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SIGNAL-BALANCED SHIELD ELECTRODE CONFIGURATION FOR USE IN CAPACITIVE DISPLACEMENT SENSING SYSTEMS AND METHODS

  • US 20050092108A1
  • Filed: 11/04/2003
  • Published: 05/05/2005
  • Est. Priority Date: 11/04/2003
  • Status: Active Grant
First Claim
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1. A capacitive-type displacement sensing device for determining a relative position between two members along a measuring axis direction, the displacement sensing device comprising:

  • a transmitter member, the transmitter member comprising a first transmitter element configuration comprising at least two transmitter electrode elements;

    a receiver member comprising a first receiver element configuration comprising at least one receiver electrode element, the first receiver element configuration fixed relative to the first transmitter element configuration and capacitively coupled to the first transmitter element configuration across an operating gap located between the first receiver element configuration and the first transmitter element configuration; and

    a scale member, the scale member comprising at least a first shield element configuration comprising at least one shield electrode element, the first shield element configuration located in the operating gap located between the first receiver element configuration and the first transmitter element configuration, the first shield element configuration movable along the measuring axis direction relative to the first transmitter element configuration and the first receiver element configuration to modulate the capacitive coupling between the first transmitter element configuration and the first receiver element configuration, and the first shield element configuration capacitively coupled to the first transmitter element configuration to provide a first shield-transmitter capacitive coupling configuration, wherein;

    the at least two transmitter electrode elements of the first transmitter element configuration are respectively operable to provide respective time-varying transmitter voltage signals during a measurement period;

    for any relative position within a range of relative positions between the transmitter member and the scale member along the measuring axis direction, the respective time-varying transmitter voltage signals are operable in combination with the first shield-transmitter capacitive coupling configuration such that if the capacitive-type displacement sensing device were operated with the first shield element configuration electrically floating a resulting net voltage change of the at least one shield electrode element of the first shield element configuration due solely to the respective time-varying voltage signals in combination with the first shield-transmitter capacitive coupling configuration would be inherently approximately zero for at least one time during the measurement period; and

    the at least one receiver electrode element of the first receiver element configuration is respectively operable to provide at least one respective receiver signal at least during the at least one time during the measurement period, and the at least one respective receiver signal is usable to determine the relative position between the transmitter member and the scale member along the measuring axis direction.

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