Liquid level measuring method

Abstract

The invention relates to a liquid level measuring method, a liquid level measuring device is used in the method, the liquid level measuring device comprises a sensor module, a pipeline and a control processing unit, the sensor module is electrically connected with the control processing unit, and a measuring cavity and an opening communicated with the measuring cavity are formed in the pipeline. The measuring cavity is communicated with the liquid storage container through the opening, and after liquid is put into the liquid storage container, part of the liquid enters the measuring cavity and forms a sealed space; the invention provides two liquid level measurement methods, one method has high requirements on liquid level measurement errors, only the initial pipeline air pressure intensity, the working pipeline air pressure intensity, the initial pipeline air temperature and the working pipeline air temperature value need to be measured, and the other method is that errors can be ignored through design and model selection of the pipeline length. Compared with the prior art, the liquid level measuring method has the advantages that the calculation process is simple, and the number of variables needing to be measured is smaller.

Description

Technical Field

[0001] This application relates to the technical field of liquid level measurement, and particularly to a liquid level measurement method. Background Art

[0002] There are various methods for liquid level measurement, such as float type, pressure type, ultrasonic, electronic water gauge (capacitive, magnetostrictive), etc. In the early days, these measurement methods were all carried out by combining large mechanical structures with electronic systems, resulting in large volume and heavy equipment. In recent years, with the development of microelectromechanical system (MEMS) technology, MEMS pressure membranes can be made to be encapsulated into chips. If it can be applied to liquid level detection, it can miniaturize liquid level detection. The most convenient to apply is the waterproof MEMS pressure sensor, but its cost is more than 5 times that of ordinary MEMS pressure sensors.

[0003] Chinese Patent with application number CN201910174363.X discloses a liquid level measurement device based on a barometric pressure sensor and its liquid level measurement method (hereinafter referred to as Patent A). The liquid level depth H 2 in Patent A is calculated by the following two formulas:

[0004]

[0005]

[0006] It can be seen that calculating the liquid level depth H 2 in Patent A requires p 0 、p 1 、p 2 、p 3 、L, S, V 0 、p 2 、p 3 a total of 9 variables, resulting in a complex calculation process.

[0007] In terms of structure, Patent A requires a horizontal alignment device and an oil dripping device to achieve liquid level measurement. Moreover, the oil dripping device causes the length L inside the sealed container of the measurement device to be greater than the maximum liquid level depth, resulting in a huge volume of the measurement device and limiting the application scenarios. Summary of the Invention

[0008] Based on this, it is necessary to provide a liquid level measurement method for the problems of complex calculation process and too large volume of the equipment for realizing liquid level measurement in the prior art.

[0009] To achieve the purpose of the above invention, the liquid level measurement method of the present invention uses a liquid level measurement device, the liquid level measurement device includes a sensor module, a pipeline and a control processing unit, the sensor module is electrically connected to the control processing unit, a measuring cavity and an opening connected to the measuring cavity are formed inside the pipeline, before the liquid storage container is placed in the liquid, the measuring cavity is connected to the liquid storage container through the opening, and after the liquid storage container is placed in the liquid, at least part of the liquid enters the measuring cavity and forms a sealed space;

[0010] In one embodiment, the sensor module includes two absolute pressure MEMS air pressure sensors, one of which is located in the measuring cavity, and the other is located outside the measuring cavity and in contact with the external atmosphere.

[0011] In one of the embodiments, the sensor module includes a gauge pressure type MEMS air pressure sensor, and the gauge pressure type MEMS air pressure sensor includes a static pressure end and a reference end, wherein the reference end is located in the measuring cavity, and the static pressure end is located outside the measuring cavity and in contact with the external atmosphere.

[0012] In one of the embodiments, the liquid level measuring device further comprises a mounting bracket, one end of the pipeline is sealedly connected to the mounting bracket, the other end of the pipeline is provided with the opening, and the sensor module is arranged on the mounting bracket.

[0013] In one of the embodiments, the pipe is detachably connected to the mounting bracket.

[0014] In one embodiment, the pipe is cylindrical and its length direction is parallel to the direction of gravitational acceleration.

[0015] In one embodiment, one end of the pipe having the opening is connected to the bottom of the liquid storage container.

[0016] In one embodiment, the pipe is inserted into the liquid storage container, and one end of the pipe having the opening is located at the bottom of the liquid storage container.

[0017] In one of the embodiments, the distance between the sensor module and the opening is not less than the maximum liquid height allowed in the measuring chamber.

