Pressure Transducer: Calibration Using a Pitot-static Tube

1. Pressure Transducer Calibration

In this demonstration, a subsonic wind tunnel with a 2.6 ft x 3.7 ft test section and maximum dynamic pressure setting of 25 psf was used. A pre-calibrated pressure transducer was used to set the dynamic pressure in the wind tunnel test section, and a differential U-tube manometer with colored water and scale was used to measure fluid height (Figure 3). A differential pressure transducer (Figure 4), standard voltage supply (to power the transducer), and multimeter (to read the output current from the transducer) were also used, shown in Figure 5.

Figure 3. Differential pressure U-tube manometer. 

Figure 4. Differential pressure transducer. 

Figure 5. Power supply (left) and multimeter (right). 

1. Mount a standard pitot-static tube (Figure 6) from the top of the wind tunnel using a vertical sting mount. Ensure that the probe is at the center of the test section and is aligned in the direction of the flow with the primary port facing directly into the flow.

Figure 6. Pitot-static tube. 

2. Align the top of the manometer fluid to the double O-ring marker on the glass tube. If the reading on the main scale (in brown, Figure 3) does not correspond to zero, choose a different reference point, align the manometer fluid to the new reference, and record the offset in height (h_off).
3. Connect the stagnation and static pressure outlets on the pitot-static tube to the corresponding ports on the U-tube manometer and the pressure transducer using flexible plastic tubing and T-channel connectors. Note that the pressure transducer can be mounted on any flat vertical surface as long as it is aligned in accordance with Figure 4.
4. Secure the wind tunnel doors and switch-on all the systems.
5. Take the reading for the no-air flow condition (zero reading).
6. Start the wind tunnel and set the dynamic pressure in the test section to 1psf.
7. Record the data corresponding to Table 1.
8. Increase the dynamic pressure setting in the wind-tunnel in steps of 1psf up to a maximum setting of 20psf and repeat step 1.7 at each dynamic pressure setting.
9. To check for transducer hysteresis, decrease the dynamic pressure in steps of 1psf down to 0psf and repeat step 1.7 at each dynamic pressure setting.
10. On completion of the test, shut down all systems.

Table 1. Data collected for the pressure calibration experiment

Ptransducer (psf)	hmanometer (in)	Itransducer (mA)
WT transducer	manometer	multimeter