JP2855423B2 - Water level measurement method and apparatus using water column pressure measurement - Google Patents

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 a water column pressure to measure a water level, and measures a water level of a river, a reservoir, a groundwater, and a tide level on the shore of a seaside. It is mainly used for Of course, it is also used for measuring the depth of other liquids.

[0002]

2. Description of the Related Art There are two types of water column pressure gauges that measure water depth by measuring the water column pressure and calculate the water level. The earliest thing that we tried to realize was the bubble type (bub
ble) A water level gauge, the most widely used and practically used one at present, is a pressure sensor type water level meter which is configured to install a pressure sensor at a constant depth in water.

[0003] The greatest advantage of the water column pressure gauge is that the installation cost is significantly lower than that of the float gauge. Float level gauges only work vertically, so a vertical tower had to be built, or a vertical water level well had to be built. (Vertical towers and vertical water level measurement wells play a role in calming water level waves.)

[0004] However, the water column pressure gauge is shown in FIG.
As shown in (b), the above-mentioned construction is not required, and the installation cost is extremely low.

As shown in FIG. 1 (a), a pressure sensor water level gauge supplies power to the pressure sensor and installs a cable for transmitting the output to a river or a reservoir at the foot of the reservoir in order to install the pressure sensor P at a constant water depth. And a thin pipe tube for compensating the atmospheric pressure Pa is built in the cable line.

In the case of a bubble type water level gauge, a water column pressure measuring pipe may be installed along the foot to a certain depth as shown in FIG.

When the water column pressure γh (γ-specific gravity of water) is measured by a pressure sensor P, or in the case of a bubble type, the pressure required to discharge water immersed in the water column pressure side constant pipe is measured to determine the water depth. h is determined, and the water level H is measured as follows. H = H ₀ −h (1) Here, H ₀ is a sea level at a certain reference point. Therefore,
Since only the water depth h is measured, hereinafter, only the water depth h measurement will be referred to.

[0008] In addition to the advantage that the installation cost is low, if the water in rivers and reservoirs freezes in winter, the float water level gauge cannot operate, but the water column pressure water level gauge cannot operate. The advantage is that the water level can also be measured. Despite these major advantages, water column pressure gauges have not been widely used for hydrological observations. The basic causes are as follows.

[0009]

[Problems to be solved by the invention]

1) The depth measurement error is large. The cause of the large depth error is as follows. When using a submersible pressure sensor,
The pressure applied to the pressure sensor is as follows.

(Equation 13) (2)

Accordingly, the water depth h is as follows.

[Equation 14] (3) where, a specific gravity of water in γ- depth h intervals, P _a
-Atmospheric pressure acting on the water surface, but it changes at any time according to the composition of air and the wind speed. The specific gravity γ of water varies according to the temperature of the water, and in particular, varies according to the concentration of suspended solids.

[0011] The temperature distribution of the water in rivers and reservoirs ranges from + 4 ° C to 25 ° C according to the water depth. Looking at the specific gravity of pure water, γ ₄ ° _C = 1.0, γ ₂₅ ° _C = 0.990707
g / cm ³ range. If γ = 1.0 is substituted into Equation (3) to measure the water depth, the troublesome water depth measurement error reaches 0.93%. Of course, it is extremely rare that the average temperature of water in the section h becomes 25 ° C. However, the average temperature of the water in the section h is about t = 18 ° C. is very common in the reservoir.

Where γ ₁₈ ° _C = 0.99862,
If this is substituted into the equation (3), the water depth measurement error is as high as 0.14%. If h = 10m, h
Is as large as Δh = 1.4 cm.

In addition to the temperature change of the water, the influence of the suspended particle concentration is great. It is common for suspended particle concentration to be 5 g / l, depending on the region. That is, 5 × 10
^-3 g / cm ³ . The water depth error accompanying the change in specific gravity of water due to such a concentration change increases by more than 0.5%. When considering this, in the above example, the depth measurement error is 5c.
m.

In addition to such errors, the compensation error of the atmospheric pressure Pa is not small. To compensate for the atmospheric pressure Pa, a thin pipe tube that transmits the atmospheric pressure on the ground to the pressure sensor is built in the cable line connecting the pressure sensor,
Atmospheric pressure change on the ground is not the same as atmospheric pressure change on the water surface. If the upper end of the atmospheric pressure compensator has a filter that absorbs moisture and is installed in a box that does not blow, there is a considerable difference between the atmospheric pressure at this point and the atmospheric pressure at the water surface. Occurs. Of course, there is also an error in the pressure sensor. Due to such errors and the like, errors in measuring the water depth h are as follows.

[0015]

(Equation 15) (4) where, [delta] _P - pressure sensor error (0.005 to 0.
1%), δγ-error in measuring the average specific gravity of water, δ _Pa -error in atmospheric pressure compensation. As a result, the absolute error 水 h
It often exceeds 10 cm.

When measuring the water depth by the bubble method, the pressure of gas (air) required to completely discharge the water filled in the water column pressure measuring tube is measured. Then, the relationship with the water column pressure is as follows. γh = P _m + ΔP _m (5) ΔP _m will be described later in detail. △
P _m is the air column pressure at the height h ₀ shown in FIG. 1B, while ΔP _m is a variable that changes according to the gas temperature and Pm. When the specific gravity of air is 1 atm and 20 ℃, about 1.2 × 1
If the air column pressure is ignored assuming that the air column pressure is as small as about 0 ^-6 kg / cm ^{3, a} large error in water depth measurement appears.

Of course, a supplementary error occurs under the condition that the specific gravity γ of water is not accurately determined. △ Ignoring P _m, the error is much larger than the water column pressure water level meter to use the water pressure sensor.

