FFT Vibration Data
FFT Vibration Data
(OP)
thread384-257416: FFT from time domain data
Am new to vibration and any help is greatly appreciated. I have around 1.4 million points of data taken over every 0.002,0.003 secs. and g's (Acceleration) in both X,Y&Z. I need to develop a vibration profile.
How do I transform these (g's vs Time) to Amplitude vs. Freq and eventually to get a PSD vs Freq?
Am familiar with matlab but don't know much about FFT and vibration profiles.
Am new to vibration and any help is greatly appreciated. I have around 1.4 million points of data taken over every 0.002,0.003 secs. and g's (Acceleration) in both X,Y&Z. I need to develop a vibration profile.
How do I transform these (g's vs Time) to Amplitude vs. Freq and eventually to get a PSD vs Freq?
Am familiar with matlab but don't know much about FFT and vibration profiles.





RE: FFT Vibration Data
Walt
RE: FFT Vibration Data
1. Do I just plot g^2/freq vs. freq?
2. Is freq. just 1/time?
3. With over 1million points of data, how do i deal with the frequencies.
5. How did you determine that F-max < 250 Hz?
RE: FFT Vibration Data
You don't have any easy task. Here is a link to FFT references: http://www.fftw.org/links.html
Q1: Yes after FFT
Q2: Yes, but you can't simply take reciprocal of waveform to get spectrum
Q3: Typically time data is divided into data blacks like 1024 points
Q4: Nyquist, another term you need to know
I use DasyLab for general signal analysis. Perhaps you could do your job with a download demo of that or similar software. You must be ready for an education, either way.
Walt
RE: FFT Vibration Data
Another good reference, see related posting about PSD:
http://c
Walt
RE: FFT Vibration Data
RE: FFT Vibration Data
page 29 in the HP/Agilent Application note 243 is a start.
For sample rate I think about the aliens that are monitoring my behaviour. If they take a sample once every 24 hours, and the first sample happens to be at about 2 in the morning, in their report they will conclude that I sleep all the time. They need to sample at a much faster rate to capture the details of my exciting, fast paced existence.