Integrated capacitive sensor system for the measurement of resistivity and dielectric constant in geophysical, environmental, groundwater and related applications
First Claim
1. A capacitive sensor system housed in a sealed tubular pressure-proof housing for the characterization of the geological properties of material intersected by boreholes, comprising:
- a capacitive array;
an oscillator coupled to the capacitive array and having a frequency of oscillation that is a function of the resistivity and dielectric constant of the material intersected by the electric field generated by the capacitive array; and
wherein the capacitive array comprises a plurality of parallel conductors arranged around a perimeter with alternate conductors connected to be driven by differing voltage potentials so that fringe electric fields from the capacitive array intersect the material when the sensor is activated in the borehole.
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Abstract
The invention relates to a capacitive sensor system for measuring environmental parameters by activating a capacitive array and causing fringe electric fields to intersect the surrounding environment. An oscillator is coupled to the capacitive array and the frequency of oscillation depends upon the capacitance of the array, which represents an environmental parameter. The sensor is suitable for measuring resistivity and dielectric constant parameters in geophysical, environmental, hydro-geological and related applications. The conductors of the capacitive array can be arranged around a perimeter for use, for example, in a borehole or the conductors can be arranged in the same plane for use, for example, beneath a raft in shallow water. In the situation where the boreholes are fluid-filled, there are economic and technical advantages in using the metal plugs (normally used to seal the probe housings at each end), as the capacitive array in galvanic contact with the fluid.
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Citations
15 Claims
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1. A capacitive sensor system housed in a sealed tubular pressure-proof housing for the characterization of the geological properties of material intersected by boreholes, comprising:
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a capacitive array; an oscillator coupled to the capacitive array and having a frequency of oscillation that is a function of the resistivity and dielectric constant of the material intersected by the electric field generated by the capacitive array; and wherein the capacitive array comprises a plurality of parallel conductors arranged around a perimeter with alternate conductors connected to be driven by differing voltage potentials so that fringe electric fields from the capacitive array intersect the material when the sensor is activated in the borehole. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A capacitive sensor system housed in a sealed tubular pressure-proof housing for the characterization of the geological properties of material intersected by boreholes, comprising:
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a capacitive array; an oscillator coupled to the capacitive array and having a frequency of oscillation that is a function of the resistivity and dielectric constant of the material intersected by the electric field generated by the capacitive array; wherein the capacitive array comprises a fixed capacitor; and end metal plugs enclosing the housing, one of the end metal plugs being electrically connected to a local ground of the oscillator and another of the end metal plugs being electrically connected to the fixed capacitor. - View Dependent Claims (9, 10, 11, 12, 13)
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14. A capacitive sensor system, comprising:
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a planar capacitive array having a plurality of parallel conductors arranged in the same plane, alternate conductors connected to be driven by differing voltage potentials; an oscillator having a frequency of oscillation that is a function of the capacitance of the capacitive array so that fringe electric fields from the capacitive array intersect the surrounding environment when the planar capacitive array is activated by the oscillator; at least one resistor bridging the capacitive array to the output of the oscillator; and an isolated power supply for the oscillator circuit; wherein the capacitance is representative of an environmental parameter. - View Dependent Claims (15)
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Specification