller, so that the on-off of the first path and the second path can be controlled respectively as needed.

[0065] In some optional embodiments, by respectively providing valves electrically connected to the controller on the first path and the second path, the on-off of the first path and the second path can also be controlled.

[0066] In this embodiment, the pump assembly includes a pump tube 6, one end of which is connected to the upper end of the metering tube 1 and the other end of which is connected to the atmosphere, and a pump 4 capable of forward and reverse rotation is provided on the pump tube 6, and the pump 4 is electrically connected to the controller. When the controller controls the pump 4 to rotate forward, the gas in the metering tube 1 can be pumped out to the outside, thereby generating negative pressure to suck the water sample or reagent into the metering tube 1, or the liquid level in the metering tube 1 can be raised; when the pump 4 is reversed, the external gas can be pumped into the metering tube 1, thereby increasing the air pressure in the metering tube 1, driving the water sample or reagent to flow out of the outside from the second path, or causing the liquid level in the metering tube 1 to drop.

[0067] In this embodiment, the pump 4 is a peristaltic pump. It is understandable that other common bidirectional pumps may also be used.

[0068] The above describes the preferred embodiments of the present invention. It should be understood that the present invention is not limited to the above-mentioned specific embodiments, and the devices and structures that are not described in detail should be understood to be implemented in a common manner in the art; any technician familiar with the art can use the above-disclosed methods and technical contents to make many possible changes and modifications to the technical solutions of the present invention without departing from the scope of the technical solutions of the present invention, or modify them into equivalent embodiments of equivalent changes, which does not affect the essential content of the present invention. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention are still within the scope of protection of the technical solutions of the present invention.

Claims

1. A defoaming metering method for water quality equipment, characterized in that: The defoaming metering method comprises the following steps: S1, driving the water sample or reagent to flow into the metering tube (1) in a positive direction along a first path until the liquid level in the metering tube (1) reaches a defoaming liquid level; S2, driving the liquid level in the metering tube (1) to rise and fall repeatedly n times within a preset range above and below the defoaming liquid level with the defoaming liquid level as a base point, wherein n≥2; S3, driving the water sample or reagent to flow out of the metering tube (1) in the reverse direction along the first path until the liquid level in the metering tube (1) reaches a target liquid level, wherein the height of the target liquid level is lower than the height of the defoaming liquid level; S4, driving the water sample or reagent in the metering tube (1) to flow out to the outside along the second path.

2. The defoaming metering method for water quality equipment according to claim 1, characterized in that: The metering pipe (1) is connected to a multi-way valve (2). In steps S1 to S3, the valve port corresponding to the first path on the multi-way valve (2) is opened and the valve port corresponding to the second path is closed. In step S4, the valve port corresponding to the first path on the multi-way valve (2) is closed and the valve port corresponding to the second path is opened, so as to realize switching between the first path and the second path.

3. The defoaming metering method for water quality equipment according to claim 1, characterized in that: In steps S1 to S3, the liquid level in the metering tube (1) is monitored in real time by a liquid level sensor (3).

4. The defoaming metering method for water quality equipment according to claim 1, characterized in that: In steps S1 to S4, the water sample or reagent is driven to flow by the pump (4).

5. The defoaming metering method for water quality equipment according to claim 1, characterized in that: When the liquid level in the metering tube (1) is at the defoaming liquid level, the liquid volume V1+V3 in the metering tube (1) is greater than the liquid volume V1+V2 to be discharged to the outside through the second path, wherein V1 represents the liquid volume in the metering tube (1) when it is at the target liquid level, V2 represents the liquid volume in the pipeline between the valve port of the multi-way valve (2) corresponding to the second path and the metering tube (1), and V3 represents the liquid volume between the target liquid level and the defoaming liquid level in the metering tube (1).

6. The defoaming metering method for water quality equipment according to claim 1, characterized in that: The height difference between the defoaming liquid level and the target liquid level In the formula, d1 is the inner diameter of the metering tube (1), d2 is the inner diameter of the pipe connecting the metering tube (1) and the multi-way valve (2), d3 is the inner diameter of the internal liquid flow channel of the multi-way valve (2), l2 is the length of the pipe connecting the metering tube (1) and the multi-way valve (2), and l3 is the length of the internal liquid flow channel between the common port of the multi-way valve (2) and the valve port corresponding to the second path on the multi-way valve (2).

7. A defoaming metering structure for water quality equipment using the method of claim 1, characterized in that: The invention comprises a first path and a second path, wherein one end of each of the first path and the second path is connected to a metering tube (1), and the metering tube (1) is provided with a liquid level sensor (3) capable of monitoring liquid levels at at least two different heights in the metering tube (1); and further comprises a pump component for providing power to drive a water sample or a reagent to flow in both positive and negative directions along the first path and to drive the water sample or the reagent to flow out of the outside through the second path; the pump component and the liquid level sensor (3) are both electrically connected to a controller.

8. The defoaming metering structure for water quality equipment according to claim 7, characterized in that: It also comprises a multi-way valve (2) and a common pipeline (5), wherein the two ends of the common pipeline (5) are respectively connected to the lower end of the metering pipe (1) and the common port of the multi-way valve (2), one of the valve ports of the multi-way valve (2) is a liquid outlet port (202) and at least another valve port on the multi-way valve (2) is a liquid inlet port (201), and when the metering pipe (1), the common pipeline (5), the multi-way valve (2) and the liquid inlet port (201) are connected in sequence, a first path is formed; when the metering pipe (1), the common pipeline (5), the multi-way valve (2) and the liquid outlet port (202) are connected in sequence, a second path is formed.

9. The defoaming metering structure for water quality equipment according to claim 7 or 8, characterized in that: The pump assembly comprises a pump tube (6), one end of which is connected to the upper end of the metering tube (1) and the other end of which is connected to the atmosphere, and a pump (4) capable of forward and reverse rotation is arranged on the pump tube (6), and the pump (4) is electrically connected to a controller.

10. The defoaming metering structure for water quality equipment according to claim 9, characterized in that: The pump (4) is a peristaltic pump.

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