阅读说明：本技术 低温至室温温度区间光纤光栅温度传感器标定系统及方法 (Calibration system and method for fiber grating temperature sensor in temperature range from low temperature to room temperature ) 是由 刘延超 尹立坤 于 2021-08-06 设计创作，主要内容包括：一种低温至室温温度区间光纤光栅温度传感器标定系统及方法,它包括标定装置、低温杜瓦、光纤光栅解调仪、温度数据采集卡、直流电源、固态继电器、信号驱动数据卡和上位机,标定装置固定于低温杜瓦内,光纤光栅解调仪和温度数据采集卡与标定装置和上位机连接,直流电源、固态继电器和信号驱动数据卡依次串联后与标定装置和上位机连接,上位机控制信号驱动数据卡产生输出电压信号,驱动固态继电器控制标定装置中加热丝的通电与关断,实现加热与冷却,实现光纤光栅温度传感器从77K-393K温度区间内的温度标定。(A calibration system and method for a fiber grating temperature sensor in a temperature range from low temperature to room temperature comprises a calibration device, a low-temperature Dewar, a fiber grating demodulator, a temperature data acquisition card, a direct current power supply, a solid-state relay, a signal driving data card and an upper computer, wherein the calibration device is fixed in the low-temperature Dewar, the fiber grating demodulator and the temperature data acquisition card are connected with the calibration device and the upper computer, the direct current power supply, the solid-state relay and the signal driving data card are sequentially connected in series and then connected with the calibration device and the upper computer, the upper computer controls the signal driving data card to generate an output voltage signal, and the solid-state relay is driven to control the energization and the shutoff of a heating wire in the calibration device, so that heating and cooling are realized, and the temperature calibration of the fiber grating temperature sensor in the temperature range from 77K to 393K is realized.)

1. A calibration system for a fiber grating temperature sensor in a temperature range from low temperature to room temperature is characterized in that: the device comprises a calibration device (1), a low-temperature Dewar (2), a fiber bragg grating demodulator (3), a temperature data acquisition card (4), a direct-current power supply (5), a solid-state relay (6), a signal driving data card (7) and an upper computer (8); the calibration device (1) is fixed in the low-temperature Dewar (2), the fiber grating demodulator (3) and the temperature data acquisition card (4) are connected with the calibration device (1) and the upper computer (8), and the direct-current power supply (5), the solid-state relay (6) and the signal driving data card (7) are sequentially connected in series and then connected with the calibration device (1) and the upper computer (8).

2. The system for calibrating a fiber grating temperature sensor in a low-temperature to room-temperature interval as claimed in claim 1, wherein: the calibration device (1) comprises a heat insulation cover (12) connected with the upper side of a fixed substrate (11), and fixed plates (13) are located on two sides of the heat insulation cover (12) and connected with the heat insulation cover (12).

3. The system for calibrating a fiber grating temperature sensor in a temperature range from low temperature to room temperature according to claim 2, wherein: the side sets up heating groove (14) on fixed baseplate (11), and heating groove (14) are located heat exchanger (12), are located and set up heater strip (15) in heating groove (14), and copper (16) are located heater strip (15), and line hole (17) run through to heating groove (14) in from fixed baseplate (11) side.

4. The system for calibrating a fiber grating temperature sensor in a temperature range from low temperature to room temperature according to claim 2, wherein: the heat shield (12) is a hollow box body with an opening at the lower side, the opening end at the lower side of the hollow box body is matched with an annular groove at the upper side of the fixed base plate (11), and the copper pipe (18) penetrates through the heat shield (12) and extends into the upper part of the copper plate (16).

5. The system for calibrating a fiber grating temperature sensor in a low-temperature to room-temperature interval as claimed in claim 1, wherein: the inner wall of the cavity of the low-temperature Dewar (2) is provided with a heat insulation layer (21), and an epoxy resin layer (22) is attached to the heat insulation layer (21).

6. The system for calibrating a fiber grating temperature sensor according to claim 5, wherein the system comprises: a filling hole (24) and a lead pipe (25) are arranged on a Dewar cover (23) of the low-temperature Dewar (2), and a protruding part on the lower side of the Dewar cover (23) is matched and sealed with the inner wall of a cavity of the low-temperature Dewar (2).

