Nyquist: sample at > 2·f_max. Alias of f at f_s: f_alias = |f − round(f/f_s)·f_s|.
f_alias = |f − round(f/f_s)·f_s|
FFT bin Δf = f_s/N; bin k → f_k = k·f_s/N. PSD = A²_rms/(Δf·ENBW). Pairs with the vibration page's PSD tooling.
Δf = f_s/N
f_k = k·f_s/N
= A²_rms/(Δf·ENBW)