JP4693200B2 - Pressure measuring device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pressure measuring device for measuring a water level in a sewer based on pressure applied from the outside.
[0002]
[Related background]
Conventionally, this type of pressure measuring device has a pressure gauge for detecting the pressure, and is used as a water level gauge for measuring the water level in a sewer, for example, as shown in FIG. Some measured changes in pressure applied to the gauge.
In such a pressure gauge, generally, a method of introducing atmospheric pressure to the detection unit for atmospheric pressure correction is employed. For example, when measuring the water level in the sewer, in order to introduce atmospheric pressure into the pressure gauge 10, a hollow pipe 12 is provided in the lead cable 11 of the pressure gauge 10 as shown in FIG. A configuration is adopted in which one end is exposed to the ground from 13 etc. 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 the measurement chamber 14 on the ground, and is converted into a water level value by a converter 15 connected to the lead cable 11.
[0003]
The pressure receiving portion of the pressure gauge 10 is external pressure, and when the specific gravity of water is ρ, the sum of the atmospheric pressure P0 and ρ × H, that is, P0 + ρ × H is applied. 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]
[Problems to be solved by the invention]
However, although the above apparatus introduces atmospheric pressure on the ground, there are many cases where it is actually difficult to provide a measurement room on a road, a sidewalk or the like, and there is a problem that the installation place is restricted.
In the above apparatus, atmospheric pressure is introduced from the ground into the water level gauge in the sewer, but the sewer in the sewer manhole or the like is a closed space, for example, based on a change in the water level of the sewer. There is a case where the atmospheric pressure in the sewer system and the atmospheric pressure on the ground are different, which causes a problem that an error occurs in the measured pressure and the water level cannot be measured accurately.
[0005]
The present invention has been made in view of the above problems, an external pressure on the pressure gauge irrespective the installation location, i.e., object to provide a pressure measuring device which can accurately measure the water level in the sewer And
[0006]
[Means for Solving the Problems]
To achieve the above object, the present invention comprises a junction box trunk cable is positioned in the space in and sewerage are connected, a pressure gauge positioned in the sewage, and a lead cable connecting the junction box and a pressure gauge A pressure measuring device for measuring the water level in the sewer, provided with an atmospheric pressure introduction pipe extending from the connection box to the outside, and connected to the extended end of the atmospheric pressure introduction pipe in an airtight manner. anda single and variable volume portion of the bag-like receiving an atmospheric pressure closed and the sewer the atmospheric pressure in the sewer at the outer lead cable transmits light for pressure detection of the pressure gauge Connecting the connection box and the pressure gauge to seal the inside of the pressure measuring device from the outside to the pressure gauge through the connection box to the pressure gauge, in cooperation with the volume variable part receiving the atmospheric pressure in the sewer. Working sewer A hollow pipe that makes the atmospheric pressure of the pressure gauge and the internal pressure of the pressure gauge substantially the same through the connection box, and the volume variable portion is at least 75% or more of the internal volume of the pressure measuring device excluding the volume variable portion. The pressure gauge is formed in a part of the optical fiber in the light propagation direction, and has a fiber Bragg grading that receives an external pressure through the pressure receiving portion of the pressure gauge. The fiber Bragg grading expands and contracts based on the amount of strain of the pressure receiving part that receives pressure, and the reflection characteristics of a specific wavelength region of light propagating through the optical fiber to the fiber Bragg grading changes, thereby measuring the external pressure applied to the pressure receiving part Then, the water level is measured from the difference between the external pressure and the pressure inside the pressure gauge (claim 1).
[0007]
That is, the pressure measuring device according to claim 1 introduces atmospheric pressure into the pressure gauge from the same space as the space in the sewer where the pressure gauge is installed, cancels fluctuations in atmospheric pressure, and adjusts to the measurement pressure associated therewith. Avoid errors. Moreover, since the volume variable part is sealed with respect to the atmospheric pressure in the sewer, inflow of moisture and moisture into the pressure gauge can be prevented. Further, since the pressure measuring device of claim 1 can measure the pressure by detecting the wavelength change of the reflected light from the fiber Bragg grading , the responsiveness can be improved with a simple configuration, the measurement accuracy can be improved, and the power source can be Because it is unnecessary, there is no need to choose a location.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
The pressure measuring apparatus according to the present invention will be described with reference to the drawings of FIGS. 1-7. In the following drawings, the same components as those in FIG. 13 are denoted by the same reference numerals for convenience of explanation.
