converting g/Hz to g^2/Hz
converting g/Hz to g^2/Hz
(OP)
Can anybody help me with convert g/Hz to g^2/Hz.
I have data curve that has data .616g at 289Hz and in the PSD plot, it become .0243g^2/Hz, how is that converted?
Thanks for the help
I have data curve that has data .616g at 289Hz and in the PSD plot, it become .0243g^2/Hz, how is that converted?
Thanks for the help





RE: converting g/Hz to g^2/Hz
I am not sure if it is really the answer since the description of the problem is very limited but here is a try. Basically I guess this is finding the equivalent sine vibration for equal random damage.
A PSD of 0.0243g2/Hz at 289Hz gives you an equivalent static acceleration of 18 grms using a Q of 30 and the Miles equation:
sqrt(Pi/2*289*30*0.0243)=18 grms
Now, the damage produce by this random environment assuming the 3 sigma value (3*grms) occurs for only 4.33% of the time and an exponent of 3 for fatigue damage you get a random damage of:
random damage = 0.0433*(3*180^3=4692
Now the peak value from a sine input to get the same damage during a sine test is (still assuming a Q of 30 and the same exponent):
(Input_Sine*30)^3=4692 gives Input_Sine= 0.616g
This approach is defined in 'Vibration Analysis for Electronic Equipment' -Dave Steinberg-Wiley Interscience-
Franck
RE: converting g/Hz to g^2/Hz
=====================================
Eng-tips forums: The best place on the web for engineering discussions.
RE: converting g/Hz to g^2/Hz
Rememher that most, if not all raw data signals contain a DC Offset and noise. That must be removed. Also before taking the PSD remove the DC offset and noise (or at least what noise you can)and then window the data (usually the Hanning window is used) It is also necessary to know the anit-aliasing filter frequency, the sampling rate which should be at least 5, preferably 10 times the highest frequency of interest, and whether the accelerometers were calibrated in G(rms) or G(peak). It is best to take the PSD of points in powers of 2 such as 1024, 2048, 4096 etc.
Hope this helps
REGARDS
Dave
RE: converting g/Hz to g^2/Hz
Regards
Dave