Glass plate liquid level gauge and liquid level measurement method

Abstract

The present invention discloses a glass plate liquid level gauge and a liquid level measurement method. The glass plate liquid level gauge is provided with a front glass plate (1), a rear glass plate (2), a front pressure cover (7), a rear pressure cover (10), a front clamping frame (6), and a rear clamping frame (11). The front pressure cover is provided with a guide hole (3), and the rear pressure cover is provided with an observation hole (12). The front glass plate, the rear glass plate, the front clamping frame, and the rear clamping frame enclose a measuring cavity (5). A front plano-convex cylindrical lens (8) is provided on the front glass plate, and a rear plano-convex cylindrical lens (9) is provided on the rear glass plate. The cylindrical surface of the front plano-convex cylindrical lens and the cylindrical surface of the rear plano-convex cylindrical lens are adjacent to the measuring cavity. A light absorbing layer (13) is provided on the surface adjacent to the measuring cavity of the front clamping frame and the surface adjacent to the measuring cavity of the rear clamping frame. The present invention discloses a method for liquid level measurement using the above-mentioned glass plate liquid level gauge. The present invention can be used in multiple industries such as petrochemical industry, metallurgy, electric power, and medicine to measure the liquid level of transparent liquids.

Description

Technical Field

[0001] The invention belongs to the technical field of liquid level measurement and relates to a glass plate liquid level gauge and a liquid level measurement method. Background Art

[0002] Glass plate level gauges are used to display liquid levels on equipment in the plant areas of petrochemical refineries. Translucent glass plate level gauges are the most commonly used type. When the measured medium is a transparent liquid and light passes through the liquid column, the light is reflected, refracted, or absorbed, and the intensity of the light passing through the liquid column is weaker than the light passing through the gas phase above the liquid column. Operators rely on the difference in light intensity between the liquid column and the gas phase to determine the liquid level. At a slightly greater distance, or on cloudy days or at night when light is dim, the difference in light intensity is minimal, making it difficult to determine the liquid level. Over time, the inner surface of a glass plate level gauge becomes dirty, weakening the intensity of light passing through it and making it difficult to determine the liquid level. Operators sometimes even need to close the root valve in front of the glass plate level gauge to cause the liquid level to fluctuate noticeably before they can clearly see the liquid level.

[0003] When the liquid medium is a colored transparent medium, the liquid level can be determined by the color difference between the medium and the gas phase above the liquid column. However, most colored oil media tend to stick to the wall, making it difficult to determine the liquid level.

[0004] Improving the visual sensitivity of glass plate level gauges is one solution. A common approach is to use red-green color difference to distinguish liquid levels. This approach leverages the principle of total internal reflection and the different refractive indices of the liquid column and the gas phase above it relative to the glass, causing the liquid column and the gas phase to respectively reflect the red and green colors of the glass filter in the background. However, this method only works against bright backgrounds. Against dim or weak backgrounds, the red and green colors are less noticeable, and the light absorption by the filter further reduces light intensity. Observation is also less effective on cloudy days or at night.

[0005] Some glass plate level gauges, particularly boiler water level gauges, use a dedicated external light source, forcing increased background light intensity. These gauges, independent of natural light and factory lighting, are bulky. Explosion-proof lamps and housings must be installed behind the glass, leading to high costs. The need for 220V AC power also requires explosion-proof design considerations, and cabling is also a significant construction effort. Explosion-proof lamps also have a limited lifespan. Running them 24 / 7 increases the risk of failure and requires frequent maintenance. The explosion-proof housing also presents safety risks. Summary of the Invention

[0006] The object of the present invention is to provide a glass plate liquid level gauge and a liquid level measurement method, so as to solve the problems of the existing glass plate liquid level gauges, such as difficulty in seeing the liquid level clearly and the need for an external light source.

[0007] In order to solve the above problems, the technical solution adopted by the present invention is: a glass plate liquid level gauge, provided with a front glass plate, a rear glass plate, a front pressure cover, a rear pressure cover, a front clamping frame, and a rear clamping frame, the front pressure cover is provided with a guide hole, and the rear pressure cover is provided with an observation hole, the guide hole is opposite to the front glass plate, and the observation hole is opposite to the rear glass plate, the front glass plate, the rear glass plate, the front clamping frame and the rear clamping frame surround a measuring cavity, which is characterized in that: a front plano-convex cylindrical lens is vertically provided on the surface of the front glass plate adjacent to the measuring cavity, a rear plano-convex cylindrical lens is vertically provided on the surface of the rear glass plate adjacent to the measuring cavity, the cylindrical surfaces of the front plano-convex cylindrical lens and the rear plano-convex cylindrical lens are adjacent to the measuring cavity, and a light-absorbing layer is provided on the surface of the front clamping frame adjacent to the measuring cavity and the surface of the rear clamping frame adjacent to the measuring cavity.