7. The system for calibrating a fiber grating temperature sensor according to claim 5, wherein the system comprises: the bottom of the cavity of the low-temperature Dewar (2) is provided with a connecting column (26) which is fixedly connected with a fixing plate (13) of the calibration device (1).

8. The system for calibrating a fiber grating temperature sensor in a temperature range from low temperature to room temperature according to claim 2, wherein: the copper pipe (18) is a hollow pipe body with one closed end, the closed end is located in the heat insulation cover (12), a fiber grating temperature sensor and a reference sensor are arranged in the hollow pipe body, the fiber grating temperature sensor is connected with a fiber grating demodulator (3), the reference sensor is connected with a temperature data acquisition card (4), the fiber grating demodulator (3) and the temperature data acquisition card (4) are connected with an upper computer (8) through Ethernet or USB, and a direct current power supply (5) is electrically connected with the heating wire (15).

9. The system for calibrating a fiber grating temperature sensor in a low-temperature to room-temperature interval as claimed in claim 1, wherein: the upper computer (8) controls the signal to drive the data card (7) to generate an output voltage signal, and drives the solid relay (6) to control the electrification and the disconnection of the heating wire (15) in the calibration device (1) so as to realize heating and cooling.

10. The calibration method of the calibration system of the fiber grating temperature sensor in the low-temperature to room-temperature interval as claimed in any one of claims 1 to 9, characterized in that it comprises the following steps:

s1, installing a sample, placing the sample, the fiber bragg grating temperature sensor and the reference sensor in the copper pipe (18), sealing the port of the copper pipe (18) by adopting a sealant, and leading out data wires of the fiber bragg grating temperature sensor and the reference sensor to the outside of the copper pipe (18);

s2, installing the calibration device, opening the Dewar cover (23), and connecting and fixing a fixing plate (13) of the calibration device (1) and a connecting column (26) in a cavity of the low-temperature Dewar (2);

s3, leading out wires of the heating wires (15), data lines of the fiber bragg grating temperature sensor and the reference sensor from a lead pipe (25) of the Dewar cover (23), sealing the port of the lead pipe (25) by adopting sealant, and sealing the Dewar cover (23) and the low-temperature Dewar (2) in a matched manner; the filling hole (24) is connected with a filling pipe of liquid nitrogen equipment;

s4, connecting, wherein the lead of the heating wire (15) is electrically connected with the direct current power supply (5), and the data wires of the fiber grating temperature sensor and the reference sensor are respectively connected with the fiber grating demodulator (3) and the temperature data acquisition card (4);

s5, calibrating a low-temperature range, wherein the temperature range is 77K-293K;

s5-1, running a program of an upper computer (8), and displaying and storing temperature data of the fiber bragg grating temperature sensor to be detected and the reference sensor in real time; in the step, the solid state relay (6) is in a closed state;

s5-2, adding liquid nitrogen into the low-temperature Dewar (2) by liquid nitrogen equipment until the calibration device (1) is completely soaked in the liquid nitrogen by the liquid nitrogen; observing the wavelength data of the fiber bragg grating temperature sensor and the temperature data of the reference sensor which are displayed by the upper computer (8) in real time; at the moment, the two groups of data have obvious downward trends, the temperature data of the reference sensor is reduced to 77K, and after the temperature data is continuously and stably maintained at 77K within a set time range, the calibration of the fiber bragg grating temperature sensor is started;

s5-3, adjusting the output current button of the DC power supply (5) to make the output current I₁Clicking a control button in the program of the upper computer (8), and driving a data card (7) to generate a driving voltage signal by a control signal to drive a solid-state relay (6) to be switched on; at this time, the DC power supply (5) starts to supply a current I₁Heating the copper plate (16), observing temperature change curves of the reference sensor and the fiber bragg grating temperature sensor, simultaneously storing data, and clicking a control button in a program of the upper computer (8) to turn off a power supply after the curves of the reference sensor and the fiber bragg grating temperature sensor are all stabilized within a set value and a set time range;

s5-4, carrying out averaging processing on the stable data within 2 minutes, wherein the data obtained after the averaging processing is the data of a temperature calibration point;

