Abstract: A method for determining the state of a piezoelectric element, in particular the piezoelectric element of a sensor apparatus, it is provided. The piezoelectric element is a component of a resonant circuit. The resonant circuit is excited to natural vibrations. The period durations of the natural vibrations of the resonant circuit are captured, and conclusions are drawn regarding the state of the piezoelectric element base on the period durations of the natural vibrations. A sensor apparatus with at least one piezoelectric element is provided. The sensor apparatus has at least one resonant circuit and that the piezoelectric element is a component of the resonant circuit. The sensor apparatus includes at least one evaluator for capturing and evaluating the natural vibrations of the resonant circuit. The evaluator includes at least one storage device for storing reference resonance frequencies that have been determined in advance.

Abstract: The invention relates to a method for addressing at least one bus subscriber, in particular a control device or sensor, which is connected to a bus system for the purpose of exchanging data, and which is supplied with DC voltage in order to supply the bus subscriber with supply voltage rectified as defined via a DC voltage input of said bus subscriber. It is proved according to the invention that the respective bus subscriber detects the polarity of the DC voltage at its DC voltage input, selects a predefined address depending on the detected polarity, and assigns the selected address to itself for the purpose of exchanging the data. The invention further relates to the bus subscriber and a system consisting of a bus system and exactly two bus subscribers of such kind. The invention also relates to a motor vehicle.

Abstract: The invention relates to a method for addressing at least one bus subscriber, in particular a control device or sensor, which is connected to a bus system for the purpose of exchanging data, and which is supplied with DC voltage in order to supply the bus subscriber with supply voltage rectified as defined via a DC voltage input of said bus subscriber. It is proved according to the invention that the respective bus subscriber detects the polarity of the DC voltage at its DC voltage input, selects a predefined address depending on the detected polarity, and assigns the selected address to itself for the purpose of exchanging the data. The invention further relates to the bus subscriber and a system consisting of a bus system and exactly two bus subscribers of such kind. The invention also relates to a motor vehicle.