CN103557985A - Differential pressure sensing method and sensor thereof - Google Patents
Differential pressure sensing method and sensor thereof Download PDFInfo
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- CN103557985A CN103557985A CN201310537492.3A CN201310537492A CN103557985A CN 103557985 A CN103557985 A CN 103557985A CN 201310537492 A CN201310537492 A CN 201310537492A CN 103557985 A CN103557985 A CN 103557985A
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Abstract
The invention discloses a differential pressure sensing method and a sensor thereof. According to the differential pressure sensing method, pressure produced through detection fluid impacts one surface of an elastic membrane (113), meanwhile narrow-spectrum laser irradiates the other surface of the elastic membrane (113), the elastic membrane (113) can deform, the output light intensity of a receiving optical fiber (41) can change after the elastic membrane (113) deforms, and pressure variation caused by the fluid on the elastic membrane (113) is judged by detecting the variation of the output light intensity of the receiving optical fiber (42). By the adoption of the method, the sensor is high in sensing accuracy, reliable in performance, simple in structure, low in volume and mass and low in manufacturing cost.
Description
Technical field
The present invention relates to differential pressure method for sensing and sensor thereof, belong to sensor technical field.
Background technology
Differential pressure pick-up DPS(Differential Pressure Sensor) be a kind of sensor that is used for measuring difference between two pressure, be generally used for measuring the pressure reduction of a certain equipment or parts rear and front end.In recent years, differential pressure pick-up all has a wide range of applications in many high-acruracy survey occasions such as micro-flow measurement, leakage test, clean room monitoring, environmental sealing detection, gas flow measurement, height of liquid level measurements.
The research of differential pressure pick-up is mainly concentrated on to traditional piezoresistance type differential pressure transducer and capacitance differential pressure transducer both at home and abroad now.Piezoresistance type differential pressure transducer is simple in structure, and operative end surface is smooth, but exists more outstanding contradiction between its sensitivity and frequency response, and temperature is also larger to the performance impact of this kind of sensor.Capacitance type sensor is highly sensitive, dynamic response characteristic is good, anti-overload ability is strong, but there is stray capacitance and the impact of distributed capacitance on sensitivity and measuring accuracy in it, and the shortcomings such as circuit more complicated that are connected with sensor, have influence on its application reliability, therefore limited its widespread use.Many deficiencies just because of traditional differential pressure sensors, start some novel differential pressure pick-ups to be studied both at home and abroad, Dong Guoqiang etc. are to utilizing a kind of little differential pressure sensor of magnetic liquid to be studied, rely on magnetic liquid displacement process under pressure to produce electric signal, realize the detection to pressure, it has limitation in application; The people such as Jose.L.A.V of the Hao-Jan Sheng Deng, U.S. in Taiwan have proposed a kind of optical fiber differential pressure pickup structure based on Bragg grating separately, the sensitivity of this fiber grating differential pressure pick-up is higher, but complex structure and cost are very high, be unfavorable for promoting.And intensity modulated is as using to obtain the most a kind of modulator approach in fiber optic sensor technology, obtained some scholars' research, but to the Research Literature of the optical fiber differential pressure pickup based on intensity modulated seldom, the Seiichiro Kinugasa of Japan has proposed a kind of design of reflection type optical fiber differential pressure pick-up, utilizes the variation of reflecting surface and fiber distance to detect the poor situation of external pressure; Tong Chengguo etc. have designed a kind of optical fiber differential pressure pickup of double C-type bourdon tube, according to intensity modulated principle, in two double C-type bourdon tubes, pressure reduction are detected.
But prior art does not still solve realization, the rationality of sonde configuration parameter, the problem that many key factors such as the duty of reflecting surface, compensation of error are brought of sensor, therefore in prior art, such sensor construction is very complicated, and performance is reliable not, processing and manufacturing cost is also very high, and volume is large conventionally, very heavy, use inconvenience, also there is very large room for improvement.This is first technical matters that prior art exists.
In addition; sensor probe is reliable and stable at work; be not vulnerable to the interference of the factors such as extraneous collision, vibration; simultaneously in order to protect sensitive element in probe, avoid the error brought due to the difference of this body structure of probe; must encapsulate probe; and the encapsulation of sensor probe, this is second technical matters that prior art exists.
