Wind speed sensor

Abstract

To provide an anemometer that can measure wind speed with high accuracy without requiring complicated temperature compensation. [Solution] This wind speed sensor measures the wind speed of a gas by detecting temperature changes due to heat transfer changes caused by a heat source, which is positioned downstream of a heat source located inside a straight pipe that flows in one direction. The heat source is placed on the main surface of an insulating main substrate, and the heat source is supported by thermal insulation between it and the main surface of the main substrate. A housing is positioned on the main substrate to cover the heat source and the heat source, forming a pipe with openings at both ends.

Description

Technical Field

[0001] The present invention relates to an air velocity sensor that detects a temperature change due to a heat transfer change of heat generated by a heating element caused by an air flow and measures the air velocity of the air flow.

Background Art

[0002] Conventionally, as a sensor for detecting the air velocity or flow rate of an air flow, a thermal air velocity sensor in which a heater and a thermopile are arranged on a substrate made of a thin film (membrane) is known. Such a thermal air velocity sensor measures the air velocity or flow rate from the thermoelectromotive force difference generated between both thermopiles due to the difference in the heat distribution on the substrate heated by the heater, with the thermopiles arranged on both sides of the heater respectively. (See Patent Documents 1 to 3).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the thermal air velocity sensor as described above, with the miniaturization of the sensor, the distance between the heater and the thermopile becomes closer, but the temperature drift due to the heat transfer in the planar direction through the substrate increases, and complicated temperature correction has been required.

[0005] The present invention has been made in view of the above circumstances, and an object thereof is to provide an air velocity sensor that detects a temperature change due to a heat transfer change of heat generated by a heating element caused by an air flow and measures the air velocity of the air flow, which does not require complicated temperature correction and can measure the air velocity with high accuracy. [Means for solving the problem]

[0006] The wind speed sensor according to the present invention is a wind speed sensor that measures the wind speed of a gas by detecting a temperature change due to a change in heat transfer of heat generated by a heating element, which is placed inside a flow path of a gas flowing in one direction in a straight pipe, and the temperature sensing element is placed at a distance downstream of the heating element. The temperature sensing element is placed on the main surface of an insulating main substrate, and the heating element is supported by thermal insulation between the main surface of the main substrate and the heating element with a space between them. The housing is placed on the main substrate so as to cover the temperature sensing element and the heating element, forming the pipe with openings at both ends.

[0007] These features allow for reduced temperature drift by suppressing heat transfer to the temperature sensor via the main substrate, eliminating the need for complex temperature correction and enabling highly accurate measurement of wind speed.

[0008] In the invention described above, the heating element may be provided at the tip of the support member and supported such that its paired rear end is positioned further away from the temperature-sensing element than the heating element. The support member may also be characterized by comprising a mounting substrate placed on the main surface of the main substrate and an insulating, elongated thin film with the heating element placed at its tip and its rear end connected to the mounting substrate. The support member may also be characterized by comprising metal wiring that conducts current to the heating element. With these features, the transfer of heat to the temperature-sensing element via the main substrate can be suppressed by the support member, thereby reducing temperature drift, eliminating the need for complicated temperature correction, and enabling highly accurate measurement of wind speed.

[0009] In the invention described above, the heating element may be characterized by being an element that generates heat when an electric current is passed through it. With this characteristic, the amount of heat generated by the heating element can be controlled simply and accurately, and wind speed can be measured with high precision without requiring complicated temperature correction.

[0010] In the invention described above, the temperature sensing element may be characterized by being a thermopile. Furthermore, the housing may be characterized by being made of metal and having its inner surface blackened. With such features, temperature changes can be measured accurately, wind speed can be measured with high precision without the need for complicated temperature correction.

[0011] In the above-described invention, one opening of the pipeline is connected to one first opening of an extension pipeline that extends the pipeline, and the second opening at the other end of the extension pipeline is opened toward an orthogonal pipeline that extends perpendicularly to the extension pipeline. Furthermore, the invention may be characterized in that a negative pressure can be formed at the second opening of the extension pipeline by the airflow in the orthogonal pipeline. Furthermore, the second opening may be characterized by having an annular wall portion that extends into the interior of the orthogonal pipeline. Furthermore, the extension pipeline may be characterized by attenuating the flow velocity of the flow path of the pipeline. Furthermore, the cross-sectional area of ​​the extension pipeline may be determined so as to attenuate the flow velocity of the pipeline to a predetermined level. With these features, wind speed can be measured with high accuracy without requiring complicated temperature correction, even at higher wind speeds.

