Wide-range optical fiber temperature sensor and testing method

Abstract

The invention discloses a wide-range optical fiber temperature sensor and a testing method. The sensor comprises a black body source, a temperature sensitive chip, a supporting rod, a base, a collimating lens, a supporting structure, an optical fiber and an optical fiber connector. The supporting rod is a hollow cylinder, and a through cylindrical channel is formed in the middle; the blackbody source and the temperature sensitive chip are sequentially fixed in a groove in the front end of the supporting rod and used for sensing the environment temperature; the other end of the supporting rod is fixed to the base, and a penetrating channel corresponding to the cylindrical channel in the center of the supporting rod is formed in the symmetric center of the base. The supporting structure is located in the through channel of the base, and the collimating lens is located in the through channel and arranged at one end of the supporting structure; the optical fiber penetrates through the supporting structure, one end contacts the collimating lens, and the other end extends out of the supporting structure to be connected with the optical fiber connector. According to the invention, a single blackbody radiation principle or a Fabry-Perot interference principle is combined, and the temperature measurement range of the sensor is effectively improved.

Description

Technical Field

[0001] The invention relates to a large-range optical fiber temperature sensor and a testing method, in particular to an optical fiber temperature sensor based on the Fabry-Perot interference principle and the blackbody radiation temperature measurement principle, and belongs to the field of optical fiber temperature sensors. Background Art

[0002] Temperature is an important physical quantity in environmental monitoring, so temperature sensors are widely used in scientific research and industrial production. In recent years, with the widespread application of short temperature sensors in aerospace, steel smelting, petrochemical and other industries, the demand for ultra-high temperature measurement has become increasingly urgent. The temperature measurement technology based on the blackbody radiation principle plays an important role in the ultra-high temperature field because of its high upper limit of measurable temperature.

[0003] The principle of blackbody radiation temperature measurement is based on the different intensities of light radiated by a substance at different temperatures, which can be used to infer the ambient temperature. This principle is difficult to achieve temperature measurement below 600°C because the light radiated by the substance is too weak at low temperatures. It cannot meet the continuous measurement from low temperature to high temperature under actual working conditions, thus limiting the application range of the sensor. Existing ultra-high temperature measurement methods mainly include thermocouples, blackbody radiation optical probes, gratings and Fabry-Perot cavities made of sapphire optical fibers, all of which are based on a single principle to achieve temperature measurement. Among them, thermocouples have the disadvantages of high-temperature oxidation and electromagnetic interference, blackbody radiation probes cannot measure low-temperature areas, and gratings and Fabry-Perot cavities made of sapphire optical fibers have poor signal stability, making them difficult to achieve engineering applications. Summary of the invention

[0004] The technical problem solved by the present invention is: to overcome the deficiencies of the prior art and provide a new large-range optical fiber temperature sensor and a testing method. The sensor overcomes the limitation that temperature sensors based on the blackbody radiation temperature measurement principle cannot measure low temperatures, innovatively introduces the Fabry-Perot interference principle, and cleverly combines the two temperature measurement principles to meet the testing needs of a larger temperature range and achieve continuous measurement from low temperature to ultra-high temperature.

[0005] The technical solution of the present invention is: in the first aspect, a large-range optical fiber temperature sensor is provided, comprising: a black body source, a temperature sensitive chip, a support rod, a base, a collimating lens, a supporting structure, an optical fiber and an optical fiber connector; wherein:

[0006] The support rod is a hollow cylinder with a cylindrical channel running through the middle; the temperature sensitive chip is fixed in the groove at the front end of the support rod close to the black body source; the other end of the support rod is fixed on the base, and a through channel corresponding to the cylindrical channel in the center of the support rod is arranged at the center of the base; the support structure is located in the through channel of the base, and the collimating lens is located in the through channel and fixed at one end of the support structure;

[0007] The optical fiber passes through the supporting structure, one end of which is located at the focus of the collimating lens, and the other end of which extends from the supporting structure to connect to the optical fiber connector.

