JP6948067B2 - Pressure measuring device - Google Patents

Description

The present invention relates to a pressure measuring device, and more particularly to a pressure measuring device suitable for measuring a minute gas pressure.

Conventionally, a Göttingen manometer using the caliper principle has been widely used as a device for accurately measuring a minute gas pressure (for example, a dynamic pressure at a wind speed).

However, since the measurement accuracy of the Göttingen manometer depends on the resolution of the caliper (0.1 mm), there is a problem that it is not possible to accurately measure a minute pressure smaller than 0.1 mm Aq (≈1 Pa).

On the other hand, in recent years, digital pressure gauges claiming high accuracy have been widely sold (for example, Patent Document 1), but the current situation is that many of them lack reliability in terms of accuracy.

Japanese Patent No. 3247732

The present invention has been made in view of the above problems in the prior art, and an object of the present invention is to provide a pressure measuring device capable of accurately measuring a minute gas pressure.

As a result of diligent studies on a pressure measuring device capable of accurately measuring a minute gas pressure, the present inventor came up with the following configuration and arrived at the present invention.

That is, according to the present invention, an electronic balance having a tare function and a weighing accuracy of 0.01 g or less, a cylindrical open container placed on the weighing pan of the electronic balance, and a pressure introduction tube are provided. A siphon tube for connecting a connected cylindrical closed container, a liquid stored in the open container, and a liquid stored in the closed container, the first cylindrical tube and the second cylindrical tube. And a siphon tube including a communication tube that communicates the upper end of the first cylindrical tube and the upper end of the second cylindrical tube, and the measured value of the electronic balance is a gas introduced from the pressure introduction tube. The feature is that the dimensions of the inner diameter of the open container, the inner diameter of the closed container, the outer diameter of the first cylindrical tube, and the outer diameter of the second cylindrical tube are designed so as to match the gauge pressure. A pressure measuring device is provided.

As described above, according to the present invention, there is provided a pressure measuring device capable of accurately measuring a minute gas pressure.

The figure which shows the pressure measuring apparatus of 1st Embodiment. The conceptual diagram for demonstrating the method of using the pressure measuring apparatus of 1st Embodiment. The conceptual diagram for demonstrating the method of using the pressure measuring apparatus of 1st Embodiment. The conceptual diagram for demonstrating the design specification of the pressure measuring apparatus of 1st Embodiment. The figure which shows the pressure measuring apparatus of 2nd Embodiment.

Hereinafter, the present invention will be described with reference to the embodiments shown in the drawings, but the present invention is not limited to the embodiments shown in the drawings. In each of the figures referred to below, the same reference numerals are used for common elements, and the description thereof will be omitted as appropriate.

(First Embodiment)
FIG. 1 is a schematic view showing a pressure measuring device 100 according to a first embodiment of the present invention. The pressure measuring device 100 of the present embodiment is a device suitable for measuring a minute gas pressure, and as shown in FIG. 1, an electronic balance 10, a cylindrical open container 20, and a cylindrical closed container. 30 and a siphon tube 40 for connecting the liquid stored in the open container 20 and the liquid stored in the closed container 30 are included.

The electronic balance 10 is a weighing device having a weighing accuracy of 0.01 grams or less, and its minimum display unit is 0.01 grams or less. That is, the measurement resolution of the electronic balance 10 is 0.01 g or less. In addition, the electronic balance 10 has a tare function, and when the button 14 is pressed, the measured value displayed on the digital display 16 is reset to zero.

The open container 20 is placed on the measuring plate 12 of the electronic balance 10.

The closed container 30 is placed on a table 50, and a pressure introduction pipe 60 for introducing a minute gas pressure into the closed container 30 is connected to the upper surface of the closed container 30 so as to penetrate the lid 32. Has been done. Note that FIG. 1 illustrates a configuration in which the wind speed is measured using the pressure measuring device 100. Here, the pressure introduction pipe 60 and the pitot tube 70 are connected via two three-way valves 62 and 64. Has been done.

The siphon pipe 40 includes a cylindrical pipe 42, a cylindrical pipe 44, and a communication pipe 46 that communicates the upper end of the cylindrical pipe 42 and the upper end of the cylindrical pipe 44. In the siphon tube 40, the cylindrical tube 44 is sealed so that the lower end of the cylindrical tube 42 is non-contact close to the inner bottom surface of the open container 20 and the lower end of the cylindrical tube 44 is non-contact close to the inner bottom surface of the closed container 30. It is fixed so as to penetrate through the lid 32 on the upper surface of the container 30. Further, among the pipes constituting the siphon pipe 40, at least the communication pipe 46 is made of a transparent material, and the air bubbles in the pipe are moved toward the closed container 30 by buoyancy in the horizontal direction. It is leaning.

