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Christoph Gollinger

Jitter on Digital Discovery Pattern output

Question

Hello Forum,

we are using the Digital Discovery to generate a pattern.

Every 10ms a trigger pulse is input to DIN0 of the Digital Discovery. This starts the pattern generation.

In the attached document a pattern is output on one channel. There are generated 5 pulses.

Sample frequency 400kHz / No of samples = 3900 / pattern length is 9.75ms

The document shows measurement of the positive edges of the pattern.

There are 5 pulses in the pattern. It can be seen that the jitter increases, the later the pulse edge is in the pattern.

 

We did not find out and do not have an explanation the reason of the jitter?

And also not for the increasing jitter?

 

Could you please explain what we did wrong?

 

Thank you very much

Best regards

Christoph

 

 

Issue_pattern_edge_20200207.docx

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Hi @Christoph Gollinger,

We tried to recreate the workspace but couldn't do it completely. Can you please save your workspace and attach it here? Also you were saying that you receive a pulse every 10ms. Where do you get it from? Is it from an external source?

Thanks,

Bianca

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Hello Bianca,

thanks for the quick response.

I added the workspace file below. I hope with this you can reproduce the behaviour.
We get the pulse with 10ms period from an external source. It is the Marker Output of a Rhode Schwarz Vector Signal Generator SMBV100A.
The output from the SMBV100A is connected to DIN0 of the Digital Discovery which we want to use to trigger the Pattern generator.

First we thought that the jitter can be caused by the bad signal integrity of the trigger pulse.
The signal did not look very nice, but then we added a termination at the end of the signal to get rising and falling edges without ripple/under-/or overshoot.
But this did not change jitter behaviour.

We think the jitter problem is caused by a wrong setting that we did.
I hope you can reproduce this and give us a hint what we should do to solve this.

Thank you and best regards

Christoph

 

20200204_1.dwf3work_test.zip

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Hi @Christoph Gollinger,

I asked Bianca about this and she let me know that they were able to reproduce the error with the Digital Discovery. We are waiting for the engineer much more familiar with the WaveForms software to get back into office (they are out on leave) to help determine the root cause and appropriate resolution.

Thanks,
JColvin

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Hi @Christoph Gollinger,

Thanks for your patience. Like James said, we were able to reproduce the error and it's not due your set-up. From the hardware point of view we couldn't find the errors while investigating the discovery so we hope to be able to fix this with software. However, our colleague responsible with Waveforms is on medical leave. 

We'll return with an answer as soon as possible. 

Best regards,

Bianca

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Hi @Christoph Gollinger,

Thanks for waiting. So, the issue was that when it was implemented the fine tuning for the new version of waveforms, it seems it has broken something and you can see that jitter. With our setup we could see what you was seeing with yours. We switch to an earlier version of waveforms and everything worked fine. We still have to investigate why the issue has appeared and how we can fix it without giving up to the new feature. Meanwhile, if you want to make your experiment and not experience the jitter, I recommend you to use an older version of Waveforms. We tested in 3.10.9 and it worked fine. Can you test it with this version and let us know if you still have troubles?

You can find it here: https://reference.digilentinc.com/reference/software/waveforms/waveforms-3/previous-versions

Regards, 

Bianca

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Hello,

we have been downloading, installing and doing a brief test of "digilent.waveforms_beta_v3.13.8_64bit.exe".

Now the jitter issue disappeared,  DD is working as expected and we can start using it for our application.

We also tested 3.10.9 and here also no jitter issue occured.

We will go with beta_V3.13.8.

Thank you for your help

Best regards

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