This is not necessarily an analysis tip. It would be better categorized as a database tip, or a data backup tip for specialized analysis work. When collecting route data the analyst may or may not want to also store Time Waveform data. Usually the TWF is not required unless the machinery operates at low speed or a gear box is involved. However, when performing specialized off-route analysis like Operating Deflection Shape, Modal Analysis, Acoustics, or any Phase analysis; you might consider saving the Time Waveform in addition to the spectrum, FRF, or other frequency-based measurement.

When performing specialized field analyses, one might forget an important setup parameter, or collect the spectra in a way that is not quite right.  The wrong "window" function may be specified. The number of averages, or average type may not be correct. The data export may be mis-formatted as a Power Spectral Density instead of an Auto Spectrum or Fourier Spectrum.  I've had cases where I forgot to check the boxes that store Cross-Channel Phase when I'm performing a phase analysis. This is especially problematic when the job is a plane ride away.

An easy safeguard for specialized analysis work is to ALWAYS store the Time Waveform. Most analysis and database software systems can still use this data to reproduce the original on-site spectral data format. Better safe than sorry!

Tip by Dan Ambre, P.E. [Modalguy]
Full Spectrum Diagnostics, PLLC