JP2023070839A - Flow sensor and gas detector - Google Patents

Abstract

To provide a flow sensor capable of accurately measuring the flow rate of a fluid even when supplying mixed gas having unknown (arbitrary) concentration or temperature of composition gas to a flow sensor.SOLUTION: A flow sensor 100 includes: a passage 10 for circulating a fluid 1 including a plurality of composition gases; a first detector element 21 arranged in the passage 10 and capable of changing output according to the flow rate of the fluid 1 by heating; a second detector element 22 arranged in the passage 10 and capable of suppressing the speed of the fluid 1 rather than the first detector element 21 and capable of changing output according to the thermal conductivity of the fluid 1 by heating; a flow rate calculation part 30 for correcting the composition gas concentration and temperature of the fluid 1 to the output of the first detector element 21 on the basis of the output of the second detector element 22 to calculate the flow rate of the fluid 1.SELECTED DRAWING: Figure 7

Description

TECHNICAL FIELD The present invention relates to a flow sensor and a gas detector, and more particularly to a flow sensor equipped with a sensing element that senses a flow rate when heated and a gas detector equipped with such a flow sensor.

Conventionally, there has been known a flow sensor provided with a sensing element that senses a flow rate when heated (see, for example, Patent Literature 1).

The aforementioned Patent Document 1 discloses a flowmeter including a flow sensor having a flow rate measuring section and a thermal conductivity measuring section, and a processing section. The processing unit of the flow meter (1) calculates the flow rate of the fluid based on the detection signal from the flow measurement unit, and (2) calculates the thermal conductivity of the fluid based on the detection signal from the thermal conductivity measurement unit. (3) identifying the type of fluid from the calculated thermal conductivity using a table; and (4) correcting the calculated flow rate to a value suitable for the identified type of fluid. This flow meter is used in a gas meter or the like, and corrects the flow rate according to the type of fluid supplied to the gas meter.

In Patent Document 1, the fluid supplied to the gas meter is fuel gas, and it is assumed that a predetermined type (composition) of gas is supplied. In the above-mentioned Patent Document 1, among predetermined fuel gases, which type (composition) of fuel gas is supplied as a fluid is specified using a table based on thermal conductivity.

JP-A-2001-165731

However, in applications other than flowmeters, such as gas meters, in which a predetermined type (composition) of gas is supplied, the composition gas concentration contained in the fluid supplied to the flow sensor may be unknown. For example, when the atmosphere (air) in the installation environment such as a factory is supplied to the flow sensor, if the gas used in the installation environment is mixed with the atmosphere gas, the composition gas concentration contained in the fluid supplied to the flow sensor becomes unknown. Become.

Therefore, even if the air is the same, if the concentration of a gas with relatively high thermal conductivity (for example, hydrogen) is higher than usual, the thermal conductivity of the fluid (air) will increase. Conversely, a higher than normal concentration of a gas with relatively low thermal conductivity (eg, carbon dioxide) results in a low thermal conductivity of the fluid (air). Also, the thermal conductivity varies depending on the temperature of the fluid.

Therefore, in the above Patent Document 1, when measuring the flow rate of a mixed gas with unknown (arbitrary) composition gas concentration and fluid temperature that constitute the fluid supplied to the flow sensor, the type of fluid and the type of fluid There is a problem that it is difficult to accurately measure the flow rate of the fluid because the corresponding correction value cannot be specified.

The present invention has been made to solve the above-described problems, and one object of the present invention is to provide a flow sensor even when a mixed gas with an unknown (arbitrary) composition gas concentration and temperature is supplied to a flow sensor. Another object of the present invention is to provide a flow sensor capable of accurately measuring the flow rate of a fluid, and a gas detector equipped with such a flow sensor.

In order to achieve the above object, a flow sensor according to a first aspect of the present invention comprises a flow path through which a fluid containing a plurality of composition gases flows, and a fluid flow rate which is arranged in the flow path and is heated to change the flow rate of the fluid. a first sensing element whose output changes according to the thermal conductivity of the fluid; 2 detection elements, and a flow rate calculation unit that calculates the flow rate of the fluid by correcting the composition gas concentration of the fluid and correcting the temperature of the fluid with respect to the output of the first detection element based on the output of the second detection element. , provided.

In the flow sensor according to the first aspect of the present invention, due to the above configuration, of the first sensing element and the second sensing element arranged in the flow channel, the flow velocity is suppressed more than that of the first sensing element. A second sensing element positioned within the passageway will be less sensitive to the flow rate of the fluid and more sensitive to the thermal conductivity of the fluid. Therefore, based on the output of the second sensing element whose sensitivity to the flow rate of the fluid is suppressed, the effect of the composition gas concentration of the fluid and the fluid temperature effects can be corrected. As a result, it is possible to calculate the flow rate in which the influence of composition gas concentration and temperature is corrected from the output of the first detection element based on the output of the second detection element, so that the composition gas concentration and temperature are unknown (arbitrary ) is supplied to the flow sensor, the flow rate of the fluid can be accurately measured.

In the flow sensor according to the first aspect, preferably, the flow rate calculation unit calculates the output fluctuation component caused by the composition gas concentration and temperature of the fluid contained in both the output of the first sensing element and the output of the second sensing element. , the output of the second sensing element is corrected to be removed from the output of the first sensing element. With this configuration, since the first sensing element and the second sensing element are arranged in the same flow path and are exposed to the same fluid, the output fluctuation component caused by the composition gas concentration and temperature is detected by the first sensing element. and the output of the second sensing element, the output fluctuation component caused by the composition gas concentration and temperature can be removed from the output of the first sensing element. In this configuration, unlike the configuration in which the gas type is specified from the table and the correction amount corresponding to the gas type is applied, there is no need to obtain the gas type and the correction amount corresponding to the gas type in advance. Appropriate output correction can be performed even when the type and concentration are unknown (arbitrary).

In this case, preferably, the flow rate calculator performs correction by subtracting the output of the second sensing element heated by the same voltage application as the first sensing element from the output of the first sensing element. With this configuration, the heating conditions for the second sensing element can be matched with those for the first sensing element. As a result, it is possible to approximate the output fluctuation components caused by the composition gas concentration and temperature in the output of each sensing element, so a simple correction of subtracting the output of the second sensing element from the output of the first sensing element is performed. can be easily corrected for the effect of the composition gas concentration of the fluid and the effect of the temperature of the fluid.

