A medical liquid level sensor and liquid level detection method
By using a variable-diameter tube design and a sensor frequency-matched medical liquid level sensor, the problem of low accuracy in liquid level change and foam detection in existing technologies has been solved, achieving high-precision liquid level detection and rapid response, thus improving the safety and accuracy of the infusion process.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- ZHEJIANG WEILIAN FENGRAN SENSOR TECH CO LTD
- Filing Date
- 2025-11-19
- Publication Date
- 2026-06-30
AI Technical Summary
Existing medical liquid level sensors have low accuracy in detecting minute liquid level changes and foam, making it difficult to achieve high-precision detection and rapid response, especially during infusion, where it is difficult to accurately determine liquid level changes and the presence of foam.
The medical liquid level sensor, which adopts a variable diameter tube design with gradually decreasing tube diameter, combined with sensors of different tube diameters and an ultrasonic module, can accurately determine the liquid level and foam by detecting capacitance value and echo intensity.
It improves the sensitivity to detect minute changes in liquid level, enhances the anti-interference capability during infusion, ensures the timeliness and accuracy of infusion termination signals, reduces false alarms, and improves the safety of the infusion process.
Smart Images
Figure CN121288093B_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of liquid level detection technology, and in particular to a medical liquid level sensor and a liquid level detection method. Background Technology
[0002] Capacitive level sensors are typically used in infusion equipment or hemodialysis equipment to detect changes in liquid level, requiring timely responses to the presence of liquid and changes in liquid level.
[0003] Currently, non-contact liquid level sensors are used in medical applications to avoid contaminating the liquid. For example, the detection method and device of capacitive sensor for liquid detection in infusion tubes (CN107569739B) and the capacitive external induction liquid level detector (CN112161674A) can be used to detect the presence and level of liquid in the pipeline and make timely judgments on the infusion status.
[0004] In the process of liquid level detection, there are various situations, such as high-precision detection of minute liquid level changes and rapid response to large-scale liquid level changes. For example, during the infusion process, the liquid level will rise slowly at the beginning, but will drop rapidly at the end of the infusion. Furthermore, it is difficult to accurately detect and identify trace amounts of foam at the end of the infusion. The liquid level sensors mentioned above are not suitable for accurate detection of liquid level or foam in various situations, and the detection accuracy is low. Summary of the Invention
[0005] To improve detection accuracy, this application provides a medical liquid level sensor and a liquid level detection method.
[0006] Firstly, the medical liquid level sensor provided in this application adopts the following technical solution.
[0007] A medical liquid level sensor includes a reducing pipe fixedly connected to and communicating with an infusion pipeline. The reducing pipe has several sections with different diameters from top to bottom, and the diameter of the reducing pipe decreases sequentially from top to bottom. Each section with a different diameter has a sensor for detecting the liquid level.
[0008] By adopting the above technical solution, the diameter of the bottom end of the variable diameter tube is the smallest, the internal volume is small, and the detected capacitance value is small. The capacitance value is related to the dielectric constant of the different media, liquid and air, in the variable diameter tube. This means that even a slight increase in liquid level can cause a large change in capacitance value due to the change in dielectric constant. This allows for highly sensitive detection of small changes in liquid level, ensuring that the liquid level is effectively rising at the beginning of infusion, rather than slowly decreasing. This allows for better adjustment of the infusion rate. Furthermore, even small capacitance changes caused by foam passing through the smallest diameter part of the tube during infusion can be detected, which helps to stop the pump in time and reduce the possibility of unexpected situations.
[0009] At the end of the infusion, the liquid level in the variable-diameter tube, which was originally full of liquid, drops rapidly from the top of the tube with the largest diameter. The area of liquid adhering to the inner wall of the tube section when the liquid level drops to the same height at the largest diameter section is larger than that at the smaller diameter section, i.e., the effective area. The overall capacitance value increases. The capacitance will only show a large change when the liquid level drops to a certain extent or even completely leaves the tube section with the largest diameter. This is to better adapt to the rapid drop rate of the liquid level at the end of the infusion. It is not easy for the slow drop of the liquid level caused by other factors during the infusion to affect the large-scale change of capacitance. This improves the anti-interference ability of the detection, effectively reduces false alarms, and also improves the timeliness and accuracy of the infusion end signal.
[0010] Optionally, the reducing pipe includes, from top to bottom, a primary pipe, a secondary pipe, a tertiary pipe, and a quaternary pipe.
