Electricity: measuring and testing – Impedance – admittance or other quantities representative of... – Lumped type parameters
Reexamination Certificate
2005-09-06
2005-09-06
Deb, Anjan (Department: 2858)
Electricity: measuring and testing
Impedance, admittance or other quantities representative of...
Lumped type parameters
C324S679000
Reexamination Certificate
active
06940292
ABSTRACT:
The circuit configuration includes a measuring capacitor having a variable capacitance, which is set by means of a physical measured quantity to be detected, a reference capacitor and a buffer amplifier. An input of the buffer amplifier is at least temporarily coupled to the measuring capacitor such that an output of the buffer amplifier supplies a signal voltage essentially proportional to a measurement voltage occurring on the measuring capacitor. At the beginning of each measuring cycle, the measuring capacitor is discharged to a predetermined residual charge, whereas the reference capacitor is charged to a predetermined reference charge. Afterwards, the reference charge is transferred as completely as possible from the reference capacitor to the measuring capacitor. To this end, the input and output of the buffer amplifier are temporarily coupled to one another via the first reference capacitor during operation. The circuit configuration thus supplies a signal voltage dependent on a reciprocal of the capacitance of the measuring capacitor and, in addition, has a current consumption that is practically independent of the instantaneous capacitance of the measuring capacitor.
REFERENCES:
patent: 5235267 (1993-08-01), Schoneberg et al.
patent: 5451940 (1995-09-01), Schneider et al.
patent: 6316948 (2001-11-01), Briefer
Bacon & Thomas
Benson Walter
Deb Anjan
Endress & Hauser GmbH & Co. KG
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