LabVIEW Sound and Vibration API Reference

SVFA FFT Spectrum (Mag-Phase) VI

  • Updated2024-06-18
  • 11 minute(s) read

SVFA FFT Spectrum (Mag-Phase) VI

Owning Palette: Baseband FFT VIs

Requires: Sound and Vibration Toolkit

Computes the Fast Fourier Transform (FFT) spectrum of scaled signal [EU]. This VI returns FFT results as the magnitude and phase of the FFT spectrum. Wire data to the scaled signal [EU] input to determine the polymorphic instance to use or manually select the instance.

Details  Example

SVFA FFT Spectrum (Mag-Phase) (1 Ch)

scaled signal [EU] specifies the scaled signal expressed in the selected engineering units. To obtain a properly scaled signal, you can use the SVL Scale Voltage to EU VI or define a virtual channel in National Instruments Measurement & Automation Explorer (MAX).
t0 specifies the start time of the waveform.
dt specifies the time interval in seconds between data points in the waveform.
Y specifies the data values of the waveform.
window specifies the time-domain window used. The default is Hanning.

0None
1Hanning (default)
2Hamming
3Blackman-Harris
4Exact Blackman
5Blackman
6Flat Top
74 Term B-Harris
87 Term B-Harris
9Low Sidelobe
11Blackman Nuttall
30Triangle
31Bartlett-Hanning
32Bohman
33Parzen
34Welch
60Kaiser
61Dolph-Chebyshev
62Gaussian
view specifies how the different results from this VI are returned. view allows you to choose whether magnitude results are displayed in dB, phase results are unwrapped, and phase results are converted from radians to degrees.
dB On specifies if results are expressed in decibels. The default is FALSE.
unwrap phase specifies whether to unwrap the phase. Unwrapping eliminates discontinuities that have an absolute value greater than pi. The default is FALSE, meaning the phase is not unwrapped. When unwrap phase is TRUE, the phase is unwrapped.
convert to degree specifies whether the phase results are converted from radians to degrees. The default is TRUE, which means that results are expressed in degrees.
error in describes error conditions that occur before this node runs. This input provides standard error in functionality.
averaging parameters specifies how the VI computes the averaging. The specifications of the parameters include the type of averaging, the type of weighting, and the number of averages.
Note  When you set averaging mode to No averaging, the VI ignores the weighting mode, number of averages, and linear mode settings.
averaging mode specifies the averaging mode.

0No averaging (default)
1Vector averaging
2RMS averaging
3Peak hold
weighting mode specifies the weighting mode. The default is exponential.
Note  RMS and vector averaging support linear and exponential weighting.


0Linear
1Exponential (default)
number of averages specifies the number of averages used by the selected weighting mode. The default is 10. If weighting mode is set to Linear, the measurement stops or automatically restarts after the value of number of averages has been reached. Whether the measurement stops or automatically restarts depends on the linear mode setting.
linear mode specifies the behavior of the averaging if you set the value of the weighting mode parameter to Linear. If you set weighting mode to Exponential, linear mode is ignored.

0One shot (default)—Specifies that the averaging process stops once the value of number of averages is reached.
1Auto restart—Specifies that the averaging process automatically restarts after the value of number of averages is reached.
restart averaging specifies if the selected averaging process has to be restarted. The default is FALSE. When you call this VI for the first time, the averaging process restarts automatically.
magnitude [dB EU] returns the magnitude of the FFT spectrum.
f0 returns the start frequency, in hertz, of the spectrum.
df returns the frequency resolution, in hertz, of the spectrum.
magnitude returns the magnitude of the FFT spectrum.
magnitude unit label returns the unit label for the selected magnitude units.
phase [degrees] returns the phase of the FFT spectrum.
f0 returns the start frequency, in hertz, of the spectrum.
df returns the frequency resolution, in hertz, of the spectrum.
phase returns the phase of the FFT spectrum.
phase unit label returns the unit label for the selected phase units.
spectrum info returns information about the spectrum needed by the Spectrum Extended Measurements VIs, the Display VIs, and the Tone and Distortion VIs.
Note  You must wire spectrum info when performing extended measurements. Do not modify the spectrum info values. If you want to view the information, you can right-click the spectrum info wire and select Custom Probe»Spectrum Info from the shortcut menu.
error out contains error information. This output provides standard error out functionality.
averages completed returns the number of averages completed by the VI at that time.
averaging done returns TRUE when averages completed is greater than or equal to the number of averages specified in averaging parameters. Otherwise, averaging done returns FALSE. averaging done is always TRUE if the selected averaging mode is No averaging.

