Patent ID: 7356423
Filing Date: 2008-04-08
Classification: G01D

Abstract:
1. An apparatus for reading out a differential capacity with a first and second partial capacity comprising: a first oscillator having a first frequency-determining element connectable to the first partial capacity; a second oscillator having a second frequency-determining element connectable to the second partial capacity; a switching means formed to switch the first frequency-determining element into a first state, so that the first oscillator has a first oscillation with a first period duration, or to switch it into a second state, so that the first oscillator has a second oscillation with a second period duration, and wherein the switching means is further formed to switch the second frequency-determining element into a third state, so that the second oscillator has a third oscillation with a third period duration, or to switch it into a fourth state, so that the second oscillator has a fourth oscillation with a fourth period duration; a first detection means connected to the first oscillator to generate a first signal indicating the first period duration and a second signal indicating the second period duration; a second detection means connected to the second oscillator to generate a third signal indicating the third period duration and a fourth signal indicating the fourth period duration; and an evaluation means for forming a quotient using the first, second, third and fourth signal, whose numerator depends on the first oscillator and whose denominator depends on the second oscillator to obtain a value indicating a quotient of the first and the second partial capacity.