Using Features for Advanced Applications
TDS 684A, TDS 744A, & TDS 784A User Manual 3–159
FFT Time Domain Record
FFT Time Domain Record After
Windowing
FFT Window
FFT Frequency Domain Record
FFT
Xs
Figure 3–93: Windowing the FFT Time Domain Record
You can often determine the best window empirically by first using the window
with the most frequency resolution (rectangular), then proceeding toward that
window with the least (Blackman-Harris) until the frequencies merge. Use the
window just before the window that lets the frequencies merge for best compro-
mise between resolution and amplitude accuracy.
NOTE. If the Hanning window merges the frequencies, try the Hamming window
before settling on the rectangular window. Depending on the distance of the
frequencies you are trying to measure from the fundamental, the Hamming
window sometimes resolves frequencies better than the Hanning.