JP2010249790A - Laser-type water gauge - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser-type water gauge, capable of measuring a dam water level having a measuring span of several tens of meters or longer, or a water level of a deep well with high accuracy in a non-contact system. <P>SOLUTION: In the laser-type water gauge, laser light is projected to a float floating on the water surface in a wave dissipating tube, and a laser by reflection is measured by a laser range finder. The laser-type water gauge can be utilized also for water level measurement in the wave dissipating tube installed on an oblique retaining wall or for water level measurement of a water passage having a small measurement span. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

Detailed Description of the Invention

Industrial application fields

The present invention provides a laser-type water level meter that measures the height of a water surface with high accuracy without bringing the sensor portion into contact with the measurement water surface and without being affected by an obstacle between the sensor portion and the water surface. Measurements up to deep water levels in dam reservoirs, etc. are possible with high accuracy in order to use laser light with good straightness. There are few restrictions on the installation of the water level gauge, and it can be installed on slant retaining walls such as ponds.

As a distance meter using a laser or a laser length measurement system, the following methods and the like have been put into practical use.
(1) Optical radar laser level meter This method includes an optical pulse method and a phase difference detection method.
In the optical pulse method, a narrow pulsed laser beam is projected onto a measurement object, and the distance to the measurement object is obtained by measuring the time when it is launched and when the reflected wave arrives. This method is also called a TOF (Time of Flight) method.
The phase difference detection method measures the distance using the fact that the phase difference between the transmission and reception waves of the frequency-modulated laser light is proportional to the propagation time.
A laser beam amplitude-modulated by the modulation frequency is emitted from the transmitter, and the phase difference between the wave returned from the object to be measured and the transmitted wave is measured.
(2) Triangulation laser level meter This is an application of the principle of triangulation, and the angle of the received wave that is diffusely reflected and returned depends on the distance to the measurement object by irradiating the measurement object vertically with the transmission wave. It uses change. The angle of the received wave is detected by a line sensor type CCD or the like.
These (1) optical radar laser level meters and (2) triangulation laser level meters are mostly applied as water level meters for rivers, dams, reservoirs, etc. because the measurement object is water and the laser does not reflect. Absent.
In the present invention, these known laser distance meters and laser length measuring systems are combined with a wave lifting tube, a float and a float pulling device using a magnetic force to constitute a laser water level meter.

Conventionally, a float method is used as a mechanical method for water level gauges such as rivers, dams, and reservoirs. This method converts the water level from the rotation angle of the reel that winds up the wire attached to the float that rises and falls as the water level rises and falls. It can obtain a water level measurement accuracy of about ± 1 cm, but it is a large water measuring tube as a civil engineering structure. Need. For this reason, dams, large rivers, etc. have not been used much recently.
A water pressure type water level gauge is often used as a contact type water level gauge for measuring in contact with the measurement water surface.
This method measures the water pressure proportional to the water depth with a pressure-sensitive element, and requires an air release tube to measure compared to atmospheric pressure, and moisture enters the pressure-sensitive part from this tube, or the pressure-sensitive part. If it is buried in sediments such as rivers, it will cause measurement errors. For this reason, stability over time has become an issue.
As the non-contact water level gauge, an ultrasonic water level gauge and a radio wave level gauge are used.
Since the sensor part does not contact the water surface, these can be measured stably over time.
However, the water level that can be measured practically for both ultrasonic and radio wave types due to the fact that the radiation angle increases depending on the distance from the sensor, and there is an obstacle that shields the ultrasonic wave or radio wave within the radiation angle. Is about 20 m.
The radio wave type has better measurement accuracy than the ultrasonic type, and an accuracy of ± 1 cm can be obtained regardless of the measurement span.
The laser-type water level meter of the present invention does not require a large-scale water measuring tube like the float type, and there is no problem of deterioration of measurement accuracy over time like the water-pressure type water level meter, like the ultrasonic type or the radio wave type. This is a water level gauge with no limit on the measurement water depth.
In addition, the measurement accuracy can be expected to be equivalent to a distance meter using a laser or a laser length measurement system.

