Manual

Functional description
Two-channel digital Oscilloscopes 23
Functional description
I - VERTICAL system / MATHematics function (cont'd)
4) Zoom and
positioning
of an FFT spectrum
You can use the zoom and the cursors to select measurements
of the FFT spectrum. The oscilloscope has an "FFT Zoom" option to effect a
horizontal zoom; use this option button to choose "1X", "2X", 5X", or "10X".
5) Measurement of
the FFT spectrum
using cursors
It is possible to make two measurements on the FFT spectral components:
the amplitude (in dB or V) and the frequency in Hz
Amplitude
1. Enter a sinusoidal signal in channel 1 and press the "AUTO" button,
then choose the Multi cycles option.
2. Press the "MATH" button to display the "MATH" menu.
3. Press the "Operation" button and choose "FFT"
4. Press the "Source" button and choose "CH1"
5. Press the "CH1" button to display the CH1 menu.
6. Turn the "S/div" knob to adjust the sampling frequency (at least twice
the frequency of the input signal).
7. For an FFT display in full screen mode, press the CH1 button again to
remove the display of the channel 1 signal.
8. Press the "CURSOR" button to display the "Cursor" menu.
9. Press the "Cursor Mode" button and choose "Manual".
10. Press the "Type" button and choose "Voltage"
11. Press the "Source" button and choose "MATH"
12. Press the "CurA" button, turn the "Adjust" knob to move Cursor A to
the highest-amplitude component of the FFT signal.
13. Press the "CurB" button, turn the "Adjust" knob to move Cursor B to
the lowest-amplitude component of the FFT signal.
14. The amplitude difference (∆V) is displayed at top left on the screen.