Three electrode AC detection
First Claim
1. Apparatus for sensing an alternating electric voltage in a conductor, comprising:
- a reference electrode, a first sensor electrode, and a second sensor electrode, all spaced apart, the electrodes responsive to the alternating electric voltage in the conductor;
a first differential amplifier connected to receive signals from the first sensor electrode and the reference electrode, and provide a first output signal indicative of a difference between the signals from the first sensor electrode and the reference electrode;
a second differential amplifier connected to receive signals from the second sensor electrode and the reference electrode, and provide a second output signal indicative of a difference between the signals from the second sensor electrode and the reference electrode;
a third differential amplifier for receiving the output signals from the first and second differential amplifiers and providing a third output signal indicative of a difference between the output signals from the first and second differential amplifiers;
a processor coupled to receive the third output signal to process the third output signal for display; and
a display driven by the processor to show presence of the alternating electric voltage in the conductor.
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Accused Products
Abstract
A sensor device and method for finding the location of a conductor such as a wire, having an alternating voltage and which is not readily visible, i.e. hidden in the wall of a structure or buried. The detector device has four plates in two balanced pairs and arranged in a quadrilateral with a central reference plate. This reference plate provides a common mode rejection of the background electric field typically present for instance on the wall, which is induced by the alternating voltage in the wire. A sharp signal peak is detectable immediately over the wire from a differential signal of a pair of the balanced plates, when the plates of the pair are located on either side of the wire. Also a determination based on the sum and difference of the signals from the two plates allows one to determine the relative phase induced in the two plates of each pair, which indicates the direction in which the sensor device should be moved in order for the plates to be immediately over the target wire.
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Citations
9 Claims
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1. Apparatus for sensing an alternating electric voltage in a conductor, comprising:
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a reference electrode, a first sensor electrode, and a second sensor electrode, all spaced apart, the electrodes responsive to the alternating electric voltage in the conductor; a first differential amplifier connected to receive signals from the first sensor electrode and the reference electrode, and provide a first output signal indicative of a difference between the signals from the first sensor electrode and the reference electrode; a second differential amplifier connected to receive signals from the second sensor electrode and the reference electrode, and provide a second output signal indicative of a difference between the signals from the second sensor electrode and the reference electrode; a third differential amplifier for receiving the output signals from the first and second differential amplifiers and providing a third output signal indicative of a difference between the output signals from the first and second differential amplifiers; a processor coupled to receive the third output signal to process the third output signal for display; and a display driven by the processor to show presence of the alternating electric voltage in the conductor. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method of locating a conductor carrying an alternating electrical voltage, comprising the steps of:
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holding three spaced apart sensor electrodes near the conductor, the sensor electrodes responsive to the alternating electrical voltage carried by the conductor; determining a difference between a voltage induced in each of the first and second electrodes to that induced in the third electrode; and indicating a location of the conductor where a difference between the two voltage differences is at a minimum.
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Specification