For the reflection type optical fiber differential pressure pick-up of intensity modulated principle, the output light intensity of different probes will certainly be subject to the impacts such as bias light, fiber lengths, fibre-optical bending degree, coupled apparatus, thereby make testing result have larger error, this is the 3rd technical matters that prior art exists.
Summary of the invention
Three problems that exist for solving prior art, must set about from the light intensity compensation of sensor probe structure, sensor package and probe output light.For this reason, can realize such object from following three aspects.
The problems such as sensor construction is complicated in order to solve, performance is reliable not and processing cost is high and volume mass is large, intend adopting such a kind of differential pressure method for sensing and sensor thereof, the main points of this method for sensing are, it carries out sensing by produce the test fluid (as hydraulic oil) of pressure for weighing measured object, the pressure that this test fluid is produced goes to impact the wherein one side of a flexible sheet, and flexible sheet is deformed; Narrow spectrum Ear Mucosa Treated by He Ne Laser Irradiation in incident optical for the another side of flexible sheet, and receive reflected light with reception optical fiber; Like this, after flexible sheet deforms, because reflection angle changes, reflected light changes thereupon, cause the output light intensity that receives optical fiber to change, the variable quantity that receives like this optical fiber output intensity by detecting judges the pressure variety that test fluid causes flexible sheet thereupon.Like this, just can change by the light intensity of being convenient to measure, judge that the pressure that is difficult for measuring changes, thereby determine the pressure difference value of different measured objects, realize the object of differential pressure sensing.
As a kind of optimal way, test fluid produces pressure by flowing into the mode of a test chamber to flexible sheet, and flexible sheet is arranged on the direction that in test chamber and in test chamber, test fluid flows into and forms the barrier sealing.Test chamber is sealed, but is provided with an opening in the direction towards measured object, when test fluid pours in test chamber from the opening of test chamber, will produce fluid pressure to the flexible sheet in test chamber, thereby cause the distortion of flexible sheet.When the media environment in chamber changes, elastic membrane sector-meeting produces distortion owing to being under pressure, and preferably the medium in test chamber is in a kind of equally distributed situation, so it will produce an equally distributed load to the surface of whole film.Adopt such test chamber, the fluid pressure that can make test fluid produce evenly and exactly makes flexible sheet produce distortion, improves the precision that detects sensing.
For fear of flexible sheet, when being subject to the pressure of test fluid generation, be subjected to displacement at edge, can adopt a sensor probe housing that described flexible sheet is fastened thereon, sensor probe housing can adopt monolithic construction with test chamber, and flexible sheet is fixedly installed between sensor probe housing and test chamber.Because flexible sheet is fixedly secured, no matter the fluid pressure that test fluid causes it is much, all only can makes, on its face, elastic deformation occurs, and can not make its edge be subjected to displacement, prevent from like this by fluid impact, being broken emat sensor because of thin slice.In addition, incident light irradiates to flexible sheet by the fixed orifice in sensor probe housing.The surface of fixed orifice and flexible sheet in vertical state, can guarantee that incident light irradiating angle or the reflection angle of working as incident optical, receiving the fibre bundle of optical fiber or the two formation can arbitrarily not be offset.
In order to make sensor there is good static properties, the winding degree that flexible sheet produces when compressive deformation so will be very little, consider the specific works situation of sensor construction flexible sheet, the performance of comprehensive various materials, preferably 35CrMnSi material carries out preparation of sections.This material claims again low-alloy super-strength steel, after thermal treatment, there is good comprehensive mechanical property, high strength, enough toughness, quenching degree, weldability (weld preheating), formability are all better, but its corrosion stability and antioxygenic property are more general, serviceability temperature, conventionally not higher than 200 ℃, is generally to use after lonneal or isothermal quenching.
