CN203551182U - Packaging structure of differential pressure probe - Google Patents

Abstract

The utility model discloses a packaging structure of a differential pressure sensor probe, which is characterized in that a gasket (86) is arranged around a detection fluid inlet of a detection chamber (111), a filter net (84) is arranged at the detection fluid inlet, and an elastic diaphragm (113) and the detection chamber (111) block the elastic membrane (113) with a retaining ring (85), and use an end cover (81) in the fixing hole to seal the elastic membrane from the direction of the retaining ring (85) outward. The sheet (113) is extruded and fixed; a threaded sleeve (82) is provided in the end cap (81) to fix the optical fiber bundle therein. This method can ensure the processing accuracy and assembly accuracy, so that the processed probes have the same structure, which is conducive to the realization of standardization, serialization, and generalization, and can also well avoid detection errors caused by structural errors. The optical fiber bundle with such a packaging structure can be well fixed.

Description

A packaging structure of a differential pressure sensor probe

technical field

The utility model relates to a packaging structure of a differential pressure sensor probe, which belongs to the field of sensor probe packaging. the

Background technique

Differential Pressure Sensor DPS (Differential Pressure Sensor) is a sensor used to measure the difference between two pressures, usually used to measure the pressure difference between the front and back ends of a device or component. In recent years, differential pressure sensors have been widely used in many high-precision measurement occasions such as micro-flow measurement, leak testing, clean room monitoring, environmental tightness testing, gas flow measurement, and liquid level measurement. the

At present, the research on differential pressure sensors at home and abroad mainly focuses on the traditional piezoresistive differential pressure sensors and capacitive differential pressure sensors. The piezoresistive differential pressure sensor has a simple structure and a flat working surface, but there is a prominent contradiction between its sensitivity and frequency response, and the temperature has a great influence on the performance of this sensor. Capacitive sensors have high sensitivity, good dynamic response characteristics, and strong overload resistance, but they have shortcomings such as the influence of parasitic capacitance and distributed capacitance on sensitivity and measurement accuracy, and the circuit connected to the sensor is relatively complicated, which affects its application reliability. , thus limiting its wide application. It is precisely because of the many shortcomings of traditional differential pressure sensors that some new types of differential pressure sensors have been studied at home and abroad. The displacement process generates electrical signals to detect pressure, which has limitations in application; Taiwan's Hao-Jan Sheng et al., and the United States' Jose.L.A.V et al. proposed a fiber optic differential pressure sensor structure based on Bragg gratings , this fiber grating differential pressure sensor has high sensitivity, but its complex structure and high cost are not conducive to popularization. Intensity modulation, as the most widely used modulation method in optical fiber sensor technology, has been studied by some scholars, but there are few research documents on optical fiber differential pressure sensors based on intensity modulation. Seiichiro Kinugasa of Japan proposed a reflection The idea of the optical fiber differential pressure sensor, using the change of the distance between the reflective surface and the optical fiber to detect the external pressure difference; Tong Chengguo et al. designed a double C-shaped spring tube optical fiber differential pressure sensor, based on the principle of intensity modulation in two double C The pressure difference is detected in the type spring tube. the

However, the existing technology still does not solve the problems caused by many key factors such as the realization of the sensor, the rationality of the probe structure parameters, the working state of the reflective surface, and the compensation of the error. Therefore, the structure of this type of sensor in the prior art is very complicated, and the performance They are not reliable enough, the processing and manufacturing costs are high, and they are usually bulky, very heavy, inconvenient to use, and there is still a lot of room for improvement. This is the first technical problem existing in the prior art. the

In addition, the sensor probe should be stable and reliable during work, and it is not easy to be disturbed by external collisions, vibrations and other factors. The packaging of the sensor probe is the second technical problem in the prior art. the

For reflective optical fiber differential pressure sensors based on the principle of intensity modulation, the output light intensity of different probes will inevitably be affected by background light, fiber length, fiber bending, coupling devices, etc., resulting in large errors in the detection results. There is a third technical problem with technology. the

Contents of the invention

In order to solve the three problems in the prior art, it is necessary to start from the structure of the sensor head, the package of the sensor and the light intensity compensation of the output light of the head. For this reason, such purpose can be achieved from the following three aspects. the

