Pneumatics 101

FORCE and PRESSURE

The relationship between force and pressure is important because in industrial applications pressure must be created to apply force. In fact:

PRESSURE is the force per unit area, and it is typically measured in pounds per square inch. Or,
PRESSURE = FORCE/AREA

FORCE is created by pressure exerted on an area. Or,
FORCE = PRESSURE x AREA

Types of Pressure
1) Atmospheric Pressure - This is the pressure produced on the earth's surface by the weight of the air surrounding the earth. Tests show that atmospheric pressure equals around 14.7 psi (pounds per square inch).
2) Gauge Pressure - Because atmospheric pressure always exists all around us without significant change, we do not notice it. Therefore, we consider atmospheric pressure to be "zero" pressure. Gauge pressure is a pressure that does not take into account the additional pressure resulting from atmospheric pressure.
3) Absolute Pressure - When dealing with the effects of pressure on gases, we must consider the total pressure on the gas. We cannot ignore the effect of atmospheric pressure as we do when measuring gauge pressure. The total pressure acting on a gas is called absolute pressure, or Absolute Pressure = Gauge Pressure + 14.7. The "14.7" is the figure that represents atmospheric pressure. Absolute pressure is measured in psi absolute.

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