JPH08166276A - Method and device for measuring water level in large scale - Google Patents

Abstract

PURPOSE: To find a water level without an error by receiving pulse waves from a sound wave pulse generator by a plurality of microphones provided at a fixed interval and measuring time interval between an advancing wave and a reflection wave which are received by the first microphone and a reception time interval of a microphone which is the closest to a water surface. CONSTITUTION: A sound wave pulse generator 1 is provided at an upper end of a waveguide 2, a microphone 51 is provided at an interval L in the lower part thereof, and microphones 52 , 53 ,... 5n are provided sequentially at an interval 1. The generator 1 is driven by pulses from an oscillator 6 to propagate sound wave pulses along the waveguide 2. The microphone 51 and the microphone 5n which is selected in a switch circuit 4 and is the closest to a water surface are connected to an amplifier 7. Its output enters an operation controller 10 through a detector 8 and a waveform forming device 9. The controller 10 measures an interval t2 between an advancing wave and a reflection wave which are received by the microphone 51 and a reception interval t1 of the microphones 51 and 52 to measure an accurate water level. It also becomes possible to provide it along an inclined face and it is unnecessary to erect a vertical tower.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for measuring distance by using sound waves. It has a large water level, and the reservoir temperature, large river, groundwater where the ambient temperature and humidity change drastically. The present invention relates to a significant water level measuring method and apparatus provided with an acoustic water level gauge which is mainly used for measuring the water level of water.

[0002]

2. Description of the Related Art The most representative type of water level gauge for sluice gates is a float level gauge. The float level gauge can operate a mechanical automatic water level recorder without a power supply, and a telemeter (telemetr) can be connected to the pulley of the float level gauge by connecting an "angle / code" converter.
y) It has the advantage that it is convenient to configure the system.

[0003]

The water level measurement range (minimum,
When the maximum water level change width is large, there are the following drawbacks in using the float water level gauge.

Since the float water level gauge operates only in the vertical direction, in order to always install the water level gauge, it is necessary to construct a vertical structure, for example, a "tower". In the reservoir, if the water level changes by several tens of meters, then several tens of meters
The tower of the above height must be built.

The sensitivity of a float water gauge is approximately proportional to the diameter of the float. Therefore, in order to perform deep groundwater level automatic recording or remote measurement, since the diameter of the groundwater level observation measuring tube (well) already installed is insufficient, a measuring tube having a large diameter must be installed.

If the water level measuring range is several tens of meters, the rope connecting the float and the water level meter will also be several tens of meters, and the water level measurement error due to the thermal extension and expansion and contraction of the rope will increase with changes in the ambient temperature.

The float water level meter / calibration inspection device must be vertical, and if the measuring range is several tens of meters, the height of the correction device must be several tens of meters. The constant device also becomes complicated.

Due to such drawbacks, the water level measuring range of the float water gauge is limited, and the water level changes greatly,
It is difficult to use for measuring the water level of large rivers and groundwater.

Further, no matter what kind of water level gauge is used, when measuring the water level of a reservoir or a river, it is necessary to take measures to suppress vibration of the water level (for example, due to a wave), but sometimes it is complicated. You have to build a structure.

Various water level gauges have been developed in consideration of the above-mentioned drawbacks of the float water level gauge. For example, in order to measure the water level of the reservoir, there is also a water depth meter that can measure the water depth of the reservoir without knowing the water level directly, and knowing the water depth before converting the water level.

As an actual example, there is also a water depth gauge in which a pressure sensor is installed at a constant depth to measure water pressure, that is, water column pressure. The drawbacks of such a depth gauge are as follows.

The pressure sensor is installed at a precisely designated position, but a cable line for connecting the pressure sensor and the pressure measuring device and a pipe for transmitting atmospheric pressure to the pressure sensor are installed along the bottom of the reservoir. Requires underwater work. In addition, the repair operation is complicated because the pressure sensor must be replaced periodically.

