Multi-parameter gas safety early warning system based on surface acoustic waves

Abstract

A multi-parameter gas safety early warning system based on surface acoustic waves comprises a phase discrimination demodulation circuit module, a temperature sensing module, a humidity sensing module, a gas sensing module, a processing module, a PC terminal and a storage module. The phase discrimination demodulation circuit module is used for generating input signals and then transmitting the input signals in a branching manner; the temperature sensing module, the humidity sensing module and the gas sensing module are used for receiving input signals of the phase discrimination demodulation circuit module, then converting the input signals and sending the oscillation frequency of the temperature sensing module, the oscillation frequency of the humidity sensing module and the oscillation frequency of the gas sensing module to the processing module through the phase discrimination demodulation circuit module; the processing module is used for calculating and obtaining a gas early warning index; the PC terminal is used for displaying the gas early warning index calculated by the processing module; the storage module is used for storing calculation parameters. The industrial harmful gas safety early warning system effectively solves the problems that an existing industrial harmful gas safety early warning system is low in detection sensitivity, poor in temperature stability and poor in real-time performance.

Description

Technical Field

[0001] This application relates to the technical field of gas safety warning, and particularly relates to a multi-parameter gas safety warning system based on surface acoustic wave. Background Art

[0002] Gases are in a gaseous state under normal temperature and pressure, usually from natural or human sources, and are collectively referred to as industrial gases. Industrial gases are classified into three types of gases with different chemical properties according to the national standard "Classification and Marking of Common Dangerous Chemicals" (GB13690-1992): toxic gases, flammable gases, and non-flammable gases (including oxidizing gases).

[0003] Currently, the sensing technologies used for industrial gas detection mainly include electrochemistry method, infrared absorption method, ion mobility method, semiconductor type, catalytic combustion type, micro-resonator type, etc. However, the electrochemistry method has a short service life, the ion mobility method has a high cost, and the semiconductor and catalytic combustion type sensors have high power consumption. Therefore, there are still problems in the existing gas detection technologies such as high cost, large power consumption and volume, and short service life. Summary of the Invention

[0004] This application provides a multi-parameter gas safety warning system based on surface acoustic wave, which can be used to solve the technical problems of high cost, low detection accuracy, poor anti-interference ability and slow detection speed existing in the current warning system.

[0005] This application provides a multi-parameter gas safety warning system based on surface acoustic wave, including a phase discrimination and demodulation circuit module, a temperature sensing module including a delay line, a humidity sensing module including a delay line, a gas sensing module including a delay line, a processing module, a PC terminal (22) and a storage module;

[0006] Among them: the phase discrimination and demodulation circuit module is respectively connected to the temperature sensing module, the humidity sensing module and the gas sensing module, and is used for generating an input signal and then splitting and sending it to the temperature sensing module, the humidity sensing module and the gas sensing module;

[0007] The temperature sensing module, the humidity sensing module and the gas sensing module are used for receiving the input signal of the phase discrimination and demodulation circuit module, then converting it, and sending the oscillation frequency of the temperature sensing module, the oscillation frequency of the humidity sensing module and the oscillation frequency of the gas sensing module to the processing module through the phase discrimination and demodulation circuit module;

[0008] The processing module is used for calculating the oscillation frequency of the temperature sensing module, the oscillation frequency of the humidity sensing module and the oscillation frequency of the gas sensing module received, and obtaining a gas warning index;

[0009] The PC terminal (22) is used for displaying the gas warning index calculated by the processing module;

[0010] The storage module is used to store calculation parameters.

[0011] Among them, the temperature sensing piezoelectric substrate of the temperature sensing module selects Y-cut quartz crystal material, which has good frequency bandwidth and temperature measurement range performance; the humidity sensing piezoelectric substrate of the humidity sensing module includes a quartz layer, a SiO2 coating layer, and a PVA film from bottom to top; ST-X90° quartz layer is used and a SiO2 layer that serves as both a waveguide layer and a moisture absorption film is plated on the quartz layer. To improve the moisture absorption performance, a PVA film is further plated on the SiO2 coating layer, which has high detection sensitivity, good temperature stability, and easy implementation.

[0012] The gas sensing piezoelectric substrate of the gas sensing module uses ST-X90° quartz and a SU-8 thin layer is covered on the quartz surface, which serves as both an acoustic waveguide layer and protects the interdigital electrodes. And the sensor device of the gas sensing module is locally encapsulated, and PDMS is bonded between the gas input interdigital transducer and the gas output interdigital transducer for gas-sensitive sensing.

[0013] Both the humidity sensing module and the gas sensing module adopt the Love wave waveguide structure. By exciting the Love wave and its propagation changes in the waveguide layer, the state changes of the waveguide layer are sensitively detected, which has high detection sensitivity, good temperature stability, and easy implementation, effectively solving the problems of low detection sensitivity, poor temperature stability, and poor real-time performance existing in the current gas safety warning system.

