A method, device and system for automatic measurement of liquid level in a storage tank

Abstract

The present application relates to the field of liquid level measurement technology, and specifically to a method, device and system for automatic measurement of liquid level in a storage tank, the method comprising: obtaining an echo signal of a guided wave radar level meter when measuring the liquid level of a liquid storage tank, and respectively obtaining the distance from the guided wave radar to the liquid surface and the distance from the guided wave radar to the bottom of the liquid storage tank measured by the guided wave radar level meter; determining a hanging material signal segment; obtaining the impedance change point of the hanging material signal segment and its corresponding reflected signal amplitude; determining the wave velocity attenuation weight of each impedance change point in the hanging material signal segment; determining the electromagnetic wave velocity of each impedance change point in the hanging material signal segment; constructing a hanging material area velocity vector; calculating the hanging material area length and the hanging material area error length; combining the distance from the guided wave radar to the liquid surface and the distance from the guided wave radar to the bottom of the liquid storage tank, determining the liquid level height of the liquid storage tank. The present application corrects the liquid level height, reduces the measurement error of the guided wave radar level meter, and can obtain more accurate liquid level measurement results in the liquid storage tank.

Description

Technical Field

[0001] The present application relates to the technical field of liquid level measurement, and in particular to a method, device and system for automatic measurement of liquid level in a storage tank. Background Art

[0002] Liquid storage tanks are commonly used liquid storage devices in the chemical industry. They require real-time monitoring of the liquid level to complete the safety monitoring of the status of chemical products. Liquid storage tanks usually use liquid level gauges to automatically measure the liquid level. Commonly used liquid level gauges can be divided into: communicating vessel type, buoyancy type, differential pressure type, capacitance type, radar type, etc. according to the measurement principle. Among them, guided wave radar type liquid level gauges have the advantages of high measurement accuracy and strong adaptability to harsh working conditions, and are widely used in liquid level measurement of liquid storage tanks.

[0003] Guided wave radar level meters measure liquid levels by propagating electromagnetic waves on a waveguide rod. Due to the difference in dielectric constants between air and liquid, the electromagnetic waves encounter impedance changes at the liquid surface, generating echoes. The level meter measures the time it takes for the transmitter to transmit the electromagnetic wave and the time it takes for the receiver to receive the electromagnetic wave, calculates the time difference, and uses the time difference to calculate the height of the liquid level. However, since the waveguide rod is in direct contact with the liquid in the storage tank, residual liquid is likely to hang on the waveguide rod. In the hanging part of the waveguide rod, the electromagnetic wave velocity is usually slower than that in the non-hanging part. Existing guided wave radar level meters do not take into account the changes in the electromagnetic wave velocity caused by hanging, which will cause measurement errors in the guided wave radar level meter. Summary of the invention

[0004] In order to solve the above technical problems, a method, device and system for automatic measurement of liquid level in a storage tank are provided to solve the existing problems.

[0005] The solution to the technical problem of the present application is to provide a method, device and system for automatic measurement of liquid level in a storage tank, including the following steps:

[0006] In a first aspect, an embodiment of the present application provides a method for automatically measuring the liquid level of a storage tank, the method comprising the following steps:

[0007] Acquire the echo signal of the guided wave radar level meter when measuring the liquid level of the liquid storage tank, and respectively obtain the distance from the guided wave radar to the liquid surface and the distance from the guided wave radar to the bottom of the liquid storage tank measured by the guided wave radar level meter;

[0008] The echo signal is divided into multiple segmented signals; the smoothness of the change of each segmented signal and the drastic degree of the change of the signal amplitude in the segmented signal are analyzed to determine the hanging material signal segment; according to the distribution of the maximum value in the hanging material signal segment and the degree of fluctuation of the maximum value, the impedance change point of the hanging material signal segment and its corresponding reflection signal amplitude are obtained;

[0009] Determine the wave velocity attenuation weight of each impedance change point in the hanging material signal segment according to the proportion of the reflected signal amplitude corresponding to each impedance change point in all impedance change points; determine the electromagnetic wave velocity of each impedance change point in the hanging material signal segment based on the wave velocity attenuation weight;

[0010] Based on the electromagnetic wave velocity, a hanging area velocity vector is constructed; based on the analysis of the distance errors when the electromagnetic wave velocity corresponding to all elements in the hanging area velocity vector propagates in the hanging area signal segment and propagates in the hanging area signal segment at the speed of light, the hanging area length and the hanging area error length are calculated respectively; and the liquid level height of the liquid storage tank is determined by combining the distance from the guided wave radar to the liquid surface and the distance from the guided wave radar to the bottom of the liquid storage tank.

[0011] Preferably, the step of determining the hanging material signal segment includes:

[0012] Calculate the discrete degree of the signal amplitude at all times in each segmented signal; record the segmented signal with a discrete degree greater than a preset threshold as an echo signal segment, otherwise, record it as a stable signal segment;

[0013] The maximum signal amplitude in each echo signal segment and the time corresponding to the maximum signal amplitude are respectively used as the reflection amplitude and reflection time of each echo signal segment;

[0014] The echo signal segment with the largest reflection amplitude among all echo signal segments is recorded as the liquid level signal segment; based on the reflection time of the liquid level signal segment, the signal on the left side of the reflection time is intercepted and recorded as the hanging material signal segment.