Even if the characteristics of the pressure sensor are excellent, the water depth H measurement is calculated by the formula H = P-P ₀ / ρ (where ρ-water density, P _0- atmospheric pressure),
This accurate compensation is not easy because the average density on the water depth line of the reservoir does not change and is not a positive number but changes according to temperature and component, and the atmospheric pressure P ₀ is also a variable.

In addition to this, the wave height in a large reservoir is also several meters.
There are many times when it becomes, and the error of water depth measurement is not small.

There is also an ultrasonic depth gauge, but when an ultrasonic transducer is installed in water like a pressure sensor, it may be larger than the error that occurs when using the pressure sensor, and installation work management The drawbacks of repairs are the same.

Ultrasonic transducers are installed at regular intervals on the liquid surface, and from the moment the ultrasonic pulse is emitted, the ultrasonic pulse propagates in the air and is reflected on the liquid surface, causing ultrasonic vibration. Many ultrasonic water level meters have been developed for industrial use, which measure the time t until the moment of reaching the child and measure the distance between the ultrasonic vibrator and the liquid surface, that is, the water level L. The water level L is

(Equation 6) It is measured by the formula. Here, C-is a sound wave propagation velocity in the air at the time of measuring the water level, that is, a sound velocity.

Since the speed of sound in air or other gas is a variable that greatly changes according to the temperature, pressure, and humidity of the gas, the sound level must be measured exactly at the moment of measuring the water level. The error becomes smaller.

Two types of methods for compensating for the speed of sound C in an ultrasonic water level gauge are widely known.

One method is that the air component is constant,
At the same time, assuming that the temperature is the same in the interval between the ultrasonic vibrator and the liquid surface, the ultrasonic vibrator and the temperature sensor are combined, the temperature is measured, and the sound velocity C is calculated.

For example, the speed of sound in air is

(Equation 7) You can also use the relational expressions with. Here, α-temperature velocity of sound velocity, T-temperature of air. C ₀ -Air temperature is 0
It is the speed of sound when it is ℃. As described above, the ultrasonic water level meter that measures the sound velocity and calculates the water level using the thermometer is mainly used in a sealed container when the water level change is not so large.

However, when measuring the water level of reservoirs, large rivers, and groundwater, the water level L changes to several tens of meters, so L
Since the air temperature distribution in the section can be drastically changed, it is not possible to accurately compensate the average sound velocity in the section L with the temperature measured at one point. Not only that, but also changes in sound velocity due to changes in gas, pressure, and components cannot be compensated.

Further, another widely known sound velocity compensating method is to install reflecting pieces or reflecting rods vertically at a constant interval l in an ultrasonic transducer so that ultrasonic waves are reflected from the reflecting rods. Then, the time t ₀ to reach the ultrasonic transducer is measured, and the water level L is

(Equation 8) This is a method of measuring with a formula. Where t ₀ = 21 / C,
It is assumed that t = 2L / C, but if this is substituted into Equation 3, it becomes L.

In such a method, the sound velocity C in the l section is
_l , and the sound velocity C _L in the L section are the same, that is,
If C _l = C _L = C, there is no sound velocity compensation error. Not only that, but the effect of compensating for the speed of sound is even greater than the method of compensating for the speed of sound using a thermometer (the above-mentioned ultrasonic water level gauge, Ultraflux, Tokim
It is developed and sold by ec etc.). However, if, when C _l and C _L is not the same, the water level L, which is measured by the formula 2 ',

[Equation 9] It will be. The water level measurement relative error obtained by comparing the measured water level L ′ and the true water level L is as follows.

[Equation 10]

As shown in FIG. 9, let us assume that the air temperature is linearly distributed with the tan in the section L. The position of the ultrasonic transducer is "0".
In the interval of temperature T ₀ , l, that is, at the point where the reflecting rod is located, where T ₁ is the temperature, and _TL is the temperature at the water surface, the average temperature of the L section and the L section are respectively.

[Equation 11]

(Equation 12) become.