[0008] The method for measuring liquid level using the above-mentioned glass plate liquid level gauge is a symmetrical structure, characterized in that: light from the outside of the glass plate liquid level gauge enters and passes through the front glass plate through the guide hole, then enters and passes through the front plano-convex cylindrical lens, and then is emitted from the cylindrical surface of the front plano-convex cylindrical lens and enters the measuring cavity. The lower part of the measuring cavity is a liquid column and the upper part is a gas phase. When the light enters the liquid column, a first light beam is formed, and when it enters the gas phase, a second light beam is formed. On a horizontal plane passing through the liquid column, the first light beam passes through the liquid column and converges at the focus of the front plano-convex cylindrical lens in the liquid column. Then, the first light beam enters the rear plano-convex cylindrical lens from the cylindrical surface of the rear plano-convex cylindrical lens and passes through the rear plano-convex cylindrical lens, then enters and passes through the rear glass plate, and then is emitted through the observation hole. At the exit of the observation hole, the human eye can see the vertical light beam formed by the first light beam facing the direction of the first light beam, thereby measuring the liquid level of the liquid column in the measuring cavity.

[0009] The present invention has the following beneficial effects: 1. The vertical light column formed by the first light beam seen by the human eye is relatively bright, and the gray background above it is clearly distinguishable. Therefore, the liquid level of the liquid column in the measuring chamber can be easily measured, thereby measuring the liquid level in the process equipment. 2. The present invention uses natural light and factory lighting, and does not require a dedicated external explosion-proof light source, which is safe and energy-saving. 3. The glass plate liquid level gauge of the present invention has a relatively simple structure and is easy to manufacture. The required effects and functions are achieved by optical path calculation. 4. The present invention does not add a filter when using natural light and factory lighting, and does not perform any attenuation treatment on the light, thereby retaining the original light intensity to the maximum extent. 5. The present invention does not have high requirements for light intensity. The higher the intensity, the clearer the resolution. When the light intensity is low, the liquid level is also easy to identify because the light intensity difference between the vertical light column formed by the first light beam and the gray background above it is obvious. 6. The glass plate liquid level gauge of the present invention can be designed into a symmetrical structure for two-way observation. 7. The glass plate level gauge of the present invention has low manufacturing requirements and high fault tolerance. The existence of some dimensional errors will not affect the use function of the glass plate level gauge.

[0010] The present invention can be used in various industries such as petrochemical industry, metallurgy, electric power, food and medicine to measure the level of transparent liquids. The transparent liquids can be colorless or colored transparent liquids.

[0011] The present invention will be further described in detail below with reference to the accompanying drawings, specific implementation methods and examples, which do not limit the scope of protection claimed in the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a cross-sectional view (partial) of the glass plate level gauge of the present invention passing through the measuring cavity in the vertical direction.

[0013] Figure 2 yes Figure 1 T-T section view in.

[0014] Figure 3 It is a partial schematic diagram of the vertical light column formed by the first light seen by the human eye, the dark background above it, and the shading area.

[0015] Figure 4 The optical principle diagram of liquid level measurement using the glass plate liquid level meter of the present invention is shown.

[0016] Figure 5 This is a schematic diagram showing the principle of calculating the focal length of a front plano-convex cylindrical lens in the gas phase within the measurement cavity.

[0017] Figures 1 to 5 In the figure, the same reference numerals represent the same technical features. Reference numerals indicate: 1—front glass plate; 2—rear glass plate; 3—guide hole; 4—bolt and nut; 5—measuring cavity; 6—front clamping frame; 7—front pressure cover; 8—front plano-convex cylindrical lens; 9—rear plano-convex cylindrical lens; 10—rear pressure cover; 11—rear clamping frame; 12—observation hole; 13—light-absorbing layer; 14—sealing gasket; 15—light-shielding area; 16—liquid column in measuring cavity 5; 17—first light beam; 18—second light beam; 19—vertical light column formed by first light beam 17; 20—dark background above vertical light column 19 formed by first light beam 17; 21—first symmetry plane of the glass plate level gauge; 22—second symmetry plane of the glass plate level gauge.