Based on aforesaid this method for sensing, can adopt a kind of like this reflection type optical fiber bundle differential pressure pick-up of intensity compensation, it comprises pressure detection probe that two structures are identical and for the incident optical to this pressure detection probe transmission light source with for receiving the radiative reception optical fiber of pressure detection probe, and incident optical and reception optical fiber are assembled formation fibre bundle in fixed orifice.This pressure detection probe inside is fixed with a flexible sheet, and the two sides that is arranged in flexible sheet in this pressure detection probe is respectively equipped with a test chamber and can inserts for fibre bundle the fixed orifice of probe.Test chamber flows in it and to flexible sheet and produces fluid pressure for detection of fluid.Test chamber is provided with at least one can flow into test fluid entrance wherein for test fluid.Preferably such: sensor is provided with two light sources, is assumed to S1, S2, two detection probe one, pop one's head in two, two photodetector D1, D2, the fiber coupler of four one-to-two, and the fiber bundle structure of incident optical and mirror based fiber optica set bunchy forms.Sensor light source is selected semiconductor laser, and this laser instrument has very narrow output spectrum live width and outstanding side mode suppression ratio, and its output peak wavelength is 1310nm.Photodetector is selected PIN photodiode, and this photodiode work wavelength coverage is 1100nm～1650nm, and dark current is 1nA to the maximum, and optical responsivity minimum is 0.85A/W, response time 0.1ns.Make like this light source mate better with the spectral characteristic of photodetector two elements.
What light source sent couples light in incident optical, by incident optical, be transferred to optical fiber outgoing end face, it is upper that emergent light is irradiated to reflection shell fragment (flexible sheet), and the part light after the reflection of reflection shell fragment enters into and receives in optical fiber, by receiving Optical Fiber Transmission to photodetector place, carry out opto-electronic conversion.Enter into the intensity of reflected light size receiving in optical fiber, by the distance between reflection shell fragment and reception fiber end face, determined, under External Force Acting, reflection shell fragment diminishes with the distance that receives optical fiber, thereby the intensity of reflected light that enters into reception optical fiber is changed, by the variable quantity of output light intensity, can determine the deformation size of reflecting surface, thereby determine the size of ambient pressure P.
Certainly, the pressure detection of this sensor probe also comprises a probing shell, within above-mentioned fixed orifice, flexible sheet and test chamber are all positioned at this probing shell.Test chamber and probing shell are preferably processed into one-piece construction.The material of probing shell is selected metal material, in processing, for convenient, preferably adopts metallic aluminium bar.
For solving the encapsulation problem of sensor probe, make to pop one's head in firmly, be convenient to processing and realize, be convenient to assembling, be convenient to maintain and replace, plan a kind of like this method for packing of employing and structure:
Differential pressure pick-up of the present invention is the free style structure that two probes are worked simultaneously, and probe segment can be freely movable, can freely select to need the position of detecting to detect; In detection, probe can be directly fixed on detection position, and need not carry out drainage, thereby has avoided freezing, stop up and sluggishness of drainage tube drainage process generation; Can also design the probe that physical dimension is different from sensing range according to detecting needs simultaneously, in order to meet some specific demands etc., require two probes symmetrical as much as possible identical.For single probe, in encapsulation, to meet following requirement: fibre bundle well aims at that the distance of center, fibre bundle and flexible sheet of flexible sheet is adjustable, fibre bundle can well be fixed, and this is also the difficult point place of this probe encapsulation.
So the present invention has adopted mechanical type packaged type, this mode can guarantee machining precision, and assembly precision, and structure of each probe that makes to process is identical, thereby be beneficial to, realize standardization, seriation, universalization, the detection error that can also well avoid structural failure to bring.
In order to realize above-mentioned requirements, the feature of this sensor package is: adopt thread bush to be fixed the fibre bundle in fixed orifice, fibre bundle can not be moved, the error of avoiding fibre bundle shake to bring.Specific practice is: with a cylindrical external thread end cap in the internal thread fixed orifice that probing shell forms from the precession of export-oriented flexible sheet direction screw thread, there is a threaded hole end cap center, with a thread bush, fibre bundle is enveloped again, the internal thread of the threaded hole of the external thread of thread bush and end cap center matches, and makes thread bush in end cap, screw in or to screw out.Therefore, the thread connection form of thread bush and end cap, realizing thread bush can precession freely in end cap, and (preferably thread pitch is 0.2mm, thread bush outer wall mark precession length scale, minimum scale is 0.1mm), thus it is adjustable to realize the distance of fibre bundle and flexible sheet; (because these two crucial static characteristicss of the detection sensitivity that the initial distance of fibre bundle and flexible sheet has directly determined sensor and the linearity, set up the initial distance of good rational fibre bundle and flexible sheet, raising detection performance.The optimum initial distance that simultaneously different fibre bundle end face structures is corresponding is different, so require the distance of fibre bundle and flexible sheet adjustable.) the hole axle of fixed orifice of threaded hole, thread bush and probe of end cap keeps coaxial, adopt so this cylindrical encapsulating structure, add the right alignment that has guaranteed each part man-hour, can guarantee that fibre bundle well aims at the center of flexible sheet, simple in structure applicable.Flexible sheet can well be fixed, and easily assembling and replacing.
