Re: 7T11 sampling timebase - how does it behave?


On Wed, May 9, 2018 at 12:07 pm, Roger Evans wrote:

The 7S14 has a delay line so that you can see the trigger point and make
accurate time measurements from the trigger to other features on the waveform.
On the 7T11 in sequential scan you are looking 10s of nsec after the trigger
so you largely lose any time reference from the trigger event.
The 7S14 is specified to "only" 1 GHz. It's very much easier to make a low-distortion (amplitude, phase) delay line for frequencies up to 1 GHz than up to say 11 or 14 GHz, which is where the 7T11 is often used.
The delay line affects the signal in the vertical stage (that would have to be e.g. the 7S11), not in the time base (7T11), so available space in the 7T11 would not be a factor.
It's not in fact the delay line that is used for making accurate time measurements like the 7S14 can; it's the accuracy of the delayed-time-base circuits that do, by showing(/measuring) the delay from one event to another. The 7S14 has a fixed delay time for the signal in the vertical circuits to make it arrive on the plates long enough after the trace starts to make it visible, like in a normal analog 'scope with vertical delay line. The 7T11 in sequential trigger mode has its special way of delaying the display of the vertical signal: It shows parts of many trigger events that happen at least one period (or triggering edge) after the actual events (one event per dot). The setting applies the same (>1 period) delay for each dot.


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