Liquid level detection method and device based on liquid surface microlens effect

Abstract

The present invention relates to the technical field of water quality detection, and discloses a liquid level detection method and device based on the liquid surface microlens effect, a light source and a light source fixing seat, wherein the light source fixing seat is provided with an emission aperture with a diameter of 0.1-2 mm. The number of the emission apertures is two, which are used to constrain the direction and diameter of the measuring light beam. The surface tension of the liquid itself is not equal to the adsorption force between the liquid and the pipe wall, causing the center of the end face of the liquid column to collapse downward, forming a liquid surface microlens. The liquid level detection method and device based on the liquid surface microlens effect adopt non-contact measurement and are suitable for highly corrosive liquids. Based on the principle of refraction and secondary refraction of the pipeline liquid surface microlens, the light enters the liquid surface after reflection and refracts again, resulting in a stronger signal, stable performance and strong anti-interference ability. Only one light source is needed to realize single-point or multi-point continuous liquid level detection, with a simple structure and low cost. By changing the diameter of the light source emission aperture, the device can be applied to liquid level detection in pipes of various inner diameters.

Description

Technical Field

[0001] The present invention relates to the technical field of water quality detection, and in particular to a liquid level detection method and device based on a liquid surface microlens effect. Background Art

[0002] Liquid level measurement methods in the field of water quality testing technology generally include two categories: contact measurement and non-contact measurement:

[0003] Contact measurement uses a sensor that is in direct contact with the liquid to be measured, ultimately converting the mechanical change in the liquid surface position into an identifiable electrical signal to detect the liquid level. This mainly includes: magnetostrictive measurement, which measures the liquid level by the time difference of the current magnetic field pulse emitted by the magnetostrictive instrument. This type of liquid level quantification method, which uses sensors such as floats on the liquid surface, is limited by the float's size, density, and corrosion resistance. This method is not suitable for tiny pipes, low-density liquids, or the level detection of highly corrosive liquids in the water quality testing industry.

[0004] Non-contact measurement methods mainly include: differential pressure measurement: This method mainly uses the principle of liquid pressure to detect the relevant pressure difference and determine the liquid level height based on the pressure difference. This type of liquid level gauge is often used to detect the liquid surface boundary measurement in irregular containers; capacitive measurement: This method uses a capacitive liquid level sensor to achieve this. The change in liquid level affects the parameters of the sensor's capacitor, which is indirectly converted into a change in capacitance to achieve liquid level measurement; vertical optical coupling measurement: This method uses an optical coupling sensor perpendicular to the pipeline axis to achieve this. The change in liquid level affects the signal strength received by the photodiode inside the optical coupling sensor, thereby achieving liquid level detection.

[0005] Among them, the differential pressure measurement method has high requirements for the air tightness of the instrument, and the capacitance measurement method and other methods have poor anti-interference ability (the properties of the liquid to be measured in the field of water quality detection technology are complex); the existing optical coupling measurement method is usually based on the refraction principle when light passes radially through a transparent circular pipe. This method has poor anti-interference ability when applied to small pipes. It is usually used for liquid level fixed point identification. When used for continuous liquid level detection, multiple sets of optical coupling sensors are required, which have complex structure and high cost. For this reason, we propose a liquid level detection method and device based on the liquid surface microlens effect. Summary of the Invention

[0006] (1) Technical problems solved

[0007] In response to the shortcomings of the existing technology, the present invention provides a liquid level detection method and device based on the liquid surface microlens effect. It has the advantages of refraction and secondary refraction based on the microlens of the pipeline liquid surface. After reflection, the light enters the liquid surface and is refracted again. It has the advantages of stronger signal, stable performance and strong anti-interference ability, solving the problems raised in the above background technology.

[0008] (2) Technical solution

[0009] The present invention provides the following technical solution: a liquid level detection device based on liquid surface microlens effect, comprising:

[0010] A light source and a light source holder. The light source holder is provided with two emission apertures with a diameter of 0.1-2 mm, which are used to constrain the direction and diameter of the measurement beam.

[0011] The surface tension of the liquid itself is not equal to the adsorption force between it and the tube wall, causing the center of the end face of the liquid column to collapse downward, forming a liquid surface microlens, a photodiode and a photodiode fixing seat. The photodiode fixing seat is provided with a receiving aperture. The entrance of the receiving aperture is located in the halo area formed by the refraction of the light source light beam through the liquid surface microlens + secondary refraction, and the angle α1 with the pipeline axis is: 45°<α1<135°. The exit position is opposite to the photodiode. The emission aperture and the measuring light beam are parallel to the axis of the transparent pipeline. The optical axis of the emission aperture is 1mm away from the inner edge of the pipeline.