2) Repair operation is inconvenient. When the pressure sensor is installed in water, an underwater plant, a microbial layer, a layer stack of fine particles and the like are formed on the sensor as time elapses. Therefore, the sensor must be periodically cleaned. In addition, since the sensors used have a high degree of precision, characteristic correction inspections must be periodically performed. Therefore, the underwater work must be performed and washed at any time, and the sensor must be pulled up to the ground to perform a correction inspection and further installed underwater.

As described above, the repair operation is inconvenient when used at the permanent water level observation station, and the repair operation cost is much higher than that of the float water level gauge.

Since the groundwater level measurement cycle is long (eg,
It is common practice that observers patrol the groundwater level measurement observation network once a day to manually measure the water level.

In such a case, if the distance from the ground to the groundwater level is more than tens of meters or more than 100 meters, it is difficult to carry a pressure sensor connected to a cable line that is as long as 100 meters. The work to install it at a certain location is also extremely complicated and takes a lot of time. Therefore, it is difficult to use the pressure sensor water gauge as a portable device when the measurement range is large.

However, it is convenient to use it temporarily for automatic water level recording, for example, when studying the water level fluctuation in detail for one month. Thus, it is not widely used due to the complexity of repair operations.

In the case of the bubble-type water level gauge, the repair operation is simple because all the pressure gauges and the like are on the ground, and the water level pressure measuring pipe is used under the condition that the water level is measured once or twice a day at a minimum. Even if a microbial layer is formed, the measuring tube is not clogged.
It is much more convenient and requires less installation cost than one that measures water depth using a submersible pressure sensor.

However, at the permanent water level observation point, when the water level is automatically recorded or when the remote measurement is performed, the most serious disadvantage is that a pressurized gas or compressed air is always required. If there is an industrial power supply, a small air compressor can be used, but in the absence of a power supply, a compressed gas cylinder is required. Therefore, although there is the inconvenience that the compressed gas cylinder must be periodically filled or replaced, the gas consumption can be significantly reduced, and the replacement period can be guaranteed for one year or more.

When measuring the water level while traveling around the observation site with a portable device, it is sufficient to carry only a simple manual air pump and a water level meter. The water column pressure measuring tube has a small inner diameter (φ2-4
mm) A low-priced pipe made of plastic may be permanently installed and placed.

If the measurement error can be significantly reduced, the bubble type is more useful and convenient among water column pressure gauges.

[0027]

SUMMARY OF THE INVENTION An object of the present invention is to provide a water level gauge for measuring a water column pressure which has a common disadvantage, that is, a large water level measurement error accompanying a change in specific gravity of water in a depth section to be measured. It is to provide a complementary water column pressure level gauge.

Another object of the present invention is to provide a water column pressure level gauge which compensates for a drawback that a constant measurement tolerance cannot be guaranteed in the entire range of water level measurement due to an error of a pressure gauge for measuring a water column pressure. Is to provide.

Yet another object of the present invention is to provide a precision bubble gauge with low gas consumption.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the accompanying drawings. Drawings explaining the first object of the present invention, a method for measuring the specific gravity of water, are shown in FIGS. FIG. 2A shows a case where a submersible pressure sensor is used, and FIG. 2B shows a case where a water column pressure is measured by a bubble method.

[0030] In Figure 2a, placing the pressure sensor 1 _'1 and 1 ₁ water depth h ₁ and the water depth h ₂ position. Altitude difference Δh = h
₂ -h ₁ is a Constant in advance precisely measured values.
Using water pressure sensor 1 _1, by using the pressure sensor 1 _'1 measures the pressure P ₂ corresponding to the water column pressure gamma ₂ h _2,
measuring a pressure P ₁ that is corresponding to gamma ₁ h _1.

[0031] h ₁ specific gravity gamma ₂ of water in the average density gamma ₁ and h ₂ section of the water in the section are those different from each other. However, γ ₁ can be expressed as γ _{2 as} follows:

[0032]

(Equation 16) Or it can be expressed as: the gamma ₂ at gamma _1.

[Equation 17] By measuring the difference between the water column pressure P ₂ and the water column pressure P ₁ is as follows.

(Equation 18) Here, if γ ₂ is obtained, it is as follows.

[Equation 19] (6)

With such a method, γ ₁ can be obtained as follows.

(Equation 20) (7)

However, δγ _{12 ′} δγ _{21 ′} and h ₁ ,
under conditions that do not know h _2, in not actually known conditions, the specific gravity measurement equations that can actually be used is as follows. γ ′ ₂ = △ P ₂₁ / △ h (8) or γ ′ ₁ = △ P ₂₁ / △ h (9)

Therefore, the specific gravity of water γ ₁ with a certain error or
It can be measured gamma _2. Equations (8) and (9) are equations when the underwater pressure sensor accurately measures the water column pressure P = γh. However, if the atmospheric pressure acting on the water surface acting on the pressure sensor is compensated by using an atmospheric pressure compensating pipe, another equation described later must be used.

In the case of the bubble type, two water column pressure measuring tubes (3 ₁ ) and (4 ₁ ) are installed at an altitude difference Δh as shown in FIG. 2b. Furthermore, (3 ₁₎ and the pressure Pm ₁ required to discharge the (4 ₁₎ in the submerged water, measured at the Pm ₂ gas pressure gauge (2 _'1) and (2 ₁₎ h ₂ This is a method of measuring the specific gravity γ ′ ₂ of water in a section. The measurement formula for measuring the specific gravity of water by the bubble method is different from the formula (8), and will be described later.

From now on, γ ′ ₂ is measured to measure the water depth h ₂ . Error of the measured specific gravity γ'according to equation (8), unless consideration the △ h measurement error and the pressure difference △ P ₂₁ is as follows.