At the another side of flexible sheet, adopt a back-up ring that flexible sheet is blocked, flexible sheet, by screw thread precession and the back-up ring squeezing fixing method of this end cap, can reach good fixation, is difficult for loosening.Meanwhile, as flexible sheet needs to change, screwing out end cap can realize, simply applicable.Meanwhile, around the test fluid entrance of the test chamber of popping one's head in, packing ring is also set, in test fluid porch, screen pack is set, to entering the fluid of test chamber, filter.
The stability of test chamber and homogeneous media are important requirements that guarantees sensing accuracy, therefore must make test chamber can reduce the disturbance of fluid.So adopt such structure: fill a cup-shaped vitreum in test chamber, vitreum is stuck between back-up ring and sensor housing, making test chamber is cup-shaped cavity structure, can reduce like this volume of test chamber, thereby makes the fluid that is detained seldom.Reduce the inhomogeneous of test chamber internal pressure, the pressure that makes to act on flexible sheet more easily becomes even simultaneously.Select vitreum to be because its easy moulding, hardness are high, the long-term corrosion of fluid-resistant etc.
In order to prevent test fluid leakage, can also between flexible sheet and back-up ring, install an O-ring seal additional.Flexible sheet is fixed by end cap, end cap and housing adopt interference fit structure, fibre bundle is fixed in thread bush, add and guarantee preferably circularity and the right alignment of sensor housing, end cap, thread bush man-hour, thereby can guarantee the center alignment issues of fibre bundle and flexible sheet, the error of avoiding certain probe in detecting to cause because of the position deviation of fibre bundle and flexible sheet.Thread bush and end cap adopt thread connection, and are carved with scale on thread bush surface, thereby can adjust by the precession of threaded engagement the distance of fibre bundle and flexible sheet.By mechanical encapsulation, can also make to form between fibre bundle and flexible sheet dark chamber, thus the noise of avoiding bias light to bring.
What fibre bundle differential pressure pick-up detection probe adopted is intensity modulated principle, by light intensity size variation being monitored to judge the variation of measurand, the light intensity that light source, optical fiber, optical fibre device and photo-detector etc. cause like this changes will cause error to testing result.For fear of or reduce this detection error, just should consider this type of intensity modulation optical fiber sensor to carry out intensity compensation, thereby improve the detection Stability and dependability of sensor.
The light intensity compensation method that this sensor of the present invention adopts is: it is alternately luminous that first sensor adopts two light sources, during one of them light source luminescent, first light wave is coupled into an incident optical, again through the Y of one-to-two type coupling mechanism, be divided into the two-way light wave that power is equal, one tunnel directly arrives a photodetector through reference path, through this detector, be converted to voltage signal output, and the size of this voltage signal has reflected half size of light source output power; Another road after testing light path arrives detection probe one, after flexible sheet reflection, through receiving optical fiber, arrive another photodetector again, through this detector, be converted to voltage signal output, the size of this voltage signal has reflected second half of light source output power, the luminous power size receiving after reflection; In the later stage, calculate the ratio of these two output voltages, this ratio size is just irrelevant with the power variation of light source again, reflects the size of detection probe one pressure by this ratio, just can eliminate the error of caused by light source fluctuation.
During another one light source luminescent, with said process in like manner, by ratio, reflect the size of another detection probe two place's pressure.
Again by calculating ratio poor of detection probe one, detection probe two outputs, or the ratio of ratio.Finally reflect the pressure difference value between two probes.And by asking the difference of ratio can realize the intensity compensation to light source fluctuation; By asking the ratio of ratio, can realize the intensity compensation of light source fluctuation, photodetector and fibre loss (but the pressure difference detection scope of this method is little).
