A double-interference hydrogen sensor based on the optical lever correction principle

Abstract

The invention discloses a double interference hydrogen sensor based on the optical lever correction principle, which consists of a broadband light source, a spectrometer, a reference optical fiber, a temperature reference optical fiber, a hydrogen reference optical fiber, a hydrogen-sensitive film, a vacuum temperature transfer tube, a deformation sheet, a telescope, a ruler, a reflector device and a bracket. The sensor is placed in a hydrogen environment, and the broadband light source generates two coherent light beams through the spectrometer. The hydrogen reference optical fiber is turned off, and the two coherent light beams pass through the reference optical fiber and the temperature reference optical fiber respectively, and only the influence of the ambient temperature is obtained by recording the information of the interference pattern. Then the temperature reference optical fiber is turned off, and the two coherent light beams pass through the reference optical fiber and the hydrogen reference optical fiber, and the information of the interference pattern is recorded. The error influence of the ambient temperature on the sensor is corrected according to the recorded temperature information, and finally the two information are comprehensively analyzed to obtain the hydrogen concentration. The invention is less affected by the environment, has high precision, long service life, has certain innovation and practical value, and has good market prospects.

Description

Technical Field

[0001] The invention belongs to the field of hydrogen sensors, and in particular relates to a double-interference hydrogen sensor based on the optical lever correction principle. Background Art

[0002] In today's society, due to the limited availability of fossil fuels and the greenhouse effect and environmental pollution they cause, clean new energy has become a research hotspot for global development and utilization. Hydrogen energy has the advantages of high combustion efficiency and no pollution to products. It is called one of the nine new energy sources along with solar energy and wind energy, and is known as the most promising secondary energy. At the same time, hydrogen is also an important industrial raw material, and is widely used in the electronics industry, automobile industry, metallurgical industry, petrochemical industry, float glass, fine organic synthesis, aerospace, food processing, etc. Hydrogen is a colorless, odorless, non-toxic, flammable and explosive gas. The molecular weight of hydrogen is very small, and it is easy to leak during production, storage, transportation, and use, and hydrogen has a strong permeability. At the same time, the ignition point of hydrogen is 585°C. When the hydrogen content in the air is in the range of 4% to 75%, it will explode when encountering an open flame, which brings great inconvenience to the storage and use of hydrogen. In view of the wide use and insecurity of hydrogen in the fields of food hygiene, energy power, military defense, etc., its concentration must be tested when using hydrogen. A lot of research on hydrogen sensors has been conducted at home and abroad. Currently, hydrogen sensors mainly include three types: electrochemical, electrical, and optical.

[0003] At present, electrochemical and electrical hydrogen sensors have a high market share. Various electrochemical hydrogen sensors have a wide operating temperature range, low power consumption and high sensitivity, but their electrode life is limited, and current or voltage needs to be provided to the sensor when working, which is not suitable for flammable and explosive places. Electrical hydrogen sensors have the advantages of simple structure, easy miniaturization and easy integration, but the temperature required for their operation is high, which increases energy consumption, and they are prone to produce electric sparks when working, which is also not suitable for flammable and explosive places. The surface acoustic wave type and photoacoustic type of optical hydrogen sensors detect hydrogen concentration by measuring the frequency offset, which is greatly affected by environmental factors, while optical fiber hydrogen sensors have the advantages of intrinsic safety, anti-electromagnetic interference, small size, corrosion resistance, etc., and their sensor sensitivity and measurement accuracy are high, and they can achieve real-time response. According to different sensing mechanisms, a variety of optical fiber hydrogen sensors suitable for single-point measurement and distributed multi-point measurement can be produced. Therefore, optical fiber hydrogen sensors will become the main content of hydrogen sensor research. With the improvement of sensor manufacturing technology and the development of signal demodulation technology, optical fiber hydrogen sensors will occupy a larger market.

[0004] The transmission medium of the fiber optic hydrogen sensor is optical fiber. Optical fiber was introduced as a medium for information transmission in the 1970s. Optical fiber has a series of advantages: small size, with a cladding diameter of only 100-150um for quartz optical fiber; good light transmission performance, which is related to the optical fiber material and structure; strong resistance to external electromagnetic interference and corrosion, because the outer surface of the optical fiber is coated with a coating of special materials. Through the research on optical fiber in communication, people have also proposed the application of optical fiber in other fields. At present, optical fiber sensing has entered a stage where research and practical application coexist. The optical fiber hydrogen sensor is based on the optical fiber as the transmission medium, and the changes in the transmitted light signal caused by the changes in hydrogen concentration.

[0005] Sensor technology supports the development of the industrial industry, and leading sensor technology has become the core competitiveness of developed industrial countries. Hydrogen sensors are the representative of sensor technology used in industrial production. As early as more than 100 years ago, people began to detect hydrogen concentration in order to ensure the purity of hydrogen fuel for spacecraft. At present, most of the hydrogen sensors used in industrial production are electrochemical, but since such sensors may generate electric sparks, they pose a serious safety hazard. In contrast, optical fiber sensors are inherently explosion-proof, and no electric sparks are generated during sensing, making them safer in a hydrogen environment. In addition, such sensors also have many advantages such as high measurement sensitivity, anti-electromagnetic interference, light weight, small size, corrosion resistance, and easy reuse. Therefore, research on sensors based on optical principles has become an important research direction in the field of hydrogen sensing.

