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trigger problem

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trigger problem

Postby adynis » Sat Oct 31, 2009 2:42 am

Hello,
I'm using the 2204 osciloscope. I have a signal with bursts at ~37Khz and when I set to Auto, Repeat or Single .. the trigger is not very precise. Sometimes it trigers at another rising edge, not the first one. The picture below it is an example. The problem is that whan viewing in Auto mode the same burst of signals, it is not stable, it moves right or left because it is not triggerd every time in the first point.

FastPrintScreen 55.png
The trigger shoud be at the first rising point of the signal, not in the middle ...
(97.36 KiB) Downloaded 7 times


What is the problem ? Hardware/software?
Thank you.

Ps. I have Pico Scope 6.2.14.0 and I have tested also 6.3.4 - I think - the beta version;
adynis
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Re: trigger problem

Postby Michael Hayes » Mon Nov 02, 2009 4:34 am

Adynis,
Just a thought, is there any pre-trigger affecting the point on waveform?
Regards,
michael
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Re: trigger problem

Postby adynis » Mon Nov 02, 2009 8:32 pm

hello,
if you are talking about the time-delay, the delay before/after the trigger event .. no, there is no trigger delay :(

I think there is a bug someware... I hope not in the hardware.
I hope that someone can confirm/infirm my problem :idea:
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Re: trigger problem

Postby Erik » Wed Nov 04, 2009 8:51 am

Assuming you have set it up to trigger on a rising edge there is no bug. It is clearly triggering on a rising edge.

To trigger on the first rising edge in a burst you need to setup a more advanced trigger criteria. You could try

Pulse Width
Negative Pulse
Greater than 200 us

That should trigger on the first edge in the burst.
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Re: trigger problem

Postby adynis » Thu Nov 05, 2009 12:17 am

Thank you for you reply, but please give me a little more help:
where do i have to set those options regarding advanced trigger criteria?
(I have picoscope 2204 and the latest picoscope software)


Thank you.
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Re: trigger problem

Postby ziko » Mon Dec 07, 2009 8:47 am

The 2204 does not support advanced triggering, only the 2205 supports it.

Kind regards
Ziko

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Re: trigger problem

Postby adynis » Sat Dec 12, 2009 10:53 pm

So ... I understand that ...
for 2204 the trigger example is a problem !
I don't think that this behavior of the osciloscope is a normal one ... No one wants that with a trigger option set ... it shows a hardly-triggering signal / a non stable image from a periodical burst of data.
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Re: trigger problem

Postby ziko » Mon Dec 14, 2009 3:20 pm

Hi, no this is normal. This is all dependant on when the trigger is enabled, or to say it in a different way when the trigger command is sent. So where on the waveform this will happen is somewhat random.

Hope this makes sense.

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Re: trigger problem

Postby Michael Hayes » Mon Dec 14, 2009 9:58 pm

Not sure of the source impedance of the waveform you want to view but if it is reasonably low, you may be able to take a parallel feed of the signal trhough a diode to rectify it and then to a parallel RC circuit say 100k // 470pF which would give a roughly square wave which goes to about half a volt just after your burst starts and trails off a few burst cycles after it finishes. It is not a perfect solution but if you trigger at the lowest possible level, it may give you a stable view of the waveform.
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