Wireless sensing system for fluid flow detection based on SAW oscillator

Abstract

The invention relates to a wireless sensing system for fluid flow detection based on an SAW oscillator. The wireless sensing system comprises a resonator, an oscillating 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 oscillating 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 resonant frequency according to temperature changes and outputs the adjusted resonant frequency to the oscillating circuit, the oscillating circuit is connected with the amplifier, the amplifier amplifies the oscillating frequency output by the oscillating circuit and then transmits the amplified oscillating frequency to the frequency mixer, and the signal generator outputs sine wave signals to the frequency mixer. The mixer outputs the difference frequency signal to the comparator. According to the invention, the linear interval of the intermediate frequency signal along with the fluid flow change is improved, the service life of the system test is prolonged, and the null drift stability is improved.

Description

Technical Field

[0001] The 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 wave (SAW) is an elastic wave that propagates along the surface of a solid. Through the interdigital transducer structure, the surface acoustic wave can be excited and detected on the surface of the piezoelectric material. Usually for a high-performance SAW temperature sensor, its core structure is an oscillator with high-frequency stability. The two-port SAW resonator structure consists of an interdigital transducer and two adjacent reflectors. It has a simple design, low loss and high Q value, which is conducive to obtaining ideal frequency stability performance. Compared with other types of sensors, the SAW resonator can directly output characteristic frequency signals without analog-to-digital conversion, which is convenient for information processing. It also has the advantages of being passive, easy to oscillate, easy to integrate, and mass-producible.

[0003] The change of SAW wave velocity induced by the external environment can be reflected as the change of the sensor output frequency signal. To obtain the change of frequency information, a matching signal acquisition system is required. By directly connecting the SAW sensor to the vector network analyzer and analyzing the S parameters of the SAW, it is easy to achieve the detection purpose. 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 corrosive, problems such as affecting the stability and service life of the oscillator may occur. 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 intermediate frequency signals changing with fluid flow, and increase the service life and zero drift stability of system testing.

[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 pipeline, 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 pipeline;

[0009] The thermostat transfers heat to the resonator through the fluid pipeline. 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] Furthermore, the wireless sensor system for fluid flow detection based on the SAW oscillator also includes: a sealed cavity, in which the thermostat and the resonator are arranged.

[0011] Furthermore, the wireless sensor system also includes: 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] Furthermore, the resonator includes: a first short-circuit grating reflector, a second short-circuit grating reflector, and an interdigital transducer arranged between the first short-circuit grating reflector and the second short-circuit grating reflector.

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

[0014] Further, 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;

[0015] 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 is connected to the linear step-down chip after being connected in parallel with the second resistor, 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 buck 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, 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.

[0016] Furthermore, the thermostat comprises: a heating wire, the heating wire is connected to the heating and temperature sensing module, and the heating and temperature sensing module adjusts the temperature of the heating wire by controlling the current and voltage of the heating wire.

[0017] Furthermore, the wireless sensor system for fluid flow detection based on the SAW oscillator also includes: a carrier plate with a hollow middle, on which a first groove, a second groove and a support plate are arranged;

[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 part, and is used to support the oscillation circuit arranged on the front side of the carrier board; 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.

[0019] Furthermore, the distance between the resonator and the thermostat 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 to provide power output to the thermostat;

[0022] 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.

[0023] The advantages of the present invention are that the resonators are respectively placed on the outer wall of the fluid pipeline, the fluid flows inside the fluid pipeline, and the resonators are not in direct contact with the toxic or corrosive environment, which greatly enhances the service life of the resonator; the resonator adopts a thick aluminum structure and a GAN substrate, and a single resonance mode and a high Q value of the resonator are obtained by adjusting the edge spacing between the interdigital transducer and the short-circuit grid reflector, so that the SAW resonator works in a single mode state, which greatly improves the frequency stability of the oscillator; the PCB carrier is provided with corresponding grooves and support plates, which not only play a role in fixing the fluid pipeline, but also reduce the influence of the PCB carrier 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 difficult-to-wire locations, 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 the environment, and ensures data transmission accuracy and reliability; convenient remote monitoring and intelligent management, mobile devices can be used to view flow data anytime and anywhere, and intelligent management can be achieved.