s5-5, repeating S5-3 and S5-4, and sequentially changing the current of the direct current power supply (5) to be I₁… In, corresponding to a temperature T₁…T_n,Respectively acquiring reference sensor temperature and fiber grating temperature sensor wavelength data which are stable in set values within the continuous set time under different electrifying currents until the calibration target temperature Tn =293K is reached, and calibrating the temperature between 77K and 293K of the fiber grating sensor by using the acquired stable data of the temperature and the wavelength under different electrifying currents;

s6, calibrating a high-temperature interval, wherein the temperature interval is 293K-393K;

s6-1, repeating S5-1;

s6-2, observing the wavelength data of the fiber bragg grating temperature sensor and the temperature data of the reference sensor which are displayed by the upper computer (8) in real time; after the temperature data of the reference sensor is kept stable at 293K and within a set time range, the calibration of the fiber bragg grating temperature sensor is started;

repeating S5-3 and S5-4 in sequence;

s5-5 is repeated again, in S5-5, until the calibration target temperature Tn =393K is reached, and the temperature between the fiber grating sensors 293K-393K is calibrated using the collected stable data of temperature and wavelength at different energizing currents.

Technical Field

The invention belongs to the technical field of sensors, and relates to a calibration system and method for a fiber grating temperature sensor in a temperature range from low temperature to room temperature.

Background

The fiber grating sensor has the characteristics of small volume, light weight, electromagnetic interference resistance, easiness in multiplexing and the like, and the special material and performance of the fiber grating sensor enable the fiber grating sensor to be considered as a sensing device capable of replacing a traditional electric signal sensor to be applied to the polar environment such as corrosion, low temperature and strong electromagnetic interference. Different from other types of optical fiber sensors, the optical fiber grating sensor is a wavelength demodulation sensor, a broadband light source emits a beam of light, the beam of light reaches the position of the optical fiber grating through a transmission optical fiber, the light meeting the Bragg condition wavelength is reflected back to a detection circuit after passing through the optical fiber grating, the reflected light has physical information such as temperature, strain and the like, and the information such as the temperature, the strain and the like of a measured point can be obtained by demodulating the wavelength of the reflected light. As with the conventional sensor, when the fiber grating sensor is used for absolute temperature measurement, the sensor is calibrated for temperature, that is, the quantitative relationship between the wavelength and the temperature of the fiber grating temperature sensor is determined experimentally.

The core of the calibration method is how to provide a temperature-adjustable environment for a measured fiber grating sensor, that is, a proper fiber grating sensor calibration device is needed. For the application of the fiber grating sensor in a non-extreme environment (293K-393K), the universal calibration methods include a water bath calibration method and a warm box calibration method, and the environment with the temperature variable above room temperature is very easy to obtain. When the fiber bragg grating temperature sensor and the like are used in extreme environments such as superconducting magnet temperature (77K-293K) measurement and the like, no mature calibration device and method exist at present due to the fact that complex technologies such as liquid nitrogen refrigeration and the like and the advanced scientific field are involved.

Chinese patent application No.: 201910758936.3, patent name: a fiber grating sensor calibration device based on liquid nitrogen conduction cooling provides a method for calibrating the temperature of a fiber grating sensor by liquid nitrogen conduction cooling, the method can realize the calibration of the sensor in a 77K-293K temperature interval by utilizing liquid nitrogen conduction cooling, however, the method is long in calibration time consumption and needs to consume a large amount of liquid nitrogen, in addition, the method can only realize the calibration of the 77K-293K temperature interval, and can not simultaneously calibrate a higher temperature interval (293K-).

Chinese patent application No.: 201811085366.8, patent name: a method for calibrating Fiber Bragg Grating (FBG) temperature based on a BP neural network is provided, the method for calibrating the FBG temperature sensor (FBG) by using the BP neural network is used for finalizing the application of the BP neural network in the processing of the wavelength and temperature data of the FBG temperature sensor, and a specific temperature change mode and a specific design of a calibration device are not given.

Chinese patent application No.: 201911182291.X, patent name: a fiber grating temperature sensor calibration device based on electromagnetic induction heating provides a method for realizing fiber grating temperature sensor calibration by electromagnetic induction heating, however, the method can only realize the calibration of the temperature above 293K and does not have the capability of low-temperature calibration.

