VectoraLab Lab

What is RMS? RMS (Root Mean Square) is the most fundamental amplitude metric in vibration analysis. It represents the effective (energy-equivalent) amplitude of a vibration signal. Formula: RMS = √( (1/N) Σ x²[n] ) Why RMS Matters: • Directly related to vibration energy and damage potential • More informative than peak for broad-band signals • Used in ISO 10816/20816 for machine severity assessment • Trending RMS over time reveals gradual degradation RMS vs Other Metrics: • Peak: highest single amplitude — sensitive to transients • RMS: energy average — stable, relates to fatigue • Crest Factor (CF = Peak/RMS): detects impulsive faults • Kurtosis: statistical measure of impulsivity (>4 = impacts) Typical RMS Values (ISO 20816 simplified): • Zone A (new machine): <0.71 mm/s • Zone B (acceptable): 0.71–2.8 mm/s • Zone C (alarm): 2.8–11.2 mm/s • Zone D (danger): >11.2 mm/s (Values depend on machine class — always check the applicable standard) RMS in Practice: • Measure in multiple directions (H, V, A) • Compare against baseline • Monitor trends, not single readings • Combine with FFT for root cause analysis Important: RMS is a broadband indicator. It will not tell you WHY vibration is elevated — that requires FFT and more specific analysis.