It is desirable that the above-mentioned open container 20, closed container 30, cylindrical tube 42, and cylindrical tube 44 are all made of the same material that is not easily deformed and has a small coefficient of thermal expansion. Further, the communication pipe 46 may be a transparent material that is not easily deformed.

Here, the pressure measuring device 100 of the present embodiment is devised so that the measured value (in grams) displayed on the electronic balance 10 matches the gauge pressure (in millimeters of water column) of the measured air, in other words. The dimensions of the open container 20, the closed container 30, the cylindrical tube 42, and the cylindrical tube 44 described above are designed so that the measured value of the electronic balance 10 matches the gauge pressure (details will be described later). As a result, the user can read the measured value displayed on the electronic balance 10 as it is as the gauge pressure (mmAq).

The configuration of the pressure measuring device 100 of the present embodiment has been described above, but subsequently, a method of measuring a minute pressure using the pressure measuring device 100 will be described. In the following, a case where the wind speed is measured using the pressure measuring device 100 and the Pitot tube 70 of the present embodiment will be taken as an example, and the description will be given with reference to FIGS. 2 and 3.

First, the three-way valve 62 connected to the pressure introduction pipe 60 and the three-way valve 64 connected to the Pitot tube 70 are opened and closed in the manner shown in FIG. 2A. Here, in FIG. 2, ◯ represents the opening of the valve, and × represents the closing of the valve (same in FIG. 3).

Subsequently, an arbitrary liquid is injected into the open container 20. At this point, the electronic balance 10 displays the total value of the weight of the open container 20 and the weight of the injected liquid. The liquid to be injected into the open container 20 may be any liquid having a low viscosity, and any liquid such as water, alcohol, or kerosene can be used. When water is used, a surfactant may be added to reduce the surface tension.

Subsequently, as shown in FIG. 2B, air is strongly sucked from the three-way valve 62 opened to the atmosphere to reduce the pressure inside the closed container 30. As a result, a part of the liquid stored in the open container 20 begins to move toward the closed container 30 through the siphon tube 40.

At this time, the user confirms that no air bubbles remain in the siphon tube 40. In this respect, in the present embodiment, the communication pipe 46 is made of a transparent material, and the air bubbles generated in the pipe of the siphon pipe 40 move toward the closed container 30 in the pipe of the communication pipe 46 due to the buoyancy. Therefore, the user can visually confirm the air bubbles moving in the pipe.

After that, when the inside of the siphon tube 40 is filled with the liquid, the liquid stored in the open container 20 passes through the siphon tube 40 and the closed container 30 as shown in FIG. 2C according to the siphon principle. Gradually moves toward, and in response to this, the weighing value displayed on the electronic balance 10 gradually decreases.

After that, the liquid level in the open container 20 and the liquid level in the closed container 30 are waited until they match, and when both liquid levels match, the user can see as shown in FIG. 3 (d). Press the button 14 to reset the measured value of the electronic balance 10 to zero. At this point, the pressure measurement is ready.

Subsequently, the total pressure of the gas pressure input from the Pitot tube 70 is measured.

When measuring the total pressure, the two three-way valves 62 and 64 are opened and closed in the manner shown in FIG. 3 (e). As a result, the closed container 30 is connected to the Pitot tube 70 by the path indicated by the broken line arrow, and the inside of the closed container 30 is pressurized. In response to this, a part of the liquid stored in the closed container 30 moves toward the open container 20 through the siphon tube 40. As a result, the liquid level of the closed container 30 is lowered, and the liquid level of the open container 20 is raised. During this time, the measured value displayed on the electronic balance 10 gradually increases and settles down at a certain point. The user reads the measured value at a time when the increase in the displayed measured value has settled down. If the read measured value is "1.154 g", the user records "1.154 mmAq" as the measured value of the total pressure.

Subsequently, the static pressure of the gas pressure input from the Pitot tube 70 is measured by the same procedure.

When measuring the static pressure, the two three-way valves 62 and 64 are opened and closed in the manner shown in FIG. 3 (f). As a result, the closed container 30 is connected to the Pitot tube 70 by the path indicated by the broken line arrow, so that the liquid level of the closed container 30 is lowered and the liquid level of the open container 20 is raised. The user reads the measured value at a time when the increase in the measured value displayed on the electronic balance 10 has settled down. If the read measured value is "0.914 g", the user records "0.914 mmAq" as the measured value of the total pressure.

