Manual

Functional description
Two-channel digital Oscilloscopes 21
Functional description
I - VERTICAL System / MATHematics function (cont'd)
1) FFT process
The FFT process mathematically converts a signal in the time domain
into its components in the frequency domain. It is possible to measure
the amplitude and frequency of the spectral components.
FFT function
page 1
FFT option
Values
Instructions
Source
CH1, CH2
Selection of the source channel for the
calculation of the FFT.
Window
Hanning
Hamming
Rectangular
Blackman
Selection of the type of FFT window
ZOOM FFT
1X
2X
5X
10X
Horizontal zoom of the FFT display.
Next page
Page 1/2
Access to the second page of the FFT menu.
FFT function
page 2
Option FFT
Values
Instructions
Scale
Vrms
The vertical scale is in Vrms
dBVrms
The vertical scale is in Vrms dB
Display
Split
Full screen
Half-screen display of the FFT
Full-screen display of the FFT
Next page
Page 2/2
Return to the first page of the FFT menu.
Procedure
To use the FFT, choose the source signal (time domain):
● Press the AUTO button to display a YT signal and choose the Multi-cycle
signal representation.
● Turn the "POSITION" knob so as to centre the YT signal vertically on the
screen (zero divisions).
● Turn the horizontal "POSITION" knob to centre the part of the YT signal to
be analysed on the 18-division screen.
The oscilloscope calculates the FFT using the 1024 central points of the
time-domain signal.
● Turn the "Volts/div" knob so as to keep the trace on the screen.
● Turn the "S/ div" knob until the desired resolution of the FFT spectrum is
reached.
Steps
To display the FFT correctly:
1. Press the "MATH" button.
2. Set the "Operation" option to FFT.
3. Press the "Source" button to choose channel "CH1" or "CH2".
4. Set the sweep coefficient "S/div" so as to obtain a sampling frequency
(parameter displayed alongside of the "Hz/div" scale factor of the FFT) of at
least twice the frequency of the input signal.