[0018] In one embodiment, the expression for calculating the maximum liquid level height allowed in the measuring chamber is:

[0019]

[0020] Among them, L set is the pipe length selected by design, Hmax is the maximum liquid height of the liquid storage container; p 0min is the minimum initial pipeline air pressure; p airmax is the maximum atmospheric pressure; T 0 max is the maximum initial duct air temperature; T 1min is the minimum working duct air temperature, h max It is the maximum liquid level allowed in the measuring chamber.

[0021] Another object of the present invention is to provide a liquid level measurement method based on the above liquid level measurement device, comprising the following steps:

[0022] Step S100a, before the liquid is placed in the liquid storage container, the sensor module obtains the initial pipeline air pressure and initial pipeline air temperature in the measuring cavity;

[0023] Step S200a, after the liquid is placed in the liquid storage container, the sensor module obtains the air pressure and air temperature of the working pipeline in the measuring cavity and the working atmospheric pressure outside the measuring cavity;

[0024] Step S300a, the control processing unit obtains the measurement data of the sensor module and executes Formula 1 or Formula 2 to calculate the liquid height of the liquid storage container;

[0025] In one embodiment, the step S300a includes the following specific steps:

[0026] Calculate X = P 1 T 0 -P 0 T 1 , determine the calculation formula according to the value of X to calculate the liquid height of the liquid storage container;

[0027] If X>0, use Formula 1 to calculate the liquid height in the liquid storage container;

[0028] If X≤0, configure P 0 =P 1 , T 0 =T 1 , update the measured value of the air pressure of the working pipeline and the measured value of the air temperature of the working pipeline in real time and calculate X again. When X>0, use formula 1 to calculate the liquid level height of the liquid storage container. When X≤0, use formula 2 to calculate the liquid level height of the liquid storage container.

[0029] The liquid level measurement method of the present invention first obtains the initial pipeline air pressure and initial pipeline air temperature in the measurement cavity when the pipeline is connected to the atmosphere through the sensor module. When the liquid storage container is placed in the liquid, due to the low static pressure of the liquid, the air in the measurement cavity is compressed, causing part of the liquid to enter the measurement cavity and form a sealed space. The working pipeline air pressure, working pipeline air temperature and atmospheric pressure in the measurement cavity are obtained by using the sensor module. Since the liquid density and the length of the pipeline are fixed, it is only necessary to substitute the measurement data of the sensor module into the above formula to obtain the liquid height of the liquid storage container. Compared with the prior art, the liquid level measurement method of the present invention has a simple calculation process and requires fewer variables to be measured.

[0030] The third object of the present invention is to provide a liquid level measurement method based on the above-mentioned liquid level measurement device, comprising the following steps:

[0031] Step S100b, determining the maximum length of the pipeline according to the measurement task;

[0032] Step S200b, after the liquid is placed in the liquid storage container, the sensor module obtains the air pressure of the working pipeline in the measuring cavity and the working atmospheric pressure outside the measuring cavity;

[0033] Step S300b, the control processing unit obtains the measurement data of the sensor module and executes formula 2 to calculate the liquid height of the liquid storage container;

[0034]

[0035]

[0036] Where ρ is the density of the liquid, in t / m 3 , unless otherwise specified, the liquid is water, with a density of 1t / m 3 ; g is the acceleration due to gravity, g = 9.8 m / s 2 ; L is the length of the pipeline, in mm; H is the liquid height in the liquid storage container, in mm; p 0 is the initial pipeline air pressure, unit: Pa; p 1 is the air pressure in the working pipe, which is equal to the pressure at the bottom of the liquid storage container, in Pa; p air is atmospheric pressure, unit is Pa; T 0 is the initial duct air temperature, in K; T 1 is the working duct air temperature, unit is K.

[0037] In one embodiment, the specific step of determining the maximum length of the pipeline according to the measurement task includes:

[0038] Step 110b, obtaining measurement threshold parameters of the measurement task, wherein the measurement threshold parameters include the maximum liquid level height allowed in the measurement chamber, the maximum liquid level height of the liquid storage container, the maximum atmospheric pressure, the minimum initial pipeline air pressure, the maximum initial pipeline air temperature, and the minimum working pipeline air temperature;

[0039] Step 120b, calculating the maximum length of the pipeline according to the measurement threshold parameter by the following formula:

[0040]

[0041] Among them, H max is the maximum liquid height of the liquid storage container; p 0min is the minimum initial pipeline air pressure; p airmax is the maximum atmospheric pressure; T 0 max is the maximum initial duct air temperature; T 1min is the minimum working duct air temperature, h max It is the maximum allowable liquid level height in the measuring chamber (that is, the maximum allowable error of the measuring device).

