SVT THD and Harmonic Components VI

Sound and Vibration Measurement Help


Edition Date: March 2018
Part Number: 372416L-01
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LabVIEW 2018 Sound and Vibration Toolkit Help
LabVIEW 2019 Sound and Vibration Toolkit Help

Owning Palette: Tone and Distortion VIs

Requires: Sound and Vibration Toolkit

Performs a total harmonic distortion analysis, including measuring the fundamental tone and harmonics, and returns the detected fundamental frequency, detected fundamental amplitude, harmonic components, and total harmonic distortion (THD). Wire data to the scaled signal [EU] input to determine the polymorphic instance to use or manually select the instance.

The following formula calculates THD:
THD = H / F
where H is the harmonic RMS level and F is the fundamental tone RMS level.

Example

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

SVT THD and Harmonic Components (Time) (1 Ch)

desired units specifies the engineering units of the returned measurements.
THD units specifies the units for THD.

0dB (default)
1Linear ratio
2%
harmonic component amplitude units specifies the unit for amplitude in harmonic components.

0EU rms (default)
1EU peak
2EU peak-peak
3dB ref fund
detected fundamental amplitude units specifies the units for the amplitude of the detected fundamental tone.

0EU rms (default)
1EU peak
2EU peak-peak
scaled signal [EU] specifies the scaled signal expressed in the selected engineering units. To obtain a properly scaled signal, you can use the SVL Scale Voltage to EU VI or define a virtual channel in National Instruments Measurement & Automation Explorer (MAX).
t0 specifies the start time of the waveform.
dt specifies the time interval in seconds between data points in the waveform.
Y specifies the data values of the waveform.
maximum harmonic specifies the maximum, or highest frequency, harmonic used to measure THD. Specify a value of -1 to select all the harmonics less than the Nyquist frequency.
harmonics to visualize specifies the individual harmonic components to return in harmonic components. This input does not affect the harmonics used to measure THD. Specify an array with the only element as -1 to visualize all harmonics up to the actual maximum harmonic.
error in describes error conditions that occur before this node runs. This input provides standard error in functionality.
expected fundamental frequency specifies the expected frequency of the fundamental tone in hertz. Use expected fundamental frequency when the fundamental tone is not the largest amplitude component of the input signal. The default is –1.00 Hz.
actual maximum harmonic returns the value for the actual maximum, or highest frequency, harmonic used to measure THD.
unit labels returns the unit label for each member of desired units.
THD unit label returns the unit label for THD.
harmonic component amplitudes unit label returns the unit label for amplitude in harmonic components.
detected fundamental amplitude unit label returns the unit label for the amplitude of the detected fundamental tone.
complex spectrum returns the complex form of the computed spectrum.
f0 returns the start frequency, in hertz, of the spectrum.
df returns the frequency resolution, in hertz, of the spectrum.
complex spectrum returns the complex form of the computed spectrum.
THD returns the measured total harmonic distortion (THD), which is defined as the ratio of the RMS energy of the harmonics to the RMS energy of the fundamental tone.
harmonic components returns the measured frequencies and amplitudes of the harmonics of the fundamental tone.
frequency [Hz] returns the measured frequency, in hertz, of an individual harmonic component specified in harmonics to visualize.
amplitude returns the measured amplitude of an individual harmonic component specified in harmonics to visualize.
error out contains error information. This output provides standard error out functionality.
detected fundamental amplitude returns the amplitude of the detected fundamental tone. High amplitude means an increase in the rate of energy transport, resulting in a louder sound.
detected fundamental frequency [Hz] returns the frequency of the detected fundamental tone in hertz. High frequency means a short wavelength, resulting in a higher pitch.

SVT THD and Harmonic Components (Spectrum) (1 Ch)

desired units specifies the engineering units of the returned measurements.
THD units specifies the units for THD.

0dB (default)
1Linear ratio
2%
harmonic component amplitude units specifies the unit for amplitude in harmonic components.

0EU rms (default)
1EU peak
2EU peak-peak
3dB ref fund
detected fundamental amplitude units specifies the units for the amplitude of the detected fundamental tone.

0EU rms (default)
1EU peak
2EU peak-peak
complex spectrum specifies the complex form of the computed spectrum.
f0 specifies the start frequency, in hertz, of the spectrum.
df specifies the frequency resolution, in hertz, of the spectrum.
complex spectrum specifies the complex form of the computed spectrum.
maximum harmonic specifies the maximum, or highest frequency, harmonic used to measure THD. Specify a value of -1 to select all the harmonics less than the Nyquist frequency.
harmonics to visualize specifies the individual harmonic components to return in harmonic components. This input does not affect the harmonics used to measure THD. Specify an array with the only element as -1 to visualize all harmonics up to the actual maximum harmonic.
error in describes error conditions that occur before this node runs. This input provides standard error in functionality.
expected fundamental frequency specifies the expected frequency of the fundamental tone in hertz. Use expected fundamental frequency when the fundamental tone is not the largest amplitude component of the input signal. The default is –1.00 Hz.
actual maximum harmonic returns the value for the actual maximum, or highest frequency, harmonic used to measure THD.
unit labels returns the unit label for each member of desired units.
THD unit label returns the unit label for THD.
harmonic component amplitudes unit label returns the unit label for amplitude in harmonic components.
detected fundamental amplitude unit label returns the unit label for the amplitude of the detected fundamental tone.
complex spectrum returns complex spectrum unchanged.
f0 returns the start frequency, in hertz, of the spectrum.
df returns the frequency resolution, in hertz, of the spectrum.
complex spectrum returns the complex form of the computed spectrum.
THD returns the measured total harmonic distortion (THD), which is defined as the ratio of the RMS energy of the harmonics to the RMS energy of the fundamental tone.
harmonic components returns the measured frequencies and amplitudes of the harmonics of the fundamental tone.
frequency [Hz] returns the measured frequency, in hertz, of an individual harmonic component specified in harmonics to visualize.
amplitude returns the measured amplitude of an individual harmonic component specified in harmonics to visualize.
error out contains error information. This output provides standard error out functionality.
detected fundamental amplitude returns the amplitude of the detected fundamental tone. High amplitude means an increase in the rate of energy transport, resulting in a louder sound.
detected fundamental frequency [Hz] returns the frequency of the detected fundamental tone in hertz. High frequency means a short wavelength, resulting in a higher pitch.

Example

Refer to the Amplitude Swept THD (DAQmx) VI in the labview\examples\Sound and Vibration\Audio Measurements directory for an example of using the SVT THD and Harmonic Components VI.

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