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How to trigger on missing pulse?
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Sören_Marodören:
Hi,
In my system I have short pulses (<0.1 uS) that comes at approx 20 kHz indicating every "frame" that is ok.
In case of a frame error, the pulse for that frame is skipped.
How can I setup an Oscilloscope to trig on this missing pulse so I can see what caused it?

I have been thinking on making a timer circuit that get reset by the pulse. If it is not reset, the timer will generate its own pulse (Like a pacemaker.)
But, shouldn't it be possible to do this kind of measurements with a modern digital oscilloscope like Keysight DSOX 3/4000 or R&S MXO4?

Can a signal generator be used as the timer mentioned above?

Cheers,
/Sören
egonotto:
Hello,

in Siglent SDS2000X HD you can use dropout trigger or Nth Edge Trigger. In the R&S MXO5 you can use interval triggers. In Agilent InfiniiVision 5000/6000/7000 Series Oscilloscopes you can use the Nth Edge Burst Trigger.

Best regards
egonotto
noisyee:
Yes off cause, most modern scope have advanced trigger can handle the task. Just translate the event to something the scope can understand.
E.g. a missing pulse of a periodic pulse sequence can be regard as an unexpected long negative "pulse"(I know it's not what we call a pulse, but scope seems don't mind), or an unexpected long interval of two edge, or a time out event...
Pulse Trigger (Some called Width Trigger, or even Glitch Trigger if you don't mind it's not a glitch at all), Interval Trigger, Timeout Trigger can do the trick.
Aldo22:

--- Quote from: noisyee on April 07, 2024, 06:31:09 am ---Yes off cause, most modern scope have advanced trigger can handle the task. Just translate the event to something the scope can understand.
E.g. a missing pulse of a periodic pulse sequence can be regard as an unexpected long negative "pulse"(I know it's not what we call a pulse, but scope seems don't mind), or an unexpected long interval of two edge, or a time out event...
Pulse Trigger (Some called Width Trigger, or even Glitch Trigger if you don't mind it's not a glitch at all), Interval Trigger, Timeout Trigger can do the trick.

--- End quote ---

Out of curiosity, I tried this out on my cheap Hantek DSO2000.
I think the settings are correct as the OP specifies (in the picture on the right)?
That seems to work.
If that's what the OP means, then it's relatively simple.

EDIT: For the OP, "Width" would of course have to be greater than 50μs in your case. I don't have a pulse generator that pulses irregularly. So it still triggers at the 49μs in the picture, but at over 50μs it would no longer trigger, or only if a pulse is missing, which is the point of the question afaiu.
Psi:
yep, most scopes have an option for trigger low / high time  'less than' / 'greater than'.
So you just trigger on a low time pulse longer than the typical time between your pulses.

I do recall that the Rigol 1052 had some issues with this. It didn't always work quite right.
But pretty much all modern scopes the the option for triggering on a pulse longer than a set value and it normally works ok.
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