device for the determination of the amount of substance or the density of fiber structures , which utilizes the elastic properties of the fiber material . by means of a sphere which is positioned in a conical opening in a duct through which the fibers pass and which presses on the fibers with a part of its surface , a nozzle is throttled , so that the pressure on the nozzle represents a measure for the force on the sphere . this pressure is in a definite relationship to the fiber pressure on the sphere and can be measured with a pressure measuring device and transformed into an electrical signal by means of a normal commercially - available converter . a small groove in the wall of the duct behind the sphere avoids the attachment of fibers between the sphere and the opening .