JPH0933373A - Differential pressure measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively remove a high frequency component from a reference side area pressure inputted to a differential pressure measuring part. SOLUTION: In the differential pressure measuring device having a reference pressure input part (a) for inputting the area pressure Pi of a reference area 2 through a reference side pressure guide passage ri having one end opened to the reference area 2, a comparison pressure input part (b) for inputting the area pressure Ps of a comparison area 1 through a comparison side pressure guide passage rs having one end opened to the comparison area 1; and a differential pressure measuring part (c) for measuring the difference ΔP of both the area pressures Pi, Ps inputted to the input parts (a), (b), the reference side guide pressure passage ri has a throttle part X for contracting the pressure guide area sectional area in one position in the longitudinal direction thereof and a cushioning capacity part Y situated on the side closer to the reference pressure input part (a) from the throttle part X and having a pressure guide passage sectional area larger than the pressure guide passage sectional area in the throttle part X.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has a reference pressure input section for inputting the regional pressure of the reference region through a reference pressure guiding passage having one end opened in the reference region, and one end opened in the comparison region. The present invention relates to a differential pressure measuring device including a contrast pressure input section for inputting the zone pressure of the comparison zone through a pressure side on the contrast side and a differential pressure measuring section for measuring a difference between both zone pressures inputted to these input sections. .

[0002]

2. Description of the Related Art Conventionally, in this type of differential pressure measuring device,
The reference-side pressure guiding path ri that guides the region pressure Pi of the reference region 2 to the reference pressure input portion a has a relatively large diameter (for example,
With the nominal diameter of 50 A), the main pressure piping 14 'having a uniform diameter over the entire length from the open end to the closed other end with respect to the reference area 2 is provided.
Extend from the reference area 2 to the vicinity of the installation location of the measuring device main body 10 including the differential pressure measuring part c (for example, extending over 40 m), and the reference in the main pressure piping 14 ′ and the measuring device main body 10. The remaining short portion between the pressure input portion a and the connection pipe 15 having a small diameter (for example, a tube having a diameter of 8 mm)
Was adopted to connect with. In the figure, 1 is a comparison area, b is a comparison pressure input section, and 13 is a small-diameter pipe such as a tube forming a comparison-side pressure guiding passage rs.

[0003]

However, in the above-described conventional structure, the area pressure Pi itself of the reference area 2 as a reference is affected by the external wind pressure and the like, and as shown in FIG. In the case of fluctuations due to frequency characteristics including, the fluctuation of the region pressure propagates through the main pressure piping 14 ′ without significantly dampening each frequency component and propagates through the small-diameter connecting pipe 15 of the terminal to the reference pressure input part a. Therefore, the high-frequency fluctuation component caused by the disturbing high-frequency component also appears in the region pressure difference ΔP between the reference region 2 and the comparison region 1 measured by the differential pressure measuring unit c. In monitoring the trend of the pressure fluctuation in the contrast zone 1 by measuring the differential pressure based on the zone pressure Pi in the reference zone 2, it becomes difficult to accurately and accurately grasp the subtle pressure fluctuations in the contrast zone 1. was there.

In particular, each clean region (=
By automatically adjusting the supply air volume and the exhaust air volume for each comparison area 1), the area pressure difference ΔP between each clean area and the general area (= reference area 2) and the area pressure difference between the clean areas are set to their respective predetermined targets. In a clean room facility where so-called differential pressure control is performed to maintain the cleanliness of each clean area by maintaining the value, in response to air volume adjustment, and as a response to disturbance factors in the clean area (for example, starting / stopping a local air supply / exhaust device or a worker Opening and closing the door by entering and leaving)
Due to the influence of the above, it is important in the maintenance management of cleanliness that it is important to accurately monitor how the area pressure Ps in each clean area fluctuates based on the measured differential pressure ΔP. Was wanted.

In contrast to the above situation, the main problem of the present invention is that even if a region pressure fluctuation including a disturbing high frequency component occurs in the reference region due to the influence of the external wind pressure, this high frequency component causes a high frequency of the measured differential pressure. It is possible to effectively suppress the appearance as a fluctuation component, and to reflect only the stable low-frequency component, which is sufficient for the reference in the differential pressure measurement, of the regional pressure fluctuation in the reference region to the measured differential pressure.

