Pressure sensing device adapted for having a liquid flowing there through and for sensing the pressure of said liquid, said device having - a casing being fluid-tightly divided into a first and a second chamber by a flexible, impermeable wall, - said first chamber having a first opening for the liquid, said opening being placed at the lower part of the chamber, - said first chamber having a second opening for the liquid, said opening being placed at the upper part of the chamber, - said second chamber having a measuring port, which is connectable to a pressure transducer for bringing the second chamber into gas-tight communication with the pressure transducer, characterised in that - the second opening for the liquid being placed at the top of the first chamber, - a first orifice for the liquid into/out of the device being placed at the upper part of the device at a higher level than the second opening of the first chamber, - a first channel is connecting the first orifice of the device with the first opening of the first chamber, - a second orifice for the liquid out of/into the device being placed at the lower part of the device at a lower level than the first opening of the first chamber, - a second channel is connecting the second opening of the first chamber with the second orifice of the device, wherein the highest level of the first chamber is at the same level as or at a higher level than the highest level of the second channel, - a first duct is provided having a lower mouth and an upper mouth, said lower mouth being placed in the top of the first chamber and the upper mouth being placed in the first channel at a higher level than the lower mouth. - a casing being fluid-tightly divided into a first and a second chamber by a flexible, impermeable wall, - said first chamber having a first opening for the liquid, said opening being placed at the lower part of the chamber, - said first chamber having a second opening for the liquid, said opening being placed at the upper part of the chamber, - said second chamber having a measuring port, which is connectable to a pressure transducer for bringing the second chamber into gas-tight communication with the pressure transducer, - the second opening for the liquid being placed at the top of the first chamber, - a first orifice for the liquid into/out of the device being placed at the upper part of the device at a higher level than the second opening of the first chamber, - a first channel is connecting the first orifice of the device with the first opening of the first chamber, - a second orifice for the liquid out of/into the device being placed at the lower part of the device at a lower level than the first opening of the first chamber, - a second channel is connecting the second opening of the first chamber with the second orifice of the device, wherein the highest level of the first chamber is at the same level as or at a higher level than the highest level of the second channel, - a first duct is provided having a lower mouth and an upper mouth, said lower mouth being placed in the top of the first chamber and the upper mouth being placed in the first channel at a higher level than the lower mouth.