CN108318062B - Fiber bragg grating temperature and humidity sensor and temperature and humidity measurement system - Google Patents
Fiber bragg grating temperature and humidity sensor and temperature and humidity measurement system Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
- G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
- G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
- G01D5/268—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light using optical fibres
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
- G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
- G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
- G01D5/32—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light
- G01D5/34—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells
- G01D5/353—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre
- G01D5/35306—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre using an interferometer arrangement
- G01D5/35309—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre using an interferometer arrangement using multiple waves interferometer
- G01D5/35316—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre using an interferometer arrangement using multiple waves interferometer using a Bragg gratings
Abstract
The application discloses a fiber bragg grating temperature and humidity sensor and a temperature and humidity measurement system, wherein the sensor comprises: the fiber core, the cladding and the protective sleeve are sleeved outside the fiber core, the fiber core comprises a first fiber core section and a second fiber core section, the cladding comprises a first layer section and a second layer section, the first layer section corresponds to the first fiber core section, and the second layer section corresponds to the second fiber core section; the protective sleeve is sleeved outside the second layer section, a first fiber grating is carved in the first fiber core section, and a second fiber grating is carved in the second fiber core section; the cladding adopts cycloolefin polymer; the protective sleeve is made of polymethyl methacrylate. The temperature and humidity measurement system comprises a light source, a collimating lens, the fiber bragg grating temperature and humidity sensor, a photoelectric converter and a signal processing circuit. The temperature and humidity measuring device can improve the precision and sensitivity of the temperature and humidity measurement of the sensor, has the advantages of electromagnetic interference resistance, high measurement precision, high response speed, reduction of equipment cost and the like, and realizes accurate temperature and humidity monitoring of the working environment of the optical transformer.
Description
Technical Field
The application relates to the technical field of optical sensing measurement, in particular to a fiber bragg grating temperature and humidity sensor and a temperature and humidity measurement system.
Background
The safe and stable operation of the power system is not separated from corresponding measuring equipment, such as a voltage transformer, a current transformer and the like. Taking a voltage transformer as an example, the traditional voltage transformer generally adopts a capacitive voltage division type, a resistive voltage division type or an electromagnetic voltage transformer type, and due to the limitation of a working principle, the voltage transformer is generally narrow in measurement frequency band and poor in insulation performance, so that the application of the voltage transformer in a power system is limited. The appearance and development of the optical transformer become an important way for solving the problem, and the optical transformer has the characteristics of passive design, small volume, good insulativity, good frequency characteristic, high sensitivity and the like.
However, the optical transformer has some problems and defects, and the measurement characteristics of the optical transformer mainly depend on the conversion characteristics of the photoelectric crystal, but the conversion characteristics of the photoelectric crystal are greatly affected by temperature and humidity. Therefore, in order to further improve the long-term monitoring accuracy of the optical transformer and ensure the working reliability of the optical transformer, the relevant environmental parameters of the operation of the optical transformer need to be effectively monitored, and the temperature and the humidity are indexes which need to be monitored in a key way.
At present, a temperature sensor and a humidity sensor are generally arranged in a working environment near an optical transformer respectively, but the existing electronic temperature sensor and humidity sensor are easy to be subjected to electromagnetic interference, such as an optical fiber type temperature sensor and a humidity sensor, and the equipment cost is additionally increased. For this reason, a separate optical fiber type sensor has been developed by those skilled in the art to measure temperature and humidity at the same time, however, there have been relatively few studies on the optical fiber type temperature and humidity sensor, and the sensitivity and accuracy of the measurement have been not ideal.
Disclosure of Invention
The application provides a fiber bragg grating temperature and humidity sensor and a temperature and humidity measurement system, which are used for solving the problem that the sensitivity and measurement accuracy of the conventional fiber bragg grating temperature and humidity sensor are low.
In a first aspect, the present application provides a fiber bragg grating temperature and humidity sensor, including: the fiber core is sleeved outside the fiber core, the fiber core comprises a first fiber core section and a second fiber core section, the fiber core comprises a first layer section and a second layer section, the first layer section corresponds to the first fiber core section, and the second layer section corresponds to the second fiber core section;
the protective sleeve is sleeved outside the second layer section, a first fiber grating is carved in the first fiber core section, and a second fiber grating is carved in the second fiber core section;
the cladding adopts cycloolefin polymer;
the protective sleeve is made of polymethyl methacrylate.
