Precise metering and calculating method for liquid level

Abstract

The invention provides a liquid level precise calculation method which comprises the following steps: arranging a detection tube with the diameter smaller than that of a sampling tube on the sampling tube, arranging n detection points on the detection tube in the axial direction, and arranging n pairs of detection sensors on the corresponding detection points; taking the axis of the detection pipe as an original point of a two-dimensional coordinate, determining abscissas x of all the detection points, calculating a distance x between the adjacent detection points, and determining the time ti when the liquid passes through the ith sensor; calculating the average flow velocity # imgabs0 # i when the liquid passes through two adjacent sensors as a constant; the total flow Q of liquid passing through the detection tube is calculated, # imgabs1 #, alpha i is a correction factor, and A is the sectional area of the detection tube. The flow velocity distribution of the detection tube is modeled, the detection error of the liquid level in the detection tube during sampling detection is corrected by using an algorithm, the liquid level detection precision is improved, and the water quality sampling detection precision is further improved.

Description

Technical Field

[0001] The present invention relates to the technical field of water quality detection, and particularly to a precise measurement and calculation method for liquid level. Background Art

[0002] Water quality monitoring is widely used in the environmental protection industry, water treatment industry, aquaculture industry, etc. Usually, the liquid sample to be detected is pumped into the detection equipment for water quality detection, and the contents of COD (chemical oxygen demand), ammonia nitrogen, total phosphorus, and total nitrogen in the detection sample are obtained through an on-line analysis device. However, the error of the liquid level of the sample obtained by the existing detection equipment is relatively large, and inaccurate liquid level will lead to inaccurate calculation of the contents of ammonia nitrogen, total phosphorus, total nitrogen, etc., seriously affecting the results of water quality detection and having a significant impact on aquatic product production and environmental protection.

[0003] In view of this, the present application proposes a high-precision calculation method for liquid level. Summary of the Invention

[0004] The present invention proposes a precise measurement and calculation method for liquid level to solve the technical problem of large error in liquid level detection data in existing sampling detection.

[0005] The present invention provides a precise measurement and calculation method for liquid level, including providing a detection tube with a diameter smaller than that of the sampling tube in the sampling tube, arranging n detection points axially on the detection tube, and arranging n pairs of detection sensors at the corresponding detection points;

[0006] Taking the axis center of the detection tube as the origin of the two-dimensional coordinate, determining the abscissas x1, x2, x3... x n of all detection points, calculating the distance Δ x between adjacent detection points, and determining the time t i when the liquid passes through the i-th sensor;

[0007] Calculating the average flow velocity when the liquid passes through two adjacent sensors

[0008] Calculating the total flow rate Q of the liquid passing through the detection tube, where α i represents a correction factor, A represents the cross-sectional area of the detection tube, A = πr 2 , and r represents the radius of the detection tube.

[0009] Optionally, the correction factor α i is determined through experiments, and the experimental conditions include the number of bubbles and the size of bubbles in the detection tube.

[0010] Optionally, if the liquid in the detection tube is in a laminar flow structure, the total flow rate Let \(L\) denote the total length of the section in the detection tube where the liquid level sensor is set, \(r\) denote the radius of the detection tube, and \(v\) max max (x) represent the maximum flow velocity among all detection points.

[0011] Optionally, the flow velocity model of the liquid in the axial direction of the detection tube is a quadratic function, \(v(x)=ax\) 2 2 +bx + c, where \(a\), \(b\), and \(c\) are obtained through calculation.

[0012] Optionally, the detection sensor is a capacitance sensor or an optoelectronic sensor.

[0013] Optionally, it further includes using a bubble isolation module to eliminate or isolate bubbles of a preset specification outside the detection tube. The bubble isolation module includes a partition board provided with a plurality of through holes in an array, and the partition board is clamped with the inner wall of the detection tube.

[0014] Optionally, the detection tube is arranged in the horizontal section of the sampling tube, and two detection tubes are spaced on the sampling tube. The total flow rate \(Q\) of the liquid in the detection tube is \(Q = Q1+Q2\), where \(Q1\) and \(Q2\) are the total flow rates measured by the two detection tubes respectively.

[0015] Optionally, the detection sensor is installed relative to the inner wall of the detection tube at a preset inclination angle.

[0016] Optionally, the preset inclination angle \(\gamma\in[45^{\circ},60^{\circ})\).

[0017] Optionally, it further includes an ultrasonic cleaning module, and the ultrasonic cleaning module is arranged at the inlet end and the outlet end of the detection tube.

