AbstractA hot wire/film probe is used with new operating conditions for measurements of velocity and concentration in helium/air mixtures. With the upstream wire much more overheated than the downstream film, the sensing elements behave almost independently and the calibration map is composed of clearly distinct iso-velocity and iso-concentration curves. This behaviour is largely explained by the difference in the heated elements diameters. Tests of the probe in a turbulent boundary layer with large density variations indicate very satisfactory measurements. The domain of use for the probe is considerably extended with these new operating conditions.