Disclosure of Invention

The invention aims to solve the technical problem of providing a system and a method for calibrating a fiber grating temperature sensor in a temperature range from low temperature to room temperature, wherein the system is simple, convenient and easy to manufacture, and can realize the temperature calibration of the fiber grating temperature sensor in the temperature range from 77K to 393K.

In order to solve the technical problems, the technical scheme adopted by the invention is as follows: a calibration system for a fiber grating temperature sensor in a temperature range from low temperature to room temperature comprises a calibration device, a low-temperature Dewar, a fiber grating demodulator, a temperature data acquisition card, a direct-current power supply, a solid-state relay, a signal driving data card and an upper computer; the calibration device is fixed in the low-temperature Dewar, the fiber grating demodulator and the temperature data acquisition card are connected with the calibration device and the upper computer, and the direct-current power supply, the solid-state relay and the signal driving data card are sequentially connected in series and then connected with the calibration device and the upper computer.

The calibration device comprises a heat shield connected with the upper side of the fixed substrate, and the fixed plates are located on two sides of the heat shield and connected with the heat shield.

The side sets up the heating groove on the PMKD, and the heating groove is located thermal shroud, is located to set up the heater strip in the heating groove, and the copper is located the heater strip, and the line hole runs through to the heating groove in from the PMKD side.

The heat shield is a hollow box body with an opening at the lower side, the opening end at the lower side of the hollow box body is matched with the annular groove at the upper side of the fixed base plate, and the copper pipe penetrates through the heat shield and goes deep into the upper part of the copper plate.

The inner wall of the cavity of the low-temperature Dewar is provided with a heat insulation layer, and the epoxy resin layer is attached to the heat insulation layer.

And the Dewar cover of the low-temperature Dewar is provided with a filling hole and a lead pipe, and a bulge part on the lower side of the Dewar cover is matched and sealed with the inner wall of the cavity of the low-temperature Dewar.

And the bottom of the cavity of the low-temperature Dewar is provided with a connecting column which is fixedly connected with a fixing plate of the calibration device.

The copper pipe is a hollow pipe body with one closed end, the closed end is located in the heat insulation cover, a fiber grating temperature sensor and a reference sensor are arranged in the hollow pipe body, the fiber grating temperature sensor is connected with a fiber grating demodulator, the reference sensor is connected with a temperature data acquisition card, the fiber grating demodulator and the temperature data acquisition card are connected with an upper computer through Ethernet or USB, and a direct-current power supply is electrically connected with the heating wire.

The upper computer control signal drives the data card to generate an output voltage signal, and drives the solid-state relay to control the electrification and the turn-off of the heating wire in the calibration device, so that heating and cooling are realized.

The calibration method of the calibration system of the fiber grating temperature sensor in the temperature range from low temperature to room temperature comprises the following steps:

s1, installing a sample, placing the sample, the fiber bragg grating temperature sensor and the reference sensor in a copper pipe, sealing the port of the copper pipe by adopting a sealant, and leading out data wires of the fiber bragg grating temperature sensor and the reference sensor to the outside of the copper pipe;

s2, installing a calibration device, opening the Dewar cover, and connecting and fixing a fixing plate of the calibration device and a connecting column in the low-temperature Dewar cavity;

s3, leading out wires of the heating wires, data lines of the fiber bragg grating temperature sensor and the reference sensor from a lead pipe of the Dewar cover, sealing the port of the lead pipe by adopting sealant, and sealing the Dewar cover and the low-temperature Dewar in a matching manner; the filling hole is connected with a filling pipe of liquid nitrogen equipment;

s4, connecting, wherein the lead of the heating wire is electrically connected with a direct current power supply, and the data wires of the fiber grating temperature sensor and the reference sensor are respectively connected with a fiber grating demodulator and a temperature data acquisition card;

s5, calibrating a low-temperature range, wherein the temperature range is 77K-293K;

s5-1, running a program of an upper computer, and displaying and storing temperature data of the fiber bragg grating temperature sensor to be detected and the reference sensor in real time; in this step, the solid state relay is in a closed state;