Optionally, the first fiber grating and the second fiber grating are fiber bragg gratings.
Optionally, the core is a single mode core.
In a second aspect, the present application further provides a temperature and humidity measurement system, including: a light sensing subsystem and a signal processing circuit;
the optical sensing subsystem includes: the optical source, the collimating lens, the photoelectric converter and the fiber grating temperature and humidity sensor are as described above;
the collimating lens is used for converting scattered light emitted by the light source into parallel light;
the fiber bragg grating temperature and humidity sensor is used for measuring temperature and relative humidity in real time and sending a first optical signal and a second optical signal to the photoelectric converter;
the photoelectric converter is used for converting the first optical signal and the second optical signal into a first electric signal and a second electric signal;
the signal processing circuit includes: an amplifying circuit, an A/D converter and a central processing unit;
and the central processing unit is used for calculating a temperature measurement value and a relative humidity measurement value according to the temperature and humidity response characteristics of the first fiber grating and the second fiber grating.
Further, the temperature and humidity response characteristics of the first fiber grating are as follows:
Δλ 1 ＝α 1 ΔT+β 1 ΔH
in the above formula, deltalambda 1 The wavelength variation value of the first fiber bragg grating; delta T is a temperature change value; Δh is the change in relative humidity; alpha 1 The temperature fitting coefficient of the first fiber bragg grating is obtained; beta 1 Fitting coefficients for the relative humidity of the first fiber grating.
Further, the temperature and humidity response characteristics of the second fiber grating are as follows:
Δλ 2 ＝α 2 ΔT+β 2 ΔH+γ 2 ΔH 2
in the above formula, deltalambda 2 The wavelength variation value of the first fiber bragg grating; delta T is a temperature change value; Δh is the change in relative humidity; alpha 2 A temperature fitting coefficient of the second fiber bragg grating; beta 2 Fitting coefficients for first-order relative humidity of the second fiber grating; gamma ray 2 Fitting coefficients for the second order relative humidity of the second fiber grating.
Further, the temperature change value Δt and the relative humidity change value Δh are calculated according to the following formulas:
in the above-mentioned method, the step of,
and calculating a temperature measurement value and a relative humidity measurement value in the current environment according to the temperature change value delta T and the relative humidity change value delta H.
Optionally, the system further comprises an alarm unit, wherein the alarm unit is connected with the central processing unit;
when the temperature measured value is lower than the lower limit value of the preset temperature range, the central processing unit sends a first alarm signal to the alarm unit; the alarm unit sends out an alarm prompt according to the first alarm signal;
when the temperature measured value is higher than the upper limit value of the preset temperature range, the central processing unit sends a second alarm signal to the alarm unit; the alarm unit sends out an alarm prompt according to the second alarm signal;
when the relative humidity measured value is lower than the lower limit value of the preset humidity range, the central processing unit sends a third alarm signal to the alarm unit; the alarm unit sends out an alarm prompt according to the third alarm signal;
when the measured value of the relative humidity is higher than the upper limit value of the preset humidity range, the central processing unit sends a fourth alarm signal to the alarm unit; and the alarm unit sends out an alarm prompt according to the fourth alarm signal.
Optionally, the system further comprises a temperature and humidity feedback adjustment unit, which is used for performing feedback adjustment on the temperature and the relative humidity of the working environment according to the measurement result of the central processing unit.
Optionally, the system further comprises a communication module, wherein the communication module comprises a man-machine interface, a WIFI unit, an RS485 interface and a USB interface; the man-machine interface is connected with the keyboard and the display.
The fiber bragg grating temperature and humidity sensor and the temperature and humidity measurement system provided by the application have the beneficial effects that:
according to the fiber bragg grating temperature and humidity sensor provided by the application, the cyclic olefin polymer is adopted as the cladding, the polymer material has good heat resistance and low hygroscopicity, the protective sleeve is sleeved on the second layer section of the cladding, and the protective sleeve is made of polymethyl methacrylate material, so that the material has high sensitivity to humidity. The first fiber bragg grating is engraved on a first fiber core section, and only a first layer section of the cladding is sleeved outside the first fiber core section; the second fiber bragg grating is engraved on the second fiber core section, the second layer section of the cladding layer and the protective sleeve are sleeved outside the second fiber core section in sequence, and the humidity sensitivity of the cycloolefin polymer is lower than that of polymethyl methacrylate, so that the temperature and humidity response characteristics of the first fiber bragg grating and the second fiber bragg grating are different, and the temperature value and the humidity value can be calculated cooperatively according to the temperature and humidity response characteristics of the first fiber bragg grating and the second fiber bragg grating, so that the measuring precision of the sensor is improved, and the sensor provided by the application has good temperature and humidity sensitivity and a large measuring range. In the temperature and humidity measurement system provided by the application, scattered light emitted by the light source is converted into parallel light through the collimating lens, the parallel light is incident into the fiber grating temperature and humidity sensor, light signals of the reflected wavelengths of the two fiber gratings are respectively obtained in the corresponding external temperature and humidity environments, and after the conversion treatment of the signals, the temperature value and the humidity value of the current environment are respectively calculated according to the temperature and humidity response characteristics of the two fiber gratings.
