A humidity FBG probe, a temperature and humidity FBG probe and a measurement system

Abstract

The present invention relates to a humidity FBG probe, a temperature and humidity FBG probe and a measuring system, comprising a base, a carbon fiber strip and a humidity-sensitive metal hairspring wound into a tape measure shape from the inside to the outside, wherein the base is used to achieve support. The end of the humidity-sensitive metal hairspring in the inner circle is fixed to the base, and the end of the humidity-sensitive metal hairspring in the outer circle is a movable end. The stress of the humidity-sensitive metal hairspring is different under different humidity, so that the humidity-sensitive metal hairspring is deformed along the winding direction. A carbon fiber strip, one end of the carbon fiber strip is fixed to the base, and the other end is suspended relative to the base. A flexural FBG is fixed on the carbon fiber strip, and the flexural FBG can be deformed synchronously with the carbon fiber strip; the movable end of the humidity-sensitive metal hairspring is connected to the suspended end of the carbon fiber strip, so that the humidity-sensitive metal hairspring can transfer its own deformation caused by humidity changes to the carbon fiber strip, and the flexural FBG can be deformed synchronously with the carbon fiber strip to change the wavelength of the laser input into the flexural FBG.

Description

Technical Field

[0001] The invention belongs to the technical field of sensors, and in particular relates to a humidity FBG probe, a temperature and humidity FBG probe and a measurement system. Background Art

[0002] In today's market, electronic temperature and humidity sensors still dominate the market with their advantages of low cost, fast response speed, and easy signal processing. However, electronic sensors have disadvantages such as poor interchangeability and insufficient long-term stability, making them difficult to be used in fields such as electrical power, petrochemicals, and other flammable and explosive harsh environments.

[0003] Fiber Bragg grating temperature and humidity sensor is a new type of temperature and humidity sensor developed with the development of optical fiber communication technology. Compared with traditional electrical temperature and humidity sensors, it has the advantages of anti-electromagnetic interference, good electrical insulation, and large dynamic range. In addition, the sensing part is light in weight, small in size, and has diverse structures and geometric shapes. It is easy to multiplex and network to realize real-time, online, and distributed sensing.

[0004] The inventors learned that currently, optical fiber sensors are used as temperature and humidity sensitive elements, and the temperature and relative humidity sensor probes are composed of dry-wet methods, so that the sensitive elements can be made fully optical. However, the later maintenance of the probes is cumbersome, and water needs to be added to create a wet environment. In some technical solutions, humidity can also be measured by coating the fiber grating or multimode optical fiber with humidity-sensitive materials. However, the process has strict requirements on the material and thickness of the coating layer. The production of humidity-sensitive sensors will result in low product qualification rates and relatively high costs. Humidity-sensitive sensors using multimode optical fibers are also unable to measure humidity over long distances. Summary of the invention

[0005] The purpose of the present invention is to provide a humidity FBG probe, a temperature and humidity FBG probe and a measurement system, which can solve the problems of cumbersome maintenance and low qualified rate of existing humidity sensors and temperature and humidity sensors.

[0006] To achieve the above objectives, a first aspect of the present invention provides a humidity FBG probe, comprising a base, a carbon fiber strip, and a humidity-sensitive metal hairspring wound in a tape measure shape from inside to outside, wherein the base is used for support.

[0007] One end of the humidity-sensitive metal hairspring in the inner circle is fixed to the base, and one end of the humidity-sensitive metal hairspring in the outer circle is a movable end. The stress of the humidity-sensitive metal hairspring is different under different humidity, so that the humidity-sensitive metal hairspring is deformed along the winding direction.

[0008] One end of the carbon fiber strip is fixed to the base, and the other end is suspended relative to the base. A flexural FBG is fixedly provided on the carbon fiber strip, and the flexural FBG can be deformed synchronously with the carbon fiber strip; the movable end of the humidity-sensitive metal hairspring is connected to the suspended end of the carbon fiber strip, so that the humidity-sensitive metal hairspring can transfer its own deformation caused by humidity changes to the carbon fiber strip, and the flexural FBG can be deformed synchronously with the carbon fiber strip to change the wavelength of the laser input into the flexural FBG.

