Q. How do you read an air flow meter?

Answer

Multiplying the air velocity by the duct's cross sectional area yields the air flow. Knowing the length width and height of the duct makes calculating the volumetric flow a breeze. The air velocity is not constant along the duct so that's something to think about. This is so due to the fact that air is moving at its slowest along the sides due to the effects of friction. Because of this it is preferable to measure velocity using an averaging Pitot tube that has numerous sensing points. The formula is Q (air flow rate)= A (area of duct) * V (air velocity)