[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 fewer 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 drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. 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 creative work.

[0028] Figure 1 It is a structural schematic diagram 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 It is a schematic structural diagram of a resonator according to an embodiment of the present invention;

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

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

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

[0033] Figure 6 Schematic diagram of the response of the intermediate frequency signal to the change of fluid flow rate according to an embodiment of the present invention.

[0034] Reference numerals:

[0035] 1: Resonator;

[0036] 2: Oscillation circuit;

[0037] 3: Thermostats;

[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: short-circuit grid reflector;

[0050] 1-3: short-circuit grid reflector;

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

[0052] l1: edge spacing between the short-circuit grid reflector 1-2 and the interdigital transducer;

[0053] l2: edge spacing between short-circuit grid reflectors 1-3 and the interdigital transducers;

[0054] 2-1: DC power supply;

[0055] 2-2: Linear buck 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: the fourth capacitor;

[0063] 2-11: The fifth capacitor;

[0064] 2-12: The 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 be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are 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 the 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 a difference frequency signal to the comparator 12.

[0081] The resonator 1 may be disposed on the fluid pipeline 5 by chip adhesive bonding, 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 so that it is maintained at a preset temperature and maintains a constant temperature.

[0085] The thermostat 3 and the heating and temperature sensing module 4 cooperate to finally 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, and the heating and temperature sensing module 4 controls the resistance fluctuation inside the thermostat 3 to continuously change 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 sensor 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 sends 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 short-circuit grating reflector 1-2, a short-circuit grating reflector 1-3 and an interdigital transducer 1-1 arranged between the short-circuit grating reflector 1-2 and the short-circuit grating reflector 1-3.

[0089] In one embodiment, the short-circuit grid reflector 1-2, the short-circuit 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, the thickness of titanium is 5nm, and λ is the wavelength of the sound wave, but the present invention is not limited thereto.

[0091] The distances between the short-circuit grid reflector 1-2 and the short-circuit grid 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 short-circuit grid reflector 1-2 and the interdigital transducer 1-1 is 1 / 4λ, and the edge spacing l2 between the short-circuit grid reflector 1-3 and the interdigital transducer 1-1 is 1 / 4λ.

[0092] In one embodiment, the IDT 1-1 may adopt a bidirectional transducer structure with a 1 / 4λ electrode width. The number of interdigital pairs in the short-circuit grating reflector 1-2 and the short-circuit grating reflector 1-3 may 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 manufactured on a silicon-based GaN substrate 1-4, and a single resonance mode and a high Q value can be obtained by adjusting the edge spacing l1 and the edge spacing l2, so that the operating frequency of the resonator 1 is more stable.

[0093] In one embodiment, if 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 buck 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 buck 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 and then connected to the linear buck chip 2-2, and the other end is connected to one end of the third inductor 2-18 and grounded; one end of the fourth resistor 2-5 is connected to the linear buck chip 2-2, and the other end is 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 slidably connected to the fourth resistor 2-5; 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, and the other end of the second inductor 2-16 is connected to one end of the fifth resistor 2-15, and the other end of the fifth resistor 2-15 is slidably connected to the third resistor 2-6. Among them, 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 voltages of the base and collector 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, if Figure 4 As shown, the thermostat 3 includes: a heating wire 3-1, which is connected to a heating and temperature sensing module 4, and 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, and 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 and constantly changing the output current and voltage of the heating module, thereby adjusting the temperature of the heating wire 3-1, so that the thermostat 3 is maintained at a preset temperature.

[0098] In one embodiment, Figure 4The working process of the thermostat 3 shown is as follows: after the heating wire 3-1 is heated, the resistance value will change until there is a slight fluctuation, and the temperature sensing module of the heating and temperature sensing module 4 controls the temperature of the heating wire 3-1 by controlling the current and voltage in the heating wire 3-1, and finally stabilizes the temperature of the thermostat 3 at the set value, and the temperature error is required to be around ±0.1°C. After the temperature of the thermostat 3 is stabilized, the heat is transferred to the SAW resonator 1 through the heating fluid pipeline 5.