[0006]

[Means for Solving the Problems]

[Regarding the Invention According to Claim 1] The invention according to Claim 1 relates to a differential pressure measuring device, which is characterized in that the regional pressure of the reference region is controlled via a reference side pressure guiding passage whose one end is opened in the reference region. The reference pressure input section for inputting, the contrast pressure input section for inputting the zone pressure of the comparison zone through the pressure guide passage on the comparison side having one end opened in the comparison zone, and the two zone pressures inputted to these input sections. In a configuration including a differential pressure measuring unit that measures a difference, in the reference-side pressure guiding path, a throttle section that reduces the pressure guiding path cross-sectional area at a part of the path length direction, and the reference rather than the throttle section. The buffer volume is located on the side of the pressure input section and has a larger pressure guiding path cross-sectional area than the pressure guiding path cross-sectional area of the throttle portion.

That is, in the invention according to claim 1,
Even if the region pressure Pi of the reference region 2 fluctuates due to the frequency characteristic including a high frequency component, the reference pressure guiding line ri is affected by the fluctuation of the region pressure of the reference region 2 introduced into the reference pressure guiding line ri. Since the buffering effect is produced by the cooperation of the throttle portion X and the buffering volume portion Y provided in the reference area 2 which is introduced into the reference side pressure guiding path ri.
The effective damping effect appears for the high-frequency component of the region pressure fluctuation of (1), while the low-frequency component propagates through the reference-side pressure guiding path ri without being greatly attenuated. The smaller the reduced pressure guiding path cross-sectional area in the throttle portion X is set, and the larger the volume of the buffer volume portion Y is set, the higher the damping effect on the high-frequency component can be made.

In other words, qualitatively speaking, the pressure-conducting fluid flows from the side of the reference area 2 into the buffer volume Y through the throttle portion X or the buffer fluid Y does not flow in accordance with the change of the area pressure Pi in the reference area 2. The pressure guiding fluid flows out from the volume section Y to the reference area 2 side through the throttle section X, and the buffer volume section Y is caused by the inflow and outflow of the pressure guiding fluid.
Of the pressure-conducting fluid is resisted against the pressure variation of the reference region 2 due to the passage resistance in the throttle portion X having a reduced pressure-conducting passage cross-sectional area. Since the inflow / outflow is limited and the ratio of the inflow / outflow amount per unit time to the volume of the buffer volume Y is smaller than that in the case where the throttle X is not provided, the internal pressure (and thereafter) in the buffer volume Y is reduced. Change speed of the internal pressure in the reference-side pressure guiding path ri) becomes smaller than the change speed of the area pressure Pi in the reference area 2 (that is, the above-described buffering effect is produced), and thus the reference area 2 Since the change in the internal pressure in the buffer volume Y is delayed with respect to the change in the region pressure, the high frequency component of the region pressure fluctuation in the reference region 2 introduced into the reference side pressure guiding path ri responds to the rapid change. Propagation characteristics that cannot be overwhelmed and a large damping effect It is.

By the way, Pi: the reference pressure, Pr: the internal pressure of the buffer volume, Po: atmospheric pressure, Vr: the volume of the buffer volume, Ko: the coefficient value of the throttle portion including the resistance coefficient, and the like. Then, the time change rate of the internal pressure Pr in the buffer volume is represented by the following equation (Equation 1),

[0010]

## EQU1 ## dPr / dt = Po (| Pi-Pr |) ^1/2 S
/ VrKo However, when Pi−Pr ≧ 0, S = 1, and when Pi−Pr <0, S = −1.

From this equation, this device is a primary delay system equivalent to the low-pass RC circuit in the electric circuit, the volume Vr of the buffer volume corresponds to the capacitor capacity C in the low-pass RC circuit, and Ko / Po including coefficient value
Corresponds to the resistance value R in the low-pass RC circuit, and the smaller the reduced pressure guiding path cross-sectional area in the throttle section is set (that is, the larger Ko is set), and the volume of the buffer volume section is increased. It can be seen that the larger Vr is set, the greater the buffering effect and the higher the damping effect on the high frequency component.

[Regarding the Invention of Claim 2] Claim 2
A feature of the invention according to claim 1 resides in that in the invention according to claim 1, a tank communicating with the throttle portion and the reference pressure input portion is used as the buffer volume portion.