As shown in equation 5, T
_{If O} = _TL , the relative error becomes δ _L ′ = 0, and
When T _o = T _{L, the} relative error becomes smaller as the 1 / L ratio approaches 1. However, under the condition that the water level L changes several tens of times as much as l, the temperature difference T _O -T _L can also increase, and the error increases as the l / L ratio decreases. Taking this into consideration, the water level measurement range is usually set to about L = 2 to 5 l.

The tolerance of water level measurement of reservoirs, rivers, and groundwater is required to be ± 1 cm or less over the entire measurement range. Therefore, the above-described method of compensating for sound velocity of an ultrasonic water level meter cannot be used. (Example: = 0.5 m, L = 20 m, T ₀
= 30 ° C., T _L = 20 ° C., α = 0.6

(Equation 13) Absolute error will be about 17 cm. If l = 5, or
Even if it is taken at 10 m, the absolute water level measurement error in the above example is Δ _L ′ = 13 cm, 8 cm. Even if
When the temperature difference becomes 5 ° C., (T ₀ = 25 ° C.) Δ _L becomes almost half of the above error. That is, 8.5, 6.5, 4
cm. )

[0027]

According to the present invention, in order to eliminate all the drawbacks of the two kinds of sound velocity compensation methods using temperature measurement and a reflection rod, even when the measurement range is large, the water level measurement error due to the change in sound velocity is eliminated. The main purpose is to provide a sonic water level meter that does not increase over the entire water level measurement range.

Another object of the present invention is to measure a water level in a reservoir or a large river without the need of constructing a vertical tower for utilizing a vertically operated water level gauge like a float level gauge. In addition, there is no need to equip water level fluctuations, and the water level gauge is installed on a slope along the slope of the reservoir or river at the foot of the river, greatly reducing installation and facility costs. The present invention relates to a significant water level measuring device and method.

Another object of the present invention is to automate groundwater level measurement in a groundwater level observation network,
The present invention relates to a significant water level measuring device and method provided with an sonic water level gauge that can directly use the groundwater level observation tube 8 (well).

The present invention relates to an apparatus and method for measuring a significant water level, in which a waveguide selected with a predetermined length in relation to the water level to be measured is caused to generate a sound wave pulse on its upper part. The sound wave pulse generator is fixed, and a first microphone, which is a sound pressure sensor, is installed at a constant interval from the sound wave pulse generator, and at the same time, at a distance l from the first microphone. 2nd, 3rd, ..., nth
With the microphone fixed, the first and second nth microphones etc. receive the forward wave and the reflected wave of the im pulse emitted from the sound wave pulse generator at a predetermined cycle, the signal etc. is amplified, and the waveform shaping is performed. Is applied to the arithmetic controller,
The time interval t _{1 at} which the first microphone receives the forward wave and the reflected wave is measured, and the nth time is the closest to the water surface.
The water level L is calculated by measuring the time interval tn−1 received by the first microphone and the first microphone.

There is a float having a spherical shape, and the float can be installed at an arbitrary inclination angle.

In a river in which the water level does not change significantly, the waveguide can of course be installed vertically, and at this time, no tool is needed.

According to the present invention, the first and second, third, and second parts are provided inside the groundwater pipe instead of the waveguide for measuring the groundwater level.
The support rod to which the nth microphone is fixed is inserted.

[0034]

The present invention will be described in detail with reference to the accompanying drawings as follows. FIG. 1 is a schematic block diagram of the sonic water level gauge of the sonic water level gauge of the present invention, in which the water level gauge is installed vertically.

First, the waveguide 2 (for example, a pipe) is
The water level to be measured is located at the lowest position and is below the water level, and the total length of the waveguide 2 is longer than the width before the water level change. A sound wave pulse generator 1 is installed at the upper end of the waveguide 2, and a microphone 5 ₁ composed of a sound pressure sensor is installed below the sound wave pulse generator 1 in the waveguide 2 at regular intervals. The microphones 5 ₂ , 5 ₃ , ..., 5 are spaced from the microphone 5 ₁ at intervals l.
_n is installed.

