JP2003215180A - Method and instrument for measuring specific resistance - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and an instrument that can easily and continuously measure a local specific resistance in a testing subject. <P>SOLUTION: The specific resistance of a testing subject S is measured by impressing a potential to the subject S via electrodes C, D for impression, and by finding a potential in each portion of the testing subject S, using measuring electrodes P1-P3, Q. A dolly 10 is provided to travel on a surface of the subject S, the electrodes for the impression and the measuring electrodes are provided on the dolly 10, or the electrodes C, D for the impression and the one side electrodes P1-P3 out of the measuring electrodes are provided on the dolly 10, and the other side electrode Q is provided on the surface of the testing subject S. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resistivity measuring method as seen in so-called resistivity imaging and a resistivity measuring device used for the method. More specifically, while applying a potential to the test body via the application electrode,
The present invention relates to a specific resistance measuring method for measuring the specific resistance at each part of the test body by electrically connecting the measuring electrode and the test body, and a measuring device used for the method.

[0002]

2. Description of the Related Art Conventionally, the resistivity imaging method, which is a kind of resistivity measuring method, is generally used for knowing the approximate resistivity of a considerably large object such as geological exploration. Further, when the resistivity imaging method is used for concrete structures and the like, conductive rubber is attached as an electrode to the concrete surface, or a flat plate electrode is fixed with clay. And
If the electrode is to be brought into sufficient electrical contact with concrete or the like, a wide contact area must be secured, and the electrode must be widened.

Therefore, in order to carry out the resistivity imaging method based on the above-mentioned conventional electrode contact method, it was not possible to secure a high density of measurement points. As a result, the method can only be used for fairly rough measurements, and the term exploration can be used to tell that point.

Moreover, in the above-mentioned rough measurement, inclusions that hinder the measurement are present in the middle of the test body, or the test body is uniformly surrounded by a member having good conductivity, and the mounting portion of the application electrode is restricted. In some cases, it was difficult to accurately obtain the local resistivity.

[0005]

SUMMARY OF THE INVENTION In view of such a conventional situation, the present invention provides a specific resistance measuring method and a specific resistance measuring apparatus capable of simply and continuously measuring the local specific resistance of a test body. To provide.

[0006]

In order to achieve the above object, the first characteristic of the method for measuring the specific resistance according to the present invention is that a potential is applied to a test body through an electrode for application and the electrode for measurement is used to A method for measuring the specific resistance of the test body by determining the potential at each site of the test body, wherein a carriage that travels on the surface of the test body is provided, and the application electrode and the measurement electrode are provided on the carriage. There is something.

According to the same feature, since the application electrode and the measurement electrode are mounted on the carriage, each electrode can be positioned at a free portion on the surface of the test body. Therefore, even if inclusions or enclosures are present in the test body, it is possible to select a portion that can avoid these effects and measure the specific resistance of that portion.

The second characteristic of the method for measuring the specific resistance according to the present invention is that a potential is applied to a test body through an applying electrode, and
A method for measuring the specific resistance of the test body by determining the potential at each site of the test body by a measuring electrode, wherein a carriage running on the surface of the test body is provided, and the applying electrode and the measuring electrode are provided. One of the electrodes is provided on the trolley, and the other of the measurement electrodes is provided on the surface of the test body. According to this feature, it is possible to measure the specific resistance at each position of the test body at each depth. Further, if the other measuring electrode and the one measuring electrode are within a certain range, the same degree of freedom of measurement as the first feature is obtained. Moreover, the distance between the measuring electrodes can be freely changed by traveling the trolley.

In the first and second characteristic methods, it is desirable that the measuring electrodes are provided in three or more electrodes and two or more electrodes are provided in the carriage. According to this feature, the voltages between the plurality of measurement electrodes can be obtained by combining them. In particular, in combination with the second characteristic method, the voltage between these two electrodes can also be obtained by the difference in voltage between the two electrodes, and this makes it possible to obtain a specific resistance for both a relatively wide range and a local portion. Can be asked.