[0014] Furthermore, the phase discrimination and demodulation circuit module includes a signal source (14), a splitter (15), a temperature sensing phase discriminator (16), a humidity sensing phase discriminator (17), a gas sensing phase discriminator (18), a first AD conversion (19), a second AD conversion (20), and a third AD conversion (21); one side of the splitter (15) is connected to the signal source (14), and the other side of the splitter (15) is respectively connected to one side of the temperature sensing module, the humidity sensing module, and the gas sensing module;

[0015] The other side of the temperature sensing module is connected to the temperature sensing phase discriminator (16), the other side of the humidity sensing module is connected to the humidity sensing phase discriminator (17), and the other side of the gas sensing module is connected to the gas sensing phase discriminator (18); the temperature sensing phase discriminator (16), the humidity sensing phase discriminator (17), and the gas sensing phase discriminator (18) are respectively connected to the first AD conversion (19), the second AD conversion (20), and the third AD conversion (21);

[0016] The first AD conversion (19), the second AD conversion (20), and the third AD conversion (21) are all connected to the PC side (22), and the temperature sensing phase discriminator (16), the humidity sensing phase discriminator (17), and the gas sensing phase discriminator (18) are also all connected to the signal source (14).

[0017] Further, the temperature sensing module includes a temperature sensing piezoelectric substrate (1), a temperature sensing input interdigital transducer (2), and a temperature sensing output interdigital transducer (3). The temperature sensing input interdigital transducer (2) and the temperature sensing output interdigital transducer (3) are deposited on the temperature sensing piezoelectric substrate (1), and the temperature sensing piezoelectric substrate (1) is a quartz piezoelectric substrate cut along the Y direction.

[0018] Further, the humidity sensing module includes a humidity sensing piezoelectric substrate (4), a humidity sensing input interdigital transducer (6), a humidity sensing output interdigital transducer (7), a humidity sensing waveguide layer (5), and a humidity sensitive film (8). Among them, the humidity sensing input interdigital transducer (6) and the humidity sensing output interdigital transducer (7) are deposited on the humidity sensing piezoelectric substrate (4); the humidity sensing waveguide layer (5) is deposited on the upper layer of the humidity sensing piezoelectric substrate (4), the humidity sensing input interdigital transducer (6), and the humidity sensing output interdigital transducer (7); the humidity sensitive film (8) is deposited between the humidity sensing input interdigital transducer (6) and the humidity sensing output interdigital transducer (7).

[0019] Among them, the humidity sensing piezoelectric substrate (4) is a quartz piezoelectric substrate cut by rotating 42.75° around the Y direction and propagating along the X 90° direction, that is, ST-90°.

[0020] The material of the humidity sensitive film (8) is an organic polymer, such as polyvinyl alcohol PVA, polyimide PI, etc., or an inorganic substance silicon dioxide SiO2, etc. The methods for depositing the humidity sensitive film include drop coating, spin coating, magnetron sputtering, atmospheric pressure chemical vapor deposition, etc. When using silicon dioxide, a sparse layer of SiO2 is prepared by atmospheric pressure chemical vapor deposition method, which serves as both a waveguide layer to excite Love waves and a moisture absorption layer to absorb moisture, and a layer of PVA is spin-coated on the SiO2 to enhance humidity sensing.

[0021] Further, the gas sensing module includes a gas sensing piezoelectric substrate (9), a gas sensing input interdigital transducer (11), and a gas sensing output interdigital transducer (12); the gas sensing input interdigital transducer (11) and the gas sensing output interdigital transducer (12) are deposited on the gas sensing piezoelectric substrate (9); the gas sensing waveguide layer (10) is deposited on the gas sensing piezoelectric substrate (9), the gas sensing input interdigital transducer (11), and the gas sensing output interdigital transducer (12); a gas sensitive region (13) is bonded between the gas sensing input interdigital transducer (11) and the gas sensing output interdigital transducer (12).

[0022] Among them, the air-borne piezoelectric substrate (9) is a quartz piezoelectric substrate cut by rotating 42.75° around the Y direction and propagating along the X90° direction, that is, ST-90°X quartz. The material of the gas-sensitive region (13) is polydimethylsiloxane PDMS, and the region shape is any one of a cylinder and a cuboid; if it is a cylinder, the bottom radius of the cylinder is 5 mm and the height is 5 mm.

[0023] Further, the structure of the air-borne input interdigital transducer (11) is the same as that of the temperature-borne input interdigital transducer (2); a dummy finger electrode with a width of 1 / 8λ x grounded at one end is filled between the comb teeth of the temperature-borne output interdigital transducer (3) to maintain the uniformity of the SAW propagation speed, where λ x is the acoustic wave wavelength along the acoustic wave propagation direction;

[0024] The structures of the humidity-borne output interdigital transducer (7) and the air-borne output interdigital transducer (12) are the same as that of the temperature-borne output interdigital transducer (3); adopting this comb structure is mainly used to achieve that there is only one phase period within the passband of the surface acoustic wave device, that is, there is only one phase corresponding frequency point that satisfies the oscillation starting condition within the device passband, thereby improving the frequency stability of the oscillator.