[0009]
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 this embodiment, a junction box 25 for relay is provided in the middle of the trunk optical cable 1, and the trunk optical cable 1 and the lead cable 27 for the pressure gauge are connected to each other in the junction box to replace the cable or perform maintenance inspection. Etc. are easy. 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).
[0010]
The pressure measuring device of this embodiment uses an optical pressure gauge 10 having a fiber Bragg grating (hereinafter referred to as “FBG”) 10a, and an atmospheric pressure introduction and pressure detection signal (pressure information) from the optical pressure gauge 10 as light. a lead cable 27 for transmitting has an end 17a, and the atmospheric pressure introduction pipe 17 made of attached stainless to the junction box 25, a variable volume portion 18 connected to one end 17a of the atmospheric pressure introduction pipe 17 It is composed of
[0011]
The pressure gauge 10, the atmospheric pressure introduction pipe 17, the volume variable section 18, the connection box 25, and the lead cable 27 are provided inside the sewer, which is the same space, and the inside of these components is sealed from the outside.
In the optical pressure gauge 10, as shown in FIG. 2, the FBG 10a formed in a part of the optical propagation direction of the optical fiber is disposed in the lower part in the case 10b, and the pressure receiving part of the diaphragm 10c distorted by pressure. It has a structure that is adhered to. In the FBG 10a, the grating characteristics (reflection characteristics) of light due to the grating changes based on the pressure applied from the outside through the diaphragm 10c.
[0012]
In a pressure gauge optical cable 27 connecting the pressure gauge 10 and the connection box 25, a hollow pipe 27a for introducing atmospheric pressure into the pressure gauge 10 and an optical fiber 27b in which the FBG 10a is formed are provided. The hollow pipe 27a is connected to the atmospheric pressure introduction pipe 17 in the connection box 25 to enable the introduction of the atmospheric pressure into the pressure gauge 10 so that the atmospheric pressure in the pressure gauge 10 matches the external atmospheric pressure. . The optical cable 27b is connected to the trunk 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.
[0013]
The FBG 10 a has a function of reflecting light in a specific wavelength region called a Bragg wavelength among light propagated from the light source 31 and transmitting light in other wavelength regions. When the diaphragm 10c bends in the FBG 10a, expansion and contraction occur in the FBG 10a, and the reflection characteristics of the FBG 10a change as shown in FIG. That is, when light is incident on the FBG 10a from the light source 31, if the FBG 10a is distorted by an external force, the wavelength inherent to the FBG changes with respect to the incident light, and the reflected light is incident on the light incident side. Will return. Since the wavelength shift changes according to the strain applied to the FBG, the pressure applied to the diaphragm 10c from the wavelength shift is changed to a wavelength measuring device 33 such as an optical spectrum analyzer provided in the remote control station 30, for example. It can be obtained by an information processing device 34 such as a personal computer. Reference numeral 32 denotes a coupler for distributing light.
[0014]
Further, the information processing unit 34 can obtain the water level from the wavelength shift amount measured by the wavelength measuring device 33. That is, when the relationship between the wavelength shift amount of the FBG and the water level is shown in the schematic diagram of FIG. 4, the measured water level h is
h = reference water level h0 + water level fluctuation Δh
Where h0 = 0m
It is represented by 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 reference value.
[0015]
Therefore, if the water level fluctuation value Δh can be measured, the measured water level h can be obtained.
Here, when the reference wavelength is set to λ0 and the measurement wavelength with respect to the strain ε of the diaphragm serving as the pressure receiving portion is λ1, the wavelength shift Δλ of the FBG is
Δλ = | λ0−λ1 |
And is proportional to the strain ε of the diaphragm. The strain ε of the diaphragm is proportional to the pressure transition, which indicates that it is proportional to the water level difference with respect to the reference water level.
