JP3274308B2 - Magnetic exploration device and its magnetic sensor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic detecting device for detecting minute magnetism and a magnetic sensor device thereof, and is particularly suitable for searching for a submarine cable laid on the seabed or a submarine resource. It is suitable for an exploration device for metal or the like.

[0002]

2. Description of the Related Art An apparatus for searching for a small magnetic metal on the earth, or a submarine cable exploration apparatus for detecting the presence of a submarine cable or a pipe laid on the sea floor, is a target for detection. To locate the body,
A magnetic sensor that detects a magnetic field generated by a DC magnetic field caused by iron or the like constituting the object to be searched or a DC current flowing in a metal that is a component of the object to be searched is mounted on a moving body,
By detecting the change in the intensity of the magnetic field output when the moving body approaches the metal to be searched, it is possible to track the submarine cable or pipe.

[0003] Hereinafter, the case where a metal to be searched is a submarine cable will be described. Many of the submarine cable failures that have occurred so far are caused by fishing nets and anchors. In order to prevent these obstacles, submarine cables laid in shallow water are buried under the sea floor. However, the buried submarine cable may also fail. To repair a fault in a buried cable, the faulty cable must be completely cut off at the sea floor, the stump must be lifted on the repair ship, and a breaker cable for repair must be connected between the stumps on both sides. Re-laying and re-burying. At this time, a remote-controlled underwater vehicle is used for exploring a failure point, investigating surrounding conditions, reburying after reconnection, and the like.

Conventionally, when searching for a buried submarine cable, an AC current of about 20 Hz is applied to the submarine cable in advance, and the generated AC magnetic field is detected by an AC magnetic sensor to detect the position of the submarine cable. Has been used. This method has high sensitivity,
It has excellent features such as measurement of relative position of cable, installation direction, burial depth, etc. However, in a long-distance buried submarine cable, there is a problem that an alternating current is attenuated with propagation and it becomes difficult to search in a distant place.
In addition, in order to prevent failures, it may be necessary to investigate in advance the installation status of commercial submarine cables. However, some old coaxial submarine cables do not allow AC current for exploration to pass through commercial cables.

On the other hand, a submarine cable exploration system using an omni-directional DC magnetic sensor has been conventionally known. In this system, the submarine cable is detected by detecting the DC current supplied to the submarine cable and the DC magnetic field generated from the iron wire of the submarine cable. DC current is supplied to supply power to a repeater inserted in the middle of the submarine cable. This DC magnetic sensor is called a proton magnetometer and measures the absolute value of a DC magnetic field. The proton magnetometer measures the strength of the magnetic field by detecting that the rotation period of the electron spin changes due to the application of a magnetic field, and has a very high sensitivity and resolution, from 40,000 to
In the 50,000 nT earth magnetic field, a DC magnetic field of several nT to several tens nT generated from a submarine cable can be clearly detected.

[0006]

However, in order to confirm the operation of the proton magnetometer, it is necessary to have a place where the magnetic field is extremely stable, and in a normal room or on a ship, the fluctuation of the geomagnetism is large. Can't do it. Therefore,
It is not very practical to mount such a magnetic sensor on a moving body to detect a magnetic field generated from a metal, and there is a problem that it is difficult to actually use the magnetic sensor.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a magnetic probe and a magnetic sensor device for solving the above problems. In order to detect the magnetic field, a three-axis orthogonal DC magnetic sensor device that measures the absolute value of the magnitude of the DC magnetic field is used. This magnetic prospecting device has one or two magnetic sensor devices in which three DC magnetic sensors for measuring the magnitude of a DC magnetic field in a specific uniaxial direction by an absolute value are arranged so that their axes are orthogonal to each other. More than one unit is mounted on a moving object, and its output is converted into a digital signal by an A / D converter, and then processed by an arithmetic processing circuit, thereby dispersing the sensitivity of each magnetic sensor, offset and orthogonality of three axes. The system is constructed so as to detect the presence of a metal or the like to be detected by correcting the deviation and displaying the absolute value of the DC magnetic field detected based on the corrected data on a display.

