Electricity: measuring and testing – Of geophysical surface or subsurface in situ – For small object detection or location
Patent
1984-03-09
1987-09-01
Strecker, Gerard R.
Electricity: measuring and testing
Of geophysical surface or subsurface in situ
For small object detection or location
G01V 311, G01B 714
Patent
active
046911650
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The subject matter of the present invention is a method and apparatus for determining the horizontal position and depth of metallic conductors located beneath ground level. According to the method provided by the invention, the electromagnetic field generated by an alternating current existing in such a buried metallic conductor is detected by two ferrite antennas, one vertically above the other. The horizontal position of the conductor and its depth are determined by means of the characteristics of the detected magnetic field. The apparatus according to the invention comprises a measuring receiver consisting of a transducer provided with an upper and a lower ferrite antenna to convert the strength of the magnetic field induced by the alternating current flowing in the metallic conductor into a voltage signal, a horizontal-position-locating unit, and a depth finder unit to determine the depth of said conductor. The method and apparatus corresponding to the present invention provides for locating underground metallic conductors faster and with a higher accuracy compared to the methods known heretofore and free of human errors.
BACKGROUND ART
Surveying and registering a densely located system of public utilities raises many problems. For example, with previous methods, determination of the horizontal position and depth of buried metallic conductors can only be accomplished with a relatively low accuracy, especially in a very "noisy" environment, i.e., in the vicinity of electrical power lines and equipment, e.g., tramway and trolley lines. The handling of known devices is sometimes difficult. Portable devices are not available; and the result of the measurements may be deteriorated by significant human errors.
A general method of locating metallic conductors is to indicate the variations of the vertical and/or horizontal components of the magnetic field generated by an alternating current existing in said conductor and detected by means of a suitable probe, usually a transducer comprising ferrite antennas. An alternating current of the required amplitude and frequency may be produced by a generator and applied to the conductor to be located at its available points. An alternating current may alternatively be induced in the conductor to be located. A common method is to connect only one pole of the generator to the conductor, the other pole being grounded.
The locating accomplished by the method described is based on the fact that if the conductor to be located is assumed to be an infinitely long straight wire, then a concentric magnetic field will exist around it. In the case of such a field pattern, the vertical and horizontal components of the magnetic field strength are equal if the wire is located at an angle of 45.degree. from the point of measurement. The position of the conductor can be determined using this fact. Theoretically, the horizontal position of the conductor can be established by detecting the maximum value of the horizontal component and the zero level of the vertical component. Both measurements are, however, uncertain; the measurement of the maximum value may be burdened by serious human errors, and measuring the zero value is illusory, especially in a noisy environment. A device has been developed by the United States company Metrotech that utilizes a microcomputer to realize the locating method describd, wherein the measuring process is based on a stored program.
Circuits have been developed to accomplish the method described above, and are shown in German Patent Specifications DE-PS Nos. 10 64 655, 25 28 511 and 20 37 865. The solution of particular partial problems are given in these Patent Specifications to increase the accuracy or stability of detection or to accomplish an energy saving construction of the generator (powering the generator from the conductor to be located is recommended by one of these specifications).
An apparatus is described in German Patent Specification No. 955 348 that comprises two coils arranged horizontally, one above the other, and in
REFERENCES:
patent: 3418572 (1968-12-01), Humphreys
patent: 3617865 (1971-11-01), Hakata
patent: 3893025 (1975-07-01), Humphreys
patent: 3988663 (1976-10-01), Slough et al.
patent: 4220913 (1980-09-01), Howell et al.
patent: 4387340 (1983-06-01), Peterman
LandOfFree
Method and apparatus including spaced antennas for determining t does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus including spaced antennas for determining t, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus including spaced antennas for determining t will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1267032