[0009] As a further limitation of the first aspect of the present invention, the regions without gratings at both ends of the flexural FBG are connecting sections, and the connecting sections are used to connect carbon fiber strips.

[0010] As a further limitation of the first aspect of the present invention, the extension direction of the carbon fiber strip is the same as the extension direction of the flexural FBG, and the humidity-sensitive metal hairspring is arranged on a side of the carbon fiber strip suspended relative to the base.

[0011] A second aspect of the present invention provides a temperature and humidity FBG probe, comprising the humidity FBG probe, and also comprising a temperature compensating FBG, wherein the temperature compensating FBG is supported by a base, and the temperature compensating FBG can generate deformation along the extension direction of the temperature compensating FBG when the temperature changes, so as to change the wavelength of the laser passing through the temperature compensating FBG;

[0012] The temperature compensation FBG and the flexural FBG are connected in series in the same optical fiber.

[0013] The third aspect of the present invention provides a temperature and humidity measurement system, including the temperature and humidity FBG probe, one end of the optical fiber is connected to a laser generating device, and the other end is connected to a laser signal processing device, and the laser signal processing device can obtain information on the temperature and humidity at the base according to changes in the laser wavelength.

[0014] The beneficial effects of one or more of the above technical solutions are:

[0015] (1) The fiber Bragg grating temperature and humidity FBG sensor probe, which uses the grating etched on the optical fiber as the sensitive element, can realize a passive and all-optical sensing terminal, which has the advantages of safety and reliability when used in electromagnetic sensitive occasions.

[0016] (2) The wavelength discrimination characteristics of fiber Bragg grating temperature sensors can be used to realize wavelength division multiplexing. Multiple temperature and humidity sensor probes use fiber Bragg gratings with different central wavelengths and can be connected in series on the same optical fiber to realize wavelength division multiplexing.

[0017] (3) The probe integrates two fiber Bragg grating temperature sensors of the same specifications and temperature-sensitive packaging. One fiber Bragg grating temperature sensor is placed in the air as a dry-end sensor to measure the ambient temperature. The other fiber Bragg grating sensor is placed on the deflected carbon fiber strip. The humidity-sensitive metal hairspring is used as a deflection power component. When the relative humidity of the environment changes, the temperature value measured by the temperature sensor and the deflection measured by the humidity sensor cause the light wavelength to change. The value is proportional to the relative humidity in the air. The relative humidity value in the environment can be obtained by converting this proportional relationship.

[0018] (4) The temperature and humidity information sensed by the fiber Bragg grating temperature and humidity sensor probe is reflected by the change of its central wavelength. This wavelength change can be converted into the wavelength change of the laser input to the probe by the remote light source. The laser carrying the temperature and humidity information can be transmitted back to the remote signal processing equipment over a long distance through the transmission optical fiber for temperature and humidity data solution. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The drawings in the specification, which constitute a part of the present application, are used to provide a further understanding of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute a limitation on the present application.

[0020] Figure 1 This is a schematic diagram of the overall structure of Example 2 of the present invention;

[0021] In the figure: 1. Base; 2. Moisture-sensitive metal hairspring; 3. Flexural FBG; 4. Temperature-compensated FBG; 5. Carbon fiber strip; 6. Dust cover. DETAILED DESCRIPTION

[0022] It should be noted that the following detailed descriptions are illustrative and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0023] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0024] For the convenience of description, if the words "up, down, left, right" appear in the present invention, it only means that they are consistent with the up, down, left, and right directions of the drawings themselves, and do not limit the structure. They are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it cannot be understood as a limitation on the present invention.

