Finding Fundamental Frequency of Power Spectrum Programmatically

Updated Apr 9, 2018

Reported In

Software

  • LabVIEW

Issue Details

I have used FFT Power Spectrum and PSD.vi to view the power spectrum of the signal on a graph. I can find the fundamental frequency by zooming into the graph, however, I am looking for a method to find the fundamental frequency programmatically.

Solution

The output from FFT Power Spectrum and PSD.vi is a cluster containing two double precision elements, and a double precision array:

  • f0: Starting Frequency
  • df: Frequency Resolution
  • Magnitude: Array of Power values for each frequency
In order to find the fundamental frequency we first need to find the largest power/amplitude within Magnitude and its index in the array. The index then be can used with f0 and df as shown in the following equation to find the fundamental frequency.

Fundamental Frequency = Index of Largest Power x Frequency Resolution(df) + Starting Frequency(f0)   

The following code shows how the cluster can be used to find the fundamental frequency:

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