[0012] The invention described above may include a control unit that controls the heating element and the temperature sensing element, wherein the control unit calculates the wind speed from the temperature change detected by the temperature sensing element. The control unit may also include an amplification unit that amplifies the signal from the temperature sensing element. With such features, wind speed can be measured simply and with high accuracy without requiring complicated temperature correction. [Brief explanation of the drawing]

[0013] [Figure 1] This is a cross-sectional view of the wind speed sensor according to the first embodiment. [Figure 2] This is a perspective view of a thermopile used as a temperature sensor in an anemometer. [Figure 3] This is a cross-sectional view of the wind speed sensor according to the second embodiment. [Figure 4] This is a cross-sectional view of the wind speed sensor according to the third embodiment. [Figure 5] It is a cross-sectional view of the wind speed sensor according to the fourth embodiment. [Figure 6] It is a circuit diagram of the measurement circuit used in the wind speed sensor. [Figure 7] It is a block diagram of the control unit used in the wind speed sensor. [Figure 8] It is a graph showing the relationship between the wind speed in the measured atmosphere and the output voltage. [Figure 9] It is a graph showing the relationship between the wind speed and the output voltage when the temperature is changed.

Mode for Carrying Out the Invention

[0014] Hereinafter, the wind speed sensor according to the embodiment of the present invention will be described with reference to FIGS. 1 to 9. In each figure, for the purpose of making each member recognizable, the scale of each member is appropriately changed for the sake of explanation. In addition, the same or corresponding parts are denoted by the same reference numerals, and redundant explanations are omitted.

[0015] (First Embodiment) The first embodiment will be described with reference to FIGS. 1 and 2.

[0016] FIG. 1 is a cross-sectional view showing a wind speed sensor 1 according to the first embodiment of the present invention. The sensor 1 includes a main substrate 2 which is a circuit board made of an electrically insulating material, and a housing 3. The housing 3 covers a temperature-sensitive body 4 and a heating body 5 disposed on the main substrate 2, and forms a linear pipe 31 serving as a gas flow path together with the main substrate 2. The housing 3 is provided with an inlet-side opening 32 and an outlet-side opening 33 at the upstream end and the downstream end of the pipe 31, respectively. That is, the pipe 31 is configured to allow gas to flow in one direction from the inlet-side opening 32 toward the outlet-side opening 33 inside it. The inlet-side opening 32 and the outlet-side opening 33 are preferably configured to easily form a laminar flow of gas in the pipe 31. For example, they are arranged so that the centers of the respective openings are aligned with the center line C of the pipe 31.

[0017] The main substrate 2 has its upper main surface 21 as the bottom surface of the pipeline 31, and the temperature sensor 4 and the heating element 5 are mounted on the main surface 21. The temperature sensor 4 is arranged at a distance downstream of the heating element 5 and can detect the temperature change caused by the heat transfer change of the heat generated by the heating element 5. The wind speed sensor 1 can measure the wind speed of the gas based on such a temperature change. In addition, the main substrate 2 can use an insulating printed circuit board (PCB board). As such a main substrate 2, a glass epoxy substrate, a glass polyimide substrate, a Teflon (registered trademark) substrate, etc. are used.

[0018] The temperature sensor 4 is placed on the main surface 21 of the main substrate 2. On the other hand, the heating element 5 is supported so as to be arranged at a position spaced upward from the main surface 21 of the main substrate 2. For such support, for example, a support member is used, and here the column member 11 is used as the support member. The column member 11 extends upward from the main surface 21 of the main substrate 2 and supports the heating element 5 from below. Thus, since the wind speed sensor 1 supports the heating element 5 with a space from the main surface 21 of the main substrate 2, the space between the heating element 5 and the main surface 21 can be thermally insulated, and the heat conduction from the heating element 5 to the main substrate 2 can be suppressed. Therefore, it is possible to suppress the heat transfer to the temperature sensor 4 through the main substrate 2 and reduce the temperature drift to such an extent that temperature correction is not required.

[0019] Also, particularly referring to FIG. (b), the column member 11 has the heating element 5 provided at its tip 11a, and the corresponding rear end 11b extends vertically downward and is fixed to the main substrate 2. Thereby, with respect to the distance L from the temperature sensor 4 to the tip 11a and the heating element 5, the rear end 11b has a longer distance from the temperature sensor 4. That is, the rear end 11b is positioned in a direction away from the temperature sensor 4 more than the heating element 5. Thereby, the path through the column member 11 and the main substrate 2 can be lengthened, and the heat transfer to the temperature sensor 4 along the same path can be further suppressed.