[0025] The temperature-borne input interdigital transducer (2), the humidity-borne input interdigital transducer (6) and the gas input interdigital transducer (11) all adopt a unidirectional single-phase EWC / SPUDT structure, and reflection electrodes are arranged between the finger pairs of all interdigital transducers; the finger pair includes two electrodes with a width of 1 / 8λ x and the distance between the two electrodes is 1 / 8λ x , the width of the reflection electrode is 1 / 4λ x , and the edge distance between the reflection electrode and its corresponding finger pair is 3 / 16λ x , the material of the reflection electrode is aluminum with a thickness of 1%-1.5%λ x , where λ x =v / f, λ x is the acoustic wave wavelength along the acoustic wave propagation direction, v is the propagation speed of the surface acoustic wave on the piezoelectric substrate, and f is the operating frequency of the humidity sensing module / gas sensing module / temperature sensing module.

[0026] Further, both the humidity sensing module and the gas sensing module adopt a Love acoustic wave guide structure of SiO2 / ST-90°X quartz. By using the waveguide layer to couple the elastic wave excited in the substrate into the surface wave waveguide layer, the attenuation of the acoustic wave can be reduced, and it is extremely sensitive to the surface load, thereby effectively improving the detection sensitivity of the sensor. Through the acoustic mode change and mass loading effect caused by gas molecule deposition, the real-time monitoring of gas can be realized, and gas, temperature and humidity can be monitored in real time.

[0027] Further, after receiving the oscillation frequencies of the temperature sensing module, the humidity sensing module, and the gas sensing module, the processing module obtains the calculation parameters stored in the storage module. The calculation parameters include a temperature transfer calculation coefficient, a humidity transfer calculation coefficient, and a gas calculation coefficient;

[0028] The process of calculating the gas warning index is as follows: Obtain the oscillation frequency of each temperature sensing module transmitted periodically and the temperature transfer calculation coefficient to calculate the temperature index; Obtain the oscillation frequency of each humidity sensing module transmitted periodically and the humidity transfer calculation coefficient to calculate the humidity index; Obtain the oscillation frequency of each gas sensing module transmitted periodically and the gas calculation coefficient to calculate the gas index; Calculate the gas warning index based on the temperature index, the humidity index, and the gas index.

[0029] In this application, the temperature transfer piezoelectric substrate of the temperature sensing module selects Y-cut quartz crystal material; the humidity transfer piezoelectric substrate of the humidity sensing module is SiO2 that serves as both a waveguide layer and a hygroscopic film, and a PVA film is further deposited on the SiO2 coating, which has high detection sensitivity and good temperature stability; the gas transfer piezoelectric substrate of the gas sensing module uses ST-X90° quartz and a SU-8 thin layer is covered on the surface, which serves as both an acoustic waveguide layer and is used to protect the interdigital electrodes. PDMS is bonded between the gas transfer input interdigital transducer and the gas transfer output interdigital transducer for gas-sensitive sensing, realizing the detection of industrial harmful gases, and effectively solving the problems of low detection sensitivity, poor temperature stability, and poor real-time performance existing in the current industrial harmful gas safety warning system. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a flowchart of the multi-parameter gas safety warning system based on surface acoustic wave of the present invention.

[0031] Figure 2 It is a schematic structural diagram of the multi-parameter gas safety warning system based on surface acoustic wave of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0032] To make the objectives, technical solutions, and advantages of this application clearer, the following will further describe the embodiments of this application in detail with reference to the accompanying drawings.

[0033] The embodiments of this application will be introduced below with reference to the accompanying drawings first.

[0034] The embodiments of this application adopt a multi-parameter gas safety warning system based on surface acoustic wave, which has high detection sensitivity, good temperature stability, and can be mass-produced and is easy to implement, effectively solving the problems of high cost, low detection accuracy, poor anti-interference ability, and slow detection speed existing in the current warning system.

[0035] Please refer to Figure 1 , an embodiment of the present invention provides a technical solution: a multi-parameter gas safety warning system based on surface acoustic wave, including a phase discrimination and demodulation circuit module, a temperature sensing module including a delay line, a humidity sensing module including a delay line, a gas sensing module including a delay line, a processing module, a PC terminal 22 and a storage module, wherein: the phase discrimination and demodulation circuit module is respectively connected to the temperature sensing module, the humidity sensing module, the gas sensing module and the PC terminal, and is used for generating an input signal and then branching and transporting it to the temperature sensing module, the humidity sensing module and the gas sensing module; the temperature sensing module, the humidity sensing module and the gas sensing module are all used for receiving the input signal of the phase discrimination and demodulation circuit module, converting it and sending the oscillation frequency of the temperature sensing module, the oscillation frequency of the humidity sensing module and the oscillation frequency of the gas sensing module to the processing module through the phase discrimination and demodulation circuit module; the processing module is used for calculating the oscillation frequency of the temperature sensing module, the oscillation frequency of the humidity sensing module and the oscillation frequency of the gas sensing module received, and obtaining a gas warning index; the PC terminal 22 is used for displaying the gas warning index calculated by the processing module; the storage module is used for storing calculation parameters.