Finally, the user calculates the dynamic pressure by subtracting the recorded static pressure from the recorded total pressure, and converts the calculated dynamic pressure into the wind speed in light of the conversion table shown in Table 1 below. In this case, the user acquires 2 [m / s] corresponding to the dynamic pressure = 0.24 mmAq (1.154 mmAq-0.914 mmAq) as the measurement result of the wind speed.

As described above, the pressure measuring device 100 of the present embodiment is designed so that the measured value (in grams) displayed on the electronic balance 10 matches the gauge pressure (in millimeters of water column) of the measured air. Therefore, the measurement accuracy of the pressure measuring device 100 is the same as the measuring accuracy of the electronic balance 10. That is, when the measurement accuracy of the electronic balance 10 is in units of 0.01 grams, the measurement accuracy of the pressure measuring device 100 is in units of 0.01 mmAq, which is 10 times the measurement accuracy of the conventional Göttingen manometer (0.1 [mmAq]). become.

Here, the design specifications of the pressure measuring device 100 of the present embodiment will be described. In the following, FIG. 4 will be referred to as appropriate.

The measured value of the electronic balance 10 at the time of pressure measurement is M [g], the amount of change in the liquid level on the open container 20 side is H1 [m], and the amount of change in the liquid level on the closed container 30 side is H2 [m]. The inner diameter of the open container 20 is D1 [m], the outer diameter of the cylindrical tube 42 is d1 [m], the inner diameter of the closed container 30 is D2 [m], and the outer diameter of the cylindrical tube 44 is d2 [m]. Then, when the gravitational acceleration is G [m / s ² ] and the density of the liquid to be used is ρ [kg / m ³ ], the following equation (1) holds from the mass conservation law. Further, since the pressure at the bottom surface of the open container 20 is ρGH1 [Pa], the following equation (2) holds.

Then, the gauge pressure p [Pa] of the measured air to be obtained is expressed by the following equation (3).

Here, the above formula (3) is converted from the above formula (1) and the above formula (2) into the following formula (4).

Here, if the following coefficients included in the fourth side of the right side of the above equation (4) ^{can be designed to 1 / m 2} as in the following equation (5), that is, D1 [m] and d1 [m]. ], D2 [m] and d2 [m] are designed to satisfy the following equation (5), then p [Pa] = M [g] × G [m / s ² ] × [1 / m]. ² ].

Here, if the measured value of the electronic balance 10 is 1 [g], the pressure of the closed container 30 is 9.8 [Pa] when ^{the gravitational acceleration of the ground is 9.8 [m / s 2].} It means that there is. Since 1 mmAq = 9.8 Pa when the density of water is 1000 [kg / m ³ ], it means that it is 1 [mmAq] when the measured value of the electronic balance 10 is 1 [g].

This relationship holds regardless of the type and density of the liquid. It is desirable that the liquid conditions are low viscosity, low volatility, and low surface tension. It is not necessary to consider the change in liquid density with temperature as in the case of the Göttingen manometer.

As for the gravitational acceleration of the ground, if the value of the gravitational acceleration G used by the electronic balance 10 is known, the same value can be used and the reading value [g] of the electronic balance 10 can be multiplied by the value of G. The pressure value [Pa] can be obtained accurately.

The features of the pressure measuring device 100 of the present embodiment as compared with the Göttingen manometer are summarized below.

The Göttingen manometer can only read up to the order of 1/10 [mmAq] to 1 [Pa], but in this embodiment, by using an electronic balance 10 that can read in 1/100 g units, 1/100 [mmAq] ] ~ 1/10 [Pa] can be read.

The Göttingen manometer needs to know the density of the liquid used accurately, and it is necessary to consider the expansion and contraction due to the temperature of the liquid. The pressure can be estimated.

In order to calculate an accurate pressure value from the measured value of the Göttingen manometer, it is necessary to know the gravitational acceleration of the area accurately. This point is the same in this embodiment, but if the value of the gravitational acceleration G used by the electronic balance 10 can be known, it is possible to calculate an accurate pressure using that value.

In the Göttingen manometer, it is necessary to move the water level level visual confirmation device to the tip of the water column by turning the knob and read the height by the caliper principle, but in this embodiment, the displayed value of the electronic balance 10 is read. Just need it.

The design specifications of the pressure measuring device 100 of the present embodiment have been described above, but subsequently, the correction of the measured value using the pressure measuring device 100 will be described.

