| 摘要 |
<P>PROBLEM TO BE SOLVED: To calculate an effective value and a harmonic component of an input signal while ensuring a sufficient precision. <P>SOLUTION: A harmonic component calculation apparatus includes: a first arithmetic unit 4 which calculates an effective value Drms of an input signal S1 outputted from an A/D conversion unit 3 on the basis of amplitude data D1 on the input signal S1; a thinning unit 8 which extracts one item of the amplitude data D1 synchronously with input timing of a synchronizing pulse S2 and outputs the extracted data item as thinning data D3; a second arithmetic unit 9 which calculates a harmonic component Dh of the input signal S1 through FFT operation on the basis of the thinning data D3; an LPF 2 which cancels frequency components, equal to or higher than a Nyquist frequency during sampling in the A/D conversion unit 3, among frequency components included in the input signal S1; a digital LPF 7 which cancels frequency components, equal to or higher than a cutoff frequency fc, by performing digital signal processing on the amplitude data D1; a frequency measuring unit 5 which measures a pulse frequency fp; and a frequency setting unit 6 which sets the cutoff frequency fc of the digital LPF 7 to be lower than or equal to half of the pulse frequency fp. <P>COPYRIGHT: (C)2012,JPO&INPIT |
