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AssigneeAgence Nationale de Valorisation de la Recherche
InventorsJacques Lewiner, Gerard Dreyfus
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A device for measuring quantities of electric charges, or other electric parameters whose magnitudes can be obtained from measurements of quantities of electric charges. The device includes a capacitor having a measuring plate and another plate or an intermediate element. The electrical parameter is applied to the capacitor so that a charge representative of its magnitude is induced on the measuring plate. This induced charge is modulated at a frequency f.sub.o and at a frequency f.sub.1, the frequency f.sub.1 being less than f.sub.o /2. An electrical signal representative of the modulation of the induced charge is generated. This signal has a first component of frequency f.sub.o whose magnitude represents the quantity of the induced charge and a second component of frequency f.sub.1 whose magnitude varies according to the distance between the measuring plate and the location at which the electrical parameter is applied to the capacitor. The second component can be used as a correction signal which reduces errors due to changes in the said distance.
A device for measuring quantities of electric charges, the device comprising a capacitor, the capacitor having a measuring element and another element, means for applying an electrical parameter to the capacitor so that an electric charge representing the magnitude of the parameter is induced on the said measuring element, means for modulating the quantity of the electric charge induced on the measuring element at a first frequency f.sub.o, means for modulating the quantity of the electric charge induced on the measuring element at a second frequency f.sub.1 which is less than f.sub.o /2, means for generating an alternating electric signal representing the modulation of the induced charge, means for deriving from the said alternating electric signal a first component which has a frequency f.sub.o and represents the quantity of the induced charge, and means for deriving from the said alternating electric signal a second component which has a frequency f.sub.1, the second component serving as a correction signal which depends upon the distance between the said measuring element and the location at which the electrical parameter is applied to the capacitor.
Dependencies are inferred from the claim text.