[0018] The beneficial effects of the present invention are as follows:

[0019] By modeling the flow velocity distribution in the detection tube, the present invention corrects the detection error of the liquid level in the detection tube during sampling detection by using an algorithm, improves the liquid level detection accuracy, and further improves the accuracy of water quality sampling detection. Description of the Drawings

[0020] Figure 1 It is a schematic diagram of the main steps of the liquid level precise measurement and calculation method provided by the present invention;

[0021] Figure 2 It is the calculation formula of the total flow rate in the liquid level precise measurement and calculation method provided by the present invention;

[0022] Figure 3 It is the calculation formula of the average flow velocity in the embodiment of the present invention;

[0023] Figure 4 It is the function model of the liquid flow velocity in the detection tube in the embodiment of the present invention;

[0024] Figure 5 This is a front structural schematic diagram of two detection side tubes arranged in the sampling tube in the embodiment of the present invention. Detailed implementation manners

[0025] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the embodiments of the invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of the present invention.

[0026] Water quality monitoring is widely used in the environmental protection industry, water treatment industry, aquaculture industry, etc. Usually, the liquid sample to be detected is pumped into the detection device for water quality detection, and the contents of COD (chemical oxygen demand), ammonia nitrogen, total phosphorus, and total nitrogen in the detection sample are obtained through an on-line analysis device. However, the error of the liquid level of the sample obtained by the existing detection device is relatively large. Inaccurate liquid level will lead to inaccurate calculation of the contents of ammonia nitrogen, total phosphorus, total nitrogen, etc., seriously affecting the results of water quality detection and having a significant impact on aquatic product production and environmental protection. In view of this, this application proposes a method for high-precision calculation of liquid level.

[0027] Hereinafter, in conjunction with the attached Figure 1 to the attached Figure 5 The present invention will be described in detail:

[0028] A method for precise measurement and calculation of liquid level, as Figure 1 shown, includes arranging a detection tube with a diameter smaller than that of the sampling tube in the sampling tube, setting n detection points axially on the detection tube, and arranging n pairs of detection sensors at the corresponding detection points;

[0029] The specific steps include:

[0030] S1 Taking the axis of the detection tube as the origin of the two-dimensional coordinate, determining the abscissas of all detection points, x1, x2, x3...x n , calculating the spacing △ x between adjacent detection points, and determining the time t i when the liquid passes through the i-th sensor;

[0031] S2 Calculating the average flow velocity when the liquid passes through two adjacent sensors

[0032] S3 Calculating the total flow rate Q of the liquid passing through the detection tube, where α i represents a correction factor, A represents the cross-sectional area of the detection tube, A = πr 2 , and r represents the radius of the detection tube.

[0033] As described above, in the present invention, a section with a diameter smaller than that of the detection tube is provided in the sampling tube. After the diameter is reduced, the property of the liquid flow in the tube is amplified, that is, a slight change in the liquid level in the sampling tube will be amplified when it enters the detection tube, and it is easy to obtain the change in the liquid level. Then, multiple pairs of detection sensors are provided in the detection tube to obtain multiple sets of detection data, and the detection data includes: the abscissa of all detection points, and the time t for the liquid to pass through each detection point i , the distance △ between adjacent detection points calculated using the abscissa data x , through t i and △ x , the average flow velocity of the liquid passing through two adjacent detection points can be calculated Specifically, the average flow velocity is calculated according to the following formula:

[0034] That is, as Figure 3 shown

[0035] Then, based on the average flow velocity between adjacent detection points , by establishing a flow velocity model, the total flow rate Q of the liquid in the detection tube is calculated using an algorithm formula

[0036] The specific algorithm formula is as Figure 2 shown, that is: where α i represents the correction factor, A represents the cross-sectional area of the detection tube, A = πr 2 , r represents the radius of the detection tube (due to formula editing reasons, the expression of the (i + 1)-th flow velocity here is different from that in the appendix Figure 2 , but both represent the average velocity).

[0037] For example:

[0038] Suppose the diameter D of the detection tube is 10 mm, and the correction factor α i is 1; the distance △ between adjacent detection points x = 20 mm, and there are 4 measurement points in total, that is, n = 4. The times t1, t2, t3, t4 for the liquid to flow through these 4 detection points are: 0.0, 0.2, 0.5, 0.9 respectively

[0039] Then,

[0040] Then, substituting into calculate

[0041] Among them, the aforementioned detection sensor can be a capacitive sensor or a photoelectric sensor. The capacitive sensor can be directly attached to the wall of the detection tube. The photoelectric sensor requires a light source emitter and a light source receiver. Since the light signal may be reflected or scattered on the liquid surface, an anti-reflection film needs to be set on the outer wall of the detection tube to reduce light loss and improve the detection quality.