[0020] Here, for example, the heating element 5 can be a resistive heating element that generates heat due to its resistance when an electric current is passed through it. Because it is an element that generates heat when an electric current is passed through it, the amount of heat generated by the heating element 5 can be controlled simply and accurately. When the heating element 5 is a resistive heating element, for example, metal wiring can be used as the support member 11. In order to suppress heat transfer from the heating element 5 to the main substrate 2, it is desirable that the support member 11 be made thin and preferably made from a material with low thermal conductivity.

[0021] As described above, the heating element 5 in this embodiment can be a resistive heating element. As the resistive heating element, metal heating elements (Ni-Cr system, Fe-Cr-Al system, molybdenum, tungsten, platinum, molybdenum disilicide) or non-metallic heating elements (silicon carbide, graphite, zirconia, lanthanum chromite) can be used. There are no restrictions on the type of resistive heating element, but if it is an SMD resistor (surface mount resistor), it is easy to connect to the metal wiring described above and easy to mount on a substrate or the like.

[0022] As shown in Figure 2, a thermopile 40 can be suitably used as the temperature-sensing element 4. The thermopile 40 is, for example, substantially square in shape with sides of 2 mm or less when viewed from above. An insulating film 42, such as silicon dioxide or silicon nitride, is provided on the upper main surface of the substrate 41, and a cavity 43 is formed in the center of the substrate 41 by anisotropic etching from the back side of the substrate 41. The substrate 41 is formed from, for example, a silicon material.

[0023] A membrane portion 44 made of an insulating film 42 is formed on the cavity portion 43. A hot junction 45 of a thermocouple made of a different metal is placed in the central part of the membrane portion 44, and an infrared absorbing portion 48, which is a film that absorbs infrared rays, is placed on top of it. On the other hand, a portion with a greater thickness of the substrate 41 is formed around the membrane portion 44 and functions as a heat sink, and a cold junction 46 of a thermocouple is placed on this heat sink portion 47. Multiple thermocouples with these hot junctions 45 and cold junctions 46 are connected in series to form a thermocouple array, which increases the output due to thermoelectric power. An electrode pad 49 for connecting lead wires for measuring the output from the thermocouple array is also formed on the heat sink portion 47. From the viewpoint of sensitivity to temperature changes, it is preferable to form 60 or more pairs of such thermocouples with hot junctions 45 and cold junctions 46, and in this embodiment, for example, 96 pairs of thermocouples are formed.

[0024] Furthermore, it is preferable that the housing 3 is designed so that heat from the heating element 5 is not transmitted to the temperature sensing element 4 even by infrared reflection. For example, if the temperature sensing element 4 is one that detects infrared rays, such as the thermopile 40 described above, it is preferable that the housing 3 is designed to prevent infrared reflection and allow the absorbed infrared heat to be easily radiated to the outside. For this reason, for example, the housing 3 is made of a metal material and its inner surface is blackened. As the metal material, aluminum can be suitably used, for example. In the blackening treatment, a black film with high infrared emissivity is formed by, for example, black oxide film treatment, black body paint coating, or low vacuum deposition treatment.

[0025] Furthermore, the distance between the temperature-sensing element 4 and the heating element 5 is preferably shortened from the viewpoint of detecting a sufficient output signal from the temperature-sensing element 4, and lengthened from the viewpoint of minimizing temperature drift. Depending on the output voltage of the temperature-sensing element 4, the amount of heat generated by the heating element 5, and the wind speed, for example, in this embodiment, the distance between the temperature-sensing element 4 and the heating element 5 is preferably about 3 to 7 mm, and particularly preferably about 5 mm.

[0026] Furthermore, it is preferable that the upper surfaces of the temperature-sensing element 4 and the heating element 5 be positioned such that the gas heated by the heating element 5 flows directly onto the temperature-sensing element 4. For example, it is also preferable to position both the upper surfaces of the temperature-sensing element 4 and the heating element 5 on the center line C.

