JPH10213618A - Wiring path probing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wiring path probing device which is comprised of a transmitter that supplies a current having a predetermined frequency to a wiring path and a receiver for probing a target wiring path by detecting a magnetic flux generated on the wiring path by virtue of the current supplied by the transmitter. SOLUTION: A receiver 1 detects a magnetic flux generated on a wiring path by virtue of current supplied by a transmitter. A probing face 2b to be opposed to the wiring path is provided to one end portion 2a in the longitudinal direction of a body 2. In the vicinity of the probing face 2b in the inner section of the body 2, probing coils L1 , L2 are disposed to be inclined at roughly the same angle in the different directions with respect to the probing face 2b and an probing coil L3 for detecting a magnetic flux which is parallel to the probing face 2b is disposed in roughly parallel to the probing face 2b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of applying a current having a frequency different from the frequency of a current normally flowing in a wiring path to a wiring path, and searching for this current on the switch side to determine the current of the wiring path. The present invention relates to a wiring path detecting device for detecting whether or not the wiring path is connected to a switch.

[0002]

2. Description of the Related Art Conventionally, as a wiring path exploration apparatus of this type, a transmitter for applying a current having a predetermined frequency different from the frequency of a current normally flowing in a wiring path, and a current generated by a current applied from the transmitter are used. And a receiver for detecting the magnetic flux that flows.A search surface facing the wiring path is provided at the tip of the receiver, and in the vicinity of the search surface of the receiver body, in a direction parallel to the search surface. One exploration coil was provided.

Here, a magnetic flux can be generated in the vicinity of the wiring path by applying a current from the transmitter to the wiring path, and a voltage corresponding to the magnetic flux can be generated by adjusting the search coil to the direction of the magnetic flux. Since it is induced in the search coil,
The target wiring path can be searched.

[0004]

In the wiring path exploration apparatus having the above structure, when the wiring path is a one-sided conductor and a circumferential magnetic flux centering on the wiring path is formed, the detection surface of the receiver is formed on the detection surface of the receiver. Since a magnetic flux in a substantially parallel direction is generated, the wiring path can be searched, but when the wiring path is a reciprocating conductor, a magnetic flux in a direction substantially orthogonal to the detection surface is generated at a substantially intermediate position of the reciprocating conductor. There is a problem that almost no voltage is induced in the search coil arranged in parallel with the search surface, and it is difficult to search for a wiring path.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a wiring path searching apparatus capable of reliably detecting a wiring path even when the wiring path is a reciprocating conductor. Is to provide. A second object of the present invention is to provide a wiring path exploration apparatus with improved operability in addition to the object of the first invention.

A third object of the present invention is to provide, in addition to the first object of the present invention, a wiring path exploration apparatus having improved detection sensitivity.

[0007]

In order to achieve the above object, according to the present invention, a transmitter for applying a current of a predetermined frequency to a wiring path, and a magnetic flux generated in the wiring path by the current of a predetermined frequency. And a receiver for detecting the target wiring path and detecting the wiring path, a search surface facing the wiring path is provided at the tip of the receiver main body, and the vicinity of the search surface inside the receiver main body. In addition, the first and second search coils are arranged at substantially the same inclination angle with respect to the search surface in different directions, and the third search coil is provided substantially parallel to the search surface. A switching means for switching and outputting a vector sum or a vector difference of magnetic flux vectors in the coil axis direction detected by the first and second search coils and a magnetic flux detected by the third search coil; To detect the magnetic flux based on Runode, by switching the switching means, it is possible to detect the both the parallel magnetic flux and magnetic flux perpendicular with respect to exploration surface.

According to a second aspect of the present invention, a transmitter for applying a current of a predetermined frequency to a wiring path, and a receiver for detecting a magnetic flux generated in the wiring path by the current of the predetermined frequency and searching for a target wiring path. In the wiring path exploration apparatus, a search surface facing the wiring path is provided at the tip of the receiver main body, and the first and second search coils are provided near the search surface inside the receiver main body. A third search coil is disposed substantially in parallel to the search surface at substantially the same tilt angle and in a different direction, and a coil axis detected by the first and second search coils is provided. Comparing means for comparing the magnitude of the vector sum or vector difference of the magnetic flux vectors in the directions with the magnitude of the magnetic flux detected by the third search coil, and the output of the first and second search coils based on the comparison result of the comparison means. And the third probe coil Among them, the display means for displaying the strength of the magnetic flux based on the larger output is provided, so that both the magnetic flux parallel to and perpendicular to the search surface are detected without performing a switching operation or the like. be able to.

