A low flow liquid volumetric flow measurement system

Abstract

This invention discloses a low-flow-rate liquid volumetric flow rate measurement system, comprising: a suction device, a temporary storage container, a computing device, and a liquid level measuring device for measuring the liquid level in the temporary storage container. The temporary storage container is located on the output side of the suction device, and the cross-sectional area of ​​the inner cavity of the temporary storage container is consistent from top to bottom. The temporary storage container is provided with an outlet end for connection to the inlet end of a pump. The data output end of the liquid level measuring device is connected to the data input end of the computing device. This system achieves dynamic range measurement from nL / min to mL / min, and maintains nanoliter-level measurement accuracy, especially in the ultra-low flow rate range below 100 μL / min, while balancing high resolution and wide measurement range requirements for liquids with different physical properties. The system provides real-time feedback of the measured flow rate data to the pump, forming a closed-loop control that actively corrects flow drift caused by external conditions such as temperature, pressure, and liquid viscosity changes, ensuring that it is unaffected by changes in the operating environment.

Description

Technical Field

[0001] This invention relates to the field of liquid transport technology, and in particular to a small-flow liquid volumetric flow rate measurement system. Background Technology

[0002] In applications requiring high-precision flow rates, such as liquid chromatography, flow chemistry, biology, pharmaceuticals, and semiconductor manufacturing, infusion pumps typically need to achieve accurate flow at the microliter level. However, the compressibility of liquids under high pressure introduces significant errors. Although the equipment is calibrated and compensated with specific liquids at the factory, this method cannot adapt to the varying media, pressures, and temperatures in real-world applications, resulting in limited actual flow rate accuracy.

[0003] To address this issue, those skilled in the art have proposed using a high-precision balance to monitor the mass loss of the mobile phase, combining this with the density value input by the user to calculate the actual volumetric flow rate, and comparing it with the pump's setpoint to dynamically adjust the pump's output. However, there is a trade-off between range and accuracy. To ensure measurement accuracy, the balance's range is typically small, resulting in a limited total material capacity and preventing the system from operating continuously for extended periods. Furthermore, it is sensitive to environmental fluctuations; for example, vibration, airflow, and temperature can all introduce errors. Additionally, the readings require settling time, making it impossible to measure continuously decreasing mass in real time, thus affecting control response speed. Moreover, the calculation of volumetric flow rate depends on density, which varies with operating conditions (temperature, pressure). The static density value input by the user cannot reflect the real-time state, and the balance cannot directly measure density, becoming a new source of error. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a small-flow-rate liquid volumetric flow rate measurement system. To provide a basic understanding of some aspects of the disclosed embodiments, a brief summary is given below. This summary is not intended as a general commentary, nor is it intended to identify key / important components or to define the scope of protection of these embodiments. Its sole purpose is to present some concepts in a simple form as a prelude to the detailed description that follows.

[0005] The present invention adopts the following technical solution:

[0006] A small-flow liquid volumetric flow rate measurement system is provided, comprising: a suction device, a temporary storage container, a computing device, and a liquid level measuring device for measuring the liquid level in the temporary storage container. The temporary storage container is disposed on the output side of the suction device, and the cross-sectional area of ​​the inner cavity of the temporary storage container is consistent from top to bottom. The temporary storage container is provided with an outlet end for connecting to the inlet end of a pump. The data output end of the liquid level measuring device is connected to the data input end of the computing device.

[0007] Furthermore, the small-flow liquid volumetric flow rate measurement system further includes: a first three-way valve; the number of temporary storage containers is two, and each temporary storage container is equipped with a liquid level measuring device; the outlet end of the suction device is connected to the inlet end of the first three-way valve, and the two outlet ends of the first three-way valve are respectively connected to the inlet ends of the two temporary storage containers.

[0008] Furthermore, the small-flow liquid volumetric flow measurement system further includes: a second three-way valve; the outlet end of the second three-way valve is connected to the inlet end of the pump, and the two inlet ends of the second three-way valve are respectively connected to the outlet ends of the two temporary storage containers.

[0009] Furthermore, the small-flow liquid volumetric flow rate measurement system further includes: a control device, wherein the first three-way valve, the second three-way valve, and the suction device are all connected to the control output terminal of the control device, and the data output terminal of the liquid level measuring device is connected to the data input terminal of the control device.

[0010] Furthermore, the small-flow liquid volumetric flow rate measurement system further includes: a communication device; the data output terminal of the communication device is connected to the data input terminal of the pump, or the data output terminal of the communication device is connected to the data input terminal of a control system for controlling the flow rate of the pump.

