KR20090128996A - Water pressure sensor using an optical fiber sensor - Google Patents

Abstract

PURPOSE: A water-pressure gauge using an optical fiber sensor is provided to measure the water pressure precisely even if the water-pressure gauge is buried under the ground for a long time. CONSTITUTION: A water-pressure gauge using an optical fiber sensor comprises a sensor unit(20), a controller(40) and a display unit(50). The sensor unit senses the water pressure. The controller detects the wavelength change of the light delivered from the sensor unit. The controller measures the pressure. The display unit receives the measured water pressure data from the controller and outputs. The sensor unit comprises a diaphragm, a water pressure measuring optical fiber lattice sensor and a housing. The diaphragm is installed inside the housing and has waterproofing and anti-rusting functions.

Description

Water pressure sensor using an optical fiber sensor

The present invention relates to a hydraulic pressure gauge using an optical fiber sensor, and more particularly, to a hydraulic pressure gauge using an optical fiber sensor capable of measuring water pressure precisely for a long time without being influenced by an external environment.

In the construction of civil engineering and construction structures, hydraulic meters are used for drainage conditions for opening and digging, hydraulic pressure for determining the safety factor during excavation or embankment, or real-time monitoring of groundwater flow and leakage of dams, artificial lakes and banks.

These hydraulic meters can be classified into pneumatic, hydraulic and vibrating strings according to the principle.

Dual vibrating hydraulic pressure gauge is composed of filter, diaphragm, vibrating string, electromagnetic coil, etc. to convert hydraulic pressure into vibration signal. That is, when the hydraulic pressure of the surrounding ground acts on the diaphragm, the diaphragm is deformed according to the pressure change, and thus the tensile force of the vibrating string is changed. When the tensile force is changed, the natural frequency is also changed, so the frequency of the AC voltage generated when the vibrating string is vibrated by the electromagnetic coil is read and converted into water pressure.

However, the vibration-type hydraulic pressure gauge as described above has a problem that the initial measurement value is unstable zero drift or the hysteresis phenomenon due to the pressure increase or decrease, and the vibration string is easily damaged by the impact. .

Particularly, in the case of the vibrating pressure gauge, since the vibrating string itself, which is a sensor unit for detecting water pressure, is made of a metal material, it may be corroded by reacting with moisture in the air.

The present invention is to solve the above problems and proposes a hydraulic pressure gauge that can measure the hydraulic pressure stably and precisely even if the hydraulic pressure gauge is embedded in the ground or underground for a long time by applying a different principle from the conventional hydraulic pressure gauge method.

More specifically, the hydraulic pressure gauge using the optical fiber sensor according to an embodiment of the present invention includes a sensor unit for detecting the water pressure; A control unit measuring pressure by detecting a change in wavelength of light transmitted from the sensor unit; And a display unit for receiving and outputting hydraulic pressure data measured from the controller, wherein the sensor unit comprises: a housing; An outer side of the diaphragm in communication with the outside, the inner side of which is mounted to be waterproof and rustproof; And a pressure measuring optical fiber having one end fixed to the inner side of the diaphragm so that the pressure applied to the diaphragm is transmitted to the hydraulic pressure measuring optical fiber, and the other end fixed to the inside of the housing to maintain the tension state. Including the grating sensor, it is possible to measure the water pressure accurately for a long time. Especially, since the optical fiber sensor itself is glass fiber, it has excellent chemical and stability, and it does not corrode even if it is submerged in water for a long time. The cost can be reduced, which is advantageous for maintenance measurement.

Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings.

1 is a block diagram showing the overall configuration of a hydraulic pressure gauge using an optical fiber sensor according to an embodiment of the present invention.

Hydraulic pressure gauge using an optical fiber sensor according to an embodiment of the present invention is a control unit 40, a display unit for displaying the light source 10, the sensor unit 20, the light detector 30 and the measurement data as shown in FIG. And 50.

As the light source 10, a light emitting diode (LED or SLD) may be used. When power is supplied to the light emitting diode, light having a constant wavelength distribution is generated, and the generated light travels to the sensor unit through a coupler.

