A wireless sensing system for fluid flow detection based on SAW oscillators

Abstract

The application relates to a wireless sensing system for fluid flow detection based on a SAW oscillator, which comprises a resonator, an oscillation circuit, a heating and temperature sensing module, a temperature stabilizer, a fluid pipeline, a frequency mixer, an amplifier, a signal generator and a comparator; the oscillation circuit, the resonator, the temperature stabilizer and the heating and temperature sensing module are sequentially arranged on the fluid pipeline; the temperature stabilizer transmits heat to the resonator through the fluid pipeline; the resonator adjusts a resonant frequency according to temperature change and outputs the adjusted resonant frequency to the oscillation circuit; the oscillation circuit is connected to the amplifier; the amplifier amplifies the oscillation frequency output by the oscillation circuit and then transmits the amplified oscillation frequency to the frequency mixer; the signal generator outputs a sine wave signal to the frequency mixer; and the frequency mixer outputs a difference frequency signal to the comparator. By using the application, the linear interval of the intermediate frequency signal changing with the fluid flow is improved, and the service life and zero drift stability of system test are increased.

Description

Technical Field

[0001] The present invention relates to a sensing technology based on an oscillator, and in particular to a wireless sensing system for fluid flow detection based on a SAW oscillator. Background Art

[0002] Surface acoustic waves (SAWs) are elastic waves that propagate along solid surfaces. Through an interdigital transducer structure, SAWs can be excited and detected on the surface of piezoelectric materials. High-performance SAW temperature sensors typically rely on a high-frequency, stable oscillator as their core structure. A two-port SAW resonator, consisting of an interdigital transducer and two adjacent reflectors, offers a simple design with low loss and a high Q factor, facilitating ideal frequency stability. Compared to other sensor types, SAW resonators can directly output characteristic frequency signals, eliminating the need for analog-to-digital conversion and facilitating information processing. They also offer the advantages of being passive, easy to oscillate, easy to integrate, and amenable to mass production.

[0003] The changes in SAW wave velocity induced by the external environment can be reflected as changes in the sensor output frequency signal. Obtaining the changes in frequency information requires a matching signal acquisition system. By directly connecting the SAW sensor to a vector network analyzer and analyzing the S parameters of the SAW, the detection purpose can be easily achieved. However, due to the high power consumption and non-portability of the instrument, this method is limited to laboratory use. In addition, some SAW resonators have a wider resonant cavity, which makes the resonator frequency response have multi-mode characteristics, and the loss between each mode is close, which will result in multiple frequency points meeting the oscillation conditions, thereby affecting the frequency stability of the oscillator. In addition, most resonators use aluminum electrodes or electrode structures composed of multiple metals. These electrodes and the core structure of the resonator are in direct contact with the environment to be tested. If the environment to be tested is toxic or highly corrosive, problems such as affecting the stability and service life of the oscillator may arise. Summary of the Invention

[0004] In response to the problems in the prior art, the present invention relates to a wireless sensing system for fluid flow detection based on a SAW oscillator, which can improve the linear range of the intermediate frequency signal as the fluid flow changes, increase the service life and zero drift stability of the system test.

[0005] In order to solve the above technical problems, the present invention relates to the following technical solutions:

[0006] In a first aspect, the present invention relates to a wireless sensing system for fluid flow detection based on a SAW oscillator, the wireless sensing system for fluid flow detection based on a SAW oscillator comprising:

[0007] a resonator, an oscillation circuit, a heating and temperature sensing module, a thermostat, a fluid pipe, a mixer, an amplifier, a signal generator and a comparator;

[0008] The oscillation circuit, resonator, thermostat and heating and temperature sensing module are sequentially arranged on the fluid pipe;

[0009] The thermostat transmits heat to the resonator through the fluid pipe, the resonator adjusts the resonant frequency according to the temperature change and outputs the adjusted resonant frequency to the oscillation circuit, the oscillation circuit is connected to the amplifier, the amplifier amplifies the oscillation frequency output by the oscillation circuit and transmits it to the mixer, the signal generator outputs a sine wave signal to the mixer, and the mixer outputs a difference frequency signal to the comparator.

[0010] Further, the wireless sensing system for fluid flow detection based on the SAW resonator further comprises a sealed cavity, and the thermostat and resonator are arranged in the sealed cavity.

