JPS5822712B2 - Electromagnetic underground metal pipe measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention generates an alternating magnetic field perpendicularly to metal conduits, cables, etc. (hereinafter simply referred to as buried conduits) buried underground from a transmitter. A metal device that measures the position and depth of buried pipes by passing a current through the pipe, using the ground as a conductor, and measuring the strength of the alternating magnetic field generated perpendicularly to the buried pipe using a receiver on the ground. The present invention relates to pipeline measuring instruments, and particularly to improvements in the detection section of the receiver that constitutes the measuring instruments.

As shown in FIG.
The maximum method is performed by setting the element coil 102 parallel to the magnetic field φ generated from the buried pipe 103, and the minimum method is performed by setting the element coil 102 perpendicular to the magnetic field φ from the buried pipe 103, as shown in FIG. It's being used.

The maximum method is to determine the maximum point of the element coil output e1 when the direction of the magnetic flux matches the direction of the element coil 101.
In contrast, the minimum method measures the minimum point of the element coil output e2 when the direction in the magnetic flux and the direction of the element coil 102 are perpendicular to the buried pipe 10.
3. However, when using the maximum method, the amount of change (degree of change) in the element coil output e1 on the buried pipe surface is smaller (slower) than that of the minimum method. Although there is a problem that the buried pipe position is difficult to detect, it has the feature that depth measurement on the buried pipe surface can be easily performed from the amount of change in output due to upward displacement of the element coil 101 position. , while when using the minimum method,
Since the amount of change in the output e2 of the element coil on the surface of the buried pipe is large, the position of the buried pipe can be detected more easily than the maximum method, but on the other hand, there is a problem in that the depth cannot be measured directly above the buried pipe.

That is, both the maximum method and the minimum method described above have advantages and disadvantages.

The present invention has been made in view of the above-mentioned problems, and aims to provide an improved electromagnetic underground metal pipe measuring instrument that can take advantage of the respective characteristics of the maximum method and the minimum method. be.

Hereinafter, illustrated embodiments embodying the present invention will be described in detail.

FIG. 1 shows an example of a detection section of a receiver constituting the measuring instrument of the present invention.

As shown in the figure, the two element coils 1 and 2 used for buried pipe measurement using the maximum method are arranged parallel to each other and are differentially connected, and the element coils 1 and 2 used for buried pipe measurement using the minimum method are arranged parallel to each other and differentially connected. The element coil 3 is located at an intermediate position on the inner cap of the pixel coils 1 and 2 for the maximum method, and is arranged so that its axis is perpendicular to the axis of the element coils 1 and 2 for the maximum method. ing.

The element coils 1 and 2 for the maximum method and the element coil 3 for the minimum method are respectively connected to the detection amplifier circuit 5 and the ground 6 via the changeover switch 4. Element coil 1 for maximum method by operation
, 2 and the minimum method element coil 3 are connected to the amplifier circuit 5.

As shown in FIG. 1, when the selector switch 4 is connected to the maximum method element coils 1 and 2, the minimum method element coil 3 is short-circuited (loop-connected) by the changeover switch 4. It is configured.

This embodiment is constructed as described above, and therefore, when measuring the position of the buried pipeline, the changeover switch 4 is set to the second position.
As shown in the figure, it is used by switching to the element coil 3 side for minimum method, and the element coil 3 is moved horizontally (
(for each receiver), the point where the element coil 3 intersects the magnetic field from the buried conduit with minimum sensitivity, that is, the minimum point of the element coil output, is detected as the point directly above the buried conduit.

be able to.

When measuring the depth of a buried pipeline, the changeover switch 4 is switched to the maximum method element coils 1 and 2 as shown in Fig. 1, and the entire detection section is moved upward a predetermined amount at a point directly above the buried pipeline. (Usually 30c1n.

The depth of the buried pipe can be measured by pulling up the pipe by a certain distance (set to 1) and directly reading the scale of the depth indicator at that time.

That is, in FIG. 5, when the current ■ is flowing through the buried pipe 103, the strength H of the magnetic field at a point h away from the buried pipe 103 can be determined by the Biot-Savart law, and the Since the voltage e1 generated across the element coil 1 is proportional to the strength of the magnetic field, the proportionality constant is expressed as follows.

If the distance between the element coils 1 and 20 is l, then the induced electromotive force in the element coil 2 at this time is e2.

Therefore, the output when differentially connected is the difference between el and e2, so let this be El. Next, calculate the differential coil output E2 when the element coils 1 and 2 are raised by a predetermined amount.

