It is essential to know the aerodynamic properties of the processed material during designing machines and devices used in agriculture and agro-food industry. This applies, in a special way, to the cleaning and separation processes. It is absolutely necessary to measure mentioned properties on special test stands. They are designed in an individual way, often without taking into consideration essential project guidelines. Therefore, the aim of this study was the analysis of methodological aspects and the elaboration of the principles in the mentioned stands design. The paper discusses the issues related to the choice of the measuring method (free fall or suspension of particle) and to the selection of the diameter of the duct test section, ensuring minimised influence of the boundary conditions on the measuring results. Special attention was paid to the section dedicated to the homogenisation of the air velocity, consisting of the honeycomb structure and the screens. This section is responsible for the reduction of turbulences, so that it is possible to obtain the homogeneous field air velocity in the measuring section. Other issues raised in the paper describe problems which cannot be omitted at the design stage of the measuring position, such as: the control-measurement system, the necessity of using flexible elements aimed at damping, and the way of placing the particles in the channel to minimise the disruption of the flow while maintaining the ease of placement. On the basis of the acknowledged project settings, the necessary calculations were carried out and the test stand to measure aerodynamic properties of the particles of plant materials was designed, which fulfils the requirements described in the conducted analysis. What is more, the functions of the offered stand were extended by the possibility of analysing the particles' trajectory in air stream.