The sensor unit 20 of the present invention includes an optical fiber grating (FBG) sensor, which only reflects a wavelength having a predetermined width that satisfies Bragg conditions and transmits other wavelengths as they are. It has a characteristic to make.

The photo detector 30 includes a photo diode (PD) to transmit reflected light of a specific wavelength reflected by the optical fiber grating sensor of the sensor unit 20 and transmit the reflected light to the photo diode. The photodiode measures and outputs the light quantity of the incident reflected light. When the differentiator and the comparator are provided together, the peak point of the reflected light and the light amount at this point are calculated and input to the control unit 40 and the display unit 50.

The controller 40 and the display unit 50 may calculate the wavelength of the reflected light from the peak point of the reflected light and the light quantity data transmitted from the light detector 30, and the amount of strain change generated in the optical fiber grating sensor from the calculated wavelength value. It is possible to calculate the pressure of the water applied to the sensor unit 20 through this.

In the hydraulic pressure gauge using the optical fiber sensor according to the present invention configured as described above, the configuration of the sensor unit 20 will be described in more detail as follows.

2 is a configuration diagram illustrating a configuration of a sensor unit in a water pressure gauge using an optical fiber sensor according to an embodiment of the present invention.

In the hydraulic pressure gauge using the optical fiber sensor according to the present invention, the sensor unit includes a fiber optic grating sensor 100 and a diaphragm 80 as shown in FIG. 2. The optical fiber grating sensor 100 for hydraulic pressure measurement is connected to the diaphragm 80 in a state in which a predetermined tensile force is applied in advance, and the pressure measurement applied to the diaphragm 80 is transmitted to the optical fiber grating sensor 100 for hydraulic pressure measurement. When the distance between the gratings of the optical fiber grating sensor 100 is changed and thus the wavelength of the reflected light changes, the change degree is calculated to measure the water pressure.

As described above, the optical fiber grating sensor reflects light of a specific wavelength, and the optical fiber grating sensor periodically reflects light of a specific wavelength by giving a refractive index change to the optical fiber core. .

That is, when the optical fiber core portion is exposed to light in the ultraviolet region, the refractive index of the exposed portion increases to some extent. For example, when the light in the ultraviolet region is exposed to the germanium-doped optical fiber core portion, the refractive index is 10 ^-5. The grating is engraved on some areas of the optical fiber to increase this degree and to have this refractive index change at regular intervals.

In the optical fiber grating sensor, the measured strain information is represented as a change in wavelength, and the rate of change of Bragg wavelength is linear with respect to the applied physical quantity. It can be calculated inversely.

Accordingly, when the sensor unit 20 according to the exemplary embodiment of the present invention is applied with a pressure such as water pressure to one surface of the diaphragm 80, the tensile force applied to the optical fiber grating sensor 100 connected to the diaphragm 80 is measured. As a result, the distance between the gratings of the optical fiber grating sensor 100 for hydraulic pressure measurement is changed, and thus the wavelength of the reflected light is changed. In addition, the pressure applied to the diaphragm 80 can be quantitatively converted by detecting and calculating the changed wavelength and inverting it.

In addition, the sensor unit 20 may be provided with a temperature compensation optical fiber grating sensor 150 for reducing the sensor measurement error due to the temperature change of the pressure measurement optical fiber grating sensor 100. In this case, the temperature compensation optical fiber grating sensor 150 is preferably arranged in a line under the same conditions as the pressure measurement optical fiber grating sensor 100 inside the hydraulic pressure gauge for accurate temperature compensation.

FIG. 3 is an exploded cross-sectional view illustrating each configuration of a sensor unit in a hydraulic pressure gauge using an optical fiber sensor according to a first embodiment of the present invention. FIG.

In addition, FIG. 4 is a view illustrating an appearance in which the sensor unit according to FIG. 3 is actually implemented.

Sensor unit 20 according to an embodiment of the present invention, as shown in Figure 3, to filter out the impurities and the like contained in the water to pass only the pure water, filter fixing unit 60 for fixing the filter The diaphragm 80 is provided at one side of the filter to which the pressure of the water passing through the filter is applied, and the first diaphragm fixing part 70 and the second diaphragm fixing part 110 to fix the diaphragm 80 are provided. .

