Owning Palette: Frequency Analysis VIs

Use the Zoom FFT VIs to perform real-time zoom FFT measurements.

Real-time zoom is also known as destructive zoom because the input time waveform data is processed through stages of filtering and decimation before reaching accumulation. When a sufficient number of processed samples have been accumulated, the VI will perform the zoom transform to measure the spectrum within the specified frequency range. When an application requires fine frequency resolution over a narrow span of the baseband frequency range, the Zoom FFT VIs can be used to reduce (compared to baseband FFT VIs) memory and processing requirements because the transform is performed on a decimated set of data.

Use the Zoom FFT VIs to perform online averaged spectral analyses on a continuous series of blocks, as might be acquired in a continuous acquisition. The data must be continuous as measured by the timestamp and the sample rate. The block size does not have to be constant because the Zoom FFT VIs effectively decouple the input block duration from the spectral frequency resolution. When sufficient data has been accumulated within the VI, the VI will return an updated averaged spectrum and the new spectrum available output will be TRUE. It is common to put the Zoom FFT VIs inside an acquisition or processing loop and continuously input time signals until the spectral result is done. The Zoom FFT VIs will continuously output updated averaged spectra as they are computed.

Use the Zoom FFT VIs to perform offline averaged spectral analyses on a single, long-duration waveform, as might be acquired in a Finite acquisition or File Read operation. Provided that sufficient data is available, the Zoom FFT VIs may be used to decouple the frequency resolution from the duration of the signal. Instead, the Zoom FFT VIs may measure an averaged spectrum at a coarser frequency resolution than the baseband resolution for the long-duration signal, as expressed by baseband df = 1 / (N*dt). The Zoom FFT VIs will output the last averaged spectrum if one is available.

The VIs on this palette can return general LabVIEW error codes or specific sound and vibration error codes.

Palette Object Description
SVFA Zoom Coherent Output Power Computes the zoom coherent output power of scaled signal X [EUx] , scaled signal Y [EUy] , and zoom settings . Data accumulates each time the SVFA Zoom Coherent Output Power VI is called. However, it returns a new spectrum only when sufficient data accumulates. Indicators and subsequent processing should only be called when new spectrum available is TRUE. Zoom coherent output power is typically an averaged measurement.
SVFA Zoom Cross Spectrum (Mag-Phase) Computes the zoom cross power spectrum of scaled signal X [EUx] , scaled signal Y [EUy] , and zoom settings . Results are returned in magnitude and phase. Data accumulates each time the VI is called. However, it returns a new spectrum only when sufficient data accumulates. Indicators and subsequent processing should only be called when new spectrum available is TRUE.
SVFA Zoom Cross Spectrum (Real-Im) Computes the zoom cross power spectrum of scaled signal X [EUx] , scaled signal Y [EUy] , and zoom settings . Results are returned as real part and imaginary part. Data accumulates each time the VI is called. However, it returns a new spectrum only when sufficient data accumulates. Indicators and subsequent processing should only be called when new spectrum available is TRUE.
SVFA Zoom FFT Spectrum (Mag-Phase) Computes the zoom FFT spectrum of scaled signal [EU] and zoom settings . Zoom FFT results are returned in magnitude and phase. Data accumulates each time this VI is called. However, it returns a new spectrum only when sufficient data accumulates. Indicators and subsequent processing should only be called when new spectrum available is TRUE. Wire data to the scaled signal [EU] input to determine the polymorphic instance to use or manually select the instance.
SVFA Zoom FFT Spectrum (Real-Im) Computes the zoom FFT spectrum of scaled signal [EU] and zoom settings . Zoom FFT results are returned as real part and imaginary part. Data accumulates each time this VI is called. However, it returns a new spectrum only when sufficient data accumulates. Indicators and subsequent processing should only be called when new spectrum available is TRUE. Wire data to the scaled signal [EU] input to determine the polymorphic instance to use or manually select the instance.
SVFA Zoom Frequency Response (Mag-Phase) Computes the zoom frequency response and the coherence of stimulus signal X [EUx] , response signal Y [EUy] , and zoom settings . Results are returned in coherence, magnitude, and phase. Data accumulates each time this VI is called. However, it returns a new spectrum only when sufficient data accumulates. Indicators and subsequent processing should only be called when new spectrum available is TRUE. Zoom frequency response is typically an averaged measurement.
SVFA Zoom Frequency Response (Real-Im) Computes the zoom frequency response and the coherence of stimulus signal X [EUx] , response signal Y [EUy] , and zoom settings . Results are returned in coherence, real part, and imaginary part. Data accumulates each time this VI is called. However, it returns a new spectrum only when sufficient data accumulates. Indicators and subsequent processing should only be called when new spectrum available is TRUE. Zoom frequency response is typically an averaged measurement.
SVFA Zoom Power Spectral Density Computes the zoom power spectral density of scaled signal [EU] and zoom settings . Data accumulates each time this VI is called. However, it returns a new spectrum only when sufficient data accumulates. Indicators and subsequent processing should only be called when new spectrum available is TRUE. Wire data to the scaled signal [EU] input to determine the polymorphic instance to use or manually select the instance.
SVFA Zoom Power Spectrum Computes the zoom power spectrum of scaled signal [EU] and zoom settings . Data accumulates each time this VI is called. However, it returns a new spectrum only when sufficient data accumulates. Indicators and subsequent processing should only be called when new spectrum available is TRUE. Wire data to the scaled signal [EU] input to determine the polymorphic instance to use or manually select the instance.