According to a third aspect of the present invention, in the first or second aspect of the present invention, the inclination angles of the first and second search coils with respect to the search surface are about 30 ° or more and less than about 90 °. Compared to a case where one search coil is arranged vertically, the first and second search coils together have a size of about 1 to 2 in total.
Doubled magnetic flux can be detected.

[0010]

Embodiments of the present invention will be described with reference to the drawings. (Embodiment 1) A wiring path exploration apparatus according to the present embodiment is configured such that a transmitter for applying a current having a predetermined frequency different from the frequency of a current normally flowing in a wiring path, and a magnetic flux generated by the current are detected. And a receiver for searching for a target wiring path.

As shown in FIG. 1, the receiver 1 has a main body 2 formed in a substantially rectangular parallelepiped shape, and at one end 2a in the longitudinal direction of the main body 2, a search surface 2b facing the wiring path is provided. The first and second search coils L ₁ and L 2 for detecting magnetic flux generated in the wiring path are formed near the search surface 2 b in the main body 2.
L ₂ and the third search coil L ₃ is arranged. The search coils L ₁ and L ₂ are disposed at substantially the same inclination angle with respect to the search surface ₂ b and in different directions, and the search coil L ₃ is disposed in a direction substantially parallel to the search surface 2 b. Will be arranged.

[0012] On the front surface of the main body 2, the light emitting diode LD ₁ for checking voltage of the battery, exploration coil L _1, L
Buzzer Bz serving display means the volume is changed in accordance with the magnitude of the magnetic flux detected by the _two or probing coil L _3, depending on the magnitude of the magnetic flux detected by the search coil L _1, L ₂ or search coil L ₃ The light emitting diodes LD _{2 to} LD _{6 as} display means for changing the number of lighting are provided.
On one side of the power switch S ₁ is, on the other side switching means serving switch S ₂ for switching the operation of the arithmetic circuit described later are disposed.

Further, as shown in FIG. 4, includes a transmitter 10 is a connector 12 projecting from the side surface of the main body 11, and a light emitting diode LD ₇ for operating the display provided on the front surface of the main body 11, the connector 12 and a wiring path are connected by a cable (not shown), a current of a predetermined frequency is applied to the wiring path from the transmitter 10 via the cable, and a magnetic flux due to this current is generated in the wiring path.

The circuit configuration of the receiver 1 will be described with reference to the circuit diagram shown in FIG. A battery (not shown) is connected between the terminals t ₁ and t ₂ , and the power supply circuit 4 uses the battery connected via the power switch S ₁ as a power supply to supply power for operation to each unit. Further, a light emitting diode LD ₁ for voltage check, a resistor R ₁₅ and a zener diode ZD ₁
Series circuit of the terminal t through the power switch S _1
1, is connected between t _2, when turned on the power switch S _1, if the voltage of the battery is greater than the Zener voltage of the Zener diode ZD _1, current flows through the light emitting diodes LD _1, the battery voltage is below a predetermined value It also displays that it is large.

The arithmetic circuit 5 obtains a vector difference between the magnetic flux vectors detected by the search coils L ₁ and L ₂ , respectively, and calculates a voltage according to the vector difference or the magnitude of the magnetic flux detected by the search coil L _3. 6 and an amplifier circuit 7. Then, the level discriminating circuit 6 turns on the five light emitting diodes LD _{2 to} LD ₆ based on the output of the arithmetic circuit 5, and determines the magnitude of the magnetic flux detected by the search coils L ₁ and L ₂ or the search coil L _3. Are displayed in five stages, for example.
Further, the amplification circuit 7 amplifies the output of the arithmetic circuit 5 and sounds the buzzer Bz at a volume according to the magnitude of the magnetic flux. Thus, where the magnetic flux detected by the search coil L _1, L ₂ or search coil L ₃ is the largest, since the volume of the lighting count and the buzzer Bz of the light emitting diode LD ₂ to Ld ₆ is maximum, the wiring of interest The road can be detected. Note that the search coils L ₁ and L ₂ or the search coils L ₃
Instead of changing the volume of the buzzer Bz in accordance with the magnitude of the magnetic flux detected by the buzzer, the level of the sound of the buzzer Bz may be changed.

