摘要 |
PURPOSE:To execute a fixed width tracking analysis with respect to fixed spectrum width, by determining a clock signal of a period for satisfying a prescribed condition based on a forecasting period, etc. of a signal source, sampling the signal, and executing a Fourier calculation. CONSTITUTION:A period forecasting circuit 17 forecasts the following period T0 from a past rotation period signal of a rotation driving source 4, etc. of a signal source, which is outputted by a period signal generating circuit 6. Subsequently, an calculating means 18 calculates a period U1=T0/H, and a constant of H: number of gear teeth ratio, etc., and a constant calailating means 19 calculates a value m0 by which the number which reduces the time window Tw of a Fourier calculation from the product of a higher harmonic order number (m) and the period U1 to be minimum. Subsequently, a value corresponding to a clock period gamma based on the expression is determined by a clock period calculating means 20, and a clock of the period gamma is outputted through a frequency dividing rate setting means 21 and a frequency divider 23. By this clock, a vibration waveform of the driving source 4, which is detected by a pickup 5 is sampled by a Fourier analyzer 7, and even if synchronizing signal frequency is varied, Fourier analysis is executed by fixed spectrum width. |