[0038]

(Equation 21) (10) Table 1 shows errors in the specific gravity measurement method of water. Table 1 shows that h ₂ =
10 m, the temperature of the surface layer of water t ₀ = 24 ° C., and h ₂ = 10 ° C. at a depth of 10 m, ie, the temperature difference is △
At t = 6 ° C. and 9 ° C., the γ ′ ₂ measurement error accompanying the change in the h ₁ / Δh ratio is recorded. However, it is assumed that the temperature of the water changes linearly according to the water depth. The error presented in Table 1 is the worst case, because the higher the concentration of suspended matter, the smaller the γ ′ ₂ measurement error.

In the winter season, especially when the ice is formed, the temperature difference with the depth of water below the frozen surface is much smaller than 6-9 ° C. Therefore, the measurement method error pointed out in Table 1 is considered to be the maximum value that can be expected.

[0040]

[Table 1]

As shown in Table 1, the specific gravity measurement error decreases as the h ₁ / Δh ratio decreases. In practice, h ₁ / △ h cannot be made small. For example, when h ₁ = 2 and h ₂ = 8 m, if the water level drops by about 2 m, the measuring tube (3 ₁ ) will not operate. Therefore,

[0042]

(Equation 22) If this is achieved, the γ ₂ measurement error can be guaranteed at δγ ₂ <0.05%. Under conditions where the water level falls and h ₁ is reduced, (Δh = const) the specific gravity measurement error becomes smaller.

For example, initially, h ₁ = 7 m, h ₂ = 10 m, △
When h = 3 m, δγ ₂ = 0.051%, and the water level is 5 m
If it descends and becomes h ₁ = 2 m, h ₂ = 5 m,

(Equation 23) And the γ ₂ measurement error is

(Equation 24) become.

The error analyzed in the above is the error in the method of measuring the average specific gravity of water, and the actual measurement error is the pressure difference ΔP
₂₁ , The measurement error δ △ _P and △ h The measurement error δ △ _h is added more.

The total measurement error is assumed to be:

(Equation 25) △ h = 3 to 5 m can be easily measured in the ± 1mm error, it is possible to guarantee _{δ △ h = 0.03% ~0.02%} . Therefore, δ which is the measurement error of the pressure difference ΔP ₂₁
△ It is important allowed to reduce the _P.

Under the condition that two pressure sensors (1 ₁ ) and (1 ′ ₁ ) are used in the pressure sensor type water level meter,
In order to significantly reduce δ △ _P , the characteristics of the two pressure sensors must be completely identical. Under such conditions, the errors of the sensors themselves should be mutually deleted by the calculation of ΔP ₂₁ = P ₂ −P ₁ .

In the case of the bubble type, _{ΔP m21} can be directly measured by a differential pressure gauge. Differential pressure gauge measurement range is γ ・ △ h
Therefore, a thorough correction test is performed in a narrow measurement range to reduce the differential pressure measurement error.

(Equation 26) The following can be guaranteed. In such a case, Σδγ
₂ Guaranteed at <0.07%. Of course, one pressure sensor is used, which allows the pressure P in the measuring tube (4 ₁ ) to be
m ₂ was measured and then replaced with a measuring tube (3 ₁ ) to replace Pm ₁
Is calculated and _{ΔP m21} is calculated, the error of _{ΔP m21} becomes smaller.

As described above, by using two underwater pressure sensors or two bubble type water column pressure measuring tubes installed at a constant altitude difference Δh, the water in the h ₂ section is relatively high. The specific gravity can be measured, and the water depth h ₂ measurement error can be significantly reduced. At this time,

[Equation 27] It is reasonable to choose a degree.

By substituting the specific gravity γ ′ ₂ of water measured in this way into equations (3) and (5), the equation for measuring water depth h ₂ is as follows.

[Equation 28] (11)

[0050]

(Equation 29) (12) (We will describe the exact measurement formula later.)

No matter how accurate the specific gravity of water is, the measurement error of the water depth h depends on the error δ _{P of the} pressure gauge for measuring the pressure P ₂ or P _m2 . Under open-air conditions (conditions in which the ambient air temperature changes by about -20 to + 40 ° C), it is not possible to guarantee the error of the pressure sensor to be 0.05 to 0.1% or less even if it is corrected by the temperature sensor of the pressure sensor. difficult.

The greater the water depth to be measured, the greater the absolute error 水_{h in the} water depth measurement due to the pressure sensor error δ _P and the allowable error

[Equation 30] (For example, ± 1 cm), and if the error δ _{P of the} pressure sensor and the total error of the specific gravity measurement of water, Σδγ ₂ (Equation 4), are known, the water depth measurement limit h _max of the water column pressure type water level gauge is determined. It can be obtained from the following equation.

(Equation 31) (13) where

(Equation 32) It is.

If the tolerance is

[Equation 33] If δ _h = 0.1% = 0.001, then h _max =
1000 cm = 10 m.

According to the present invention, the measuring range ΔH = H _max −
When H _min is many times larger than h _max , several water pressure sensors or bubble type water column pressure observation tubes are installed at altitude difference Δh to measure the water depth. ing. If the altitude difference △ h

(Equation 34) If the pressure sensor is selected, the number n of the pressure sensor or the bubble type water column pressure measuring tube is as follows. n = △ H / △ h + 1 (14)

[0055]

(Equation 35) Is substituted into Expression (14), and the result is as follows.

[Equation 36] (15)

At this time, if the water level is H _max , the specific gravity and the water depth of the water are measured by the first and second pressure sensors or the water column pressure measuring pipes, and the water level is lowered, and H ₂ = H _max − △ h + △
Then, the specific gravity and water depth of the water are measured by the second and third pressure sensors or the water column pressure measuring pipe. Here, △ is the water depth corresponding to the minimum allowable pressure measurement value of a pressure sensor or the like.

If the underwater or gas pressure sensor guarantees a given measurement characteristic, the minimum pressure measurement is P _min
= 0.01 atm

(37) become.