In the configuration in which correction is performed by subtracting the output of the second sensing element heated by the application of the same voltage as the first sensing element from the output of the first sensing element, preferably the first sensing element and the second sensing element The devices have similar output characteristics with respect to fluid composition gas concentration and temperature. With this configuration, when the first sensing element and the second sensing element are operated under the same heating conditions, the output fluctuation components caused by the composition gas concentration and temperature included in the output of each sensing element match with high accuracy. can be made As a result, by subtracting the output of the second sensing element from the output of the first sensing element, the output fluctuation component caused by the composition gas concentration and temperature can be removed from the output of the first sensing element with high accuracy.

In the flow sensor according to the first aspect, preferably, the first sensing element and the second sensing element are gas-heated, the resistance value of which changes according to heat conduction to the fluid due to contact with the fluid in a heated state. It is a conductive element. With this configuration, flow rate measurement can be performed using a gas heat conducting element with a simple configuration. In other words, unlike a thermal sensing element that has a separate heater and temperature sensor inside the sensing element, the gas heat conduction element measures the change in the resistance value of the heating element itself due to the contact of the heated heating element with the fluid. Therefore, it is not necessary to separately provide a heater or a temperature sensor in the element. Therefore, the configuration of the flow sensor can be simplified.

A gas detector according to a second aspect of the present invention comprises the flow sensor according to the first aspect and a gas sensor.

In the gas detector according to the second aspect of the present invention, by including the flow sensor according to the first aspect, even when a mixed gas with an unknown (arbitrary) composition gas concentration and temperature is supplied to the flow sensor, the fluid flow rate can be measured with high accuracy. Even if a mixed gas with unknown (arbitrary) composition gas concentration and temperature is supplied to the gas detector, the flow rate of the gas (fluid) supplied to the gas sensor can be determined based on the accurately measured flow rate of the fluid. Since it can be grasped with high accuracy, it is possible to improve the accuracy of gas detection by the gas sensor.

According to the present invention, as described above, even when a mixed gas with an unknown (arbitrary) composition gas concentration and temperature is supplied to the flow sensor, it is possible to accurately measure the flow rate of the fluid.

FIG. 4 is a schematic cross-sectional view showing a cross section along the flow path of the flow sensor; FIG. 2 is a combined cross-sectional view showing a cross section taken along line 301-301 and a cross section taken along line 302-302 of FIG. 1; FIG. 4 is a schematic diagram showing a first detection element and a flow control member in a first detection chamber; FIG. 3 is a schematic cross-sectional view showing a configuration example of a gas heat conduction element; FIG. 5 is a schematic plan view showing a detection region of the gas heat conduction element shown in FIG. 4; FIG. 4 is a diagram showing an example of a detection circuit of a flow sensor; It is a figure for demonstrating a flow volume calculation part. 4 is a graph showing experimental results of measuring output characteristics of a sensing element with respect to fluid flow rate. 4 is a graph showing experimental results of measuring the output characteristics of the sensing element with respect to the compositional gas concentration of the fluid. 4 is a graph showing changes in corrected output value obtained by correcting the output of the first sensing element by the output of the second sensing element, with respect to the composition gas concentration of the fluid. 4 is a graph showing changes in corrected output value with respect to fluid flow rate for each composition gas concentration. 4 is a graph showing experimental results of measuring the flow rate characteristic of the first sensing element with respect to the environmental temperature; 4 is a graph showing changes in corrected output value with respect to environmental temperature for each flow rate condition; 1 is a schematic diagram showing a configuration example of a gas detector provided with a flow sensor; FIG.

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings.

The configuration of a flow sensor 100 according to one embodiment will be described with reference to FIGS. 1 to 13. FIG.

(Configuration of flow sensor)
The flow sensor 100 of this embodiment is a device that measures the flow rate of the fluid 1 supplied into the channel 10 .

A fluid 1 whose flow rate is to be measured is a gas. A fluid 1 is a mixed gas composed of a plurality of composition gases. The mixed gas is not particularly limited and may be any gas. An example of a mixed gas is air (atmosphere). Air is a mixed gas containing many types of composition gases, including nitrogen, oxygen, carbon dioxide, hydrogen, and the like.

Although the composition of air is known, for example, in international standard atmospheres, air as fluid 1 supplied to flow sensor 100 may differ from the standard composition, reflecting the environment in which fluid 1 is taken. For example, the atmosphere in a factory or the like where a particular gas (hydrogen, carbon dioxide, etc.) is used or emitted can be sampled and supplied to the flow sensor 100 . In this case, the flow sensor 100 can be supplied with air as the fluid 1 in which the ratio of hydrogen gas and carbon dioxide gas is higher than the standard value.

As described above, the fluid 1 in this embodiment is a mixed gas such as air, but it can be a mixed gas with an unknown composition gas ratio. The flow sensor 100 of the present embodiment can accurately measure the flow rate even when the fluid 1 having an unknown (arbitrary) composition gas ratio is supplied.

As shown in FIG. 1, the flow sensor 100 includes a channel 10, a first detection element 21, a second detection element 22, and a flow rate calculator 30 (see FIG. 7).

A flow path 10 is a passage through which a fluid 1 containing a plurality of composition gases flows. The channel 10 has a hollow tubular structure. The flow path 10 is a tubular space having one end with an inlet opening 10 a and the other end with an outlet opening 10 b , and is formed in the housing 40 of the flow sensor 100 .

Flow path 10 includes a first sensing chamber 11 and a second sensing chamber 12 between inlet opening 10a and outlet opening 10b.

Flow path 10 includes first flow path section 13 , second flow path section 14 and third flow path section 15 . The first flow path portion 13 connects the inlet opening 10 a and the first detection chamber 11 . The second flow path part 14 connects the first detection chamber 11 and the second detection chamber 12 . The third channel portion 15 connects the second detection chamber 12 and the outlet opening 10b. In FIG. 1, the second channel portion 14 has a U-turned structure, but the channel 10 may extend linearly from the inlet opening 10a to the outlet opening 10b.

The first detection chamber 11 is a space having a predetermined volume formed in the middle of the flow path 10 . A first supply port 13 a serving as an inlet for the fluid 1 and a first outlet 11 a serving as an outlet for the fluid 1 are opened in the first detection chamber 11 .

The first sensing element 21 is arranged in the first sensing chamber 11 inside the channel 10 . The first sensing element 21 has a characteristic that its output changes according to the flow rate of the fluid 1 by being heated.

The first channel portion 13 is connected to the inlet opening 10 a and the first supply port 13 a that supplies fluid to the first detection element 21 . The fluid 1 flowing into the first detection chamber 11 is supplied to the first detection element 21 through the inlet opening 10a, the first flow path portion 13, and the first supply port 13a.

The second detection chamber 12 is a space having a predetermined volume formed downstream of the first detection chamber 11 in the channel 10 . A second supply port 14 a serving as an inlet for the fluid 1 and a second outlet 12 a serving as an outlet for the fluid 1 are opened in the second detection chamber 12 .