By the way, the arithmetic circuit 5, as shown in FIG. 3, exploration coil L via the switch S ₂ between the output terminals
_1, a series circuit of L _2, and search coil L ₃ are connected in parallel, exploration coil L _1, L ₂ is the winding direction of the coil is connected in reverse. By switching the switch S ₂ , _one of the vector difference between the magnetic flux vectors detected by the search coils L ₁ and L ₂ and the magnetic flux detected by the search coil L ₃ is selected, and the output of the arithmetic circuit 5 is selected. And

Here, as shown in FIG. 5, when the wiring path 20 connected to the switch 21 is a one-sided conductor, and a current flows through the wiring path 20 from the front side to the back side of the drawing, the wiring path 20 Around the circumference, a clockwise circumferential magnetic flux 30 centered on the wiring path 20 is generated, so that a magnetic flux (arrow A) in a direction substantially parallel to the search surface 2b is generated near the search surface 2b,
Voltage corresponding to the magnitude of the magnetic flux is induced in the exploration surface 2b and exploration coil L ₃ which substantially disposed parallel to.

On the other hand, as shown in FIG.
The two wiring paths 20a and 20b connected to 1 are reciprocating conductors, and a current flows from one side of the paper to the other side of the paper in one wiring path 20a, and flows from the other side of the paper to the other side in the other wiring path 20b. When a current flows, the wiring path 20
a, 20b, the wiring paths 20a, 20b
b, a clockwise circumferential magnetic flux 30a centered on the wiring path 20a and a counterclockwise circumferential magnetic flux 30b centered on the wiring path 20b are generated.
At a substantially intermediate position between 0a and 20b, a magnetic flux [arrow B pointing downward in FIG. 6A] is generated in a direction substantially perpendicular to the search surface 2b.

[0019] At this time, as shown in FIG. 6 (b), search coil L ₁ flux vector detected by v ₂ has a terminal a from the terminal b exploration coil L ₁ (the winding end of the coil)
(The start of coil winding)
Detected by the probe coil L ₂ magnetic flux vector (-v
₃₎ exploration coil L ₂ of the terminal c (winding end of the coil)
From the magnetic flux vector v ₂ , (−v ₃ ), that is, the vector difference between the magnetic flux vectors v ₂ , v ₃ , Magnetic flux in a direction perpendicular to the search surface 2b can be detected. That is, the search coils L ₁ and L ₂
Are connected in series with their winding directions reversed, the voltages induced in the search coils L ₁ and L ₂ by the magnetic flux vectors v ₂ and v ₃ have the same polarity. Therefore, it is possible to increase the output of the arithmetic circuit 5 by adding the voltages induced in the two search coils L ₁ and L ₂ by the vector components of the magnetic flux vectors v ₂ and v _{3 in} the direction orthogonal to the search surface 2b. it can.

[0020] Thus, if the magnetic flux of the exploration surface 2b parallel direction is generated by switching the switch S ₂ exploration coil L ₃ side detects a magnetic flux of exploration surface 2b in a direction parallel exploration If vertical direction of the magnetic flux on the surface 2b occurs, it switches the switch S ₂ exploration coil L _1, L ₂ side, seeking vector difference of the flux vector detected by both probes coils L _1, L _2, since detecting the magnetic flux in the direction perpendicular to the exploration surface 2b, by switching the switch S _2, it is possible to detect both a magnetic flux perpendicular to the direction of magnetic flux in a direction parallel with respect to exploration surface 2b.

In this embodiment, the winding directions of the coils are mutually
Search coil L ₁, L_TwoConnected in series
And search coil L₁, L_TwoOf the magnetic flux vector detected by
By determining the difference between the vectors,
Direct magnetic flux is detected, but the winding direction of the coil is
Search coil L so that it is in the same direction₁, L_TwoConnected in series
And search coil L₁, L_TwoOf the magnetic flux vector detected by
By determining the vector sum, the probe surface 2b
A magnetic flux in a straight direction may be detected.

Here, the arithmetic circuit 5 will be described with reference to a specific circuit diagram shown in FIG. The exploration coil L ₁ and capacitor C ₁ and resistor R ₁ is connected in parallel, exploration coil L
₁ , a capacitor C ₁ and a resistor R ₁ constitute a resonance circuit. The resonance frequency of the resonance circuit substantially matches the frequency of the current applied to the wiring path by the transmitter 10,
Other frequency components are attenuated.

