CN110361073A - A kind of liquid-level detecting method based on liquid waveguide - Google Patents
A kind of liquid-level detecting method based on liquid waveguide Download PDFInfo
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- 238000004364 calculation method Methods 0.000 claims abstract description 14
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- 238000012958 reprocessing Methods 0.000 claims description 21
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- 230000003287 optical effect Effects 0.000 description 19
- 238000010586 diagram Methods 0.000 description 10
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- 239000013307 optical fiber Substances 0.000 description 5
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- 238000002791 soaking Methods 0.000 description 2
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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
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Abstract
The invention discloses a kind of liquid-level detecting methods based on liquid waveguide, it is related to Technology of Level Detection field, for measuring the liquid level of transparency liquid, it uses photoelectric liquid-levle detection device to be detected, include the following steps: S1 under no light condition, measure the light intensity curve of array photoelectric detector part and preservation, as the dark current noise of system, S2 opens light source, repeatedly read the light intensity curve of array photoelectric detector part under same level conditions, signal averaging processing is carried out to the light intensity curve repeatedly read, with smooth light intensity curve to reduce array photoelectric detector part bring shot noise, S3 processing obtains the light intensity curve of testing liquid, analytical calculation is carried out to testing liquid light intensity curve using signal acquisition process unit, during analytical calculation, reduce the dark current noise and shot noise, it obtains Obtain liquid level calculated value.Detection method is convenient and simple for operation practical, low in cost.
Description
Technical field
The present invention relates to Technology of Level Detection fields, and in particular to a kind of photoelectric liquid-levle detection side based on liquid waveguide
Method.
Background technique
Level sensing has in the equipment such as many intelligent controls and industrial production to be widely applied very much, and existing application is wider
Liquid-level detecting method mainly have condenser type, ultrasonic type, optical fiber type etc..
Capacitance type liquid level detection is to immerse capacitor in liquid, medium material when liquid level changes, between capacitor the two poles of the earth
Material and quantity change and capacitance are caused to change, and detection capacitance variations can detect liquid level indirectly and change, but due to
Detect capacitor precision is not high and circuit in noise it is larger, it is difficult to realize that high-precision liquid level measures, and capacitance type liquid level detects
It is the contact type measurement with electric attribute, is not capable of measuring inflammable and explosive liquid.
Ultrasonic type level sensing belongs to non-cpntact measurement, and device emission pulse ultrasonic gets to liquid table when detecting liquid level
Face reflection echo, the time for detecting echo reflection can measure liquid level indirectly, but since the velocity of sound is too fast and reflection echo compares
In a jumble, ultrasonic type level sensing is difficult to realize high-precision liquid level detection and there are check frequency, general supersonic liquid level inspections
Survey the error that device is both greater than ± 1mm.
Effective refractive index changes to examine when optical fiber type level sensing principle is by the way that specific optical fiber is immersed liquid
The effective refractive index variation of fiber grating can cause resonance wavelength meeting when surveying liquid level, such as long-period fiber grating being immersed liquid
It changes, the light wave of broad spectrum light source incident optical grating, corresponding resonance wavelength can be filtered out, the resonance wave of fiber grating
Length can change with the fiber grating length for immersing liquid and be changed, and then detect liquid level by testing and analyzing resonance wavelength
(bibliography Khaliq S, James S W, Tatam R P.Fiber-optic liquid-level sensor using a
Long-period grating [J] .Optics letters, 2001,26 (16): 1224-1226.) such optical fiber liquid
Although position detection precision is very high, specific optical fiber and spectrometer is needed to analyze spectrum, structure is complicated and cost is very high.
Therefore, it is necessary to develop a kind of practical, low-cost liquid-level detecting method novel, convenient and simple for operation.
Summary of the invention
Aiming at the above defects or improvement requirements of the prior art, the present invention provides a kind of photoelectric liquid-levles of liquid waveguide
Detection method, this method are based on photoelectric liquid-levle detection device and carry out level sensing, and the liquid level detection device will be common
Optical texture is cleverly connected, and a kind of high-precision is formed, and structure is simple, inexpensive photoelectric liquid-levle detection device, base
Level sensing is carried out in such equipment, detection method is convenient and simple for operation practical, low in cost.
