JPH04240585A - Buried object position search method and device - Google Patents

Abstract

PURPOSE:To exactly discriminate the buried position of a target buried object of a plurality of buried objects. CONSTITUTION:Alternating current is allowed to flow in a buried object 3 of a metal pipe and the like which is requested to detect a buried position to generate an alternating magnetic field, when a receiving coil is moved to a buried equivalent position of the buried object 3, induced current varied in accordance with both distance is detected, the detection of the fluctuation of a resonance point is performed when a resonance coil excited in the neighborhood of the resonance point is moved to buried equivalent position and the buried position of the buried object 3 from both detection information is discriminated.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a buried object position detection method and a buried object position detection apparatus for detecting the position of long buried objects such as metal pipes buried in walls, floors, etc.

0002

2. Description of the Related Art A method that has been commonly used to locate buried objects is a method that uses a device called an electromagnetic induction locator, which is composed of a transmitter and a receiver. The one shown in Fig. 4 is a method called the two-point method (loop method), in which the output of the transmitter 11 is connected to two exposed parts P and Q of the buried pipe 10 whose buried position is to be detected. A loop is formed and an alternating current of 100 KHz is applied. Then, an alternating magnetic field is generated around the buried pipe 10. On the ground surface, a detector 12 equipped with a receiving coil is moved along the ground near where a buried pipe is believed to be buried.

An induced current is generated in the receiving coil by the alternating magnetic field, and since the magnitude of this induced current is inversely proportional to the distance between the receiving coil and the buried pipe 10, it is largest right above the buried pipe 10. Therefore, if this induced current is processed by the receiver 13 and the detected value obtained is displayed and output, or if it is converted into sound and output from the speaker, the change will be detected in the buried pipe 1.
The buried position of 0 can be determined.

In addition to the two-point method mentioned above, there are also methods called one-point method and three-point method, which are based on the induction generated in the receiving coil by the alternating magnetic field generated around the buried pipe when an alternating current is passed through the buried pipe whose buried position is to be detected. This method is the same as the two-point method described above in that current is detected, and the only difference is in how the alternating current is passed.

[0005] There is also a method of detecting the position of a buried object, which uses a device called a radar locator shown in FIG. 5 to detect the buried position from the reflection of radio waves emitted near the buried pipe 10.

[0006]

[Problems to be Solved by the Invention] In the method using the electromagnetic induction type locator, the influence of the magnetic field generated by the lead wires 14 and 15 from the transmitter 11 to the exposed parts P and Q of the buried pipe 10 is large, and the buried pipe This caused a serious error in the position detection of 10. That is, as shown in FIG. 6, the original detection value distribution 16 due to the magnetic field generated in the buried pipe 10
The distribution 17 of detection values due to the magnetic field generated in the lead wires 14 and 15 is superimposed on the distribution 17, and the distribution of detection values obtained from the induced current actually generated in the receiving coil becomes like the broken line. As a result, the peak of the distribution occurs at a location shifted from directly above the buried pipe 10. In order to eliminate the influence of the magnetic field generated on the lead wires 14 and 15, the lead wires 14 and 1
If you try to move 5 to a far away place, the work efficiency will be poor.

Furthermore, in the method using a radar locator, it is not possible to distinguish the buried pipe whose buried position is to be detected from other pipes buried near the buried pipe. Therefore, it may be possible to use an electromagnetic induction locator and a radar locator together, but the radar locator is heavy and large, which poses problems in terms of portability and workability.

The present invention has been made in view of the above circumstances, and its purpose is to overcome the drawbacks of the buried object location detection method using an electromagnetic induction locator as described above without deteriorating workability. The purpose is to solve this problem and make it possible to accurately detect the position of a buried pipe.

[0009]

[Means for Solving the Problems] A feature of the buried object position detection method of the present invention is that an alternating current is passed through a long buried metal object whose buried position is to be detected to generate an alternating magnetic field. Detects the induced current that changes depending on the distance between the two when the receiving coil is moved at the buried position, and detects resonance when the resonant coil excited near the resonance point is moved at the buried position. The point is that a change in the point is detected and the buried position of the long buried object is determined from both detection information.

[0010] A feature of the buried object position detecting device used in the above buried object position detecting method is that the receiving coil and the resonant coil are integrally provided in the detecting section.

[0011]

[Operation] According to the buried object location detection method of the present invention, similarly to the conventional electromagnetic induction type locator described above, the detection data based on the induced current generated in the receiving coil is added to the detection data by the resonant coil. The position of the .