[0036] Specifically, as Figure 2 shown, the phase discrimination and demodulation circuit module includes a signal source 14, a splitter 15, a temperature sensing phase discriminator 16, a humidity sensing phase discriminator 17, a gas sensing phase discriminator 18, a first AD converter 19, a second AD converter 20 and a third AD converter 21. The splitter 15 is connected to the signal source 14, and the splitter 15 is also respectively connected to one side of the temperature sensing module, the humidity sensing module and the gas sensing module; the other side of the temperature sensing module is connected to the temperature sensing phase discriminator 16, the other side of the humidity sensing module is connected to the humidity sensing phase discriminator 17, the other side of the gas sensing module is connected to the gas sensing phase discriminator 18, and the temperature sensing phase discriminator 16, the humidity sensing phase discriminator 17 and the gas sensing phase discriminator 18 are respectively connected to the first AD converter 19, the second AD converter 20 and the third AD converter 21; the first AD converter 19, the second AD converter 20 and the third AD converter 21 are all connected to the PC terminal 22, and the temperature sensing phase discriminator 16, the humidity sensing phase discriminator 17 and the gas sensing phase discriminator 18 are also all connected to the signal source 14.

[0037] Specifically, the temperature sensing module includes a temperature sensing piezoelectric substrate 1, a temperature sensing input interdigital transducer 2, and a temperature sensing output interdigital transducer 3. The temperature sensing input interdigital transducer 2 and the temperature sensing output interdigital transducer 3 are deposited on the temperature sensing piezoelectric substrate 1, and the temperature sensing piezoelectric substrate 1 is a quartz piezoelectric substrate cut along the Y direction.

[0038] Specifically, the humidity sensing module includes a humidity-transducing piezoelectric substrate 4, which is a quartz piezoelectric substrate cut by rotating 42.75° around the Y direction and propagating along the X 90° direction, i.e., ST-90°X quartz. A humidity-transducing input interdigital transducer 6 and a humidity-transducing output interdigital transducer 7 deposited on the humidity-transducing piezoelectric substrate 4, a humidity-transducing waveguide layer 5 deposited on the humidity-transducing piezoelectric substrate 4, the humidity-transducing input interdigital transducer 6, and the humidity-transducing output interdigital transducer 7, and a humidity-sensitive film 8 deposited between the humidity-transducing input interdigital transducer 6 and the humidity-transducing output interdigital transducer 7. The material of the humidity-sensitive film 8 can be an organic polymer, such as polyvinyl alcohol PVA, polyimide PI, etc., or an inorganic substance silicon dioxide SiO2, etc. The methods of depositing the humidity-sensitive film include drop coating, spin coating, magnetron sputtering, atmospheric pressure chemical vapor deposition, etc. When using silicon dioxide, a sparse layer of SiO2 is prepared by atmospheric pressure chemical vapor deposition method, which serves as both a waveguide layer to excite Love waves and a moisture absorption layer to absorb moisture, and a layer of PVA is spin-coated on the SiO2 to enhance humidity sensing.

[0039] Specifically, the gas sensing module includes a gas-transducing piezoelectric substrate 9, a gas-transducing input interdigital transducer 11 and a gas-transducing output interdigital transducer 12 deposited on the gas-transducing piezoelectric substrate 9. The gas-transducing piezoelectric substrate 9 is a quartz piezoelectric substrate cut by rotating 42.75° around the Y direction and propagating along the X 90° direction, i.e., ST-90°X quartz. A gas-transducing waveguide layer 10 deposited on the gas-transducing piezoelectric substrate 9, the gas-transducing input interdigital transducer 11, and the gas-transducing output interdigital transducer 12, and a gas-sensitive region 13 bonded between the gas-transducing input interdigital transducer 11 and the gas-transducing output interdigital transducer 12. The gas sensing module is locally encapsulated, and the gas-sensitive region 13 bonded between the gas-transducing input interdigital transducer 11 and the gas-transducing output interdigital transducer 12 detects the gas. The material of the gas region can use polydimethylsiloxane PDMS to achieve shaping, and the region shape can be a cylinder, a cuboid, etc. The bottom radius of the cylinder is 5 mm and the height is 5 mm.

[0040] The structure of the gas-transducing input interdigital transducer 11 is the same as that of the temperature-transducing input interdigital transducer 2; the width of the false finger electrodes filled between the teeth of the temperature-transducing output interdigital transducer 3 is 1 / 8λ x and one end of the false finger electrode is grounded to maintain the uniformity of the SAW propagation speed, where λ x is the acoustic wave wavelength along the acoustic wave propagation direction. The structures of the humidity-transducing output interdigital transducer 7 and the gas-transducing output interdigital transducer 12 are the same as that of the temperature-transducing output interdigital transducer 3. The comb-like structure is mainly used to achieve that there is only one phase period in the passband of the surface acoustic wave device, that is, there is only one phase corresponding frequency point that satisfies the oscillation starting condition in the device passband, thereby improving the frequency stability of the oscillator.

