JP2001108548A - Pressure measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately measure an external pressure applied to a pressure gauge regardless of a set position. SOLUTION: In this pressure measurement device, the occurrence of an error in a measuring pressure accompanying an atmospheric pressure fluctuation is prevented by leading atmospheric pressure into the pressure gauge 10 from an atmospheric pressure lead-in pipe 17 provided in the same space as a space inside a sewer set with the pressure gauge 10 to offset the atmospheric pressure fluctuation, while the inflow of water and moisture into the pressure gauge 10 is prevented by blocking up an atmospheric pressure application part 17a with a variable capacity part 18.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure measuring device for detecting an externally applied pressure.

[0002]

2. Related Background Art Conventionally, this type of pressure measuring device has a pressure gauge for detecting the above-mentioned pressure, and is used as a water level gauge for measuring a water level in a sewer, for example, as shown in FIG. Some of them measure changes in pressure applied to a pressure gauge due to fluctuations in water level. With such a pressure gauge,
In general, a method of introducing atmospheric pressure to a detection unit for atmospheric pressure correction has been adopted. For example, when measuring the water level in the sewage system, a hollow pipe 12 is provided in a lead cable 11 of the pressure gauge 10 as shown in FIG. It is configured such that it is brought out to the ground from 13 or the like and one end is opened to the atmospheric pressure in the measurement chamber 14. A water level signal (a signal indicating a pressure value) from the pressure gauge 10 is sent to a measurement room 14 on the ground, and is converted into a water level value by a converter 15 connected to a lead cable 11.

When the specific gravity of water is ρ, the pressure receiving portion of the pressure gauge 10 is the sum of the atmospheric pressure P0 and ρ × H, that is, P0
+ Ρ × H is added. If the internal pressure of the pressure receiving portion is set to the atmospheric pressure P0, a pressure of ρ × H is applied to the pressure receiving portion, and the water level can be obtained from this pressure.

[0004]

However, in the above apparatus, atmospheric pressure is introduced on the ground. However, in many cases, it is very difficult to provide a measurement room on a road, a sidewalk, or the like. Had the problem of receiving Further, in the above apparatus, the atmospheric pressure is introduced into the water level meter in the sewer from the ground, but the sewer such as a sewage manhole is a closed space from the ground, and for example, based on a change in the water level of the sewer. The atmospheric pressure in the sewer may be different from the atmospheric pressure on the ground, which causes an error in the measured pressure, and the water level cannot be measured accurately.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a pressure measuring device capable of accurately measuring an external pressure applied to a pressure gauge irrespective of an installation place.

[0006]

According to the present invention, in order to achieve the above object, the present invention has a pressurizing section provided in a connection box and to which the atmospheric pressure is applied. An atmospheric pressure introducing section for introducing into the pressure gauge, and a volume variable section provided so as to close the pressurizing section, and having a variable volume, hermetically seal the inside of the pressure gauge and the inside of the atmospheric pressure introducing section from the outside. A pressure measuring device is provided.

That is, the atmospheric pressure is introduced into the pressure gauge from the same space as the space in which the pressure gauge is installed, and the fluctuation in the atmospheric pressure is canceled to prevent an error from being caused in the measurement pressure. In addition, by closing the atmospheric pressure pressurizing section with the variable volume section, it is possible to prevent moisture and moisture from flowing into the pressure gauge.

[0008]

FIG. 1 shows a pressure measuring device according to the present invention.
12 through FIG. In the following figures, the case where the pressure measuring device according to the present invention is used in, for example, a sewer will be described, and the same components as those in FIG. 13 will be denoted by the same reference numerals for convenience of description.

FIG. 1 is a configuration diagram showing a first embodiment of the configuration of the pressure measuring device according to the present invention. In the figure, in the present embodiment, a junction box 25 for relay is provided in the middle of the trunk optical cable 1.
The main optical fiber cable 1 and the lead cable 27 for the pressure gauge are connected to each other in the connection box to facilitate cable replacement, maintenance and inspection. The trunk optical cable 1
Is a trunk cable of the present invention connected to a light source 31 provided in a remote control station 30 such as a pump station (not shown).