[0008] Preferably, the external structure and size of the base are designed according to the installation environment, and the entire large-range optical fiber temperature sensor is fixed at the measuring point.

[0009] Preferably, the collimating lens, the supporting structure and the optical fiber form a collimating light path to receive the radiation light emitted by the black body source and the interference signal of the temperature sensitive chip.

[0010] Preferably, the black body source is fixed in the support rod groove by gluing or welding.

[0011] Preferably, the temperature sensitive chip is made of quartz or sapphire crystal, and the two end faces are flat and smooth, and is fixed in the support rod groove by gluing or pressing.

[0012] Preferably, the optical fiber is quartz optical fiber or sapphire optical fiber.

[0013] In a second aspect, a method for testing a large-range optical fiber temperature sensor is provided, comprising:

[0014] Insert a large-range fiber optic temperature sensor into the flow channel to test the fluid temperature, or contact a black body source with the structure to be tested to measure the temperature of the solid;

[0015] Fix the optical fiber temperature sensor at a designated position;

[0016] The optical fiber connector at the tail end of the optical fiber temperature sensor is connected to the optical fiber signal demodulation equipment;

[0017] Connect the signal demodulation device to the PC, open the data processing software on the PC and run it;

[0018] When the temperature of the structure to be tested changes, the data processing software displays the real-time strain value.

[0019] Compared with the prior art, the present invention has the following advantages:

[0020] (1) The present invention combines the blackbody radiation principle and the Fabry-Perot interference principle, realizes temperature measurement in the low temperature zone through a temperature-sensitive chip, and realizes temperature measurement in the high temperature zone through a blackbody source. On the one hand, it solves the problem that the blackbody radiation principle cannot measure low temperatures, and the temperature measurement range is expanded. On the other hand, it solves the problem that the Fabry-Perot interference composed of optical fiber and temperature-sensitive chip is easily affected by complex mechanical and thermal factors at high temperatures, causing the optical path to shift, thereby causing the interference signal to weaken or disappear; in summary, the single blackbody radiation principle or the Fabry-Perot interference principle both have major defects. The design of the present invention combines the above two principles to effectively improve the temperature measurement range of the sensor.

[0021] (2) The present invention introduces fiber collimation technology, which can collect blackbody radiation signals and Fabry-Perot interference signals at a long distance, greatly reducing the restrictions on the operating temperature of the optical fiber under ultra-high temperature conditions, and avoiding signal instability and complex demodulation caused by the use of sapphire optical fiber. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a schematic diagram of the structure of the optical fiber temperature sensor of the present invention;

[0023] Figure 2 This is a schematic diagram of the test connection of the optical fiber temperature sensor of the present invention;

[0024] Figure 3 This is a schematic diagram of installing the optical fiber temperature sensor of the present invention. DETAILED DESCRIPTION

[0025] The principle of the present invention is to form Fabry-Perot interference through two end face reflections of the temperature-sensitive chip. The interference signal has a fixed corresponding relationship with the thickness H of the temperature-sensitive chip (which is also the cavity length of the interference cavity). Under the action of thermal expansion and contraction, the Fabry-Perot interference principle can be used to complete the low temperature interval measurement. At the same time, the high temperature section temperature measurement can be performed using the blackbody radiation principle that the object radiates different light at different temperatures. The combination of the Fabry-Perot interference principle and the blackbody radiation principle effectively solves the problem of weak blackbody radiation signal at low temperatures and weakened or even disappeared Fabry-Perot interference signal caused by optical path deflection at high temperatures. A fiber optic temperature sensor with a larger range is formed.

