Products > Test Equipment
Pocket-Sized 6 GHz 1 TS/s ET Scope
joeqsmith:
Showing the bigger problem, which you can't address with software. If we want to increase the resolution as shown for example, the signal can very well drift enough during a single sweep to throw off the measurement. In this case a sweep is more than 10 minutes. Imagine the errors at 128pts/div. Having a way to collect the data faster with slower trigger rates and without the need for a pre-trigger is really what I would want. It's obvious and I doubt causes users to publish bad data.
joeqsmith:
Users have to try and balance the drift and resolution to get accurate data. Here shown with 128pts/div. 20ish minutes for the sweep. We know that time has drifted a lot during the measurement and appears to have added a few ps of error. Still, we are below that typical number and we are certainly pushing your scope's limits.
joeqsmith:
--- Quote from: SJL-Instruments on June 09, 2024, 04:24:24 pm ---
--- Quote from: joeqsmith on June 09, 2024, 04:14:10 pm ---It may be nice to be able to adjust (drag) the reference independent from the other channels. For example, if I collect data from channel 2, then change the setup to collect on channel 3 as shown. I want to manually align the two edges.
--- End quote ---
On a reference waveform, you can open the channel settings and enter a timebase shift to adjust the horizontal position.
On a "physical" channel, this setting only relabels the timebase (due to hardware limitations). The behavior for a reference waveform differs in order to allow exactly the application you're describing.
--- End quote ---
While it certainly allows me to adjust it. I have to select the advanced tab and type in a number. Personally I would like the option to be able to select and drag the reference waveform with the mouse rather than having to resort to typing on the keyboard.
SJL-Instruments:
--- Quote from: joeqsmith on June 09, 2024, 05:04:32 pm ---Users have to try and balance the drift and resolution to get accurate data. Here shown with 128pts/div. 20ish minutes for the sweep. We know that time has drifted a lot during the measurement and appears to have added a few ps of error. Still, we are below that typical number and we are certainly pushing your scope's limits.
--- End quote ---
With a 70 ktrig/s source, we were able to get sweep times of less than 30 seconds @ 128 pts/div by setting all the CDF settings (Nmin, Nmax, K) to 20.
Of course, this only gives good results in vector trace mode. The settings will need to be increased to accurately resolve the rare parts of the distribution. But consider that a traditional ADC-based sampling scope would also need to run for a minute or so to get a good sense of the tails of the distribution.
That said, the speed-quality tradeoff is inherent to the architecture. As long as the user is aware of it, they can choose settings appropriately for the application.
In the long-term, we agree that getting rid of the pre-trigger is ideal, and is something we are currently working on.
--- Quote from: joeqsmith on June 09, 2024, 05:13:30 pm ---While it certainly allows me to adjust it. I have to select the advanced tab and type in a number. Personally I would like the option to be able to select and drag the reference waveform with the mouse rather than having to resort to typing on the keyboard.
--- End quote ---
Got it. We can assign middle click + drag to this functionality. Currently, dragging horizontally with either the left or the middle mouse button do the same thing.
Figuring out if the user is trying to interact with a specific waveform based on mouse position is error-prone (especially in point mode).
joeqsmith:
--- Quote from: SJL-Instruments on June 09, 2024, 05:31:35 pm ---Got it. We can assign middle click + drag to this functionality. Currently, dragging horizontally with either the left or the middle mouse button do the same thing.
Figuring out if the user is trying to interact with a specific waveform based on mouse position is error-prone (especially in point mode).
--- End quote ---
I was thinking the user would click on far right area to select the waveform they want to work with. Maybe change the box thickness or some other way to graphically denote it is the selected waveform. Then just drag away.
Indeed playing with CDF settings will improve sweep rates, but at a cost. Shown with 202020.
There does appear to be some strange interaction with the CDF settings and trigger that I could never explain. I can reproduce it on this end and it has worked this way for some time. I'll try and walk you through what I see using the Tektronixs pulser.
Power up unit using defaults. Set the trigger level to 500mV. Set the position to center the waveform (86ish ps). Set the Base to 20ps/div. Set resolution to 128 pts/div. Set the holdoff to 150ns. Sweeping should be very slow (>10 minutes). Next select the CDF sampling options and use your 202020 settings and apply. Change the resolution to 4 pts/div, sweep is maybe 2 seconds.
Now the fun part, change the CDF sampling options back to auto and apply. Now, select a resolution of 128 pts/div. This should get us back to the initial state but the sweep rates will be much faster. Here is the trick. Set the trigger level to 100mV. Now change it back to 500mV. If all is right, I am expecting it to again sweep very slowly as it did in the start. Now why this trigger level being set to something else and then returned to the initial value has any effect on the sweep time, you would need to chime in. I'm sure it's a user problem and some misunderstanding I have. Guessing the settings are not critical as I have ran into this before. The order does not seem to matter. Nor does changing the holdoff. It seems tied to having to change the trigger level. Like the act of doing that is somehow causing some state of the software to change.
If this is too confusing to follow (I take no offense to that :-DD), I can make a small video for you demonstrating what I am seeing.
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It appears that when selecting the "Automatically determine from holdoff" the software does not immediately calculate the new values. Rather is seems to require some event such as changing the trigger level or the holdoff time. Maybe this is by design but personally, I would rather it calculate the new values based on the current settings instead of having to change values to get it update.
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Also, if I load settings that do not have the CDF settings set to auto, they will take effect immediately. If I then load settings that use auto for the CDF, the software does not appear to update to the correct values. Lots of clues.
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