In order to solve the problems of complex sensor structure, unreliable performance, high processing cost and large volume quality, it is proposed to adopt such a differential pressure sensing method and its sensor. The main point of this sensing method is that it is used to measure The detection fluid (such as hydraulic oil) that generates pressure from the measured object is used for sensing, so that the pressure generated by the detection fluid impacts one side of an elastic diaphragm to deform the elastic diaphragm; the other side of the elastic diaphragm is used The narrow-band laser in the incident fiber is irradiated, and the receiving fiber is used to receive the reflected light; in this way, when the elastic diaphragm is deformed, due to the change of the reflection angle, the reflected light changes accordingly, resulting in the output light intensity of the receiving fiber. In this way, the amount of pressure change caused by the detection fluid to the elastic diaphragm is judged by detecting the amount of change in the output light intensity of the receiving optical fiber. In this way, the pressure change that is difficult to measure can be judged by the light intensity change that is easy to measure, so as to determine the pressure difference of different measured objects and realize the purpose of differential pressure sensing. the

As a preferred manner, the detection fluid flows into a detection chamber to generate pressure on the elastic diaphragm, and the elastic diaphragm is arranged in the detection chamber and forms a closed barrier in the direction of the detection fluid flowing into the detection chamber. The detection chamber is closed, but there is an opening facing the direction of the measured object. When the detection fluid pours into the detection chamber from the opening of the detection chamber, it will generate liquid pressure on the elastic diaphragm in the detection chamber, thus forming the elastic membrane sheet deformation. When the medium environment in the cavity changes, the elastic diaphragm will be deformed due to the pressure. It is best to detect that the medium in the cavity is in a uniform distribution, so it will produce a uniform distribution on the surface of the entire film. load. By adopting such a detection chamber, the liquid pressure generated by the detection fluid can evenly and accurately deform the elastic membrane, thereby improving the detection and sensing accuracy. the

In order to avoid the edge displacement of the elastic diaphragm when it is subjected to the pressure generated by the detection fluid, a sensor probe housing can be used to fasten the elastic diaphragm on it. The sensor probe housing can adopt an integral structure with the detection chamber, and the elastic The diaphragm is fixedly arranged between the sensor probe housing and the detection chamber. Since the elastic diaphragm is firmly fixed, no matter how much liquid pressure the detection fluid exerts on it, it will only cause elastic deformation on its surface, and will not cause displacement of its edge, which prevents the sensor from being damaged due to the impact of the thin film by the fluid . In addition, the incident light is irradiated to the elastic diaphragm through the fixing hole in the sensor head case. The fixing hole is perpendicular to the surface of the elastic diaphragm, which can ensure that the incident light irradiation angle or the reflection angle of the optical fiber bundle formed by the incident optical fiber, the receiving optical fiber or the two will not be shifted arbitrarily. the

In order to make the sensor have better static performance, the elastic diaphragm will have a small twist when it is deformed under pressure. Considering the specific working conditions of the elastic diaphragm of the sensor structure and the properties of various materials, 35CrMnSi material is preferred Preparation of thin slices is carried out. This material is also called low-alloy ultra-high-strength steel. After heat treatment, it has good comprehensive mechanical properties, high strength, sufficient toughness, hardenability, weldability (preheating before welding), and good processing formability. Corrosion and oxidation resistance are relatively general, and the service temperature is usually not higher than 200°C, and it is generally used after low-temperature tempering or austempering. the

Based on the aforementioned sensing method, such an intensity-compensated reflective optical fiber bundle differential pressure sensor can be used, which includes two pressure detection probes with the same structure and incident optical fibers for transmitting light sources into the pressure detection probes and The receiving optical fiber is used to receive the emitted light of the pressure detection probe, and the incident optical fiber and the receiving optical fiber are gathered in the fixing hole to form an optical fiber bundle. An elastic diaphragm is fixed inside the pressure detection probe, and a detection cavity and a fixing hole for inserting an optical fiber bundle into the probe are respectively provided on both sides of the pressure detection probe. The detection chamber is used to detect fluid flowing into it and generate liquid pressure on the elastic diaphragm. The detection chamber is provided with at least one detection fluid inlet through which detection fluid can flow into it. It is best to be like this: the sensor is equipped with two light sources, assumed to be S1 and S2, two detection probes one and two, two photodetectors D1 and D2, four fiber couplers divided into two, and incident optical fibers It consists of a fiber bundle structure that is bundled with reflective fibers. The sensor light source is a semiconductor laser, which has a very narrow output spectral linewidth and excellent side-mode suppression ratio, and its output peak wavelength is 1310nm. The photodetector is a PIN photodiode. The working wavelength range of the photodiode is 1100nm-1650nm, the maximum dark current is 1nA, the minimum photoresponsivity is 0.85A/W, and the response time is 0.1ns. In this way, the spectral characteristics of the light source and the photodetector are better matched. the