To achieve the above object, the present invention provides a kind of liquid-level detecting methods based on liquid waveguide, for measuring
The liquid level of prescribed liquid uses photoelectric liquid-levle detection device to be detected, photoelectric liquid-levle detection device include light source,
Array photoelectric detector part and signal acquisition process unit, include the following steps:
S1: under no light condition, the light intensity curve that receives of measurement array photoelectric detector part and preservation, as being
The dark current noise of system,
S2: opening light source, repeatedly read the light intensity curve of array photoelectric detector part under same level conditions, reads multiple
The light intensity curve taken carries out signal averaging processing, with smooth light intensity curve to reduce array photoelectric detector part bring shot
Noise,
S3: measurement obtains the light intensity curve of testing liquid, using signal acquisition process unit to testing liquid light intensity curve
Analytical calculation is carried out, during analytical calculation, reduces the dark current noise and shot noise, obtains liquid level calculated value.
Further, in step S3, the detailed process of the analytical calculation are as follows:
S31: seeking the difference curve of the light intensity curve of testing liquid after filtering first, and acquiring a length is array
The difference curves that photoelectric device vertical direction pixel quantity subtracts one,
S32: the difference curves binaryzation that step S31 is obtained selects 0 as threshold value, threshold is more than or equal in difference curves
The data correction of value is 1, and the data correction less than threshold value is -1, then obtained binaryzation data are carried out second of first-order difference
Operation, differential direction is identical as first time difference, obtain one group only have 0,2, and -2 reprocessing difference curves, wherein 2 are
Wave crest, -2 be trough,
S33: the analytical procedure S32 reprocessing difference curves obtained, obtain correct Wave crest and wave trough,
S34: after obtaining correct Wave crest and wave trough, the position of trough vertical direction pixel on array photoelectric detector part is calculated
It sets, the liquid level for obtaining testing liquid can be calculated.
Further, in step S33, the reprocessing difference curves detailed process of analytical procedure S32 acquisition are as follows:
If only there are two say if having a trough between wave crest and two wave crests in the reprocessing difference curves that S32 is obtained
Bright detection is correct,
If Wave crest and wave trough is more in the reprocessing difference curves that S32 is obtained, illustrate in light intensity curve as caused by noise
Small Wave crest and wave trough affects the detection of target Wave crest and wave trough, needs to remove the influence of the small Wave crest and wave trough, until obtaining
The reprocessing difference curves that can be used,
If the Wave crest and wave trough quantity detected is less than theoretical quantity, illustrates not detect liquid level, need to detect again.
Further, the method that removal Wave crest and wave trough small as caused by noise influences is to increase first time difference fortune
Then the difference order of calculation carries out identical subsequent arithmetic again, until obtaining the reprocessing difference curves that can be used.
In general, through the invention it is contemplated above technical scheme is compared with the prior art, can obtain down and show
Beneficial effect:
Firstly, the precision of level sensing is limited only in the precision of array photoelectric detector part, due to current array photoelectric
Device such as CCD is detected, CMOS etc. has had reached high precision, and pixel size can reach micron order, select such array
Photoelectricity testing part can be realized as high-precision liquid level detection；And the liquid level detection device core in the present invention only has light
Source, container, optically focused cylindrical lens, optical filter and array photoelectric detector part belong to the lower device of fairly simple easy-to-use and price,
So the apparatus structure in the present invention is simple, it is easy maintenance and cost is relatively low.
The method of the present invention carries out level sensing based on above photoelectric liquid-levle detection device, considers system first
Dark current noise and array photoelectric detector part bring shot noise, can increase substantially accuracy of detection, to testing liquid
Light intensity curve carry out calculus of differences twice, after accurately capable of obtaining Wave crest and wave trough, calculate trough in array photoelectric detector
The position of vertical direction pixel on part can calculate the liquid level for obtaining testing liquid.The method of the present invention has also comprehensively considered to be located again
Manage three kinds of situations of difference curves, it is ensured that obtain correct Wave crest and wave trough, and then ensure that the correctness of detection method.
