JPS5841480Y2 - Potential measurement device for soil - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a potential measuring device for soil, which is used to measure the ground potential and ground surface potential gradient of a metal body buried underground.

Generally, by measuring the ground potential of metal pipes buried underground, it is possible to determine the presence or absence of stray current or battery action, as well as the inflow and
The location of the spill and the corrosion status of underground metal pipes are being determined.

In the prior art of the present invention, as shown in FIG. 1, one terminal of a DC voltmeter 12 is connected to an underground metal pipe 1, and the other terminal of this voltmeter 12 is connected to a conventional A copper sulfate electrode 6 is connected, and this copper sulfate electrode 6 is installed on the ground surface directly above the underground metal pipe 1 to measure the tube lighting potential.

As is well known, the copper sulfate electrode 6 is constructed by fixing a copper electrode in a container filled with a saturated copper sulfate aqueous solution. Some are made of synthetic resin and are plugged with a plug made of porous material such as wood.

Since such a copper sulfate electrode 6 has a relatively large shape,
It is difficult to insert the reference electrode deep underground.

Particularly on roads paved with asphalt or the like, pavement breaking work is required in order to insert the copper sulfate electrode 6 into the ground, and restoration work is also required accordingly.

Therefore, if the area directly above the underground metal pipe is paved, the paving work is not done, and the copper sulfate electrode is grounded to a groundable place such as the soil near the paved road.

Therefore, the grounding point is no longer directly above the underground metal pipe,
The reliability of potential measurements is poor.

FIG. 2 is the equivalent circuit of FIG.

E is the potential difference between the underground metal pipe 1 and the copper sulfate electrode 6,
R1 is the internal resistance of the voltmeter 12, and R2 is the grounding resistance between the copper sulfate electrode 6 and the soil.

The potential difference measurement value (2) by the voltmeter 12 is expressed by the first equation.

If the grounding location of the copper sulfate electrode 6 is in a place where there is gravel or the like, or in a dry place, the grounding resistance R2 of the copper sulfate electrode 6 may reach, for example, about 105 to 106 g. In such a case, from the first equation,
It can be seen that the error in the measured value (2) of the voltmeter 6 with respect to the tube lighting potential E becomes large.

In order to make the hole formed for inserting the copper sulfate electrode 6 into the ground on a paved road as small as possible, it is simply conceivable to make the shape of the copper sulfate electrode 6 thinner.

If the copper sulfate electrode 6 is made thinner, it becomes difficult to introduce copper sulfate crystals to keep the copper sulfate aqueous solution saturated in the container, and it becomes difficult to maintain measurement accuracy due to contamination of the copper sulfate aqueous solution. It becomes difficult to replenish the copper aqueous solution into the container, and since the copper electrode is small, potential changes due to polarization are large, and measurement accuracy is therefore reduced.

In other prior art techniques of the present invention, in order to solve this problem, iron rods are used as electrodes, and the iron electrodes are driven into the soil.

Such an iron electrode cannot function as a reference electrode, and in order to measure the corrosion potential of this iron electrode, the reference electrode must be used to measure the potential again, making the measurement operation complicated. .

Therefore, the main purpose of the present invention is to provide a potential measuring device for soil that can easily measure the potential with high precision even on asphalt-paved roads.

FIG. 3 is a sectional view showing an entire embodiment of the present invention.

This embodiment is applied to measure the ground potential of a metal tube 1 made of a material such as steel and buried underground in an asphalt-paved road or the like.

Casing 2 made of electrically insulating material such as synthetic resin
A cock 3 made of electrically insulating material is attached to the lower part of the cock.

A tubular body consisting of a flexible tube 4 that is transparent (including a semi-transparent interior so that a plug 17 described below can be seen from the outside) and an insertion tube 5 is connected to the cock 3.

A transparent flexible tube 4 connected to the cock 3 at one end is made of a flexible electrically insulating material such as silicone rubber or vinyl chloride resin, and an insert connected to the other end of the flexible tube 4 The tube 5 is made of a relatively rigid electrically insulating material, such as Teflon (trade name).

In practice, the insertion tube 5 has, for example, an outer diameter of 5 mm and a length of 20 cm.
It may be a degree.

The casing 2, the cock 3, the flexible tube 4 and the insertion tube 5 constitute a salt bridge forming body.

It is sufficient that at least the entire inner surface of the salt bridge forming body is made of electrically insulating material.

Inside the casing 2, a so-called copper sulfate electrode 6 is provided as a reference electrode.

The copper sulfate electrode 6 is produced by filling a container 9 with a saturated copper sulfate aqueous solution 10 in which the bottom of a cylindrical body 7 made of synthetic resin, which is an electrically insulating material, is closed with a plug 8 made of wood such as paulownia wood. A copper electrode 11 is immersed in the saturated copper sulfate aqueous solution 10 of No. 9.

