JPS634669B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field to which the invention pertains] The present invention relates to a sensor device for measuring fluid flow, and particularly to a fluid flow measuring device suitable for measuring the dynamics of groundwater, etc., which exhibit minute movements.

[Prior art and its problems]

In recent years, it has become increasingly necessary to accurately measure the flow of groundwater (flow velocity, flow direction, or both) in order to determine whether to adopt freezing construction methods or to investigate groundwater contamination. A stationary tracer method has been widely used as a method for measuring groundwater flow. This method involves injecting salt or dye into one of multiple boreholes, examining changes in electrical resistance or concentration over time between it and other boreholes, and measuring the flow from the arrival time and location. It is something. However, in the above-mentioned conventional technology, a large number of boreholes must be excavated, which increases the survey cost, and it also takes a long time to measure when the groundwater flow rate is slow, and during this time, the groundwater flow is interrupted by rainwater etc. This has the inherent drawback that it is difficult to make accurate measurements.

Recently, as an attempt to improve the drawbacks of the above-mentioned conventional technology, a propeller-type current meter has been used to measure the flow velocity and flow direction based on the propeller rotation speed and its changes.
In addition, as in the invention disclosed in Japanese Patent Publication No. 45-25029, a disk is lowered into a borehole, and the groundwater flow condition is determined from the pressure difference due to the upward flow and downward flow of water in the hole acting on the disk. Alternatively, methods have been devised to measure the flow velocity and direction by injecting radioisotopes into flowing water and tracing changes in the radiation dose distribution due to the flowing water.

However, when using methods that drive mechanical measuring means such as propellers, it is extremely difficult to accurately measure the flow velocity when the flow velocity is as small as 2 cm per second or less, and methods that use radioactive materials Not only is it dangerous to handle, but it also has drawbacks such as the equipment being extremely expensive.

[Purpose of the invention]

The present invention has been made in view of the drawbacks of the prior art, and has a simple and durable structure that allows accurate measurement of at least the flow direction of a fluid having an extremely small flow velocity with a single measuring borehole. The object of the present invention is to provide a sensor device for measuring the flow of a fluid.

[Means for solving problems]

Therefore, the present invention includes an observation section in which a plurality of rod-shaped measurement electrode sections are arranged concentrically and radially at regular intervals, and each rod-shaped measurement electrode section is connected to a pair of current electrodes and the current electrodes mutually. The structure utilizes a four-electrode method consisting of a pair of voltage electrodes installed between each pair of current electrodes, and one current electrode of each pair of current electrodes is formed in the shape of a small disk, and the other current electrode is formed in the shape of a small disk. The present invention attempts to achieve the above object by adopting a configuration in which a single current electrode plate is formed in common with the other current electrodes on the same side.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described based on FIGS. 1 to 10.

FIG. 1 is a schematic explanatory diagram showing an example of actual measurement using the sensor device for measuring fluid flow according to the present invention.

In FIG. 1, reference numeral 1 denotes a measuring borehole drilled in the ground E from the ground surface to a predetermined depth into the groundwater layer (sand layer, gravel layer, etc.). A measurement probe (hereinafter simply referred to as "probe") 3 suspended via a boring rod 2 is inserted into the borehole 1 down to the test depth. Here, the direction of the probe 3 is determined by a compass 4 (see FIG. 2) built into the upper part of the probe 3.
It is designed to be installed and fixed in a predetermined direction while being confirmed by the following. In the groundwater layer in the ground E, there is a flow of groundwater as shown by arrow F in the diagram.
Therefore, groundwater W gushes out in the borehole 1 below the groundwater level, and the probe 3 is immersed in this groundwater W. The probe 3 is electrically connected to an external measuring device (not shown) by a cable 5 extending inside the boring rod 2, thereby allowing groundwater flow measurement and recording. It is starting to be done.

