04-04-2011 03:31 PM
Hello,
I'm trying to measure the time and frequency spectrum of a vibrations signal.
My time plot seems to be ok, but my FFT graph doesn't look right.
An expected vibration FFT graph of a bearing should look like peaks at various frequencies, but my FFT graph looks only like a linear line.
Does anyone know what's wrong with my attached program?
Thank you.
Y.Yang
04-05-2011 04:42 PM
Hi Y. Yang. Can you also post a screenshot of what you're seeing? Without looking at that, I can make a speculation based off of what you wrote.
Since your FFT graph looks like a line, we can modify the 'Spectral Measurements' result to function in a logarithmic scale instead of a linear scale. Maybe that is what you're looking for.
04-05-2011 08:00 PM
Hello,
I've attached a word document with the screenshot of my problematic FFT and a picture of what it should like for my application.
Thank you.
Y.Yang
04-06-2011 03:27 PM
Your code looks fine. I double checked how you're acquiring data, and it seems fine. I'm pretty sure that you are acquiring an FFT and the graph is just not scaled correctly. Do the following:
Right Click Waveform Graph 2 >> X Scale >> AutoScale X
Right Click Waveform Graph 2 >> Y Scale >> AutoScale Y
I've also attached an example of what I've done to get the FFT from a simulated signal.