CN1352378A - Single optical fiber tracing type high precision continuous liquid level measuring method - Google Patents
Single optical fiber tracing type high precision continuous liquid level measuring method Download PDFInfo
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- CN1352378A CN1352378A CN 01138789 CN01138789A CN1352378A CN 1352378 A CN1352378 A CN 1352378A CN 01138789 CN01138789 CN 01138789 CN 01138789 A CN01138789 A CN 01138789A CN 1352378 A CN1352378 A CN 1352378A
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- liquid level
- optical fiber
- sensing head
- liquid
- feedback signal
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- 239000007788 liquid Substances 0.000 title claims abstract description 46
- 239000013307 optical fiber Substances 0.000 title claims abstract description 18
- 238000000034 method Methods 0.000 title claims abstract description 17
- 230000003287 optical effect Effects 0.000 claims abstract description 8
- 238000010891 electric arc Methods 0.000 claims abstract description 6
- 239000000835 fiber Substances 0.000 claims description 12
- 238000005259 measurement Methods 0.000 abstract description 10
- 230000007774 longterm Effects 0.000 abstract description 4
- 238000005516 engineering process Methods 0.000 abstract description 3
- 238000003723 Smelting Methods 0.000 abstract 1
- 239000000523 sample Substances 0.000 description 8
- 238000001514 detection method Methods 0.000 description 3
- 239000004809 Teflon Substances 0.000 description 2
- 229920006362 Teflon® Polymers 0.000 description 2
- 230000008901 benefit Effects 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 238000004891 communication Methods 0.000 description 2
- 238000004880 explosion Methods 0.000 description 2
- 239000012530 fluid Substances 0.000 description 2
- 238000003754 machining Methods 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 230000035945 sensitivity Effects 0.000 description 2
- 229910000838 Al alloy Inorganic materials 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 230000008878 coupling Effects 0.000 description 1
- 238000010168 coupling process Methods 0.000 description 1
- 238000005859 coupling reaction Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- JEIPFZHSYJVQDO-UHFFFAOYSA-N ferric oxide Chemical compound O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
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- Measurement Of Levels Of Liquids Or Fluent Solid Materials (AREA)
Abstract
The preent invention relates to measurement and control technology. The end of single multiple-mode optical fiber is processed through electric arc smelting pull or optical grinding to form conic tip as sensing head, which is combined with computer controlled servo mechanism to realize the continuous liquid level measurement. The press invention features that the servo mechanism to drive the optical fiber sensing ehad consists of stepped motor, screw arbor, block and outer casing tube with guide groove; its motion direction to trace liquid surface is determined by the strength of the feedback signal from the sensing head and the liquid surface position is calculated from the step number of the stepped motor corresponding to the change in the feedback signal the sensing head produces while passing through the air-liquid interface. The method has a measurement precision within 0.1 mm in the 2 mm range, is not affected by the liquid density, has no long term drift, and may be used in the petrochemical system.
Description
Technical field
The invention belongs to the observation and control technology field, is a kind of high precision continuous liquid level measuring method based on optical fiber frustrated total internal reflection sensing, relates to the accurate measurement and the control of liquid level in the petrochemical complex industry.
Background technology
The traditional relatively electric sensor of Fibre Optical Sensor has many advantages, and as the detection sensitivity height, anti-electromagnetic interference (EMI) and essential safety etc. are used widely in Aero-Space and petrochemical complex industry in recent years.The continuous liquid level measuring of petrochemical industry at present adopts the method for measuring pressure conversion liquid level mostly, and this method exists measurement result to be subject to the influence of liquid density variation influence and sensor long term drift, is difficult to realize high-acruracy survey.Another kind method is to utilize optical fiber frustrated total internal reflection sensor measurement liquid level, as patent (95231166.6) and patent (00252608.5), though such sensor has very high bearing accuracy, can only carry out the discrete discontinuous measurement usually or do fixed point warning or control.
Summary of the invention
The objective of the invention is in conjunction with the highly sensitive characteristics of single fiber frustrated total internal reflection liquid level sensor and the accurate mechanical positioning and the tracking technique of micro-processor controlled feed service system, a kind of new high precision is provided, does not have drift, the method for continuous and direct measuring liquid level.
Technical scheme of the present invention is that the employing electric arc melting draws the method for awl or optical grinding directly to make the pointed gas-liquid two-phase interface sensing head of circular cone in the end of common multi-mode communication optical fiber, makes the gas-liquid two-phase signal contrast of sensing head reflected back surpass 10dB.In order to realize continuous liquid level measuring, sensing head need be installed to one micro-processor controlled can pinpoint servo control mechanism on, this is raised clothes mechanism and mainly is made up of the sleeve pipe and the explosion-resistant enclosure of micro-step motor, screw rod, slide block, band guide groove.Sensing head is fixed on the slide block, drive by stepper motor-screw rod-slide block and guide groove mechanism, the light signal strength that feeds back to according to optical fiber sensor head is determined the direction of motion of sensing head, the dynamic tracking liquid level, when sensing head contact liquid level, computing machine promptly calculates and demonstrates the liquid level of this moment stepper motor position correspondence.System controlled by computer and process of measurement partly are made up of pulse generation and counting, umber of pulse-liquid level conversion and demonstration, variable step tracking, bound warning and historical data demonstration, record etc.
