Liquid level calibration system for cryogenic liquid nitrogen biological containers by pressure difference

Abstract

The present application discloses a liquid level calibration system for a low-temperature liquid nitrogen biological container by pressure difference, comprising a liquid nitrogen container, a nitrogen filling device, an initialization module, a pressure difference measurement module, a liquid level calculation module, a processing module, a communication interface and a display terminal; after the system is initialized, a fixed volume of nitrogen is filled into the liquid nitrogen container by the nitrogen filling device, and the pressure difference after the filling is measured and recorded; after each filling, the difference between the volume of the liquid nitrogen container and the pressure difference is calculated, and organized into a pressure difference change data set; based on the data set, the liquid level calculation module calculates the relationship between the actual volume and the liquid level height of the liquid nitrogen container; the processing module receives the liquid level height information and performs abnormal verification; the communication interface and the display terminal realize the visual display of the liquid level height information, including real-time curves, information sets and abnormal alarms; the system indirectly infers the liquid level change in the liquid nitrogen container by controlling the volume of nitrogen filled and monitoring the pressure difference change, thereby realizing non-contact liquid level calibration.

Description

Technical Field

[0001] The invention relates to the technical field of pressure difference liquid level calibration, and in particular to a liquid level calibration system for a low-temperature liquid nitrogen biological container through pressure difference. Background Art

[0002] In the field of cryogenic storage technology, especially in the liquid level monitoring and management of liquid nitrogen biological containers, the accuracy of the liquid level calibration system is crucial to ensure the safety and preservation quality of biological samples. At present, traditional liquid level measurement methods, such as contact capacitance level gauges, have many shortcomings. First, due to the extremely low temperature of liquid nitrogen (-196°C), traditional sensors can hardly withstand such a harsh environment, resulting in easy damage to the equipment and high maintenance costs. Secondly, the measurement accuracy of the capacitance level gauge at low temperatures is limited, the error is large, the liquid level resolution is poor, and the range is fixed and cannot be adjusted according to actual needs. In addition, traditional liquid level gauges usually need to be built into liquid nitrogen containers, which not only increases the difficulty of installation, but may also cause internal electronic equipment to short-circuit or be damaged by lightning, thereby affecting the stability and reliability of the entire system.

[0003] For example, the Chinese patent application number CN202410625606.8, a liquid nitrogen level height isolation detection system and detection method based on differential pressure calculation, by simulating and calculating the pressure height difference between the liquid bottom and the liquid surface of the liquid nitrogen tank, the pressure difference signal between the return air pipe 3 and the gas measuring pipe is obtained, and the pressure height difference between the liquid bottom and the liquid surface of the liquid nitrogen tank is calculated based on the pressure formula, so as to obtain the height position of the liquid nitrogen in the liquid nitrogen tank and perform liquid replenishment control. The pressure difference measurement system completely isolates the outside of the liquid nitrogen tank, eliminates the extremely harsh environment inside the tank, and ensures the long-term stable operation of the measuring equipment; the high-precision pressure difference measurement unit can accurately measure the liquid nitrogen height to within 1 mm, with high accuracy; just insert the gas measuring pipe into the lowest position of the liquid level, and the corresponding range of detection can be automatically matched, without adding any circuit, and the range is adjustable; it is suitable for any sealed or non-sealed tank or even tank-less liquid level measurement, avoiding short circuit of internal electronic equipment and lightning strike.

[0004] Although this method has made significant progress in accuracy, stability and adaptability, there is still room for further improvement. For example, the existing differential pressure measurement process relies on manual judgment of the time from the start of the air pump to the bubbling at the bottom of the gas tube, which may cause measurement errors due to human factors. In addition, real-time monitoring of the pressure changes inside the liquid nitrogen container and calibration of the liquid level are also key to improving system performance. Summary of the invention

[0005] The present application provides a liquid level calibration system for a low-temperature liquid nitrogen biological container through a pressure difference. The system uses the pressure difference and temperature change to accurately measure and calibrate the liquid level, effectively overcoming the influence of the low-temperature environment on the measuring equipment, significantly improving the accuracy and stability of the liquid level measurement, realizing the intelligent management of the liquid level calibration, greatly reducing the need for manual intervention, thereby improving the overall operating efficiency, and aims to solve the problems existing in the prior art.

[0006] The present application provides a liquid level calibration system for a low-temperature liquid nitrogen biological container by pressure difference, comprising: a liquid nitrogen container, a nitrogen filling device, an initialization module, a pressure difference measurement module, a liquid level calculation module, and a processing module;

[0007] S101, the initialization module is used to initialize the entire system state and complete the establishment of the communication connection;

[0008] S102, the pressure difference measurement module is used to fill a fixed volume of nitrogen gas Vi into the liquid nitrogen container, and measure and record the pressure difference Pi after the filling, including:

[0009] S201, start the nitrogen filling device, and use the volume metering device to fill a fixed volume Vi of nitrogen into the liquid nitrogen container;

[0010] S202, each time nitrogen is filled, record the pressure difference Pi in the liquid nitrogen container after filling;

[0011] S203, calculating the difference ΔPi between the volume ΔVi of the liquid nitrogen container and the pressure difference before and after each filling;

[0012] S204, matching the fixed volume Vi of each inflation, the total volume △Vi of the liquid nitrogen container after inflation, the pressure difference Pi after inflation, and the difference △Pi of the pressure difference to generate pressure difference change data, and organizing the pressure difference change data generated multiple times into a pressure difference change data set;

[0013] S103, based on the pressure difference change data set obtained by the pressure difference measurement module, obtain the relationship between the actual volume of the liquid nitrogen container and the liquid level height, and generate liquid level height information;

[0014] S104, the processing module is used to receive the liquid level height information calculated by the liquid level calculation module and perform abnormality verification on the liquid level height information.

