Figure 3-3 Block diagram for calibration and velocity profile measurement for the air tunnel.




                    70                                            70

                    6 0 -- - - - - - - - - - - - - - - - - - -     0

                    ~5 0   - - - - - - - - - - - - - - - - - - - - 5 0 
                                                                     E
                  cc    - - - - - - - -   - - -       - -- - -  - 4 0ci,
                            I                                        
                               Cr                                    C.)
                             3 0 - - - - - - - - - - - -- - - - - -L  - - - -3 0 .2
                  0                                                  >
                  6 2 0 -- - - --          - - - - - - - - - - -  20

                    1 0 - - - - - - -     - - -   - - -   - - - - 1 0

                                                                  0
                           0   2        4       6        8       10
                                   DAQ \toltage (Volts)


Figure 3-4 Motor frequency and velocity of air tunnel plotted as a function of DAQ input voltage.

    Data from the UIP 34970A DAQ unit (output voltage from the Validyne P855A) is used to calibrate the P855A with respect to the Heise gauge. Velocity Profiles

    The block diagram for the velocity profile measurements is shown in Figure 3-3. For the velocity profile measurement, the pitot-static probe is traversed from the bottom of the tunnel to the top of the tunnel in steps of 2 mm while keeping v, constant. Then, v, is steadily increased from 0 - 10 V DC in steps of 0.2 V. An average of 25 readings from