Re: 11801 triggering

Albert Otten


I think you gave the answer yourself: the rising edges of the waveforms are very close, so there is not enough time between trigger event and start of Cal output rising edge.
In my CSA803A I can view the rising edge of the FP clock output on a SD-26 when I set the CSA for internal triggering. And that is the rising edge starting at about 30 ns, so not the next one after 10 us. The (in my case slow) Cal output starts at about the same time position.
I tried the same as what you did when I was interested in trigger jitter of the external trigger input. IIRC Autoset even refused to obey.
As a nice exercise have a look at that next rising edge of the FP clock output (after 10 us). Jitter is about 200 ps rms.


On Thu, Apr 4, 2019 at 04:27 PM, Reginald Beardsley wrote:

Why can't I trigger off the internal clock output using the external trigger

The rising edge of the waveforms is very close, but the falling edge of the
calibrator is around 60 ns later than the falling edge of the internal clock

Leo's square wave pulser triggers fine, so it's not an issue with the external
trigger input.

The user manual says nothing about the required delay time between the trigger
and the waveform and appears to have been written by someone who had never
used a sampling scope.

I have tried both slopes, AC & DC coupling and the whole range of trigger
levels, but it refuses to trigger. I've compared the 11801 internal clock and
calibrator signals and Leo's pulser signals on a 200 MHz DSO.

I'm quite baffled. I thought I understood how a sampling scope works, but
there is clearly something important that I don't understand.


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