This example shows how to analyze rotation speed fluctuation (rate of rotation variability) of a take-up roller for paper pulp, a magnetic tape, an industrial film, or a similar product. The RP-7400 roller encoder (1200 pulses/1 rotation) is used for the analysis. The RP-7400 detects line speed of an object to be measured with its roller in direct contact with the object. Then the FV-1500 high-response F/V converter calculates the variable period of the line speed and outputs it to the CF-9200 Portable 2ch FFT analyzer. On the CF-9200, the rate of speed fluctuation is obtained by performing frequency analysis of the speed fluctuation. If additionally the LG-9200 optical detector is deployed to generate a pulse timing signal per a rotation of the roller, which is used as a trigger and enables measurement in synchronization with the roller rotation, speed fluctuation per a rotation of the roller and its timing can be checked.