When the resonant coil excited near the resonance point approaches a buried metal object, its inductance and stray capacitance change, and as a result, the resonance point shifts. Therefore, as in the case of using an electromagnetic induction locator, the change in the resonance point when the resonant coil is moved at a position equivalent to the buried position is detected as a change in the ratio of the resonant voltage to the resonant current (resonant impedance) of the resonant coil. For example, changes in the distance to long buried objects can be seen. In the case of resonant impedance, it is lowest directly above the buried object (in the case of buried objects on the floor). However, if there are other buried pipes in the vicinity of the buried pipe whose buried position is to be detected, the change in resonance impedance becomes a distribution having a plurality of minimum points.

[0013] Therefore, the buried position of the buried object is determined by superimposing detection data based on the induced current generated in the receiving coil and detection data based on the change in the resonance point by the resonance coil.

Furthermore, since the receiving coil and the resonant coil are integrally provided in the detecting section of the buried object position detecting device, the above two detection data can be obtained by moving one detecting section.

[0015]

[Effects of the Invention] According to the buried object position detection method of the present invention,
The drawbacks of the buried object location detection method using an electromagnetic induction locator have been overcome by the detection method using a resonant coil, making it possible to accurately detect the location of buried pipes. Since the oscillation circuit for exciting the resonant coil and the circuit for detecting changes in the resonance point can be constructed with well-known simple circuits, they can also be incorporated into a detector of an electromagnetic induction locator. Therefore, the above effects can be obtained without deteriorating portability and workability.

[0016] Furthermore, since the receiving coil and the resonant coil are integrally provided in one detection part as a buried object position detection device, there is no need to prepare separate detection parts, and one detection part can be used in the above two ways. It can also be used to detect
Workability has further improved.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. First, the buried object position detecting device used in the buried object position detecting method of the present invention includes a sensor probe 1 as a detection section shown in FIG. 2, a receiver 2, and a transmitter. The transmitter is for passing an alternating current of 100 KHz through the buried pipe 3 whose buried position is to be detected, and is the same as the transmitter 11 in the conventional example shown in FIG. 4, and is omitted in FIG. 2.

The sensor probe 1 includes a receiving coil 1a for detecting the strength of the alternating magnetic field generated by the alternating current flowing through the buried pipe 3 as the magnitude of the induced current (hereinafter abbreviated as the induction method), and a resonance point. Resonant coil 1 for detecting the position of buried pipe 3 from changes in (hereinafter abbreviated as resonance method)
b is built-in. As shown in the figure, a differential coil is used as the receiving coil 1a in order to improve the detection accuracy. The lead wires of both coils 1a and 1b are connected to a receiver 2.

The receiver 2 has the function of a conventional electromagnetic induction locator receiver (13 in FIG. 4) with a detection circuit based on a resonance method added thereto. As shown in the block diagram of FIG. 3, a mode switch 25 that selectively switches between detection using the induction method and detection using the resonance method processes the signal from the receiving coil 1a and the signal from the resonance coil 1b. can be switched.

The differential voltage due to the induced current generated in the receiving coil 1a is inverted and amplified by the amplifier 20a, passes through a band-pass filter 20b, is detected by the detector 20c, and is integrated by the integrator 20d. A DC voltage corresponding to the strength of the magnetic field is applied to one contact 25a of the mode switch 25.

The resonant coil 1b is excited to a resonance point (around 20 MHz) by an oscillator 21a. The resonant voltage V1 is generated by the amplifier 22a, the bandpass filter 22b, the detector 22c, and the integrator 22d, similar to the differential voltage described above.
The signal is input to the divider 24 through . Similarly, the voltage V2 generated across the resonance current detection resistor 21b is also applied to the amplifier 23a.
, bandpass filter 23b, detector 23c, integrator 2
3d and is input to the divider 24. The divider 24 divides both input voltages, generates a DC voltage proportional to the reciprocal of the resonance impedance, and applies it to the other contact 25b of the mode switch 25.

One of the voltage signals selected by the mode switch 25 is converted into a digital value by the A/D converter 26 and inputted to the microcomputer 27. Based on the input value, the microcomputer 27 displays a bar graph on a level display 28a and a numerical value on a two-digit 7-segment display 28b. Also, buzzer 28c
The period of the intermittent sound is changed so that the higher the voltage signal, the shorter the period of the intermittent sound.

Next, a method for detecting the buried position of a buried pipe buried in a wall using the buried object position detecting device as described above will be explained. As shown in FIG. 2, a buried pipe 3 is buried inside a concrete wall 4, and a steel frame 5 is buried in parallel near it. Note that the buried pipe 3 and the steel frame 5 are buried in the vertical direction, and the figure is a plan view.

