| CPC H03K 17/955 (2013.01) [G01R 27/2605 (2013.01); G01R 35/005 (2013.01); G06Q 10/087 (2013.01)] | 20 Claims |

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1. An apparatus comprising:
a cover layer;
a first sensor element comprising:
a first conductive element located beneath the cover layer;
a second conductive element located beneath the first conductive element;
a first electrical insulator between the first conductive element and the second conductive element;
a third conductive element;
a second electrical insulator between the second conductive element and the third conductive element;
a third electrical insulator beneath the third conductive element;
a fourth conductive element, wherein the third electrical insulator is between the third conductive element and the fourth conductive element; and
a fourth electrical insulator beneath the fourth conductive element;
first electronics to operate the first sensor element to determine first capacitance data; and
a first set of conductors that couple the first conductive element, the second conductive element, the third conductive element, and the fourth conductive element to the first electronics.
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