Drawings
FIG. 1 is a diagram of a fiber grating temperature and humidity sensor according to an embodiment of the present application;
FIG. 2 is a block diagram of a temperature and humidity measurement system according to an embodiment of the present application;
FIG. 3 is a graph showing the humidity response of the first fiber grating and the second fiber grating at 50deg.C according to an embodiment of the present application;
FIG. 4 is a graph showing temperature response of a first fiber grating and a second fiber grating at 50% relative humidity according to an embodiment of the present application;
FIG. 5 is a graph showing the comparison of the check values and the sensor measurement values according to an embodiment of the present application.
Legend description:
1-an optical fiber grating temperature and humidity sensor; 11-cores; 111-a first core segment; 112-a second core segment; 12-cladding; 121-a first interval; 122-a second interval; 13-protecting the sleeve; 113-a first fiber grating; 114-a second fiber grating; 2-a light source; 3-a collimating lens; a 4-photoelectric converter; a 5-signal processing circuit; 51-an amplifying circuit; a 52-A/D converter; 53-a central processing unit; 54 an alarm unit; 55-a temperature and humidity feedback regulating unit; a 56-communication module; 561-WIFI unit; 562-RS485 interface; 563-USB interface; 564-a human-machine interface; 565-keyboard; 566-display.
Detailed Description
In order to enable those skilled in the art to better understand the technical solutions of the present application, the technical solutions of the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings.
As shown in fig. 1, an embodiment of the present application provides a fiber bragg grating temperature and humidity sensor, including: the fiber core 11, the cladding 12 and the protective sleeve 13, wherein the cladding 12 is sleeved outside the fiber core 11, the fiber core 11 comprises a first fiber core section 111 and a second fiber core section 112, the cladding 12 comprises a first layer section 121 and a second layer section 122, the first layer section 121 corresponds to the first fiber core section 111, and the second layer section 122 corresponds to the second fiber core section 112;
the protection sleeve 13 is sleeved outside the second layer section 122, a first fiber grating 113 is carved in the first fiber core section 111, and a second fiber grating 114 is carved in the second fiber core section 112;
the cladding 12 is made of cycloolefin polymer;
the protective sleeve 13 is made of polymethyl methacrylate.
In the technical solution provided in this embodiment, the first fiber bragg grating 113 is engraved on the first fiber core section 111, the outer portion of the first fiber core section 111 is correspondingly sleeved with the first layer section 121 of the cladding 12, and the first layer section 121 is made of a cyclic olefin polymer, such as a cyclic olefin polymer material of ZEONEX480R type; the second fiber bragg grating 114 is carved on the second fiber core section 112, the second layer section 122 of the cladding 12 and the protective sleeve 13 are sequentially sleeved outside the second fiber core section 112, the second layer section 122 adopts cycloolefin polymer, and the protective sleeve 13 adopts polymethyl methacrylate (Polymethyl Methacrylate, PMMA).
Cycloolefin polymers have high heat resistance, low moisture absorption, high transparency, low elastic modulus and good optical properties. Polymethyl methacrylate has good insulativity and mechanical strength, high light transmittance, impact resistance, high temperature resistance and high sensitivity to humidity. Due to the different packaging conditions and sealing materials of the first fiber grating 113 and the second fiber grating 114, the first fiber grating 113 and the second fiber grating 114 have different temperature and humidity response characteristics. According to the temperature and humidity response characteristics of the two fiber gratings, the temperature value and the humidity value of the environment are calculated cooperatively. Compared with the traditional fiber bragg grating temperature and humidity sensor which adopts a mode of measuring temperature and humidity separately or compensating, the sensor provided by the embodiment can measure two environmental parameters of temperature and humidity simultaneously, can reduce equipment cost, reduces occupation of installation space, is higher in measurement accuracy, is better in temperature and humidity sensitivity, and is more stable and reliable in measurement result due to the fact that the fiber bragg grating has strong electromagnetic interference resistance, particularly in an electric power system.
