Abstract: In an exemplary embodiment, a measuring cell is disposed in an outer tube. A chamber in the outer tube adjacent the measuring cell can be directly connected via an opening to the liquid in a liquid vessel whose pressure is to be measured. In order to also be able to calibrate the pressure transducer at any time in the liquid vessel, an elastic container is inventively disposed in the chamber, the container being connected to a connecting line likewise lying in the outer tube for the purpose of filling and emptying. In its filled state, the container closes the opening of the chamber without interrupting the connection between a fluid line used for calibration and the measuring cell.