CN104089682B - A kind of liquid level detection device and its detection method - Google Patents
A kind of liquid level detection device and its detection method Download PDFInfo
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- CN104089682B CN104089682B CN201410342643.4A CN201410342643A CN104089682B CN 104089682 B CN104089682 B CN 104089682B CN 201410342643 A CN201410342643 A CN 201410342643A CN 104089682 B CN104089682 B CN 104089682B
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Abstract
A kind of liquid level detection device and its detection method, are related to level sensing.Provided with light source, three port circulators, spectrometer, testing liquid container and liquid level sensor.Testing liquid container is inserted the sensors into, the sensor other end is connected with the output port of circulator the 1st；Light source is connected with circulator input；2nd output port of circulator is connect into spectrometer；Flashlight enters circulator, then is exported from the 1st output port of circulator, after flashlight reaches sensor, reflects through silverskin, is interfered at fiber grating；Reflected light reenters circulator by the 1st output port of circulator, is then output to spectrometer from the 2nd output port of circulator, measures the spectrum of reflected light, produces the spectrum of output light；Pass through the drift of spectrometer measurement interference fringe wavelength, you can obtain the height of extraneous liquid level and the relation of interference fringe wavelength, analyze spectrum, you can measure liquid level.The continuous measurement of liquid level is realized, and measurement accuracy is high, security is good.
Description
Technical field
The present invention relates to level sensing, more particularly, to a kind of liquid level detection device and its detection method.
Background technology
Level measuring technology has extremely wide application in engineering field., in the enterprise production process of modernization
Ask the object of measurement wide, the precision of measurement is high, has good reliability and practicality, and to be applied to particular surroundings
In measurement, for example fluid to be measured has corrosivity and inflammable and explosive property.This just proposes higher want to level measuring technology
Ask.Optical fiber sensing technology has small volume, in light weight, high sensitivity, can remotely measure and corrosion-resistant, suitable for inflammable and explosive survey
The advantage of occasion is measured, therefore develop a wide range of continuous level measuring method based on optical fiber sensing technology there is highly important meaning
Justice.
Chinese patent CN203688041U discloses a kind of Full-optical optical fiber oil tank level detection means.Filled at the top of oil tank
There is rotating disk, the side of the first rotating disk sets float, and opposite side sets weight, and being evenly equipped with multi-disc around center of turntable in the first rotating disk filters
Mating plate, a pair of coupled lens are arranged on the both sides of the first rotating disk, and the light that light source is sent is successively through a coupled lens, a piece of optical filtering
Spectroanalysis instrument is reached after piece, another coupled lens, described spectroanalysis instrument is connected with Computer signal；Described float
Change up and down with liquid level, weight drives the first turntable rotation, and the information of liquid level is converted into the angle information of the first rotating disk, detected
First rotating disk rotational angle can calculate oil tank level change.
Chinese patent CN202119506U discloses a kind of liquid level detection device for liquid reservoir compensating cylinder, including with liquid
The glass tube of body reservoir compensating cylinder connection and the launching fiber and reception optical fiber that glass tube both sides are arranged in relative shape, are received
Optical fiber is used for receiving the optical signal of launching fiber transmitting and sends an optical-electrical converter to, and optical-electrical converter is used for turning optical signal
It is changed to electric signal output.
The content of the invention
It is an object of the invention to for existing level measuring method measurement accuracy is poor, stability is poor, is easily measured
The problems such as environment influences, there is provided the continuous measurement of liquid level can be realized, and also measurement accuracy is high, security is good, and can be severe
Measuring environment in a kind of liquid level detection device for playing a role and its detection method.
The liquid level detection device is provided with light source, three port circulators, spectrometer, testing liquid container and level sensing
Device；The light source is connected with the input port of three port circulators, and the 1st output port of three port circulators passes through optical fiber and liquid
Level sensor connects, in the testing liquid of liquid level sensor insertion testing liquid container, the 2nd output port of three port circulators
It is connected with the detection signal input of spectrometer；
The liquid level sensor is provided with sandwich layer, covering, and sandwich layer is located in covering, fiber grating is provided with sandwich layer, in sandwich layer
End face be coated with silverskin.
The fiber grating can use LPFG.