In view of the above-mentioned design principle, the open container 20, the closed container 30, and the siphon pipe 40 (cylindrical pipe 42, cylindrical pipe 44, communication pipe 46), which are the components of the pressure measuring device 100 of the present embodiment, are all deformed. If the temperature of the environment in which the pressure measuring device 100 is used is significantly different from the assumed temperature (for example, 20 ° C.), the temperature of each element is high. It is necessary to consider expansion and contraction due to change.

Regarding this point, in the present embodiment, the correction coefficient corresponding to the air temperature in the usage environment of the pressure measuring device 100 is obtained by calculation in advance. Specifically, assuming that the difference between the air temperature in the usage environment assumed at the time of designing the pressure measuring device 100 and the air temperature in the actual usage environment is ΔT and the coefficient of linear expansion of each element of the pressure measuring device 100 is α, each element. Since the dimension of is (1 + αΔT) times, the correction coefficient for each temperature can be obtained by substituting this value into the right side of the above equation (5).

Table 2 below shows the dimensions of each component (open container 20, closed container 30, siphon tube 40) of the pressure measuring device 100, assuming that the assumed temperature of the usage environment is 20 ° C., and these are made of brass. The correction coefficient of the case is illustrated as an example. In this example, the user can acquire the correction coefficient according to the air temperature at the time of measurement from Table 2, and use the value obtained by multiplying the measured value displayed on the electronic balance 10 by the acquired correction coefficient as the measured value. can.

The electronic balance 10 is a device that elastically deforms when a load is applied, causing the measuring plate 12 to sink slightly, and detects this deformation to determine the mass. When the amount of sinking of the measuring pan 12 per unit load was tested and the error caused by this displacement on the pressure measurement was estimated, it was confirmed that the influence could be ignored.

The first embodiment of the present invention has been described above, but then the second embodiment of the present invention will be described. In the following, the description of the parts common to the contents of the first embodiment will be omitted, and only the differences from the first embodiment will be described.

(Second Embodiment)
FIG. 5A is a schematic view showing a pressure measuring device 200 according to a second embodiment of the present invention. The pressure measuring device 200 of the second embodiment differs only in that the pressure measured value conversion device 80 is adopted instead of the electronic balance 10 described above, and the procedure for measuring the gauge pressure of the measured air is the same as that of the first embodiment. It's the same.

FIG. 5B shows the functional configuration of the pressure measurement value conversion device 80. The pressure measurement value conversion device 80 includes a measuring means 82, a digital display 84, an operation button 85, a temperature sensor 86, and a microcomputer 87.

The measuring means 82 is a measuring means having a measuring accuracy of 0.01 g or less, and outputs a measured value [g] of the open container 20 (and the liquid) placed on the measuring plate 83 to the microcomputer 87. Here, the weighing means 82 has the same function as the tare function of the electronic balance 10 described above, and resets the weighing value to zero in response to the operation button 85a being pressed.

The air temperature sensor 86 is a means for outputting the detected air temperature to the microcomputer 87.

The microcomputer 87 is a calculation means for calculating the gauge pressure of the gas introduced through the pressure introduction pipe 60 based on the measurement value input from the measurement means 82.

In the present embodiment, when starting the pressure measurement, the user stores the liquid in both the open container 20 and the closed container 30 in the same procedure as in the first embodiment, and when the liquid levels of the two match. The operation button 85a is pressed to reset the weighing value of the weighing means 82 to zero.

When the operation button 85c is pressed during pressure measurement, the microcomputer 87 converts the measurement value [g] input from the measurement means 82 into millimeter units of water columns based on the conversion formula shown in the following formula (6). Converted to gauge pressure [mmAq] and output.

In the above formula (6), M indicates a measurement value [g] input from the measurement means 82, and F indicates a conversion coefficient. In the present embodiment, the conversion coefficient F calculated in advance based on the following equation (7) is stored in the storage area 88.

In the above formula (7), D1 indicates the inner diameter [m] of the open container 20, d1 indicates the outer diameter [m] of the cylindrical tube 42, D2 indicates the inner diameter [m] of the closed container 30, and d2 indicates the cylinder. The outer diameter [m] of the pipe 44 is shown.

The microcomputer 87 inputs the measurement value [g] input from the measurement means 82 and the conversion coefficient F stored in the storage area 88 into the above equation (6) to calculate the gauge pressure [mmAq], and digitally calculates the calculation result. Output to the display 84.

In response to this, the digital display 84 displays the output value of the microcomputer 87 with a unit of [mmAq].

On the other hand, when the operation button 85d is pressed during pressure measurement, the microcomputer 87 converts the measurement value [g] input from the measurement means 82 into Pascal units based on the conversion formula shown in the following formula (8). It is converted to the gauge pressure [Pa] of and output.