In constructing the application electrode or the measurement electrode, at least one of them is a conductive jet port for jetting a conductive liquid toward the test body, and the liquid flow is used to pass through the liquid flow. The measurement may be performed by electrically connecting the electrode and the test body. According to this configuration, the electrically conductive liquid is ejected from the ejection port, and the ejection port and the test body are electrically connected by this liquid, so that the test body and the electrode are reliably stabilized regardless of the surface-like body of the test body. Can be made to conduct. Also, because it has no mechanical contact with wheels or sleds,
The reaction force is also extremely small, which is very advantageous for continuous movement.

Further, the measuring electrode may be constructed such that at least one of them is a non-contact electrode for measuring the potential of the surface of the test body by an electrostatic measuring surface potential meter.

The characteristics of the resistivity measuring device according to the present invention are as follows:
What is used for any of the above characteristic methods, at least for measuring the specific resistance of the test body by determining the potential at each part of the test body and the application electrode for applying a potential to the test body. It is equipped with a measuring electrode. In particular, if each element is loaded on the moving carriage, it is possible to continuously move and measure the specific resistance at each position of the test body with high density.

[0013]

As described above, according to the features of the resistivity measuring method and the resistivity measuring device according to the present invention, the resistivity of the local portion can be easily and continuously measured by the movement of each electrode. It became so. As a result, it has become possible to perform more detailed inspections of concrete structures and steel structures. Other objects, configurations and effects of the present invention will become apparent in the section of the following embodiments of the invention.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Next, a first embodiment of the present invention will be described with reference to FIGS. The test body S to which the present embodiment is applied includes all kinds of concrete structures, structures using steel members, bedrock, and the like. Water is used as the conductive liquid in the present embodiment, and particularly when the conductivity is improved, for example, a saline solution in which sodium chloride is dissolved may be used. In the experiment, good results were obtained with a saline solution having a salt concentration of about 0.4%. In addition, a liquid metal such as mercury can be used as the conductive liquid.

As shown in FIG. 4, the resistivity measuring apparatus 1 according to the present invention comprises a carriage 10 and a control unit 60. This trolley 10 is further provided with four electrode wheels 30 described later. Then, a voltage is applied between the first electrode wheel 31 (C) and the second electrode wheel 32 (D), and in FIG.
By measuring the potential between any one of the plurality of ejection electrodes 40 (P1 to Pn) whose electrodes are only illustrated and the ground 69 (Q), for example, the measurement of the specific resistance between them shown by points R1, R2, and R3. I do.

As the power supply 61 in the control unit 60, an inverter power supply or the like having a DC or AC rectangular wave and a single voltage of 100 V or 150 V can be used, and a voltmeter 63 on the application side connected in parallel to the shunt resistor 62 can be used. The current applied by the power supply 61 is measured. A voltage is applied between the first electrode wheel 31 (C) and the second electrode wheel 32 (D) of the carriage 10.

Of the plurality of ejection electrodes 40, the first ejection electrode P1, the second ejection electrode P2, ..., And the nth ejection electrode Pn are independent electrodes so that the voltage can be read by the measuring side voltmeter 68. It is selectively used by switching the first relay 67a. The measurement side voltmeter 68 can be configured as a single-ended input measuring device, and in this case, the potential between the terminals can be obtained by obtaining the input difference between the terminals as described later. If a multi-channel type measuring instrument is used, the input of each electrode can be processed in parallel.

The other electrode of the measuring side voltmeter 68 is the ground 6
It is connected to the test body S by 9 (Q). In addition, earth 6
The pile 9 may be driven into the test piece S as shown in FIG.
Specimen S using wire brush or clay
It is desirable to ensure sufficient electrical contact without damaging the. The travel distance of the dolly 10 may be measured by a scale or the like, but it can also be measured by the encoder 80 attached to the test body S.

Further, the test body S may correspond to, for example, the inner wall of the tunnel, and it is necessary to bring the carriage 10 into contact with the test body S from below. In this case, for example, the carriage may be supported and moved by the robot arm mechanism, and the coordinate address of the carriage 10 can be derived from the drive amount of the robot arm.

Here, the distances C and D are La, P1, P
2 ... Let Lb be the distance between Pn and Q. This embodiment adopts a so-called Schramberger arrangement. In this case,
The above distance La needs to be five times or more the distance Lb.

The potential V between Pn and Q due to the voltage application to C and D is as follows.

V = 4Lb · ρI / ((La ² −Lb ² ) π) (1)

Therefore, the specific resistance ρ of the test body S between Pn and Q
Is as follows.

