JP2002107204A - Water level measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To correctly measure a water level even when the water level momently changes, or even in turbid waters or a billow caused by bad weather. SOLUTION: A communication unit 13 conducts the reception of a control instruction from a control department and the transmission of a measured result of the water level. A power source unit 12 supplies an electric power to all units within a device. A measuring electronic circuit 11 radiates leaser beam emitted from a light emitting device 12 to a water surface of a measuring object and receives a reflected wave from the measuring object. The time difference between the radiate time of radiated laser beam and the received time of the reflected wave, or the difference of a physical quantity held in a modulating signal of the irradiated laser beam and a physical quantity held in the modulating signal of the reflected wave corresponding to the laser beam are used to calculate the water level. In addition, the water level is determined from the distribution of the measured results of water level measurement repeated plural times.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a water level measuring device, and more particularly to a water level measuring device using laser light.

[0002]

2. Description of the Related Art Conventionally, one method of measuring the water level uses a float floating above the water surface. As a specific method, the float is wound up to a predetermined position, a method of converting the rotation speed of the winding reel into an electric signal at that time, a magnet is built in the float, and the float is used as a guide with a change in the water surface. A method of converting the water level into an electric quantity by turning the reed switch arranged along the guide on or off with the magnet, along with the guide, a laser fixed at a distance from the float to a reference point such as a guide There is a method of measuring with a measuring instrument.

[0003] There is also used a method of setting up a column on which a scale is printed, observing it with a camera, and performing image processing. Furthermore, a method of measuring the pressure at the bottom of the water is also used.

In recent years, a distance measuring method using a laser beam has been put to practical use. For example,
In the technique disclosed in Japanese Patent Publication No. 7-6822, a distance measuring device of a type that measures a distance to a laser beam target is used as a water level gauge.

More specifically, a laser beam is scanned and emitted in a predetermined direction, an image including the outer edge of the laser beam band is photographed by a light-receiving camera, and only the upper edge signal is detected from the outer edge, and this is coordinated. Converted to water level data.

In this case, since the target surface constantly fluctuates, conventionally, a method of averaging the measured values as they are using a moving average method or the like, or averaging after rounding down the upper and lower parts, has been used.

[0007]

However, the conventional method using a float as described above has a problem that the equipment is large.

In addition, when the water level changes every moment,
When large waves are formed due to turbid currents or bad weather, the position of the water surface becomes unstable, and the measurement value naturally differs between the top and bottom of the wave, so high measurement accuracy cannot be obtained. There was a problem that it became impossible.

Further, in the method of measuring the pressure at the bottom of the water,
Naturally, it is affected by the flow velocity, so unless you use a large-scale device to measure and correct this flow velocity,
There is a problem that the measurement accuracy becomes unstable.

The technique disclosed in Japanese Patent Publication No. 7-6822 does not employ a method of measuring the distance from the water surface by directly reflecting the laser light on the water surface, so that the response to the water level change is low. There is a problem that it is not good and the measurement accuracy is not improved.

Even if the motion of the target surface can be predicted theoretically, no measurement method has been proposed in consideration of this fact, and a simple moving average is used as an averaging algorithm. Since the method was adopted, there was still a problem that the measurement accuracy was not improved.

The present invention has been made in view of the above-mentioned problems in the conventional water level measuring apparatus, and can be accurately performed even when the water level changes every moment, or when a surge occurs due to turbid current or bad weather. An object of the present invention is to provide a water level measuring device capable of measuring a water level.

[0013]

According to the present invention, in order to solve the above-mentioned problems, a water level measuring device for measuring the water level of a pond or a river using a laser beam receives a control command from a management source, Communication means for transmitting the measurement result of the water level, power supply means for supplying power to all equipment in the apparatus, laser light irradiation means for irradiating laser light to the surface of water to be measured, and A laser light receiving means for receiving a reflected wave of laser light, and a time difference between the irradiation time of the irradiated laser light and the reception time of the reflected wave corresponding to the laser light, or a modulation signal of the irradiated laser light. A water level measurement unit that calculates a water level using a difference between a predetermined physical amount to be held and the physical amount held by the modulation signal of the reflected wave corresponding to the laser light, and the water level measurement unit Water level measuring apparatus characterized by having a water level determination means for determining the water level from the distribution of several measurements is provided.

