Ifm Electronic Gmbh

Huf Huelsbeck & Fuerst Gmbh & Co Kg

Joerg Schulz

Martin Witte

Jaromir Palata

Werner Hoch

Bernd Steegmann

Gianni Uselli

Markus Von Ehr

Gerhard Heilig

Heidrun Richter

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 ().

Circuit arrangement for detecting the capacitance or change of capacitance of a capacitive circuit element or of a component

A capacitive proximity switch for detecting the change in the capacitance relative to a setpoint capacitance by the approach or retreat of an object in the sensitive area of a proximity switch, especially for use in the door handle of a motor vehicle, provides reliable error detection and error suppression at a fundamentally high sensitivity of the capacitive proximity switch by utilizing an evaluation unit that evaluates a measured value of the change in capacitance over time and depending on the time behavior of the measured value activates changes the operating threshold from a first threshold (which can be caused by a false object coming into or out of the sensitive area of the proximity switch) to a higher second threshold which can be reached only at a relatively greater change in capacitance caused by a target object coming into or out of the sensitive area of the proximity switch.

Capacitive proximity switch

A circuit arrangement for detecting the capacitance or capacitance change of a capacitive circuit element or component, in which there is a capacitive noise voltage compensation element, which corresponds to the sensor capacitor, represented as a noise voltage compensation capacitor, and a noise voltage compensation electrode of the noise voltage compensation capacitor, which corresponds to the first electrode of the sensor capacitor, is connected to the second electrode of a storage capacitor. The noise voltage compensation capacitor can be influenced in the same way as the sensor capacitor by the LF noise voltage. In this way, the adulteration of the measurement result by LF noise voltages which otherwise occurs no longer takes place.

Circuit arrangement for detecting the capacitance or capacitance change of a capacitive circuit element or component

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Lustenau, Austria

Joerg Schulz