When the metal to be detected is a submarine cable laid on the seabed, the moving body is an underwater robot that can be controlled from a mother ship by a remote control method. The absolute value output of the DC magnetic field of each magnetic sensor is obtained by storing in advance the magnetic field intensity distribution data obtained by rotating the underwater robot 360 degrees in the horizontal direction in water, in the memory of the arithmetic processing circuit, The correction is performed based on the data read from the memory in accordance with the body orientation of the underwater robot.

According to a second aspect of the present invention, there is provided a pressure vessel made of an insulating material, a cylindrical vessel made of fused quartz installed in the pressure vessel via a buffer member,
The three uniaxial DC magnetic sensors are arranged so that their axes are orthogonal to each other, and a magnetic sensor main body embedded in a cylindrical synthetic resin is provided together with a circuit board. The magnetic sensor main body is inserted into the cylindrical container and moved. A magnetic sensor device to be mounted on a body.

Each of the magnetic sensors is constituted by a flux gate type sensor, and an underwater connector for outputting an electric signal of the magnetic sensor and supplying power to the circuit board is attached to a side surface of the pressure-resistant container. I have.

[0011]

The feature of the present invention is to measure the absolute value of the magnitude of the DC magnetic field in order to detect, for example, a DC current flowing through a submarine cable and a DC magnetic field generated from an armored wire constituting the submarine cable. A three-axis orthogonal DC magnetic sensor device is used, and the three-axis orthogonal DC magnetic sensor device is mounted on a remote-controlled underwater vehicle. Then, the sensitivity variation of each sensor and the offset and the deviation of the orthogonality of the three axes are corrected. For example, by rotating the underwater vehicle 360 degrees, the influence of the terrestrial magnetism and the magnetic field generated from the vehicle is canceled. By obtaining the correction data and displaying the absolute value of the DC magnetic field detected based on the corrected result on a display on the mother ship, the presence of a cable or the like can be detected.

Each magnetic sensor is fixed in a container having a large Young's modulus and a small coefficient of thermal expansion, such as quartz, in order to prevent distortion of the sensor axis due to expansion or contraction caused by a change in water pressure and temperature in the deep sea. In addition, by fixing to a pressure-resistant container via a soft buffer such as rubber, the magnetic field can be detected as accurately as possible without being affected by the environment of the exploration system. Metals are usually used as the material for pressure vessels for deep seas, but in metal pressure vessels, eddy currents are generated by turning off the earth's magnetic field when moving at high speed in water, resulting in magnetic fields Therefore, in the present invention, the pressure vessel is made of a high-strength insulating material.

[0013]

FIG. 1 is an explanatory view of searching for a submarine cable or the like by a magnetic exploration apparatus according to the present invention. Reference numeral 10 denotes a mother ship, and 11 denotes an electronic circuit container of an underwater robot 12 constituting a moving body from the mother ship 10. A signal and power are supplied to the underwater robot 13 and various information obtained by the underwater robot 12, for example, an output video signal of a television camera 14 mounted on the underwater robot 12 is detected by two magnetic sensors 15 </ b> A and 15 </ b> B. It is a composite cable (hereinafter referred to as a dither cable) for transmitting a magnetic field strength signal and the like. In addition, the underwater robot 12 is
The propulsion unit 16 and the like are controlled by a command from the remote controller, and are remotely controlled so that they can freely operate at a predetermined water depth.

That is, the underwater robot 12 is equipped with a buoyancy material (not shown), and can move freely back and forth and left and right by a plurality of propulsion units with zero underwater weight. It is connected to the ship with a dither cable 11 and the mother ship 1
0, and is remotely controlled by an onboard operator. In addition to the DC magnetic sensor of the present invention, the underwater robot body is equipped with a TV camera, various sensors, a water jet (not shown) for burying a submarine cable, and the like. The signals from the various sensors and the television camera are transmitted on the mother ship 10 in real time via the signal transmission device in the electronic circuit container 13 and the dither cable 11, and are monitored by the operator.

