CN112729427A - Thermal differential pressure flow sensor - Google Patents

Abstract

The invention provides a thermal differential pressure flow sensor, which comprises a shell, a sensing integrated assembly and a laminar flow element, wherein the shell is provided with a first end and a second end; the shell is internally provided with an air guide passage, two ends of the air guide passage are respectively and correspondingly communicated with an air inlet passage and an air outlet passage, and the other end of the air inlet passage is communicated with a pipeline for air transmission so as to lead the air flow circulating in the pipeline into the air guide passage; the other end of the gas outlet channel is communicated with the pipeline so as to discharge the gas in the gas guide channel to the pipeline; the laminar flow element is arranged in the pipeline and used for changing the flow direction of part of gas on the gas flow path of the pipeline and guiding the part of gas into the gas inlet channel; the sensing integrated assembly is arranged in the air guide channel and comprises two thermistors which are sequentially arranged along the circulation path of the air guide channel and used for detecting the temperature of the air, and the sensing integrated assembly converts the temperature difference between the two thermistors into air pressure information to be output. The thermal differential pressure flow sensor leads in and feeds back gas from the pipeline through the gas guide channel, the gas inlet channel and the gas outlet channel, so that the sensing integrated assembly detects the gas pressure of the pipeline.

Description

Thermal differential pressure flow sensor

Technical Field

The invention belongs to the technical field of sensing measurement, and particularly relates to a thermal differential pressure flow sensor.

Background

With the rapid development of sensing technology, accurate detection of pipeline airflow is an index of gas transmission technology. Currently, a differential pressure sensor is mostly used for detecting the airflow flow in a pipeline, so as to realize the detection of the airflow flow in the pipeline. However, the conventional differential pressure sensor mainly collects pressure data at both ends of the differential pressure sensor through two pressure chips, and processes the collected data through a processing chip to convert and output gas flow rate or pressure information. However, since the measurement range of the pressure chip is usually high, it is impossible to measure a change in a minute differential pressure. In addition, the differential pressure sensor usually has a large fluctuation degree, and the fluctuation interference is larger than the sensor signal when measuring the small differential pressure, so that the common differential pressure sensor cannot be applied to the application scene of the small differential pressure.

However, in some scenarios, a small measurement of the duct air flow differential is required to achieve accurate control. For example, in the fields of gas delivery for patients, precision manufacturing, chemical experiments and the like, the air flow pressure difference needs to be accurately detected so as to realize accurate control.

Therefore, there is a need for a flow sensor capable of accurately measuring the differential pressure in the pipeline, so as to accurately measure the minute differential pressure.

Disclosure of Invention

The invention aims to provide a thermal differential pressure flow sensor suitable for accurately measuring airflow differential pressure.

The invention is suitable for the purpose of the invention and adopts the following technical scheme:

the invention provides a thermal differential pressure flow sensor which comprises a shell, a sensing integration component and a laminar flow element, wherein the shell is provided with a first end and a second end;

the shell is internally provided with an air guide passage, two ends of the air guide passage are respectively and correspondingly communicated with an air inlet passage and an air outlet passage, and the other end of the air inlet passage is communicated with a pipeline for air transmission so as to lead the air flow circulating in the pipeline into the air guide passage; the other end of the gas outlet channel is communicated with the pipeline so as to discharge the gas in the gas guide channel to the pipeline;

the laminar flow element is arranged in the pipeline and used for changing the flow direction of part of gas on the gas flow path of the pipeline and guiding the part of gas into the gas inlet channel;

the sensing integrated assembly is arranged in the air guide channel and comprises two thermistors which are sequentially arranged along the circulation path of the air guide channel and used for detecting the temperature of the air, and the sensing integrated assembly converts the temperature difference between the two thermistors into air pressure information to be output.

Further, the sensing integrated component further comprises a wheatstone bridge, and the wheatstone bridge is used for detecting voltage output differential signals of the two thermistors.

Further, the two thermistors are respectively a first thermistor and a second thermistor, and the first thermistor and the second thermistor are arranged in parallel.

Specifically, the sensing integrated assembly further comprises a heating resistor connected with the first thermistor and the second thermistor in parallel, and the heating resistor is used for heating the temperature of gas flowing into the gas guide channel so as to provide a high-temperature working environment for the first thermistor and the second thermistor.