Detailed description of the invention
Fig. 1 is the light path principle schematic diagram of apparatus of the present invention；
Fig. 2 is the structural schematic diagram of apparatus of the present invention；
Fig. 3 is that apparatus of the present invention carry out the structural schematic diagram after Range Extension；
Fig. 4 is the flow diagram of the liquid-level detecting method based on apparatus of the present invention.
In all the appended drawings, identical appended drawing reference is used to denote the same element or structure, in which:
1- transparent liquid container 2- light source
3- optically focused cylindrical lens 4- optical filter
5- array photoelectric detector part 6- signal acquisition process unit
7- testing liquid 8- fluid communication pipe
Specific embodiment
In order to make the objectives, technical solutions, and advantages of the present invention clearer, with reference to the accompanying drawings and embodiments, right
The present invention is further elaborated.It should be appreciated that the specific embodiments described herein are merely illustrative of the present invention, and
It is not used in the restriction present invention.As long as in addition, technical characteristic involved in the various embodiments of the present invention described below
Not constituting a conflict with each other can be combined with each other.
Fig. 1 is the light path principle schematic diagram of apparatus of the present invention, and Fig. 2 is the structural schematic diagram of apparatus of the present invention, as seen from the figure,
The present invention provides a kind of photoelectric liquid-levle detection devices, are used to measure the liquid level of transparency liquid comprising transparent liquid
Body container 1, light source 2, optically focused cylindrical lens 3, optical filter 4, array photoelectric detector part 5 and signal acquisition process unit 6,
In, the bulk container of the connection accommodating testing liquid of transparent liquid container 1, and the height of the transparent liquid container is sufficiently high with energy
Actual liquid level is observed by transparent liquid container 1, i.e., intuitively, naked eyes are it is observed that liquid level, testing liquid is in transparency liquid
Inclined liquid surface is formed in container 1 at chamber wall, light source 2 is divergent light source, it is located at the bottom of transparent liquid container 1,
The divergent beams that light source 2 is launched hold for entering in testing liquid from 1 bottom incidence of transparent liquid container, and from transparency liquid
The side wall of device 1 is emitted, and emergent light carries testing liquid liquid level information, and optically focused cylindrical lens 3 are close to transparent liquid container 1
Outer wall, and 3 length long enough of optically focused cylindrical lens is emitted with that can receive simultaneously from 1 actual liquid level of transparent liquid container from above and below
Light, optical filter 4 setting optically focused cylindrical lens 3 be emitted light direction on, it is spuious in 3 emergent light of optically focused cylindrical lens for filtering out
Light, the setting of array photoelectric detector part 5 is emitted on light direction in optical filter 4, for receiving by filtering out carrying for stray light
The optical signal of testing liquid liquid level information, and the optical signal is converted into electric signal, signal acquisition process unit 6 connects battle array
Column photoelectricity testing part 5, for handling electric signal, to obtain liquid level.
Detailed, transparent liquid container is transparent light guide medium.Light source should be the light source of certain angle of divergence, also be to send out
Astigmatism source, collector lens can be used the suitable plano-convex cylindrical lens of focal length, the light in same horizontal line are gathered together.It filters
Piece can be with the stray light of influence level sensing in filtering environmental.Array photoelectric detector part can be any be able to detect that centainly
The linear array of light intensity or face battle array photoelectricity testing part in space.Signal sampling and processing unit is detected for acquisition process array photoelectric
Device light intensity data simultaneously calculates liquid level.
