A positioning device for capacitively detecting an object enclosed in a medium includes a measuring electrode, a reference electrode, and a receiving electrode. The measuring electrode with the receiving electrode forms a measuring capacitance, which can be influenced by the object. The reference electrode with the receiving electrode forms a reference capacitance, which cannot be influenced by the object. The positioning device further includes an oscillator configured to supply the measuring capacitance and the reference capacitance with phase-shifted AC voltages and a control device configured to control amplitudes of at least one of the AC voltages, in order to adapt effects of electrical fields of the measuring electrode or of the reference electrode on the receiving electrode to one another. The measuring, reference, and receiving electrodes are planarly formed. The measuring electrode has a larger surface area than the reference electrode.