Periodicity Prepare by Ji Kim, Bokman Kim

FFT spectrum FFT Spectrum Analyzers, such as the SR760, SR770, SR780 and SR785, take a time varying input signal, like you would see on an oscilloscope trace, and compute its frequency spectrum. Fourier's theorem states that any waveform in the time domain can be represented by the weighted sum of sins and cosines. The FFT spectrum analyzer samples the input signal, computes the magnitude of its sine and cosine components, and displays the spectrum of these measured frequency components.

Electronic Test Instrument Function generator FFT (Fast Fourier Function) Spectrum Oscilloscope SPC Gauge

Formula and Data  F=C/λ  F= Frequency  C=Line speed  λ=Wave length  Wave length is given by customer (Defect Spacing) λ 65 FPM 100 FPM 200 FPM ft HZ 3.07 HZ 6.14 HZ ft HZ HZ 7.31 HZ ft 4.25 HZ 6.54 HZ HZ ft 4.45 HZ 6.86 HZ HZ RFS Provided Data March (2009)

Applied Formula  Defect spacing are given by customer.  Line speed=300FPM  Example F=(300/60)/(6.516/12) =9.208HZ T=1/(9.21)=0.108S Defect Spacing HZT (sec) Inch 9.21 HZ S 3.06 Inch HZ S Inch HZ S

Justify of the FFT Analyzer HZ Test with 24.41HZ span

Justify of the FFT Analyzer HZ Test with 48.82Hz span

Justify of the FFT Analyzer HZ Test with HZ span

How to Avoid the Frequency band?  V=2 p R/T  V=2 p RF  V=DF  D=V/F  Change Rolling Mill and Bearing. Bearing Rolling Mill

Conclusion  Line speed and Wave Length to determine the affects on periodicity.  Ready to set up with FFT to Gamma Gauge.  FFT analyzer is functionally correct, Ready to test at Rolling Mill.