Capacitive sensor device with selective loading and coupling measurement mode

A capacitive sensing device, comprising:

• a plurality of electrically conductive antenna electrodes,
• a capacitive measurement circuit comprising:
• a measurement signal voltage source that is configured to provide an alternating measurement voltage at a voltage output port;
• a remotely controllable switching unit that includes a plurality of ports and a plurality of switching members that are configured to operatively and selectively provide electrical connections between selected ports;
• and
• a current measurement circuit operatively connected to one of the ports of the switching unit,
• wherein the voltage output port is operatively connected to another port of the switching unit, and wherein each antenna electrode of the plurality of electrically conductive antenna electrodes is individually connectable to a distinct port of the switching unit,
• a signal processing unit configured to receive and process output signals from the current measurement circuit, and
• an electronic control unit configured to:
• automatically control the switching unit, and
• evaluate the processed signals received from the signal processing unit during a measurement cycle,
• wherein the capacitive measuring circuit, within a same measurement cycle, is configured to:
• a) by the switching unit, selectively connect a single antenna electrode of the plurality of antenna electrodes, or a group of antenna electrodes of the plurality of antenna electrodes, to the voltage output port and the current measurement circuit in a loading mode, wherein each group includes at least two electrically connected antenna electrodes, and
• b) by the current measurement circuit, measure a complex current flowing through the selected single antenna electrode, or the selected group of electrodes, in response to the alternating measurement voltage at the voltage output port,
• wherein the signal processing unit, within the same measurement cycle, is configured to:
• c) receive and process an output signal from the current measurement circuit that represents the measured complex current,
• wherein the electronic control unit, within the same measurement cycle, is configured to:
• d) receive and store the processed output signal from the current measurement circuit, and
• e) control an automatic repetition of a)-d) in loading mode operation for each of the plurality of antenna electrodes, or for each group of antenna electrodes of the plurality of antenna electrodes,
• wherein the capacitive measuring circuit, within the same measurement cycle, is further configured to:
• f) by the switching unit, selectively connect one of two distinct antenna electrodes of the plurality of antenna electrodes or one of two distinct groups of antenna electrodes of the plurality of antenna electrodes, to the voltage output port, and the other of the two distinct antenna electrodes of the plurality of antenna electrodes or the other of the two distinct groups of antenna electrodes of the plurality of antenna electrodes to the current measurement circuit in a coupling mode, wherein each group includes at least two electrically connected antenna electrodes, and
• g) by the current measurement circuit, measure a complex current flowing through the antenna electrode, or the group of electrodes, that is connected to the current measurement circuit in response to the alternating measurement voltage at the voltage output port,
• wherein the signal processing unit, within the same measurement cycle, is further configured to:
• h) receive and process an output signal from the current measurement circuit that represents the measured complex current,
• wherein the electronic control unit, within the same measurement cycle, is further configured to:
• i) receive and store the processed output signal from the current measurement circuit, and
• j) control an automatic repetition of f)-h) in coupling mode operation for two other distinct antenna electrodes of the plurality of antenna electrodes, or for two other distinct groups of antenna electrodes of the plurality of antenna electrodes,
• wherein a first antenna electrode of the plurality of antenna electrodes is a circular ring and circumferentially arranged at a rear surface along an outer rim of a vehicle steering wheel;
• a second antenna electrode of the plurality of antenna electrodes is a circular half ring and circumferentially arranged at a left-hand side of a front surface of the outer rim of the steering wheel;
• and a third antenna electrode of the plurality of antenna electrodes is a circular half ring and circumferentially arranged at a right-hand side of the front surface of the outer rim of the steering wheel.