How to change the waveform graph from time domain to frequency domain?

[Mal1279]

I want to change the x-component of the waveform graph from time to frequency domain after getting the signal from my accelerometer.

[stu22]

Hi, before your x-component inputs to the graph, invert the x-component, 1/x. U should now have the frequency as your x-component.

Stuart

[markwysong]

I don't believe this is how you should do it. If you simply change the X values as described above, your Y values still represent what your accelerometer did at time X, not frequency 1/X. There is a big difference.

You'll need to take your signal information and pass it through an FFT VI (Fourier Transform), which will change your data from the time domain to the frequency domain. You can then wire this to a graph, and it will show the frequency domain, and your X values will be in frequency. Your Y values will then be in dB.

Mark

[JETLI_626]

I am having a similar problem. I understand that an FFT will convert the time to frequency, but there is a weird bit of pseudocode which I am trying to take care of. It basically wants me to take the magnitude of a sine wave that has been FFT'd and graph it using a Waveform Graph, not an XY graph. I can't figure out what I should be using for the "magnitude" bit of code. There's some magnitude-related FFT's, but they seem to have too many variables for what I'm trying to accomplish. I've fiddle with the logarithmic scales for X and Y, too, but it's not working very well.

If you wouldn't mind taking a gander at my VI, I'd appreciate any input you might have. The pseudocode is contained in the block diagram.

Message Edited by JETLI_626 on 05-15-2006 04:45 AM

[Jeff_T.]

Changing the properties of the graph in that nature can be done with property nodes but will not be trivial.  You may want to consider using two different graphs with a tab control.  This allows you to have two graphs on the front panel, but by programmatically switching between the tabs only one would be visible at a time.