Capacitive loading mode measurement circuit with compensation of measurement errors due to parasitic sensor impedances

An impedance measurement circuit for determining a sense current of a guard-sense capacitive sensor operated in loading mode. The circuit includes a periodic signal voltage source for providing a periodic measurement voltage, a sense current measurement circuit, a differential amplifier that is conf...

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Bibliographische Detailangaben
1. Verfasser:	Lamesch, Laurent
Format:	Patent
Sprache:	eng
Schlagworte:	AMPLIFIERS ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVEREDIN A SINGLE OTHER SUBCLASS BASIC ELECTRONIC CIRCUITRY ELECTRICITY MEASURING MEASURING ELECTRIC VARIABLES MEASURING MAGNETIC VARIABLES MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR PERFORMING OPERATIONS PHYSICS SEATS SPECIALLY ADAPTED FOR VEHICLES TARIFF METERING APPARATUS TESTING TRANSPORTING VEHICLE PASSENGER ACCOMMODATION NOT OTHERWISE PROVIDEDFOR VEHICLES IN GENERAL VEHICLES, VEHICLE FITTINGS, OR VEHICLE PARTS, NOT OTHERWISEPROVIDED FOR
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Beschreibung
Zusammenfassung:	An impedance measurement circuit for determining a sense current of a guard-sense capacitive sensor operated in loading mode. The circuit includes a periodic signal voltage source for providing a periodic measurement voltage, a sense current measurement circuit, a differential amplifier that is configured to sense a complex voltage difference between the sense electrode and the guard electrode, a demodulator for obtaining, with reference to the periodic measurement voltage, an in-phase component and a quadrature component of the sensed complex voltage difference, and control loops for receiving the in-phase component and the quadrature component, respectively. An output signal of the first control loop and an output signal of the second control loop are usable to form a complex voltage that serves as a complex reference voltage for the sense current measurement circuit.