That is, in the present invention, it is assumed that the laser light of the laser range finder is directly reflected on the water surface to measure the distance from the water surface, and that the wave height of the object to be measured is normally distributed. By providing a means for predicting the center value from the frequency distribution characteristics of the measurement results, it is possible to accurately measure the water level even when the water level changes every moment, or when a large wave rises due to turbid current or bad weather I can do it.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an explanatory diagram showing the overall configuration of a water level measuring device according to an embodiment of the present invention and its installation environment.

The water level measuring device according to the present embodiment includes a housing 1 supported by a column 2 and housing the water level measuring device. The housing 1 emits a laser beam and receives the reflected light to measure the water level by measuring the water level; a power supply 12 for supplying power to each component in the housing 1; It includes a communication facility 13 for receiving commands and transmitting the measurement results.

The measuring electronic circuit 11 includes a light emitter 112 for emitting laser light and a light receiver 113. The support 2 is set up in a water area having a water surface 3 to be measured.

The housing 1 protects the entire water level measuring device from animals and protects it from external weather conditions such as wind and rain.
It is necessary for stable measurement without being shaken by waves or wind.

When a commercial power supply can be taken in from the outside, the power supply equipment 12 includes a light emitter 112 for emitting laser light, a light receiver 113 for receiving the reflected wave, an electronic circuit 11 for measurement, and a communication equipment. 13 (DC low-voltage power supply). When commercial power cannot be taken, it is possible to use a primary or secondary battery, or charge and use a secondary battery with a fuel cell, a solar battery, a wind power generator, or the like.

The communication facility 13 receives a control command from the outside of the water level measuring device, and transmits the measurement result to the management source. A communication circuit connecting the communication facility 13 and the management source is wired or wireless. In the case of a wired connection, a coaxial cable, a communication cable, an optical fiber cable, or the like can be used. In the case of a wireless connection, a mobile phone network (i. Mode) or a communication network to which a dedicated frequency is assigned.

Hereinafter, the function of the water level measuring device according to the present embodiment will be described. Light emitting device 112 of measurement electronic circuit 11
Emits a laser beam having the same phase and wavelength, that is, a coherent laser beam, toward the water surface to be measured and at an angle perpendicular to the water surface in accordance with a control signal from the measurement electronic circuit 11.

The photodetector 113 of the measuring electronic circuit 11 receives the reflected light of the laser light from the water surface 3, converts it into an electric signal, and sends it to the measuring electronic circuit 11. The measurement electronic circuit 11 controls the intensity of the laser light emitted from the light emitter 112 and uses the electric signal transmitted from the light receiver 113 that has received the reflected light of the laser light to reach the water surface 3. Calculate the distance.

The above distance calculation methods are roughly classified into the following two methods. FIG. 2 is a block diagram illustrating an example of a distance calculation circuit of the water level measurement device according to the embodiment of the present invention.

The distance calculation circuit shown in this embodiment is included in the measurement electronic circuit 11. The measurement principle is called a time of flight method. That is, assuming that the time from when the laser light is emitted until the reflected light returns is τ seconds, the distance X to be obtained is

[0025]

X１τ × 1.5 × 10 ⁸ (m)

In the circuit shown in FIG.
An on / off signal is transmitted from the switch 22 to the laser light power supply 23 and the counter 27 at the time intervals of (2). Now switch 2
The time at which the ON signal is output from 2 is 0 seconds. At this time,
The laser element 24 oscillates and sends out an optical signal (laser light), and the counter 27 starts counting the number of clock pulses of the frequency f output from the oscillator 28.
The laser light hitting the water surface 3 is reflected and is incident on the light receiving element 25 after τ seconds from the emission of the laser light,
The laser light receiver 26 converts the electric signal into an electric signal and sends it to the counter 27, whereby the counter 27 stops its counting operation.