[0042] The liquid level measurement method of the present invention selects a pipeline length that is not greater than the maximum length of the pipeline corresponding to the measurement task, so that the maximum liquid height in the measuring chamber is less than the maximum allowable error of the liquid height measurement. Therefore, the liquid height in the measuring chamber is treated as an error and is not calculated. Only formula two is required to obtain the liquid height that satisfies the error, and the number of measurement variables is further reduced to two. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 is a first flow chart of a liquid level measurement method in one embodiment;

[0044] Figure 2 is a second flow chart of a liquid level measurement method in one embodiment;

[0045] Figure 3 Schematic diagram of the principle of a liquid level measurement method in one embodiment;

[0046] Figure 4 is a first structural schematic diagram of a liquid level measuring device in one embodiment;

[0047] Figure 5 Schematic diagram of the second structure of the liquid level measurement method in one embodiment.

[0048] Reference numerals:

[0049] 10 sensor module, 20 pipeline, 30 liquid storage container, 40 mounting bracket, 201 opening. DETAILED DESCRIPTION

[0050] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0051] The components of the embodiments of the present invention generally described and shown in the drawings herein may be arranged and designed in a variety of different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0052] Hereinafter, the terms "including", "having" and their cognates, which may be used in various embodiments of the present invention, are intended only to indicate specific features, numbers, steps, operations, elements, components or combinations of the foregoing items, and should not be understood as first excluding the existence of one or more other features, numbers, steps, operations, elements, components or combinations of the foregoing items or adding the possibility of one or more features, numbers, steps, operations, elements, components or combinations of the foregoing items.

[0053] Unless otherwise defined, all terms (including technical terms and scientific terms) used herein have the same meanings as those generally understood by those skilled in the art to which the various embodiments of the present invention belong. Terms (such as those defined in generally used dictionaries) will be interpreted as having the same meanings as the contextual meanings in the relevant technical field and will not be interpreted as having idealized meanings or overly formal meanings unless clearly defined in the various embodiments of the present invention.

[0054] Example 1

[0055] like Figure 3 As shown, an embodiment of the present application provides a liquid level measuring device, which includes a sensor module 10, a pipeline 20 and a control processing unit (not shown in the figure). The sensor module 10 is electrically connected to the control processing unit. A measuring cavity 202 and an opening 201 connected to the measuring cavity 202 are formed inside the pipeline 20. Before the liquid is placed in the liquid storage container 30, the measuring cavity 202 is connected to the liquid storage container 30 through the opening 201. After the liquid is placed in the liquid storage container 30, at least part of the liquid enters the measuring cavity 202 and forms a sealed space.

[0056] It should be noted that Figure 3The pipe 20 in the measurement refers to the vertical portion of the pipe 20, and the liquid level height in the measuring chamber 202 refers to the liquid level height of the vertical portion of the pipe 20, which means that the horizontal section of the pipe 20 needs to be short enough or the diameter of the pipe 20 is small enough so that the liquid level error caused by the liquid in the horizontal direction of the pipe 20 can be ignored.

[0057] It should be noted that the height of the liquid entering the measuring cavity 202 is the liquid level error. As the liquid in the liquid storage container 30 increases or decreases, and the atmospheric pressure changes, the static pressure of the air inside the measuring cavity 202 is also changed, resulting in a change in the height of the liquid in the measuring cavity 202. At the same time, the temperature and volume of the air inside the measuring cavity 202 will also change. Among them, the air pressure in the measuring cavity 202 can be balanced with the atmospheric pressure through the liquid pressure, which is expressed as:

[0058] p 1 =ρg(Hh)+p air Formula 5

[0059] According to the ideal gas state equation PV=nRT, the relationship between the initial pipeline air pressure, the initial pipeline air temperature, the working pipeline air pressure, the working pipeline air temperature, the length of the pipeline 20, and the liquid level height of the measuring chamber 202 is obtained, which is specifically expressed as:

[0060]

[0061] By combining Formula 5 and Formula 6 and eliminating h, we can obtain Formula 1 for calculating the liquid height in the liquid storage container 30.

[0062] Furthermore, when P 1 T 0 ≤P 0 T 1 When , it means that the volume of the sealed gas increases with the temperature increase is greater than the volume decreased by the increase of the atmospheric and liquid pressures. The gas in the pipe 20 expands and is discharged from the pipe 20, and then discharged to the atmosphere through the liquid outside the pipe 20. The gas content decreases. At this time, the inside of the pipe 20 is full of gas without water. The ideal gas state equation condition is not satisfied, and the calculation can no longer be directly performed using formula 1. Let P 1 T 0 -P 0 T 1 =0, simplify formula 1 and get formula 2.