[0006] In 1984, Professor MABulter and Professor Ginley of the United States proposed and began to study fiber optic hydrogen sensors, applying optical fiber to hydrogen detection technology for the first time, which led to the development of this type of sensing technology. In the following decades, more and more countries and scientific research institutions have begun to devote themselves to the research of fiber optic hydrogen sensors, and have made great progress. They have conducted a lot of research on their respective scheme designs and achieved good results. In China, many scientific research institutions and colleges, and even companies and enterprises have begun to study fiber optic hydrogen sensors. However, so far, most of the research in China is still in the experimental stage and cannot meet the practical standards. Therefore, the use of fiber optic sensing technology to detect hydrogen is still a topic worthy of continued research. Summary of the invention

[0007] In view of the shortcomings of the prior art, the present invention aims to use a dual interference sensor as a basis, and to perform temperature correction by means of an optical lever. The hydrogen-sensitive film and hydrogen combine, and the volume expands, thereby stretching the optical fiber, increasing the optical path, and causing the phase of the optical signal in the signal arm to change, thereby increasing the optical path difference of the optical signal in the reference optical fiber (3) and the hydrogen reference optical fiber (5), and the interference pattern will become thinner and denser; at the same time, it will also cause a slight displacement of the reflector device (11), and after being magnified by the optical lever optical path, a visible spatial displacement will be formed, thereby enhancing the accuracy of the result. Through another interference pattern only related to the ambient temperature and the optical lever information, the hydrogen concentration result is corrected accordingly, and the independent accuracy of the result is improved.

[0008] The present invention is realized by the following technical scheme: the light emitted by the broadband light source (1) is first incident on the reference optical fiber (3) and the temperature reference optical fiber (4) via the beam splitter (2), and then incident on the reference optical fiber (3) and the hydrogen reference optical fiber (5) via the beam splitter (2). During the test process, the broadband light source (1) simultaneously provides light to the two optical lever devices, and the position angle of the light source is adjusted so that the light source is reflected onto the ruler (10) after passing through the reflector device (11), and the scale of the ruler (10) in the reflector device (11) is observed through the telescope (9). By comparing the two interference pattern information and the difference in the scale of the ruler (10), the error caused by the ambient temperature on the hydrogen concentration measurement can be corrected, thereby improving the accuracy of the detection result.

[0009] The hydrogen sensitive film (6) is a Pt / WO3 sensing film, and is prepared by a sol-gel method and an immersion-coating method.

[0010] The vacuum temperature transfer tube (7) is a PVC transparent hose with an inner diameter of 10 mm.

[0011] The deformable sheet (8) is adhered to the outer side of the cladding of the temperature reference optical fiber (4) and the hydrogen reference optical fiber (5), and is parallel to the plane where the support (12) is located.

[0012] The working principle of the present invention is as follows: for the double interference part: in a hydrogen environment, the hydrogen-sensitive film with high selectivity for hydrogen combines with hydrogen, expands in volume, and thus stretches the optical fiber, increases the optical path, causes the phase of the optical signal in the hydrogen reference optical fiber (5) to change, thereby increasing the optical path difference of the optical signal in the reference optical fiber (3) and the hydrogen reference optical fiber (5), and the interference pattern becomes thinner and denser; by analyzing the interference pattern information, it is possible to know the influence of the ambient temperature and hydrogen concentration acting together on the device and the influence of the ambient temperature on the device. For the optical lever part: the ambient temperature will cause the hydrogen-sensitive material and the optical fiber to have a certain degree of thermal expansion and contraction. In the case of a large temperature difference, the error caused by this influence on the detection result cannot be ignored. Therefore, the ambient temperature will also cause a certain slight deformation of the optical fiber, thereby causing the deformation sheet (8) to flip a certain angle. The optical lever, an optical amplification device, is used to detect this small angle change, thereby knowing the influence of only the ambient temperature on the device measurement result. By comprehensively analyzing the influence of the ambient temperature on the device measurement result, the influence of the temperature factor is corrected, thereby obtaining a more accurate hydrogen concentration measurement result.