In the method described above, the water level can vary greatly, for example, by changing the water level of an artificial reservoir to a given allowable absolute error.

(38) To measure. Of course, Δh <h _max / 2
May be selected.

FIG. 3 shows a case where n = 5. In FIG. 3, (6) is a water level meter for calculating the water depth h and the water level H, and (5) is a converter for converting the output of a pressure sensor or the like and inputting the converted output to (6). (7) is a valve control device for operating a valve for connecting a water column pressure measuring pipe or the like to the pressure sensors (2 ₁ ) and (2 ₂ ). The compressed gas supply diagram is not shown in FIG.

Underwater pressure sensors (1 ₁ ), (1 ' ₂ ),
(1 ₂₎ Further, the position of (1 _'3), or, water column pressure measuring tube (4 _1), (3 _2), (4 _2), the position of (3 _3), above sea level height h _02, h _{At 03} , h ₀₄ , and h ₀₅ , the water level was previously measured and input to the water level gauge (6) together with the reference sea level elevation H ₀ . The water level _Hi is calculated as follows. H _i = H ₀ −h _0i + h _ij (16)

If the reference point H ₀ coincides with the origin of h ₀₁ , the water level is as follows. H = h _0i −h _ij

As shown in FIG. 3, when the underwater pressure sensor is used, the number of underwater pressure sensors increases. Therefore, a major drawback is that the repair operation of the pressure sensor and the periodic characteristic inspection correction work become more complicated.

When measuring the water column pressure and the water depth by the bubble method, the pipes are made of a small number of internal diameters (eg, d = 2 to 4 mm), and several pipes made of plastic or copper are bundled and installed. Yes, it is convenient because there is no need to repair. The only disadvantage is that the valve control device (7) is slightly more complicated than the electronic converter (5).

In measuring the water column pressure and measuring the water level in this way, according to the present invention, a given allowable absolute error can be guaranteed regardless of the water level measurement range.

Another object of the present invention is to propose the accuracy of the bubble type water depth measurement, which will be described in detail as follows.

FIG. 4 shows the gas pressure and water column pressure in the water column pressure measuring tube.
Is shown when the pressure is matched. Surplus pressure Pm
Before adding to the water column pressure measuring tube (4), also add water to the measuring tube (4).
Is satisfied, and if the capillary phenomenon is ignored, the water surface
The water level is the same as the surrounding water level H. At this time (4)
P on the water surface_a2+ Γ_ah_a= P_a1 The pressure is acting
I have. Where P_alAnd P_a2Is H point and pressure sensor (2)
H where is located ₀The atmospheric pressure at_aIs H
To H₀Up to the height of the air layer. γ_aIs h_aIn
Air specific gravity.

The pressure at the end point of the water column pressure measuring tube (4) is P _a1 + γh. Excess air pressure P in water column pressure measuring tube
m, the water inside the measuring tube (4) is completely discharged and stabilized. At this time, the pressure sensor (2)
Only the Pm pressure is measured.

The relational expression between the pressure and the like at this time is as follows.

[Equation 39] Here, gamma _am is the time obtained by adding the excess pressure _{P m h 0 = h + h} a
This is the specific gravity of the gas in the section. Therefore, the water depth h is as follows.

(Equation 40) (17) (ΔP _m pointed out in equation (5) is exactly γ _am
h is _{0 -γ a} h _a).

Suppose that instead of using compressed air to measure the water column pressure, another gas, for example nitrogen, is used. At this time, γ _am and γ _a are set to the reference state (P ₀ = 1.03 kgf / cm ² ,
Specific gravity γ _g0 of gas and specific gravity γ _{a0 of} air at T ₀ = 293K)
Can be expressed as follows.

[Equation 41] If the water depth h is obtained by substituting such a relationship into the equation (17), the following is obtained.

(Equation 42) (18)

If the water column pressure is measured with compressed air, h is as follows:

[Equation 43] (19)

It is convenient to use the following equation instead of equations (18) and (19).

[Equation 44] (20) Further, when γ _g0 = γ _a0, that is, when α = 1,

[Equation 45] (21) Here, γ ′ _a0 = γ _a0 / P ₀ (1 / cm). In the above formula

[Equation 46] It is.

Γ _g0 is the specific gravity of the gas used for measuring the water column pressure in the standard state, and γ _a0 is the specific gravity of air in the normal state. (Equations (18), (19) and (20),
The difference from (21) is small enough to be ignored. h ₀ = 10
0m, specific gravity of water is γ = (0.998 to 1.01) × 10
^-3 kgf / cm ³ , gas and air temperature T = 263-303K
When changing in range, the difference of the above formulas does not exceed 0.2 mm).

If the water depth is simply measured at h ′ = P _m / γ without using equation (19) or (21), a large error occurs.

Table 2 shows the specific gravity of water as γ = 10 ⁻³ kgf / cm ³ and the specific gravity of air in the standard state.

[Equation 47] , Different air temperatures t, and when h ⁰ ,
The water depth measurement error △ _h = h−h ′ (cm) is presented.

[0075]

[Table 2]

The values presented in Table 2 are the same as those obtained by converting the air column pressure into the water column pressure. Since the temperature T of the gas in the water column pressure measuring tube is the average temperature within the total length of the water column pressure measuring tube, such an average temperature measurement is practically impossible.

In the worst case in Table 2, h ₀ = 100 m
At this time, the average temperature of the gas was 20 ° C, but if the measured temperature was 25 ° C, the error would be (13.2-12.
8) / 2 = approximately 0.2 cm. Therefore, the gas temperature measurement tolerance has little effect.

Under such conditions, it is sufficient to measure the temperature of the gas at a convenient point, for example, by inserting a temperature sensor into the buffer container (8) shown in FIG.