The search coil L_TwoHas a capacitor C_Two
And resistance R_TwoAre connected in parallel, and the search coil L_Two,
Capacitor C_TwoAnd resistance R_TwoForm a resonant circuit,
It has a similar function. Here, the subtractor 5a operates
Amplifier OP₁And resistance R_Three~ R₆Consists of Operation
Amplifier OP₁The non-inverting input terminal of_ThreeExploring through
Inspection coil L₁Output voltage V₁Is input and the operational amplifier O
P₁The inverting input terminal of_FiveThrough the search coil L
_TwoOutput voltage V_TwoIs entered. And the operational amplifier O
P₁Is the voltage V₁And gain [R_Four(R_Five+ R₆) / ｛R
_Five(R_Three+ R_Four)｝], The voltage V_TwoGay
(R₆/ R_FiveOutput the result of subtracting the value multiplied by
You. The resistance R_Three~ R₆If all resistance values are equal,
The output of the subtractor 5a is (V_Two-V ₁).

The amplifier circuit 5b includes an operational amplifier OP ₂
And the resistors R ₇ and R _8, and the operational amplifier OP
₂ gain voltage across the probe coil L ₃ (-R ₈ /
R ₇ ) is output. Then, the subtracter 5a and the output of the amplifier circuit 5b via the switch S ₂ output terminal t
₃ are connected to, by switching the switch S _2, of the output of the subtractor 5a or amplifier circuit 5b, it is possible to output either the output from the output terminal t _3. Therefore, when detecting the magnetic flux of the exploration surface 2b perpendicular direction switches the switch S ₂ to the subtractor 5a side,
When detecting the magnetic flux of the exploration surface 2b and parallel direction by switching the switch S ₂ to the amplifier circuit 5b side,
Both the magnetic flux in the direction parallel to the search surface 2b and the magnetic flux in the direction perpendicular to the search surface 2b can be detected. (Embodiment 2) FIG. 8A is a front view of a receiver of the wiring path exploration apparatus of the present embodiment, FIG. 8B is a side view of the receiver, and FIG. 9 is a circuit diagram of an arithmetic circuit.

FIG. 8A shows a receiver 1 according to this embodiment.
(B), since except that the switch S ₂ is not provided is the same as the receiver 1 shown in FIG. 1, the same symbols are assigned to the same components and description thereof will not be repeated .
The circuit configuration of the arithmetic circuit 5 will be described with reference to the circuit diagram of FIG. The search coils L ₁ and L ₂ are connected in series with the winding direction being reversed, and the search coils L connected in series
_1, L ₂ and capacitor C ₃ and resistor R ₉ are connected in parallel, exploration coil L _1, a series circuit of L _2, a capacitor C ₃
And the resonance circuit is composed of resistor R _9. The resonance frequency of the resonance circuit is set to be substantially the same as the frequency of the current applied to the wiring path by the transmitter 10, and other frequency components are attenuated.

The amplifier circuit 5c and the operational amplifier OP ₁ resistor R
It is composed of ₁₀ to R _12, and outputs a value obtained by multiplying the exploration output voltage of the coil L _1, L ₂ gain (-R ₁₁ / R _10). Buffer circuit 5d includes a diode D _1, the output terminal and the inverting input terminal is composed of an operational amplifier OP ₃ connected via a diode D _1, the operational amplifier OP _3, the amplification circuit is input to the non-inverting input terminal 5c output voltage
Output from the output terminal with the same value.

Further exploration a coil L ₃ and capacitor C ₄ and a resistor R ₁₃ in parallel are connected exploration coil L _3, the resonant circuit consists of capacitor C ₄ and a resistor R _13.
Similarly, the resonance frequency of the resonance circuit is set to be substantially the same as the frequency of the current applied by the transmitter 10, and other frequency components are attenuated. Amplification circuit 5b and the operational amplifier OP ₂ resistors R _7, R _8, R ₁₄
Consists, in the voltage across the probe coil L ₃ Gain (-
R ₈ / R ₇ ) is output. Buffer circuit 5e
Includes a diode D _2, the output terminal and the inverting input terminal is composed of an operational amplifier OP ₄ connected via the diode D _2, the operational amplifier OP ₄ are the amplification circuit 5b that is input to the non-inverting input terminal and an output The voltage is output from the output terminal as it is.

