An automated analysis method for an impactor used as a measuring transducer for the selective determination of oil mist or aerosols. The process includes the steps of rotating the deflector plate (5) of the measuring transducer (1) about the symmetry axis thereof and of determining the quantity of oil deposited by means of an optical analyzing device from the extinction of a light beam reflected from deflector plate (5) due to the alternation between the background and the pattern produced by the micronozzles (4).