A sensor apparatus for generating electrical signals which indicate the position or movement of limbs relative to a reference area has a transmitter electrode apparatus, a voltage generator for applying an alternating voltage to the transmitter electrode, a first receiver electrode apparatus, a second receiver electrode apparatus, and a third receiver electrode apparatus, wherein the first, second, and third receiver electrode apparatuses are each connected to high-impedance tapping systems. The first, second, and third receiver electrode apparatuses are preferably each connected to high-impedance inputs of an impedance transformer system, wherein information indicative of a location or movement is obtained on the basis of differences between the electrical events present at the outputs of the respective impedance transformer.