In addition, the pressure measurement optical fiber grating sensor 100 is connected to the diaphragm 80 and the first and second optical fiber grating sensor stator (90, 140) for fixing the hydraulic pressure grating sensor 100 is included. . The filter fixing part 60 is disposed in front of the diaphragm 80 so that only pure water is delivered to the diaphragm 80, thereby measuring the water pressure more accurately.

In addition, the sensor unit 20 according to an embodiment of the present invention is connected to the optical fiber grating sensor 100 for the hydraulic pressure measurement strain to apply a tensile force of a predetermined size to the optical fiber grating sensor 100 for measuring the pressure in advance. Adjuster 130, and strain adjustment mechanism 160.

The diaphragm 80 may prevent corrosion of the hydraulic system as well as waterproof and rust preventive when made of special stainless steel as a means of transmitting the applied hydraulic pressure.

In addition, the diaphragm 80 has a circumference suitable for grooves formed in the first and second diaphragm fixing parts 70 and 110 and is fixed to the first and second diaphragm fixing parts 70 and 110. The hydraulic fiber optic grating sensor 100 is fixed to the first and second optical fiber grating sensor stators 90 and 140.

Since the first optical fiber grating sensor stator 90 is in contact with one surface of the diaphragm 80, when the hydraulic pressure is applied to the diaphragm 80, the diaphragm 80 is slightly expanded around the center portion. As a result, the fixed hydraulic fiber grating sensor 100 moves in the direction of application of the hydraulic pressure, thereby weakening the tensile force of the optical fiber grating sensor 100, and the distance between the gratings of the optical fiber grating sensor 100 for hydraulic pressure measurement. Will be reduced. As the distance between the gratings is reduced, the wavelength of the light reflected from the optical fiber grating sensor 100 for hydraulic pressure measurement is changed, thereby converting the water pressure transmitted to the diaphragm 80 in reverse.

The second diaphragm fixing part 110 and the second optical fiber grating sensor stator 140 are coupled with the intermediate connecting part 120 disposed therebetween. The intermediate connector 120 prevents the hydraulic fiber optic grating sensor 100 located therein from moving in a direction perpendicular to the axis on which the hydraulic pressure acts, so that the intermediate connector 120 can move only in the direction in which the hydraulic pressure acts. In addition, a part of the second optical fiber grating sensor stator is engaged with the groove of the intermediate connector 120 to prevent the phenomenon of twisting or rotating by the hydraulic pressure applied to the hydraulic grating sensor 100 for measuring the pressure.

The intermediate connector 120 is coupled with the strain adjusting means. Strain control means is a means provided to apply a certain amount of tension to the pressure grating optical fiber grating sensor (100), the pressure grating optical fiber grating using the characteristics of the fiber grating sensor that changes linearly with respect to the physical force After applying a predetermined amount of tensile force to the sensor 100 in advance, the pressure between the gratings is changed by the water pressure applied to the diaphragm 80, and accordingly the wavelength of the reflected light is changed, so that the water pressure can be measured more accurately.

The strain adjusting means includes a strain adjusting unit 130 and a strain adjusting mechanism 160, and the strain adjusting unit 130 is connected to the second optical fiber grating sensor stator 140 so that the optical fiber grating sensor 100 for hydraulic pressure measurement is provided. It is fixed. In addition, a thread is formed in one part of the strain adjusting unit 130 so that the tensile force of the optical fiber grating sensor 100 for hydraulic pressure measurement may be adjusted through the strain adjusting mechanism 160.

That is, the pressure measurement optical fiber grating sensor 100 is fixed to the diaphragm 80 and the first optical fiber grating sensor stator 90 with respect to the optical fiber grating sensor 100 as described above, and the other side is It is fixed to the strain adjusting unit 130 and the second optical fiber grating sensor stator 140. At this time, when the strain adjusting mechanism 160 is inserted into a threaded position and rotated clockwise or counterclockwise, the strain adjusting unit 130 translates into and out of the intermediate connector 120 while being engaged with the thread.

