CN106595807B - Long-distance passive liquid level sensor based on distributed optical fiber - Google Patents
Long-distance passive liquid level sensor based on distributed optical fiber Download PDFInfo
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- CN106595807B CN106595807B CN201611032131.3A CN201611032131A CN106595807B CN 106595807 B CN106595807 B CN 106595807B CN 201611032131 A CN201611032131 A CN 201611032131A CN 106595807 B CN106595807 B CN 106595807B
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- 239000013307 optical fiber Substances 0.000 title claims abstract description 123
- 239000007788 liquid Substances 0.000 title claims abstract description 49
- 238000005259 measurement Methods 0.000 claims abstract description 22
- 238000005086 pumping Methods 0.000 claims abstract description 4
- 239000000835 fiber Substances 0.000 claims description 16
- 239000010453 quartz Substances 0.000 claims description 6
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 6
- 239000011521 glass Substances 0.000 claims description 4
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- 238000000034 method Methods 0.000 claims description 3
- 230000004927 fusion Effects 0.000 claims description 2
- 239000007769 metal material Substances 0.000 claims description 2
- 239000011368 organic material Substances 0.000 claims description 2
- 239000013308 plastic optical fiber Substances 0.000 claims description 2
- 238000001514 detection method Methods 0.000 abstract description 8
- 230000008859 change Effects 0.000 abstract description 5
- 238000009826 distribution Methods 0.000 abstract description 2
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 4
- 238000005516 engineering process Methods 0.000 description 4
- 230000003287 optical effect Effects 0.000 description 3
- 229910052782 aluminium Inorganic materials 0.000 description 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 2
- 230000008901 benefit Effects 0.000 description 2
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- 239000003822 epoxy resin Substances 0.000 description 2
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- 229920000647 polyepoxide Polymers 0.000 description 2
- 239000004065 semiconductor Substances 0.000 description 2
- 230000008054 signal transmission Effects 0.000 description 2
- 238000010923 batch production Methods 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 230000007123 defense Effects 0.000 description 1
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- 238000012360 testing method Methods 0.000 description 1
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Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F23/00—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm
- G01F23/22—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water
- G01F23/28—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water by measuring the variations of parameters of electromagnetic or acoustic waves applied directly to the liquid or fluent solid material
- G01F23/284—Electromagnetic waves
- G01F23/292—Light, e.g. infrared or ultraviolet
- G01F23/2921—Light, e.g. infrared or ultraviolet for discrete levels
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E30/00—Energy generation of nuclear origin
- Y02E30/30—Nuclear fission reactors
Abstract
The invention discloses a long-distance passive liquid level sensor based on distributed optical fibers, which aims to solve the problems of low precision and poor stability of the conventional optical fiber liquid level sensor. The liquid level sensor comprises a light source, a comparison circuit, a wavelength division multiplexer array consisting of N wavelength division multiplexers and an optical fiber array consisting of N optical fibers; the pumping arms of the N wavelength division multiplexers are connected with the light source, the signal arms of the N wavelength division multiplexers are connected into the comparison circuit, the beam combining arms of the N wavelength division multiplexers are correspondingly connected with the head ends of the N optical fibers one by one, and the tail ends of the N optical fibers are measuring ends; the vertical distance between the end faces of the tail ends of two adjacent optical fibers is x, and x is the measurement precision required to be achieved. The invention determines the position of the liquid level through the position of the sudden change of the light intensity, is similar to digital detection, has the measurement precision mainly determined by the distribution distance of the optical fibers, can eliminate the influence of the energy jitter of the light source and the external disturbance on the measurement, and has small influence by the environment, high measurement precision and good stability.
Description
Technical Field
The invention belongs to the technical field of optical fiber sensing, and particularly relates to a long-distance passive liquid level sensor based on distributed optical fibers.
Background
The liquid level sensor has very important application in the fields of industry, national defense and the like, and the most commonly used liquid level sensors at present mainly comprise ultrasonic sensors, radar sensors and electronic sensors. These sensors have a common disadvantage that the electric current is brought into the measurement site, and therefore, the sensors cannot be used in the situations of strong electromagnetic interference, flammability, explosiveness and the like.
The optical fiber liquid level sensor uses the electrically insulated optical fiber as a signal transmission medium and uses light as a detection signal, so that the probe end can be free of electricity, and the optical fiber liquid level sensor is particularly suitable for liquid level detection in dangerous occasions such as an oil depot. However, due to the immature technology, the current optical fiber liquid level sensor has low measurement accuracy, high demodulation difficulty and poor system stability, and practical application of the optical fiber liquid level sensor is limited.