Next, the specific configuration of the probe 3 described above will be explained in the second section.
As shown in the figure. The probe main body 3A, which is the main part of the probe 3, includes a cylindrical probe main body 6 with a compass 4 installed in the upper part, a disc-shaped head 7 attached to the lower end of the probe main body 6, and a probe main body 3A that is a main part of the probe 3. 7 and a bottom plate 8 disposed below it at a predetermined interval.

The head 7 is made of an insulating material, and a fourth electrode 9 formed in the shape of a common large disk is fixed to the lower end surface of the head 7. Further, a plurality of cylindrical electrode rods 10 to 18 are concentrically implanted protruding downward from the fourth electrode 9 as shown in FIG. And this head 7
are four pillars 20, 20, 20, 20, 20, 20, 20,
... is screwed to the lower end surface of the probe main body 6 at its upper end, thereby allowing it to be attached to the probe main body 6 in a hermetically sealed manner.

A support plate 21 that supports the lower end of the cable 5 is fixed to the upper surface side of the head 7 in FIG. ing. On the other hand, the bottom plate 8 is fixed to the lower end portions of the columns 20, 20, . . . by nuts 22, 22, . (Observation part) 23 is formed, and groundwater can flow into this observation part 23. This bottom plate 8 has a function as a bottom of a container filled with an electrolytic solution (for example, NaCl solution) 24 as a replacement substance, as will be described later.
Even if the probe 3 is accidentally pressed against the bottom of the borehole 1, it has the function of preventing damage to the electrode rods 10 to 18 and further stabilizing the flow within the observation section 23.

Between the peripheral end of the head 7 and the peripheral end of the bottom plate 8, there are electrode rods 10, 1 implanted in the head 7.
A cylindrical wire mesh 25 is disposed surrounding 1, . This wire mesh 25 is a hole wall 1A of the borehole 1.
(See Figure 1) Due to collapse of the observation unit 23, etc.
In addition to preventing foreign matter from entering the electrode rod 10,
11... portion is electrically shielded to remove the influence of external noise due to earth current, etc., and as described later, to suppress the generation of turbulence that occurs when the sleeve 30 rises, and furthermore, together with the bottom plate 8, the observation section 23
This is for rectifying the current inside the tank.

A guide rod 26 having a smaller diameter than the outer diameter of the probe body 6 is fixed to the upper end of the probe body 3A configured as described above, and the entire body is configured in a piston shape. The boring rod 2 is further connected to the upper end of the shaft. An annular stopper 27 is fitted onto the upper end of the guide rod 26 to limit upward movement of a sleeve 30, which will be described later.

A sleeve 30 surrounding the outer periphery of the probe body 3A is provided over the entire length of the probe body 3A so as to be movable up and down. This sleeve 30
The sleeve 30 is formed in a bottle-like cylinder shape with an open bottom. In other words, the sleeve 30 includes a cylindrical portion 31 that covers the side surface of the probe body 3A, and a portion near the upper end of the cylindrical portion 31 that covers the probe body 6. It consists of a shoulder portion 32 bent inwardly into a substantially conical shape at its upper end, and a neck portion 33 extending upward from the circular end of the shoulder portion 32 in contact with the guide rod 26. The cylindrical portion 31 and the probe body 3 are connected by O-rings 34 to 36 attached to the vicinity of the upper and lower ends of the probe body 6 and the lower end of the bottom plate 8.
A, and an O-ring 37 attached to the upper end of the neck 33 seals the space between the neck 33 and the guide rod 26, and the entire sleeve 30 can slide vertically. It is formed so that The sleeve 30 configured in this way,
The guide rod 26 and the probe body 6 form a piston-cylinder mechanism 38.

To explain this in more detail, a discharge port 39 is bored in the shoulder portion 32 of the sleeve 30 as a cylinder portion, as shown on the left side of FIG. A nozzle 41 connected to the nozzle 41 is fitted. And this hose 40
A predetermined amount of pressurized water is supplied to the shoulder portion 32 of the sleeve 30 from a water pressure pump (not shown) provided externally through the
and the upper end surface of the probe body 6 serving as a piston portion. (See arrow A in Figure 2). By injecting this pressurized water, the sleeve 30
is moved upward by the reaction force (see Figure 4). On the other hand, the downward movement (return) of the sleeve 30 can be easily performed by opening the release valve 42 provided on the right side of the shoulder portion 32 in FIG. 2 and pushing down the entire sleeve 30. .