Furthermore, the inlet channel has been seted up on the pipeline and has been led the gas port, the gas outlet channel has been seted up the gas vent on the pipeline correspondingly, and the gas in the pipeline flows to the gas vent direction from leading the gas port direction.

Further, the laminar flow member is disposed on an inner circumference of the pipe, and the laminar flow member is disposed between the air guide opening and the air discharge opening.

Preferably, the laminar flow element is in a circular ring shape, a fence shape or an air duct shape.

Preferably, lead the air flue include with the air inlet of intake duct intercommunication and with the gas outlet of gas outlet channel intercommunication, lead the air flue and include the straight-through portion that is being close to circuitous portion and two circuitous portions of intercommunication that its air inlet and gas outlet department set up respectively, whole air flue symmetry sets up.

Further, the circuitous part is provided with a corner, and the area of at least one cross section of the corner is larger than that of any cross section of the straight-through part.

Specifically, the straight-through part is located on one side of a connecting line of the air inlet and the air outlet, and the roundabout part extends from the air inlet/the air outlet to a direction far away from the air outlet/the air inlet, then extends to a direction on one side of the straight-through part and then turns back to be communicated with the straight-through part after extending beyond the position of the straight-through part.

Further, the gas guide channel is designed such that the average flow velocity of the gas at the detour portion is smaller than the average flow velocity of the gas at the straight portion.

Specifically, the sensing integrated assembly further comprises a processing chip, and the processing chip receives the differential pressure signal and converts the differential pressure signal into air pressure information.

Furthermore, the sensing integrated component is arranged in the middle of the air guide channel.

Furthermore, the air guide channel, the air inlet channel and the air outlet channel are closed air channels.

Compared with the prior art, the invention has the following advantages:

firstly, the air guide channel arranged in the shell of the thermal differential pressure flow sensor is respectively communicated with the pipeline through the air inlet channel and the air outlet channel which are correspondingly communicated with each other at two ends of the air guide channel, partial air in the pipeline is guided into the air inlet channel through the laminar flow element arranged in the pipeline, the partial air enters the air guide channel through the air inlet channel and is finally returned into the pipeline through the air outlet channel, and a complete air flow loop is formed, so that the sensing integrated component can detect the air pressure of the pipeline in real time.

Secondly, a sensing integrated assembly of the thermal differential pressure flow sensor is arranged in the air guide channel, two thermistors of the sensing integrated assembly are sequentially arranged at intervals along the circulation path of the air guide channel to respectively detect the temperature of the gas flowing to different positions, the two thermistors generate different voltage values due to different heating to form a voltage difference, and the pressure information in the pipeline is obtained by converting and calculating the voltage difference. The two thermistors can sense the tiny temperature change so as to reflect the tiny temperature change to the voltage, and then the thermal differential pressure flow sensor can detect the tiny air pressure change of the pipeline gas.

Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.

Drawings

The foregoing and/or additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:

fig. 1 is a schematic view of the construction of a thermal differential flow sensor and a pipe of the present invention.

Fig. 2 is a cross-sectional view of a thermal differential flow sensor of the present invention.

Fig. 3 is a schematic structural diagram of a housing of the thermal differential pressure flow sensor of the present invention.

Fig. 4 is a schematic diagram of a detection circuit of a sensing integrated component of the thermal differential pressure flow sensor according to the present invention.

Fig. 5 is a first level shift circuit of the sensing integrated component of the thermal differential pressure flow sensor of the present invention.

Fig. 6 is a second level shift circuit of the sensing integrated component of the thermal differential pressure flow sensor of the present invention.

FIG. 7 is a voltage regulator circuit of the sensing integrated component of the thermal differential pressure flow sensor of the present invention.

Detailed Description

Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below by referring to the drawings are exemplary only for the purpose of illustrating the present invention and are not to be construed as limiting the present invention.

As used herein, the singular forms "a", "an", "the" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. It will be understood that when an element is referred to as being "connected" or "coupled" to another element, it can be directly connected or coupled to the other element or intervening elements may also be present. Further, "connected" or "coupled" as used herein may include wirelessly connected or wirelessly coupled. As used herein, the term "and/or" includes all or any element and all combinations of one or more of the associated listed items.