[0041] The temperature transmission input interdigital transducer 2, the humidity transmission input interdigital transducer 6, and the gas transmission input interdigital transducer 11 all adopt a unidirectional single-phase EWC / SPUDT structure. Reflective electrodes are arranged between the finger pairs of all the interdigital transducers; the finger pair consists of two electrodes with a width of 1 / 8λ x and the distance between the two electrodes is 1 / 8λ x . The width of the reflective electrode is 1 / 4λ x , and the edge distance between the reflective electrode and its corresponding finger pair is 3 / 16λ x . The material of the reflective electrode is aluminum with a thickness of 1%-1.5%λ x , where λ x =v / f, λ x is the acoustic wave wavelength along the acoustic wave propagation direction, v is the propagation speed of the surface acoustic wave on the piezoelectric substrate, and f is the operating frequency of the humidity sensing module / gas sensing module / temperature sensing module.

[0042] Both the humidity sensing module and the gas sensing module adopt a Love acoustic waveguide structure of SiO2 / ST-90°X quartz. The elastic wave excited in the substrate can be coupled into the surface wave waveguide layer by the waveguide layer, which can reduce the attenuation of the acoustic wave and is extremely sensitive to the surface load, thus effectively improving the detection sensitivity of the sensor. Through the acoustic mode change and mass loading effect caused by gas molecule deposition, real-time monitoring of gas can be achieved, and gas, temperature, and humidity can be monitored in real time.

[0043] Specifically, after the processing module receives the oscillation frequencies of the temperature sensing module, the humidity sensing module, and the gas sensing module, it obtains the calculation parameters stored in the storage module. The calculation parameters include the temperature transmission calculation coefficient, the humidity transmission calculation coefficient, and the gas calculation coefficient. The process of calculating the gas warning index is as follows: Obtain the oscillation frequency of each temperature sensing module transmitted periodically and the temperature transmission calculation coefficient to calculate the temperature index; Obtain the oscillation frequency of each humidity sensing module transmitted periodically and the humidity transmission calculation coefficient to calculate the humidity index; Obtain the oscillation frequency of each gas sensing module transmitted periodically and the gas calculation coefficient to calculate the gas index; Calculate the gas warning index based on the temperature index, the humidity index, and the gas index.

[0044] Specifically, the implementation steps of this system are as follows:

[0045] S1: The signal source 14 generates an input signal, which is divided into 6 paths by the splitter 15 and enters the temperature sensing module, the humidity sensing module, the gas sensing module, and the temperature sensing phase discriminator 16, the humidity sensing phase discriminator 17, and the gas sensing phase discriminator 18 respectively;

[0046] S2: The temperature transmission output interdigital transducer 3 of the temperature sensing module converts the input electrical signal into a surface acoustic wave signal and propagates it on the surface of the temperature transmission piezoelectric substrate 1;

[0047] S3: The temperature transmission input interdigital transducer 2 of the temperature sensing module receives the converted surface acoustic wave signal and converts the surface acoustic wave signal into an electrical signal;

[0048] S4: The converted electrical signal is differentiated with the branch of the signal source 14 through the temperature sensing phase discriminator 16, and the differential signal is input into the first AD converter 19 to complete analog-to-digital conversion and upload it to the PC terminal 22;

[0049] S5: The humidity transmission output interdigital output transducer 7 of the humidity sensing module converts the input electrical signal into a surface acoustic wave signal and propagates it on the surface of the humidity transmission piezoelectric substrate;

[0050] S6: The humidity transmission input interdigital transducer 6 of the humidity sensing module receives the converted surface acoustic wave signal and converts the surface acoustic wave signal into an electrical signal;

[0051] S7: The converted electrical signal is differentiated with the branch of the signal source 14 through the humidity sensing phase discriminator 17, and the differential signal is input into the second AD converter 20 to complete analog-to-digital conversion and upload it to the PC terminal 22;

[0052] S8: The gas transmission output interdigital transducer 12 of the gas sensing module converts the input electrical signal into a surface acoustic wave signal and propagates it on the surface of the gas transmission piezoelectric substrate;

[0053] S11: The gas transmission input interdigital transducer 11 of the gas sensing module receives the converted surface acoustic wave signal and converts the surface acoustic wave signal into an electrical signal;

[0054] S12: The converted electrical signal is differentiated with the branch of the signal source 14 through the gas sensing phase discriminator 18, and the differential signal is input into the third AD converter 21 to complete analog-to-digital conversion and upload it to the PC terminal 22;

[0055] S14: The PC terminal 22 displays the temperature index, humidity index, and gas index to be detected, and calculates and displays the gas warning index based on the temperature index, humidity index, and gas index.

[0056] In this implementation scheme, it is allowed to consider the data of multiple humidity sensing modules, and this integration helps to improve the accuracy of the humidity index.

