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Eliminating Aliasing
Use the following methods to eliminate aliases:
 Increase the sample rate by adjusting the horizontal scale to a faster time-per-division setting.
Since you increase the Nyquist frequency as you increase the time per division, the aliased
frequency components should appear at their proper frequency. If the increased number of
frequency components shown on the screen makes it difficult to measure individual
components, use MultiView Zoom to magnify the FFT waveform.
 Use a filter on the source signal to limit the bandwidth of the signal to frequencies below that
of the Nyquist frequency. If the frequency components that you want to view are below the
built-in bandwidth settings, set the source channel bandwidth to the appropriate value.
 Push the AUTOSET button.
 Switch the acquisition to Envelope mode or Peak Detect mode. Envelope mode searches for
samples with the highest and lowest values over multiple acquisitions and can detect faster
signal components over time. In Peak Detect mode, the acquisition alternates between saving
the highest sample in one acquisition interval and lowest sample in the next acquisition
interval.
Nyquist frequency
The highest frequency that any digital oscilloscope can measure without errors is one-half of the
sample rate or frequency. This frequency is called the Nyquist frequency. The FFT waveform
displays the input signal frequency components from DC (0 Hz) to the Nyquist frequency.
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