The specific gravity of liquid (water) is determined by the bubble method mentioned above.
In the method for measuring₀₂-H ₀₁= △ h
Measured in a water column pressure measuring pipe installed_m2
And P _m1The formula for measuring the specific gravity of liquid (water) using
become that way.

In equation (17), P _m2 , h ₀₂ and P _m1 , h
_When the specific gravity γ is obtained by substituting ₀₁ , the following is obtained.

[Equation 48] (22) Here, A = αγ _a0 × T ₀ / T and α = γ _go / γ _a0 .

It is convenient to use the following equation (23) instead of equation (22). (If it is water)

[Equation 49] (23) The equation for measuring the specific gravity of water is as follows.

[Equation 50] (24) Here, the specific gravity of air at T ₀ = 293 K, P ₀ = 1.03 kgf / cm ² is considered as γ _a0 = 1.2 · 10 ⁻⁶ kgf / cm ³ ,
This is the derived expression. Further, P ′ _m1 = P _m1 / P ₀ is a dimensionless number having no unit.

The variables to be directly measured are P _m2 and P _m1 and only the gas temperature T, and α, h _{02 ′} Δh and the like are constants.

In this way, the specific gravity of another liquid can be measured. Substituting equation (24) into equation (20) yields the following.

(Equation 51) (25) In the case of using compressed air, since α = 1, the water depth is expressed as follows.

(Equation 52) (26) where

(Equation 53) It is.

The specific gravity of river and reservoir water changes gradually without changing at a high speed. In particular, the specific gravity of deep groundwater does not change much according to the season. Under such conditions, if the water level is continuously measured frequently, for example, once an hour, it is not necessary to measure the specific gravity of water every time the depth-water level is measured. Once or twice a day, in the case of groundwater, once every 10 days, measure the specific gravity according to another formula (24) and substitute it into the water depth measurement formulas (20) and (21) as constants It is reasonable to save gas consumption and power required for valve operation.

In particular, when the tide level of seawater is measured continuously, or when the river water level changes significantly during the rainy season (flow
Ding) When measuring the river water level continuously, it is sufficient to measure the specific gravity of water once a day.

There are many cases where the water surface position of the artificial reservoir is several tens of meters above the position of the water level measurement point. In such a case, in order to calculate the water level by measuring the water depth by the bubble method, the water depth must be measured by the following measurement formula.

(Equation 54) (27)

If the specific gravity of water is to be measured with two water column pressure measuring tubes (ends are installed at a height difference of Δh),
The following formula must be used:

[Equation 55] (28) Here, P ′ _m1 = P _m1 / P _{0 is a} unitless dimensionless number.

When a tank for storing a certain liquid, not a reservoir, is above the water level measuring point, the liquid depth can be measured by using the equations (27) and (28).
However, it is necessary to substitute n = P ₀ / γ instead of 10 ³ . Here, γ is the average specific gravity of the liquid.

As described above, according to the present invention, the specific gravity of water (liquid) can be separately measured by a bubble method, or can be precisely measured. Often it is necessary to measure water depth and specific gravity separately. For example, when measuring the tide level of the sea, the specific gravity of sea water may be measured at the same time to indirectly observe changes in salinity, or the specific gravity of rivers and reservoirs may be measured to measure the concentration of suspended particles. If you do not need to know the specific gravity of water (liquid) but only measure the water depth, measure the water depth using the following simplest formula.

[0090]

[Equation 56] (29) Or

[Equation 57] (30) In parentheses in equations (27) and (28), (-) and (+)
Is when the water level fixed point is higher than the water surface, or (+)
And (-) are when the camera is at a low position. The above equation is given by equation (2)
5) can be obtained by conversion. Also, it can be obtained by the following relational expression.

[0091]

[Equation 58] When measuring the water depth using a water pressure sensor, high difference across the but atmospheric pressure P _a at the water surface acting on the pressure sensor compensates for atmospheric pressure compensation pipe coupled to the sensor compensation tube When it is large, the water depth measurement error increases. (Table 2
The upper end of the way) atmospheric pressure compensating tube of the atmospheric pressure P _'a for transmitting the pressure sensor because the higher the water surface position is the less than atmospheric pressure at the water surface;

[0092]

[Equation 59] Here, h _a is the high difference between the compensating tube upper end to the water surface. h _a = h ₀ −h. h ₀ is high difference compensating tube end tube, h is the water depth. Therefore, the pressure measured by the submersible pressure sensor is as follows:

[Equation 60] From here the water depth h must be measured using the following formula:

[Equation 61] (31)

If the denominator of equation (31)

(Equation 62) If neglect, water depth measurement error occurs about 0.13%. h
Is 10 m, this error is 1.3 °. As shown in Table 2, if h ₀ = 60 m (eg, water depth at the reservoir,
When measuring the water level) If the measurement formula (31) is not used, the water depth measurement error becomes 8 ° or more. Therefore, the exact equation for measuring the specific gravity of water (liquid) using two underwater pressure sensors is as follows:

[Equation 63] (32) It is a feature of the present invention to precisely measure the water depth by substituting the specific gravity measurement formula (32) into the water depth measurement formula (31).

When measuring the specific gravity of water (liquid) with an error of 0.1% or less,

[Equation 64] Can not be ignored. If it is not necessary to separately measure the specific gravity γ, the measurement formula of the water depth h ₂ is as follows.

[Equation 65]

Even if the air column pressure is compensated precisely, a large error may occur depending on the inner diameter d of the water column pressure measuring tube and the supply amount of compressed air.

The basic causes that the bubble type water level meter has not been widely used for hydrological observation are as follows. The water level gauge for the bubble type reservoir, which was initially developed, had a large error in the water level measurement because the pressure at the time when air bubbles came out was measured in the water column pressure measuring pipe. Of course, the specific gravity of water was not measured, and the air column pressure was certainly ignored.

