A method for operating a capacitive touch-sensitive switch having a capacitive sensor element and a sensor circuit includes initially setting a scanning frequency of the capacitive touch-sensitive switch with a good signal-to-noise ratio and then operating the capacitive touch-sensitive switch at a scanning frequency which has been set to detect switch actuation. The process of setting the scanning frequency includes operating the touch-sensitive switch using a first measurement method and at a selected scanning frequency, detecting the measurement signals from the sensor circuit and checking whether the detected measurement signals contain or could contain a critical alias effect. If no critical alias effect and no possibility of a critical alias effect are detected during the check, the scanning frequency can be set as the selection frequency for detection operation of the touch-sensitive switch. A capacitive touch-sensitive switch is also provided.

An impedance measurement circuit for determining a complex impedance of a capacitive sensor having at least one sense electrode operable in loading mode and at least one guard electrode. The measurement circuit includes: a pulse generator unit for providing a periodic electric measurement signal and a periodic electric guard signal; a signal sensing circuit for sensing a sense current flowing through the at least one sense electrode or the sense electrodes in response to the pulse generator unit measurement signal; and a control and evaluation unit. The control and evaluation unit is configured for determining a complex impedance from the determined sense currents with reference to a complex reference potential.

A sensor electrode has an upper side portion arranged on an automobile, a lower side portion arranged with a predetermined spacing from the upper side portion, and a connecting portion that connects the upper side portion and the lower side portion. A control unit inputs a signal for detecting a user to the upper side portion, the lower side portion, and the connecting portion, which are electrically connected. The lower side portion is arranged farther from an area through which the user passes than the upper side portion. The installation height of the upper side portion is greater than or equal to the installation height of the lower side portion.

An input device includes a clocked comparator configured to actively drive a capacitive sensor electrode at a signal input of the clocked comparator with a first periodic reference voltage, and provide a digital representation of a sensing current resulting from driving the capacitive sensor electrode with the first periodic reference signal. The clocked comparator produces the digital representation of the sensing current based on a comparison of the signal input of the clocked generator with the first periodic reference signal. A feedback path provides negative feedback of the digital representation of the sensing current to the signal input of the clocked comparator. The input device further includes a demodulator configured to demodulate the digital representation of the sensing current using the first periodic reference signal to obtain a first digital measurement.

A capacitive sensor including a sensor electrode connected to a signal generation circuit and a signal evaluation circuit. The signal generation circuit contains a signal generator that is a noise generator or a pseudo-noise generator, the signal evaluation circuit includes a synchronous rectifier. The synchronous rectifier is connected for synchronization to the signal generator.

A capacitance measurement circuit for determining a sense current of a capacitive sensor with a sense electrode and a guard electrode. The measurement circuit includes a periodic signal voltage source, a sense current measurement circuit configured for determining the sense current with reference to a reference voltage, and at least one remotely controllable switch member. In a first switching state, the at least one switch member electrically connects the sense current measurement circuit to the periodic signal voltage source for providing a first reference voltage, and in a second switching state, the at least one switch member electrically connects the sense current measurement circuit to a second reference voltage that is different from the first reference voltage.

A noise cancellation circuit includes a first switch to a fourteenth switch, a first/second analog buffer, a first/second feedback capacitor, a first/second parallel capacitor, a first/second current conveyor, a first/second operation amplifier and a first/second series capacitor. In a first phase, the first switch and second switch are turned on and the remaining switches are not turned on. In a second phase, the third to fifth switches, the eighth to ninth switches and the twelfth to fourteenth switches are turned on and the remaining switches are not turned on. In a third phase, the first switch and the second switch are turned on and the remaining switches are not turned on. In a fourth phase, the third to fifth switches, the seventh switch, the tenth switch and the twelfth to fourteenth switches are turned on and the remaining switches are not turned on.

A sensor apparatus and method of installation, and a system for controlling at least one electrical device and a method of use of such system. The apparatus comprises a mount adapted to be attached to a support and a sensor element adapted to be detachably connected to the mount. The method of installing a sensor apparatus comprises providing a sensor apparatus according to the first aspect of the present invention. The method further comprises the steps of retainably affixing the mount to, or within, the support and detachably connecting the sensor element to the mount. The system for controlling at least one electrical device comprises at least one sensor apparatus, at least one electrical device, and a controller, wherein the at least one sensor apparatus and the at least one electrical device are electrically connected to the controller.

An input device includes a clocked comparator configured to actively drive a capacitive sensor electrode at a signal input of the clocked comparator with a first periodic reference voltage, and provide a digital representation of a sensing current resulting from driving the capacitive sensor electrode with the first periodic reference signal. The clocked comparator produces the digital representation of the sensing current based on a comparison of the signal input of the clocked generator with the first periodic reference signal. A feedback path provides negative feedback of the digital representation of the sensing current to the signal input of the clocked comparator. The input device further includes a demodulator configured to demodulate the digital representation of the sensing current using the first periodic reference signal to obtain a first digital measurement.

A capacitance sensing circuit includes a buffer circuit, a modulation circuit, and an integral circuit. The buffer circuit is coupled to an external capacitor through a touch-sensing pad, and includes a pull-up device and a pull-down device. The modulation circuit includes a first current mirror device having a current drivability corresponding to one N.sup.th (where N denotes a positive real number) a current drivability of the pull-up device and a second current mirror device having a current drivability corresponding to one N.sup.th a current drivability of the pull-down device. The integral circuit integrates voltage values at an output node of the modulation circuit to output the integrated voltage values. The pull-up device and the first current mirror device constitute a current mirror circuit, and the pull-down device and the second current mirror device constitute another current mirror circuit.