[0015] Preferably, the S203 includes:

[0016] Calculate the volume of the liquid nitrogen container ΔVi=V0+i*Vi, where ΔVi represents the total volume of the liquid nitrogen container after the i-th filling;

[0017] The difference in air pressure difference before and after each inflation ΔPi=Pi-P(i-1) represents the difference in air pressure difference between the i-th inflation and the i-1-th inflation. For the first inflation, P(i-1) is the initial air pressure difference P0; wherein, the initial air pressure P0 and the nitrogen volume V0 are the reference values ​​recorded after the liquid nitrogen container and the liquid nitrogen container are in a stable temperature and pressure state.

[0018] Preferably, S103 comprises: for each inflation, according to Boyle's law that the pressure of the gas under isothermal conditions is inversely proportional to the volume, the equation is written: P0V0=Pi(V0+ΔVi), wherein ΔVi represents the volume increment of the gaseous nitrogen above the liquid nitrogen after the i-th inflation; through algebraic transformation, ΔVn=(P0V0 / Pi)-V0 is solved, and ΔVn represents the increase in the volume of the gaseous nitrogen caused by the inflation operation; if multiple inflation operations are performed, the volume increment ΔVn after each inflation needs to be accumulated to obtain the total volume change Vx: Vx=ΣΔVn; and the total volume Vx is converted into a specific liquid level height of the liquid nitrogen in combination with the geometric dimensions of the liquid nitrogen container.

[0019] Preferably, the pressure difference measurement module in step S102 is also used for:

[0020] S301, start the nitrogen filling device, fill the low-temperature liquid nitrogen biological container with an initial volume of nitrogen V_initial, record the air pressure values ​​before and after the filling, and calculate the air pressure difference ΔP_1;

[0021] S302, recording and plotting the pressure change points after the first nitrogen filling;

[0022] S303, continuously filling different volumes of nitrogen gas V_i into the container, recording the air pressure value after each filling of nitrogen gas, and calculating the air pressure difference ΔP_i;

[0023] S304, plotting the pressure change points after each nitrogen filling on a graph and connecting them into a line graph;

[0024] S305, for each pressure difference ΔP_i before and after nitrogen filling and the volume of nitrogen filled V_i, calculate the slope k_i=ΔP_i / V_i, compare the difference between adjacent slopes |k_i-k_(i-1)|, and determine whether it is within the set threshold range;

[0025] S306, for each nitrogen filling, calculate the nitrogen filling volume ratio w_i=V_i / V_total, where V_total is the total nitrogen filling volume, use the nitrogen filling volume ratio as a weight, and calculate the weighted pressure difference ΔP_weighted=Σ(w_i*ΔP_i).

[0026] Preferably, the S302 includes: recording the air pressure value after the first filling of nitrogen on a data recording table, marking the air pressure change point after the initial filling on a chart, with the horizontal axis representing the filling volume and the vertical axis representing the air pressure difference.

[0027] Preferably, the S305, judging whether it is within a set threshold range, comprises: for each time of nitrogen filling, calculating the slope k_i=ΔP_i / V_i, recording each slope value in a data recording table, calculating the difference between adjacent slopes, i.e. |k_i-k_(i-1)|, comparing the difference with a set threshold, and judging whether the difference is within the threshold range; if the difference exceeds the threshold, it means that the air pressure in the liquid nitrogen container is abnormal, the pressure difference data calculation is inaccurate, and the filling of nitrogen into the liquid nitrogen container is stopped.

[0028] Preferably, the S306 includes: for each inflation, recording the volume of nitrogen charged V_i, calculating the total inflation volume V_total, that is, the sum of all inflation volumes V_total=ΣV_i, and calculating the intake volume ratio w_i of each inflation according to the formula of intake volume ratio w_i=V_i / V_total; for each inflation, recording the air pressure difference ΔP_i before and after inflation, using the intake volume ratio w_i as a weight, weighting the air pressure difference of each inflation, and calculating the weighted air pressure difference of all inflation processes according to the formula of weighted air pressure difference ΔP_weighted=Σ(w_i*ΔP_i).

[0029] Preferably, the pressure difference measurement module calculates the liquid level by measuring the pressure difference measurement module in the liquid nitrogen container and the pressure difference measurement module at the mouth of the V-tube, and performs liquid level calibration in the processing module, wherein the V-tube comprises: the V-tube is built in the liquid nitrogen container, the right mouth of the tube extends outside the tank, and an internal thread ball joint rotary switch is provided above the mouth of the tube to control the up and down movement of the V-tube; an inflation valve plug is provided below, and when filling nitrogen, the V-tube is moved up by rotating the ball joint rotary switch, and the lower mouth of the tube is separated from the inflation valve plug, allowing nitrogen to enter the liquid nitrogen container; after the inflation is completed, the ball joint rotary switch is rotated in the opposite direction to move the V-tube down, and the lower mouth of the tube is re-embedded in the inflation valve plug to prevent the nitrogen from continuing to be filled; a conductive connection device is installed at the left mouth of the tube, and the heights of the tubes on the left and right sides are different, and the right V-tube is higher than the left side.

[0030] Preferably, the pressure difference measurement module calculates the liquid level by measuring the pressure difference measurement module in the liquid nitrogen container and the pressure difference measurement module at the mouth of the V-shaped tube, and performs liquid level calibration in the processing module. The specific steps include:

[0031] S401, turn on the internal thread ball joint rotary switch on the V-tube to start filling with nitrogen;

[0032] S402, after each nitrogen filling, turn the internal thread ball joint rotary switch to connect and embed the V-shaped tube with the charging valve plug;

[0033] S403, measuring and calculating the pressure difference and liquid level in the liquid nitrogen container and the pressure difference at the opening of the V-shaped tube and the liquid level of the V-shaped tube;

[0034] S404, calibrating the liquid level height in the liquid nitrogen container measured by the liquid level height of the V-shaped tube.

