Manual

Functional description
22 Two-channel digital Oscilloscopes
Functional description
I - VERTICAL system / MATHematics function (cont'd)
2) Display of the
FFT spectrum
Press the MATH button to display the Math menu. Use the options to select
the Source channel, the Window, and the FFT Zoom factor. Only one FFT
can be displayed at a time. You can choose "Full Screen" or "Split Screen" in
the "Display" option to display the FFT full screen, or to display the signal
and its FFT simultaneously on two half screens.
3) Selection of the
FFT window
The FFT window reduces the peaks of the FFT spectrum. The FFT
assumes that the YT signal continues to infinity. With a whole number of
cycles, the YT signal begins and ends at the same amplitude and the
signal is free of irregularities. A non-integer number of cycles of the YT
signal gives starting and ending points at different amplitudes. The
transition between the starting and ending points creates a discontinuity
of the signal that causes high-frequency transients.
Window
Specialization
Correct test content
Rectangular
Better frequency resolution,
worse amplitude resolution.
This is equivalent to no
window.
Pulses or symmetrical
transients.
Sine waves of equal
amplitude at fixed
frequency. Broad-band
random noise with a
spectrum that varies rather
slowly.
Hanning
Hamming
Better frequency resolution
and less good precision in
amplitude than Rectangular.
Frequency resolution is
slightly better with Hamming
than with Hanning.
Sinusoidal, periodic, and
narrow-band random
noise. Pulses or
asymmetrical transients.
Blackman
Better amplitude resolution,
worse frequency resolution.
Signals at single
frequency, to find higher
harmonics