Ρ = V · (La ² −Lb ² ) π / (4Lb · I) (2)

By sequentially selecting the first relays 67a based on such a principle, the specific resistance between the different electrodes Pn-Q can be obtained.

Next, with reference to FIGS.
The structure of will be described. The trolley 10 is a main frame 20,
The electrode wheel 30 and the ejection electrode 40 are provided. The main frame 20 is a plate-shaped body made of an insulating material, and the electrode wheels 30 are attached to the front and rear lower surfaces thereof by small angles 23.

As shown in FIG. 3, an electrode wheel 30, which is an example of a traveling means for traveling on the surface of the test body S, has many wires 37 arranged radially around an axle 35 and fixed to a disk 36. . Then, as shown in FIG. 2, by inserting the pair of electrode wheels 30, 30 into the respective small angles 23, 23 in the front and rear of the bogie, and connecting the axles 35, 35 with a resin coupler 39 which is an insulator. Insulation between the electrode wheels 30 is ensured. That is,
The left first electrode wheel 31a, the right first electrode wheel 31b, the left second electrode wheel 32a, and the right second electrode wheel 32b are in a mutually insulated relationship, and one truck has two systems of two rows. It is possible to easily perform the measurement or the measurement in which the two systems are combined.

A lower frame 22 made of the same insulating material as that of the main frame is attached to the lower surface of the main frame 20 through a plurality of square bars 21. A plurality of ejection electrodes 40 are independently supported between the main frame 20 and the lower frame 22.

In each ejection electrode 40, a metal base 45 penetrating the main frame 20 and the lower frame 22 is fixed to the lower frame 22 by a nut 46. Further, another nut 46 fixes the terminal 47 to which the conducting wire 47a is connected to the intermediate portion of the base 45.

However, the conductor wire 47a may be fixed to the metal base 45 by soldering.

The base 45 is hollow and has a jet port 45a of water supplied through an insulating pipe 48 at its lower end. As shown in FIGS. 1 and 4, each insulating tube 48 connected to each ejection electrode 40 is connected by being drawn around a distance (a considerably long distance) longer than the clearance between the ejection port 45a and the surface of the test body, and connected to the pump 49. Connected. The water ejected from the ejection port 45a has a columnar shape as shown by reference numeral Wa in FIGS. 1 and 11 (a), and collides with the surface of the test body S to ensure conductivity with the test body S. Since it scatters in all directions as indicated by the symbol Wb, this conductivity can be secured in all directions by the water flow.

A plurality of ejection electrodes 40 are arranged at equal intervals in the longitudinal direction of the carriage 10 as with the conductive wheel 30, and
A row of electrodes is arranged on the left and right sides orthogonal to the longitudinal direction. The ejection electrodes 40 may be arranged at unequal intervals. And
In addition to combining the first to nth ejection electrodes P1a to Pna in the right column and the right first conductive wheel 31a, for example, combining the first to nth ejection electrodes P1b to Pnb in the left column and the left first conductive wheel 31b. Good. The measurement point is each electrode wheel 30 selected
A position between the and the conductive electrode is defined.

Now, with reference to FIGS. 4 and 5, the measurement of the specific resistance by the above-mentioned structure will be described in more detail. In the drawing, a case where either the right column or the left column of the conductive wheels 30 and the ejection electrodes 40 is used will be described. First,
As shown in FIG. 4, the electrode Q is brought into contact with the test body S, and the carriage 10 is further brought into contact with the test body S. The electrodes C and D are the first and second electrode wheels 31 and 32, and a voltage is applied between the electrodes CD by the power supply 61. Then, by using the first to nth ejection electrodes P1 to Pn selected by 67a and the electrode Q, the voltages V1, V2, V3 ... Vn of FIG. 5 corresponding to points R1, R2, R3 of FIG. 4 respectively. Is required. Further, by obtaining the difference between the voltages V1, V2, V3 ... Vn by calculation, the difference voltages ΔV12, ΔV13, ΔV23 ... Are obtained corresponding to the points R12, R13, R23, respectively. Then, using these voltages, the specific resistance in the vicinity of each point is obtained by the above equation (2).