When work, from container bottom incidence, light beam will pass in transparent testing liquid 7 light beam that light source 2 issues in container
Defeated (liquid level that apparatus of the present invention can only measure transparency liquid).When there is the testing liquid 7 for capableing of soaking vessel wall in container 1
Due to the presence of surface tension of liquid, liquid level can be higher than intermediate at chamber wall on testing liquid 7 surface, thus forms close
Inclined liquid surface at chamber wall, optical effect are similar to a prism.The light that light source 2 issues enters from container bottom
When penetrating, the array photoelectric inspection that liquid jet is got to by collector lens 3 and optical filter 4 in container of the biggish light a part of angle
It surveys on device 5, another part gets to array photoelectric inspection by same path after above-mentioned inclination liquid surface is totally reflected
It surveys on device 5, then just has the lesser region of light intensity among two parts light, thus form in vertical direction light intensity
There are the minimums of light intensity between two intensity maximas on curve, detect the minimum institute by data acquisition process unit 6
Place position can measure liquid level.The liquid container 1 of liquid level detection device in the termination present invention of fluid connection pipe 8 one, separately
One end can connect the primary tank of testing liquid 7,1 liquid of liquid container due to the presence of fluid connection pipe 8, in primary tank and device
Position height is identical, and liquid level in primary tank can be measured by measuring the container in liquid container 1.
Fig. 3 is that apparatus of the present invention carry out the structural schematic diagram after Range Extension, as seen from the figure, in order to increase liquid in the present invention
The measuring range of level detecting apparatus can increase the quantity of optical filter, cylindrical lens and array photoelectric part.In Practical Project
In practice, optically focused cylindrical lens 3, optical filter 4 and array photoelectric detector part 5 can form a set of optical detection unit, according to reality
Border requirement of engineering, optical detection unit have more sets, and more set optical detection units are tight along the short transverse of transparent liquid container 1
It is close to be disposed adjacent, the different liquid level of various height can be detected.Utilize individual signals acquisition and processing unit while acquisition process
The signal of multiple array photoelectric parts realizes large range measuring, shows only two array photoelectric parts in Fig. 3
Apparatus structure schematic diagram theoretically can be used numerous array photoelectric and realize unlimited range level gauging.
In one embodiment of the invention, optically focused cylindrical lens 3 are parallel with the outside wall surface of transparent liquid container 1.In fact,
Be also possible to it is not parallel, the outside wall surface of optically focused cylindrical lens 3 and transparent liquid container 1 fit closely or it is close it is adjacent have it is micro-
Small narrow peak, it is also possible.
In yet another embodiment of the present invention, which further includes fluid communication pipe 8, and the fluid communication pipe 8 is arranged
In 1 bottom of transparent liquid container, the bottom of the bulk container of connection accommodating testing liquid, for by the liquid of liquid level to be measured
It is introduced in transparent liquid container 1.The cross section of transparent liquid container 1 is round, rectangle or ellipse.That is, transparent liquid
Body container can be columned, rectangular cylinder body shape or ellipsoid shaped.The cross-section center of transparent liquid container 1 can be with
It, can also be slightly offset from a little, in short, needing to guarantee the outgoing beam of light source 2 as far as possible on the central axes of 2 outgoing beam of light source
Bottom can be covered all by being incident to the spot size at transparent liquid container bottom.
In yet another embodiment of the present invention, 5 three of optically focused cylindrical lens 3, optical filter 4 and array photoelectric detector part
It is parallel to each other.
The operation principle of the present invention is that: light source issue light beam from container bottom incidence, light beam will in container transparent liquid
It is transmitted in body.When there is the liquid for capableing of soaking vessel wall in container, due to the presence of surface tension of liquid, liquid surface is leaned on
Liquid level can be higher than intermediate at nearly chamber wall, thus forms close to inclined liquid surface at chamber wall, optical effect is approximate
In a prism.When light reaches liquid level, segment beam will transmit at liquid level.Still further aspect, due to approximate at liquid level
The presence of prism, segment beam can be totally reflected here.This two parts light beam container side walls transmits, and then passes through
Collector lens collects light, and optical filter filters out stray light, receives these light beams by array photoelectric detector part and be converted to telecommunications
Number, finally handled by signal acquisition process unit.A light intensity smaller area is just had among this two parts light, by
This forms on vertical direction light intensity curve that there are the minimum of a light intensity, the poles of the light intensity between two intensity maximas
Small value position is liquid level position.
