The Basics of Time Waveform Analysis

Dennis Swanepoel, Lead Technician, WearCheck


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.


I started my career attaining my National Diploma(S4) in Mechanical Engineering and becoming a Performance and Testing Technician in the Power Generation Industry. I have been in the field of Condition Monitoring for past 16 years. Starting out as an apprentice I managed to improve my knowledge in condition monitoring in various industries and becoming involved in training. In my first years in condition monitoring I managed to be certified by Technical Associates as a trainer for their courses and started specializing in ODS and Modal Analysis. I have worked in various industries and are qualified in Vibration, Thermography and Oil analysis. I also specialize in operational Deflection shape analysis. Currently my main duties is shared between starting up new service contracts, Special Investigations, Training (Mobius Training Partner).
Industries that I have worked in include Power Generation, Coal Mining, Platinum/chrome refinery and mining, Waste Water Treatment, Food, Paper and Sugar Mills. My most recent achievement was to pass the Mobius CAT IV course and starting up two service contracts in the Power Generation Industry that include vibration, thermography, oil analysis, alignment.