In this embodiment, the first fiber grating 113 and the second fiber grating 114 are fiber bragg gratings (Fiber Bragg Grating, FBG). The fiber core 11 is a single-mode fiber core, which is beneficial to the long-distance transmission of optical signals.
The embodiment shows a manufacturing method of the fiber bragg grating temperature and humidity sensor, which comprises the following specific steps:
first, the cladding 12 is put on the outside of the core 11, and the PMMA pipe is put on the outside of the whole cladding 12, and finally, the fiber with the average diameter of 150 μm is obtained. The diameter of the cladding 12 is 100 μm and the thickness of the protective sleeve 13 is 25 μm, i.e. the outer diameter of the protective sleeve 13 is 150 μm. The core 11 is a single mode core with a diameter of 8 μm and a hole pitch ratio of 0.42.
Then, the end of the optical fiber manufactured as described above was connected to an optical fiber having a length of 50cm, and a corresponding section of the PMMA tube 5cm in front was etched with acetone (corresponding to the broken line portion in fig. 1) from the front end of the optical fiber, so that the first layer section 121 of the clad 12 was exposed, and the remaining unetched portion of the PMMA tube formed a protective sheath 13, and the protective sheath 13 only wrapped around the second layer section 122 of the clad 12. In the first core segment 111 corresponding to the first layer segment 121, a first fiber grating (FBG 1) having a bragg wavelength of 865.62nm was engraved 4cm from the front end of the optical fiber, and then the FBG1 was annealed in a conventional oven at 90 ℃ for 3 hours with its bragg wavelength blue shifted to 847.79nm. After the FBG1 is annealed by 2 cm, a second fiber grating (FBG 2) is etched in the second core segment 112, the bragg wavelength of FBG2 being 866.11nm. The grating inscription technique used in the method can be performed with reference to the prior art. Finally, in an ambient climatic chamber (CLIMACELL, MMM group), the two fiber gratings were annealed together at 85 ℃ and 90% relative humidity (Relative Humidity, RH) for 24 hours to stabilize the operation of the sensor. The new Bragg wavelengths of the annealed FBGs 1 and 2 are 841.21nm and 855.32nm, respectively. The sensor is fabricated from fibers derived from microstructured polymeric materials and can be used to measure both temperature and humidity.
The manufacturing material of the fiber bragg grating temperature and humidity sensor adopts the microstructure polymer, and the polymer fiber bragg grating sensor has the characteristics of low processing temperature, high bending flexibility, high fracture toughness, easiness in operation and the like, so that the manufacturing difficulty and cost of the sensor can be reduced. In addition, the sensor material has low Young modulus, high elastic strain limit and biocompatibility, and is beneficial to research and application of temperature and humidity detection based on fiber bragg gratings. The sensor of the embodiment has good high temperature and high humidity resistance and high sensitivity to temperature and humidity, can realize simultaneous measurement of temperature and humidity double parameters, and can ensure good measurement accuracy and response speed.
The embodiment of the application also provides a temperature and humidity measurement system, as shown in fig. 2, which comprises: a light sensing subsystem and a signal processing circuit 5;
the optical sensing subsystem includes: a light source 2, a collimating lens 3, a photoelectric converter 4 and the fiber grating temperature and humidity sensor 1;
the light source 2 can adopt an LD light source for providing incident light for the fiber bragg grating temperature and humidity sensor 1;
a collimator lens 3 for converting scattered light emitted from the light source 2 into parallel light;
the fiber bragg grating temperature and humidity sensor 1 is used for measuring temperature and relative humidity in real time and sending a first optical signal and a second optical signal to the photoelectric converter 4;
a photoelectric converter 4 for converting the first optical signal and the second optical signal into a first electric signal and a second electric signal;
the signal processing circuit 5 includes: an amplifying circuit 51, an a/D converter 52, and a central processing unit 53;
an amplifying circuit 51 for amplifying the first electric signal and the second electric signal; an a/D converter 52 for a/D converting the amplified first and second electric signals;
the central processing unit 53 is configured to calculate a temperature measurement value and a relative humidity measurement value according to the temperature and humidity response characteristics of the first fiber grating 113 and the second fiber grating 114.