[0018] A—edge point of the front plano-convex cylindrical lens 8; ∠a—incident angle of the external light at point A; B—intersection of the tangent line of the cylindrical surface of the front plano-convex cylindrical lens 8 at point A and the optical axis OF; ∠b—exit angle of the second light 18 at point A; C—optical center of the front plano-convex cylindrical lens 8; d—thickness of the front plano-convex cylindrical lens 8; E—position of the external incident light; F—focus of the front plano-convex cylindrical lens 8 in the gas phase in the measurement cavity 5; G—intersection of the NF extension line and AC; H—second light 18 from point A through The point where the focal point F is projected onto the light-absorbing layer 13; h—the half-width of the front plano-convex cylindrical lens 8; K—the optical center of the rear plano-convex cylindrical lens 9; L—the length of the measuring cavity 5; M—the focus of the front plano-convex cylindrical lens 8 in the liquid column 16 in the measuring cavity 5; N—the edge point of the rear plano-convex cylindrical lens 9; O—the center of the cylinder of the front plano-convex cylindrical lens 8; r—the radius of the cylinder of the front plano-convex cylindrical lens 8; s—the half-width of the shading area 15; u—the width of the guide hole 3; v—the width of the observation hole 12; w—the width of the measuring cavity 5. DETAILED DESCRIPTION

[0019] See also Figure 1 and Figure 2 The glass plate level gauge of the present invention is provided with a front glass plate 1, a rear glass plate 2, a front pressure cover 7, a rear pressure cover 10 and a main body, and the main body is provided with a front clamping frame 6 and a rear clamping frame 11. The front glass plate 1, the rear glass plate 2, the front pressure cover 7, the rear pressure cover 10, the front clamping frame 6 and the rear clamping frame 11 are all arranged vertically. The front pressure cover 7 and the rear pressure cover 10 are connected with bolts and nuts 4. One vertical side of the front glass plate 1 is clamped between the front pressure cover 7 and the front clamping frame 6, and the other vertical side of the front glass plate 1 is clamped between the front pressure cover 7 and the rear clamping frame 11; one vertical side of the rear glass plate 2 is clamped between the rear pressure cover 10 and the front clamping frame 6, and the other vertical side of the rear glass plate 2 is clamped between the rear pressure cover 10 and the rear clamping frame 11; a sealing gasket 14 is provided at each clamping position.

[0020] A guide hole 3 is provided on the front pressure cover 7, and an observation hole 12 is provided on the rear pressure cover 10. The guide hole 3 is opposite to the front glass plate 1, and the observation hole 12 is opposite to the rear glass plate 2. Both the guide hole 3 and the observation hole 12 are vertical long strip holes, and multiple holes are provided. The guide holes 3 are aligned in a row in the vertical direction, and the observation holes 12 are aligned in a row in the vertical direction. Each guide hole 3 and observation hole 12 has two side surfaces, a top surface, and a bottom surface; the side surfaces are arranged vertically, and the top and bottom surfaces are arranged horizontally. The two side surfaces of the guide hole 3 are parallel to each other, and the two side surfaces of the observation hole 12 are parallel to each other.

[0021] The front glass plate 1, rear glass plate 2, front clamping frame 6, and rear clamping frame 11 enclose a measuring cavity 5, which is rectangular in shape when viewed in horizontal section (without the front plano-convex cylindrical lens 8 and rear plano-convex cylindrical lens 9). Both the front glass plate 1 and rear glass plate 2 are cuboid in shape and are arranged vertically. The glass plate level gauge of the present invention generally has a symmetrical structure. A vertical plane passing through the midpoints of the two long sides of the rectangle of the measuring cavity 5 when viewed in horizontal section defines the first symmetry plane 21 of the glass plate level gauge, while a vertical plane passing through the midpoints of the two short sides of the rectangle defines the second symmetry plane 22 of the glass plate level gauge. The areas between the front and rear glass plates 1 and 2, between the front and rear glands 7 and 10, between the guide hole 3 and the observation hole 12, between the two parts of the front clamping frame 6 on either side of the first symmetry plane 21 of the glass plate level gauge, between the two parts of the rear clamping frame 11 on either side of the first symmetry plane 21 of the glass plate level gauge, and between the front and rear plano-convex cylindrical lenses 8 and 9 described below are all symmetrical with respect to the first symmetry plane 21 of the glass plate level gauge. The areas between the front and rear clamping frames 6 and 11, as well as between the two parts of any of the aforementioned components on either side of the second symmetry plane 22 of the glass plate level gauge, are all symmetrical with respect to the second symmetry plane 22 of the glass plate level gauge.

[0022] Measuring chamber 5 is sealed, with its top and bottom connected to the process equipment (not shown) where the liquid level needs to be measured via pipes. Liquid in the process equipment enters the bottom of measuring chamber 5 through the pipes and rises until the liquid level in measuring chamber 5 equals the level in the process equipment.