[0026] A large-range optical fiber temperature sensor, such as Figure 1 As shown, it includes a black body source 1, a temperature sensitive chip 2, a support rod 3, a base 4, a collimating lens 5, a supporting structure 6, an optical fiber 7 and an optical fiber connector 8;

[0027] The support rod 3 is a hollow cylinder with a cylindrical channel running through the middle; the temperature sensitive chip 2 is fixed in the groove at the front end of the support rod 3 next to the black body source 1, and is used to sense the ambient temperature, wherein the temperature sensitive chip 2 is attached to the side of the black body source 1 facing the cylindrical channel of the support rod 3. The other end of the support rod 3 is fixed on the base 4, and the symmetric center of the base 4 is also provided with a through channel corresponding to the central cylindrical channel of the support rod 3; the support structure 6 is located in the through channel of the base 4, the collimating lens 5 is located in the through channel, and is fixed at one end of the support structure 6, and the optical fiber 7 runs through the support structure 6, one end of which is located at the focus of the collimating lens, and the other end extends from the support structure 6 to connect the optical fiber connector 8. While fixing the support rod 3, the base 4 also has the function of matching the installation interface, and can firmly fix the entire large-range optical fiber temperature sensor at the measuring point position. The collimating lens 5, the support structure 6 and the optical fiber 7 form a collimated optical path, which is used to receive the radiation light emitted by the black body source 1 and the interference signal of the temperature sensitive chip 2. The optical fiber 7 transmits the received optical signal out of the high temperature area, and transmits the signal to the optical fiber signal demodulation device through the optical fiber connector 8 in the low temperature area.

[0028] The black body source 1 should be made of a material with high emissivity and can be fixed in the support rod groove by gluing, welding or the like.

[0029] The temperature sensitive chip 2 is made of a light-transmitting material, and the two end faces should be flat and smooth with light reflection function. It can be fixed in the support rod groove by gluing, pressing, etc., and the optional materials include but are not limited to quartz and sapphire crystal.

[0030] The base 4 is designed with a support rod fixing groove inside, and the external structure and size are designed with bosses, threads, etc. according to the installation environment.

[0031] The optical fiber 7 can be selected according to actual conditions, including but not limited to quartz optical fiber and sapphire optical fiber.

[0032] A method for testing a wide-range optical fiber temperature sensor, the steps are as follows:

[0033] 1) Insert the optical fiber temperature sensor into the flow channel to test the fluid temperature, or contact the black body source 1 with the structure to be tested to measure the temperature of the solid. Fix the optical fiber temperature sensor at the specified position by screwing, welding, crimping, etc.;

[0034] 2) The optical fiber connector 8 at the tail end of the optical fiber temperature sensor is connected to the optical fiber signal demodulation device;

[0035] 3) Connect the signal demodulation device to the PC, open the data processing software on the PC and run it;

[0036] 4) When the temperature of the structure to be tested changes, the data processing software displays the real-time strain value.

[0037] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

[0038] It should be noted that in the drawings or descriptions, similar or identical parts are all marked with the same figure numbers. The sizes of the parts in the drawings are not proportional to the actual sizes for the convenience of marking. Furthermore, the elements or implementations not shown or described in the drawings are forms known to those of ordinary skill in the art. In addition, although examples of parameters including specific values ​​may be provided herein, it should be understood that the parameters do not need to be exactly equal to the corresponding values, but can be approximated to the corresponding values ​​within an acceptable error tolerance or design constraint.

[0039] The present invention proposes a new type of large-range optical fiber temperature sensor, which effectively combines the Fabry-Perot interference principle and the blackbody radiation principle. The Fabry-Perot interference principle is used to measure the low temperature area, and the blackbody radiation principle is used to measure the high temperature area, so that the temperature measurement over a large temperature range can be realized. The tail end of the sensor is made into an optical fiber connector, which can be directly connected to the signal demodulation equipment. The entire sensor can realize temperature signal perception and signal transmission.

