From 9:00 AM  12:00 PM CDT on Saturday, June 6th, ni.com will be undergoing system upgrades that may result in temporary service interruption.
We appreciate your patience as we improve our online experience.
From 9:00 AM  12:00 PM CDT on Saturday, June 6th, ni.com will be undergoing system upgrades that may result in temporary service interruption.
We appreciate your patience as we improve our online experience.
LabVIEW 2016 Help  
LabVIEW 2017 Help  
LabVIEW 2018 Help  
LabVIEW 2019 Help  
LabVIEW 2020 Help 
Owning Palette: Signal Analysis Express VIs
Requires: Full Development System
Performs FFTbased spectral measurements, such as the averaged magnitude spectrum, power spectrum, and phase spectrum on a signal.
Dialog Box Options 
Block Diagram Inputs 
Block Diagram Outputs 
Parameter  Description 

Selected Measurement  Contains the following options:

Result  Contains the following options:

Window  Specifies the window to apply to the signal.

Averaging  Specifies whether the Express VI performs averaging. 
Mode  Contains the following options:

Weighting  Contains the following options:

Number of Averages  Specifies the number of packets to average. The default is 10. 
Produce Spectrum  Contains the following options:

Phase  Contains the following options:

Windowed Input Signal  Displays the first channel of Signals. This graph displays the incoming signal with windowing applied. If you wire data to the Express VI and run it, Windowed Input Signal displays real data. If you close and reopen the Express VI, Windowed Input Signal displays sample data until you run the VI again. 
Magnitude Result Preview  Displays a preview of the magnitude measurement of the signal. If you wire data to the Express VI and run it, Magnitude Result Preview displays real data. If you close and reopen the Express VI, Magnitude Result Preview displays sample data until you run the VI again. 
Phase Result Preview  Displays a preview of the phase measurement of the signal. If you wire data to the Express VI and run it, Phase Result Preview displays real data. If you close and reopen the Express VI, Phase Result Preview displays sample data until you run the VI again. 
Parameter  Description 

Signals  Contains the input signal or signals. 
Restart Averaging  Specifies whether to restart the selected averaging process. The default is FALSE. When you call this Express VI for the first time, the averaging process starts automatically. This input appears only if you place a checkmark in the Averaging checkbox. 
error in  Describes error conditions that occur before this node runs. 
Parameter  Description 

FFT  (RMS)  Returns the FFT magnitude spectrum and displays the results in RMS units. 
Power Spectrum  Returns the FFT power spectrum and displays the results in RMSsquared units. To compute the FFT power spectrum, LabVIEW converts the twosided power spectrum to the singlesided power spectrum. 
PSD  Returns the FFT power spectral density and displays the results in RMSsquared per Hz units. 
FFT  (Peak)  Returns the FFT magnitude spectrum and displays the results in peak units. 
averaging done  Returns TRUE when the number of averages completed equals or exceeds Number of Averages. 
Phase  Returns the FFT phase spectrum and displays the results in degrees or radians. 
error out  Contains error information. This output provides standard error out functionality. 
FFTbased spectral computations assume that the finite block of signal data represents one period of a periodic signal. The computed spectrum of this effective periodically extended signal shows energy spreading into frequencies that were not present in the original signal. To reduce this spectral leakage, use smoothing windows to taper the sharp transitions in the effective signal. You do not typically use windows if you can acquire an integer number of cycles of each frequency component measured or if you are analyzing noise spectra.
This Express VI operates similarly to the following VIs and functions:
FFT Spectrum (MagPhase)
FFT Spectrum (RealIm)
FFT Power Spectrum and PSD
Refer to the following VIs for examples of using the Spectral Measurements Express VI:
Helpful
Not Helpful