The liquid-level detecting method, using the liquid level detection device, comprise the following steps：
1) liquid level sensor is inserted in the testing liquid of testing liquid container, the other end of liquid level sensor and three ports
1st output port of circulator is connected；
2) light source is connected with the input port of three port circulators；
3) the detection signal input of the 2nd output port of three port circulators and spectrometer is connected；
4) light source is opened, flashlight can enter three port circulators from the input port of three port circulators, then from three
The 1st output port output of port circulator, after flashlight reaches liquid level sensor, reflected through silverskin, can be in long period light
Interfered at fine grating；
5) reflected light can reenter three port circulators by the 1st output port of three port circulators, then from three
2nd output port of port circulator is output to spectrometer, the spectrum of reflected light is at this moment measured, if the spectrum of input light is Si
(λ), you can the spectrum for obtaining output light is：
So(λ)=Si(λ)R(λ)
6) when the height of testing liquid changes, for liquid level sensor, the refractive index outside its covering can be sent out
Changing, the change of the refractive index of external environment can influence the effective refractive index of covering, the refractive index of fibre cladding and sandwich layer it
Poor Δ n will also change, so as to influence the phase difference of interferometer and cause the drift of resonance wavelength；
7) drift of spectrometer measurement interference fringe wavelength is passed through, you can obtain the height and interference fringe ripple of extraneous liquid level
Long relation, analyze spectrum, you can measure liquid level.
The present invention forms liquid level sensor using the LPFG of end face silvered mirror, and its advantage is to utilize
The reflection-type LPFG Mach-Zehnder interferometer that LPFG end face silvered mirror is formed, realizes liquid level
Continuous measurement, and measurement accuracy is high, stability is good, can use again in the adverse circumstances such as inflammable and explosive.
Brief description of the drawings
Fig. 1 is the structure composition schematic diagram of liquid level detection device embodiment of the present invention.
Fig. 2 is the liquid level sensor structure composition schematic diagram of liquid level detection device embodiment of the present invention.
Fig. 3 is the spectrogram of reflected light.Curve a represents that liquid height 10mm, curve b represent liquid height 20mm, curve c
Represent that liquid height 30mm, curve d represent that liquid height 40mm, curve e represent liquid height 50mm.
Embodiment
Following examples will the present invention is further illustrated with reference to accompanying drawing.
Referring to Fig. 1 and 2, the liquid level detection device embodiment is provided with light source 1, three port circulators 2, spectrometer 3, to be measured
Liquid container 4 and liquid level sensor 5；The light source 1 is connected with the input port 21 of three port circulators 2, three port circulators 2
The 1st output port 22 be connected by optical fiber with liquid level sensor 5, liquid level sensor 5 inserts the prepare liquid of testing liquid container 4
In body, the 2nd output port 23 of three port circulators 2 is connected with the detection signal input of spectrometer 3.
The liquid level sensor is provided with sandwich layer 51, covering 52, and sandwich layer 51 is located in covering 52, and optical fiber light is provided with sandwich layer 51
Grid 53, silverskin 54 is coated with the end face of sandwich layer 51.The fiber grating uses LPFG.
The action principle of the liquid level sensor is as follows：
The silver-plated LPFG in end face forms a kind of Mach-Zehnder interferometer of self-interference, long period optical fiber
Grating serves the effect of beam splitter in interferometer.Flashlight can couple at LPFG, in sandwich layer
The pattern of transmission can be coupled to cladding mode, and by taking 3dB LPFG as an example, 50% light can be coupled to covering biography
Broadcast, remaining light continues to propagate in sandwich layer.
When two-beam reaches the end face of optical fiber, can be reflected at silverskin.From light path principle, it is reflected back
The cladding mode come is coupled to sandwich layer pattern again at fiber grating, and is interfered with sandwich layer transmission mode, produces interference
Striped.The reflectivity R of this liquid level sensor and the relation of wavelength X are as follows：
Discounting for loss, this expression formula can be reduced to：
Wherein Tco(λ) is the transmissivity of fiber core layer, Tcl(λ) is transmissivity of the fiber core layer to covering, and Δ n is sandwich layer
With the difference of cladding-effective-index, θ is phase shift caused by cross-couplings, LcavIt is the chamber length of interferometer.The reflectance spectrum is pectination
Interference fringe.
When the liquid level of extraneous testing liquid changes, the reflectivity R of sensor can also change therewith, so as to rise
To the effect of level sensing.
