Agilent Technologies 54621D, 24A, 42A, 54621A, 22A, 41A manual Important Oscilloscope Considerations

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Important Oscilloscope Considerations

Whether the oscilloscope is stopped or running, you see more detail as you zoom in, and less as you zoom out. Zoom means you expand the waveform using either the main or delayed sweep window. Panning the waveform means you use the Horizontal Delay time knob( )to move it horizontally. To keep from losing detail as you zoom out, switch to the Peak Detect acquisition mode.

Peak Detect acquire mode Peak Detect for the 54620-series and for the

54640-series functions as follows:

•54620-seriesIn Peak Detect acquisition mode, any noise, peak, or signal wider than 5 ns will be displayed, regardless of sweep speed. In Normal acquisition mode, at sweep speeds faster than 1 ms/div, you would see a 5-ns peak, so peak detect has no effect at sweep speeds faster than 1 ms/div.

•54640-seriesIn Peak Detect acquisition mode, any noise, peak, or signal

wider than 1 ns will be displayed, regardless of sweep speed. In Normal acquisition mode, at sweep speeds faster than 500 ∝ s/div, you would see a

1-ns peak, so peak detect has no effect at sweep speeds faster than 500 ∝ s/div.

Using Peak Detect and infinite persistence together is a powerful way to find spurious signals and glitches.

Average acquire mode Averaging is a way to pull a repetitive signal out of noise. Averaging works better than either a brightness control or a bandwidth limit because the bandwidth is not reduced except when smoothing (number of averages=1) is selected.

The simplest averaging is smoothing (number of averages = 1). For example, on the 54620-series, the sample rate at a Time/Div setting of 2 ms/div allows the extra 5-ns samples to be smoothed together, smoothing the data into one sample, which is then displayed. Averaging (number of averages > 1) needs a stable trigger, because in this mode multiple acquisitions are averaged together. See the “MegaZoom Concepts and Oscilloscope Operation” chapter for more information about smoothing.

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