SVFA FFT Spectrum (Mag-Phase) (N Ch)

scaled signals [EU] specifies the scaled signals expressed in the selected engineering units. To obtain a properly scaled signal, you can use the SVL Scale Voltage to EU VI or define virtual channels in National Instruments Measurement & Automation Explorer (MAX).
t0 specifies the start time of the waveform.
dt specifies the time interval in seconds between data points in the waveform.
Y specifies the data values of the waveform.
window specifies the time-domain window used. The default is Hanning.

0None
1Hanning (default)
2Hamming
3Blackman-Harris
4Exact Blackman
5Blackman
6Flat Top
74 Term B-Harris
87 Term B-Harris
9Low Sidelobe
11Blackman Nuttall
30Triangle
31Bartlett-Hanning
32Bohman
33Parzen
34Welch
60Kaiser
61Dolph-Chebyshev
62Gaussian
view specifies how the different results from this VI are returned. view allows you to choose whether magnitude results are displayed in dB, phase results are unwrapped, and phase results are converted from radians to degrees.
dB On specifies if results are expressed in decibels. The default is FALSE.
unwrap phase specifies whether to unwrap the phase. Unwrapping eliminates discontinuities that have an absolute value greater than pi. The default is FALSE, meaning the phase is not unwrapped. When unwrap phase is TRUE, the phase is unwrapped.
convert to degree specifies whether the phase results are converted from radians to degrees. The default is TRUE, which means that results are expressed in degrees.
error in describes error conditions that occur before this node runs. This input provides standard error in functionality.
averaging parameters specifies how the VI computes the averaging. The specifications of the parameters include the type of averaging, the type of weighting, and the number of averages.
Note  When you set averaging mode to No averaging, the VI ignores the weighting mode, number of averages, and linear mode settings.
averaging mode specifies the averaging mode.

0No averaging (default)
1Vector averaging
2RMS averaging
3Peak hold
weighting mode specifies the weighting mode. The default is exponential.
Note  RMS and vector averaging support linear and exponential weighting.


0Linear
1Exponential (default)
number of averages specifies the number of averages used by the selected weighting mode. The default is 10. If weighting mode is set to Linear, the measurement stops or automatically restarts after the value of number of averages has been reached. Whether the measurement stops or automatically restarts depends on the linear mode setting.
linear mode specifies the behavior of the averaging if you set the value of the weighting mode parameter to Linear. If you set weighting mode to Exponential, linear mode is ignored.

0One shot (default)—Specifies that the averaging process stops once the value of number of averages is reached.
1Auto restart—Specifies that the averaging process automatically restarts after the value of number of averages is reached.
restart averaging specifies if the selected averaging process has to be restarted. The default is FALSE. When you call this VI for the first time, the averaging process restarts automatically.
magnitudes [dB EU] returns the magnitude of each spectrum.
f0 returns the start frequency, in hertz, of the spectrum.
df returns the frequency resolution, in hertz, of the spectrum.
magnitude returns the magnitude of the FFT spectrum.
magnitude unit labels returns the magnitude unit label of each spectrum.
phases [degrees] returns the phase of each spectrum.
f0 returns the start frequency, in hertz, of the spectrum.
df returns the frequency resolution, in hertz, of the spectrum.
phase returns the phase of the FFT spectrum.
phase unit labels returns the phase unit label of each spectrum.
spectrum info is an array of clusters that contain information about the spectrum needed by the Spectrum Extended Measurements VIs and the Display VIs.
Note  You must wire spectrum info when performing extended measurements. Do not modify the spectrum info values. If you want to view the information, you can create a custom probe.
error out contains error information. This output provides standard error out functionality.
averages completed returns the number of averages completed by the VI at that time.
averaging done returns TRUE when averages completed is greater than or equal to the number of averages specified in averaging parameters. Otherwise, averaging done returns FALSE. averaging done is always TRUE if the selected averaging mode is No averaging.

SVFA FFT Spectrum (Mag-Phase) Details

Each block of data corresponds to a single FFT block and has to be passed individually to the SVFA FFT Spectrum (Mag-Phase) VI.

Example

Refer to the Level with Human Vibration Filter (DAQmx) VI in the labview\examples\Sound and Vibration\Vibration Level Measurements directory for an example of using the SVFA FFT Spectrum (Mag-Phase) VI.

Log in to get a better experience