WIRA
It involves a rotating shaft with a spiral groove machined in it. Once end of the fiber to be measured is gripped by a pair of tweezers whose point is then placed in the moving spiral. This has the effect of moving the tweezers to the right and so steadily drawing the fiber through the pressure plate. This ensures that the fiber is extended under a standard tension. A fine wire rests on the fiber and is arranged so that when the far end of the fiber passes under the wire it allows it to drop into a small cup of mercury and thus complete an electrical circuit. This causes the shaft to stop moving, so halting the tweezers, at this point the tweezers are then raised to lift the counter immediately above where it has stopped. The counters are arranged in 0.5 cm sections and each time one is lifted it adds a unit to the appropriate length group so contributing to a cumulative total. The advantage of the apparatus is that it gives a standard tension to the fibers, it involves less operator fatigue and it gives semi-automatic recording of the results to 0.5 cm intervals. The apparatus is claimed to be able to measure up to 500 fibers per hour However, the detector wire that is used to sense the end of the fiber is very delicate and it is difficult to set up.
Fiber Sorter Method
This is done by holding the fibers in one hand and extracting the fibers by their ends with the other hand. This first step produces a bundle of fiber ends together. The fibers are then taken from this bundle by hand a few a time starting with the longest fibers and are laid down next to one another in descending order of length. This produces a fiber diagram as show in fig.