The upward movement of the sleeve 30 is limited by the stopper 27 described above, and at this time, the observation section 2
3 is now exposed in its entirety. (See Figure 4). Further, the downward movement of the sleeve 30 is restricted by the step portion 43 provided inside the shoulder portion 32 coming into contact with the upper edge of the probe body 6. At this time, the lower end of the cylindrical portion 31 is It is designed to fit on the side. (See Figures 2 and 3). Therefore, the observation section 23 is sealed from the outside.

The sleeve 30 configured in this manner is placed downward before the start of measurement, and is used to hermetically fill the observation section 23 with a liquid replacement substance (for example, NaCl solution) 24 having a conductivity different from that of groundwater. Moreover, at the start of measurement, it is moved upward to allow groundwater to enter the observation section 23, thereby forcing the replacement substance to the outside according to the flow of the groundwater. This sleeve 30 also allows the probe 3 to be connected to the borehole 1.
It has a function of protecting the probe body 3A from the hole wall 1A when the probe is lowered into the hole.

Next, electrode rods 10 to 1 protruding from the head 7
The configuration of 8 and the flow measurement method are shown in Figures 6 to 8.
This will be explained based on the diagram.

First, in FIG. 7, a center electrode rod 10 is provided at the center of the head, and outer electrode rods 11 to 18 are arranged concentrically in eight equal parts with this center electrode rod 10 as the center. There is. These electrode rods 10 to 18 are configured in the same shape,
For example, as shown in FIG. 6, the electrode rod 10 includes an electrode rod main body 82 made of an insulating member that protrudes downward through the head 7 and has a disk-shaped protrusion 81 at the lower end, and a small annular first electrode 10A mounted on the upper surface side of the portion 81 in FIG.
It is composed of annular second and third electrodes 10B and 10C mounted on the outer periphery of the electrode rod main body 82 at intermediate positions between the first electrode 10A and the fourth electrode 9 at a predetermined distance from each other. The first to third electrodes 10A to 10C are connected to the cable 5 by lead wires through holes 83 formed in the electrode rod body 82, while the fourth electrode 9 is connected to the head 7. It is designed to be connected to a cable 5 via a drilled through-hole plating (not shown).

The aforementioned first to fourth electrodes 9, 10A to 10C
In principle, this forms a four-electrode method which is one of the so-called liquid conductivity measurement methods, in which the first and fourth electrodes 10A and 9 have the function of current electrodes, and the second and fourth electrodes 10A and 9 have the function of current electrodes. The third electrodes 10B and 10C have a function as voltage electrodes for voltage detection, and form a set of measurement electrodes.

Generally, the electrical conductivity of a measured object is determined from the relationship between the voltage and current applied to the measured object, but when a current is passed through a liquid, an electrode reaction occurs and the current gradually becomes difficult to flow, resulting in measurement errors. . The four-electrode method adjusts the voltage applied to a pair of current electrodes so that the voltage applied between a pair of voltage electrodes is always constant, thereby eliminating the measurement error described above. A measuring circuit 50 according to this embodiment is shown in FIG. In the figure, a predetermined voltage is applied to the first electrodes 10A to 18A and the fourth electrode 9 of each electrode rod 10 to 18 from an AC power source 51 via a voltage control section 52, and the liquid near the electrode rod is applied. Electric current is allowed to flow through it. Here, each first electrode 1
Application of voltage to 0A to 18A is performed by switching at predetermined timing using an analog switch 53. On the other hand, each electrode rod 10~
18 second and third electrodes 10B, 10C, and 1
1B, 11C... (voltage generated when a current flows near the electrode rod) is sequentially switched and detected by a pair of analog switches 54 and 55, which are switched in synchronization with the analog switch 53. , and are sent to the voltage control section 52 via an amplifier 56. This voltage control section 52
The voltage applied between each of the first electrodes 10A to 18A and the fourth electrode 9 is adjusted to each electrode so that the detection voltage input from the amplifier 56 is always constant for each electrode rod 10 to 18. The function is to control each rod 10 to 18 independently. On the other hand, a resistor R for current measurement is inserted between the voltage control section 52 and the analog switch 53, and the current flowing through this resistor R is converted into a voltage across the rectifier circuit 53.
7 and a sampling circuit 58 synchronized with analog switches 53 to 55, a multichannel recorder 59 records each of the electrode rods 10 to 18. Here, the current I flowing through the resistor R
The conductivity G of the liquid can be accurately measured from the relationship G=I/V by the voltage V between the voltage electrodes, but V
Since I is constant, changes in conductivity can be directly measured from changes in I. Therefore, due to the difference in electrical conductivity between groundwater and the replacement substance, groundwater flows through each electrode rod 10.
It becomes possible to detect the time when the time reaches 18.