[0063] In some embodiments, the sensor module 10 includes two absolute MEMS pressure sensors, one of which is located in the measurement cavity 202 and the other is located outside the measurement cavity 202 and in contact with the external atmosphere.

[0064] In some embodiments, the sensor module 10 includes a gauge pressure MEMS air pressure sensor, which includes a static pressure end and a reference end, wherein the reference end is located in the measuring cavity 202 and the static pressure end is located outside the measuring cavity 202 and in contact with the external atmosphere.

[0065] It should be noted that both the absolute pressure type MEMS pressure sensor and the gauge pressure type MEMS pressure sensor in the present invention have a built-in temperature measurement unit and an air pressure measurement unit.

[0066] In some embodiments, the liquid level measuring device further includes a mounting bracket 40 , one end of the pipe 20 is sealedly connected to the mounting bracket 40 , and the other end of the pipe 20 is provided with an opening 201 , and the sensor module 10 is disposed on the mounting bracket 40 .

[0067] In some embodiments, the pipe 20 is cylindrical and its length direction is parallel to the direction of gravity acceleration.

[0068] In some embodiments, one end of the pipe 20 having an opening 201 is connected to the bottom of the liquid storage container 30 .

[0069] In some embodiments, the pipe 20 is inserted into the liquid storage container 30 , and one end of the pipe 20 having an opening 201 is located at the bottom of the liquid storage container 30 .

[0070] In one of the embodiments, the distance between the sensor module and the opening is not less than the maximum liquid height allowed in the measuring chamber.

[0071] It should be noted that no matter the sensor module 10 adopts an absolute pressure MEMS air pressure sensor or a gauge pressure MEMS air pressure sensor, it is necessary to avoid damage caused by contact with liquid.

[0072] In one embodiment, the expression for calculating the maximum allowable liquid level height in the measuring chamber is:

[0073]

[0074]

[0075] Among them, L set is the pipe length selected by design, H max is the maximum liquid height of the liquid storage container; p 0min is the minimum initial pipeline air pressure; p airmax is the maximum atmospheric pressure; T 0 max is the maximum initial duct air temperature; T 1min is the minimum working duct air temperature, h max It is the maximum liquid level allowed in the measuring chamber.

[0076] It should be noted that when the liquid level measurement device is used in scenarios where the liquid level measurement accuracy requirement is not high, such as Figure 5 The liquid level measurement of the liquid storage container 30 shown in the figure uses formula 4 to calculate the maximum allowable liquid level height in the measuring cavity 202 under the usage scenario, so that the distance between the sensor module 10 and the opening 201 is not less than the maximum allowable liquid height in the measuring cavity 202.

[0077] Example 2

[0078] like Figure 2 As shown, the embodiment of the present application provides a schematic diagram of the implementation process of a liquid level measurement method, and the liquid level measurement method includes the following steps:

[0079] Step S100a, before the liquid is placed in the liquid storage container 30, the sensor module 10 obtains the initial pipeline air pressure and initial pipeline air temperature in the measuring cavity 202;

[0080] Step S200a, after the liquid is placed in the liquid storage container 30, the sensor module 10 obtains the working pipe air pressure and working pipe air temperature in the measuring cavity 202 and the working atmospheric pressure outside the measuring cavity 202;

[0081] Step S300a, the control processing unit obtains the measurement data of the sensor module 10 and executes Formula 1 or Formula 2 to calculate the liquid height of the liquid storage container 30;

[0082]

[0083]

[0084] Where ρ is the density of the liquid, in t / m 3 , unless otherwise specified, the liquid is water, with a density of 1t / m 3 ; g is the acceleration due to gravity, g = 9.8 m / s 2 ; L is the length of the pipeline 20, in mm; H is the liquid height of the liquid storage container 30, in mm; p 0 is the initial pipeline air pressure, unit: Pa; p 1 is the air pressure in the working pipe, which is equal to the pressure at the bottom of the liquid storage container 30, in Pa; p air is atmospheric pressure, unit is Pa; T 0 is the initial duct air temperature, in K; T 1 is the working duct air temperature, unit is K.

[0085] It should be noted that the initial pipeline air pressure and the initial pipeline air temperature are the pressure and temperature in the measuring cavity 202 obtained by using the sensor module 10 when the pipeline 20 is connected to the atmosphere. At this time, the initial pipeline air pressure is the same as the atmospheric pressure, and the temperature inside and outside the measuring cavity 202 is the same; the working pipeline air pressure and the working pipeline air temperature are when the liquid is placed in the liquid storage container 30, the air inside the pipeline 20 is compressed due to the large static pressure of the liquid, causing part of the liquid to enter the measuring cavity 202 and form a sealed space in the measuring cavity 202. The sensor module 10 measures the pressure and temperature in the measuring cavity 202 where the sealed space has been formed.

