Low frequency analysis - Big obstacle, easy solution

[Murtugh]

I'm trying to analyze a signal between 0-2 Hz. The signal is a clean sine curve where amplitude and frequency changes.

I wanted to use the ExpressVI called "Tone Measurement" as I'm not that experienced with Labview.

I've used a signal generator to simulate, and it seems like it works fine for signals above 10 Hz. Lower than that returns higher frequencies and bogus amplitudes.

Please help me out here. The signal I'm generating is sampled at 100 Hz with n=10.

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[Murtugh · Accepted solution]

Well, i sort of figured it out while reading my own question. Increasing number of samples did it...

[johnsold]

For a better explanation: Tone Measurements uses FFT internally. The FFT implementation works well for signals having 3 to 5 cycles of the lowest frequency or more.  It does not work well for shorter signals. It may work fairly well if you have exactly one cycle of the signal although that is generally not feasible, especially with variable frequency signals.

Lynn