When we measure the pressure of general gas, water and oil, we can choose general pressure gauge: when measuring nitric acid. For the pressure of phosphoric acid and strong alkali, a stainless steel pressure gauge can be used. But when the measured medium is very corrosive (such as hydrochloric acid, wet chlorine, ferric chloride), has a high viscosity (such as latex), is easy to crystallize (such as salt water), and is easy to solidify (such as hot asphalt), If there is solid floating matter (such as sewage), it is not feasible to use the above pressure gauge, because the SUS316 stainless steel pipe will also be corroded by hydrochloric acid, and the floating matter in the asphalt and sewage will quickly block the pressure guiding hole of the pressure gauge. And make the meter lose its use function. Pressure gauge with Diaphragm Seal can solve these problems. User can choose different corrosion-resistant diaphragm materials according to different strong corrosive media to play a role in corrosion protection.