EEVblog #159 – Oscilloscope Trigger Holdoff Tutorial

One of the more obscure controls on an oscilloscope is the Trigger Holdoff control. A dedicated control on most high end analog oscilloscopes, and a main menu option in modern digital scopes, yet often poorly understood. What does it do and how does it work?

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    • George Graves

      That was just what I needed! Thanks!

      I assume if your digital signal isn’t repeating at regular intervals then this doesn’t work?

      • John R

        Great tut. George – It doesnt need to be the same data, it just needs to be bursty or show a big enough break between segments – the first few triggers will be crap (you won’t even see them usually) but it will then stabilise at the end of the dead period.

    • masterburner

      Interesting tutorial, Dave. Finally some more advanced stuff on Youtube. I was getting tired of all the “How to hook up an LED” type video’s…

    • Adam Ward

      I wish I hadn’t bought my cheapo analog scope, that Rigol digi looks so much nicer to use.

      Interesting vid.

    • Tony Viera

      This is just outstanding; your blog and videos have hit on something that is really needed out here, which is practical electronic shop demonstrations. I just purchased an Agilent 2024 o-scope after I saw your review of it. Thanks.

    • Sébastien

      I just bought an “old” 20MHz oscilloscope (metrix OX800) and it has this feature. Of course, I did’nt understand what it does… :-) And even if I had the user’s manual (It’s not the case unfortunately), I am not sure that I would have understood this well the benefit of the “hol doff” function. So, thank you for this video. You are really a good teacher.

      Super blog ! 😉

    • Dwayne Dibbley

      Nice one Dave…

      Back when I was a lad (An you were still swimming … :-0) I was working on mainframes using tektronix 100Mhz jobbies. We used A delayed by B a fair bit, which is a very useful mode with clocked digital signals. Do the modern digital scopes have that feature?

    • Eric Hill

      Dave, you have no idea how much closet electronic geeks are starving for this kind of information! Keep up the awesome blogs! *thumbs up*

      New blog ideas:
      RF tuning and troubleshooting
      Creative Arduino uses
      Soldering tips

    • Ramzi

      Thank you very much Dave for this TUT.

      Q. Is this “Holdoff” same as Trigger Pulse as in some USB-DSO?

      Thanks again…

    • Minde

      This tutorial was really useful. Features of scope like this are sitting there and never used. Thanks.

    • Hans

      Awesome Dave, keep up these awesome blogs 😀

    • Edisonobilly

      Hi dave. this is another very nice one. I had been in situations in the past, where i would have really used this feature, that was just lying down there wasting on the scope. Thanks so much Dave.
      As for the auto button in those digital scopes, the firmware could be designed to seek out the longest delay in the waveform after a number of samples, and then adjust the hold off time automatically. this shouldnt take too many lines of code to implement.It will also take care of the problem of non-regularly repeating waveforms, mentioned by George Graves. I am quite surprised the New Tektronix didnt have that capability, it is still a great scope anyway.

      Thanks Dave, keep up this good work.
      Edison C.O.

    • Sven Killig

      Nice one, I have to try this with RS 232 data! Perhaps the stop bit is enough…
      I just watched this episode @720p in my hotel room via my mobile’s 3G HSDPA. Sometimes technology is indistinguishable from magic :-)

    • Nick

      Awesome! I was wondering what that dial was for. Thanks!

    • Greg Fordyce

      Great tutorial Dave. How about one on maths functions on o-scopes, in particular the FFT function, That’s an obscure one, is it useful? What is it used for? And for that matter what would you use the other math functions for? More o-scope tutorials please, I have bought a Rigol so I can follow along. :)

    • Magicmushroom666

      Great tutorial. I knew of the delay that knob created, but never realised what situations could benefit from it. You made it really clear thanks.

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    • Brian J Hoskins

      Great tutorial.

      I consider myself to be pretty handy with a scope, even on more complex triggering situations, but I have to confess that I didn’t really know about this feature!

      Every day is a school day!

      Someone on YouTube is suggesting that you used poor practical examples. I’m not sure what he (I’m assuming it was a he) is getting at there to be honest?
      While watching the tutorial I was able to fully understand how you used the feature and also the circumstances under which it would be beneficial to use it. You could say we were on the same wavelength (groan).

      So yeah I’m not quite understanding that to be honest – I didn’t see any problem with the practical example you used, nor can I see how the tutorial would have been better explained with a different practical example…

      Keep up the blogging!


      • Karl (not that Karl, the other Karl)

        I think you should forget about that youtube guy. There are millions of signals out there where a trigger holdoff can help. Just because Dave didn’t pick the guy’s pet signal doesn’t mean there was anything wrong with Dave’s examples.

        But if you need a second opinion, get Tektronix’s The XYZ of Oscilloscopes and compare their example signal with Dave’s.

        • EEVblog

          Not surprising that Tek use the same example, because IMO it’s one of the easiest and simplest to understand.
          You get all sorts on Youtube!

    • Robert

      Great tutorial, a new blog going about how the triggering process works would be nice!

    • Martin M.

      yep it’s now in wikipedia!

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