Agilent Technologies 42A, 54621D, 24A, 54621A, 22A, 41A manual Realtime Mode

MegaZoom Concepts and Oscilloscope Operation

Acquisition Modes

If you cannot acquire multiple triggers, you can still reduce noise and increase resolution at slower sweep speeds by setting # Avgs to 1.

54620-series	54640-series	Bits of resolution
Sweep speed	Sweep speed	(# Avgs=1)
≤ 2 us/div	200 ns/div	8
5 us/div	1 us/div	9
20 us/div	5 us/div	10
100 us/div	20 us/div	11
500 us/div	100 us/div	12

Realtime Mode

In Realtime mode, the oscilloscope produces the waveform display from samples collected during one trigger event. The sample rate for the

54620-series is 200 MSa/s for single channel or 100 MSa/s with channel pairs 1 and 2, 3 and 4, or pod 1 and pod 2 running. The sample rate for the 54640-series is 2 GSa/s for single channel or 1 GSa/s with channel pairs 1 and 2, or pod 1 and pod 2 running.

When less than 1000 samples can be collected in the time spanned by the screen, a sophisticated reconstruction filter is used to fill in and enhance the waveform display.

To accurately reproduce a sampled waveform, the sample rate should be at least four times the highest frequency component of the waveform. If not, it is possible for the reconstructed waveform to be distorted or aliased. Aliasing is most commonly seen as jitter on fast edges.

When Realtime mode is off, the oscilloscope produces the waveform display from samples collected from multiple triggers, when on fast sweep speeds. In this case, the reconstruction filter is not used. When the trigger is stable, this produces the highest fidelity waveform.

Realtime mode is only necessary at sweep speeds of 200 ns/div and faster for the 54620-series and 2 ∝ s/div and faster for the 54640-series, since on these ranges <1000 samples can be collected on each trigger. While the effective bandwidth of the channel is reduced slightly, Realtime mode produces a complete waveform for each trigger.

Realtime can be turned on when any other acquisition mode is turned on. Use Realtime to capture infrequent triggers, unstable triggers, or complex changing waveforms, such as eye diagrams.

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