This is the traditional approach, in which the pressure increases continuously at a constant rate (figure 1), which can be modified depending the instrument and the user's requirements, and the gas flow through the sample is measured. Again, the number of data points acquired can be adjusted by the user.
It is a fast and reproducible method that is generally recommended for quality control work and for samples with all pores identical. However it is important to take into account that when the samples present a complex structure and with a considerable amount of pores of different tortuosity it is possible that during the pressure scan pores with the same diameter but longer pore path are not emptied at the pressure corresponding to their diameter (if the scan is fast there is not time to allow the gas flow to displace the wetting liquid through the pore length). As a consequence, the pores with longer pore length will be report smaller pore sizes than the actual ones.