It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the prior art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

The invention provides a thermal differential pressure flow sensor 10, and the thermal differential pressure flow sensor 10 is used for accurately measuring the change of micro differential pressure of gas in a pipeline 50.

In an exemplary embodiment of the present invention, and with reference to FIG. 1, the thermal differential pressure flow sensor 10 includes a housing 30, a sensing assembly, and a laminar flow member 20. The thermal differential pressure flow sensor 10 of the present invention may be disposed on a pipe 50 for gas transmission to detect a minute differential pressure change of gas in the pipe 50.

Referring to fig. 2, the housing 30 includes a gas guiding channel 31 disposed therein, and both ends of the gas guiding channel 31 are respectively communicated with the duct 50 to obtain a partial gas flow from the gas flowing through the duct 50, and the partial gas flow flows in from one end of the gas guiding channel 31 and flows back into the duct 50 from the other end of the gas guiding channel 31. The sensing integrated component is disposed in the gas guide channel 31 to detect a pressure difference change of the gas in the pipeline 50.

Specifically, the gas guiding duct 31 includes a gas inlet 32 and a gas outlet 33 respectively disposed at both end portions thereof, wherein the gas inlet 32 is used for guiding a portion of the gas in the duct 50 into the gas guiding duct 31, and the gas outlet 33 is used for guiding the gas guided into the gas guiding duct 31 back into the duct 50.

The air guide duct 31 further comprises a circuitous part 34 and a straight part 35, the circuitous part 34 and the straight part 35 form the whole air guide duct 31, and the circuitous part 34 and the straight part 35 are both bent to prolong the length of the air guide duct 31.

The detour portion 34 is bent, and the detour portion 34 includes at least one corner, and the area of at least one cross section of the corner is larger than that of the straight portion 35, so as to enlarge the volume of the gas guide channel 31 at the detour portion 34, prolong the length of the gas guide channel 31, and reduce the flow rate of the gas flowing into the gas guide channel 31. In the present embodiment, the detour 34 has two corners. Preferably, the detour 34 is U-shaped.

In an exemplary implementation of the present invention, the air guide duct 31 includes two detours 34, and the two detours 34 are respectively disposed near the air inlet 32 and the air outlet 33. The bypass portion 34 corresponding to the air inlet 32 is a first bypass portion 341, and the bypass portion 34 corresponding to the air outlet 33 is a second bypass portion 342.

The through portion 35 is disposed between the first winding portion 341 and the second winding portion 342, and both ends of the through portion 35 communicate with the first winding portion 341 and the second winding portion 342, respectively. The through portion 35 extends in the dummy connection line direction between the air inlet 32 and the air outlet 33.

In one embodiment, the through portion 35 includes two through segments, which are a first through segment 351 and a second through segment 352, respectively, where the first through segment 351 and the second through segment 352 are connected to be a middle point of an extending path of the gas guide duct 31, the first through segment 351 and the second through segment 352 are symmetrical with respect to a middle line passing through the middle point and perpendicular to the dummy connection line, and the first detour portion 341 and the second detour portion 342 are also symmetrical with respect to the middle line, that is, the gas guide duct 31 is symmetrical with respect to the gas guide duct 31. Preferably, the through section has a corner, the angle of which is between 90-180 degrees.

Specifically, the other end of the first straight section 351 communicates with the first bypass portion 341, and the first straight section 351 turns back to communicate with the first straight portion 35 after extending from the air inlet 32 in a direction away from the air outlet 33 and then continuing to extend in a direction on the side of the first straight section 351 to a position beyond the first straight portion 35. The other end of the second straight-through section 352 is communicated with the second roundabout part 342, and after the second straight-through section 352 extends from the air outlet 33 to a direction away from the air inlet 32 and then continues to extend to a side direction where the second straight-through section 352 is located beyond the position where the second straight-through section 352 is located, the second straight-through section 352 is turned back and communicated with the second roundabout part 35.

Thus, the number and angle of the corners of the detour 34 are larger than those of the straight-through portion 35, so that the average flow rate of the gas entering the gas guide passage 31 at the detour 34 is smaller than that at the straight-through portion 35.

