JP3193241B2 - 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 apparatus for quantitatively evaluating the thermal influence of a fluid on a thin film material. For example, the present invention relates to an apparatus that performs at least one of the following items. (1) Measurement of fluid flow or flow velocity. (2) Measurement of thermal conductivity and specific heat of fluid. (3) Fluid identification. (4) Measurement of the mixing ratio of multiple fluids. (5) Measurement of the concentration of a substance contained in a fluid (for example, measurement of humidity).

[0002]

2. Description of the Related Art As a device (flow sensor) for measuring a flow rate, a device using a thermistor is known. This is based on the fact that the temperature of the thermistor portion is reduced by the heat being removed from the thermistor heated directly or indirectly by the fluid. In general, when the thermistor portion is in contact with the fluid, the amount of heat taken from the thermistor portion depends on the flow rate (or flow velocity), so that the output from the thermistor has a certain correlation with the flow rate. By utilizing this, the flow rate can be calculated from the output of the thermistor.

[0003] The flow rate is defined as a ratio of the volume or mass of the fluid flowing through the cross section to time, considering a cross section having a certain area in the flow of the fluid.
Generally, the ratio of the volume of flowing fluid to time is referred to as volume flow rate (or volume flow rate), and the ratio of the mass of flowing fluid to time is referred to as mass flow rate.

[0004] The volume flow rate is determined by the product of the cross-sectional area of the fluid and the flow velocity. For example, if a fluid having a flow velocity v is flowing through a circular pipe having an inner diameter r, vπr ² is a volume 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.

[0005] The mass flow rate is represented by the volume flow rate and the density of the flowing fluid. For example, if a fluid having a density ρ is flowing at a flow velocity v in a circular pipe having an inner diameter r, ρ
vπr ² becomes the mass flow rate.

Generally, a thermistor refers to a semiconductor having a large negative temperature coefficient. However, a thermistor is essentially a heat-sensitive 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 referred to as a thermistor.

Elements using a material whose resistance changes with temperature, such as a thermistor, are collectively called a resistance temperature detector, a temperature sensing element, a temperature sensing element, or a resistance thermometer. In addition, a material whose resistance changes with temperature can also be referred to as a material having a thermistor function. Hereinafter, a material whose resistance changes with temperature is referred to as a temperature measuring resistor.

A flow rate measuring device using a thin-film resistance thermometer is known as a boundary layer mass flow meter or Thermal Mass-Flow Meters.
of the Boundary-Type, Senser A Comprehens
ive Survey Volume 4 (W. Gopel, J. Hesse, JNZemel
Authored by VCH (Verlagsgesellschaft mbH) (1990)
Page 328, 9.2.3, and the details are described below.

FIG. 10 shows an outline of a typical flow rate measuring device using a resistance temperature detector described in the above-mentioned document.
The configuration shown in FIG. 10 has a bridge composed of resistance temperature detectors 301 and 302, and furthermore, resistances 303 and 304.

In the configuration shown in FIG. 10, in order to keep the temperature difference between the two resistance temperature detectors 301 and 302 constant,
The two resistance thermometers whose resistance values are finely adjusted are used. For example, a resistor whose resistance value of the resistance bulb 302 is about 10 times the resistance value of the resistance bulb 301 is used.

In actual operation, the resistance temperature detectors 301 and 302 are heated by flowing a bias current,
Further, by applying feedback from the amplifier 305, the temperature difference between the resistance temperature detectors 301 and 302 is made constant. That is, by applying appropriate feedback using the amplifier 305, the temperature measuring resistor 30
In this state, the bridge composed of the resistors 1, 302 and the resistors 303, 304 can always be balanced.

Temperature measuring resistors 301 (resistance value R ₁ ) and 302
If the temperature dependence of the resistance value is the same as that of (resistance value R ₂ ), the value of (R ₁ / R ₂ ) does not change with a change in the fluid temperature. Therefore, the balance of the bridge does not collapse. As a result, the value of the feedback applied from the amplifier 305 does not change.

On the other hand, when the flow rate of the fluid 307 changes, the value of (R ₁ / R ₂ ) changes according to the flow rate. Therefore, appropriate feedback is applied so that the temperature difference between the two resistance temperature detectors becomes constant, so that the temperature difference shown in FIG.
Can be balanced.

At this time, the value of the feedback applied by using the amplifier 305 depends on the flow rate. Also, as described above, this value does not depend on the temperature of the fluid. Therefore, by detecting the output of the amplifier 305, the fluid 30
7 can be obtained.

In the configuration shown in FIG. 10, the two resistance temperature detectors are heated to a considerably high temperature in order to enhance the measurement sensitivity, the dynamic range, and the temperature compensation function. In general, the temperature difference between two resistance temperature detectors
The temperature is set to about 100 ° C.

A flow sensor as shown in FIG.
In practical use, there are the following problems. [Problems of the prior art 1] In order to obtain high sensitivity and dynamic range, it is necessary to heat the resistance bulb to a high temperature. The need to increase the thermal stability of the device complicates the structure and increases production costs. [Problem 2 of Prior Art] In connection with the above-mentioned first problem, variations in characteristics are likely to occur in mass production. Particularly, since a delicate DC balance needs to be taken, a difference in characteristics is likely to occur, and the tolerance in manufacturing is extremely small. [Problem 3 of the Related Art] When the resistance bulb is heated to a high temperature by applying a DC voltage, the power consumption is increased. [Problem 4 with Prior Art] There is a fundamental problem that the absolute value of a measurement value drifts with the passage of measurement time.

The first and second problems described above are caused by the poor response of the resistance thermometer to the movement of minute heat quantity. The resistance is heated to the highest possible temperature.
It is necessary to secure measurement sensitivity and dynamic range. It is necessary to ensure the measurement sensitivity and dynamic range by increasing the temperature difference between the two resistance temperature detectors as much as possible. It is considered that this occurs because it is necessary to adopt such a configuration.

The first and second problems become more remarkable as the sensitivity of the resistance temperature detector is increased. That is, if the measurement sensitivity is to be increased, it becomes obvious. This is basically a difficult problem to solve.

The third problem is important when the power consumption of the entire apparatus is to be reduced. In particular, when the apparatus is driven by using a battery as a power source, this becomes a serious problem. As a method of solving the problem of power consumption, there is a method of making the element itself extremely small and reducing its power consumption. However, in the case of performing a thermal operation, reducing the size of the element causes variation in the characteristics of the element to be likely to occur, which greatly reduces the practicality.

The fourth problem is that, in the configuration shown in FIG. 10, even if the flow value of the fluid 307 is constant,
This is a phenomenon that the output flow value gradually changes. This phenomenon is caused by the fact that when a bridge circuit as shown in FIG. 10 is employed, the absolute value of the measured value cannot be determined even if the relative sensitivity can be ensured. This variation appears as a DC drift component in the measured value of the flow rate, and greatly hinders accurate flow rate measurement.

As a method of solving the problem of the DC drift, there is a method of providing a complicated correction circuit or performing correction by adding digital processing. However, this leads to higher costs and lower device reliability,
Not practical.

[0022]

SUMMARY OF THE INVENTION An object of the invention disclosed in this specification is to provide an apparatus having a relatively simple configuration and having at least one of the following functions. (1) No DC drift and no influence of temperature
In addition, flow measurement with high sensitivity and high dynamic range is performed with low power consumption. (2) Perform fluid identification without DC drift and without being affected by temperature. (3) Measure the mixing ratio of multiple fluids without DC drift and without being affected by temperature. (4) There is no DC drift and the concentration of a substance contained in the fluid is measured (for example, measurement of humidity) without being affected by temperature.

[0023]

The structure of the main invention disclosed in this specification will be described below. Note that, in the configurations of the respective inventions, the overlapping components have the same contents. That is, in a plurality of configurations of the present invention, when the same component A exists, they have the same technical scope,
Have the same technical content.

Further, each component constituting the invention disclosed in this specification is not limited to the specific examples described in this specification, but has a function defined by each component. If it is, it can be replaced with another component.

One of the main constitutions disclosed in this specification is as follows.
A thin-film material disposed in contact with a fluid, a means for performing pulse-like heating on the thin-film material, a means for measuring a response characteristic of the thin-film material according to the heating by the means, and an output corresponding to the temperature of the fluid And means for obtaining

In the above structure, examples of the thin film material include a diamond thin film, an aluminum nitride thin film, a cubic boron nitride thin film, and other thin film materials having high thermal conductivity and low specific heat. In particular, it is effective to use a diamond thin film or a nitrogen-based hard thin film.

As the fluid in the invention disclosed in this specification, gas, liquid, atomized fluid (atomized fluid or gas or liquid containing solid powder), or fluid such as liquid crystal material Materials having properties.

As means for performing pulse-like heating (heating), a resistance heating element provided in contact with a thin film material can be cited. Various metal thin films can be used as the resistance heating element. In order to cause the resistance heating element to generate heat in a pulse shape, a predetermined voltage or a predetermined current may be applied to the resistance heating element at an appropriate timing.

As the means for performing the pulse-like heating, a semiconductor of one conductivity type may be used. in this case,
A resistor may be formed by using a semiconductor material as the thin film material and doping impurity ions imparting one conductivity type into the thin film or the surface of the thin film. As a means for performing the pulse-like heating, a resistance heating element may be formed of a semiconductor material having one conductivity type on the thin film material.

As a means for measuring the response characteristics of the thin film material following the pulsed heating, there is a method of measuring the resistance change of a resistance temperature detector (for example, a platinum thin film) in contact with the thin film material by an appropriate electronic circuit. it can. In this case, the response characteristic of the thin-film material is measured by a temperature-measuring resistor as a temperature change of the thin-film material itself in response to pulse-like heating.

As the temperature measuring resistor, a semiconductor material having one conductivity type may be used. In this case, a semiconductor material having one conductivity type may be selectively formed on the thin film material to serve as a temperature measuring resistor. Further, the thin film material is composed of a semiconductor material, and impurity ions imparting one conductivity type are implanted into or on the surface of the thin film material made of the semiconductor,
A temperature measuring resistor may be formed.

FIG. 5 shows the response characteristics (temperature change of the diamond thin film) when pulsed heating is actually performed on the diamond thin film. FIG. 5 shows a state in which the diamond thin film is rapidly heated by the pulse-like heating, and is cooled after the completion of the heating. The waveform shown in FIG. 5 shows that the resistance change (corresponding to the temperature change of the diamond thin film) of the platinum thin film arranged in contact with the diamond thin film is output as the change of the bias current, and the voltage is obtained by performing I / V conversion. Changes are displayed on an oscilloscope.

It can be understood that what is shown in FIG. 5 is a transient response characteristic of the diamond thin film to the pulsed heating. This transient response characteristic depends on, for example, the flow rate of the fluid flowing in contact with the thin film material. Therefore, by quantitatively evaluating the transient response characteristics, the flow rate of the fluid flowing in contact with the thin film material can be calculated.

Although two response waveforms are shown in FIG. 5, each response waveform is obtained when the flow rate is changed under the same pulse-like heating condition.
The larger response waveform corresponds to the case where the flow rate is zero, and the smaller response waveform corresponds to the case where the flow rate is present.

The difference between the two response waveforms can be understood by considering the following. That is, when there is a flow rate, a large amount of heat is deprived of the fluid from the diamond thin film, so that the diamond thin film is hard to be heated and easily cooled during pulse-like heating. Conversely, when there is no flow rate, the fluid is not deprived of much heat from the diamond thin film, so that the diamond thin film is easily heated and hardly cooled during pulsed heating.

The response characteristic of the thin film material to the pulse-like heating can be obtained by measuring the response characteristic by: (1) an operation of integrating a parameter corresponding to the temperature of the thin film material before the pulse-like heating; This operation is performed by performing an operation of integrating a parameter corresponding to the temperature of the thin film material after the pulse-shaped heating and (3) an operation of calculating a difference between the two integrated values.

