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Capacitive angular position sensor

  • US 6,774,642 B2
  • Filed: 08/27/2002
  • Issued: 08/10/2004
  • Est. Priority Date: 08/27/2002
  • Status: Expired due to Fees
First Claim
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1. A sensor assembly for sensing an angular position of a rotatable body, comprising:

  • a stationary transmitter capacitor plate defining a transmitter surface area, the transmitter surface area including at least one transmitter electrode;

    a stationary receiver capacitor plate defining a receiver surface area generally corresponding in size to the transmitter surface area, the receiver surface area including at least a first receiver electrode and a second receiver electrode, the electrodes of the capacitor plates facing each other;

    a rotor formed of a dielectric material positioned in an air gap between the capacitor plates and adapted to be fixedly secured to the rotatable body so as to rotate with the rotatable body, the rotor defining a rotor are larger than the transmitter surface area and the receiver surface area and sized so that, in response to angular movement of the rotatable body, the rotor varies a capacitance between each transmitter electrode and each of the receiver electrodes, respectively; and

    means for measuring charges induced on each of the receiver electrodes whereby the charges indicate the angular position of the rotatable body;

    wherein at least one of the transmitter capacitor plate and receiver capacitor plate includes a guard trace on the at least one surface area, the guard trace being adjacent an outside edge of the at least one plate, the guard trace being located so as to prevent the interaction of adjacent electric fields.

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