With reference to fig. 1 and 3, the air guide passage 31 further extends to the air inlet passage 40 and the air outlet passage 42 outside the housing 30, so that two ends of the air guide passage 31 are respectively communicated with the passages 50. The air guide passage 31, the air inlet passage 40 and the air outlet passage 42 are all closed air passages.

The intake duct 40 is tubular, and it is protruding to be located on the casing 30, the one end of intake duct 40 and the air inlet 32 intercommunication of leading the way 31, the other end and pipeline 50 intercommunication, and intake duct 40 corresponds and has seted up the air guide mouth 43 on pipeline 50 to make intake duct 40 can communicate with pipeline 50 in air guide mouth 43 department.

The air outlet channel 42 is tubular and is convexly arranged on the shell 30, one end of the air outlet channel 42 is communicated with the air outlet 33 of the air guide channel 31, the other end of the air outlet channel is communicated with the pipeline 50, and the air outlet channel 42 is provided with an air outlet 44 corresponding to the pipeline 50, so that the air outlet channel 42 can be communicated with the pipeline 50 at the air outlet 44.

In one embodiment, inlet channel 40 and outlet channel 42 have the same inner diameter and the same size. And the axial directions of the inlet and outlet passages 40, 42 are perpendicular to the axial direction of the duct 50. Preferably, inlet channel 40 and outlet channel 42 are symmetrical about the centerline.

Therefore, two ends of the gas guide channel 31 can be respectively communicated with the pipeline 50 through the gas inlet channel 40 and the gas outlet channel 42 to form a gas guide branch of the pipeline 50, so that part of gas in the pipeline 50 can flow into the gas guide channel 31 and flow out of the gas guide channel 31, and the gas circulation is realized in the gas guide channel 31.

The laminar flow member 20 is disposed inside the duct 50, and is used for changing the flow direction of a part of the gas on the gas flow path in the duct 50, guiding the part of the gas to flow into the gas inlet passage 40 and further flow into the gas guide passage 31.

The laminar flow member 20 is disposed in a section of the duct 50 corresponding to a space between the gas introduction port 43 and the gas discharge port 44, and a flow direction of the gas in the duct 50 is a direction from the gas introduction port 43 to the gas discharge port 44. The laminar flow member 20 is used to reduce the area of the cross section of the duct 50, so that when the gas flows to the position of the laminar flow member 20, a part of the gas is turned back to flow toward the gas guide opening 43 due to the blocking effect of the laminar flow member 20, so that the part of the gas can flow from the inside of the duct 50 to the gas inlet duct 40 from the gas guide opening 43 and flow into the gas guide duct 31. Specifically, the laminar flow member 20 functions by using the bernoulli principle, and when the gas in the pipe 50 flows through the laminar flow member 20, a pressure difference is generated across the laminar flow member 20, so that a part of the gas returns to flow toward the gas guide passage 31.

The laminar flow member 20 has an annular shape, and the annular laminar flow member 20 is disposed around the pipe 50 to reduce the size of the flow path of the pipe 50 and guide a part of the gas to the gas guide port 43. In one embodiment, the laminar flow member 20 may also be in the form of a fence or air channel.

The sensing integrated component is disposed in the gas guide passage 31 to detect the pressure of the gas flowing into the gas guide passage 31. The sensing integrated assembly comprises a detection circuit, which is shown in fig. 4 and comprises two parallel thermistors, and the two thermistors are sequentially arranged along the gas flow path of the gas guide channel 31. Specifically, the two thermistors are a first thermistor S1 and a second thermistor S2, respectively, the first thermistor S1 is closer to the first winding portion 341 than the second thermistor S2, and the second thermistor S2 is closer to the second winding portion 342 than the first thermistor S1. Preferably, the resistance value of the first thermistor S1 and the resistance value of the second thermistor S2 are the same.

Because the air duct 31 is disposed outside the duct 50, the temperature inside the air duct 31 is different from the temperature inside the duct 50, and generally, the temperature inside the air duct 31 is lower than the temperature inside the duct 50. The gas flowing into the gas guide passage 31 reduces the flow rate and temperature of the gas due to the upper corners of the bypass 34 and the through part 35, and the first thermistor S1 and the second thermistor S2 have a certain distance therebetween, so that the temperature of the gas flowing through the first thermistor S1 and the second thermistor S2 is different, and the pressure of the first thermistor S1 and the pressure of the gas flowing through the second thermistor S2 are different.