[0040] Example:

[0041] For the measurement of gas temperature with a maximum temperature of 1500℃. To meet the use requirements, the blackbody source is made of iridium material, the temperature sensitive chip is made of 0.5mm thick sapphire crystal disc, the support rod is made of alumina ceramic tube, the base is made of GH3128 high temperature alloy, the collimating lens is made of quartz lens, the supporting structure is made of quartz tube, and the optical fiber is made of gold-coated quartz fiber.

[0042] like Figure 2 and Figure 3 As shown, the completed fiber optic temperature sensor is installed on the high-temperature airflow pipeline, the front end of the sensor is inserted into the flow channel, and the sensor base is fixed on the pipeline by welding. After the installation is completed, the fiber optic temperature sensor is connected to the signal demodulation equipment through the tail fiber connector, and the test and data recording are started. During the test, when the temperature is lower than 800℃, the blackbody radiation effect is weak, and the sapphire wafer expands and contracts under the influence of the airflow temperature. The airflow temperature can be obtained by demodulating the Fabry-Perot interference signal. When the temperature is higher than 800℃, the blackbody radiation signal gradually increases. At this time, the Fabry-Perot interference signal is affected by heat and strong radiation light interference, and the interference signal is weakened, distorted, or even disappears. The iridium sheet acts as a blackbody source to sense the airflow temperature and emits radiation light outward. The airflow temperature can be calculated based on the intensity of the radiation light.

[0043] The contents not described in detail in the specification of the present invention belong to the prior art known to the professional and technical personnel in this field.

Claims

1. A wide-range optical fiber temperature sensor, characterized in that include: A black body source (1), a temperature sensitive chip (2), a support rod (3), a base (4), a collimating lens (5), a supporting structure (6), an optical fiber (7) and an optical fiber connector (8); wherein: The support rod (3) is a hollow cylinder with a cylindrical channel running through the middle; the temperature sensitive chip (2) is fixed in the groove at the front end of the support rod (3) close to the black body source (1); the other end of the support rod (3) is fixed on the base (4), and a through channel corresponding to the cylindrical channel at the center of the support rod (3) is arranged at the center of the base (4); the support structure (6) is located in the through channel of the base (4), and the collimating lens (5) is located in the through channel and fixed at one end of the support structure (6); The optical fiber (7) passes through the supporting structure (6), one end of which is located at the focus of the collimating lens, and the other end of which extends out from the supporting structure (6) to connect to the optical fiber connector (8).

2. A wide-range optical fiber temperature sensor according to claim 1, characterized in that: The external structure and size of the base (4) are designed according to the installation environment, and the entire large-range optical fiber temperature sensor is fixed at the measuring point.

3. The large-range optical fiber temperature sensor according to claim 1, characterized in that: The collimating lens (5), the supporting structure (6) and the optical fiber (7) form a collimating light path for receiving the radiation light emitted by the black body source (1) and the interference signal of the temperature sensitive chip (2).

4. The large-range optical fiber temperature sensor according to claim 1, characterized in that: The black body source (1) is fixed in the groove of the support rod (3) by gluing or welding.

5. The large-range optical fiber temperature sensor according to claim 1, characterized in that: The temperature sensitive chip (2) is made of quartz or sapphire crystal, and has two flat and smooth end surfaces, and is fixed in the support rod groove by means of gluing or pressing.

6. The large-range optical fiber temperature sensor according to claim 1, characterized in that: The optical fiber (7) is made of quartz optical fiber or sapphire optical fiber.

7. A method for testing a large-range optical fiber temperature sensor according to any one of claims 1 to 6, characterized in that include: Insert a large-range optical fiber temperature sensor into the flow channel to test the fluid temperature, or place a black body source (1) in contact with the structure to be tested to measure the temperature of the solid; Fix the optical fiber temperature sensor at a designated position; The optical fiber connector (8) at the tail end of the optical fiber temperature sensor is connected to an optical fiber signal demodulation device; Connect the signal demodulation device to the PC, open the data processing software on the PC and run it; When the temperature of the structure to be tested changes, the data processing software displays the real-time strain value.

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