[0016]
This can be expressed as a relational expression as follows.
Δλ = | λ0−λ1 |
∝ε
∝ | p0−p1 |
∝Δh = | h0−h1 |
Here, p0 is the reference pressure at the reference wavelength λ0, and is “0”.
p1: Measurement pressure at the measurement wavelength λ1 h1: Measurement water level at the measurement wavelength λ1, h = h1
Therefore, if the FBG wavelength shift Δλ is measured, the water level fluctuation value Δh, that is, the water level measurement h can be measured.
[0017]
In the present embodiment, since the pressure applied from the outside can be obtained by detecting the wavelength change of the reflected light from the FBG, the responsiveness is fast with a simple configuration and the measurement accuracy can be improved.
The pressure meter of the present embodiment, the power supply rather than the name to choose the unnecessary and installation site, electrodeposition is a no fear of fire in Ino air.
[0018]
As shown in the cross-sectional view of FIG. 5 , the volume variable section 18 of the first embodiment is made up of a bellows 18a made of vinyl, and has a small differential pressure between the internal pressure of the pressure measuring device and the atmospheric pressure in the sewer. Can be varied, and the atmospheric pressure of the pressure measuring device is corrected by making the internal pressure and the atmospheric pressure substantially equal to each other.
The connection between the atmospheric pressure introduction pipe 17 and the volume variable portion 18 is performed by fitting the stainless steel pipe 20 fixed and sealed to the opening 18 b of the bellows 18 a with the self-adhesive adhesive tape 19 with the atmospheric pressure introduction pipe 17. Is done by. The fitting portion is sealed with an O-ring 21 because airtightness is required.
[0019]
Next, setting of the initial volume of the volume variable unit 18 will be described. First, in the pressure measuring device, the relationship between the internal volume, the internal pressure, and the temperature is expressed by the following equation (1).
P × V = k × (273 + t) (1)
However, P: Internal pressure of the pressure measuring device V: Internal volume of the pressure measuring device (including the variable volume portion) k: Constant t: Temperature In this equation (1), when the temperature t is constant, the internal pressure P It means that the internal volume V 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.
[0020]
When the internal pressure P and the atmospheric pressure P0 become the same by changing the volume,
V / V0 = P / P0
However, P: internal pressure P0 of pressure measuring device: atmospheric pressure V: internal volume after change V0: initial volume of the variable volume section is established. That is, it is only necessary to change the volume by the ratio of the atmospheric pressure fluctuation.
[0021]
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 this internal pressure P constant, assuming that the initial temperature is t0 and the initial capacity is V0,
V / V0 = (273 + t) / (273 + t0)
However, the equation of t: temperature of the pressure measuring device is established. That is, it is only necessary to change the volume by the change in ambient temperature.
[0022]
Accordingly, the initial volume of the variable volume portion may be at least the following volume.
V0 = (volume of pressure measuring device) × (temperature change rate + atmospheric pressure change rate)
The atmospheric pressure is generally considered to be about 850 hPa to 1100 hPa, and the internal capacity of the pressure measuring device varies about 0 to −30% based on the lowest atmospheric pressure (850 hPa).
[0023]
Moreover, although a temperature fluctuation changes with the environment where a pressure gauge is used, it is about 0-40 degreeC, for example in the water level gauge used for the sewer field | area. For this reason, the internal capacity | capacitance of a pressure measuring apparatus fluctuates about 0 to -13% when the temperature of 40 degreeC is made a reference | standard.
Therefore, considering the temperature and atmospheric pressure fluctuation, the initial capacity V0 varies 43% of the total volume of the pressure measuring device.
[0024]
The initial volume of the variable volume portion, the pressure gauge, the total volume of the atmosphere pressure introduction pipe (if any elements of the pressure measuring device In addition to this also includes that element. However, the initial volume of the variable volume portion is excluded.) Assuming that V1 and the capacity of the variable volume portion are k · V1, any volume that satisfies the following expression is sufficient.