[0011] Further, the wireless sensing system further comprises a transmitting antenna and a receiving antenna, the transmitting antenna is connected to the oscillation circuit, the receiving antenna is connected to the amplifier, and the transmitting antenna sends the oscillation frequency to the amplifier through the receiving antenna.

[0012] Further, the resonator comprises a first short-circuit grid reflector, a second short-circuit grid reflector and an interdigital transducer arranged between the first short-circuit grid reflector and the second short-circuit grid reflector.

[0013] Further, the distance between the first short-circuit grid reflector and the second short-circuit grid reflector and the interdigital transducer is 1 / 4λ, and λ is the wavelength of the acoustic wave.

[0014] Further, the oscillation circuit comprises a first inductor, a second inductor, a third inductor, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a first capacitor, a second capacitor, a third capacitor, a fourth capacitor, a fifth capacitor, a sixth capacitor, a direct current power supply, a linear step-down chip and a high-frequency triode.

[0015] The positive pole of the direct current power supply, one end of the first capacitor, one end of the second capacitor, one end of the fourth capacitor, one end of the fifth capacitor, one end of the first resistor and one end of the third resistor are connected to the linear voltage reduction chip; the negative pole of the direct current power supply, the other end of the first capacitor, the other end of the second capacitor, the other end of the fourth capacitor, the other end of the fifth capacitor, the other end of the first resistor and the other end of the third resistor are connected to one end of the third inductor and grounded; one end of the third capacitor connected in parallel with the second resistor is connected to the linear voltage reduction chip, and the other end is connected to one end of the third inductor and grounded; one end of the fourth resistor is connected to the linear voltage reduction chip, and the other end is grounded; one end of the first inductor, one end of the resonator and the collector of the high-frequency triode are connected to one end of the sixth capacitor, and the other end of the sixth capacitor is connected to the transmitting antenna; the other end of the first inductor is connected to the fourth resistor in a sliding manner; the emitter of the high-frequency triode is connected to the other end of the third inductor; one end of the second inductor is connected to the base of the high-frequency triode and the other end of the resonator, and the other end of the second inductor is connected to one end of the fifth resistor, and the other end of the fifth resistor is connected to the third resistor in a sliding manner; the third resistor and the fourth resistor are sliding resistors.

[0016] Further, the temperature stabilizer comprises a heating wire connected with the heating and temperature sensing module, and the heating and temperature sensing module adjusts the temperature of the heating wire by controlling the current voltage of the heating wire.

[0017] Further, the wireless sensing system based on the SAW oscillator fluid flow detection further comprises an intermediate hollow carrier plate, wherein the carrier plate is provided with a first groove, a second groove and a support plate;

[0018] The first groove and the second groove are coaxially arranged, and the fluid pipeline is accommodated in the first groove and the second groove; the support plate is arranged in the hollow portion and used for supporting the oscillation circuit arranged on the front surface of the carrier plate; and the height of the support plate is lower than the groove bottom of the first groove and the second groove, so that the support plate is not in contact with the fluid pipeline.

[0019] Further, the distance between the resonator and the temperature stabilizer is 1 mm to 3 mm.

[0020] Further, the heating and temperature sensing module comprises a heating module and a temperature sensing module.

[0021] The heating module is used for providing power output to the temperature stabilizer.

[0022] The temperature sensing module is used for adjusting the output power of the heating module according to the resistance fluctuation of the temperature stabilizer so that the output power is kept at a preset temperature.

[0023] The advantages of the present invention are that the resonators are respectively placed on the outer wall of the fluid pipeline, and the fluid flows through the fluid pipeline. The resonators are not in direct contact with the toxic or corrosive environment, which greatly enhances the service life of the resonators; the resonators adopt a thick aluminum structure and a GAN substrate, and a single resonant mode and a high Q value of the resonator are obtained by adjusting the distance between the interdigital transducer and the edge of the short-circuit grid reflector, so that the SAW resonator operates in a single mode state, greatly improving the frequency stability of the oscillator; the PCB carrier board is provided with corresponding grooves and support plates, which not only fix the fluid pipeline, but also reduce the influence of the PCB carrier board on the thermal field source, thereby improving the fluid flow monitoring performance.

