Reynolds measurement
The dynamic pressure in the test section is measured by a precision differential pressure transducer: Mensor model DPG II 1500. It has a full-scale range of ±0.75 psi, with an accuracy of ± 0.01% of full scale. The transducer is calibrated every six months using a primary standard traceable to the National Institute of Standards & Technology (NIST).
The static pressure in the test section is measured by an absolute pressure transducer: Omega model PX425-030AV. It has a full-scale range of 0 to 30 psi with an accuracy of ±0.05 % of full scale.
Test section temperature RTD
The test section static temperature is measured by a Resistive Temperature Device (RTD), manufactured by National Semiconductor. It has a full-scale range of 5 to 300 degree Fahrenheit with an accuracy of ± 1 degree Fahrenheit.
Primary balance
The main balance is a six-component (three forces, three moments) external balance located beneath the test section floor. The balance simultaneously measures all forces and moments with respect to the wind axes at the virtual balance moment center located at the center of the test section. These forces and moments are converted to voltages by electromagnetic potentiometers. The output voltages are amplified and converted to digital numbers in engineering units. The balance limits are:
Balance resolution and limits
| Balance Component | Resolution | Full Scale Limit |
|---|---|---|
| Lift | 0.090 lbs | 2,500 lbs |
| Drag | 0.013 lbs | 250 lbs |
| Side Force | 0.01 lbs | 250 lbs |
| Pitching Moment | 0.232 in-lbs | 5,000 in-lbs |
| Yawing Moment | 0.205 in-lbs | 5,000 in-lbs |
| Rolling Moment | 0.169 in-lbs | 5,000 in-lbs |
The external balance has passive damping for reducing vibrations induced by the model. All signals from the external balance are sent through a 1 Hz low-pass filter before being sent to the data acquisition computer.
A breeze shield protects the external balance area from the effects of drafts.
6-component external balance