The sensing integrated assembly further comprises a Wheatstone bridge, the Wheatstone bridge is electrically connected with the first thermistor S1 and the second thermistor S2, the voltage values of the first thermistor S1 and the second thermistor S2 are collected, the voltage difference between the first thermistor S1 and the second thermistor S2 is obtained, and the voltage difference is output in a differential signal mode. Specifically, the wheatstone bridge includes a first resistor R1 in series with a first thermistor S1 and a second resistor R2 in series with a second thermistor S2.

The sensing integrated assembly further comprises a processing chip, the processing chip acquires a differential signal output by the Wheatstone bridge, and the processing chip calculates and acquires a gas pressure value according to the differential signal, so that the detection of the gas pressure in the pipeline 50 is realized.

The detection circuit further comprises a heating resistor S4 and a gas temperature detection resistor S3, wherein the heating resistor S4 and the gas temperature detection resistor S3 are respectively connected with the first thermistor S1 and the second thermistor S2 in parallel. The heating resistor S4 is used to provide a high temperature working environment for the first thermistor S1 and the second thermistor S2, so that when gas flows through the first thermistor S1 and the second thermistor S2, the temperature difference of the gas between the first thermistor S1 and the second thermistor S2 is amplified. The gas temperature detection resistor S3 and the gas temperature detection resistor S3 are used for detecting the temperature in the gas guide channel 31 and assisting in pressure calculation.

The detection circuit further comprises a voltage division matching resistor R3 and a current limiting resistor R4. The voltage division matching resistor R3 is connected with the gas temperature detection resistor S3 in series and is used for accessing signals of pins of the processing chip to facilitate detection. The current-limiting resistor R4 is connected in series with the heating resistor S4, and the current-limiting resistor R4 is used for limiting the current of the heating resistor S4, preventing the heating resistor S4 from being burnt out by large current, and protecting the heating resistor S4.

The sensing integrated component further comprises a field effect transistor Q1, and the field effect transistor Q1 is connected with the detection circuit in series to maintain the stability of the detection circuit.

With reference to fig. 7, the sensing integrated component further includes a voltage regulator circuit U4, the voltage regulator circuit U4 includes a voltage regulator chip and two capacitors connected in series with the voltage regulator chip, and the voltage regulator circuit is configured to regulate the 5V supply voltage of the detection circuit to a 3.3V power supply.

The sensing integrated assembly further comprises two level conversion circuits, and the two level conversion circuits are used for converting communication IO of the 3.3V processing chip into 5V signal level. Referring to fig. 5 and 6, the two level shift circuits are the first level shift circuit U3 and the second level shift circuit U4, respectively.

In one embodiment, the sensing integrated components may be integrated on the same chip.

In one embodiment, the detection circuit of the sensing integrated component is integrated on the same chip, the fet Q1, the regulator circuit U4 and the two level shifters are integrated on the same circuit board, and the chip integrated with the detection circuit is disposed on the circuit board.

The casing 30 is cuboid, and a groove is seted up on the casing 30 of cuboid form, air guide channel 31 sets up in the tank bottom of this groove, and air guide channel 31 is equipped with air inlet 32 and gas outlet 33 on the one side that the tank bottom is right for the connection of intake duct 40 and gas outlet 42. The circuit board is disposed on the air guide duct 31 to seal the air guide duct 31.

In one embodiment, the housing 30 is integrally formed with the inlet duct 40 and the outlet duct 42.

In summary, the thermal differential pressure flow sensor of the present invention is connected to the pipeline for transporting air through the air guide channel disposed on the housing and the air inlet channel and the air outlet channel disposed at two ends of the air guide channel, the air inlet channel introduces a portion of air flow from the pipeline, the portion of air flow is re-transported back to the pipeline through the air guide channel and the air outlet channel, and the laminar flow element disposed in the pipeline guides the portion of air flow from the pipeline to the air inlet channel, so that the air inlet channel can obtain the portion of air flow. The sensing integrated assembly arranged in the gas guide channel respectively detects the gas temperature on different path positions in the gas guide channel through two thermistors of the sensing integrated assembly to obtain a temperature difference value, and the temperature difference value is converted to obtain pipeline air pressure information

The foregoing description is only exemplary of the preferred embodiments of the invention and is illustrative of the principles of the technology employed. It will be appreciated by those skilled in the art that the scope of the invention according to the present invention is not limited to the specific combination of the above-mentioned features, but also encompasses other embodiments in which any combination of the above-mentioned features or their equivalents is possible without departing from the scope of the invention as defined by the appended claims. For example, the above features and (but not limited to) features having similar functions of the present invention are mutually replaced to form the technical solution.