FIG. 5 shows the measured values at the upper part of the water column pressure measuring tube.
The air pressure Pm changes according to the compressed air supply q
The situation is illustrated. As shown in FIG.
And large d₁When using the tube, until the bubble is generated
The required pressure Pm is greater than the water column pressure and bubbles start to appear
And the pressure pulsates. Pulsation amplitude and Pm are compressed
The larger the air supply and the larger the inner diameter, the larger
Become. Smaller inner diameter d _Two<D₁No, compressed air supply
 q_Two<Q₁ In this case, Pm and the pulsation rate become smaller.

[0098] Due to such a phenomenon, the water depth measurement error may increase. Of course, if the water column pressure measuring tube inner diameter and the gas consumption are selected to be extremely small, the error may become small, but the water level measurement time becomes extremely long.

According to the present invention, the method of measuring the water depth and therefore the water level by the water depth measurement formula (18) or (19) is as follows.

[0100] As was shown in FIG. 6, the valve (9) pressure sensors to gradually opened while compressed air P _{0 m} (2), further, through the compressed air buffer vessel (8), a fixed becomes time t ₁ And close valve (9). The pressure P _{0m of the} supplied air is maintained at a pressure slightly higher than the water column pressure γh corresponding to the measurement range of the water column pressure measurement pipe (4).

In FIG. 6, (6) is a water depth level calculator (water level gauge), (11) is a temperature sensor, and (10) is a water discharge valve.

If the water depth is h ₁ and the water column pressure γ ₁ h ₁ is P
_When the pressure is slightly smaller than _{0 m} , the pressure sensor (2) measures the pressure of the compressed air which changes as shown by the curve a in FIG. As shown in FIGS. 6 and 7,
While somewhat pulsating pressure from the moment t ₁ to close the valve (9) (air bubbles out) is reduced, is stable unchanged from t ₂ moment. The pressure at this time is exactly γ ₁ h ₁ − △ P _m1
= _Pm1 . When γ ₂ h ₂ > γ ₁ h ₁ , the pressure change mode is shown by the curve b in FIG. The volume V of the compressed air and the buffer container (8) is calculated as follows:
^{(Πd 2/4) · h} 0 than is good to select at least five times.

[0103]

[Equation 66] If the volume of the buffer container is too large, the compressed air supply time becomes longer. A temperature sensor (11) is built in the buffer container. The buffer container (8) plays the following role.

As shown in FIG. 7, the pressure Pm is gradually reduced and released to the last bubble, and the pressure becomes γh- △ P
_Plays a role to be stabilized at _m . (Of course, if a portable water gauge, at ensuring the pressure P _{0 m} manually pump, the pressure pulsation is severe, forms a role of buffering the pressure pulsation in the measuring tube (4) inside) buffer vessel (8) In the absence of this, the depth measurement repeatability is reduced.

The temperature of the air in the buffer container is measured by a temperature sensor (1).
The temperature measured in 1) is the measuring tube (4) when the air in the buffer container is discharged as bubbles at the end of the water column pressure measuring tube (4) (between t _{1 and} t ₂ time intervals). It is very close to the internal air temperature. Therefore, even if the air temperature T ′ is measured at one point, there is no difference from the average air temperature T inside the measurement pipe (4).

When the water level drops after measuring the water depth once,
The water level drop can be measured continuously for a long time at the excess pressure of the buffer container.

When a wave occurs in a river or a reservoir,
The pressure pulsation associated with the surf is significantly reduced.

According to the present invention, the pressure of the air when the air bubbles are constantly being discharged is not measured, the supply of the compressed air is interrupted, and while the pressure is gradually reduced, (using the buffer container 8) ) Measure the pressure Pm when the pressure is stabilized, and
Measure the air temperature in the buffer container and calculate the water depth (18)
Or, it is configured to use (19), and the water depth measurement error is reduced.

As described above, according to the present invention, the water level can be measured with sufficient accuracy by the bubble method, the installation which is the advantage of the bubble water level gauge is simple, and the repair operation is easy. By taking advantage of this, it can be widely used for portable use, automatic recording, and remote measurement.

FIG. 8 is a diagram of a bubble water level meter device taking all the above into consideration. In FIG. 8, reference numeral (12) denotes a pressure safety valve, which maintains a pressure slightly higher than γ ₂ h _{2 at the} outlet even if a high pressure is applied. (13) is a pressure gas cylinder or an air compressor. (10) is a water discharge valve when water contained in the compressed air is condensed in the buffer container (8).

In the initial state, the valve (9_Three) And ba
Lube (9₁) Is closed and the valve (9_Two) Open
Have been. Operation of valve control device (7) when starting measurement
At the valve (9_ThreeOpen the compressed air buffer container
(8), valve (9_Two) Through the water column pressure measuring tube (4)
Supply and valve (9_Three) Is closed. The pressure is stabilized and P_m2
= Γ_Twoh _Two− △ P_m2Until it becomes (t in FIG. 7).
_TwoUntil).

The output of the pressure sensor (2) is input to the water level calculator (6). At the same time, the compressed air temperature measured by the temperature sensor (11) is input to (6).

After the P _m2 measurement is completed and P _m2 and T are recorded (stored) in (6), the valve (9 ₂ ) is closed.
(9: ₁₎ it is opened. Then, the compressed air (pressure P _m2 > γ ₁ h ₁ ) in the buffer container is supplied to the water column pressure measuring tube (3), and the water filled in the measuring tube (3) is discharged, and the remaining water is discharged. Bubbles are generated at the surplus pressure, and the air pressure is stabilized at P _m1 = γ ₁ h ₁ − △ P _m1 . P _m1 and T are further input to the water level calculator (6).