[0024] The resonator uses a double-layer electrode of aluminum / titanium alloy and has a single resonance mode and a high-Q resonator.

[0025] The oscillation circuit is wirelessly connected to the mixer, which has the following advantages: convenient installation, especially in locations where wiring is difficult, such as small spaces and hazardous areas; cost savings, no need to lay cables or other material expenses; flexible installation location, the flow meter position can be adjusted and moved at any time as needed; reliable data transmission, the wireless flow meter data transmission is very reliable, can penetrate obstacles such as walls, is not affected by environmental interference, and ensures data transmission accuracy and reliability; convenient remote monitoring and intelligent management, allowing mobile devices to view flow data anytime and anywhere, realizing intelligent management.

[0026] In addition, the wireless sensor system for fluid flow detection based on the SAW oscillator of the present invention has a small structure, is lightweight, uses few components, has a simple circuit, low power consumption, is stable, and is portable, and can easily achieve the purpose of fluid flow detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0028] Figure 1 Schematic diagram of the structure of a wireless sensing system for fluid flow detection based on a SAW oscillator according to an embodiment of the present invention;

[0029] Figure 2 Schematic diagram of the structure of a resonator according to an embodiment of the present invention;

[0030] Figure 3 Schematic diagram of the structure of an oscillator according to an embodiment of the present invention;

[0031] Figure 4 This is a structural diagram of a thermostat 3 according to an embodiment of the present invention;

[0032] Figure 5 This is a schematic structural diagram of a carrier board 6 according to an embodiment of the present invention;

[0033] Figure 6 FIG. 1 is a schematic diagram showing the response of an intermediate frequency signal to changes in fluid flow rate according to an embodiment of the present invention.

[0034] Reference numerals:

[0035] 1: resonator;

[0036] 2: Oscillation circuit;

[0037] 3: Thermostat;

[0038] 4: Heating and temperature sensing module;

[0039] 5: Fluid pipeline;

[0040] 6: carrier board;

[0041] 7: Sealed cavity;

[0042] 8: Receiving antenna;

[0043] 9: amplifier;

[0044] 10: Signal generator;

[0045] 11: mixer;

[0046] 12: Comparator;

[0047] 13: Transmitting antenna;

[0048] 1-1: interdigital transducer;

[0049] 1-2: shorting grid reflector;

[0050] 1-3: shorting grid reflector;

[0051] 1-4: GaN-on-silicon substrate;

[0052] l1: the edge distance between the shorting grid reflector 1-2 and the interdigital transducer;

[0053] l2: edge spacing between shorting grid reflectors 1-3 and the IDT;

[0054] 2-1: DC power supply;

[0055] 2-2: Linear step-down chip;

[0056] 2-3: high frequency transistor;

[0057] 2-5: the fourth resistor;

[0058] 2-6: the third resistor;

[0059] 2-7: first capacitor;

[0060] 2-8: Second capacitor;

[0061] 2-9: The third capacitor;

[0062] 2-10: fourth capacitor;

[0063] 2-11: fifth capacitor;

[0064] 2-12: Sixth capacitor;

[0065] 2-13: first resistor;

[0066] 2-14: second resistor;

[0067] 2-15: fifth resistor;

[0068] 2-16: Second inductor;

[0069] 2-17: First inductor;

[0070] 2-18: The third inductor;

[0071] 3-1: Heating wire;

[0072] 6-1: groove;

[0073] 6-2: groove;

[0074] 6-3: support plate;

[0075] 6-4: Hollow part. DETAILED DESCRIPTION

[0076] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0077] The present invention relates to a wireless sensing system for fluid flow detection based on a SAW oscillator, such as Figure 1 As shown, the wireless sensing system for fluid flow detection based on a SAW oscillator includes: a resonator 1, an oscillation circuit 2, a thermostat 3, a heating and temperature sensing module 4, a fluid pipeline 5, a mixer 11, an amplifier 9, a signal generator 10 and a comparator 12.

[0078] The resonator 1 , the oscillation circuit 2 , the thermostat 3 and the heating and temperature sensing module 4 are sequentially arranged on the fluid pipeline 5 .

[0079] In one embodiment, the fluid pipeline 5 is a fluid corrosion resistant pipeline.