[0011] By adopting the above technical solution, the capacitance values detected during the rise of the liquid level in the secondary and tertiary tubes are different, and the rate of change is also different. This allows for more accurate differentiation and judgment of the liquid level at the upper or lower part of the variable diameter tube, which helps to more accurately control the infusion rate.
[0012] Optionally, the frequencies of the sensors corresponding to the first-stage transistor to the fourth-stage transistor increase sequentially from low to high.
[0013] By adopting the above technical solution, the detection of capacitance by the single-stage transistor requires good anti-interference performance, so low-frequency detection is used to improve anti-interference performance; the detection of capacitance changes by the quaternary transistor requires high sensitivity, so high-frequency detection is used, which is conducive to collecting more subtle capacitance changes and also helps the accuracy of foam detection.
[0014] Optionally, the bottom of the variable diameter pipe is provided with an ultrasonic module for detecting whether foam is passing through.
[0015] By adopting the above technical solution, the echo intensity detected when foam passes through the quadrupole is less than the echo intensity when air passes through. Combined with the change in capacitance value, it is possible to accurately determine whether foam has passed through.
[0016] Secondly, the liquid level detection method provided in this application adopts the following technical solution.
[0017] A liquid level detection method, using the aforementioned medical liquid level sensor, specifically includes the following steps.
[0018] S1. Establish a pipe segment-threshold mapping table between different pipe diameter sections of the variable pipe and their corresponding thresholds;
[0019] S2. Real-time acquisition of capacitance values detected by all sensors;
[0020] S3. Compare the capacitance values of different sections of the reducer with the corresponding thresholds to determine the position of the liquid level inside the reducer.
[0021] S4. Calculate the liquid level height based on the variable diameter pipe where the liquid level is located and the corresponding capacitance value;
[0022] S5. Based on the capacitance fluctuation of the quaternion and the echo intensity detected by the ultrasonic module, determine whether there is foam passing through the quaternion to determine whether the pump needs to be stopped.
[0023] By adopting the above technical solution, the liquid level height inside the variable diameter pipe can be obtained and determined for precise adjustment of the infusion rate.
[0024] Optionally, the method for establishing the pipe segment-threshold mapping table in S1 includes introducing air and liquid into the infusion pipeline to fill the variable diameter pipe with air or liquid, and detecting the steady-state capacitance obtained at different pipe diameters of the variable diameter pipe corresponding to the filling of liquid or air as the threshold interval at the corresponding pipe diameter portion of the variable diameter pipe.
[0025] By adopting the above technical solution, an accurate threshold range can be obtained at the initial power-on.
[0026] Optionally, in step S3, the capacitance value detected by the corresponding pipe segment of the variable diameter pipe is normalized in combination with the steady-state capacitance obtained by filling liquid or air at different pipe diameters of the variable diameter pipe to obtain a normalized capacitance value. If the normalized capacitance value of the corresponding pipe segment of the variable diameter pipe is between 0 and 1, it indicates that the liquid level is at the pipe segment corresponding to the variable diameter pipe.
[0027] By adopting the above technical solution, the specific pipe section location of the variable diameter pipe where the liquid level is located can be accurately determined.
[0028] Optionally, in step S4, the normalized capacitance value of the corresponding pipe segment of the variable diameter pipe at the liquid level location is multiplied by the length of the corresponding pipe segment of the variable diameter pipe, and then added to the length of the pipe segment of the variable diameter pipe below the liquid level and the reference height of the bottom of the variable diameter pipe to obtain the liquid level height.
[0029] The liquid level height value is obtained by adopting the above technical solution.
[0030] Optionally, the capacitance fluctuation in S5 is the quotient of the standard deviation and the average value of all capacitance values collected by the quaternion sensor in 0.5s.
[0031] By adopting the above technical solution, the capacitance fluctuation is parameterized so that the presence of erroneous bubbles can be accurately judged by the quadrupole.
[0032] Optionally, in step S5, the echo intensity detected by the ultrasonic module... echo intensity of a quaternary tube in an empty tube state If a comparison is made, If the capacitance fluctuation exceeds the corresponding threshold, the pump will be stopped.
[0033] By adopting the above technical solution, combining ultrasonic detection and capacitance fluctuation to accurately detect foam, false alarms can be reduced and foam alarms can be triggered in a timely and accurate manner.
[0034] In summary, this application includes at least the following beneficial effects:
[0035] 1. It can detect minute changes in liquid level with high sensitivity to determine that the liquid level is rising effectively at the beginning of infusion, rather than slowly declining, so as to better adjust the infusion rate. It can also detect small capacitance changes caused by foam passing through the smallest part of the tube during infusion, which helps to stop the pump in time and reduce the possibility of unexpected situations.
