In order to calculate it, you must place one of the ends of a manometer where the fan inlet is. The other end of the manometer must be placed at the end of the fan outlet. Now you simply measure the difference between the liquid height on both sides of the manometer in order to measure the total pressure.
Place the vane anemometer at different points of the fan face, in order to take more than one velocity measurement. After you have done that, average all of those readings in order to accurately measure air speed. The recommended amount of different velocity measurements is nine, according to the University of Connecticut.
