JP2001091334A - Optical water level sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical water level sensor which a failure or a malfunction by lightening strike does not occurs and a power source and a data transmission device are unnecessary. SOLUTION: When a pressure is added to a Bourdon tube 10 placed in a sensor head 16 arranged at water bottom, the Bourdon tube 10 swells, a pressure/strain conversion member 13 or an optical strain sensor 11 bridged on the surface of the Bourdon tube 10 causes optical change due to the pressure proportional to the water level, which is optically detected with a water level detector 2 arranged on the ground by way of optical fibers 41 and 43 and the water level at the position that the sensor head 16 is arranged is obtained with a signal processor so that lighting effect is prevented. As water level is detected by using a Boudon tube 10, a pressure/strain conversion member 13 or an optical strain sensor 11, no power source and no data transmission device is made necessary.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical water level sensor for measuring a water level of a river or a lake.

[0002]

2. Description of the Related Art The structure and operation of a conventional water level sensor will be described.

[0003] A method in which a sensor head is arranged on the bottom of the water and the water pressure at that position is detected to determine the water level is known as a method capable of detecting the water level with high accuracy. In this method, a quartz oscillator for detecting water pressure is provided in a waterproof-structured sensor head disposed at the bottom of the water, and the water level is measured by utilizing the fact that the vibration frequency changes with the water pressure. In order to detect the oscillation frequency of the crystal unit, a frequency measurement unit is provided in the sensor head, and the measurement result is transmitted to the detection unit located on the ground via an electric signal line, and the detection unit outputs the water level. ing. The water level data output by the detection unit is recorded by a recorder arranged at the site, or sent to a monitoring station by wire or wireless transmission.

[0004]

The conventional water level sensor electrically measures the water level (water pressure) with a sensor head, and uses an electronic circuit to transmit the obtained measurement result to a detection unit on the ground. As a result, the design was made in consideration of electrical insulation.

[0005] However, since the water level gauge is generally placed outdoors, it may be damaged by lightning, and the electrical insulation may be destroyed. Also, the output of the water level sensor may have an incorrect value due to electromagnetic induction. Water level observation under meteorological conditions in which lightning strikes occur is more problematic than usual in terms of disaster prevention. In addition, a power supply is required to detect the water level, and it cannot be applied to places where it is difficult to secure the power supply. Furthermore, when observing the water level in a remote place, it is necessary to arrange a wireless transmitter or a transmission device using a communication line at each water level observing place, and there is a problem that data transmission is costly. .

SUMMARY OF THE INVENTION It is an object of the present invention to provide an optical water level sensor that solves the above-mentioned problems, does not cause a failure or malfunction due to a lightning strike, and does not require a power supply or a data transmission device.

[0007]

In order to achieve the above object, an optical water level sensor according to the present invention has a waterproof sensor head disposed at the bottom of a water, and detects a pressure applied to the sensor head provided in the sensor head. Bourdon tube, a pressure / strain converting member bridged to the surface of the Bourdon tube,
An optical strain sensor attached to the strain conversion member, a detection unit arranged on the ground and connected to the pressure / strain sensor via an optical fiber to detect strain, and a sensor head based on the strain detected by the detection unit are arranged. And a signal processing unit for obtaining a water level at the position where the water is located.

In addition to the above configuration, the optical water level sensor of the present invention may be bridged between the pressure / strain conversion member and the position where the length of the pressure / strain conversion member is maximized on the Bourdon tube. .

[0009] In addition to the above configuration, in the optical water level sensor of the present invention, the pressure / strain converting member may be bridged from the tip of the Bourdon tube to the base of the Bourdon tube.

[0010] The optical water level sensor of the present invention is a sensor head having a waterproof structure disposed at the bottom of the water, a Bourdon tube provided in the sensor head for detecting pressure applied to the sensor head, and a bridge between the surface of the Bourdon tube. Optical strain sensor, a detection unit disposed on the ground, connected to the optical strain sensor via an optical fiber to detect distortion, and a water level at a position where the sensor head is disposed based on the distortion detected by the detection unit. And a required signal processing unit.

In addition to the above configuration, the optical water level sensor of the present invention may be bridged between the optical strain sensor and the position where the length of the optical strain sensor is maximized on the Bourdon tube.

[0012] In addition to the above configuration, in the optical water level sensor of the present invention, the optical strain sensor may be bridged from the tip of the Bourdon tube to the base of the Bourdon tube.

According to the present invention, when pressure is applied to the Bourdon tube provided in the sensor head disposed at the bottom of the water, the Bourdon tube expands, and the pressure / strain converting member or the optical fiber bridged to the surface of the Bourdon tube. The strain sensor produces an optical change due to the pressure proportional to the water level, and this change is optically detected by a detection unit arranged on the ground via an optical fiber, and the sensor head is arranged by the signal processing unit. By determining the water level at a location, the location is not affected by a lightning strike and no failure or malfunction occurs. Bourdon tube and pressure /
Since the water level is detected using the strain conversion member or the optical strain sensor, a power supply and a data transmission device are not required.

