Gene Vogel
EASA Pump & Vibration Specialist 

As we communicate internationally, language barriers persist. In the technical fields, the metric-imperial units clash is slowly diminishing. (It’s been said the U.S. is going to the metric system an inch at a time.) In the vibration analysis field, metric and imperial units for vibration amplitude both remain prolific. Many vibration analysts are “bilingual” in that respect and are comfortable using either system. But for more casual users who may only encounter vibration data in regard to meeting specs, unfamiliar vibration amplitude units can be a challenge. 

Complicating the situation is the fact that even within one of the systems (metric or imperial), conversion between different vibration amplitude parameters is often not understood. Common vibration amplitude parameters are displacement, velocity and acceleration, and the conversion between them requires applying a factor for the frequency of the vibration. Frequency itself has three different units: cycles per minute (CPM), cycles per second (Hz) and multiples of rotating speed (Orders). Throw in the issue of Peak to Peak (Pk-Pk), Peak (pk) and root-mean-squared (rms), and applying vibration amplitude specifications can be challenging even before one encounters a metric-imperial units situation. (For an easy solution skip to the end of this article.)

MEMBERS ONLY CONTENT - LOGIN REQUIRED