[0015] Preferably, the step of obtaining the impedance change point of the hanging material signal segment and its corresponding reflected signal amplitude includes:

[0016] Obtain all the maximum values ​​of the hanging material signal segment; record the moment corresponding to each maximum value as the impedance change point;

[0017] Taking the mean of the signal amplitudes at all times in all the stable signal segments as the DC component amplitude;

[0018] The difference between the maximum value corresponding to each impedance change point and the DC component amplitude is used as the reflection signal amplitude of each impedance change point.

[0019] Preferably, the step of determining the wave velocity attenuation weight of each impedance change point in the hanging material signal segment includes:

[0020] The sum of the reflected signal amplitudes of all impedance change points in the hanging material signal segment is recorded as the first sum;

[0021] The ratio of the reflected signal amplitude at each impedance change point to the first sum value is used as the wave velocity attenuation weight at each impedance change point in the hanging material signal segment.

[0022] Preferably, the electromagnetic wave velocity at each impedance change point is calculated as follows: ,in, , , Respectively , No. and The electromagnetic wave velocity at the impedance change point is is the speed of light in a vacuum, It is The wave velocity attenuation weight of each impedance change point, is the number of all impedance change points in the hanging signal segment, is the sequence number corresponding to the impedance change point in the hanging signal segment arranged in time; among them, , For the The relative dielectric constant of the impedance change point is For the The relative permeability of the impedance change point.

[0023] Preferably, the constructing of the material hanging area velocity vector comprises:

[0024] Construct a null vector with the same length as the length of the hanging signal segment; the first element of the null vector is the speed of light in a vacuum;

[0025] The electromagnetic wave velocities of all impedance change points in the hanging material signal segment are filled into the corresponding positions in the empty vector, and the remaining positions in the empty vector are interpolated and filled to obtain the hanging material area velocity vector.

[0026] Preferably, the calculation of the length of the hanging area and the error length of the hanging area includes:

[0027] The length of the hanging area is calculated as follows: ,in, is the length of the hanging area, is the velocity vector in the hanging area elements, is the velocity vector in the hanging area elements, is the sampling period, is the length of the hanging signal segment;

[0028] The error length of the hanging area is calculated by the formula: ,in, is the error length of the hanging area, is the speed of light in a vacuum.

[0029] Preferably, the liquid level height is calculated as follows: ,in, is the liquid level height, is the distance from the guided wave radar to the bottom of the liquid storage tank, is the distance from the guided wave radar to the liquid surface, is the error length of the hanging area, is the length of the hanging area.

[0030] In a second aspect, an embodiment of the present application further provides a tank liquid level automatic metering device, the device comprising:

[0031] The signal acquisition module is used to obtain the echo signal of the guided wave radar level meter when measuring the liquid level of the liquid storage tank, and respectively obtain the distance from the guided wave radar to the liquid surface and the distance from the guided wave radar to the bottom of the liquid storage tank measured by the guided wave radar level meter;

[0032] The error measurement module divides the echo signal into multiple segmented signals; analyzes the change of signal amplitude and the degree of discreteness in each segmented signal to determine the hanging signal segment; obtains the impedance change point and its reflected signal amplitude of the hanging signal segment according to the distribution of the maximum value in the hanging signal segment and the degree of fluctuation change of the maximum value; determines the wave velocity attenuation weight of each impedance change point in the hanging signal segment according to the proportion of the reflected signal amplitude corresponding to each impedance change point in all impedance change points, and determines the electromagnetic wave velocity of each impedance change point in the hanging signal segment based on the wave velocity attenuation weight; constructs the hanging area velocity vector based on the electromagnetic wave velocity; calculates the hanging area length and the hanging area error length based on the analysis of the distance errors when the electromagnetic wave velocity corresponding to all elements in the hanging area velocity vector propagates in the hanging signal segment and propagates in the hanging signal segment at the speed of light;

[0033] The height correction module determines the liquid level height of the liquid storage tank by combining the distance from the guided wave radar to the liquid surface and the distance from the guided wave radar to the bottom of the liquid storage tank.

[0034] In a third aspect, an embodiment of the present application further provides a system for automatic tank liquid level measurement, comprising a memory, a processor, and a computer program stored in the memory and running on the processor, wherein the processor implements the steps of any one of the above-mentioned methods for automatic tank liquid level measurement when executing the computer program.

[0035] This application has at least the following beneficial effects:

[0036] The present application analyzes the smoothness of the change of each segmented signal and the drastic degree of the change of the signal amplitude in the segmented signal to determine the hanging material signal segment; according to the distribution of the maximum value in the hanging material signal segment and the degree of fluctuation of the maximum value, the impedance change point of the hanging material signal segment and its corresponding reflected signal amplitude are obtained. The beneficial effect is that the moment and change intensity of the signal change in the hanging material signal segment are taken into account, and the influence of the DC component is eliminated to reflect the moment and wave velocity change of the electromagnetic wave affected by the hanging material liquid; according to the proportion of the reflected signal amplitude corresponding to each impedance change point in all impedance change points, the wave velocity attenuation weight of each impedance change point in the hanging material signal segment is determined, and based on the wave velocity attenuation weight, the hanging material signal segment is determined. The electromagnetic wave velocity at each impedance change point in the material signal segment; based on the electromagnetic wave velocity, constructing the material hanging area velocity vector, which has the beneficial effect of taking into account the change in the electromagnetic wave velocity in the material hanging area affected by the residual material content of the liquid on the waveguide rod, and obtaining a change in the electromagnetic wave velocity that is closer to the actual one, so as to obtain a more accurate liquid level measurement result in the subsequent process; calculating the material hanging area length and the material hanging area error length; combining the distance from the guided wave radar to the liquid surface and the distance from the guided wave radar to the bottom of the liquid storage tank, determining the liquid level height of the liquid storage tank, which has the beneficial effect of correcting the liquid level height through the change in the speed of the electromagnetic wave in the material hanging area, reducing the measurement error of the guided wave radar level meter, and being able to obtain a more accurate liquid level measurement result of the liquid storage tank. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The following is a further detailed description of a method for automatic tank liquid level measurement of the present application in conjunction with the accompanying drawings.