The pressure measuring device of the present embodiment is a fiber Bragg grating (hereinafter referred to as "FBG") 10a.
, A lead cable 27 for optically transmitting atmospheric pressure introduction and a pressure detection signal (pressure information) from the optical pressure gauge 10, and one end 17 constituting a pressurizing unit of the present invention.
a, and a stainless steel atmospheric pressure introducing pipe 17 constituting the atmospheric pressure introducing section of the present invention attached to the connection box 25, and a volume provided to close one end 17a of the atmospheric pressure introducing pipe 17 And a variable section 18.

The pressure gauge 10, the atmospheric pressure introducing pipe 17, the variable volume section 18, the connection box 25, and the lead cable 27 are provided inside the same space, ie, a sewer, and the inside of these components is sealed from the outside. ing. Optical pressure gauge 1
In FIG. 2, the FBG 10a formed in a part of the optical fiber in the light propagation direction is disposed at the lower part in the case 10b as shown in FIG.
0c is bonded to the pressure receiving portion. FBG1
At 0a, the grating characteristics (reflection characteristics) of light by the grating change based on the pressure applied from the outside via the diaphragm 10c.

A pressure gauge optical cable 27 connecting the pressure gauge 10 and the connection box 25 is provided with a hollow pipe 27a for introducing atmospheric pressure into the pressure gauge 10 and an optical fiber 27b on which an FBG 10a is formed. I have. Hollow pipe 27a
Is connected to the atmospheric pressure introduction pipe 17 in the connection box 25 to enable introduction of the atmospheric pressure into the pressure gauge 10 and
The atmospheric pressure in 0 and the external atmospheric pressure are matched. The optical cable 27b is connected to the main optical cable 1 in the connection box 25, and propagates light from the light source 31 of the remote control station 30 to the FBG 10a via the optical cables 1 and 27b.

The FBG 10a has a function of reflecting light in a specific wavelength region called a Bragg wavelength and transmitting light in other wavelength regions out of the light transmitted from the light source 31. The FBG 10a is a diaphragm 10
When c is bent, expansion and contraction occur in the FBG 10a, and FIG.
As shown in FIG. 7, the reflection characteristics of the FBG 10a change. That is, when light is incident on the FBG 10a from the light source 31 and the FBG 10a is distorted by an external force,
The wavelength unique to the FBG changes with respect to the incident light, and the reflected light returns to the light incident side. The wavelength shift is F
Since the pressure changes according to the amount of distortion applied to the BG, the pressure applied to the diaphragm 10c is converted from the amount of wavelength shift to a wavelength measuring device 33 such as an optical spectrum analyzer provided in the remote control station 30 and an information processing device such as a personal computer. 34
Can be obtained by Reference numeral 32 denotes a coupler for distributing light.

The information processing unit 34 includes a wavelength measuring device 33
It is possible to obtain the water level from the wavelength shift measured in the above. That is, the relationship between the wavelength shift amount of the FBG and the water level is shown in FIG.
The measured water level h is expressed as follows: h = reference water level h0 + water level fluctuation Δh where h0 = 0m. That is, the measured water level h is represented by the sum of a preset reference water level h0 and a water level fluctuation value Δh from the above-described reference value.

Therefore, if the water level fluctuation value Δh can be measured,
The measured water level h is obtained. Here, when the reference wavelength is set to λ0, and the measured wavelength for the strain ε of the diaphragm as the pressure receiving portion is λ1, the wavelength shift Δλ of the FBG becomes Δλ = | λ0−λ1 |, and the strain ε of the diaphragm Proportional. The strain ε of the diaphragm is proportional to the pressure transition, which means that it is proportional to the water level difference with respect to the reference water level.

This can be expressed by the following relational expression. Δλ = | λ0−λ1 | ∝ε∝ | p0−p1 | ∝Δh = | h0−h1 | where p0 is the reference pressure at the reference wavelength λ0, and “0” p1 is the measurement at the measurement wavelength λ1 Pressure h1: h = h1 at the measurement water level at the measurement wavelength λ1 Therefore, if the wavelength shift Δλ of the FBG is measured, the water level fluctuation value Δh, that is, the water level measurement h can be measured.