[0011] The beneficial effects of this invention are as follows:

[0012] 1. This application achieves real-time measurement of the volume and flow rate of the delivered reagent by monitoring the liquid level change of the temporary storage container. In particular, the high-pressure infusion pump can directly obtain real-time measurement data, which is not affected by environmental factors such as liquid type, temperature, environmental vibration, downstream pressure and corrosiveness, thereby ensuring delivery accuracy.

[0013] 2. This application can balance resolution and dynamic range, and the flow measurement accuracy can be accurate to nL / min to mL / min;

[0014] 3. This application provides a method for measuring liquid flow rate from nanoliters to milliliters per minute without presetting liquid characteristic parameters;

[0015] 4. Simple structure, easy to deploy, and low cost. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of one embodiment of a small-flow liquid volumetric flow rate measurement system according to the present invention;

[0018] Figure 2 This is another schematic diagram of a small-flow liquid volumetric flow rate measurement system according to the present invention. Detailed Implementation

[0019] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be understood that the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0020] like Figure 1 As shown in some illustrative embodiments, a small-flow liquid volumetric flow rate measurement system is provided to solve the problem of insufficient accuracy caused by the compressibility of liquids, variable operating conditions, and limitations of traditional measurement methods in high-pressure micro-flow transportation. By directly converting liquid level to volume, high-precision and high-stability volumetric flow rate measurement and control are achieved.

[0021] The measurement system of this application is used to measure the volume and flow rate of the delivered reagent, that is, to measure the instantaneous flow rate and cumulative volume of the liquid flowing out of the temporary storage container 400. Specifically, it includes: a suction device 300, a temporary storage container 400, a liquid level measuring device 500, and a controller. The controller includes a computing device 600, a control device 700, and a communication device 800.

[0022] The liquid to be transferred is contained in the reagent storage tank 200, and the inlet end of the suction device 300 is connected to the outlet end of the reagent storage tank 200. The temporary storage container 400 is located on the output side of the suction device 300, that is, the outlet end of the suction device 300 is connected to the inlet end of the temporary storage container 400, so that the suction device 300 can quantitatively and steadily replenish the liquid to be transferred from the reagent storage tank 200 to the temporary storage container 400, thereby maintaining the liquid level in the temporary storage container 400 within a measurable range.

[0023] The aspiration device 300 is a pump body capable of conveying liquids. This application does not limit the type of the aspiration device 300; in specific implementations, the aspiration device 300 can be a peristaltic pump or a diaphragm pump. The advantages of a peristaltic pump are that the liquid flows only within the pump tube and does not contact the pump body, resulting in no contamination, easy cleaning, and low shear force, making it ideal for conveying bioactive samples, corrosive liquids, or high-purity reagents. The advantages of a diaphragm pump are its good sealing performance, no leakage, and ability to handle corrosive liquids, while also providing a certain pressure to ensure a stable and reliable replenishment process.

[0024] The temporary storage container 400 is equipped with an outlet end for connection to the inlet end of the pump 100, used to stably deliver liquid to downstream applications under normal pressure. The pump 100 mentioned in this application is one such device in the downstream application. A liquid level measuring device 500 is used to measure the liquid level height within the temporary storage container 400. The liquid level measuring device 500 is a displacement sensor with a liquid level detection resolution ≤1μm. In specific implementations, the liquid level measuring device 500 can be a laser rangefinder or a magnetic scale. The laser rangefinder is a non-contact measurement device with a fast response speed. It determines the distance by measuring the time or phase difference of the laser beam from emission to reflection from the liquid surface. Its advantages are that it does not contaminate the sample and is unaffected by liquid conductivity, color, etc. The magnetic scale measures the liquid level by sensing the position of a float. Its advantages are high accuracy, good stability, and excellent repeatability.

[0025] The inner cavity of the temporary storage container 400 is a cavity with a regular cross-section, meaning the cross-sectional area of ​​the inner cavity of the temporary storage container 400 is consistent from top to bottom. Because of its regular cross-section, the flow rate and volume change of the delivered reagent can be calculated by measuring the change in the liquid level height within a timing period. Preferably, the inner cavity cross-section of the temporary storage container 400 is usually circular, but it can also be square. To avoid measurement errors caused by liquid level changes due to evaporation, a piston can be installed at the inlet of the temporary storage container 400 to achieve a seal.

[0026] The data output terminal of the liquid level measuring device 500 is connected to the data input terminal of the computing device 600, thereby sending the measurement data to the computing device 600. The computing device includes: a computing unit, used to calculate the supply volume and flow rate of the reagent within the timing cycle based on the cross-sectional area of ​​the inner cavity of the temporary storage container 400, the liquid level height measured by the liquid level measuring device 500, and the duration of the timing cycle; and a timing unit, used to record the duration and send a notification message to the computing unit every timing cycle. That is, the timing unit is used to accurately record the time interval Δt and trigger the computing unit to perform a flow rate calculation once at a set frequency (such as 10 times per second, 100 times per second, etc.).