Specifically, the temperature and humidity response characteristics of the first fiber grating 113 are:
Δλ 1 ＝α 1 ΔT+β 1 ΔH
in the above formula, deltalambda 1 The wavelength variation value of the first fiber bragg grating; delta T is a temperature change value; Δh is the change in relative humidity; alpha 1 The temperature fitting coefficient of the first fiber bragg grating is obtained; beta 1 Fitting coefficients for the relative humidity of the first fiber grating.
The temperature and humidity response characteristics of the second fiber grating 114 are:
Δλ 2 ＝α 2 ΔT+β 2 ΔH+γ 2 ΔH 2
in the above formula, deltalambda 2 The wavelength variation value of the first fiber bragg grating; delta T is a temperature change value; Δh is the change in relative humidity; alpha 2 A temperature fitting coefficient of the second fiber bragg grating; beta 2 Fitting coefficients for first-order relative humidity of the second fiber grating; gamma ray 2 Fitting coefficients for the second order relative humidity of the second fiber grating.
The temperature change value Δt and the relative humidity change value Δh are calculated according to the following formulas:
in the above-mentioned method, the step of,
and calculating a temperature measurement value and a relative humidity measurement value in the current environment according to the temperature change value delta T and the relative humidity change value delta H.
Temperature fitting coefficient alpha of first fiber grating 1 Relative humidity fitting coefficient beta of first fiber bragg grating 1 Temperature fitting coefficient alpha of second fiber grating 2 First-order relative humidity fitting coefficient beta of second fiber bragg grating 2 Fitting coefficient gamma for second-order relative humidity of second fiber grating 2 These coefficients are related to the structural and material characteristics of the sensor, and therefore, by fitting a polynomial to the experimental data multiple times, corresponding coefficient values are obtained, and then combining the wavelength signals Δλ of the two fiber gratings 1 And Deltalambda 2 The temperature change value deltat and the relative humidity change value deltah can be calculated, so that the temperature measurement value and the relative humidity measurement value in the current environment can be calculated.
As an alternative of this embodiment, the system further includes an alarm unit 54 and a temperature and humidity feedback adjustment unit 55, where the alarm unit 54 is connected to the central processing unit 53; in order to make the optical sensor in a stable working environment, a temperature range/interval and a humidity range/interval may be preset in the central processing unit 53 to avoid the abnormality of the temperature and the humidity in the environment, when the temperature measured value is not in the temperature range/interval or the relative humidity measured value is not in the humidity range/interval, an alarm is sent, and the temperature and humidity feedback adjustment unit 55 may also perform feedback adjustment on the temperature and the relative humidity of the working environment according to the measured result of the central processing unit 53.
When the temperature measured value is lower than the lower limit value of the preset temperature range, the central processing unit sends a first alarm signal to the alarm unit; the alarm unit sends out an alarm prompt according to the first alarm signal;
when the temperature measured value is higher than the upper limit value of the preset temperature range, the central processing unit sends a second alarm signal to the alarm unit; the alarm unit sends out an alarm prompt according to the second alarm signal;
when the relative humidity measured value is lower than the lower limit value of the preset humidity range, the central processing unit sends a third alarm signal to the alarm unit; the alarm unit sends out an alarm prompt according to the third alarm signal;
when the measured value of the relative humidity is higher than the upper limit value of the preset humidity range, the central processing unit sends a fourth alarm signal to the alarm unit; and the alarm unit sends out an alarm prompt according to the fourth alarm signal.
The alarm prompts sent by the four alarm signals are different, such as sending different sounds and/or different colors of prompt lights, so that the field personnel can better distinguish the abnormal state of the current environment, and the abnormal state comprises: too high a temperature, too low a temperature, too high a relative humidity, and too low a relative humidity.
The system further comprises a communication module 56, the communication module 56 comprising a man-machine interface 564, a WIFI unit 561, an RS485 interface 562 and a USB interface 563. The man-machine interface 564 is connected with the keyboard 565 and the display 566, the display 566 is used for displaying the change and state of the current ambient temperature and relative humidity in real time, realizing remote monitoring, and modifying the preset parameters of the system through the keyboard 565, etc., so that the system can achieve a remote monitoring, dynamic and controllable working mode. The system can also be connected with an upper management machine through a WIFI unit 561 and an RS485 interface 562, namely, the monitoring, the management and the data sharing of the system are realized through a wired/wireless connection mode. The export and the storage of the measurement data can also be realized through the USB interface 563.