A specific example of this operation will be described with reference to FIG. FIG. 4 corresponds to FIG. 5 and shows a change over time of the output f from the resistance temperature detector corresponding to the temperature of the thin film material. The output f is a parameter corresponding to a change in the resistance value of the resistance bulb arranged in contact with the thin film material. Generally, as f, a change in the resistance value of the resistance temperature detector is detected as a change in the value of the current flowing through the resistance temperature detector, and a value obtained by performing I / V conversion to obtain a voltage change is used. Can be

First, the output f is integrated between t ₀ and t ₀ + Δt ₀ before the pulse-shaped heating is performed. This integration is represented by the following [Equation 1]. The value calculated by this [Formula 1] corresponds to the area of the hatched portion 41 in FIG. The above corresponds to the operation (1).

[0039]

(Equation 1)

Next, the temperature change of the thin film material according to the pulsed heating performed during the time from t ₁ to t ₁ + Δt ₁ (42
The temperature rises rapidly as shown by (3) and is cooled as shown by (43)) from time t ₂ to time t ₂ + Δt ₂ . This integration is represented by the following [Equation 2]. The above corresponds to the above operation (2).

[0041]

(Equation 2)

Next, the result of the operation of [Equation 1] and [Equation 2]
Is calculated according to the following equation (3). The result of the operation of [Equation 3] is shown in FIG.
Corresponds to the area of the hatched portion 44. The above corresponds to the operation (3).

[0043]

(Equation 3)

By performing the above operations (1) to (3),
The response characteristics of the thin film material to the pulsed heating can be accurately evaluated. That is, by performing the operation (1), every time the pulse-like heating is performed, the temperature of the diamond thin film immediately before the pulse-like heating is always determined, so that the pulse-like heating to be measured is determined. In this case, the transient response characteristics of the thin film material may not include a DC drift component. The measured value of the transient response characteristic corresponds to the area of the region indicated by the hatched portion 44 in FIG.

Evaluation results of this transient response characteristic (Equation 3)
) Includes, for example, information on the flow rate of the fluid, the temperature of the fluid, the type of the fluid, and the impurity concentration.

The "means for obtaining an output corresponding to the temperature of the fluid" is a means having a function of measuring the temperature of the fluid to be measured, for example, means functioning as a suitable thermometer. is there. Specifically, a known resistance thermometer (generally marketed as various thermistors) can be used.

FIGS. 1 and 2 show specific examples of the configuration described above. In FIG. 1 and FIG.
Is a thin film material (in this case, a polycrystalline diamond thin film) arranged to be in contact with the substrate. Numeral 11 denotes a means for heating the diamond thin film 13 in a pulsed manner (resistance heating element), which is constituted by a platinum thin film formed on the surface of the diamond thin film. The response characteristic of the diamond thin film 13 to the pulsed heating performed by the heating element 11
5, is converted into a digital signal by the A / D converter 106, and is processed by the CPU 107.

The amplifier 105 and the A / D converter 1
06, the CPU 107 constitutes a means for measuring the response characteristics of the diamond thin film 13. Then, the CPU 107 performs calculations as shown in [Equation 1] to [Equation 3]. Here, as means for measuring response characteristics, an amplifier 105, an A / D converter 106,
Although the configuration including the CPU 107 has been described, a semiconductor memory and a required configuration can be added. As a means for measuring the response characteristic, a configuration that can perform the same function as the configuration shown in FIGS. 1 and 2 may be adopted.

Reference numeral 111 denotes a resistance temperature sensor in contact with the fluid, which constitutes means for obtaining an output corresponding to the temperature of the fluid 202. Using the output from the resistance temperature detector 111 and the result of [Equation 3], the CPU 107 performs a predetermined calculation, and calculates a flow rate measurement value in which the temperature of the fluid is compensated.

According to another aspect of the present invention, there is provided a thin film material arranged in contact with a fluid, a means for performing pulse-like heating on the thin film material, and a means for measuring a response characteristic of the thin film material according to the heating by the means. And the means for evaluating the response characteristics has a temperature compensation function for the temperature of the fluid and / or the measurement environment.

In the above configuration, the temperature compensation function is a function of eliminating the influence of temperature, a function of obtaining a measurement value that is not affected by temperature, or a function of being affected by temperature when performing a target measurement. Function that corrects the measured value to an appropriate value.

The details of the temperature compensation function will be described later. Further, an evaluation method (operation method or operation form) performed by the means for evaluating the response characteristics will be described later.

According to another aspect of the present invention, there is provided a thin film material arranged in contact with a fluid, a means for performing pulse-like heating on the thin film material, and a means for measuring a response characteristic of the thin film material according to the heating by the means. And a means for evaluating the response characteristics measured by the means, wherein the means for performing the pulse-like heating has a temperature compensation function corresponding to the temperature of the fluid and / or the measurement environment. I do.

In the above configuration, the means for performing the pulse-shaped heating has the temperature compensation function corresponding to the temperature of the fluid and / or the measurement environment because the heating means does not depend on the influence of the temperature or the influence of the temperature. Means that a function is provided for performing heating so as to obtain a response characteristic (transient response characteristic of the thin film material to pulse-like heating) that is not greatly affected by the heating.

As an example of such a temperature compensating function, there can be mentioned an example of using a material such as a constantan whose change in resistance due to temperature is as small as possible as means for performing pulse-like heating (heating). As a material whose change in resistance due to temperature is as small as possible, the change in resistance value is preferably 10 ppm or less within the operating temperature range.

As described above, when a material whose resistance value changes with respect to temperature as small as possible is used as a means for performing pulse-like heating, the pulse-like heating is performed with a constant amount of heat almost without depending on the temperature change of the fluid. It can be carried out. Then, the flow rate measurement can be performed while greatly reducing the influence of the temperature change of the fluid. (About this point, [Operation section]
Will be described in detail)

As a method of heating the thin film material with a fixed amount of heat regardless of the temperature of the fluid, a method of irradiating the thin film material with a laser beam can be mentioned. in this case,
If the laser light oscillation device is not affected or hardly affected by a temperature change, a constant amount of heat can always be supplied to the thin film material during pulsed heating.

As a temperature compensation function of the means for performing the pulse-like heating, there can be mentioned a configuration in which the amount of heat generated by the heating element is changed according to the temperature of the fluid and / or the measurement environment. For example, an output from the resistance temperature detector for detecting the temperature of the fluid is fed back to the heating element by performing an appropriate gain adjustment, and a configuration in which the amount of heat generated from the heating element is changed according to the temperature of the fluid, A function of determining the voltage to be supplied to the resistance heating element in the CPU based on the output from the temperature measuring resistor for detecting the temperature, and changing the amount of heat generated from the resistance heating element in accordance with the temperature of the fluid can be given.

For example, as shown in FIG. 11, the heating element 11 is referred to by referring to the output of the resistance bulb 111 in contact with the fluid.
In which the CPU 107 determines the voltage for controlling the voltage.

The above configuration is inconsistent with the above-described configuration in which the heat generation amount of the heating element or the heat amount supplied from the heating element to the thin film material is constant. However, these are different approaches for performing temperature compensation, and to a greater or lesser extent, both configurations are effective. A more effective temperature compensation function is a configuration in which the amount of heat generated by the latter heating element is changed according to the temperature of the fluid and / or the measurement environment.

According to another aspect of the present invention, there is provided a thin film material arranged in contact with a fluid, a means for performing pulse-like heating on the thin film material, and a means for measuring a response characteristic of the thin film material according to the heating by the means. And means for obtaining an output corresponding to the temperature of the fluid, and means for obtaining information about the fluid from the response characteristic and the output corresponding to the temperature of the fluid.

In the above configuration, “means for obtaining information about the fluid from the response characteristic and the output corresponding to the temperature of the fluid” means that the temperature compensation is performed by referring to the output corresponding to the temperature of the fluid. It has the function of obtaining information about the fluid in a done form. For information on fluids,
Examples include a flow rate and a flow velocity of a fluid, a type of a fluid, a mixing ratio of a fluid in which two types of fluids are mixed, a presence or absence of impurities in a fluid, and a concentration thereof.

According to another aspect of the present invention, there is provided a thin-film material arranged in contact with a fluid, a means for performing pulse-like heating on the thin-film material, and a means for measuring a response characteristic of the thin-film material according to the heating by the means. Wherein the means for performing the pulse-like heating has a function of supplying a constant amount of heat without depending on a temperature change of a fluid and / or a measurement environment.

According to another aspect of the present invention, there is provided a thin film material arranged in contact with a fluid, a means for performing pulse-like heating on the thin film material, and a means for measuring a response characteristic of the thin film material according to the heating by the means. And means for changing a parameter for controlling the amount of heat generated by the heating element in accordance with a change in temperature of the fluid and / or the measurement environment. The means for measuring the response characteristic has a function of performing temperature compensation. It is characterized by the following.

In the above configuration, as a means for changing the parameter for controlling the amount of heat generated by the heating element in accordance with the temperature change of the fluid and / or the measurement environment, a configuration as shown in FIG. 8 can be mentioned. In the configuration shown in FIG. 8, the voltage supplied to the resistance heating element 811 made of a platinum thin film is changed by the change in the resistance value of the temperature measuring resistor 804 also made of the platinum thin film (this change in the resistance value becomes the output change of the bridge 2). ).

The resistance temperature detector 804 is formed on the surface of the diamond thin film 805 disposed in contact with the fluid, and its resistance value changes according to the temperature of the fluid. Then, the resistance change causes imbalance in the bridge 2.
The imbalance of the bridge 2 (referred to as the output of the bridge 2) is amplified by the amplifier 812 to drive the heating element 811 formed on the surface of the diamond thin film 809. At this time, the voltage supplied to the heating element 811 reflects the temperature of the fluid detected by the resistance temperature detector 804. That is, a voltage (a parameter for controlling the amount of heat generated by the heating element 811) corresponding to the temperature of the fluid is supplied to the heating element 811.

In the configuration shown in FIG.
The response characteristic of the diamond thin film 809 to the pulse-like heating from the heating element 811 is measured by the method 15.
The measurement of this response characteristic is based on the method shown in FIG. Further, the CPU 815 uses the measured value of the response characteristic (result of quantitatively evaluating the response characteristic) and the output from the temperature measuring resistor 819 indicating the change in the resistance value corresponding to the temperature of the fluid, to determine the temperature of the fluid. Is calculated in a form that compensates for.

FIGS. 11 and 12 show examples of means for changing a parameter for controlling the amount of heat generated by the heating element in accordance with a change in temperature of the fluid and / or the measurement environment. In the configuration shown in FIGS. 11 and 12, the fluid 202 detected by the resistance bulb 111
The voltage supplied to the heating element 11 is controlled by the CPU 107 on the basis of the temperature and the information stored in the memory 1102.

According to another aspect of the present invention, there is provided a thin film material arranged in contact with a fluid, a means for performing pulse-like heating on the thin film material, and a means for measuring a response characteristic of the thin film material according to the heating by the means. And means for compensating for the temperature of the fluid and / or the measurement environment and calculating the flow rate or the flow velocity of the fluid from the response characteristics.

The “means for performing temperature compensation for the temperature of the fluid and / or the measurement environment and calculating the flow rate or flow velocity of the fluid from the response characteristics” in the above configuration includes:
The configuration shown in FIG. 1 can be given. In the configuration shown in FIGS. 1 and 2, the evaluation result of the response characteristic of the diamond thin film 13 to the pulsed heating (performed by the CPU 107 by the method shown in FIG.
The flow rate of the fluid 202 is calculated by the CPU 107 in a form that compensates for the temperature of the fluid 202 based on the resistance change of the resistance temperature detector 111 arranged in contact with 2.

It is to be noted that, instead of or in addition to the resistance temperature detector 111, another resistance temperature detector is arranged so as to detect the temperature of the measurement environment, thereby compensating for the temperature of the measurement environment. You can also.

According to another aspect of the present invention, there is provided a thin film material arranged in contact with a fluid, a means for performing pulse-like heating on the thin film material, and a means for measuring a response characteristic of the thin film material according to the heating by the means. And means for calculating the flow rate or flow rate of the fluid from the response characteristics, wherein the means for calculating the flow rate or flow rate has a temperature compensation function for the temperature of the fluid and / or the measurement environment. I do.

In the above-mentioned configuration, the configuration in which “the means for calculating the flow rate or the flow velocity has a temperature compensating function for the temperature of the fluid and / or the measurement environment” can be, for example, the configuration shown in FIGS. 1 and 2. .