When the sonic level gauge is operated, the oscillator 6 for applying the im pulse to the sonic pulse generator 1 oscillates as shown in FIG. (Of course, the sonic pulse generator 1 may be operated with a pulse having a sine wave of 1 to 2 cycles instead of the im pulse.)

The sound wave pulse from the sound wave pulse generator 1 is shown in FIG.
-It is generated like II and propagates along the waveguide. When the first sound wave emission signal is applied to the sound wave pulse generator 1, the microphone switch circuit 4 is in a state in which the second microphone 5 ₂ is connected to the input of the amplifier 7. The microphone 5 ₁ is always connected to the amplifier 7.

Therefore, as shown in FIG. 2 and III, the microphone 5 _{1 first} receives the forward wave, and the microphone 5 ₂ receives the time difference of 1 / C, and the reflected sound wave pulse is received by the microphone 5 _1. 5 ₂ and then 5 ₁ will be received in this order.

The output signals of the microphones 5 ₁ and 5 ₂ that appear in sequence are input to the amplifier 7 and amplified. Amplifier 7
After the sound wave emission signal is generated by the arithmetic controller 10,
After a certain period of time has elapsed, the amplification level increases with time, and if the microphone output signal of 4 degrees appears, the amplification level returns to the original state. Is reflected,
It becomes constant as shown in FIG. 2 and IV (detailed description is omitted because the circuit is not patent symmetric).

The output of the amplifier 7 is input to the detector 8,
The detector 8 captures the moment (1.5 cycles are shown in FIG. 2) at which the half cycle when the maximum amplitude of the input signal becomes the zero crossing point “0” is captured, and FIG. Generate a pulse like E. The pulse can be used directly, or can be input to the wave shaper 9 to generate a pulse as shown in FIG. 2 VI, and the time measurement, the number of repeated measurements and the average value can be calculated to determine the water level. Input to the arithmetic controller 10 for calculation. Reference numeral 11 is a digital display.

Reference numeral 12 is a digital / digital converter for converting the output signal of the arithmetic unit 10 into an analog signal (current, frequency).
It is an analog converter. The output of the digital-to-analog converter 12 may be input to an automatic water level recorder or it may be added to a telemetry system transmission input.

On the other hand, the position of the microphone 5 ₁ is the measurement "0" point. As the four shaped pulses are input to the control calculator 10, the time intervals t ₂ and t ₁ shown in FIG. 2 VI are measured, and the approximate value of the water level L to be measured is calculated by the following equation. calculate. That is,

[Equation 14] Since the sound speed C ₂ in the l section and the sound speed C ₁ in the L section are not the same, the water level value calculated by the equation 6 is not accurate. The L'value is calculated, and the microphone 5 _n located closest to the liquid surface is calculated by the following equation and selected.

(Equation 15) if the n + alpha, select the n-th microphone 5 _n, if if the n, the control arithmetic unit 10 that the n-1 th microphone 5 _n-1) must be selected is determined , The switch circuit 4 is operated to connect the selected microphone (5 _{n in} FIG. 1) to the amplifier 7.

When the operation of the switch circuit 4 is completed, the sound wave emission signal is applied to the sound wave pulse oscillator 6 in the control arithmetic unit 10, and the sound wave pulse generator 1 is activated.
At this time, the signals received by the microphones 5 ₁ and 5 _n are as shown in FIG.
become that way.

The control calculator 10 measures the time intervals t ₂ and t ₁ and calculates an accurate water level L by the following formula.

[Equation 16] Where n is the operating microphone number, l
Is the distance between microphones.

Microphone 5 _n selected instead of equation 8
Since the length L _{0 up to} is already known, the water level L can be calculated by the following equation.

[Equation 17]

However, the sound speed C ₂ in the L ₀ section and the sound speed C ₁ in the L section cannot be perfectly matched, and the water level measured by the equation 9 is as follows.

(Equation 18) Water level measurement error due to this

[Formula 19] It seems to be.

Like the error analysis of the prior art,
Assuming that the temperature difference between the “0” point and the “L” point is distributed in a straight line, the relative error of water level measurement is as follows.