In this embodiment, since the pressure applied from the outside can be obtained by detecting the change in the wavelength of the reflected light from the FBG, the responsiveness can be increased with a simple configuration, and the measurement accuracy can be improved. In addition, the pressure gauge of this embodiment is:
Since there is no need for a power source and there is no need to select an installation location, and there is no danger of ignition because there is no electricity, it can be used, for example, in gas generation places such as storage tanks in treatment plants.

As shown in the sectional view of the first embodiment in FIG. 5, the variable volume section 18 comprises a bellows 18a made of vinyl, and has a small difference between the internal pressure of the pressure measuring device and the atmospheric pressure in the sewer. The volume can be varied by the pressure, and the internal pressure and the atmospheric pressure are made substantially the same, thereby correcting the atmospheric pressure of the pressure measuring device. The connection between the atmospheric pressure introducing pipe 17 and the variable volume section 18 is made by fitting a stainless steel pipe 20 fixed and sealed to the opening 18b of the bellows 18a with a self-adhesive adhesive tape 19 to the atmospheric pressure introducing pipe 17. This is done by: This fitting portion is sealed with an O-ring 21 because airtightness is required.

Next, the setting of the initial volume of the volume variable section 18 will be described. First, in the pressure measuring device, the relationship between the internal volume, the internal pressure, and the temperature is represented by the following equation (1). P × V = k × (273 + t) (1) where P: internal pressure of the pressure measuring device V: internal volume of the pressure measuring device (including the variable volume section) k: constant t: temperature In the equation (1), If the temperature t is constant, it means that the internal pressure P and the internal volume V are in inverse proportion to each other. That is, when the pressure P is higher than the atmospheric pressure, the volume V increases by the ratio, thereby reducing the internal pressure. When the pressure P is low, the volume V decreases by the ratio. Thus, the internal pressure may be increased.

When the internal pressure P becomes equal to the atmospheric pressure P0 due to the change in volume, V / V0 = P / P0, where P: internal pressure of the pressure measuring device P0: atmospheric pressure V: internal volume after change V0: The initial volume of the variable volume section is established. That is, it is sufficient that the volume changes by the ratio of the atmospheric pressure fluctuation.

Further, even if the temperature changes, the internal pressure P changes because the gas inside the pressure measuring device expands and contracts. In order to keep the internal pressure P constant, assuming that the initial temperature is t0 and the initial capacity is V0, V / V0 = (273 + t) / (273 + t0) where t: temperature of the pressure measuring device is satisfied. That is, it is sufficient that the volume is changed by the change in the ambient temperature.

Therefore, the initial volume of the variable volume section only needs to have at least the following volumes. V0 = (volume of pressure measurement device) × (temperature change rate + atmospheric pressure change rate) Atmospheric pressure may be usually about 850 hPa to 1100 hPa, and the internal capacity of the pressure measuring apparatus is based on the minimum atmospheric pressure (850 hPa). Then, it fluctuates about 0 to -30%.

The temperature fluctuation varies depending on the environment in which the pressure gauge is used. For example, a water level gauge used in the field of sewerage is about 0 to 40 ° C. For this reason, the internal capacity of the pressure measuring device is about 0 to -1 based on a temperature of 40 ° C.
It fluctuates about 3%. Therefore, considering the temperature and the atmospheric pressure fluctuation, the initial volume V0 is 43% of the total volume of the pressure measuring device.
Is variable.

The initial volume of the variable volume portion is the sum of the pressure gauge and the atmosphere introduction pipe (including the components constituting the pressure measuring device, if any, except for the initial volume of the variable volume portion). Assuming that the volume is V1 and the volume of the volume variable section is k · V1, any volume that satisfies the following equation is sufficient. 0.43 × (V1 + kV1) <k × V1 Here, k: 0.75 according to the volume ratio of the volume variable portion to V1. From this, it is possible to select, as one standard, the volume of the variable volume section, which is 75% or more of the internal volume of the pressure measuring device excluding the volume of the variable volume section. The larger the volume of the variable volume unit is, the larger the force acting on the variable volume unit is, and it is easy to change with respect to the pressure difference between the internal pressure of the pressure measuring device and the atmospheric pressure in the sewer and temperature change. However, in consideration of economy and installation workability, the larger the volume of the variable volume section becomes, the more difficult it becomes to realize. Therefore, the volume of the variable volume section is actually 75% to several times the internal volume of the pressure measuring device. Preferably, it is used in a degree.