FIG. 2 is a block diagram showing a relation of processing of information applied to the magnetic surveying apparatus.
0 is an outline of the signal processing circuit and device on board, and 30 is
Is a block diagram showing a magnetic sensor on the underwater robot 12 side and processing of a signal output from the magnetic sensor.

In this embodiment, a fluxgate type magnetic sensor is used as a magnetic sensor having a sensitivity in a specific axial direction, and three magnetic sensors are combined in three axial directions.
It is made to detect on the table. The two three-axis orthogonal DC magnetic sensors 31A and 31B shown in FIG. 2 include three fluxgate type single-axis DC magnetic sensors 31AX, 31AY, 31AZ, and 31BX, whose axes are orthogonal to each other, as described later.
It is composed of 31BY and 31BZ. The output signals are respectively represented by V _1x , V _1y , V _1z , V _2x , V _2y ,
V _2z . These total six output signals are converted into digital signals via the signal converters 32A, 32B, 32C, 32D, 32E, and 32F including six low-pass filters and A / D converters.

Each signal converter 32 (A, B, C, D, E,
The output of F) is an interface circuit (I / O)
An arithmetic unit (CPU) 34 performs arithmetic processing via the bus 33 and the bus. In addition, a memory (RAM) 35, a non-volatile memory (ROM) 36, and an interface circuit (I / O) 37 with an electronic circuit 38 of the underwater robot main body are connected to the bus. The information detected by each magnetic sensor in this way is subjected to A / D conversion, is subjected to predetermined arithmetic processing, and is transmitted from the signal transmission device in the electronic circuit 38 in the underwater robot body to the signal transmission path in the dither cable 11. And transmitted to the mother ship 10.

On the shipboard side, the received information is processed by a circuit having substantially the same signal processing circuit. That is, the signal received via the dither cable 11 is amplified by the electronic circuit 41 on the hull so as to have a predetermined level, and the signal waveform is shaped and the interface (I /
O) The data is fetched from an arithmetic unit (CPU) 43 via a bus 42 and is partially stored in a hard disk 44 and a memory 45. 46 is a keyboard for operating the arithmetic unit, 47 is a video interface, and the information signal of the magnetic sensor, which is the output, is displayed on a display 48. Further, the apparatus is configured so that the detected magnetic field data received by the interface 49A and the printer 49B is printed out.

Next, an outline of the three-axis orthogonal DC magnetic sensor 15 (A, B) which can be used in the system of the present invention will be described. FIG. 3 is an exploded view of the main part of the magnetic sensor. Three uniaxial DC magnetic sensors 31
X, 31Y and 31Z are arranged such that their axes (X, Y and Z) are orthogonal to each other, and are positioned together with an attached electronic circuit board 51 by a synthetic resin (not shown). The magnetism detecting section 52 is formed by being buried, a cylindrical container 53 made of quartz into which the magnetic detecting section 52 is inserted, and a pressure-resistant container 54 into which the cylindrical container 53 is inserted. Cylindrical container 5 made of quartz
Reference numeral 3 denotes a cushioning material 55 made of rubber, a part of the outer periphery of which is covered with the cushioning material 55, and is housed in a pressure-resistant container 54 made of an insulating material. An underwater connector 56 for connecting to the electronic circuit board 51 is attached to the pressure-resistant container 54 so as to supply power to the electronic circuit board 51 and to take out an output signal from the magnetic sensor.

According to the present embodiment, the strain generated in the pressure-resistant container 54 due to the fluctuation of the water temperature and the water pressure is absorbed by the buffer material 55 and is not transmitted to the magnetic detecting section 52. Therefore, the problem of axis deviation due to fluctuations in water temperature and water pressure can be greatly reduced. Further, a metal is usually used as a material of the pressure vessel 54 for deep sea, but in a metal pressure vessel, an eddy current is generated by turning off the earth's magnetic field when moving in water, and as a result, the magnetic field is disturbed. Will be. According to the present invention, the problem of the eddy current can be solved by making the pressure-resistant container from a synthetic resin having high tensile strength, which is an insulating material.