The second sensing element 22 is arranged in the second sensing chamber 12 inside the channel 10 . The second sensing element 22 has a characteristic that its output changes according to the thermal conductivity of the fluid 1 when heated.

The second flow path portion 14 is connected to the first outlet 11 a of the first detection chamber 11 and the second supply port 14 a that supplies the fluid to the second detection element 22 . The fluid 1 flowing into the second detection chamber 12 is supplied to the second detection element 22 through the first outlet 11a of the first detection chamber 11, the second flow path portion 14, and the second supply port 14a.

The third channel portion 15 is connected to the second outlet 12a of the second detection chamber 12 and the outlet opening 10b.

<Installation position of each detection element>
The second sensing element 22 is arranged in the flow path 10 in which the velocity of the fluid 1 is lower than that of the first sensing element 21 . In other words, the first sensing element 21 is arranged in the flow path 10 where the velocity of the fluid 1 is higher than that of the second sensing element 22 .

<First detection element>
Specifically, as shown in FIG. 1, the inner diameter d1 of the first supply port 13a is formed smaller than the inner diameter d3 of the first flow path portion 13. As shown in FIG. Therefore, the fluid 1 flows into the first detection chamber 11 at a relatively high flow rate by narrowing the inner diameter of the flow path 10 at the first supply port 13a. Note that the inner diameter d1 of the first supply port 13a is smaller than the inner diameter of the first outlet 11a of the first detection chamber 11 .

Further, as shown in FIG. 2, the first detection element 21 is arranged in the first detection chamber 11 at a position facing the front of the first supply port 13a. That is, the first sensing element 21 is provided on the upper surface of the holding member 23a, and the holding member 23a is mounted on the substrate 25 with the spacer 24 interposed therebetween. The height H1 of the spacer 24 is set to a size corresponding to the difference between the height H0 from the substrate 25 to the first supply port 13a and the height dimension of the holding member 23a. As a result, the height from the substrate 25 to the first detection element 21 (upper surface of the holding member 23a) substantially matches the height from the substrate 25 to the first supply port 13a. As a result, the first detection element 21 is arranged in front of the fluid 1 flowing into the first detection chamber 11 from the first supply port 13a.

Further, in this embodiment, as shown in FIG. 3, a flow control member 26 is provided inside the first detection chamber 11 . The flow control member 26 forms a guide passage 26a between the first supply port 13a and the first detection element 21. As shown in FIG. The guide passage 26a has a width substantially equal to the inner diameter d1 (see FIG. 1) of the first supply port 13a. As a result, even inside the first detection chamber 11 , the fluid 1 maintains a high flow rate from the first supply port 13 a to just before the first detection element 21 . 1 and 2, illustration of the flow control member 26 is omitted for the sake of convenience.

<Second detection element>
On the other hand, as shown in FIG. 1, the inner diameter d2 of the second supply port 14a opening into the second detection chamber 12 is larger than the inner diameter d1 of the first supply port 13a. Therefore, the flow velocity of the fluid 1 flowing into the second detection chamber 12 from the second supply port 14a is lower than the flow velocity of the fluid 1 flowing into the first detection chamber 11 from the first supply port 13a. . The inner diameter d2 of the second supply port 14a is, for example, approximately three times the inner diameter d1 of the first supply port 13a.

In addition, the inner diameter d2 of the second supply port 14a is larger than the inner diameter d3 of the first flow path portion 13 . The inner diameter d<b>2 of the second supply port 14 a is equal to the inner diameter of the first outlet 11 a of the first detection chamber 11 and the inner diameter of the second flow path section 14 . In addition, the inner diameter of the second flow path part 14 is the entire range from the first outlet 11a of the first detection chamber 11 to the second supply port 14a, and the inner diameter d3 of the first flow path part 13 and the first supply port 13a Consistently larger than the inner diameter d1. In addition, the inner diameter d2 of the second supply port 14a is larger than the inner diameter d4 of the third flow path portion 15 . The inner diameter d4 of the third channel portion 15 is substantially equal to the inner diameter d3 of the inner diameter d3 of the first channel portion 13 .

Further, as shown in FIG. 2, in the second detection chamber 12, the second detection element 22 is arranged at a position away from the position facing the front of the second supply port 14a. That is, the second detection element 22 is provided on the upper surface of the holding member 23b. Unlike the holding member 23a of the first sensing element 21, the holding member 23b is mounted on the substrate 25 without the spacer 24 interposed therebetween. Although the holding member 23a and the holding member 23b have the same shape, the height H2 from the substrate 25 to the second detection element 22 (upper surface of the holding member 23b) is small because the spacer 24 is not provided. A height H2 from the substrate 25 to the second detection element 22 is smaller than a height H4 from the substrate 25 to the second supply port 14a. The height H2 is two thirds or less of the height H4. As a result, the arrangement position of the second detection element 22 is shifted from the front of the second supply port 14a toward the substrate 25 side.

Thus, the flow velocity of the fluid 1 flowing into the second detection chamber 12 is sufficiently reduced reflecting the size of the inner diameter d2 of the second supply port 14a. Further, since the second detection element 22 is arranged at a position away from the front surface of the second supply port 14 a, the fluid 1 flowing into the second detection chamber 12 does not flow toward the second detection element 22 . Therefore, as will be described later, the second sensing element 22 is not affected by the flow velocity of the fluid 1 and the output of the second sensing element 22 does not depend on the flow rate of the fluid 1 .

<Structure of detection element>
The first sensing element 21 and the second sensing element 22 are gaseous heat conducting elements whose resistance values change according to heat conduction to the fluid 1 due to contact with the fluid 1 in a heated state.

4 and 5 show one configuration example of the gas heat conducting element 50 used for the first sensing element 21 and the second sensing element 22. FIG. The gas heat conducting element 50 is formed by MEMS (Micro Electro Mechanical Systems) technology that forms a mechanical structure in a semiconductor substrate using a semiconductor manufacturing process. That is, the gas heat conducting element 50 is a MEMS sensor, and has a size of about 0.1 mm on one side, for example.

The gas heat conducting element 50 as the first sensing element 21 and the second sensing element 22 is connected to a power supply section 61 (see FIG. 6) and supplied with current from the power supply section 61 . As shown in FIG. 3, the gas heat conducting element 50 includes a pair of electrode portions 50a connected to the power supply portion 61 (see FIG. 6). The holding member 23a (23b) has a pair of terminal portions 23c that are connected to the pair of electrode portions 50a by wiring.

Returning to FIG. 4 , the gas heat conducting element 50 includes an insulating support layer 51 , a resistor pattern 52 and an inert coating layer 53 . In the example of FIG. 4, an insulating support layer 51, a resistor pattern 52 and an inert coating layer 53 are formed on a base material layer 54 by a semiconductor manufacturing process.