[0035] Preferably, during the process of flushing nitrogen, the conductive connection device senses and records the amount of nitrogen flushed in real time, and measures and calibrates the liquid level. The specific steps include:

[0036] S501, when the nitrogen liquid level contacts the conductive connection device, the conductive connection device senses the height of the liquid level contact and converts it into a digital signal for recording;

[0037] S502, obtaining the current liquid level according to the output signal of the conductive connection device;

[0038] S503, comparing the liquid level in the nitrogen tank with the liquid level obtained by the left conductive connection device to perform liquid level calibration.

[0039] One or more technical solutions provided in this application have at least the following technical effects or advantages:

[0040] By precisely controlling the amount of nitrogen gas charged and monitoring the change in the pressure difference, non-contact calibration of the liquid level in the liquid nitrogen container is achieved. This method avoids the freezing and clogging problems that may occur in traditional liquid level gauges in low-temperature environments, and improves the accuracy and reliability of liquid level measurement. At the same time, since there is no need to directly contact liquid nitrogen, it also reduces operational risks and maintenance costs.

[0041] By recording and calculating the pressure difference before and after each nitrogen filling, real-time and accurate monitoring of the pressure changes in the liquid nitrogen container is achieved, thereby improving safety. The drawn line graph of pressure changes intuitively shows the relationship between air pressure and nitrogen filling volume, which is convenient for subsequent analysis. At the same time, calculating the slope and comparing its difference can effectively judge the stability of air pressure, and detect and deal with abnormalities in time. More importantly, using the nitrogen filling volume ratio as the weight to calculate the weighted pressure difference more scientifically reflects the impact of each filling, and provides a strong basis for evaluating the performance of liquid nitrogen containers and optimizing nitrogen filling strategies. At the same time, this also provides more accurate and reliable measurement data for subsequent liquid level calibration and biological sample preservation.

[0042] By adopting a V-tube structure and equipping it with an internal thread ball joint rotary switch to control the filling of nitrogen, accurate calibration of the liquid level in the liquid nitrogen container is achieved. This solution not only ensures the sealing during the nitrogen filling process and effectively prevents nitrogen leakage, but also measures the pressure difference between the liquid nitrogen container and the V-tube mouth, and calculates the nitrogen volume and liquid level in the V-tube in combination with Boyle's law, and then uses the same relationship between the V-tube liquid level and the liquid nitrogen container liquid level to accurately calibrate the theoretical liquid level in the liquid nitrogen container.

[0043] The amount of nitrogen gas introduced is sensed and recorded in real time through the conductive connection device, and the liquid level is sensed and converted into a digital signal for recording when the nitrogen liquid level contacts the device, thus achieving accurate measurement of the liquid level. At the same time, the scheme compares the liquid level obtained by the conductive connection device with the liquid level calculated by the pressure difference at the right pipe mouth. The two should be equal within the threshold range, so as to perform liquid level calibration. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 This is a schematic diagram of the structure of a system for realizing liquid level calibration of a low-temperature liquid nitrogen biological container through pressure difference according to an embodiment of the present invention;

[0045] Figure 2 This is a schematic structural diagram of a system for realizing liquid level calibration of a low-temperature liquid nitrogen biological container through pressure difference according to another embodiment of the present invention;

[0046] Figure 3 It is a schematic diagram of the interior side of the liquid nitrogen container of the present invention when it is inflated. DETAILED DESCRIPTION

[0047] To facilitate the understanding of the present invention, the present application will be described more comprehensively below with reference to the relevant drawings; the drawings show preferred embodiments of the present invention, but the present invention can be implemented in many different forms and is not limited to the embodiments described herein; on the contrary, the purpose of providing these embodiments is to enable a more thorough and comprehensive understanding of the disclosed content of the present invention.

[0048] It should be noted that the terms “vertical”, “horizontal”, “up”, “down”, “left”, “right” and similar expressions used in this document are only for illustrative purposes and do not represent the only implementation method.

[0049] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which the present invention belongs; the terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention; the term "and / or" used herein includes any and all combinations of one or more related listed items. Embodiment 1

[0050] like Figure 1 As shown, the liquid level calibration system for a low-temperature liquid nitrogen biological container by pressure difference includes: a liquid nitrogen container, a nitrogen filling device, an initialization module, a pressure difference measurement module, a liquid level calculation module, a processing module, a communication interface and a display terminal.

[0051] In some embodiments, the liquid level calibration system of a cryogenic liquid nitrogen biological container by pressure difference of the embodiment of the present invention is specifically used to perform the following steps:

[0052] S101, the initialization module is used to initialize the entire system state and complete the establishment of the communication connection.

[0053] Specifically, make sure that the liquid nitrogen container, nitrogen filling device, initialization module, pressure difference measurement module, liquid level calculation module, processing module, communication interface and display terminal components are installed correctly and connected firmly. At this time, turn on the system power supply to put all devices in standby state, and establish a communication connection between the processing module and the display terminal to ensure smooth data transmission; close all valves of the liquid nitrogen container except the filling valve, ensure that the liquid nitrogen container and the liquid nitrogen container are in a stable temperature and pressure state, and then record the initial air pressure P0 and nitrogen volume V0 as the reference value. In this article, the liquid nitrogen container is called the liquid nitrogen biological container.

[0054] S102, the pressure difference measurement module is used to fill a fixed volume of nitrogen gas Vi into the liquid nitrogen container, and measure and record the pressure difference Pi after the filling.

[0055] In some embodiments, step S102 specifically includes the following contents:

[0056] S201, start the nitrogen filling device, and use the volume metering device to fill a fixed volume Vi of nitrogen into the liquid nitrogen container.