(Equation 20) Here, ΔL is the interval length from the selected microphone 5 _n to the liquid surface. Therefore, the maximum error that can be expected is when ΔL≈l.

[Equation 21]

Contrary to the prior art (see equation 5), according to the present invention, the larger the measurement range L, the smaller the relative error, and the absolute error does not change regardless of the measurement range. Absolute error delta _L varies in the next section.
(Sound velocity compensation error)

[Equation 22]

If the absolute error Δ _L is allowed, the maximum temperature difference T _O −T _L and the temperature sum T _O + T _{L are obtained.}
Given l, the spacing l between the microphones is chosen as

(Equation 23)

For example, in the observation of the water gate (hydrology), the water level measurement permissible error is ±
0.01m (1cm) is recommended, T _o = 40 ° C, T _L = 25 ° C in summer season, T _{o in} winter season
Assuming that = 0 ° C. and T _L = 15 ° C., ∫ is as follows.

[Equation 24]

However, the temperature distribution inside the waveguide at the site does not change in a straight line, and since it is a further relaxed distribution, the summer season and the winter season are all taken into consideration.
Approximately 1 m is enough.

When the length of the waveguide exposed in the air in the reservoir is 82 m, the test was conducted at l = 2 m. As a result, the ambient temperature was 0 ° C. to 42 ° C., and the water surface temperature of the reservoir was 1.
Maximum absolute error is ± 1 under the condition of 5 to 24 ℃
cm and did not exceed ± 4 mm on average.

In addition to the above-described measuring method, in order to further reduce the error, the sound wave pulse transit time between two microphones fixed at the position closest to the liquid surface can be measured to calculate ΔL. However, according to the experimental results, the error is rather increased.

Substituting a practical example of the error of the prior art into equation 13, the maximum absolute error is 4 mm. The error in the prior art was 168 mm.

In the present invention, the sound wave pulse frequency f is selected according to the waveguide inner diameter D as follows.

(Equation 25) Such frequency sound pulse propagates in the waveguide as a substantially plane wave.

In order to guarantee a water level measuring range of about 100 m, it is sufficient to select the waveguide inner diameter at D = 0.1 m. At this time, the sound wave pulse frequency has a sound velocity of C ≈ 350 m
In terms of / s, f ≦ 350/2 0.1 = 1750 Hz. 20
Do not use ultrasonic pulses above kHz. Therefore,
Since the attenuation is small, the measurement range is large and the measurement error is small.

The unique point of the present invention is that, unlike the prior art, the transducers for transmitting and receiving sound waves are separated, and when measuring the sound wave propagation time, the delay time that occurs in electronic circuits, cable lines, etc. There is no need to compensate. When measuring the sound wave propagation time, only one of the delay times generated in the prior art will be inspected.

When using one sonic (ultrasonic) emitting and receiving switch, the sonic emitting electrical signal is transmitted by the transducer.
The moment at which the sound wave propagation time measurement starts. Of course, although the sound wave is not emitted at that moment, if the transducer delay time is ignored, the sound wave reflected by the reflecting rod and the ultrasonic pulse reception signal reflected by the liquid surface are as shown in FIG. It was shown to.

If the instant at which the reflected wave arrives is crossed at, for example, the "0" point, 1.5 to 2 cycles of the ultrasonic signal are detected. If the ultrasonic pulse signal frequency is 20 kHz
If so, it means that the period is 1.5 to 2 (0.75
~ 1.0). It will be 10 ^-4 seconds. If such a delay time τ is ignored, a water level measurement error occurs. At this time, the water level L measurement absolute error ΔL is as follows.

(Equation 26) Here, C is the speed of sound and l is the distance from the ultrasonic transducer to the reflecting rod. τ = 10 ⁻⁴ , C = 350 m / s, L / l =
If it is 10, then ΔL = 11 cm.

The larger the measurement range, the greater the error in water level measurement. Therefore, the delay time must be thoroughly compensated.