[0057] Specifically, obtain the oscillation frequency of the temperature sensing module and the temperature transmission calculation coefficient k periodically transmitted by each temperature sensing module w Calculate the temperature index T w The calculation formula is: where \(i = 1, 2, 3, \cdots, n\) is the number of temperature sensing modules, and \(j = 1, 2, 3, \cdots, m\) is the oscillation frequency of the temperature sensing module periodically transmitted by each temperature sensing module. is the \(j\)-th oscillation frequency of the temperature sensing module periodically transmitted by the \(i\)-th temperature sensing module, and \(\gamma\) w is the modulation parameter for single-group temperature calculation, and \(\nu\) w is the modulation parameter for temperature index calculation, and \(e\) is the natural constant.

[0058] In this implementation, the parameters and summation symbols in the formula allow the system to consider the data of multiple temperature sensing modules. Each sensing module can provide different information. This comprehensive consideration helps to improve the accuracy of gas warning. By multiplying appropriate coefficients and parameters, that is, \(\gamma\) w is the modulation parameter for single-group temperature calculation, and \(\nu\) w is the modulation parameter for temperature index calculation, which can adjust the weight of the data of each sensing module. The temperature transmission calculation coefficient \(k\) w is related to the selected temperature transmission piezoelectric substrate and waveguide layer materials.

[0059] Specifically, obtaining the oscillation frequency of the humidity sensing module periodically transmitted by each humidity sensing module and the humidity transmission calculation coefficient \(k\) rh Calculating the humidity index \(RH\) s The calculation formula is: where \(i = 1, 2, 3, \cdots, h\) is the number of humidity sensing modules, and \(j = 1, 2, 3, \cdots, q\) is the oscillation frequency of the humidity sensing module periodically transmitted by each humidity sensing module. is the \(j\)-th oscillation frequency of the humidity sensing module periodically transmitted by the \(i\)-th humidity sensing module, and \(\delta\) s is the modulation parameter for single-group humidity calculation, and \(\theta\) s is the modulation parameter for mean value calculation, and \(rh\) s is the humidity mean value, where

[0060] In this implementation, it is allowed to consider the data of multiple humidity sensing modules. This integration helps to improve the accuracy of the humidity index. The humidity mean value is introduced in the formula, which is based on the average humidity data of multiple sensing modules. The mean value helps to reduce the influence of noise or error of a single sensor on the final result. The parameters and calculation methods can be adjusted according to specific situations to meet the requirements of different applications. The humidity transmission calculation coefficient \(k\) rh is related to the selected humidity-sensitive film 8.

[0061] Specifically, obtaining the oscillation frequency of the gas sensing module periodically transmitted by each gas sensing module and the gas transmission calculation coefficient \(k\) b Calculating the gas index \(T\) b The calculation formula is as follows: where \(i = 1, 2, 3,\cdots\), \(o\) is the number of gas sensing modules, \(j = 1, 2, 3,\cdots\), \(p\) is the oscillation frequency of each gas sensing module transmitted periodically, is the \(j\)-th oscillation frequency of the \(i\)-th gas sensing module transmitted periodically, \(\rho\) b is the calculation modulation parameter of single-group gas temperature, \(\psi\) b is the calculation modulation parameter of gas index.

[0062] In this implementation, it is allowed to consider the data of multiple gas sensing modules. Using the data of multiple sensing modules comprehensively can improve the accuracy of gas index. Introducing the modulation parameters (\(\rho\) b and \(\psi\) b ) can adjust the calculation method of the index as needed. This flexibility allows the system to be customized according to different environmental conditions and application scenarios. By summing the oscillation frequencies, the information collected from different sensing modules is integrated together, which helps to understand the gas situation more comprehensively. Calculating the coefficient \(k\) b is related to the materials of the selected gas-transmitting piezoelectric substrate 9 and the gas-transmitting waveguide layer 10.

[0063] Specifically, the calculation formula for calculating the gas warning index based on the temperature index, humidity index and gas index is: where \(\xi_1\), \(\xi_2\) and \(\xi_3\) are the weight coefficients of the temperature index \(T\) w , humidity index \(RH\) s and gas index \(T\) b respectively.

[0064] In this implementation, the temperature index, humidity index and gas index are integrated, which means it considers multiple factors, including temperature, humidity and gas situation, to comprehensively evaluate the gas risk. The weight coefficients (\(\xi_1\), \(\xi_2\) and \(\xi_3\)) in the formula allow the weight adjustment of different indexes according to the needs of the application, which helps to adapt to different application scenarios and environmental conditions.

