Patent ID: 9541590
Date: 2017-01-10
CPC Classifications: G01M,G01R,H03K

Claim:
1. A circuit arrangement for detecting a capacitance of a capacitive component and/or a change in the capacitance of a capacitive component, the circuit arrangement comprising: a monostable flipflop controllable by a control signal and having at least two inputs and one output, wherein a first input of the flipflop is provided for the control signal, a capacitive component which is connected to a second input of the monostable flipflop, a conversion device which is connected to the output of the monostable flipflop and is configured to convert an output signal generated at the output into a signal voltage, and an evaluation unit which is connected to the conversion device in order to evaluate the signal voltage and to generate at least one detection value based on the signal voltage and which indicates the capacitance and/or a change in the capacitance of the capacitive component, wherein the monostable flipflop is configured to generate at least one output signal at its output on actuation by the control signal, the duration of said output signal being dependent on the capacitance of the capacitive component, and wherein the conversion device converts the at least one output signal into a signal voltage whose course is proportional to a duration of the output signal, wherein the conversion device comprises an integrator having an operational amplifier, wherein the integrator is connected between the output of the monostable flipflop and the evaluation unit and configured such that an output signal of the monostable flipflop is present at an amplifier input of the operational amplifier and results in a signal voltage which changes linearly over time, wherein the values which can be assumed by the signal voltage are preset by the output signal and dependent directly from the output signal, and wherein a magnitude of the signal voltage is controllable and/or a characteristic for the signal voltage is variable via a switchable setting device whose switching state is independent from the output signal, the magnitude of the signal voltage being controllable and/or the characteristic for the signal voltage being variable by setting a gain of the integrator between the output signal generated at the output of the monostable flipflop and the signal voltage generated via the conversion device, wherein a plurality of discrete values for the gain are preset and selectable via the switchable setting device.