[0027] The calculation unit acquires the liquid level data from the liquid level measuring device 500, such as H1 and H2, as well as the timestamps t1 and t2 from the timing unit. The timestamp t1 corresponds to the liquid level height H1, and the timestamp t2 corresponds to the liquid level height H2.

[0028] Volume ΔV calculation:

[0029] ΔV=S×(ΔH)=S×(H1-H2);

[0030] S is the cross-sectional area of ​​the inner cavity of the temporary storage container 400.

[0031] Flow Q calculation:

[0032] Q=ΔV÷(t2-t1)=S×(ΔH / Δt);

[0033] t2-t1 is the duration of the timing cycle.

[0034] Since the temporary storage container 400 is a container with highly precise geometry, changes in liquid volume are directly reflected as changes in liquid level. Taking the inner cavity of the temporary storage container 400 as an example, with a height of 50mm and an inner diameter of 10mm, the cross-sectional area S = π × (5mm). 2 ≈78.54mm 2 If the level measurement device 500 has a level detection resolution ≤ 1 μm, then the corresponding volume resolution = S × 1 μm = 78.54 mm. 2 ×0.001mm=0.07854μL (or 78.54nL), which means that the system can distinguish volume changes at the nanoliter level.

[0035] like Figure 2 As shown, it also includes: a first three-way valve 101 and a second three-way valve 102.

[0036] There are two temporary storage containers 400, and each temporary storage container 400 is equipped with a liquid level measuring device 500. In this application, the installation position of the liquid level measuring device 500 is not limited, as long as it can measure the liquid level of the temporary storage container 400. The outlet end of the suction device 300 is connected to the inlet end of the first three-way valve 101, and the two outlet ends of the first three-way valve 101 are respectively connected to the inlet ends of the two temporary storage containers 400. The inlet end of the pump 100 is connected to the outlet end of the second three-way valve 102, and the two inlet ends of the second three-way valve 102 are respectively connected to the outlet ends of the two temporary storage containers 400.

[0037] The first three-way valve 101, acting as the outlet distributor of the suction device 300, determines which temporary storage container 400 the liquid pumped from the reagent storage tank 200 flows to. Under the command of the control device, the first three-way valve 101 can switch between two positions, allowing the liquid to flow to two different containers. It can be a solenoid valve or an electric valve. The second three-way valve 102, acting as the inlet selector of the pump 100, determines which temporary storage container 400 to draw liquid from for delivery. It also operates under the command of the control device, working in coordination with the first three-way valve 101 to ensure that the pump 100 always draws liquid from a container that is currently supplying liquid. By using two temporary storage containers 400 and a liquid level measuring device 500, and by adding two three-way valves at the inlet and outlet of the temporary storage containers 400 for switching, the alternating and coordinated operation of the two temporary storage containers 400 achieves uninterrupted, continuous online measurement.

[0038] The control input terminals of the first three-way valve 101, the second three-way valve 102, and the suction device 300 are all connected to the control output terminal of the control device 700 to receive control signals issued by the control device 700. The communication device 800 is used to send the calculation results of the calculation unit to the pump 100. The data output terminal of the communication device 800 is connected to the data input terminal of the pump 100, or the data output terminal of the communication device 800 is connected to the data input terminal of the control system used to control the flow rate of the pump 100. The data output terminal of the liquid level measuring device is connected to the data input terminal of the control device 700 to send its own measurement data to the control device 700.

[0039] The control device 700 includes:

[0040] The acquisition unit is used to obtain the liquid level height of the two temporary storage containers 400 measured by the liquid level measuring device.

[0041] The first judgment unit is used to switch the two outlet ends of the first three-way valve 101 and start the suction device 300 when the liquid level of one of the temporary storage containers 400 drops to a low threshold, so that the suction device 300 supplies the delivery reagent to the temporary storage container with a liquid level lower than the preset value, and at the same time switches the two inlet ends of the second three-way valve 102 so that the pump 100 pumps the delivery reagent from the other temporary storage container.

[0042] The second judgment unit is used to shut down the suction device 300 when the liquid level in the temporary storage container 400 rises to the high threshold.

[0043] The system workflow is as follows:

[0044] Initialization: The system starts up, pump 100 and suction device 300 are in standby mode, the controller is initialized, and a certain amount of liquid is injected into the temporary storage container 400 through suction device 300, and the liquid level is within the initial working range.

[0045] Flow transmission and measurement:

[0046] The user sets the target flow rate Qm, and pump 100 starts working, drawing liquid from temporary storage container 400 and delivering it downstream. As liquid is drawn out, the liquid level in temporary storage container 400 continuously decreases. Liquid level measuring device 500 monitors the liquid level in real time and sends the data to computing device 600.