[0013] The beneficial effects of the present invention are as follows: the present invention improves on the premise of interferometry to measure hydrogen concentration, adopts a double interference method, increases certain system fault tolerance and stability, and uses optical levers as the main weight to correct the error of ambient temperature on the system measurement result in the traditional interferometry method, so that the accuracy of the measurement result is greatly improved. At the same time, the Pt / WO3 sensing film is prepared by the sol-gel method and the immersion pulling method, which not only increases the selectivity for hydrogen, but also shortens the response time, and makes the system have certain repeatability and stability. The present invention is less affected by the environment, has high precision, long life, has certain innovation and practical value, and has good market prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a structural schematic diagram of a double-interference hydrogen sensor based on the optical lever correction principle. DETAILED DESCRIPTION

[0015] The reference optical fiber (3), the temperature reference optical fiber (4), and the hydrogen reference optical fiber (5) are made of the same optical fiber. The temperature reference optical fiber (4) and the hydrogen reference optical fiber (5) are coated with the same hydrogen-sensitive film (6). The difference is that the hydrogen-sensitive film (6) on the temperature reference optical fiber (4) is covered by a vacuum temperature transfer tube (7). The telescope (9) is composed of an objective lens, an eyepiece, and a cross-reticle plate. The ruler (10) is a general ruler. The device is installed in a hydrogen environment. The front two legs of the reflector device (11) are placed on the support (12) platform, and the rear legs are placed on the deformation plates (8) of the temperature reference optical fiber (4) and the hydrogen reference optical fiber (5). Outside the hydrogen environment, the telescope (9) and the ruler (10) are placed 1-2 meters in front of the reflector device (11). The heights of the telescope (9), the ruler, and the reflector are adjusted to be equal. The barrel of the telescope (9) is horizontally aligned with the reflector, and the ruler is vertical. The eyepiece of the telescope (9) is adjusted so that the crosshairs in the telescope (9) are clearest (i.e., imaged on the focal plane of the eyepiece), and the objective lens is adjusted so that the ruler image is clear. At this time, the positions of the telescope (9) and the ruler (10) are fixed. By observing the difference in the scale of the ruler in the telescope, the influence of the ambient temperature on the double interference device can be understood. By observing the difference in the double interference pattern information and correcting the temperature factor, accurate hydrogen concentration information can be obtained.

Claims

1. A double interference hydrogen sensor based on the optical lever correction principle, comprising a broadband light source (1), a beam splitter (2), a reference optical fiber (3), a temperature reference optical fiber (4), a hydrogen reference optical fiber (5), a hydrogen-sensitive film (6), a vacuum temperature transfer tube (7), a deformation plate (8), a telescope (9), a ruler (10), a reflector device (11), and a bracket (12); the reference optical fiber (3), the temperature reference optical fiber (4), and the hydrogen reference optical fiber (5) are selected from the same optical fiber, and the temperature reference optical fiber (4) and the hydrogen reference optical fiber (5) are coated with the same hydrogen-sensitive film (6), and the difference is that the temperature reference optical fiber (4) has a hydrogen-sensitive film (6) on it. The hydrogen sensitive film (6) is coated by a vacuum temperature transfer tube (7); the hydrogen sensitive film (6) is a Pt / WO3 sensing film, and is prepared by a sol-gel method and an immersion pulling method; the telescope (9) is composed of an objective lens, an eyepiece, and a cross-reticle plate; the front two legs of the reflector device (11) are placed on a support (12) platform, and the rear legs are placed on the deformation sheet (8) of the temperature reference optical fiber (4) and the hydrogen reference optical fiber (5); the deformation sheet (8) is adhered to the outer side of the cladding of the temperature reference optical fiber (4) and the hydrogen reference optical fiber (5), and is at the same time level with the plane where the support (12) is located; a telescope is placed 1-2 meters in front of the reflector device (11) A telescope (9) and a ruler (10) are used to adjust the heights of the telescope (9), the ruler and the reflector so that they are at the same height, the barrel of the telescope (9) is horizontally aligned with the reflector, and the ruler is vertical; the eyepiece of the telescope (9) is adjusted so that the crosshairs in the telescope (9) are clearest, that is, the image is formed on the focal plane of the eyepiece, and the objective lens is adjusted so that the image of the ruler is clear; the sensor is installed in a hydrogen environment, and the broadband light source (1) generates two laser beams to provide light sources for the optical lever; at the same time, two coherent light beams are generated through the beam splitter (2), and the hydrogen reference optical fiber (5) is first closed, and the two coherent light beams pass through the reference optical fiber (3) and the temperature reference optical fiber (4) respectively, The influence of the ambient temperature is obtained by detecting and recording the information of the interference pattern and the optical lever respectively. Then, the temperature reference optical fiber (4) is turned off, and the two coherent light beams are respectively passed through the reference optical fiber (3) and the hydrogen reference optical fiber (5). The position angle of the light source is adjusted so that the light source is reflected onto the ruler (10) after passing through the reflector device (11). The scale of the ruler (10) in the reflector device (11) is observed through the telescope (9). The information of the interference pattern and the optical lever is recorded again, and the influence of the ambient temperature on the accuracy of the sensor is corrected according to the recorded temperature information. Finally, the two types of information are comprehensively analyzed to obtain the hydrogen concentration.

2. According to claim 1, a dual interference hydrogen sensor based on the optical lever correction principle is characterized in that The vacuum temperature transfer tube (7) is made of a 10mm inner diameter PVC transparent hose.

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