A glass sheet level gauge and method of level measurement

Abstract

This invention discloses a glass plate level gauge and a method for measuring liquid level. The glass plate level gauge comprises 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 has a guide hole (12), and the rear pressure cover has an observation hole (3). The front glass plate, the rear glass plate, the front clamping frame, and the rear clamping frame enclose a measuring cavity (5), which is trapezoidal in shape on a horizontal cross-section. The intersection of the front glass plate ejection surface (15) and the rear glass plate incident surface (16) with the horizontal cross-section forms the two sides of the trapezoid, and the intersection of the inner surface (8) of the front clamping frame and the inner surface (9) of the rear clamping frame with the horizontal cross-section forms the two bases of the trapezoid. This invention discloses a method for measuring liquid level using the above-mentioned glass plate level gauge. This invention can be used in multiple industries such as petrochemicals, metallurgy, power, food, and pharmaceuticals to measure the liquid level of colorless and colored transparent liquids.

Description

Technical Field

[0001] This invention belongs to the field of liquid level measurement technology, and relates to a glass plate liquid level gauge and a liquid level measurement method. Background Technology

[0002] In petrochemical refinery units, glass plate level gauges are used to display liquid levels, with the transparent glass plate level gauge being the most common type. When the measured medium is a transparent liquid, 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 intensity of the light passing through the gas phase above it. Operators rely on the difference in light intensity between the liquid and gas phases to determine the liquid level. However, when the distance is slightly greater, or on cloudy days or at night when the light is dim, the difference in light intensity is not significant, making it difficult to judge the liquid level. After prolonged use, the inner wall of the glass plate becomes dirty, reducing the intensity of light transmission and making it even harder to distinguish the liquid level. Sometimes, operators even need to temporarily close the root valve in front of the glass plate level gauge to cause a noticeable fluctuation in the liquid level before they can clearly see it.

[0003] Improving the visual sensitivity of glass plate level gauges is one solution. A common method is to use red-green color difference to distinguish liquid levels. This utilizes the principle of total internal reflection and the difference in refractive index between the liquid column and the gaseous medium above it relative to the glass, allowing the liquid column and the gaseous phase to display the red and green colors of the glass filter in the background, respectively. However, this method is only suitable for strong light backgrounds. When the background light is relatively dark or weak, the red and green colors are not very noticeable against a dark background, and the absorption of light by the filter further reduces the light intensity. The observation effect is also poor on cloudy days or at night.

[0004] Some glass plate level gauges use a dedicated external light source to artificially increase the intensity of background light (especially boiler water level gauges), eliminating reliance on natural light and factory lighting. This results in a significantly larger glass plate level gauge. An explosion-proof light with a housing needs to be installed at the rear of the glass plate, increasing the cost. Because 220V AC power is required, explosion-proof measures must be taken into account; additional cabling is also necessary, leading to extensive construction work. The explosion-proof light also has a limited lifespan; continuous 24-hour operation increases the failure rate and necessitates frequent maintenance; the explosion-proof housing also poses safety hazards. Summary of the Invention

[0005] The purpose of this invention is to provide a glass plate level gauge and a level measurement method to solve the problems of existing glass plate level gauges, such as difficulty in clearly seeing the level and the need for a dedicated external light source.

[0006] To solve the above problems, the technical solution adopted by the present invention is: a glass plate level gauge, comprising 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 has a guide hole, and the rear pressure cover has an observation hole. The guide hole is opposite to the incident surface of the front glass plate, and the observation hole is opposite to the exit surface of the rear glass plate. The front glass plate, rear glass plate, front clamping frame, and rear clamping frame enclose a measuring cavity. The surface of the front glass plate adjacent to the measuring cavity is the exit surface of the front glass plate, and the surface of the rear glass plate adjacent to the measuring cavity is the incident surface of the rear glass plate. The front clamping frame has an inner surface adjacent to the measuring cavity, and the rear clamping frame has an inner surface adjacent to the measuring cavity. The measuring cavity is trapezoidal in shape on the horizontal section plane. The intersections of the front glass plate ejection surface and the rear glass plate incident surface with the horizontal section plane form the two sides of the trapezoid. The intersections of the inner surfaces of the front and rear clamping frames with the horizontal section plane form the two bases of the trapezoid. The length of the intersection of the inner surface of the rear clamping frame with the horizontal section plane is greater than the length of the intersection of the inner surface of the front clamping frame with the horizontal section plane.