Based on apparatus above, the present invention provides one kind liquid-level detecting methods comprising following steps:
S1: under no light condition, the light intensity curve of array photoelectric detector part and preservation are measured, as the dark of system
Current noise,
S2: opening light source, repeatedly read the light intensity curve of array photoelectric detector part under same level conditions, reads multiple
The light intensity curve taken carries out signal averaging processing, with smooth light intensity curve to reduce array photoelectric detector part bring shot
Noise,
S3: measurement obtains the light intensity curve of testing liquid, using signal acquisition process unit to testing liquid light intensity curve
Analytical calculation is carried out, during analytical calculation, reduces the dark current noise and shot noise, obtains liquid level calculated value.
The detailed process of the analytical calculation are as follows:
S31: seeking the difference curve of the light intensity curve of testing liquid after filtering first, and acquiring a length is array
The difference curves that photoelectric device vertical direction pixel quantity subtracts one,
S32: the difference curves binaryzation that step S31 is obtained selects 0 as threshold value, threshold is more than or equal in difference curves
The data correction of value is 1, and the data correction less than threshold value is -1, then obtained binaryzation data are carried out second of first-order difference
Operation, differential direction is identical as first time difference, obtain one group only have 0,2, and -2 reprocessing difference curves, wherein 2 are
Wave crest, -2 be trough,
S33: the analytical procedure S32 reprocessing difference curves obtained, obtain correct Wave crest and wave trough,
The reprocessing difference curves detailed process that analytical procedure S32 is obtained are as follows:
If only there are two say if having a trough between wave crest and two wave crests in the reprocessing difference curves that S32 is obtained
Bright detection is correct,
If Wave crest and wave trough is more in the reprocessing difference curves that S32 is obtained, illustrate in light intensity curve as caused by noise
Small Wave crest and wave trough affects the detection of target Wave crest and wave trough, needs to remove the influence of the small Wave crest and wave trough, until obtaining
The reprocessing difference curves that can be used.The method that removing small Wave crest and wave trough as caused by noise influences is to increase first
Then the difference order of secondary calculus of differences carries out identical subsequent arithmetic again, until obtaining the reprocessing difference that can be used
Curve.
If the Wave crest and wave trough quantity detected is less than theoretical quantity, illustrates not detect liquid level, need to detect again.
S34: after obtaining correct Wave crest and wave trough, the position of trough vertical direction pixel on array photoelectric detector part is calculated
It sets, the liquid level for obtaining testing liquid can be calculated.
Liquid level calculation method described in S31 to S34 as above is only a kind of preferable liquid level calculation method of the invention, and is not had to
To limit the present invention, other through the invention in light intensity curve detection calculate algorithms of liquid level and such as seek extremum extracting Peak Intensity Method, small
Wave detects Peak Intensity Method etc., should all be included in the protection scope of the present invention.
Fig. 4 is the flow diagram of the liquid-level detecting method based on apparatus of the present invention, as seen from the figure, the device in the present invention
Specific workflow is as follows:
In order to eliminate dark current noise present in array photoelectric detector part, it is necessary first to be detected in the case where unglazed
The light intensity curve of array photoelectric device and preservation, are regarded as dark current noise, during subsequent level gauging, read
The influence for all first subtracting the dark current noise after light intensity curve to prevent dark current noise to level sensing.
Light source is opened, starts level sensing, makes an uproar to reduce the shot in array photoelectric detector part and its driving circuit
Sound, smooth light intensity curve, the light intensity curve for needing high speed repeatedly to read same liquid level array photoelectric device carry out at signal averaging
Reason is to reduce noise.
It obtains and identification calculating, the identification computational algorithm flow diagram of liquid level is carried out to liquid level after having handled light intensity curve
As shown in Fig. 3, specific:
(1) difference curve for seeking light intensity curve after filtering first, i.e., subtract the pixel light intensity of entire light intensity curve
The light intensity (can also take opposite direction calculus of differences) of previous position pixel, obtaining a length is array photoelectric device vertical direction
The difference curves that pixel quantity subtracts one.
(2) the subsequent judgement to Wave crest and wave trough position for convenience, the difference curves binaryzation for needing to obtain select 0
As threshold value, the data correction that threshold value is more than or equal in difference curves is 1, and the data correction less than threshold value is -1, then will be obtained
Binaryzation data carry out second of first-order difference operation, differential direction is identical as first time difference, obtain one group and there was only 0,2,
With -2 data, 2 be wave crest at this time, and -2 be trough.
