Medical liquid level sensor and liquid level detection method

Abstract

The invention relates to the technical field of liquid level detection, in particular to a medical liquid level sensor which comprises a reducer pipe fixedly connected and communicated with a liquid conveying pipeline, the reducer pipe is provided with a plurality of parts with different pipe diameters from top to bottom, and the pipe diameters of the reducer pipe are sequentially reduced from top to bottom. A sensor for detecting the liquid level is arranged at each part with different pipe diameters of the reducer pipe, so that quick response or precise detection of the liquid level can be carried out by utilizing different capacitance changes caused by liquid level changes in different pipe diameters.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of liquid level detection technology, in particular to a medical liquid level sensor and a liquid level detection method. BACKGROUND

[0002] The capacitive liquid level sensor is generally used for the change of the related liquid level height in the infusion device or hemodialysis device, and needs to respond to the presence or absence of liquid and the change of the liquid level height in time.

[0003] The capacitive liquid level sensor for medical treatment at present avoids pollution to the liquid by selecting a non-contact liquid level sensor. For example, the detection method and device of the capacitive sensor for liquid detection of the infusion tube with the publication number CN107569739B and the capacitive external induction liquid level detector with the publication number CN112161674A are used to detect whether there is liquid in the pipeline and the liquid level height, and to make a judgment on the infusion situation in time.

[0004] In the liquid level detection process, there are various situations such as high-precision detection of small liquid level changes and rapid response to large-range liquid level changes. For example, the liquid level slowly rises at the beginning of the infusion process, and the liquid level in the infusion tube rapidly decreases at the end of the infusion. It is difficult to accurately detect and identify the trace foam at the end of the infusion stage. The above liquid level sensors are difficult to adapt to the accurate detection of the liquid level or foam in various situations, and the detection precision is low. SUMMARY

[0005] In order to improve the detection precision, the present application provides a medical liquid level sensor and a liquid level detection method.

[0006] In the first aspect, the medical liquid level sensor provided by the present application adopts the following technical scheme.

[0007] A medical liquid level sensor, comprising a variable diameter pipe fixedly connected and communicated with an infusion pipeline, the variable diameter pipe is provided with a plurality of parts with different diameters from top to bottom, the diameters of the variable diameter pipe decrease from top to bottom in turn, and each part with different diameters of the variable diameter pipe is provided with a sensor for detecting the liquid level.

[0008] By adopting the technical scheme, the diameter of the bottom end of the variable-diameter tube is the smallest, the internal volume is smaller, and the detected capacitance value is smaller. The capacitance value is related to the dielectric constant of different media of the liquid and air in the variable-diameter tube. Even if the liquid level rises slightly, the change of the dielectric constant can cause a large change in the capacitance value, so that the slight change of the liquid level can be detected with high sensitivity. It is determined that the liquid level is effectively rising at the initial stage of infusion, rather than in the process of slow decline, so as to better adjust the infusion speed. When the foam passes through the smallest part of the tube diameter during the infusion process, the small change in capacitance caused by the foam can also be detected, which helps to stop the pump in time and reduces the possibility of accidents.

[0009] At the end of infusion, the liquid level in the variable-diameter tube originally filled with liquid rapidly decreases from the upper part with the largest diameter. The area of the liquid adhering to the inner wall of the tube segment, i.e. the effective area, caused by the liquid level falling by the same height at the largest diameter is larger than that at the smaller diameter. The overall capacitance value increases. When the liquid level falls to a certain extent or even completely separates from the tube segment with the largest diameter, a large change in capacitance occurs. This better adapts to the rapid falling rate of the liquid level at the end of infusion and is not easily affected by the slow falling of the liquid level caused by some other factors during the infusion process, thereby improving the anti-interference ability of detection, effectively reducing false positives, and improving the timeliness and accuracy of the infusion end signal.

[0010] Optionally, the variable-diameter tube comprises a first tube, a second tube, a third tube and a fourth tube from top to bottom.

[0011] By adopting the technical scheme, the capacitance values detected during the process of the liquid level rising in the second tube and the third tube are different, and the change rates are also different. The height of the liquid level in the middle or lower part of the variable-diameter tube can be more accurately distinguished and judged, which helps to more accurately control the infusion speed.

[0012] Optionally, the frequencies of the sensors corresponding to the first tube to the fourth tube increase from low to high.

[0013] By adopting the technical scheme, the detection of the capacitance by the first tube requires good anti-interference performance, so low-frequency detection is adopted to improve the anti-interference performance. The detection of the capacitance change by the fourth tube requires high sensitivity, so high-frequency detection is adopted, which is helpful for collecting more subtle capacitance changes and improving the accuracy of foam detection.

[0014] Optionally, the bottom of the variable-diameter tube is provided with an ultrasonic module for detecting whether there is foam passing through.

[0015] By adopting the technical scheme, the echo intensity detected when the foam passes through the fourth tube is smaller than that when the air passes through. Combined with the change in the capacitance value, the situation of the foam passing through can be accurately judged.

[0016] In a second aspect, the application provides a liquid level detection method using the following technical solution.

[0017] A liquid level detection method using the above medical liquid level sensor, specifically comprising the following steps.

