The lowest pressure that a compound gauge can measure is typically in the vacuum range, which extends down to -30 inHg or close to a full vacuum.
#compoundgauge
https://www.ourmechanicalworld.com/archives/712

What Is The Lowest Pressure On A Compound Gauge? - Ourmechanicalworld.com

In the world of mechanical engineering and industrial applications, pressure measurement is an essential task. The accurate measurement of pressure in systems