JP3502085B2 - Measuring device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a measuring device and a measuring method which are digitally temperature-compensated and are not affected by temperature changes of an object to be measured or a measurement environment. The present invention can be used for the following measurement targets. (1) Measurement of flow rate or flow velocity (2) Measurement of thermal conductivity and specific heat of fluid. (3) Identification of fluids (4) Measurement of mixing ratio of multiple fluids (5) Measurement of concentration of substances contained in fluid (eg measurement of humidity)

Furthermore, it is also possible to evaluate the difference in the thermal conductivity and the specific heat of the substance to be measured (gas, liquid or solid).

SUMMARY OF THE INVENTION In the present invention, a thin film material having high thermal conductivity such as a diamond thin film is heated in a pulsed manner, and the response characteristic at this time is measured as a temperature change of the thin film, and the response is measured. The basic configuration is to evaluate the thermal influence of the thin film material from the substance to be measured in contact with the thin film material from the characteristics.

The sensor for measuring the thermal influence of the substance to be measured having the above structure and the sensor for measuring the temperature of the substance to be measured or the temperature of the measuring environment are used.
Basically, by processing the output from one sensor according to a predetermined relational expression, an output that does not depend on the temperature of the substance to be measured or the temperature of the measurement environment is obtained.

As the output, for example, an output based on the flow rate of the fluid flowing in contact with the thin film material can be mentioned.
That is, in this case, it is possible to obtain a value corresponding to the flow rate value that does not depend on the temperature of the fluid or the temperature of the measurement environment. here,
Although one of the basic configurations of the present invention has been outlined, the present invention has various forms and embodiments as will be described later.

[0006]

2. Description of the Related Art As a device for measuring a flow rate (generally called a flow sensor), a device using a thermistor is known. This utilizes the fact that the temperature of the thermistor portion drops due to the heat being taken away by the fluid. Generally, when the thermistor portion is in contact with a fluid, the amount of heat taken from the thermistor portion depends on the flow rate (or flow velocity). Therefore, there is a certain correlation between the output from the thermistor and the flow rate. Utilizing this fact, the flow rate can be calculated from the output of the thermistor.

The flow rate is the product of the cross-sectional area of the fluid and the flow velocity,
For example, if a fluid having a flow velocity v flows in a circular pipe having an inner diameter r, vπr ² is the flow rate. Therefore, if the cross-sectional area of the fluid is known, the flow rate and the flow velocity can be obtained at the same time.

The thermistor generally refers to a semiconductor having a large negative temperature coefficient. However, the thermistor is essentially a thermosensitive resistor (Thermally Sensitive Resistor).
or) and is not particularly limited by the positive or negative of the temperature coefficient or the material. Therefore, a metal such as platinum having a positive temperature coefficient may be called a thermistor.

Elements such as a thermistor that use a material whose resistance changes with temperature are collectively referred to as a resistance temperature detector or a temperature sensing element, or a temperature sensing element or a resistance thermometer. Further, a material whose resistance changes with temperature can also be referred to as a material having a thermistor function. In the following, a material whose resistance changes with temperature is called a resistance temperature detector.

As a method for measuring the flow rate, in addition to the structure using the thermistor as described above, a resistance heating element which is heated by Joule heat is exposed to a fluid, and depending on the flow rate,
There is also a method that utilizes the fact that heat is taken from the resistance heating element. In this method, the flow rate can be calculated by measuring the current flowing through the resistance heating element.

Further, the heat generated by the heating element in contact with the fluid is absorbed by the fluid, and the amount of heat carried by the fluid is measured by a resistance temperature detector (for example, a platinum sensor) provided separately,
There is also a method of calculating the flow rate.

In order to obtain high sensitivity in these methods, it is effective to increase the amount of heat taken by the fluid. Further, in order to increase the response speed, it is necessary to minimize the heat capacity of the resistance temperature detector part.

The flow rate measuring device (flow sensor) having the above-mentioned structure has a problem that the range of measurable flow rate is narrow. That is, there is a problem that the dynamic range is narrow. Specifically, 20 sccm to 300 sc
There is a problem that accurate flow rate measurement can be performed only in the range of cm, 200 sccm to 2000 sccm.

It is considered that these problems are mainly due to the following reasons. (1) Since the resistance temperature detector is placed in an extremely thermally unstable state, the linearity of the response to heat is poor, and it cannot follow a wide range of thermal changes. (2) With respect to (1) above, the heating method is particularly difficult, and effective heating cannot be performed over a wide flow rate range. (3) If the heat capacity of the resistance temperature detector is reduced to increase the response speed, a large amount of heat cannot be handled.

The cause of the above (1) is to adopt a structure in which the fluid is effectively deprived of the amount of heat from the resistance temperature detector over a wide flow rate range, and at the same time, the amount of heat is effectively supplied to the resistance temperature detector. Because it is difficult.

Further, since the resistance temperature detector sensitively detects not only the flow rate but also the temperature change of the environment (for example, the temperature change of the fluid), there is a problem in use in an environment where the temperature changes. . Although various methods for solving this problem have been proposed, in the actual use, the present situation is that the measurement of the flow rate greatly varies depending on the measurement environment or the temperature of the fluid.

[Background of the Invention] The present inventors manufactured a flow rate measuring device as shown in FIG. In FIG. 1, 13 is 5 μm vapor-phase synthesized by using a magnetic field microwave CVD method.
It is a thick polycrystalline diamond thin film. Reference numeral 12 is a 0.1-μm-thick platinum resistance temperature detector formed by a sputtering method. No. 11 is the same as that formed by the sputtering method.
It is a platinum heating resistor having a thickness of 1 μm. 10 and 15 are those electrodes, and 17 is a gold wire for bonding. Reference numeral 18 denotes a Teflon (R) substrate which holds the diamond thin film 13. The resistances of the resistance temperature detector 12 and the heating element 11 are different from each other. The resistance of the resistance temperature detector 12 is about 1 KΩ, and the resistance of the heating element 11 is about 100Ω.

In the flow rate measuring device shown in FIG. 1, the diamond thin film 13 is held on the Teflon (R) substrate 18, and is held while being thermally insulated from other than the fluid. By thermally insulating and holding the thin film material in this way, a structure in which heat is not lost to the thin film material other than the fluid can be obtained, and the thermal interaction between the fluid and the thin film material can be accurately evaluated. can do.

Further, the fluid 19 has a structure of flowing in contact with the surface opposite to the surface on which the resistance temperature detector 12 and the heating element 11 are formed. Specifically, the device shown in FIG. 1 is fitted in a part of a plastic pipe through which a fluid flows, and one side of the diamond thin film (the side on which the circuit is formed) faces the outside of the pipe. And the other side faces the inside of the pipe. The Teflon (R) substrate 18 is in contact with the pipe, and the diamond thin film is not in direct contact with the pipe.

FIG. 2 shows an actual measurement system. In FIG. 2, reference numeral 22 is a flow rate measuring device whose outline is shown in FIG. In the system shown in FIG. 2, the amplifier 21
A pulsed voltage is applied to the heating element 11 and the heating element 1
1 performs pulsed heating on the diamond thin film 13 (see FIG. 1). This pulsed heating is performed for an extremely short time, for example, 0.18 seconds. Due to this pulse-shaped heating, the diamond thin film 13 is heated in an extremely short time.

The transient response characteristic of the diamond thin film 13 subjected to the pulsed heating by the heating element 11 is as follows.
Is detected as a temperature change of the diamond thin film 13. A constant bias voltage is applied to the resistance temperature detector 12, and the temperature change of the diamond thin film 13 is output as a change in the current value flowing through the resistance temperature detector.

The output from the resistance temperature detector 12 is converted into a voltage signal by the I / V amplifier 24, and further converted into a digital signal in the A / D converter 25. Further, the output from the A / D converter 25 is processed by the CPU 28 by a predetermined calculation method, and the D / A converter 27 outputs a value corresponding to the measured value. The amplifier 21 and the A / D converter 25 are controlled by the timing pulse generator 23. The predetermined calculation method will be described in detail in the section [Basic operation method of sensor] described later.

The nitrogen gas flow rate was measured using the flow rate measuring device shown in FIG. 1 and the system shown in FIG. 2 using the same, and the following experimental facts were obtained. (1) The response characteristics of the diamond thin film to instantaneous heating (pulse-shaped heating) depend on the flow rate of the fluid flowing in contact with the diamond thin film. Then, by quantitatively evaluating this response characteristic, the flow rate (or flow velocity)
Can be measured. (2) However, the response characteristic of (1) above also changes depending on the temperature of the fluid. That is, even if the flow rate of the fluid is the same,
When the temperature of the fluid or the temperature of the measurement environment is different, the corresponding response characteristics are also different. This means that it is difficult to distinguish the change in the flow rate from the change in the temperature of the fluid or the measurement environment.

FIG. 3 is a photograph showing the experimental fact of (1) above.
Shown in. FIG. 3 shows the output from the I / V amplifier 24 displayed on an oscilloscope. In FIG. 3, the vertical axis corresponds to the temperature of the diamond thin film, and the horizontal axis represents time. FIG. 3 shows that the diamond thin film is rapidly heated and then rapidly cooled by the nitrogen gas fluid. It can be said that this state shows the transient response characteristic of the diamond thin film with respect to the pulsed heating. The heating time was 0.18 seconds and the gas temperature was constant (room temperature). Further, the bias voltage to the resistance temperature detector 12 is V _CC = 0.3V.

The two curves shown in FIG. 3 show response characteristics corresponding to different flow rates. This means that the response characteristics of the diamond thin film to pulsed heating differ depending on the flow rate. The larger waveform shown in FIG. 3 is for a smaller flow rate, and the smaller waveform is for a larger flow rate.

This is understood as the following mechanism. That is, when the flow rate is low, the amount of heat taken from the diamond thin film is small, so that the diamond thin film is heated rapidly and greatly during the pulse heating, and is slowly cooled. Therefore, the response waveform becomes large. On the other hand, when the flow rate is high, the amount of heat taken from the diamond thin film also increases, so the diamond thin film is not heated to a too high temperature, and is rapidly cooled after the heating is completed. Therefore, the response waveform becomes small.