[0025] Example 1

[0026] like Figure 1 As shown in the structure of the middle part, this embodiment provides a humidity FBG probe, including a base 1, a carbon fiber strip 5, and a humidity-sensitive metal hairspring 2 wound into a tape measure shape from the inside to the outside, and the base 1 is used to achieve support. The end of the humidity-sensitive metal hairspring 2 in the inner circle is fixed to the base 1, and the end of the humidity-sensitive metal hairspring 2 in the outer circle is a movable end. The stress of the humidity-sensitive metal hairspring 2 is different under different humidity, so that the humidity-sensitive metal hairspring 2 is deformed.

[0027] One end of the carbon fiber strip 5 is fixed to the base 1, and the other end is suspended relative to the base 1. A deflection FBG3 is fixedly provided on the carbon fiber strip 5, and the deflection FBG3 can be deformed synchronously with the carbon fiber strip 5; the movable end of the humidity-sensitive metal hairspring 2 is connected to the suspended end of the carbon fiber strip 5, so that the humidity-sensitive metal hairspring 2 can transfer its own deformation caused by humidity changes to the carbon fiber strip 5, and the deflection FBG3 can be deformed synchronously with the carbon fiber strip 5 to change the wavelength of the laser input into the deflection FBG3.

[0028] The areas without gratings at both ends of the flexure FBG3 are connecting sections, which are used to connect the carbon fiber strip 5. The extension direction of the carbon fiber strip 5 is the same as that of the flexure FBG3, and the humidity-sensitive metal hairspring 2 is arranged on one side of the carbon fiber strip 5 suspended relative to the base 1.

[0029] The outer cover of the base 1 is provided with a dust cover 6, and the dust cover 6 is used to realize dust prevention of the moisture-sensitive metal hairspring 2 and the flexure FBG 3. Through holes for optical fibers to pass through are provided at both ends of the base 1, and the flexure FBG 3 is connected in series in the optical fiber, one end of the optical fiber is used to connect to a remote light source, and the other end is used to connect to a laser signal processing device.

[0030] The movement direction of the active end of the humidity-sensitive metal hairspring 2 is the same as the tangent direction at the active end.

[0031] Specifically, the humidity-sensitive metal hairspring 2 is a hairspring of a mechanical hygrometer used on the market, and its humidity change causes the humidity-sensitive metal hairspring 2 to drive the pointer angle to change. This type of humidity-sensitive metal hairspring 2 is used in the present invention, assuming that the ambient humidity value is RH, the tangential force generated by the humidity-sensitive metal hairspring 2 is F, and the humidity change unit stress of the humidity-sensitive metal hairspring 2. The humidity-sensitive metal hairspring 2 is composed of a beryllium copper film and a humidity-sensitive paper. The elastic modulus of the metal beryllium copper is E3, the film thickness is h2, and the beryllium copper width of the humidity-sensitive metal hairspring 2 is b2. It is wound into an Archimedean spiral with an inner diameter of 2r1, an outer diameter of 2r2, and a number of turns of n. In the full range, the inner diameter drives the pointer to rotate at an angle of α.

[0032] but

[0033] Assume the K value is as follows:

[0034]

[0035] The length, width and thickness of the pulled carbon fiber strip 5 are l1, b, and h respectively; the elastic modulus of the carbon fiber is E1; the radius of the optical fiber is r, the fixed length attached to the carbon fiber strip 5 is l2, and the elastic modulus of the optical fiber is E2;

[0036] Then the force F1 of the carbon fiber strip 5 and the strain ε1 are as follows:

[0037]

[0038] The force on the optical fiber is F2, the strain on the fiber Bragg grating is ε2, and the length of the two fixed points of the fiber Bragg grating is l2;

[0039]

[0040] According to mechanical equilibrium, we can get

[0041] F·l1=F1·l1+F2·l2

[0042] At the same time, the strain of the optical fiber should be the same as the strain of the carbon fiber, then ε1=ε2=ε, so

[0043]

[0044] Therefore, the humidity value RH and the strain ε have a linear relationship as follows

[0045]

[0046] The unit strain ε of the fiber Bragg grating is related to the return wavelength λ of the fiber Bragg grating and its drift Δλ. The elastic coefficient of the fiber is p, then

[0047]

[0048] The wavelength drift Δλ measured by the fiber Bragg grating system has a linear relationship with the humidity value as follows:

[0049]

[0050] The following is an example of the present application with specific data: the outer diameter of the humidity-sensitive metal hairspring 2 is 12 mm, the inner diameter is 2 mm, the number of turns is 4, the thickness of the metal beryllium copper film is 0.05 mm, the width is 2 mm, and the elastic modulus of the metal beryllium copper is 1.31×10 11 N / m 2 , the full-scale pointer change is 3π / 2. Then we can calculate

[0051]

[0052] Then the K value is 0.133N / 100%.