On the other hand, the decoder 29 outputs the distance from the water surface 3 to the water level measuring device as distance information by interpreting the digital signal (that is, the wave number of the oscillation clock pulse of the frequency f) from the counter 27 during this time. .

In order to obtain a resolution of 1.5 mm, the frequency f of the oscillator 28 needs to be 100 [GHz]. FIG. 3 is a block diagram showing another example of the distance calculation circuit of the water level measuring device according to the embodiment of the present invention.

The distance calculation circuit shown in this embodiment is included in the measurement electronic circuit 11. Further, according to the measurement principle, the intensity of the emitted laser light is modulated to a constant frequency such as a sine wave or a rectangular wave, and the distance is measured from the phase change of the reflected wave.

Assuming that the frequency of the intensity modulation is f and the angle of change of the phase of the received wave is Φ radian, the distance X to be obtained is

[0031]

X = Φ × 1.5 × 10 ⁸ / 2πf (m)

Generally, in the case of the circuit example shown in FIG. 2, when measuring a distance of about 10 (m), it is necessary to set the frequency f of the clock pulse output from the oscillator 28 to a very high value. Yes. On the other hand, in the circuit shown in FIG. 3, the frequency of the clock pulse used may be lower.

In the circuit shown in FIG. 3, a modulation frequency oscillator 311 outputs an electric signal for intensity modulation of a frequency f, is distributed by a distributor 312, and
13 and the mixer 315.

The laser intensity modulator 313 uses the electric signal for intensity modulation of the frequency f to generate the laser element 31.
The intensity of the laser light emitted from 4 is modulated. Frequency f
If the signal for intensity modulation is assumed to be a sine wave, this signal included in the laser beam can be expressed as Sinωt. Further, the laser light reflected on the water surface is reflected by the light receiving element 321 and the laser light receiver 322 on the above-mentioned frequency f.
Sin (ωt +
Φ).

The oscillator 319 outputs an electric signal having a frequency that is different from the frequency f by Δf.
{(Ω + Δω) t + β}. Here, β is the phase of the oscillator 319. The output of the oscillator 319 is distributed by the distributor 320, and the mixer 315 and the mixer 323
Supplied to

Further, in the mixer 315, the output of the distributed oscillator 319 is multiplied by a signal for intensity modulation of the frequency f from the laser intensity modulator 313, and the signal is output from the sinusoid.
{(2ω + Δω) t + β} and Sin (Δωt + β) are output as two sine waves, and the low-pass filter 31
6 is input.

In the low-pass filter 316, if the former harmonic component of Sin {(2ω + Δω) t + β} is cut out of the above input, the zero-crossing detector 317 outputs only the latter signal component of Sin (Δωt + β). Is entered.

On the other hand, in the mixer 323, the output of the distributed oscillator 319 is multiplied by the reception signal from the laser light receiver 322, and Sin ｛(2ω + Δω) t + β +
It is output as two sine waves, Φ｝ and Sin (Δωt + β + Φ), and is input to the low-pass filter 324.

As described above, the low-pass filter 324
In the above input, the former Sin ｛(2ω + Δω) t
If the higher harmonic component of + β + Φ カ ッ ト is cut, only the latter signal component of Sin (Δωt + β + Φ) is input to the zero-crossing detector 317.

Here, by examining the output of the low-pass filter 324, it is found that the distance information Φ of the received signal is stored and the frequency is Δf (frequency Δf
Is a very low frequency).

The distance information Φ to be obtained is a low-pass filter 3
This is obtained by comparing the output of the low-pass filter 324 with the output of the low-pass filter 16, which is performed by the operations of the zero-crossing detectors 317 and 325 and the counter 318.