[0023] A front plano-convex cylindrical lens 8 is vertically provided on the surface of the front glass plate 1 adjacent to the measuring cavity 5, and a rear plano-convex cylindrical lens 9 is vertically provided on the surface of the rear glass plate 2 adjacent to the measuring cavity 5. The front glass plate 1 and the front plano-convex cylindrical lens 8 are an integral structure and are polished as a whole. The rear glass plate 2 and the rear plano-convex cylindrical lens 9 are an integral structure and are polished as a whole. The cylindrical surfaces (part of the cylindrical surfaces) of the front plano-convex cylindrical lens 8 and the rear plano-convex cylindrical lens 9 are adjacent to the measuring cavity 5. The planes of the front plano-convex cylindrical lens 8 and the rear plano-convex cylindrical lens 9 described in the present invention are the planes that these two lenses have when they exist alone; when these two lenses are an integral structure with the front glass plate 1 and the rear glass plate 2 respectively, the planes are only imaginary planes. The vertical edges of the front plano-convex cylindrical lens 8 and the vertical edges of the rear plano-convex cylindrical lens 9 are aligned with the edges of the measuring cavity 5 (including the sealing gasket 14), as shown in FIG. Figure 4 shown.

[0024] The guide hole 3, the front plano-convex cylindrical lens 8, the measuring cavity 5, the rear plano-convex cylindrical lens 9 and the observation hole 12 are aligned with each other, as shown in FIG. Figure 2 shown.

[0025] A light absorbing layer 13 is provided on the surface of the front clamping frame 6 adjacent to the measuring cavity 5 and on the surface of the rear clamping frame 11 adjacent to the measuring cavity 5. The light absorbing layer 13 can be a coarse sand polishing layer, a sintered carbon deposition layer or a black light absorbing paint layer.

[0026] The width u of the guide hole 3, the width v of the observation hole 12, the width w of the measurement cavity 5, the width 2h of the front plano-convex cylindrical lens 8, and the width 2h of the rear plano-convex cylindrical lens 9 are generally the same, all ranging from 15 to 30 mm. The front and rear glass plates 1 and 2 are generally made of quartz glass. The thickness t of the front and rear glass plates 1 and 2 is generally 15 to 30 mm, primarily determined by the pressures of the liquid column 16 and the gas phase within the measurement cavity 5.

[0027] The front clamping frame 6, the rear clamping frame 11, the front gland 7, and the rear gland 10 can be made of carbon steel or stainless steel, etc., depending on the corrosiveness of the liquid column 16 and the gas phase in the measuring chamber 5. The sealing gasket 14 is made of an elastic corrosion-resistant material.

[0028] In the case of a symmetrical structure of the glass plate liquid level gauge, the front plano-convex cylindrical lens 8 and the rear plano-convex cylindrical lens 9 have the same shape, size, and material. On the same horizontal plane, the distance (KC length) between the optical centers of the front plano-convex cylindrical lens 8 and the rear plano-convex cylindrical lens 9 is twice the focal length of the front plano-convex cylindrical lens 8 in the liquid column 16 in the measuring chamber 5, that is, KC = 2MC (according to the principle of reversible optical path, the focal length of the rear plano-convex cylindrical lens 9 in the liquid column 16 in the measuring chamber 5 is also M). Figure 4 、 Figure 5 、 Figure 2 as well as Figure 1 and Figure 3 , explaining the method of using this glass plate level gauge to measure the liquid level. Light from outside the glass plate level gauge (referred to as external light) enters and passes through the front glass plate 1 through the guide hole 3, then enters and passes through the front plano-convex cylindrical lens 8, and then is emitted from the cylindrical surface of the front plano-convex cylindrical lens 8 and enters the measuring cavity 5. The lower part of the measuring cavity 5 is the liquid column 16, and the upper part is the gas phase. The refractive index of the gas phase is different from that of the liquid phase in the liquid column 16. When the light enters the liquid column 16, it forms the first light 17 (as shown in FIG. Figure 4 ), and forms a second light 18 (as shown in the thick solid line in FIG) when entering the gas phase. Figure 4As shown by the dotted line in the figure). The first light ray 17 is the main light ray, which is located below the second light ray 18. Both the first light ray 17 and the second light ray 18 are in the form of planes perpendicular to the horizontal plane. On a horizontal plane passing through the liquid column 16, the first light ray 17 passes through the liquid column 16, is converged at the focus M in the liquid column 16 in the measuring chamber 5 by the front plano-convex cylindrical lens 8, and then enters the rear plano-convex cylindrical lens 9 from the cylindrical surface of the rear plano-convex cylindrical lens 9 and passes through the rear plano-convex cylindrical lens 9, and then enters and passes through the rear glass plate 2. Finally, the first light ray 17 is emitted through the observation hole 12, and the light intensity remains basically unchanged except for a small amount of absorption by the liquid phase medium in the liquid column 16. At the exit of the observation hole 12 (corresponding to the lower part of the observation hole 12), the human eye can see the vertical light column 19 formed by the first light ray 17 facing the direction of the light of the first light ray 17, thereby measuring the liquid level of the liquid column 16 in the measuring chamber 5, see Figure 3 .

