Keysight Technologies 3458A Guide D'utilisation page 483

Figure E-3
Using the track-and-hold path for direct or sequential sampling
The track-and-hold path is the solution to capturing the amplitude of narrow
pulses. This path has a bandwidth of 12 MHz and a fixed aperture of 2 ns. With
trigger jitter of 2 ns, you can, with a little searching, capture the peak amplitude of
a pulse as narrow as 40 ns without measurement degradation, as indicated in
Figure
measurement; hence, if it is likely that signals with these frequency components
will be applied to the input of the 3458A, then bandlimit the signal by filtering.
Direct digitizing with the track-and-hold path allows the capture of signals with
frequency components up to 12 MHz. The same path is used to subsample
repetitive signals up to 12 MHz.
Programming the 3458A for direct or subsampled (sequential) digitizing using the
track-and-hold path is simple. Only one command is required. For example, DSAC
provides direct sampling, AC coupled, or SSAC provides sequential sampling, AC
coupled. These commands automatically use default parameters that can be
changed.
Keysight 3458A User's Guide
The 3458A multimeter provides two different digitizing paths,
the standard DCV path and a track-and-hold path.
E-4. Rise times of less than 10 ns will cause overshoot in a digitized
High Resolution Digitizing With the 3458A E
483