[0038] Figure 1 A flowchart of a method for automatic tank liquid level measurement provided in an embodiment of the present application;

[0039] Figure 2 A schematic diagram of an original echo signal provided in an embodiment of the present application;

[0040] Figure 3 A schematic diagram of a filtered echo signal provided in an embodiment of the present application;

[0041] Figure 4 A flowchart of the steps of the method for obtaining the hanging material signal segment provided in an embodiment of the present application;

[0042] Figure 5 A block diagram of an automatic tank liquid level metering device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0043] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the following is a further detailed description of a method, device and system for automatic measurement of liquid level in a storage tank proposed in the present application in combination with the accompanying drawings and implementation examples. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0044] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0045] See also Figure 1 , which shows a flow chart of a method for automatic tank liquid level measurement provided by an embodiment of the present application, the method comprising the following steps:

[0046] Step 1: Obtain an echo signal of a guided wave radar level meter when measuring the liquid level of a liquid storage tank, and respectively obtain a distance from the guided wave radar to the liquid surface and a distance from the guided wave radar to the bottom of the liquid storage tank measured by the guided wave radar level meter.

[0047] The guided wave radar level meter is a liquid level meter that uses direct contact to immerse the level meter probe into the measured medium for measurement. The guided wave radar level meter is installed on the top of the liquid storage tank. The transmitter of the level meter will emit an electromagnetic wave signal, which will propagate downward along the waveguide rod; therefore, the electromagnetic wave is sent to the waveguide rod inserted into the liquid storage tank through the transmitter of the guided wave radar level meter, and the original echo signal is received through the receiver of the guided wave radar level meter. The sampling frequency is set to f Hz, the sampling period is T, and the noise reduction processing is performed to eliminate the high-frequency noise in the original echo signal to obtain the echo signal of the liquid storage tank.

[0048] Preferably, in this embodiment, the sampling frequency is set to 6 GHZ, and the corresponding sampling period is Seconds, as other implementation methods, the implementer can set them according to the actual situation. Secondly, the original echo signal is filtered and denoised using a Butterworth filter, wherein the filtering method of the Butterworth filter is a well-known technology and will not be repeated here.

[0049] Furthermore, the schematic diagram of the original echo signal and the filtered echo signal provided in the embodiment of the present application is as follows: Figure 2 and Figure 3 As shown, the horizontal axis is the acquisition order corresponding to each moment, and the vertical axis represents the signal amplitude of the echo signal.

[0050] It should be noted that the data storage form of the original echo signal is a vector with a length of N=1000, where The element value of each element represents The size of the original echo signal at time.

[0051] At the same time, the guided wave radar level meter can obtain the distance from the guided wave radar to the liquid surface and the distance from the guided wave radar to the bottom of the liquid storage tank.

[0052] At this point, the echo signal of the guided wave radar level meter when measuring the liquid level of the liquid storage tank is obtained, and the distance from the guided wave radar to the liquid surface and the distance from the guided wave radar to the bottom of the liquid storage tank measured by the guided wave radar level meter are obtained respectively.

[0053] Step 2: Analyze the smoothness of the change of each segmented signal and the drastic change of the signal amplitude within the segmented signal to determine the hanging signal segment; obtain the impedance change point of the hanging signal segment and its corresponding reflected signal amplitude based on the distribution of the maximum value in the hanging signal segment and the degree of fluctuation of the maximum value.

[0054] In the waveguide rod, the larger the dielectric constant of the material near the measuring position of the waveguide rod, the smaller the impedance of the electromagnetic wave propagating along the waveguide rod and the slower the propagation speed.

[0055] The signal emitted by the guided wave radar level meter in this embodiment is an electromagnetic wave. The calculation formula for the propagation speed of the electromagnetic wave in the medium is: ,in, is the speed of electromagnetic waves, c is the speed of light in a vacuum m / s, is the relative permittivity of the medium, is the relative magnetic permeability of the medium.

[0056] It should be noted that the method for calculating the propagation speed of electromagnetic waves in a medium is a well-known technique; the method for obtaining the relative dielectric constant and the relative magnetic permeability is also a well-known technique.

[0057] Preferably, in this embodiment, the liquid storage tank contains an aqueous solution. When measuring the liquid level of the water, the relative dielectric constant of the water is 80, the relative dielectric constant of the air is 1, and the relative magnetic permeabilities of the air and the water are both 1. The liquid stored in the liquid storage tank is usually a non-metallic liquid, so its relative magnetic permeability can be approximately 1.