Next, the sensitivity of the above-described three-axis orthogonal magnetic sensor, the offset of the output signal, and the orthogonality correction will be described. As shown in FIG. 1, assuming that there are variations in the sensitivity of the two DC magnetic sensors 15A and 15B and that the output signals thereof have no offset and the orthogonality is perfect,
The absolute values | B ₁ | and | B ₂ |
= 1 and 2 can be expressed as in equation (1).

(Equation 1) Here, c ₁ and c ₂ are constants, and V _ix , V _iy , and V _iz are the outputs of the sensors of each axis. However, since an actual signal has an offset of an output signal, an error in sensitivity, and an error in orthogonality of each axis, the calculation result of Expression (1) fluctuates by several hundred nT. In other words, if you rotate the sensor at the same point,
Fluctuations of several hundred nT occur depending on the direction of the sensor. Then
Generally, considering that the magnetic field of the terrestrial magnetism is 40,000 nT to 50,000 nT, it is difficult to detect a practical magnetic field fluctuation due to the above-described fluctuation.

Therefore, in the present invention, in order to solve the above-mentioned problems, the offset, the sensitivity error and the orthogonality error of each axis are corrected by the following equation (2).

(Equation 2) Here _{V ix ', V iy',} V iz ' are corrected output of each _{sensor, V ixo, V iyo, V} izo the offset of the output of each sensor, a _I11 ~a _I33 is a correction factor As described later, the orthogonality and sensitivity of each axis are corrected. By performing correction using such a determinant, it is possible to reduce the variation in the measurement of the absolute value of the DC magnetic field to several nT.

Next, a method of removing the influence of the magnetic field generated from the underwater robot 12 will be described. When a DC magnetic sensor is mounted on an underwater robot, it is affected by a DC magnetic field generated by the underwater robot. The magnetic field to be measured is a magnetic field obtained by vector-combining the terrestrial magnetism, the magnetic field generated from the cable, and the magnetic field generated from the underwater robot. It is known that the effect of the magnetic field generated by the underwater robot substantially depends on the body orientation of the underwater robot. Therefore, in the present invention, in order to remove the influence of the DC magnetic field generated from the underwater robot, the DC magnetic field when the underwater robot makes one rotation in the sea where the magnetic field is constant is measured, and the azimuth of the underwater robot and the fluctuation of the DC magnetic field are measured. The relationship between the magnitudes of the quantities is measured in advance and stored in the aforementioned memory (RAM) or the hard disk 44, and the DC magnetic field measured at the time of submarine cable exploration is stored in the aforementioned memory (RAM) or the hard disk. Corrected according to the data. That is, the influence of the DC magnetic field generated from the underwater robot is removed by subtracting the amount of variation depending on the orientation of the underwater robot.

FIG. 4 shows an example of the actual measurement of the azimuth of the underwater robot and the absolute value | B | of the DC magnetic field. The axis is the intensity of the detected magnetic field (about 50 nT per scale)
Is shown. The sinusoidal curve B (R) shows the strength of the magnetic field fluctuation output when the underwater robot makes one rotation in the horizontal direction, and the curve B (S) shows the magnetic field strength calculated to remove the above-described magnetic field fluctuation. Is shown. Although noise is superimposed on both curves, the fluctuation of the magnetic field due to the submarine cable is usually about 100 nT, so this noise does not hinder the detection of the submarine cable.

FIG. 5 shows the results of the above-described correction on board the ship.
Alternatively, an example is shown in which data corrected on the underwater robot side is displayed on a monitor on a ship. In this embodiment, the absolute values of the magnetic fields measured by the three-axis orthogonal DC magnetic sensors 15A and 15B mounted on the starboard and port sides of the underwater robot 12 are displayed. The horizontal axis is the time axis, and the vertical axis is the absolute value of the magnetic field. In order to emphasize and display the variation of the magnetic field, the vertical axis indicates the result of processing by the modulo function of the following equation (3), for example.