The calculation in the CPU 28 is performed by calculating the area of the waveform as shown in FIG. 3 within a predetermined time. Specifically, it is basically the same as the operation of the sensor described in the examples below.

FIG. 4 shows the relationship between the nitrogen gas flow rate (Sl, liter / minute) obtained by this method and having a constant temperature, and its measurement tolerance. The tolerance indicates the reliability of the measurement data, and is a parameter indicating the deviation of the measurement value from the accurate value. Further, in the flow rate measurement shown in FIG. 4, the Reynolds number of the fluid in contact with the flow rate measuring device was measured to be smaller than 2000. This is to suppress the increase in tolerance due to the influence of turbulence.

From FIG. 4, when the temperature of the fluid is constant,
From 2 (liter / min) to 42 (liter / min),
If you can measure within 3% (± 1.5%) and allow a tolerance of 50%, 0.05 (liter / min) (5
It is understood that the measurement can be performed from 0 sccm), and the flow rate can be measured over 3 digits or more.

Next, the experimental facts regarding the inability to distinguish between the temperature change of the fluid and the change of the flow rate of the fluid shown in (2) above will be shown below.

FIG. 5A shows that the sensor portion 22 (having the structure shown in FIG. 1) shown in FIG. 2 is brought into a temperature-controlled room, and the temperature of the fluid (air) is 10 de when the flow rate is 0.
This is the output from the D / A converter 27 when the value is changed from g to 35 deg.

In this case, even if the flow rate does not change (in this case, by changing the temperature (in this case, it can be understood as the temperature of the fluid), as shown by the curve shown in FIG. 5A. The output from the measurement system shown in FIG. 2 changes when the flow rate is zero.

From the experimental data of FIG. 5, the following can be concluded. "When a measurement system such as that shown in FIG. 2 is used, if the temperature and flow rate of the fluid change at the same time, it cannot be determined in principle which one has changed."

[0034]

DISCLOSURE OF THE INVENTION The present invention uses the temperature change of a fluid or a measurement environment as shown by A in FIG.
An object of the present invention is to provide a configuration in which the flow rate measurement value is prevented from changing and an output that depends only on the flow rate (or flow velocity) is obtained.

Furthermore, it is an object of the present invention to provide a structure for obtaining a measurement value independent of the temperature of the non-measuring substance or the measuring environment in the measuring device for evaluating the thermal interaction between the thin film material and the non-measuring substance. To do.

[Basic Principle of the Invention] As described above, when the sensor shown in FIG. 1 is brought into contact with a fluid using the system shown in FIG. 2, the output from the D / A converter is It depends on two variables, the temperature of the fluid and the measurement environment.

Now consider two sensors. These sensors are assumed to have the structure shown in FIG. The operating method is also based on measuring the response characteristics of the diamond thin film to pulse heating as described above. In this case, the output from the sensor is
It corresponds to the area of the response waveform of.

First, as one sensor, it is considered to use a temperature measuring sensor that detects the temperature of the fluid without contacting it. That is, it is assumed that the temperature measuring sensor is in contact with the fluid but the flow rate of the fluid in contact with the temperature measuring sensor is zero. in this case,
The output from the temperature measurement sensor does not depend on the flow rate but depends on the temperature of the fluid and / or the temperature of the measurement environment.

As another sensor, in order to obtain an output depending on the flow rate of the fluid and the temperature of the fluid and / or the measurement environment (hereinafter referred to as the fluid temperature), a sensor which is in direct contact with the fluid flow. Think of things. This sensor is called a fluid measurement sensor.

Here, it is assumed that the two sensors have the same electrical and thermal characteristics. In this case, the output from the temperature measuring sensor depends on the temperature of the fluid. On the other hand, the output from the fluid measurement sensor depends on the flow rate and the temperature of the fluid. Therefore, it is understood that the difference between the outputs from these two sensors corresponds to the flow rate.

These things can be considered as follows. (1) The output from the fluid measurement sensor can be considered to be equal to the sum of the output that depends on the temperature and the output that depends on the flow rate. (2) The temperature dependent output of (1) is equal to the output from the temperature sensor. (3) Therefore, it can be considered that the difference between the output of the fluid measurement sensor and the output of the temperature measurement sensor does not depend on the temperature but corresponds to the flow rate.

By thus preparing the temperature measuring sensor and the fluid measuring sensor having the same characteristics and determining the difference between the outputs of the two sensors, the flow rate can be measured accurately regardless of the temperature value of the fluid or the measuring environment. Can be done.

The above-mentioned basic operation principle will be described using measured data. FIG. 6 shows the relationship between the output of the temperature measurement sensor (REFERENCE: horizontal axis (arbitrary value)) and the output of the fluid measurement sensor (SENSOR OUTPUT: vertical axis (arbitrary value)).

Here, the temperature measuring sensor and the fluid measuring sensor have the same structure. Specifically, it has a configuration as shown in FIG.

As shown by 802 in FIG. 8, the temperature measuring sensor is arranged so as not to be directly exposed to the flow 90 of the fluid flowing in the pipe 91, but to be in contact with the fluid flowing into the space 98 from the slit 95. There is. When such a configuration is adopted, the fluid in contact with the temperature measuring sensor 802 can be regarded as having a flow rate of 0, so the temperature measuring sensor 80
2 does not detect the flow rate. That is, since the fluid with which the temperature measurement sensor 802 is in contact can be regarded as having almost no flow, it can be considered that the output of the temperature measurement sensor 802 is hardly affected by the flow rate.

The fluid measuring sensor is arranged so as to be in direct contact with the fluid flow 90, as indicated by 803 in FIG. 8, and detects the flow rate. However, the temperature of the fluid is also detected at the same time.

FIG. 6 shows that the apparatus shown in FIG. 8 is arranged in a temperature-controlled room, the temperature inside the temperature-controlled room is changed from −20 ° C. to 60 ° C. at a flow rate of 0, and the temperature at that time is changed. It shows the relationship between the output (horizontal axis) of the measurement sensor (REFERENCE sensor) and the output (vertical axis) of the fluid measurement sensor (SENSOR). The fluid here is air. Further, the output of the sensor referred to here is one which has been arithmetically processed by the method described later.

When the flow rate is 0, the fluid measuring sensor functions as a temperature measuring sensor. Therefore, if the characteristics of the two sensors are the same, the plot point shown in FIG. 6 is a linear line with a slope of 1 and an intercept of 0. However, in reality, the straight line connecting the plot points shown in FIG. 6 has a slope slightly smaller than 1 and the intercept is not 0 because of variations in the characteristics of the sensors and offset voltage of the output from the analog circuit.

The graph shown in FIG. 6 shows the case where the flow rate is 0, but consider the case where there is a flow. In this case, since the output of the temperature measurement sensor (REFERENCE) does not depend on the flow of the fluid, the value on the horizontal axis of FIG. 6 does not change. On the other hand, the output from the fluid measurement sensor is the sum of the value corresponding to the temperature of the fluid and the value corresponding to the flow rate, so the value on the vertical axis changes by the value corresponding to the flow rate. Further, in this case, the flow rate can be regarded as not changing with temperature. Therefore, each plot point in FIG. 6 moves in the vertical axis direction by a predetermined value corresponding to the flow rate.

As a result, when there is a flow, the straight line shown in FIG. 6 moves substantially parallel to the vertical axis direction. In this case, the amount of movement of this straight line corresponds to the flow rate.

As shown in FIG. 3, as the flow rate increases, the response waveform decreases. Therefore, the output from the sensor is small. Therefore, the parallel movement of the straight line shown in FIG. 6 when there is a flow rate is in the minus direction of the vertical axis of FIG.

As described above, when the temperature measuring sensor and the fluid measuring sensor have the same characteristics, the relationship between the output of the temperature measuring sensor and the output of the fluid measuring sensor is expressed by a linear function. That is, the output R of the temperature measurement sensor
The relationship between (corresponding to the horizontal axis in FIG. 6) and the output S of the fluid measurement sensor (corresponding to the vertical axis in FIG. 6) is represented by the following [Formula 1].

[0053]

[Equation 1]

In the above [Formula 1], A and B are constants. Here, if the temperature measurement sensor and the fluid measurement sensor have the same characteristics, A = 1. Further, if the temperature measurement sensor and the fluid measurement sensor have the same characteristics and the offset voltage of the circuit is 0, B = 0. Further, F is a value corresponding to the flow rate that is not affected by the measurement environment and the temperature of the fluid.

Since the data shown in FIG. 6 is the case where there is no flow (flow rate = 0), naturally F = 0. Note that in the data shown in FIG. 6, A = A due to problems such as variations in the characteristics of the sensors and offset voltage of the circuit.
1 and B = 0 are not established.

What is required in the flow rate measurement is that a value corresponding to the flow rate can be obtained without depending on the temperature. Also, in the formula shown in the above [Formula 1], A and B can be obtained at the stage of calibration performed in advance. For example, the values of A and B can be easily obtained from FIG.

Therefore, if the output R from the temperature measuring sensor and the output S from the fluid measuring sensor are known, the value F corresponding to the flow rate which does not depend on the temperature of the fluid is given by the above [Formula 1].
You will need more.

[Formula 1] is satisfied when the temperature measurement sensor and the fluid measurement sensor have almost the same characteristics or when they have substantially the same characteristics. Generally, the output R from the temperature measurement sensor is And the output S from the fluid measurement sensor are expressed by the relationship represented by the following [Equation 2].

[0059]

[Equation 2]

In the above [Formula 2], f (R) is a function of R. The shape of this function is determined by the difference in characteristics between the temperature measurement sensor and the fluid measurement sensor. If both sensors have substantially the same characteristics, f (R) = AR + B (A and B are constants), which is in agreement with [Equation 1].

By using this [Equation 2], it is possible to obtain the value of the flow rate or flow velocity which does not depend on the temperature of the fluid or the measurement environment even when the characteristics of the temperature measurement sensor and the fluid measurement sensor are different. .