The light emitted by the light source is coupled into the incident fiber, transmitted to the exit end face of the fiber through the incident fiber, and the exit light is irradiated on the reflective shrapnel (elastic diaphragm), and part of the light reflected by the reflective shrapnel enters the receiving fiber and is transmitted by the receiving fiber to the photodetector for photoelectric conversion. The intensity of reflected light entering the receiving fiber is determined by the distance between the reflecting shrapnel and the end face of the receiving fiber. Change, the deformation of the reflective surface can be determined by the change of the output light intensity, so as to determine the magnitude of the external pressure P. the

Of course, the pressure detection probe of this sensor also includes a probe housing, and the above-mentioned fixing hole, elastic diaphragm and detection cavity are all located in the probe housing. The detection cavity and the probe housing are preferably processed into an integral structure. The material of the probe shell is selected from metal materials, and for convenience in processing, metal aluminum rods are preferably used. the

In order to solve the packaging problem of the sensor probe and make the probe stable, easy to process, easy to assemble, and easy to maintain and replace, it is proposed to adopt such a packaging method and structure:

The packaging method of this differential pressure sensor probe includes the method of packaging the sensor probe with an elastic diaphragm inside, and the fixing holes for optical fiber bundle insertion and a detection cavity are respectively arranged on both sides of the elastic diaphragm in the probe. The utility model adopts a threaded sleeve structure to fix the optical fiber bundle in the fixing hole. Since the optical fiber bundle is stuck in the threaded sleeve, and then the threaded sleeve is screwed into the probe, the shaking of the optical fiber bundle caused by directly inserting the optical fiber bundle into the probe can be avoided.

Further, the specific method is to use a cylindrical end cover to screw in from the outside to the direction of the elastic diaphragm in the fixing hole formed by the probe housing. There is a threaded hole in the center of the end cover, and a threaded sleeve is used to cover the optical fiber bundle. live. The external thread of the threaded sleeve matches the internal thread of the threaded hole of the end cap, so that the threaded sleeve can be screwed in or out of the end cap (. The threaded hole of the end cap, the threaded sleeve and the fixing hole in the probe The bore axes remain coaxial.

Further, on the other side of the elastic diaphragm, that is, on the side of the detection chamber, a retaining ring is used to clamp the elastic diaphragm, and the elastic diaphragm is screwed into the thread of the end cap and squeezed and fixed by the retaining ring. the

According to the above-mentioned method, a packaging structure of a differential pressure sensor probe of the present utility model includes a differential pressure sensor probe housing and an elastic diaphragm and a detection cavity in it, and an optical fiber bundle for transmitting optical signals is formed through the probe housing. The fixed hole of the detection chamber is inserted into the probe, the detection chamber is provided with a detection fluid inlet, and the elastic diaphragm is located between the fixed hole and the detection chamber, wherein a gasket is arranged around the detection fluid inlet of the detection chamber, and a filter is arranged at the detection fluid inlet. A retaining ring is used to block the elastic diaphragm between the diaphragm and the detection chamber, and an end cap is used to squeeze and fix the elastic diaphragm from the direction of the retaining ring in the fixing hole; a threaded sleeve is provided in the end cap to hold the optical fiber The bundle is fixed in it. the

Further, a cup-shaped glass body is filled in the detection chamber, and the glass body is clamped between the retaining ring and the probe housing, so that the detection chamber has a cup-shaped cavity structure. A sealing ring is arranged between the elastic diaphragm and the retaining ring. The end cap and the probe housing adopt a tight fitting structure. The threaded sleeve and the end cap are connected by threads, and the surface of the threaded sleeve is engraved with a scale. the

The differential pressure sensor of the utility model is a free structure with two probes working at the same time, the probe part can move freely, and the position to be detected can be freely selected for detection; during detection, the probe can be directly fixed at the detection position without draining, This avoids freezing, blockage and hysteresis in the drainage process of the drainage tube; at the same time, according to the detection needs, probes with different geometric dimensions and detection ranges can be designed to meet some special needs, etc., requiring the two probes to be as symmetrical as possible same. For a single probe, the following requirements must be met in the package: the optical fiber bundle is well aligned with the center of the elastic diaphragm, the distance between the optical fiber bundle and the elastic diaphragm is adjustable, and the optical fiber bundle can be well fixed. The difficulty of encapsulation. the