0.43 × (V1 + kV1) <k × V1
However, the volume ratio of the variable volume portion to k: V1 Therefore, k> 0.75. From this, the volume of the variable volume portion can be selected as one guideline with 75% or more of the internal volume of the pressure measuring device excluding the volume of the variable volume portion. Note that the larger the volume of the volume variable section, the greater the force acting on the volume variable section, and it becomes easier to vary with respect to the differential pressure between the internal pressure of the pressure measuring device and the atmospheric pressure in the sewer and the temperature change. However, in consideration of economy and installation workability, the larger the volume of the variable volume part, the more difficult the realization becomes. Therefore, the volume of the variable volume part is actually 75% to several times the internal volume of the pressure measuring device. It is preferable to be used in a degree.
[0025]
Thus, in the pressure measuring device of the present embodiment, by introducing atmospheric pressure into the pressure gauge from the same space as the space where the pressure gauge is installed, through the volume variable portion , the atmospheric pressure introduction pipe, and the hollow pipe , Since the atmospheric pressure fluctuations are offset so that no error occurs in the measurement pressure associated therewith, the external pressure applied to the pressure gauge can be accurately measured regardless of the installation location.
[0026]
Further, in this embodiment, by providing a volume variable section that is airtightly connected to the atmospheric pressure introduction pipe, it is possible to prevent the inflow of moisture and moisture into the pressure gauge, which is good even in an environment with a lot of moisture and moisture. Pressure measurement can be performed.
Note that the variable volume portion is not limited to the above configuration, and may be configured as shown in FIG. FIG. 6 is a cross-sectional view of the volume variable portion of the second embodiment . The volume variable portion is provided between, for example, two sets of plastic side plates 18c and 18d and side plates 18c and 18d, and both ends are side plates 18c and 18c. It is composed of a spring 18e fixed to each of 18d, and a plastic film 18f covering the side plates 18c, 18d and the spring 18e, and the pressure measurement is performed by making the internal pressure of the pressure measuring device and the atmospheric pressure in the sewer system substantially the same pressure. This is for correcting the atmospheric pressure of the apparatus.
[0027]
In the variable volume portion 18, a spring 18e is sandwiched between the side plates 18c and 18d, 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 introduction pipe 17 and the volume variable portion 18 is performed by fitting a stainless steel pipe 23 fixed to the side plate 18c with, for example, a fixing screw via the rubber packing 22 with the atmospheric pressure introduction pipe 17. The fitting portion is sealed with an O-ring 24 because airtightness is required.
[0028]
In addition, the variable volume portion may be configured to fix and seal a rubber bag to the atmospheric pressure introduction pipe with a self-adhesive adhesive tape.
By using such a variable volume portion, a pressure measuring device, without being affected by air fluctuations, accurately can pressure measurement, for example, the pressure measuring apparatus the water level in the sewer can accuracy be measured, In addition, it is possible to perform highly reliable water level measurement without intrusion of sewage and moisture from the atmospheric pressure introduction pipe.
[0029]
Figure 7 is a block diagram showing the configuration of the pressure measuring device of the third embodiment according to the present invention. In the figure, in this embodiment, an atmospheric pressure introduction pipe 17 is attached to a connection box 25, and a volume variable portion 18 is hermetically connected to an end thereof. Reference numeral 1 denotes a trunk cable connected to a remote control station 30 such as a pump station.
The volume variable section 18 of the third embodiment shown in FIG. 7 is made of a rubber bag 18g, and is formed of a self-adhesive adhesive tape on an L-shaped atmospheric pressure introduction pipe 17 whose end is directed downward. Fixed and sealed.
[0030]
Thus, in this embodiment, the bag 18g made of rubber in a state of Tsu Taresaga communicates connected to the junction box 25 to the end of the atmospheric pressure introduction pipe 17, to offset the change in atmospheric pressure Since the accompanying measurement pressure is prevented from causing an error, 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 that is airtightly connected to the atmospheric pressure introduction pipe, it is possible to prevent the inflow of moisture and moisture into the pressure gauge. Good pressure measurement can be performed even in a humid environment.