The form of the function f (R) can be known at the stage of calibration performed in advance. That is, by measuring the data as shown in FIG. 6 at a predetermined flow rate, this function f (R)
You can know the shape of.

[0063]

The main constitution of the present invention will be described below. In the following, the case where a diamond thin film is used as the thin film material used for the sensor portion is mainly shown, but as other materials, single crystal silicon, polycrystalline silicon, silicon carbide, aluminum nitride, nitride nitride, Aluminum nitride and other materials with high thermal conductivity (at least single crystal silicon (148 Wm
⁻¹ K ⁻¹ , a material having a thermal conductivity of 300 K) or more) can be used. Of course, the most remarkable effect can be obtained when a diamond thin film is used.

As the substance to be measured, a fluid can be mentioned first, but it may be a solid material. For example, when the substance to be measured is a fluid, the flow rate and flow velocity of the fluid can be measured and the type of the fluid can be determined. This utilizes that the way the temperature of the thin film material changes with respect to the heating of the thin film material (in other words, the response characteristic) depends on the flow rate and the type of the fluid flowing in contact with the thin film material. Further, it is also possible to detect impurities in a fluid by utilizing the phenomenon that the fluid has different thermal conductivity and specific heat due to the inclusion of impurities in the fluid.

When the substance to be measured is a solid, the way the temperature of the thin film material changes with respect to the heating of the thin film material varies depending on the difference in the thermal conductivity and the specific heat of the solid and the difference in the heat capacity. That is, the response characteristics are different. Utilizing this, it is possible to determine the type of solid material and measure the difference in volume.

The present invention relates to the "first response characteristic determined by the main variables α and β and the second response characteristic determined by the variable α".
And the response characteristic of (1) to obtain an output corresponding to the variable β "as one of the main configurations.

Here, an example can be given in which α is the temperature of the fluid and β is the flow rate of the fluid. Further, there can be given an example in which α is the temperature of the fluid, and β is a variable corresponding to the type of fluid or the difference in its physical properties.

When β is a variable corresponding to the type and physical properties of the fluid, the difference in the type and physical properties of the fluid can be known from the value of β. This can be used for gas detection sensors.

The response characteristic means a response characteristic to a pulsed heating of a thin film material having high thermal conductivity. The main variables α and β mean that the main factors are α and β.

[0070] In more generalized the above configuration, the "n is a natural number represented by 1, 2, 3, variable alpha _1, alpha
₂ ... A first response characteristic determined by α _{n + 1} and a second response characteristic determined by variables α ₁ , α ₂ ... α _n
And obtain the output corresponding to the variable α _{n + 1} ”.

For example, in the measurement of the flow rate, when the flow rate and the temperature of the fluid are problems, that is, when these two factors are considered as the main factors, the flow rate is the variable α ₁ and the fluid temperature is the variable α _2. , The above-mentioned configuration has the above-mentioned “first response characteristic determined by the main variables α and β and the above-mentioned variable α”.
The second response characteristic determined by the above is compared to obtain an output corresponding to the variable β ”.

However, the response characteristic as shown in FIG.
Besides the flow rate and the temperature of the fluid, factors such as the type of fluid and the concentration and density of impurities also contribute. Therefore, in the above configuration, these factors are represented as variables α ₁ , α _2, ... α _{n + 1} ,
The feature is that the output for one factor α _{n + 1} among these factors is obtained.

For example, when the configuration shown in FIG. 9 which will be described in detail in Example 2 is adopted, the sensor indicated by 802 is the temperature of the fluid corresponding to the variable α ₁ and the fluid corresponding to the variables α _{2 to} α _n. The response characteristics depend on various physical property values of. Here, various physical properties are variables indicating the thermal properties of a substance such as thermal conductivity of fluid, kinematic viscosity of fluid, density of fluid, specific heat of fluid, and the like.

On the other hand, the sensor indicated by 803 exhibits a response characteristic that depends on the variable α _{n + 1} corresponding to the flow rate of the fluid flowing through the pipe 91 in addition to the variables α _{1 to} α _n .

Here, each response characteristic is quantitatively evaluated, and the above two response characteristics are compared with each other, whereby the output corresponding to the variable α _{n + 1} corresponding to the flow rate can be obtained. This output indicates the flow rate and is not affected by the factors indicated by the variables α _{1 to} α _n .

One of the main constitutions of the present invention is that a thin film material having a high thermal conductivity, for example, a diamond thin film, is subjected to pulsed heating, and the response of the thin film material to the pulsed heating by the means. A plurality of sensors having means for measuring characteristics, at least one of these sensors is a sensor for measuring the temperature of a fluid, and at least another one is a fluid measurement sensor arranged in contact with the fluid. And a means for processing the output from the temperature measuring sensor and the output from the fluid measuring sensor based on a predetermined functional relationship.

In the above structure, the temperature measuring sensor and the fluid measuring sensor basically have the same structure, which simplifies the structure and simplifies the operation. The temperature measurement sensor is for obtaining an output that depends on the temperature of the fluid or the measurement environment. For example, when a system as shown in FIG. 2 is exposed to a fluid that does not flow, the output is as shown in FIG.
As shown in (A), the output corresponds to the temperature of the fluid.
In this case, the sensor indicated by 22 in FIG. 2 functions as a temperature measuring sensor.

When the sensor shown in FIG. 1 is used as a temperature measuring sensor, it should be prevented from being directly exposed to the fluid flow 90, as indicated by 802 in FIG.

The fluid measurement sensor must be configured to be directly exposed to the fluid flow 90, as shown at 803 in FIG. With such a configuration, an output depending on the flow rate of the fluid can be obtained. At the same time, however, this output also depends on the temperature of the fluid and the environment.

The predetermined functional relationship in the above configuration is the relationship between the output R from the temperature measuring sensor and the output S from the fluid measuring sensor as shown in [Equation 1] or [Equation 2]. By processing the outputs from both sensors according to this relational expression, it is possible to obtain a flow rate measurement value that does not depend on the temperature of the fluid or the measurement environment.

The output from the sensor referred to here is
It is obtained by performing the basic operation described later. To put it simply, the output is a value obtained by integrating the areas of the waveforms showing the response characteristics of the thin film material as shown in FIG. (See [Basic sensor operation method] below.)

In the above structure, a resistance heating element provided in direct contact with the thin film material is generally used as a means for heating the thin film material in a pulsed manner. However, it is also possible to indirectly heat the thin film material, to apply Joule heating by energizing the thin film material itself, or to heat the thin film material with light, laser light, or microwave.

The response characteristic of the thin film material is measured by measuring the temperature of the thin film material. For example, in FIG.
In the configuration as shown in FIG. 2, the response characteristic of the diamond thin film 13 to the pulsed heating from the heating element 11 is measured by the resistance temperature detector 12 as a temperature change of the diamond thin film 13. As a result of this measurement, the output from the resistance temperature detector 12 changes as shown in FIG. Then, this output change shows the response characteristic to the pulse-like heating of the diamond thin film 13.

As a means for measuring the temperature of the thin film material, it is general to use a resistance temperature detector (for example, platinum) provided in contact with the thin film material, but a semiconductor is used as the thin film, A layer having a function as a resistance temperature detector may be formed in or on the surface of the thin film material by forming a semiconductor layer having one conductivity type on the surface by ion implantation or the like. Further, the thin film material itself can be used as a resistance temperature detector. For example, when a diamond thin film added with B (boron) and imparted with P-type during vapor phase synthesis is used as the thin film material, the thin film itself can be used as a resistance temperature detector. A method of detecting heat rays emitted from the thin film material (for example, thermography) can also be used as a means for measuring the temperature of the thin film material.

It is important that the means for measuring the temperature of the thin film material is to detect only the temperature of the thin film material. For example, consider a structure in which a diamond thin film is used as the thin film material, the diamond thin film is arranged on a silicon substrate, and a resistance temperature detector is provided between the diamond thin film and the silicon substrate. In this case, the resistance temperature detector simultaneously measures the temperatures of both the diamond thin film and the silicon substrate. The thermal conductivity of the silicon substrate is 148 (Wm ^-1 K ^-1 , 300K), and the thermal conductivity of the diamond thin film is about 1000 (Wm ^-1 K ^-1 , 300K).
K) or higher, the value is considerably smaller. Therefore, in this case, the response characteristic to the pulsed heating detected by the resistance temperature detector becomes dull, and good characteristic cannot be obtained.

When a resistance heating element provided directly in contact with the thin film material is used as a means for heating the thin film material and a resistance temperature detector is used as a means for measuring the temperature of the thin film material, this heat generation is performed. It is necessary that the body and the resistance temperature detector are thermally coupled only through the thin film material.

This is irrespective of the response of the thin film material.
This is because if the resistance temperature detector detects the amount of heat from the heating element, the measured response characteristic includes elements other than the response characteristic of the thin film material.

Further, it is necessary that the thin film material is kept in a thermally floated state without being brought into contact with the fluid other than the fluid to be measured as much as possible. This is also to prevent the response characteristics of materials other than the thin film material from affecting the measurement results during pulsed heating. For example, when a diamond thin film is used as the thin film material and a fluid to be measured is a constant temperature, the higher the thermal insulation property when holding the diamond thin film, the higher the response characteristics of the diamond thin film to pulse heating. Has been confirmed to be dependent on the flow rate of the fluid.

That is, when measuring the flow rate, the amount of heat escaping from the thin film material is (1) escaping from the surface of the thin film material to the fluid. (2) A material that escapes to the substrate that holds the thin film material. (3) From a lead connected to a heating element or a resistance temperature detector provided in contact with the thin film material. There are three forms, but among them, it is important to minimize the influence of the factors (2) and (3).

Further, the temperature of the substance to be measured and / or the measurement environment means the following three cases. (1) When both the substance to be measured and the temperature of the measurement environment are problems (2) When the temperature of the substance to be measured is a problem (3) When the temperature of the measurement environment is a problem

Generally, since the temperature of the substance to be measured also changes as the temperature of the measurement environment changes, (1)
It is considered that it is normal to perform measurement in the state of.

