Real-time sampling is the only way to capture fast, single-shot, transient signals with a digital oscilloscope. Real-time sampling is ideal for signals whose frequency range is less than half the oscilloscope’s maximum sample rate. Here, the oscilloscope can acquire more than enough points in one “sweep” of the waveform to construct an accurate picture.
Real-time sampling presents the greatest challenge for digital oscilloscopes because of the sample rate needed to accurately digitize high-frequency transient events. These events occur only once, and must be sampled in the same time frame that they occur. If the sample rate isn’t fast enough, high-frequency components can “fold down” into a lower frequency, causing aliasing in the display. In addition, real-time sampling is further complicated by the high-speed memory required to store the waveform once it is digitized.
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