[0065] In summary, this application has at least the following effects:

[0066] For the temperature sensing module of the multi-parameter gas safety warning system based on surface acoustic wave, the temperature sensing piezoelectric substrate selects Y-cut quartz crystal material, which has good frequency bandwidth and temperature measurement range performance; for the humidity sensing module, the humidity sensing piezoelectric substrate 4 uses ST-X90° quartz and is coated with a layer of SiO2 that serves as both a waveguide layer and a moisture absorption film. To improve the moisture absorption, a layer of PVA film is further coated on the SiO2 coating, which has high detection sensitivity, good temperature stability, and easy implementation; for the gas sensing module, the gas sensing piezoelectric substrate 9 uses ST-X90° quartz and a SU-8 thin layer is covered on the surface, which serves as both an acoustic waveguide layer and a protection for the interdigital electrodes. And the sensor device of the gas sensing module is locally encapsulated, and PDMS is bonded between the gas input interdigital transducer 11 and the gas output interdigital transducer 12 for gas-sensitive sensing. Both the humidity sensing module and the gas sensing module adopt the Love wave waveguide structure. By exciting the Love wave and its propagation changes in the waveguide layer, the state changes of the waveguide layer are sensitively detected, which has high detection sensitivity, good temperature stability, and easy implementation, effectively solving the problems of low detection sensitivity, poor temperature stability, and poor real-time performance existing in the current gas safety warning system.

[0067] Those skilled in the art should understand that the embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present invention can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0068] The present invention is described with reference to the flowcharts and / or block diagrams of systems, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each flow and / or block in the flowchart and / or block diagram, as well as the combination of flows and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing devices generate means for implementing the functions specified in Figure 1 one flow or multiple flows and / or blocks Figure 1 the functions specified in one block or multiple blocks.

[0069] These computer program instructions can also be stored in a computer-readable manner that can direct a computer or other programmable data processing devices to work in a specific manner or the functions specified in multiple blocks.

[0070] These computer program instructions can also be loaded onto a computer or other programmable data processing apparatus, so that a series of operation steps are performed on the computer or other programmable apparatus to produce a computer-implemented process, and thus the instructions executed on the computer or other programmable apparatus provide steps for realizing the functions specified in one process or a plurality of processes and / or blocks Figure 1 one process or a plurality of processes and / or blocks Figure 1 steps for realizing the functions specified in one block or a plurality of blocks.

[0071] Although the preferred embodiments of the present invention have been described, additional changes and modifications can be made by those skilled in the art once they learn the basic creative concept. Therefore, the appended claims are intended to be construed to cover the preferred embodiments as well as all changes and modifications falling within the scope of the present invention.

[0072] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention is also intended to include these modifications and variations.

Claims

1. A multi-parameter gas safety early warning system based on surface acoustic wave, characterized in that, The system includes a phase discrimination and demodulation circuit module, a temperature sensing module including a delay line, a humidity sensing module including a delay line, a gas sensing module including a delay line, a processing module, a PC terminal, and a storage module; Among them, the phase discrimination and demodulation circuit module is respectively connected to the temperature sensing module, the humidity sensing module, and the gas sensing module, and is used to generate an input signal and then branch and transmit it to the temperature sensing module, the humidity sensing module, and the gas sensing module; The temperature sensing module, the humidity sensing module, and the gas sensing module are used to convert after receiving the input signal of the phase discrimination and demodulation circuit module, and send the oscillation frequencies of the temperature sensing module, the humidity sensing module, and the gas sensing module to the processing module through the phase discrimination and demodulation circuit module; The processing module is used to calculate the oscillation frequencies of the temperature sensing module, the humidity sensing module, and the gas sensing module received, and obtain a gas warning index; The PC terminal is used to display the gas warning index calculated by the processing module; The storage module is used to store calculation parameters.

2. The system according to claim 1, wherein, Among them, The temperature sensing piezoelectric substrate of the temperature sensing module selects Y-cut quartz crystal material; the humidity sensing piezoelectric substrate of the humidity sensing module sequentially includes a quartz layer, an SiO2 coating, and a PVA film from bottom to top; The gas sensing piezoelectric substrate of the gas sensing module uses ST-X90° quartz and a layer of SU-8 thin film is covered on the quartz surface; and the sensor device of the gas sensing module is locally encapsulated, and PDMS is bonded between the gas input interdigital transducer and the gas output interdigital transducer for gas-sensitive sensing; Both the humidity sensing module and the gas sensing module adopt the Love wave waveguide structure.

3. The system according to claim 1, wherein The phase discrimination and demodulation circuit module includes a signal source (14), a splitter (15), a temperature sensing phase discriminator (16), a humidity sensing phase discriminator (17), a gas sensing phase discriminator (18), a first AD conversion (19), a second AD conversion (20), and a third AD conversion (21); one side of the splitter (15) is connected to the signal source (14), and the other side of the splitter (15) is respectively connected to one side of the temperature sensing module, the humidity sensing module, and the gas sensing module; The other side of the temperature sensing module is connected to the temperature sensing phase discriminator (16), the other side of the humidity sensing module is connected to the humidity sensing phase discriminator (17), and the other side of the gas sensing module is connected to the gas sensing phase discriminator (18); the temperature sensing phase discriminator (16), the humidity sensing phase discriminator (17), and the gas sensing phase discriminator (18) are respectively connected to the first AD conversion (19), the second AD conversion (20), and the third AD conversion (21); The first AD conversion (19), the second AD conversion (20), and the third AD conversion (21) are all connected to the PC terminal (22), and the temperature sensing phase discriminator (16), the humidity sensing phase discriminator (17), and the gas sensing phase discriminator (18) are also all connected to the signal source (14).

