The Basics of Time Waveform Analysis

Scott Dow, Director of Training & Development, Mobius Institute


All vibration data begins as a digitized time sample – the “raw data”. Despite that, many analysts limit themselves by failing to develop a thorough understanding of the various aspects of the TW plot, aspects that range from proper setup (the technical details and how they relate to spectrum) to analysis (understanding what you are seeing) and diagnosis (relating it back to the machine). While the FFT is a powerful tool and the resulting spectrum remains our “go to” plot for analysis, the fact of the matter is that the FFT has weaknesses that make certain types of faults more difficult – even virtually impossible – to assess. Many of these are the very same faults that are easiest to analyze using the TW – once you understand it!
This presentation will begin by using case study examples comparing TW and spectral data for known faults that show you the necessity of utilizing the TW plot (or missing a severe fault) before a brief primer on understanding the TW setup, including the “2.56” relationship between the TW and spectrum settings and some practical tips to being successful.