(3) if the effect detected be only there are two wave crest and between have a trough if illustrate that detection is correct, if
The Wave crest and wave trough detected is more to illustrate that Wave crest and wave trough small as caused by noise in light intensity curve affects target wave crest wave
Paddy detection, in order to remove the influence of these small Wave crest and wave troughs, can increase the difference order of first time calculus of differences, then again
It is secondary to carry out identical subsequent arithmetic until detecting correct result；If the Wave crest and wave trough quantity detected is less than theory
Quantity explanation does not detect liquid level, needs to adjust device and detects again.
(4) after obtaining correct Wave crest and wave trough, the position of trough vertical direction pixel on array photoelectric detector part is calculated
The liquid level measured can be calculated by setting.
As it will be easily appreciated by one skilled in the art that the foregoing is merely illustrative of the preferred embodiments of the present invention, not to
The limitation present invention, any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should all include
Within protection scope of the present invention.
Claims (4)
1. a kind of liquid-level detecting method based on liquid waveguide, which is characterized in that for measuring the liquid level of transparency liquid,
Detected using photoelectric liquid-levle detection device, photoelectric liquid-levle detection device include light source, array photoelectric detector part with
And signal acquisition process unit, include the following steps:
S1: under no light condition, the light intensity curve of array photoelectric detector part and preservation are measured, as the dark current of system
Noise,
S2: light source is opened, the light intensity curve of array photoelectric detector part under same level conditions is repeatedly read, to what is repeatedly read
Light intensity curve carries out signal averaging processing, is made an uproar with smooth light intensity curve to reduce array photoelectric detector part bring shot
Sound,
S3: measurement obtains the light intensity curve of testing liquid, is carried out using signal acquisition process unit to testing liquid light intensity curve
Analytical calculation during analytical calculation, reduces the dark current noise and shot noise, obtains liquid level calculated value.
2. a kind of liquid-level detecting method based on liquid waveguide as described in claim 1, which is characterized in that in step S3, institute
State the detailed process of analytical calculation are as follows:
S31: seeking the difference curve of the light intensity curve of testing liquid after filtering first, and acquiring a length is array photoelectric
The difference curves that device vertical direction pixel quantity subtracts one,
S32: the difference curves binaryzation that step S31 is obtained selects 0 as threshold value, threshold value is more than or equal in difference curves
Data correction is 1, and the data correction less than threshold value is -1, then obtained binaryzation data are carried out second of first-order difference fortune
Calculate, differential direction is identical as first time difference, obtain one group only have 0,2, and -2 reprocessing difference curves, wherein 2 be wave
Peak, -2 be trough,
S33: the analytical procedure S32 reprocessing difference curves obtained, obtain correct Wave crest and wave trough position,
S34: after obtaining correct Wave crest and wave trough, calculating the position of trough vertical direction pixel on array photoelectric detector part,
The liquid level for obtaining testing liquid can be calculated.
3. a kind of liquid-level detecting method based on liquid waveguide as claimed in claim 2, which is characterized in that in step S33, point
Analyse the reprocessing difference curves detailed process that step S32 is obtained are as follows:
If only there are two illustrate to examine if having a trough between wave crest and two wave crests in the reprocessing difference curves that S32 is obtained
It surveys correctly,
If Wave crest and wave trough is more in the reprocessing difference curves that S32 is obtained, illustrate small as caused by noise in light intensity curve
Wave crest and wave trough affect the detection of target Wave crest and wave trough, need to remove the influence of the small Wave crest and wave trough, can be with until obtaining
The reprocessing difference curves used,
If the Wave crest and wave trough quantity detected is less than theoretical quantity, illustrates not detect liquid level, need to detect again.
4. a kind of liquid-level detecting method based on liquid waveguide as claimed in claim 3, which is characterized in that removal is drawn by noise
The method that the small Wave crest and wave trough risen influences is to increase the difference order of first time calculus of differences, then carry out again identical
Subsequent arithmetic, until obtaining the reprocessing difference curves that can be used.
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