Technical Guide to the TAD-2 Wind Tunnel

5. Instrumentation

5.1 Six Component Strain Balance

The main balance is six-component external strain gauge balance with strip support. It permits measurement of all the six components of full loading on the model and converts them into three forces and tree moments in wind axes. Force sensors are industrial strain gauge transducers of "Veda" company (Kiev) and are located above the test section out of the flow boundaries. Under the test section passive hydraulic dampers and counterloads for support strips tension are installed. Balance is equipped with model weight compensation system, that permits to narrow down the measuring range and thus to increase accuracy. The output signals are increased by tensor amplifiers CMJ-CEB CARTE manufactured by France and then in data acquisition and processing system their conversion to digital form and further processing is performed.
Balance calibration is made using the multibase six-component loading unit. Special weights with 0.1% accuracy are used as reference. Relative error of any component is not greater than 0.7% of measuring range at 90% confidential probability. Measuring ranges for loads measuring are as follows: Lift - 0...1200 N, Drag - 0...400 N, Side force - 0...400 N. Moments measuring range depends upon measured forces and support bases used.

5.2 Dynamic Pressure Transducer

It is used the air pressure sensor MPXV 5004 G manufactured by USA, which is the inductive differential pressure transducer with built-in electronic modulator-demodulator. It is powered with stabilized DC source and output signal is a high-level DC voltage, functionally dependent on applied pressure difference. Output voltage in data acquisition and processing system is converted to digital form and further processed.
The vacuum side of transducer is connected to a pipeline, in which the pressure from Eiffel chamber is supplied. Pressure side is vented to atmosphere. The dynamic pressure is calculated using the so-called "dynamic pressure field coefficient", which is determined during test section flow calibration.
The transducer is calibrated every six month using standard liquid pressure gauge MKB-250 with an accuracy of +0.1 Pa. Stream metrological certification in wind tunnel working part was fulfilled with the use of pressure tube Pito type TNP-05 calibrated in Berlin physical-technological university (Germany) with the use of laser-Doppler anemometer.

5.2 Angle-of-Attack Transducer

Angle-of-attack measurement is performed using F5071 instrumentation, based on multi-revolution selsyn-type transducer, installed on the angle-of-attack alteration drive. Measuring error is not greater then 5'.
The system is calibrated using optical inclinometer with accuracy of 1'.