Real-time oscilloscopes operating in real-time acquisition mode capture an entire waveform in a single trigger event. This method guarantees a sample rate that is fast enough to get all the samples required to accurately reconstruct the waveform. However, some situations call for higher timing resolution. This can be achieved through equivalent-time sampling. There are two types of equivalent-time sampling:
1) a real-time oscilloscope operating in random equivalent time sampling mode
2) the sequential sampling of a sampling oscilloscope In random equivalent-time mode, a real-time oscilloscope acquires portions of waveforms during multiple trigger events. Over time, these portions are assembled into a complete waveform. While equivalent-time sampling provides higher timing resolution and accuracy (even in very high bandwidth signals), it requires a repetitive waveform and therefore cannot be used for single-shot acquisitions.
Using sequential equivalent-time sampling, sampling oscilloscopes acquire one sample from each trigger event, with a fixed interval between each acquisition. Over time, the instrument accumulates enough samples to reconstruct the waveform. This type of sampling provides the extremely high bandwidths (65 GHz and higher) and timing resolution needed for telecommunications and device characterization needs.
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