Magnetometer circuitry for use in bore hole detection of AC magnetic fields
First Claim
1. Apparatus for locating subterranean electrically conductive anomalies, comprising:
- means for injecting current having a predetermined time-varying characteristic into the earth in the region of an anomaly to produce a corresponding current flow in the anomaly and to thereby produce a corresponding time-varying magnetic field surrounding the anomaly and superimposed on the ambient magnetic field;
a sonde for measuring the magnetic field near the anomaly, the sonde having a longitudinal axis and including(a) first and second fluxgate magnetometers each having a single sensor with an axis of sensitivity, the sensor axes being at right angles to each other to define an X axis sensor and a Y axis sensor, said X and Y sensor axes being perpendicular to said longitudinal axis,(b) oscillator means connected to drive said X and Y axis sensors,(c) X axis and Y axis detector and null circuit means connected to said X axis and Y axis sensors, respectively, to receive output signals from said sensors representing the X axis and Y axis components, respectively, of the total magnetic field at said sonde and to produce corresponding X axis and Y axis null feedback signals to said sensors, said feedback signals representing the X axis and Y axis components of said total magnetic field,(d) X axis and Y axis signal conditioning circuits responsive to said X axis and Y axis feedback signals respectively, for conditioning the time varying and the static components of the respective feedback signals, to produce corresponding composite modified field component signals,(e) transmitter circuit means for selecting and digitizing said X axis and Y axis composite modified field component signals and for transmitting said digitized signals to a remote location; and
(f) receiver means at said remote location responsive to said digitized signals for determining, from said signals representing said X axis and Y axis modified field components, the distance and direction to said anomaly from said sonde location.
1 Assignment
0 Petitions
Accused Products
Abstract
A system for measuring X and Y vector components of a composite magnetic field including static portions such as those produced by the earth'"'"'s magnetic field, and time varying portions such as those produced by current flowing in a target anomaly to thereby permit determination of the distance and direction from a sensor to the anomaly is disclosed. Highly sensitive fluxgate magnetometers sense total field X and Y axis vector components of the composite magnetic field of interest and produce output signals which are fed through corresponding detector and null circuits to produce total field signals corresponding to the components being measured. These total field component signals are fed through corresponding signal conditioning circuits to equalize the time varying and static field portions of the signal components. Thereafter, the X and Y axis equalized signals are supplied by way of a multiplexer and an analog to digital converter to suitable transmission circuitry which transmits the digital signals via a wireline to a receiver. At the receiver, the signals are decoded and supplied to a computer for deconvolving and for determination of the distance and direction to the anomaly from the sensor.
108 Citations
8 Claims
-
1. Apparatus for locating subterranean electrically conductive anomalies, comprising:
-
means for injecting current having a predetermined time-varying characteristic into the earth in the region of an anomaly to produce a corresponding current flow in the anomaly and to thereby produce a corresponding time-varying magnetic field surrounding the anomaly and superimposed on the ambient magnetic field; a sonde for measuring the magnetic field near the anomaly, the sonde having a longitudinal axis and including (a) first and second fluxgate magnetometers each having a single sensor with an axis of sensitivity, the sensor axes being at right angles to each other to define an X axis sensor and a Y axis sensor, said X and Y sensor axes being perpendicular to said longitudinal axis, (b) oscillator means connected to drive said X and Y axis sensors, (c) X axis and Y axis detector and null circuit means connected to said X axis and Y axis sensors, respectively, to receive output signals from said sensors representing the X axis and Y axis components, respectively, of the total magnetic field at said sonde and to produce corresponding X axis and Y axis null feedback signals to said sensors, said feedback signals representing the X axis and Y axis components of said total magnetic field, (d) X axis and Y axis signal conditioning circuits responsive to said X axis and Y axis feedback signals respectively, for conditioning the time varying and the static components of the respective feedback signals, to produce corresponding composite modified field component signals, (e) transmitter circuit means for selecting and digitizing said X axis and Y axis composite modified field component signals and for transmitting said digitized signals to a remote location; and (f) receiver means at said remote location responsive to said digitized signals for determining, from said signals representing said X axis and Y axis modified field components, the distance and direction to said anomaly from said sonde location. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
-
Specification