If spg shows 200 bar at the surface (gauge pressure), that means the absolute pressure in the tank is 201 bar.
If we go down to 30m and don’t use any gas, the absolute pressure in the tank is still 201 bar (because the cylinder doesn’t deform).
But would the spg still show 200 bar, or 197 bar?
Basically 1) is an spg a gauge pressure vs atmospheric pressure (closed chamber in the spg), 2) or vs ambient pressure (atmospheric + hydrostatic at whichever depth the reading is made)?
If we go down to 30m and don’t use any gas, the absolute pressure in the tank is still 201 bar (because the cylinder doesn’t deform).
But would the spg still show 200 bar, or 197 bar?
Basically 1) is an spg a gauge pressure vs atmospheric pressure (closed chamber in the spg), 2) or vs ambient pressure (atmospheric + hydrostatic at whichever depth the reading is made)?