In particular, when a low frequency is used in the significant water level gauge, for example, when 2 kHz is used, the delay time in the above example is τ≈10 ⁻³ seconds. Therefore, even if the error of delay time compensation is 1%, the error is 1 cm in the above example.

However, the present invention uses separate transmitter and receiver converters, as shown in FIG.
Even if the frequency is low, the above delay time does not occur.

As described above, since the sound velocity is thoroughly compensated and there is no delay time generated in the propagation time measurement, it is possible to measure the water level significantly by using the sound wave of low frequency.
Further, the error can be guaranteed small regardless of the measurement range.

FIG. 5 shows an actual example in which the sonic water level gauge according to the present invention is used for groundwater level measurement, and the groundwater level observation tube 14 is directly used as the waveguide. Water level observation tube 1
4, the sound wave pulse generator 1 is installed on the upper part thereof.

The microphones 5 ₁ and 5 _n are first fixed to the microphone support rod 13 at a predetermined interval. The microphone support rod 13 is inserted into the groundwater level observation pipe 14. Of course, installing a water level meter is not for observing the groundwater level while observing the patrol, but when the water level of the groundwater level monitoring network is remotely and automatically measured at regular time intervals,
Or used when using a water level recorder.

FIG. 5 shows an example of remote measurement. Reference numeral 15 is a circuit including the electronic circuit shown in FIG. 1, and 16 is a wireless transmitter for wirelessly transmitting the measurement result. 17
Is a timer and a power supply for supplying power to 15 and 16 to operate at specified time intervals.

Normally, the inner diameter of the water level observation pipe 14 is 10 to 2
It will be about 0 cm. If a sound pulse frequency of 1 to 1.5 kHz is used from a pipe having such an inner diameter, the maximum measuring range can be guaranteed up to about 200 m.

In FIG. 5, the curve indicated by the dotted line is
It is a groundwater embossing (depression) curve. The temperature distribution inside the groundwater observation pipe changes drastically depending on the season at a depth of about 5 m from the ground surface.
The deeper the temperature change, the smaller it becomes. Taking this into consideration, it is not necessary to install many microphones even if the groundwater level measurement range is large.

Furthermore, in another embodiment of the present invention, a sonic level gauge waveguide is installed at the base of a reservoir or river without installing a vertical tower to install the level gauge. It is possible to significantly reduce the installation cost of the water level gauge by installing the water level gauge along the surface, and FIG. 6 shows a case where the water level gauge of the present invention is installed at an inclination.

[0070]

[Equation 27]

According to the experiment, according to the inclination angle of the reflecting surface,
The sound wave pulse forward waveform and the reflected waveform are not the same. Of course, good reflection can be achieved. Therefore, it is necessary to correct the measurement result by detecting the difference between the measured value and the distance to the liquid surface along the waveguide center line in the water level metering process depending on the inclination of the liquid surface.

As described above, rather than calculating and applying the correction counts for various tilt angles, the spherical float 19 is thrown into the waveguide as shown in FIG. 6 for the tilt angle. Regardless, the correction value is the same. The diameter of the float 19 is
It is about 5 to 10% smaller than the inner diameter of the waveguide. In addition, the weight of the float 19 is adjusted so that the part of the float immersed in the liquid has a radius of the float 19. Of course, the float is made of a solid that does not absorb sound waves.

According to the experiment, the sound wave pulse reception signal when reflected on the hemispherical surface is only about 2% weaker than when it is reflected on the flat surface. (1
When using ˜2 kHz) At this time, the measured distance is about 3/5 of the radius of the spherical float. Such a difference Δ is accurately measured during the trimming inspection, and when the water level gauge is installed, the position of the microphone 5 ₁ is moved to the reference “0” point by the above difference to fix the waveguide. Just go.

By using a spherical float, the correction value is constant regardless of the inclination angle of the waveguide, and most importantly, the float hits the waveguide wall and there is no friction. However, as the float floats along the surface of the water as the water level changes, it is highly reliable. The water level H is measured as follows.

