A vibronic sensor for determining and/or monitoring at least one process variable of a medium in a container. The sensor at least comprising: a unit which can oscillate mechanically; a driving/receiving unit; and an electronic unit. The driving/receiving unit is designed to excite, by means of an electrical excitation signal, mechanical oscillations in the unit which can oscillate mechanically and is designed to receive the mechanical oscillations of the unit which can oscillate mechanically, and to convert them into an electrical receiving signal. The electronic unit is designed to generate the excitation signal on the basis of the receiving signal and to determine the at least one process variable from the receiving signal; The electronic unit comprises at least one adaptive filter; and the electronic unit is designed to set the filter characteristic of the adaptive filter in such a way that there is a target phase shift between the excitation signal and the receiving signal.