However, the temperature of the measurement environment may mean the temperature of the fluid as it is. In this case, the temperature measurement sensor does not need to measure the temperature of the fluid, and the temperature of the measurement environment may be measured. That is, in this case, 8 in FIG.
It is not necessary to maintain the state as indicated by 02, and the temperature measurement sensor may be configured to measure the temperature of the atmosphere outside the pipe 91.

One of the main constitutions of the present invention comprises a plurality of thin film materials, means for performing pulsed heating on the thin film material, and means for measuring the response characteristics of the thin film material according to the pulsed heating. Of the plurality of sensors, at least one of which is a temperature measurement sensor having a function of measuring the temperature of a reference fluid and / or the temperature of a measurement environment, wherein:
At least another one is a fluid measurement sensor arranged so as to be in contact with the fluid to be measured, and means for processing the output from the temperature measurement sensor and the output from the fluid measurement sensor based on a predetermined functional relationship. It is characterized by having.

The above configuration can be used for the measurements listed below. Identification of the type of fluid to be measured, detection of specific fluid, measurement and identification of impurities in fluid (for example, measurement of humidity in air), measurement of mixing ratio of different fluids, measurement of fluid density, heat transfer of fluid Measurement of rate, measurement of specific heat of fluid. Of course, it can also be used for measuring the flow rate.

In the above structure, it is necessary that the flow rate of the reference fluid in contact with each sensor, and further the flow rate of the fluid to be measured, is always constant, preferably zero. This is to prevent the influence of the flow of fluid from entering the measured value. Further, the reference fluid and the fluid to be measured need to be kept at the same temperature.

In the following, a case of identifying the type of fluid will be described. When the type of fluid is different, the physical properties such as thermal conductivity and specific heat are naturally different. Therefore, when the measurement is performed by using the measurement system as shown in FIG. 2 in the state of a specific flow rate (for example, the flow rate is 0), the response characteristics of the thin film material as shown in FIG. 3 are naturally different.

What contributes to this difference in response characteristics is the physical property value related to the thermal properties of the fluid. For example, thermal conductivity, specific heat, density, etc.

Further, the difference in output as shown in FIG. 3 is influenced by the temperature of the fluid to be measured and the temperature of the measurement environment, and it is necessary to eliminate this influence. Therefore, using a temperature measurement sensor that measures the temperature of the reference fluid and / or the temperature of the measurement environment as in the above configuration,
The output R from the temperature measurement sensor in contact with the reference fluid and the output S from the fluid measurement sensor in contact with the fluid to be measured are processed according to a predetermined relational expression shown in [Equation 1] or [Equation 2]. As a result, the output F corresponding to the physical properties of the fluid to be measured can be obtained without depending on the temperature of the fluid or the measurement environment.

In this case, the value F calculated by the calculation based on this predetermined relationship is different depending on the kind of the fluid to be measured. Therefore, the type of the fluid to be measured can be identified from the value of F.

The measurement principle described above is the same even when the objects to be measured are listed above. For example, when the object to be measured is the impurity concentration in the fluid, the value of F differs depending on the impurity concentration in the fluid to be measured, and the impurity concentration can be known from this. Further, when the densities of the fluids are different, the values of F are also different due to the different densities, and by utilizing this fact, the density of the fluids can be measured.

In the above structure, the reference fluid is necessary to give a relative meaning to the measured value of the fluid to be measured. For example, consider the case where nitrogen is used as a reference fluid when identifying the type of fluid. In this case, it is determined from the output whether or not the measured fluid has different physical properties than the nitrogen fluid.

[0102]

EXAMPLES Example 1 In this example, a method for manufacturing the sensor shown in FIG. 1 will be described. The sensor shown in FIG. 1 has a heating element 11 made of a platinum (Pt) thin film on the surface of a polycrystalline diamond thin film 13 having a size of 4 mm × 4 mm and a thickness of 5 μm, and a resistor 12 functioning as a resistance temperature detector, Furthermore, those electrodes 10 and 15 are provided.

The manufacturing process of the sensor shown in FIG. 1 will be described below. First, a silicon substrate having a diameter of 4 inches is prepared. Then, the surface of the surface on which the silicon substrate is formed is scratched with diamond powder. A diamond thin film having a thickness of 5 μm is vapor-phase synthesized on the diamond thin film by a magnetic field microwave CVD method. In this magnetic field microwave CVD method, a strong magnetic field and a microwave of 2.45 GHz are used to form high-density plasma and perform gas phase synthesis.

The film forming conditions are shown below. Substrate temperature 800 ° C. Reaction pressure 0.25 Torr Microwave power 4 KW Reaction gas CH ₃ OH: H ₂ = 1: 4 Film formation time 10 hours Film thickness 5 μm The silicon substrate was placed at a position of magnetic field strength of 875 gauss. The diamond thin film obtained under the above film forming conditions was a polycrystalline diamond thin film, and had a structure in which crystals were grown vertically from the substrate.

The film forming method is not limited to the above method, and other vapor phase synthesis methods may be used. Alternatively, natural diamond or high-pressure synthesized diamond may be used.
Further, the diamond thin film may be doped with impurities to control the thermal characteristics and electrical characteristics. The crystal structure is not limited to polycrystal, and a single crystal diamond thin film may be used.

As the diamond thin film, a thin film having a small amount of impurities and a high thermal conductivity as much as possible is preferable. Further, the thickness of the diamond thin film is preferably as thin as mechanical strength allows, in consideration of productivity.

The diamond thin film formed on the silicon substrate can be obtained as a single diamond thin film by peeling it off from the silicon substrate. This step is easily performed by mechanically peeling or melting the silicon substrate with hydrofluoric acid or the like.

The diamond thin film thus obtained is cut into 4 mm square. Then, by sputtering, a platinum thin film of 800 to 1 is formed on the diamond thin film.
Form a film with a thickness of 000Å. For sputtering, a platinum target was used, and the air as the sputtering gas was 1K.
It is accelerated to about eV. The sheet resistance of the platinum thin film thus formed on the diamond thin film is about 100Ω / □.

Then, by patterning, as shown in FIG. 1, the heating element 11 and the resistance temperature detector 12 are formed on the diamond thin film 13. Specifically, the area of the heating element 11 is adjusted so that the resistance of the heating element 11 is about 100Ω and the resistance of the resistance temperature detector 12 is about 1 KΩ.
1 and the resistance temperature detector 12 are made separately. This making is
It may be performed by changing the film thicknesses of the heating element 11 and the resistance temperature detector 12. Then, a diamond thin film is held on a Teflon (R) substrate 18, electrodes 10 and 15 are further formed, and bonding is performed with a gold wire 17 of 10 μmφ. Thus, the sensor as shown in FIG. 1 is completed.

Since the resistance temperature detector 12 has a function of changing its resistance sensitively to temperature, it can be said to be a layer having a thermistor function.

Further, even when the number of resistance temperature detectors, the number of heat generating elements, and the arrangement method thereof are changed, the above manufacturing process may be basically used. Further, the size of the diamond thin film may be further reduced. In this case, reduction in power consumption and improvement in sensitivity can be expected.

The thermistor parameter of the resistance temperature detector 12 made of the platinum thin film shown in FIG. 1 was about 200 ppm. This corresponds to a resistance change of 0.02% with respect to a temperature change of 1 degree. In general, since the thermistor parameter of the resistance temperature detector using platinum is 100 to 3,000 ppm, if the manufacturing conditions are optimized, a higher sensitivity resistance temperature detector can be obtained.

In the structure shown in FIG. 1, the heat capacity of the resistance temperature detector 12 made of a platinum thin film is one-hundredth or less of the heat capacity of the diamond thin film 13. Therefore, comparing with the heat capacity of diamond thin film,
The heat capacity of the resistance temperature detector can be almost ignored, and the resistance temperature detector 12 can detect the temperature change of the diamond thin film at extremely high speed and with high sensitivity. If the heat capacity of the resistance temperature detector is not negligible compared to the heat capacity of the diamond thin film, the temperature change of the resistance temperature detector itself has an influence, and the temperature change of the diamond thin film cannot be accurately detected. Specifically, the heat capacity of the diamond thin film needs to be 100 times or more that of the resistance temperature detector.

[Embodiment 2] FIG. 7 shows an outline of the configuration of the present embodiment.
~ Shown in FIG. In this embodiment, an example is shown in which the flow rate of the fluid is measured. The main factors are the flow rate and the temperature of the flow rate.
Therefore, the type of fluid and its physical properties are not considered. This embodiment can be used for a gas flow meter that can measure an accurate flow rate without being affected by the temperature of the gas when the type of the measurement gas is known.

The present embodiment has a structure embodying the basic structure described below. "Means for obtaining a first response characteristic corresponding to the flow rate of the fluid and temperature of the fluid, means for obtaining a second response characteristic corresponding to the temperature of the fluid, the first response characteristic and the second response A measuring device having means for comparing the characteristics with each other to calculate the flow rate of the fluid, and means for detecting the response characteristics as a temperature change of the thin film material due to pulsed heating "

In the above basic structure, “means for obtaining first response characteristic corresponding to fluid flow rate and fluid temperature” corresponds to the fluid measurement sensor 803.
Also, this fluid measurement sensor 803, amplifier 87, A / D
The converter 804 and the CPU 88 can also be referred to as the above means.

Further, in the above basic structure, the “means for obtaining the second response characteristic corresponding to the fluid temperature” corresponds to the temperature measuring sensor 802. Further, the temperature measuring sensor 802, the amplifier 87, the A / D converter 8
04 and the CPU 88 can also be referred to as the above means.

Further, in the above basic structure, the "first
The means for comparing the response characteristic of No. 2 and the second response characteristic to calculate the flow rate of the fluid corresponds to the CPU 88.

Further, in the above basic structure, the "means for detecting the response characteristic as the temperature change of the thin film material due to the pulse-like heating" corresponds to the resistance temperature detectors 83 and 84. Further, in addition to the temperature measuring resistors 83 and 84, the amplifier 87, the A / D converter 804, and the CPU 88 can also be referred to as the above means.