[0058] When electromagnetic waves propagate in the waveguide rod, the greater the amplitude of the reflected echo signal, the greater the impedance change at the reflection position. According to the definition of wave impedance (intrinsic impedance), the impedance encountered by the electromagnetic wave is also related to the relative dielectric constant and relative magnetic permeability of the medium, that is: , where Z is the wave impedance of the electromagnetic wave, is the relative permittivity of the medium, is the relative magnetic permeability of the medium. When it increases, the wave impedance of electromagnetic waves decreases.

[0059] Since the waveguide rod is in direct contact with the liquid, residual liquid is likely to hang on the waveguide rod. When the electromagnetic wave propagates above the liquid surface and has not reached the hanging position, its impedance remains unchanged and no echo signal segment is generated. When the electromagnetic wave reaches the hanging position, the impedance changes and a reflected signal is generated. The greater the change in the amplitude of the reflected signal, the more drastic the change in wave impedance. When reaching the liquid surface, the intensity of the wave impedance change encountered by the electromagnetic wave reaches the maximum, and the amplitude of the reflected signal reaches the maximum.

[0060] Based on the above analysis, it is necessary to eliminate the interference of hanging materials on the guided wave radar ranging, process the echo signal, and extract the echo signal segment corresponding to the hanging material position.

[0061] First, the echo signal is segmented and analyzed to distinguish the echo signal segment and the stable signal segment to reflect whether the signal segment contains the reflection information of the electromagnetic wave. Specifically:

[0062] The double sliding window pulse energy detection method is used to divide the echo signal into multiple segmented signals;

[0063] Preferably, in this embodiment, the signal-to-noise ratio value in the dual sliding window pulse energy detection method is set to 15dB, the sliding window length value is 32, and the energy decision threshold value is 500. As other implementation methods, the implementer can set them according to actual conditions.

[0064] It should be noted that the double sliding window pulse energy detection method is a well-known technology and will not be described in detail here; secondly, the data storage form of each segmented signal is a vector.

[0065] Calculate the discrete degree of the signal amplitude at all moments in each segmented signal;

[0066] The segmented signals whose discreteness is greater than a preset threshold are recorded as echo signal segments, and the segmented signals whose discreteness is less than or equal to the preset threshold are recorded as stable signal segments;

[0067] Preferably, in this embodiment, the standard deviation of the signal amplitude at all times in each segmented signal is calculated. As other implementations, the implementer can use other methods of the prior art to measure the degree of discreteness, such as variance, coefficient of variation, etc. This embodiment does not impose any special restrictions on this. The preset threshold value is 300. As other implementations, the implementer can set it according to the situation.

[0068] It should be noted that the signal amplitude changes dramatically in the echo signal segment, which is a segmented signal containing electromagnetic wave reflection information; the signal amplitude changes slightly in the stable signal segment, which is a segmented signal that does not contain electromagnetic wave reflection information.

[0069] It should be noted that, for all echo signal segments, the first echo signal segment is usually caused by the reflection of electromagnetic waves by the flange structure used when the waveguide rod is installed. Therefore, the first echo signal segment is not analyzed subsequently, and each echo signal segment analyzed below does not include the first echo signal segment.

[0070] Further, according to the change of the signal amplitude in the echo signal segment, the echo signal segment corresponding to the material hanging position is extracted to determine the material hanging signal segment, specifically:

[0071] The time corresponding to the maximum signal amplitude in each echo signal segment is taken as the reflection time of each echo signal segment;

[0072] The maximum signal amplitude in each echo signal segment is taken as the reflection amplitude of each echo signal segment;

[0073] The echo signal segment with the largest reflection amplitude among all echo signal segments is recorded as the liquid level signal segment;

[0074] Based on the reflection moment of the liquid level signal segment, a portion of the signal on the left side of the reflection moment is intercepted and recorded as the hanging material signal segment;

[0075] It should be noted that since the impedance change intensity of electromagnetic waves is usually the largest at the liquid surface position, the echo signal segment with the largest reflection amplitude is usually the echo signal segment corresponding to the liquid surface position, and its reflection time indicates the time when the electromagnetic wave reaches the liquid surface position. Secondly, since the hanging position is usually connected to the liquid surface, the part of the signal on the left side of the reflection time in the liquid surface signal segment corresponds to the propagation of the electromagnetic wave at the hanging position.

[0076] Further, the step flow chart of the method for obtaining the hanging material signal segment provided in the embodiment of the present application is as follows: Figure 4 shown.

[0077] Furthermore, in the hanging part of the waveguide rod, the amount of residual liquid in different positions is different. When the electromagnetic wave touches the part where the residual liquid is significantly increased, the impedance encountered by the electromagnetic wave becomes significantly smaller and the wave speed of the electromagnetic wave decreases. At this time, it is reflected as a signal pulse in the hanging signal segment, and the corresponding moment of the maximum value point of the signal pulse is usually the moment when the electromagnetic wave is reflected by the residual liquid, which corresponds to the maximum value point of the hanging signal segment.