[Equation 28]

When the waveguide is installed at an inclination, the sensitivity of the water level gauge is further increased.

In FIG. 6, reference numeral 21 denotes the end portion of the waveguide, but in order to suppress the fluctuation of the water level, the cross-sectional area of the end of the waveguide must be made small. However, as the water level rises and falls, the diff
t) may occur.

If the particles are not fully stacked, it is very difficult to remove them. In consideration of this, as shown in FIG. 6, the cross-sectional area is provided only on one side so that stacking does not occur, that is, small particles are not precipitated, as shown in FIG. Create an inclined surface to narrow. Even in this case, after a long time, a stacked layer may be formed and the waveguide may be clogged. Therefore, the rocking and calming part of the water level is an assembled type so that a new one can be easily replaced.

[0078]

As described above, according to the present invention, the water level gauge waveguide can be installed at an inclination along the inclined surface at the foot of a reservoir or a river, and a float level meter or the like is used. There is no need to construct a vertical tower, which requires a lot of construction costs.

If the inclination angle β is small, there is a drawback that the length of the waveguide becomes much larger even in the same water level measuring range. However, like the artificial reservoir that regulates the amount of upstream water according to the season, the annual water level change is 50 ~
When it becomes 80 m, for example, if β = 45 °,
The length of the waveguide must be 72-115 m or more. Thus, it is difficult to install a very long waveguide.

In such a case, the shortest waveguide is
For example, a 30 m long waveguide can be used. FIG. 7 shows an example of the change in the water level L of the reservoir, but as shown in FIG. 7, the time range in which the water level changes by 20 m for each season is very large. Therefore, it is not so difficult to move the water level calculation waveguide along the support 18 made of U-shaped iron once in several months.

FIG. 8 illustrates an example of using a short waveguide. In FIG. 8, reference numeral 22 denotes a hoisting machine, and the waveguide 2 is connected to the hoisting machine by a rope 23. The hoisting machine is operated once every several months to determine the position of the waveguide 2. I will change it. For example, when the water storage amount increases in the summer season, the waveguide 2 is pulled up and placed.

In a small river or artificial open channel where the water level does not change significantly, it is rational to install the water level gauge of the present invention vertically, and a waveguide with an inner diameter of 50 mm and a length of about 5 m should be installed. Vertical installation is very easy (eg roped) and inexpensive.

[Brief description of drawings]

FIG. 1 is a block diagram showing a basic configuration of a water level gauge of the present invention.

FIG. 2 is a time diagram for explaining the principle of the water level gauge operation of the present invention.

FIG. 3 is a delay time distribution chart generated in the conventional water level gauge and the water level gauge of the present invention.

FIG. 4 is a delay time distribution chart generated in the conventional water level gauge and the water level gauge of the present invention.

FIG. 5 is a structural diagram when the groundwater level is measured by the water level gauge of the present invention.

FIG. 6 is a structural diagram when the water level gauge of the present invention is installed at an inclination.

FIG. 7 is a water level change diagram of a reservoir.

FIG. 8 is another method of using the water level gauge of the present invention in a reservoir.

FIG. 9 is an explanatory view of the principle of sonic speed compensation using a reflector or a reflector rod in a conventional ultrasonic water level meter.

[Explanation of symbols]

 1 Sound wave pulse generator 2 Waveguide 4 Switch circuit 6 Oscillator 7 Amplifier 8 Detector 9 Waveform shaping 10 Control calculator 13 Microphone support rod 14 Water level observation tube 18 Support 19 Float 22 Hoisting machine 23 Rope

Claims (7)