4. The system according to claim 1, wherein The temperature sensing module includes a temperature sensing piezoelectric substrate (1), a temperature sensing input interdigital transducer (2), and a temperature sensing output interdigital transducer (3). The temperature sensing input interdigital transducer (2) and the temperature sensing output interdigital transducer (3) are deposited on the temperature sensing piezoelectric substrate (1), and the temperature sensing piezoelectric substrate (1) is a quartz piezoelectric substrate cut along the Y direction.

5. The system according to claim 1, wherein The humidity sensing module includes a humidity sensing piezoelectric substrate (4), a humidity sensing input interdigital transducer (6), a humidity sensing output interdigital output transducer (7), a humidity sensing waveguide layer (5), and a humidity sensitive film (8); wherein, the humidity sensing input interdigital transducer (6) and the humidity sensing output interdigital output transducer (7) are deposited on the humidity sensing piezoelectric substrate (4); the humidity sensing waveguide layer (5) is deposited on the upper layer of the humidity sensing piezoelectric substrate (4), the humidity sensing input interdigital transducer (6), and the humidity sensing output interdigital output transducer (7); the humidity sensitive film (8) is deposited between the humidity sensing input interdigital transducer (6) and the humidity sensing output interdigital output transducer (7); Among them, the humidity sensing piezoelectric substrate (4) is a quartz piezoelectric substrate cut by rotating 42.75° around the Y direction and propagating along the X90° direction, that is, ST-90°. The material of the humidity sensitive film (8) is an organic polymer or an inorganic substance.

6. The system according to claim 1, wherein The gas sensing module includes a gas sensing piezoelectric substrate (9), a gas sensing input interdigital transducer (11), and a gas sensing output interdigital transducer (12); the gas sensing input interdigital transducer (11) and the gas sensing output interdigital transducer (12) are deposited on the gas sensing piezoelectric substrate (9); the gas sensing waveguide layer (10) is deposited on the gas sensing piezoelectric substrate (9), the gas sensing input interdigital transducer (11), and the gas sensing output interdigital transducer (12); a gas sensitive region (13) is bonded between the gas sensing input interdigital transducer (11) and the gas sensing output interdigital transducer (12); Among them, the gas sensing piezoelectric substrate (9) is a quartz piezoelectric substrate cut by rotating 42.75° around the Y direction and propagating along the X90° direction, that is, ST-90°X quartz; the material of the gas sensitive region (13) is polydimethylsiloxane PDMS, and the region shape is any one of a cylinder and a cuboid; if it is a cylinder, the bottom radius of the cylinder is 5 mm and the height is 5 mm.

7. The system according to claim 3, wherein The structure of the gas sensing input interdigital transducer (11) is the same as that of the temperature sensing input interdigital transducer (2); a dummy finger electrode with one end grounded and a width of 1 / 8λx is filled between the comb teeth of the temperature sensing output interdigital transducer (3), where λx is the acoustic wave wavelength along the acoustic wave propagation direction.

8. The system according to claim 3, characterized in that, The structures of the humidity sensing output interdigital output transducer (7) and the gas sensing output interdigital transducer (12) are the same as that of the temperature sensing output interdigital transducer (3).

9. The system according to claim 3, characterized in that The temperature transmission input interdigital transducer (2), the humidity transmission input interdigital transducer (6), and the gas transmission input interdigital transducer (11) all adopt a unidirectional single-phase EWC / SPUDT structure. Reflective electrodes are arranged between the finger pairs of all the interdigital transducers; the finger pair includes two electrodes with a width of 1 / 8λ x , and the distance between the two electrodes is 1 / 8λ x . The width of the reflective electrode is 1 / 4λ x , and the edge distance between the reflective electrode and its corresponding finger pair is 3 / 16λ x . The material of the reflective electrode is aluminum with a thickness of 1%-1.5%λ x , where λ x = v / f, λ x is the acoustic wavelength along the acoustic wave propagation direction, v is the propagation speed of the surface acoustic wave on the piezoelectric substrate, and f is the operating frequency of the humidity sensing module / gas sensing module / temperature sensing module.

10. The system according to claim 3, wherein After the processing module receives the oscillation frequencies of the temperature sensing module, the humidity sensing module, and the gas sensing module, it obtains the calculation parameters stored in the storage module. The calculation parameters include a temperature sensing calculation coefficient, a humidity sensing calculation coefficient, and a gas sensing calculation coefficient; The process of calculating the gas warning index is as follows: Obtain the oscillation frequency of each temperature sensing module and the temperature transfer calculation coefficient periodically transmitted by the temperature sensing module to calculate the temperature index; Obtain the oscillation frequency of each humidity sensing module and the humidity transfer calculation coefficient periodically transmitted by the humidity sensing module to calculate the humidity index; Obtain the oscillation frequency of each gas sensing module and the gas calculation coefficient periodically transmitted by the gas sensing module to calculate the gas index; Calculate the gas warning index based on the temperature index, humidity index and gas index.

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