(Equation 3) Here, y represents an excess when x is divided by an integer n. The latest measurement result is displayed at the right end of the figure. Past points are scrolled to the left in order. Output signals B (S) and A of the right sensor 15B and the left sensor 15A
(S) is distinguished by changing the display color.

In FIG. 5, in section A, the underwater robot 12 is far away from the cable, and no change appears in the output signals A (S) and B (S) of the two sensors. Note that the right sensor 15B and the left sensor 15A do not overlap,
The display is slightly shifted in the vertical direction. In the section B, the fluctuation of the output signal B (S) of the right sensor is large, and it can be seen that the cable is approaching the right side of the underwater robot 12. In section C, the underwater robot crossed the cable, indicating that the cable came to the left. In section D, a cable exists at the center of approximately two sensors. As described above, in the apparatus of the present invention, since the relative direction and position of the cable cannot be measured, the underwater robot follows the cable zigzag while traversing the cable from side to side.

FIG. 6 shows an example of the measurement of the absolute value of the DC magnetic field when the cable in which a current of 1 amperes flows by the magnetic sensor of this embodiment crosses the cable at a speed of about 30 cm / S at a right angle. The vertical axis corresponds to approximately 50 nT on one scale, and the horizontal axis represents the moving time. The DC magnetic sensor is mounted on an underwater robot, and the change in the absolute value of the magnetic field due to the change in its direction is corrected. In FIG. 5, the magnitude of the magnetic field is large near the cable, but in the case of FIG. 6, it is small. This is because the direction of the magnetic vector of the terrestrial magnetism and the direction of the magnetic vector of the DC magnetic field generated from the submarine cable are opposite in the case of FIG. As described above, the submarine cable can be clearly detected by using the submarine cable exploration apparatus using the three-axis orthogonal DC magnetic sensor of the present invention.

As described above, the magnetic exploration apparatus of the present invention needs to detect the intensity of a magnetic field which is extremely small with respect to the earth's magnetism, so that the sensitivity characteristics in the three-axis direction of the magnetic sensor need to be corrected quite accurately. However, it is extremely difficult to mechanically equalize the sensitivity, offset, and axis deviation of the sensor in the three axial directions.

Therefore, the three-axis magnetic sensor device of the present invention measures the sensitivity and offset of the sensor on land while assembled with a certain degree of accuracy, and obtains the predetermined correction coefficient a _ij
It is preferable to incorporate and use. Hereinafter, the correction coefficients V _ixo , V _iyo , V _izo ,
An example of an asymptotic estimation method of a _{i11 to} a _i33 will be described with reference to (a) to (h). In the following discussion, the subscript i is omitted.

(A) The axes of the sensor are x-axis, y-axis, and z-axis. For example, as shown in FIG. 7, a rotary shaft 64 of a rotary table 63 and a sensor 65 are mounted on a rotary table that rotates around one axis.
The sensor 65 is mounted so that the x-axis of the sensor 65 coincides. At this time,
The rotation axis 64 and the x-axis need not be precisely aligned. Next, the output voltage of the sensor 65 is measured n ₁ times by a voltmeter while changing the rotation angle of the turntable 63. Similarly, place the sensor as y-axis and z-axis of the turntable rotation axis sensor coincide, the output voltage of each sensor by voltmeter while changing the rotation angle of the turntable n ₂ times and n ₃ measurements I do. A height adjustment table 66 is used so that the height of each sensor from the rotation table 63 matches. The output voltages of the sensor obtained by rotating around the x-axis, y-axis, and z-axis are represented by V _x (i), V _y (i), V _z (i), i = 1, 2, 3, ... N, n = n ₁ + n ₂ + n ₃ . V _x (i), V _y (i), and V _z (i) are outputs of the x-axis, y-axis, and z-axis sensors. Further, the initial values of the coefficients used for correction are as follows: a ₁₁ ⁽⁰⁾ = a ₂₂ ⁽⁰⁾ = a ₃₃ ⁽⁰⁾ = 1 a ₁₂ ⁽⁰⁾ = a ₁₃ ⁽⁰⁾ = a ₂₃ ⁽⁰⁾ = V _xo ⁽⁰⁾ = V _yo ⁽⁰⁾ = V _zo ⁽⁰⁾ = 0.