The reference sea level elevation H _{0 ′} Δh, h ₀₂ has been input to the water level calculator (6) in advance. The water level calculator (6) calculates the water depth (h) according to the equation (25) or (26).
₂ ) is calculated, the water level is calculated in accordance with the equation (1), the display is also made on the indicator, and an electric signal necessary for automatic recording or remote measurement is output.

When used portable, the pressure sensor (2), the temperature sensor (11) and the water level calculator (6) are portable, and are compressed using a portable manual pump. Supply air. At this time,
The ground water level measurement views well, water column pressure measuring tube (3) and (4), the valve (9 ₁₎ and (9 _2), is installed only buffer vessel (8), valve controller (7) and the safety There is no valve (12). Valve (9 _1), (9 ₂₎ is operated manually.

For remote measurement or automatic recording, the compressed air cylinder is connected to the pressure relief valve (12), or when there is an industrial power supply, a small air compressor is connected. Furthermore, the valve (91 _to 93 ₃₎ uses an electromagnet valve and the like, by a signal coming out from the timer to the specified time, so that the valve control device (7) is operated.

The inner diameter of the water column pressure measuring tube or the like is d = 2 to 4 mm
Use non-corrosive plastic or copper pipes.

There are times when the water levels of reservoirs and rivers are measured. Even if the average value is obtained by repeated measurements, the water level measurement error may increase. In such a case, the water column pressure measuring pipes (3) and (4) are built in a large calm wave sedation pipe (14), and a pipe (15) with a small internal diameter is installed at the end of (14). ing. Wave sedation tube (1
4) simultaneously serves to protect the water column pressure measuring tubes (3) and (4).

FIG. 9 shows a drawing in which a water column pressure measuring pipe and the like are installed in a groundwater level measuring well in one example. In FIG. 9, (17) is a thin steel wire steel or a non-stretchable, rigid but soft wire steel made of another material, and (16) is a weight.

Wire steel (17) with weight (16)
Then, tie the water column pressure measurement pipes (3) and (4). The steel (17) with the weight (16) is put into the groundwater level observation well (18) to the required depth. By measuring the length of the wire steel (17) charged into the water level measurement well (18), _h02 is known.

As described above, the installation of the water column pressure measuring tube is simple, and the cost is greatly reduced as compared with the case where the pressure sensor is provided. In this way, all groundwater level observation wells
As was shown in, water column pressure measuring tube (3) and (4), the valve (9 _{1-91 3),} further, buffer vessel (8)
It is very technically and economically advantageous to use a water level gauge that uses a submersible pressure sensor, because the water level is measured while the observer patrols.

Since the specific gravity of the groundwater does not change frequently, there is no need to provide a water column pressure measuring tube (3) for measuring the specific gravity. The specific gravity is measured and stored once every several months by another method. You should do it.

FIG. 10 shows an example of a process of installing a water column pressure measuring pipe for measuring the water level of a reservoir or measuring the tide level of the sea. The water column pressure measurement tube group and the like are housed in the protection tube and the sedation tube (14) having a large inner diameter, but the water column pressure measurement tube in the protection tube is not shown in FIG.

In FIG. 10, (19) is an anchor-shaped weight, but the weight (19) is attached to the wave sedation pipe (14) at regular intervals, and a water column pressure measurement pipe, (3n) , (4
The protection tube (14) in which n) is built cannot be moved by the wave.

The method for measuring the position of the end of the water column pressure measuring tube is omitted because it is not the subject of the present invention.

Compressed gas (or air) consumption is very small when measured once. When the total length of the measuring tube is 100 m, even if its inner diameter becomes 0.4 cm, if the compressed gas consumption is converted in the reference state, it does not exceed 1.5 l.

When the water level drops, the pressure of the buffer container (8) is high, so that no additional compressed gas is consumed during measurement.

If a compressed gas cylinder (eg, nitrogen, air, etc.) having a capacity of 25 l is used without using a micro air compressor, if the pressure of the compressed gas is 50 atm, about 800 Times can be measured.

If the water level of a reservoir or a major river is measured twice a day, it can be used for 400 days. It is not so difficult to change the compressed gas cylinder about once a year.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing the principle of installation of a submerged pressure sensor water gauge and a bubble type water gauge.

FIG. 2 is a schematic diagram illustrating a method for measuring the specific gravity of water or another liquid in a water depth section to be measured according to the present invention.

FIG. 3 shows a case where a water level change measurement range according to the present invention is large.
The schematic diagram explaining the method of measuring a water depth water level with the tolerance given in the whole water depth measurement range.

FIG. 4 is a pressure distribution diagram in a bubble-type water depth measurement method.

FIG. 5 is a graph showing a form of a compressed gas pressure that changes in accordance with a compressed gas supply amount in a bubble type water level meter.

FIG. 6 is a schematic view of a bubble type water column pressure measuring device according to the present invention.

FIG. 7 is a graph showing a change in compressed gas pressure in the bubble type water column pressure measuring method according to the present invention.

FIG. 8 is a schematic diagram of a bubble type water level measuring device according to the present invention.

FIG. 9 is a schematic view showing one example of a bubble-type groundwater level measuring apparatus according to the present invention.

FIG. 10 shows one of installation methods of a water column pressure measuring pipe in measuring a reservoir water level or a tide level at the seaside by a bubble method.
The schematic diagram which shows an example.