[0078] Based on the above analysis, the thickness of the hanging materials at different positions on the waveguide rod is different, resulting in different effects of the hanging materials on the electromagnetic wave velocity at different positions. In the hanging material signal segment, when a more obvious peak appears in the signal, it usually means that the electromagnetic wave enters a thicker hanging material from a thinner hanging material area. At this time, the electromagnetic wave velocity will change accordingly. Therefore, the moments when the electromagnetic wave velocity changes significantly are selected from the hanging material signal segment to obtain the impedance change point to reflect the change in the electromagnetic wave velocity at the entire hanging material position, specifically:

[0079] Obtain all the maximum values ​​of the hanging material signal segment; record the moment corresponding to each maximum value as the impedance change point;

[0080] Preferably, in this embodiment, the difference method is used to obtain the maximum value. As other implementation methods, the implementer can use other methods of the prior art, such as the local extremum method, the difference method, etc. This embodiment does not impose any special restrictions on this.

[0081] Furthermore, in the hanging material signal segment, the DC component of the signal is usually not 0, which will affect the judgment of the change of electromagnetic impedance. Therefore, it is necessary to eliminate the DC component in the hanging material signal segment, specifically:

[0082] The mean of the signal amplitudes at all moments of all stationary signal segments is taken as the DC component amplitude;

[0083] The difference between the maximum value corresponding to each impedance change point and the DC component amplitude is used as the reflection signal amplitude of each impedance change point;

[0084] It should be noted that the impedance change point indicates a moment in the hanging signal segment when the impedance change is more obvious, which is the moment when the electromagnetic wave velocity changes obviously; since DC shunt dominates the signal components of the stable signal segment, the mean of the signal amplitude at all moments in the stable signal segment can be approximated as the amplitude of the DC component. The reflected signal amplitude at the impedance change point eliminates the influence of the DC component, which indicates the size of the electromagnetic wave reflection signal caused by the impedance change.

[0085] At this point, the impedance change point of the hanging material signal segment and its corresponding reflected signal amplitude are obtained.

[0086] Step 3: Determine the wave velocity attenuation weight of each impedance change point in the hanging signal segment according to the proportion of the reflected signal amplitude corresponding to each impedance change point in all impedance change points; determine the electromagnetic wave velocity at each impedance change point in the hanging signal segment based on the wave velocity attenuation weight; and construct the hanging area velocity vector based on the electromagnetic wave velocity.

[0087] Since the relative magnetic permeability of air and the liquid in the storage tank is usually the same, the velocity of the electromagnetic wave is proportional to the impedance; and the larger the amplitude of the reflected signal corresponding to the impedance change point, the faster the impedance decreases at the corresponding moment, and the faster the rate of change of the electromagnetic wave velocity at the corresponding moment; and since the dielectric constant of the storage liquid is usually greater than that of air, the velocity of the electromagnetic wave usually changes in a decreasing direction.

[0088] Therefore, the amplitude of the reflected signal corresponding to the impedance change point corresponds to the attenuation of the electromagnetic wave velocity, and the last impedance change point corresponds to the moment when the electromagnetic wave reaches the liquid surface. At this time, the waveguide rod is completely surrounded by the liquid surface. At this time, the relative dielectric constant and relative magnetic permeability of the last impedance change point are 80 and 1 respectively. Therefore, the electromagnetic wave velocity at the last impedance change point is obtained based on the calculation formula of the propagation velocity of the electromagnetic wave in the medium, which is:

[0089] Based on the relative dielectric constant and relative magnetic permeability of the last impedance change point in the hanging signal segment, the electromagnetic wave velocity at the last impedance change point is calculated;

[0090] In this embodiment, it is assumed that there is impedance change point, the calculation method of the electromagnetic wave velocity at the last impedance change point is: ,in, For the The electromagnetic wave velocity at the impedance change point is is the speed of light in vacuum, For the The relative dielectric constant of the impedance change point is For the The relative permeability of the impedance change point, in this embodiment, The value is 80. The value is 1.

[0091] Furthermore, the attenuation of the wave velocity is analyzed based on the amplitude of the reflected signal corresponding to the impedance change point, and the wave velocity attenuation weight is determined, which is specifically:

[0092] The sum of the reflected signal amplitudes of all impedance change points in the hanging material signal segment is recorded as the first sum value;

[0093] The ratio of the reflected signal amplitude at each impedance change point in the hanging material signal segment to the first sum value is used as the wave velocity attenuation weight at each impedance change point in the hanging material signal segment;

[0094] In this embodiment, the calculation method of the wave velocity attenuation weight of each impedance change point in the hanging material signal segment is: ,in, For the The wave velocity attenuation weight of each impedance change point, For the The reflected signal amplitude at each impedance change point is It is the number of all impedance change points in the hanging signal segment.

[0095] It should be noted that since the reflection signal amplitude at the impedance change point is positively correlated with the electromagnetic wave velocity attenuation rate, the larger the reflection signal amplitude at the impedance change point, the larger the corresponding wave velocity attenuation weight, which means that the electromagnetic wave velocity at the corresponding waveguide rod position attenuates faster.

[0096] Further, based on the wave velocity attenuation weight, the electromagnetic wave velocity at each impedance change point is determined, specifically:

[0097] The calculation method of the electromagnetic wave velocity at each impedance change point is: ,in, , , They are , No. and The electromagnetic wave velocity at the impedance change point is is the speed of light in a vacuum, It is The wave velocity attenuation weight of each impedance change point, is the number of all impedance change points in the hanging signal segment, It is the sequence number corresponding to the impedance change points in the hanging signal segment arranged in time.