[0053] The carbon fiber strip 5 has a length of 50 mm, a width of 3 mm, a thickness of 0.1 mm, and an elastic modulus of 1.7×10 11 N / m 2 The whole structure is a cantilever beam, so the relationship between the force F1 on the carbon fiber strip 5 and the micro strain ε generated is as follows:

[0054]

[0055] The fixed length of the fiber Bragg grating is 30 mm, the diameter is 0.125 mm, and its elastic modulus is 0.7×10 11 N / m 2 , so the relationship between the force F2 on the fiber Bragg grating and the strain ε generated is as follows:

[0056]

[0057] The fiber Bragg grating uses a grating with a central wavelength of 1550nm, a Poisson's ratio of 0.2, and an elastic coefficient p 11 =0.121,p 12 =0.27, the effective refractive index is 1.457, then the effective elastic-optic coefficient is:

[0058]

[0059] The wavelength drift of the fiber Bragg grating is

[0060] Δλ=(1-p)ε·λ=0.00127nm / με

[0061] The humidity value RH and the strain ε have a linear relationship as follows:

[0062]

[0063] The linear slope is 0.68% / pm.

[0064] Example 2

[0065] like Figure 1 As shown, this embodiment provides a temperature and humidity FBG probe, including the humidity FBG probe described in Example 1, and also includes a temperature compensating FBG4, wherein the temperature compensating FBG4 is supported by a base 1, and the temperature compensating FBG4 can generate deformation along the extension direction of the temperature compensating FBG4 when the temperature changes, so as to change the wavelength of the laser passing through the temperature compensating FBG4; the temperature compensating FBG4 and the flexural FBG3 are connected in series in the same optical fiber.

[0066] The relative position of the temperature compensation FBG4 and the base 1 is set such that the temperature compensation FBG4 does not affect the deformation of the humidity-sensitive metal hairspring 2 and the carbon fiber strip 5. A groove is provided on the base 1, and the temperature compensation FBG4 is arranged in the groove.

[0067] Production process:

[0068] 1) First, apply a certain tension to the flexure FBG (3) and then place it on the carbon fiber strip. Heat the flexure FBG and the carbon fiber strip together through a heating plate, and apply 343ND glue to both ends of the flexure FBG to heat and solidify it. The tension here can be measured by a fiber Bragg grating demodulator. The tension causes the central wavelength of the flexure FBG to drift by about 0.5nm. The distance for glue fixation is 30mm, and the fiber Bragg grating should not be glued.

[0069] 2) After the heat curing is completed, the flexural FBG and the carbon fiber strip are removed from the hot plate and fixed on the base so that the length of the carbon fiber strip is 50 mm and the carbon fiber strip is in a cantilever state.

[0070] 3) Apply 353ND glue to the temperature FBG and heat it on a hot plate to fix the temperature FBG in the groove of the base. The temperature FBG is required not to affect the mechanical movement of the humidity-sensitive metal hairspring and the carbon fiber strip.

[0071] 4) Fix the humidity-sensitive metal hairspring on the base, close to the movable end of the carbon fiber strip. Connect the movable end of the humidity-sensitive metal hairspring to the movable end of the carbon fiber strip through a Kevlar soft rope. The center of the humidity-sensitive metal hairspring is fixed on the base, and the outer movable end is connected to the Kevlar rope.

[0072] 5) The parameters of the humidity-sensitive metal hairspring, FBG, and carbon fiber strip are as shown in the above implementation plan design.

