A system for measuring the density of a hydrostatic liquid in a container includes a pair of serially connected pressure sensors mounted in the liquid, a constant volume gas flow source connected to an inlet of one pressure sensor, a second pressure sensor connected to the outlet of the first pressure sensor, and a vent is connected between the second pressure sensor outlet and the atmosphere. A gauge or pressure transducer in the gas conduit from the source to the first pressure sensor provides pressure measurements that can be used to determine the level of liquid in the container and a differential pressure transducer across the first pressure sensor can be used to determine density of the liquid. Exhaust gas from the pressure sensors is passed to the atmosphere through a pressure buffering device in one construction of the system. The pressure sensors each have a rigid body with a generally circular resting surface over which a flexible diaphragm member is positioned. A gas inlet communicates to the peripheral portion of the resting surface through the annular groove. A gas outlet is provided at a central portion of the resting surface for communication with an outlet conduit.