air velocity transmitter 0-2m/s, 0-5m/s, 0-20m/s HVAC Measuring TheoryASP-U-D air velocity transmitter is a ideal opotion for accurate vetilation control. The innovation of the working theory is using the pitot tube(The pitot tube is for testing the pressure).Becuase of the simple stucture, the convenient use, and the perfect theoretical study, this methord is widely used. Pitot tube test ...