A wave-dissipating tube with a cavity inside is installed under the surface of the measurement water. A laser distance meter is installed at the top of the quenching tube, and the laser beam is transmitted from the laser rangefinder into the quenching tube.
Float floats on the water surface inside the wave-dissipating tube. The float moves up and down by the same distance as the water surface. The transmitted laser beam floats, and the reflection is received by a laser rangefinder to determine the distance to the float.
The distance between the top of the float and the water surface is always kept constant by the buoyancy of the float, so the distance between the top of the float and the water surface is added to the distance measured by the laser rangefinder. It can be determined accurately.
The silencer tube has a function of holding the float up and down by waves on the water surface and a function of preventing an obstacle from entering between the laser distance meter and the float.
Also, the wave-dissipating tube is provided with a plurality of small holes or mesh-shaped holes for ingress and discharge of water and discharge of dust.
It is assumed that the float is partially made of a magnetic material, and can be maintained by attracting the float by pulling the float with the magnet with a wire from the upper portion of the protective tube into the protective tube.

In the case of dams, rivers, and regulating ponds, the retaining wall of the water level measurement location is not vertical, but if the retaining wall has an inclination, it is necessary to install a wave-dissipating tube obliquely with respect to the vertical. In this case, it is necessary that the upper surface of the float in the quenching tube is always perpendicular to the central axis of the quenching tube and that the laser beam is reflected as in the case where the quenching tube is vertical.
In the present invention, the mass distribution inside the float is adjusted according to the inclination angle from the vertical of the wave-dissipating tube so that the float upper surface is always perpendicular to the central axis of the wave-dissipating tube due to the buoyancy of the float. .

The effects obtained by solving the problems of the conventional water level gauge are as follows.
First, there is no need for a measuring tube with a large diameter required for the installation of a float type water level meter because there is no need for a reel mechanism that winds the wire in balance with buoyancy, unlike the conventional mechanical float type water level meter. It is.
Second, since the pressure sensitive part is not a contact type that is used by being submerged in water like a hydraulic pressure gauge, stable measurement can be performed over a long period of time.
Third, the transmission laser beam of the laser water level gauge has a smaller radiation angle and superior straightness compared to the transmission ultrasonic wave and transmission radio wave beam, as in the ultrasonic or radio wave type water level gauge. Can be secured.
Fourth, the measurement accuracy can be expected to be the same as that of a laser distance meter as a transmitter / receiver, and the same accuracy as that of the radio wave type water level meter, which is the highest accuracy of the conventional method.

The basic configuration of the present invention is shown in FIGS. FIG. 1 shows a configuration at the time of measurement. FIG. 2 shows a configuration in which the float is lifted during maintenance.
FIG. 3 shows that the 13 float tube center axis is not perpendicular to the measured water surface, but the 14 float top surface is always perpendicular to the 13 quench tube center axis when installed at an angle θ with respect to the vertical. A configuration when configured is shown.
The configuration at the time of measurement is composed of a laser rangefinder, 3 quenching tube, and 2 float composed of 6 transmitters, 7 receivers, 8 protective cases, 10 processing circuits, etc.
The structure at the time of maintenance is composed of 3 breaker tubes, 2 floats, 11 magnets, and 12 float lifting wires.

At the time of measurement, a narrow-band four-wave laser beam is emitted from two transmitters of a laser distance meter toward two floats. Five reflected laser beams reflected from the upper surface of the float are received by the seven receivers of the laser distance meter. The four transmission laser beams and the five reflected laser beams are processed by the 10 processing circuits of the laser rangefinder, and a 9 water level output signal is output from the processing circuit.

During maintenance. FIG. 2 shows a method for lifting the float when it is necessary to raise the float for inspection. A part or the whole of the two floats is made of a magnetic material. First, remove the laser rangefinder that is fixedly installed at the top of the three silencers in FIG. Next, the 12 float pulling wire with 11 magnets shown in FIG. 2 is lowered by the gravity of the 11 magnets until the 2 floats are in close contact with the 2 floats. With the 11 magnets and 2 floats adsorbed by magnetic force in the close contact state, the 12 float lifting wire is pulled up, and 2 floats are collected at the upper part of the 3 quenching tubes. There are two methods for returning the float after inspection and maintenance to the water surface. The first is a method of allowing natural fall from the upper part of the three silencers into the silencer. Secondly, in FIG. 2, 11 magnets are electromagnets, and the 12 float pulling wires are gradually stretched while the 2 floats are attracted to the 11 magnets in the same manner as when pulling, and the 2 floats are lowered into the 3 quenching tubes. This is a method in which the 11 magnets are separated from the 2 float by opening the 11 magnets by turning off the power supply of the 11 magnets when it reaches near the water surface.