Disclosure of Invention
Aiming at the problems of low precision and poor stability of the conventional optical fiber liquid level sensor, the invention provides a long-distance passive liquid level sensor based on a distributed optical fiber.
The basic principle of the invention is as follows:
according to the characteristic that the light intensity reflected by the optical fiber immersed in liquid is far less than that reflected by the optical fiber not immersed in liquid, when the light intensity reflected by two adjacent optical fibers is suddenly changed, the position of the end face of the tail end of any one of the two corresponding optical fibers is the liquid level position, and the height of the end face of the tail end of the optical fiber from the bottom of the container is the liquid level height.
The technical scheme of the invention is as follows:
a long-distance passive liquid level sensor based on a distributed optical fiber comprises a light source and a comparison circuit; it is characterized in that:
the liquid level sensor also comprises a wavelength division multiplexer array consisting of N wavelength division multiplexers and an optical fiber array consisting of N optical fibers; the pumping arms of the N wavelength division multiplexers are connected with the light source, the signal arms of the N wavelength division multiplexers are connected into the comparison circuit, the beam combining arms of the N wavelength division multiplexers are correspondingly connected with the head ends of the N optical fibers one by one, and the tail ends of the N optical fibers are measuring ends;
the N optical fibers are numbered sequentially and marked as a first optical fiber, a second optical fiber, a fiber 8230; and a fiber N; the vertical distance between the end face of the tail end of the second optical fiber and the end face of the tail end of the first optical fiber, and the vertical distance between the end face of the tail end of the third optical fiber and the end face of the tail end of the second optical fiber, \ 8230;, the vertical distance between the end face of the tail end of the Nth optical fiber and the end face of the tail end of the N-1 optical fiber are all equal to x (namely, the vertical distances between the end faces of the tail ends of two adjacent optical fibers are both x), and the x is the measurement precision required to be achieved;
light emitted by the light source enters the optical fiber array after being coupled by the wavelength division multiplexer array, a part of light signals after being transmitted to the tail end of the optical fiber are reflected back to the optical fiber array, the reflected light signals are transmitted to the comparison circuit through a signal arm of the wavelength division multiplexer array, and the comparison circuit obtains the optical fiber serial number corresponding to the light intensity mutation, so that the liquid level height information is obtained.
The number N of the optical fibers in the optical fiber array is determined by the measuring range and the measuring precision, namely N is more than or equal to h/x, wherein h is the measuring range, x is the measuring precision required to be achieved, and N is an integer.
For convenient use, the liquid level sensor further comprises a support plate for fixing the tail ends of the optical fibers of the N optical fibers.
The support plate is made of a metal material, a glass material or an organic material.
The light source is an LED light source or a laser.
The N optical fibers are single-mode quartz optical fibers, multi-mode quartz optical fibers, large-core-diameter quartz optical fibers, multi-component glass optical fibers or plastic optical fibers.
The beam combining arms of the optical fiber array and the wavelength division multiplexer array are connected in a fusion mode.
Compared with the existing optical fiber liquid level sensor, the invention has the following advantages:
1. the invention determines the liquid level position through the sudden change position of the light intensity, is similar to digital detection, the measurement precision is mainly determined by the distribution distance of the optical fibers (the smaller the distance is, the higher the measurement precision is), and compared with the existing optical fiber liquid level meter (the existing optical fiber liquid level meter mainly utilizes the optical fiber leakage mode principle to represent the measurement technology of the liquid level height through the continuous attenuation of the light intensity, for example, the technologies disclosed in application No. 201510795296.5 and application No. 201510133317.7, because the method takes the final light intensity value as the liquid level information, the light energy fluctuation caused by the light source energy jitter, the environmental change and the like can influence the test result, so the measurement precision is low, and the stability is poor). The invention can eliminate the influence of light source energy jitter and external disturbance on measurement, and is less influenced by the environment such as temperature, humidity, external stress and the like, so the measurement precision is higher, the stability is better, the measurement repeatability is better, and the measuring range is large.
2. Compared with the technology disclosed in the patent 201510795296.5, the device has a simple structure, complex devices such as an optical circulator, a photon counter and the like are not needed, an expensive picosecond laser is not needed as a light source, an expensive optical time domain reflectometer is not needed as signal demodulation equipment, and the demodulation of the measurement signal can be realized only through a simple comparison circuit, so that the signal demodulation is simple, the batch production is easy, the cost is low, and the commercialization is facilitated.