s5-2, adding liquid nitrogen into the low-temperature Dewar by liquid nitrogen equipment until the calibration device is completely soaked in the liquid nitrogen by the liquid nitrogen; observing the wavelength data of the fiber grating temperature sensor and the temperature data of the reference sensor which are displayed by the upper computer in real time; at the moment, the two groups of data have obvious downward trends, the temperature data of the reference sensor is reduced to 77K, and after the temperature data is continuously and stably maintained at 77K within a set time range, the calibration of the fiber bragg grating temperature sensor is started;

s5-3, adjusting the output current button of the DC power supply to make the output current I₁Clicking a control button in an upper computer program, and driving a data card to generate a driving voltage signal by a control signal to drive a solid-state relay to be switched on; at this point, the DC power supply begins to supply current I₁Heating the copper plate, observing temperature change curves of the reference sensor and the fiber bragg grating temperature sensor, simultaneously storing data, and clicking a control button in an upper computer program to turn off a power supply after the curves of the reference sensor and the fiber bragg grating temperature sensor are all stabilized within a set numerical value and a set time range;

s5-4, carrying out averaging processing on the stable data within 2 minutes, wherein the data obtained after the averaging processing is the data of a temperature calibration point;

s5-5, repeating S5-3 and S5-4, and sequentially changing the current of the direct current power supply to be I₁… In, corresponding to a temperature T₁…T_n,Respectively acquiring reference sensor temperature and fiber grating temperature sensor wavelength data which are stable in set values within the continuous set time under different electrifying currents until the calibration target temperature Tn =293K is reached, and calibrating the temperature between 77K and 293K of the fiber grating sensor by using the acquired stable data of the temperature and the wavelength under different electrifying currents;

s6, calibrating a high-temperature interval, wherein the temperature interval is 293K-393K;

s6-1, repeating S5-1;

s6-2, observing the wavelength data of the fiber grating temperature sensor and the temperature data of the reference sensor displayed by the upper computer in real time; after the temperature data of the reference sensor is kept stable at 293K and within a set time range, the calibration of the fiber bragg grating temperature sensor is started;

repeating S5-3 and S5-4 in sequence;

s5-5 is repeated again, in S5-5, until the calibration target temperature Tn =393K is reached, and the temperature between the fiber grating sensors 293K-393K is calibrated using the collected stable data of temperature and wavelength at different energizing currents.

The beneficial effects of the invention are mainly embodied in that:

the system adopts the calibration device with the heating wires and the copper plate as core components to calibrate the fiber grating temperature sensor, and the calibration device is placed in a designed low-temperature Dewar, so that the temperature calibration of the fiber grating temperature sensor in a 77K-393K or even higher temperature interval can be realized.

The calibration device and the low-temperature Dewar in the system have the advantages of simple structure, simple calibration method, less time consumption and high efficiency, and the sealed low-temperature Dewar is filled with liquid nitrogen, so that the volatilization of the liquid nitrogen is reduced, the liquid nitrogen is saved, and the economy is high.

The fiber grating temperature sensor and the reference sensor in the system are sealed with the copper pipe by adopting a sealant, and the parameters such as the size of the copper pipe can be expanded according to actual requirements, so that the calibration of a plurality of fiber grating temperature sensors can be completed at one time.

Drawings

The invention is further illustrated by the following examples in conjunction with the accompanying drawings:

FIG. 1 is a diagram of a calibration system of the present invention.

FIG. 2 is a schematic front view of the low temperature dewar of the present invention.

Fig. 3 is a schematic top view of fig. 2.

Fig. 4 is a schematic structural diagram of the calibration device of the present invention.

Fig. 5 is a schematic structural diagram of a fixing substrate of the calibration device of the present invention.

FIG. 6 is a schematic view showing the connection structure of copper pipes and copper plates according to the present invention.

Fig. 7 is a side view of fig. 6.

FIG. 8 is a schematic view of the heat shield of the present invention.

In the figure: the device comprises a calibration device 1, a fixed substrate 11, a heat insulation cover 12, a fixed plate 13, a heating groove 14, a heating wire 15, a copper plate 16, a wire hole 17, a copper pipe 18, a low-temperature Dewar 2, a heat insulation layer 21, an epoxy resin layer 22, a Dewar cover 23, a filling hole 24, a lead pipe 25, a connecting column 26, a fiber grating demodulator 3, a temperature data acquisition card 4, a direct-current power supply 5, a solid-state relay 6, a signal driving data card 7 and an upper computer 8.