The calibration experiment of the sensor obtained with the aforementioned manufacturing method is shown below, using a supercontinuum light source (SuperK Compact, NKT Photonics) as a broadband light source in a climatic chamber, using a spectrometer (CCS 175-Compact Spectrometer, thorlabs) to continuously track and record the operating state of the grating during the climatic chamber experiment. Firstly, the relative humidity measurement is carried out under the condition of constant temperature of 50 ℃ and relative humidity of 10-90%RH, as shown in figure 3, and the humidity response diagram of the first fiber grating FBG1 and the second fiber grating FBG2 at 50 ℃ is shown in the figure 3; and, the temperature measurement is performed under the condition that the relative humidity is 50% and the temperature is 20-80 ℃, as shown in fig. 4, which is a temperature response chart of the first fiber grating FBG1 and the second fiber grating FBG2 when the relative humidity is 50%.
Under different temperature and humidity conditions in the climate chamber, according to a spectrometer, the wavelength changes of the first fiber bragg grating FBG1 and the second fiber bragg grating FBG2 can be obtained, and delta lambda is obtained 1 And Deltalambda 2 Calculating to obtain the temperature fitting coefficient alpha of the first fiber grating 1 Relative humidity fitting coefficient beta of first fiber bragg grating 1 Temperature fitting coefficient alpha of second fiber grating 2 First-order relative humidity fitting coefficient beta of second fiber bragg grating 2 Fitting coefficient gamma for second-order relative humidity of second fiber grating 2 As shown in table 1 below:
TABLE 1
As shown in fig. 5, according to the data of table 1 and the above formula, the measured value/Reconstruction value (Reconstruction) of the temperature and humidity of the sensor can be obtained by calculation through the measurement system, and according to the standard data (Calibration) obtained in the experimental process, the root mean square deviation of the relative humidity of the obtained Reconstruction value is only 1.04% rh, and the root mean square deviation of the temperature is only 0.8 ℃, which illustrates that the fiber bragg grating temperature and humidity sensor and the measurement system thereof provided by the application not only can effectively realize simultaneous measurement of the temperature and humidity double parameters, but also can improve the precision and reliability of temperature and humidity measurement.
According to the technical scheme, the cladding of the fiber bragg grating temperature and humidity sensor is made of cycloolefin polymer, the polymer material has good heat resistance and low hygroscopicity, the second layer section of the cladding is sleeved with the protective sleeve, and the protective sleeve is made of polymethyl methacrylate material, so that the material has high sensitivity to humidity. The first fiber bragg grating is engraved on a first fiber core section, and only a first layer section of the cladding is sleeved outside the first fiber core section; the second fiber bragg grating is engraved on the second fiber core section, the second layer section of the cladding layer and the protective sleeve are sleeved outside the second fiber core section in sequence, and the humidity sensitivity of the cycloolefin polymer is lower than that of polymethyl methacrylate, so that the temperature and humidity response characteristics of the first fiber bragg grating and the second fiber bragg grating are different, and the temperature value and the humidity value can be calculated cooperatively according to the temperature and humidity response characteristics of the first fiber bragg grating and the second fiber bragg grating, so that the measuring precision of the sensor is improved, and the sensor provided by the application has good temperature and humidity sensitivity and a large measuring range. In the temperature and humidity measurement system provided by the application, scattered light emitted by the light source is converted into parallel light through the collimating lens, the parallel light is incident into the fiber grating temperature and humidity sensor, light signals of the reflected wavelengths of the two fiber gratings are respectively obtained in the corresponding external temperature and humidity environments, and after the conversion treatment of the signals, the temperature value and the humidity value of the current environment are respectively calculated according to the temperature and humidity response characteristics of the two fiber gratings.
Other embodiments of the application will be apparent to those skilled in the art from consideration of the specification and practice of the application disclosed herein. This application is intended to cover any variations, uses, or adaptations of the application following, in general, the principles of the application and including such departures from the present disclosure as come within known or customary practice within the art to which the application pertains. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the application being indicated by the following claims.
It is to be understood that the application is not limited to the precise arrangements and instrumentalities shown in the drawings, which have been described above, and that various modifications and changes may be effected without departing from the scope thereof. The scope of the application is limited only by the appended claims.