Note that the frequency Δf enables distance measurement with high resolution even at a very low frequency. By the way, the time difference τ between the irradiation of the laser beam and the return of the reflected light is

[0043]

## EQU3 ## It can be obtained from τ ÷ (1 / Δf) × 2π = Φ [radian].

FIG. 4 is a graph showing a method of processing the measurement result of the water level measuring device according to the embodiment of the present invention. Generally, the measurement result of the water level fluctuates due to the influence of wind, waves, turbidity, and the like, and an accurate value is not determined.

Therefore, the measurement of the water level is repeatedly performed a plurality of times, and an accurate value is determined by averaging each measured value. However, before that, first, a circuit for executing an algorithm for ignoring data outside a predetermined measurement range is provided in a measurement result processing device (this processing device can be installed in the measurement electronic circuit 11, for example). Include it in advance.

That is, the range (upper limit value, lower limit value) that the measured value should take can be estimated in advance from the installation conditions of the water level measuring device. Therefore, the measured value outside the range is excluded, and the remaining measured value is excluded. Take the average only. This measure prevents a shift in the average value due to the use of incorrect measurements.

In the present embodiment, it is assumed that the measured values that fluctuate for the above reasons are distributed in the form of a Gaussian distribution or a sinusoidal function. Therefore, for example, based on the measurement results performed a plurality of times (several hundred times), the range of the variation of the measurement distance is set to 10 to 5
After the division into 0, a plurality of measured values (data) are put into any of these 10 to 50 divisions.

In the graph shown in FIG. 4, the distribution of measured values is shown in which the horizontal axis represents the division and the vertical axis represents the number of data in each division as frequency. This graph has a bell-shaped distribution in the case of a normal distribution, and has a central value (μ) as shown in FIG.
And the distribution characteristic is determined by two values of σ representing the variance. Here, since the center of the distribution is used as the measured value, only the center value (μ) is required, and σ representing the variance is unnecessary.

As a specific algorithm to be incorporated in the measurement result processing device, the maximum value and the minimum value based on the above are determined, the interval is divided at regular intervals, and the number of data in the division is totaled for each division. By doing so, the frequency is calculated, and the section having the highest calculated frequency is determined as the central value (μ).

FIGS. 5, 6, and 7 are explanatory views showing specific examples of a method of installing the water level measuring device according to the embodiment of the present invention. In the installation method shown in FIG. 5, a support 52 is constructed in a water area having the water surface 3, and a housing 51 containing the water level measuring device according to the present embodiment is installed above the support 52.

FIG. 5 shows a method of transmitting a laser beam to the outside of the column 52. Alternatively, a method of transmitting a laser beam to the inside of the column 52 is possible. In this case, the laser beam is transmitted. There is an advantage that the window (opening) is not stained by rain or the like.

In the installation method shown in FIG. 6, a structure 61 such as a bridge, which is a facility in a body of water having a water surface 3, is used, and a housing 61 in which a water level measuring device according to the present embodiment is housed below. Is fixed.

In this case, the housing 61 can be easily installed, and the power can be easily taken in from the outside. In addition, since the strut is not used, there is no influence of drifting substances or stones flowing when the water is raised.

In the installation method shown in FIG. 7, a column 72 for taking in the laser opening of the casing 71 is set up outside the water area having the water surface 3 (a place away from the water basin), and the inside of the column 72 is taken from the water area having the water surface 3. It is a communication pipe 73 for drawing water.

The water level of the water surface 3 is determined by the water level 74 in the communication pipe 73.
Since the height is the same as the height of the water surface 3, the water level of the water surface 3 can be measured by measuring the water level 74 in the communication pipe 73. In this case, since the pillar 72 is set up outside the water area having the water surface 3 (a place distant from the water basin), there is no influence of the drifting substances or stones that are washed away when the water is increased.

Further, by providing a thin orifice pipe in the communication pipe 73, it is possible to block a small fluctuation in the external water level, and to stabilize the water surface of the portion irradiated with the laser beam.