Light path adopts the distribution form of light bridge-type, make the reference path of two light sources arrive same photodetector through Y type coupling mechanism, the reflected light receiving light path of two detection probe arrives another photodetector through Y type coupling mechanism, thereby simplified the whole light channel structure of sensor, make light path optical fiber layout simple, reduce detector number simultaneously, the data processing module in later stage is also simplified.Finally realize the design of economy and reliability.
Accompanying drawing explanation
Fig. 1 is differential pressure pick-up sonde configuration schematic diagram;
Fig. 2 is differential pressure method for sensing schematic diagram;
Fig. 3 is differential pressure pick-up probe encapsulating structure schematic diagram;
Fig. 4 is the fibre bundle index path of differential pressure method for sensing;
Fig. 5 is fiber bundle structure schematic diagram;
Fig. 6 is light bridge balance strength compensation schematic diagram;
Incident optical coordinate diagram when Fig. 7 is light intensity calculating;
Fig. 8 is the EF schematic cross-section in Fig. 7;
Fig. 9 receives fiber end face and reflective taper position relationship;
Figure 10 is P-M curve when parameter d changes in Fig. 7;
Figure 11 is P-M curve when parameter r changes in Fig. 7;
Figure 12 is P-M curve when parameter l changes in Fig. 7;
Figure 13 is the data and curves of experiment (1);
Figure 14 is the data and curves of experiment (2);
Figure 15 be experiment (1) and (2) in two sensing probes under different pressure-actings, while forming different differential pressure Δ P, the R value situation of change of output.
Description of reference numerals: 11-probe one, 111-test chamber, 112-probing shell, 113-flexible sheet, 12-probe two, 21-photodetector one, 22-photodetector two, 31-measured object one, 32-measured object two, 4-fibre bundle, 41-receives optical fiber, 42-incident optical, 51-light source one, 52-light source two, 61-coupling mechanism one, 62-coupling mechanism two, 63-coupling mechanism three, 64-coupling mechanism four, 71-signal processor one, 72-signal processor two, 81-end cap, 82-thread bush, 83-O-ring seal, 84-screen pack, 85-back-up ring, 86-packing ring, 87-vitreum.
Embodiment
Below in conjunction with drawings and Examples, the present invention is described in further detail.
First see Fig. 1, Fig. 1 has shown the structural principle of differential pressure pick-up probe of the present invention, as we can see from the figure, differential pressure pick-up has two probes, pop one's head in 1 and probe 2 12, two probes structure identical, in probing shell 112, occupy probe near middle position and be provided with a flexible sheet 113, this flexible sheet 113 becomes two parts by probing shell 112 interior separations, Yi Bian be a test chamber 111, another side is a fixed orifice.Test chamber 111 can flow into for test fluid, and fixed orifice can insert for fibre bundle 4.Fibre bundle 4 is gathered bunchy (can see the structure of fibre bundle 4 in conjunction with Fig. 5) by 1 incident optical 42 and 10 reception optical fiber 41 through processing.
See Fig. 2, Fig. 2 has shown probe sensing principle of the present invention, and in conjunction with the sonde configuration shown in Fig. 1, what light source sent couples light in incident optical, by incident optical, be transferred to optical fiber outgoing end face, it is upper that emergent light is irradiated to reflection shell fragment (being the flexible sheet 113 in Fig. 1), and the part light after the reflection of reflection shell fragment enters into and receives in optical fiber, by receiving Optical Fiber Transmission to photodetector place, carry out opto-electronic conversion.Enter into the intensity of reflected light size receiving in optical fiber, by the distance between reflection shell fragment and reception fiber end face, determined, under External Force Acting, reflection shell fragment diminishes with the distance that receives optical fiber, thereby the intensity of reflected light that enters into reception optical fiber is changed, by the variable quantity of output light intensity, can determine the deformation size of reflecting surface, thereby determine the size of ambient pressure P.