Base material layer 54 is, for example, Si (silicon). The base material layer 54 has recesses 54a formed by etching. The concave portion 54a is formed over the entire lower portion of the detection area SA, which will be described later. The insulating support layer 51 existing within the formation range of the concave portion 54 a is provided away from the base material layer 54 in a non-contact state with the base material layer 54 .

The insulating support layer 51 is formed on the surface of the base material layer 54 and is made of an insulator. The insulating support layer 51 includes, in a plan view, a rectangular holding portion 51a (see FIG. 5) forming the detection area SA, a beam portion 51b (see FIG. 5) for supporting the holding portion 51a, and an outer peripheral portion. 51c. In the example of FIG. 5, a plurality (four) of beam portions 51b are connected to the holding portion 51a and the outer peripheral portion 51c, respectively, and support the holding portion 51a. The insulating support layer 51 is composed of, for example, a single layer or a composite layer (laminated structure of multiple types of insulators) of insulators such as SiO ₂ (silicon dioxide) and SiN (silicon nitride).

As shown in FIG. 4, the resistor pattern 52 is formed on the surface of the insulating support layer 51 and made of a conductor. As shown in FIG. 5, the resistor pattern 52 includes a heater portion 52a formed on the holding portion 51a and a wiring portion 52b formed on the beam portion 51b. The heater portion 52a is formed by folding a single linear structure in a meandering manner so as to be distributed over substantially the entire holding portion 51a. The wiring portion 52b connects one end and the other end of the heater portion 52a to the pair of electrode portions 50a one by one through the beam portion 51b. The heater portion 52a generates heat due to current supply from the pair of electrode portions 50a. A conductor forming resistor pattern 52 is made of, for example, Pt (platinum). The structure of the resistor pattern 52 may be a single layer structure or a composite layer structure of a conductor (such as Pt) and an insulator (such as Ta ₂ O ₅ (tantalum pentoxide)). Incidentally, in FIG. 5, the resistor pattern 52 is hatched for the sake of convenience.

As shown in FIG. 4, the inert coating layer 53 is formed to cover the surfaces of the insulating support layer 51 and the resistor pattern 52 . The inert coating layer 53 covers at least the entire surface of the heater section 52a. The inert coating layer 53 is made of an inert material having low reactivity to gas even when heated by the resistor pattern 52 . An inert material is, for example, _SiO2 . 5, illustration of the inert coating layer 53 is omitted for the sake of convenience. The inert coating layer 53 covers the entire insulating support layer 51 and resistor pattern 52 in FIG.

As shown in FIG. 5, the sensing area SA is composed of a holding portion 51a, a heater portion 52a, and an inert coating layer 53 covering these. When the heater portion 52a generates heat, heat is released due to heat conduction due to contact between the sensing area SA and the surrounding gas. Under the condition that the fluid 1 is supplied to the gas heat conducting element 50, the detection area SA contacts with the fluid 1, so that the heat release amount changes according to the flow rate. At this time, the electrical resistance of the heater portion 52a (resistor pattern 52) changes in accordance with the temperature change of the heater portion 52a. In the gas heat conduction element 50, it is possible to calculate the flow rate of the fluid 1 that caused the temperature change based on the change in electrical resistance of the heater portion 52a (resistor pattern 52).

As can be seen from the principle of calculating the flow rate, even if the flow rate is the same, the heat dissipation amount of the detection area SA (the electrical resistance of the heater portion 52a) changes depending on the magnitude of the thermal conductivity of the fluid 1. Therefore, the thermal conductivity of the fluid 1 is Changes in the rate affect the output of the sensing element. For example, when the fluid 1 is air, if hydrogen gas, which has a higher thermal conductivity than air, is mixed in the air, the thermal conductivity of the fluid 1 increases as the hydrogen gas concentration in the air increases. The output of the sensing element becomes larger than the output value corresponding to the flow rate.

On the other hand, when carbon dioxide gas, which has a lower thermal conductivity than air, is mixed in the air, the thermal conductivity of the fluid 1 decreases as the concentration of carbon dioxide gas in the air increases, and the output according to the actual flow rate The output of the sensing element becomes smaller than the value. Thus, the gas heat transfer element 50 is sensitive to the constituent gas concentrations. Moreover, since the thermal conductivity depends on the temperature, the gas heat conducting element 50 is affected by the temperature of the fluid 1 (environmental temperature).

In the present embodiment, both the first sensing element 21 and the second sensing element 22 are composed of gas heat conducting elements 50 having the same structure as described above. In this embodiment, the first sensing element 21 and the second sensing element 22 have the same output characteristics with respect to the constituent gas concentration and temperature of the fluid 1 . More specifically, the first sensing element 21 and the second sensing element 22 are composed of gas heat conducting elements 50 having the same specifications. Therefore, the output characteristics of the first sensing element 21 and the second sensing element 22 are substantially the same from any point of view. The term “substantially the same” as used herein means that differences in output characteristics at the level of individual differences between the gas heat conducting elements 50 having the same specifications are regarded as the same.

<Detection circuit>
Referring to FIG. 6, a configuration example of the detection circuit 60 of the first detection element 21 and the second detection element 22 in the flow sensor 100 is shown. The sensing circuit 60 includes a first sensing element 21 and a second sensing element 22 , a power supply section 61 , fixed resistors 62 and 63 .

The first sensing element 21 and the second sensing element 22 are connected in parallel to the positive electrode of the power supply section 61 . Therefore, the same voltage is applied to the first sensing element 21 and the second sensing element 22 . If there is no flow velocity of the fluid 1 , the first sensing element 21 and the second sensing element 22 are heated to approximately the same temperature by the power supply from the power supply section 61 .

The fixed resistor 62 has one end connected to the first detection element 21 and the other end connected to the negative electrode of the power supply section 61 . The fixed resistor 63 has one end connected to the second detection element 22 and the other end connected to the negative electrode of the power source section 61 . The resistance value of fixed resistor 62 and the resistance value of fixed resistor 63 are the same.

The voltage value across the fixed resistor 62 changes according to the resistance value of the first sensing element 21 . The flow rate calculation unit 30 acquires the voltage value across the fixed resistor 62 as the output of the first detection element 21 . Similarly, the voltage value across the fixed resistor 63 changes according to the resistance value of the second sensing element 22 . The flow rate calculator 30 acquires the voltage value across the fixed resistor 63 as the output of the second sensing element 22 .

<Flow rate calculator>
Next, with reference to FIG. 7, processing by the flow rate calculator 30 will be described.

