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2. Press the “Cursor Mode” button to select “Manual”.
3. Press the “Type” option button to select “Time”.
4. Press the “Source” option button to select “MATH”.
5. Press the “CurA” option button, turn the “Universal”
button to move Cursor A to the highest position of
the FFT waveform.
6. The value of CurA displaying on the top of the left
screen is FFT frequency. This frequency should be
the same as input signal frequency.
Figure 3.17 – Measuring FFT Frequency
The FFT of a waveform that has a DC component or offset can
cause incorrect FFT waveform magnitude values. To minimize the
DC component, choose AC Coupling on the source waveform.
To display FFT waveforms with a large dynamic range, use the
dBVrms scale. The dBVrms scale displays component magnitudes
using a log scale.
The Nyquist frequency is the highest frequency that any real-time
digitizing oscilloscope can acquire without aliasing. This frequency
is half that of the sample rate provided it is within the analog
bandwidth of the oscilloscope. Frequencies above the Nyquist
frequency will be undersampled, which causes aliasing.
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