These are used for liquid / gas / Steam service under normal conditions. The bourdon tube is 'C' shaped and closed at one end. When this is subjected to fluid pressure from the other end, the deflection is created and transmitted via movement to thte indicating pointer over dial. These are calibrated by comparison against master gauges and the accuracy is +/-1% of span with test certificates traceable to national standard. Connection is threaded 1/4", 3/8", 1/2" BSP/NPT. Range upto 1000 Kg/cm2, -760 mm Hg to 0 (Vacuum).These are used for liquids or gaseous media, for viscous, corrosive, slurry service. The diaphragm is hel between two flanges and deflects under pressure. This deflectin is transmitted through a link and movement to indicating pointer on the dial. Diaphragm and Flange material is selected depending upon the type of fluid. These are also available with chemical sealing fluid like silicon.