[0036] 2. It is better adapted to the rapid drop rate of the liquid level at the end of infusion, and is less likely to affect the large-scale change of capacitance due to the slow drop of the liquid level caused by other factors during the infusion process. This improves the anti-interference ability of the detection, effectively reduces false alarms, and also improves the timeliness and accuracy of the infusion end signal. Attached Figure Description
[0037] Figure 1 This is a schematic diagram of the structure of a medical liquid level sensor;
[0038] Figure 2 This is a flowchart of a liquid level detection method.
[0039] Explanation of reference numerals in the attached diagram: 1. Infusion tubing; 2. Reducing tube; 21. Primary tube; 22. Secondary tube; 23. Tertiary tube; 24. Quaternary tube; 25. Ultrasonic module; 3. Sensor. Detailed Implementation
[0040] The present application will be further described in detail below with reference to the accompanying drawings.
[0041] This application discloses a medical liquid level sensor, referring to... Figure 1 It includes a reducing pipe 2 that is fixedly connected to the infusion pipeline 1. The reducing pipe 2 is located below the infusion bag and is arranged vertically. The reducing pipe 2 is divided into several sections in the vertical direction. In this embodiment, the reducing pipe 2 is divided into four pipe sections, which are, from top to bottom, a primary pipe 21, a secondary pipe 22, a tertiary pipe 23, and a quaternary pipe 24.
[0042] Reference Figure 1 The diameters of the primary pipe 21, secondary pipe 22, tertiary pipe 23, and quaternary pipe 24 increase sequentially. For example, the diameter of the primary pipe 21 can be 6-8 mm, the secondary pipe 22 can be 4-5 mm, the tertiary pipe 23 can be 2.5-3 mm, and the quaternary pipe 24 can be 1.2-1.5 mm. Furthermore, the lengths of the four pipe sections also differ. For example, the length of the primary pipe 21 can be 8-12 mm, the secondary pipe 22 can be 5-8 mm, the tertiary pipe 23 can be 4-6 mm, and the quaternary pipe 24 can be 3-5 mm.
[0043] Reference Figure 1 Each of the four sections of the reducing pipe 2 has a sensor 3 installed close to its outer wall, which detects the liquid level based on the principle of capacitance change. The sensors have different frequencies. For example, the frequency of the sensor 3 in the primary tube 21 can be 50-100kHz, the frequency of the sensor 3 in the secondary tube 22 can be 300-500kHz, the frequency of the sensor 3 in the tertiary tube 23 can be 1-2MHz, and the frequency of the sensor 3 in the quaternary tube 24 can be 4-8MHz.
[0044] Reference Figure 1 An ultrasonic module 25 is also provided at the position of the quaternion tube 24 away from the sensor 3. The ultrasonic module 25 emits sound waves to the quaternion tube 24 and receives the echoes to provide a basis for judging whether there are bubbles passing through the quaternion tube 24.
[0045] This application also discloses a liquid level detection method, referring to... Figure 2 Specifically, it includes the following steps.
[0046] S1. Establish a pipe segment-threshold mapping table between different pipe diameter sections of the variable pipe 2 and their corresponding thresholds.
[0047] One method for establishing a pipe segment-threshold mapping table is to introduce air and liquid into the infusion pipe 1 respectively so that the reducer 2 is filled with air or liquid. The steady-state capacitance obtained at different pipe diameters of the reducer 2 corresponding to the liquid or air filling is used as the threshold range at the corresponding pipe diameter portion of the reducer 2.
[0048] S2. Real-time acquisition of capacitance values detected by all sensors 3. The average value of the capacitance values detected within a 0.2-second window can be used as real-time data.
[0049] S3. Compare the capacitance values of different sections of the reducer 2 with the corresponding threshold values to determine the position of the liquid level within the reducer 2.
[0050] The capacitance value detected in the corresponding pipe section of reducer 2 is normalized by combining it with the steady-state capacitance obtained by filling liquid or air at different pipe diameters of reducer 2 to obtain the normalized capacitance value. The specific calculation formula is as follows.
[0051] ;
[0052] in, For specific pipe sections of strain gauge pipe 2, such as the section corresponding to primary pipe 21 For 1, the diode 22 corresponds to The value is 2, and so on. for The capacitance of the transistor when air is introduced. for The capacitance of the stage tube when liquid is introduced.