Each component will be described in detail below. 7 to 9, FIG. 7 shows a block diagram, FIG. 8 shows a state of arrangement of the sensors 802 and 803 on the pipe 91, and FIG. 10 shows a state of wiring. These drawings show the same thing from different perspectives. Figure 7
In FIG. 9, reference numerals 802 and 803 denote sensors having the configuration shown in FIG. In this embodiment,
The respective sensors 802 and 803 are configured to have the same structure and size and the same characteristics.

Reference numeral 802 is for measuring the temperature of the fluid and functions as a temperature measuring sensor. The sensor shown in FIG. 1 can be used as a temperature measurement sensor for the following reasons.

As shown in FIGS. 8 and 9, the sensor 802
If the structure is not in contact with the flow, the thermal effect on 802 is only due to the temperature of the fluid or the environment. Therefore, the sensor 802 can be used as a temperature sensor. In the temperature measurement sensor 802, 85 is a heating element, which has a function of performing pulsed heating on the diamond thin film and supplying a predetermined amount of heat. Reference numeral 83 denotes a resistance temperature detector, which has a function of detecting the response characteristic of the diamond thin film to the pulsed heating by the heating element 85 as a temperature change of the diamond thin film.

On the other hand, the sensor indicated by 803 functions as a flow rate measuring sensor. This flow measurement sensor 8
03 is arranged so as to be in direct contact with the flow. In the flow rate measuring sensor 803, 86 is a heating element, which has a function of performing pulsed heating on the diamond thin film and supplying a predetermined amount of heat. Further, reference numeral 84 is a resistance temperature detector, which has a function of detecting the response characteristic of the diamond thin film heated by the heating element 86 in a pulsed manner as a temperature change of the diamond thin film.

The two sensors 802 and 803 are
The resistors 81 and 82 form a bridge circuit. In the actual configuration, as shown in FIG. 9, a variable resistor is connected in parallel with one resistor 81 to perform offset adjustment.

The output from this bridge circuit is the amplifier 8
The data is input to the A / D converter 804 via 7. A /
The output from the D converter is input to the CPU 88, where a predetermined calculation is performed. CPU used in this embodiment
Has a memory in one chip, and the relational expression represented by [Equation 1] is stored in this memory. Then, in the CPU, the output F corresponding to the flow rate is calculated based on the output R from the temperature measurement sensor 802 and the output S from the fluid measurement sensor 803.

Then, the output from the D / A converter 801 becomes the output indicating the flow rate. On the other hand, the D / A converter 89 has a function of applying a pulse voltage to the heating element 85 of the temperature measurement sensor 802 and the heating element 86 of the fluid measurement sensor 803 at a predetermined timing.

8 and 9 show a state in which the temperature measuring sensor 802 and the fluid measuring sensor 803 are actually arranged. In FIGS. 8 and 9, reference numeral 91 is a pipe through which a fluid flows. Note that 90 indicates the flow of fluid.
The pipe 91 is made of a suitable material (here, plastic). A part of the pipe 91 is hollowed out, and a Teflon (R) substrate 92 is fitted in the part. It is important that the base 92 be made of a material that can be regarded as a thermal insulator as compared with diamond such as Teflon (R) or epoxy resin.

As shown in FIG. 8, a part of the base 92 is also hollowed out, and the fluid measuring sensor 8 is formed in this part.
03 is incorporated. By adopting such a configuration, the diamond thin film can be thermally insulated and held, and the measurement accuracy can be improved.

In FIG. 8, the temperature measuring sensor 802
And the details of the fluid measurement sensor 803 are not shown,
As shown in FIG. 9, in practice, the diamond thin films 191 and 192 have heating elements 85 and 86 and resistance temperature detectors 83 and 84, respectively.

Further, a plastic flat plate 96 is arranged via an O-ring 97 to block the space 98 from the outside. On the other hand, slits or openings 95 are formed in the base body 92, and a part of the fluid 90 is configured to flow into the space formed by the flat plate 96 and the O-ring. The space denoted by 98 may communicate with the outside, but if the pressure of the fluid is high, the fluid will leak from that portion to the outside, so it is desirable that the space communicates only with the inside of the pipe 91.

Further, as shown in FIG. 8, the temperature measuring sensor 802 is also thermally insulated and held by a base 94 made of a thermal insulator such as Teflon (R) or epoxy resin. When the configuration as shown in FIG. 8 is adopted, the fluid in contact with the temperature sensor 802 has a flow velocity of almost 0 or a flow velocity that can be regarded as constant. Therefore,
The output from the temperature measurement sensor 802 can be regarded as substantially dependent on the temperature of the fluid.

Further, it has been found that the direction of the fluid flow 90 does not affect the measured value even if it is the direction opposite to that shown in the figure.

[Basic sensor operation method]
The basic operation method of the sensor will be described below by taking the temperature measurement sensor 802 shown in FIGS. 7 and 9 as an example. This operation is common to each sensor. Further, the sensor is assumed to have a structure as shown in FIG. The output from the sensor is obtained by the operation method described below. Further, the method of measuring the flow rate, the result of which is shown in FIG. 4, is also performed according to the operation method described below.

First, FIG. 10 will be described. FIG. 10 shows a change in output from the amplifier 87 in the system shown in FIGS. 7 and 9, that is, a change in output 101 from the resistance temperature detector 83 of the temperature measuring sensor 802 and a change in the fluid measuring sensor 803. Output change 1 from the resistance temperature detector 84
02 is shown. The specific operation procedure will be described below.

(First Operation) At t _OR to t _OR + Δt _OR , the output from the D / A converter 804 is sent to the CPU 88.
Total in. This calculation is the following formula [Formula 3]
Run on. The integrated value is S _OR .

[0136]

[Equation 3]

By this first operation, the reference point for temperature measurement by the temperature measurement sensor 802 can be determined. This operation is extremely important for obtaining an accurate evaluation without drift.

(Second Operation) A constant voltage Δ is applied to the heating element 85.
The diamond thin film constituting the temperature measuring sensor 802 is pulse-heated by energizing for a time of t _1R .

The temperature change of the diamond thin film heated by the second operation is output as the change of the resistance value of the resistance temperature detector 83. For example, when the output from the amplifier 87 is observed with an oscilloscope, a waveform as shown by 101 in FIG. 10 is observed. This shows that the diamond thin film is rapidly heated and cooled by the pulsed heating.

[0140] In (third operation) Here, it is integrated in t _2R + Δt _2R output from t _2R from A / D converter 804 according to [Equation 4] below. This integration is CPU88
Executed in. The integrated value is S _2R . Note that t _1R <t _2R . _Assuming that t _1R = t _2R ,
This is because noise appears in the output.

[0141]

[Equation 4]

(Fourth Operation) In the CPU 88, S _OR
And S _2R is calculated. This calculation is performed by hatching 1 in FIG.
This is equivalent to obtaining the area indicated by 03. By this calculation, it is possible to obtain only the response characteristic of the diamond thin film which is not influenced by the drift component.

Specifically, the fourth operation is (S _OR /
Δt _OR ) − (S _2R / Δt _2R ), or (Δt _2R / Δ
t _OR ) S _OR −S _2R , or S _OR − (Δt _OR / Δt _2R ) S
_It is performed by executing the operation indicated by _2R . Of course, what is necessary is the absolute value of the difference between S _OR and S _2R , so the order of subtraction may be the reverse of the above description. The result of this calculation is the output from the sensor.

FIG. 10 obtained by the fourth operation described above.
The area of the shaded portion of the waveform indicated by 103 reflects the thermal effect on the diamond thin film, and changes depending on, for example, the temperature of the fluid in contact with the diamond thin film and its flow rate.

Here, it is assumed that the diamond thin film forming the sensor 802 is in contact with the fluid flow having a constant temperature. Then, the output obtained by the fourth operation is indicative of the flow rate of this fluid. The data shown in FIG. 4 is obtained in such a case. Note that FIG.
The conditions for obtaining the data shown in are: Δt _OR = 0.
1 second, Δt _1R = 0.18 seconds, Δt _2R = 0.36 seconds, applied voltage to the heating element 3.2V, bias voltage V _CC applied to the resistance temperature detector 83 = 0.3V is there.

Further, as shown by 802 in FIG. 8 and FIG. 9, when the above operation is executed when the sensor is arranged so as not to be exposed to the fluid flow 90, the sensor 802 obtained as a result of the operation Output depends on the temperature of the fluid and the environment. In other words, the output corresponding to the temperature of the fluid or the environment can be obtained. (Fig. 5
(See (A))

In the above operation procedure, S _OR and S _2R
It is important to evaluate the response characteristics of the diamond thin film by determining the difference between By performing such an operation, a drift component does not appear in the output, and accurate measurement without change with time can be performed.

[Calibration of Sensor Performed in Advance] It is necessary to perform calibration in advance before operating the sensor for measuring the flow rate. This calibration operation is performed as follows. This work needs to be performed at least after assembling the configuration shown in FIGS. In the following, FIGS.
It is assumed that the configuration shown in is used. In the following, an example of measuring the flow rate will be described.

(1) The configuration shown in FIG. 8 is placed in an atmosphere in which the fluid to be actually measured is filled and the temperature of the fluid can be precisely changed. For example, if the flow rate of nitrogen gas is to be measured, it is placed in a temperature-controlled room filled with nitrogen gas. In this state, the flow rate becomes 0 (constant flow rate).

(2) In this state, the temperature measuring sensor 802 is operated by the method described in the explanation of the basic operation. The output from the temperature measurement sensor at this time corresponds to the area 103 of the waveform 103 in FIG.
As constants at this time, for example, V _CC = 0.3 V, voltage applied to the heating element 3.2 V, Δt _OR = 0.1 second, Δt _1R =
0.18 seconds and Δt _2R = 0.36 seconds.