That is, in the invention according to claim 2 (see FIG. 1), the tank 18 communicating with the throttle portion X and the reference pressure input portion a is provided in the formation of the reference side pressure guiding path ri. , The tank 18 is made to function as the buffer volume Y, and the buffer volume Y is set by the tank volume.
By ensuring a large volume, the required high attenuation effect for high frequency components can be obtained.

[Regarding the Invention of Claim 3] Claim 3
A feature of the invention according to claim 2 is that, in the invention according to claim 2, a plurality of the tanks as the buffer volume portion are provided.

That is, in the invention according to claim 3,
Instead of obtaining the required volume of the buffer volume Y by selecting various sizes of one tank, the required volume of the buffer volume Y is secured by selecting the number of tanks 18 to be installed. To obtain the required high damping effect for.

[Regarding the Invention of Claim 4] Claim 4
The invention according to claim 3 is characterized in that, in the invention according to claim 3, a representative tank among the plurality of tanks is provided in a pipe for forming the reference-side pressure guiding path, and another tank is provided with a communication pipe. It is in communication with the representative tank.

That is, in the invention according to claim 4 (see FIG. 7), when the plurality of tanks 18 are provided, the plurality of tanks are connected in parallel by branching the piping for forming the reference-side pressure guiding path to all of the plurality of tanks. Instead of the configuration in which the reference side pressure guiding passage forming pipe is installed in the arrangement, or the plurality of tanks are all arranged in series in the reference side pressure guiding passage forming pipe, a representative one of these tanks 18 is used. Only the tank 18A of No. 1 is installed in the pipe for forming the reference pressure guide passage ri, and the other tank 1
8B is directly connected to the representative tank 18A by using the communication pipe 19, or the representative tank 18A is connected.
The tank 18B connected to A is further connected to the representative tank 18A in a form in which the tank 18B is connected to the representative tank 18A, and thus the plurality of tanks 18 as a whole function as the buffer volume Y.

[Regarding the Invention of Claim 5] Claim 5
The feature of the invention according to claim 1 is that in the invention according to claim 1, 2, 3 or 4, the pipe forming a part of the reference side pressure guiding path closer to the reference pressure input part than the throttle part is buffered. It is for use as a volume section.

That is, in the invention according to claim 5,
Of the reference side pressure guide passage ri, the pressure guide passage having a larger cross-sectional area than the reduced pressure guide passage in the throttle portion X, for the pipe 14 forming the portion on the reference pressure input portion a side of the throttle portion X. By selecting an appropriate pipe diameter that is a cross-sectional area, the pipe 14 itself in this portion is made to function as the buffer volume portion Y, and the buffer volume portion is selected by selecting an appropriate diameter and the facility length of the pipe 14. By securing a large required volume of Y, a desired high attenuation effect for high frequency components is obtained.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION FIG. 1 shows a clean room facility, 1 is a clean area in the building (comparative area), 2 is a general area in the building (reference area), and each clean area 1 is an air supply fan. 3, clean air SA is supplied through the air supply air passage 4 and the high-performance filter 5, and the in-area air is discharged from each clean area 1 through the exhaust air passage 6 by the exhaust fan 7.

The branch air supply air passage 4a for each clean area 1 is provided with a constant air volume device 8 together with the high performance filter 5, and the branch exhaust air passage 6a for each clean area 1 is for adjusting the area pressure. An air volume adjusting damper 9 is interposed, and the air volume adjusting damper 9 finely adjusts the exhaust air volume from each clean area 1 while the constant air volume device 8 keeps the supply air volume to each clean area 1 constant. Thus, the supply / exhaust amount balance of each clean area 1 is adjusted to adjust the area pressure Ps of each clean area 1.

For each clean area 1, the reference-side pressure guiding path ri
The region pressure Pi of the general region 2 guided by
Based on the differential pressure measurement meter 10 for measuring the difference ΔP from the region pressure Ps of the corresponding clean region 1 and the measured differential pressure ΔP (= Ps−Pi) of this differential pressure measurement 10, each clean region 1 A zone pressure controller 11 for operating the air volume adjusting damper 9 is provided so that the zone pressure Ps of 1 is higher than the zone pressure Pi of the general zone 2 by a predetermined value ΔPm set for each clean zone 1. Yes, this prevents the invasion of polluted air from the general zone 2 to each clean zone 1 and the ingress of polluted air from the clean zone 1 with low required cleanliness to the clean zone 1 with high required cleanliness. The required cleanliness of each clean zone 1 is maintained in cooperation with clean air supply through the filter 5.