[0031]
8 and 9, but not in the embodiment of the present invention, it is a block diagram showing the configuration of the pressure measuring device of the first embodiment. In the figure, the first reference example, the variable volume portion 18 made of rubber bag 18g shown in FIG. 7, directly into the opening 25a of the connection box 25 is fixed and sealed with self-bonding of the adhesive tape Is.
Thus, in the first reference example, without using the atmospheric pressure introduction pipe, the variable volume portion is connected to the opening of the junction box, even in this case, the internal pressure gauge internal及beauty connection box is sealed from the outside Thus, the inflow of moisture and moisture into the pressure gauge can be prevented.
[0032]
Also in the pressure measuring apparatus of the first reference example, pressure from being propagated to FBG10a pressure measuring device light via the coupler 32 and the optical cable 1 from the light source 31, a pressure measuring device, a pressure based on the water level in the diaphragm The diaphragm is distorted by the water pressure, and the distortion is detected by the FBG 10a. When the FBG 10a is distorted, the wavelength of the light reflected by the FBG shifts, and the shift of the wavelength is detected by the information processing unit 34. The information processing unit 34 applies the external pressure applied to the pressure gauge 10 from the detected wavelength shift amount. It is possible to measure and further determine the water level based on this external pressure.
[0033]
Further, FIG. 10 is a view to diagram the configuration of the pressure measuring device of the second embodiment. In the figure, in the second reference example , a partition wall portion 28 is provided in the connection box 25 to create a partition chamber 29, and the volume variable portion 18 is attached in the partition chamber 29. In the second reference example , the inside of the connection box 25 sealed by the partition wall portion 28 is separated from the partition wall chamber 29. The partition chamber 29 is provided with an opening 29 a, and atmospheric pressure is introduced into the partition chamber 29. It is also possible to attach a protective net to the opening 29a.
[0034]
The volume variable section 18 of the second reference example is the same as that shown in the first embodiment of FIG. 5, and one end is connected to the hollow pipe in the optical cable 27 and introduces atmospheric pressure through the partition wall section 28. is connected to the other end of the pipe 17, it is offset atmospheric pressure fluctuations.
Thus, in the second reference example as well as in the above embodiment, good pressure measurement can be performed, and the volume variable portion is provided inside the junction box and does not protrude to the outside . Instead of being restricted by the volume, it is possible to prevent the variable volume portion from being damaged by floating substances such as sewage.
[0035]
Figure 11 is a configuration diagram of a variable volume portion of the third reference example. In the figure, the variable volume portion 18 includes a U-shaped tube 18h and an oil seal portion 18i using silicon oil or the like inserted into the U-shaped tube 18h. One end of the U-shaped pipe 18h is coupled to the end of the atmospheric pressure introduction pipe 17 by a coupling portion 35, and the other end is opened so that atmospheric pressure can be introduced.
[0036]
As described above, in the third reference example , when the atmospheric pressure fluctuation occurs, the oil seal moves in the U-shaped pipe 18h, and the volume is changed by the difference between the atmospheric pressure and the internal pressure of the pressure gauge (not shown). It is possible to cancel the fluctuation in the atmospheric pressure and to prevent an error in the measured pressure.
Further, FIG. 12 is a configuration diagram of a variable volume portion of the fourth reference example, in place of the U-shaped tube of the third reference example, showing a variable volume portion of the case of using a spiral tube 18j. Also in the fourth reference example , as in the third reference example , when the atmospheric pressure fluctuation occurs, the oil seal portion moves in the spiral tube 18j, and the volume is changed by the difference between the atmospheric pressure and the internal pressure of the pressure gauge. It is possible to cancel the atmospheric pressure fluctuation and prevent an error in the measured pressure.
[0037]
In addition, a stainless steel pipe, a plastic pipe, a transparent vinyl chloride pipe | tube, etc. can be used for the said U-shaped pipe and a spiral pipe.