FIG. 3 shows a case where the 13 wave-dissipating tube center axis is not vertical but is inclined at an angle θ with respect to the vertical. In order to efficiently reflect the transmitted laser light emitted from the laser rangefinder toward the receiver, the mass distribution in the float is such that the angle formed by the 14 float upper surface and the 13 quencher tube central axis is always perpendicular. Adjust.
That is, when the angle axis θ of the 13 wave-dissipating tube is set to the angle θ with respect to the vertical, the float is rotated by the angle θ with respect to the vertical axis by adjusting the mass distribution in the float, and the balance of buoyancy is maintained. 3, the angle between the center axis of the 13 wave-dissipating tube and the upper surface of the 14 float can be kept at a right angle.

FIG. 4 shows an embodiment in which a directional reflective material is disposed on the upper part of the float. In general, the upper part of the float reflects the four-wave laser light efficiently, so the reflective part is white and the like is processed with good reflectivity. However, in FIG. This is an example in which laser light is reflected in the direction of four-wave laser light. The 5-reflected laser light reflected from the 15-directional reflective material is reflected at a narrow 16-reflecting angle with respect to the same direction as the 4-transmit laser light, and can be efficiently received by the 7 receivers. As the 15-directional reflective material, a sheet in which a large number of small prisms are arranged has been put into practical use.
In addition, a steel pipe, a vinyl chloride pipe, or the like is used as the three silencer tubes. When the inner surface of the pipe has a high optical reflectance, a black coating process is performed to reduce the reflection, thereby reducing the reflectance.

FIG. 5 shows an embodiment in which the water depth is shallow and one measurement water surface is close to the bottom of the water channel. Make a 20 water channel bottom depression at the bottom of 19 water canals around 3 silencers, and lower the 3 wave sink bottom to 20 water channel bottom depressions. As a result, the upper surface of the two floats is lifted by buoyancy from one measurement water surface to a predetermined height, and one measurement water surface up to the bottom surface of the 18 water channel can be measured.

The invention's effect

The laser-type water level meter according to the present invention can be expected to have the following effects as compared with a conventionally used water level meter.

Compared to a float-type water level gauge, there is no mechanical mechanism, and measurements that do not require a large water meter are possible.

Compared with pressure-type water level gauges such as quartz-type water level gauges and semiconductors, the non-contact type where the sensor part does not come into contact with water is small, so the elements that change over time are small, and there is no need for an air release tube. Can do.

First, the laser is less spread in propagation than non-contact ultrasonic water level gauges and radio wave level gauges, and there is no influence of obstacles on the propagation path because the laser light is confined in the tube for measurement. Measurement of a long measurement span of several tens of meters or more, such as a dam water level, becomes possible. Secondly, the water level can be measured along a wave-dissipating tube along a retaining wall having an inclined cross section.
Third, since a wave-dissipating tube is used, measurement can be performed without the influence of water surface suspended matter.
Fourth, measurement accuracy can be as high as laser distance meters.

Basic configuration during measurement Basic configuration during maintenance Configuration when the center axis of the filter tube is not vertical Explanatory drawing of Example 1 Explanatory drawing of Example 2.

Claims (2)

(B) A quenching tube with a cavity inside is provided below the surface of the measurement water, and a laser distance meter is placed at the top of the quenching tube, and a laser beam is transmitted from the laser rangefinder into the quenching tube.
(B) The float floats on the water surface inside the wave-dissipating tube with buoyancy. The float moves up and down the same distance as the water surface by the top and bottom of the water surface.
(C) The transmitted laser beam is projected onto the float, and the reflection is received by a laser rangefinder to determine the distance to the float.
(D) The float has a magnetic structure. During maintenance of the float, the magnet with the wire is lowered from the upper part of the wave-dissipating tube, the float is attracted by magnetic force, the wire is pulled up, and the float is taken out from the upper part of the wave-dissipating tube Shall be able to.
Laser type water level meter comprising the above method and configuration 2. The laser-type water level gauge according to claim 1, wherein when the wave-dissipating tube is installed obliquely with respect to the vertical, the float upper surface is always perpendicular to the central axis of the wave-dissipating tube by buoyancy. Laser water level gauge with internal mass distribution adjusted

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