The flow rate calculation unit 30 acquires output signals of each of the first detection element 21 and the second detection element 22 and calculates the flow rate of the fluid 1 supplied into the channel 10 . The flow rate calculator 30 is configured by a processor such as a CPU.

In this embodiment, the flow rate calculator 30 corrects the composition gas concentration of the fluid 1 and corrects the temperature of the fluid 1 with respect to the output of the first sensing element 21 based on the output of the second sensing element 22. The flow rate of fluid 1 is calculated.

The flow rate calculation unit 30 calculates the output fluctuation component caused by the composition gas concentration and temperature of the fluid 1 contained in both the output of the first detection element 21 and the output of the second detection element 22 by the output of the second detection element 22. Correction processing 31 for removing from the output of the first sensing element 21 is performed. Specifically, the flow rate calculation unit 30 performs the correction process 31 by subtracting the output of the second sensing element 22 heated by the application of the same voltage as the first sensing element 21 from the output of the first sensing element 21. conduct.

That is, as shown in FIG. 7, when the output of the first detection element 21 is V1 and the output of the second detection element 22 is V2, the correction process 31 is a process of calculating the corrected output value V=V1-V2. is.

Based on the corrected output value V, the flow rate calculator 30 acquires a flow rate value corresponding to the corrected output value V. FIG. For example, corrected output values V for various flow rate values are experimentally acquired in advance, and conversion information such as a regression equation or table that associates flow rate values with corrected output values V is created in advance. The flow rate calculator 30 acquires the flow rate value corresponding to the corrected output value V based on conversion information created in advance.

(Principle of output correction of detection element)
Next, the principle of correction based on the output of the first sensing element 21 and the output of the second sensing element 22 by the flow sensor 100 of the present embodiment will be described together with experimental results with reference to FIGS. 8 to 13. FIG.

8 is a graph showing experimental results of output characteristics of the first sensing element 21 and the second sensing element 22 with respect to the flow rate of the fluid 1. FIG. In the graph of FIG. 8, the horizontal axis is the flow rate [mL/min] of the fluid 1 supplied to the flow sensor 100, and the vertical axis is the output voltage value [mV] of the sensing element. The output voltage value on the vertical axis is indicated by a difference value ΔV from the output voltage value at a flow rate of 500 mL/min. Fluid 1 is air.

As shown in FIG. 8, the output V1 of the first sensing element 21 increases as the flow rate of the fluid 1 increases, indicating that the output characteristic is approximately linear in accordance with the flow rate. On the other hand, the output V2 of the second sensing element 22 was substantially constant regardless of the flow rate, and it was confirmed that the output characteristic did not change substantially with respect to the flow rate. In other words, in the flow sensor 100, the first sensing element 21 has high sensitivity to the flow rate due to the structure of the flow path 10 and the arrangement of the sensing elements in the flow path 10 shown in FIGS. A configuration is realized in which the second sensing element 22 has no sensitivity to the flow rate.

FIG. 9 is a graph showing experimental results of the output characteristics of the first sensing element 21 and the second sensing element 22 with respect to changes in the compositional gas concentrations of the fluid 1 . In this experiment, hydrogen gas was mixed in the fluid 1 (air), and the output values at the same flow rate of 500 mL/min were confirmed at multiple hydrogen gas concentrations. In the graph of FIG. 9, the horizontal axis is the hydrogen gas concentration [vol%] in the fluid 1, the vertical axis is the output voltage value [mV] of the detection element, and the difference value ΔV from the output voltage value when the hydrogen gas concentration is 0 vol% is shown.

As shown in FIG. 9, in both the first detection element 21 and the second detection element 22, the output value increases as the hydrogen gas concentration increases, and the output is positive with respect to the hydrogen gas concentration. It can be seen that there is a correlation of Moreover, it can be seen from the results of FIG. 9 that the first sensing element 21 and the second sensing element 22 have the same output characteristics with respect to the composition gas concentration of the fluid 1 . The second sensing element 22 does not have sensitivity to the flow rate of the fluid 1 as shown in FIG. Affected by thermal conductivity change. The difference between the output values of the first sensing element 21 and the second sensing element 22 in FIG. 9 is the individual difference level.

8, the first sensing element 21 has sensitivity to the flow rate of the fluid 1, and the second sensing element 22 has no sensitivity to the flow rate of the fluid 1. On the other hand, from FIG. It can be seen that the resulting output fluctuations are substantially the same between the first sensing element 21 and the second sensing element 22 . Therefore, the correction processing 31 (see FIG. 7) for subtracting the output of the second sensing element 22 from the output of the first sensing element 21 causes the output component corresponding to the flow rate of the fluid 1 contained in the output value of the first sensing element 21 to be calculated. , the output fluctuation component caused by the composition gas concentration of the fluid 1 can be removed.

FIG. 10 is a graph showing the corrected output value V obtained by the correction processing 31 for subtracting the output of the second sensing element 22 from the output of the first sensing element 21 shown in FIG. In the graph of FIG. 10, the horizontal axis is the hydrogen gas concentration [vol%] in the fluid 1 and the vertical axis is the corrected output value, which is shown as a difference value ΔV from the corrected output value when the hydrogen gas concentration is 0 vol%.

From FIG. 10, it can be seen that the corrected output value V obtained by the correction process 31 does not change with respect to fluctuations in hydrogen gas concentration and is substantially constant.

FIG. 11 is a graph showing changes in the corrected output value V by the correction process 31 with respect to the flow rate for a plurality of fluids 1 having different composition gas concentrations. In FIG. 11, as the fluid 1, air (without hydrogen gas), air with a hydrogen gas concentration of 1 vol%, air with a hydrogen gas concentration of 2 vol%, air with a hydrogen gas concentration of 3 vol%, and air with a hydrogen gas concentration of 4 vol%. Experimental results with species are plotted respectively. The horizontal axis of FIG. 11 is the flow rate [mL/min] of the fluid 1, and the vertical axis is the corrected output value V, which is indicated by the difference value ΔV from the corrected voltage value at the flow rate of 0 mL/min.

As can be seen from FIG. 11, substantially the same corrected output value V was obtained over the entire flow rate measurement range (0 mL/min to 1000 mL/min) for fluid 1 with any hydrogen gas concentration. From this, it was confirmed that according to the correction process of the present embodiment, only the output fluctuation component caused by the composition gas concentration can be removed without impairing the output characteristics according to the flow rate of the fluid 1 .

Next, FIG. 12 shows output characteristics of the first sensing element 21 with respect to the environmental temperature (temperature of the fluid 1). The horizontal axis of FIG. 12 is the environmental temperature [° C.], and the vertical axis is the output voltage value of the first detection element 21, which is indicated by the difference value ΔV from the output voltage value at the environmental temperature of 20° C. and the flow rate of 500 mL/min. In FIG. 12, the fluid 1 is air (no hydrogen gas is mixed), and the experimental results are plotted on a graph under four flow rate conditions of 0 mL/min, 300 mL/min, 500 mL/min, and 1000 mL/min. .

