total harmonic distortion level

7.32  total harmonic distortion level. Ten times the logarithm to the base ten of the ratio of the sum of the squared amplitudes of the second and higher harmonic components of a signal to the square of the amplitude of the fundamental component. Abbreviation, THD.

Annotation            An alternative definition (IEC) is ten times the logarithm to the base ten of the ratio of the sum of the squared amplitudes of the second and higher harmonic components of a signal to the sum of the squares of the amplitude of the fundamental and higher harmonic components. For low THD values, the two methods yield similar results.