Although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.

Claims (14)

1. A thermal differential pressure flow sensor is characterized by comprising a shell, a sensing integrated assembly and a laminar flow element;

the shell is internally provided with an air guide passage, two ends of the air guide passage are respectively and correspondingly communicated with an air inlet passage and an air outlet passage, and the other end of the air inlet passage is communicated with a pipeline for air transmission so as to lead the air flow circulating in the pipeline into the air guide passage; the other end of the gas outlet channel is communicated with the pipeline so as to discharge the gas in the gas guide channel to the pipeline;

the laminar flow element is arranged in the pipeline and used for changing the flow direction of part of gas on the gas flow path of the pipeline and guiding the part of gas into the gas inlet channel;

the sensing integrated assembly is arranged in the air guide channel and comprises two thermistors which are sequentially arranged along the circulation path of the air guide channel and used for detecting the temperature of the air, and the sensing integrated assembly converts the temperature difference between the two thermistors into air pressure information to be output.

2. The thermal differential pressure flow sensor of claim 1, wherein the sensing assembly further comprises a wheatstone bridge for sensing the voltage output differential signal of the two thermistors.

3. The thermal differential pressure flow sensor according to claim 2, wherein the two thermistors are a first thermistor and a second thermistor, respectively, and the first thermistor and the second thermistor are arranged in parallel.

4. The thermal differential pressure flow sensor of claim 3, wherein the sensing assembly further comprises a heating resistor connected in parallel with the first thermistor and the second thermistor for heating the temperature of the gas flowing into the gas conducting channel to provide a high temperature operating environment for the first thermistor and the second thermistor.

5. The sensor according to claim 1, wherein the inlet channel has an inlet opening corresponding to the pipeline, the outlet channel has an outlet opening corresponding to the pipeline, and the gas in the pipeline flows from the inlet opening to the outlet opening.

6. The differential thermal pressure flow sensor of claim 5, wherein the laminar flow member is disposed on an inner circumference of the conduit, the laminar flow member being disposed between the air-guide opening and the air-discharge opening.

7. The thermal differential pressure flow sensor of claim 6, wherein the laminar flow element is in the shape of a circular ring or a fence or a gas channel.

8. The thermal differential pressure flow sensor according to claim 1, wherein the air guide passage includes an air inlet communicating with the air inlet passage and an air outlet communicating with the air outlet passage, the air guide passage includes a detour portion provided near the air inlet and the air outlet thereof, respectively, and a straight portion communicating the two detour portions, and the entire air guide passage is symmetrically provided.

9. The thermal differential pressure flow sensor according to claim 8, wherein the detour portion is provided with a corner having at least one cross-sectional area larger than an area of any cross-section of the straight portion.

10. The thermal differential pressure flow sensor according to claim 8, wherein the straight portion is located on one side of a line connecting the air inlet and the air outlet, and the detour portion extends from the air inlet/outlet in a direction away from the air outlet/inlet and then continues to extend beyond a position of the straight portion on one side of the straight portion, and then turns back to communicate with the straight portion.

11. The differential thermal pressure flow sensor according to any one of claims 8 to 10, wherein the gas guide passage is designed such that an average flow velocity of gas at the detour portion is smaller than an average flow velocity of gas at the straight portion.

12. The thermal differential pressure flow sensor of claim 2, wherein the sensing assembly further comprises a processing chip that receives the differential pressure signal and converts the differential pressure signal into air pressure information.

13. The thermal differential pressure flow sensor of claim 1, wherein the sensing assembly is disposed in a middle portion of the gas conduction channel.

14. The thermal differential pressure flow sensor of claim 1, wherein the gas conduction channel, the gas inlet channel, and the gas outlet channel are closed gas channels.

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