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Capacitive sensor signal processing arrangement using switch capacitor structures

  • US 5,451,940 A
  • Filed: 05/22/1992
  • Issued: 09/19/1995
  • Est. Priority Date: 12/20/1989
  • Status: Expired due to Fees
First Claim
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1. Arrangement for processing sensor signals furnished by a capacitive sensorwhich includes a measuring capacitor having a measuring capacitance influenceable by a physical measured quantity to be determined and at least one reference capacitor having a reference capacitance which is substantially unaffected by said physical measured quantity andwhich includes an operational amplifier,which furnishes a measuring effect dependent on said measuring capacitance and said reference capacitance, comprising a signal processing circuitwhich operates by the principle of quantized charge transport by means of switch-capacitor structures and charge balancing at least in time average andwhich receives said sensor signals representing said measuring effect and furnishes an output signal corresponding to said measuring effect,wherein first electrodes of said measuring capacitor and said reference capacitor of said sensor lie at a fixed potential and second electrodes of said measuring capacitor and said reference capacitor for performing said charge transport are selectively coupled through a selected portion of the switch-capacitor structures to a first input of the operational amplifier, a second input of which lies at a reference potential, andwherein a reverse charging of said measuring capacitor and said reference capacitor of said sensor necessary for forming transported charge packets is effected by switching over said reference potential of said second input of said operational amplifier between different voltage levels.

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