Abstract: A sensor with a wireless power supply includes, as a sensor unit, a resonant circuit having a capacitance and a coil, the coil being used not only for measurement but also for reception of electromagnetic waves for supplying power to the sensor. In a first preferred embodiment of the invention, the sensor has a filter for frequency separation of the sensor signal into a supply component and payload signal component. In such a case, the sensor can be supplied during a measurement. In a second preferred embodiment of the invention, the sensor has a changeover switch for time separation of the sensor signal into the supply component and the payload signal component. In such a case, the sensor is supplied on an alternating cycle with a measurement.

Abstract: An electronic circuit for a proximity sensor, which is target-independent and is based on a phase projection transformation, is configured in such a way that the oscillating circuit can be driven by a square-wave voltage. A synchronous demodulator is used for the phase projection transformation. The electronic circuit can be miniaturized and only low requirements are placed on the stability of the feed voltage. A method for operating a proximity sensor is also provided.

Abstract: A proximity sensor, in particular a proximity switch is described. A component that pertains to a system variable and is independent from the material of a trigger or target is elected and transformed into a non-periodic signal that depends upon the distance of the trigger. The trigger of a proximity sensor can thus be exchanged randomly without requiring subsequent adjustments. The impedance of an oscillation circuit which pertains to the proximity sensor, the impedance of an oscillation circuit coil, the amplitude of the oscillation circuit signal or a voltage divider ratio between the oscillation circuit and the additional resistance can be used s system variables for instance.

Abstract: The present invention discloses a capacitive filling-level sensor, which is suitable in particular for filling-level determination in oil separator tanks. The capacitive sensor includes a measuring probe with at least one sensor electrode. According to the invention, the measuring probe is at least partially sheathed with at least one outer layer of a fluorinated plastic and at least one inner layer of a mica-filled plastic. Important exemplary embodiments concern an outer layer of perfluoroethylene-perfluoropropylene copolymer (FEP), an inner layer of mica-coated glass fiber tape impregnated with epoxy resin and possibly silanized and an incompressible, thermally adapted filling of the measuring-probe pipe with silicone oil and glass spheres or glass polyhedrons and/or an inner rod of AlMgSi-filled epoxy resin. The sheathing is electrically insulating, chemically inert, hydrophobic, oleophobic, waterproof, mechanically robust and easy to produce.