[0007] The method for measuring liquid level using the aforementioned glass plate level gauge is characterized in that: light from outside the glass plate level gauge is incident on the front glass plate through a guide hole, then enters and passes through the front glass plate, and then exits from the front glass plate exit surface 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, it forms a first light path, and when it enters the gas phase, it forms a second light path. The first light path passes through the liquid column, and the second light path passes through the gas phase above the liquid column. Then, the two light paths enter and pass through the rear glass plate through the rear glass plate incident surface, and then exit from different positions on the rear glass plate exit surface. The first light path exits through an observation hole. At the exit of the observation hole, the human eye can see the vertical light column formed by the first light path facing the direction of the incoming light, but cannot see the second light path. The liquid level of the liquid column in the measuring cavity is measured based on the vertical light column.

[0008] The present invention offers the following advantages: 1. The vertical light column formed by the first beam of light seen by the human eye is relatively bright, with a dark background above it, making the distinction clear. Therefore, the liquid level in the measuring chamber can be easily measured, thereby measuring the liquid level in the process equipment. 2. The present invention can use natural light and factory lighting, eliminating the need for a dedicated external explosion-proof light source, thus ensuring safety and energy saving. 3. The glass plate level gauge of the present invention has a relatively simple structure and is easy to manufacture. The required effects and functions are achieved through optical path calculations. 4. When using natural light and factory lighting, the present invention does not use filters or perform any light attenuation processing, preserving the original light intensity to the maximum extent. 5. The present invention does not have high requirements for light intensity. Higher intensity results in clearer distinction. When the light intensity is low, the liquid level is still easily identified because the difference in light intensity between the vertical light column formed by the first beam of light and the dark background above it is significant. 6. The glass plate level gauge of the present invention can be designed with a symmetrical structure for bidirectional observation. 7. The glass plate level gauge of the present invention has undemanding manufacturing requirements. The wider the guide hole, the stronger the tolerance of the guide angle, without affecting the functionality of the glass plate level gauge.

[0009] This invention can be used in various industries such as petrochemicals, metallurgy, power, food, and pharmaceuticals to measure the level of transparent liquids. The transparent liquid can be colorless or colored.

[0010] The present invention will now be described in further detail with reference to the accompanying drawings, specific embodiments, and examples. The accompanying drawings, specific embodiments, and examples do not limit the scope of protection claimed by the present invention. Attached Figure Description

[0011] Figure 1 This is a partial cross-sectional view of the glass plate level gauge of the present invention through the measuring cavity in the vertical direction.

[0012] Figure 2 yes Figure 1 The T-T sectional view in the image.

[0013] Figure 3 This is an optical principle diagram of using the glass plate level gauge of this invention for liquid level measurement.

[0014] Figure 4 It is a partial schematic diagram of the vertical light column formed by the first ray of light seen by the human eye and the dark background above it.

[0015] Figures 1 to 4In this drawing, the same reference numerals indicate the same technical features. Reference numerals indicate: 1—front glass plate; 2—rear glass plate; 3—observation hole; 4—bolt and nut; 5—measuring cavity; 6—front clamping frame; 7—front pressure cap; 8—inner surface of the front clamping frame; 9—inner surface of the rear clamping frame; 10—rear pressure cap; 11—rear clamping frame; 12—guide hole; 13—front glass plate incident surface; 14—sealing gasket; 15—front glass plate ejection surface; 16—rear glass plate incident surface; 17—rear glass plate ejection surface; 18—liquid column; 19—first ray; 20—second ray; 21—normal; 22—vertical light column formed by the first ray 19; 23—dark background above the vertical light column 22 formed by the first ray 19.