Assuming that the amount of lifting is l, as in the previous case, solving for the current I from equation (IX2), we get El,
Since E2 and 21j are known values, the distance between the element coil 1 and the buried pipe is determined, and the value of h is displayed on the scale of the depth indicator.

In this depth measurement, the present invention short-circuits the element coil 3 for the minimum method, but when the magnetic flux passing through the element coil 3 changes, a voltage is generated at both ends of the element coil 3. The voltage e follows Faraday's law and is expressed as follows, where e: induced electromotive force, N: number of coil turns, and φ: magnetic flux.

At this time, if both ends of the element coil 3 are short-circuited, a current flows due to the induced electromotive force e, but the direction of this current must flow in a direction that prevents changes in magnetic flux. is exactly opposite to the direction of the magnetic flux that initially penetrated the element coil 3.

As a result, the magnetic flux in the element coil 3 cancels each other out, and since this is a constant effect on changes in the magnetic flux generated from the buried pipe, when viewed in a steady state, the voltage in the element coil 3 also increases. This can be seen as a state in which no current is generated and no current flows, and an adverse effect on the maximum wide element coils 1 and 2 can be prevented.

Moreover, as a result of experiments, it was found that when the element coils 1, 2.3 for the maximum method and the minimum method are assembled together, the element coils 1, 2 for the maximum method when the element coil 3 for the minimum method is short-circuited. Assuming that the differential connection output E is 100%, the maximum modulus element coil 1 when the minimum modulus element coil 3 is released by turning off the switch 4 in this integrated state
. It has been found that the output E is the same as the output when it is removed.

In other words, this measuring device is equipped with element coils 1 and 2 for the maximum method and an element coil 3 for the minimum method in the detection section of the receiver, and can be used by appropriately switching between them with a changeover switch 4. Therefore, the features of the maximum method suitable for depth measurement and the minimum method suitable for position measurement can be fully utilized.

Therefore, when the element coils 1 and 2 for maximum method and the element coil for minimum method are combined, pixel element coils 1, 2 and 3
However, as mentioned above, when using the maximum method element coils 1 and 2, the minimum method element coil 3 is Since the structure is short-circuited by the changeover switch 4, this causes the element coils 1 and 2 for the maximum method to
The magnetic influence of the element coil 3 on Since the configuration is arranged perpendicular to the axis of the element coils 1 and 2 for the maximum method, this allows the element coil 1 and 2 for the maximum method to be There is no magnetic influence.

That is, this measuring device has a structure that can prevent mutual magnetic influence between the element coils 1 and 2 for the maximum method and the element coil 3 for the minimum method, so that the detection sensitivity is not impaired.

In this example, the two element coils 1゜2 are connected differentially, so that the measurement can be made from the buried pipe without being substantially disturbed by the external uniform magnetic field and the magnetic field from the transmitter. can detect circular magnetic fields.

As described in detail above, the present invention provides an element coil for the maximum method and an element coil for the minimum method in the detection section, and allows them to be used by switching between them as appropriate using a changeover switch. It is possible to effectively measure the position and depth of buried pipes by making full use of the features of each of the drawing methods, and it is still possible to effectively measure the position and depth of buried pipes. As long as the structure is such that the influence can be prevented, there is no risk of deterioration of detection sensitivity due to this, and it is useful for effective measurement.

[Brief explanation of the drawing]

1 and 2 are circuit diagrams showing one embodiment of the present invention,
FIGS. 3 and 4 are explanatory diagrams showing measurement modes using the maximum method and minimum method, and FIG. 5 is an explanatory diagram showing the depth measurement state of this embodiment. 1.2... Element coil for maximum method, 3... Element coil for minimum method, 4... Changeover switch, 5... Amplification circuit.

Claims (1)

[Claims] 1 Two maximum modulus element coils 1 arranged in parallel on the same plane with a predetermined interval and differentially connected to each other.
2, and one element coil 3 for the minimum method arranged so that the axis line is perpendicular to the center of the element coils 1 and 2, and the element coil 3 for the maximum method and the element coil 3 for the minimum method are arranged. The element coil 3 for the minimum method is connected to the amplifier circuit via a changeover switch 4, and the element coil 3 for the minimum method is switched when the changeover switch is connected to the element coils 1 and 2 for the maximum method. An electromagnetic underground metal conduit measuring device characterized in that it is configured to be short-circuited by a switch 4.