One caution about liquid filled gauges. I like them because they dampen the vibration that can kill a gauge but.........
The liquid filled gauge housing is sealed, otherwise the liquid will leak out. The problem arises when the gauge body see a temperature difference. Since the gauge is sealed, the pressure inside the gauge body can (and will) change with a change in the temperature of the gauge. This can cause an errror in the reading that can be pretty significant. I have seen errors of over 5 pounds in an industrial envirionment. ALWAYS burp the gauge before using it for reference work (like setting base pressure). There's usually a black rubber push-in seal or sometimes there a plastic vent lever built into the seal. If the gauge is installed upright, the vent lever is best left open. If the gauge is attached to the end of a hose, leave it closed and burp it with the lever before reading it.