Diaphragm seals are used to protect the pressure measuring instrument from aggressive, adhesive, crystallising, corrosive, highly viscous, environmentally hazardous or toxic media. A diaphragm made of the appropriate material provides for the separation from the medium to be measured. Thus even the most difficult measuring requirements can be met by combining measuring instruments with diaphragm seals. A fluid inside the system, which can be chosen to suit the particular application, hydraulically transmits the pressure to the measuring instrument. The diaphragm is welded to the upper body, to ensure separation of filling fluid from process medium. The “in-line” diaphragm position enables deep cleaning of their surfaces. Flange clamping with metallic sealing guarantees the system against leakage at high process fluid temperatures and pressures