As described above, in the pressure measuring device according to the present embodiment, the atmospheric pressure is introduced into the pressure gauge from the same space as the space in which the pressure gauge is installed, via the variable volume section and the atmospheric pressure introduction section. Since the fluctuations in the atmospheric pressure are offset to prevent an error from occurring in the measured pressure, the external pressure applied to the pressure gauge can be accurately measured regardless of the installation location.

Further, in this embodiment, by providing the variable volume portion so as to close the atmospheric pressure pressurizing portion, it is possible to prevent the inflow of moisture and moisture into the pressure gauge, and to reduce the amount of moisture and moisture. Good pressure measurement can be performed even in an environment. Note that the volume variable section is not limited to the above configuration, and may be configured as shown in FIG. 6, for example. FIG. 6 is a cross-sectional view of a second embodiment of the variable volume portion. The variable volume portion includes, for example, two sets of plastic side plates 18c and 18d and a side plate 1.
8c, 18d are provided between the side plates 18c, 18d.
And springs 18e fixed to the side plates 18c and 18c, respectively.
d and a plastic film 18f covering the spring 18e
The internal pressure of the pressure measuring device and the atmospheric pressure in the sewage system are made substantially the same, and the atmospheric pressure of the pressure measuring device is corrected.

In the variable volume section 18, the side plates 18c, 18d
A spring 18e is interposed therebetween, the outside is covered with a bellows-like plastic film 18f, and the film 18f and the side plates 18c and 18d are fixed and sealed with an adhesive. The connection between the atmospheric pressure introducing pipe 17 and the variable volume section 18 is performed by connecting the stainless steel pipe 23 fixed to the side plate 18 c via a rubber packing 22 with a fixing screw, for example, to the atmospheric pressure introducing pipe 1.
7. This fitting part
It is sealed with an O-ring 24 because airtightness is required.

In addition, the variable volume portion may be configured so that a rubber bag is fixed and sealed to the atmospheric pressure introduction pipe with a self-adhesive adhesive tape. By using such a volume variable section, the pressure measuring device can accurately measure the pressure without being affected by atmospheric fluctuations. For example, the pressure measuring device was used as a water level meter for measuring the water level in a sewer. In this case, the water level can be measured with high accuracy, and the pressure can be measured with high reliability without sewage or moisture entering from the atmospheric pressure introduction pipe.

FIG. 7 is a configuration diagram showing a second embodiment of the configuration of the pressure measuring device according to the present invention. In the figure, in this embodiment, the connection box 25 has a configuration in which an atmospheric pressure introduction pipe 17 is attached, and a volume variable portion 18 is attached to an end of the connection box 25 and closed. Reference numeral 1 denotes a main cable connected to a remote control station 30 such as a pump station. The volume variable portion 18 of the third embodiment shown in FIG. 7 is made of a rubber bag 18g, and the self-fusing adhesive tape is attached to the L-shaped atmospheric pressure introduction pipe 17 whose end is directed downward. Fixed and sealed.

Thus, in the present embodiment, the rubber bag 1
Since 8 g hangs down, the end of the atmospheric pressure introducing pipe 17 is closed, and the atmospheric pressure is released in the connection box 25, the atmospheric pressure fluctuation is canceled out, so that an error does not occur in the resulting measured pressure. The external pressure applied to the pressure gauge can be accurately measured regardless of the installation location. Further, in the present embodiment, similarly to the above-described embodiment, by providing a volume variable portion so that the atmospheric pressure pressurizing portion is closed, it is possible to prevent the inflow of moisture and moisture into the inside of the pressure gauge. And good pressure measurement can be performed even in a humid environment.

