Takes a signal in, finds the single tone with the highest amplitude or searches a specified frequency range, and returns the single tone frequency, amplitude, and phase. The input signal can be real or complex and single-channel or multichannel. Wire data to the time signal in input to determine the polymorphic instance to use or manually select the instance.


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Inputs/Outputs

  • cmsdt.png time signal in —

    time signal in is the time-domain waveform.

  • 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
    2detected signal—Single tone
    3residual signal—Signal minus tone
  • 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, center frequency, and width. You use advanced search for narrowing the single tone search range.

  • cdbl.png approx freq. (optional) —

    approx freq. is the center frequency used of the frequency domain search for the single tone. The default is NaN, which means the VI searches the tone in the full frequency range of (–Fs/2, Fs/2).

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

    search is the frequency width, as a percentage of the sampling rate, for the frequency domain search for the single 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 frequency —

    detected frequency is the frequency of the detected single tone in Hz.

  • idbl.png detected amplitude —

    detected amplitude is the peak amplitude of the detected single tone.

  • idbl.png detected phase (deg) —

    detected phase is the phase of the detected single tone in degrees.

    Use the Wrap Angle VI to change the units of detected phase. Wire detected phase to the angle in input on the Wrap Angle VI, and select degree in, degree out or degree in, radians out for the angle units input.

  • 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.

    • A real tone signal can be expressed as shown in the following equation:

    where A, f, and φ are the amplitude, frequency, and phase of the tone signal, respectively, and Fs is the sample rate in samples per second of the input waveform signal.

    A complex tone signal can be expressed as shown in the following equation:

    where A, f, and φ are the amplitude, frequency, and phase of the tone signal, respectively, and Fs is the sample rate in samples per second of the input waveform signal.

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

    For a real signal, the frequency range is (min frequency, max frequency) = (0, Fs/2). For a complex signal, the frequency range is (min frequency, max frequency) = (–Fs/2, Fs/2).

    Examples

    Refer to the following example files included with LabVIEW.

    • labview\examples\Signal Processing\Waveform Conditioning\Correct for MIO inter-channel delay (continuous).vi
    • labview\examples\Signal Processing\Waveform Measurements\Single Tone Measurements.vi
    • labview\examples\Signal Processing\Waveform Measurements\Complex Single Tone Measurements.vi