[0012] Preferably, the diameter of the receiving aperture is 1-3 mm; and the number of the receiving aperture is not less than one.

[0013] Preferably, the measuring light beam enters the liquid surface microlens, is refracted multiple times by the liquid surface and the tube wall, etc., to obtain refracted light, and is received by the photodiode after passing through the receiving aperture.

[0014] Preferably, the signal received by the photodiode is composed of refracted light and the light beam.

[0015] A liquid level detection method based on liquid surface microlens effect, the measurement step includes the following steps:

[0016] S1: Turn on the light source, and the light beam emitted by the light source passes through the emission aperture on the light source fixing seat to obtain the measurement beam;

[0017] S2: Turn on the photodiode to read the blank value a;

[0018] S3: When the liquid enters the transparent tube and the liquid level reaches the receiving aperture, the signal value of the photodiode begins to increase and reaches a maximum value b;

[0019] S4: Continue to add liquid until the liquid level exceeds the receiving aperture and the photodiode signal value stabilizes to c;

[0020] S5: Push the liquid back, and stop when the signal value of the photodiode reaches the maximum value b again, and the liquid level detection is completed.

[0021] Preferably, the emission aperture diameter is 1 mm;

[0022] Receiving aperture diameter: 2.0mm;

[0023] The optical axis of the emission aperture is 1.0 mm away from the inner edge of the pipe;

[0024] The angle between the receiving aperture entrance and the pipe axis is: α1 = 90°;

[0025] The transparent tube has an outer diameter of 10 mm and an inner diameter of 6 mm.

[0026] Compared with the prior art, the present invention provides a liquid level detection method and device based on the liquid surface microlens effect, which has the following beneficial effects:

[0027] This liquid level detection method and device based on the liquid surface microlens effect adopts non-contact measurement and is suitable for highly corrosive liquids. Based on the principle of refraction and secondary refraction of the microlens on the pipeline liquid surface, light enters the liquid surface after reflection and refracts again, resulting in a stronger signal, stable performance and strong anti-interference ability. Only one light source is needed to achieve single-point or multi-point continuous liquid level detection, with a simple structure and low cost. By changing the diameter of the light source's emitting aperture, it can be applied to liquid level detection in pipelines of various inner diameters. It has the advantages of stable performance, strong anti-interference ability, simple structure, low cost and wide application. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a structural schematic diagram of the present invention.

[0029] Among them: 1. Light source; 2. Emitting aperture; 3. Measuring light beam; 4. Receiving aperture; 5. Refracted light; 6. Liquid level; 7. Light beam; 8. Photodiode; 9. Transparent pipe; 10. Photodiode fixing seat; 11. Light source fixing seat. DETAILED DESCRIPTION

[0030] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0031] See also Figure 1 , a liquid level detection method and device based on liquid surface microlens effect, comprising:

[0032] A light source and a light source holder. The light source holder is provided with two emission apertures with a diameter of 0.1-2 mm, which are used to constrain the direction and diameter of the measurement beam.

[0033] The surface tension of the liquid itself is not equal to the adsorption force between it and the tube wall, causing the center of the end face of the liquid column to collapse downward, forming a liquid surface microlens, a photodiode and a photodiode fixing seat. The photodiode fixing seat is provided with a receiving aperture. The entrance of the receiving aperture is located in the halo area formed by the refraction of the light source light beam through the liquid surface microlens + secondary refraction, and the angle α1 with the pipeline axis is: 45°<α1<135°. The exit position is opposite to the photodiode. The emission aperture and the measuring light beam are parallel to the axis of the transparent pipeline. The optical axis of the emission aperture is 1mm away from the inner edge of the pipeline.

[0034] The diameter of the receiving aperture is 1-3mm; the number of receiving apertures is not less than 1. The measuring light beam enters the liquid surface microlens, and obtains refracted light after multiple refractions by the liquid surface and tube wall. After passing through the receiving aperture, it is received by the photodiode. The signal received by the photodiode is composed of the refracted light and the light beam.