In the configuration shown in FIGS. 1 and 2, the CP
In U107, the temperature of the fluid 202 is compensated based on the resistance change of the resistance temperature detector 111 which performs the resistance change corresponding to the temperature of the fluid 202 and the response characteristic of the diamond thin film 13 to the pulsed heating by the heating element 11. The flow rate of the fluid 202 is calculated in this manner.

According to another aspect of the present invention, there is provided a thin film material arranged in contact with a fluid, a means for performing pulse-like heating on the thin film material, and a means for measuring a response characteristic of the thin film material according to the heating by the means. And means for causing the parameter to be measured to be constant or approximately constant or within a constant range or approximately within a constant range.

In the above configuration, the parameters to be measured include those relating to the flow rate of the fluid, those relating to the type of fluid, those relating to the ratio of specific components contained in the fluid, and those relating to the mixing ratio of the two types of fluid. , And a fluid related to air humidity.

In the above configuration, “means for making the response characteristic be constant or approximately constant or within a constant range or approximately within a constant range when the parameter to be measured is constant or approximately constant” is as shown in FIG. 11 can be cited. In FIG. 11, the flow rate of the fluid is adopted as the parameter to be measured. In the configuration shown in FIG. 11, at least the resistance bulb 111 and the CP
The above means is constituted by U107 and the semiconductor memory 1102.

The semiconductor memory has a diamond thin film 1
In the case where the flow rate of the fluid flowing in contact with 3 (being a measured parameter) is a constant value F _i (for example, the flow rate is 0),
Response characteristic of the diamond thin film when the pulsed heating from the heating element 11 (assessed as the area represented by 44 in FIG. 4), such as S _i is constant, the fluid to be detected by the RTD the combination of the voltage V _n is supplied to the heating element 11 (resistance heating element) and the temperature T _n is stored. The stored contents are shown in, for example, Table 5 below.

[0079]

[Table 5]

Table 5 means that the resistance temperature detector 11
With respect to the temperature T _n of the fluid 1 is detected, the corresponding voltage V
_n , the heating element 11 is heated to a predetermined flow rate F _i
, A constant response characteristic S _i is always obtained.

[0081] Further, if the another perspective, in order to obtain a response characteristic constant for a given flow rate, the heating element at a voltage V _i corresponding to the value of the temperature T _i of the fluid as shown in Table 5 11
That is, it is only necessary to supply a voltage.

[0082] That is, according to the data shown in Table 5, by heating the heating element 11 at a predetermined voltage V _n,
Regardless of the temperature T _n of the fluid can be made to the measured parameters at a constant or approximately constant in the state, the response characteristic of the diamond thin film to the pulse-like heating and constant or substantially constant.

As a result, the response characteristics of the diamond thin film to the pulse-like heating correspond to the flow rate, and the flow rate can be measured with the temperature compensated.

[0084] In the configuration shown in FIG. 11 illustrated herein uses a temperature of the fluid as T _n. However, if the influence of the temperature of the measurement environment is dominant it may be used the temperature of the measurement environment as T _n. Further, both the temperature of the fluid and the temperature of the measurement environment may be used.

Here, the description has been given of the configuration for compensating for the temperature change of the fluid. However, it is also possible to compensate for not the temperature of the fluid but other parameters such as the pressure of the fluid. In this case, as data as shown in Table 5, values of other parameters such as fluid pressure (Table 5)
(Corresponding to T _i ) is obtained in advance, and the data on what voltage should be applied to the heating element 11 may be obtained in advance and stored in the semiconductor memory 1102. Further, a pressure sensor may be provided instead of the resistance temperature detector 111.

As a means for making the response characteristics of the thin film material constant to the pulse-like heating, there is a method of controlling the amount of heat generated by the means for performing the pulse-like heating. As a specific example of this method, as a means for performing pulse-like heating, a resistance heating element arranged in contact with the thin film material is used, and by changing a voltage to add a heating value generated by the heating element, An example of controlling may be given.

As a means for making the response characteristic of the thin film material to the pulsed heating constant, there is a method of controlling a parameter for changing the amount of heat supplied to the thin film material by the means for performing the pulsed heating. be able to.

One example of a method of controlling these parameters is to use a resistive heating element arranged in contact with the thin film material and control the voltage supplied to the heating element as means for performing pulse-like heating. Can be mentioned.

As another example of a method for controlling the above parameters, a means for irradiating a laser beam to the thin film material as a means for performing pulsed heating and controlling the irradiation energy density of the laser beam is used. Can be mentioned.

As the thin film material used in the structure of the main invention disclosed in this specification, it is most preferable to use a diamond thin film formed by a vapor phase method (CVD method). Since the diamond thin film has a higher thermal conductivity and a lower specific heat than other materials, it responds with high sensitivity to pulsed heating. Further, in the case of a diamond thin film of the degree used in the invention disclosed in this specification (that is, it does not need to be a single crystal), its manufacturing method has been established, and there is no great industrial difficulty. There is.

As will be described in detail in the examples below, when a flow rate measuring sensor is actually manufactured using the invention disclosed in this specification, a remarkable effect is obtained by using a diamond thin film as the thin film material. be able to.

As a material that can be used other than the diamond thin film, it is useful to use aluminum nitride or cubic boron nitride, but there is a problem that the production is difficult. Although single crystal silicon or silicon carbide can be used, there is a drawback that the measurement range (dynamic range) when measuring the measurement accuracy and the flow rate is narrowed.

As a thin film material that can be used in the invention disclosed in this specification, it is desirable that the time constant τ shown by the following [Equation 11] is 0.2 ms or less. By satisfying this condition, the thermal conductivity becomes 1000
(Wm / K) It is possible to obtain a flow rate measuring device having characteristics similar to or higher than the case of using a polycrystalline diamond thin film.

[0094]

[Equation 11]

The time constant τ obtained by the above [Equation 11]
Is a parameter for quantitatively evaluating the time that the thin-film resistance temperature sensor responds thermally.
d Actuators, A21-A23 (1990) 425-430.

According to the findings of the present inventors, this [Equation 1]
1) can be used as a measure of how long the thin film material responds upon heating. That is,
It can be understood that the thinner the time constant τ shown in [Equation 11], the faster the thin film material responds to heating. In addition, it can be understood that the smaller the time constant τ is, the more easily the time constant τ is affected by the surrounding thermal influence. That is,
It can be considered that the smaller the time constant τ is, the more thermally sensitive it is.

Table 4 below shows what value the time constant shown by the above [Equation 11] takes for various materials.

[0098]

[Table 4]

Table 4 shows the values of the above [Equation 11] based on the physical property values of various thin film materials at 300K.
It is the result of calculating the time constant indicated by. The physical properties of each material are as thin as possible. Note physical properties of standing orthorhombic boron nitride is an ideal value, a value different from the actually obtained value (it is difficult to obtain in practice a thin film of standing orthorhombic boron nitride). The time constant τ of the standing orthorhombic boron nitride thin film actually obtained is considered to become more significant.

As will be described later in detail in Examples, it has been found that when a diamond thin film is used as the thin film material in the invention disclosed in this specification, remarkable characteristics can be obtained as a flow sensor. When a diamond thin film is used, remarkable characteristics can be obtained because the time constant τ calculated by the above [Equation 11] is larger than that of other thin film materials as shown in the above [Table 4]. It is considered that this is due to the fact that it is remarkably small.

That is, the smaller time constant shown in Table 4 is more susceptible to the influence of the surrounding heat, and therefore the response characteristic of the thin film material to the pulsed heating influences the influence of the surrounding heat. Is easily reflected, for example, it can be considered that a minute change in the flow rate accurately appears in this response characteristic.

This means that when the response characteristics to pulsed heating as shown in FIGS. 4 and 5 are observed using a thin film material such as zirconium, the ratio of the change in the response waveform to the change in the flow rate or the change in the temperature. Is smaller (i.e., lower in sensitivity) than when a diamond thin film is used.

From the above, it can be concluded that the flow rate sensor having better characteristics can be obtained as the material having a smaller time constant shown in Table 4 is used. For example, when a thin film material having a time constant τ equal to or less than the time constant τ in the case of a polycrystalline diamond thin film formed by the CVD method is used, it is possible to obtain the same characteristics as those shown in Examples described later. it can.

This is not limited to the flow rate sensor.
This is also true for gas sensors and the like.

From the viewpoint of economy and the like, it is useful to use single crystal silicon or silicon carbide. In this case, there is a demerit that the measurement accuracy and the sensitivity are reduced as compared with the case where the diamond thin film is used, but it is possible to obtain an advantage that the fabrication is easy and the material is easily available.

According to the knowledge of the present inventors, the time constant τ is 2
By using a thin film material having a length of less than millisecond, its characteristics are lower than when a diamond thin film is used, but it is possible to obtain a flow sensor and a gas sensor which are sufficiently practical. As apparent from Table 4 above, single-crystal silicon, silicon carbide, and aluminum nitride can be used as a thin film material satisfying such requirements. When such a material is used, a sensor having the following characteristics when a diamond thin film is used (a sensor here has a broad meaning including a flow sensor including a gas sensor) can be obtained.

As described above, a high-performance sensor can be obtained by using a thin film material having a time constant τ of 2 ms or less, preferably 0.2 ms or less. When a resistance temperature detector arranged in contact with the thin film material is used as a means for detecting the response characteristics of the thin film material, the thin film material is preferably a semiconductor or an insulator. In the case where a semiconductor material is used as the thin film material, a heating element or a temperature measuring resistor can be formed of a semiconductor layer having one conductivity type in or on the surface of the thin film material.

When a conductor is used as the thin film material and a resistance temperature detector is used as a means for measuring the response characteristics to pulsed heating, it is necessary to form an insulating film on the surface of the thin film material. However, when the temperature change of the thin film material is measured by a measuring means (for example, means such as thermography) other than the resistance temperature detector, a conductor can be used as the thin film material as it is.

[0109]

The flow rate can be measured, for example, by evaluating the (transient) response characteristics of the thin film material following the pulsed heating. When a thin film material is brought into contact with a fluid, there is a thermal interaction between the fluid and the thin film material according to the flow rate of the fluid. This interaction has some thermal effect on the thin film material. For example, when the flow rate is large, the cooling of the thin film material after the constant heating is easy to proceed quickly, and when the flow rate is small, the cooling of the thin film material after the constant heating is difficult to progress.

When a predetermined pulsed heating is performed on the thin film material, the thin film material is rapidly heated and cooled according to the pulsed heating. In this case, the heating state (the state where the temperature of the thin film material rises) and the cooling state (the state where the temperature of the thin film material falls) are greatly affected by, for example, the flow rate of the fluid flowing in contact with the thin film material. become.
The state of heating and the state of cooling of the thin film material with respect to the pulse-like heating can be referred to as a transient response characteristic to the pulse-like heating of the thin film material.

This transient response characteristic involves only a change from the temperature of the thin film material immediately before performing the pulse-like heating (the temperature change of the thin film material). It is hardly affected by temperature, which fluctuates considerably.

Therefore, by evaluating this transient response characteristic, it is possible to obtain a measured value that does not include a DC drift component. For example, in a flow rate measurement, a measurement value in which a DC drift component does not appear in the measurement value can be obtained.

The transient response characteristic can be understood to be related to the number and speed of molecules constituting the fluid that collides with the thin film material. Therefore, the flow rate in this specification can be understood to mean a mass flow rate.

When a material having no change in resistance to temperature change (or a material having little change in temperature (eg, constantan)) is used as a temperature compensation function of the means for performing pulse-like heating, the temperature is reduced for the following reasons. Compensation can be made. Here, it is assumed that the thermal properties of the fluid do not change with the temperature, and the thermal properties of the thin film material do not change. (In reality, the parameters based on the above assumptions are approximate because the fluid parameters change with temperature.)

In this case, the voltage or current required for heating,
If the time for applying a voltage or the time for flowing a current is determined, the heating element generates a substantially constant amount of heat regardless of the temperature of the environment in which it is placed. Therefore, the thin-film material is supplied with a heat quantity that is independent (or almost independent) of the temperature of the fluid during the pulse-like heating.

In this case, if there is no change in the flow rate, the thin film material is heated to a temperature having a constant temperature difference with respect to the temperature of the fluid. Of course, if the amount of heat to be supplied to the thin film material is determined, the ultimate temperature (heated temperature) of the thin film material is determined by the specific heat, mass, and shape of the thin film material.
Is an approximation that holds when it is considered that is determined.

