Pressure sensing device and use of the same in a connecting structure

A pressure sensing device (1) adapted for having a liquid flowing there through and for sensing the pressure of said liquid. The device has a casing (2) being fluid-tightly divided into a first (3) and a second chamber (4) by a flexible, impermeable wall (5). The first chamber (3) has a first opening (6) for the liquid, said opening being placed at the lower part of the chamber (3), and a second opening (7) for the liquid, said opening being placed at the top of the first chamber (3). The second chamber (4) has a measuring port (8), which is connectable to a pressure transducer (9) for bringing the second chamber (4) into gas-tight communication with the pressure transducer (9). The device has a first orifice (10) for the liquid into/out of the device (1), which orifice is placed at the upper part of the device at a higher level than the second opening (7). A first channel (11) is connecting the first orifice (10) with the first opening (6). A second orifice (12) for the liquid out of/into the device (1) is placed at the lower part of the device at a lower level than the first opening (6). A second channel (13) is connecting the second opening (7) with the second orifice (12). In a first embodiment the highest level of the first chamber (3) is at the same level as or at a higher level than the highest level of the second channel (13). Use of such a pressure sensing device in a connecting structure for an extracorporeal blood treatment machine is also included.