FIGS. 8 and 9 are configuration diagrams showing a third embodiment of the configuration of the pressure measuring device according to the present invention. In the figure, in this embodiment, the rubber bag 18g shown in FIG.
Is fixed and sealed with a self-adhesive adhesive tape directly to the opening 25a of the connection box 25, which is the pressurizing part of the present invention. Thus, in this embodiment, the opening of the connection box can be closed by the variable volume portion without using the atmospheric pressure introduction pipe, and the inside of the pressure gauge and the inside of the connection box constituting the atmospheric pressure introduction portion can be externally provided. By sealing, it is possible to prevent water and moisture from flowing into the pressure gauge.

In such a pressure measuring device, the light source 3
1 is transmitted to the FBG 10a of the pressure measuring device via the coupler 32 and the optical cable 1. The pressure measuring device receives the water pressure based on the water level by the diaphragm, and the diaphragm is distorted by the water pressure.
0a is detected. When the FBG 10a is distorted, the wavelength of the light reflected by the FBG shifts, and this wavelength shift is detected by the information processing unit 34, and the information processing unit 34 detects the external pressure applied to the pressure gauge 10 from the detected wavelength shift amount. The water level based on this external pressure can be determined.

FIG. 10 is a configuration diagram showing a fourth embodiment of the configuration of the pressure measuring device according to the present invention. In the figure, in the present embodiment, a partition wall section 29 is provided in a connection box 25 to form a partition wall chamber 29, and the volume variable section 18 is mounted in the partition wall chamber 29. In this embodiment, the inside of the connection box 25 hermetically sealed by the partition 28 is separated from the partition chamber 29. An opening 29 a is provided in the partition chamber 29, and the atmospheric pressure is introduced into the partition chamber 29. In addition, it is also possible to attach a protective net to the opening 29a.

The variable volume section 18 is the same as that shown in the first embodiment of FIG. 5, and has one end connected to the hollow pipe in the optical cable 27 and the atmospheric pressure introduction pipe 17 penetrating the partition wall section 28. Is connected to the other end (atmospheric pressure introducing section of the present invention) to cancel the atmospheric pressure fluctuation. As described above, in the present embodiment, similarly to the above-described embodiment, good pressure measurement can be performed, and since the variable volume portion is provided inside the connection box and does not protrude to the outside, suspended matter such as sewage can be obtained. This can prevent the variable volume section from being damaged.

FIG. 11 shows a fourth embodiment of the variable volume section according to the present invention.
It is a lineblock diagram of an example. In FIG.
Has a U-shaped pipe 18h and an oil seal portion 18i using silicon oil or the like inserted in the U-shaped pipe 18h. One end of the U-shaped tube 18h is
5 is connected to the end of the atmospheric pressure introduction pipe 17 and the other end is open so that atmospheric pressure can be introduced.

As described above, in this embodiment, when the atmospheric pressure fluctuates, the oil seal moves in the U-shaped tube 18h, and the volume is changed by the difference between the atmospheric pressure and the internal pressure of a pressure gauge (not shown). In addition, the fluctuation of the atmospheric pressure can be offset so that no error occurs in the measurement pressure accompanying the fluctuation. Also, FIG.
It is a block diagram of the 5th Example of the variable volume part similarly, and shows the variable volume part in the case of using the spiral tube 18j instead of the U-tube of the 4th Example. In this embodiment, as in the fourth embodiment, when the atmospheric pressure fluctuates, the oil seal portion is connected to the spiral tube 1.
8j, the volume is changed by the difference between the atmospheric pressure and the internal pressure of the pressure gauge, so that the fluctuation of the atmospheric pressure can be canceled out and the error in the measurement pressure accompanying the change can be prevented.

It should be noted that stainless steel pipes, plastic pipes, transparent vinyl chloride pipes and the like can be used for the U-shaped pipe and the spiral pipe. The present invention is not limited to these embodiments, and various modifications can be made without departing from the spirit of the present invention. For example, the present invention
Not only for use in measuring the water level in sewers, for example, LN
It can be used for measuring the liquid level of G tanks and oil tanks, measuring the water level of rivers and the like, measuring the tide level at bays and the like, and detecting sludge at sewage treatment plants and the like.

