The resulting pressure, that's measured from the capsules, is definitely the differential pressure of the two process pressures. Most commonly this technology consist of a diaphragm with patterned metallic pressure gauge embedded into it. Raising pressure will cause the diaphragm, and subsequently, the gauge to deform which results it’s resistivity. https://cashtogvm.ourcodeblog.com/33294973/indicators-on-bourdon-tube-plastic-or-painted-steel-case-gauge-you-should-know