Vacuum presssure to absolute pressure
Vacuum presssure to absolute pressure
(OP)
How does one convert vacuum pressure reading to absolute pressure reading. I have a manomenter reading 25 " Hg - what is that in absolute pressure
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Vacuum presssure to absolute pressure
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RE: Vacuum presssure to absolute pressure
750 mm Hg equals 1 bar
which means the absolute pressure in your system is about 866 mbar.
RE: Vacuum presssure to absolute pressure
In your case, you would get 25 + 29.9 = 54.9" Hg.
I hope you are not up in the Rockies or something...
Cheers,
Joerd
RE: Vacuum presssure to absolute pressure
Cheers,
Joerd
RE: Vacuum presssure to absolute pressure
RE: Vacuum presssure to absolute pressure
yes, you're right... where do i have my brains nowadays...
RE: Vacuum presssure to absolute pressure
25" HgA pressure reading is 844 mBarA.
RE: Vacuum presssure to absolute pressure
Nowadays, by convention, atmospheric pressure is 1 atm abs = 760 mm Hg @ 0oC = 760 torr = 14.696 psi = 29.92 in. Hg @ 0oC = 1013.25 mB = 101.325 kPa = 101,325 N/m2. We see that 1 bar = 100,000 Pa = 1,000,000 dynes/cm2 = 100,000 newtons per square meter or N/m2.
The right interpretation of the present thread is whether dideyjohn speaks of a manometer, and means a barometer thus its reading is absolute pressure:
(25 in x 25.4 mm/in) /750 mm/bar = 0.8467 bar = 846.7 mB abs.
Otherwise, if it is a vacuum reading, then it is {[760-(25x25.4)]/750}1000 = 166.7 mB vacuum.
The more accepted SI unit nowadays is the Pa = 1 N/m2 = 10 dyn/cm2 = 1 kg/(m.s2). Thus 1 atm = 0.101325 Mpa = 101.325 kPa.
Units as mm Hg, or in. Hg, or in. H2O must be given in reference to temperature. 1 in. H2O @ 60oF = 248.8 Pa.
1 in. Hg @ 60oF = 3,377 Pa.
It is always advisable to add the words "absolute pressure" or "vacuum", or their abbreviations, as befits the case in hand.
RE: Vacuum presssure to absolute pressure
i thnk i am beginning to see why nature abhors a vacuum, more or less
RE: Vacuum presssure to absolute pressure
Initial Vacuum pressure - we run a vacuum of 25 " Hg on a monometer at sea level - so I would say this value is 25 " Hg
Atmospheric pressure - 29.92 " Hg -
Would this be correct or where am I off - If I saw a value of 25 " Hg, how do I differtiate it from being vacuum or positve pressre and if vacuum, I do I show it on the same scale as the atmosheric pressure
RE: Vacuum presssure to absolute pressure
Hg by it self, is usually referenced to local ambient(i.e. a u-tube or inclined manometer), at least that is my usage.
there is a lot of ambiguous usage, i am guilty of it in routine conversations as much as any one, it is all context driven and satisfys a need to simplify the information being communicated.
differential manometry is far mor common than abs. meas, but both are important.