本帖最后由 H-RH 于 2014-9-26 17:17 编辑 # `9 k* v/ E* I" o8 z4 E
Nezof 发表于 2014-9-26 16:37 3 `* I. q& I0 H* F$ i- Y& N
有具体计算公式的,我一般都是按照IEC61000-3-2里面的计算方法来的
/ D; M- C1 v% }0 E) d, r+ e$ r5 f维基百科: When the main performance criterion is the ″purity″ of the original sine wave (in other words, the contribution of the original frequency with respect to its harmonics), the measurement is most commonly defined as the ratio of the RMS amplitude of a set of higher harmonic frequencies to the RMS amplitude of the first harmonic, or fundamental, frequency , z% Q. l+ p8 f/ o8 O8 N/ g) W
where Vn is the RMS voltage of nth harmonic and n = 1 is the fundamental frequency. For many standard signals, the above criterion may be calculated analytically in a closed-form. 1 e) }9 u) U! z3 Q5 Q$ J! B: T
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