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Pocket-Sized 6 GHz 1 TS/s ET Scope

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joeqsmith:

--- Quote from: SJL-Instruments on January 18, 2024, 12:59:49 am ---Can you specify exactly which delays you are trying to take data at, and the delay/number of commands at which you start seeing an error (for e.g. a trigger holdoff of 50 ns and at 500 ns)? This will help us when trying to reproduce your error.

--- End quote ---

See attached image.  Post trigger delay set to 110000, trigger holdoff set to 50, stepping by 500ps for 1ns or 20 steps.  Third response was a timeout.  Increasing the trigger holdoff will allow it to run without the timeout.  The smaller I step the post trigger delay,  the more I must increase the trigger holdoff for it not to timeout.  Stepping by 5ps for example requires a trigger holdoff of around 2500.   I suspect there is more to the holdoff than the simple explanation in the manual. 



--- Quote from: SJL-Instruments on January 18, 2024, 12:59:49 am ---To clarify what you mean by "behaves the same:" are you referring to the need to start our software first, or that you are seeing errors past some number of samples? If the former, then the extra parameters to the R command should have resolved the issue. If the latter, then the level settings are likely not related to the root cause.

--- End quote ---
Behaves the same meaning it will send the NO TRIG ZERO SJLI or NO TRIG TIMEOUT nn SJLI in response to the R command.  Startup is now fine. 

SJL-Instruments:
The screenshot shows a "current trigger delay" of 2210000. Does this mean you are sending the command D2210000? This corresponds to a delay of 221 nanoseconds and would explain the error message.

joeqsmith:
 :-DD :-DD :-DD    :palm: :palm: :palm: |O |O |O

Good catch!!  It is now working as expected.  2ns of recording a 2GHz signal with 10ps resolution.  Calibration is ran every half second with linear interpolation. 

I would like to know more about how you perform the fit. 

--- Quote ---When you perform your Gaussian fit, you truncated the CDF within 10-90%) then  mirror the CDF, then fit to that shape?  I assume you are not fitting to the CDF's S shape directly.
--- End quote ---

I could toss something in there easy enough. 

Good to see the basics now working.  Thanks!!

SJL-Instruments:

--- Quote from: joeqsmith on January 18, 2024, 01:42:36 am ---Good catch!!  It is now working as expected.  2ns of recording a 2GHz signal with 10ps resolution.  Calibration is ran every half second with linear interpolation. 

--- End quote ---
We've been there before too  ;). Glad your custom software is working now!


--- Quote from: joeqsmith on January 18, 2024, 01:42:36 am ---I would like to know more about how you perform the fit. 

--- Quote ---When you perform your Gaussian fit, you truncated the CDF within 10-90%) then  mirror the CDF, then fit to that shape?  I assume you are not fitting to the CDF's S shape directly.
--- End quote ---

--- End quote ---
You can fit to the CDF's S shape directly after truncating all points between 0.1 and 0.9. This works fine but is processor-intensive. You may also want to experiment with reducing the truncation bounds (e.g. to 0.2-0.8 ). Narrower bounds will use fewer samples and thus increase noise, but will also improve robustness to outliers.

In the official software we use a more efficient method that turns out to be equivalent to first-order (in a precise statistical sense) - more details are in our response #97:

--- Quote ---We don't mirror the CDF, but instead apply the inverse CDF to the data, such that a perfect Gaussian error CDF would become a straight line. When you do this, the points on the edges will have their noise significantly amplified, and you need to weight them by 1 over the squared derivative of the inverse CDF to avoid blowing up the fit. The points are truncated to the 10-90% CDF region, as well as dropping any points that are more than 2 standard deviations from the central value determined via the interpolation method.
--- End quote ---

joeqsmith:
Checked your specified rise time.  35 and change, pretty impressive.  Plan is to run this through that coax filter and see if you can de-embed it. 

https://www.eevblog.com/forum/testgear/show-us-your-square-wave/msg5284957/#msg5284957

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