[0057]

As described above, in the present invention, the laser beam of the laser distance meter is directly reflected on the water surface,
Measures the distance from the water surface, and then predicts the center value from the frequency distribution characteristics of the measurement results assuming that the wave height at the measurement target is normally distributed, so the water level changes every moment The water level can be accurately measured even when the turbulence or bad weather causes a surge.

Further, the measurement accuracy can be improved by a method of mixing the frequency of the minute change with the intensity modulation signal of the light emitting laser. Furthermore, compared to the conventional float type or pneumatic type, there are no moving parts, so measurement work is easy, and the need for maintenance can be confirmed by monitoring measurement data from a remote place, so maintenance and adjustment Labor can be greatly reduced.

Further, since the power consumption is small, it is possible to adopt a method of self-supply by solar light or wind power, and it is possible to install the apparatus in a remote place such as a river in the mountains. Furthermore, the responsiveness to a water level change is higher than that of a conventional float type or pneumatic type.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing an overall configuration of a water level measuring device according to an embodiment of the present invention and its installation environment.

FIG. 2 is a block diagram illustrating an example of a distance calculation circuit of the water level measurement device according to the embodiment of the present invention.

FIG. 3 is a block diagram showing another example of the distance calculation circuit of the water level measuring device according to the embodiment of the present invention.

FIG. 4 is a graph showing a method of processing a measurement result of the water level measuring device according to the embodiment of the present invention.

FIG. 5 is an explanatory diagram showing a specific example of a method of installing the water level measuring device according to the embodiment of the present invention.

FIG. 6 is an explanatory diagram showing another specific example of the installation method of the water level measuring device according to the embodiment of the present invention.

FIG. 7 is an explanatory diagram showing another specific example of the installation method of the water level measuring device according to the embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Casing, 2 ... Prop, 3 ... Water surface, 11 ... Electronic circuit for measurement, 12 ... Power supply equipment, 13 ... Communication equipment, 11
2 ... Light emitter, 113 ... Receiver

Claims (8)

[Claims] 1. A water level measuring device for measuring a water level of a pond or a river using a laser beam, comprising: communication means for receiving a control command from a management source and transmitting a measurement result of the water level; Power supply means for supplying power to all the facilities, laser light irradiation means for irradiating laser light on the surface of water to be measured, laser light receiving means for receiving a reflected wave of the irradiated laser light, and irradiation The time difference between the irradiation time of the irradiated laser light and the reception time of the reflected wave corresponding to the laser light, or the predetermined physical quantity held by the modulation signal of the irradiated laser light and the reflected light corresponding to the laser light. A water level measuring means for calculating a water level using a difference between the physical quantity held by the modulation signal, and a water level determining means for determining a water level from a distribution of a plurality of measurement results by the water level measuring means. A water level measuring device, comprising: a step; 2. The water level determining means according to claim 1, wherein said water level determining means includes an elapse means for elapse of an elapsed time from a time point of irradiating said laser beam to a time point of receiving said reflected wave. Water level measurement device. 3. The water level measuring device according to claim 1, wherein a phase of a modulation signal used for modulating the intensity of the irradiated laser beam is the predetermined physical quantity. 4. The communication device according to claim 1, wherein said communication means uses at least one of a coaxial cable, a communication cable, an optical fiber cable, a mobile telephone network, and a communication network to which a dedicated frequency is allocated. Water level measuring device as described. 5. The power supply unit using at least one of a commercial power supply, a battery, a wind power supply, a solar power supply, and a fuel cell.
Water level measuring device as described. 6. The water level measuring device according to claim 1, wherein the water level measuring device is attached to a support standing on a water surface to be measured. 7. The water level measuring device according to claim 1, wherein the water level measuring device is attached to an existing structure existing on a water surface to be measured. 8. The water level measuring device according to claim 1, further comprising a communication pipe, the water level measuring apparatus being attached to a column that is set up at a position distant from a basin to be measured.