Author Topic: Rigol MSO4000 triggering/holdoff question  (Read 451 times)

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Offline omegahacker

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Rigol MSO4000 triggering/holdoff question
« on: May 03, 2017, 05:07:41 AM »
I just got a new Rigol MSO4024 for work, and so far it's not really working all that great.  Immediately I ran into a bug where the serial decode (CAN) would just spontaneously drop off the screen while scrolling horizontally, and not come back without retriggering.

But the biggest bummer for me right now is that it's not showing the most recent trigger after holdoff.  Specifically, the signal I'm looking at right now consists of a low pulse for ~2mSec caused by the reset of the generating microcontroller, then ~160mSec later a CAN packet being transmitted.  The scope is in Normal mode with the min 100nS holdoff.

On my previous scope (Keysight MSOX2014), it would trigger on the boot pulse, then trigger on the CAN leading edge, and stop on the CAN leading edge.  Alternately, if I had the timebase zoomed in enough, it would actually trigger several times and show me the last one (the retrigger window seemed to be the width of the screen).

On the Rigol unit, all it shows me is the boot pulse, unless I go through many extra steps to either do segmented record and find the right edge, or set up Nth edge which only works until it doesn't.  However, if I hit the reset button on the MCU a couple times ~250mSec apart, I can see the scope showing me the 1st boot pulse, then the 2nd, then *usually* stopping at the 2nd-boot CAN packet.

Am I missing anything here?  I've been through all the options, and nothing seems conceptually different from the Keysight scope (or even my really old Tek TDS224), but the Rigol just isn't matching behavior with what I expect (and need).

Thanks!
 

Offline Teuobk

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Re: Rigol MSO4000 triggering/holdoff question
« Reply #1 on: May 03, 2017, 11:36:06 AM »
Do you have your memory depth set to "auto" (or at least a relatively low value)? If not, it's possible the scope isn't triggering on the CAN leading edge because it's still recording the waveform from the trigger on the boot pulse. Try changing the memory depth to "auto" and then zooming in so the span is well under 160 ms.
 

Offline jjoonathan

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Re: Rigol MSO4000 triggering/holdoff question
« Reply #2 on: May 03, 2017, 03:00:15 PM »
https://goo.gl/photos/bFrMoT86Rt2UtddK7

My Rigol DS4014 has 30ms of dead time in a similar, simulated setup. Not great, but I really don't think that should be a show-stopper for your particular use case. Is your scope behaving differently from mine? Or do I just not understand the problem?
 


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