Next, the overall operation of the above embodiment is shown in FIGS. 9 and 1.
This will be explained based on Figure 0.

First, in advance, the observation section 23 of the probe 3 is supplied with a substituent having a conductivity different from that of the groundwater to be measured (for example, an electrolytic solution such as NaCl solution if the groundwater has low conductivity); If the conductivity is relatively high, use pure water, etc. (Here, we will use NaCl solution.) 24 and move the sleeve 30 to the lowest position (see Figure 3). , the probe 3 is lowered to a predetermined depth within the borehole 1. At this time, the direction of the probe 3 is arranged in a predetermined direction by the above-mentioned compass 4.

Next, the borehole 1 is lowered by lowering the probe 3.
After the groundwater disturbance in the area has subsided, the hose 40
Pressurized water is poured into the sleeve 30 through the sleeve 30, and the sleeve 30 is gently moved upward. At this time, as the sleeve 30 rises, the sleeve 3
Although turbulent flow occurs near the lower end of 0, the turbulent flow is suppressed inside the observation section 23 by the function of the wire mesh 25.
Almost no outflow of the NaCl solution 24 occurs (fifth
(see figure).

Then, when the sleeve 30 moves to the uppermost end,
As the groundwater W flows, the groundwater W gradually flows into the observation section 23, and along with this, the NaCl solution 24
is pushed out. At this time, the wire mesh 2 mentioned above
5, the turbulent flow generated by the borehole 1 hardly flows into the observation section 23, and the wire mesh 2
5 and the bottom plate 8, the flow within the observation section 23 is rectified, so that the inside of the observation section 23 is in a laminar flow state that is substantially the same as the flow within the groundwater layer.

Here, the groundwater W is, for example, the external electrode rod 11
When the groundwater W flows in the direction of the external electrode 15 (direction S in FIG. 7), if the groundwater W has not yet reached the external electrode 11, all the electrodes 10 to 18 are in the NaCl solution, and each electrode 10 to The conductivity detected by 18 is high (1 in Fig. 9, T ₀ in Fig. 10).
()reference).

Next, when the groundwater W first begins to reach the external electrode rod 11, the conductivity of the liquid detected by the external electrode rod 11 first decreases due to the low conductivity of the groundwater (2 in Fig. 9). , see T ₁ () in Figure 10).

As the groundwater W progresses, the groundwater W and NaCl
As the replacement with the solution progresses and the leading edge of the groundwater reaches the position of the center electrode 10, the conductivity measured by the center electrode 10 decreases (see 2 and 2 in FIG. 9).
(See T ₁ () in Figure 10). As a result, it is detected that the flow direction of the groundwater W is from the external electrode rod 11 to 15, and the timing at which the groundwater W reaches the external electrode rod 11 is determined. on the other hand,
For other external electrode rods, for example 12, the arrival timing of the groundwater W is delayed compared to the external electrode rod 11, so that the change in conductivity is also delayed (see T ₂ () in FIG. 9).