Detailed Description

As shown in fig. 1 to 8, a calibration system for a fiber grating temperature sensor in a temperature range from low temperature to room temperature comprises a calibration device 1, a low-temperature dewar 2, a fiber grating demodulator 3, a temperature data acquisition card 4, a direct current power supply 5, a solid-state relay 6, a signal driving data card 7 and an upper computer 8; the calibration device 1 is fixed in the low-temperature Dewar 2, the fiber grating demodulator 3 and the temperature data acquisition card 4 are connected with the calibration device 1 and the upper computer 8, and the direct-current power supply 5, the solid-state relay 6 and the signal driving data card 7 are sequentially connected in series and then connected with the calibration device 1 and the upper computer 8. When the device is used, the calibration device 1 is located in the sealed low-temperature Dewar 2, the fiber bragg grating temperature sensor and the reference sensor are located in the calibration device 1, low-temperature interval calibration is achieved under the condition that nitrogen is filled in the low-temperature Dewar 2, the temperature interval range is 77K-293K, high-temperature interval calibration is achieved under the condition that nitrogen is not filled in the low-temperature Dewar 2, and the temperature interval range is 293K-393K or even higher.

Preferably, the reference sensor is of the type PT 100.

Preferably, the program software of the upper computer 8 is Labview.

In a preferred scheme, the calibration device 1 comprises a heat shield 12 connected to the upper side of a fixed substrate 11, and fixed plates 13 are located on both sides of the heat shield 12 and connected to the heat shield 12. The fixed base plate 11 and the fixed plate 13 are made of epoxy resin materials, so that the mechanical property under a low-temperature environment is improved; the heat shield 12 is provided with an interlayer filled with a foam material for heat insulation and exchange between the ambient temperature of the sample to be tested and the external temperature.

In a preferred scheme, a heating groove 14 is arranged on the upper side surface of the fixed base plate 11, the heating groove 14 is positioned in the heat shield 12, a heating wire 15 is arranged in the heating groove 14, a copper plate 16 is positioned on the heating wire 15, and a wire hole 17 penetrates into the heating groove 14 from the side surface of the fixed base plate 11. The copper plate 16 is fixed with the heating wire 15 through special low-temperature heat-conducting glue, the heating wire 15 is fixed with the heating groove 14 through the special low-temperature heat-conducting glue, the wire hole 17 is used for penetrating through a wire of the heating wire 15, and the wire is led out and then sealed through low-temperature epoxy resin.

In a preferred embodiment, the heat shield 12 is a hollow box with an opening at the lower side, the opening end at the lower side of the hollow box is matched with an annular groove at the upper side of the fixed substrate 11, and the copper pipe 18 penetrates through the heat shield 12 and extends to the upper side of the copper plate 16. The copper pipe 18 is fixed on the copper plate 16 through special low-temperature heat-conducting glue, and the heat shield 12 is matched with the fixed substrate 11 and then sealed by low-temperature sealant.

In a preferred scheme, a heat insulation layer 21 is arranged on the inner wall of the cavity of the low-temperature Dewar 2, and an epoxy resin layer 22 is attached to the heat insulation layer 21. Epoxy has good low temperature mechanicalness, and insulating layer 21 can reduce the inside and outside temperature exchange of low temperature dewar 2 for the temperature in the low temperature dewar 2 is more stable, is carrying out the low temperature calibration simultaneously, reduces the waste of liquid nitrogen.

In a preferable scheme, a filling hole 24 and a lead pipe 25 are arranged on a Dewar cover 23 of the low-temperature Dewar 2, and a convex part on the lower side of the Dewar cover 23 is matched and sealed with the inner wall of the cavity of the low-temperature Dewar 2. The filling hole 24 is connected with a conveying pipe of liquid nitrogen equipment and is used for adding liquid nitrogen during low-temperature calibration; in order to reduce waste of liquid nitrogen and disturb the temperature of a sample when the liquid nitrogen is added, a conveying pipe for adding the liquid nitrogen is inserted into the bottom of the low-temperature Dewar 2 through the filling hole 24, then the liquid nitrogen is slowly added into the low-temperature Dewar 2 through the conveying pipe until the liquid nitrogen submerges the calibration device 1, and after the liquid nitrogen is added, the filling hole 24 is plugged by a foam sealing plug to reduce heat exchange between the internal temperature and the external temperature of the low-temperature Dewar 2.