[0053] If the normalized capacitance value of the pipe segment corresponding to reducer 2 is between 0 and 1, it indicates that the liquid level is at the corresponding pipe segment of reducer 2. Furthermore, to ensure the accuracy of the detection, the normalized capacitance values of two adjacent pipe segments of reducer 2 can be subtracted to obtain a normalized difference value. If the normalized difference value is greater than 0.1, the location of the liquid level can be accurately determined.
[0054] S4. Calculate the liquid level height based on the variable diameter pipe 2 where the liquid level is located and the corresponding capacitance value.
[0055] The liquid level height can be obtained by multiplying the normalized capacitance value of the pipe segment corresponding to the liquid level location by the length of the corresponding pipe segment of the reducer 2, and then adding it to the length of the pipe segment of the reducer 2 below the liquid level and the reference height of the bottom of the reducer 2.
[0056] S5. Based on the capacitance fluctuation of the quaternion 24 and the echo intensity detected by the ultrasonic module 25, determine whether there is foam passing through the quaternion 24 to determine whether the pump needs to be stopped.
[0057] The capacitance fluctuation value is specifically the quotient of the standard deviation and the average value of all capacitance values collected by sensor 3 of quaternion 24 in 0.5s. The echo intensity detected by ultrasonic module 25... echo intensity of quaternion 24 in empty tube state If a comparison is made, If the capacitance fluctuation value is greater than 0.25, it indicates that a certain amount of foam has passed through the quaternary tube 24. In this case, the pump should be stopped and the relevant checks should be carried out to determine whether the infusion tubing needs to be replaced or the infusion rate adjusted.
[0058] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.
Claims
1. A liquid level detection method, using a medical liquid level sensor for detection, the medical liquid level sensor including a variable diameter pipe (2) fixedly connected and connected to an infusion pipeline (1), the variable diameter pipe (2) having several sections with different diameters from top to bottom, the diameter of the variable diameter pipe (2) decreasing sequentially from top to bottom, and each section of the variable diameter pipe (2) having a sensor (3) for detecting the liquid level. The reducing pipe (2) includes, from top to bottom, a primary pipe (21), a secondary pipe (22), a tertiary pipe (23) and a quaternary pipe (24). The frequencies of the sensors (3) corresponding to the first-stage transistor (21) to the fourth-stage transistor (24) increase sequentially from low to high; The bottom of the variable diameter pipe (2) is equipped with an ultrasonic module (25) for detecting whether foam passes through. The liquid level detection method is characterized by: Specifically, the steps include the following: S1. Establish a pipe segment-threshold mapping table between different pipe diameter sections and corresponding thresholds of the variable diameter pipe (2); S2. Real-time acquisition of capacitance values detected by all sensors (3); S3. Compare the capacitance values of different sections of the reducer (2) with the corresponding threshold values to determine the position of the liquid level in the reducer (2); S4. Calculate the liquid level height based on the variable diameter pipe (2) where the liquid level is located and the corresponding capacitance value; S5. Based on the capacitance fluctuation of the quaternion (24) and the echo intensity detected by the ultrasonic module (25), determine whether there is foam passing through the quaternion (24) to determine whether the pump needs to be stopped.
2. The liquid level detection method according to claim 1, characterized in that: The method for establishing the pipe segment-threshold mapping table in S1 includes introducing air and liquid into the infusion pipe (1) to fill the variable diameter pipe (2) with air or liquid, and detecting the steady-state capacitance obtained by filling liquid or air at different pipe diameters of the variable diameter pipe (2) as the threshold range at the corresponding pipe diameter portion of the variable diameter pipe (2).
3. The liquid level detection method according to claim 2, characterized in that: The capacitance value detected in the corresponding pipe section of the variable diameter pipe (2) in S3 is normalized by combining the steady-state capacitance obtained by filling liquid or air at different pipe diameters of the variable diameter pipe (2) to obtain the capacitance normalization value. If the capacitance normalization value of the corresponding pipe section of the variable diameter pipe (2) is between 0 and 1, it indicates that the liquid level is at the pipe section corresponding to the variable diameter pipe (2).
4. The liquid level detection method according to claim 3, characterized in that: In step S4, the normalized capacitance value of the pipe segment corresponding to the variable diameter pipe (2) at the liquid level is multiplied by the length of the pipe segment corresponding to the variable diameter pipe (2), and then added to the length of the pipe segment of the variable diameter pipe (2) below the liquid level and the reference height of the bottom of the variable diameter pipe (2) to obtain the liquid level height.
5. The liquid level detection method according to claim 1, characterized in that: In S5, the capacitance fluctuation is the quotient of the standard deviation and the average value of all capacitance values collected by the sensor (3) of the quaternion (24) in 0.5s.