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Trigger Holdoff

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Trigger Holdoff

Postby mikel » Tue Feb 01, 2005 11:45 pm

I'm using a PicoScope 3205 to capture data wavefoms (amongst other things). One waveform is a burst of data about 10ms long followed by a 90ms gap. I've set the scope to repeat triggering and 2ms per division in the expectation that it will then trigger on the beginning of the burst of data. Much of the time it triggers as expected. However some of the time it misses the beginning of the data and triggers later in the data burst. If I pre-trigger, then it is clear that when the trigger is late it is not that the data has been missed - it's just that the trigger is late.

Any ideas for ways of avoiding this behaviour so that the trigger is more reliable?

Most conventional scopes have 'trigger holdoff' which helps resolve such triggering difficulties. Is there something similar available here?

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Postby Sarah » Wed Feb 02, 2005 11:42 am


Thank you for your post.

This problem that you are seeing is due to the fact that the scope will start sampling at an arbitrary point in time and therefore the trigger circuit will be armed at an arbitrary point in time.

Most of the time the trigger circuit will be armed in the 90ms gap
between data bursts because the signal being measured is in this
state for the longest period of time and therefore it's more likely that
the trigger will be armed in this period. In fact, because it's a 9:1 ratio of data to no-data, it should trigger in the wrong place 1 in 10 times on average.

There are two possible ways that you could overcome this:

1. If the data can be turned on and off then one possibility is to turn
the data off and set the scope running. The trigger point will therefore definatley be armed when the data is reactivated.

2. Increase the timebase and number of points that are acquired. The trigger point should be set to the middle of the screen and the sample rate increased so that no matter where the trigger catches the data, the entire burst is captured and displayed on the screen. If the number of points are now increased (512kS max for PS3205) then the acquired data can be zoomed in on.

Hope this helps

Best Regards

Re: Trigger Holdoff

Postby s.voulaz » Thu Oct 26, 2017 11:07 pm

I'd like to jump on this (quite) old topic to refresh it. I must admit I'm a newbie in Pico's world, and while I appreciate much of its functionality I really (really!) miss the trigger hold-off feature. I find myself (too) often switching to my old fellow 54645D to see what I just can't comfortably see with the 3000 - which is definitely always the case with repetitive bursts.

I really think that this feature deserves much more consideration than it had so far. I sincerely hope to see it in some future firmware and software upgrade.

Thanks for the good products - and for listening.
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Re: Trigger Holdoff

Postby Hitesh » Fri Oct 27, 2017 8:37 am

Hi s.voulaz,

We do welcome Customer feedback, so thank you for your comments - I have added your comments to an existing feature request.

Our Development Team are busy on current projects, so it may be some time if this is deemed to be feasible.


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Re: Trigger Holdoff

Postby rossgbaker2 » Wed Nov 08, 2017 4:28 am

This is BY FAR the normal oscilloscope function I miss the most on my Picoscope 5000 series.

I am really shocked that it appears that some engineers at Picotech do not seem to really understand this function and its value. It is simply setting a controllable amount of time after a trigger event before which another trigger event will not be detectable (a refractory period). It is simple and very useful. It would be very easy to add to any programmable logic device like an FPGA. It should take less than an hour to code the Verilog or VHDL.
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Re: Trigger Holdoff

Postby Martyn » Wed Nov 08, 2017 7:31 am

We do understand, however there are so many features already packed into PicoScopes that there is very little, if any space left, so adding new features has to be considered very carefully, alongside all the other additions that have been requested, and the availability of engineers to do the work.

For some cases where Holdoff would be a good choice, it is often possible to use the Advanced Trigger features to achieve the same result.
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