FIELD: measuring engineering. ^ SUBSTANCE: device (10) comprises source of fluid (14), which is under virtually constant pressure and connected with tank (16) filled with the fluid through pipe (11). The tank has measuring pressure transducer (18) connected with the amplifier and indicator (22) for the control of source (14) through wires (20). The impenetrable member, e.g. disk (24), is mounted on the surface of the material to define a space for flowing fluid between disk (24) and the surface. Disk (24) is connected with pipe (30) of lesser cross-section through pipeline (32). Pipe (30) provides high resistance to the fluid flow. The opposite end of pipe (30) is in communication with tank (16). Gauge (34) is connected with the ends of pipe (30) to measure the rate of the fluid flow. The impenetrable seal is arranged over periphery of the disk (24) and extended in the radial directions over the surface. If the material is permeable, the air penetrates through the material to the space. This flow provides a p