[0086] The liquid level measurement method of the present invention uses the sensor module 10 to obtain the initial pipeline air pressure and initial pipeline air temperature in the measuring cavity 202 when the pipeline 20 is connected to the atmosphere. When the liquid storage container 30 is placed in the liquid, due to the large static pressure of the liquid, the air in the measuring cavity 202 is compressed, causing part of the liquid to enter the measuring cavity 202 and form a sealed space. The sensor module 10 is used to obtain the working pipeline air pressure, working pipeline air temperature and atmospheric pressure in the measuring cavity 202. Since the liquid density and the length of the pipeline 20 are fixed, it is only necessary to substitute the measurement data of the sensor module 10 into the above formula to obtain the liquid height of the liquid storage container 30. Compared with the prior art, the liquid level measurement method of the present invention has a simple calculation process and fewer variables to be measured.

[0087] In some embodiments, executing step S300a includes the following specific steps:

[0088] Calculate X = P 1 T 0 -P 0 T 1 , determine the calculation formula according to the value of X to calculate the liquid height of the liquid storage container 30;

[0089] If X>0, the liquid height of the liquid storage container 30 is calculated using Formula 1;

[0090] If X≤0, configure P 0 =P 1 ,T 0 =T 1 , update the measured values ​​of the working pipe air pressure and the working pipe air temperature in real time and calculate X again. When X>0, use formula 1 to calculate the liquid level height of the liquid storage container 30. When X≤0, use formula 2 to calculate the liquid level height of the liquid storage container 30.

[0091] It should be noted that, because the liquid density ρ and the length L of the pipe 20 are fixed values, when the measuring device needs to measure the current liquid level, it only needs to measure p again. 1 、p air , T1 , and then we can get the theoretically error-free liquid depth H by substituting it into formula 1. Among them, formula 1 is only suitable for P 1 T 0 >P 0 T 1 In the case of P 1 T 0 ≤P 0 T 1 When the sealed gas increases in volume due to the temperature increase, it is greater than the volume decreased due to the increase in atmospheric and liquid pressure. The gas in the pipeline 20 expands and is discharged from the pipeline 20, and then discharged into the atmosphere through the liquid outside the pipeline 20. The gas content decreases, and the conditions of the ideal gas state equation are not met. Formula 1 can no longer be used directly.

[0092] For example, Figure 4 As shown, the present embodiment provides a liquid level measuring device for machine lubricating oil, the liquid level measuring device adopts an absolute pressure MEMS air pressure sensor, optionally, the model of the absolute pressure MEMS air pressure sensor is LPS12HH, and the number is two; a mounting bracket 40 is installed at one end above the pipe 20, and two absolute pressure MEMS air pressure sensors are mounted on the mounting bracket 40, one of the absolute pressure MEMS air pressure sensors is located in the measuring cavity 202, and the other is located outside the measuring cavity 202 and exposed to the atmosphere, the sensor module 10, the fixing bracket and the pipe 20 in the present embodiment are as a whole, the pipe 20 is inserted into the liquid storage container 30 filled with lubricating oil, and the pipe 20 is provided with an end of the opening 201 extending to the bottom of the liquid storage container 30, and further, the liquid storage solution has no structural connection, so that the liquid level measuring device in the present embodiment can be moved at will and adapted to a variety of application scenarios.

[0093] Since the liquid level measurement accuracy of the lubricating oil is required to be high, it is necessary to use Formula 1 to calculate the liquid level height of the liquid storage container 30. Specifically, Figure 4 The liquid level measurement process of lubricating oil is as follows:

[0094] First, the sensor module 10 obtains the initial pipeline air pressure and initial pipeline air temperature before the pipeline 20 is inserted into the liquid storage container 30. At this time, the air pressure and temperature inside and outside the pipeline 20 are the same;

[0095] Then, the pipe 20 is inserted into the liquid storage container 30 filled with lubricating oil and one end of the pipe 20 with the opening 201 is extended to the bottom of the liquid storage container 30. The sensor module 10 obtains the working pipe air pressure and working pipe air temperature and atmospheric pressure every 1 second.

[0096] Finally, the control processing unit obtains the measurement data of the sensor module 10 and calculates X=P 1 T 0 -P0 T 1 ,

[0097] According to the value of X, use Formula 1 or Formula 2 for calculation.

