[cavani]

I am trying to measure pressure drop of air through a pipe. What are the necessary stages required to do this?

[-mAx-]

Report total pressure at inlet, then at outlet.
Pressure drop will be the difference between the 2 values.
If I remember, you can compute average value on surface, with report/surface integral/area-weighted-average

[kbaker]

I can add to max reply after reporting the pressuer at inlet & outlet substract the pressure values then divide the resulting value by pipe length hence you get the pressure drop.

k.baker