Reference numeral 12 is a recorder for recording the change over time of the differential pressure ΔP measured by each differential pressure measuring device 10. As a maintenance control of cleanliness, the recording pressure is used as a reference for the regional pressure Pi of the general area 2. The trend of pressure fluctuation in each clean area 1 is monitored.

Each of the differential pressure measuring instruments 10 has a region pressure Pi of the general region 2.
The reference pressure input part a for inputting, the contrast pressure input part b for inputting the region pressure Ps of the clean region 1, and the difference ΔP between the two region pressures Pi, Ps input to these input parts a, b are measured. The apparatus main body is provided with a differential pressure measuring unit c for outputting a differential pressure signal corresponding to the measured differential pressure ΔP to the regional pressure controller 11 and the recorder 12, and the regional pressure Ps of the clean region 1 is compared with the comparison pressure input unit. The comparison-side pressure guiding passage rs leading to b is formed by a small-diameter pressure guiding tube 13 (for example, a tube having a diameter of about 8 mm) having one end connected to the comparison pressure input portion b and the other end opened to the clean area 1. There is.

On the other hand, the reference-side pressure guiding passage ri for guiding the reference region pressure Pi of the general region 2 to the reference pressure input portion a has a relatively large diameter (for example, a nominal diameter of 32A to 65A).
The standard pressure pipe 14 with a uniform diameter over the entire length is
To the vicinity of the installation location of each differential pressure measuring instrument 10, and the remaining short portion between the reference pressure pipe 14 and the reference pressure input part a of each differential pressure measuring instrument 10 is connected to a small diameter connecting pipe. 15 (for example, a tube having a diameter of 8 mm) is connected. The end of the reference pressure pipe 14 on the side of the differential pressure measuring device 10 is a closed end.

Further, in the general area 2, a tank 18 having the inside of the tank opened to the general area 2 by an attached pipe 17 having an intermediate diameter (for example, a nominal diameter of 20 A) through which an orifice 16 (for example, an orifice hole is 2φ) is provided. Is installed, and the end portion of the reference pressure pipe 14 on the general region side is connected to the tank 18.

That is, the attached pipe 17, the tank 18, and the
The reference-side pressure guiding path ri is formed by the reference-pressure piping 14 and the connecting pipe 15. In the reference-side pressure guiding path ri, the attached pipe 1
The orifice 16 provided in 7 constitutes a throttle portion X that reduces the cross-sectional area of the pressure guiding path at a portion in the path length direction, and the tank 18 and the reference pressure pipe 14 having a relatively large diameter have the above-mentioned structure. The buffer volume Y is located closer to the reference pressure input portion a than the throttle portion X and has a larger pressure guiding passage cross-sectional area than the pressure guiding passage cross-sectional area of the throttle portion X.

By providing the throttle portion X and the buffer volume portion Y as described above in the reference side pressure guiding path ri, the buffering effect against the regional pressure fluctuation of the general region 2 introduced into the reference side pressure guiding path ri is provided. As a result, of the fluctuations in the area pressure of the general area 2 introduced into the reference-side pressure guiding path ri as shown in FIG. By so doing, it is possible to prevent the high frequency fluctuation component caused by this high frequency component from appearing in the differential pressure measured by the differential pressure measuring instrument 10, and to satisfy the standard for differential pressure measurement in the differential pressure measurement of the general region 2 (see FIG. Only stable low frequency components as shown in () are input to the reference pressure input section a and reflected in the measured differential pressure ΔP.

Incidentally, (a) to (c) of FIG. 3 show damping characteristics obtained when the experimental conditions of the tank 18 and the reference pressure pipe 14 are changed by using the orifice 16 having an orifice hole of 3φ. The experimental conditions in each of 3 (a) to (c) are as follows.

Figure 3 (a): No tank, standard pressure piping 32A x 40m Figure 3 (b): No tank, standard pressure piping 65A x 40m Figure 3 (c): Tank 425 x 425 x 1200mm, standard pressure piping 3
2A x 40m

Further, FIG. 4 shows the tank 18 and the reference pressure pipe 1.
4 shows the change of the damping effect when the diameter of the orifice hole is changed from 2φ to 6φ under each experimental condition (-) for No. 4, and the vertical axis value represents the frequency 0. 0 for the attenuation curve as shown in FIG. The integrated value (that is, the reciprocal of the strength of the damping effect) in the section from 06 Hz to 0.5 Hz is taken. As the attenuation curve to be integrated, the attenuation curve in the front part of the reference pressure pipe is used when the reference pressure pipe 14 is provided, and the attenuation curve in the tank 18 is used when the reference pressure pipe 14 is not provided. .