[0047] Real-time calculation:

[0048] The timing unit triggers a calculation every time a timing cycle occurs. The calculation unit calculates the liquid level change ΔH, and combined with the known cross-sectional area S, calculates the volume change ΔV within the timing cycle, and further calculates the instantaneous actual flow rate Qs.

[0049] Closed-loop feedback and control:

[0050] The control unit in pump 100 obtains the calculated actual flow rate Qs and compares it with the target flow rate Qm set by the user to obtain the error. Based on the error, it outputs a compensation command. The compensation command is used to adjust the motor speed or valve opening of the pump to control pump 100, so that pump 100 fine-tunes its output according to the compensation command, with the goal of making the actual flow rate Qs close to the target flow rate Qm.

[0051] In the above process, the two temporary storage containers are distinguished and designated as the current temporary storage container and the standby temporary storage container, respectively. Pump 100 draws liquid from the current temporary storage container through the second three-way valve 102 and pumps it downstream. At the same time, the liquid level measuring device 500 monitors the drop in liquid level in the current temporary storage container in real time, and the calculation device 600 calculates the flow rate and cumulative transport volume in real time based on the liquid level change and cross-sectional area. This allows pump 100 to dynamically adjust its speed or stroke, forming a closed-loop control to ensure transport accuracy.

[0052] Simultaneously, the suction device 300 is activated, pumping liquid into the backup temporary storage container through the first three-way valve 101 until the liquid level rises to the high threshold, at which point the suction device 300 is shut off. During this process, the backup temporary storage container does not participate in measurement or liquid supply, but continuously monitors the liquid level in the current temporary storage container. When the liquid level drops to the low threshold, a switching procedure is immediately triggered to prevent cavitation and flow interruption. The second three-way valve 102 is switched from the current temporary storage container to the backup temporary storage container, and the first three-way valve 101 is switched from the backup temporary storage container back to the current temporary storage container, preparing for liquid replenishment in the current temporary storage container.

[0053] This system achieves an ultra-wide dynamic range measurement from nL / min to mL / min. Especially in the ultra-low flow range below 100μL / min, it can still maintain nanoliter-level measurement accuracy for liquids with different physical properties, taking into account both high resolution and wide range measurement requirements.

[0054] This system will immediately feed back the real-time measured flow data to Pump100 to form a closed-loop control. It can actively correct flow drift caused by external conditions such as changes in temperature, pressure, and liquid viscosity, ensuring that the pump's output flow is stable and accurate over a long period of time, unaffected by changes in the operating environment.

[0055] By switching between dual temporary storage containers and a three-way valve, uninterrupted online continuous measurement is achieved. The liquid replenishment process and the measurement process are physically isolated, ensuring that the pump's suction inlet pressure is stable and will not cause any disturbance or impact on the pump's normal operating pressure.

[0056] It is suitable for conveying corrosive liquids and for applications where the pump inlet is at normal pressure. Moreover, the overall design is simple, the manufacturing cost is low, and it is easy to integrate and deploy.

[0057] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A low flow liquid volumetric flow measurement system characterized by, include: The device includes a suction device, a temporary storage container, a computing device, and a level measuring device for measuring the liquid level in the temporary storage container. The temporary storage container is located on the output side of the suction device, and the cross-sectional area of ​​the inner cavity of the temporary storage container is consistent from top to bottom. The temporary storage container is provided with an outlet end for connecting to the inlet end of a pump. The data output end of the level measuring device is connected to the data input end of the computing device.

2. A low flow liquid volumetric flow rate measurement system according to claim 1, wherein, Also includes: The first three-way valve; the number of temporary storage containers is two, and each temporary storage container is equipped with a liquid level measuring device. The outlet end of the suction device is connected to the inlet end of the first three-way valve, and the two outlet ends of the first three-way valve are respectively connected to the inlet ends of the two temporary storage containers.

3. The small-flow-rate liquid volumetric flow rate measurement system according to claim 2, characterized in that, Also includes: The second three-way valve; the outlet end of the second three-way valve is connected to the inlet end of the pump, and the two inlet ends of the second three-way valve are respectively connected to the outlet ends of the two temporary storage containers.

4. The small-flow-rate liquid volumetric flow rate measurement system according to claim 3, characterized in that, Also includes: The control device includes the first three-way valve, the second three-way valve, and the suction device, all of which are connected to the control output terminal of the control device. The data output terminal of the liquid level measuring device is connected to the data input terminal of the control device.

5. A low flow liquid volumetric flow rate measurement system according to claim 4, wherein, Also includes: A communication device; the data output terminal of the communication device is connected to the data input terminal of the pump, or the data output terminal of the communication device is connected to the data input terminal of a control system for controlling the flow rate of the pump.

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