(3) The fluid measurement sensor 803 is operated under the condition that the output obtained by the above operation (2) is constant. That is, the fluid measurement sensor 803 is operated under the condition that the temperature of the fluid is constant. This fluid measurement sensor 8
The operation method of 03 also follows the above-described operation method. That is, the two sensors 802 and 803 are operated under exactly the same driving method and driving conditions. Output of fluid measurement sensor at this time 8
03 corresponds to the area 104 of the waveform 102 in FIG.

As a result of this operation, one set of the output of the temperature measuring sensor and the output of the fluid measuring sensor is obtained. This means that one plot point shown in FIG. 6 is defined. (4) The atmosphere in the temperature-controlled room is changed within a required temperature range, and the above operation is repeated for each predetermined temperature.

For example, if the operating range is from -10 ° C to 50 ° C, -10 ° C, 0 ° C, 10 ° C, 20 ° C, 30
The temperature is changed to ℃, 40 ℃, 50 ℃, and the function as shown in FIG. 6 is created with the output of the temperature measurement sensor 802 (horizontal axis) and the output of the fluid measurement sensor 803 (vertical axis) at that time as coordinates. To do.

As described above, the temperature measuring sensor 802
If the fluid measurement sensor 803 and the fluid measurement sensor 803 have the same characteristics, the function obtained in the above operation is a linear function with an inclination of 1 and an intercept of 0 under ideal conditions. However, the slope is not 1 and the intercept is not 0 in reality due to factors such as variations in characteristics of each sensor and offset voltage of the circuit.

That is, what is actually obtained is a function represented by the following [Equation 7]. Here, R is an output from the temperature measurement sensor, S ₀ is an output from the fluid measurement sensor, and A and B are constants. Further, here, A and B can be obtained as specific numerical values. The following [Formula 7]
In, S ₀ indicates the output of the fluid measurement sensor when the flow rate is 0.

[0156]

[Equation 7]

When the temperature measurement sensor and the flow rate measurement sensor have the same size and the same structure so as to have the same characteristics, the function obtained by the above operation is as shown in [Equation 7]. It becomes an almost perfect linear function.
Therefore, in this case, it is practical to use only two plot points.

By this operation, the constants A and B in [Equation 1] or the function f (R) in [Equation 2] can be obtained.

(5) The function obtained by the above operation is stored in the CPU
It is stored in the memory in 88. Alternatively, the CPU 88 is programmed with a calculation method based on this function.

The calibration performed in advance is completed by the above operation.
The function shown in FIG. 6 obtained in this calibration does not need to be obtained in the state where the flow rate is 0. The method described above can also be used when the temperature measuring sensor and the fluid measuring sensor have different configurations and characteristics. in this case,
The function f (R) of [Equation 2] is obtained.

Further, it is necessary to previously obtain the relationship between the output from the D / A converter 801 and the flow rate of the fluid to be measured. Although this relationship is not shown in FIG. 8, it may be stored in a memory provided separately.

[Operation During Flow Rate Measurement] A specific operation method in the case of actually measuring the flow rate will be described below. Before measuring the flow rate, it is necessary to complete the above-mentioned calibration work.

Basically, the configuration is performed according to the following operation procedure. (1) The temperature measurement sensor 802 is operated to obtain a measurement value corresponding to the temperature of the fluid. (2) The fluid measurement sensor 803 is operated to obtain a measurement value depending on the temperature and flow rate of the fluid. (3) A predetermined calculation is executed in the CPU 88 based on the functions shown in [Equation 1] and [Equation 2] which are obtained in advance.

The operation procedure will be specifically described below. The following description will be given with reference to FIG. Figure 10
It is a change in the output when the output of the amplifier shown by 87 in FIGS. 7 and 9 is observed with an oscilloscope.

In FIG. 10, first, the waveform indicated by 101 is output from the amplifier 87 according to the change in the resistance value of the resistance temperature detector 83 of the temperature measurement sensor 802, and subsequently the resistance of the resistance temperature detector 84 of the fluid measurement sensor 803 is changed. 1 depending on the change in value
The waveform indicated by 02 is output from the amplifier 87. FIG. 11 shows a photograph of an actual oscilloscope display corresponding to FIG.

(First Operation) From t _OR to t _OR + Δt _OR , the output from the D / A converter 804 is sent to the CPU 88.
Total in. This calculation is the following formula [Formula 3]
Run on. The integrated value is S _OR . Here, Δt _OR = 0.1 second and V _CC = 0.3V.

[0167]

[Equation 3]

By the first operation, the reference point for temperature measurement by the temperature measurement sensor 802 can be determined. This operation is extremely important for obtaining an accurate evaluation without drift.

(Second Operation) The heating element 85 is energized with a constant voltage of 3.2 V for a time of Δt _1R = 0.18 seconds, and the diamond thin film constituting the temperature measuring sensor 802 is pulsed heated. .

The temperature change of the diamond thin film heated by the second operation is output as the change of the resistance value of the resistance temperature detector 83. For example, when the oscilloscope observes the output of the amplifier 87, a waveform such as 101 in FIG. 10 is observed. This shows that the diamond thin film is rapidly heated and cooled by the pulsed heating. According to the calculation, the heating temperature of the diamond thin film is about 20K.

[0171] In (third operation) Here, the t _2R + Δt _2R output from t _2R from RTD 83 integrates.
This integration is calculated by the following formula (Equation 4)
At 88. The integrated value is S _2R . Here, Δt _2R = 0.36 seconds. Also, t _1R <
t _2R . This is because noise appears in the output when t _1R = t _2R .

[0172]

[Equation 4]

(Fourth operation) In the CPU 88, S _OR
And S _2R is calculated. This calculation is performed by hatching 1 in FIG.
This is equivalent to obtaining the area indicated by 03. By this calculation, it is possible to obtain only the response characteristic of the diamond thin film which is not influenced by the drift component.

Specifically, this operation is performed by (S_OR/ Δ
t_OR)-(S_2R/ Δt_2R), Or (Δt _2R/ Δt_OR)
S_OR-S_2R, Or S_OR− (Δt_OR/ Δt_2R) S_2R,so
Done. Needless to say, S_ORAnd S_2RAbsolute value of the difference from
Therefore, the order of subtraction may be the reverse of the above description.

In this way, the temperature measuring sensor 802
From, an output R that depends only on the temperature of the fluid that does not depend on the flow rate is obtained. Further, the series of operations described above is performed in 4 seconds.

(Fifth Operation) Next, the fluid measurement sensor is operated. First, in the fluid sensor 803, the output from the resistance temperature detector 84 is integrated between t _OS and t _OS + Δt _OS . This calculation is executed by the CPU 88 by the calculation shown in the following [Formula 5]. Again, Δt _OS = 0.
V _cc = 0.3V for 1 second.

[0177]

[Equation 5]

The calculation result of this [Formula 5] is S _OS .
The fifth operation is performed to determine the reference point of the measurement operation of the fluid measurement sensor 803.

(Sixth Operation) At the constant voltage of 3.2 V, Δt _1R = 0.18 is applied to the heating element 86 of the fluid measurement sensor 803.
The diamond thin film constituting the fluid measurement sensor 803 is pulse-heated by energizing for a time of 2 seconds.

According to the sixth operation, a temperature change of the diamond thin film occurs, which is measured as an output change of the resistance temperature detector 84. At this time, when the output of the amplifier 87 is monitored by an oscilloscope, a waveform as shown by 102 in FIG. 10 is observed. This waveform shows the heating element 86
Measuring sensor 803 for pulsed heating from the
3 shows the response characteristics of the diamond thin film constituting the.

(Seventh Operation) The output from the A / D converter 804 is calculated according to the following [Equation 6] between t _2S and t _2S + Δt _2S . Further, the calculation result of this [Formula 6] is S _2S . In this example, Δ
Although t _2R = Δt _2S = 0.36 seconds and the measurement timings thereof are also the same, these may not be the same.

[0182]

[Equation 6]

In the above [Formula 6], t _1S <t _2S . This is because if t _1S = t _2S , noise is included in the output from the resistance temperature detector 84, and the measurement accuracy decreases.

(Eighth operation) S_OSAnd S_2SCalculate the difference between
It Specifically, (S_OS/ Δt_OS)-(S_2S/ Δ
t_2S), Or (Δt_2S/ Δt_OS) S_OS-S_2S, Or
S_OS− (Δt _OS/ Δt_2S) S_2S, Done in. Needed of course
What is S_OSAnd S_2SSince it is the absolute value of the difference with
The order may be reversed from the above description.

By the eighth operation, 104 in FIG.
A value S corresponding to the area of the shaded portion indicated by is obtained. This value S depends on the temperature of the fluid and the temperature of the environment. The fifth to eighth operations are also performed in 4 seconds.

(Ninth Operation) Output (output from temperature measuring sensor 802) R obtained as a result of fourth operation and output (output from fluid measuring sensor 803) S as a result of eighth operation Using the and, the CPU 88 performs the calculation according to the calculation formula shown in the following [Formula 1].

[0187]

[Equation 1]

Here, since the constants A and B have been obtained in the stage of calibration performed in advance, the value of F can be fixed. This F is a value that does not depend on the temperature of the fluid but only on the flow rate or the flow velocity. Then, the output corresponding to the flow rate is obtained from the D / A converter 801.

In the present embodiment, each sensor operates for 4 seconds, so that the time required for one flow rate measurement is 8 seconds. In other words, the flow rate is measured once every 8 seconds. This operating time can be further shortened.
Specifically, it can be set to 2 seconds or less. However, in this case, the pulse heating time (Δt _1R and Δt _1S ) needs to be 100 ms or less.

FIG. 5B shows the data when the measurement is performed by the above operation method. FIG. 5B shows that a sensor having the configuration shown in FIGS. 7 to 9 is arranged in a thermostatic chamber filled with air, and the temperature is set to 10 deg.
D / A converter 801 when changed to 40deg
Shows the change over time in the output from.

In this case, it can be considered that the flow rate is zero and constant, and the temperature of the environment and the temperature of the fluid are the same. Figure 5
From the data shown in (B), it is understood that an output reflecting the flow rate value (here, the flow rate is 0) is obtained regardless of the temperature change of the fluid.