See Fig. 3, Fig. 3 has shown the encapsulating structure of probe, adopt after such encapsulating structure, test fluid flows into from intake, after screen pack 84, enter test chamber 111(in conjunction with Fig. 1), in order to reduce the disturbance of fluid, the interior vitreum 87 with cup-shaped cavity of having installed of test chamber 111, vitreum 87 is fixed by probing shell 112 and back-up ring 85.In order to prevent revealing, between flexible sheet 113 and back-up ring 85, installed O-ring seal 83 additional.Flexible sheet 113 is fixed by end cap 81, end cap 81 adopts thread connection form with probing shell 112, fibre bundle 4 is fixed in thread bush 82, add and guarantee preferably circularity and the right alignment of sensor probe housing 112, end cap 81, thread bush 82 man-hour, thereby can guarantee fibre bundle 4 and flexible sheet 113 center alignment issues, the error of avoiding certain probe in detecting to cause because of the position deviation of fibre bundle 4 and flexible sheet 113.Thread bush 82 adopts thread connection with end cap 81, and is carved with scale on thread bush 82 surfaces, thereby can adjust by the precession of threaded engagement the distance of fibre bundle 4 and flexible sheet 113.By mechanical encapsulation can also fibre bundle 4 and flexible sheet 113 between form dark chamber, thereby the noise of avoiding bias light to bring.
See Fig. 4, Fig. 4 has shown the light intensity compensation schematic diagram of this differential pressure method for sensing of the present invention, as we can see from the figure, sensor adopts two light sources alternately luminous (by Control), be that light source 1 and light source 2 52 are alternately luminous, when light source 1 is luminous: the light that light source 1 sends is divided into two-way ，Yi road through coupling mechanism 1 and enters probe 1, through coupling mechanism 2 62, arrive photodetector 1 after reflection, another road directly arrives photodetector 2 22.The light path that arrives photodetector 2 22 is reference path, the size that has reflected light source one 51 Output optical power, arrive the light path of photodetector 1 for detecting light path, reflected through probe 1 and be reflected back and receive optical fiber 41(and now receive optical fiber 41 and assemble fibre bundle 4 with incident optical 42, in conjunction with Fig. 1) luminous power size (size of this power and extraneous tested pressure correlation).Again by asking the now ratio of two detector output voltage signals, realize the error that light source power fluctuation etc. is caused and compensate.The ratio finally obtaining has just embodied probe one under extraneous pressure P 1 effect, the output valve of sensor.
When light source 2 52 is luminous: the light that light source 2 52 sends is divided into two-way ，Yi road through coupling mechanism 3 63 and enters probe 2 12, arrives photodetector 1 after reflection through coupling mechanism 4 64, and another road directly arrives photodetector 2 22.When its principle and above-mentioned light source 1 are luminous in like manner.Signal in photodetector 1 and photodetector 2 22 is processed by signal processor 71 and signal processor 72 respectively, and the ratio finally obtaining has just embodied probe 2 12 under extraneous pressure P 2 effects, the output valve of sensor.
Pressure difference value △ P between ambient pressure P1 and P2, by popping one's head in, one 11 output valves represent with ratio or the difference of probe 2 12 output valves.
See Fig. 6, Fig. 6 has shown principle and the light intensity compensation schematic diagram of differential pressure method for sensing of the present invention, two light sources are under the control of the time relay, one after the other luminous (be light source S1 when luminous light source S2 not luminous), in Fig. 6, two light source S1, S2 are luminous in turn etc. time, and t1 represents S1 fluorescent lifetime, and t2 represents S2 fluorescent lifetime, M1, M2 are two differential pressure probes, and D1, D2 are photodetector.T1 is in the time, and the light that light source S1 sends is divided into two-way ，Yi road through Y type coupling mechanism and enters probe M1, arrives after reflection photodetector D1, and another road directly arrives photodetector D2; T2 is in the time, and the light that light source S2 sends is divided into two-way ，Yi road through Y type coupling mechanism and enters probe M2, arrives after reflection photodetector D1, and another road directly arrives photodetector D2.Later stage to the electric signal of photodetector D1, D2 output amplify, filtering, A/D conversion, again t1 times two detector output signal is divided by, t2 times two detector output signal is divided by and time delay, then t1, t2 times two division signal are divided by, can process by settling signal.Sensor light source is selected semiconductor laser LD, and this laser instrument has very narrow output spectrum live width and outstanding side mode suppression ratio, and its output peak wavelength is 1310nm.Photodetector is selected PIN photodiode, and this photodiode work wavelength coverage is 1100nm～1650nm, and dark current is 1nA to the maximum, and optical responsivity minimum is 0.85A/W, response time 0.1ns.In setting sensor probe, the initial distance of fibre bundle and diaphragm is 0.5mm, and diaphragm material is stainless steel surfaces aluminized mirror, and fibre bundle is that multiply incident optical and sub-thread outgoing optical fiber are processed into bundle.
