Importing CSV data for FFT analysis

[johnBURL]

Not sure if that made a difference, really. If I can, I am going to upload my VI and the simpler dataset I was using for testing. I made a few changes but I think my main problem now, is that the FFT chart is using and X and Y axis labeled Time and Amplitude. The Amplitude label is fine, but I was hoping to see the frequency of the signal as the X-Axis.Not sure how to change that label or what info I need to pull from the CSV file.

To make it easier to show, I used a dataset that contained a 220khz signal being generated. So I would expect to see on the FFT a large spike for the 220khz and any smaller spikes for harmonics that may be present.

Thanks again, guys. I feel like with your help, I'm really close to accomplising my task. 

Eric: I appreciate your help but I feel a bit lost with your function because the graph is not at all what I was expecting! Lol. Thanks again, brother.

[RavensFan]

Just double click on the word "time" and edit it.  You can also change it in the properties dialog fo that graph.

[johnBURL]

Doesn't that just change the label, though? What I meant was, the FFT was defaulting "time" (or in this case, the record length, which is 10k) as the x-axis.The FFT should be an amplitude v frequency graph, time/record length shouldn't be a factor, I believe. Right now the FFT is showing me amplitude v time, so I see spikes of the amplitude but I cannot tell what frequency they are.

[RavensFan]

FFT gives you amplitude vs. frequency.

The axis on the graph says "time", but that is just a label.

But that FFT function puts out an array of frequency bins, you just need to scale those bins.  The dF of that graph is the frequency of your incoming data divided by the number of data points.

Here is a subVI I put together to graph an FFT for me from the basic FFT function, so I didn't have to deal with the Express VI's.

[sowji25]

Hi all,

     I want to implement the Fast Fourier Transform to Technical data management streaming, in this file format one is time stamp data and other are sensors data, I create an array to select the sensor with respect to time data, when i run the VI the sensor data waveform spectrum shows correctly but sensor 2 data waveform spectrum is not showing, please the check other sensors data also, i want the frequency spectrum peaks at 2400 Hz and 3250 Hz. once check the code and please correct the VI in correct format

     I also implement the fast Fourier transform to different file formats also  but it not showing the correct waveform spectrum , please once check the code whether it is right or not