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Probe Calibration
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The intrusive measurement probes such as pneumatic probes or fast-response response probes need to be calibrated prior to the measurements. In that purpose the laboratory owns in-house state-of the-art calibration facilities: the static calibration facility and the aerodynamic calibration facility probe (weblink calibration facilities). Static calibration The static calibration facility is primarily used to calibrate the piezo-resistive pressure sensors and the thin-film gages temperature sensors of the fast response probes over the pressure and temperature range of interest. For the measurements, polynomial interpolations based on the sensors raw voltage are used to determine the pressure and temperature from the measured sensor signals. Fig1.a. shows a typical static calibration results of the piezoresistive sensor over a range of pressures (0-570 mbar) and temperature (40-130°C). It can be seen that the output signal U is weakly temperature dependent, while the excitation signal Ue is decoupled from the pressure. Fig.1 (b) shows the temperature-resistance calibration of the thin film gages with their respective temperature coefficients of resistance αr and βr. |
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Aerodynamic calibration Pneumatic and fast-response aerodynamic probes require to be aerodynamically calibrated over the Mach number and flow angles range of interest. Based on the pressure distribution around the probe tip, the calibration coefficients can be derived. As an example Eq.1 gives the common calibration coefficients used for 4-hole probes. Where Kφ and Kγ are the yaw and pitch angle calibration coefficients; and KT and KS are the total and static pressure calibration coefficients. Fig. 2 shows the correspondent calibration curves for a Mach number of 0.3.  |
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