[0018] S1, establishing a pipe section-threshold mapping table between different pipe diameter sections of the variable diameter pipe and corresponding thresholds;

[0019] S2, collecting the capacitance values detected by all sensors in real time;

[0020] S3, comparing the capacitance values of different pipe section sections of the variable diameter pipe with the corresponding thresholds to determine the position of the liquid level in the variable diameter pipe;

[0021] S4, calculating the liquid level height according to the variable diameter pipe where the liquid level is located and the corresponding capacitance value;

[0022] S5, judging whether there is foam passing through the fourth pipe according to the capacitance fluctuation of the fourth pipe and the echo intensity detected by the ultrasonic wave module to determine whether the pump needs to be stopped.

[0023] By using the above technical solution, the liquid level height in the variable diameter pipe is obtained and judged, which is used for precise adjustment of the infusion rate.

[0024] Optionally, the method of S1 establishing the pipe section-threshold mapping table comprises: respectively 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 by filling the corresponding liquid or air at different pipe diameters of the variable diameter pipe as the threshold interval of the corresponding pipe diameter section of the variable diameter pipe.

[0025] By using the above technical solution, accurate threshold intervals are obtained when the machine is initially started.

[0026] Optionally, in S3, the capacitance value detected by the corresponding pipe section of the variable diameter pipe is normalized in combination with the steady-state capacitance obtained by filling the corresponding liquid or air at different pipe diameters of the variable diameter pipe to obtain a capacitance normalized value, and if the capacitance normalized value of the corresponding pipe section of the variable diameter pipe is between 0-1, it indicates that the liquid level is at the corresponding pipe section of the variable diameter pipe.

[0027] By using the above technical solution, the specific pipe section position of the variable diameter pipe where the liquid level is located can be accurately judged.

[0028] Optionally, in S4, the capacitance normalized value of the corresponding pipe section of the variable diameter pipe where the liquid level is located is multiplied by the length of the corresponding pipe section of the variable diameter pipe, and then added to the length of the pipe section 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] By adopting the technical scheme, the liquid level height value is obtained.

[0030] Optionally, in S5, the capacitance fluctuation is a quotient of a standard deviation and an average value of all capacitance values collected by the inductor of the four-stage tube in 0.5s.

[0031] By adopting the technical scheme, the capacitance fluctuation is parameterized to accurately determine whether there is false foam passing through the four-stage tube.

[0032] Optionally, in S5, the echo intensity detected by the ultrasonic module is compared with the echo intensity in the empty tube state of the four-stage tube. If and the capacitance fluctuation exceeds the corresponding threshold value, the pump is stopped.

[0033] By adopting the technical scheme, the ultrasonic detection and the capacitance fluctuation are combined to accurately detect the foam, reduce false alarms, and timely and accurately alarm the foam.

[0034] In summary, the present application has at least the following beneficial effects:

[0035] 1. The small liquid level change is detected with high sensitivity to determine that the liquid level is effectively rising at the beginning of the infusion, rather than slowly decreasing, so as to better adjust the infusion speed, and the small capacitance change caused by the foam passing through the minimum tube diameter during the infusion process can also be detected, which helps to stop the pump in time and reduces the possibility of accidents;

[0036] 2. Better adapt to the fast liquid surface falling rate at the end of the infusion, and not easy to be affected by the slow liquid surface falling caused by some other factors during the infusion process to cause large-scale change of the capacitance, improve the anti-interference ability of detection, effectively reduce false alarms, and also improve the timeliness and accuracy of the infusion end signal. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 is a structural schematic diagram of a medical liquid level sensor;

[0038] Figure 2 is a flowchart of a liquid level detection method.

[0039] Marked with 1, infusion pipeline; 2, variable diameter pipe; 21, first-stage tube; 22, second-stage tube; 23, third-stage tube; 24, four-stage tube; 25, ultrasonic module; 3, inductor. DETAILED DESCRIPTION

[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 medical liquid level sensor, characterized in that: Includes a reducing pipe (2) that is fixedly connected to and connected to the infusion pipeline (1). The reducing pipe (2) has several sections with different diameters from top to bottom. The diameter of the reducing pipe (2) decreases from top to bottom. Each section of the reducing pipe (2) with a different diameter has a sensor (3) for detecting the liquid level.

2. The medical liquid level sensor according to claim 1, characterized in that: 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).

3. A medical liquid level sensor according to claim 2, characterized in that: 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.

4. A medical liquid level sensor according to claim 1, characterized in that: The bottom of the reducing pipe (2) is equipped with an ultrasonic module (25) for detecting whether foam passes through.

5. A liquid level detection method, using a medical liquid level sensor according to any one of claims 1-4, characterized in that: 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.

6. The liquid level detection method according to claim 5, 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).

7. The liquid level detection method according to claim 6, 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).

8. The liquid level detection method according to claim 7, 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.

9. The liquid level detection method according to claim 5, 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.

10. The liquid level detection method according to claim 5, characterized in that: In S5, the echo intensity detected by the ultrasonic module (25) is... Echo intensity of a quaternary tube (24) in an empty tube state If a comparison is made, If the capacitance fluctuation exceeds the corresponding threshold, the pump will be stopped.

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