3. The invention realizes the detection of the liquid level and the signal transmission by utilizing the optical fiber, has the advantage of no electricity at the detection end, can realize the long-distance liquid level detection, and can be widely applied to the liquid level detection in the flammable and explosive dangerous fields such as an oil depot.
Drawings
FIG. 1 is a schematic structural view of the present invention;
FIG. 2 is a graph showing the intensity of light reflected from each fiber when the alcohol level is 40 cm;
FIG. 3 is a graph showing the intensity of light reflected from each fiber when the alcohol level is 50 cm;
in the figure: 101-light source, 102-optical fiber array, 103-wavelength division multiplexer, A-pump arm, B-signal arm, C-beam combining arm, 104-comparison circuit and 105-support plate.
Detailed Description
The invention is further described with reference to the following figures and specific embodiments.
Example 1:
a long-distance passive liquid level sensor based on a distributed optical fiber is 10m long, and requires measurement accuracy x =1cm and measuring range h =1m.
The liquid level sensor includes: 1 1550nm semiconductor laser 101 with output power of 3W; an optical fiber array 102 including 100 (the number of optical fibers N = h/x = 100) communication multimode optical fibers, and having a length of 10 m/fiber; a wavelength division multiplexer array 103 consisting of 100 3dB one-to-two wavelength division multiplexers; a comparison circuit 104 for comparing the intensity of the return light signal; and an aluminum material support plate 105 for fixedly supporting the tail end of the optical fiber. The optical fibers in the optical fiber array 102 correspond to the beam combining arms C of the wavelength division multiplexers in the wavelength division multiplexer array 103 one by one and are welded together.
During measurement, the tail ends of the 100 optical fibers are 1cm,2cm, 8230, 100cm, the corresponding optical fiber numbers are 1#,2#, 8230, 8230and 100#, and the 100 optical fibers are fixed on the supporting plate 105 by epoxy resin glue.
Example 2:
a long-distance passive liquid level sensor based on distributed optical fibers is 10m long, and requires measurement accuracy x =1.5cm and measuring range h =1m.
The liquid level sensor includes: 1 1550nm semiconductor laser 101 with output power of 3W; the optical fiber array 102 is composed of 67 optical fibers (the number of the optical fibers N = h/x is approximately 66.7 is approximately 67, wherein, the length is 10 m/fiber, and the required number of the optical fibers is calculated, so long as decimal uniformly carries forward to ensure the measurement precision); a wavelength division multiplexer array 103 of 67 3dB one-to-two wavelength division multiplexers; a comparison circuit 104 for comparing the intensities of the return light signals; an aluminum material support plate 105 for fixedly supporting the end of the optical fiber. The optical fibers in the optical fiber array 102 correspond to the beam combining arms of the wavelength division multiplexers in the wavelength division multiplexer array 103 one by one and are welded together.
During measurement, the heights of the tail ends of the 67 optical fibers from the bottom of the container are 1.5cm,3cm, 8230, 100.5cm, the numbers of the corresponding optical fibers are 1#,2#, \8230, 8230, 67#, and the 67 optical fibers are fixed on the supporting plate 105 by epoxy resin glue.
The measurement principle and process of the invention are as follows:
light emitted by a light source 101 is coupled into an optical fiber array 102 through a pumping arm A of a wavelength division multiplexer 103, after the light is transmitted to the tail end of an optical fiber, because part of light reflected by an end face is reflected back to the optical fiber, the intensity of the reflected light is related to the refractive index of a medium around the end face of the optical fiber, and the intensity of light reflected back by the optical fiber immersed in liquid is far smaller than that of the optical fiber not immersed in liquid, when the intensity of light signals reflected back by two adjacent optical fibers changes suddenly, the position of one optical fiber in the two optical fibers is selected as the liquid level position of the liquid to be measured at the moment.
The reflected optical signals are transmitted to the comparison circuit 104 through the signal arm B of the wavelength division multiplexer array 103, the comparison circuit obtains the serial number of the optical fiber corresponding to the light intensity mutation, and the liquid level value corresponding to the optical fiber is directly output, so that the liquid level height information of the liquid to be measured is measured. The comparison circuit 104 is a simple and commonly used signal processing circuit in electronics, and can be designed autonomously according to specific needs. The comparison circuit can output the serial number value of the optical fiber or directly output the level value.
FIG. 2 shows the intensity of light reflected from each fiber when the alcohol level in a container is 40cm, as measured in example 1. Because the tail end of the 1-40# optical fiber is immersed in alcohol at this time, the reflected light intensity is very small; the tail ends of the rest optical fibers are in air, and the intensity of reflected light is far greater than that of the 1-40# optical fibers. The sudden change of the intensity of the reflected light occurred between the 40# and 41# fibers, and the height information of the 40# fiber was used as the height information of the liquid level, i.e., indicating that the measured liquid level value was 40 × 1=40cm.