Then, in the comparison circuit 5f as the comparison means,
Buffer circuit 5d, the output of 5e is connected to the output terminal t ₃ together, the outputs of the buffer circuit 5d, 5e, the output of the larger is outputted to the output terminal t _3. That is,
When detecting the magnetic flux of the exploration surface 2b perpendicular direction, exploration coil L ₃ can not hardly detecting the magnetic flux, the output of the buffer circuit 5e becomes substantially 0V, exploration coil L _1,
The output of the buffer circuit 5d corresponding to the vector difference of the detected magnetic flux vector by L ₂ is outputted to the output terminal t _3. On the other hand, when the magnetic flux in the direction parallel to the search surface 2b is detected, the voltages induced in the search coils L ₁ and L ₂ cancel each other out, so that the voltage according to the magnitude of the magnetic flux detected by the search coil L ₃ is determined. The output of buffer circuit 5e is output terminal t
Output to ₃ .

As described above, since the comparison circuit 5f selects and outputs the larger value of the vector difference between the search coils L ₁ and L ₂ and the output of the search coil L ₃ , the switch and the like are switched. Without using the switching operation, the magnetic flux in the direction parallel to the search surface 2b and the magnetic flux in the direction perpendicular to the search surface 2b can be detected, and the operability of the receiver 1 is improved. FIG.
As shown in, the switch S ₂ in the arithmetic circuit 5 of FIG. 7
Instead, the same effect as in the present embodiment can be obtained by providing a comparison circuit 5f at the next stage of the subtractor 5a and the amplification circuit 5b. Here, the same components as those in the circuits of FIGS. 7 and 9 are denoted by the same reference numerals, and description thereof will be omitted.

The configuration other than the arithmetic circuit 5 is the same as that of the first embodiment.
Therefore, the description is omitted. (Embodiment 3) In this embodiment, as shown in FIGS. 11A and 11B, the search coils L ₁ and L ₂ are substantially moved relative to the search surface 2b in the wiring path search device of Embodiment 1 or 2. 30
It is arranged to be inclined in different directions at an inclination angle of °.

Here, in the direction perpendicular to the search surface 2b,
When a magnetic flux is generated, the search coil L ₁, L_TwoBy husband
Of the magnetic flux vector detected in the direction perpendicular to the search surface 2b
The magnitude of the vector component is as follows.
On the other hand, it is approximately (1/2) times that of the case where it is arranged vertically. I
Therefore, the search coil L₁, L_TwoFlux vector detected by
If one takes the vector difference between the two, one coil will be
Detects magnetic flux of almost the same size as when placed perpendicular to
can do.

[0032] In Thus, exploration coil L _1, L ₂ exploration surface 2
Assuming that the inclination angle with respect to b is approximately 30 ° or more and less than approximately 90 °, the magnitude of the vector component of the magnetic flux vector detected by the search coils L ₁ and L _{2 in the} direction perpendicular to the search surface 2b is one. This is approximately (1/2) times or more and less than 1 time when the coil is arranged perpendicular to the search surface 2b. Therefore, if the vector difference between the magnetic flux vectors detected by the search coils L ₁ and L ₂ is calculated, the magnetic flux having a magnitude approximately 1 to 2 times that of a case where one coil is arranged perpendicular to the search surface 2 b is obtained. Can be detected, and the detection sensitivity of the magnetic flux can be increased.

[0033] Note that the configuration other than the search coil L _1, L ₂ are the same as in Embodiment 1 or 2, and a description thereof will be omitted.

[0034]

As described above, an object of the present invention is to provide a transmitter for applying a current of a predetermined frequency to a wiring path and a magnetic flux generated in the wiring path by the current of a predetermined frequency. In a wiring path exploration apparatus comprising a receiver for exploring a wiring path, a search surface facing the wiring path is provided at a front end portion of the receiver main body, and a first surface is provided near the search surface inside the receiver main body.
And the second search coil is arranged to be inclined in different directions at substantially the same inclination angle with respect to the search surface, and the third search coil is arranged substantially parallel to the search surface, Switching means for switching and outputting a vector sum or a vector difference of magnetic flux vectors in the coil axis direction detected by the second search coil and a magnetic flux detected by the third search coil;
The magnetic flux is detected based on the output of the switching means, and by switching the switching means, both the magnetic flux parallel to the search surface and the magnetic flux perpendicular to the search surface can be detected. There is an effect that a road can be detected.

