Pascal (Pa)
Pa=N/m² : The Pascal (Pa) is the SI unit, 1
Bar = 10E5.Pa = 101 kPa = 0.1 MPa
A pressure of 1 Pa applied on a surface A=1m² generates a force F=1N (1N=1
kg.m.s-²).
That relative Vacuum in %: V% = (Po-P)/Po,
300mbar => (1013-300)/1013= 70% Vacuum
or P=Po-(Po.V%), 30% in Torr => 760-(760.0.3)=532 Torr
atmospheric pressure (1 Atm.)
1.013 bar = 1013 millibars (mbar)
= 101325 Pascal (Pa), = 101 kPa
= 760 Millimetre mercury column (mmHgA) = 760 Torr (1 Torr = 1 mm HgA)
= 29.92 inches of mercury absolute (in HgA),
= 14.7 pounds per square inch absolute (lb/in², PSIA)
Atmospheric pressure is often measured with a mercury barometer, and a height
of approximately 760 millimetres (30 in) of mercury is often used to illustrate
(and measure) atmospheric pressure. However, since mercury is not a substance
that humans commonly come in contact with, water often provides a more
intuitive way to visualize the pressure of one atmosphere:
One atmosphere (101 kPa or 14.7 psi) is the amount of pressure that can lift
water approximately 10.3 m (34 ft).
10.3 m (34 ft) is also the maximum height to which a column of water can be
drawn up by suction / via a vacuum.