PeakTech 1280 Bedienungsanleitung Seite 96

Notes for using FFT
 Select "Scale" to magnify the FFT wave form if necessary.
 Use the default dB scale for details of multiple frequencies, even if they have very different
amplitudes. Use the Vrms scale to compare frequencies.
 DC component or offset can cause incorrect magnitude values of FFT waveform. To minimize the
DC component, choose AC Coupling on the source signal.
 To reduce random noise and aliased components in repetitive or single-shot events, set the
oscilloscope acquisition mode to average.
What is Nyquist frequency?
The Nyquist frequency is the highest frequency that any real-time digitizing oscilloscope can acquire
without aliasing. This frequency is half of the sample rate.
Frequencies above the Nyquist frequency will be under sampled, which causes aliasing. So pay more
attention to the relation between the frequency being sampled and measured.
Note：
In FFT mode, only support to set coupling, voltage division and zero position in Channel window, other
operations are prohibited. If you want to enter other menus, uncheck "FFT" first.
16. How to zoom the waveform
to show Function menu, choose "Horizon".
Click
16.1. Main Time Base
The setting of the horizontal main time base is used to display the waveform.
16.2. Assist Set
A window area is defined by two cursors, which will be expanded to the full screen size in Window
Expansion.
Choose W value from the combo box to adjust the size of this window area. Click
slider bar. You can adjust the horizontal position of the area in main window by it.
Note: In Assist Set status, the time base and horizontal trigger position cannot be set.
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