[0014]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a conceptual diagram showing one embodiment of the optical water level sensor of the present invention.

Reference numeral 16 denotes a waterproof sensor head made of stainless steel or the like. An opening is formed at the bottom in the sensor head 16, and a cap-shaped pedestal 14 with a built-in filter 15 is attached. The base (the lower end in the figure) of the Bourdon tube 10 is attached to the pedestal 14, and the water pressure below the sensor head 16 is applied to the inside of the Bourdon tube 10. The filter 15 guides the water pressure outside the sensor head 16 to the inside of the Bourdon tube 10, but has a structure to block dust particles and the like in the water. A pressure / strain conversion plate 13 made of copper (or stainless steel) or the like bridged between the tip (the upper left end in the figure) of the Bourdon tube 10 and a position on the Bourdon tube 10 where the length is maximized. Has been bridged. An optical strain sensor (water pressure detection sensor) 11 such as an optical fiber Bragg grating is attached to the pressure / strain conversion plate 13.
Optical fibers 41 and 42 are connected to both ends of the optical strain sensor 11, respectively. A second optical strain sensor (temperature calibration sensor) 12 having the same structure as the first optical strain sensor 11 is connected to the optical fiber 42. An optical fiber 43 is connected to the second optical strain sensor 12. The optical strain sensor 12 is mounted on a base 14. The material of the pedestal 14 is the same as that of the pressure / strain conversion plate 13.

The optical fiber 41 and the optical fiber 43 are connected through a hollow pipe 17 to a detector (not shown) arranged on the ground. The hollow pipe 17 is shown as a straight pipe in the drawing, but a flexible hollow pipe such as a corrugated pipe or a spiral pipe may be used.

Next, the operation of the optical water level sensor will be described.

The inside of the sensor head 16 has a waterproof structure that is shielded from the outside, but the atmospheric pressure is applied through a hollow pipe 17.

On the other hand, inside the Bourdon tube 10,
Since the water pressure is applied through the filter 15, a water pressure proportional to the water level is applied to the Bourdon tube 10, and a force that expands in the radial direction is generated. When the Bourdon tube 10 tries to spread in the radial direction, a tensile strain almost in proportion to the water pressure (water level) is also generated in the pressure / strain conversion plate 13 attached to the surface of the Bourdon tube 10, and the pressure / strain conversion plate 13 The optical strain sensor 11 attached to the sensor also generates a strain substantially proportional to the water pressure (water level). In the optical strain sensor 11, a strain is also generated in which the pressure / strain conversion plate 13 is thermally contracted in accordance with the ambient temperature. The distortion of the optical strain sensors 11 and 12 is optically measured by a detection unit (not shown) connected to the other end of the optical fiber 41.

The strain epsilon ₁₁ of the optical type strain sensors 11 and the strain epsilon _P due to the water pressure P, are applied the sum of the strain epsilon _T due to ambient temperature T, it is applied to the optical type strain sensors 12 The strain ε ₁₂ is only the strain ε _T due to the ambient temperature T.

Therefore, the strain ε _P caused only by the water pressure P (water level) can be obtained by the calculation of ε ₁₁ −ε ₁₂ . Relationship between water level and water pressure P ((1 kg / cm ² ) / 10
It is generally known that m) can be calculated from the specific gravity of water. Therefore, if beforehand understand the relationship of the distortion generated in the pressure P and the pressure / strain conversion plate 13, it is possible to determine the level of the position where the sensor head 16 is placed from the strain epsilon _P.

[0023]

An embodiment in which a plurality of water gauges are arranged on a river for measurement will be described with reference to FIGS. FIG. 2 is a configuration diagram of a system for measuring a water level using a plurality of optical water level sensors shown in FIG.

A water level gauge (sensor head) 1a is submerged on the water bottom near the revetment of the river 91, and a water level gauge 1b is arranged on the water bottom near the pier 92 and fixed to the pier 92. These water level gauges 1 a and 1 b are connected to a water level detector 2 arranged at a monitoring station 93 by an optical fiber cable 4 arranged along a bank 90. The water level detector 2 includes a detection unit and a signal processing unit, and is connected to the monitor 21.

An optical fiber connection between the plurality of water level gauges 1a, 1b and the water level detector 2 is shown in FIG. FIG. 3 is an optical fiber connection diagram of the system shown in FIG.