According to a second aspect of the present invention, there is provided a transmitter for applying a current of a predetermined frequency to a wiring path, and a receiver for detecting a magnetic flux generated in the wiring path by the current of the predetermined frequency and searching for a target wiring path. In the wiring path exploration device composed of
At the end of the receiver body, a search surface facing the wiring path is provided,
The first and second search coils are arranged near the search surface inside the receiver body in such a manner that the first and second search coils are inclined at substantially the same inclination angle in different directions with respect to the search surface, and the third search coil is mounted on the search surface. And the magnitude of the vector sum or vector difference of the magnetic flux vectors in the coil axis direction detected by the first and second search coils is compared with the magnitude of the magnetic flux detected by the third search coil. And a display means for displaying the strength of the magnetic flux based on the larger one of the output of the first and second search coils and the output of the third search coil based on the comparison result of the comparison means. Since it is provided, it is possible to detect both a magnetic flux parallel to the search surface and a magnetic flux perpendicular to the search surface without performing a switching operation or the like, and there is an effect that operability is improved.

According to a third aspect of the present invention, the inclination angles of the first and second search coils with respect to the search surface are approximately 30 ° or more and approximately 90 °.
As compared with the case where one search coil is arranged perpendicular to the search surface, the first and second search coils can detect approximately 1-2 times the total magnetic flux, There is an effect that the detection sensitivity of the receiver can be increased.

[Brief description of the drawings]

FIG. 1 shows a receiver according to a first embodiment, where (a) is a front view,
(B) is a side view.

FIG. 2 is a circuit diagram of the receiver of the above.

FIG. 3 is a circuit diagram showing an arithmetic circuit of the receiver of the above.

FIG. 4 shows the transmitter of the above, (a) is a front view, (b)
Is a side view.

FIG. 5 is an explanatory diagram for explaining the operation of the above receiver.

FIGS. 6A and 6B are explanatory diagrams illustrating another operation of the above receiver.

FIG. 7 is a specific circuit diagram showing an arithmetic circuit of the receiver of the above.

FIG. 8 shows a receiver according to the second embodiment, where (a) is a front view,
(B) is a side view.

FIG. 9 is a circuit diagram showing an arithmetic circuit of the receiver of the above.

FIG. 10 is a circuit diagram showing another arithmetic circuit of the above receiver.

FIG. 11 (a) is an arrangement diagram illustrating an arrangement of a search coil of a receiver according to a third embodiment. (B) It is explanatory drawing explaining operation | movement of a receiver same as the above.

[Explanation of symbols]

1 receiver 2 body 2a end 2b exploration surface L _1, L _2, L ₃ exploration coil

Claims (3)

[Claims] 1. A transmitter for applying a current of a predetermined frequency to a wiring path, and a receiver for detecting a magnetic flux generated in the wiring path by the current of the predetermined frequency and searching for a target wiring path. A search surface facing the wiring path is provided at a distal end portion of a receiver main body, and first and second search coils are connected to the search surface in the vicinity of the search surface inside the receiver main body. And a third search coil is disposed substantially in parallel to the search surface at substantially the same tilt angle with respect to the first and second search coils.
Switching means for switching and outputting the vector sum or vector difference of the magnetic flux vectors in the coil axis direction detected by the search coil and the magnetic flux detected by the third search coil, and the magnetic flux based on the output of the switching means. A wiring path exploration device characterized by detecting the following. 2. A transmitter for applying a current of a predetermined frequency to a wiring path, and a receiver for detecting a magnetic flux generated in the wiring path by the current of the predetermined frequency and searching for a target wiring path. A search surface facing the wiring path is provided at a distal end portion of a receiver main body, and first and second search coils are connected to the search surface in the vicinity of the search surface inside the receiver main body. And a third search coil is disposed substantially in parallel to the search surface at substantially the same tilt angle with respect to the first and second search coils.
Comparison means for comparing the magnitude of the vector sum or the vector difference of the magnetic flux vectors in the coil axis direction detected by the search coil with the magnitude of the magnetic flux detected by the third search coil, and a comparison result of the comparison means: The first and second
And a display means for displaying the strength of the magnetic flux based on the larger one of the output of the search coil and the output of the third search coil. 3. The apparatus according to claim 1, wherein an inclination angle of the first and second search coils with respect to the search surface is about 30 ° or more and less than about 90 °.