[0038]

As described above, according to the present invention, a pressure gauge for detecting a pressure applied from the outside, a lead cable for transmitting a pressure detection signal from the pressure gauge and introducing atmospheric pressure, and A pressure measurement device having a connection box for connecting a cable and a main cable transmitting the pressure detection signal, and measuring a pressure applied from outside by introducing atmospheric pressure into the pressure gauge, By an atmospheric pressure introducing section provided in the connection box, an atmospheric pressure applied from a pressurizing section is introduced into the pressure gauge, and a volume variable section having a variable volume is provided so as to close the pressurizing section. ,
Since the inside of the pressure gauge and the inside of the atmospheric pressure introducing section are sealed from the outside, the external pressure applied to the pressure gauge can be accurately measured regardless of the installation location.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a first embodiment of a configuration of a pressure measuring device according to the present invention.

FIG. 2 is an enlarged sectional view of the pressure gauge shown in FIG.

FIG. 3 is a characteristic diagram showing reflection characteristics of the pressure gauge shown in FIG.

FIG. 4 is a schematic diagram showing a relationship between a wavelength shift amount of FBG and a water level.

FIG. 5 is a cross-sectional view of the first embodiment of the variable volume section shown in FIG. 1;

FIG. 6 is also a cross-sectional view of a second embodiment of the variable volume unit.

FIG. 7 is a configuration diagram showing a second embodiment of the configuration of the pressure measuring device according to the present invention.

FIG. 8 is a configuration diagram showing a third embodiment of the configuration of the pressure measuring device.

FIG. 9 is an enlarged view of a main part showing a main part of the pressure measuring device shown in FIG. 8;

FIG. 10 is a configuration diagram showing a fourth embodiment of the configuration of the pressure measuring device according to the present invention.

FIG. 11 is a configuration diagram of a fourth embodiment of the variable volume unit.

FIG. 12 is a configuration diagram of a fifth embodiment of the variable volume unit.

FIG. 13 is a configuration diagram showing a configuration of a conventional pressure measuring device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Main optical cable 2-4 Pressure measuring device 5 Sewer 10 Pressure gauge 10a FBG 10c Diaphragm 11 Lead cable 12,27a Hollow pipe 13 Manhole 14 Measurement room 15 Converter 17 Atmospheric pressure introducing pipe 17a One end of atmospheric pressure introducing pipe 18 Variable volume Unit 18a Bellows 18f Plastic film 18g Rubber bag 18h U-shaped tube 18i Oil seal unit 18j Spiral tube 25 Connection box 27 Pressure gauge optical cable 28 Partition wall 29 Partition wall 30 Remote control station 31 Light source 32 Coupler 33 Wavelength measuring device 34 Information processing unit

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Miichi Matsuda 2-6-1 Marunouchi, Chiyoda-ku, Tokyo Inside Furukawa Electric Co., Ltd. (72) Toshiki Sakamoto 2-6-1 Marunouchi, Chiyoda-ku, Tokyo No. Furukawa Electric Co., Ltd. (72) Inventor Masakazu Ikoma 1-11-2 Osaki, Shinagawa-ku, Tokyo Fuji Electric Machinery Co., Ltd. (72) Kinya Tanabe 1 Fujimachi, Hino City, Tokyo Fuji Electric Inside the Tokyo Plant Co., Ltd. (72) Hiroshi Saito 2-6-2 Otemachi, Chiyoda-ku, Tokyo Inside Tokyo Sewerage Service Co., Ltd. (72) Toshiro Harada 2-6-1 Otemachi, Chiyoda-ku, Tokyo Tokyo Metropolitan Sewerage Service Co., Ltd.

Claims (1)

[Claims] 1. A pressure gauge for detecting a pressure applied from the outside, a lead cable for transmitting a pressure detection signal from the pressure gauge and for introducing atmospheric pressure, and a trunk for transmitting the lead cable and the pressure detection signal. A connection box for connecting a cable, and a pressure measuring device for introducing atmospheric pressure into the pressure gauge and measuring a pressure applied from the outside, the pressure measuring device being provided in the connection box, An atmospheric pressure introducing unit for introducing atmospheric pressure applied to the pressure unit into the pressure gauge; and an air pressure introducing unit for closing the pressure unit, and having a variable volume. A pressure measuring device comprising: a volume variable section; and sealing the inside of the pressure gauge and the inside of the atmospheric pressure introducing section from the outside.