[0029] On a horizontal plane passing through the gas phase above the liquid column 16 in the measuring chamber 5, the second light 18 passes through the gas phase above the liquid column 16 and converges at the focal point F in the gas phase in the measuring chamber 5 at the front plano-convex cylindrical lens 8. Because the refractive index of the liquid is quite different from that of the gas, FC is much smaller than MC. According to the optical principle of the plano-convex cylindrical lens, most of the second light 18 converged at the focal point F (about 85% to 95% when the shading area 15 is not set) is incident on the light-absorbing layer 13, diffusely reflected or absorbed by the light-absorbing layer 13, and is difficult to enter the rear plano-convex cylindrical lens 9, the rear glass plate 2 and the observation hole 12. Therefore, the background 20 above the vertical light column 19 formed by the first light 17 observed at the exit of the observation hole 12 is gray. The bright vertical light column 19 is in sharp contrast to the gray background 20 and is easy to observe, see. Figure 3 The top of the vertical light column 19 is the liquid level of the liquid column 16 .

[0030] The light outside the glass plate level gauge is natural light (generally daytime sunlight) and factory lighting (nighttime lighting). The liquid phase in the liquid column 16 is a transparent liquid. The transparent liquid can be colorless (such as water, methanol, or ethanol) or colored (such as gasoline). The gas phase above the liquid column 16 is air and / or gas volatilized from the liquid phase in the liquid column 16.

[0031] In the accompanying drawings, the meanings of various letters refer to the description of the accompanying drawings. Figure 4 and Figure 5Regarding the letters in the figure, it is necessary to explain that the optical center C of the front plano-convex cylindrical lens 8 is a point on a horizontal plane, and the optical centers C on different horizontal planes are located on a vertical line. The focus F of the front plano-convex cylindrical lens 8 in the gas phase in the measuring chamber 5 is a focus on a horizontal plane, and the focus F on different horizontal planes is located on a vertical line. The focus M of the front plano-convex cylindrical lens 8 in the liquid column in the measuring chamber 5 is a focus on a horizontal plane, and the focus M on different horizontal planes is located on a vertical line. The optical center K of the rear plano-convex cylindrical lens 9 is a point on a horizontal plane, and the optical centers K on different horizontal planes are located on a vertical line. The center O of the cylindrical surface of the front plano-convex cylindrical lens 8 is the center of a circle on a horizontal plane, and the center O on different horizontal planes is located on a vertical line. The situations of other letters A, B, E, G, H, and N are similar, and their explanation is omitted. The present invention chooses to describe and calculate the light propagation path through the horizontal planes of the liquid column 16 and the gas phase in the measuring chamber 5. For a selected horizontal plane, the letters and their connections, as well as various angles, distances, and lines of light, are all located on that selected horizontal plane. The same letters used on different horizontal planes may be displayed on the same drawing, but in reality they are located on different horizontal planes. This can be determined based on the description of the present invention and common knowledge in the art. Furthermore, for the sake of clarity, the drawings are not drawn to exact scale.

[0032] See also Figure 4 Connect edge point N of rear plano-convex cylindrical lens 9 to focal point F, then extend NF so that it intersects AC at intersection point G. The distance from intersection point G to C is s. On the plane of front plano-convex cylindrical lens 8, within a width s on each side of the second symmetry plane 22 of the glass plate liquid level gauge, external light entering from the sight hole 3 and front glass plate 1 can pass through front plano-convex cylindrical lens 8 and focal point F, and as part of second light 18, pass through rear plano-convex cylindrical lens 9 and rear glass plate 2, and emerge from observation hole 12. This increases the brightness of the dark background 20 above vertical light column 19 formed by first light 17, reducing the brightness contrast with vertical light column 19, and affecting the observation effect. To address this issue, a light-shielding area 15 can be vertically provided on the surface of front glass plate 1 adjacent to sight hole 3. Light-shielding area 15 faces the center of the plane width of front plano-convex cylindrical lens 8, and its vertical height is substantially the same as that of front plano-convex cylindrical lens 8. In the vertical direction, the midpoints of the upper and lower edges of the shading area 15 are both located on the second symmetry plane 22 of the glass plate level gauge. The half-width of the shading area 15 is s (half-width is half of the width), and the width is 2s. Figure 4The optical center of rear plano-convex cylindrical lens 9 is K. According to the principle of similar triangles, triangles FNK and FGC are similar triangles, and s / h = FC / (2×MC-FC). Given h, MC, and FC, s and s / h can be calculated. Based on s / h, the percentage of the area of shading region 15 to the plane of front plano-convex cylindrical lens 8 can be calculated, which is typically 5% to 15%. The plane of shading region 15 and front plano-convex cylindrical lens 8 can be rectangular, in which case s is also typically 5% to 15% of h.