Claims (4)
1. A temperature and humidity measurement system, comprising: a light sensing subsystem and a signal processing circuit;
the optical sensing subsystem includes: the device comprises a light source, a collimating lens, a photoelectric converter and a fiber bragg grating temperature and humidity sensor; the fiber bragg grating temperature and humidity sensor comprises a fiber core (11), a cladding layer (12) and a protective sleeve (13), wherein the cladding layer (12) is sleeved outside the fiber core (11), the fiber bragg grating temperature and humidity sensor is characterized in that the fiber core (11) comprises a first fiber core section (111) and a second fiber core section (112), the cladding layer (12) comprises a first layer section (121) and a second layer section (122), the first layer section (121) corresponds to the first fiber core section (111), and the second layer section (122) corresponds to the second fiber core section (112); the protection sleeve (13) is sleeved outside the second layer section (122), a first fiber grating (113) is carved in the first fiber core section (111), and a second fiber grating (114) is carved in the second fiber core section (112); the cladding (12) is made of cycloolefin polymer; the protective sleeve (13) adopts polymethyl methacrylate;
the collimating lens is used for converting scattered light emitted by the light source into parallel light;
the fiber bragg grating temperature and humidity sensor is used for measuring temperature and relative humidity in real time and sending a first optical signal and a second optical signal to the photoelectric converter;
the photoelectric converter is used for converting the first optical signal and the second optical signal into a first electric signal and a second electric signal;
the signal processing circuit includes: an amplifying circuit, an A/D converter and a central processing unit;
the central processing unit is used for calculating a temperature measurement value and a relative humidity measurement value according to the temperature and humidity response characteristics of the first fiber grating and the second fiber grating;
the temperature and humidity response characteristics of the first fiber grating are as follows:
Δλ 1 ＝α 1 ΔT+β 1 ΔH
in the above, deltaλ 1 The wavelength variation value of the first fiber bragg grating; delta T is a temperature change value; Δh is the change in relative humidity; alpha 1 The temperature fitting coefficient of the first fiber bragg grating is obtained; beta 1 Fitting coefficients for the relative humidity of the first fiber grating;
the temperature and humidity response characteristics of the second fiber grating are as follows:
Δλ 2 ＝α 2 ΔT+β 2 ΔH+γ 2 ΔH 2
in the above formula, deltalambda 2 The wavelength variation value of the second fiber bragg grating; delta T is a temperature change value; Δh is the change in relative humidity; alpha 2 A temperature fitting coefficient of the second fiber bragg grating; beta 2 Fitting coefficients for first-order relative humidity of the second fiber grating; gamma ray 2 Fitting coefficients for second-order relative humidity of the second fiber grating;
the temperature change value Δt and the relative humidity change value Δh are calculated according to the following formulas:
in the above-mentioned method, the step of,
and calculating a temperature measurement value and a relative humidity measurement value in the current environment according to the temperature change value delta T and the relative humidity change value delta H.
2. The temperature and humidity measurement system of claim 1, further comprising an alarm unit connected to the central processing unit;
when the temperature measured value is lower than the lower limit value of the preset temperature range, the central processing unit sends a first alarm signal to the alarm unit; the alarm unit sends out an alarm prompt according to the first alarm signal;
when the temperature measured value is higher than the upper limit value of the preset temperature range, the central processing unit sends a second alarm signal to the alarm unit; the alarm unit sends out an alarm prompt according to the second alarm signal;
when the relative humidity measured value is lower than the lower limit value of the preset humidity range, the central processing unit sends a third alarm signal to the alarm unit; the alarm unit sends out an alarm prompt according to the third alarm signal;
when the measured value of the relative humidity is higher than the upper limit value of the preset humidity range, the central processing unit sends a fourth alarm signal to the alarm unit; and the alarm unit sends out an alarm prompt according to the fourth alarm signal.
3. The temperature and humidity measurement system according to claim 1, further comprising a temperature and humidity feedback adjustment unit for performing feedback adjustment on the temperature and relative humidity of the working environment according to the measurement result of the central processing unit.
4. The temperature and humidity measurement system of claim 1, further comprising a communication module comprising a man-machine interface, a WIFI unit, an RS485 interface, and a USB interface; the man-machine interface is connected with the keyboard and the display.
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| CN112254749A (en) * | 2020-10-30 | 2021-01-22 | 杭州柔米科技有限公司 | High polymer double-fiber grating micro-detection system and preparation method thereof |
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