[0031]

(Equation 4) (B) In equation (4), i = 0, and the calculation results are expressed as V _x ^(j) (i), V _y ^(j) (i), V _z ^(j) (i), i = 1, 2, 3,..., N, j = 0.

(C) The absolute value of the corrected magnetic field is defined by equation (5), and the average value of the absolute value of the magnetic field before correction is defined by equation (6).

(Equation 5)

(Equation 6) α (i) is a coefficient for weighting data. The sensor is usually used with the x-axis being vertical. Therefore, when estimating the correction coefficient of Expression (4), the accuracy of the estimation may be improved by increasing the weight of the data obtained by rotating around the x-axis. For example, x
Α (i) = 1 for the data obtained by rotating around the axis
Α (i) = 0.5 for other data. The reason why the accuracy of the estimation can be improved in this way is that the magnitude of the DC magnetic field fluctuates with time due to the fluctuation of the earth's magnetic field when measuring data.

(D) If the sensor is ideal, | V
^(j) (i) | is always constant irrespective of the arrangement of the sensor, but varies due to offset, sensitivity errors, and errors in orthogonality of each axis. The dispersion of this variation is defined by the following equation (7).

(Equation 7)

(E) Let Δa ₁₁ be a positive constant sufficiently smaller than 1. In Expressions (4) to (7), a ₁₁ ^{(j) in} Expression
Is substituted for a ₁₁ ^(j) −Δa ₁₁ and a ₁₁ ^(j) + Δa ₁₁ , and the dispersion equation σ _V (j) ² | a ₁₁ ^(j) = a ₁₁ ^(j) + Δa ₁₁ and σ _V (j) ² | a ₁₁ ^(j) = a ₁₁ ^(j) −Δa ₁₁ is obtained.

(F) From the following equations (8) and (9),
∂σ _V (j) / ∂a ₁₁ and ∂ ² σ _V (j) / ∂a ₁₁ ² are calculated,
A ₁₁ ^{(j + 1)} is estimated by equation (10).

(Equation 8)

(Equation 9)

(Equation 10) K in the equation (10) is a constant of 0 <k <1 and is experimentally determined.

(G) a ₂₂ ^{(j + 1)} , a ₃₃ ^{(j + 1)} , a ₁₂ ^{(j + 1)} a ₁₃ ^{(j + 1) by the} same procedure as in equations (8) to (10 ^). , A ₂₃ ^{(j + 1)} V _xo ^{(j + 1)} , V _yo ^{(j + 1)} , and V _zo ^{(j + 1)} .

(H) Hereinafter, j = j + 1 and the variance
Steps (b) to (g) are repeated until σ _V (j) ² becomes sufficiently small. The finally obtained values are referred to as a ₁₁ , a ₂₂ , a ₃₃ ,
_{a 12, a 13, a 23} , V xo, V yo, the estimated value of V _zo.

The configuration of the magnetic survey device and the magnetic sensor device of the present invention is not limited to the search for the above-mentioned submarine cable, and those skilled in the art using this technology can use a submarine pipe or a small magnetic field on the ground surface. Needless to say, it can be used for exploration of metals and the like having the above.

[0039]

As described above, the magnetic exploration apparatus and its magnetic sensor according to the present invention are mounted on the earth and mount a magnetic sensor on a metal or magnetic substance which generates an extremely weak magnetic field. The influence of the magnetic field generated from the moving body is taken into the arithmetic unit (CPU) as a correction value in advance, and the position of the metal is determined based on the detection output corrected by the correction value at the time of actual measurement. In particular, there is an effect that when detecting a metal or a magnetic body having a weak magnetic field, extremely high accuracy and its position can be determined.