In this case, the response characteristic of the thin film material to the pulsed heating does not largely depend on the temperature of the fluid but depends on the flow rate of the fluid. Therefore, by evaluating the response characteristics of the thin film material to the pulsed heating, the influence of the fluid temperature can be greatly reduced, and the flow rate value can be measured. That is, the flow rate can be measured while performing temperature compensation. The above discussion is based on the above-mentioned assumption (assuming that the parameters of the fluid do not change with temperature), and cannot perform perfect temperature compensation. Actually, the operating speed of the CPU, the resistance value of the resistors constituting the circuit, the characteristics of the amplifier, and the like also change depending on the temperature. Therefore, when measuring with higher accuracy, it is necessary to compensate for the effects. is there.

On the other hand, as a temperature compensation function of the means for performing pulse-like heating, there can be mentioned a configuration in which the amount of heat generated by the heating element is changed according to the temperature of the fluid and / or the measurement environment. In this case, it is possible to compensate to some extent the effects of various parameters (viscosity, density, thermal conductivity, etc.) according to the change in the temperature of the fluid and changes in the circuit constants on the temperature change. Here, the predetermined number of circuits means the operating speed of the CPU, the resistance value of the resistor, the gain of the amplifier, and the like.

In the case of this configuration, the amount of heat supplied to the thin film material at the time of the pulse-like heating is changed in accordance with the change of the parameter of the fluid and the change of the values of the various constants of the circuit with respect to the temperature change of the fluid and / or the measurement environment. Change. That is, under a constant flow rate condition, the voltage applied to the heating element is adjusted so that the area of the waveform of the response characteristic shown in FIGS. 4 and 5 becomes constant with respect to the fluid temperature and / or the temperature change of the measurement environment. And control the current. Then, it is possible to realize a situation in which the effects of the above-described changes in the parameters do not appear in the response characteristics shown in FIGS. 4 and 5 or the effects can be minimized.

As shown in FIG. 1 and FIG.
2 is detected by the resistance temperature detector 111, and this data and
The response characteristic of the diamond thin film 13 according to the pulsed heating by the heating element 11 is used by the CPU 107 by using data evaluated by the method shown in FIG.
The flow rate of the fluid 202 can be calculated while compensating for the temperature of the fluid 202.

Further, under a constant condition of a parameter to be measured (for example, a flow rate), a response characteristic of the thin film material to pulse-like heating as shown by an area 44 in FIG. Is set to be constant or approximately constant or within a constant range or within a substantially constant range, so that the response characteristic does not depend on the temperature of the fluid and / or the measurement environment, or the influence thereof is largely eliminated. it can.

As a result, the response characteristic can be made to correspond to the parameter to be measured. And for example
The flow rate can be measured while performing highly accurate temperature compensation.

As the thin film material used in the invention disclosed in this specification, it is useful to use a thin film material having a time constant represented by the following [Equation 11] of 5 ms or less, preferably 1 ms or less. By using such a thin film material, a sensor (for example, a flow sensor) having high sensitivity and high dynamic range can be obtained. In particular,
By using a material having the above time constant τ of 1 ms or less as a thin film material: ・ It has an extremely wide dynamic range.・ It has extremely high sensitivity. -Power consumption can be kept low. (E.g., a flow sensor) having such significance.

[0124]

【Example】

[Embodiment 1] FIG. 3 shows an example of a flow rate measuring element (basic sensor unit) required for carrying out the invention disclosed in this specification. In FIG. 3, reference numeral 13 denotes a 5 μm-thick 3 ×, which is vapor-phase synthesized using a magnetic field microwave CVD method.
It is a polycrystalline diamond thin film having a size of 5 mm. Reference numeral 12 denotes a 0.1 μm-thick platinum resistance temperature detector formed by a sputtering method. Reference numeral 11 denotes a heating resistor of platinum having a thickness of 0.1 μm similarly formed by a sputtering method. Reference numerals 10 and 15 denote the electrodes, and reference numeral 17 denotes a gold wire for bonding. 18 is a diamond thin film 13
Is a Teflon-made substrate that holds The resistance of the resistance bulb 12 and that of the heating element 11 are different only. Here, the resistance of the resistance bulb 12 is about 1 KΩ, and the resistance of the heating element 11 is about 100Ω.

The flow rate measuring element shown in FIG. 3 has a configuration in which the diamond thin film 13 is held on a Teflon base 18. This is to ensure that the diamond thin film 13 is thermally insulated from other than the fluid. In this manner, by holding the thin film material (in this case, the diamond thin film) in a thermally insulated manner, it is possible to provide a structure in which heat other than the fluid does not flow away from the thin film material, and the thermal conductivity between the fluid and the thin film material is reduced. Interaction can be accurately evaluated.

Hereinafter, a method for producing a diamond thin film will be described. The method for producing a diamond thin film described here is a gas phase synthesis method using high-density plasma. Here, an example in which a diamond thin film is formed using a magnetic field microwave plasma CVD method will be described. Magnetic field microwave plasma CV
The method D is a method of synthesizing a vapor phase of a diamond thin film using an interaction between a strong magnetic field and a microwave.

The film forming conditions are shown below. Substrate temperature 800 ° C. Reaction pressure 0.25 Torr Microwave power 4 KW (2.45 GHz) Reaction gas CH ₃ OH: H ₂ = 1: 4 Film formation time 10 hours Film thickness 5 μm Substrate Single crystal silicon wafer Single crystal silicon under the above conditions A diamond thin film synthesized in a vapor phase on a wafer has a polycrystalline structure. The thermal conductivity of this polycrystalline diamond thin film is 1000 (W /
mK).

Although the example using the magnetic field microwave CVD method has been described, a diamond thin film may be obtained by using another vapor phase synthesis method. Alternatively, a diamond thin film may be obtained using a method other than the gas phase synthesis method. The impurity concentration in the diamond thin film should be as low as possible. This is because the smaller the impurity concentration in the diamond thin film, the lower its specific heat and its thermal conductivity.

Hereinafter, a flow rate measuring system using the flow rate measuring element shown in FIG. 3 will be described. FIG. 1 shows a block diagram of the entire system. FIG. 2 shows a schematic configuration of the entire system. FIG. 1 shows a schematic block diagram of the entire system shown in FIG. 1 and 2, 1
The resistors denoted by 2, 102, 103 and 104 constitute a bridge circuit. The resistors 12 and 102 are formed of platinum thin films formed on the surfaces of the diamond thin films 13 and 101, respectively. The resistor 102 has substantially the same resistance as the resistor (temperature measuring resistor) 12.

The diamond thin films 13 and 101 are both arranged in contact with the fluid. In addition, diamond thin film 13
And 101 are formed by the same film forming method and have the same dimensions. The resistors 103 and 104 are made of a material having a resistance change as small as possible with respect to a temperature change.

The temperature measuring resistor indicated by reference numeral 102 is formed on the surface of the diamond thin film 101 so that when the temperature of the fluid and / or the measuring environment changes significantly, the DC balance of the bridge circuit does not change significantly. In order to

The output of the bridge circuit is amplified by the amplifier 105 and input to the A / D converter 106. A / D
The signal converted into a digital signal by the converter 106 is C
It is input to PU107. On the other hand, the CPU 107
The output from the resistance thermometer 111 converted into a digital signal by the / A converter 110 is input. The resistance temperature detector 111 is for measuring the temperature of the fluid,
It is arranged in contact with the fluid. In addition, by selecting the resistance values of the resistors 112 and 113 so that the resistance bulb 111 is not heated, the output from the resistance bulb 111 hardly depends on the flow rate of the fluid. Sex can be neglected). That is, the resistance temperature detector 111 can function as a means for detecting the temperature of the fluid 202.

In the CPU 107, predetermined arithmetic processing described later is performed based on the output from the A / D converter 106 and the output from the A / D converter 110.
The output from the CPU is displayed on a display device 109 composed of an LCD. A predetermined voltage or current is supplied to the heating element 11 at a predetermined timing by a switch 108 controlled by the CPU 107.

In this embodiment, the voltage applied to the heating element 11 at the time of the pulsed heating is 3 V, and the energizing time is 0.2 seconds. It is estimated that the temperature of the diamond thin film rises by about 20 K by heating from the heating element.

In this embodiment, a one-chip integrated circuit indicated by a dotted line 114 having A / D converters 110 and 106 and a switch 108 in addition to the CPU 107 is used. In this embodiment, a TSS400AFW which is a microprocessor of Texas Instruments is used as the integrated circuit 114. This microprocessor can be used for various sensors, and has various D / A converters and switching functions.

The output processed by the CPU 107 is displayed on an external LCD 109. Here, LCD10
Although an example of displaying the output is shown in FIG. 9, the output from the CPU 107 may be stored in an appropriate memory or output to the outside of the apparatus.

[0137] As shown in FIG. 2, the die Ya Mondo films 13
One surface of each of the pipes 101 and 101 is configured to directly contact a fluid (for example, a nitrogen fluid) 202 flowing in the pipe 201.
The resistance temperature detector 111 is also arranged so as to directly contact the fluid 202.

The resistance temperature detector 111 is arranged so as to first touch the fluid flowing through the pipe 201. this is,
This is for accurately measuring the temperature of the fluid. The resistance temperature detector 111 is made of a material 20 having high thermal insulation such as Teflon.
Is held in. In FIGS. 1 and 2, the voltage supplied to the bridge circuit (indicated by V _CC ) and the voltage supplied to the resistance bulb 111 are the same,
This may be a required voltage.

(Operation Method) An example in which the flow rate of a fluid 202 (here, a nitrogen gas fluid) flowing through a pipe 201 is measured using the system shown in FIGS. 1 and 2 will be described. The following operations are all controlled by the CPU 107. The following operation will be described with reference to FIG. The vertical axis in FIG. 4 shows the output (voltage output) from the amplifier 105, and the horizontal axis shows the elapsed time.

(1) In the CPU 107, the amplifier 10
The output f from 5 is integrated between t ₀ and t ₀ + Δt ₀ . This calculation is performed in the CPU 107. This calculation is equivalent to performing the calculation shown in Expression 1 below.

[0141]

(Equation 1)

The value S ₀ obtained by the above operation is calculated as shown in FIG.
Corresponds to the area indicated by the oblique line 41. The operation shown in the above (1) is performed to determine the reference point of the measured value. Here, the above calculation is performed with Δt ₀ = 0.1 seconds.

(2) In response to a command from the CPU 107, the switch 108 operates to supply a current to the heating element 11,
Heating element 11 is heated between t ₁ and t ₁ + Δt ₁ . Here, this heating is performed with Δt ₁ = 0.2 seconds.

The diamond thin film 13 is rapidly heated by the operation process (2) and rapidly cooled by the fluid 202. The temperature change (response to pulsed heating) of the diamond thin film is measured by the resistance thermometer 1
2 is detected as a change in the resistance value. A change in the resistance value of the resistance temperature detector 12 results in a change in the output from the bridge circuit,
CPU 1 via amplifier 105 and A / D converter 106
07. That is, the response characteristic of the diamond thin film 101 to the pulsed heating from the heating element 11 is input to the CPU 107 as an output of the bridge circuit.

The output f of the amplifier 105 changes as indicated by 42 in FIG. 4 according to the heating of the heating element 11. Further, the output f of the amplifier 105 changes as indicated by 43 in FIG. 4 according to cooling after heating (cooling of the diamond thin film). This is shown in FIG. FIG.
5 is a display photograph when the output of No. 5 is connected to an oscilloscope and the output change is displayed on an oscilloscope screen.

[0146] (3) the output f from the amplifier 105 according to the heating in the operation process of the above (2) is integrated in between t ₂ of t ₂ + Delta] t _2. Here, it is assumed that t ₁ <t ₂ . This is t ₁ =
This is because if t ₂ , noise appears in the output f from the amplifier 105. Here, it is assumed that t ₂ = 0.4 seconds. The operation performed here is equivalent to executing the calculation represented by the following Expression 2.