As shown in Figure 5, that middle be incident optical TF to the fibre bundle sectional view at probe place, around be reception fiber-optic RF.The radical that increases reception optical fiber is in order to receive more reflected light.This fiber bundle structure is coaxial type fibre bundle, and this fibre bundle is more conventional, and its detection sensitivity is higher, is easier to processing and realizes, and be conducive to the analytical calculation in later stage.
Below by the mathematical analysis of flexible sheet deformation is further explained to know-why of the present invention:
When 1, the media environment in chamber changes, elastic membrane sector-meeting produces distortion owing to being under pressure, and the medium in chamber is in a kind of equally distributed situation conventionally, so it will produce an equally distributed load to the surface of whole film.Suppose that cavity pressure is P, the radius of film is R
b, the bending stiffness of film basic unit is k.
2, intensity modulated model:
Owing to being subject to the restriction of structure and light intensity modulation characteristic effective coverage etc., the deflection of flexible sheet is relatively little, so for the ease of analyzing, its reflector space, at y=d(optical fiber, being d with the distance between film) cross section (claiming afterwards reflective taper cross section) in plane can approximate processing become a rounded face (in front view, can see that its diameter is EF), below utilize its front view to carry out two-dimentional quantitative analysis research to the incident optical situation symmetrical with receiving optical fiber.
In Fig. 7, incident optical left margin light l
aBbe irradiated on distortion film, with film curve intersection in B point, and incident optical right margin light l
cDbe irradiated to distortion film on, with film curve intersection in D point.B, the coordinate figure of two intersection points of D in this coordinate system, be the curvilinear equation of distortion film in front view, with two incident ray l
aB, l
cDmatrix equation (10), simultaneous solution system of equations, the solution of gained.
Again as shown in Figure 7, left incident ray l
aBafter film reflection, its left reflection ray is l
bE, right incident optical l
cDafter film reflection, its right reflection ray is l
dF.Obtain the straight-line equation of mirror based fiber optica, first should obtain the slope of this straight-line equation, and know on its line certain any coordinate figure, and the coordinate figure of putting B, D on its line obtained, so now just should obtain straight line l
bEslope k
5, straight line l
dFslope k
6.
Establish again incident ray l
aBbe the tangent line L that B is ordered
1between angle be α, tangent line L
1to reflection ray l
bEbetween angle be also α; Same incident ray l
cDbe the tangent line L that D is ordered
2between angle be β, tangent line L
2to reflection ray l
dFbetween angle be also β.If reflection ray l
bE, l
dFslope be respectively k
5, k
6thereby, can set up following equation:
3, simulation calculation:
If Figure 10, Figure 11, Figure 12 are that initial distance d between flexible sheet and optical fiber is respectively 150 μ m, 200 μ m, 250 μ m, 300 μ m, fiber radius r is respectively 45 μ m, 50 μ m, 55 μ m, 60 μ m, when optical fiber spacing l is respectively 15 μ m, 18 μ m, 21 μ m, 24 μ m, flexible sheet is applied to the pressure P of certain limit, make it to approach the protruding modification of optical fiber, thus the reception optical fiber output intensity rate of change curve drawing.
From Figure 10, be not difficult to find out, d value is less, and flexible sheet and optical fiber lean on closelyer, and its initial output intensity ratio is just larger so, and d value is larger, and its initial output intensity ratio is just less; Under a certain definite d value, along with the increase of pressure P, the distance of flexible sheet and optical fiber can diminish simultaneously, thereby make output intensity ratio take the lead in increasing, reduces again, and this and actual conditions match.Scarp slope curve in figure is wider, can obtain larger sensing range; And adverse grade curve is narrower, can obtain the good linearity and detection sensitivity;
As can be seen from Figure 11,, along with the variation of fiber core radius r, scarp slope curve wide variety is not obvious; But along with the increase of fiber core radius r value, the peak value of curve increases to some extent;
As can be seen from Figure 12, along with the variation of spacing l value, scarp slope curve wide variety is little, little on the sensing range impact of pressure P; Along with the increase of spacing l value, the peak value of curve can decline.