Therefore, the utility model adopts a mechanical packaging method, which can ensure the processing accuracy and assembly accuracy, so that the structures of the processed probes are the same, thereby facilitating the realization of standardization, serialization, and generalization, and can also avoid Detection errors caused by structural errors. the

In order to achieve the above requirements, the characteristics of the sensor package are: the fiber bundle in the fixing hole is fixed with a threaded sleeve, so that the fiber bundle cannot move, and the error caused by the vibration of the fiber bundle is avoided. The specific method is: use a cylindrical external threaded end cap to screw in from the outside to the direction of the elastic diaphragm in the internal threaded fixing hole formed by the probe housing. Covering, the external thread of the threaded sleeve matches the internal thread of the threaded hole at the center of the end cap, so that the threaded sleeve can be screwed in or out of the end cap. Therefore, the threaded connection form of the threaded sleeve and the end cap enables the threaded sleeve to be screwed freely in the end cap (the preferred thread pitch is 0.2mm, and the outer wall of the threaded sleeve is marked with a screw-in length scale, the minimum scale is 0.1mm), thus realizing The distance between the optical fiber bundle and the elastic diaphragm is adjustable; (because the initial distance between the optical fiber bundle and the elastic diaphragm directly determines the two key static characteristics of the sensor’s detection sensitivity and linearity, a reasonable adjustment between the optical fiber bundle and the elastic diaphragm The initial distance to improve the detection performance. At the same time, the optimal initial distance corresponding to different fiber bundle end-face structures is different, so the distance between the fiber bundle and the elastic diaphragm is required to be adjustable.) The threaded hole of the end cap, the threaded sleeve and the fixing hole of the probe The axis of the hole remains coaxial, so that the package structure of this cylinder can ensure the coaxiality of each part during processing, which can ensure that the optical fiber bundle is well aligned with the center of the elastic diaphragm, and the structure is simple and applicable. The elastic diaphragm can be well fixed and easy to assemble and replace. the

On the other side of the elastic diaphragm, a retaining ring is used to clamp the elastic diaphragm, and the elastic diaphragm can achieve a good fixing effect and is not easy to loose through the thread screwing of the end cap and the extrusion and fixing method of the retaining ring. At the same time, if the elastic diaphragm needs to be replaced, it can be realized by unscrewing the end cover, which is simple and applicable. At the same time, a gasket is arranged around the detection fluid inlet of the detection chamber of the probe, and a filter is arranged at the detection fluid inlet to filter the fluid entering the detection chamber. the

The stability of the detection chamber and the uniformity of the medium are an important requirement to ensure the sensing accuracy, so the detection chamber must be able to reduce the disturbance of the fluid. Therefore, such a structure is adopted: a cup-shaped glass body is filled in the detection chamber, and the glass body is stuck between the retaining ring and the sensor housing, so that the detection chamber is a cup-shaped cavity structure, which can reduce the volume of the detection chamber, thereby making the retention There is very little fluid. At the same time, the unevenness of the pressure in the detection chamber is reduced, so that the pressure acting on the elastic diaphragm becomes more uniform. The vitreous body is chosen for its ease of molding, high hardness, resistance to long-term corrosion by fluids, etc. the

In order to prevent leakage of the detection fluid, a sealing ring can also be installed between the elastic diaphragm and the retaining ring. The elastic diaphragm is compressed and fixed by the end cover. The end cover and the housing adopt a tight fitting structure, and the optical fiber bundle is fixed in the threaded sleeve. During processing, it is better to ensure that the roundness of the sensor housing, end cover, and threaded sleeve is the same as the same The axiality can ensure the center alignment of the fiber bundle and the elastic diaphragm, and avoid the error caused by the position deviation of a certain probe during the detection due to the position deviation between the fiber bundle and the elastic diaphragm. The threaded sleeve and the end cap are connected by threads, and the surface of the threaded sleeve is engraved with a scale, so that the distance between the optical fiber bundle and the elastic diaphragm can be adjusted by screwing in the threaded fit. Through mechanical packaging, a dark cavity can be formed between the fiber bundle and the elastic diaphragm, thereby avoiding noise caused by background light. the