[0016] A—The angle of incidence of light rays from outside the glass plate level gauge onto the front glass plate incident surface 13; B—The angle of refraction of light rays from the front glass plate incident surface 13 into the front glass plate 1; C—The angle between the front glass plate exit surface 15 and the rear glass plate incident surface 16; D—The angle of exit of the first light ray 19 from the front glass plate exit surface 15 into the liquid column 18 in the measuring chamber 5; E—The angle of incidence of the second light ray 20 from the gas phase above the liquid column 18 in the measuring chamber 5 onto the rear glass plate incident surface 16; F—The angle of incidence of the second light ray 20 from the rear glass plate incident surface 16 into the rear glass plate. The refraction angle of glass plate 2; G—the difference in the exit angle between the second ray 20 exiting from the rear glass plate exit surface 17 and the first ray 19 exiting from the rear glass plate exit surface 17; H—the angle between the second ray 20 and the front glass plate exit surface 15 when the second ray 20 enters the gas phase above the liquid column 18 in the measuring cavity 5 from the front glass plate exit surface 15; K—the guiding angle of the guide hole 12; P—the calculated position of an optional external incident ray; R—the observation position at the exit of the observation hole 3, where the vertical light column 22 formed by the first ray 19 is located. Detailed Implementation

[0017] See Figure 1 and Figure 2 The glass plate level gauge of the present invention comprises a front glass plate 1, a rear glass plate 2, a front pressure cover 7, a rear pressure cover 10, and a body. The 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 vertically arranged. The front pressure cover 7 and the rear pressure cover 10 are connected by bolts and nuts 4. One vertical side sealing part 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 sealing part of the front glass plate 1 is clamped between the front pressure cover 7 and the rear clamping frame 11; one vertical side sealing part 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 sealing part 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 point.

[0018] The front cover 7 has a guide hole 12, and the rear cover 10 has an observation hole 3. The guide hole 12 is opposite to the incident surface 13 of the front glass plate, and the observation hole 3 is opposite to the exit surface 17 of the rear glass plate. Both the guide hole 12 and the observation hole 3 are vertical elongated holes, and multiple holes are provided. The guide holes 12 are aligned in a vertical row, and the observation holes 3 are aligned in a vertical row. Each guide hole 12 and observation hole 3 has two sides, a top surface, and a bottom surface; the sides are vertically arranged, and the top and bottom surfaces are horizontally arranged. The two sides of the guide hole 12 are parallel to each other, and the two sides of the observation hole 3 are parallel to each other.

[0019] The front glass plate 1, rear glass plate 2, front clamping frame 6, and rear clamping frame 11 enclose the measuring cavity 5. The surface of the front glass plate 1 adjacent to the measuring cavity 5 is the front glass plate exit surface 15, the surface of the rear glass plate 2 adjacent to the measuring cavity 5 is the rear glass plate incident surface 16, the surface of the front clamping frame 6 adjacent to the measuring cavity 5 is the front clamping frame inner surface 8, and the surface of the rear clamping frame 11 adjacent to the measuring cavity 5 is the rear clamping frame inner surface 9. The front glass plate incident surface 13 is parallel to the front glass plate exit surface 15, and the rear glass plate incident surface 16 is parallel to the rear glass plate exit surface 17.

[0020] The measuring chamber 5 is sealed, and its top and bottom are connected to the process equipment whose liquid level needs to be measured via pipes (figure omitted). The liquid in the process equipment enters the bottom of the measuring chamber 5 through the pipes and rises until the liquid level in the measuring chamber 5 is the same as the liquid level in the process equipment.