As the groundwater W progresses, it further forms with the groundwater W.
When the replacement with the NaCl solution progresses and the leading edge of the groundwater reaches the center electrode 10 position, the center electrode 1
0 (see 3 in FIG. 9, T ₃ () in FIG. 10). This decrease in conductivity can be expressed as L/(T ₃ - T _{1 )} , where L is the distance between the outer electrode 11 and the center electrode 10, by representing the timing when the groundwater W reaches the center electrode 10 position. The groundwater flow velocity can be determined from the calculation formula. Therefore, the flow velocity can be determined in a relatively short time. The same is true even if groundwater flows from other directions.

According to this example, since the four-electrode method was used to measure changes in conductivity, it is possible to accurately measure the flow, and among the four electrodes forming each measurement site, one current electrode is replaced with a pair of voltage electrodes. are integrally equipped, and
Since the other current electrodes are integrally formed over all the measurement parts, the wiring is simplified and the configuration is simple. Therefore, it is possible to make the device compact, and at the same time, it is possible to It is possible to prevent groundwater from flowing in and improve reliability. Furthermore, since a single measurement circuit can be used to measure changes in conductivity at each measurement site (electrode rod), the cost of the entire device can be reduced. In addition, the sleeve can be raised simply by injecting pressurized water from the outside using a piston-cylinder mechanism. Therefore, a complicated structure such as extending the outer wall of the sleeve to the ground and raising it is not required. Moreover, when lifting with a wire or the like, incorrect insertion such as entanglement of wires can be prevented, and the upward movement can be performed reliably.

In the above example, an electrolytic solution was used as the replacement substance, but the measurement sensitivity may be improved by, for example, making use of the difference in dielectric constant or using a composite substance mixed with metal particles. In short, any liquid substance (including sol-like substances) that has electrical (conductivity, permittivity, etc.) properties different from those of the groundwater to be measured and similar specific gravity and viscosity is sufficient. In addition, as a substitute substance, by discharging etc. in the object to be measured,
A material with an ion layer formed thereon may also be used.

〔Effect of the invention〕

Since the present invention is configured and functions as described above, by using the present invention, for example, the flow direction of groundwater can be measured with high precision only within a single borehole, and one of the current electrodes of each pair The current electrode is formed in the shape of a small disk, and the other current electrode facing it is formed from a single current electrode plate that is common to each of the other current electrodes on the same side, so the structure is simple and simple. Therefore, it is possible to provide a sensor device for measuring fluid flow, which can improve productivity and durability, and can stabilize the operation because the opposing area of the current electrodes can be set relatively large.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing a state in which measurement is performed using the sensor device for measuring fluid flow according to the present invention, FIG. 2 is a detailed partial sectional view showing the probe portion of FIG. 1, and FIG. 4 and 4 are explanatory diagrams of the operation of the sleeve according to a part of FIG. 2, FIG. 7 is a partially omitted cross-sectional view taken along the - line in FIG. 2, FIG. 8 is a block diagram showing the measurement principle according to the present invention, and FIG. 1 to 3 are explanatory diagrams showing measurement conditions, and FIG. 10 is a diagram showing an example of measurement results. 3...Probe, 9...4th as current electrode
Electrode, 10-18... Electrode rod having a group of measurement electrodes, 10A-18A... First electrode as current electrode, 10B-18B... Second electrode as voltage electrode, 10C-18C... As voltage electrode Third electrode, 23...observation section.

Claims (1)

[Scope of Claims] 1. An observation unit including a plurality of rod-shaped measurement electrodes arranged concentrically and radially at regular intervals, each rod-shaped measurement electrode being connected to a pair of current electrodes and the current The configuration utilizes a four-electrode method consisting of a pair of voltage electrodes installed between the electrodes, and one current electrode of each pair of current electrodes is formed in the shape of a small disk, and the current electrode opposite to this is formed in the shape of a small disk. A sensor device for measuring fluid flow, characterized in that the other current electrode is formed by a single current electrode plate common to each other current electrode on the same side.