According to FIG. 5B, the maximum drift according to the temperature change is about 30 mV, which is about 20 s.
It is an output corresponding to a flow rate of a little less than ccm. The characteristics (relationship between the flow rate and the tolerance) in the flow rate measurement of this embodiment are almost the same as those in FIG. However, due to the influence of the drift component due to the temperature change, the measurement accuracy will be slightly lowered below 1 slm (liter / min).

When actually measuring the flow rate, the output from the D / A converter 801 is checked by comparing it with the relationship between the flow rate value and the output from the D / A converter 801 which have been obtained in advance. The flow rate value can be obtained.

As described above, by adopting the configuration of this embodiment, it is possible to obtain a flow rate sensor capable of performing flow rate measurement over 50 sccm to 50000 sccm without being affected by temperature.

In this embodiment, the temperature measuring sensor 8
02 and the fluid measurement sensor 803 have the same structure, and their characteristics are also the same. The heating time and the output calculation time (Δt _2R and Δt _2S ) were the same for both. However, different settings may be used. Also,
The value of each parameter may be a value that is required at a proper time.

Further, when the temperature of the fluid is governed by the temperature of the environment, the temperature measuring sensor may measure the temperature of the environment instead of the structure shown in FIG. For example, in the structure as shown in FIG. 8, the temperature measuring sensor is arranged outside the pipe, whereby the temperature of the measurement environment can be measured. Of course, in this case, it is necessary to devise the temperature measurement sensor so that it is not directly exposed to the fluid flow.

Even if the temperature of the fluid to be measured does not change, the output drift may occur due to the temperature change of the measurement environment. This is because a change in the temperature of the measurement environment causes a change in the resistance value of the resistors forming the bridges 81 and 82 in FIG. 7 and a drift in the amplifier.

To solve this problem, both the temperature of the fluid to be measured and the temperature of the measurement environment are measured, and the changes in the temperature of the measurement environment are dealt with in [Equation 1] and [Equation 2]. A correction term should be entered.

It is also possible to use a plurality of temperature measuring sensors and a plurality of fluid measuring sensors and average the outputs of the respective sensors.

[Third Embodiment] In the second embodiment, the thermal influence of the fluid on the temperature measurement sensor 802 is the temperature of the fluid (here, only the temperature of the fluid matters), and the fluid measurement sensor The heat that 803 receives from the fluid is
The case of the temperature of the fluid and the flow rate of the fluid is shown.

This embodiment is based on the premise that the structure shown in Embodiment 2 is used, and a case where the concentration of impurities in the flowing fluid changes and the temperature of the fluid also changes will be described. That is, in this case, the thermal effect on each sensor includes that due to the concentration of impurities in the fluid.

As such a situation, there may be mentioned a case where the flow rate of temperature-controlled air flowing through pipes and ducts is measured in an air conditioner of a house, a building, or a public facility.

In the air conditioning equipment as described above, the temperature of the flowing air differs depending on the weather and the season. The humidity of the flowing air also varies greatly depending on the weather and season.

In such a situation, when trying to measure only the flow rate of the air flowing in the pipe or duct, the output corresponding to the flow rate alone is not affected by the temperature and humidity of the air flowing in the pipe or duct. Need to get

In the structure of the second embodiment shown in FIGS. 7 to 9, the temperature measuring sensor is in contact with the fluid, but not in the flow 90 of the fluid, as shown in FIG. The fluid measurement sensor 803 is in contact with the fluid flow 90. Therefore, in this case, the difference in the thermal effects on the two sensors is only due to the fluid flow 90.

Therefore, even in the case of measuring the flow rate of air in the above-mentioned air conditioning equipment, in an ideal situation, by executing the operation method of the second embodiment, the output depending only on the air flow, That is, the main force depending on the flow rate can be obtained. This output is the output from the D / A converter 801.

The ideal situation is that the sensor 802
And sensor 801 have the same characteristics, and it can be considered that A = 1 and B = 0 in [Equation 1].
However, in reality, A = 1 is not satisfied and B = 0 is not satisfied.
Therefore, in this case, it is necessary to add a correction term to [Equation 1].

As a method other than adding the correction term,
The following method can be adopted. That is,
At the stage of calibrating each sensor in advance, by determining the calculation method so that the output from each sensor satisfies [Equation 1] when A = 1 and B = 0, a situation close to the above ideal situation can be realized. . For example, with the configurations shown in FIGS. 7 to 9, in measurement at a flow rate of 0, calibration may be performed so that the output from the sensor 802 and the output from the sensor 803 are the same. Such calibration is easily realized by changing the program of the calculation performed by the CPU 88.

Further, this calibration is performed when the temperature is changed and when the humidity is changed, and it is necessary to satisfy a predetermined allowable range with respect to changes in both variables within the measurement range. is there. This is completely A = for changes in both variables.
This is because that [Formula 1] where 1 and B = 0 is not always satisfied.

In a situation in which the situation of A = 1 and B = 0 in [Equation 1] is substantially realized, the measurement of the air flow rate of the air conditioning equipment is performed by "n is 1, 2,
The variables α ₁ , α ₂ ...
The first response characteristic determined by α _{n + 1} and the variables α ₁ , α
₂ ... The second response characteristic determined by α _n is compared, and an output corresponding to the variable α _{n + 1} is obtained. ”, N = 2, α ₁ is the air temperature, and α ₂ Is the humidity of the air, and α ₃ is the flow rate of the air flowing through the pipes and ducts of the air conditioning equipment.

In this structure, the means for obtaining the first response characteristic is the fluid measuring sensor 803 shown in FIGS. 7 and 9, and the means for obtaining the second response characteristic is the temperature measuring sensor 80.
It can be said to be 2. Also, the fluid measurement sensor 803, the amplifier 87, the A / D converter 804, the CPU
It can also be said that the system constituted by 88 is a means for obtaining the first response characteristic. Similarly, a temperature measurement sensor 802, an amplifier 87, an A / D converter 804, a CPU
It can also be said that the system constituted by 88 is a means for obtaining the second response characteristic. Further, it can be said that the means for comparing the two response characteristics is the CPU 88.

[Embodiment 4] This embodiment relates to a method for measuring the flow rates of different kinds of fluids in the configuration shown in Embodiment 2. In the configuration shown in the second embodiment, when the outputs from the sensors 802 and 803 are the same when the flow rate is 0, that is, A = 1 and B = 0 in [Equation 1].
If it can be considered that the flow rate can be measured regardless of the type of fluid as long as the physical properties are not significantly different even if the type of fluid is different.

This is a sensor 802 and a sensor 803.
This is because the thermal effects of and on the fluid are only due to the flow rate of the fluid. That is, the influence on the temperature of the fluid and its physical properties is due to cancellation at the stage of calculation.

However, when measuring fluids having greatly different physical properties, the difference in the thermal effect of the fluids on the thin-film materials that make up the sensor becomes significant, so even if the flow rate is the same, the flow rate will be compatible. The difference in response characteristics is a problem. For example, the same response characteristics cannot be obtained with water and air. In order to solve this problem, some correction is necessary in measurement.

In actual flow rate measurement, it is necessary to make the output from the D / A converter 801 (see FIGS. 7 and 9) change linearly according to the flow rate. That is, D
It is necessary that the output from the / A converter 801 and the flow rate have a relationship represented by a linear function with a slope of 1 and an intercept of 0. This is a software problem and can be easily implemented.

The slope of this linear function depends on the type of fluid. That is, the slope of this linear function differs depending on the type of fluid. Therefore, for example, when the fluid A is measured and when the fluid B is measured, the above 1
By appropriately changing the relationship between the output from the D / A converter 801 and the flow rate, which is expressed by the following function, it is possible to perform accurate flow rate measurement regardless of the type of fluid. Specifically, by changing the slope of the linear function according to the type of fluid, it is possible to perform flow rate measurement independent of the type of fluid.

Further, even if the output from the D / A converter 801 and the flow rate are not linear functions,
The functional relationship may be changed appropriately depending on the fluid.

In order to realize the structure of this embodiment, the relationship between the output of the system (for example, the output from the D / A converter 801) and the flow rate in a predetermined fluid is checked in advance, and the correction method is determined by the CPU 88 or other means. It may be stored in the memory provided in. Then, at the time of the measurement operation, the measurement operation may be performed according to the type of fluid.

The measurement principle of this embodiment can be applied to the case as shown in the third embodiment. That is, the calibration is performed only for the temperature, and for the change in the humidity, the output of the D / A converter is corrected by referring to the output of the separately provided humidity measuring sensor. By doing so, the influence of factors other than the flow rate can be eliminated as much as possible, or eliminated within an allowable range, and the flow rate can be measured.

[Embodiment 5] This embodiment is an example in which a known platinum sensor is used as a temperature measurement sensor and the sensor shown in Embodiment 1 is used as a fluid measurement sensor. This embodiment is different from the second embodiment in that the output from the platinum temperature sensor can be compared with the output of the fluid measurement sensor by an A / D converter. The operation method of the fluid measurement sensor is exactly the same as that shown in the second embodiment.

Further, it is the same as in the case of the second embodiment that the temperature measuring sensor is kept out of contact with the flow.

The basic operation method is the same as that shown in the second embodiment. That is, a state in which the output from the platinum sensor that is the temperature measurement sensor is converted into a digital signal by the A / D converter and can be compared with the output from the fluid measurement sensor (corresponding to the value of the area 104 of the waveform 102 in FIG. 10) If it is realized, then the operation may be performed according to the procedure described in the second embodiment.

In the case of this embodiment, the function shown in FIG. 6 is not a simple linear function. This is because the temperature measurement sensor and the fluid measurement sensor have different characteristics with respect to temperature. In this example, the temperature measuring sensor was a platinum temperature sensor. However, other temperature sensors such as semiconductor thermistors can also be used.

[Embodiment 6] This embodiment corresponds to FIG.
~ An example of identifying the type of fluid using a system having the configuration shown in Fig. 9 will be described.

