Magnetic Field Cancellation for Strain Sensors
First Claim
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1. An electronic device comprising:
- an enclosure housing a display;
a cover sheet positioned over the display and forming an external surface of the electronic device;
a magnetic interference source positioned within the enclosure; and
a strain-sensing layer positioned beneath the cover sheet and comprising;
a substrate comprising an upper surface and a lower surface;
a first strain-sensing element comprising;
a first upper resistive structure comprising a first set of conductive traces and coupled to the upper surface of the substrate; and
a first lower resistive structure comprising a second set of conductive traces aligned along an axis passing perpendicular through the substrate with the first set of conductive traces and coupled to the lower surface of the substrate; and
a second strain-sensing element positioned adjacent the magnetic interference source and comprising;
a second upper resistive structure comprising a third set of conductive traces and coupled to the upper surface of the substrate; and
a second lower resistive structure comprising a fourth set of conductive traces and coupled to the lower surface of the substrate;
whereinat least a portion of the fourth set of conductive traces does not align along the axis with the third set of conductive traces.
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Abstract
A strain-responsive sensor incorporating a strain-sensitive element is disclosed. The strain-sensitive element includes a matched-pair of resistive structures disposed on opposite sides of a substrate. One resistive structure is coupled to a crossover, either a physical crossover or a soft crossover, such that current within the resistive structures of the matched pair flows in the same direction. In addition, one resistive structure of the matched pair has a different loop area than the other resistive structure.
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Citations
20 Claims
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1. An electronic device comprising:
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an enclosure housing a display; a cover sheet positioned over the display and forming an external surface of the electronic device; a magnetic interference source positioned within the enclosure; and a strain-sensing layer positioned beneath the cover sheet and comprising; a substrate comprising an upper surface and a lower surface; a first strain-sensing element comprising; a first upper resistive structure comprising a first set of conductive traces and coupled to the upper surface of the substrate; and a first lower resistive structure comprising a second set of conductive traces aligned along an axis passing perpendicular through the substrate with the first set of conductive traces and coupled to the lower surface of the substrate; and a second strain-sensing element positioned adjacent the magnetic interference source and comprising; a second upper resistive structure comprising a third set of conductive traces and coupled to the upper surface of the substrate; and a second lower resistive structure comprising a fourth set of conductive traces and coupled to the lower surface of the substrate;
whereinat least a portion of the fourth set of conductive traces does not align along the axis with the third set of conductive traces. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A strain-responsive sensor comprising:
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a substrate comprising; a first surface; and a second surface opposite the first surface; and a strain-sensitive element comprising; a first resistive structure comprising a first set of conductive traces coupled to the first surface; a second resistive structure substantially aligned with the first resistive structure, comprising a second set of conductive traces coupled to the second surface; and a crossover coupling the first resistive structure to the second resistive structure such that current flows within the second resistive structure in the same direction as the first resistive structure;
whereinat least a portion of the first set of conductive traces does not align along an axis passing perpendicular through the substrate with the second set of conductive traces. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16)
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17. A method of operating a strain-responsive sensor comprising:
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applying a first voltage of a first polarity to a first resistive structure of the strain-responsive sensor; applying a second voltage of the first polarity to a second resistive structure of the strain-responsive sensor such that current flows through the second resistive structure in the same direction as through the first resistive structure, the second resistive structure separated from the first resistive structure by a substrate and having at least one conductive trace not aligned with a corresponding conductive trace of the first resistive structure; measuring an output voltage of a balancing network electrically coupled to the first resistive structure and the second resistive structure; and associating the measured output voltage with an amount of strain experienced by one or both of the first resistive structure and the second resistive structure. - View Dependent Claims (18, 19, 20)
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Specification