In the above formula (8), p indicates the gauge pressure [Pa], M indicates the measured value [g] input from the measuring means 82, F indicates the conversion coefficient, and G indicates the gravitational acceleration [m / s]. ² ] is shown.

In response to this, the digital display 84 displays the output value of the microcomputer 87 with a unit of [Pa].

On the other hand, when the operation button 85b is pressed during the pressure measurement, the microcomputer 87 corrects the temperature of the measured value.

In the present embodiment, the same correction coefficient (see Table 2 above) as described in the first embodiment is stored in the storage area 88 of the microcomputer 87, and the microcomputer 87 is input from the air temperature sensor 86. The correction coefficient corresponding to the air temperature is read out from the storage area 88, and the value obtained by multiplying the calculated gauge pressure [mmAq / Pa] by the read-out correction coefficient is output to the digital display 84.

As described above, according to the pressure measuring device of the present invention, it is possible to measure a minute gas pressure with high accuracy according to the measuring accuracy of the measuring means (electronic balance).

Although the present invention has been described above with embodiments, the present invention is not limited to the above-described embodiments, and the actions and effects of the present invention can be exhibited within the scope of other embodiments that can be conceived by those skilled in the art. As long as it works, it is included in the scope of the present invention.

10 ... Electronic balance, 12 ... Weighing pan, 14 ... Button, 16 ... Digital display, 20 ... Open container, 30 ... Sealed container, 32 ... Lid, 40 ... Siphon tube, 42 ... Cylindrical tube, 44 ... Cylindrical tube, 46 ... communication pipe, 50 ... stand, 60 ... pressure introduction pipe, 62 ... three-way valve, 64 ... three-way valve, 70 ... pitot pipe, 80 ... pressure measurement value converter, 82 ... measuring means, 83 ... weighing pan, 84 ... digital Display, 85 ... Operation button, 86 ... Temperature sensor, 87 ... Microcomputer, 88 ... Storage area, 100 ... Pressure measuring device, 200 ... Pressure measuring device

Claims (5)

An electronic balance with a tare function and a weighing accuracy of 0.01 grams or less,
A cylindrical open container placed on the weighing pan of the electronic balance and
A cylindrical airtight container to which the pressure introduction pipe is connected,
A siphon tube for connecting the liquid stored in the open container and the liquid stored in the closed container, the first cylindrical tube, the second cylindrical tube, and the upper end of the first cylindrical tube. And a siphon tube comprising a communicating tube communicating with the upper end of the second cylindrical tube.
The inner diameter of the open container, the inner diameter of the closed container, the outer diameter of the first cylindrical tube and the second diameter so that the measured value of the electronic balance matches the gauge pressure of the gas introduced from the pressure introduction tube. A pressure measuring device characterized in that the outer diameter of the cylindrical tube is designed. The open container, the closed container, the first cylindrical tube, and the second cylindrical tube are designed to satisfy the following formula (1).
The pressure measuring device according to claim 1.

(In the above formula (1), D1 indicates the inner diameter [m] of the open container, d1 indicates the outer diameter [m] of the first cylindrical tube, and D2 indicates the inner diameter [m] of the closed container. , D2 indicate the outer diameter [m] of the second cylindrical tube.) A weighing means with a tare function and a weighing accuracy of 0.01 grams or less,
A cylindrical open container placed on the weighing pan of the weighing means and
A cylindrical airtight container to which the pressure introduction pipe is connected,
A siphon tube for connecting the liquid stored in the open container and the liquid stored in the closed container, the first cylindrical tube, the second cylindrical tube, and the upper end of the first cylindrical tube. A siphon tube and a communication tube that communicates with the upper end of the second cylindrical tube.
A pressure measuring device including a calculation means for calculating a gauge pressure p of a gas introduced from the pressure introduction pipe based on the following formula (2).

(In the above formula (2), M indicates the measured value [g] of the measuring means, G indicates the gravity acceleration [m / s ² ], D1 indicates the inner diameter [m] of the open container, and d1 indicates the inner diameter [m] of the open container. The outer diameter [m] of the first cylindrical tube is shown, D2 is the inner diameter [m] of the closed container, and d2 is the outer diameter [m] of the second cylindrical tube.) The siphon tube
The second cylindrical tube penetrates and is fixed to the upper surface of the closed container.
The pressure measuring device according to any one of claims 1 to 3. The communication pipe is made of a transparent material and is characterized in that the air bubbles in the pipe are tilted in the horizontal direction so as to move toward the closed container by buoyancy.
The pressure measuring device according to any one of claims 1 to 4.

Images