A gage reading of 30 psig is taken. What will an absolute pressure instrument read under the same conditions? An absolute reading of 60 psia is taken. What will a gage pressure instrument read under the same conditions? Determine the inches in H2O value if a measurement of 1.8 psi is made. The liquid in the reference column of a manometer rises 3 inches and the liquid in the pressure column lowers 3 inches. If mercury is used as the liquid, what is the gage pressure being measured? Mercury has a constant of 0.491 psi per inch.