[0033] After the shading area 15 is provided, light incident upon the shading area 15 can be partially or completely blocked. Because the shading area accounts for a small proportion of the total light-collecting area (i.e., the area of the plane of the front plano-convex cylindrical lens 8), based on the optical properties of the plano-convex cylindrical lens, the provision of the shading area 15 does not significantly affect the brightness of the vertical light column 19 formed by the first light 17, reducing it by only a few to a dozen percent. However, after the shading area 15 is provided, almost all of the second light 18 converging at the focal point F is incident upon the light-absorbing layer 13, with virtually no second light 18 escaping from the observation aperture 12. This makes the gray background 20 above the vertical light column 19 formed by the first light 17 even darker, creating a greater and more striking brightness contrast with the vertical light column 19, thereby facilitating observation of the vertical light column 19.

[0034] The light-shielding area 15 is generally a frosted area, a painted area, or an area where an opaque colored tape is pasted on the surface of the front glass plate 1 adjacent to the guide hole 3 .

[0035] When the glass plate level gauge of the present invention has a symmetrical structure, based on the principle of reversible optical paths, the guide hole 3 and the observation hole 12 can be used interchangeably, that is, the guide hole 3 can serve as the observation hole 12, and the observation hole 12 can serve as the guide hole 3. This allows observation from another location when observation is inconvenient at one location. In this case, a light-shielding area 15 is also provided on the surface of the rear glass plate 2 adjacent to the observation hole 12, symmetrically with the light-shielding area 15 provided on the surface of the front glass plate 1 relative to the first symmetry plane 21 of the glass plate level gauge.

[0036] The present invention has a certain degree of tolerance for the length L of the measurement cavity 5 (including the thickness of the sealing gasket 14). If there is an error in the length L of the measurement cavity 5, resulting in the KC length not being exactly 2 times MC, no measurement function is affected; it only causes the vertical light column 19 formed by the first light beam 17 to dim or narrow. When the KC length is exactly 2 times MC, the vertical light column 19 has the highest light intensity and is the widest.

[0037] Example

[0038] Use the glass plate level gauge of the present invention to measure the liquid level, see Figures 1 to 5. The measurement is carried out during the day, and the light outside the glass plate level gauge is natural light. The glass plate level gauge has a symmetrical structure, and the front plano-convex cylindrical lens 8 and the rear plano-convex cylindrical lens 9 have the same shape and size. The liquid column 16 at the bottom of the measuring cavity 5 is a water column, and the refractive index of water is 1.333; the measuring cavity 5 above the liquid column 16 is filled with air, and the refractive index of air is 1.00029. The refractive indices mentioned in the present invention that are not specified are all refractive indices relative to vacuum. The materials of the front glass plate 1, the rear glass plate 2, the front plano-convex cylindrical lens 8 and the rear plano-convex cylindrical lens 9 are all quartz glass with a refractive index of 1.55.

[0039] The principle diagram for calculating the focal length of the front plano-convex cylindrical lens 8 in the gas phase of the measurement cavity 5 is shown in FIG. Figure 5 . Figure 5 In the figure, the cross-section of the front plano-convex cylindrical lens 8, the letters and the quantities they represent, and the second light ray 18 are all displayed on a horizontal projection plane passing through the gas phase above the liquid column 16 in the measuring chamber 5. To simplify calculations, all calculations and principle descriptions are based on this projection plane. Light from outside the glass plate level gauge enters the edge point A of the front plano-convex cylindrical lens 8 from the air and the external incident light position E. O is the center of the cylinder of the front plano-convex cylindrical lens 8, F is the focus of the front plano-convex cylindrical lens 8 in the gas phase in the measuring chamber 5, then OF is the optical axis, and OA is the normal. The intersection of the tangent line at point A and the optical axis OF is B. The half-width of the front plano-convex cylindrical lens 8 is h, the radius of the cylinder is r, the thickness is d, and the optical center is C. When EA is incident parallel to OB, the outgoing light from point A (belonging to the second light ray 18) will intersect the optical axis at the focus F and pass through the focus F to hit point H on the light-absorbing layer 13.

[0040] The functional relationship between the focal length FC of the front plano-convex cylindrical lens 8 in the gas phase and the thickness d and half-width h of the front plano-convex cylindrical lens 8 is derived as follows:

[0041] 1. Calculate the radius r of the cylindrical surface of the front plano-convex cylindrical lens 8:

[0042] According to the Pythagorean theorem, r 2 =h 2 +(rd) 2 ,r=(h 2 +d 2 ) / 2d;

[0043] 2. Assume that the angle of incidence of the second light 18 at point A is ∠b, and the angle of incidence of the external light at point A is ∠a.