[0042] It should be noted that the aforementioned correction factor α i is determined through experiments. The experimental conditions include the number of bubbles and the size of bubbles in the detection tube. Because the bubbles in the detection tube will affect the detection accuracy at or around the detection point, and even cause the photoelectric sensor to misdetect. Therefore, it is necessary to determine the coefficient of the influence of the bubbles and the number of bubbles on the detection data when detecting in the detection tube of this specification and the corresponding liquid through multiple tests. It is possible to analyze whether there are abnormal data, the number of times of abnormal data, and the percentage of abnormal data to normal data from the data of multiple detections, and obtain this correction factor.

[0043] In addition, it should be noted that the flow velocity model of the liquid in the axial direction of the detection tube is a quadratic function, that is, v(x) = ax 2 + bx + c, as Figure 4 shown. Among them, a, b, and c are obtained through calculation. Among them, min refers to the minimum value. The principle of the calculation formula for solving a, b, and c is the least squares method for solving quadratic equations. The specific derivation process of a, b, and c in this embodiment will not be elaborated here. Refer to the existing least squares method for calculating the coefficients of quadratic functions.

[0044] In practical applications, the flow state of the liquid in the detection tube may be a laminar flow structure. In this case, the total flow Q is calculated according to the formula:

[0045]

[0046] where L represents the total length of the section corresponding to the liquid level sensor in the detection tube, r represents the radius of the detection tube, and v max (x) represents the maximum flow velocity among all detection points.

[0047] That is, if the flow state of the liquid is closer to the laminar flow structure, the calculation of the liquid level in the tube is simpler. Moreover, the influence of bubbles and other factors that naturally affect the detection results will be reduced. Therefore, when the size of the sampling tube and the size of the detection tube satisfy a certain ratio, the liquid flow in the detection tube is closer to the laminar state, and the detection result is more accurate. This certain ratio is related to the type of liquid in the sampling tube, the turbidity of the liquid, etc. This embodiment does not make specific restrictions on this.

[0048] In some embodiments, in the present invention, a bubble isolation module is further included in the detection tube to eliminate or isolate bubbles of a preset specification outside the detection tube. The bubble isolation module includes a partition board arrayed with a plurality of through holes, and the partition board is snap-fitted with the inner wall of the detection tube. Eliminating the bubbles in the sampling tube or the bubbles generated inside the detection tube can effectively reduce the value of the correction factor α, making the detection result more accurate. The function of this partition board is to isolate the foam in the liquid surface layer outside the detection tube, or to break up some large-sized foams into small bubbles that are too small to affect the sensor detection. i The value can make the detection result more accurate. The function of this partition board is to isolate the foam in the liquid surface layer outside the detection tube, or to break up some large-sized foams into small bubbles that are too small to affect the sensor detection.

[0049] In some embodiments, as Figure 5 shown, the detection tube is arranged in the horizontal section of the sampling tube, and two detection tubes are arranged at intervals on the sampling tube. Then, the total flow rate of the liquid in the detection tube Q1 and Q2 are the total flow rates measured by the two detection tubes respectively. In this embodiment, by setting two detection tubes at two different positions in the same sampling tube, the flow rates Q1 and Q2 of the liquid in the corresponding detection tubes are respectively obtained, and then their average value is the total flow rate of the liquid in the detection tube. This method of averaging multiple-section detections can further reduce the calculation error and improve the accuracy of liquid level detection.

[0050] In some embodiments, the detection sensor is installed relative to the inner wall of the detection tube at a preset inclination angle; the preset inclination angle γ is in the range of [45°, 60°). Installing the sensor and the inner wall of the detection tube at a preset inclination angle is convenient for obtaining signals because the outer wall of the detection tube is a curved surface, which brings difficulties to the pasting of capacitive sensors; at an installation inclination angle of 45°, it is convenient for the installation of capacitive sensors or photoelectric sensors, and the same is true for 60°. In addition, this installation angle also needs to consider the height of the liquid filled in the detection tube. Generally, the more liquid there is in the detection tube, the smaller the preset inclination angle γ, and vice versa. In addition, installation inclination angles such as 50° and 55° in practice all have the effects described above.

