WT4401-D is a laboratory grade benchtop wind tunnel designed to give a highly uniform flow rate over a 6" test section. A powerful 12A motor with variable speed from 0 to 10,000RPM is adjustable to give a particular flowrate by a precise motor control unit. Each wind tunnel is supplied with an NIST traceable certificate. The uniform flowrate is determined by monitoring a highly repeatable differential pressure sensor which has been calibrated to each individual wind tunnel as a system. Each wind tunnel is supplied with two restrictive plates for achieving optimum low flowrates. The established differential pressure measurements versus flowrates are listed from 25 to 9000FPM. Calibration sheets are included, which makes calibrating different flow sensors simple. The differential pressure measurement used to establish known flowrates will be affected by barometric pressure and temperature conditions during testing. Depending on the probe being calibrated, humidity may also be a factor.