[0098] It should be noted that when When the electromagnetic wave speed It is an iterative calculation process. First, , and then use calculate , further use calculate , and so on, the electromagnetic wave velocity at each impedance change point is obtained.

[0099] It should be noted that the speed of light represents the velocity of the electromagnetic wave before entering the hanging position; the difference between the velocity of the electromagnetic wave before entering the hanging position and the velocity after passing the hanging position is the total decreasing speed of the electromagnetic wave in the hanging area; for each impedance change point, the electromagnetic wave decreases a part of its speed, and the decreasing speed is distributed according to the wave speed attenuation weight to obtain the electromagnetic wave velocity at each impedance change point; the obtained electromagnetic wave velocity is closer to the actual electromagnetic wave propagation situation, which helps to obtain more accurate liquid level measurement results.

[0100] Furthermore, the interpolation method is used to determine the electromagnetic wave velocity at the non-impedance change point of the hanging signal segment, and the velocity vector of the hanging area is obtained, which is specifically:

[0101] Construct a null vector with the same length as the length of the hanging signal segment; the first element of the null vector is the speed of light in a vacuum;

[0102] Fill the electromagnetic wave velocities of all impedance change points into the corresponding positions in the empty vector, and interpolate and fill the remaining positions in the empty vector to obtain the velocity vector of the hanging area;

[0103] It should be noted that, assuming The impedance change point is the first point in the hanging signal segment. elements, corresponding to the first positions, then the first The position is The electromagnetic wave velocity at the impedance change point is The electromagnetic wave velocity at each impedance change point is filled into the corresponding position in the empty vector.

[0104] Preferably, in this embodiment, a weighted average algorithm is used for interpolation, specifically: assuming that the first If the position is a non-impedance change point, then the first If there is no corresponding value at the position, the first The elements at position are: ,in, The first The elements at the positions, The first The position number of each position, is the distance from the left to the left in the empty vector The closest position corresponds to the electromagnetic wave speed, is the distance from the left to the left in the empty vector The position number corresponding to the electromagnetic wave velocity of the nearest position, is the distance from the right side of the empty vector The electromagnetic wave speed corresponding to the nearest position is is the distance from the right side of the empty vector It should be noted that, as other implementations, the implementer can use other methods of the prior art to perform interpolation filling, such as mean interpolation and cubic spline interpolation, and this embodiment does not impose any special restrictions on this.

[0105] It should be noted that, for ease of understanding, it is assumed that the length of the hanging signal segment is 7, and the number of all impedance change points is 3, which are respectively , , , filling it into an empty vector: ,but , and The electromagnetic wave velocity at the position is null, then The electromagnetic wave speeds at the closest positions on the left and right are and ,use and ,get Electromagnetic wave speed at position , then The electromagnetic wave speeds at the closest positions on the left and right are and ,get Electromagnetic wave speed at position , thus, all empty value positions are filled to obtain the velocity vector of the hanging area.

[0106] It should be noted that, taking the difference between the position numbers of the elements as the weight, the electromagnetic wave velocities corresponding to the positions of two elements with electromagnetic wave velocities that are close to each other are weighted averaged, the electromagnetic wave velocity of each element is calculated, and the velocity vector of the hanging area is obtained, which reflects the magnitude of the electromagnetic wave velocity at different times in the hanging area.

[0107] At this point, the velocity vector of the hanging area is obtained.

[0108] Step 4, based on the analysis of the distance error when the electromagnetic wave velocity corresponding to all elements in the hanging area velocity vector propagates in the hanging area signal segment and propagates in the hanging area signal segment at the speed of light, respectively, calculate the length of the hanging area and the error length of the hanging area; combine the distance from the guided wave radar to the liquid surface and the distance from the guided wave radar to the bottom of the liquid storage tank to determine the liquid level height of the liquid storage tank.

[0109] Based on the above analysis, the velocity vector of the hanging area reflects the wave velocity of the electromagnetic wave at different times in the hanging area. If all elements in the velocity vector are converted into a curve, the corresponding accumulation area under the curve is the length of the hanging area. Therefore, the length of the hanging area is:

[0110] The calculation formula for the length of the hanging area is: ,in, is the length of the hanging area, is the velocity vector in the hanging area elements, is the velocity vector in the hanging area elements, is the sampling period, It is the length of the hanging signal segment.

[0111] It should be noted that the sampling period is the interval time between any two adjacent elements in the hanging area velocity vector. Therefore, taking any two adjacent elements as the upper and lower bases of the trapezoid and the sampling period as the height, the area of ​​the trapezoid is calculated, which is approximately equivalent to finding the area under the curve between any two elements in the hanging area velocity vector; further, the area under the curve is accumulated and summed to obtain the area under the curve corresponding to the hanging area velocity vector, that is, the length of the hanging area.

[0112] Furthermore, without considering the decreasing velocity of electromagnetic waves in the hanging area, that is, the velocity of electromagnetic waves in the hanging area is always the speed of light c, then the calculated length of the hanging area has a certain error. Therefore, the error length of the hanging area is:

[0113] ,in, is the error length of the hanging area, is the speed of light in vacuum, is the sampling period, is the number of cycles that the electromagnetic wave passes through the hanging area, that is, the length of the hanging signal segment, where: Indicates the time it takes for electromagnetic waves to pass through the hanging area.

