What does the abbreviation PSIA refer to in pressure measurement?

The abbreviation PSIA stands for "Pounds per Square Inch Absolute." This measurement is crucial in pressure readings because it accounts for atmospheric pressure in addition to the pressure of the gas being measured. When you add atmospheric pressure to the pressure gauge reading (PSIG, or Pounds per Square Inch Gauge), you convert it into an absolute measurement (PSIA).

This distinction is important in many applications, such as those involving thermodynamics and fluid mechanics, where knowing the absolute pressure is vital for accurate calculations and system performance. The other calculations, like subtracting atmospheric pressure or dividing or multiplying it by the gauge pressure, would not yield the definition of absolute pressure, which is why they do not represent the correct interpretation of PSIA.