annular slot or circular hole drilled in the wall of a conduit in such a way that the edge of the hole is flush with the internal surface of the conduit, rõngakujuline pilu või ümmargune ava, mis on puuritud torujuhtme seina nii, et ava serv on kanali sisepinnaga samal tasapinnal, hole drilled in the wall of a conduit to measure the static pressure of the flowing gas in the conduit
