Patent ID: 7893603

Claim:
An apparatus for determining and/or monitoring a process variable of a medium, comprising: a membrane; an oscillatable unit secured to said membrane; a sending/receiving unit, which excites said oscillatable unit to oscillate and which receives oscillations of said oscillatable unit; a control/evaluation unit, which, on the basis of the oscillations of said oscillatable unit, monitors and/or determines the process variable, wherein: said sending/receiving unit comprises a disk-shaped, piezoelectric element; said disk-shaped, piezoelectric element has two segments, which are essentially polarized oppositely to one another; said two segments of said disk-shaped, piezoelectric element are connected in series; exactly two electrodes of opposite polarity are applied to the side of said disk-shaped, piezoelectric element; and said exactly two electrodes of opposite polarity are applied to said disk-shaped, piezoelectric element facing away from said membrane.