The optical fiber bundle differential pressure sensor detection probe adopts the principle of intensity modulation, and judges the change of the measured physical quantity by monitoring the change of the intensity of light, so that the light intensity change caused by the light source, optical fiber, optical fiber device and optical detector will be cause errors in the test results. In order to avoid or reduce this detection error, intensity compensation should be considered for this type of intensity modulation optical fiber sensor, so as to improve the detection stability and reliability of the sensor. the

The light intensity compensation method adopted by this sensor of the utility model is as follows: firstly, the sensor uses two light sources to emit light alternately, when one of the light sources emits light, the light wave is first coupled into an incident optical fiber, and then passes through a Y-shaped coupler that splits into two , divided into two light waves with equal power, one path directly reaches a photodetector through the reference optical path, and is converted into a voltage signal output by the detector. The magnitude of the voltage signal reflects half of the output power of the light source; the other path is detected The optical path reaches the detection probe one, and after being reflected by the elastic diaphragm, it reaches another photodetector through the receiving optical fiber, which is converted into a voltage signal output by the detector, and the magnitude of the voltage signal reflects the other half of the output power of the light source. The light power received after reflection; and then calculate the ratio of these two output voltages in the later stage. This ratio has nothing to do with the power change of the light source. By using this ratio to reflect the pressure on the detection probe 1, it can eliminate The error caused by the fluctuation of the light source. the

When the other light source emits light, it is the same as the above process, and the pressure at the two places of the other detection probe is reflected by the ratio. the

Then, the difference between the output ratios of the detection probe 1 and the detection probe 2, or the ratio of the ratios, is calculated. Finally, it reflects the pressure difference between the two probes. The intensity compensation of the light source fluctuation can be realized by calculating the difference of the ratio; the intensity compensation of the light source fluctuation, photodetector and fiber loss can be realized by calculating the ratio of the ratio (but the pressure difference detection range of this method is small). the

The optical path adopts the layout form of optical bridge, so that the reference optical path of the two light sources reaches the same photodetector through the Y-type coupler, and the reflected light receiving optical path of the two detection probes reaches the other photodetector through the Y-type coupler, thus simplifying the The overall optical path structure of the sensor simplifies the optical fiber layout, reduces the number of detectors, and simplifies the later data processing modules. Ultimately realize the design of economy and reliability. the

Description of drawings

Figure 1 is a schematic diagram of the structure of the differential pressure sensor probe;

Figure 2(a) and Figure 2(b) are schematic diagrams of the differential pressure sensing method;

Figure 3 is a schematic diagram of the package structure of the differential pressure sensor probe;

Fig. 4 is the optical path diagram of the optical fiber bundle of the differential pressure sensing method;

Fig. 5 is a schematic diagram of the structure of an optical fiber bundle;

Fig. 6 is a schematic diagram of optical bridge balance intensity compensation;

Figure 7 is a coordinate diagram of the incident optical fiber during light intensity calculation;

Fig. 8 is a schematic cross-sectional view of EF in Fig. 7;

Figure 9(a), Figure 9(b), and Figure 9(c) are the positional relationship between the end face of the receiving fiber and the reflected light cone;

Fig. 10 is the P-M curve when parameter d changes among Fig. 7;

Fig. 11 is the P-M curve when parameter r changes among Fig. 7;

Fig. 12 is the P-M curve when parameter 1 changes among Fig. 7;

Fig. 13 is the data curve of experiment (1);

Fig. 14 is the data curve of experiment (2);

Figure 15 shows the change of the output R value when the two sensing probes form different differential pressures ΔP under different pressures in experiments (1) and (2).

Description of reference signs: 11-probe one, 111-detection chamber, 112-probe housing, 113-elastic diaphragm, 12-probe two, 21-photodetector one, 22-photodetector two, 31-measured Object 1, 32-object 2, 4-fiber bundle, 41-receiving fiber, 42-incident fiber, 51-light source 1, 52-light source 2, 61-coupler 1, 62-coupler 2, 63-coupling Device three, 64-coupler four, 71-signal processor one, 72-signal processor two, 81-end cover, 82-thread sleeve, 83-sealing ring, 84-filter, 85-retaining ring, 86- Gasket, 87-Vitreous. the

Detailed ways

Below in conjunction with accompanying drawing and embodiment the utility model is described in further detail. the