[0021] In this invention, the measuring cavity 5 is trapezoidal in shape on the horizontal section plane. The intersections of the front glass plate ejection surface 15 and the rear glass plate incident surface 16 with the horizontal section plane form the two sides of the trapezoid, and the intersections of the inner surfaces 8 and 9 of the front and rear clamping frames with the horizontal section plane form the two bases of the trapezoid (the intersections of the sealing gasket 14 and the measuring cavity 5 with the horizontal section plane are respectively included in the two bases of the trapezoid). The length of the intersection of the inner surface 9 of the rear clamping frame with the horizontal section plane is greater than the length of the intersection of the inner surface 8 of the front clamping frame with the horizontal section plane.

[0022] In a preferred embodiment of the present invention, the measuring cavity 5 is an isosceles trapezoid in shape on the horizontal cross-section, and the vertical plane passing through the midpoints of the two bases is the symmetry plane of the glass plate level gauge. The areas between the front glass plate 1 and the rear glass plate 2, between the front pressure cover 7 and the rear pressure cover 10, and between the guide hole 12 and the observation hole 3 are symmetrical with respect to the symmetry plane of the glass plate level gauge.

[0023] The angle C between the front glass exit surface 15 and the rear glass incident surface 16 is generally 30° to 90°. The angle between the side of the guide hole 12 and the plane parallel to the inner surface 9 of the rear clamping bracket is the guide angle K of the guide hole 12, which is generally 5° to 25°, and the symbol "°" indicates degree.

[0024] The optimal solution of the present invention is that the included angle C between the front glass plate ejection surface 15 and the rear glass plate incident surface 16, the included angle between the front glass plate ejection surface 15 and the inner surface 9 of the rear clamping frame, and the included angle between the rear glass plate incident surface 16 and the inner surface 9 of the rear clamping frame are all 60°.

[0025] The width u of the guide hole 12 is generally 20-30 mm, the width v of the observation hole 3 is generally 20-30 mm, and the length of the intersection line between the inner surface 9 of the rear clamping frame and the horizontal cutting plane is generally 30-80 mm.

[0026] The thickness of the front glass plate 1 and the rear glass plate 2 are generally 15-30 mm, mainly determined by the pressure of the liquid column 18 and the gas phase in the measuring chamber 5. The thickness of the front glass plate 1 is measured between the front glass plate incident surface 13 and the front glass plate ejection surface 15, and the thickness of the rear glass plate 2 is measured between the rear glass plate incident surface 16 and the rear glass plate ejection surface 17.

[0027] The materials of the front clamping bracket 6, the rear clamping bracket 11, the front pressure cover 7, and the rear pressure cover 10 can be carbon steel or stainless steel, depending on the corrosiveness of the liquid column 18 and the gas phase in the measuring chamber 5. The sealing gasket 14 is made of an elastic corrosion-resistant material.

[0028] See Figure 3 , Figure 4 as well as Figure 1 and Figure 2 The method for measuring liquid level using the glass plate level gauge of the present invention is as follows: light from outside the glass plate level gauge is incident on the front glass plate incident surface 13 through the guide hole 12, then enters the front glass plate 1 and passes through the front glass plate 1, and then exits from the front glass plate exit surface 15 and enters the measuring cavity 5. The lower part of the measuring cavity 5 is a liquid column 18, and the upper part is a gas phase. When the light enters the liquid column 18, it forms a first light beam 19 (e.g., ...). Figure 3 As shown by the thick solid line in the image), a second ray 20 is formed when it enters the gas phase (as shown by the thick solid line in the image). Figure 3 (As shown by the double-dotted line in the image). The first ray 19 is the main ray, passing through the liquid column 18; the second ray 20 passes through the gas phase above the liquid column 18. Then, the two rays enter the rear glass plate 2 from the incident surface 16 of the rear glass plate and pass through the rear glass plate 2, then exit from different positions on the exit surface 17 of the rear glass plate. The first ray 19 is located below the second ray 20, and the first ray 19 exits through the observation hole 3, at the exit of the observation hole 3 (…). Figure 3 At position R in the middle, the human eye can see the vertical light column 22 formed by the first light 19 when facing the direction of the light 19, but cannot see the second light 20. The liquid level of the liquid column 18 in the measuring cavity 5 can be measured based on the vertical light column 22.