[0073] 6) Install the dust cover on the device, mainly to prevent the moisture-sensitive metal hairspring from being contaminated by dust and changing its efficiency.

[0074] 7) Lead out the two FBG optical fibers in the device and then demodulate the FBG using a fiber grating demodulator.

[0075] Example 3

[0076] This embodiment provides a temperature and humidity measurement system, which utilizes the temperature and humidity FBG probe described in Example 2. One end of the optical fiber is connected to a laser generating device, and the other end is connected to a laser signal processing device. The laser signal processing device can obtain information on the temperature and humidity at the base based on changes in the laser wavelength.

[0077] Although the above describes the specific implementation mode of the present invention in conjunction with the accompanying drawings, it is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art on the basis of the technical solution of the present invention without creative work are still within the scope of protection of the present invention.

Claims

1. A humidity FBG probe, characterized in that: include, A base, the base being used to achieve support; A humidity-sensitive metal hairspring is wound in a tape measure shape from the inside to the outside, wherein one end of the humidity-sensitive metal hairspring in the inner circle is fixed to the base, and one end of the humidity-sensitive metal hairspring in the outer circle is a movable end. The stress of the humidity-sensitive metal hairspring is different under different humidity, so that the humidity-sensitive metal hairspring is deformed along the winding direction; A carbon fiber strip, one end of which is fixed to the base, and the other end of which is suspended relative to the base, and a flexural FBG is fixedly provided on the carbon fiber strip, and the flexural FBG can be deformed synchronously with the carbon fiber strip; The active end of the humidity-sensitive metal hairspring is connected to the suspended end of the carbon fiber strip, so that the humidity-sensitive metal hairspring can transmit its own deformation caused by humidity changes to the carbon fiber strip, and the flexural FBG can be deformed synchronously with the carbon fiber strip to change the wavelength of the laser input into the flexural FBG; The humidity-sensitive metal hairspring is made of beryllium copper film and humidity-sensitive paper; The movement direction of the active end of the humidity-sensitive metal hairspring is the same as the tangent direction at the active end; The regions at both ends of the flexural FBG without gratings are connecting sections, and the connecting sections are used to connect carbon fiber strips; The extending direction of the carbon fiber strip is the same as the extending direction of the flexural FBG, and the humidity-sensitive metal hairspring is arranged on a side of the carbon fiber strip that is suspended relative to the base.

2. The humidity FBG probe according to claim 1, characterized in that: The outer cover of the base is provided with a dust cover, and the dust cover is used to realize dust prevention of the moisture-sensitive metal hairspring and the flexural FBG.

3. The humidity FBG probe according to claim 1, characterized in that: Through holes for optical fibers to pass through are provided at both ends of the base, the flexural FBG is connected in series in the optical fiber, one end of the optical fiber is used to connect to a remote light source, and the other end is used to connect to a laser signal processing device.

4. A temperature and humidity FBG probe, comprising the humidity FBG probe according to any one of claims 1 to 3, characterized in that: It also includes a temperature-compensated FBG, which is supported by a base and can generate deformation along the extension direction of the temperature-compensated FBG when the temperature changes, so as to change the wavelength of the laser passing through the temperature-compensated FBG; The temperature compensation FBG and the flexural FBG are connected in series in the same optical fiber.

5. The temperature and humidity FBG probe according to claim 4, characterized in that: The relative position of the temperature compensating FBG and the base is set so that the temperature compensating FBG does not affect the deformation of the humidity-sensitive metal hairspring and the carbon fiber strip.

6. The temperature and humidity FBG probe according to claim 4, characterized in that: The base is provided with a groove, and the temperature compensation FBG is arranged in the groove.

7. A temperature and humidity measurement system, using the temperature and humidity FBG probe according to any one of claims 4 to 6, characterized in that: One end of the optical fiber is connected to a laser generating device, and the other end is connected to a laser signal processing device. The laser signal processing device can obtain information on temperature and humidity at the base according to changes in laser wavelength.

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