The capsule pressure gauges are instruments intended for measuring low pressures or depressions usually indicated by the mbar scale, or in mmH20 for gaseous and clean fluids. Due to the internal measuring “capsule” they are not suitable for liquid fluids, aggressive gases or gases with condensation.
They are usually used for gas distribution systems or for air conditioning systems.
The internal “capsule” is made up of a pair of membranes, welded together, and placed in parallel with respect to the quadrant inside the case.
They can be made both in copper alloy (brass) and in stainless steel, with parts in contact with the fluid in AISI 316.