[0027] Incidentally, while the wind speed sensor 1 can measure the wind speed inside the conduit 31, what is intended to be measured using the wind speed sensor 1 is the wind speed of the ambient air outside the wind speed sensor 1. The wind speed inside the conduit 31 and the wind speed outside the wind speed sensor 1 have a certain relationship depending on the shape of the conduit 31, including the inlet opening 32 and the outlet opening 33, and its direction relative to the external airflow. Therefore, by defining conversion coefficients and conversion tables based on this relationship, the wind speed outside the wind speed sensor 1 can be measured. Furthermore, if the external wind speed and the output of the temperature sensor 4 are experimentally correlated, the wind speed outside the wind speed sensor 1 can be measured directly without determining the wind speed inside the conduit 31.

[0028] With the above configuration, the wind speed sensor 1 can obtain an output from the temperature sensing element 4 corresponding to the wind speed of the gas flowing in one direction through the conduit 31 from the inlet opening 32 to the outlet opening 33. In other words, it can measure wind speed. In particular, as described above, by positioning the heating element 5 above the main surface 21 of the main substrate 2, temperature drift can be reduced. As a result, the wind speed sensor 1 can measure wind speed with high accuracy without requiring complicated temperature correction.

[0029] (Second embodiment) A second embodiment will be described with reference to Figure 3.

[0030] Figure 3 is a cross-sectional view showing an anemometer sensor 1' according to a second embodiment of the present invention. An electrically connected mounting substrate 22 is disposed on the main surface 21 of the main substrate 2, and a film substrate 23 made of an insulating longitudinal film is attached to the mounting substrate 22 with a portion of it protruding downstream from the end of the mounting substrate 22 and electrically connected. In other words, the leading edge 23a of the film substrate 23 protrudes and is connected to the mounting substrate 22 at its rear end 23b. Furthermore, a heating element 5 is attached on the leading edge 23a of the film substrate 23 and positioned at a predetermined distance from the temperature sensing element 4. In other words, the film substrate 23 and the mounting substrate 22 become support members that support the heating element 5, keeping it separated from the main substrate 2.

[0031] Even with this wind speed sensor 1', the film substrate 23, which is the support member, separates the heating element 5 from the main surface 21 of the main substrate 2 by the thickness of the mounting substrate 22, thus providing thermal insulation between the heating element 5 and the main surface 21, and suppressing heat conduction from the heating element 5 to the main substrate 2. Furthermore, the rear end portion 23b of the film substrate 23 is positioned in a direction that separates it from the temperature sensing element 4 more than the heating element 5. This lengthens the path through the film substrate 23, which is the support member, the mounting substrate 22, and the main substrate 2, further suppressing heat transfer to the temperature sensing element 4 along this path. As a result, the wind speed sensor 1' can reduce temperature drift and measure wind speed with high accuracy without requiring complicated temperature correction.

[0032] Preferably, the mounting substrate 22 and the film substrate 23 are made of materials with low thermal conductivity. Furthermore, it is preferable that the film substrate 23 has a small cross-sectional area to suppress heat conduction. As such a mounting substrate 22, for example, an electrically insulating printed circuit board (PCB) can be used. Examples of such printed circuit boards include glass epoxy substrates, glass polyimide substrates, and Teflon substrates. As for the film substrate 23, materials such as glass epoxy resin, polyimide resin, PEEK (polyetheretherketone) resin, and polyester resin can be used. Wiring connecting the heating element 5 and the mounting substrate 21 is formed on the film substrate 23. The film substrate 23 is attached to the mounting substrate 22 with its main surfaces parallel to each other, and is electrically connected to the mounting substrate 22 by soldering, conductive paste connection, wire bonding, etc.

[0033] (Third embodiment) A third embodiment will be described with reference to Figure 4.

[0034] Figure 4 is a cross-sectional view showing an anemometer sensor 1'' according to a third embodiment of the present invention. The heating element 5 is disposed on the tip portion 24a of a flexible substrate 24 connected to the main substrate 2. The flexible substrate 23 has its tip portion 24a facing the direction of the temperature sensing element 4 downstream, and its rear end portion 24b positioned upstream. The flexible substrate 24 has its rear end portion 24b connected to the upper surface 21 of the main substrate 2, and its tip portion 24a is spaced apart from the upper surface 21 of the main substrate 2. A support plate 25 is placed between the tip portion 24a and the main substrate 2, supporting the tip portion 24a so as to be spaced apart from the upper surface 21.

[0035] Even with this wind speed sensor 1'', the flexible substrate 24, which acts as a support member, separates the heating element 5 from the main surface 21 of the main substrate 2, thus providing thermal insulation between the heating element 5 and the main surface 21, and suppressing heat conduction from the heating element 5 to the main substrate 2. Furthermore, the rear end 24b of the flexible substrate 24 is positioned to be further away from the temperature sensing element 4 than from the heating element 5. This lengthens the path through the flexible substrate 24 and the main substrate 2, which act as support members, further suppressing heat transfer to the temperature sensing element 4 along this path. As a result, the wind speed sensor 1'' can reduce temperature drift and measure wind speed with high accuracy without requiring complicated temperature correction.