[0035] The measurement procedure includes the following steps:

[0036] S1: Turn on the light source, and the light beam emitted by the light source passes through the emission aperture on the light source fixing seat to obtain the measurement beam;

[0037] S2: Turn on the photodiode to read the blank value a;

[0038] S3: When the liquid enters the transparent tube and the liquid level reaches the receiving aperture, the signal value of the photodiode begins to increase and reaches a maximum value b;

[0039] S4: Continue to add liquid until the liquid level exceeds the receiving aperture and the photodiode signal value stabilizes to c;

[0040] S5: Push the liquid back, and stop when the signal value of the photodiode reaches the maximum value b again, and the liquid level detection is completed.

[0041] Emission aperture diameter: 1mm;

[0042] Receiving aperture diameter: 2.0mm;

[0043] The optical axis of the emission aperture is 1.0 mm away from the inner edge of the pipe;

[0044] The angle between the receiving aperture entrance and the pipe axis is: α1 = 90°;

[0045] The transparent tube has an outer diameter of 10 mm and an inner diameter of 6 mm.

[0046] The present invention proposes a new measurement method and device, which solves the shortcomings of the existing liquid level detection background technology in the field of water quality detection technology and has the following advantages:

[0047] Non-contact measurement, suitable for highly corrosive liquids;

[0048] Based on the principle of refraction of the micro-lens on the liquid surface of the pipeline + secondary refraction, the light enters the liquid surface after reflection and refracts again, which has stronger signal, stable performance and strong anti-interference ability;

[0049] Only one light source is needed to realize single-point or multi-point continuous liquid level detection, with simple structure and low cost;

[0050] By changing the diameter of the light source emitting aperture, it can be applied to liquid level detection of pipes with various inner diameters, including tiny pipes, 1.5mm-6mm;

[0051] In summary, it has the advantages of stable performance, strong anti-interference ability, simple structure, low cost and wide application.

[0052] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A liquid level detection device based on liquid surface microlens effect, characterized in that: include: A light source and a light source holder. The light source holder is provided with two emission apertures with a diameter of 0.1-2 mm, which are used to constrain the direction and diameter of the measurement beam. The surface tension of the liquid itself is not equal to the adsorption force between it and the tube wall, causing the center of the end face of the liquid column to collapse downward, forming a liquid surface microlens, a photodiode and a photodiode fixing seat. The photodiode fixing seat is provided with a receiving aperture. The entrance of the receiving aperture is located in the halo area formed by the refraction of the light source light beam through the liquid surface microlens + secondary refraction, and the angle α1 with the pipeline axis is: 45°<α1<135°. The exit position is opposite to the photodiode. The emission aperture and the measuring light beam are parallel to the axis of the transparent pipeline. The optical axis of the emission aperture is 1mm away from the inner edge of the pipeline.

2. The liquid level detection device based on liquid surface microlens effect according to claim 1, characterized in that: The diameter of the receiving aperture is 1-3 mm; the number of receiving apertures is not less than 1.

3. The liquid level detection device based on liquid surface microlens effect according to claim 1, characterized in that: The measuring light beam enters the liquid surface microlens, and after multiple refractions by the liquid surface and tube wall, the refracted light is obtained, which is received by the photodiode after passing through the receiving aperture.

4. The liquid level detection device based on liquid surface microlens effect according to claim 1, characterized in that: The signal received by the photodiode is composed of refracted light and light beam.

5. The liquid level detection method according to any one of claims 1 to 4, characterized in that: The measurement procedure includes the following steps: S1: Turn on the light source, and the light beam emitted by the light source passes through the emission aperture on the light source fixing seat to obtain the measurement beam; S2: Turn on the photodiode to read the blank value a; S3: When the liquid enters the transparent tube and the liquid level reaches the receiving aperture, the signal value of the photodiode begins to increase and reaches a maximum value b; S4: Continue to add liquid until the liquid level exceeds the receiving aperture and the photodiode signal value stabilizes to c; S5: Push the liquid back, and stop when the signal value of the photodiode reaches the maximum value b again, and the liquid level detection is completed.

6. The liquid level detection method based on liquid surface microlens effect according to claim 5, characterized in that: Emission aperture diameter: 1mm; Receiving aperture diameter: 2.0mm; The optical axis of the emission aperture is 1.0 mm away from the inner edge of the pipe; The angle between the receiving aperture entrance and the pipe axis is: α1 = 90°; The transparent tube has an outer diameter of 10 mm and an inner diameter of 6 mm.

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