First look at Fig. 1, Fig. 1 shows the structural principle of the differential pressure sensor probe of the present utility model, as can be seen from the figure, the differential pressure sensor has two probes, namely probe one 11 and probe two 12, the structure of the two probes Exactly the same, an elastic membrane 113 is arranged near the middle of the probe in the probe housing 112, and the elastic membrane 113 divides the interior of the probe housing 112 into two parts, one side is a detection cavity 111, and the other side is a Fixing hole. The detection cavity 111 can allow the detection fluid to flow in, and the fixing hole can allow the optical fiber bundle 4 to be inserted. The optical fiber bundle 4 is processed into a bundle by one incident optical fiber 42 and ten receiving optical fibers 41 (the structure of the optical fiber bundle 4 can be seen in conjunction with FIG. 5 ). the

See Figure 2(a) and Figure 2(b), Figure 2(a) and Figure 2(b) show the sensing principle of the probe of the present invention, and combined with the probe structure shown in Figure 1, the optical coupling emitted by the light source into the incident fiber, transmitted to the exit end face of the fiber through the incident fiber, and the outgoing light is irradiated on the reflective shrapnel (that is, the elastic diaphragm 113 in Figure 1), and part of the light reflected by the reflective shrapnel enters the receiving fiber, and is transmitted by the receiving fiber It is transmitted to the photodetector for photoelectric conversion. The intensity of reflected light entering the receiving fiber is determined by the distance between the reflecting shrapnel and the end face of the receiving fiber. Change, the deformation of the reflective surface can be determined by the change of the output light intensity, so as to determine the magnitude of the external pressure P. the

See Figure 3, Figure 3 shows the packaging structure of the probe. After adopting such a packaging structure, the detection fluid flows in from the inlet, passes through the filter 84, and then enters the detection chamber 111 (combined with Figure 1). In order to reduce the disturbance of the fluid, the detection chamber A glass body 87 with a cup-shaped cavity is installed in 111 , and the glass body 87 is fixed by the probe housing 112 and the retaining ring 85 . In order to prevent leakage, a sealing ring 83 is installed between the elastic diaphragm 113 and the retaining ring 85 . The elastic diaphragm 113 is compressed and fixed by the end cap 81, the end cap 81 and the probe housing 112 adopt a threaded connection form, the optical fiber bundle 4 is fixed in the threaded sleeve 82, and the sensor probe housing 112 and the end cap are better ensured during processing. 81. The roundness and coaxiality of the threaded sleeve 82 can ensure the center alignment of the optical fiber bundle 4 and the elastic diaphragm 113, and avoid a certain probe in the detection caused by the positional deviation between the optical fiber bundle 4 and the elastic diaphragm 113 error. The threaded sleeve 82 and the end cap 81 are threadedly connected, and a scale is engraved on the surface of the threaded sleeve 82, so that the distance between the optical fiber bundle 4 and the elastic diaphragm 113 can be adjusted by screwing in the threaded fit. A dark cavity can also be formed between the optical fiber bundle 4 and the elastic diaphragm 113 through mechanical packaging, thereby avoiding noise caused by background light. the

See Figure 4. Figure 4 shows a schematic diagram of light intensity compensation for this differential pressure sensing method of the present invention. It can be seen from the figure that the sensor uses two light sources to emit light alternately (controlled by a relay), that is, light source one 51 and The light source 2 52 emits light alternately. When the light source 51 emits light: the light emitted by the light source 51 is divided into two paths through the coupler 61, and all the way enters the probe 11, and after reflection, it reaches the photodetector 1 21 through the coupler 62. The other path directly reaches the second photodetector 22 . The optical path arriving at photodetector two 22 is a reference optical path, which reflects the size of the output optical power of light source one 51, and the optical path arriving at photodetector one 21 is a detection optical path, reflecting that the light path reflected by probe one 11 is returned to receiving optical fiber 41 (receiving at this time The optical fiber 41 and the incident optical fiber 42 are combined to form an optical fiber bundle 4, referring to FIG. 1 ) the optical power (the power is related to the measured external pressure). Then by calculating the ratio of the output voltage signals of the two detectors at this time, the error caused by the power fluctuation of the light source is realized. The finally obtained ratio reflects the output value of the sensor under the action of the external pressure P1 of the probe one. the