Effect of the present invention and benefit are, draw or single fiber frustrated total internal reflection sensing head that optical grinding is made through electric arc is molten by common multimode optical fiber, level detection sensitivity can reach the micron number magnitude, and compare with two optical fiber frustrated total internal reflection sensing heads, structure and manufacture craft are simple, good reliability, cost is low, but the measuring accuracy of whole measuring system also depends on the machining accuracy of screw rod, slide block and guide groove.Under the standard machinery processing conditions, the measuring accuracy of total system can be higher than ± 0.1mm (2m measurement range).In addition, this measuring method is a kind of method of direct measuring liquid level, and there is not the long term drift problem in the not influence of liquid body variable density, can be widely used in the level gauging and the control of the multiple liquid of petrochemical system, be specially adapted to the liquid level accurate measurement of miniature liquid jar.
Description of drawings
Accompanying drawing is the structure and the principle of work synoptic diagram of single optical fiber tracing type high precision liquid level sensor.(1) microcomputer among the figure, (2) step motor drive control, the light emission, light-receiving and detection of electrons case, (3) led light source, (4) PIN photodetector, (5) 1 fens 2 fiber couplers, (6) single fiber cable, (7) 5 core safety cables, (8) aluminium alloy explosion-resistant enclosure, (9) 5 phase micro-step motors, (10) hermetic fiber articulation, (11) motor shaft-screw rod adapter sleeve, (12) screw rod, (13) tapered cylindrical optical fiber probe, (14) carry the slide block that fibre-optical probe is followed the tracks of motion of melt surface, and (15) are with the stainless steel sleeve pipe of vertical guide groove, (16) liquid in the horizontal fluid reservoir, (17) screw rod bottom end bearing and end cap.
Embodiment
Describe most preferred embodiment of the present invention in detail below in conjunction with accompanying drawing.
The centre wavelength of sending as LED in the accompanying drawing (3) is that the light signal of 850nm is transferred to the optical fiber sensor head (13) that is fixed on the slide block (14) through fiber coupler (5), single fiber cable (6) and hermetic fiber articulation (10).Sensing head is to draw or the epiconuses of 80 to 90 degree that the method for optical grinding is made into electric arc is molten in the end of common multi-mode communication optical fiber.When probe placed air, a part of light can transmit back PIN photodetector (4) via same optical fiber (6) and coupling mechanism (5) in the most advanced and sophisticated formation of awl total reflection, and the intensity of establishing this signal is I0; When sensing probe places liquid (16), because liquid refractive index is higher than the refractive index of air, make light destroyed at the total reflection condition at sensing head place, most of light leaks in the liquid, and the light signal strength of return detector (4) is weakened, and is made as I
1Common contrast R=10Log (I
0/ I
1) can reach more than the 10dB, utilize and return the tangible difference of light intensity in both sides, gas-liquid two-phase interface, the position that promptly can tell liquid level.Because the SENSITIVE SIZE of fiber tip only is about 60 μ m, adds the suction-operated when fiber tip contacts with liquid level, this sensing head can reach the micron number magnitude to the orientation sensing precision of liquid level.
What need explanation a bit is, because the difference of manufacture craft level, the angle of fibre-optical probe point or shape may depart from 90 desirable degree cone shapes, this can cause that the R value diminishes, though the R value can make system works within a large range, the too small meeting of R value influence the reliability and the serviceable life of system.Therefore utilize electric arc to draw awl or grinding fibre-optical probe, should make it as far as possible near desirable 90 degree cone shapes.
Slide block in the accompanying drawing (14) is used for carrying fibre-optical probe (13) and moves up and down and follow the tracks of liquid level, and the motion of slide block is that when screw rod rotated, slide block moved up and down along the guide groove of sleeve pipe (15) by screw rod (12) driving that is connected with stepper motor (9).The lower end of screw rod is supported by a teflon bearing (17).The minimum step angle of miniature 5 phase step motors (9) is 0.36 degree, if adopt the screw rod of 2m stroke, pitch is 1.25mm, the minimum theoretical resolution that its optical fiber is followed the tracks of liquid level can reach 1.25 μ m, in fact consider the machining accuracy of screw rod (12) and guide groove and the factors such as influence of surface tension of liquid, actual level gauging absolute precision can be better than ± 0.1mm, when range is 2m relative accuracy can reach ± 5 * 10
-5The outstanding feature of this measuring method is a level gauging precision height, does not have the problem of long term drift.Owing to only transmit the light signal of nW level at the fibre-optical probe of fluid reservoir inside, the micro-step motor of external container is the brushless machine of low voltage drive (24V), taked the explosive-proof sealed structure of teflon between motor shaft and ring flange, belong to the essential safe type sensor, the liquid level that can be applicable to the multiple liquid container of petrochemical enterprise is accurately measured.