Then, the carriage 10 is moved by an arbitrary pitch and the same operation is performed. As a result, it is possible to obtain the specific resistance of another portion. Further, as described above, according to the above-described configuration, it is possible to measure the specific resistance in the plane direction and the multi-step depth direction, and thereby the test body S can be inspected three-dimensionally. In the above description, the earth 69 is used as the other measuring electrode. However, it is also possible to switch the second relay 67b by interlocking with the first relay 67a and use the first to third electrodes P1 to P3 as both of the pair of measurement differential input electrodes.

Next, another embodiment of the present invention will be listed. The same members as those in the above-described embodiment are designated by the same reference numerals. In the second embodiment shown in FIG. 6,
The difference is that the ejection electrodes Pe, P1 to n are used for all the measurement electrodes. Further, in the present embodiment, the electrode for application is the electrode wheel 31.32, and all the electrodes are movable relative to the surface S of the test body.

According to this structure, the points Rn and Rnm are formed by combining the ground ejection electrode Pe and the ejection electrodes P1 to Pn.
The specific resistance corresponding to (n and m are integers) can be obtained. Further, even if the obstacles S1 and S2 such as iron plates are present inside and outside the test body S such as concrete, the specific resistance can be calculated by obtaining the above-mentioned difference. For example, P
It is also possible to obtain the specific resistance corresponding to the point R34 by obtaining the difference between the voltage of e-P3 and the voltage of Pe-P4.

Further, according to the configuration, even if the wheel 32 is set on the projecting plate S3 from the test body S, the measurement can be performed. When the overhanging plate S3 is a member such as a steel plate having a low specific resistance, the above-mentioned distance La is corrected to, for example, the distance La '. Further, if a jetting electrode is used as the applying electrode, a wider range of measurement becomes possible. If all the application electrodes are mounted on the dolly 10, accurate measurement can be performed even if the steel plate S3 or the like exists around the test body S.

In the third embodiment shown in FIG. 7A, the first to third non-contact electrodes 71, 72, 73 ... (P1, P2, P).
3 ...) is used. The power supply 61 is a DC power supply,
One end thereof is connected to the first electrode wheel 31 (C), and the other end side thereof is connected to the second electrode wheel 32 (D).

The measuring side voltmeter 68 is configured as a non-contact type vibration capacitance type electrostatic voltmeter 100. In this voltmeter 100, at each electrode, as shown in FIG.
The pulse from the oscillator 101 is applied to the tuning fork 75 in the electrode unit 74, and the electrode 76 fixed to the tuning fork 75 vibrates. The electrode unit 74 is not shown in the drawing, but each electrode 71 to 7
Each voltmeter 3 is provided and selectively connected to a single voltmeter 100 by a changeover switch not shown.

The electrode 76 is exposed to the outside through a hole 74a formed in the electrode unit 74. The capacitance Ci generated between the electrode 76 and the surface of the test body S fluctuates due to the vibration, and a signal in which the surface potential is AC-modulated is generated at the electrode 76.

This AC modulation signal is amplified by the preamplifier 77 and the amplifier 102, and is synchronously detected by the synchronous detector 103 to obtain an output signal of the surface potential. This output signal depends on the electrostatic capacitance Ci, and the electrostatic capacitance Ci depends on the distance d between the electrode 76 and the test body S, and the vertical movement of the trolley 10 during traveling affects the measurement error.

Therefore, the synchronous detection output is integrated by the integrator 104, input to the high voltage generator and fed back to the electrode unit 74 via the reference point 106. As a result, the potential of the electrode unit 74 rises to the same potential as the surface to be measured of the test body S, and the capacitance Ci is erased. Then, the impedance matching circuit 107 is used to generate the high voltage generator 1.
Since the voltage generated inside 05 is divided and the output impedance is output as 0.01 ohm or less, an accurate potential can be obtained without depending on the distance d.

In the above embodiment, the electrode wheel 30 is composed of the steel wire 37. However, the electrode wheel 30 can be composed of the wire 37 of a conductive member such as carbon or conductive plastic. The electrode wheel 30 may be formed of an elastic conductive member, and may be formed by winding a conductive member such as conductive rubber or steel wool around a shaft or a disk. However, it is most desirable to use the electrode wheel 30 in which the wires are radially arranged from the viewpoint of good contact with the surface of concrete or cast iron and durability. In addition, since wire and steel wool can form fine irregularities on the surface and this bites into the surface irregularities of the test body,
In that sense, the contact state is good.