4, experimental data:
After sensor probe 1,2 is fixing, complete respectively following process experiment: the applied pressure of (1) sensor probe 2 is 0, the applied pressure that changes sensor probe 1, makes two detection positions realize the positive pressure differential of 0KPa, 20 KPa, 40 KPa, 60 KPa, 80 KPa, 100 KPa, 120 KPa; (2) applied pressure of sensor probe 1 is 0, changes the applied pressure of sensor probe 2, makes two detection positions realize the Negative Pressure Difference of-120 KPa ,-100 KPa ,-80 KPa ,-40 KPa ,-20 KPa.
Obtain following experimental result (as shown in Table 1 and Table 2):
The experimental data curve simultaneously obtaining is as shown in Figure 13, Figure 14:
Figure 15 is for two sensing probes in experiment (1) and (2) are under different pressure-actings, while forming different differential pressure △ P, the R value situation of change of output, in figure, be not difficult to find out that negative pressure (here for probe two pressure are greater than probe 1 pressure) is better with the front end curve linear degree of malleation (here for probe one pressure is greater than probe two pressure), so follow-uply again intensity compensation R value is carried out to translation, and linearization demarcates and can make output valve better corresponding with each pressure difference, thereby realize the detection of pressure reduction to external world.
Certainly, be more than concrete exemplary applications of the present invention, the present invention also has other embodiment, and all employings are equal to the technical scheme of replacement or equivalent transformation formation, within all dropping on protection domain of the presently claimed invention.
Claims (9)
1. a differential pressure method for sensing, is characterized in that: the pressure that it produces by test fluid goes to impact the wherein one side of a flexible sheet (113), and flexible sheet (113) is deformed; Narrow spectrum Ear Mucosa Treated by He Ne Laser Irradiation in the incident optical for another side (42) of flexible sheet (113), and receive reflected light with receiving optical fiber (41), after flexible sheet (113) deforms, the output light intensity that receives optical fiber (41) will change thereupon, and the variable quantity that receives optical fiber (42) output intensity by detecting judges the pressure variety that test fluid causes flexible sheet (113).
2. differential pressure method for sensing according to claim 1, it is characterized in that: described test fluid produces pressure by flowing into the mode of a test chamber (111) to flexible sheet (113), flexible sheet (113) is arranged on the barrier of the direction formation sealing that in test chamber (111) and in test chamber (111), test fluid flows into.
3. differential pressure method for sensing according to claim 2, is characterized in that: the medium in described test chamber (111) is in a kind of equally distributed situation.
4. differential pressure method for sensing according to claim 2, is characterized in that: adopt a sensor probe housing (112) that described flexible sheet (113) is fastened, sensor probe housing (112) adopts monolithic construction with test chamber (111).
5. differential pressure method for sensing according to claim 4, is characterized in that: incident optical (42) and mirror based fiber optica (41) assemble fibre bundle (4) and by being located at fixed orifice in sensor probe housing (112) to described flexible sheet (113) transmitting optical signal.
6. according to the differential pressure method for sensing described in claim 1～5 any, it is characterized in that: described flexible sheet (113) adopts the preparation of 35CrMnSi material.
7. a reflection type optical fiber bundle differential pressure pick-up that adopts the intensity compensation of method claimed in claim 1, it is characterized in that: it comprises pressure detection probe one (11) that two structures are identical and probe two (12) and for the incident optical to these two probe transmission light sources (42) with for receiving the radiative reception optical fiber (41) of pressure detection probe, incident optical (42) and reception optical fiber (41) assemble fibre bundle (4); The probing shell of these two probes (112) inside is fixed with a flexible sheet (113), the two sides that is arranged in flexible sheet (113) in probe be respectively equipped with a test chamber (111) and can supply fibre bundle (4) insert probe fixed orifice.
8. the reflection type optical fiber bundle differential pressure pick-up of intensity compensation according to claim 7, is characterized in that: described test chamber (111) is processed into one-piece construction with probing shell (112).
9. the reflection type optical fiber bundle differential pressure pick-up of intensity compensation according to claim 7, is characterized in that: described detecting device (111) is provided with at least one can flow into test fluid entrance wherein for test fluid.
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