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Total Harmonic Distortion

Measure total harmonic distortion (THD) of signal



A discrete version of this block is available in the Extras/Discrete Measurements library.


The Total Harmonic Distortion block measures the total harmonic distortion (THD) of a periodic distorted signal. The signal can be a measured voltage or current.

The THD is defined as the root mean square (RMS) value of the total harmonics of the signal, divided by the RMS value of its fundamental signal. For example, for currents, the THD is defined as

total harmonic distortion (THD) = IH/IF,



In = RMS value of the harmonic n
IF = RMS value of the fundamental current.

The THD has a null value for a pure sinusoidal voltage or current.

Dialog Box and Parameters

Fundamental frequency

The frequency, in hertz, of the fundamental signal.

Inputs and Outputs


Connect this input to the voltage or current you want to measure the total harmonic distortion.


The output returns the THD of the input signal.

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