Basic FAQ for FFT Analyzer

In the power spectrum, a single line value (i.e., frequency band) represents the root mean square value, so its linear spectrum is the effective value. However, since the analysis width (frequency resolution) of the usual FFT analysis is small, its output can be approximated by a sine wave (or cosine wave). Therefore, the amplitude value at that frequency (amplitude value or peak value, half amplitude value) can be approximately calculated as √2 times the effective value. This approximate peak value may be referred to as the equivalent peak value. Similarly, the P-P value (peak-to-peak value, full amplitude value) is obtained by multiplying the effective value by 2 √2.

As an example, the input signal isThen, the effective value is A / √2, the amplitude value (peak value) is A, and the P-P value is 2 A.

	Power Spectrum (Glossary of Basic Terms for FFT Analyzer)