[0080] The thermostat 3 transfers heat to the resonator 1 through the fluid pipe 5. The resonator 1 adjusts the resonant frequency according to the temperature change and outputs the adjusted resonant frequency to the oscillation circuit 2. The oscillation circuit 2 is connected to the amplifier 9. The amplifier 9 amplifies the oscillation frequency output by the oscillation circuit and transmits it to the mixer 11. The signal generator 10 outputs a sine wave signal to the mixer 11, and the mixer 11 outputs the difference frequency signal to the comparator 12.

[0081] The resonator 1 may be disposed on the fluid conduit 5 by chip gluing, but the present invention is not limited thereto.

[0082] It should be noted that the thermostat 3 is fixed on the fluid pipeline 5 , but the present invention is not limited thereto.

[0083] The mixer 11 can select a suitable mixer frequency band so that it can be directly connected to the comparator 12 without subsequent filtering processing.

[0084] In one embodiment, the heating and temperature sensing module 4 includes a heating module and a temperature sensing module. The heating module provides power output to the thermostat 3. The temperature sensing module adjusts the output power of the heating module according to the resistance fluctuation of the thermostat 3 to maintain the preset temperature and maintain a constant temperature.

[0085] The thermostat 3 and the heating and temperature sensing module 4 work together to stabilize the thermostat 3 at a preset temperature and maintain a constant temperature. Specifically, the thermostat 3 is connected to the heating and temperature sensing module 4, which controls the fluctuation of the resistance value within the thermostat 3, continuously changing the current and voltage output by the heating module, thereby adjusting the temperature of the thermostat 3.

[0086] In one embodiment, the oscillating circuit 2 and the amplifier 9 can be connected wirelessly. Figure 1 As shown, the wireless sensing system includes a transmitting antenna 13 and a receiving antenna 8. The transmitting antenna 13 is connected to the oscillation circuit 2, and the receiving antenna 8 is connected to the amplifier 9. The transmitting antenna 13 transmits the oscillation frequency output by the oscillation circuit 2 to the amplifier 9 through the receiving antenna 8.

[0087] In order to ensure that the heat is not disturbed by the outside world, in one embodiment, a sealed cavity 7 may be provided outside the thermostat 3 .

[0088] In one embodiment, the resonator 1 is a SAW resonator, such as Figure 2As shown, the resonator 1 includes a shorting grating reflector 1-2, a shorting grating reflector 1-3, and an interdigital transducer 1-1 disposed between the shorting grating reflector 1-2 and the shorting grating reflector 1-3.

[0089] In one embodiment, the shorting grid reflector 1 - 2 , the shorting grid reflector 1 - 3 and the interdigital transducer 1 - 1 all adopt a double-layer electrode structure of thick aluminum and thin titanium, but the present invention is not limited thereto.

[0090] In one embodiment, the thickness of aluminum is 0.05λ, and that of titanium is 5nm, where λ is the wavelength of the sound wave, but the present invention is not limited thereto.

[0091] The distances between the shorting grating reflector 1-2 and the shorting grating reflector 1-3 and the interdigital transducer 1-1 can be set according to specific circumstances. In one embodiment, the edge spacing l1 between the shorting grating reflector 1-2 and the interdigital transducer 1-1 is 1 / 4λ, and the edge spacing l2 between the shorting grating reflector 1-3 and the interdigital transducer 1-1 is 1 / 4λ.

[0092] In one embodiment, the IDT 1-1 can adopt a bidirectional transducer structure with a 1 / 4λ electrode width. The number of interdigital pairs in the shorting grid reflector 1-2 and the shorting grid reflector 1-3 can be set to 20 pairs respectively, and the number of interdigital pairs in the IDT 1-1 is 250 pairs. Figure 2 As shown, the resonator 1 can be fabricated on a silicon-based GaN substrate 1-4. By adjusting the edge spacing l1 and the edge spacing l2, a single resonant mode and a high Q value can be obtained, making the operating frequency of the resonator 1 more stable.

