Distortionmeter

Harmonic distortion is equivalent to adding harmonics to a signal. When a purely sinusoidal signal is in this way, a series of harmonics is superimposed on the original signal, and can be detected with suitable equipment.

If the input is

${\displaystyle {f_{i}}=a_{1}\cdot sin(\omega t)}$

The normalized output is

${\displaystyle {f_{o}}=a_{1}\cdot sin(\omega t)+a_{2}\cdot sin(2\omega t)+a_{3}\cdot sin(3\omega t)+..}$

The value of Total Harmonics Distortion (THD) is defined as the ratio of the harmonics to the fundamental; ^[1] i.e.,

${\displaystyle THD={\frac {\sqrt {{a_{2}}^{2}+{a_{3}}^{2}+..}}{a_{1}}}}$

This ratio can be given in dB or in percentage.