The article focuses on the study of a measuring aspiration chamber with blowing grids for a light aeroion counter. To improve the reliability of the chamber it is proposed to perform it in the form of a flat electrode lens. Its mathematical model is proposed. The calculations of the electric field strength of the lens and the study of trajectories of aeroions movement in its working volume allowed to establish the necessary constructive dimensions of electrodes and to obtain the dependences allowing to choose the mode parameters of the aspiration chamber according to the given limiting mobility of aeroions.