From 04:00 PM CDT – 08:00 PM CDT (09:00 PM UTC – 01:00 AM UTC) Tuesday, April 16, ni.com will undergo system upgrades that may result in temporary service interruption.
We appreciate your patience as we improve our online experience.
I have an array of data sampled by known (500Hz) frequency. If I plot that, I get x-axis in samples. I am able to rescale it by using a scale settings. But the problem is, when I want to do FFT. The axis is in samples or in time, but I need frequency there.
So, the question is how to add to that array another column, which has same length and values corresponding to each sampling step and how to plot everything in right units. I am new to LabVIEW. Thanks
when you connect output of a FFT vi to a waveform indicator, what you see on X-scale is nothing but frequency range. Make sure you have enabled the autoscale X asis to get the FFT peak on the right frequency on the scale.
Well, the length of my data is 4000 and if I perform FFT I get spectrum range from 0 to 4000 (it corresponds to number of samples). Is there way how to "tell" Labview "my fs is xxx Hz" ?
What you just had to do is enable autoscale X axis, and connect the output of the FFT to your waveform graph. Definitely you will see half of the spectrum (real) and imaginary part is not visible.
More, Your frame lenght will always be half of your Scanning Frequency. Simply by Δf=fs/N. where Δf is the frequency resolution, T is the acquisition time, fs is the sampling frequency, and N is the block size of the FFT.
