| mathematical expression used for the evaluation of characteristics of magnetic materials and expressed in decibels by:
, where Vn is the amplitude of the n-th harmonic component of the waveform,
Vf is the amplitude of its fundamental component,
μea is the amplitude permeability,
CCF is the Circuit Correction Factor
Note 1 – In practice, stands for the Circuit Correction Factor and is given in the approximation for the third harmonic, which is valid for measurements without applied DC bias. L1 is the primary inductance. Rs is the total source resistance (50 Ω).
Note 2 – THDF is sometimes expressed in decibels.