[0147]

(Equation 2)

(4) The calculation represented by the following equation 3 is performed by the CPU 1
07. By this calculation, the hatched portion 4 in FIG.
A value S corresponding to the area of the portion indicated by 4 is obtained. It can be understood that this value S is a quantitative representation of the response characteristics of the diamond thin film 13 to the pulsed heating from the heating element 11.

[0149]

(Equation 3)

(5) In the CPU 107, the above (4)
Based on the value S obtained in the operation process and the output from the resistance bulb 111, the flow rate is calculated based on a calculation method described later.

The operations described in the above (1) to (5) are performed with four seconds as one cycle. That is, the flow rate is calculated once every four seconds.

The values of the parameters Δt ₀ , Δt ₁ , and Δt _{2 described above} can be changed according to the embodiment. When performing the operations shown in the above (1) to (5), Δ
(The upper limit is not particularly operation interval to be longer prolonged, leading to an increase in power consumption) the value of t ₁ or 50ms may be. It is desirable that the value of Δt ₂ has a length of Δt ₁ or more. The value of Δt ₀ can be arbitrarily determined, but is desirably 100 ms or more in order to improve measurement accuracy.

(Operations Performed in CPU)
Hereinafter, a calculation method performed by the CPU in the operation process (5) will be described.

The value S calculated through the above-mentioned operation steps (1) to (5) substantially depends on the flow rate and the fluid temperature. Accordingly, if the flow rate value is Y and the fluid temperature is T, a functional relationship represented by the following [Equation 4] is obtained using an appropriate function L.

[0155]

(Equation 4)

Here, the value of T can be obtained from the output from the resistance bulb 111. Therefore, if the form of the function L is obtained in advance, a flow rate value Y that does not depend on the temperature of the fluid can be obtained by using the calculation result S expressed by Expression 3.

An example in which the flow rate of nitrogen is measured using the configuration shown in FIGS. 1 and 2 will be described below.

In the following, S is an output value (corresponding to the area indicated by oblique lines 44 in FIG. 4) processed by the above-described operation method. This output S contains information on the flow rate. Further, T is the output of the temperature measuring resistor 111 (corresponding to a change in the resistance value). If necessary, these parameters are given appropriate subscripts.

First, the relationship between the output T _0i from the resistance temperature detector 111 and S in a state where the flow rate is 0 is obtained. This relationship can be said to indicate the relationship between the response characteristics of the diamond thin film 13 to pulsed heating from the heating element 11 and the temperature of the fluid detected by the resistance temperature detector 111 as shown in FIG. . The relationship between T _0i and S is a function represented by the following [Equation 5]. The specific form of the function may be obtained using appropriate data processing software.

[0160]

(Equation 5)

In the flow rate measurement, [Equation 1] to
The value S obtained by the method shown in FIG. 4 using [Equation 3] is standardized as shown in the following [Equation 6] using the function A (T _i ) obtained by the above [Equation 5] ( normalize).

[0162]

(Equation 6)

In the above [Equation 6], the parameter indicated by T _i corresponds to the output from the resistance bulb 111. S _norm indicates a standardized measurement value.

The relationship between the value of S _norm obtained by the above [Equation 6] and the actual flow rate value F (measured by a fair mass flow sensor or the like) F is calculated using an appropriate function B (S _norm ).
It is obtained as a functional relationship represented by the following [Formula 7].

[0165]

(Equation 7)

The function B represented by the above [Equation 7]
By using (S _norm ), the measured value of the flow rate is calculated.

FIG. 6 shows how much the measured value calculated using the function B (S _norm ) has a tolerance with respect to the actual flow value P measured by the fair mass flow meter. It is the result of having investigated. FIG. 6 shows the tolerance expressed by Error on the vertical axis and the flow rate (liter / liter) shown on the horizontal axis using the calculation formula shown in [Equation 8] below.
Data).

[0168]

(Equation 8)

FIG. 6 shows that the temperature of the fluid is minus 20 ° C.
Minus 10 ° C, 0 ° C, 10 ° C, 40 ° C, 55 ° C, 70
All plot points for ° C are shown. In FIG.
Approximately 50
It shows that accurate flow rate measurement can be performed while performing temperature compensation within a tolerance of ± 1.5% over a flow rate range of (liter / hour) to 1800 (liter / hour). The mass flow rate is measured by the mass flow meter. To be precise, it is necessary to use Kg / h or the like as a unit, but here, liters / hour, which is commonly used in practice, is used. .

As described above, in this embodiment, the heating element 1
The voltage applied to 1 is 3 V, and the time during which the voltage is applied to the heating element 11 is 0.4 V in one operation cycle of 4 seconds.
2 seconds. This means that the device can be operated with extremely low power consumption. In the actual operation, power consumption is consumed by the integrated circuit 114. However, the driving power consumption of the heating element 11 that consumes the most power is extremely low as described above, and as shown in FIG. Obtaining characteristics having high sensitivity and high dynamic range is extremely significant for industrial use.

In implementation, [Equation 5] and [Equation 7]
The functions A (T _i ) and B (S _norm ) indicated by may be stored in a separately arranged semiconductor memory (not shown). Further, the specific form of the function can be set as appropriate in view of the capacity of the CPU, the capacity of the memory, and the measurement accuracy.

[Embodiment 2] In this embodiment, in the flow rate measuring method using the configuration shown in FIGS. 1 and 2, the output T from the resistance temperature detector 111 and the output from the
4 relates to a method of obtaining a flow rate value Y corresponding to the output S processed by the method shown in FIG. 4 in U107 (this output S reflects the response characteristic of the diamond thin film 13 to pulsed heating). .

In the present embodiment, Y corresponding to the value of (T, S) is obtained in a required combination within the measurement range, and the corresponding data (correspondence table) is stored in a memory (FIG. 1 and FIG. 2). (Not shown), and the measurement value Y is obtained based on the corresponding data. An example of this correspondence data is shown in Table 1 below.

[0174]

[Table 1]

In the memory, the values of Y (flow rate value) corresponding to the values of T and S shown in Table 1 previously obtained are stored. In actual measurement, T and S
Is determined, and the value of Y is determined based on the corresponding data shown in Table 1. This calculation is performed by the CPU 107 or another external CPU. Table 1 above can be seen as showing the function L of the following [Equation 4].

[0176]

(Equation 4)

The resolution of the various parameters used in Table 1 may be determined according to the required measurement accuracy.

When the configuration of this embodiment is employed, the flow rate can be measured while performing the temperature compensation with high accuracy. However, there are disadvantages that the load on the CPU increases and that a large memory capacity must be used.

[Embodiment 3] In this embodiment, a temperature measuring resistor (not shown) for measuring the temperature of the measurement environment is further provided in the configuration shown in FIGS. 1 and 2 to compensate for the influence of the temperature of the measurement environment. This is an example of a configuration that can be used. In order to realize the configuration of the present embodiment, in addition to the parameters in Table 1 shown in Embodiment 2 (in the case of Table 1, T and S are measured parameters), a parameter indicating the temperature around the measurement environment is used. You can add In this case, the corresponding data as shown in Table 2 below may be stored in a separately provided memory.

It is useful to prepare as many combinations of correspondence data as shown in Table 2 as much as possible in order to increase measurement accuracy.

[0181]

[Table 2]

Here, T _1i is a parameter corresponding to the temperature of the fluid, and T _2j is a parameter corresponding to the temperature of the measurement environment. S is an output processed using the method shown in FIG. Y is the corresponding flow value. In addition, if Table 2 is described more accurately, in three-dimensional orthogonal coordinates, T _1i , T _2j , and S _k are used as coordinate components, and (T _1i ,
T _2j , S _k ) must correspond to the flow rate value Y _n .

In the case of the present embodiment, the relationship between each parameter and the measured value Y of the flow rate is represented by the following [Equation 9] using an appropriate function L.

[0184]

(Equation 9)

The configuration as in this embodiment can reduce or prevent the flow rate value measured by the temperature of the measurement environment from being affected. However, since the number of combinations of parameters increases exponentially, there is a disadvantage that the amount of data to be handled becomes enormous.

[Embodiment 4] This embodiment is different from the embodiment shown in FIGS.
The present invention relates to a configuration in which a sensor for detecting the humidity of a fluid is added to the configuration shown in FIG.

The configuration of this embodiment can be used, for example, in a system for measuring the flow rate of a fluid (usually air) flowing in a duct of an air conditioning system.

In order to realize the structure of this embodiment, a sensor for measuring the humidity of the fluid may be added to the structure shown in FIGS. 1 and 2 so that the output H is input to the CPU 107. Then, based on the output T from the thermistor 111 reflecting the temperature of the fluid, the output S calculated by the method shown in FIG. 4, and the output H from the humidity sensor (not shown), the flow rate value Y may be obtained. .

In this embodiment, the flow rate value Y is obtained based on the parameters T, S, and H using the functional relationship shown in the following [Equation 10].

[0190]

(Equation 10)

Here, the function L in the above [Equation 10] is used.
May be obtained as appropriate specific ones, or may be based on correspondences as shown in Table 3 below. It should be noted that the data shown in Table 3 below can increase the measurement accuracy by increasing the number of combinations as much as possible.

[0192]

[Table 3]

Example 5 According to the findings of the present inventors,
In the configuration of the invention disclosed in this specification, the amount of heat supplied to the thin film material at the time of pulse-like heating is made constant, so that the thermal response characteristic of the diamond thin film to this pulse-like heating is changed by the temperature of the fluid. It can be concluded that it can be made to correspond to the flow rate without being greatly affected by the flow rate.

This can be concluded by considering the following. That is, assuming that the specific heat of the diamond thin film does not change with respect to the temperature, the temperature of the diamond thin film can be regarded as substantially constant with the temperature of the surrounding fluid. In this state, it is assumed that a constant amount of heat ΔQ is supplied to the diamond thin film regardless of the temperature of the fluid. In this case, the temperature rise of the diamond thin film is represented by ΔQ / mc using the specific heat c and the mass m of the diamond thin film.

When the temperature of the fluid changes, the thermal parameters (for example, thermal conductivity) of the fluid change, so that the amount of heat per unit time escaping from the heated diamond thin film to the fluid changes. However, when the temperature of the fluid changes in the range of about ± 50 ° C., the influence of the temperature change in that range on the temperature change (response characteristics) of the diamond thin film with respect to the pulsed heating is considered to be about several percent. Can be

That is, when the amount of heat supplied to the diamond thin film (the amount of heat supplied in pulse-like heating) is constant regardless of the temperature of the fluid, the response characteristic of the diamond thin film to the supply of this heat is as follows. The temperature is not so large.

Generally, the resistance of a heating element using platinum greatly changes depending on the temperature of the fluid. Therefore, the amount of heat generated also changes greatly due to the temperature change. For example, when a platinum thin film showing a resistance change of 1000 ppm with respect to a temperature change of 1 ° C. is used as a heating element, 100 mm
A temperature change of 10 ° C. indicates a 10% change in resistance. Therefore, when the constant voltage driving is considered, a change in the amount of generated heat of 10% occurs.

Therefore, in the configuration shown in this embodiment,
By using a heating element whose change in resistance value due to temperature is as small as possible, flow rate measurement that is hardly affected by the temperature of the fluid is realized. Specifically, a configuration using a material made of constantan as the heating element and adopting a configuration in which the amount of heat generated from the heating element does not change with the temperature of the fluid is adopted. Constantan is Ni 45
%, Cu is an alloy of 55%, and the change in the resistance value with respect to the temperature change is extremely small.

The structure of the element is the same as that shown in FIG. 3 except for the heating element, and the configuration of the entire system is the same as that shown in FIGS. The operation method is also the same as that shown in the first embodiment. In addition, it is effective that the heating element in another embodiment of the present specification is a constantan as shown in this embodiment.

Even when constantan is used as the heating element, it is very useful to use a temperature compensating resistance temperature detector (means for measuring the temperature of the fluid) as indicated by 111 in FIG. is there. When the temperature of the fluid changes, various characteristics of the fluid, such as specific heat and kinematic viscosity, also change. Therefore, the measured value of the flow rate is affected by changes in these thermal parameters. Further, the operating speed of the CPU, the gain of the amplifier, and the like also change depending on the temperature, and the change affects the measured value. Therefore, in order to calculate the flow rate without depending on a change in the thermal properties of the fluid or a predetermined number of circuits, it is effective to remove the influence based on information on the temperature of the fluid.

