A pressure sensor includes an outer body defining a sensor cavity and a resonator element located at least partially within the sensor cavity. The pressure sensor also includes a bellows having an outer side and an inner side and that is located at least partially within the outer body. the inner side of the bellows defines an internal volume and is configured to receive a measured fluid into the internal volume. The pressure sensor also includes a measuring fluid filling at least a portion of an area between the outer side and the outer body.