[Explanation of symbols]

1 '_1' 1 ₁ : Pressure sensor 2 '_1' 21 ₁ : Gas pressure gauge 2: Pressure sensor 3 ₁ '41 ₁ : Water column pressure measuring tube 5: Converter 6: Water level calculator (water level gauge) 7: Valve control Apparatus 8: Buffer container 9: Valve 10: Moisture discharge valve 11: Temperature sensor 12: Pressure relief valve 13: Air compressor or compressed gas cylinder 14: Protective tube 15: Tube 16: Weight 17: Wire steel 18: Kansai 19 ： Anchor weight 20 ： Ship

Claims (6)

(57) [Claims] 1. A water depth measuring the water column pressure at the two finger point h, further, a method of measuring the water level, when installing two pressure sensors are in the water, one sensor is h ₁ depth The other one is installed at a depth of h ₂ = h ₁ + Δh.
Placed h ₂ depth; the number of water column pressure measurement pipe lower end h ₁ depth, also lower ends other water column pressure measuring tube, when installed in order to position the h ₂ = h ₁ + Delta] h depth is the output of the pressure sensor was measured by water column pressure P ₂ has a pressure sensor output installed in the h ₁ depth measured by P _1, when measuring the water column pressure in the bubble equation, h ₂ filled in water column pressure measurement pipe which is installed to a depth of water measured gas pressure P _m1 which to discharge the water in the water column pressure measurement pipe which is installed to the gas pressure P _{m @ 2} and h ₁ depth to discharge the (liquid) (liquid) stages; in the above-mentioned condition, when the average specific gravity of water (liquid) in the water depth h ₂ sections using a water pressure sensor is determined by the following equation, equation 1] (A) When the water column pressure is measured by the bubble method, the specific gravity of water (liquid) is measured by the following equation, and (B) (When the water level measurement point is higher than the water level) (C) (When the water level is measured at a position lower than the water level) A method of substituting the water depth h _{2 into the} measurement equation and measuring the water depth at the water level. In the above equation, _h02 is an altitude difference between the end of the water column pressure measuring pipe and the pressure measuring point. (Equation 4) α = γ _go / γ _{a0 −the} ratio of the specific gravity of gas and air used for water column pressure measurement, and 10 ³ = P ₀ / γ. When measuring the specific gravity γ _e of another liquid other than water, P ₀ / γ _e must be calculated and used instead of 10 ³ . 2. The water column pressure measuring pipe according to claim 1, wherein the water column pressure is measured by a water column pressure measuring tube.
The gas is supplied at a slightly higher pressure P, and the gas pressure becomes P
When the pulsation is reached, the gas supply is interrupted and the gas pressure
Pressure Pm when the pressure is stabilized_iMeasure the water (liquid)
Into the specific gravity equation of_i(H_TwoOr
h₁How to measure). The water level measurement point is higher than the water level
When in position(D) or(E) When the water level measurement point is lower than the water level,(F) or(G) where γ_a0(Kgf / cm^Three ) Is the reference state P₀ =
1.03kgf / cm^Two, T₀ = Ratio of air at 293K
Weight, absolute temperature of gas in T-water column pressure measuring tube, h _0i− Water column
Altitude difference between the lower end of the pressure measuring pipe and the pressure measuring point, h_a (C
m)-Water column pressure measuring tube end and water column pressure measuring tube bent down
It is the altitude difference between the landing points. P_'mi= P_mi/ P₀In
[Equation 9]That is, it is the reciprocal of the specific gravity of water. A ratio completely different from the specific gravity of water
Heavy γ_e When measuring the depth of liquid^ThreeInstead of
P₀/ Γ_eUse However, use of a submersible pressure sensor
When measuring the water column pressure using_iIs measured by the following formula.
Set. (Equation 10)(H) where P_iIs a pressure sensor connected to an atmospheric pressure compensator
The measured water column pressure. h_0iIs the upper and lower ends of the atmospheric pressure compensator
Is the high order difference between How to measure the water depth h in the following measurement equation if specific gravity without measuring separately measures only water depth h _i bubbles formula wherein water in claim 1 and 2 (liquid), Equation 11 ] (I) (J) In parentheses, (-) in equation (i) and (+) in equation (j) are for the case where the water depth and water level are measured at a position lower than the water level. [1 / 〓] when γ ′ _a0 = γ _a0 / P ₀ . 4. When the water level measurement range differs according to the water depth, the water column pressure cannot be measured with a set of pressure sensors or pressure gauges with the absolute tolerance given in the entire range of the water depth change. Install several underwater pressure sensors or water column pressure measurement pipes at a constant equivalent altitude difference interval,
Using a water sensor using a submersible pressure sensor or a pressure sensor arranged within a measurement range that can be measured with a given absolute tolerance given a gas manometer according to a change in water level, or a water column pressure measuring tube, etc. The specific gravity of the liquid)
3. The method according to claim 1, wherein the water level is measured. 5. A bubble type water depth and water level measuring device, wherein a water column pressure measuring tube is constituted by a plastic or copper tube having an inner diameter of 2 to 4 mm, and two water column pressure measuring tubes are connected between lower ends thereof. The upper end is connected to the buffer container through a valve, and the pressure sensor for measuring gas pressure and the temperature sensor for measuring gas temperature in the buffer container are connected to each other through a valve. It is installed, the buffer vessel is connected to the compressed gas supply pipe with the valve at the same time, the temperature sensor and the pressure sensor output, the device calculates the specific gravity of water (liquid), water depth, water level according to the second term The arithmetic unit is a display, a device that converts the calculated water level value by an electric signal or a code signal, the height between the upper and lower ends of a water column pressure measuring tube, the lower end of a water column pressure measuring tube, etc. while Built-in device to input and store the altitude difference of the water level, the altitude of the water level measurement reference point above sea level, the pressure and absolute temperature of the compressed gas and air to be used in the reference state, and the specific gravity value in the reference state. When measuring, open the valve connected to the long water column pressure measurement pipe, open the compressed gas supply valve, then close the long water column pressure measurement pipe valve, and open the short water column pressure measurement pipe valve. A water level measuring device, wherein the valve control device is connected to a valve or the like. 6. A water column pressure measuring tube or the like is disposed inside a wave sedation tube having a large inner diameter, and a pipe having an inner diameter smaller than the wave sedation tube inner diameter is connected to a lower end of the wave sedation tube. The water level measuring device according to claim 5, wherein