In the above embodiment, all the wheels are electrode wheels 30.
And However, a part of the wheels may be the electrode wheels 30, and the rest may be rubber or plastic rolling wheels.

In the above embodiment, the C and D electrodes are fixed to the first and second electrode wheels 31 and 32. However, the C and D electrodes may be switched by any one of the electrode wheels 31 to 34 and the ejection electrode 40.

In the above embodiment, the plurality of ejection electrodes 40 are selected at each carriage position and the measurement is performed for each channel. However, it is also possible to provide the measurement side voltmeter 68 for a plurality of channels, or to switch the multiple channels by a clock with a personal computer and perform the above-mentioned measurement in parallel on the plurality of channels.

In the above embodiment, only one truck is used. However, using two carriages, one of which has a C electrode
The D electrode may be provided on another device.

In the above embodiment, the present invention is implemented as a so-called Schramberger arrangement, but the present invention is not limited to this. In the three-electrode method shown in FIG. 8, for example, the first electrode wheel 31 and the first to third ejection electrodes P1 to P3 in FIG. 6 are D poles and C poles, and the fourth to nth ejection electrodes P4 to n are P poles, It is advisable to allocate the second electrode wheel 32 to the Q pole, respectively. Instead of the above equation (2), the following equation holds between the C and P poles.

[0049] ρ = 2n (n + 1) πaV / I (3)

In the quadrupole dipole / dipole arrangement shown in FIG. 9, for example, the first electrode wheel 31 of FIG.
It is advisable to allocate the second electrode wheel 32 to the P pole, the first ejection electrode P1 to the D pole, and the nth ejection electrode Pn to the Q pole. Instead of the above equation (2), the following equation holds between the D and Q poles.

[0051] ρ = n (n + 1) (n + 2) πaV / I (4)

In the quadrupole Wenna arrangement shown in FIG.
For example, it is preferable to assign the ground ejection electrode Pe of FIG. 6 to the C pole, the first ejection electrode P1 to the P pole, the second ejection electrode P2 to the Q pole, and the third ejection electrode P3 to the D pole. Instead of the equation (2), the following equation holds between the P and Q poles.

[0053] ρ = n (n + 1) (n + 2) πaV / I (5)

In the above embodiment, the mouthpiece 45 is attached to the frame 22 (the trolley 10) so that the ejection center axis X of the ejection port 45a is orthogonal to the surface of the test body S as shown in FIG. 11 (a). However, as shown in FIG. 11B, the mouthpiece 45 may be attached to the frame 22 (the trolley 10) so that the ejection center axis X intersects the surface of the test body S at an inclination angle A in an inclined state. By inclining in this way, the reflected water flow Wb can be biased to one side instead of four directions, and water as the conductive liquid can be easily collected. For example, by disposing the water recovery device 90 on the lower side of the reflected water flow Wb, it is possible to reduce the amount of water scattered around the water.

In the above embodiment, the wheels 3 are used as the traveling means.
0 was used. The traveling means only needs to be able to move the carriage 10 along the surface of the test body, and may be configured as a sled or the like. In addition, the device may be fixed on the test body S by the fixed legs without using the traveling means, and the measurement may be performed by batch processing.

The reference numerals in the claims are merely for convenience of comparison with the drawings, and the present invention is not limited to the configurations of the accompanying drawings by the reference. .

[Brief description of drawings]

FIG. 1 is a side view of a carriage that constitutes a specific resistance measuring device according to the present invention.

FIG. 2 is a bottom view of FIG.

FIG. 3 is a side view of an electrode wheel.

FIG. 4 is a block diagram of an apparatus for measuring a specific resistance according to the present invention.

FIG. 5 is a graph showing the relationship between voltage measurement and electrode distance according to the present invention.

FIG. 6 is a view corresponding to FIG. 4 showing a second embodiment according to the present invention.

FIG. 7 (a) is a view showing a third embodiment according to the present invention.
FIG. 3B is a schematic diagram showing a partial configuration near the electrodes.

FIG. 8 is a principle diagram of a triode method used in another embodiment of the present invention.

