Total Harmonic Distortion

The RMS value of the distortion appearing at multiples (harmonics) of the input frequency to the RMS value of the input (or output) sine wave. Only harmonics within the Nyquist limit are included in the measurement. It is typically expressed in decibels.

Example showing 2nd, 3rd, 4th, 5th, 6th and 7th harmonics. In this case the THD is more than 40dB down on the input signal.

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Subjects: Electronics Noise & Vibration