[0099] In one embodiment, the size of the thermostat 3 may be 2×2 mm, the resistance of the heating wire 3 - 1 is 70-90Ω at room temperature, and the resistance after heating and stabilization is (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 center distance between the SAW resonator 1 and the thermostat 3 is 1-3 mm.

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

[0102] In one embodiment, if Figure 1 As shown, the wireless sensor system for fluid flow detection based on the SAW oscillator of the present invention also includes: a carrier plate 6 with a hollow middle, such as 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 pipeline 5 can be accommodated in the first groove 6 - 1 and the second groove 6 - 2 at the same time.

[0104] The support plate 6-3 is arranged in the hollow portion 6-4, and is used to support the oscillation circuit 2 (not shown in the figure) arranged on the front of the carrier. In one embodiment, the height of the support plate 6-3 is lower than the bottom of the first groove 6-1 and the second groove 6-2, so that the support plate 6-3 does not contact the fluid pipeline 5, which can prevent the carrier 6 from becoming a heat load of the thermostat 3, and is used to increase the temperature difference of the system test.

[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 one embodiment, the carrier board 6 may be a PCB carrier board. The structural design of the carrier board 6 can not only fix the fluid pipeline 5, the oscillation circuit 2, the thermostat 3 and the heating and temperature sensing module 4, but also prevent them from becoming a heat load.

[0109] Figure 6 FIG. 1 is a schematic diagram showing the response of the intermediate frequency signal to the change of the fluid flow rate according to an embodiment of the present invention. Figure 6 It can be observed that the intermediate frequency signal changes with the fluid flow rate. In order to avoid using a filter later, the output frequency of the signal generator 10 needs to be adjusted so that the intermediate frequency starts at 1Mhz-50Mhz. When different fluid flows flow through the fluid pipeline 5, the intermediate frequency after mixing will also change accordingly.

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

[0111] The oscillation circuit is wirelessly connected to the mixer, which has the following advantages: convenient installation, especially in difficult-to-wire locations, 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 the environment, and ensures data transmission accuracy and reliability; convenient remote monitoring and intelligent management, mobile devices can be used to view flow data anytime and anywhere, and intelligent management can be achieved.

[0112] 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 fewer components, has a simple circuit, low power consumption, is stable, and is portable, and can easily achieve the purpose of fluid flow detection.

[0113] In the present specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction. The above is only an embodiment of the embodiment of the present specification and is not intended to limit the embodiment of the present specification. For those skilled in the art, the embodiment of the present specification may have various changes and variations. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the embodiment of the present specification shall be included in the scope of the claims of the embodiment of the present specification.

Claims

1. A wireless sensing system for fluid flow detection based on a SAW oscillator, characterized in that: include: 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; The thermostat transfers heat to the resonator through the fluid pipeline. 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.

2. The wireless sensing system for fluid flow detection based on a SAW oscillator according to claim 1 is characterized in that: Also includes: A sealed cavity, wherein the temperature stabilizer and the resonator are arranged in the sealed cavity.

3. 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.

4. 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 short-circuit grating reflector, a second short-circuit grating reflector, and an interdigital transducer arranged between the first short-circuit grating reflector and the second short-circuit grating reflector.

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

6. The wireless sensing system for fluid flow detection based on a SAW oscillator according to claim 3 is 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 is connected to the linear step-down chip after being connected in parallel with the second resistor, 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 buck 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, 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.

7. The wireless sensing system for fluid flow detection based on a SAW oscillator according to claim 2, characterized in that: The thermostat comprises a heating wire, wherein the heating wire is connected to the heating and temperature sensing module, and the heating and temperature sensing module adjusts the temperature of the heating wire by controlling the current and voltage of the heating wire.

8. The wireless sensing system for fluid flow detection based on a SAW oscillator according to claim 1, characterized in that: Also includes: A carrier plate with a hollow middle, wherein the carrier plate 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 plate, and is used to support the oscillation circuit arranged on the front side of the carrier plate; 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.

9. 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.

10. 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 comprises: 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.

Images