As a result, when the strain adjusting mechanism 160 is rotated along the thread, the strain adjusting unit 130 is moved closer to or farther from the diaphragm 80, so that the tensile force applied to the optical fiber grating sensor 100 for hydraulic pressure measurement varies according to the degree. do.

On the other hand, the optical fiber grating sensor 100 for pressure measurement causes the reflected wavelength to change not only by physical force but also by temperature change. Accordingly, the temperature compensation optical fiber grating sensor 150 is provided as a reference sensor for excluding the influence of temperature, and thus the water pressure is more precisely compensated by the temperature compensation of the optical fiber grating sensor 100. I can measure it.

2 and 3 together, when the temperature rises or falls, the temperature compensation optical fiber grating sensor 150 and the hydraulic pressure optical fiber grating sensor 100 exhibit the same strain. However, in the case of the optical fiber grating sensor 100 for hydraulic pressure measurement, one side is fixed to the diaphragm 80 and the first fiber grating sensor stator 90, and the other side is the strain adjusting unit 130 and the second fiber grating sensor stator 140. On the other hand, the temperature compensation optical fiber grating sensor 150 is connected to both sides of the second optical fiber grating sensor stator 140 and fixed only so that when the hydraulic pressure is applied to the diaphragm 80, the optical fiber grating sensor for hydraulic measurement ( 100) only.

At this time, the pressure measurement optical fiber grating sensor 100 and the temperature compensation optical fiber grating sensor 150 is protected by the optical fiber grating sensor protection unit 170, one side of the optical fiber grating sensor protection unit 170 is the optical cable 200 Combine with

Therefore, the optical fiber drawn out from the optical cable 200 and the optical fiber grating sensor 100 and the temperature compensation optical fiber grating sensor 150 are formed in the optical fiber grating sensor protection unit 170, the intermediate connector 120, the second optical fiber grating Components such as the sensor stator 140, the strain adjusting unit 130, the first optical fiber grating sensor stator 90, and the second diaphragm fixing unit 110, the first diaphragm fixing unit 70, the diaphragm 80, and the like. By connecting through in order to form a water pressure gauge using one optical fiber sensor.

Hydraulic pressure gauge using the optical fiber sensor, as shown in Figure 4, each component forming the appearance is made of a stainless steel material that can be waterproof and rust prevents accurate measurement even if in contact with water for a long time The advantages are not limited to those made of stainless steel, but can be obtained even if the producers are made of other materials that can be waterproofed and rusted.

In addition, each component provided as described above may be coupled in sequence according to the arrangement order as shown in Figure 3, the optical fiber grating at the point where the optical fiber grating sensor protection unit 170 and the optical cable 200 is connected. The government 250 is provided, which is protected by a waterproof cap to prevent water from seeping into the water pressure gauge using the optical fiber sensor.

5 is an enlarged view of a part of a sensor unit in a hydraulic pressure gauge using an optical fiber sensor according to a second exemplary embodiment of the present invention.

In the sensor unit according to the exemplary embodiment of the present invention, the strain adjusting unit may perform a translational movement of the strain adjusting unit according to the rotation of the strain adjusting screw, and the strain adjusting unit may rotate together with the movement of the strain adjusting mechanism. . As the strain adjusting unit and the second optical fiber grating sensor stator rotate together, the fixed optical fiber grating sensor 100 and the temperature compensation optical fiber grating sensor 150 may rotate together to cause twisting. Optical fibers forming the optical fiber grating sensor 100 and the temperature compensation optical fiber grating sensor 150 may be broken.

Therefore, as a method for preventing the rotation of the strain control unit 130 ', as shown in Figure 5, to form a cut surface in a portion in the axial direction with respect to the strain control unit 130' formed in a circular pipe shape. Can be. The strain adjusting part 130 'may be engaged with and interlocked with the intermediate connecting part 120'. The same shape as that of the cross-sectional shape of the strain adjusting part 130 'is formed on the engaging surface of the intermediate connecting part 120' and is engaged with it. When engaged, even if there is movement or rotation, it is caught in the formed portion of the coupling surface of the intermediate connecting portion 120 ′ to prevent rotation.

