CN113759145B - Thermal type wind speed and wind direction sensor and preparation method of graphene film - Google Patents
Thermal type wind speed and wind direction sensor and preparation method of graphene film Download PDFInfo
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- CN113759145B CN113759145B CN202111050655.6A CN202111050655A CN113759145B CN 113759145 B CN113759145 B CN 113759145B CN 202111050655 A CN202111050655 A CN 202111050655A CN 113759145 B CN113759145 B CN 113759145B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
- G01P5/00—Measuring speed of fluids, e.g. of air stream; Measuring speed of bodies relative to fluids, e.g. of ship, of aircraft
- G01P5/10—Measuring speed of fluids, e.g. of air stream; Measuring speed of bodies relative to fluids, e.g. of ship, of aircraft by measuring thermal variables
- G01P5/12—Measuring speed of fluids, e.g. of air stream; Measuring speed of bodies relative to fluids, e.g. of ship, of aircraft by measuring thermal variables using variation of resistance of a heated conductor
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
- G01P13/00—Indicating or recording presence, absence, or direction, of movement
- G01P13/02—Indicating direction only, e.g. by weather vane
Abstract
The invention relates to a thermal wind speed and wind direction sensor and a preparation method of a graphene film. The sensor includes: the device comprises a graphene film, a wind speed and direction calculation module and two resistance modules; the output ends of the two resistance modules are connected with the input end of the wind speed and direction calculation module; the resistance module comprises two resistance units; two resistance units in the same resistance module are connected in series; the four resistance units are arranged around the graphene film in a centrosymmetric distribution mode. The wind speed and direction sensor is higher in sensitivity and easy to package on the basis of not changing a substrate material and increasing the heat insulation groove.
Description
Technical Field
The invention relates to the field of sensors, in particular to a thermal wind speed and wind direction sensor and a preparation method of a graphene film.
Background
In the production of environmental monitoring, air conditioning and industry and agriculture, the wind speed has very important function, the fast and accurate wind speed measurement has important practical significance, the correctness of the measurement data is closely related to the sensitivity, the response time and the like of the sensor, the current thermal wind speed and wind direction sensor based on the MEMS manufacturing process has small volume and high stability, but most of the current wind speed sensors are prepared on a silicon substrate, although the process is mature, the silicon thermal conductivity coefficient is high, and the sensitivity of the sensor is reduced, therefore, how to reduce the transverse heat transfer of the wind speed sensor and reduce the response time and improve the sensitivity of the sensor is always one of research hotspots, the current method for reducing the transverse heat transfer is to prepare a heat insulation groove on the silicon substrate, the substrate with low heat conductivity such as ceramics, glass, PI film and the like is used, but the heat insulation groove can weaken the sensor, it is not easy to package, and therefore a sensor with easy packaging and high sensitivity is required.
Disclosure of Invention
The invention aims to provide a thermal wind speed and direction sensor and a preparation method of a graphene film, which improve the sensitivity of the wind speed and direction sensor and are easy to package on the basis of not changing a substrate material and increasing a heat insulation groove.
In order to achieve the purpose, the invention provides the following scheme:
a thermal anemometry sensor comprising: the device comprises a graphene film, a wind speed and direction calculation module and two resistance modules; the input ends of the two resistance modules are connected with a power supply; the output ends of the two resistance modules are connected with the input end of the wind speed and direction calculation module; the resistance module comprises two resistance units; two resistance units in the same resistance module are connected in series; the four resistance units are arranged around the graphene film in a centrosymmetric distribution manner.
Optionally, the resistance units each include: a first resistor and a second resistor; two first resistors in the same resistance module are connected in series, and two second resistors in the same resistance module are connected in series.
Optionally, a distance between the first resistor and the second resistor in the same resistor unit is equal to a distance between the first resistor and the graphene film; the first resistor is located between the graphene film and the second resistor.
Optionally, the thermal wind speed and direction sensor further includes: and the differential voltage amplification module is respectively connected with the resistance module and the wind speed and direction calculation module.
Optionally, the differential voltage amplifying module is an operational amplifier.
Optionally, the output end of the resistance module includes a first output port and a second output port; the positive input end of the operational amplifier is connected with the first output port of the resistance module, and the negative input end of the operational amplifier is connected with the second output port of the resistance module.
