Patent ID: 6851295

Claim:
A check rod for apparatus for measuring properties of longitudinally permeable rods, the check rod comprising an elongate, substantially hollow, substantially cylindrical body; first, second and third transverse walls which are spaced longitudinally of the body; a first longitudinal chamber defined by the body and the first and second transverse walls; a second longitudinal chamber defined by the body and the second and third transverse walls; at least one first ventilation window for allowing air to flow from outside the body laterally into the first chamber; at least one second ventilation window for allowing air to flow from outside the body laterally into the second chamber; and tubes which are open at each end and provide for laminar airflow therethrough which is the only flow of air through the transverse walls, said tubes comprising at least one short laminar flow tube which passes through the first transverse wall and opens into the first chamber; at least one intermediate length laminar flow tube which passes through the first and second transverse walls and opens into the second chamber; and at least one long laminar flow tube which passes through the first, second and third transverse walls to allow passage of air through a full length of the check rod.