General > General Technical Chat
How to trigger a combined signal
RAPo:
--- Quote from: tom66 on October 14, 2022, 03:41:19 pm ---The only way you could get a circuit like this to work is to have the scope sweeping fast enough that in the modes that use intensity grading the traces overlap. Generally that occurs once the timebase is much below one whole display frame (assuming the screen refreshes at 60Hz and 12 div horizontally, that starts to happen below 1ms/div)
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Yes I discovered that just a moment ago (are you telepathic ;)
--- Quote from: tom66 on October 14, 2022, 03:41:19 pm ---However note that such modes give relatively poor performance for measurement functions etc and single shot modes will show one of the 3 different traces.
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Not necessarily because there is only one trace. If the frequencies are near each other of an exact multiple of a specific frequency, it gets easier.
--- Quote from: tom66 on October 14, 2022, 03:41:19 pm ---Really this does not work well with digital scopes due to how digital phosphor modes work, they behave only superficially like an analog scope does.
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indeed but trying this out on a digital scope triggered (pun intended) a nice dicovery/learning process.
--- Quote from: tom66 on October 14, 2022, 03:41:19 pm ---You still need to find some way to trigger the scope to the tracer's pulse output and you would not be able to trigger on the actual waves themselves, a quick think about how digital oscilloscopes manage pre and post trigger times will make that clear pretty quickly.
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On an analogue scope using an external trigger tied the trigout-BNC of the apparatus triggers on the selected input signal. Of course the other signals start to roll.
--- Quote from: tom66 on October 14, 2022, 03:41:19 pm ---What you want to buy is an analog capture card of some kind, they often capture 16+ channels at one at low frequencies. You cannot do what you want for any reasonable real world application with a DSO. Sorry.
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Sorry is not needed, many thanks from my side is. I have no real application for this apparatus, it was an impulse buy from the local craigslist thinking: that looks like an interesting device, lets try it.
For 65 euro's one can have a lot of fun.
tautech:
One normally starts an exercise like this by learning about the many and various trigger types a DSO has over a CRO and how to use them.
Another useful trigger tool is Holdoff however one must first decide where on a complex waveform one wants/needs to trigger and then apply the trigger type and Holdoff if required to get the result needed.
RAPo:
--- Quote from: tautech on October 14, 2022, 08:59:59 pm ---One normally starts an exercise like this by learning about the many and various trigger types a DSO has over a CRO and how to use them.
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Life throws things sometimes in a different order.
I already had some scopes then this apparatus came and then one wants to find out how the heck it works.
--- Quote from: tautech on October 14, 2022, 08:59:59 pm ---Another useful trigger tool is Holdoff however one must first decide where on a complex waveform one wants/needs to trigger and then apply the trigger type and Holdoff if required to get the result needed.
--- End quote ---
indeed:
--- Quote from: RAPo on October 13, 2022, 05:52:09 pm ---I think I am getting to answer my own question.
Step 1: arrange signal heights so there is a space to set an edge trigger with a level, not in the signal regions. This stabilizes the overall image.
Step 2:The apparatus has a pot, with it you can arrange a chop_freq (between 6.5kHz and 23.8kHz).
Try (the pot is very sensitive) to get the chop frequency such that it divides the frequency of one of the input signals.
The chop_frequency is not a constant
Step 3: Put an holdoff slightly larger than 1/chop_freq.
See https://www.flickr.com/photos/renseposthumus/52425634949/in/photostream/
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StillTrying:
If you want to trigger separately on 3 or 4 channels there's no way to do that, there's no analogue ALT like option. All the sampling and displaying timing is locked to the one trigger channel so you can't stabilize different frequency inputs.
You'd have to look a single shots?
Triggering on the yellow conbined is not much use because its switching frequency isn't related to the analoge input frequency(s).
You might be able to make 1 DSO channel look a bit like 3 inputs by using persistance and dots mode?
https://www.batronix.com/files/Rigol/Oszilloskope/MSO5000/MSO5000_UserGuide_EN-V2.0.pdf
RAPo:
--- Quote from: StillTrying on October 16, 2022, 01:32:12 pm ---If you want to trigger separately on 3 or 4 channels there's no way to do that, there's no analogue ALT like option. All the sampling and displaying timing is locked to the one trigger channel so you can't stabilize different frequency inputs.
You'd have to look a single shots?
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I'm trying to trigger on 1 channel (the yellow one), not 3 channels
--- Quote from: StillTrying on October 16, 2022, 01:32:12 pm ---Triggering on the yellow conbined is not much use because its switching frequency isn't related to the analoge input frequency(s).
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That goes for a *digital* scope, the analogue scope can (within bounds) trig on the yellow signal and one of the 3 input signals, see images.
--- Quote from: StillTrying on October 16, 2022, 01:32:12 pm ---You might be able to make 1 DSO channel look a bit like 3 inputs by using persistance and dots mode?
--- End quote ---
yes, will try that.
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