As can be seen from FIG. 12, the first sensing element 21 has a substantially linear output characteristic with respect to temperature. That is, under any flow rate condition, the lower the environmental temperature, the higher the difference value ΔV, and the higher the environmental temperature, the lower the difference value ΔV.

As described above, the second sensing element 22 has substantially the same output characteristics as the first sensing element 21 and is heated with the same applied voltage. As shown in FIG. 8, the output value of the second sensing element 22 does not change from the output value at a flow rate of 0 mL/min even if the flow rate is increased. Therefore, although omitted in FIG. 12, the output characteristic of the second sensing element 22 with respect to temperature substantially matches the output characteristic under the flow rate condition of 0 mL/min in FIG. 12, and does not change under any flow rate condition.

Therefore, the correction processing 31 (see FIG. 7) for subtracting the output of the second detection element 22 from the output of the first detection element 21 is performed to maintain the output component corresponding to the flow rate of the fluid 1 included in the output value. It is possible to remove the output fluctuation component caused by the temperature of 1.

FIG. 13 is a graph showing the corrected output value V obtained by the correction processing 31 for subtracting the output of the second sensing element 22 from the output of the first sensing element 21 shown in FIG. The vertical axis and horizontal axis of the graph in FIG. 13 are the same as the vertical axis and horizontal axis of the graph in FIG.

As can be seen from FIG. 13, it was confirmed that the output of the corrected output value V under the flow rate condition of 0 mL/min is substantially constant without depending on the environmental temperature. Moreover, even under the flow conditions of 300 mL/min, 500 mL/min, and 1000 mL/min, the output fluctuation (slope of the plot) due to the environmental temperature is reduced as compared with FIG. On the other hand, the corrected output values V for each flow rate condition are clearly separated from each other in the vertical axis direction, and it can be seen that the output characteristics according to the flow rate of the fluid 1 are not impaired. From this, it was confirmed that according to this embodiment, the output fluctuation component caused by the temperature can be removed without impairing the output characteristics according to the flow rate of the fluid 1 .

Based on the above experimental results, the correction processing 31 by the flow rate calculation unit 30 of the present embodiment can remove each output fluctuation component caused by the composition gas concentration and temperature of the fluid 1 from the output of the first detection element 21. confirmed.

(Configuration of gas detector)
Next, a gas detector 200 including the flow sensor 100 will be described as an application example of the flow sensor 100 of the present embodiment with reference to FIG. 14 .

The gas detector 200 includes the flow sensor 100 and the gas sensor 121 according to this embodiment. In the configuration example shown in FIG. 14, the gas detector 200 includes a flow rate detection unit 110 including a flow sensor 100, a gas detection unit 120 including a gas sensor 121, a pump 130, a control unit 140, a storage unit 141, and a communication unit. A portion 142 is further provided. The gas detector 200 includes a gas flow path 101 connecting an inlet 101a for introducing a fluid 1 to be detected and an outlet 101b for leading the fluid 1 therefrom. The gas flow path 101 is provided with a gas sensor 121, a flow sensor 100, and a pump 130 in this order. The fluid 1 introduced into the gas flow path 101 from the inlet 101a passes through the gas sensor 121, the flow sensor 100, and the pump 130 in order, and is led out from the outlet 101b.

The gas detector 200 shown in FIG. 14 is a gas detector that takes in the atmosphere (air) of the environment to be monitored and detects the detection target gas contained in the atmosphere. The gas detector 200 has a function of notifying that a high-concentration gas to be detected has been detected when the concentration of the gas to be detected in the sampling gas is higher than or equal to a preset value. The gas to be detected is not particularly limited, but is a gas that requires monitoring, such as a gas that is toxic to the human body or a combustible gas.

The flow rate detection unit 110 includes a flow sensor 100 and a detection circuit 60 (see FIG. 6). In FIG. 14 , the flow rate calculator 30 of the flow sensor 100 is provided in the controller 140 .

Gas detection unit 120 includes a gas sensor 121 and a gas detection circuit for acquiring the output of gas sensor 121 . The type and detection principle of the gas sensor 121 are not particularly limited and are arbitrary. The pump 130 is a gas pump that sucks gas from the inlet port 101a side of the gas flow path 101 and discharges it to the outlet port 101b side. The fluid 1 is drawn into the inlet 101a by the negative pressure generated by the pump 130, and is discharged from the outlet 101b by forced flow.

The control unit 140 is configured by a processor such as a CPU. The control unit 140 has a determination unit 140a that performs gas detection determination processing and a flow rate calculation unit 30 as functional blocks by executing a program.

The control unit 140 controls the gas detection operation of the gas sensor 121 by controlling power supply to the gas detection circuit of the gas detection unit 120 . The determination unit 140 a acquires the detection gas concentration of the detection target gas based on each output of the gas detection unit 120 . When the concentration of the detection target gas is equal to or higher than a predetermined value (determination threshold value) set in advance, the determination unit 140a executes a predetermined notification process according to the concentration of the detection target gas. The predetermined notification process includes outputting a notification signal (alarm) via the communication unit 142 .

The control unit 140 controls the flow rate detection operation of the flow sensor 100 by controlling power supply to the detection circuit 60 of the flow rate detection unit 110 . As described above, the flow rate calculation unit 30 acquires the outputs of the first detection element 21 and the second detection element 22 of the flow sensor 100, and calculates the output of the first detection element 21 based on the output of the second detection element 22. , the composition gas concentration correction of the fluid 1 and the temperature correction of the fluid 1 are performed, and the flow rate of the fluid 1 is calculated.

The control unit 140 controls the flow rate of the fluid 1 flowing through the gas flow path 101 by controlling power supply to the pump 130 . The controller 140 controls the pump 130 based on the flow rate value calculated by the flow rate calculator 30 . The control unit 140 controls the pump 130 so that the flow rate of the fluid 1 becomes a predetermined value.

The storage unit 141 stores various setting information such as a determination threshold value for the detected gas concentration and a flow rate setting value, programs executed by the processor, and the like. Storage unit 141 includes, for example, a semiconductor storage element. A communication unit 142 is an interface with an external device. The communication unit 142 is connected to an external device by wire and/or wirelessly, outputs a signal to the external device, and receives a signal input from the external device. The control unit 140 can output a notification signal to an external notification device via the communication unit 142 . The control unit 140 can acquire setting information and the like from the host computer via the communication unit 142 and perform various setting processes such as the determination threshold of the determination unit 140 a and the flow rate of the pump 130 .