[0093] In one embodiment, Figure 3 As shown, the oscillator includes a resonator 1 and an oscillation circuit 2. The oscillation circuit 2 includes: a first inductor 2-17, a second inductor 2-16, a third inductor 2-18, a first resistor 2-13, a second resistor 2-14, a third resistor 2-6, a fourth resistor 2-5, a fifth resistor 2-15, a first capacitor 2-7, a second capacitor 2-8, a third capacitor 2-9, a fourth capacitor 2-10, a fifth capacitor 2-11, a sixth capacitor 2-12, a DC power supply 2-1, a linear step-down chip 2-2, and a high-frequency transistor 2-3;

[0094] The positive electrode of the DC power supply 2-1, one end of the first capacitor 2-7, one end of the second capacitor 2-8, one end of the fourth capacitor 2-10, one end of the fifth capacitor 2-11, one end of the first resistor 2-13, and one end of the third resistor 2-6 are respectively connected to the linear step-down chip 2-2. The negative electrode of the DC power supply 2-1, the other end of the first capacitor 2-7, the other end of the second capacitor 2-8, the other end of the fourth capacitor 2-10, the other end of the fifth capacitor 2-11, the other end of the first resistor 2-13, and the other end of the third resistor 2-6 are connected to one end of the third inductor 2-18 and grounded. The third capacitor 2-9 and the second resistor 2-14 are connected in parallel, with one end connected to the linear step-down chip 2-2 and the other end connected to one end of the third inductor 2-18 and grounded. The fourth resistor 2-5 has one end connected to the linear step-down chip 2-2 and the other end grounded. One end of the first inductor 2-17, one end of the resonator 1, and the collector of the high-frequency transistor 2-3 are connected to one end of the sixth capacitor 2-12, and the other end of the sixth capacitor 2-12 is connected to the transmitting antenna 13. The other end of the first inductor 2-17 is connected to the fourth resistor 2-5 in a sliding manner. The emitter of the high-frequency transistor 2-3 is connected to the other end of the third inductor 2-18. One end of the second inductor 2-16 is connected to the base of the high-frequency transistor 2-3 and the other end of the resonator 1. The other end of the second inductor 2-16 is connected to one end of the fifth resistor 2-15. The other end of the fifth resistor 2-15 is connected to the third resistor 2-6 in a sliding manner. The third resistor 2-6 and the fourth resistor 2-5 are sliding resistors.

[0095] In one embodiment, the high-frequency transistor 2 - 3 may be a high-frequency transistor KT9041.

[0096] Figure 3 In the oscillator circuit 2 shown, the base and collector voltages of the high-frequency transistor 2-3 are changed by adjusting the resistance values ​​of the third resistor 2-6 and the fourth resistor 2-5, thereby changing the operating frequency state of the oscillator.

[0097] In one embodiment, Figure 4 As shown, the thermostat 3 includes a heating wire 3-1, which is connected to a heating and temperature sensing module 4. The heating and temperature sensing module 4 adjusts the temperature of the heating wire 3-1 by controlling the resistance fluctuation of the heating wire 3-1. The heating wire 3-1 is connected to the heating and temperature sensing module 4. The heating and temperature sensing module 4 controls the resistance fluctuation of the heating wire 3-1 by continuously changing the output current and voltage of the heating module, thereby adjusting the temperature of the heating wire 3-1 and maintaining the thermostat 3 at a preset temperature.

[0098] In one embodiment, Figure 4The illustrated thermostat 3 operates as follows: After heating, the resistance of heating wire 3-1 changes until there is a slight fluctuation. The temperature sensing module of heating and temperature sensing module 4 controls the temperature of heating wire 3-1 by controlling the current and voltage in heating wire 3-1. Finally, the temperature of thermostat 3 is stabilized at the set value, with a temperature error of approximately ±0.1°C. Once the temperature of thermostat 3 stabilizes, heat is transferred to SAW resonator 1 via heating fluid pipe 5.

[0099] In one embodiment, the size of the thermostat 3 may be 2×2 mm, the resistance of the heating wire 3 - 1 may be 70-90 Ω at room temperature, and the resistance after heating and stabilization may be (110±0.05) Ω.

[0100] In one embodiment, the fluid conduit 5 has an outer diameter of 0.5 mm, an inner diameter of 0.2 mm, and a length greater than 50 mm. The SAW resonator 1 is 1-3 mm away from the center of the thermostat 3 .

[0101] In one embodiment, the heating wire 3 - 1 is a nickel-chromium heating wire with variable resistance.

