You are here: NI Home > Support > Product Reference > Manuals > Sound and Vibration Measurement Suite 7.0 Help

Owning Palette: Spectrum Extended Measurements VIs

Installed With: Sound and Vibration Measurement Suite

Performs a peak search on a spectrum or spectra. The spectrum or spectra can be in either the frequency domain or the order domain. Detects single or multiple peaks in Power, PSD, and COP spectra. The data type you wire to the spectrum input determines the polymorphic instance to use.

The time-domain window previously applied to the signal is used to accurately estimate the frequency and amplitude of the peak.

Details  

Use the pull-down menu to select an instance of this VI.

Select an instance SVFA Spectrum Peak Search (1 Spectrum)SVFA Spectrum Peak Search (N Spectra)

SVFA Spectrum Peak Search (1 Spectrum)

	spectrum specifies the abscissa scaling and the magnitude of the spectrum. x0 specifies the start frequency or order of the spectrum. dx specifies the frequency or order resolution of the spectrum. magnitude specifies the magnitude of the spectrum.
	peak search settings specifies the criteria for the peak search. single/multiple specifies whether the VI returns a single max peak or multiple peaks (default). 0 Multiple Peaks (default) 1 Single Max Peak threshold specifies the level a peak must exceed to be considered a valid peak. Set threshold to the same units as spectrum.
	spectrum info specifies properties of the computed spectrum. The properties contained in spectrum info include channel name, spectrum type, spectrum scale as linear or dB, applied window, window size, FFT size, units, x-axis units, dB reference, applied weighting, peak units, and spectral density. Note  spectrum info must be connected when performing extended measurements. Do not modify the spectrum info values.
	error in describes error conditions that occur before this VI or function runs. The default is no error. If an error occurred before this VI or function runs, the VI or function passes the error in value to error out. This VI or function runs normally only if no error occurred before this VI or function runs. If an error occurs while this VI or function runs, it runs normally and sets its own error status in error out. Use the Simple Error Handler or General Error Handler VIs to display the description of the error code. Use exception control to treat what is normally an error as no error or to treat a warning as an error. Use error in and error out to check errors and to specify execution order by wiring error out from one node to error in of the next node. status is TRUE (X) if an error occurred before this VI or function ran or FALSE (checkmark) to indicate a warning or that no error occurred before this VI or function ran. The default is FALSE. code is the error or warning code. The default is 0. If status is TRUE, code is a nonzero error code. If status is FALSE, code is 0 or a warning code. source specifies the origin of the error or warning and is, in most cases, the name of the VI or function that produced the error or warning. The default is an empty string.
	peaks returns the frequency or order and value for each peak that meets the search criteria. freq. or order returns the frequency or order of the peak. value returns the peak value of the peak in the same units as the spectrum input.
	number of peaks indicates the number of peaks that satisfied the search criteria.
	unit label returns the selected engineering units.
	error out contains error information. If error in indicates that an error occurred before this VI or function ran, error out contains the same error information. Otherwise, it describes the error status that this VI or function produces. Right-click the error out front panel indicator and select Explain Error from the shortcut menu for more information about the error. status is TRUE (X) if an error occurred or FALSE (checkmark) to indicate a warning or that no error occurred. code is the error or warning code. If status is TRUE, code is a nonzero error code. If status is FALSE, code is 0 or a warning code. source describes the origin of the error or warning and is, in most cases, the name of the VI or function that produced the error or warning.

SVFA Spectrum Peak Search (N Spectra)

	spectra specifies the data for each spectrum. spectrum specifies the abscissa scaling and the magnitude of the spectrum. x0 specifies the start frequency or order of the spectrum. dx specifies the frequency or order resolution of the spectrum. magnitude specifies the magnitude of the spectrum.
	peak search settings specifies the criteria for the peak search. single/multiple specifies whether the VI returns a single max peak or multiple peaks (default). 0 Multiple Peaks (default) 1 Single Max Peak threshold specifies the level a peak must exceed to be considered a valid peak. Set threshold to the same units as spectrum.
	spectrum info specifies properties of the computed spectrum. The properties contained in spectrum info include channel name, spectrum type, spectrum scale as linear or dB, applied window, window size, FFT size, units, x-axis units, dB reference, applied weighting, peak units, and spectral density. Note  spectrum info must be wired when performing extended measurements. Do not modify the spectrum info values.
	error in describes error conditions that occur before this VI or function runs. The default is no error. If an error occurred before this VI or function runs, the VI or function passes the error in value to error out. This VI or function runs normally only if no error occurred before this VI or function runs. If an error occurs while this VI or function runs, it runs normally and sets its own error status in error out. Use the Simple Error Handler or General Error Handler VIs to display the description of the error code. Use exception control to treat what is normally an error as no error or to treat a warning as an error. Use error in and error out to check errors and to specify execution order by wiring error out from one node to error in of the next node. status is TRUE (X) if an error occurred before this VI or function ran or FALSE (checkmark) to indicate a warning or that no error occurred before this VI or function ran. The default is FALSE. code is the error or warning code. The default is 0. If status is TRUE, code is a nonzero error code. If status is FALSE, code is 0 or a warning code. source specifies the origin of the error or warning and is, in most cases, the name of the VI or function that produced the error or warning. The default is an empty string.
	peaks returns the peaks for each spectrum. peaks returns the frequency or order and value for each peak that meets the search criteria. freq. or order returns the frequency or order of the peak. value returns the peak value of the peak in the same units as the spectrum input.
	number of peaks indicates the number of peaks that satisfied the search criteria for each spectrum.
	unit labels returns the unit label for each channel.
	error out contains error information. If error in indicates that an error occurred before this VI or function ran, error out contains the same error information. Otherwise, it describes the error status that this VI or function produces. Right-click the error out front panel indicator and select Explain Error from the shortcut menu for more information about the error. status is TRUE (X) if an error occurred or FALSE (checkmark) to indicate a warning or that no error occurred. code is the error or warning code. If status is TRUE, code is a nonzero error code. If status is FALSE, code is 0 or a warning code. source describes the origin of the error or warning and is, in most cases, the name of the VI or function that produced the error or warning.

SVFA Spectrum Peak Search Details

The SVFA Spectrum Peak Search VI finds all the peaks within the spectrum and performs amplitude/frequency or amplitude/order estimation on each individual peak. The VI operates on magnitude and power spectra.

Usually, the spectrum is computed based on a windowed input signal. The closed form of any cosine window, such as Hanning, Hamming, Blackman-Harris, and so on, is known. The presence of three dominant bins indicates a local maximum on the power spectrum. Therefore, when the SVFA Spectrum Peak Search VI locates three dominant bins, a curve fitting algorithm maps the window shape onto the three bins and estimates the true frequency and amplitude of that particular tone. The following illustration diagrams the concept of the algorithm.