Gas detector 200 is installed, for example, in a factory that uses a gas to be detected. As an example, the gas detector 200 is installed in a semiconductor manufacturing factory to detect leakage of combustible gas such as semiconductor material gas and hydrogen gas. In this case, the monitored environment from which the gas is sampled is, for example, the location where the gas supply device is installed, the exhaust duct, the work area of the worker, and the like.

Therefore, depending on the environment to be monitored, the fluid 1 (air), which is the sampled gas, may be mixed with the detection target gas or a gas that is not the detection target but is used or generated in the factory. Further, when the detection target gas leaks, the detection target gas is mixed in the fluid 1 . Therefore, the flow sensor 100 can be supplied with a fluid 1 of unknown (arbitrary) composition gas concentration different from the standard composition.

In this embodiment, even if the fluid 1 having an unknown composition gas concentration and an unknown temperature is supplied to the flow sensor 100, the composition gas concentration correction of the fluid 1 and the temperature correction of the fluid 1 are performed as described above. can be obtained with high accuracy. Based on the obtained flow rate, the flow rate control of the fluid 1 using the pump 130 can be performed with high accuracy, so that the flow rate fluctuation of the fluid 1 supplied to the gas sensor 121 can be effectively suppressed. As a result, the output of the gas sensor 121 is suppressed from fluctuating depending on the flow rate value, and the detection accuracy of the detection target gas using the gas sensor 121 can be improved.

(Effect of this embodiment)
The following effects can be obtained in this embodiment.

In the present embodiment, as described above, the flow sensor 100 is arranged in the flow path 10 through which the fluid 1 containing a plurality of composition gases flows, and is arranged in the flow path 10 and is heated according to the flow rate of the fluid 1. The first detection element 21 whose output changes as the pressure changes, and the first detection element 21 are arranged in the flow path 10 in which the velocity of the fluid 1 is suppressed more than the first detection element 21, and are heated to output according to the thermal conductivity of the fluid 1. The composition gas concentration correction of the fluid 1 and the temperature correction of the fluid 1 are performed on the output of the first detection element 21 based on the output of the second detection element 22 and the output of the second detection element 22 . and a flow rate calculation unit 30 that calculates the flow rate of 1.

With the above configuration, of the first sensing element 21 and the second sensing element 22 arranged in the flow channel 10, the velocity of the fluid 1 is suppressed more than the first sensing element 21, which is arranged in the flow channel 10. The second sensing element 22 becomes less sensitive to the flow rate of the fluid 1 and sensitive to the thermal conductivity of the fluid 1 . Therefore, based on the output of the second sensing element 22 whose sensitivity to the flow rate of the fluid 1 is suppressed, the composition gas of the fluid 1 that causes variations in thermal conductivity in the output of the first sensing element 21 in the same flow path 10 Concentration effects and fluid 1 temperature effects can be corrected. As a result, it is possible to calculate the flow rate in which the influence of composition gas concentration and temperature is corrected from the output of the first detection element 21 based on the output of the second detection element 22, so that the composition gas concentration and temperature are unknown. Even if the (optional) gas mixture is supplied to the flow sensor 100, the flow rate of the fluid 1 can be accurately measured.

Moreover, the gas detector 200 of this embodiment includes the flow sensor 100 and the gas sensor 121 . As a result, even when a mixed gas with an unknown (arbitrary) composition gas concentration and temperature is supplied to the flow sensor 100, the flow rate of the fluid 1 can be accurately measured. Even when a mixed gas with an unknown (arbitrary) composition gas concentration and temperature is supplied to the gas detector, the gas (fluid 1) supplied to the gas sensor 121 can be determined based on the accurately measured flow rate of the fluid 1. Since the flow rate of the gas can be grasped with high accuracy, the accuracy of gas detection by the gas sensor 121 can be improved.

Further, in the present embodiment, as described above, the flow rate calculation unit 30 calculates the output resulting from the composition gas concentration and temperature of the fluid 1 included in both the output of the first sensing element 21 and the output of the second sensing element 22. Correction is performed to remove the fluctuation component from the output of the first detection element 21 by the output of the second detection element 22 . As a result, since the first sensing element 21 and the second sensing element 22 are arranged in the same flow path 10 and exposed to the same fluid 1, the output fluctuation component caused by the composition gas concentration and temperature is detected by the first sensing element. 21 and the second detection element 22 , the output fluctuation component caused by the composition gas concentration and temperature can be removed from the output of the first detection element 21 . In this configuration, unlike the configuration in which the gas type is specified from the table and the correction amount corresponding to the gas type is applied, there is no need to obtain the gas type and the correction amount corresponding to the gas type in advance. Appropriate output correction can be performed even when the type and density are unknown (arbitrary).

Further, in the present embodiment, as described above, the flow rate calculation unit 30 subtracts the output of the second sensing element 22 heated by the application of the same voltage as the first sensing element 21 from the output of the first sensing element 21. Correction is performed by Thereby, the heating condition of the second sensing element 22 can be matched with that of the first sensing element 21 . As a result, it is possible to approximate the output fluctuation component caused by the composition gas concentration and temperature in the output of each sensing element. The influence of the composition gas concentration of the fluid 1 and the influence of the temperature of the fluid 1 can be easily corrected only by performing such correction.

In addition, in the present embodiment, as described above, the first sensing element 21 and the second sensing element 22 have the same output characteristics with respect to the constituent gas concentration and temperature of the fluid 1 . As a result, when the first detection element 21 and the second detection element 22 are operated under the same heating conditions, the output fluctuation components caused by the composition gas concentration and temperature contained in the output of each detection element can be matched with high accuracy. can be done. As a result, by subtracting the output of the second sensing element 22 from the output of the first sensing element 21, the output fluctuation component caused by the composition gas concentration and temperature can be removed from the output of the first sensing element 21 with high accuracy.

Further, in the present embodiment, as described above, the resistance values of the first sensing element 21 and the second sensing element 22 change according to heat conduction to the fluid 1 due to contact with the fluid 1 in a heated state. It is a gas heat conduction element 50 that does. Accordingly, flow rate measurement can be performed using the gas heat conduction element 50 having a simple configuration. In other words, unlike the thermal sensing element of the type in which a heater and a temperature sensor are separately provided in the sensing element, the gas heat conducting element 50 changes the resistance value of the heating element itself when the heated heating element comes into contact with the fluid 1. , there is no need to separately provide a heater or temperature sensor in the element. Therefore, the configuration of the flow sensor 100 can be simplified.

[Modification]
It should be noted that the embodiments disclosed this time should be considered as examples and not restrictive in all respects. The scope of the present invention is indicated by the scope of claims rather than the description of the above-described embodiments, and includes all modifications (modifications) within the scope and meaning equivalent to the scope of claims.