[0029] The external light source for the glass plate level gauge is natural light (generally sunlight during the day) and factory lighting (nighttime lighting). The liquid phase in the liquid column 18 is a transparent liquid. The transparent liquid can be colorless (e.g., water, methanol, or ethanol) or colored (e.g., gasoline). The gas phase above the liquid column 18 is air and / or the gas evaporated from the liquid phase in the liquid column 18.

[0030] See Figure 3 Light refracts when passing through the front glass incident surface 13, the front glass exit surface 15, the rear glass incident surface 16, and the rear glass exit surface 17. The meanings of the letters representing various angles such as the angle of incidence and the angle of emission are explained in the accompanying drawings. In this invention, all angles of incidence and the angle of emission are simply referred to as angles. The normal 21 at each point on the front glass incident surface 13, the front glass exit surface 15, the rear glass incident surface 16, and the rear glass exit surface 17 refracts... Figure 3 The middle part is represented by a dashed line.

[0031] The width u and viewing angle K of the adjustable guide hole 12, as well as the width v of the observation hole 3 and the angle between its side surface and the plane parallel to the inner surface 9 of the rear clamping frame, ensure that the vertical light column 22 formed by the first light ray 19 can always be viewed at the exit (position R) of the observation hole 3. Position R corresponds to the lower part of the observation hole 3. Both the first light ray 19 and the second light ray 20 are planar perpendicular to the horizontal plane. The aforementioned exit angle difference G is actually the angle between the light surface of the first light ray 19 emitted from the rear glass plate exit surface 17 and the light surface of the second light ray 20. After the second light ray 20 is emitted from the rear glass plate exit surface 17, it is generally projected onto one side of the observation hole 3 and does not exit from the observation hole 3. When a small amount of the second ray 20 emerges from the observation hole 3, due to the presence of angle G and the fact that the first ray 19 is located below the second ray 20, when viewing from position R facing the direction of the first ray 19, only the vertical light column 22 formed by the first ray 19 can be seen; the second ray 20 cannot be seen. Therefore, the background of the observation hole 3 above the vertical light column 22 formed by the first ray 19 is dark. The bright vertical light column 22 formed by the first ray 19 contrasts sharply with the dark background 23, making it easy to observe. (See [reference]). Figure 4 The top of the vertical light column 22 is the liquid level of the liquid column 18.

[0032] Angles C and D can be adjusted. When the shape of the measuring cavity 5 on the horizontal section plane is an isosceles trapezoid, and angles D and C have a fixed relationship of "angle D = 90° - (180° - angle C) / 2 = angle C / 2", the part of the first light ray 19 passing through the liquid column 18 in the measuring cavity 5 is parallel to the inner surface 9 of the rear clamping frame. At this time, the front glass plate 1 and the rear glass plate 2, the front pressure cover 7 and the rear pressure cover 10, and the guide hole 12 and the observation hole 3 of the glass plate level gauge are symmetrical with respect to the glass plate level gauge. The light path of the light rays that hit and pass through the front glass plate 1 and the light path of the first light ray 19 that passes through the rear glass plate 2 and exits from the rear glass plate exit surface 17 are symmetrical with respect to the glass plate level gauge. The two parts of the first light ray 19 that pass through the liquid column 18 and are located on both sides of the symmetrical plane of the glass plate level gauge are symmetrical with respect to the glass plate level gauge. The value of the exit angle of the first light ray 19 exiting from the rear glass plate exit surface 17 is the same as that of angle A. Based on the principle of optical path reversibility, the guide hole 12 and the observation hole 3 can be used interchangeably; that is, the guide hole 12 can be used as the observation hole 3, and the observation hole 3 can be used as the guide hole 12. This allows for observation from another location if it is inconvenient to observe from one position. Under the above conditions, the correspondence between angle C, the guiding angle K, and the difference in the exit angle G can be calculated, as shown in Table 1. Other calculation conditions for the data in Table 1 are: the liquid column 18 at the bottom of the measuring cavity 5 is a water column, the measuring cavity 5 above the liquid column 18 is filled with air, and the front glass plate 1 and the rear glass plate 2 are made of quartz glass. The data in Table 1 can be calculated using the method described in the embodiments of this invention.