The tank 18 and the reference pressure pipe 1 in FIG.
Each experimental condition (-) of 4 is as follows. : Tank (425 x 425 x 1200mm) 1 piece, without reference pressure piping: Tank (425 x 425 x 1200mm) 2 pieces, without reference pressure piping: Tank (425 x 425 x 1200mm) 3 pieces, without reference pressure piping: Tank None, standard pressure piping 32A x 40m: No tank, standard pressure piping 50A x 40m: No tank, standard pressure piping 65A x 40m: 1 tank (425 x 425 x 1200mm), standard pressure piping 32A
× 40m: One tank (425 × 425 × 1200mm), standard pressure piping 50A
× 40m: 1 tank (425 × 425 × 1200mm), standard pressure piping 65A
× 40m

[Another embodiment of the invention] As shown in the above experimental conditions, the tank 18 is omitted as shown in FIG. 5, and only the reference pressure pipe 14 having a relatively large diameter is used for the buffer volume Y.
Alternatively, as shown in FIG. 6, the reference pressure pipe 14 may be omitted and the buffer volume Y may be formed only by the tank 18.

When a plurality of tanks 18 are provided as the buffer volume section Y, as shown in FIG. 7, a representative tank 18A of the plurality of tanks 18 is provided in the pipe forming the reference pressure guide passage ri, and The tank 18B of the
It is also possible to adopt a configuration in which the representative tank 18A is connected to the representative tank 18A via a hose). In some cases, multiple tanks 1
8, a plurality of tanks 18 are connected in parallel to each other to form a piping for forming a reference pressure guide passage ri, or a plurality of tanks 18 are arranged in parallel in the piping for forming a reference pressure guide passage ri. The arrangement may be such that the arrangement is such that the reference side pressure guiding passage ri is interposed in the forming pipe.

Instead of forming the throttle portion X by the orifice 16 as in the above-mentioned embodiment, the throttle portion X may be formed by a venturi or a nozzle, or a small diameter tube or valve.

What is the cross sectional area of the pressure guiding path in the throttle portion X, and how much is the cross sectional area of the pressure guiding passage in the buffer volume Y larger than the reduced pressure guiding path cross sectional area in the throttle portion X? As a matter of course, the volume of the buffer volume Y should be appropriately determined according to the required damping effect and the like.

In the above-described embodiment, the case where the clean area 1 in the clean room facility is set as the contrast area and the general area 2 is set as the reference area is shown. However, the reference area and the contrast area are used for any purpose. It may be.

The area pressure Pi input from the reference pressure input section a
Various differential pressure measurement types can be used for the differential pressure measuring unit c that measures the difference ΔP between the region pressure Ps input from the contrast pressure input unit b.

It should be noted that although reference numerals are given in the claims for convenience of comparison with the drawings, the present invention is not limited to the configurations of the accompanying drawings by the entry.

[0040]

【The invention's effect】

According to the invention according to claim 1, even if the regional pressure fluctuation including the high frequency component occurs in the reference region, only the high frequency component is effective in the regional pressure fluctuation of the reference region introduced into the reference side pressure guiding path. Since the high frequency component can be effectively suppressed from appearing as a high frequency fluctuation component of the measured differential pressure, a stable low frequency that is sufficient for the standard of differential pressure measurement in the regional pressure fluctuation of the reference range can be effectively suppressed. Only the component can be reflected in the measured differential pressure, which allows monitoring the trend of regional pressure fluctuations in the contrast range by differential pressure measurement based on the regional pressure in the reference range.
It is possible to always accurately and accurately grasp a subtle regional pressure fluctuation in the contrast region in a state where the influence of the high frequency component in the regional pressure fluctuation in the reference region is less than that in the conventional device described above.

In the clean room facility for performing the differential pressure control as described above, how the area pressure in the clean area (= contrast area) fluctuates as a response to the air volume adjustment and due to the influence of disturbance factors in the clean area. Since it can be accurately and accurately monitored based on the measured pressure difference, the cleanliness maintenance management can be carried out to a higher degree.