That is, from the water level detector 2 to the optical fiber 4
The optical strain sensor 11a of the water level meter 1a is connected via 1a, and thereafter, the optical fiber 42a, the optical strain sensor 12a, the optical fiber 43a (41b), the optical strain sensor 11b of the water level meter 1b,. As shown, multiple water gauges
The optical fibers are connected in series by the optical fibers. With such a configuration, the water level at a plurality of locations can be remotely measured using a single optical fiber with a water level detector installed at one location.

FIG. 4 is a conceptual diagram showing another embodiment of the optical water level sensor of the present invention. Note that the same members as those shown in FIG. 1 are denoted by the same reference numerals.

The optical level sensor differs from the optical level sensor shown in FIG. 1 in that the pressure / strain converter plate 13 is bridged between the tip and base of the Bourdon tube 10.
The optical water level sensor can efficiently convert a radially generated force generated in the Bourdon tube 10 into a strain, so that the accuracy of the water level sensor can be improved.

It should be noted that a diaphragm having a pressure transmitting function may be used in place of the filter 15 arranged on the way to guide the water pressure to the Bourdon tube 10. In this case, the water pressure is transmitted through the liquid filled in the Bourdon tube 10 through the diaphragm. However, since the sensor head 16 has a closed structure, it is possible to completely shut off dirt and particles in the water. it can.

In the embodiment described above, the Bourdon tube 10
Has been described in the case of the C type, but is not limited thereto, and may be any of a spiral type, a helical type, and a twist type.

As described above, by arranging the optical water level sensor of the present invention along a river, it is possible to remotely monitor water level information at a plurality of places along the river.

[0032]

In summary, according to the present invention, the following excellent effects are exhibited.

It is possible to provide an optical water level sensor that does not cause a failure or malfunction due to lightning and does not require a power supply or a data transmission device.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing one embodiment of an optical water level sensor of the present invention.

FIG. 2 is a configuration diagram of a system for measuring a water level using a plurality of optical water level sensors shown in FIG.

FIG. 3 is an optical fiber connection diagram of the system shown in FIG. 2;

FIG. 4 is a conceptual diagram showing another embodiment of the optical water level sensor of the present invention.

[Explanation of symbols]

 Reference Signs List 10 Bourdon tube 11, 12 Optical strain sensor 13 Pressure / strain conversion plate 16 Sensor head 41, 43 Optical fiber

Continued on the front page (72) Inventor Shuji Umino 1-3-3 Kojimachi, Chiyoda-ku, Tokyo Inside the Foundation Information Center (72) Inventor Morio Matsushita 3-6-6 Kandanishikicho, Chiyoda-ku, Tokyo Inside Electric Construction Consultants Co., Ltd. (72) Inventor Satoshi Yamamoto 5-1-1, Hidaka-cho, Hitachi City, Ibaraki Prefecture Within the Opto-System Research Laboratory, Hitachi Cable, Ltd. (72) Inventor Kenichi Saito 2-1-2, Marunouchi, Chiyoda-ku, Tokyo F term in reference (reference) 2F014 AB04 BA10 2F065 AA09 AA65 BB08 CC00 EE01 FF58 FF69 FF70 LL02 PP01 2F073 AA01 AB01 AB06 BB06 BC04 CC02 CD01 CD22 DD02 DD04 FH01 GG01

Claims (6)

[Claims] 1. A sensor head having a waterproof structure disposed on a water bottom, a Bourdon tube provided in the sensor head for detecting a pressure applied to the sensor head, and a pressure / strain converter bridged to a surface of the Bourdon tube. A member, an optical strain sensor attached to the pressure / strain conversion member, a detection unit disposed on the ground and connected to the pressure / strain sensor via an optical fiber to detect strain, and the detection unit detects the strain. An optical water level sensor, comprising: a signal processing unit that obtains a water level at a position where the sensor head is disposed from the generated distortion. 2. The optical water level sensor according to claim 1, wherein the pressure / strain conversion member is bridged from a tip of the Bourdon tube to a position on the Bourdon tube where its length is maximized. . 3. The optical water level sensor according to claim 1, wherein the pressure / strain conversion member is bridged between a tip of the Bourdon tube and a base of the Bourdon tube. 4. A sensor head having a waterproof structure disposed on the bottom of the water, a Bourdon tube provided in the sensor head for detecting pressure applied to the sensor head, and an optical strain sensor bridged over the surface of the Bourdon tube. A detection unit disposed on the ground and connected to the optical strain sensor via an optical fiber to detect distortion; and a signal processing for obtaining a water level at a position where the sensor head is disposed from the distortion detected by the detection unit. And an optical water level sensor. 5. The optical water level sensor according to claim 4, wherein the optical strain sensor is bridged from the tip of the Bourdon tube to a position on the Bourdon tube where the length thereof is maximized. 6. The optical water level sensor according to claim 4, wherein the optical strain sensor is bridged between a tip of the Bourdon tube and a base of the Bourdon tube.