[0033] As shown in Table 1, the larger the angle C, the larger the angle G. When the angle C decreases, the angle G decreases. When the angle C is 0°, the visual effect of a conventional transparent glass plate level gauge will occur, which is not required by this invention.

[0034] When the light outside the glass plate level gauge is white, it is composed of various colored lights of different wavelengths. The glass plate and liquid column have different refractive indices for different wavelengths of light, resulting in different exit positions for different wavelengths. When light passes through the liquid column 18 at the bottom of the measuring cavity 5, if the liquid column 18 contains a colorless and transparent liquid medium, the white light will undergo dispersion. The vertical light column 22 formed by the first ray 19 seen at the outlet of the observation hole 3 will have a rainbow-colored edge, with the rainbow colors being red, orange, yellow, green, cyan, blue, and violet. The human eye is very sensitive to rainbow-colored light, and because rainbow-colored light does not require a filter and retains its original light intensity to the maximum extent, it is very conspicuous and easy to observe against the dark background 23, and is also easy to distinguish from a distance. The more transparent the liquid column 18, the larger the angle C, and the more obvious the rainbow effect. When the medium of the liquid column 18 is a colored and transparent liquid, the vertical light column 22 will not form the aforementioned rainbow-colored edge. However, the vertical light column 22 formed by the first ray 19 is still bright, clearly distinguishable from the dark background 23 above it, and is still easy to observe.

[0035] The guiding angle K and the exit angle difference G can be calculated based on the refractive index of the gas phase in the measuring chamber 5, the refractive index of the liquid phase medium in the liquid column 18, the refractive index of the glass material in the front glass plate 1 and the rear glass plate 2, the refractive index of air, and the selected angle C, to achieve the best effect in distinguishing liquid levels. Angle C is best chosen at 60°, as this provides better dispersion and other effects (such as the symmetry of the glass plate level gauge).

[0036] Example

[0037] Liquid level measurement is performed using the glass plate level gauge of this invention. See [link to relevant documentation]. Figures 1-4 Measurements are performed during the day, using natural light outside the glass plate level gauge. The liquid column 18 at the bottom of the measuring chamber 5 is a water column, with a refractive index of 1.333; the measuring chamber 5 above the liquid column 18 is filled with air, with a refractive index of 1.00029. All refractive indices mentioned in this invention are relative to a vacuum. The front glass plate 1 and the rear glass plate 2 are made of quartz glass with a refractive index of 1.55. The measuring chamber 5 has an isosceles trapezoidal shape on a horizontal cross-section. The front glass plate 1 and the rear glass plate 2, the front pressure cap 7 and the rear pressure cap 10, and the guide hole 12 and the observation hole 3 are symmetrically symmetrical with respect to the glass plate level gauge. The angle C between the front glass plate ejection surface 15 and the rear glass plate incident surface 16, the angle between the front glass plate ejection surface 15 and the inner surface 9 of the rear clamping frame, and the angle between the rear glass plate incident surface 16 and the inner surface 9 of the rear clamping frame are all 60°.

