What records the difference between still air and air that is being rammed into the system?

Still air is at atmospheric pressure and atmospheric temperature whereas rammed air has a higher pressure, higher density than the atmosphere and as a result, its temperature also increases.

Explanation:

Still air is at atmospheric pressure and atmospheric temperature whereas rammed air has a higher pressure than the atmosphere and as a result, its temperature also increases. Rammed air is under pressure and has a higher density. Rammed air has a greater mass in less volume. The rammed air is used in compressors and gas turbines to produce energy in the desired form.