The present invention is not limited to the first to third embodiments described above, and various modifications can be made without departing from the spirit of the present invention .
[0038]
【The invention's effect】
As described above, the pressure measurement equipment according to the present invention is to introduce the atmospheric pressure from the same space as the space in the sewer pressure gauge Ru placed inside a pressure gauge, accompanying to offset atmospheric pressure variation An error can be prevented from occurring in the measurement pressure, and therefore the pressure can be accurately measured regardless of the installation location. Of course, since the volume variable portion is airtightly connected to the atmospheric pressure introduction pipe, the inflow of moisture and moisture into the pressure gauge can be prevented. The pressure measurement equipment according to the present invention, fast response with a simple structure, and can improve the measurement accuracy, also because the power is it not necessary, no and fear of fire without choosing a location.
[Brief description of the drawings]
1 is a block diagram showing the configuration of the pressure measuring device of the first embodiment according to the present invention.
FIG. 2 is an enlarged cross-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. 1;
FIG. 4 is a schematic diagram showing the relationship between the amount of FBG wavelength shift and the water level.
FIG. 5 is a cross-sectional view of the variable volume portion of the first embodiment shown in FIG. 1;
FIG. 6 is a cross-sectional view of a variable volume portion of the pressure measuring device according to the second embodiment .
7 is a block diagram showing a pressure measurement equipment of the third embodiment.
8 is a block diagram showing a pressure measurement equipment of the first embodiment.
9 is a main part enlarged view showing a main part of the pressure measuring device shown in FIG. 8;
10 is a block diagram showing a pressure measurement equipment of the second reference example.
FIG. 11 is a configuration diagram of a volume variable section of a third reference example .
FIG. 12 is a configuration diagram of a volume variable section of a fourth reference example .
FIG. 13 is a configuration diagram showing a configuration of a conventional pressure measuring device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Main line 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 Measuring chamber 15 Converter 17 Atmospheric pressure introduction pipe 17a One end of atmospheric pressure introduction pipe 18 Volume variable part 18a Bellows 18f Plastic film 18g Rubber bag 18h U-shaped pipe 18i Oil seal part 18j Spiral tube 25 Connection box 27 Optical cable for pressure gauge 28 Bulkhead part 29 Bulkhead room 30 Remote control station 31 Light source 32 Coupler 33 Wavelength measuring instrument 34 Information processing part

Claims (1)

A connection box to which a main line cable is connected and positioned in a space in the sewer, a pressure gauge positioned in the sewer, and a lead cable connecting the connection box and the pressure gauge are used to measure the water level in the sewer. A pressure measuring device,
An atmospheric pressure introduction pipe extending from the junction box to the outside;
A single and bag-shaped airtightly connected to the extended end of the atmospheric pressure introduction pipe, sealed against the atmospheric pressure in the sewer outside the connection box, and receiving the atmospheric pressure in the sewer With variable volume part
Further comprising
The lead cable includes an optical fiber that transmits light for pressure detection in the pressure gauge, and the inside of the pressure measurement device that reaches the pressure gauge from the volume variable section through the connection box to the outside. The connection box and the pressure gauge are connected, and in cooperation with the volume variable unit that receives the atmospheric pressure in the sewer, the atmospheric pressure in the sewer and the internal pressure of the pressure gauge are substantially the same throughout the connection box. Built-in hollow pipe and
The volume variable portion has a volume of at least 75% or more of the internal volume of the pressure measuring device excluding the volume variable portion,
The pressure gauge is formed in a part of the optical fiber in the light propagation direction, and has a fiber Bragg grading that receives an external pressure through a pressure receiving portion of the pressure gauge,
In the pressure measuring device, the fiber Bragg grading expands and contracts based on the strain amount of the pressure receiving part that receives external pressure, and the reflection characteristic of light propagating to the fiber Bragg grading through the optical fiber changes. Thus, an external pressure applied to the pressure receiving unit is measured, and the water level is measured from a difference between the external pressure and the pressure inside the pressure gauge .

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