FFT Spectrum (Mag-Phase) VI

Computes the averaged FFT spectrum of time signal. This VI returns the FFT results as magnitude and phase. Wire data to the time signal input to determine the polymorphic instance to use or manually select the instance.


icon

The FFT Spectrum (Mag-Phase) VI completes the following steps to compute magnitude and phase:

  1. Computes the FFT of time signal.
  2. Averages the current FFT spectrum of time signal with the FFT spectra computed by the VI since the last time the averaging process was reset.
  3. Returns the magnitude and phase of the averaged spectrum.

The single-channel version of this VI can perform single-channel measurements in both one-shot mode, meaning a single call, and continuous mode, meaning multiple calls with history. The single-channel version can perform multichannel measurements only in one-shot mode. If you want to make multichannel measurements in continuous mode, use the multichannel version of this VI.

The single-channel version of this VI maintains internal state information for a single channel only. Calling the single-channel version to process another channel without using the restart averaging control to clear the history results in an unexpected behavior of this VI. The unexpected behavior results from the VI passing the internal state information from one channel to another.

Note The single-channel version of this VI is intended primarily for continuous processing of a single channel. Do not generalize this behavior to the multichannel case and use the single-channel version in a For Loop to continuously process multiple channels by indexing an array of waveforms.

Refer to the following LabVIEW project for examples of using a multichannel version of a VI like the FFT Spectrum (Mag-Phase) VI in a loop:

labview\examples\Signal Processing\Waveform Measurements\Waveform Measurements.lvproj

Related Information

Output Units for FFT-Based Vis