FIG. 9 is a principle diagram of a quadrupole method used in another embodiment of the present invention.

FIG. 10 is a principle view of a wenna arrangement used in another embodiment of the present invention.

FIG. 11 shows the relationship between the jet central axis and the surface of the test body,
(A) shows the case where the coaxial is almost orthogonal to the surface of the test piece, (b)
Is the case where the coaxial crosses the surface of the test piece in an inclined state.

[Explanation of symbols]

1: Specific resistance measuring device, 10: trolley, 20: main frame, 21: square bar, 22: lower frame, 23: small angle, 30: electrode wheel, 31: first electrode wheel (31a left first electrode wheel) , 31b right first electrode wheel), 32: second electrode wheel, 35: axle, 36: disk, 37: wire, 38:
Wheel body, 39: resin coupler, 40: ejection electrode, 4
1: First ejection electrode (41a left first ejection electrode, 41b right first ejection electrode), 42: Second ejection electrode (42a left second ejection electrode, 42b right second ejection electrode), 45: Base, 45a:
Jet port, 46: Nut, 47: Terminal, 47a: Conductor wire, 4
8: Insulation pipe, 49: Pump, 60: Control unit, 6
1: power supply, 62: shunt resistance, 63: voltmeter on application side,
64: diode, 65: application side relay, 66: ground, 67a: first relay, 67b: second relay, 68:
Measurement side voltmeter, 69: ground, 71-73: first to third non-contact electrodes, 74: electrode unit, 74a: hole, 75:
Tuning fork, 76: Electrode, 77 preamplifier, 80: Encoder, 90: Water recovery device, 100: Electrostatic voltmeter, 10
1: oscillator, 102: amplifier, 103: synchronous detector, 1
04: integrator, 105: high-voltage generator, 106: reference point,
107: impedance matching circuit, S: test body, Ci:
Virtual capacitance

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 2G028 AA02 AA04 BC06 CG02 DH03                       DH04 FK01 HN02 HN12 HN13                       HN14                 2G060 AA10 AA14 AA20 AE01 AF07                       AG07 AG11 EA01 EA06 EB04                       HA02

Claims (6)

[Claims] 1. An electric potential is applied to a test body (S) through application electrodes (C, D), and measurement electrodes (P, P1 to
A specific resistance measuring method for measuring the specific resistance of the test body (S) by determining the electric potential at each site of the test body (S) by using n, Q), and traveling on the surface of the test body (S). A carriage (10) is provided, and the application electrodes (C, D) are provided.
And a method for measuring a specific resistance, characterized in that the measuring electrodes (P, P1 to n, Q) are provided on the carriage (10). 2. An electric potential is applied to the test body (S) through the application electrodes (C, D) and the measurement electrodes (P, P1 to P1).
A specific resistance measuring method for measuring the specific resistance of the test body (S) by determining the electric potential at each site of the test body (S) by using n, Q), and traveling on the surface of the test body (S). A carriage (10) is provided, and the application electrodes (C, D) are provided.
And one of the measurement electrodes (P, P1 to n, Q) is provided on the carriage (10), and the other of the measurement electrodes is provided on the surface of the test body. . 3. The measuring electrodes (P, P1 to n, Q) are provided in three or more electrodes, and two or more electrodes are in the carriage (10).
The specific resistance measuring method according to claim 2, wherein the specific resistance measuring method is provided in. 4. A conductive material in which at least one of the applying electrodes (C, D) or the measuring electrodes (P, P1 to n, Q) ejects a conductive liquid toward the test body (S). And the test body (S) is electrically connected to the electrodes (C, D, P, P1 to n, Q) and the test body (S) through this liquid flow. The specific resistance measuring method according to claim 1. 5. A non-contact electrode (7) for at least one of said measuring electrodes (P, P1 to n, Q) for measuring the potential on the surface of said test body (S) by an electrostatic measurement surface electrometer.
1, 72, 73).
The method for measuring specific resistance according to any one of 1. 6. A resistivity measuring device for use in the resistivity measuring method according to claim 1, further comprising an application electrode (C, D) for applying a potential to the test body (S). ,
Ratio comprising a measuring electrode (P, P1 to n, Q) for measuring the specific resistance of the test body (S) by obtaining the potential at each site of the test body (S) Resistance measuring device.