[0114] Further, based on the length of the material hanging area and the error length of the material hanging area, the liquid level height is determined, specifically:

[0115] The calculation method of liquid level is: ,in, is the liquid level height, is the distance from the guided wave radar level gauge to the bottom of the liquid storage tank, The distance from the guided wave radar to the liquid surface calculated for the guided wave radar level gauge. is the error length of the hanging area, is the length of the hanging area.

[0116] It should be noted that the error length of the hanging area minus the length of the hanging area is the error distance between the traditional guided wave radar level meter and the liquid surface calculated without considering the hanging of the waveguide rod. Subtracting the error distance indicates the actual distance from the guided wave radar level meter to the liquid surface; further, the overall height Subtracting the actual distance gives the liquid level height, thereby completing the automatic measurement of the liquid level in the liquid storage tank. The influence of the material hanging on the waveguide rod on the measurement error of the radar waveguide level meter is taken into account, and a more accurate waveguide calculation result is obtained.

[0117] The present application also provides a tank liquid level automatic metering device, comprising:

[0118] The signal acquisition module is used to obtain the echo signal of the guided wave radar level meter when measuring the liquid level of the liquid storage tank, and respectively obtain the distance from the guided wave radar to the liquid surface and the distance from the guided wave radar to the bottom of the liquid storage tank measured by the guided wave radar level meter;

[0119] The error measurement module divides the echo signal into multiple segmented signals; analyzes the change of signal amplitude and the degree of discreteness in each segmented signal to determine the hanging signal segment; obtains the impedance change point and its reflected signal amplitude of the hanging signal segment according to the distribution of the maximum value in the hanging signal segment and the degree of fluctuation change of the maximum value; determines the wave velocity attenuation weight of each impedance change point in the hanging signal segment according to the proportion of the reflected signal amplitude corresponding to each impedance change point in all impedance change points, and determines the electromagnetic wave velocity of each impedance change point in the hanging signal segment based on the wave velocity attenuation weight; constructs the hanging area velocity vector based on the electromagnetic wave velocity; calculates the hanging area length and the hanging area error length based on the analysis of the distance errors when the electromagnetic wave velocity corresponding to all elements in the hanging area velocity vector propagates in the hanging signal segment and propagates in the hanging signal segment at the speed of light;

[0120] The height correction module determines the liquid level height of the liquid storage tank by combining the distance from the guided wave radar to the liquid surface and the distance from the guided wave radar to the bottom of the liquid storage tank.

[0121] Furthermore, a block diagram of an automatic tank liquid level metering device provided in an embodiment of the present application is as follows: Figure 5 shown.

[0122] Based on the same inventive concept as the above method, an embodiment of the present application also provides a tank liquid level automatic measurement system, including a memory, a processor, and a computer program stored in the memory and running on the processor, and when the processor executes the computer program, the steps of any one of the above-mentioned tank liquid level automatic measurement methods are implemented.

[0123] It should be understood that although Figure 1 The steps in the flowchart are shown in sequence as indicated by the arrows, but these steps are not necessarily executed in the order indicated by the arrows. Unless otherwise specified in this document, there is no strict order restriction for the execution of these steps, and these steps can be executed in other orders. Moreover, Figure 1 At least part of the steps may include multiple sub-steps or multiple stages. These sub-steps or stages are not necessarily executed at the same time, but can be executed at different times. The execution order of these sub-steps or stages is not necessarily sequential, but can be executed in turn or alternately with other steps or at least part of the sub-steps or stages of other steps.

[0124] The technical features of the above embodiments may be arbitrarily combined. 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.

[0125] The above-mentioned 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 present application. It should be pointed out that, for those of ordinary skill in the art, several modifications and improvements can be made without departing from the concept of the present application. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present application without departing from the content of the technical solution of the present application, shall fall within the protection scope of the technical solution of the present application.

Claims

1. A method for automatic measurement of tank liquid level, characterized in that: The method comprises the following steps: Acquire the echo signal of the guided wave radar level meter when measuring the liquid level of the liquid storage tank, and respectively obtain the distance from the guided wave radar to the liquid surface and the distance from the guided wave radar to the bottom of the liquid storage tank measured by the guided wave radar level meter; The echo signal is divided into multiple segmented signals; the smoothness of the change of each segmented signal and the drastic degree of the change of the signal amplitude in the segmented signal are analyzed to determine the hanging material signal segment; according to the distribution of the maximum value in the hanging material signal segment and the degree of fluctuation of the maximum value, the impedance change point of the hanging material signal segment and its corresponding reflection signal amplitude are obtained; Determine the wave velocity attenuation weight of each impedance change point in the hanging material signal segment according to the proportion of the reflected signal amplitude corresponding to each impedance change point in all impedance change points; determine the electromagnetic wave velocity of each impedance change point in the hanging material signal segment based on the wave velocity attenuation weight; Based on the electromagnetic wave velocity, a velocity vector of the hanging area is constructed; the distance error when the electromagnetic wave velocity corresponding to all elements in the hanging area velocity vector is propagated in the hanging signal segment and when it is propagated in the hanging signal segment at the speed of light is analyzed, and the hanging area length and the hanging area error length are calculated respectively. Combined with the distance from the guided wave radar to the liquid surface and the distance from the guided wave radar to the bottom of the liquid storage tank, the liquid level height of the liquid storage tank is determined.

