For a spheric probe with five measuring points on its surface, the magnitude and the direction of the inflow velocity is a function of three pressure coefficients. These inflow quantities can therefore be determined by measuring the pressure coefficients. Wind tunnel tests of such a probe revealed that there is a linear relation between the measured and the theoretical value of the inflow quantities, provided that the geometric base angle is not too large and the effective base angle is determined experimentally. The base angle defines the position of the measuring points. If the resolution of the pressure measurements is not sufficient, these relations must be used as calibration lines. 21 figs., 2 tabs., 4 appendices, 8 refs.