In this embodiment, constantan is selectively formed on a diamond thin film on which a metal mask is arranged by using a vapor deposition method, and a thin film of constantan is formed in a predetermined pattern. The vapor deposition is performed using Ni and Cu as materials.

When the structure shown in this embodiment is adopted, the amount of heat generated by the heating element (the amount of heat supplied to the thin film material) does not depend on the temperature. Therefore, the temperature dependence of the characteristics of the CPU and the amplifier becomes remarkable. Therefore, in order to further reduce the temperature dependence of the measured value,
It is necessary to take measures to prevent the characteristics of the CPU and the amplifier from being affected by the temperature of the fluid and / or the measurement environment.

In this embodiment, an example is shown in which constantan is used as a heating element. In addition to constantan, a material such as manganin which has a very low change in resistance to temperature changes can be used. As such a material, it is desirable to use a material whose change in resistance value is 10 ppm or less in the temperature range used.

[Embodiment 6] This embodiment relates to FIGS.
Is an example in which a method of irradiating a laser beam is employed as a means for heating the diamond thin film 13 in a pulsed manner. FIG. 7 shows the configuration of this embodiment. FIG. 7 shows the heating element 1 in the configuration shown in FIG.
In this example, a laser oscillation device 600 controlled by a switch 108 is provided instead of 1. In FIG.
2 are the same as those in FIG.

Here, by using the laser oscillation device 600 whose output does not change as much as possible due to temperature change, a constant amount of heat is always applied to the diamond thin film without being affected by the temperature change of the fluid and / or the measurement environment. Can be given. As the laser oscillation device 600,
What oscillates red laser light or infrared laser light may be used. When a polycrystalline diamond thin film formed by a CVD method is used as the diamond thin film 13, infrared light is absorbed by crystal grain boundaries, and thus heating can be performed by irradiation with infrared light.

The operation method is the same as that shown in the first embodiment. That is, instead of Joule heating the heating element, a laser beam may be applied to the diamond thin film 13 from the laser oscillation device 600 for a predetermined time.

[Embodiment 7] In this embodiment, the output from the temperature measuring sensor is fed back in an analog manner, and the voltage supplied to the heating element of the flow rate measuring sensor is controlled based on the fed back output, and the fluid and The present invention relates to a configuration for performing flow measurement that does not depend on a measurement environment (or greatly reduces the dependency thereof).

In this embodiment, at least two sensor elements as shown in FIG. 3 are used. Each sensor is incorporated in two bridge circuits, and the voltage supplied to the heating element of the sensor incorporated in one bridge circuit is controlled using the output of the other bridge circuit.

FIG. 8 schematically shows the structure of this embodiment. FIG.
In the bridge 1, a sensor having a heating element 811 and a resistance temperature detector 810 formed on a diamond thin film 809 is disposed. This sensor has a configuration in which one surface of a diamond thin film is in contact with a fluid.
The configuration of this sensor is the same as that shown in FIG. That is, on one surface of the diamond thin film 809, a temperature measuring resistor 810 made of a platinum thin film is formed similarly to the heating element 811 made of a platinum thin film.

It is preferable that the resistors 807 and 808 have a small resistance change with respect to a temperature change. One resistor 806 constituting the bridge 1 is formed of a platinum thin film formed on a diamond thin film 805 similar to 809. It is desirable that the resistance value of the resistor 806 made of the platinum thin film is approximately equal to that of the resistance temperature detector 810.

The diamond thin film 805 has another resistor 804 formed of a platinum thin film. The platinum thin film forming the resistor 804 must have the same (or as close as possible) characteristics of a change in resistance value with respect to temperature to the heating element 811 (formed of a platinum thin film). .

The resistor 804 forms the bridge 2 with the resistors 801 to 803 whose change in resistance value with respect to temperature change is as small as possible. The output of the bridge 2 is amplified by the amplifier 812. The output of the amplifier 812 is
Drive. The output of the bridge 1 is amplified by an amplifier 813, and the signal amplified by the amplifier 813 is converted into a digital signal by an A / D converter 814.
5 is input.

The CPU 815 includes an A / D converter 814
Is processed according to a predetermined procedure. On the other hand, the temperature measuring resistor 819 is in contact with the fluid to be measured, and has a resistance value corresponding to the temperature of the fluid. And the resistance temperature detector 81
9 and appropriate resistors 818 and 820 output a value corresponding to the temperature of the fluid.
It is converted into a digital signal by the / D converter 817,
Further, it is input to the CPU 815. In the CPU 815,
The output from the bridge 1 and the output from the resistance temperature detector 819 are subjected to arithmetic processing according to a predetermined calculation method, and the flow rate of the fluid flowing in contact with the diamond thin film 809 is calculated. Then, the flow value (or a value corresponding to the flow value) calculated by the CPU 815 is displayed on the LCD 816. Also C
The PU 815 has a function of controlling the voltage supplied to the bridge 1 and the bridge 2.

The operation of the system shown in FIG. 8 is basically the same as the operation method shown in FIG. Hereinafter, the operation method will be described in detail.

(First Operation) Between t ₀ and t ₀ + Δt ₀ , an operation represented by the following [Equation 1] is executed by the CPU 81.
Perform in step 5.

[0216]

(Equation 1)

By executing the first operation, the reference point of the operation is determined.

(Second Operation) Between t ₁ and t ₁ + Δt ₁ , a predetermined voltage is applied to V ₂ . At this time, the output of the bridge 2 changes according to the resistance value of the resistor 804.
The resistance value of the resistor 804 depends on the temperature of the fluid.
Then, the output of the bridge 2 changes according to the change of the resistance value 804, and the output is amplified by the amplifier 812 to drive the heating element 811. Therefore, the voltage for driving the heating element 811 changes according to the temperature of the fluid.

The diamond thin film 809 changes in temperature as shown by f (t) in FIG. 4 due to the pulse-like heat generated by the heating element 811. That is, it is rapidly heated between t ₁ and t ₁ + Δt _1, and then rapidly cooled. It can be understood that the temperature change of the diamond thin film shown by f (t) in FIG. 4 is a response characteristic to the pulsed heating of the diamond thin film. In addition,
Δt ₁ may be selected between approximately 50 ms and _{1 s} .

(Third Operation) Between t ₂ and t ₂ + Δt ₂ , the output of the amplifier 813 digitally converted by the A / D converter 814 is integrated by the CPU 815. This integration is performed by calculating the operation shown in the following [Equation 2] by CP
This is performed by performing in U815. Here,
It is assumed that t ₁ <t ₂ .

[0221]

(Equation 2)

(Fourth Operation) The difference between the value obtained in the above (first operation) and the value obtained in the above (third operation) is expressed by CP
The calculation is performed in U815. Specifically, an operation represented by the following [Equation 3] is performed.

[0223]

(Equation 3)

(Fifth Operation) The result of the fourth operation and A
CPU based on the output from D / D converter 817
By performing a predetermined calculation in 815, the flow rate of the fluid in contact with the diamond thin film 809 is calculated.

The predetermined operation performed in the fifth operation is as follows.
This is the same as the method described in the second embodiment. Of course, it goes without saying that the specific form of the function used is different from that of the second embodiment.

The first to fifth operations described above are performed in accordance with a predetermined procedure according to a command from CPU 815. The necessary mathematical expressions such as [Equation 1] to [Equation 3] may be stored in a semiconductor memory (not shown).

Here, consider a situation where the temperature of the fluid gradually increases. In this case, the resistance of the resistor 804 made of a platinum thin film increases with the temperature of the fluid. Then, the output of the bridge 2 increases accordingly. This output is amplified by an amplifier 812 and supplied to a heating element 811. That is, the voltage supplied to the heating element 811 follows the rise in the temperature of the fluid. Therefore, a voltage corresponding to the rise in the temperature of the fluid is supplied to the heating element 811.

On the other hand, the resistance of the heating element 811 increases as the temperature of the fluid increases. Therefore, by setting the gain of the amplifier 812 as appropriate, when the constant voltage driving is performed, the heating value P of the heating element represented by Ohm's law (P = V ² / R) is shifted to the temperature of the fluid. It is possible to adopt a configuration in which the heat value does not substantially change or does not change so much.

As a result, the diamond thin film 809 is supplied with an amount of heat which is not greatly affected by the temperature change of the fluid. In addition, the response characteristic of the diamond thin film 809 (as shown by f (t) in FIG. 4) to the pulsed heating from the heating element 811 can also be made not to largely depend on the temperature of the fluid. Alternatively, the effect of the temperature of the fluid on its response characteristics can be greatly reduced.

In the structure shown in FIG.
The heating element 811 and the heating element 811 must be made of the same material or the same material having the same temperature dependence of resistance. This is because it is necessary to provide the heating element 811 with appropriate feedback corresponding to a change in the temperature of the fluid.

[Embodiment 8] In this embodiment, in the configuration shown in FIG. 8, the gain of the amplifier 812 is changed as needed according to the temperature of the fluid, and the heating element 811 is driven by a voltage according to the temperature of the fluid. It is characterized by the following.

The gain of the amplifier 812 can be varied by changing various parameters (viscosity, density, thermal conductivity, etc.) according to a change in the temperature of the fluid, and changes in various constants of the circuit (resistance values, etc., of resistors constituting the circuit) with respect to the temperature change. It is necessary to set so as to compensate for the influence of to some extent.

That is, under the condition that the flow rate is constant, the temperature of the fluid and / or the temperature of the measurement environment are shown in FIGS.
It is necessary to vary the gain of the amplifier 812 so that the area of the waveform of the response characteristic shown in (1) becomes constant.

By adopting such a configuration, the effects of changes in various parameters caused by changes in the temperature of the fluid and / or the measurement environment do not appear in the response characteristics shown in FIGS. 4 and 5, or the effects thereof can be minimized. The situation can be realized. The response waveforms shown in FIGS. 4 and 5 can be made to follow the flow rate without depending on the temperature of the fluid.

As shown in this embodiment, in order to change the gain of the amplifier 812 in accordance with the temperature change of the fluid and / or the measurement environment, a separately provided means for detecting the temperature change of the fluid and / or the measurement environment ( (Not shown)
The gain of the amplifier 812 may be controlled by a separately provided CPU (not shown). That is, in a state where the flow rate is constant, the temperature of the fluid is changed.
The gain of the amplifier 812 may be controlled by the CPU so that the area (corresponding to 44 in FIG. 4) of the response waveform shown in FIG. The operation performed by the CPU 815 is the same as that described in the first embodiment.

With such a configuration, it is possible to measure the flow rate while eliminating the temperature dependence of various parameters.

When the temperature compensator 819 shown in FIG. 8 is used together and the temperature compensation as shown in the first embodiment is further performed in the CPU 815, the gain of the amplifier 812 is not controlled so strictly. Is also good. This is because the temperature measuring resistor 819 has a temperature compensation function. In addition,
When the gain of the amplifier 812 is strictly set with respect to the temperature change of the fluid and / or the measurement environment, the resistance bulb 819 is not always necessary. However, it is difficult as a matter of fact to perform complete temperature compensation. Therefore, in addition to the configuration shown in this embodiment, temperature compensation using a resistance temperature sensor 819 is used together to further enhance the temperature compensation function. Is practically useful.

[Embodiment 9] A block diagram of this embodiment is shown in FIG.
Shown in This embodiment is a modification of the configuration shown in the first embodiment. The configuration shown in the first embodiment employs a configuration in which a temperature measuring resistor 111 is separately provided as a means for measuring the temperature of the fluid. However, in the present embodiment, the platinum thin film 102 formed on the diamond thin film 101 is used as a temperature measuring resistor, and the resistance value of the platinum thin film 102 changes.
In this configuration, the temperature of the fluid is detected.

The resistance temperature detector 102 must be made of the same material as the resistance temperature detector 12 or a material having the same or similar temperature-resistance characteristics (characteristics of a resistance value that changes with temperature). In this embodiment, the resistance temperature detectors 12 and 102 use platinum thin films formed by the sputtering method and have the same temperature-resistance characteristics. Of course, it is necessary to set the dimensions and the film thickness of the resistance thermometer 12 and the resistance thermometer 102 so as to have a required resistance value. The configuration other than that described above is the same as that shown in FIG. 1, and the operation method is also the same as that shown in the first embodiment.