2. A method for automatic tank liquid level measurement as claimed in claim 1, characterized in that: The step of determining the hanging material signal segment comprises: Calculate the discrete degree of the signal amplitude at all times in each segmented signal; record the segmented signal with a discrete degree greater than a preset threshold as an echo signal segment, otherwise, record it as a stable signal segment; The maximum signal amplitude in each echo signal segment and the time corresponding to the maximum signal amplitude are respectively used as the reflection amplitude and reflection time of each echo signal segment; The echo signal segment with the largest reflection amplitude among all echo signal segments is recorded as the liquid level signal segment; based on the reflection time of the liquid level signal segment, the signal on the left side of the reflection time is intercepted and recorded as the hanging material signal segment.

3. A method for automatic tank liquid level measurement as claimed in claim 2, characterized in that: The step of obtaining the impedance change point of the hanging material signal segment and the corresponding reflected signal amplitude includes: Obtain all the maximum values ​​of the hanging material signal segment; record the moment corresponding to each maximum value as the impedance change point; Taking the mean of the signal amplitudes at all times in all the stable signal segments as the DC component amplitude; The difference between the maximum value corresponding to each impedance change point and the DC component amplitude is used as the reflection signal amplitude of each impedance change point.

4. The method for automatic tank liquid level measurement according to claim 1, characterized in that: The step of determining the wave velocity attenuation weight of each impedance change point in the hanging material signal segment includes: The sum of the reflected signal amplitudes of all impedance change points in the hanging material signal segment is recorded as the first sum; The ratio of the reflected signal amplitude at each impedance change point to the first sum value is used as the wave velocity attenuation weight at each impedance change point in the hanging material signal segment.

5. The method for automatic tank liquid level measurement according to claim 1, characterized in that: The electromagnetic wave velocity at each impedance change point is calculated as follows: ,in, , , Respectively , No. and The electromagnetic wave velocity at the impedance change point is is the speed of light in a vacuum, It is The wave velocity attenuation weight of each impedance change point, is the number of all impedance change points in the hanging signal segment, is the sequence number corresponding to the impedance change point in the hanging signal segment arranged in time; among them, , For the The relative dielectric constant of the impedance change point is For the The relative permeability of the impedance change point.

6. The method for automatic tank liquid level measurement according to claim 1, characterized in that: The constructing of the speed vector of the hanging area includes: Construct a null vector with the same length as the length of the hanging signal segment; the first element of the null vector is the speed of light in a vacuum; The electromagnetic wave velocities of all impedance change points in the hanging material signal segment are filled into the corresponding positions in the empty vector, and the remaining positions in the empty vector are interpolated and filled to obtain the hanging material area velocity vector.

7. The method for automatic tank liquid level measurement according to claim 1, characterized in that: The calculating of the length of the hanging area and the error length of the hanging area includes: The length of the hanging area is calculated as follows: ,in, is the length of the hanging area, is the velocity vector in the hanging area elements, is the velocity vector in the hanging area elements, is the sampling period, is the length of the hanging signal segment; The error length of the hanging area is calculated by the formula: ,in, is the error length of the hanging area, is the speed of light in a vacuum.

8. The method for automatic tank liquid level measurement according to claim 1, characterized in that: The liquid level height is calculated as follows: ,in, is the liquid level height, is the distance from the guided wave radar to the bottom of the liquid storage tank, is the distance from the guided wave radar to the liquid surface, is the error length of the hanging area, is the length of the hanging area.

9. An automatic tank liquid level metering device, characterized in that: The device comprises: The signal acquisition module is used to obtain the echo signal of the guided wave radar level meter when measuring the liquid level of the liquid storage tank, and respectively obtain the distance from the guided wave radar to the liquid surface and the distance from the guided wave radar to the bottom of the liquid storage tank measured by the guided wave radar level meter; The error measurement module divides the echo signal into multiple segmented signals; analyzes the change of signal amplitude and the degree of discreteness in each segmented signal to determine the hanging signal segment; obtains the impedance change point and its reflected signal amplitude of the hanging signal segment according to the distribution of the maximum value in the hanging signal segment and the degree of fluctuation change of the maximum value; determines the wave velocity attenuation weight of each impedance change point in the hanging signal segment according to the proportion of the reflected signal amplitude corresponding to each impedance change point in all impedance change points, and determines the electromagnetic wave velocity of each impedance change point in the hanging signal segment based on the wave velocity attenuation weight; constructs the hanging area velocity vector based on the electromagnetic wave velocity; calculates the hanging area length and the hanging area error length based on the analysis of the distance errors when the electromagnetic wave velocity corresponding to all elements in the hanging area velocity vector propagates in the hanging signal segment and propagates in the hanging signal segment at the speed of light; The height correction module determines the liquid level height of the liquid storage tank by combining the distance from the guided wave radar to the liquid surface and the distance from the guided wave radar to the bottom of the liquid storage tank.

10. A tank liquid level automatic measurement system, comprising a memory, a processor, and a computer program stored in the memory and running on the processor, characterized in that: When the processor executes the computer program, the steps of the method for automatic measurement of the liquid level of a storage tank as described in any one of claims 1-8 are implemented.

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