[0102] In one embodiment, Figure 1 As shown, the wireless sensor system for fluid flow detection based on the SAW oscillator of the present invention further includes: a carrier plate 6 with a hollow middle, as shown in FIG. Figure 5 As shown, the carrier plate 6 is provided with a first groove 6 - 1 , a second groove 6 - 2 and a support plate 6 - 3 .

[0103] The first groove 6 - 1 and the second groove 6 - 2 are coaxially arranged, so that the fluid pipe 5 can be accommodated in the first groove 6 - 1 and the second groove 6 - 2 at the same time.

[0104] A support plate 6-3 is positioned within the hollow portion 6-4 to support the oscillator circuit 2 (not shown) mounted on the front of the carrier board. In one embodiment, the support plate 6-3 is lower than the bottom of the first and second grooves 6-1, 6-2, eliminating contact between the support plate 6-3 and the fluid conduit 5. This prevents the carrier board 6 from becoming a heat load for the thermostat 3, thereby increasing the temperature differential during system testing.

[0105] In one embodiment, the depth and width of the first groove 6 - 1 and the second groove 6 - 2 are greater than the outer diameter of the fluid pipe 5 .

[0106] In one embodiment, the length of the groove is about 3 mm.

[0107] In one embodiment, the length of the middle hollow portion is greater than 20 mm and the width is about 17 mm.

[0108] In an embodiment, the carrier plate 6 can be a PCB carrier plate. Through the structural design of the carrier plate 6, not only the fluid pipe 5, the oscillation circuit 2, the temperature stabilizer 3, and the heating and temperature sensing module 4 can be fixed, but also they can be avoided to become a thermal load.

[0109] Figure 6 The response diagram of the intermediate frequency signal changing with the fluid flow for an embodiment of the present application is shown in the figure. By adjusting the output frequency of the signal generator 10, the starting point of the intermediate frequency can be set at 1Mhz-50Mhz, so that the change of the intermediate frequency with the fluid flow can be observed. When different fluid flows through the fluid pipe 5, the mixed intermediate frequency will also change. Figure 6 The response diagram of the intermediate frequency signal changing with the fluid flow for an embodiment of the present application is shown in the figure. By adjusting the output frequency of the signal generator 10, the starting point of the intermediate frequency can be set at 1Mhz-50Mhz, so that the change of the intermediate frequency with the fluid flow can be observed. When different fluid flows through the fluid pipe 5, the mixed intermediate frequency will also change.

[0110] The resonator adopts a double-layer electrode of aluminum / titanium alloy, and has a single resonance mode and a high-Q resonator.

[0111] The oscillation circuit and the mixer are wirelessly connected, which has the following advantages: convenient installation, especially in difficult wiring locations such as narrow spaces and dangerous areas; cost saving, without the need for cable or other material expenses; flexible installation location, the flowmeter position can be adjusted and moved at any time according to needs; reliable data transmission, the wireless flowmeter data transmission is very reliable, can penetrate through walls and other obstacles, is not affected by the environment, and ensures the accuracy and reliability of data transmission; convenient remote monitoring and intelligent management, the mobile device can view the flow data at any time and anywhere, and intelligent management is realized.

[0112] In addition, the wireless sensing system for fluid flow detection based on the SAW oscillator has the advantages of small structure, light weight, few components, simple circuit, low power consumption, stability, portability, and easy realization of the fluid flow detection purpose.

[0113] In the specification of the present application, the illustrative description of the above-mentioned terms does not necessarily refer to the same embodiment or example. In addition, those skilled in the art can combine and combine different embodiments or examples described in the specification and the features of different embodiments or examples without contradiction. The above is only an embodiment of the embodiment of the present application and is not used to limit the embodiment of the present application. Those skilled in the art can make various changes and changes to the embodiment of the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the embodiment of the present application shall be included in the scope of the claims of the embodiment of the present application.