[0057] Among them, when performing differential pressure measurement at a certain stage, the volume of nitrogen filled is fixed at that stage. If you need to modify the volume of nitrogen filled at this stage, you must stop the filling operation at the current stage. To ensure the accuracy of the measurement, different filling volumes can be set at different stages. For example, when performing differential pressure measurement in the first stage, if you choose to fill 1 liter, then starting from the minimum storage capacity of the liquid nitrogen container, you can only increase the filling by 1 liter each time until the maximum storage capacity of the liquid nitrogen container is reached. If the remaining capacity of the liquid nitrogen container is less than 1 liter at the last filling, the filling should be stopped.

[0058] S202, each time nitrogen is charged, the pressure difference Pi in the liquid nitrogen container after charging is recorded.

[0059] Specifically, 1 liter of nitrogen is charged into the liquid nitrogen container for the first time. After the charging is completed, the charging valve is immediately closed, and the newly charged nitrogen is allowed to fully mix with the original nitrogen in the tank to reach a state of equilibrium. At this time, the air pressure difference in the liquid nitrogen container is measured and recorded as P1; 1 liter of nitrogen is also charged into the liquid nitrogen container for the second time. After the charging is completed, the charging valve is immediately closed, and the newly charged nitrogen is allowed to fully mix with the original nitrogen in the tank to reach a state of equilibrium. At this time, the air pressure difference in the liquid nitrogen container is measured and recorded as P2; and so on to record the air pressure difference value.

[0060] Among them, the judgment standard for waiting for the newly charged nitrogen to be fully mixed with the original nitrogen in the tank to reach a balanced state is that when the fluctuation of the pressure difference within a period of time is less than a certain threshold, it can be considered that the nitrogen has been fully mixed and reached a stable state. The threshold setting of the equilibrium state judgment standard should be based on experimental data or experience to ensure that a stable state can be achieved in most cases. In this embodiment, when the pressure difference fluctuates less than 0.01 kPa within 5 consecutive minutes, it is considered that the nitrogen in the liquid nitrogen container has been fully mixed and reached a stable state.

[0061] S203, calculating the volume ΔVi of the liquid nitrogen container and the difference ΔPi between the pressure difference before and after each filling.

[0062] Among them, ΔVi=V0+i*Vi, ΔVi represents the total volume of the liquid nitrogen container after the i-th filling;

[0063] ΔPi=Pi-P(i-1), which represents the difference in air pressure between the i-th inflation and the i-1-th inflation (for the first inflation, P(i-1) is the initial air pressure difference P0).

[0064] S204, the fixed volume Vi of each inflation, the total volume ΔVi of the liquid nitrogen container after inflation, the pressure difference Pi after inflation, and the difference ΔPi of the pressure difference are matched to generate pressure difference change data, and the pressure difference change data generated multiple times are organized into a pressure difference change data set.

[0065] The data set is presented in the form of a table or array. The data set will be used for subsequent analysis and processing to calibrate the liquid level calibration system of the liquid nitrogen container and improve the accuracy and reliability of measurement and calibration. By controlling the volume of nitrogen filled and monitoring the change in the pressure difference, the compressibility change of nitrogen at low temperature can be reduced, and the liquid level change in the liquid nitrogen container can be indirectly inferred, thereby realizing non-contact liquid level calibration; this data set is used as a basic data set, and the pressure difference can be compared with this data set when nitrogen is filled in the future.

[0066] S103, based on the pressure difference change data set obtained by the pressure difference measurement module, obtain the relationship between the actual volume of the liquid nitrogen container and the liquid level height, and generate liquid level height information.

[0067] Specifically, for each inflation, according to Boyle's law, the pressure of the gas under isothermal conditions is inversely proportional to the volume. Therefore, for the situation before and after inflation, the equation can be written as: P0V0=Pi(V0+ΔVi), where ΔVi represents the volume increment of gaseous nitrogen above the liquid nitrogen after the i-th inflation;

[0068] Through algebraic transformation, ΔVn is solved: ΔVn=(P0V0 / Pi)-V0. This ΔVn represents the increase in the volume of gaseous nitrogen caused by the inflation operation. If multiple inflation operations are performed, the volume increment ΔVn after each inflation needs to be accumulated to obtain the total volume change Vx: Vx=ΣΔVn.

[0069] Combined with the geometric dimensions of the liquid nitrogen container, the total volume Vx is converted into a specific liquid level height of liquid nitrogen.

[0070] S104, the processing module is used to receive the liquid level height information calculated by the liquid level calculation module and perform abnormality verification on the liquid level height information.

[0071] Among them, the data anomaly detection and analysis are based on the normal fluctuation range of the liquid level height, the pressure difference change data set of step S204, and the liquid level height under the geometric dimensions of the liquid nitrogen container in step S103. The liquid level height information set is obtained by combining and associating, and the normal fluctuation range is obtained. The anomaly detection threshold is set according to the normal fluctuation range, and the liquid level height anomaly detection is performed to give a comparative verification result (liquid level height abnormal, liquid level height normal).

[0072] S105, the communication interface and the display terminal are used to enable the processing module to visualize the liquid level information through the display terminal.

[0073] Among them, the visual display includes the real-time curve of liquid level height, liquid level height information set, and abnormal alarm prompts.

