Before diving into the world of vacuum chuck workholding there are some basic definitions that are helpful to know.

• Air Consumption – The volume of compressed air required to power a venturi style vacuum generator.
• Atmospheric Pressure – The atmosphere that surrounds the Earth can be considered a reservoir of low pressure air. Its weight exerts a pressure that varies with temperature, humidity and altitude.
• Barometer – A device usually filled with mercury that measures atmospheric pressure.
• Vacuum Flow – The volume of free air induced by a vacuum pump per unit of time, expressed as standard cubic feet per minute – SCFM or LPM (liters per minute).
• Vacuum Level – The magnitude of the suction created by the vacuum pump.  The unit of measure is inches of Hg (“Hg).
• Vacuum Force – Equal to the vacuum level multiplied by the surface area of the vacuum surface, i.e. vacuum cup, vacuum chuck surface.
• Vacuum Fade – For each 1,000 of elevation, vacuum level decreases by 1″ of Hg.