In another lesson, we defined pressure as the force per unit area, and gave the SI units as Newtons per meter squared, or Pascals. There are actually a couple of different ways to measure pressure based on our frame of reference. We will further define pressure in terms of absolute pressure and gauge pressure. 1  Absolute pressure: The total pressure exerted on a system referenced to zero Pascals, and equal to the gauge pressure plus atmospheric pressure. Gauge Pressure: Pressure referenced to one atmosphere, and is the pressure actually shown on the dial of a gauge that registers pressure relative to atmospheric pressure. For example, an ordinary pressure gauge reading of zero does not mean there is no pressure, it means there is no pressure in excess of atmospheric pressure. Atmospheric Pressure: The pressure exerted by the weight of the atmosphere. Absolute pressure = gauge pressure + atmospheric pressure. Units of pressure - in the SI ...
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