[0074] For example, in a biological laboratory, there is a low-temperature liquid nitrogen biological container for storing liquid nitrogen and biological samples. In order to accurately calibrate the liquid level of the container, a system that realizes liquid level calibration through pressure difference is now used:

[0075] After checking all devices to ensure that the connection is correct, turn on the system power supply to enable the processing module to successfully establish a communication connection with the display terminal. Next, close all valves on the liquid nitrogen container except the inflation valve to ensure the sealing of the system. After confirming that both the liquid nitrogen container and the liquid nitrogen container have reached a stable state of temperature and pressure, record the initial air pressure P0 = 100kPa and the initial volume V0 = 50L of the liquid nitrogen container;

[0076] Start the nitrogen filling device, and use the volumetric metering device to fill 1L of nitrogen (Vi=1L) into the liquid nitrogen container. After the filling is completed, close the filling valve immediately and wait for the air pressure to stabilize. When the pressure difference fluctuates less than 0.01kPa for 5 consecutive minutes, record the pressure difference P1=101kPa; repeat the above steps, filling 1L of nitrogen each time, and record the pressure difference P2, P3,..., Pn after each filling. Calculate the total volume ΔVi of the liquid nitrogen container and the pressure difference ΔPi after each filling. For example, after the first filling, ΔV1=V0+1×Vi=51L, ΔP1=P1-P0=1kPa. Organize into a pressure difference change data set, the table contains the number of fillings, the filling volume Vi, the total volume ΔVi, the pressure difference Pi, and the pressure difference ΔPi;

[0077] Assume that the liquid nitrogen container is a cylinder with a bottom radius of r = 0.25 m (25 cm). After multiple inflations and calculations, the total volume change Vx = 0.02 m3 and the liquid level height H = ≈1.02 m (102 cm);

[0078] According to the pressure difference variation data set and the geometric dimensions of the liquid nitrogen container, it can be obtained that the normal fluctuation range of the liquid level height in the cylindrical liquid nitrogen container is ±5%, that is, the normal fluctuation range is between 95 cm and 105 cm; the calculated liquid level height of 102 cm is compared with the normal fluctuation range. Since 102 cm is within the normal fluctuation range (95 cm to 105 cm), the liquid level calibration is considered normal; if the calculated liquid level height exceeds the normal fluctuation range, such as 110 cm, the system will immediately issue an abnormal alarm to prompt the operator to check the liquid nitrogen container and the calibration system;

[0079] The display terminal can display the liquid level information after each inflation in real time, as well as the comparison between the current liquid level and the normal fluctuation range.

[0080] It should be noted that the liquid level height information set in step S104 needs to enumerate Vi, Pi, and the geometric dimensions of the liquid nitrogen container multiple times to obtain the normal floating range of the liquid level height.

[0081] The technical solutions in the above embodiments of the present application have at least the following technical effects or advantages:

[0082] The system achieves non-contact calibration of the liquid level in the liquid nitrogen container by precisely controlling the amount of nitrogen charged and monitoring the change in the pressure difference. This method avoids the freezing and clogging problems that may occur in traditional liquid level gauges in low-temperature environments, and improves the accuracy and reliability of liquid level measurement. At the same time, since there is no need to directly contact liquid nitrogen, it also reduces operational risks and maintenance costs. Embodiment 2

[0083] In Example 1, a fixed volume of nitrogen is filled into the liquid nitrogen container using a volumetric metering device, and no filling method is provided for increasing the filling frequency or single filling volume to maintain a suitable low-temperature environment when the number of samples in the low-temperature liquid nitrogen biological container increases and the consumption of liquid nitrogen accelerates.

[0084] Therefore, the embodiments of the present application are optimized to a certain extent based on the above embodiments.

[0085] In some embodiments, the pressure difference measuring module in step S102 is further used for:

[0086] S301, start the nitrogen filling device, fill the low-temperature liquid nitrogen biological container with an initial volume of nitrogen V_initial, record the air pressure values ​​before and after the filling, and calculate the air pressure difference ΔP_1.

[0087] Among them, the pressure difference before and after inflation is calculated, that is, ΔP_1=P_after_initial-P0.

[0088] S302, recording and plotting the pressure change points after the first nitrogen filling.

[0089] Among them, the air pressure value after the first filling of nitrogen is recorded on the data recording table, and the air pressure change point after the initial inflation is marked on the chart. The horizontal axis represents the inflation volume (V_initial at this time), and the vertical axis represents the air pressure difference (ΔP_1 at this time).

[0090] S303, continuously filling different volumes of nitrogen gas V_i into the container, recording the air pressure value after each filling of nitrogen gas, and calculating the air pressure difference ΔP_i.

[0091] Specifically, for each nitrogen filling, the steps in S301 are repeated, but the volume of nitrogen filled is V_i (i=2,3,...,n). After each nitrogen filling, the air pressure value after nitrogen filling is recorded, and the air pressure difference with the previous nitrogen filling is calculated, that is, ΔP_i=P_after_i-P_before_i (for nitrogen filling after the first time, the initial air pressure difference P0=P_before_i).

[0092] S304, plotting the pressure change points after each nitrogen filling on a graph and connecting them into a line graph.

[0093] Specifically, with the volume of nitrogen filled as the horizontal axis and the air pressure difference as the vertical axis, a line graph of the air pressure change after each push of different volumes of nitrogen is drawn.

[0094] S305, for the pressure difference ΔP_i before and after each nitrogen filling and the nitrogen filling volume V_i, calculate the slope k_i=ΔP_i / V_i, compare the difference between adjacent slopes |k_i-k_(i-1)|, and determine whether it is within the set threshold range.

[0095] Specifically, for each time nitrogen is charged, the slope k_i=ΔP_i / V_i is calculated, each slope value is recorded on the data recording table, the difference between adjacent slopes is calculated, i.e. |k_i-k_(i-1)|, the difference is compared with the set threshold, and it is determined whether the difference is within the threshold range (for example, if the threshold is set to 0.05, the difference is less than 0.05 and the slope is considered to be similar). If the difference exceeds the threshold, it means that the air pressure in the liquid nitrogen container is abnormal, the pressure difference data calculation is inaccurate, and the filling of nitrogen into the liquid nitrogen container is stopped. The specific threshold limit can be set after multiple experiments according to the actual situation.

