Harmonic Distortion Analyzer 1 Chan VI

Takes a signal in and performs a full harmonic analysis, including measuring the fundamental frequency tone and harmonics, and returning the fundamental frequency, all harmonic amplitude levels, and the total harmonic distortion (THD). Wire data to the signal in input to determine the polymorphic instance to use or manually select the instance.


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Inputs/Outputs

  • cbool.png stop search at Nyquist —

    stop search at Nyquist should be set to TRUE (default) to include only frequencies less than the Nyquist frequency, or half the sampling rate, in the harmonic search.

    When set to FALSE, this VI continues searching the frequency domain beyond Nyquist by assuming that these higher frequency components have aliased according to the following equation. aliased f = Fs – (f modulo Fs) where Fs = 1/dt = sampling rate.

  • cmsdt.png signal in —

    signal in is the input time-domain signal.

  • cenum.png export mode —

    export mode selects the source of the signal and spectrum to export to exported signals.

    0none—Fastest computation
    1input signal—Input signal only
    2fundamental signal—Single sine tone
    3residual signal—Signal minus tone
    4harmonics only—Detected harmonics
    5noise and spurs—Signal minus tone and harmonics
  • ci32.png highest harmonic —

    highest harmonic controls the highest harmonic, including the fundamental tone, used for the harmonic analysis. For example, for 3rd harmonic analysis, this control should be set to 3 to measure the fundamental, second, and third harmonic.

  • cerrcodeclst.png error in (no error) —

    error in describes error conditions that occur before this node runs. This input provides standard error in functionality.

  • cnclst.png advanced search —

    advanced search controls the frequency domain search area, which is the center frequency and width, used for finding the fundamental frequency tone of the signal.

  • cdbl.png approx freq. (optional) —

    approx freq. is the center frequency used in the frequency domain search for the fundamental tone frequency. If set to the default value of –1.0, the tone with the highest amplitude is used as the fundamental tone.

  • cdbl.png search (+/- % of Fsampl.) —

    search is the frequency width, as a percentage of the sampling rate, for the frequency domain search for the fundamental tone frequency.

  • icclst.png exported signals —

    exported signals contains the signals specified by export mode.

  • imsdt.png exported time signal —

    exported time signal is the waveform containing the exported time signal as selected by export mode.

  • icclst.png exported spectrum (dB) —

    exported spectrum (dB) is the spectrum of the exported time signal as selected by export mode.

  • idbl.png f0 —

    f0 returns the start frequency, in hertz, of the spectrum.

  • idbl.png df —

    df returns the frequency resolution, in hertz, of the spectrum.

  • i1ddbl.png dB Spectrum (Hann) —

    dB Spectrum (Hann) is the magnitude spectrum of the (Hanning) windowed input signal, expressed in dB relative to 1.0 Vrms^2 for input signals in units of volts (V).

  • idbl.png detected fundamental frequency —

    detected fundamental frequency contains the detected fundamental frequency resulting from searching the frequency domain. Use advanced search to set the frequency search range. All harmonics are measured at integer multiples of this fundamental frequency.

  • idbl.png THD —

    THD contains the measured total harmonic distortion up to and including the highest harmonic. THD is defined as the ratio of the RMS sum of the harmonics to the amplitude of the fundamental tone. To compute THD as a percentage, you must multiply it by 100.

  • i1ddbl.png components level —

    components level contains the array of amplitudes of the measured harmonics in volts if the signal in is in volts. The array index is the harmonic number including 0 (DC), 1 (fundamental), 2 (second harmonic),... n (nth harmonic), up to and including the highest harmonic.

  • ierrcodeclst.png error out —

    error out contains error information. This output provides standard error out functionality.

  • icclst.png measurement info —

    measurement info returns information about your measurement, mainly warnings for inconsistencies in your input signal.

  • idbl.png uncertainty —

    uncertainty is reserved for future use.

  • ibool.png Warning —

    Warning is TRUE if a warning is generated during processing.

  • istr.png comments —

    comments contains a warning message when Warning is TRUE.

    • This VI is designed to process a single channel or multiple channels continuously, typically from within a For Loop or a While Loop.

    Examples

    Refer to the following example files included with LabVIEW.

    • labview\examples\Signal Processing\Waveform Measurements\Multitone with Amplitudes and Phases.vi