[0038] SinA / SinB = 1.55 / 1.00029, SinD / SinB = 1.55 / 1.333. Angle D is angle C / 2. The portion of the first ray 19 passing through the liquid column 18 in the measuring cavity 5 is parallel to the inner surface 9 of the rear clamping frame. The light path of the ray hitting and passing through the front glass plate 1 is symmetrical with respect to the glass plate level gauge, as is the light path of the first ray 19 passing through the rear glass plate 2 and exiting from the rear glass plate exit surface 17. The two portions of the first ray 19 passing through the liquid column 18 and located on both sides of the symmetrical plane of the glass plate level gauge are symmetrical with respect to the symmetrical plane of the glass plate level gauge. At this time, the value of the exit angle of the first ray 19 exiting from the rear glass plate exit surface 17 is the same as that of angle A.

[0039] The second light ray 20 enters the measuring chamber 5 from the front glass plate exit surface 15 at an exit angle equal to angle A, with the included angle H = 90° - angle A. Angle E = 90° - (180° - angle C - angle H), SinE / SinF = 1.55 / 1.00029. The second light ray 20 exits from the rear glass plate exit surface 17 at the same value as angle E.

[0040] When angle C is 60° and angle D is 30°, the angles calculated using the above method are: angle A = 41.8° and angle E = 18.2°. The difference in the exit angle G = angle A - angle E = 23.6°. The incident light ray emitted from position P passes through the guide hole 12 at angle K, where angle K = angle A - angle D = angle A - angle C / 2 = 11.8°.

[0041] The above calculations and combinations Figure 3 It can be seen that when external natural light from the same vertical direction enters the guide hole 12 and passes through the front glass plate 1, the liquid column 18 and gas phase in the measuring cavity 5, and the rear glass plate 2, the angle G (i.e., the difference in the emission angle G) between the light surface of the first light ray 19 emitted from the emission surface 17 of the rear glass plate and the light surface of the second light ray 20 is relatively large, and the second light ray 20 is greatly deflected relative to the first light ray 19. At position R, the vertical light column 22 formed by the first light ray 19 can be clearly seen, but the second light ray 20 cannot be seen, and the area above the vertical light column 22 is a dark background 23.

[0042] Table 1

[0043] Angle C, unit: ° (degrees) Angle K, unit: ° Angle G, unit: ° 0 0 0 10.0 1.7 3.3 20.0 3.4 6.8 30.0 5.2 10.4 40.0 7.1 14.2 50.0 9.3 18.6 60.0 11.8 23.6 70.0 14.9 29.7 80.0 18.9 37.9 90.0 25.4 50.9 97.2 39.8 79.6

Claims

1. A glass plate level gauge, comprising a front glass plate (1), a rear glass plate (2), a front pressure cover (7), a rear pressure cover (10), a front clamping bracket (6), and a rear clamping bracket (11). The front pressure cover (7) is provided with a viewing hole (12), and the rear pressure cover (10) is provided with an observation hole (3). The viewing hole (12) is opposite to the incident surface (13) of the front glass plate, and the observation hole (3) is opposite to the exit surface (17) of the rear glass plate. The front glass plate (1), the rear glass plate (2), and the front clamping bracket (6) are respectively positioned as a front glass plate (1), a rear glass plate (2), and a rear clamping bracket (11). The clamping frame (6) and the rear clamping frame (11) enclose the measuring cavity (5). The surface of the front glass plate (1) adjacent to the measuring cavity (5) is the front glass plate ejection surface (15), the surface of the rear glass plate (2) adjacent to the measuring cavity (5) is the rear glass plate incident surface (16), the surface of the front clamping frame (6) adjacent to the measuring cavity (5) is the front clamping frame inner surface (8), and the surface of the rear clamping frame (11) adjacent to the measuring cavity (5) is the rear clamping frame inner surface (9). The characteristic feature is that: The measuring cavity (5) is trapezoidal in shape on the horizontal section plane. The intersection of the front glass plate ejection surface (15) and the rear glass plate incident surface (16) with the horizontal section plane is the two waists of the trapezoid. The intersection of the front clamping frame inner surface (8) and the rear clamping frame inner surface (9) with the horizontal section plane is the two bases of the trapezoid. The length of the intersection of the rear clamping frame inner surface (9) with the horizontal section plane is greater than the length of the intersection of the front clamping frame inner surface (8) with the horizontal section plane. The measuring cavity (5) is an isosceles trapezoid in shape on the horizontal section plane. The vertical plane passing through the midpoint of the two bases is the symmetry plane of the glass plate level gauge. The front glass plate (1) and the rear glass plate (2), the front pressure cover (7) and the rear pressure cover (10), and the guide hole (12) and the observation hole (3) are symmetrical with respect to the symmetry plane of the glass plate level gauge, respectively. The included angle C between the front glass plate ejection surface (15) and the rear glass plate incident surface (16) is 30° to 90°. The two sides of the guide hole (12) are parallel to each other, and the two sides of the observation hole (3) are parallel to each other; The angle between the side of the guide hole (12) and the plane parallel to the inner surface (9) of the rear clamping frame is the guide angle K of the guide hole (12), which is 5° to 25°.