[0096] S306, for each nitrogen filling, calculate the nitrogen filling volume ratio w_i=V_i / V_total, where V_total is the total nitrogen filling volume, use the nitrogen filling volume ratio as a weight, and calculate the weighted pressure difference ΔP_weighted=Σ(w_i*ΔP_i).

[0097] Specifically, for each inflation, record the volume of nitrogen charged, V_i, and calculate the total inflation volume V_total, which is the sum of all inflation volumes: V_total=ΣV_i. According to the intake volume ratio formula w_i=V_i / V_total, calculate the intake volume ratio w_i for each inflation; by calculating the intake volume ratio, quantify the contribution of each inflation to the total inflation volume.

[0098] For each inflation, the pressure difference ΔP_i before and after inflation is recorded, and the intake volume ratio w_i is used as the weight to weight the pressure difference of each inflation. According to the formula of weighted pressure difference ΔP_weighted=Σ(w_i*ΔP_i), the weighted pressure difference of all inflation processes is calculated.

[0099] It should be noted that by calculating the weighted pressure difference, the effect of nitrogen volume change on the pressure difference can be more accurately reflected. Since the volume of each inflation may be different, its effect on the pressure difference may also be different. Through weighted processing, the effect of each inflation can be comprehensively considered to improve the accuracy and reliability of the pressure difference calculation. The technical solution in the above embodiment of the present application has at least the following technical effects or advantages:

[0100] By recording and calculating the pressure difference before and after each nitrogen filling, real-time and accurate monitoring of the pressure changes in the liquid nitrogen container is achieved, thereby improving safety. The drawn line graph of pressure changes intuitively shows the relationship between air pressure and nitrogen filling volume, which is convenient for subsequent analysis. At the same time, calculating the slope and comparing its difference can effectively judge the stability of air pressure, and detect and deal with abnormalities in time. More importantly, using the nitrogen filling volume ratio as the weight to calculate the weighted pressure difference more scientifically reflects the impact of each filling, and provides a strong basis for evaluating the performance of liquid nitrogen containers and optimizing nitrogen filling strategies. At the same time, this also provides more accurate and reliable measurement data for subsequent liquid level calibration and biological sample preservation. Embodiment 3

[0101] For low-temperature liquid nitrogen biological containers, the liquid nitrogen level is crucial for the preservation of biological samples, because too low a liquid level may cause the sample to be exposed to gaseous nitrogen, affecting the preservation effect. In the above embodiment, the processing module associates the pressure difference change data set obtained by the liquid level calculation module and the pressure difference module to obtain a liquid level height information set, and uses the normal range of liquid level fluctuations to perform abnormal detection of liquid level height. This will lead to inaccurate calculation of liquid level height due to the instability of nitrogen and temperature, and the calibration method and results are unscientific and inaccurate.

[0102] Therefore, this embodiment is further optimized based on the above embodiment.

[0103] In some embodiments, the liquid nitrogen container is equipped with a V-shaped tube (the V-shaped tube is built into the liquid nitrogen container) for filling nitrogen. The right side of the V-shaped tube extends outside the tank, and an internal threaded ball-jointed rotary switch is provided above the tube mouth to control the up and down movement of the V-shaped tube. An inflation valve plug is provided below the V-shaped tube. When filling nitrogen, the V-shaped tube is moved up by rotating the ball-jointed rotary switch, and the lower tube mouth is separated from the inflation valve plug, allowing nitrogen to enter the liquid nitrogen container. After the inflation is completed, the ball-jointed rotary switch is rotated in the opposite direction to move the V-shaped tube down, and the lower tube mouth is re-embedded in the inflation valve plug, thereby preventing the continued filling of nitrogen. Among them, the heights of the tubes on the left and right sides are different, and the V-shaped tube on the right is higher than the left.

[0104] In some embodiments, Figure 2 As shown, the pressure difference measurement module calculates the liquid level by measuring the pressure difference measurement module in the liquid nitrogen container and the pressure difference measurement module at the outlet of the V-shaped tube, and performs liquid level calibration in the processing module, which specifically includes:

[0105] S401, turn on the internal thread ball joint rotary switch on the V-tube to start flushing nitrogen.

[0106] Among them, before flushing in nitrogen, ensure that the liquid nitrogen container and its V-shaped tube are in normal working condition, the internal threaded ball joint rotary switch and the inflation valve plug of the V-shaped tube are connected normally, and the inflation valve plug is embedded and sealed with the lower tube opening of the V-shaped tube without any leakage.

[0107] S402, each time after nitrogen is charged, the internal thread ball joint rotary switch is turned to connect and embed the V-shaped tube with the charging valve plug.

[0108] S403, measuring and calculating the pressure difference and liquid level in the liquid nitrogen container and the pressure difference at the opening of the V-shaped tube and the liquid level of the V-shaped tube.

[0109] Among them, after the inflation is completed, nitrogen of a certain pressure will remain in the V-shaped tube, so the pressure difference at the mouth of the V-shaped tube and the liquid level height of the V-shaped tube can be calculated. The pressure difference ΔP_iG and the liquid level height calculation method in the liquid nitrogen container are steps S102 to S103;

[0110] In some embodiments, the pressure difference at the orifice of the V-shaped tube and the liquid level height of the V-shaped tube are measured and calculated. Specifically:

[0111] Measure and record the pressure difference ΔP_ig at the V-tube orifice after nitrogen is flushed in each time;

[0112] Use Boyle's law to perform algebraic transformation to calculate the volume of nitrogen in the V-tube;

[0113] The liquid level height in the tube is calculated based on the geometric volume of the V-tube.

[0114] S404, calibrating the liquid level height in the liquid nitrogen container measured by the liquid level height of the V-shaped tube.