For example, in the above embodiment (FIGS. 8 to 11), an example in which the hydrogen gas concentration is changed as the composition gas concentration of the fluid 1 is shown, but the present invention is not limited to this. The composition gas can be any gas. For example, when carbon dioxide gas, whose thermal conductivity is lower than that of air, is mixed with air, the output characteristics of the sensing element with respect to the composition gas concentration shown in FIG. However, since the output characteristics of the outputs V1 and V2 are equivalent, by calculating the corrected output value V=V1-V2, similarly to the graph shown in FIG. 10, the output fluctuation caused by the carbon dioxide gas concentration Components can be removed.

Moreover, although the example which provided the 1st detection element 21 and the 2nd detection element 22 in the one flow path 10 was shown in the said embodiment, this invention is not limited to this. If the same fluid 1 is supplied, the first sensing element 21 and the second sensing element 22 may be provided in separate channels.

Further, in the above-described embodiment, an example is shown in which the inner diameter d2 of the second supply port 14a of the flow path 10 is larger than the inner diameter d1 of the first supply port 13a, but the present invention is not limited to this. In the present invention, the inner diameter d2 of the second supply port 14a may be the same size as the inner diameter d1 of the first supply port 13a.

Further, in the above-described embodiment, an example is shown in which the second detection element 22 is arranged at a position away from the front surface of the second supply port 14a toward the substrate 25, but the present invention is not limited to this. If the flow velocity of the fluid 1 flowing from the second supply port 14a is sufficiently low, the second detection element 22 may be arranged at a position facing the front of the second supply port 14a.

Moreover, in the above-described embodiment, an example in which the flow control member 26 is provided inside the first detection chamber 11 is shown, but the present invention is not limited to this. In the present invention, the flow control member 26 may not be provided.

Further, in the above-described embodiment, an example is shown in which the first sensing element 21 and the second sensing element 22 are sensing elements having substantially the same characteristics, but the present invention is not limited to this. The first sensing element 21 and the second sensing element 22 may be sensing elements having different characteristics. The first sensing element 21 and the second sensing element 22 may have different structures. In that case, a coefficient or a relational expression that relates the output of the first detection element 21 and the output of the second detection element 22 is created, and the correction value is calculated from the output of the second detection element 22 using the created coefficient or relational expression. may be obtained and the obtained correction value may be subtracted from the output of the first sensing element 21 .

Further, in the above-described embodiment, an example is shown in which the same voltage is applied to the first detection element 21 and the second detection element 22 to detect the flow rate, but the present invention is not limited to this. In the present invention, different voltages may be applied to the first sensing element 21 and the second sensing element 22 to detect the flow rate. For example, the second sensing element 22 may be applied with a lower voltage than the first sensing element 21 . In this case also, by creating a coefficient or a relational expression that relates the output of the first detection element 21 and the output of the second detection element 22, the first detection element 21 is corrected from the output of the second detection element 22. You may calculate the correction value for.

Further, in the above-described embodiment, an example in which the first sensing element 21 and the second sensing element 22 are the gas heat conducting elements 50 was shown, but the present invention is not limited to this. The influence of the thermal conductivity of the fluid on the output of the sensing element is not limited to the gas thermal conduction element, but is a type of sensing element that outputs a signal according to the flow rate using heat conduction from the heated sensing element to the fluid 1. This phenomenon is common to Therefore, in the present invention, the first sensing element 21 may be a sensing element having any structure and detection principle as long as the output changes according to the flow rate of the fluid 1 when heated. . Further, the second sensing element 22 may be a sensing element having any structure and detection principle as long as it is a sensing element whose output changes according to the thermal conductivity of the fluid 1 when heated.

Also, the structure of the gas heat conducting element 50 shown in the above embodiment is merely an example, and the present invention is not limited to this. The gas heat conducting element 50 may have any structure. For example, the shape of the resistor pattern 52 is arbitrary. The constituent materials of the insulating support layer 51, the resistor pattern 52, and the inert coating layer 53 are also not particularly limited.

Further, in the above-described embodiment, an example in which the first sensing element 21 and the second sensing element 22 are MEMS sensors is shown, but the present invention is not limited to this. The first sensing element 21 and the second sensing element 22 may be conventional (large) sensing elements that do not use a semiconductor manufacturing process. For example, the gas heat conducting element may have a structure in which a resistor pattern such as platinum wire is formed on an insulating substrate such as ceramics, and the resistor pattern is covered with an inert coating material such as glass.

Moreover, in the above-described embodiment, an example of the gas detector 200 that controls the pump 130 based on the flow rate value acquired by the flow sensor 100 was shown, but the present invention is not limited to this. In the present invention, the gas detector 200 does not have to include the pump 130 . In this case, the output of the gas sensor 121 may be corrected according to the flow rate acquired by the flow sensor 100 . That is, instead of making the flow rate of the fluid 1 supplied to the gas sensor 121 constant, the output of the gas sensor 121 may be corrected by removing the fluctuation component caused by the flow rate.

Reference Signs List 1 fluid 10 flow path 21 first detection element 22 second detection element 30 flow rate calculator 50 gas heat conduction element 100 flow sensor 121 gas sensor 200 gas detector

Claims (6)

a channel through which a fluid containing a plurality of composition gases flows;
a first sensing element that is arranged in the flow path and whose output changes according to the flow rate of the fluid by being heated;
a second sensing element arranged in the flow path in which the velocity of the fluid is lower than that of the first sensing element and whose output changes according to the thermal conductivity of the fluid when heated;
a flow rate calculation unit configured to perform composition gas concentration correction of the fluid and temperature correction of the fluid on the output of the first detection element based on the output of the second detection element, and calculate the flow rate of the fluid; A flow sensor, comprising: The flow rate calculation unit calculates the output fluctuation component caused by the composition gas concentration and temperature of the fluid contained in both the output of the first sensing element and the output of the second sensing element, using the output of the second sensing element. 2. The flow sensor of claim 1, wherein the correction removes from the output of the first sensing element. 3. The flow rate calculation unit according to claim 2, wherein said flow rate calculation unit performs correction by subtracting an output of said second sensing element heated by application of the same voltage as said first sensing element from an output of said first sensing element. flow sensor. 4. The flow sensor according to claim 3, wherein said first sensing element and said second sensing element have equivalent output characteristics with respect to compositional gas concentration and temperature of said fluid. The first sensing element and the second sensing element are gaseous heat conducting elements whose resistance values change according to heat conduction to the fluid due to contact with the fluid in a heated state. 5. The flow sensor according to any one of 4. a flow sensor according to any one of claims 1 to 5;
A gas sensor and a gas detector.

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