[0044] ∠a and ∠AOB are alternate interior angles, ∠a=∠AOB, sin∠AOB=h / r, sin∠a=h / r;

[0045] 3. Let n be the relative refractive index. Here n is the refractive index of quartz glass relative to air, and the sine value of the incident angle ∠b is sin∠b.

[0046] sin∠b=(sin∠a) / n=(h / r) / n=(h×n) / r,

[0047] ∠b=arcsin[(h×n) / r];

[0048] ∠AFO=180°-∠OAF-∠AOF=∠b-∠AOB=arcsin[(h×n) / r]-arcsin(h / r), tan∠AFO=tan{arcsin[(h× n) / r]-arcsin(h / r)}=AC / FC=h / FC, focal length FC=h / tan∠AFO=h / tan{arcsin[(h×n) / r]-arcsin(h / r)}

[0049] When d=3 mm, h=10 mm, n=1.55 / 1.00029≈1.55, and the focal length FC of the front plano-convex cylindrical lens 8 in the gas phase can be calculated to be 21.3 mm.

[0050] When calculating the focal length MC of the front plano-convex cylindrical lens 8 in the liquid column 16, the relative refractive index n is taken as the refractive index of quartz glass relative to water = 1.55 / 1.333 = 1.16. Figure 4 、 Figure 5 , it can be obtained that the focal length MC of the front plano-convex cylindrical lens 8 in the liquid column 16 is 89.2 mm.

[0051] Referring to the above method, the focal lengths of rear plano-convex cylindrical lens 9 in the gas phase and liquid column 16 can be calculated; the following description is omitted. If rear plano-convex cylindrical lens 9 and front plano-convex cylindrical lens 8 have the same shape, size, and material, the focal lengths of rear plano-convex cylindrical lens 9 in the gas phase and liquid column 16 are the same as those of front plano-convex cylindrical lens 8, respectively. Therefore, the aforementioned focal length of rear plano-convex cylindrical lens 9 need not be calculated; the aforementioned focal length of front plano-convex cylindrical lens 8 can be directly used.

[0052] The distance between the optical centers of the front plano-convex cylindrical lens 8 and the rear plano-convex cylindrical lens 9 is 2 times MC.

[0053] The front glass panel 1 is provided with a light-shielding area 15. Substituting the above FC and MC into s / h = FC / (2×MC-FC), we obtain s / h = 13.6%, indicating that the area of the light-shielding area 15 accounts for only 13.6% of the total light-receiving area. A similar light-shielding area 15 is also provided on the rear glass panel 2.

[0054] The methods described in the embodiments can be used to perform relevant calculations when the dimensions of various components, and the liquid and gas phases within the measurement chamber 5, change. The general process is as follows: Based on the refractive index of the gas phase within the measurement chamber 5, the refractive index of the liquid medium in the liquid column 16, the refractive index of the glass material of the front glass plate 1 and the front plano-convex cylindrical lens 8, and the half-width h and thickness d of the front plano-convex cylindrical lens 8, the focal length of the front plano-convex cylindrical lens 8 in the gas phase and liquid column 16 within the measurement chamber 5 is calculated. Subsequently, the focal length of the rear plano-convex cylindrical lens 9 in the gas phase and liquid column 16 within the measurement chamber 5 is obtained. By strictly following the calculation results of the method of the present invention, the dimensions of the various components of the glass plate liquid level gauge of the present invention are determined so that the focal points of the front plano-convex cylindrical lens 8 and the rear plano-convex cylindrical lens 9 in the liquid column 16 within the measurement chamber 5 are located on the first symmetry plane 21 of the glass plate liquid level gauge, thereby achieving optimal liquid level measurement results.

