摘要:
A method is disclosed for locating a receiver in a borehole having a conductive liner by inducing an electromagnetic field from a transmitter in a first borehole, detecting at a first location by at least one receiver located in a second borehole having a conductive liner, a first electromagnetic field induced by the transmitter, detecting at a second location by the at least one receiver, a second electromagnetic field induced by the transmitter and calculating a set of geometry coordinates for the first location based on the first electromagnetic field and the second electromagnetic field.
摘要:
A metal detector having a plurality of phase delay discrimination regions with corresponding selectable exception spaces therein. A metal detector for indicating the presence of a metal target, comprising a transmitting module for transmitting a time-varying electromagnetic wave to the target, a receiving module for receiving said wave as modified by the target, an analyzing module for determining the phase delay of the modified said wave and providing a characterization to a user of the target based on said phase delay, said analyzing module being further adapted in a normal mode of operation of the metal detector to report said characterization to the user in a circumstance (a) wherein said phase delay exceeds a predetermined discrimination level and to not report said characterization to the user in a circumstance (b) wherein said phase delay does not exceed said discrimination level, and an exception space circuit cooperating with said analyzing module for comparing said phase delay with a limited range of one or more predetermined values for said phase delay and, in a first exception space mode of operation of the metal detector, causing said analyzing module to not report said characterization in said circumstance (a) when said range of values exceeds said discrimination level and, in a second exception space mode of operation of the metal detector, report said characterization in circumstance (b) wherein said range of values does not exceed said discrimination level, is provided.
摘要:
The invention relates to a metal detector with at least one driver circuit 2, at least one transmitter winding 4 having two external terminals 4a, b, and at least one receiver winding 5 having two external terminals 5a, b. The efficiency is increased in comparison to conventional metal detectors by providing at least one tap subdividing the transmitter winding 4, whereby a transformed electrical AC voltage is provided at the external terminals 4a, b of the transmitter winding 4 by the driver circuit via the tap 4c.
摘要:
Tracking a boring tool is performed within an underground region using a locating signal. The boring tool is moved through the ground during a series of distance movements such that potential movement of the boring tool during any one of the distance movements is less than a maximum movement value. A current positional relationship is determined for a current one of the distance movements based on: a last-determined positional relationship established for an immediately preceding one of the distance movements, certain orientation parameters, the maximum movement value and the determined signal strength of the locating signal in the current positional relationship. Target coordinates are accepted and a target position, based on the target coordinates, is included as part of the current positional relationship. The position of the target is unconstrained with respect to system geometry. Steering command features are provided along with steering warnings.
摘要:
A method and apparatus for distinguishing metal objects employing multiple frequency interrogation. In one aspect, the method includes interrogating a target with at least two frequencies, obtaining respective response signals for the two frequencies, resolving the response signals into at least respective resistive component portions, comparing the magnitudes of at least two of the resistive component portions, selecting one response signal from among the response signals based on the comparison, and characterizing the target with the selected response signal. In other aspects, the method includes obtaining response data by interrogating the target at at least two frequencies, normalizing the response data and comparing the normalized response data. A signal is provided indicating the extent of any disagreement in the normalized response data.
摘要:
An excavator vehicle has sensors thereon at different heights. Each sensor may have a coil which is generally horizontal and which detects the magnetic field generated by a current in a buried conductor. By detecting the relative magnitudes of the component of the field parallel to the ground, as detected by the sensors, it is possible to determine whether or not the excavator vehicle is proximate the buried conductor. A warning may be generated, or the excavating tool of the excavator vehicle controlled, to prevent the excavating tool damaging the buried conductor.
摘要:
A unique time-domain electromagnetic system and data processing technique which, using low frequency electromagnetic fields, can localize, in three-dimensions, the position of buried metallic objects is disclosed. The measurement system uses time-domain electromagnetic techniques on a scanning frame similar to a X-Y plotter. The system collects magnetic data over a large area above the buried object. The spatial information of the field detected on the ground is then processed with an unique nullnearfield holographicnull data processing method to reconstruct the field image of the buried object.
摘要:
An electromagnetic tomography system for determining properties of geological formation penetrated by at least one borehole lined with a conductive tubular includes a transmitter disposed in a first borehole and adapted to induce a magnetic field, a first receiver disposed in the first borehole and adapted to detect a magnetic field induced in the conductive tubular by the transmitter, and a second receiver adapted to detect a magnetic field induced in the geological formation by the transmitter. A method for determining a conductive tubular correction constant includes generating a magnetic field inside a representative piece of the conductive tubular, determining a first magnetic field amplitude inside the representative piece of the conductive tubular at a location proximate to a position of the generating a magnetic field, determining a second magnetic field amplitude outside the representative piece of the conductive tubular, and deriving the conductive tubular correction constant from a ratio of the first magnetic field amplitude and the second magnetic field amplitude.
摘要:
A conductivity meter for measuring conductivity of terrain, including a first transmitter coil, a signal generator connected to the first transmitter coil to supply a time-varying current thereto for inducing eddy currents in the terrain, a first receiver coil horizontally spaced from the first transmitter coil, a temperature sensing device for measuring temperature, and a signal processor, including a memory storing a plurality of temperature dependent correction values, for isolating from a signal received by the first receiver coil a secondary signal representative of a secondary magnetic field generated in the terrain by the eddy currents, and determining an apparent terrain conductivity based on the isolated secondary signal and a selected temperature dependent correction value selected from the stored temperature dependent correction values according to a measured temperature received from the temperature sensing device.
摘要:
A time-domain electromagnetic target discriminator (ETD) sensor system and method are provided capable of measuring a metal target's time decay response based on the physical parameters of the metal target and its environment and for identifying the metal target. The ETD sensor system includes a pulse transmitter connected to a receiver via a data acquisition and control system. The transmitter and receiver include coil configurations for placement in proximity to a visually obscured, e.g., buried, metal target (or underground void) for inducing eddy currents within the metal target. The ETD sensor system measures the eddy current time decay response of the metal target in order to perform target recognition and classification. The identification process entails comparing the metal target's (or, underground void or other object's) time decay response with a library of normalized object signatures, e.g., time decay responses and other characteristics.