Absolute Pressure

    

Absolute Pressure Formula
\( p_a \;=\; p_g  +  p_{atm} \)     (Absolute Pressure) \( p_g \;=\; p_a  -  p_{atm} \) \( p_{atm} \;=\; p_a  -  p_g \)
Symbol	English	Metric
\( p_a \) = Absolute Pressure	\(lbf \;/\; in^2\)	\(Pa\)
\( p_g \) = Gauge Pressure	\(lbf \;/\; in^2\)	\(Pa\)
\( p_{atm} \) = Atmospheric Pressure	\(lbf \;/\; in^2\)	\(Pa\)

Absolute pressure, abbreviated as \(p_a\), refers to the total pressure exerted by a fluid, including atmospheric pressure, relative to an absolute vacuum.  It is the measurement of pressure relative to absolute zero pressure.  Absolute pressure is used in various fields, including physics, engineering, and fluid dynamics, where an accurate and consistent reference point is required.

In contrast, gauge pressure is measured relative to atmospheric pressure.  Gauge pressure readings do not take into account the atmospheric pressure, which can vary depending on the location and altitude.  Gauge pressure is commonly used in everyday pressure measurements, such as tire pressure or pressure gauges in mechanical systems.  To convert between absolute pressure and gauge pressure, atmospheric pressure must be added or subtracted accordingly.  For example, if the atmospheric pressure is 101.3 kilopascals (kPa) and a gauge pressure reading is 150 kPa, the corresponding absolute pressure would be 251.3 kPa.

Absolute pressure is typically measured using instruments such as absolute pressure gauges or transducers.  These devices are designed to provide pressure readings relative to absolute zero pressure, and they account for both atmospheric pressure and the pressure of the fluid being measured.

Absolute pressure is essential in many applications, such as in the study of fluid dynamics, gas laws, and calculations involving pressure differentials and fluid behavior.  It ensures accurate and consistent measurements and provides a standardized reference point for pressure analysis and comparison.