[0098] For example, the current parameter p 0 =100800Pa,p air =100000Pa, ρ = 0.8t / m 3 , T 0 =298K, T 1 =298K, p 1 =100200Pa, at this time X>0, then the liquid level height of the liquid storage container 30 is:

[0099]

[0100] When T 1 =318K, X≤0, then the liquid level height of the liquid storage container 30 is:

[0101]

[0102] Furthermore, the material of the pipe 20 in this embodiment is a metal material with good thermal conductivity, so that the temperature of the gas in the pipe 20 can quickly be equal to the temperature of the liquid in the liquid storage container 30.

[0103] It should be noted that in the present embodiment, one end of the pipe 20 having an opening 201 needs to extend to the bottom of the liquid storage container 30 so that the air pressure of the working pipe measured by the sensor module 10 is consistent with the liquid pressure at the bottom of the liquid storage container 30. Therefore, if it is necessary to measure liquid storage containers 30 of different depths, the pipe 20 and the mounting bracket 40 are detachably connected, and it is only necessary to change the pipe 20 of the corresponding length, without the need to repeatedly purchase multiple sets of equipment.

[0104] Example 3

[0105] The present application embodiment provides another implementation flow diagram of a liquid level measurement method, the liquid level measurement method comprising the following steps:

[0106] Step S100b, determining the maximum length of the pipeline according to the measurement task;

[0107] Step S200b: After the liquid is placed in the liquid storage container, the sensor module obtains the air pressure of the working pipeline in the measurement chamber and the working atmospheric pressure outside the measurement chamber;

[0108] Step S300b: The control processing unit obtains the measurement data of the sensor module and executes Formula 2 to calculate the liquid height of the liquid storage container.

[0109] It should be noted that when the liquid level measurement object does not have high requirements on measurement accuracy, the pipe length can be designed so that the maximum allowable liquid height in the measurement chamber is not greater than the maximum allowable error of the liquid height measurement. In this way, the liquid height in the measurement chamber is treated as an error and is not calculated. Only formula 2 needs to be executed to obtain the liquid height that meets the error.

[0110] In some embodiments, the specific steps of determining the maximum length of the pipeline according to the measurement task include:

[0111] Step 110b, obtaining measurement threshold parameters of the measurement task, the measurement threshold parameters including the maximum liquid level height allowed in the measurement chamber, the maximum liquid level height of the liquid storage container, the maximum atmospheric pressure, the minimum initial pipeline air pressure, the maximum initial pipeline air temperature and the minimum working pipeline air temperature;

[0112] Step 120b, calculate the maximum length of the pipeline according to the measurement threshold parameter using the following formula:

[0113]

[0114] Among them, H max is the maximum liquid height of the liquid storage container; p 0min is the minimum initial pipeline air pressure; p airmax is the maximum atmospheric pressure; T 0 max is the maximum initial duct air temperature; T 1min is the minimum working duct air temperature, h max It is the maximum allowable liquid level height in the measuring chamber (that is, the maximum allowable error of the measuring device).

[0115] It should be noted that Formula 3 is the combination of Formula 5 and Formula 6 to eliminate p 1 It is found that when the length of the pipeline is selected to be less than the maximum length of the pipeline during design, the liquid height in the measuring chamber can be taken as an error and not calculated. Only formula 2 is required to obtain the liquid height that satisfies the error, and the number of measurement variables is further reduced to two.

[0116] For example, Figure 5 As shown in the figure, in the application scenarios where the liquid level measurement accuracy is not high, such as humidifiers or cooling fans, the parameter p 0 =100000Pa, p air =100800Pa, g=9.8m / s 2 , T 0 =40℃、T 1 =10℃、ρ=1t / m 3, the liquid level height in the measuring cavity 202 corresponding to different internal lengths of the pipe 20 and the liquid level height of the liquid storage container 30 is calculated by the above expression of the liquid level height in the measuring cavity 202. That is to say, when the liquid level measurement accuracy requires that the liquid level error is allowed to be ±2mm, as long as the liquid level height of the liquid storage container 30 does not exceed 2000mm and the length of the pipe 20 does not exceed 8mm, the liquid level height of the measuring cavity 202 and the length of the pipe 20 meet the liquid level measurement accuracy requirements; similarly, when the liquid level measurement accuracy requires that the liquid level error is allowed to be ±7.51mm, as long as the liquid level height of the liquid storage container 30 does not exceed 2000mm and the length of the pipe 20 does not exceed 30mm, the liquid level height of the measuring cavity 202 and the length of the pipe 20 meet the liquid level measurement accuracy requirements, and at this time, the liquid level height of the liquid storage container 30 can be calculated using Formula 2.