FIG. 3 is the intensity values of light reflected from each fiber at a gasoline level of 50cm in a certain vessel measured by the above example 2. Because the tail ends of the 1-33# optical fibers are immersed in gasoline at the moment, the reflected light intensity is very small; the tail ends of the rest optical fibers are in air, and the intensity of reflected light is far greater than that of the 1-33# optical fibers. The sudden change of the intensity of the reflected light occurred between the fibers 33# and 34# and the height information of the fiber 33# was used as the height information of the liquid level, i.e., the value of the measured liquid level was 33 × 1.5=49.5cm.
The above embodiments are merely illustrative of the technical solutions of the present invention, and should not be considered as limiting the scope of the claims of the present invention, and any other modifications, substitutions, combinations, simplifications, which do not depart from the spirit and principle of the present invention, should be regarded as being equivalent replacements within the scope of the present invention.
Claims (4)
1. A long-distance passive liquid level sensor based on a distributed optical fiber comprises a light source and a comparison circuit; the method is characterized in that:
the optical fiber array is composed of N optical fibers; the pumping arms of the N wavelength division multiplexers are connected with the light source, the signal arms of the N wavelength division multiplexers are connected into the comparison circuit, the beam combining arms of the N wavelength division multiplexers are correspondingly connected with the head ends of the N optical fibers one by one, and the tail ends of the N optical fibers are measuring ends;
the N optical fibers are numbered sequentially and marked as a first optical fiber, a second optical fiber, a fiber 8230; and a fiber N; the vertical distance between the end face of the tail end of the second optical fiber and the end face of the tail end of the first optical fiber, and the vertical distance between the end face of the tail end of the third optical fiber and the end face of the tail end of the second optical fiber are (8230) \ 8230, the vertical distance between the end face of the tail end of the Nth optical fiber and the end face of the tail end of the N-1 th optical fiber are both equal to x, and the x is the measurement precision required to be achieved;
the light source is an LED light source or a laser;
the N optical fibers are single-mode quartz optical fibers, multi-mode quartz optical fibers, large-core-diameter quartz optical fibers, multi-component glass optical fibers or plastic optical fibers;
and the beam combining arms of the optical fiber array and the wavelength division multiplexer array are connected in a fusion mode.
2. The distributed fiber optic-based long-range passive level sensor of claim 1, wherein: n is more than or equal to h/x, wherein h is the measuring range.
3. The distributed optical fiber-based long-range passive level sensor of claim 1 or 2, wherein: the optical fiber connector also comprises a supporting plate used for fixing the tail ends of the optical fibers of the N optical fibers.
4. The distributed fiber optic-based long-range passive level sensor of claim 3, wherein: the support plate is made of a metal material, a glass material, or an organic material.
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| CN107515033B (en) * | 2017-08-09 | 2019-11-29 | 武汉隽龙科技股份有限公司 | Point type liquid level sensor device and its measurement method based on optical frequency domain reflection technology |
| CN107607175A (en) * | 2017-08-31 | 2018-01-19 | 广东华中科技大学工业技术研究院 | A kind of point type fibre optic liquid level sensor |
| CN107576369B (en) * | 2017-08-31 | 2020-01-21 | 广东华中科技大学工业技术研究院 | Optical fiber continuous liquid level sensor based on end face reflection coupling |
| CN107607174B (en) * | 2017-08-31 | 2019-11-26 | 广东华中科技大学工业技术研究院 | A kind of optical fiber point type liquid level sensor based on end face reflection coupling |
| CN110763306B (en) * | 2019-09-30 | 2020-09-01 | 中国科学院西安光学精密机械研究所 | Monocular vision-based liquid level measurement system and method |
| CN113701853B (en) * | 2021-07-09 | 2022-12-27 | 北京航天控制仪器研究所 | Real-time liquid level measurement and analysis method based on distributed optical fiber liquid level sensor |
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| US7313157B2 (en) * | 2003-12-19 | 2007-12-25 | Novera Optics, Inc. | Integration of laser sources and detectors for a passive optical network |
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| CN1995934A (en) * | 2006-11-15 | 2007-07-11 | 北京航空航天大学 | Distribution type fiber-optic vibration sensor |
| CN101216326A (en) * | 2008-01-08 | 2008-07-09 | 西安石油大学 | Long distance optical fiber grating sensing and transmitting device |
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