Preferably, the data lines of the fiber grating temperature sensor and the reference sensor in the calibration device 1 and the conducting wires of the heating wire 15 are all led out from the lead tube 25, and after the leading-out, the sealing glue is used for sealing the port of the lead tube 25.

In a preferred scheme, a connecting column 26 is arranged at the bottom of the cavity of the low-temperature dewar 2 and is fixedly connected with a fixing plate 13 of the calibration device 1. The connecting column 26 is used for connecting the calibration device 1, and fixing the calibration device 1 in the cavity of the low-temperature dewar 2.

In a preferred scheme, the copper pipe 18 is a hollow pipe body with one closed end, the closed end is positioned in the heat insulation cover 12, a fiber grating temperature sensor and a reference sensor are arranged in the hollow pipe body, the fiber grating temperature sensor is connected with a fiber grating demodulator 3, the reference sensor is connected with a temperature data acquisition card 4, the fiber grating demodulator 3 and the temperature data acquisition card 4 are connected with an upper computer 8 through Ethernet or USB, and the direct-current power supply 5 is electrically connected with the heating wire 15. After the sample, the fiber bragg grating temperature sensor and the reference sensor are arranged in the copper pipe 18 from the opening end of the copper pipe 18, sealing glue is used for plugging and fixing, so that the fiber bragg grating temperature sensor and the reference sensor are convenient to detach and beneficial to replacement.

Preferably, the Labview program of the upper computer 8 realizes the demodulation, display and storage of the wavelength of the fiber grating temperature sensor.

Preferably, the Labview program of the upper computer 8 realizes the display and storage of the temperature data of the reference sensor.

In the preferred scheme, the upper computer 8 controls the signal to drive the data card 7 to generate an output voltage signal, and drives the solid-state relay 6 to control the energization and the shutoff of the heating wire 15 in the calibration device 1, so as to realize heating and cooling.

Preferably, the heating wire 15 and the circuit of the direct current power supply 5 are connected in series with the solid-state relay 6 and the signal driving data card 7, the signal driving data card 7 is connected with the upper computer 8 through the ethernet or the USB, when the calibration is performed, the direct current power supply 5 is in a normally open state, the upper computer 8 controls the signal driving data card 7 to generate an output voltage signal, so that the solid-state relay 6 is driven to be switched on and off, the heating wire 15 in the calibration device 1 is powered on and switched off, and heating and cooling are achieved.

Preferably, in the above technical solution, the calibration may be divided into two cases according to whether liquid nitrogen is added to the low-temperature dewar 2, so as to realize calibration of two temperature intervals. When liquid nitrogen is added into the low-temperature Dewar 2, the calibration device 1 is soaked in the liquid nitrogen by the liquid nitrogen, the temperature of the environment position where the fiber grating temperature sensor in the calibration device 1 is located is reduced to 77K in a conduction cooling mode, and at the moment, calibration of a temperature range of 77K-293K can be achieved; when liquid nitrogen is not added, the initial temperature of the environment position where the fiber bragg grating temperature sensor in the calibration device 1 is located is the same as room temperature 293K, and calibration in a temperature range of 293K-393K or even higher can be achieved.

Preferably, the control programs of the devices involved in the above scheme are all integrated in a Labview program of the upper computer 8, so as to realize real-time and synchronous operation of all the devices, and a Labview program interface can realize real-time display, visualization, data storage and post-processing of a calibration program.

In a preferred embodiment, the calibration method for the calibration system of the fiber grating temperature sensor in the temperature range from low temperature to room temperature includes the following steps:

s1, installing a sample, placing the sample, the fiber bragg grating temperature sensor and the reference sensor in the copper pipe 18, sealing the port of the copper pipe 18 by adopting a sealant, and leading out data wires of the fiber bragg grating temperature sensor and the reference sensor to the outside of the copper pipe 18;

s2, installing the calibration device, opening the Dewar cover 23, and connecting and fixing the fixing plate 13 of the calibration device 1 and the connecting column 26 in the cavity of the low-temperature Dewar 2;