[0117] It should be noted that Formula 1 involves a large number of floating-point operations with decimals. Since the 8051 series MCUs used in the liquid level measurement devices in the industry do not support floating-point operations, Formula 2 only involves the variable p. air 、p 1 , ρ and g, when the measured liquid is water (ρ = 1t / m 3 ), take g = 10m / s 2 , Formula 2 can be further simplified as: H = (p 1 -p air )÷10. Therefore, the liquid level measurement method of the present invention can use such MCU to perform liquid level measurement in application scenarios where the liquid level measurement accuracy requirement is not high.

[0118] Specifically, Figure 4 As shown, this embodiment provides a liquid level measuring device for a humidifier, the liquid level measuring device adopts a gauge pressure MEMS air pressure sensor, and optionally, the model of the gauge pressure MEMS air pressure sensor is Honeywell's MPRLS0010KG00001A; wherein, a mounting bracket 40 is installed at one end above the pipe 20, the gauge pressure MEMS air pressure sensor is fixedly installed on the mounting bracket 40, and the reference end of the gauge pressure MEMS air pressure sensor is located outside the measuring cavity 202 and exposed to the atmosphere, the static pressure end of the gauge pressure MEMS air pressure sensor is located inside the measuring end, and the pipe 20 It is connected to the bottom of the liquid storage container 30, similar to the communicating vessel structure, wherein the length of the pipe 20 refers to the vertical portion of the pipe 20, and similarly, the liquid level height of the measuring chamber 202 refers to the liquid level height entering the vertical portion of the pipe 20; when the liquid storage container 30 is placed in liquid, the water pressure at the bottom of the liquid storage container 30 is transmitted to the gas in the measuring chamber 202, and then transmitted to the static pressure end of the gauge pressure type MEMS air pressure sensor through the gas in the measuring chamber 202, and the pressures at each position in the measuring chamber 202 are equal. At this time, the working pipe air pressure obtained by the static pressure end is the water pressure at the bottom of the liquid storage container 30.

[0119] When the measurement threshold parameters in the measurement task are set to: maximum working water level 300mm, allowable water level error ±5mm, maximum atmospheric pressure 100800Pa, minimum initial pipeline air pressure 100000Pa, maximum initial pipeline air temperature 40℃, minimum pipeline air temperature 10℃. According to formula three, the maximum length of the pipeline 20 is 38.8mm, and the design selection of the pipeline is 20mm (vertical part). Then, according to formula four, the maximum allowable liquid level height in the measurement cavity is 2.58mm. The liquid level height of the measurement cavity 202 and the length of the pipeline 20 meet the water level error requirement of ±5mm. Therefore, formula two can be used to directly calculate the liquid level height of the liquid storage container 30. Set the working pipeline air pressure measured by the sensor module 10 to 100800Pa, the working pipeline air temperature to 100000Pa, and take ρ=1t / m 3 , g = 10 m / s 2 , substituting the above parameters into Formula 2, the liquid level height of the liquid storage container 30 is calculated to be 80 mm.

[0120] It should be noted that Figure 4 Liquid level measuring device and Figure 5 Compared with the liquid level measuring device in Figure 5 The liquid level measuring device in the horizontal direction of the pipeline 20 has a liquid level error, so its measurement accuracy is better than Figure 4 The level measuring device in the Figure 4 The liquid level measuring device is suitable for measuring machine lubricating oil and other liquid level measurement scenarios with high accuracy requirements. Figure 5 The liquid level measuring device is suitable for use in scenarios such as humidifiers and cooling fans where the liquid level measurement accuracy requirements are not high.

[0121] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0122] The above embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A liquid level measurement method, It is characterized in that include: The liquid level measurement method uses a liquid level measurement device, which includes a sensor module, a pipeline and a control processing unit. The sensor module is electrically connected to the control processing unit. A measuring cavity and an opening communicating with the measuring cavity are formed inside the pipeline. Before the liquid storage container is filled with liquid, the measuring cavity is communicated with the liquid storage container through the opening. After the liquid storage container is filled with liquid, at least part of the liquid enters the measuring cavity and forms a sealed space. The liquid level measurement method comprises the following steps: Step S100a, before the liquid is placed in the liquid storage container, the sensor module obtains the initial pipeline air pressure and initial pipeline air temperature in the measuring cavity; Step S200a, after the liquid is placed in the liquid storage container, the sensor module obtains the air pressure and air temperature of the working pipeline in the measuring cavity and the working atmospheric pressure outside the measuring cavity; Step S300a, the control processing unit obtains the measurement data of the sensor module and executes Formula 1 or Formula 2 to calculate the liquid height of the liquid storage container; or, The liquid level measurement method comprises the following steps: Step S100b, determining the maximum length of the pipeline according to the measurement task; Step S200b, after the liquid is placed in the liquid storage container, the sensor module obtains the air pressure of the working pipeline in the measuring cavity and the working atmospheric pressure outside the measuring cavity; Step S300b, the control processing unit obtains the measurement data of the sensor module and executes formula 2 to calculate the liquid height of the liquid storage container; Where, ρ is the density of the liquid, unit t / m 3 , unless otherwise specified, the liquid is water, with a density of 1t / m 3 ; g is the acceleration due to gravity, g = 9.8 m / s 2 ; L is the length of the pipeline, in mm; H is the liquid height in the liquid storage container, in mm; p 0 is the initial pipeline air pressure, unit: Pa; p 1 is the air pressure in the working pipe, which is equal to the pressure at the bottom of the liquid storage container, in Pa; p air is atmospheric pressure, unit is Pa; T 0 is the initial duct air temperature, in K; T 1 is the working duct air temperature, unit is K.

