When and why are diaphragm seals used with pressure transmitters?

Diaphragm seals isolate pressure transmitters from process fluids that are corrosive, viscous, high-temperature, or prone to solidification. The seal consists of a flexible diaphragm connected to the transmitter via capillary tubing filled with inert oil. Applications include: corrosive chemicals (HF, H2SO4), sanitary processes (food, pharma with flush diaphragms), high-temperature processes (using remote seals with cooling), and slurries/crystallizing fluids. Consider response time degradation due to capillary length.