The liquid-level detecting method, using the liquid level detection device, comprise the following steps：
1) liquid level sensor 5 is inserted in the testing liquid of testing liquid container 4, the other end of liquid level sensor 5 and three
1st output port 22 of port circulator 2 is connected；
2) light source 1 is connected with the input port 21 of three port circulators 2；
3) the 2nd output port 23 of three port circulators 2 is connected with the detection signal input of spectrometer 3；
4) light source 1 is opened, flashlight can enter three port circulators 2 from the input port 21 of three port circulators 2, then
Export from the 1st output port 22 of three port circulators 2, after flashlight reaches liquid level sensor 5, reflected through silverskin 54, meeting
Interfered at LPFG 53；
5) reflected light can reenter three port circulators 2 by the 1st output port 22 of three port circulators 2, then
Spectrometer 3 is output to from the 2nd output port 23 of three port circulators 2, at this moment measures the spectrum of reflected light, if input light
Spectrum is Si(λ), you can the spectrum for obtaining output light is：
So(λ)=Si(λ)R(λ) ⑶
6) when the height of testing liquid changes, for liquid level sensor 5, the refractive index meeting outside its covering 52
Change, the change of the refractive index of external environment can influence the effective refractive index of covering 52, fibre cladding 52 and sandwich layer 51
Specific refractivity Δ n will also change, so as to influence the phase difference of interferometer and cause the drift of resonance wavelength；
7) drift of interference fringe wavelength is measured by spectrometer 3, you can obtain the height and interference fringe of extraneous liquid level
The relation of wavelength, analyze spectrum, you can measure liquid level.
Fig. 3 is that liquid height is respectively 10mm, 20mm, 30mm, when 40mm, 50mm, the spectrum of reflected light.
The light source can use wideband light source.
Claims (1)
1. a kind of liquid-level detecting method, it is characterised in that using liquid level detection device, the liquid level detection device is provided with light source, three
Port circulator, spectrometer, testing liquid container and liquid level sensor；The input port of the light source and three port circulators connects
Connect, the 1st output port of three port circulators is connected by optical fiber with liquid level sensor, and liquid level sensor insertion testing liquid holds
In the testing liquid of device, the 2nd output port of three port circulators and the detection signal input of spectrometer connect；The liquid level
Sensor is provided with sandwich layer, covering, and sandwich layer is located in covering, fiber grating is provided with sandwich layer, silverskin is coated with the end face of sandwich layer；Institute
State fiber grating and use LPFG；
It the described method comprises the following steps：
1) liquid level sensor is inserted in the testing liquid of testing liquid container, the other end of liquid level sensor and three ports annular
1st output port of device is connected；
2) light source is connected with the input port of three port circulators；
3) the detection signal input of the 2nd output port of three port circulators and spectrometer is connected；
4) light source is opened, flashlight can enter three port circulators from the input port of three port circulators, then from three ports
The 1st output port output of circulator, after flashlight reaches liquid level sensor, reflected through silverskin, can be in long period optical fiber light
Interfered at grid；
5) reflected light can reenter three port circulators by the 1st output port of three port circulators, then from three ports
2nd output port of circulator is output to spectrometer, the spectrum of reflected light is at this moment measured, if the spectrum of input light is Si(λ),
The spectrum for obtaining output light is：
So(λ)=Si(λ)R(λ)
6) when the height of testing liquid changes, for liquid level sensor, the refractive index outside its covering can become
Change, the change of the refractive index of external environment can influence the specific refractivity Δ n of the effective refractive index of covering, fibre cladding and sandwich layer
Also will change, so as to influence the phase difference of interferometer and cause the drift of resonance wavelength；
7) by the drift of spectrometer measurement interference fringe wavelength, that is, the height of extraneous liquid level and the pass of interference fringe wavelength are obtained
System, spectrum is analyzed, that is, measures liquid level.
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| CN105444839B (en) * | 2015-11-18 | 2019-09-20 | 中北大学 | Plastic optical fiber liquid level sensor and measurement method based on optical time domain reflection technology |
| CN106441495A (en) * | 2016-08-30 | 2017-02-22 | 深圳市光子传感技术有限公司 | Fiber optical liquid level measuring apparatus |
| DE102016125614A1 (en) * | 2016-12-23 | 2018-06-28 | fos4X GmbH | Optical level measuring device and method for measuring a level |
| CN107389154B (en) * | 2017-08-09 | 2023-04-25 | 武汉昊衡科技有限公司 | Hollow fiber continuous liquid level sensing device and measuring method based on OFDR |
| CN109029360B (en) * | 2018-09-10 | 2020-07-10 | 曲阜师范大学 | Optical fiber one-way level gauge based on interference principle |
| CN109029359B (en) * | 2018-09-10 | 2020-07-10 | 曲阜师范大学 | Optical fiber tilt angle sensor based on interference principle |
| CN109029361B (en) * | 2018-09-10 | 2020-07-10 | 曲阜师范大学 | Optical fiber level gauge based on interference principle |
| CN110057426B (en) * | 2019-05-06 | 2021-03-16 | 武汉理工大学 | Dark pool liquid level measurement system and method based on strain layer around Bragg grating |
| CN113982565A (en) * | 2021-10-27 | 2022-01-28 | 中国地质科学院勘探技术研究所 | Device and method for identifying mud liquid level based on correlation optical fiber type turbidity sensor |
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