[0036] Furthermore, it is preferable that the material and dimensions of the flexible substrate 24 be designed to suppress heat conduction to the main substrate 2. Similarly, it is preferable that the material and dimensions of the support plate 25 be designed to suppress heat conduction to the main substrate 2.

[0037] (Fourth embodiment) A fourth embodiment will be described with reference to Figure 5.

[0038] Figure 5 is a cross-sectional view showing a wind speed sensor 10 according to a fourth embodiment of the present invention. The wind speed sensor 10 further includes a cover portion 50 which is installed on the outside of the housing of the wind speed sensor 1, 1', or 1'' of the first, second, or third embodiment described above.

[0039] The cover section 50 is installed on the downstream side of the housing 3 and includes a right-angle conduit 51 that extends perpendicularly to the conduit 31. The right-angle conduit 51 is connected to an extension conduit 34 that extends the conduit 31 and is connected to the outlet-side opening 33. In other words, the extension conduit 34 has an opening 34a at one end connected to the outlet-side opening 33, and an opening 34b at the other end that opens towards the inside of the right-angle conduit 51. Furthermore, it is preferable that the opening 34b has an annular wall section 35, which is an annular wall that protrudes so as to extend into the inside of the right-angle conduit 51.

[0040] As a result, the airflow flowing along the orthogonal conduit 51 (up and down direction on the paper) creates a negative pressure at the opening 34b of the extension conduit 34 due to the Venturi effect, generating an airflow in conduit 31 with a velocity corresponding to the airflow velocity in extension conduit 34. In other words, the airflow generated in the orthogonal conduit 51 draws out the gas inside conduit 31, and by measuring the velocity of the resulting airflow, the wind speed inside the orthogonal conduit 51 can be indirectly measured.

[0041] Therefore, for example, when measuring the wind speed of a gas containing dust or exhaled breath containing moisture, flowing the gas through the orthogonal conduit 51 prevents dust and moisture from directly contacting the temperature sensor 4. As a result, it is possible to measure the wind speed while reducing the influence of dust and moisture. Furthermore, by making the inner diameter of the extension conduit 34 smaller than the outlet opening 33 and measuring the wind speed indirectly, the flow velocity of the gas in the conduit 31 is attenuated compared to when the cover portion 50 is not provided, making it possible to measure wind speeds in a higher speed range. Moreover, by appropriately adjusting the inner diameter of the extension conduit 34 according to the wind speed to be measured, it is also possible to adjust the attenuation rate of the gas flow velocity in the conduit 31 relative to the gas flow velocity in the orthogonal conduit 51. In other words, the cross-sectional area of ​​the extension conduit 34 is determined so as to attenuate the gas flow velocity in the conduit 31 to a predetermined level.

[0042] (Fifth embodiment) A fifth embodiment will be described with reference to Figure 6.

[0043] Figure 6 is a circuit diagram of a measurement circuit in an anemometer, which is provided on the main board 2, a circuit board, and measures the output of the temperature sensing element 4. The measurement circuit may also include an amplification unit to amplify the output of the temperature sensing element 4. By providing an amplification unit, measurement can be made easier even if the output signal from the temperature sensing element 4 is minute.

[0044] (Sixth embodiment) The sixth embodiment will be discussed with reference to Figure 7.

[0045] Figure 7 is a block diagram of the control unit 100 used in the wind speed sensor. The control unit 100 has a temperature calculation unit 102 that calculates a temperature rise value from the temperature change detected by the temperature sensing element 4 of the wind speed sensor, and a wind speed determination unit 103 that determines the wind speed from the temperature rise value obtained by the temperature calculation unit 102. As described above, the wind speed determination unit 103 may determine the wind speed based on the correspondence between the output of the temperature sensing element 4 and the wind speed, which has been experimentally determined. The control unit 100 may also include the amplification unit 101 described above to amplify the output from the temperature sensing element 4. Furthermore, the control unit 100 can also control the amount of heat generated by the heating element 5 by controlling the power supplied to the heating element 5.

[0046] Next, the output characteristics of the wind speed sensor will be explained with reference to Figures 8 and 9.

