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Pocket-Sized 6 GHz 1 TS/s ET Scope

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SJL-Instruments:

--- Quote from: joeqsmith on January 24, 2024, 02:01:53 am ---One possible clue is that when I mentioned that the glitches are commonly negative, it seems to depend on the level of the signal when it first starts acquiring data. 

--- End quote ---

--- Quote from: joeqsmith on January 24, 2024, 03:44:41 am ---To be clear again, my software makes no attempt to correct these glitches.  Your software may behave differently  What I can show you with my software is the min/max capturing six different events and they all occur prior to 12ns.   If I allow it to run long enough, I will see glitches in other areas but the majority happen towards the start of the sweep.

--- End quote ---
Thanks for this information - it's useful as we try to trace the issue. We can reproduce this behavior when directly querying the serial interface.

Just to confirm, you're using v2.5.5 downloaded from the website, correct?
So far, we can reproduce the glitches between 11-12 ns with the last pre-release version (v2.5.5_preview2) we sent you, but not with the latest (website) version. We increased the strictness of the check prior to the public release.

joeqsmith:

--- Quote from: SJL-Instruments on January 24, 2024, 02:00:42 am ---
--- Quote from: joeqsmith on January 24, 2024, 01:53:37 am ---A more pressing problem is that the new software does not always seem to catch the glitches.    They still appear to happen towards the start of the sweep as before. 

--- End quote ---
Thanks for catching this - we'll see if we can reproduce this with extended testing. We've increased the urgency of the debugging/firmware fix. Do you ever see any glitches from the software after 12 ns?

***
And just to double-check - you are using v2.5.5 downloaded from the website, not any of the v2.5.5 pre-release versions we sent, correct?

--- End quote ---

You should always have some way distinguish your versions of software that you let out.  If you make any changes, I would roll it to make it easier to track.  I wasn't even aware you had made further changes so I just downloaded the latest. 

It behaves a lot different than the previous two versions of 2.5.5.   It has never been this unstable towards the start of the sweep.   

SJL-Instruments:

--- Quote from: joeqsmith on January 24, 2024, 04:00:48 am ---You should always have some way distinguish your versions of software that you let out.  If you make any changes, I would roll it to make it easier to track.  I wasn't even aware you had made further changes so I just downloaded the latest.

--- End quote ---
Noted - in the future, we'll add a visible marker to any pre-release versions we send.


--- Quote from: joeqsmith on January 24, 2024, 04:00:48 am ---It behaves a lot different than the previous two versions of 2.5.5.   It has never been this unstable towards the start of the sweep.

--- End quote ---
Thanks for the information. What kind of signal are you putting into CH1? We'll see if we can reproduce this behavior.

joeqsmith:

--- Quote ---We increased the strictness of the check prior to the public release.
--- End quote ---
Testing the pre-release software in private was a good idea, IMO.  I just assumed when you released it, you had made no additional changes or you would have ran those by me first. 


--- Quote from: SJL-Instruments on January 24, 2024, 04:07:38 am ---Thanks for the information. What kind of signal are you putting into CH1? We'll see if we can reproduce this behavior.

--- End quote ---

Interesting you ask as it means that you suspect the glitches are shape dependent.  This doesn't give me a lot of comfort as I am always going to be questioning if what I am seeing is real or not.  With that in mind, I do believe that the settings at least have something to do with it.  Assuming that the software I downloaded last night is still the most recent 2.5.5, here are two images.  I used the LiteVNA64 as the source (its normally sitting on the desk and makes a convenient source).  It was set to 150MHz CW.  Using the supplied cable attached directly to channel 1 of the GigaWave. 

Notice if I set the Base to 1ns/div with 32pts/division, we see how unstable the start of the sweep is (below 12ns).  If I change the Base to 2ns/div and 64pts/division (to achieve the same resolution), the displayed waveform is stable below 12ns.  Again, without a min/max or some means to detect these glitches, I can't tell you if it never glitches.   

You used the phrase "... small fraction of returned CDFs may have an error".  I suspect our views on what a small fraction means, differ.  Say for example I want to look at a noise free signal and there is nothing in the environment that can cause an discontinuity in the measurement.  Everything is perfect but, we don't know that.  Now the scope shows the signal has a glitch.   Maybe it's once an hour.  Maybe once a day.   I'm sure many of us have hunted problems like these.   This glitch problem IMO, is the biggest issue you have going.  I'm sure it can be solved but I don't think spending time trying to filter it is a good solution, or use of your time. 

SJL-Instruments:

--- Quote from: joeqsmith on January 24, 2024, 01:07:20 pm ---Interesting you ask as it means that you suspect the glitches are shape dependent.  This doesn't give me a lot of comfort as I am always going to be questioning if what I am seeing is real or not.

You used the phrase "... small fraction of returned CDFs may have an error".  I suspect our views on what a small fraction means, differ.  Say for example I want to look at a noise free signal and there is nothing in the environment that can cause an discontinuity in the measurement.  Everything is perfect but, we don't know that.  Now the scope shows the signal has a glitch.   Maybe it's once an hour.  Maybe once a day.   I'm sure many of us have hunted problems like these.   This glitch problem IMO, is the biggest issue you have going.  I'm sure it can be solved but I don't think spending time trying to filter it is a good solution, or use of your time. 

--- End quote ---
Yes, we're on the same page about this. We've put everything else on pause to fix the problem.

We've traced down the problem to a CDC bug in the FPGA. Patching this and running overnight, we took 10 million samples with no errors (no software filtering). This seems promising so far. We'd like to add CRC checks and test to a higher confidence level before declaring the problem "solved," but we'll be in contact shortly about the firmware upgrade procedure.

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