[0051] In some embodiments, an ultrasonic cleaning module is further included, and the ultrasonic cleaning module is arranged at the inlet end and the outlet end of the detection tube. This ultrasonic cleaning module is used to periodically remove the dirt on the inner wall of the pipeline, improve the cleanliness inside the detection tube, and reduce the influence of impurities on the detection result. In addition, a temperature compensation module can be set. The liquid entering the sampling tube may reduce its temperature, and the temperature compensation module can compensate for the lost temperature, and then the liquid flows out of the sampling tube after temperature compensation. In addition, some liquids may be too cold, and they are preheated before entering the detection tube to avoid affecting the normal detection of the subsequent sensor due to too low temperature. The temperature compensation module can be a heating unit that is powered on for heating, such as the heating tube in a common kettle, or a patch-type PCT heating sheet. This embodiment does not make specific limitations on this.

[0052] Finally, the present invention provides a precise calculation method for liquid level, which includes setting a detection tube with a diameter smaller than that of the sampling tube in the sampling tube, arranging n detection points axially on the detection tube, and arranging n pairs of detection sensors at the corresponding detection points; taking the axis of the detection tube as the origin of the two-dimensional coordinate, determining the abscissas of all detection points, x1, x2, x3... x n , calculating the spacing △ between adjacent detection points x , and determining the time t when the liquid passes through the i-th sensor i ; calculating the average flow velocity when the liquid passes through two adjacent sensors Calculating the total flow rate Q of the liquid passing through the detection tube, where α i represents a correction factor, A represents the cross-sectional area of the detection tube, A = πr 2 , and r represents the radius of the detection tube. By modeling the flow velocity distribution of the detection tube, the present invention corrects the detection error of the liquid level in the detection tube during sampling detection by using an algorithm, improves the liquid level detection accuracy, and further improves the accuracy of water quality sampling detection.

[0053] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for precise measurement and calculation of liquid level, characterized in that: The method comprises arranging a detection tube having a diameter smaller than that of the sampling tube in the sampling tube, arranging n detection points in the axial direction of the detection tube, and arranging n pairs of detection sensors at the corresponding detection points; Take the axis of the test tube as the origin of the two-dimensional coordinate system and determine the horizontal coordinates of all test points, x1, x2, x3...x n , calculate the distance △ between adjacent detection points x , and determine the time t when the liquid passes the i-th sensor i ; Calculate the average flow rate of the liquid passing through two adjacent sensors Calculate the total flow rate Q of the liquid passing through the detection tube, Among them, α i Represents the correction factor, A represents the cross-sectional area of ​​the detection tube, A=πr 2 , r represents the radius of the detection tube.

2. A liquid level precision measurement and calculation method according to claim 1, characterized in that: The correction factor α i Determined through experiments, the experimental conditions include the number of bubbles in the detection tube and the size of the bubbles in the detection tube.

3. A liquid level precision measurement and calculation method according to claim 1, characterized in that: If the liquid in the detection tube is a laminar flow structure, the total flow L represents the total length of the section in the detection tube where the liquid level sensor is installed, r represents the radius of the detection tube, and v max (x) represents the maximum flow rate among all detection points.

4. A method for precise measurement and calculation of liquid level according to claim 1, characterized in that: The flow velocity model of the liquid in the axial direction of the detection tube is a quadratic function, v(x) = ax 2 +bx+c, where a, b, and c are Obtained by calculation.

5. The method for precise measurement and calculation of liquid level according to claim 1, characterized in that: The detection sensor is a capacitive sensor or a photoelectric sensor.

6. A method for precise measurement and calculation of liquid level according to claim 2, characterized in that: It also includes using a bubble isolation module to eliminate or isolate bubbles of preset specifications outside the detection tube, and the bubble isolation module includes a partition with a plurality of through holes arranged in an array, and the partition is clamped with the inner wall of the detection tube.

7. A method for precise measurement and calculation of liquid level according to claim 5, characterized in that: The detection tube is arranged at the horizontal section of the sampling tube. Two detection tubes are arranged at intervals on the sampling tube. The total flow rate of the liquid in the detection tube is Q=Q1+Q2. Q1 and Q2 are the total flow rates measured by the two detection tubes respectively.

8. A method for precise measurement and calculation of liquid level according to claim 5, characterized in that: The detection sensor is installed at a preset inclination angle relative to the inner wall of the detection tube.

9. A method for precise measurement and calculation of liquid level according to claim 8, characterized in that: The preset inclination angle γ∈[45°, 60°).

10. A method for precise measurement and calculation of liquid level according to claim 6, characterized in that: It also includes an ultrasonic cleaning module, which is arranged at the inlet end and the outlet end of the detection tube.

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