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Shielded flat-plate proximity/dielectric properties sensor

  • US 6,249,130 B1
  • Filed: 08/03/1999
  • Issued: 06/19/2001
  • Est. Priority Date: 12/21/1998
  • Status: Expired due to Term
First Claim
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1. A capacitive sensor element, comprising:

  • (a) a dielectric substrate having a planar configuration;

    (b) a pair of sensing electrodes arranged on one surface of said substrate in spaced relation; and

    (c) shielding electrode means being grounded and arranged between and parallel to said pair of sensing electrodes for interrupting at least a portion of the electric field lines generated from one of said sensing electrodes when an electric current is supplied thereto, thereby to direct the electric field lines in a given direction while preventing interference from the dielectric substrate, said shielding electrode means comprising (1) a first shield electrode arranged on a surface of said substrate opposite said one surface, said first shield electrode being parallel to said sensing electrodes and limiting a measuring field defined by said electric field lines to 180°

    on said one surface of said dielectric substrate; and

    (2) a second shield electrode arranged on said one surface of said substrate between and co-planar with said sensing electrodes in spaced parallel relation to prevent the dense electric field very near the sensor element from severely dominating a measurement, whereby when a substance being measured is proximate the sensor element, changes in the electric field lines are detected as a function of the characteristics of the substance.

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