Further, the magnetic sensor device of the present invention enables high-accuracy measurement without fluctuation of the detected magnetic field by selecting the material and shape so that the influence of water pressure and geomagnetism is reduced, especially in the deep sea. There are advantages.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a magnetic exploration system for exploring a submarine cable using a three-axis orthogonal DC magnetic sensor of the present invention.

FIG. 2 shows a circuit block diagram for constructing a magnetic survey device of the present invention.

FIG. 3 is an exploded view showing an embodiment of a three-axis orthogonal DC magnetic sensor.

FIG. 4 is a graph showing actual fluctuations in the magnitude of the DC magnetic field depending on the orientation of the underwater vehicle and the magnitude of the DC magnetic field after removing the fluctuation.

FIG. 5 is an explanatory diagram when a state of a detected magnetic field is shown on a monitor screen.

FIG. 6 is a graph showing an absolute value of a DC magnetic field when a cable passing a current of 1 amperage traverses at a right angle.

FIG. 7 is an explanatory diagram for obtaining correction coefficients of magnetic sensors arranged in three axial directions.

[Explanation of symbols]

 Reference Signs List 10 mother ship 11 dither cable 12 underwater robot 15A, 15B magnetic sensor 52 magnetic detection unit 53 cylindrical container 54 pressure-resistant container 55 buffer member

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-6-102358 (JP, A) JP-A-62-148877 (JP, A) JP-A-55-35204 (JP, A) JP-A-55-35204 59352 (JP, A) JP-A-3-276002 (JP, A) JP-A-4-259872 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01V 3/08 G01R 33 / 02 G01R 33/04 G01V 3/165 B63C 11/48

Claims (6)

(57) [Claims] 1. A magnetic prospecting device for detecting a direct current magnetic field generated from a metal to be detected or the like, wherein three direct current magnetic sensors having sensitivity in only one specific axial direction are arranged so that their axes are orthogonal to each other. A three-axis orthogonal DC magnetic sensor device for measuring the absolute value of the DC magnetic field of two or more units is mounted on a moving object, and its output is converted into a digital signal by an A / D converter, and then an arithmetic processing circuit By correcting the deviation of the sensitivity of each DC magnetic sensor, the offset and the orthogonality of the three axes,
A magnetic surveying device characterized in that the absolute value of a DC magnetic field detected on the basis of the corrected data is displayed on a display, thereby detecting the presence of the metal to be searched or the like. 2. The underwater robot according to claim 1, wherein the metal to be searched is a submarine cable attached to the seabed, and the moving body is an underwater robot that can be controlled from a mother ship by a remote control system. 2. The magnetic prospecting device according to 1. 3. An absolute value output of a DC magnetic field of each of the DC magnetic sensors is obtained by preliminarily storing data of a magnetic field intensity distribution obtained by rotating the moving body 360 degrees in a horizontal direction in a memory of the arithmetic processing circuit, 2. The magnetic exploration apparatus according to claim 1, wherein the correction is performed based on the data read from the memory corresponding to the body orientation of the moving body. 4. A pressure-resistant container made of an insulating material, a cylindrical container made of quartz installed in the pressure-resistant container via a buffer member, and three DC magnetic sensors having sensitivity in only one axial direction. Are arranged so that the axes are orthogonal to each other, and a magnetic sensor body embedded in a cylindrical synthetic resin is provided together with the circuit board.The magnetic sensor body is inserted into the cylindrical container, and the inserted cylindrical container is A magnetic sensor device being inserted into the pressure-resistant container via the buffer member. 5. The magnetic sensor device according to claim 4, wherein each of the DC magnetic sensors is constituted by a flux gate type sensor. 6. The underwater connector for outputting an electric signal of the DC magnetic sensor and supplying power to the circuit board is attached to a side surface of the pressure vessel. Item 7. A magnetic sensor device according to Item 1.