Abstract: Apparatus for capacitive electrical detection or measurement relating to a medium, comprising at least one electrode having a given surface extension and an oscillator circuit the output frequency of which is a function of the capacitance being associated with the electrode and the dielectric constant of the medium, and is taken as a basis for the detection or measurement. The effective spacing of the electrode from a counter electrode or from earth is of the same or a substantially higher order of magnitude as seen in relation to the surface extension of the electrode. A conductor connecting the electrode to the oscillator circuit has a length that is a small fraction as seen in relation to the surface extension of the electrode.