[0115] Among them, the theoretical height of the liquid level in the V-tube is the same as the liquid level in the liquid nitrogen container. The V-tube is used as a calibration tool to compare the liquid level heights. If the two heights are consistent, it means that the liquid level height is normal. If the two are inconsistent, the liquid level height in the liquid nitrogen container is remeasured and calculated.

[0116] The technical solutions in the above embodiments of the present application have at least the following technical effects or advantages:

[0117] By adopting a V-tube structure and equipping it with an internal thread ball joint rotary switch to control the filling of nitrogen, accurate calibration of the liquid level in the liquid nitrogen container is achieved. This solution not only ensures the sealing during the nitrogen filling process and effectively prevents nitrogen leakage, but also measures the pressure difference between the liquid nitrogen container and the V-tube mouth, and calculates the nitrogen volume and liquid level in the V-tube in combination with Boyle's law, and then uses the same relationship between the V-tube liquid level and the liquid nitrogen container liquid level to accurately calibrate the theoretical liquid level in the liquid nitrogen container. Embodiment 4

[0118] In the third embodiment, the liquid level height of the liquid nitrogen container is calibrated theoretically using the liquid level height of the V-tube. However, in practical applications, there may be some errors in the pressure difference calculation or the liquid level calculation. In this regard, this embodiment is optimized on the basis of the third embodiment.

[0119] like Figure 3 As shown, the liquid nitrogen container is equipped with a V-shaped tube for filling nitrogen, and a conductive connection device (sensor) is installed at the left pipe opening of the V-shaped tube.

[0120] During the process of flushing nitrogen, the conductive connection device senses and records the amount of nitrogen flushed in real time.

[0121] And measure and calibrate the liquid level. The specific steps include:

[0122] S501, when the nitrogen liquid level contacts the conductive connection device, the conductive connection device senses the height of the liquid level contact and converts it into a digital signal for recording.

[0123] S502, obtaining the current liquid level height according to the output signal of the conductive connection device.

[0124] Among them, the liquid level height obtained by the conductive connection device on the left is equal to the liquid level height calculated by the pressure difference of the pipe mouth on the right.

[0125] There is a threshold gap between the two, which can be obtained through experiments.

[0126] S503, comparing the liquid level in the nitrogen tank with the liquid level obtained by the left conductive connection device to perform liquid level calibration.

[0127] If the two heights are consistent, it means that the liquid level measurement is accurate and no calibration is required. If the two heights are inconsistent, the liquid level height in the nitrogen tank is re-measured and calculated based on the measurement results of the conductive connection device.

[0128] The technical solutions in the above embodiments of the present application have at least the following technical effects or advantages:

[0129] The amount of nitrogen charged is sensed and recorded in real time through the conductive connection device, and the liquid level is sensed and converted into a digital signal for recording when the nitrogen liquid level contacts the device, thus achieving accurate measurement of the liquid level. At the same time, the scheme compares the liquid level obtained by the conductive connection device with the liquid level calculated by the pressure difference at the right nozzle. The two should be equal within the threshold range, so as to perform liquid level calibration.

[0130] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, 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 liquid level calibration system for a cryogenic liquid nitrogen biological container is realized by pressure difference, characterized in that: include: Liquid nitrogen container, nitrogen filling device, initialization module, pressure difference measurement module, liquid level calculation module, processing module; S101, the initialization module is used to initialize the entire system state and complete the establishment of the communication connection; S102, the pressure difference measurement module is used to fill a fixed volume of nitrogen gas Vi into the liquid nitrogen container, and measure and record the pressure difference Pi after the filling, including: S201, start the nitrogen filling device, and use the volume metering device to fill a fixed volume Vi of nitrogen into the liquid nitrogen container; S202, each time nitrogen is filled, record the pressure difference Pi in the liquid nitrogen container after filling; S203, calculating the difference ΔPi between the volume ΔVi of the liquid nitrogen container and the pressure difference before and after each filling; S204, matching the fixed volume Vi of each inflation, the total volume △Vi of the liquid nitrogen container after inflation, the pressure difference Pi after inflation, and the difference △Pi of the pressure difference to generate pressure difference change data, and organizing the pressure difference change data generated multiple times into a pressure difference change data set; S103, the liquid level calculation module is used to obtain the relationship between the actual volume of the liquid nitrogen container and the liquid level height based on the pressure difference change data set obtained by the pressure difference measurement module, and generate liquid level height information; S104, the processing module is used to receive the liquid level height information calculated by the liquid level calculation module and perform abnormality verification on the liquid level height information.

2. The liquid level calibration system for low-temperature liquid nitrogen biological container by pressure difference according to claim 1, characterized in that: The S203 includes: calculating the volume of the liquid nitrogen container ΔVi=V0+i*Vi, ΔVi represents the total volume of the liquid nitrogen container after the i-th inflation; the difference of the air pressure difference before and after each inflation ΔPi=Pi-P(i-1), represents the difference of the air pressure difference after the i-th inflation and after the i-1-th inflation, for the first inflation, P(i-1) is the initial air pressure difference P0; wherein the initial air pressure P0 and the nitrogen volume V0 are reference values ​​recorded after the liquid nitrogen container and the liquid nitrogen container are in a stable temperature and pressure state.

3. The liquid level calibration system for low-temperature liquid nitrogen biological container by pressure difference according to claim 1, characterized in that: The S103 includes: for each inflation, according to Boyle's law that the pressure of the gas under isothermal conditions is inversely proportional to the volume, the equation is written: P0V0=Pi(V0+ΔVi), where ΔVi represents the volume increment of the gaseous nitrogen above the liquid nitrogen after the i-th inflation; through algebraic transformation, ΔVn=(P0V0 / Pi)-V0 is solved, and ΔVn represents the increase in the volume of the gaseous nitrogen caused by the inflation operation; if multiple inflation operations are performed, the volume increment ΔVn after each inflation needs to be accumulated to obtain the total volume change Vx: Vx=ΣΔVn; combined with the geometric dimensions of the liquid nitrogen container, the total volume Vx is converted into a specific liquid level height of the liquid nitrogen.