Claims

1. A wireless sensing system for fluid flow detection based on a SAW oscillator, characterized in that: include: A sealed cavity, a carrier plate with a hollow center, a resonator, an oscillation circuit, a heating and temperature sensing module, a thermostat, a fluid pipeline, a mixer, an amplifier, a signal generator, and a comparator; The oscillation circuit, resonator, thermostat and heating and temperature sensing module are sequentially arranged on the fluid pipeline, and the thermostat and resonator are arranged in the closed cavity; The thermostat and the heating and temperature sensing module cooperate to stabilize the thermostat at a preset temperature; the thermostat transfers heat to the resonator through the fluid pipe, the resonator adjusts the resonant frequency according to temperature changes and outputs the adjusted resonant frequency to the oscillation circuit, the oscillation circuit is connected to the amplifier, the amplifier amplifies the oscillation frequency output by the oscillation circuit and transmits it to the mixer, the signal generator outputs a sine wave signal to the mixer, and the mixer outputs a difference frequency signal to the comparator; The carrier is provided with a first groove, a second groove and a support plate; the first groove and the second groove are coaxially arranged, and the fluid pipeline is accommodated in the first groove and the second groove; the support plate is arranged in the hollow part of the carrier, and is used to support the oscillation circuit arranged on the front side of the carrier; and the height of the support plate is lower than the bottom of the first groove and the second groove, so that the support plate does not contact the fluid pipeline.

2. The wireless sensing system for fluid flow detection based on a SAW oscillator according to claim 1, characterized in that: Also includes: Transmitting antenna and receiving antenna; The transmitting antenna is connected to the oscillation circuit, the receiving antenna is connected to the amplifier, and the transmitting antenna sends the oscillation frequency to the amplifier via the receiving antenna.

3. The wireless sensing system for fluid flow detection based on a SAW oscillator according to claim 1, characterized in that: The resonator includes a first shorting grating reflector, a second shorting grating reflector, and an interdigital transducer arranged between the first shorting grating reflector and the second shorting grating reflector.

4. The wireless sensing system for fluid flow detection based on a SAW oscillator according to claim 3, characterized in that: The distance between the first shorting grating reflector and the second shorting grating reflector and the interdigital transducer is 1 / 4λ, where λ is the wavelength of the acoustic wave.

5. The wireless sensing system for fluid flow detection based on a SAW oscillator according to claim 2, characterized in that: The oscillation circuit includes: a first inductor, a second inductor, a third inductor, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a first capacitor, a second capacitor, a third capacitor, a fourth capacitor, a fifth capacitor, a sixth capacitor, a DC power supply, a linear step-down chip and a high-frequency transistor; The positive electrode of the DC power supply, one end of the first capacitor, one end of the second capacitor, one end of the fourth capacitor, one end of the fifth capacitor, one end of the first resistor and one end of the third resistor are respectively connected to the linear step-down chip; the negative electrode of the DC power supply, the other end of the first capacitor, the other end of the second capacitor, the other end of the fourth capacitor, the other end of the fifth capacitor, the other end of the first resistor and the other end of the third resistor are connected to one end of the third inductor and grounded; the third capacitor and the second resistor are connected in parallel with each other at one end connected to the linear step-down chip, and the other end is connected to one end of the third inductor and grounded; One end of the fourth resistor is connected to the linear step-down chip, and the other end is grounded; one end of the first inductor, one end of the resonator and the collector of the high-frequency transistor are connected to one end of the sixth capacitor, and the other end of the sixth capacitor is connected to the transmitting antenna; the other end of the first inductor is slidingly connected to the fourth resistor; the emitter of the high-frequency transistor is connected to the other end of the third inductor; one end of the second inductor is connected to the base of the high-frequency transistor and the other end of the resonator, and the other end of the second inductor is connected to one end of the fifth resistor, and the other end of the fifth resistor is slidingly connected to the third resistor; the third resistor and the fourth resistor are sliding resistors.

6. The wireless sensing system for fluid flow detection based on a SAW oscillator according to claim 1, characterized in that: The thermostat includes a heating wire connected to the heating and temperature sensing module. The heating and temperature sensing module adjusts the temperature of the heating wire by controlling the current and voltage of the heating wire.

7. The wireless sensing system for fluid flow detection based on a SAW oscillator according to claim 1, characterized in that: The distance between the resonator and the thermostat is 1 mm to 3 mm.

8. The wireless sensing system for fluid flow detection based on a SAW oscillator according to claim 1, characterized in that: The heating and temperature sensing module includes: a heating module and a temperature sensing module; The heating module is used to provide power output to the thermostat; The temperature sensing module is used to adjust the output power of the heating module according to the resistance fluctuation of the thermostat so that it is maintained at a preset temperature.

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