The design principle and the material selection of pressure gauges allows them to meet the stringent demands occuring in service and industrial processing plants. Diaphragm pressure gauges have a relatively high actuating force. The annular clamped diaphragm is insensitive to jarring or vibration. An extremely high resistance to overpressure is achieved by underpropping the diaphragm. In processes with chemically aggressive media, diaphragm pressure gauges have a special material coating on the components in contact with the medium which protect them from corrosion. With highly viscous, crystallizing or strongly heterogeneous media, open process connections which ensure that the gauges are easy to clean, e. g. by flushing, are used.