4. The liquid level calibration system for low-temperature liquid nitrogen biological container by pressure difference according to claim 1, characterized in that: The S102 differential pressure measurement module is also used for: S301, start the nitrogen filling device, fill the low-temperature liquid nitrogen biological container with an initial volume of nitrogen V_initial, record the air pressure values ​​before and after the filling, and calculate the air pressure difference ΔP_1; S302, recording and plotting the pressure change points after the first nitrogen filling; S303, continuously filling different volumes of nitrogen gas V_i into the container, recording the air pressure value after each filling of nitrogen gas, and calculating the air pressure difference ΔP_i; S304, plotting the pressure change points after each nitrogen filling on a graph and connecting them into a line graph; S305, for each pressure difference ΔP_i before and after nitrogen filling and the volume of nitrogen filled V_i, calculate the slope k_i=ΔP_i / V_i, compare the difference between adjacent slopes |k_i-k_(i-1)|, and determine whether it is within the set threshold range; S306, for each nitrogen filling, calculate the nitrogen filling volume ratio w_i=V_i / V_total, where V_total is the total nitrogen filling volume, use the nitrogen filling volume ratio as a weight, and calculate the weighted pressure difference ΔP_weighted=Σ(w_i*ΔP_i).

5. The liquid level calibration system for low-temperature liquid nitrogen biological container by pressure difference according to claim 4, characterized in that: The S302 includes: recording the air pressure value after the first filling of nitrogen on a data recording table, marking the air pressure change point after the initial filling on a chart, with the horizontal axis representing the filling volume and the vertical axis representing the air pressure difference.

6. The liquid level calibration system for low-temperature liquid nitrogen biological container by pressure difference according to claim 4, characterized in that: The S305, judging whether it is within the set threshold range, includes: for each time of filling nitrogen, calculating the slope k_i=ΔP_i / V_i, recording each slope value in the data recording table, calculating the difference between adjacent slopes, i.e. |k_i-k_(i-1)|, comparing the difference with the set threshold, and judging whether the difference is within the threshold range; if the difference exceeds the threshold, it means that the air pressure in the liquid nitrogen container is abnormal, the pressure difference data calculation is inaccurate, and the filling of nitrogen into the liquid nitrogen container is stopped.

7. The liquid level calibration system for low-temperature liquid nitrogen biological container by pressure difference according to claim 4, characterized in that: The S306 includes: for each inflation, recording the volume of nitrogen V_i charged, calculating the total inflation volume V_total, that is, the sum of all inflation volumes V_total=ΣV_i, and calculating the intake volume ratio w_i of each inflation according to the formula of intake volume ratio w_i=V_i / V_total; for each inflation, recording the air pressure difference ΔP_i before and after inflation, using the intake volume ratio w_i as a weight, weighting the air pressure difference of each inflation, and calculating the weighted air pressure difference of all inflation processes according to the formula of weighted air pressure difference ΔP_weighted=Σ(w_i*ΔP_i).

8. The liquid level calibration system for low-temperature liquid nitrogen biological container by pressure difference according to claim 1, characterized in that: The pressure difference measurement module calculates the liquid level by measuring the pressure difference measurement module in the liquid nitrogen container and the pressure difference measurement module at the outlet of the V-tube, and performs liquid level calibration in the processing module; wherein, the V-tube is built into the liquid nitrogen container, and the right outlet extends out of the tank, and an internal threaded ball joint rotary switch is provided above the outlet to control the up and down movement of the V-tube; an inflation valve plug is provided below, and when filling nitrogen, the V-tube is moved up by rotating the ball joint rotary switch, and the lower outlet is separated from the inflation valve plug, allowing nitrogen to enter the liquid nitrogen container; after inflation is completed, the ball joint rotary switch is rotated in the opposite direction to move the V-tube down, and the lower outlet is re-embedded in the inflation valve plug to prevent further filling of nitrogen; a conductive connection device is installed at the left outlet, and the heights of the left and right tubes are different, and the right V-tube is higher than the left.

9. The liquid level calibration system for low-temperature liquid nitrogen biological container by pressure difference according to claim 8, characterized in that: The pressure difference measurement module calculates the liquid level by measuring the pressure difference measurement module in the liquid nitrogen container and the pressure difference measurement module at the outlet of the V-shaped tube, and performs liquid level calibration in the processing module. The specific steps include: S401, turn on the internal thread ball joint rotary switch on the V-tube to start filling with nitrogen; S402, after each nitrogen filling, turn the internal thread ball joint rotary switch to connect and embed the V-shaped tube with the charging valve plug; S403, measuring and calculating the pressure difference and liquid level in the liquid nitrogen container and the pressure difference at the opening of the V-shaped tube and the liquid level of the V-shaped tube; S404, calibrating the liquid level height in the liquid nitrogen container measured by the liquid level height of the V-shaped tube.

10. The liquid level calibration system for a low-temperature liquid nitrogen biological container by pressure difference according to claim 8, characterized in that: During the nitrogen injection process, the conductive connection device senses and records the amount of nitrogen injected in real time, and measures and calibrates the liquid level. The specific steps include: S501, when the nitrogen liquid level contacts the conductive connection device, the conductive connection device senses the height of the liquid level contact and converts it into a digital signal for recording; S502, obtaining the current liquid level according to the output signal of the conductive connection device; S503, comparing the liquid level in the nitrogen tank with the liquid level obtained by the left conductive connection device to perform liquid level calibration.

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