EEVblog #685 – What Is Oscilloscope AC Trigger Coupling?

In this tutorial Dave describes what AC trigger coupling is on an oscilloscope and why it can be useful. Not only on old analog CRT oscilloscopes, but modern digital scopes as well.
How and why is it different to AC channel input coupling?
Also, use of the 50% trigger control, and how the venerable DS1052E is still more usable than the new DS1054Z.

Previous video on Rigol DS1054Z and DS2000 Jitter Problem

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  1. Thank you. Very informative. Although one question about the video, were parts of it sped up? The voice sounds normal, but the hand movements were very fast. Maybe I’m just not used to watching videos from really good cameras.

  2. My DS1074 show level line when AC trigger is selected.
    And as I can see, channel coupling does effect on trigger coupling. But as far as I know channel coupling shouldn’t affect trigger coupling.

    • Channel coupling has effect, bcs the trigger signal is derived after the input channel frontend. There is no second AFE for trigger signal chain, where you could select DC coupling to input when the input is set for AC.

      • I was came to same conclusion…

        If channel is selected to AC coupling there is no way to use that channel for DC trigger.

        So I was correct when I wrote in last video comment that you can change channel coupling, instead of trigger coupling for DS1000Z series to workaround jitter issue.
        There is 4 channels, and you can use one for trigger. Sometimes not simple as it should be, but hey that is not way scope should work, but for that price, you can’t expect dedicated trigger AFE.

        Any way I’m satisfied with my scope…

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