2. The liquid level measurement method according to claim 1, It is characterized in that The sensor module comprises an absolute pressure type MEMS air pressure sensor, the number of the absolute pressure type MEMS air pressure sensors is two, one of the absolute pressure type MEMS air pressure sensors is located in the measuring cavity, and the other absolute pressure type MEMS air pressure sensor is located outside the measuring cavity and in contact with the external atmosphere; or The sensor module comprises a gauge pressure type MEMS air pressure sensor, and the gauge pressure type MEMS air pressure sensor comprises a static pressure end and a reference end, wherein the reference end is located in the measuring cavity, and the static pressure end is located outside the measuring cavity and in contact with the external atmosphere.

3. The liquid level measurement method according to claim 1, It is characterized in that The liquid level measuring device further comprises a mounting bracket, one end of the pipeline is sealedly connected to the mounting bracket, the other end of the pipeline is provided with the opening, and the sensor module is arranged on the mounting bracket.

4. The liquid level measurement method according to claim 3, It is characterized in that The pipeline is detachably connected to the mounting bracket.

5. The liquid level measurement method according to claim 1, It is characterized in that The pipe is columnar and its length direction is parallel to the direction of gravity acceleration.

6. The liquid level measurement method according to claim 1, It is characterized in that One end of the pipeline provided with the opening is connected to the bottom of the liquid storage container; or The pipeline is inserted into the liquid storage container, and one end of the pipeline provided with the opening is located at the bottom of the liquid storage container.

7. The liquid level measurement method according to claim 1, It is characterized in that The step S300a includes the following specific steps: Calculate X = P 1 T 0 -P 0 T 1 , determine the calculation formula according to the value of X to calculate the liquid height of the liquid storage container; If X>0, use Formula 1 to calculate the liquid height in the liquid storage container; If X≤0, configure P 0 =P 1 ,T 0 =T 1 , update the measured value of the air pressure of the working pipeline and the measured value of the air temperature of the working pipeline in real time and calculate X again. When X>0, use formula 1 to calculate the liquid level height of the liquid storage container. When X≤0, use formula 2 to calculate the liquid level height of the liquid storage container.

8. The liquid level measurement method according to claim 1, It is characterized in that The specific steps of determining the maximum length of the pipeline according to the measurement task include: Step 110b, obtaining measurement threshold parameters of the measurement task, wherein the measurement threshold parameters include the maximum liquid level height allowed in the measurement chamber, the maximum liquid level height of the liquid storage container, the maximum atmospheric pressure, the minimum initial pipeline air pressure, the maximum initial pipeline air temperature, and the minimum working pipeline air temperature; Step 120b, calculating the maximum length of the pipeline according to the measurement threshold parameter by the following formula: Among them, H max is the maximum liquid height of the liquid storage container; p 0min is the minimum initial pipeline air pressure; p airmax is the maximum atmospheric pressure; T 0 max is the maximum initial duct air temperature; T 1min is the minimum working duct air temperature, h max It is the maximum allowable liquid level height in the measuring chamber (that is, the maximum allowable error of the measuring device).

9. The liquid level measurement method according to claim 1, It is characterized in that The distance between the sensor module and the opening is not less than the maximum liquid height allowed in the measuring cavity.

10. The liquid level measurement method according to claim 9, It is characterized in that The expression for calculating the maximum liquid level height allowed in the measuring chamber is: Among them, L set is the pipe length selected by design, H max is the maximum liquid height of the liquid storage container; p 0min is the minimum initial pipeline air pressure; p airmax is the maximum atmospheric pressure; T 0 max is the maximum initial duct air temperature; T 1min is the minimum working duct air temperature, h max It is the maximum liquid level allowed in the measuring chamber.

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