When the light source 2 52 emits light: the light emitted by the light source 2 52 is divided into two paths by the coupler 3 63, one path enters the probe 2 12, and after being reflected, it reaches the photodetector 1 21 through the coupler 64, and the other path directly reaches the photodetector Apparatus 2:22. Its principle is the same as when the above-mentioned light source one 51 emits light. The signals in the first photodetector 21 and the second photodetector 22 are respectively processed by the signal processor 71 and the signal processor 72, and the finally obtained ratio reflects the output value of the sensor of the second probe 12 under the external pressure P2. the

The pressure difference ΔP between the external pressure P1 and P2 is represented by the ratio or difference between the output value of the probe one 11 and the output value of the probe two 12 . the

See Figure 6. Figure 6 shows the principle of the differential pressure sensing method of the present invention and a schematic diagram of light intensity compensation. Under the control of the time relay, the two light sources alternately emit light in turn (that is, the light source S1 emits light while the light source S2 does not emit light), as shown in Fig. In 6, the two light sources S1 and S2 emit light at equal times in turn, t1 represents the light emitting time of S1, t2 represents the light emitting time of S2, M1 and M2 are two differential pressure probes, and D1 and D2 are photodetectors. During the time t1, the light emitted by the light source S1 is divided into two paths by the Y-type coupler, one path enters the probe M1, and reaches the photodetector D1 after reflection, and the other path directly reaches the photodetector D2; within the time t2, the light emitted by the light source S2 The light is divided into two paths by the Y-type coupler, one path enters the probe M2, and reaches the photodetector D1 after reflection, and the other path directly reaches the photodetector D2. In the later stage, the electrical signals output by photodetectors D1 and D2 are amplified, filtered, and A/D converted, and then the output signals of the two detectors are divided at time t1, and the output signals of the two detectors are divided and delayed at time t2, and then The signal processing can be completed by dividing the two division signals at time t1 and t2. The sensor light source is a semiconductor laser LD, which has a very narrow output spectral linewidth and excellent side mode suppression ratio, and its output peak wavelength is 1310nm. The photodetector is a PIN photodiode. The working wavelength range of the photodiode is 1100nm-1650nm, the maximum dark current is 1nA, the minimum photoresponsivity is 0.85A/W, and the response time is 0.1ns. The initial distance between the optical fiber bundle and the diaphragm in the sensor probe is set to 0.5mm, the diaphragm material is a mirror coated with aluminum on the surface of stainless steel, and the optical fiber bundle is processed into a bundle of multiple incident optical fibers and a single outgoing optical fiber. the

The cross-sectional view of the fiber bundle at the probe is shown in Figure 5, the middle one is the incident fiber TF, and the surrounding one is the receiving fiber RF. Increasing the number of receiving optical fibers is to receive more reflected light. The structure of this fiber bundle is a coaxial fiber bundle, which is commonly used, has high detection sensitivity, is easier to process and realize, and is beneficial to later analysis and calculation. the

Further explain the technical principle of the present utility model through the mathematical analysis to elastic diaphragm deformation below:

1. When the medium environment in the cavity changes, the elastic diaphragm will be deformed due to the pressure. Usually the medium in the cavity is in a uniform distribution, so it will produce a uniform distribution on the surface of the entire film. load. Assume that the pressure in the chamber is P, the radius of the membrane is R _B , and the bending stiffness of the base layer of the membrane is k.

2. Intensity modulation model:

Due to the limitation of the effective area of the structure and light intensity modulation characteristics, the deformation of the elastic diaphragm is relatively small, so for the convenience of analysis, the cross-section of the reflection area on the plane y=d (the distance between the optical fiber and the film is d) (hereinafter referred to as the reflected light cone section) can be approximated as a circular surface (in the front view, its diameter can be seen as EF), and the two-dimensional quantification of the symmetrical distribution of the incident fiber and the receiving fiber is performed using its front view. Analysis.

The effective area S of the end face of the receiving fiber that can receive the reflected light can be obtained in three cases as shown in Figure 9(a), Figure 9(b), and Figure 9(c). In the RIM-FOS modeled in this paper, the elastic The deformation of the diaphragm is small, and the receiving fiber with a larger numerical aperture is selected, so it can be considered that the reflected light can be transmitted to the detector by the receiving fiber within the range of the receiving fiber. the

3. Simulation calculation:

As shown in Figure 10, Figure 11, and Figure 12, the initial distance d between the elastic diaphragm and the optical fiber is 150 μm, 200 μm, 250 μm, and 300 μm, the fiber radius r is 45 μm, 50 μm, 55 μm, and 60 μm, and the fiber spacing l is 15 μm. , 18μm, 21μm, and 24μm, apply a certain range of pressure P to the elastic diaphragm to make it close to the convex deformation of the optical fiber, and thus obtain the output light intensity ratio change curve of the receiving optical fiber.

