Iee International Electronics and Engineering S.a.

Thomas Meyers

Laurent Lamesch

Michael Virnich

David Hoyer

Michael Puetz

Martin Thinnes

Frank Althaus

Andreas Petereit

Thomas Faber

Michael Pütz

Oliver Lion

Alan Koehler

Micheal Puetz

A method of operating a capacitive sensing device that includes a capacitive sensor having at least one sense electrode, a measurement signal source for providing an alternating electric measurement signal with at least three fixed predefined signal frequencies to the at least one sense electrode, and an impedance measurement circuit for determining an unknown complex impedance of the at least one sense electrode from a response to the provided electric measurement signal. The method includes, for each predefined signal frequency: determining statistical quantities and signal parameters regarding a number of determined momentary values of an unknown complex impedance; eliminating portions up to a predefined hand touch movement lower limit frequency and from a predefined high-frequency limit down to a predefined hand touch movement upper limit frequency; excluding statistical outliers from determined momentary values; and using an eliminated frequency portion for calculating a momentary reference value for the unknown complex impedance.

Robust 'hands on steering wheel' classification based on a relative measurement system

A combined heating and capacitive seat occupant sensing system comprises a common mode choke configured so as to satisfy at least one of a plurality of conditions, which is taken into account by a decision unit of the system in such a way that an influence of the common mode choke on the decision is compensated.

Combined heating and capacitive seat occupant sensing system

A capacitive occupancy or proximity detector () comprises a heating circuit, an impedance measurement circuit () and a diagnostic circuit. The heating circuit includes a heating element (). The impedance measurement circuit is connected to the heating element so as to measure impedance between the heating element and a node at ground potential. The diagnostic circuit is configured for measuring electrical resistance across the heating circuit and includes a heating current sensor (), configured for sensing a heating current across the heating circuit, a current supply device () for driving a diagnostic current across the heating circuit and a current limiting ground path (), configured for draining the diagnostic current and for blocking the heating current.

Diagnostic capacitive occupancy or proximity detector

A capacitive sensor for a vehicle seat comprises an antenna electrode and a control and evaluation circuit operatively connected to the antenna electrode. The control and evaluation circuit is configured to operate in a first mode of operation, during which it measures alternating electrical current flowing between the antenna electrode and ground. The capacitive sensor comprises a seat frame connector for connecting the control and evaluation circuit to the seat frame of the vehicle seat. The control and evaluation circuit is configured to operate in a second mode of operation, during which it measures electrical current flowing into the seat frame connector.

Capacitive sensor

A combined seat heater and capacitive occupancy sensor comprises a heater network including a heating element () and a capacitive sensing circuit connected to the heating element to sense a capacitive load. A first and a second interface are provided for connecting the heating element to a first and a second terminal of a power source, respectively. Each interface comprises electronically controlled switches () arranged in series and defining an intermediate node (). An oscillator () is AC-coupled to the intermediate nodes to apply an oscillating voltage thereto. A current measuring means (), AC-coupled between the oscillator and the heating element, keeps the AC-potential of the heating element at least substantially equal, in amplitude and phase, to the oscillating voltage on the intermediate nodes and to derive the capacitive load from a thus resulting current flowing into the heating element.

Heating element operated as capacitive sensing electrode

A capacitive sensing system for a heating element comprises a capacitive detector connectable to the heating element and a common mode choke for connecting the heating element with a heating current supply. The detector drives an alternating current into the heating element and produces an output depending on the capacitive load, which the alternating current is subject to. Depending on the object sensed, the load varies in a range between a minimum and a maximum value. The choke represents an inductive load in parallel of the capacitive load. The capacitive load and the inductive load contribute to a complex impedance dominated by the inductive load. A compensation capacitor arranged parallel to the choke represents an additional capacitive load also contributing to the complex impedance. The compensation capacitor is dimensioned such that the sum of additional capacitive load and maximum value amounts to at least 50% of the inductive load.

Capacitive sensing system configured for using heating element as antenna electrode

A capacitive sensing system for being connected to a heating element comprises a capacitive detector connectable to the heating element and a common mode choke for essentially preventing alternating current from flowing from the heating element to the heating current supply. The capacitive detector is configured for driving an alternating current into the heating element and for producing an output indicative of capacitance based upon the alternating current. The choke has a first and a second winding for connecting the heating element with the heating current supply. The choke comprises a third winding connected in parallel of the first and/or second winding. The capacitive detector is configured for measuring a portion of the alternating current flowing across the third winding and for taking into account the measured portion of alternating current when producing the output.

Capacitive sensing system able of using heating element as antenna electrode

A plural-frequency capacitive occupancy sensing system comprises an antenna electrode and a detection circuit, which is configured to drive the antenna electrode at least with a first and a second signal at a first and a second frequency, respectively, so as to obtain at least a first and a second measurement value indicative of at least one of conductance, susceptance, resistance, reactance and capacitance between the antenna electrode and a reference node, at the first frequency and the second frequency, respectively. The detection circuit compares the capacitance between the antenna electrode and the reference node with a threshold capacitance, the threshold capacitance being derived from a difference between the first and second measurement values and/or the capacitance between the antenna electrode and the reference node being corrected based upon the difference between the measurement values. The detection circuit outputs an occupancy state signal depending on the comparison.

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Bitburg, Germany

Thomas Meyers