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Distortion Measurements (THD) (G Dataflow)

Version:
    Last Modified: January 9, 2017

    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).

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    export mode

    Source of the signal and spectrum to export.

    Name Description
    none Uses the fastest computation.
    input signal Exports the input signal only.
    fundamental signal Exports the single sine tone.
    residual signal Exports the signal minus tone.
    harmonics only Exports detected harmonics only.
    noise and spurs Exports the signal minus tone and harmonics.

    Default: none

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    signal

    The input signal.

    This input can be a waveform or an array of waveforms.

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    center frequency

    Center frequency to use in the frequency-domain search for the fundamental tone frequency.

    Default: -1

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    frequency width

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

    Default: 5

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    highest harmonic

    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.

    Default: 19

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    error in

    Error conditions that occur before this node runs. The node responds to this input according to standard error behavior.

    Default: No error

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    stop search at Nyquist

    A Boolean specifying whether to include only frequencies less than the Nyquist frequency, or half the sampling rate, in the harmonic search.

    True Includes only frequencies less than the Nyquist frequency.
    False Searches the frequency domain beyond the Nyquist frequency by assuming that these higher frequency components have aliased.

    Default: True

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    exported spectrum

    Spectrum of the exported signal.

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    f0

    Start frequency, in Hz, of the spectrum.

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    df

    Frequency resolution, in Hz, of the spectrum.

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    spectrum

    Computed spectrum.

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    exported signal

    Waveform of the exported signal.

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    fundamental frequency

    Detected fundamental frequency resulting from searching the frequency domain.

    Use the center frequency and frequency width to set the frequency domain search range. All harmonics are measured at integer multiples of this fundamental frequency.

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    THD

    Measured total harmonic distortion up to and including the highest harmonic. This output 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.

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    components level

    Array of amplitudes of the measured harmonics in volts if the input 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.

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    error out

    Error information. The node produces this output according to standard error behavior.

    Where This Node Can Run:

    Desktop OS: Windows

    FPGA: Not supported


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