Apparatus for determining or monitoring a process variable of automation technology

Apparatus for determining or monitoring a process variable, especially a predetermined fill level, density or viscosity of a medium in a container, comprising:

• a housing and an oscillatable unit, which oscillatable unit has a membrane with an inner surface and an outer surface and, in given cases, at least one oscillatory element secured on said outer surface of said membrane and which apparatus is placed at the height of the predetermined fill level or which is so placed in the container that it extends to a defined immersion depth in the medium;
• a transmitting/receiving unit, which with a predetermined exciter frequency excites said oscillatable unit to execute oscillations and which receives oscillations of said oscillatable unit;
• a control/evaluation unit, which signals reaching of the predetermined fill level or ascertains the density, respectively the viscosity, of the medium;
• and
• a disc shaped bimorph element of a magnetostrictive material, which has an area force transmitting connection with said inner surface of said membrane, wherein:
• said transmitting/receiving unit is an electromagnetic drive comprising a coil, and a coil core;
• and
• said electromagnetic drive is so arranged within the housing that a gap is provided between said disc shaped element of magnetostrictive material and the corresponding end region of said electromagnetic drive.