[Claims] 1. In a significant water level measuring device, a pipe for propagating an acoustic pulse in the form of a pipe: a generator installed on the upper part of the waveguide for generating an acoustic pulse: for receiving the acoustic pulse from an oscillating means The first, second, ..., Nth are installed along the waveguide at a constant interval ∫.
Sensing means formed by a microphone for receiving the forward and reflected waves of the sound wave pulse: Switching means for switching the required microphones according to the water level: Amplifying the pulse from the first sensing means and corrugated The received signal is received, the time interval between the received forward wave and reflected wave, and the sound wave propagation time to the sensing means installed near the first sensing means and the liquid surface is measured to calculate the water level, Arithmetic control means for performing sensing means switching means control and sound wave pulse repetitive oscillation control: display means for displaying data from the arithmetic control means, digital / analog converter for converting digital data from the arithmetic control means into analog signals: A significant water level measuring device comprising an automatic recording means for receiving data from the arithmetic control means and recording the result. 2. A water level gauge having a waveguide with an inner diameter of 90
By inserting a spherical float with a diameter of about 95% to suspend half of the body, the waveguide is installed at an inclination and the water level can be measured. The significant water level measuring device according to claim 1, wherein the significant water level measuring device is configured as described above. 3. When using a groundwater level observation tube instead of a waveguide, a support rod for supporting a microphone or the like at a predetermined interval is installed along the inner wall of the observation tube. The significant water level measuring device according to claim 1. 4. The lower end portion of the waveguide is formed by a conical end portion whose apex smaller than the cross-sectional area of the waveguide body is cut, and a replaceable end fixing device is installed at the end portion. The significant water level measuring device according to claim 1, wherein the significant water level measuring device is configured as described above. 5. A method of measuring a water level by measuring a distance L from an origin designated on the upper surface of the water to the surface of the water, wherein a sound wave pulse generator installed on the upper portion of the waveguide has a predetermined frequency. Generating the pulse: The waveguide has
A first microphone, which is installed above the first microphone at a distance of a predetermined drainage distance, and a second, ..., Nth number of microphones which are installed below the first microphone and separated by about l. Receiving separately the forward wave and the reflected wave of the forward wave emitted from the sound wave pulse generator: amplifying these received signals and inputting them to a detector, and determining the zero-crossing point of the maximum amplitude of these signals. Detecting and generating a pulse: corrugating the pulse with a shaping wave of a predetermined width; and detecting rising edges of each corrugation of these corrugated signals with a first microphone and a second microphone. The time interval t ₁ between the forward sound wave pulse and the reflected wave received by the first microphone and the time interval t _{2 at} which the _second sound wave is received by the second microphone are measured and approximated by the signals received by the microphone. Water level L ' And the step of calculating the approximate value of the water level to be measured, selecting the microphone installed near the liquid level, and operating the switch to connect it to the amplifier input: , The time interval t ₁ at which the sound wave pulse is emitted and the first microphone receives the forward wave and the reflected wave, and the time t _{n at} which the sound wave pulse propagates to the microphone installed near the liquid surface in the first microphone is A step of measuring and calculating an accurate water level L; and a method of measuring the water level at the step of reducing the water level L measured at the sea level height of the water level gauge measurement origin when the water level is measured at the sea level . 6. The acoustic pulse vibration frequency f is selected according to the diameter D of the waveguide as follows: Waveguide inner diameter D is selected according to the maximum measurement range, but L≈
When it is 100 m, D ≧ 100 mm, and when L ≦ 20 m, D ≧ 50 mm, and the separation distance l between the microphones installed along the waveguide is selected as follows. The water level measuring method according to claim 5, wherein [Equation 2] Here, Δ _L- permissible absolute error over the entire water level measurement, T _O- air at the point where the first microphone is arranged in the upper part of the waveguide, or other gas temperature, T _L- air in the lower end of the waveguide , Or the temperature of other gases, the speed of sound when the temperature of C _O -air or other gases is 0 ° C., the speed of sound of α-air or other gases, temperature coefficient. 7. First, an approximate value of a distance L from the origin of the first microphone to the water surface is measured by the following method, According to this result, the nth microphone installed near the liquid surface is selected, and the accurate water level is determined by the following method using the time t _n when the sound pulse propagates to the first microphone and the nth microphone. The method according to claim 5, characterized by measuring. [Equation 4] If the waveguide is installed at an inclination, However, in this case, the origin of the first microphone is located at a point at which the interval Δ becomes constant along the inclined line at the origin.