[Embodiment 10] This embodiment relates to a configuration for performing temperature compensation by changing a voltage supplied to a resistance heating element arranged on the surface of a diamond thin film in accordance with the temperature of a fluid. 11 and 12 show a schematic configuration of the present embodiment. 11 and 12 are equivalent, and FIG. 12 shows the configuration shown in FIG. 11 more specifically. 11 and 12, the same reference numerals as those used in FIGS. 1 and 2 denote the same components as those described in the first embodiment. The detailed description is the same as that shown in FIGS. In this embodiment, an external D / A converter 1101 and a memory 1102 are attached to a one-chip integrated circuit indicated by 114.
Is arranged. As the integrated circuit 114, similarly to the first embodiment, a TSS400AFW which is a microprocessor of Texas Instruments can be used.

The configuration shown in FIGS. 11 and 12 controls the voltage supplied to the heating element 11 by the D / A converter 1101 based on the correspondence shown in Table 5 below stored in the memory 1102. It is characterized by. Particularly, the present invention is characterized in that the voltage supplied to the heating element 11 is changed in accordance with the temperature of the fluid.

[0242]

[Table 5]

Table 5 shows that the value S _i of the area 44 of the response waveform of FIG. 4 is constant or approximately constant or within a constant range or approximately constant range at a constant fluid flow rate F _i . shows the combination of the value of the voltage V _n is supplied to the value and the heating element 11 of the temperature T _n of the fluid required to so made.

In other words, the relationship shown in Table 5 indicates that, at a predetermined flow rate V _i (for example, V _i = 0), the relationship shown in FIG.
In the case where the area S _{i of the} response waveform represented by is set to be constant or approximately constant or within a constant range or within a substantially constant range, the temperature of the fluid represented by T _n and the supply to the heating element 11 it can be said that shows the relationship between the voltage V _n to.

As for T ₁ , T _2, ..., T _n shown in Table 5, the measurement accuracy can be increased by taking as many as possible in the measurement range.

As the value of the flow rate V _i , any value within the measurement range can be selected. However, in order to improve the measurement accuracy, it is more desirable to obtain the relationship as shown in Table 5 for a plurality of flow rates. For example, the relationship shown in Table 5 flow V _i is 0 (l / h),
10 (liter / hour), 50 (liter / hour), 100
(Liter / hour), 500 (liter / hour), 1000
(Liter / hour)
It is very effective for improving the measurement accuracy. In this case, the relationship shown in Table 5 to previously obtain odor when the plurality of flow V _i, or allowed to store in the memory 1102, V _n =
The functional relationship represented by F (T _n), when a plurality of flow V _i to previously obtain smell, may be stored in the memory 1102.

It is effective to obtain the relationship shown in Table 5 for a plurality of flow rates for the following reasons. That is, as the flow rate changes, the relationship shown in Table 5 changes little by little due to the influence of the pressure and the like. Therefore, the measurement accuracy can be improved by obtaining the relationship shown in Table 5 in the flow rate range divided into a plurality.

In order to operate the configuration as shown in FIGS. 11 and 12, it is necessary to store the relationship as shown in Table 5 in the memory 1101 in advance. In addition, the diamond thin film 1 with respect to the pulse heating by the heating element 11 is used.
The specific method of measuring the response characteristic of No. 3 (shown in FIG. 4) is the same as that shown in the first embodiment.

To operate the configuration shown in this embodiment, the following may be performed. First, according to the temperature T _n of the fluid 202 RTD 111 is disposed in contact with the fluid is detected on the basis of the data shown in Table 5 which CPU107 is stored in the memory 1102, heat is generated corresponding voltage V _n A command is issued to the D / A converter 1101 to drive the body 11. Then the voltage V _n is supplied corresponding to T _n in the heating element 11 by the D / A converter 1101.

V _n shown in Table 5 corresponds to a predetermined fluid temperature T _n when the area indicated by 44 in FIG. 4 is constant or approximately constant or within a constant range or within a substantially constant range. Required to drive the heating element 11.

Therefore, when the flow rate of the fluid 202 does not change, the response characteristic corresponding to the area S _i indicated by 44 in FIG. 4 is constant or approximately constant or within a certain range with respect to the temperature T _{n of} the fluid. It is generally within a certain range.

That is, the area indicated by 44 in FIG. 4 is not greatly affected by the temperature of the fluid 202, and corresponds to the flow rate of the fluid 202. Thus, the voltage by changing in correspondence with the temperature of the fluid supplied to the heating element 11, the response characteristic (quantified response characteristics) represented by the area S _i shown by 44 in FIG. 4 of the fluid flow rate Can be used. And the flow rate measurement which is not affected by the temperature of the fluid can be performed.

When the configuration shown in this embodiment is adopted, it is possible to compensate in a form including all the effects of changes in various parameters in accordance with the temperature change of the fluid and / or the measurement environment, and thus the flow rate can be measured with extremely high accuracy. It can be performed.
These various parameters include all physical properties of the fluid and a predetermined number of circuits.

For example, in an environment actually used,
By obtaining the relationship shown in Table 5, it is possible to provide a configuration that compensates not only the temperature of the fluid but also the temperature of the measurement environment.

In this embodiment, a resistance heating element arranged in contact with the diamond thin film 13 is used as means for heating the diamond thin film in a pulsed manner.
An example in which the voltage supplied to the resistance heating element is controlled has been described.
However, for example, when a device that irradiates laser light is used as a means for performing pulse-like heating of the diamond thin film, a parameter that changes the irradiation intensity of laser light may be controlled according to the temperature of the fluid. Good.

[Embodiment 11] This embodiment is an example in which the configuration shown in Embodiment 1 is used for a gas sensor. The gas sensor shown in this embodiment can be used for detecting a specific gas, for example. For example, it can be used for detecting gases harmful to the human body.

The structure of the gas sensor shown in this embodiment is basically the same as that shown in FIG. The operation method is basically the same. Therefore, the description of each component shown in FIG. 1 may refer to the description of the first embodiment unless otherwise specified. In order to use the configuration shown in FIG. 1 as a gas sensor, it is necessary to bring the diamond thin films 13 and 101 into contact with the gas to be measured. It is necessary to make the flow of the gas to be measured in contact with the diamond thin films 13 and 101 constant. This is because if there is a change in the gas flow, the effect of the flow of the gas will appear on the output. Further, it is necessary to bring the temperature measuring resistor 111 for detecting the temperature of the gas to be measured into contact with the gas to be measured.

The operation method is basically the same as that shown in the first embodiment. When the configuration shown in FIG. 1 is used as a gas sensor, the area 44 of the response waveform shown in FIG. 4 changes depending on the concentration of a specific gas contained in the gas to be measured. That is, the area of the response waveform indicated by 44 in FIG. 4 includes information on the concentration of the specific gas in the measured gas. Accordingly, the concentration C of the characteristic gas in the gas to be measured is
Is the area S of the response waveform shown at 44 in FIG.
Using the temperature T of the gas to be measured detected in step 11,
It will be indicated by F (S, T).

That is, the relationship shown in Table 6 below is obtained in advance and stored in a memory (not shown in FIGS. 1 and 2) to obtain a specific gas concentration C _mn. Can be.

[0260]

[Table 6]

By adopting the configuration as shown in this embodiment, it is possible to greatly reduce the influence of the temperature of the gas to be measured and to measure and detect the concentration of the characteristic gas.

[0262] In this embodiment, an example of a case of measuring the concentration of a specific gas, to be measured gas as air, if humidity C _i in the above Table 6, to measure the humidity in the air be able to.

[Embodiment 12] This embodiment shows an example in which a gas sensor is realized using the configuration shown in FIG. When the configuration shown in FIG. 11 is used for a gas sensor,
The gas to be measured needs to contact the diamond thin films 13 and 101. The flow rate of the gas to be measured in contact with the diamond thin films 13 and 101 needs to be constant.
Further, it is necessary that the resistance temperature detector 111 is also in contact with the gas to be measured.

In order to realize the gas sensor shown in this embodiment, the diamond thin films 13 and 101 and the resistance temperature detector 11 are added to the gas to be measured containing a gas having a predetermined composition or a predetermined concentration.
In a state where the diamond thin film 13 is in contact with the heating element 11, the response characteristic of the diamond thin film 13 to the pulsed heating from the heating element 11 (FIG.
To) evaluated as the area S _i represented by 44, such as is constant ones, the voltage supplied from the D / A converter 1101 to the heating element 11 and the temperature T _n of the gas detected by the RTD it is necessary to find a combination of V _n. Shows a combination of the T _n and V _n in Table 7 below.

[0265]

[Table 7]

[0266] Shown in Table 7, to the response characteristic of the diamond thin film 13 shown at 44 in FIG. 4 and fixed ones, the temperature T _n gas containing a predetermined composition or a predetermined concentration of the gas respect, it can be said that indicates whether or if any value voltage V _n is supplied to the heating element 11. Here, n is an arbitrary natural number.

[0267] In other words where the table 7 means if, relative to the temperature T _n of the measurement gas detected by the resistance temperature detector 111, if the supply voltage represented by V _n to the heating element 11, a predetermined This means that a constant response characteristic can be obtained for a gas to be measured containing a gas having a predetermined composition or a predetermined concentration.

In the actual measurement, the temperature measuring resistor 111
Obtains the temperature T _n of the measurement gas by, based on the value of this T _n, the semiconductor memory 110 in CPU107
2 based on the relationship shown in Table 7 stored in
seek _n, a voltage is supplied to the heating element 11 with the A / D converter 1101 in this V _n. The response characteristic S _i obtained as a result is not affected by the temperature of the gas to be measured.
Or it is hard to receive.

Note that the measurement accuracy can be improved by increasing the number of n as much as possible. Further, it is effective to select not only one composition of the fluid to be measured but also a plurality of compositions within the measurement range, and obtain the relationship shown in Table 7 in each case.

By adopting the structure shown in this embodiment, it is possible to measure and detect the concentration of the characteristic gas while performing temperature compensation with high accuracy. Of course, it is also possible to measure the humidity in the air.

Further, the configuration shown in this embodiment can also be used for measuring the mixing ratio of two different gases. In this case, the gas concentration of the gas to be measured may be replaced with the mixture ratio of the two gases.

[0272]

By evaluating the response characteristics of the thin film material to pulsed heating, it is possible to obtain a measurement value without drift with a simple configuration. -Power consumption can be reduced by using pulsed heating. Such an effect can be obtained.

In particular, when a diamond thin film is used as the thin film material, in addition to the effects described above, a high sensitivity and a high dynamic range can be achieved without the need for a complicated correction circuit for drift correction which has been required conventionally. Can be measured. -The amount of heat to be supplied during pulse-like heating can be reduced, and power consumption can be further reduced.

Further, by calculating the flow rate value using the response characteristic of the thin film material during the pulse-like heating and the temperature of the fluid and / or the measurement environment detected separately, the flow rate of the fluid and / or the measurement environment can be calculated. Flow rate measurement independent of temperature can be performed.

Further, by providing the means for performing pulse-like heating with the following temperature compensation function, accurate flow rate measurement can be performed. (1) The influence of the flow rate measurement value due to the temperature of the fluid and / or the measurement environment can be reduced by using a means in which the calorific value does not change due to the temperature of the fluid and / or the measurement environment or the change is small. (2) As means for performing pulse-like heating, fluid and / or
Alternatively, by changing a parameter (for example, a driving voltage) for driving the heating element in accordance with the temperature of the measurement environment, it is possible to reduce the influence of the flow rate measurement value due to the temperature of the fluid and / or the measurement environment.

When the parameter to be measured (for example, the flow rate of the fluid) is constant, the response characteristic of the thin film material to the heating from the means for performing the pulse-like heating can be changed with respect to the temperature change of the fluid and / or the measurement environment. By making it constant, the value of the parameter to be measured can be obtained from the response characteristic while performing temperature compensation for a temperature change of the fluid and / or the measurement environment.

In addition to the effects described above, the following effects can be obtained: Measurement of the thermal conductivity and specific heat of a fluid. -Fluid identification. -Measurement of the mixing ratio of multiple fluids. -It can also be obtained when measuring the concentration of a substance contained in a fluid (for example, measuring humidity).