At this time, as shown in Figure 4 (b) to the coupling surface of the strain adjusting unit 130 'and the intermediate connecting portion 120' may be made of at least one arc and a straight line or may have a variety of shapes, such as polygons. Strain control unit 130 'can be translated by the strain control mechanism 160 and the strain control unit 130' can be variously modified by the producer in a manner that is coupled and fixed to the intermediate connection portion 120 '. Can be.

FIG. 6 is a measured hydraulic pressure graph when a hydraulic pressure gauge using an optical fiber sensor as shown in FIG. 4 is implemented.

Hydraulic pressure gauge using an optical fiber sensor according to an embodiment of the present invention configured as described above can measure the water pressure in the following manner.

First, the hydraulic pressure gauge using the optical fiber sensor is erected vertically so that the filter fixing part faces upward. Pure water filtered by the filter fixed to the filter holder reaches the diaphragm to apply water pressure. At this time, to install a hydraulic pressure measuring pipe for the hydraulic pressure test using the optical fiber sensor, the diameter of the experimental pipe is preferably formed to 60mm or more.

When the hydraulic pressure gauge using the optical fiber sensor is positioned vertically, the reflection wavelength of the optical fiber grating sensor for hydraulic pressure is detected to confirm the initial value, and the hydraulic pressure gauge using the optical fiber sensor is placed in a laboratory pipe filled with a large amount of water. At this time, mark the optical cable with a certain length unit on the basis of the diaphragm and insert the hydraulic pressure gauge using the optical fiber sensor according to the unit. In general, when the cross-sectional area of the experimental pipe is constant, the pressure varies according to the height, so the hydraulic pressure applied to the diaphragm varies according to the height of the hydraulic gauge using the optical fiber sensor. Therefore, the strain value applied to the optical fiber grating sensor for the hydraulic pressure measurement of the hydraulic pressure gauge using the optical fiber sensor for each position placed in the experimental pipe is different and it is possible to calculate the water pressure at the corresponding water level by calculating it.

FIG. 6 is a graph showing the results of experiments using a fiber pressure sensor using the optical fiber sensor. The strain values according to water pressure and the change of strain values according to water depth are theoretically calculated and shown together with the test results.

According to FIG. 6, the water pressure measured in the hydraulic pressure gauge using the optical fiber sensor according to an embodiment of the present invention is almost identical to the change in water pressure according to the theoretically calculated strain value, and from this, the optical fiber according to the embodiment of the present invention. It can be seen that the pressure gauge using the sensor has high accuracy.

On the other hand, in the hydraulic pressure gauge using the optical fiber sensor according to an embodiment of the present invention, since the sensor unit can detect and transmit the physical quantity to one strand of the optical fiber grating sensor, a plurality of grating sensor unit is formed to output light of different reflection wavelengths It is possible to measure the water pressure at several points at the same time by arranging each at several points which are separated from each other. In addition, a wideband light source may be used for this purpose, but is not limited thereto.

In addition, when a plurality of sensor units are disposed at positions spaced apart from each other that require measurement, components such as a light source, a coupler, a control unit, and a display unit except for the sensor unit may be disposed in one place, and the optical cable has less noise according to the installation length. It is not affected by electrical external environment. Therefore, by connecting each sensor unit with an optical cable, it is possible to receive the reflected light from each sensor unit arranged in various places without loss or interference, and to accurately measure the water pressure at the corresponding position through the received reflected light. This can be implemented.

In particular, since the fiber optic grating sensor itself is glass fiber, it is stable due to its low chemical reactivity, and it is not corroded even after being immersed in water for a long time, thereby reducing the replacement cost and maintenance cost due to damage or loss of the sensor. It is advantageous.

Although the hydraulic pressure gauge using the optical fiber sensor according to the present invention has been described with reference to the illustrated drawings, the present invention is not limited to the embodiments and the drawings disclosed herein, but the optical fiber grating sensor is applied to a tensile force of a predetermined size. It is apparent that the technical idea of the present invention to accurately measure the water pressure can be easily applied by those skilled in the art within the scope of protection.

1 is a configuration diagram showing the overall configuration of a hydraulic pressure gauge using an optical fiber sensor according to an embodiment of the present invention,

FIG. 2 is a configuration diagram illustrating a configuration of a sensor unit in a water pressure gauge using an optical fiber sensor according to an embodiment of the present invention; FIG.

