Ifm Electronic Gmbh

Markus Von Ehr

Werner Hoch

Joerg Schulz

A circuit arrangement is described for detecting the capacitance or change of capacitance of a capacitive circuit element or of a component, specifically of a sensor capacitor (), with a control unit () ,with a monostable multivibrator () triggered by the control unit (), and with an evaluation unit (), the monostable multivibrator () having a first input () which is connected to the control unit (), a second input ()which is connected to the sensor capacitor (), and one output (), of the monostable multivibrator () is triggered by the control unit () at the output () of the monostable multivibrator () an output signal or output signals appearing, with a time duration which is proportional to the capacitance of the sensor capacitor (), the output signal or output signals of the monostable multivibrator ()being converted into a signal voltage proportional to its or their duration, and in the evaluation unit () a detection value corresponding to the capacitance or change of capacitance of the sensor capacitor () being obtained from the signal voltage, The circuit arrangement as claimed in the invention is improved compared to the prior art in the output () of the monostable multivibrator () is connected upstream of a constant current generator () which can be controlled by its output signal or output signals and that an integrator () which converts the current delivered from the constant current generator ()into the signal voltage is connected to the constant current generator ().

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Langenargen, Germany

Markus Von Ehr