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a schematic configuration of a flow measurement sensor according to an embodiment.

FIG. 2 is a diagram showing a schematic configuration of a flow measurement sensor according to the embodiment.

FIG. 3 is a diagram showing a configuration of an element of the flow rate measurement sensor according to the embodiment.

FIG. 4 is a diagram showing a transient response characteristic of a diamond thin film to pulsed heating.

FIG. 5 is a photograph showing an oscilloscope waveform.

FIG. 6 is a diagram showing a relationship between a flow rate of a nitrogen fluid measured by the flow rate measurement sensor of the embodiment and a tolerance.

FIG. 7 is a diagram showing a schematic configuration of a flow rate measurement sensor according to the embodiment.

FIG. 8 is a block diagram illustrating a schematic configuration of a flow rate measurement sensor according to the embodiment.

FIG. 9 is a block diagram illustrating a schematic configuration of a flow rate measurement sensor according to the embodiment.

FIG. 10 is a diagram showing a schematic configuration of a flow measurement sensor using a conventionally known resistance temperature detector.

FIG. 11 is a block diagram illustrating a schematic configuration of a flow measurement sensor according to the embodiment.

FIG. 12 is a diagram showing a schematic configuration of a flow rate measurement sensor according to the embodiment.

[Explanation of symbols]

 Reference Signs List 11 heating element (platinum thin film) 12 temperature measuring resistor (platinum thin film) 13 diamond thin film 101 diamond thin film 102 temperature measuring resistor 103, 104 resistor 105 amplifier 106 A / D converter 107 CPU 108 switch 109 LCD (external display device) Reference Signs List 110 amplifier 111 resistance temperature detector 112 resistor 113 resistor 114 one-chip integrated circuit 201 pipe 202 fluid 10, 15 electrode 17 bonding wire 18, 20 substrate made of Teflon 19 fluid 600 laser light oscillation device 601 laser light 801 to 803 Resistor 804 Resistance thermometer (platinum thin film) 805 Diamond thin film 806 Resistor (platinum thin film) 807, 808 Resistor 809 Diamond thin film 810 Resistance temperature detector (platinum thin film) 811 Heating element (platinum thin film) 812, 813 Amplifier 814 A / D converter 815 CPU 816 LCD (display device) 817 A / D converter 818 Resistor 819 Resistance temperature detector 820 Resistance element 301, 302 Resistance temperature detector 303, 304 Resistor 305 Amplifier 307 Fluid

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-62-231174 (JP, A) JP-A-3-283601 (JP, A) JP-A-3-97201 (JP, A) JP-A-63-231 241457 (JP, A) JP 3-33221 (JP, B2) (58) Field surveyed (Int. Cl. ⁷ , DB name) G01F 1/68-1/699 G01P 5/12

Claims (29)

(57) [Claims] 1. A measuring apparatus comprising: a thin film material arranged to be in contact with a fluid; means for performing pulse-like heating on the thin film material; and means for measuring a response characteristic of the thin film material according to the heating by the means. An operation of integrating a parameter corresponding to the temperature of the thin film material before the pulsed heating; an operation of integrating a parameter corresponding to the temperature of the thin film material after the pulsed heating; And an operation of calculating a difference between the two integrated values. 2. A thin film material arranged to be in contact with a fluid, means for performing pulsed heating on the thin film material, and means for measuring a response characteristic of the thin film material according to the heating by the means, The means for performing the pulse-shaped heating may be the fluid or the measurement.
A measuring device having a function of changing a calorific value according to an environmental temperature . 3. An operation for integrating a parameter corresponding to the temperature of the thin film material before the pulsed heating, an operation for integrating a parameter corresponding to the temperature of the thin film material after the pulsed heating, 3. The measuring device according to claim 2, wherein an operation of calculating a difference between the two integrated values is performed. 4. The means for performing the pulse-like heating uses a resistance change with respect to a temperature change of the fluid or the measurement environment.
The measuring device according to any one of claims 1 to 3, wherein the measuring device comprises a resistance heating element of 10 ppm or less in a temperature range . 5. The measuring device according to claim 1, further comprising a temperature measuring resistor disposed in contact with the fluid. 6. The measuring apparatus according to claim 1, wherein the means for evaluating the response characteristic has a temperature compensating function for the temperature of the fluid or the measurement environment. 7. A thin film material arranged to be in contact with a fluid, means for performing pulsed heating on the thin film material, means for measuring a response characteristic of the thin film material according to the heating by the means, A measuring device having means for obtaining an output corresponding to a temperature, and means for obtaining information on the fluid from the response characteristic and an output corresponding to the temperature of the fluid, wherein the means for measuring the response characteristic includes: An operation of integrating a parameter corresponding to the temperature of the thin film material before the pulsed heating, an operation of integrating a parameter corresponding to the temperature of the thin film material after the pulsed heating, and a difference between the two integrated values. And an operation for calculating the following. 8. A thin film material arranged to be in contact with a fluid, means for performing pulsed heating on the thin film material, means for measuring a response characteristic of the thin film material according to the heating by the means, A measuring device comprising: means for obtaining an output corresponding to a temperature; and means for obtaining information about the fluid from the response characteristic and an output corresponding to the temperature of the fluid, wherein the information about the fluid relates to a type of the fluid. A measuring device characterized in that: 9. A thin film material arranged to be in contact with a fluid, means for performing pulse-like heating on the thin film material, means for measuring a response characteristic of the thin film material according to the heating by the means, A measuring device comprising: means for obtaining an output corresponding to a temperature; and means for obtaining information about the fluid from the response characteristic and an output corresponding to the temperature of the fluid, wherein the information about the fluid is an impurity in the fluid. Alternatively, the measuring device is related to an impurity concentration in the fluid. 10. The measuring apparatus according to claim 7, wherein the information on the fluid is related to a flow rate or a flow velocity of the fluid. 11. An operation for integrating a parameter corresponding to the temperature of the thin film material before the pulsed heating, an operation for integrating a parameter corresponding to the temperature of the thin film material after the pulsed heating, 11. The measuring device according to claim 8, wherein an operation of calculating a difference between the two integrated values is performed. 12. The means for performing the pulse-like heating uses a resistance change with respect to a temperature change of the fluid or the measurement environment.
The measuring device according to any one of claims 7 to 11, comprising a resistance heating element of 10 ppm or less within a service temperature range . 13. The measuring apparatus according to claim 7, wherein the means for performing the pulse-like heating is a means for irradiating a laser beam. 14. A thin film material arranged to be in contact with a fluid, means for performing pulsed heating on the thin film material, means for measuring a response characteristic of the thin film material according to the heating by the means, Means for calculating the flow rate or flow velocity of the fluid from the response characteristic by performing temperature compensation for the temperature of the measurement environment, wherein the response characteristic is measured by the thin film before the pulse-shaped heating. An operation of integrating a parameter corresponding to the temperature of the material, an operation of integrating a parameter corresponding to the temperature of the thin film material after the pulse-like heating, and an operation of calculating a difference between the two integrated values are performed. A measuring device characterized by being measured. 15. A thin-film material arranged to be in contact with a fluid, means for performing pulse-like heating on the thin-film material, means for measuring a response characteristic of the thin-film material according to heating by the means, and the heating element Means for changing a parameter for controlling the calorific value of the fluid in accordance with a temperature change of the fluid or the measurement environment, and the means for measuring the response characteristic has a function of performing temperature compensation. . 16. The means for measuring a response characteristic includes an operation of integrating a parameter corresponding to a temperature of the thin film material before the pulse-like heating, and an operation corresponding to a temperature of the thin film material after the pulse-like heating. The measuring device according to claim 1, wherein an operation of integrating the parameters to be performed and an operation of calculating a difference between the two integrated values are performed. 17. The means for performing the pulse-like heating uses a resistance change with respect to a temperature change of the fluid or the measurement environment.
The measuring device according to any one of claims 14 to 16, wherein the measuring device comprises a resistance heating element of 10 ppm or less in a use temperature range . 18. The measuring apparatus according to claim 14, wherein the means for performing the pulse-like heating is a means for irradiating a laser beam. 19. A thin film material arranged to be in contact with a fluid, means for performing pulsed heating on the thin film material, means for measuring a response characteristic of the thin film material according to the heating by the means, and a parameter to be measured. Means for making the response characteristic be constant or approximately constant or within a constant range or approximately constant range in a constant or approximately constant state, wherein the response characteristic is measured. An operation of integrating a parameter corresponding to the temperature of the thin film material before the pulsed heating; an operation of integrating a parameter corresponding to the temperature of the thin film material after the pulsed heating; And an operation for calculating a difference between the values. 20. A thin film material arranged to be in contact with a fluid, means for performing pulsed heating on the thin film material, means for measuring a response characteristic of the thin film material according to the heating by the means, and a parameter to be measured. In a constant or substantially constant state, means for causing the response characteristic to be constant or substantially constant or within a constant range or within a substantially constant range, wherein the thin film material is a diamond thin film. The means for performing the pulse-shaped heating is a resistance heating element disposed in contact with the diamond thin film, The means for measuring the response characteristic is, by a temperature measuring resistor disposed in contact with the diamond thin film, has the function of measuring the temperature change of the diamond thin film according to the pulsed heating, the object to be measured parameter is the flow rate of the fluid, the response characteristic The means for causing the flow rate to be constant or approximately constant or within a constant range or within a substantially constant range may be a condition where the flow rate is constant and the response characteristic is constant or approximately constant or within a constant range or within a substantially constant range. It has a function of supplying a voltage corresponding to the temperature of the fluid or the measurement environment to the resistance heating element based on a relationship between the temperature of the fluid or the measurement environment and the voltage supplied to the resistance heating element. Measuring device. 21. A thin film material arranged to be in contact with a fluid, means for performing pulsed heating on the thin film material, means for measuring a response characteristic of the thin film material according to heating by the means, and a parameter to be measured. Means for making the response characteristic be constant or approximately constant or within a constant range or approximately constant range in a constant or approximately constant state, wherein the response characteristic is constant or approximately constant. The means for controlling the heat generation amount of the means for performing the pulse-shaped heating so that the response characteristic is constant or substantially constant is provided. A measuring device comprising: 22. A thin film material arranged to be in contact with a fluid, means for performing pulse-like heating on the thin film material, means for measuring a response characteristic of the thin film material according to the heating by the means, and a parameter to be measured. In a constant or approximately constant state, means for making the response characteristic be constant or approximately constant or within a constant range or approximately within a constant range, wherein the response characteristic is constant or approximately Means to be within a constant or constant range or approximately within a constant range, by controlling a parameter that changes the amount of heat supplied to the thin film material by means for performing pulsed heating on the thin film material, A measuring device having a function of setting the response characteristic to a constant or approximately constant or within a constant range or within a substantially constant range. 23. The measuring apparatus according to claim 22, wherein the means for performing the pulse-shaped heating is a resistance heating element, and the parameter for changing the amount of heat is a voltage applied to the resistance heating element. 24. The measuring apparatus according to claim 19, wherein the parameter to be measured is a flow rate of a fluid. 25. The measuring apparatus according to claim 19, wherein the parameter to be measured relates to a predetermined component contained in the fluid. 26. The means for measuring a response characteristic, comprising: an operation of integrating a parameter corresponding to a temperature of the thin film material before the pulse-shaped heating; and an operation corresponding to a temperature of the thin film material after the pulse-shaped heating. The measuring device according to any one of claims 20 to 25, wherein an operation of integrating parameters to be performed and an operation of calculating a difference between the two integrated values are performed. 27. The thin film material has a thermal conductivity at 300 K of K _S , a specific heat of C _S , a density of ρ _S , and a size of L =
As 1mm square, claim value represented by _{τ = (C S ρ S L} 2 / K S π 2) is equal to or less than 0.2 ms 1
27. The measuring device according to any one of to 26. 28. The thin film material has a thermal conductivity at 300 K of K _S , a specific heat of C _S , a density of ρ _S , and a size of L =
As 1mm _{square, τ = (C S ρ S} L 2 / K S π 2) measuring apparatus according to any one of claims 1 to 26 values shown is equal to or less than 2 ms. 29. The measuring apparatus according to claim 1, wherein the thin film material is a diamond thin film, single crystal silicon, silicon carbide, aluminum nitride, or boron nitride.