Claims (1)
1. single optical fiber tracing type high precision continuous liquid level measuring method, be utilize with the end of single multimode optical fiber through electric arc molten draw or epiconus that the method for optical grinding is made into as sensing head, by realizing continuous liquid level measuring, it is characterized in that driving the cephalomotor clothes mechanism of raising of Fibre Optical Sensor and constitute by the outer tube of stepper motor-screw rod-slide block with the band guide groove in conjunction with the computer-controlled clothes mechanism of raising; Determine its direction of motion by the intensity of sensing head feedback signal, follow the tracks of liquid level; Pairing stepper motor steps calculates liquid level position when being changed through gas-liquid two-phase interface optical feedback signal by sensing head.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB011387890A CN1168955C (en) | 2001-12-06 | 2001-12-06 | Single optical fiber tracing type high precision continuous liquid level measuring method |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB011387890A CN1168955C (en) | 2001-12-06 | 2001-12-06 | Single optical fiber tracing type high precision continuous liquid level measuring method |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN1352378A true CN1352378A (en) | 2002-06-05 |
| CN1168955C CN1168955C (en) | 2004-09-29 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CNB011387890A Expired - Fee Related CN1168955C (en) | 2001-12-06 | 2001-12-06 | Single optical fiber tracing type high precision continuous liquid level measuring method |
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| Country | Link |
|---|---|
| CN (1) | CN1168955C (en) |
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102914347A (en) * | 2012-11-09 | 2013-02-06 | 中国计量学院 | Liquid level sensor having self-calibration function and sensing method thereof |
| CN104034393A (en) * | 2013-10-16 | 2014-09-10 | 王琪伟 | Optical fiber liquid level dynamic monitor |
| CN104677462A (en) * | 2015-02-10 | 2015-06-03 | 浙江沁园水处理科技有限公司 | Self-adapted non-immersion type liquid level detection device and detection method |
| CN104729628A (en) * | 2015-03-25 | 2015-06-24 | 浙江工业大学 | Fiber-based liquid level sensor and liquid level measurement method |
| CN106989796A (en) * | 2017-04-20 | 2017-07-28 | 常熟理工学院 | Liquid level sensor |
| CN112304393A (en) * | 2020-10-28 | 2021-02-02 | 浙江传媒学院 | Liquid level measuring device and method and oiling machine verification system and method |
| CN113916326A (en) * | 2021-10-05 | 2022-01-11 | 桂林电子科技大学 | Inclined to one side double-core optic fibre level gauge |
-
2001
- 2001-12-06 CN CNB011387890A patent/CN1168955C/en not_active Expired - Fee Related
Cited By (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102914347A (en) * | 2012-11-09 | 2013-02-06 | 中国计量学院 | Liquid level sensor having self-calibration function and sensing method thereof |
| CN102914347B (en) * | 2012-11-09 | 2015-02-25 | 中国计量学院 | Liquid level sensor having self-calibration function and sensing method thereof |
| CN104034393A (en) * | 2013-10-16 | 2014-09-10 | 王琪伟 | Optical fiber liquid level dynamic monitor |
| CN104677462A (en) * | 2015-02-10 | 2015-06-03 | 浙江沁园水处理科技有限公司 | Self-adapted non-immersion type liquid level detection device and detection method |
| CN104729628A (en) * | 2015-03-25 | 2015-06-24 | 浙江工业大学 | Fiber-based liquid level sensor and liquid level measurement method |
| CN104729628B (en) * | 2015-03-25 | 2017-08-22 | 浙江工业大学 | A kind of liquid level sensor and level measuring method based on optical fiber |
| CN106989796A (en) * | 2017-04-20 | 2017-07-28 | 常熟理工学院 | Liquid level sensor |
| CN112304393A (en) * | 2020-10-28 | 2021-02-02 | 浙江传媒学院 | Liquid level measuring device and method and oiling machine verification system and method |
| CN112304393B (en) * | 2020-10-28 | 2023-08-08 | 浙江传媒学院 | Liquid level measuring device and method, oiling machine verification system and method |
| CN113916326A (en) * | 2021-10-05 | 2022-01-11 | 桂林电子科技大学 | Inclined to one side double-core optic fibre level gauge |
Also Published As
| Publication number | Publication date |
|---|---|
| CN1168955C (en) | 2004-09-29 |
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