thank you for clarifying that. however i have a client who would like to convert the vibration reading in G's to dB. is there an equation to convert such G number to dB.
There was a draft ISO standard for a reference level, but can't remember what they came up with. I typically use 1g RMS or 1 m s-2 RMS, since that gives sensible numbers for engine vibration.
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
Floor vibration standards are typical defined in terms of velocity.
Furthermore, some ISO standards require the floor velocity in terms of a one-third octave spectrum. The amplitude in each band is represented in terms of RMS velocity.
This format is called "Generic Vibration Criteria (VC) for Vibration-Sensitive Equipment."
I look at this that you want the difference (dB) between the acceleration levels from one reading (before a fix) compared to another (after fix) at a certain frequency (Hz). Thus a phrase would be “ the fix is good the difference between the G levels dropped 6 dBs at 500 Hz”. Is this what you are asking?