Capacitive sensor signal processing arrangement using switch capacitor structures
First Claim
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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Accused Products
Abstract
The arrangement serves for the processing of sensor signals which are furnished by a capacitive sensor which 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 influenceable in another manner and furnishing a measuring effect dependent on the measuring capacitance and the reference capacitance. The arrangement comprises a signal processing circuit which operates by the principle of quantized charge transport by means of switch-capacitor structures and charge balancing at least in time average and which receives the sensor signals representing the measuring effect and furnishes an output signal corresponding to the measuring effect. The first electrodes of the capacitors of the sensor are at a fixed potential and their second electrodes are connectable for performing the charge transport to the first input of an input operational amplifier, the second input of which lies at a reference potential. The reverse charging of the capacitors of the sensor necessary for forming the transported charge packets is effected by switching over the reference potential of the input operational amplifier. This permits a one-sided fixed binding of the sensor capacitors to any desired potential.
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Citations
14 Claims
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1. Arrangement for processing sensor signals furnished by a capacitive sensor
which 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 and which includes an operational amplifier, which furnishes a measuring effect dependent on said measuring capacitance and said reference capacitance, comprising a signal processing circuit which operates by the principle of quantized charge transport by means of switch-capacitor structures and charge balancing at least in time average and which 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, and wherein 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.
- 8. An apparatus for processing sensor signals furnished by a capacitive sensor which includes a measuring capacitor having a first electrode and a second electrode for providing a measuring capacitance influenceable by a physical measured quantity to be determined and at least one reference capacitor having a first electrode and a second electrode for providing a reference capacitance which is substantially unaffected by said physical measured quantity and which furnishes a measuring effect dependent on said measuring capacitance and said reference capacitance, the apparatus comprising a signal processing circuit which operates by the principle of quantized charge transport by means of switch-capacitor structures and charge balancing at least in time average and which receives said sensor signals representing said measuring effect and furnishes an output signal corresponding to said measuring effect, the first electrodes of said measuring capacitor and said reference capacitor of said sensor being coupled to a fixed potential, and wherein the 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 an operational amplifier in the signal processing circuit, a second input of the operational amplifier being coupled to the reference potential, and wherein a reverse charging of said measuring capacitor and said reference capacitor of said sensor necessary for forming transported charge packets is effected by selectively switching over said reference potential of said second input of said operational amplifier between different voltage levels.
Specification