Now, consider the case where the operation as shown in the second embodiment is performed without flowing the fluid. Such a situation is easily realized by closing both ends of the pipe shown in FIGS. 8 and 9. In this case, the D / A converter 8
The output from 01 depends on the type of fluid.

This is because different types of fluids naturally have different thermal conductivities and specific heats, and therefore the way heat is taken from the diamond thin film is different, and the response waveforms shown in FIGS. 3, 10, and 11 are different. Is.

According to the experiments conducted by the present inventors, it was confirmed that nitrogen gas and krypton gas were caused to flow at the same flow rate, and the flow rates were measured by the system shown in FIG. . This means that nitrogen gas and krypton gas can be discriminated from each other, and it can be said that the fact suggests that the gas sensor can be used.

The operation as the gas sensor is basically the same as the flow rate measuring method shown in the second embodiment. The difference from the case of measuring the flow rate is that the type of gas is identified by checking the relationship between the type of gas and the output from the D / A converter 801 in advance and comparing the actual measured value with this relationship. That is. Also, the fluid measurement sensor 80
It is also different in that the fluid in contact with 3 has a constant flow rate.

Further, it is necessary that the temperature measuring sensor 802 is arranged in a closed space and is in contact with a reference gas (for example, nitrogen gas or air). in this case,
It is necessary that the reference gas be the same as the ambient temperature or the temperature of the fluid to be measured. Specifically, it is necessary to form the closed space using a material having a high thermal conductivity such as aluminum and to arrange the temperature measurement sensor 802 therein.

According to the knowledge of the present inventors, it is the thermal conductivity of the fluid that is the most contributing factor to the difference in output when the gas sensor is operated. Further, the next factor contributing to the thermal conductivity is the specific heat. It has also been found that density and pressure also affect output.

As the fluid, not only gas but also a fluid can be used as a sensor for identifying the type of fluid. However, in this case, it is necessary to change the amount of heat supplied to the heating element.

As described above, the sensor according to the second embodiment can be made to function as it is as a gas sensor or a fluid sensor by making some changes in the arrangement of the temperature measuring sensor. For example, it can be used as a sensor for detecting that the concentration of a specific gas in the air exceeds a certain level. It can also be used as a sensor for measuring the humidity in the air.

These operations are extremely practical because they can be performed in a state that does not depend on the temperature of the fluid or the environment. Further, in principle, even if the substance to be measured is a solid material, it is possible to measure the difference in thermal conductivity or specific heat.

[Embodiment 7] This embodiment relates to a construction for performing accurate flow rate measurement in a wider temperature range in the construction shown in Embodiment 2. In the second embodiment, an example is shown in which the functional relationship represented by [Equation 1] is used regardless of the output from the temperature measurement sensor, that is, regardless of the temperature of the fluid.

This is [Equation 1] regardless of the temperature of the fluid.
It is assumed that the relational expression shown by is satisfied. However, if the temperature range is extremely wide under the conditions of use,
It may be possible that the relational expression shown in [Equation 1] is different between the low temperature region and the high temperature region. Specifically, the values of the constant A and the constant B may be different.

There may be a case where it is necessary to change the amount of heat supplied from the heating element between the low temperature region and the high temperature region. This is because, depending on the heat capacity of the thin film material and the type of fluid to be measured, it is necessary to make the amount of heat supplied to the thin film material different in the high temperature region and the low temperature region in order to obtain the required response characteristics.

In this case, a method in which the voltage applied to the heating element is changed depending on the temperature of the fluid and / or the temperature of the measurement environment can be considered. However, in this case, the measurement cannot be performed by the method shown in the second embodiment.

Therefore, in this embodiment, the temperature range in which measurement is performed is divided into a plurality of ranges, and one temperature range is used in the second embodiment.
It is characterized in that the measurement is performed by the method shown in.
For example, when it is necessary to perform measurement in the range of -30 ° C to 100 ° C, -30 ° C to 10 ° C, 10 ° C to 50 ° C.
The temperature measurement range is divided into a plurality of ranges, such as 50 ° C. and 50 ° C. to 100 ° C., and the measurement as shown in the second embodiment is performed therein.

In this case, it is necessary to obtain the relational expressions shown in [Equation 1] and [Equation 2] in each temperature range. That is, it is necessary to calibrate for each temperature range. Needless to say, it is not necessary to adopt the method of this embodiment if the relational expressions shown in [Equation 1] and [Equation 2] are the same in each temperature range.

By adopting the configuration of this embodiment,
Appropriate conditions can be set in each temperature range,
Highly accurate flow rate measurement and gas detection can be performed in a wide temperature range. Further, the configuration of this embodiment is characterized in that it can be implemented only by storing necessary conditions in a memory. Specifically, the configurations shown in FIGS. 7 to 9 can be used as they are.

[Embodiment 8] In the present embodiment, a configuration will be described in which a temperature measuring sensor is brought into contact with a fluid to measure the flow rate. 7 to 9 described in the second embodiment
In the configuration shown in, the temperature measurement sensor 802 was not in direct contact with the fluid flow 90, but was in contact with the fluid. This is to prevent the output from the temperature measurement sensor from being affected by the flow rate.

However, if the type of the fluid to be measured is known in advance, a temperature measurement sensor is brought into contact with a separately prepared fluid to be measured to measure the temperature of the fluid to be measured or the temperature of the measurement environment. You can

In this case, the slit or opening shown by 95 in FIG. 8 is not necessary. However, it is necessary to ensure that the fluid whose flow is indicated at 90 and the fluid with which the temperature measurement sensor is in contact have the same temperature.

[0244]

[Effect] For example, when measuring the flow rate of a fluid, a temperature measurement sensor that obtains an output that depends on the temperature of the fluid and a fluid measurement sensor that is arranged in contact with the flow of the fluid and that obtains an output that depends on the flow rate and the temperature of the fluid Based on the relationship between the output of the temperature measurement sensor and the output of the fluid measurement sensor, which is arranged in advance, the temperature of the fluid or the environment is calculated from the output of the temperature measurement sensor and the output of the fluid measurement sensor for each measurement. It is possible to obtain an output that depends on the flow rate that does not depend on

Particularly, by making the operation of each sensor use the response characteristic of the thin film material according to the pulsed heating, the measurement accuracy can be improved. Also. By using the diamond thin film having high thermal conductivity as the thin film material, the flow rate can be measured over a wide measurement range.

Further, it is possible to operate as a gas sensor based on the same principle as that of measuring the flow rate, and it is possible to realize a gas sensor which is not affected by the temperature of the gas.

[Brief description of drawings]

FIG. 1 shows an outline of the structure of a sensor.

FIG. 2 shows a configuration of a flow rate measuring system.

FIG. 3 shows a photograph of the display of the oscilloscope.

FIG. 4 shows the relationship between flow rate and tolerance in flow rate measurement.

FIG. 5 shows changes with time in output with respect to changes in temperature.

FIG. 6 shows the relationship between the output from the temperature measurement sensor and the output from the fluid measurement sensor.

FIG. 7 shows a configuration of a measurement system according to an embodiment.

FIG. 8 shows an arrangement state of sensors.

FIG. 9 shows a configuration of a measurement system of an example.

FIG. 10 shows response characteristics of a diamond thin film to pulsed heating.

FIG. 11 shows a photograph of the oscilloscope display.

[Explanation of symbols]

11 Heating element (platinum thin film) 12 Resistance temperature detector (platinum thin film) 13 Diamond thin film 15 electrodes 10 electrodes 17 Gold wire for bonding 19 fluid 21 amplifier 22 Flow rate measuring device 802 Temperature measurement sensor 803 Fluid measurement sensor 83 Resistance temperature detector 84 Resistance temperature detector 85 Heating element (heater) 86 Heater 87 amplifier 90 Fluid flow 91 pipes 92 holding substrate (made of Teflon (R)) 94 holding substrate (made of Teflon (R)) 96 flat plate (sealing member) 97 O-ring 191 diamond thin film 192 diamond thin film

Continuation of front page (56) References JP-A-63-140921 (JP, A) JP-A-62-231174 (JP, A) JP-A-2-213767 (JP, A) n-film Diamond, Sensor and Materials, 1991, 2, 6, 329-346 (58) Fields investigated (Int.Cl. ⁷ , DB name) G01F 1/684 G01P 5/10 G01N 25/18

Claims (3)

(57) [Claims] 1. A first determined by variables α ₁ , α ₂ , α ₃ .
Means for measuring the response characteristics of the _first and _second means, and a means for measuring the second response characteristics determined by the variables α ₁ and α ₂ .
Of comparing the response characteristics and said second response characteristic, a measuring device with a means for obtaining an output corresponding to the variable alpha _3, wherein the variables alpha ₁ is the temperature of the fluid, the variable alpha ₂ is the concentration of impurities in the fluid, the variable alpha ₃ is Ri flow or velocity der of the fluid, the fluid flowing means for measuring a first response characteristic
The means for measuring the second response characteristic, which are arranged so as to be in contact with each other, can be regarded as zero flow rate.
A measuring device, which is arranged so as to be in contact with the fluid . 2. A first determined by variables α ₁ , α ₂ , α ₃ .
Means for measuring the response characteristics of the _first and _second means, and a means for measuring the second response characteristics determined by the variables α ₁ and α ₂ .
And a means for comparing the second response characteristic with the second response characteristic to obtain an output corresponding to the variable α ₃ , wherein the variable α ₁ is the temperature of air, and the variable α ₁ is ₂ is a humidity of the <br/> air, the alpha ₃ is Ri flow der of the air flowing through the air conditioning piping or duct, means for measuring the first response characteristic to the air flow
The means for measuring the second response characteristic, which are arranged so as to be in contact with each other, can be regarded as zero flow rate.
A measuring device, wherein the measuring device is arranged so as to be in contact with the air . 3. An apparatus according to claim 1 or claim 2, wherein the first response characteristic and the second response characteristic is a response characteristic of the thin-film material to the pulse-like heating, the thin film material is diamond, single crystal A measuring device comprising silicon, polycrystalline silicon, silicon carbide, boron nitride, or aluminum nitride.