It is not difficult to see from Figure 10 that the smaller the value of d, that is, the closer the elastic diaphragm is to the optical fiber, the greater the ratio of the initial output light intensity, and the larger the value of d, the smaller the ratio of the initial output light intensity; At the same time, under a certain d value, as the pressure P increases, the distance between the elastic diaphragm and the optical fiber will become smaller, so that the output light intensity ratio first increases and then decreases, which is consistent with the actual situation . The front slope curve in the figure is wider, which can obtain a larger detection range; while the back slope curve is narrower, which can obtain better linearity and detection sensitivity;

It can be seen from Figure 11 that as the core radius r changes, the width of the foreslope curve does not change significantly; but as the core radius r increases, the peak value of the curve increases;

It can be seen from Figure 12 that with the change of the distance l value, the width of the foreslope curve does not change much, that is, it has little influence on the detection range of the pressure P; as the distance l value increases, the peak value of the curve will decrease.

4. Experimental data:

After the sensor probes 1 and 2 are fixed, the following process experiments are completed respectively: (1) The acting pressure of the sensor probe 2 is 0, and the acting pressure of the sensor probe 1 is changed to make the two detection positions realize 0KPa, 20 KPa, 40 KPa, and 60 KPa , 80 KPa, 100 KPa, 120 KPa positive pressure difference; (2) The acting pressure of sensor probe 1 is 0, change the acting pressure of sensor probe 2, so that the two detection positions can achieve -120 KPa, -100 KPa, -80 KPa , -40 KPa, -20 KPa negative pressure difference.

The following experimental results were obtained (as shown in Table 1 and Table 2):

The experimental data curves obtained at the same time are shown in Figure 13 and Figure 14:

Figure 15 shows the changes in the output R value when the two sensing probes form different differential pressures △P under different pressures in experiments (1) and (2). It is not difficult to see the negative pressure (here is the probe The linearity of the front-end curves of pressure two is greater than that of probe 1) and positive pressure (here, the pressure of probe one is greater than the pressure of probe two) is better, then the subsequent translation of the intensity compensation R value and linear calibration can make the output value and Each pressure difference value corresponds better, so as to realize the detection of the external pressure difference.

Of course, the above are only specific application examples of the utility model, and the utility model also has other implementation modes, and all technical solutions formed by equivalent replacement or equivalent transformation all fall within the scope of protection required by the utility model. the

Claims (5)

1. the encapsulating structure of differential pressure pick-up probe, comprise differential pressure pick-up probing shell (112) with and interior flexible sheet (113), test chamber (111), fibre bundle (4) for transmitting optical signal inserts in probe by the fixed orifice forming in probing shell (112), test chamber (111) is provided with test fluid entrance, flexible sheet (113) is positioned between fixed orifice and test chamber (111), it is characterized in that: the test fluid entrance in test chamber (111) arranges packing ring (86) around, screen pack (84) is set in test fluid porch, between flexible sheet (113) and test chamber (111), with a back-up ring (85), flexible sheet (113) is blocked, from the direction of export-oriented back-up ring (85), flexible sheet (113) extruding is fixing with an end cap (81) in fixed orifice, in end cap (81), be provided with a thread bush (82) fibre bundle is fixing within it.

2. the encapsulating structure that differential pressure pick-up according to claim 1 is popped one's head in, it is characterized in that: in test chamber (111), fill a cup-shaped vitreum (87), vitreum (87) is stuck between back-up ring (85) and probing shell (112), makes test chamber (111) for cup-shaped cavity structure.

3. the encapsulating structure of differential pressure pick-up probe according to claim 1, is characterized in that: between flexible sheet (113) and back-up ring (85), be provided with an O-ring seal (83).

4. the encapsulating structure of differential pressure pick-up probe according to claim 1, is characterized in that: described end cap (81) adopts interference fit structure with probing shell (112).

5. the encapsulating structure of differential pressure pick-up probe according to claim 1, is characterized in that: described thread bush (82) adopts thread connection with end cap (81), and is carved with scale on thread bush surface.

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