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Laws
We present here an abbreviated history and overview of fundamental
Laws dealing with pressure and flow measurement.
Pressure
In physics, pressure is a force measured in terms of its distribution over an
area of an opposing force. This is expressed as force (F) divided by unit
area (A) of the surface area to which the force is applied. Air pressure
most commonly refers to a force exerted uniformly in all directions. Force
X Area = pressure.
Absolute pressure is pressure measured with respect to zero pressure (a
very high vacuum)
Gauge pressure is pressure measured with respect to surrounding air
pressure (the pressure exerted by the weight of the atmosphere).
Barometric pressure is the surrounding pressure caused by the
atmosphere. At average sea level, barometric pressure is about 14.7
pounds per square inch, or 29.9 inches of mercury. This is equivalent to
101.3 Kilopascals.
Negative Pressure (Vacuum)
A vacuum can be defined as a volume of space that contains no matter.
For practical purposes, this means a volume where as much matter as
possible has been removed. A perfect vacuum does not exist even in the
depths of space. Any given volume will probably contain one or more
particles of matter or one or more units of energy, which is the equivalent
of matter (relativity). Even a vacuum with no measurable energy level is
only a “virtual” vacuum.
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