According to the second aspect of the invention, since the buffer volume section is constructed by using the tank originally used for securing the volume and having a simple structure and a large volume securing rate with respect to the required installation space, While reducing the required installation space of the entire device, a large volume of the buffer volume can be secured to obtain a high damping effect for high frequency components. In particular, the measurement device main body including the reference pressure input unit and the reference region It becomes easy to secure the volume of the buffer volume when the separation distance is small.

According to the invention of claim 3, the required volume of the buffer volume is secured by selecting the number of tanks to be installed. Therefore, the required volume of the buffer volume differs depending on the installation case. Compared to manufacturing a tank with a volume corresponding to the volume for each installation case, it is possible to easily cope with various installation cases by preparing a plurality of tanks of one kind or a small number of kinds.

According to the invention of claim 4, the tanks other than the representative tanks provided in the reference-side pressure guide passage forming pipes are additionally installed without the need to change the pressure guide passage forming pipes. Since it can be installed or removed, it is possible to easily install or modify the device in such a form that the required volume of the buffer volume is obtained by selecting the number of installed tanks.

According to the invention of claim 5, since the buffer volume is formed by using the forming pipe itself of the reference-side pressure guiding path, the buffer device is easily manufactured and installed while the buffer device is used. The required volume of the volume section can be secured to obtain a high damping effect for high-frequency components. In particular, the facility distance between the measuring device main body equipped with the reference pressure input section and the reference area is large, and the facility length of the pressure guiding passage forming pipe is long. It becomes easy to secure the volume of the buffer volume when the size becomes large.

[Brief description of drawings]

[Figure 1] Device configuration diagram when applied to a clean room facility

2A and 2B are graphs showing pressure fluctuations, in which FIG. 2A shows the pressure fluctuations before the high-frequency component is attenuated, and FIG. 2B shows the pressure fluctuations after the high-frequency component is removed by the attenuation.

FIG. 3 is a graph showing attenuation characteristics of experimental results.

FIG. 4 is a graph showing the damping effect of experimental results.

FIG. 5 is a schematic device configuration diagram showing another embodiment.

FIG. 6 is a schematic device configuration diagram showing another embodiment.

FIG. 7 is a connection structure portion of a tank showing another embodiment.

FIG. 8 is a diagram showing a configuration of a conventional device.

[Explanation of symbols]

 2 Reference area ri Reference pressure guide path Pi Reference area pressure a Reference pressure input section 1 Contrast area rs Comparison side guide path Ps Comparison area pressure b Comparison pressure input section ΔP Area pressure difference (differential pressure) c Differential pressure Measuring unit X Throttling unit Y Buffer volume 18 Tank 18A Representative tank 18B Other tank 19 Communication pipe 14 Piping

Claims (5)

[Claims] 1. A region pressure (P) of the reference region (2) is provided via a reference-side pressure guiding passage (ri) having one end opened to the reference region (2).
The reference pressure input section (a) for inputting i) and the area pressure (Ps) of the comparison area (1) are input via the comparison side pressure guiding path (rs) having one end opened in the comparison area (1). And a differential pressure measuring section (c) for measuring a difference (ΔP) between the two area pressures (Pi), (Ps) input to these input sections (a), (b). A differential pressure measuring device comprising: a throttle portion (X) for reducing the pressure guide passage cross-sectional area in a part of the reference side pressure guide passage (ri) in the path length direction; ), Which is located closer to the reference pressure input portion (a) than the reference pressure input portion (a), and has a buffer volume (Y) having a pressure guiding path cross-sectional area larger than the pressure guiding path cross-sectional area in the throttle portion (X). Differential pressure measuring device. 2. The differential pressure measuring device according to claim 1, wherein a tank (18) communicating with the throttle portion (X) and the reference pressure input portion (a) is used as the buffer volume portion (Y). 3. The differential pressure measuring device according to claim 2, wherein a plurality of the tanks (18) are provided as the buffer volume (Y). 4. A representative tank (18A) of the plurality of tanks (18) is provided in a pipe for forming the reference side pressure guide passage (ri), and another tank (18B) is connected to a communication pipe (19). )
The differential pressure measuring device according to claim 3, which is communicated with the representative tank (18A) via a. 5. A pipe (14) forming a portion of the reference-side pressure guide path (ri) closer to the reference pressure input portion (a) than the throttle portion (X) is connected to the buffer volume portion (). The pressure difference measuring device according to claim 1, 2, 3, or 4.