A preparation method of a graphene thin film, which is used for preparing the graphene thin film, and comprises the following steps:
preparing a graphene oxide solution;
filtering the graphene oxide solution to form a film, and freeze-drying the film to form a porous graphene oxide film;
and heating the porous graphene oxide film to a set temperature, cooling, and taking out to form a graphene film.
Optionally, the concentration of the graphene oxide solution is specifically: 0.5mg/ml to 5 mg/ml.
Optionally, the heating the porous graphene oxide film to a set temperature and cooling the porous graphene oxide film, and then taking out the porous graphene oxide film to form a graphene film specifically includes:
heating the porous graphene oxide film to 500-800 ℃ at the speed of 5-20 ℃/min, maintaining for 1h, heating to 2800-3000 ℃ at the speed of 5-20 ℃/min, maintaining for 1h, cooling, and taking out to form the graphene film.
According to the specific embodiment provided by the invention, the invention discloses the following technical effects: the invention starts from the angle of the heating element, sets the heating element as the graphene film on the basis of not changing the substrate material and increasing the heat insulation groove, utilizes the excellent heat conductivity coefficient and uniformity of the graphene film, on one hand, reduces the time required by the heating element to be increased to a certain temperature under the same voltage so as to improve the sensitivity and response time of the sensor, on the other hand, utilizes the high heat diffusion performance of the heating element to improve the uniformity of the heating element and improve the sensitivity, and the device can not cause the fragile structure to cause the packaging difficulty while improving the sensitivity.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to these drawings without creative efforts.
Fig. 1 is a schematic structural diagram of a thermal wind speed and direction sensor according to an embodiment of the present invention;
FIG. 2 is a block diagram of a thermal anemometry sensor according to an embodiment of the present invention;
fig. 3 is a circuit diagram of a thermal wind speed and direction sensor according to an embodiment of the present invention.
Description of the symbols:
RT 1-upper inner resistance, RT 2-lower inner resistance, RT 3-left inner resistance, RT 4-right inner resistance, RTO 1-upper outer resistance, RTO 2-lower outer resistance, RTO 3-left outer resistance, and RTO 4-right outer resistance.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.
An embodiment of the present invention provides a thermal wind speed and direction sensor, as shown in fig. 1 and 2, the thermal wind speed and direction sensor includes: the device comprises a graphene film (a heating element of a thermal type wind speed and direction sensor), a wind speed and direction calculation module and two resistance modules; the input ends of the two resistance modules are connected with a power supply; the output ends of the two resistance modules are connected with the input end of the wind speed and direction calculation module; the resistance module comprises two resistance units; two resistance units in the same resistance module are connected in series; four resistance unit with the graphene film is central symmetry distribution and sets up around the graphene film, graphene film and two resistance module one-tenth voltage sampling module collect voltage output signal, the external 3.3V voltage of graphene film.
As an alternative embodiment, the graphene film may be fixed on the substrate by a conductive adhesive.
As an optional implementation, the resistance units each include: a first resistor and a second resistor; two first resistors in the same resistance module are connected in series, and two second resistors in the same resistance module are connected in series; the four resistors are connected in series with two temperature-sensitive resistors at the inner side (an upper inner resistor RT1 and a lower inner resistor RT2) and then connected in parallel with resistors (an upper outer resistor RTO1 and a lower outer resistor RTO2) connected in series at the outer side to form a Wheatstone bridge output, and the four resistors at the left side and the right side are connected in series with two temperature-sensitive resistors at the inner side (a left inner resistor RT3 and a right inner resistor RT4) and then connected in parallel with resistors (a left outer resistor RTO3 and a right outer resistor RTO4) connected in series to form a Wheatstone bridge output, as shown in FIG. 1, the four temperature-sensitive resistors at the inner side of RT1-RT4 and the four temperature-sensitive resistors at the outer side of RTo1-RTo4 are used for forming a Wheatstone bridge shown at the left side of FIG. 3, wherein the four temperature-sensitive resistors at the inner side of RT1 and RT2 are connected in series and then connected in parallel with RTo1 and RTo2 to form an upper Wheatstone bridge; the left and right resistors are connected in the same manner to form another wheatstone bridge.
As an optional implementation, the wind speed and direction calculation module: the wind speed and the wind speed direction are calculated through the change of the voltage signals, the wind speed and the wind speed direction are monitored through the connection of the Arduino development board and the computer in a serial port communication mode after the Arduino development board performs A/D conversion, and the wind speed direction are monitored through the connection of the Arduino development board and the computer.
