Pressure mapping system with capacitive measuring pad

  • US 4,827,763 A
  • Filed: 04/11/1986
  • Issued: 05/09/1989
  • Est. Priority Date: 04/11/1986
  • Status: Expired due to Term
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First Claim
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1. A system for monitoring the distribution of forces on a surface, comprising:

  • a pad having first and second sheets of compressible insulating material, a first array of linear electrodes disposed between said sheets of insulating material, a second array of linear electrodes disposed on a side of said first sheet of insulating material that is opposite said first array of electrodes and being oriented in a direction other than the direction of the electrodes of said first array to thereby form a matrix of nodes each of which is located at an intersection of an electrode of said first array with an electrode of said second array and which has a capacitance that varies in accordance with compression of said first sheet of said intersection, and a third array of linear electrodes disposed on a side of said second sheet of insulating material that is opposite said first array of electrodes, the electrodes in said third array being oriented parallel to and in alignment with the electrodes of said first array, wherein each array of linear electrodes comprises conductive strips disposed on a substrate, and wherein the conductive strips of at least said first and third arrays are disposed on opposite sides of the substrate in an alternating fashion;

    means for sequentially selecting each electrode of said second and third arrays in correspondence and applying an electrical driving signal to the selected electrodes;

    means for sequentially selecting each electrode of said first array and sensing the electrical potential of the selected electrode of said first array to thereby measure the capacitance of the node at the intersection of the selected electrodes;

    means for providing a signal related to the measured capacitance at each node in the matrix to thereby indicate the distribution of forces on the surface of said pad; and

    means for applying a feedback potential related to said sensed potential to each of the non-selected electrodes of said second and third arrays to thereby isolate the sensed potential from the effects of changes in capacitance of nodes other than said node whose capacitance is being measured.

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