s3, leading out the lead wire of the heating wire 15, the data wire of the fiber bragg grating temperature sensor and the reference sensor from the lead pipe 25 of the Dewar cover 23, sealing the port of the lead pipe 25 by adopting sealant, and sealing the Dewar cover 23 and the low-temperature Dewar 2 in a matching way; the filling hole 24 is connected with a filling pipe of liquid nitrogen equipment;

s4, connecting, wherein the lead of the heating wire 15 is electrically connected with the direct current power supply 5, and the data wires of the fiber grating temperature sensor and the reference sensor are respectively connected with the fiber grating demodulator 3 and the temperature data acquisition card 4;

s5, calibrating a low-temperature range, wherein the temperature range is 77K-293K;

s5-1, running a program of the upper computer 8, and displaying and storing temperature data of the fiber bragg grating temperature sensor to be detected and the reference sensor in real time; in this step, the solid-state relay 6 is in a closed state;

s5-2, adding liquid nitrogen into the low-temperature Dewar 2 by liquid nitrogen equipment until the calibration device 1 is completely soaked in the liquid nitrogen by the liquid nitrogen; observing the wavelength data of the fiber bragg grating temperature sensor and the temperature data of the reference sensor which are displayed by the upper computer 8 in real time; at the moment, the two groups of data have obvious downward trends, the temperature data of the reference sensor is reduced to 77K, and after the temperature data is continuously and stably maintained at 77K within a set time range, the calibration of the fiber bragg grating temperature sensor is started;

s5-3, adjusting the output current button of the DC power supply 5 to make the output current I₁Clicking a control button in the program of the upper computer 8, and driving the data card 7 to generate a driving voltage signal by a control signal to drive the solid-state relay 6 to be switched on; at this time, the DC power supply 5 starts to supply the current I₁Heating the copper plate 16, observing temperature change curves of the reference sensor and the fiber bragg grating temperature sensor, simultaneously storing data, and clicking a control button in a program of the upper computer 8 to turn off a power supply after the curves of the reference sensor and the fiber bragg grating temperature sensor are all stabilized within a set numerical value and a set time range;

s5-4, carrying out averaging processing on the stable data within 2 minutes, wherein the data obtained after the averaging processing is the data of a temperature calibration point;

s5-5, repeating S5-3 and S5-4, and sequentially changing the current of the direct current power supply 5 to be I₁… In, corresponding to a temperature T₁…T_n,Respectively acquiring reference sensor temperature and fiber grating temperature sensor wavelength data which are stable in set values within the continuous set time under different electrifying currents until the calibration target temperature Tn =293K is reached, and calibrating the temperature between 77K and 293K of the fiber grating sensor by using the acquired stable data of the temperature and the wavelength under different electrifying currents; in this step, the temperature rise amplitude and rate are controlled by varying the thickness of the copper plate 16 and the parameters of the heating wire 15 before installation.

S6, calibrating a high-temperature interval, wherein the temperature interval is 293K-393K;

s6-1, repeating S5-1;

s6-2, observing the wavelength data of the fiber grating temperature sensor and the temperature data of the reference sensor which are displayed by the upper computer 8 in real time; after the temperature data of the reference sensor is kept stable at 293K and within a set time range, the calibration of the fiber bragg grating temperature sensor is started;

repeating S5-3 and S5-4 in sequence;

s5-5 is repeated again, in S5-5, until the calibration target temperature Tn =393K is reached, and the temperature between the fiber grating sensors 293K-393K is calibrated using the collected stable data of temperature and wavelength at different energizing currents. In the step, the calibration of a higher temperature range beyond 293K-393K is realized, which depends on the parameter design of the direct current power supply 5, the copper plate 16 and the heating wire 15. The method can realize the low-temperature interval calibration of the fiber grating sensor, the temperature interval range is 77K-293K, and the interval calibration with the temperature interval range being 293K-393K can also be realized.

The above-described embodiments are merely preferred embodiments of the present invention, and should not be construed as limiting the present invention, and features in the embodiments and examples in the present application may be arbitrarily combined with each other without conflict. The protection scope of the present invention is defined by the claims, and includes equivalents of technical features of the claims. I.e., equivalent alterations and modifications within the scope hereof, are also intended to be within the scope of the invention.