3 is an exploded cross-sectional view showing each configuration of the sensor unit in the hydraulic pressure gauge using the optical fiber sensor according to the first embodiment of the present invention;

Figure 4 is an appearance of the actual implementation of the hydraulic pressure gauge using the optical fiber sensor according to an embodiment of the present invention,

5 is an enlarged view of a partial configuration of a sensor unit in a water pressure gauge using an optical fiber sensor according to a second embodiment of the present invention; and

FIG. 6 is a result of measuring a hydraulic pressure gauge using the optical fiber sensor shown in FIG. 5.

<Explanation of symbols for the main parts of the drawings>

10: light source 20: sensor

30: photodetector 40: controller

50: display unit 60: filter fixing unit

70: first diaphragm fixing part 80: diaphragm

90: first optical fiber grating sensor stator 100: optical fiber grating sensor for hydraulic pressure measurement

110: second diaphragm fixing part 120: intermediate connection part

130: strain adjusting unit 140: second optical fiber grating sensor stator

150: optical fiber grating sensor for temperature compensation 160: strain adjustment mechanism

170: optical fiber grating sensor protection unit 200: optical cable

250: optical cable fixing part A: filter

Claims (10)

Sensor unit for detecting the water pressure; A control unit measuring pressure by detecting a change in wavelength of light transmitted from the sensor unit; And It includes a display unit for receiving and outputting the hydraulic pressure data measured by the control unit, The sensor unit, housing; An outer side of the diaphragm in communication with the outside, the inner side of which is mounted to be waterproof and rustproof; And One end of the diaphragm is fixed so as to be fixed to the inside of the diaphragm, the other end is fixed to the inside of the housing so that the pressure applied to the diaphragm is transmitted to the hydraulic pressure measurement optical fiber grating to maintain a tension state Hydrometer using a fiber optic sensor comprising a sensor. The method of claim 1, An optical fiber including strain adjusting means provided at the other end of the optical fiber grating sensor for measuring hydraulic pressure, and fixing the other end of the optical fiber grating sensor for measuring pressure, and adjusting strain applied to the hydraulic fiber grating sensor for translation through a translational motion; Hydrometer with sensor. The method of claim 2, The strain adjusting means may include a strain adjusting unit to which the other end of the optical fiber grating sensor for measuring hydraulic pressure is fixed; And And a strain adjusting mechanism coupled to the strain adjusting unit, the strain adjusting unit moving in the axial direction according to the rotational direction so that a tensile force applied to the optical fiber grating sensor for hydraulic pressure measurement is adjusted. The method of claim 3, wherein The strain adjusting part is a hydraulic pressure gauge using an optical fiber sensor having a cut surface formed on the outer circumferential surface thereof to prevent twisting of the optical fiber grating sensor for measuring the pressure. The method of claim 1, The sensor unit is disposed in series with the optical fiber grating sensor for measuring the pressure of the optical fiber using the optical fiber sensor including a temperature compensation optical fiber grating sensor for compensating for the change in the reflected light wavelength of the optical fiber grating sensor for measurement by the temperature change system. The method of claim 1, And a diaphragm fixing part which is in contact with one surface of the diaphragm and fixed to one end of the optical fiber grating sensor for measuring pressure so that the hydraulic pressure applied to the diaphragm is transferred to the optical fiber grating sensor for measuring pressure. The method of claim 1, The diaphragm is a water pressure gauge using an optical fiber sensor made of stainless steel that is waterproof and rustproof. The method of claim 1, And a filter positioned on the diaphragm and filtering the impurities contained in the water to allow pure water to reach the diaphragm. The method of claim 1, A hydrometer using a fiber optic sensor comprising a plurality of the sensor unit is formed in the lattice to have a different reflection wavelength, the sensor unit is disposed at each position to be measured. The method of claim 9, Each sensor unit is connected to the control unit via an optical cable, A pressure gauge using an optical fiber sensor, which allows the reflected light output from each of the sensor units to be finally transmitted to the controller disposed remotely through the optical cable.

Images