Copper electrode 11 is connected to a negative terminal of DC voltmeter 12 .

A positive terminal of the voltmeter 12 is connected to the underground metal pipe 1.

The casing 2 is filled with an aqueous sodium sulfate solution 13.

The upper part of the casing 2 is provided with an inlet 14 for injecting the aqueous sodium sulfate solution, a handle 15 for convenient portability, and a handle 15 for making the copper sulfate electrode 6 removable from the casing 2. A mounting port 16 is provided.

The injection port 14 and the mounting port 16 are not airtight, and no backflow of the solution occurs.

FIG. 4 is a cross-sectional view of a portion of the flexible tube 4. FIG.

The plug 17 inserted into the flexible tube 4 consists of a plug body 18 and an annular body 19 fitted onto the body 18a of the plug body.

The plug body 18 is made of a porous material having pores communicating in the axial direction of the flexible tube 4, such as wood such as cedar or paulownia.

The axis-perpendicular cross section of the body portion 18a of the stopper body 18 is circular;
The end portion 18b on the insertion tube 5 side, that is, on the soil side, is formed in the shape of a tapered truncated cone.

The end 18C of the stopper body 18 on the side of the copper sulfate electrode 6, that is, on the side of the cock 3, is also formed in the shape of a truncated cone.

The outer ring of the body 18a is made of a hard electrically insulating material, such as synthetic resin.

An adhesive is interposed between the inner surface of the ring body 19 and the outer surface of the body portion 18a of the stopper body 18 to create an airtight seal.

Further, the outer surface of the ring body 19 can be brought into close contact with the inner surface of the flexible tube 4 in a natural state where no external force is applied by the elastic force of the flexible tube 4.

In this way, the inside of the flexible tube 4 is closed. Next, a procedure for measuring the tube lighting potential of the underground metal tube 1 will be described.

Directly above the underground metal pipe 1, a hole 20 having a size that allows the insertion pipe 5 to be partially inserted into the ground is bored.

For this purpose, the hole 20 can be easily formed by, for example, driving a steel rod that is slightly larger than the outer diameter of the insertion tube 5 to a depth of about 15 cm, and then pulling out the steel rod.

The length of the insertion tube 5 and the depth of the hole 20 are selected so that the bottom 21 of the hole 20 is a location suitable for potential measurement.

Next, the cock 3 is opened, and as shown in FIG. 5, the part of the flexible tube 4 into which the stopper 17 is inserted is crushed with fingers in the continuous radial direction 22 of the flexible tube 4 from the outer periphery.

Therefore, the function of blocking the flexible tube 4 by the stopper 17 is released, and the sodium sulfate aqueous solution 13 inside the casing 2 flows down to the insertion tube 5 side.

Since the end 18b of the plug 17 is a truncated cone, the aqueous sodium sulfate solution 13 flows into the flexible tube 4 rather than flowing into the center of the flexible tube 4 immediately downstream of the plug 17. Easy to flow along the inner surface.

Therefore, the generation of air bubbles near the end 18b of the plug 17 is prevented as much as possible, and the portion of the flexible tube 4 downstream of the plug 17 and the inside of the insertion tube 5 are filled with the sodium sulfate aqueous solution, resulting in a liquid column. tends to form immediately.

Therefore, it is possible to prevent the sodium sulfate aqueous solution from continuing to flow with a relatively large amount of bubbles generated near the end 18b of the stopper 17 as much as possible.

After a liquid column is formed in the flexible tube 4 and the insertion tube 5, the pressure on the flexible tube 4 is stopped as shown in Figure 5, and the liquid column is maintained.

Note that since the end 18C of the stopper 17 is formed into a truncated cone, the air bubbles 23 generated near the end 18C are
8C, and by squeezing this tip 24 from the outside of the flexible tube 4, the air bubbles 23 can be lifted away from the end 18C of the stopper 17.

In this case, since the flexible tube 4 is transparent, the presence or absence of the bubbles 23 can be easily confirmed from the outside.

In order to facilitate the formation of a liquid column, the free end of the insertion tube 5 may be airtightly suctioned with a dropper-like pump.

Since the ring body 19 is fitted onto the plug body 18, the upstream and downstream portions of the plug 17 are reliably closed.

Further, even if air bubbles 25 are generated near the conical inclined surface of the end 18b of the stopper 17, the ionic conductivity is reliably maintained above and below the stopper 17 because the end 18b extends downward.

A flexible tube is used as part of the salt bridge, and a porous plug with pores extending in the axial direction of the tube is inserted into the flexible tube, which functions as an ion conductor and prevents electrolyte solution from flowing out. I can escape.

In this embodiment, by forming the insertion tube 5 thin, the hole 20 formed in the soil may be relatively small.