As an alternative embodiment, the distance between the first resistor and the second resistor in the same resistor unit is equal to the distance between the first resistor and the graphene thin film; the first resistor is located between the graphene film and the second resistor, and the eight resistors are symmetrically distributed by taking the graphene film as a center.
As an optional implementation, the thermal anemometry sensor further includes: and the differential voltage amplification module is respectively connected with the resistance module and the wind speed and direction calculation module and is used for amplifying the acquired weak signals.
As an alternative implementation, the differential voltage amplifying module is an operational amplifier, the model is AD623, the differential voltage amplifying module can amplify 500 times, and the operating voltage is 5V.
As an optional implementation, the differential voltage amplifying module further includes: and the external load is connected with the output end of the operational amplifier.
As an optional implementation, the output end of the resistance module comprises a first output port and a second output port; the positive input end of the operational amplifier is connected with the first output port of the resistance module, and the negative input end of the operational amplifier is connected with the second output port of the resistance module.
The embodiment also provides a preparation method of a graphene film, which can be used for preparing the graphene film in the embodiment, and the method includes:
preparing a graphene oxide solution;
filtering the graphene oxide solution to form a membrane, and freeze-drying to form a porous graphene oxide membrane;
and heating the porous graphene oxide film to a set temperature, cooling, and taking out to form a graphene film.
In practical application, the concentration of the graphene oxide solution is specifically as follows: 0.5mg/ml to 5 mg/ml.
In practical application, the step of heating the porous graphene oxide film to a set temperature and cooling the porous graphene oxide film and then taking out the porous graphene oxide film to form a graphene film specifically comprises the following steps:
heating the porous graphene oxide film to 500-800 ℃ at the speed of 5-20 ℃/min, maintaining for 1h, heating to 2800-3000 ℃ at the speed of 5-20 ℃/min, maintaining for 1h, cooling, and taking out to form the graphene film. The defects of the graphene are repaired due to high temperature, sp 3 Conversion to sp 2 The heat conductivity is greatly improved by the graphite crystallization compared with the common platinum metal (24.86 mm) 2 S) and nickel metal (21.98 mm) 2 /s), the thermal diffusion coefficient of the graphene film prepared by the method can reach 759mm 2 Above s, the response capability of the heating element portion is greatly improved.
In practical application, the graphene film can be prepared from 0.5mg/ml solution, is subjected to suction filtration to form a film, is immediately subjected to freeze drying to obtain a porous graphene oxide film, is heated to 500 ℃ at a heating rate of 5 ℃/min and is maintained for 1h, is continuously heated at a speed of 5 ℃/min per minute, and is naturally cooled and taken out when the temperature reaches 2800 ℃ and is maintained for 1 h. Or preparing the porous graphene oxide film from a 2mg/ml solution, performing suction filtration to form the film, immediately performing freeze drying to obtain the porous graphene oxide film, and then performing freeze dryingHeating to 600 deg.C at a heating rate of 10 deg.C/min and maintaining for 1h, then heating at a rate of 10 deg.C/min per minute to 2900 deg.C and maintaining for 1h, and naturally cooling and taking out. The graphene oxide film can also be prepared from a solution of 5mg/ml, is subjected to suction filtration to form a film, is immediately subjected to freeze drying to obtain a porous graphene oxide film, is heated to 800 ℃ at a heating rate of 20 ℃/min and is maintained for 1h, is continuously heated at a speed of 20 ℃/min per minute, and is naturally cooled and taken out when the temperature reaches 3000 ℃ and is maintained for 1 h. Third party tests show that in the table 1, the thermal diffusion coefficient of the graphene film prepared by the three methods is 759.261 +/-10 mm 2 The thermal conductivity was 56 w/mk.
TABLE 1
The sensor is a temperature difference type wind speed sensor, and the working principle is as follows: can produce the heat current on graphite alkene film surface when wind blows over, thereby the resistance change of resistance around can arouse to the heat current can produce voltage signal, wind speed and direction calculation module calculates according to voltage signal's change and obtains wind speed and wind direction, there is not the difference in temperature difference differential voltage to be 0 under the windless condition, the wind speed produces the difference in temperature when not 0, thereby the differential voltage output that produces is to AD623 amplifier circuit, export to Arduino's simulation input port after 500 times enlargies, Arduino development board passes through serial communication mode and links to each other with the computer, obtain the size and the direction of wind speed through the processing to the amplified signal on the computer.