2. The glass plate level gauge according to claim 1, characterized in that: The guide hole (12) and the observation hole (3) are interchangeable.

3. The glass plate level gauge according to claim 1, characterized in that: The angle C between the front glass plate ejection surface (15) and the rear glass plate incident surface (16), the angle between the front glass plate ejection surface (15) and the inner surface (9) of the rear clamping frame, and the angle between the rear glass plate incident surface (16) and the inner surface (9) of the rear clamping frame are all 60°.

4. The glass plate level gauge according to claim 1, characterized in that: The width u of the guide hole (12) is 20-30 mm, the width v of the observation hole (3) is 20-30 mm, and the length of the intersection line between the inner surface (9) of the rear clamping frame and the horizontal cutting surface is 30-80 mm.

5. The glass plate level gauge according to any one of claims 1 to 4, wherein the front glass plate (1) and the rear glass plate (2) are made of quartz glass, characterized in that: The thickness of the front glass panel (1) and the rear glass panel (2) are both 15 to 30 mm.

6. A method for measuring liquid level using the glass plate level gauge according to claim 1, characterized in that: Light from outside the glass plate level gauge is directed through the guide hole (12) to the front glass plate incident surface (13), then enters the front glass plate (1) and passes through it. Afterwards, it exits from the front glass plate exit surface (15) and enters the measuring chamber (5). The lower part of the measuring chamber (5) is a liquid column (18), and the upper part is a gas phase. When the light enters the liquid column (18), it forms a first light path (19), and when it enters the gas phase, it forms a second light path (20). The first light path (19) passes through the liquid column (18), and the second light path (20) passes through the gas phase above the liquid column (18). Then, the two light rays enter the rear glass plate (2) from the incident surface (16) of the rear glass plate and pass through the rear glass plate (2), and then exit from different positions on the exit surface (17) of the rear glass plate. The first light ray (19) is emitted through the observation hole (3). At the exit of the observation hole (3), the human eye can see the vertical light column (22) formed by the first light ray (19) facing the direction of the light from the first light ray (19). The second light ray (20) cannot be seen. The liquid level of the liquid column (18) in the measuring cavity (5) is measured based on the vertical light column (22).

7. The method according to claim 6, characterized in that: The exit angle D of the first light ray (19) from the front glass plate exit surface (15) into the liquid column (18) is equal to half of the angle C between the front glass plate exit surface (15) and the rear glass plate incident surface (16). The part of the first light ray (19) passing through the liquid column (18) in the measuring cavity (5) is parallel to the inner surface (9) of the rear clamping frame.

8. The method according to claim 6 or 7, characterized in that: Based on the refractive index of the gas phase in the measuring cavity (5), the refractive index of the liquid phase medium in the liquid column (18), the refractive index of the glass material in the front glass plate (1) and the rear glass plate (2), the refractive index of air, and the selected angle C, the guiding angle K and the exit angle difference G are calculated. The exit angle difference G is the angle between the light surface of the first ray (19) emitted from the exit surface (17) of the rear glass plate and the light surface of the second ray (20).

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