[0047] Figure 8 shows the relationship between wind speed in the measured atmosphere and the output voltage from the temperature sensor 4. In the figure, the horizontal axis represents wind speed (m / s) and the vertical axis represents voltage (V). From the measurement results, it can be seen that the output voltage increases as the wind speed increases. This confirms that changes in wind speed can be detected.

[0048] Figure 9 shows the temperature characteristics of the wind speed sensor, illustrating the relationship between the wind speed in the measured atmosphere and the output voltage of the temperature-sensing element 4 when the temperature of the measured atmosphere is varied from 0°C to 40°C. From the measurement results, it can be seen that there is almost no difference in the output voltage even when the temperature of the measured atmosphere is changed. This indicates that the wind speed sensor of this embodiment can accurately measure wind speed without temperature compensation.

[0049] As described above, with wind sensors 1, 1', 1'', and 10, the arrangement of the temperature-sensing element 4 and the heating element 5 can be optimized to prevent temperature drift, and the transfer of heat from the heating element 4 to the main substrate 2 can be suppressed. This makes it possible to measure wind speed simply and with high accuracy without requiring complicated temperature correction. Furthermore, with wind sensor 10, wind speed can be measured indirectly by providing an extension pipe 34 and a right-angle pipe 51 at the outlet opening 33 on the downstream side of the pipe 31, which is the gas flow path. This makes it possible to measure the velocity of gas in the medium to high speed range, and also enables high-precision measurement of gases containing dust and moisture.

[0050] Although embodiments and modifications based thereon have been described, the present invention is not necessarily limited to these examples. Furthermore, those skilled in the art will be able to find various alternative embodiments and modifications without departing from the spirit of the present invention or the scope of the attached claims. [Explanation of Symbols]

[0051] 1. Wind speed sensor 2 Main board 3 cabinets 4. Thermometer 5. Heating element 21 Main surface 31 Pipeline 32 Entrance side opening 33 Exit side opening

Claims

1. An air velocity sensor that measures the air velocity of a gas by detecting temperature changes due to changes in heat transfer generated by a heat source, which is positioned at a distance downstream of a heat source located inside a straight pipe that is flowing in one direction, An anemometer is characterized in that the temperature sensing element is placed on the main surface of an insulating main substrate, the heating element is supported by thermal insulation between it and the main surface of the main substrate, and the housing is arranged on the main substrate so as to cover the temperature sensing element and the heating element, forming the conduit with openings at both ends.

2. The wind speed sensor according to claim 1, characterized in that the heating element is provided at the tip of the support member and supported such that its paired rear ends are positioned in a direction that separates it from the temperature sensing element more than the heating element.

3. The wind speed sensor according to claim 2, characterized in that the support member comprises a mounting substrate placed on the main surface of the main substrate, and an insulating, elongated thin film on which the heating element is placed at its tip and whose rear end is connected to the mounting substrate.

4. The wind speed sensor according to claim 2, characterized in that the support member consists of metal wiring that conducts current to the heating element.

5. The wind speed sensor according to claim 1, characterized in that the heating element is an element that generates heat when an electric current is passed through it.

6. The wind speed sensor according to claim 1, characterized in that the temperature sensing element is a thermopile.

7. The wind speed sensor according to claim 1, characterized in that the housing is made of metal and its inner surface is blackened.

8. The wind speed sensor according to claim 1, characterized in that one opening of the aforementioned conduit is connected to one first opening of an extension conduit that extends the aforementioned conduit, and the second opening at the other end of the extension conduit is opened toward an orthogonal conduit that extends perpendicularly to the extension conduit.

9. The wind speed sensor according to claim 8, characterized in that a negative pressure can be formed at the second opening of the extension pipe by the airflow in the orthogonal pipe.

10. The wind speed sensor according to claim 9, characterized in that the second opening has an annular wall portion extending into the interior of the orthogonal conduit.

11. The wind speed sensor according to claim 9, characterized in that the extension pipe attenuates the flow velocity in the flow path of the pipe.

12. The wind speed sensor according to claim 11, characterized in that the cross-sectional area of ​​the extension pipe is determined such that the flow velocity of the pipe is attenuated to a predetermined level.

13. An air velocity sensor according to one of claims 1 to 12, comprising a control unit that controls the heating element and the temperature sensing element, wherein the control unit calculates the air velocity from the temperature change detected by the temperature sensing element.

14. The wind speed sensor according to claim 13, characterized in that the control unit includes an amplification unit for amplifying the signal from the temperature sensing element.

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