The invention has the following technical effects:
1. the upper resistor, the lower resistor, the left resistor, the right resistor and the left resistor are arranged at equal intervals to avoid zero drift caused by different passing distances of heat flows.
2. The graphene film has the advantages that the thermal diffusion coefficient is high, so that the heating is uniform; meanwhile, the heat conductivity is low, the heat preservation is good, the heating rate is high, the intermediate heating element is made of the graphene film, the sensitivity is improved, the response time is shortened, the energy is saved, the environment is protected, the sensitivity is improved, and meanwhile, the packaging difficulty caused by the fragile structure is avoided.
3. The eight temperature-sensitive resistors are utilized to improve the output amplitude of the differential voltage.
The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other.
The principles and embodiments of the present invention have been described herein using specific examples, which are provided only to help understand the method and the core concept of the present invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, the specific embodiments and the application range may be changed. In view of the foregoing, the description is not to be taken in a limiting sense.
Claims (6)
1. A thermal anemometry sensor, comprising: the device comprises a graphene film, a wind speed and direction calculation module and two resistance modules; the input ends of the two resistance modules are connected with a power supply; the output ends of the two resistance modules are connected with the input end of the wind speed and direction calculation module; the resistance module comprises two resistance units; two resistance units in the same resistance module are connected; two resistance units in the same resistance module are arranged around the graphene film in a centrosymmetric manner; the four resistance units are symmetrically distributed around the graphene film by taking the graphene film as a center; the resistance units each include: a first resistor and a second resistor; two first resistors in the same resistance module are connected in series, and two second resistors in the same resistance module are connected in series; the distance between the first resistor and the second resistor in the same resistor unit is equal to the distance between the first resistor and the graphene film; the first resistor is located between the graphene film and the second resistor.
2. The thermal anemometry sensor of claim 1, further comprising: and the differential voltage amplification module is respectively connected with the resistance module and the wind speed and direction calculation module.
3. The thermal wind speed and direction sensor according to claim 2, wherein the differential voltage amplification module is an operational amplifier.
4. The thermal anemometry sensor of claim 3, wherein the output of said resistive module comprises a first output and a second output; the positive input end of the operational amplifier is connected with the first output port of the resistance module, and the negative input end of the operational amplifier is connected with the second output port of the resistance module.
5. A method for preparing a graphene thin film, which is used for preparing the graphene thin film in the thermal anemorumbome sensor according to claim 1, the method comprising:
preparing a graphene oxide solution;
filtering the graphene oxide solution to form a membrane, and freeze-drying to form a porous graphene oxide membrane;
heating the porous graphene oxide film to a set temperature, cooling, and taking out to form a graphene film;
the method comprises the following steps of heating the porous graphene oxide film to a set temperature, cooling, and taking out to form a graphene film, and specifically comprises the following steps:
heating the porous graphene oxide film to 500-800 ℃ at the speed of 5-20 ℃/min, maintaining for 1h, heating to 2800-3000 ℃ at the speed of 5-20 ℃/min, maintaining for 1h, cooling, and taking out to form the graphene film.
6. The method for preparing the graphene film according to claim 5, wherein the concentration of the graphene oxide solution is specifically as follows: 0.5mg/ml to 5 mg/ml.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| US4648271A (en) * | 1985-12-09 | 1987-03-10 | Ga Technologies Inc. | Anemometer having a graphite fiber hot wire |
| CN1523360A (en) * | 2003-09-10 | 2004-08-25 | 中国电子科技集团公司第十三研究所 | Minisize heat flow accelerometer and method for making same |
| JP4850105B2 (en) * | 2007-03-23 | 2012-01-11 | 日立オートモティブシステムズ株式会社 | Thermal flow meter |
| CN102749473B (en) * | 2012-06-30 | 2014-04-16 | 东南大学 | Two-dimensional hot-film wind speed and direction sensor and preparation method thereof |
| CN104743551B (en) * | 2015-03-27 | 2017-03-01 | 上海应用技术学院 | A kind of preparation method of redox graphene heat conduction thin film |
| CN106990262A (en) * | 2017-05-05 | 2017-07-28 | 厦门大学 | A kind of thermal convection current accelerometer |
| CN108051610B (en) * | 2017-10-16 | 2022-04-12 | 东南大学 | Intelligent double-detection-mode wind speed and direction sensor and measurement method |
| CN211348306U (en) * | 2020-02-27 | 2020-08-25 | 华云升达(北京)气象科技有限责任公司 | MEMS constant-temperature differential thermal film type anemometer |
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