Claims

1. A glass plate level gauge, comprising a front glass plate (1), a rear glass plate (2), a front gland (7), a rear gland (10), a front clamping frame (6), and a rear clamping frame (11), wherein the front gland (7) is provided with a guide hole (3), the rear gland (10) is provided with an observation hole (12), the guide hole (3) is opposite to the front glass plate (1), the observation hole (12) is opposite to the rear glass plate (2), the front glass plate (1), the rear glass plate (2), the front clamping frame (6), and the rear clamping frame (11) enclose a measuring cavity (5), characterized in that: A front plano-convex cylindrical lens (8) is vertically provided on the surface of the front glass plate (1) adjacent to the measuring cavity (5), a rear plano-convex cylindrical lens (9) is vertically provided on the surface of the rear glass plate (2) adjacent to the measuring cavity (5), the cylindrical surfaces of the front plano-convex cylindrical lens (8) and the rear plano-convex cylindrical lens (9) are adjacent to the measuring cavity (5), and a light absorbing layer (13) is provided on the surface of the front clamping frame (6) adjacent to the measuring cavity (5) and the surface of the rear clamping frame (11) adjacent to the measuring cavity (5); The glass plate level gauge has a symmetrical structure, wherein the front glass plate (1) and the rear glass plate (2), the front pressure cover (7) and the rear pressure cover (10), the guide hole (3) and the observation hole (12), the front clamping frame (6) is located between two parts on both sides of the first symmetry plane (21) of the glass plate level gauge, the rear clamping frame (11) is located between two parts on both sides of the first symmetry plane (21) of the glass plate level gauge, the front plano-convex cylindrical lens (8) and the rear plano-convex cylindrical lens (9) are symmetrical with respect to the first symmetry plane (21) of the glass plate level gauge, and the front clamping frame (6) and the rear clamping frame (11) are located between two parts on both sides of the first symmetry plane (21) of the glass plate level gauge. Any one of the above components is located between two parts on both sides of the second symmetry plane (22) of the glass plate liquid level gauge, and is symmetrical with respect to the second symmetry plane (22) of the glass plate liquid level gauge. The distance between the optical centers of the front plano-convex cylindrical lens (8) and the rear plano-convex cylindrical lens (9) is twice the focal length of the front plano-convex cylindrical lens (8) in the liquid column (16) in the measuring cavity (5). Wherein, any one of the above components refers to the front pressure cover (7), the rear pressure cover (10), the guide hole (3), the observation hole (12), the front glass plate (1), the rear glass plate (2), the front plano-convex cylindrical lens (8), and the rear plano-convex cylindrical lens (9); A light shielding area (15) is vertically provided on the surface of the front glass plate (1) adjacent to the guide hole (3), the light shielding area (15) faces the center of the plane width direction of the front plano-convex cylindrical lens (8), and the half width s of the light shielding area (15) is 5% to 15% of the half width h of the front plano-convex cylindrical lens (8). A light shielding area (15) is vertically provided on the surface of the rear glass plate (2) adjacent to the observation hole (12), the light shielding area (15) faces the center of the plane width direction of the rear plano-convex cylindrical lens (9), and the half width s of the light shielding area (15) is 5% to 15% of the half width h of the rear plano-convex cylindrical lens (9).

2. The glass plate level gauge according to claim 1, wherein: The light-absorbing layer (13) can be a coarse sand polishing layer, a sintered carbon deposition layer or a black light-absorbing paint layer.

3. The glass plate level gauge according to claim 1, wherein: The width u of the guide hole (3), the width v of the observation hole (12), the width w of the measuring cavity (5), the width of the front plano-convex cylindrical lens (8) and the width of the rear plano-convex cylindrical lens (9) are the same, all ranging from 15 to 30 mm.

4. The glass plate level gauge according to claim 1, wherein: The thickness t of the front glass plate (1) and the thickness t of the rear glass plate (2) are both 15 to 30 mm.

5. A method for measuring liquid level using the glass plate liquid level gauge according to claim 1, wherein the glass plate liquid level gauge has a symmetrical structure and is characterized in that: Light from outside the glass plate level gauge enters through the guide hole (3) and passes through the front glass plate (1), then enters and passes through the front plano-convex cylindrical lens (8), and then is emitted from the cylindrical surface of the front plano-convex cylindrical lens (8) and enters the measuring cavity (5). The lower part of the measuring cavity (5) is a liquid column (16) and the upper part is a gas phase. When the light enters the liquid column (16), it forms a first light beam (17), and when it enters the gas phase, it forms a second light beam (18). On a horizontal plane passing through the liquid column (16), the first light beam (17) passes through the liquid column (16). The light is collected at the focal point M in the liquid column (16) by the front plano-convex cylindrical lens (8), enters the rear plano-convex cylindrical lens (9) from the cylindrical surface of the rear plano-convex cylindrical lens (9), passes through the rear plano-convex cylindrical lens (9), then enters and passes through the rear glass plate (2), and is emitted through the observation hole (12). At the exit of the observation hole (12), the human eye can see the vertical light column (19) formed by the first light (17) in the direction of the light, thereby measuring the liquid level of the liquid column (16) in the measuring cavity (5).

6. The method according to claim 5, characterized in that: On a horizontal plane passing through the gas phase above the liquid column (16) in the measuring chamber (5), the second light (18) passes through the gas phase above the liquid column (16) and is converged at the focus F in the gas phase by the front plano-convex cylindrical lens (8). Almost all of the second light (18) converged at the focus F is incident on the light absorbing layer (13).

7. The method according to claim 5 or 6, characterized in that: The focal length of the front plano-convex cylindrical lens (8) in the gas phase and the liquid column (16) in the measuring cavity (5) is calculated based on the refractive index of the gas phase in the measuring cavity (5), the refractive index of the liquid medium in the liquid column (16), the refractive index of the glass material in the front glass plate (1) and the front plano-convex cylindrical lens (8), and the half width h and thickness d of the front plano-convex cylindrical lens (8).

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