First, position detection is performed using the resonance method. The mode switch 25 of the receiver 2 is switched to the contact 25b side, and the sensor probe 1 is moved horizontally along the wall 4 in the vicinity of the buried position of the buried pipe 3. And buzzer 2
The position of the sensor probe 1 when the period of the intermittent sound 8c becomes the shortest or when the value displayed on the level indicator 28a and the 7-segment indicator 28b becomes the maximum is marked on the wall. Note that if there is no other buried metal object near the buried pipe 3, this position is one, and it can be determined that the buried pipe 3 is buried directly behind it.

In this example, there is a steel frame 5 near the buried pipe 3.
is buried, the change in the buzzer sound or the change in the displayed value has a distribution that takes maximum values directly in front of the buried pipe 3 and directly in front of the steel frame 5, as shown by the curve 8 in FIG. Therefore,
Since it is not possible to determine in which position the buried pipe 3 is buried by this alone, two positions where the maximum value is obtained are marked for the time being.

Next, the buried position is detected by the guidance method. As described in the conventional example, the oscillator output is connected to the exposed part of the buried pipe 3 and an alternating current of 100 KHz is applied to the buried pipe 3.
generates an alternating magnetic field around the The mode switch 25 of the receiver 2 is switched to the contact 25a side, and the sensor probe 1 is moved horizontally along the wall 4 in the same way as in the resonance method.

The distribution of the magnetic field strength on the surface of the wall 4 is shown in FIG.
It should look like a curve 7a shown in FIG. However, if there is a lead wire 6 from the oscillator to the exposed part of the buried pipe 3 nearby, it will be affected by the magnetic field 7b, so the peak will actually be slightly lower as shown in the superimposed distribution of these, that is, curve 7. This results in a distribution with a slightly deformed mountain shape. In any case,
It can be seen that the buried pipe 3 is buried behind this deformed mountain.

Therefore, by superimposing the detection results obtained by this guidance method, it is possible to determine which of the two marks obtained by the above-mentioned resonance method is where the buried pipe 3 is buried.

[0029] If there are two or more buried metal objects near the buried pipe 3, the maximum value of the displayed value based on the resonance method will be at three or more locations, but in this case, the induction method is similar to the above. By superimposing the detection results obtained by the method, it is possible to determine which position corresponding to the maximum value is the buried position of the buried pipe 3.

When detecting the position of a buried pipe using the resonance method, the method for detecting changes in the resonance point is not limited to the method of determining based on the ratio of resonance voltage to resonance current (resonance impedance), as described above. do not have. For example, both (V1
and V2) may be input to the phase discrimination circuit to detect a change in the resonance point from a change in the phase difference between the two. In addition, if the resonance point changes significantly, the oscillator 21 in FIG.
A change in the resonant frequency, that is, a change in the resonance point, may be directly detected by using a circuit configuration in which the oscillation frequency caused by a is made variable and the resonant frequency at which the resonant voltage V1 becomes the maximum can be measured. Moreover, the circuit configuration of the receiver 2 is not limited to the one that processes the detection signal into a digital signal and outputs it for display or output to a buzzer. It can also display it on a needle-type meter as an analog signal, or convert it to volume from a buzzer or speaker. You can also output it. Other configurations of the device can also be modified in various ways using well-known techniques.

[0031] Note that although reference numerals are written in the claims for convenience of comparison with the drawings, the present invention is not limited to the structure shown in the accompanying drawings.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a buried object position detection method according to an embodiment of the present invention.

[Figure 2] Schematic diagram showing part of the device used in the buried object location detection method and its operation

[Figure 3] Circuit block diagram of the receiver of the buried object location detection device

[Figure 4] Schematic diagram of a buried object location detection method using a conventional electromagnetic induction locator

[Figure 5] Schematic diagram of a buried object location detection method using a conventional radar locator

[Figure 6] An explanatory diagram of a buried object location detection method using a conventional electromagnetic induction locator

[Explanation of symbols]

1 Detection part 1a Receiving coil 1b Resonance coil 3. Long buried objects

Claims (2)

[Claims] 1. An alternating current is passed through a metal long buried object (3) whose buried position is to be detected to generate an alternating magnetic field, and a receiving coil (1a
) is moved, an induced current that changes depending on the distance between the two is detected, and the resonance point changes when the resonant coil (1b) excited near the resonance point is moved at the buried position. is detected, and the long buried object (3
) is a buried object location detection method that determines the buried location of objects. 2. A buried object position detecting device used in the buried object position detecting method according to claim 1, comprising: a detecting section (1);
) includes the receiving coil (1a) and the resonant coil (1b).
) is an integrated buried object location detection device.