Since the free end of the insertion tube 5 comes into contact with the bottom 21 of the hole 20 by the aqueous sodium sulfate solution, there is an advantage that the grounding resistance is extremely reduced.

In the stopper body of another embodiment of the present invention shown in FIG. 6, the body is a cylindrical body, and both ends thereof are conical in shape with the same diameter as the body in FIG. In Figure 6C, the tip of the body is a rounded cone, and in Figure 6D, the upper end of the body is a cone. The lower end is a truncated cone.

The body does not have to be cylindrical, and may be prismatic, for example.

In addition to wood, the material of the stopper body 18 may be an unglazed perforated plate, styrofoam, glass capillary, or the like.

The ring body 19 may be omitted if the outer surface of the stopper body 18 can be brought into close contact with the inner surface of the flexible tube 4.

FIG. 7 is a sectional view of still another embodiment of the present invention.

A notable feature of this embodiment is that the cock 3 is omitted and the flexible tube 4 is immersed from the top of the casing 2.

When measuring the potential, the flexible tube 4 is deformed with a finger to release the blocking function of the flexible tube 4 by the stopper 17, and suction is applied from the free end of the insertion tube 5 with a pump or dropper to form a siphon.

At this time, by removing air from the flexible tube 4 via the valve 26, a liquid column is formed in the flexible tube 4 and the insertion tube 5.

Since the other configurations are the same as those of the previous embodiment, corresponding parts will be given the same reference numerals and explanations will be omitted.

FIG. 8 is a cross-sectional view for explaining the operation of measuring the ground surface potential gradient using the soil potential measuring device according to the present invention.

A salt bridge forming body is provided between the two casings 2, and a DC voltmeter 12 is connected between the reference electrodes 6.

The other configurations are the same as those of the previous embodiment.

As described above, according to the present invention, the reference electrode is grounded via a salt bridge, which enables stable and highly accurate potential measurement with good reproducibility, and the insertion tube inserted into the soil has a small diameter. Therefore, it is easy to form holes in the soil in advance, improving work efficiency,
Particularly on paved roads, the effort required to break and restore the pavement is further reduced, greatly improving work efficiency.

Furthermore, since a plug made of rigid porous material is provided inside the flexible tube, it is possible to flow only the amount of electrolyte solution required for ion conduction, without wasting the electrolyte solution, and thus allowing the potential measuring device to maintenance becomes easier.

Ion conduction through this porous material is stable, and the resistance for ion conduction is extremely low.

In addition, the plug made of a rigid porous material has a tapered end on the soil side, that is, the lower part, so that even if air bubbles rise from below and are blocked by the plug, the tapered end will cause the electrolyte below to flow. It is in constant contact with the solution, allowing reliable measurement of potential.

Moreover, since the flexible tube is transparent, the presence or absence of air bubbles can be easily confirmed from the outside.

Therefore, when the flexible tube is crushed to remove air bubbles generated in the stopper, the situation can be visually observed, and air bubbles can be reliably removed.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of a prior art for measuring pipe-to-ground potential, Fig. 2 is an equivalent circuit of the prior art shown in Fig. 1, and Fig. 3 is an embodiment of the present invention for measuring pipe-to-ground potential. A cross-sectional view of
4 is a sectional view of a part of the flexible tube 4, FIG. 5 is a sectional view for explaining the function of the plug 18, and FIG. 6 is a sectional view of a plug to replace the plug 18 according to another embodiment of the present invention. FIG. 7 is a front view, FIG. 7 is a cross-sectional view of another embodiment of the present invention, and FIG. 8 is a cross-sectional view for measuring a ground surface potential gradient using a potential measuring device for soil according to the present invention. 1... Underground metal pipe, 2... Casing, 3... Cock, 4... Flexible pipe,
5... Insertion tube, 6... Copper sulfate electrode, 1
7... Plug, 19... Ring body, 12...
...DC voltmeter.

Claims (2)

[Scope of utility model registration request] (1) one terminal of the DC voltmeter is connected to a reference electrode, the reference electrode is immersed in a casing filled with an electrolyte solution, and one end of the tube is communicated with the casing;
The other end of the tube is inserted into the soil, thereby grounding the reference electrode through a salt bridge, and part of the tube consists of a transparent flexible tube, within which a plug is installed. The plug has pores communicating in the axial direction of the tube and is made of a rigid porous material; the end of the plug on the soil side is tapered; 1. A potential measuring device for soil, characterized in that the device is elastically in close contact with the inner surface of the flexible tube in its natural state. (2) The plug has a plug main body made of a porous material having a tapered end on the soil side and having pores communicating in the tube axis direction;
The utility model is registered as a utility model characterized by a ring body made of a rigid material that is airtightly fitted to the outside of the plug body and whose outer surface is elastically adhered to the inner surface of the flexible tube in a natural state where no external force is applied. A potential measuring device for soil according to claim 1.