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Siglent SDS2000 new V2 Firmware

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Performa01:

--- Quote from: Mark_O on January 05, 2016, 12:35:15 pm ---It was 6 ns, and I didn't feel it was ridiculous to try to compensate for that.  But it's OK if you did.

--- End quote ---

Sorry, my response on this was sloppy and 6ns would indeed justify the use of the deskew option in certain situations.
The true reason why I didn’t mention it in my review was because I thought it’s just too obvious and goes without saying that one could use the deskew to align the channels, and the fact that the sample uncertainty adds some jitter that makes it pointless to try to compensate for better than +/- 2ns.



--- Quote ---OK.  You are correct, that I did need to look closer.  Thanks.

--- End quote ---

What I forgot to mention was that if you look close, you can see that the digital edge is at a time where the analogue channel has not even started slewing, so apart from the fact that the transition times aren’t as bad as 18ns, the traces on the screen clearly indicate that they cannot play a role for the amount of lag observed.



--- Quote ---That sounds a bit ironic.  Analog channels having digital triggers.  And digital channels having analog triggers.  :)

--- End quote ---

Well, that’s what I thought too when I wrote this :)
But then again, nothing wrong with an analogue trigger when we expect fairly fast transitions. Every single logic gate has an analogue (sometimes Schmitt) trigger built in after all :)

rf-loop:

--- Quote from: Performa01 on January 05, 2016, 02:41:08 pm ---Sequence Mode Speed reviewed

When looking at the table published by rf-loop, the maximum waveform update rate for 5ns/div timebase (140 points/segment) ahould be 440k, whereas I’ve never seen more than 290k in my tests, so I thought I’d take a closer look at that discrepancy.

First I  want to share some general thoughts about sequence mode. It should be obvious that this mode is meant for situations where we have periodic events with considerable idle states (that are of no interest) between them. Segmented memory (or Sequence Mode, as it is called here) is the ideal tool if we want to capture as many events as possible without wasting precious memory by recording the idle phases as well.
----
On the other hand, a 50MHz sine isn’t a realistic test scenario, as no one would use segmented memory for a signal like this. 10MHz should be fast enough and it really shouldn’t make any noticeable difference as long as we’re talking about waveform update rates well below 1000k.

--- End quote ---

Yes, this is also what I think but for finding maximum speed I have used this signal. (also searched wide span of frequencies and there is big freq band where I can get same result, not only 50MHz what is some kind of middleway compromise)

Why it is also important that segmented memory acquisition is fast. As you tell mostly this function is used for - just as you tell.  But still it is important it can capture fast agen if there happend some spike or extra pulse, high glitch etc. This is why also Hewlett-Packard (so sorry it is today Keyshit after Fiona catastrophe when it was destroyed to Agilent)  argument for segmented memory speed (trigger recovery time).

In different aplications user need find optimal settings for just this individual case and for this, there ismportant thing: "Know your equipment".

----

This whole case need bit more inspections because in FW there is something wrong and/or not optimal.
Example why heck Sinc is mixed there in sequence mode for timebases 1ns/div to 20ns/div. Segmented memory cquistion do not need anything but push as fast as possible raw ADC data to memory and nothing - nothing else. When scope is stopped for analyzing captured segments there user can use Sinc and/or vectors or what ever he want. (and tools for inspect these segments need develop better. There is not even  possible stack segments over segments in playback (or select buffer how many is stacked (overlayed) for better finding anomalies, no persistence available, etc. But first acquisition need work without any problems and - please Siglent - do something for this multifunction knob useability/ergonomy)

There is also some other mystery with wfm/s speed (time ago I have also informed Siglent about some problem with scope wfm speed in some "semirandom" cases). Some times it go only bit over 70kwfm/s and then suddenly after some playing with knobs/buttons and then it reach full 140kwfm/s.  I have not find "logick" how this happend. And do this have also something to do with second channel group (CH3 and CH4) speed. Next I will check what maximum I can find with CH4 (or 3). Limiting factor is some lack of time for this...


Add:

---------

--- Quote ---Finally I tried the fastest setting, according to rf-loop’s table, i.e. 50ns/div. It was indeed a little faster, about 315800 waveforms per second, but nowhere near the claim of 500k.
--- End quote ---

I can confirm this. (Measured)  If CH3 or CH4 alone on, just this.
If both, CH3 and 4 are open, just around 10kwfm/s more.

But after then I find also more interesting things related to CH on off combination and also together with t/div settings that this need check better. Question is how much is wise to do investigations if next FW agen change things (and hope remove difference between channel groups)

Also there is intersting finding for rare glitch hunting if think average wfm/s speed.

But here two of these intersting findings (but only for 1GSa/s speed)

1. I find in Sequence mode setting what give max  segment speed around  545ksegment/s
(measured with second scope and calculated also from history timestamps.

2. Case where CH1 and CH2 are both on and Sinc off and display dots etc.   timebase 10ns/div and Sequence mode.   Sequence repeating interval is more short what I have find before.

Add agen:

There is one open question.
Example. Sequence mode. If example in one sequence is 80000 segments. After these are acquired then acquisition of course stop and scope start do many things including display update for show waveform before it start new sequence. Question is, how many segments it display overlayed on the display before it start new sequence. It is least some hundreds in this case but how much really?  I do not believe it stack all segments. If I change amount of segments from 1 to hundreds it clearly give more and more intensity grading when I rise number of segments.

I found it intersting because with some settings and Sequence mode in use it can capture  over  300ksegment/s continuously (10s average). Checked using second scope for analyzing trig out signal and also using simple trig out signal pulse counting. For this I use HP53131 counter in pulse count mode with 10s gate time. Second oscilloscope triggercounter and HP give same result, over 300kwfm/s. In this case inside one sequence segment speed is 545ksegment/s.  This amazing speed is reached using CH1 + CH2 on, 10ns/div (segment lenght is 140pts and sampling rate 1GSa/s) , 50MHz signal in and Sinc off, display dots.  Of course display update speed is not high but intersting is how many segments are stacked for display in every turn.

Performa01:
@rf-loop

Regarding the number of segments used for a single display update I’ve tried a little experiment.

Display dots, peak detect, 70Mpts, fast acquisition, x interpolation.
Sequence mode, 5ns/div == 140 points.

Used my darling channel 4 again (even though it's slow), sorry ;)

I fed the scope with a 50MHz sinewave, 100% amplitude modulated with a 10kHz sawtooth and tried to count the individual traces on the screen, but it were still too many  (Sequence_RT_50MHz_Mod_10kHz)




In a 2nd attempt I increased modulation frequency to 40kHz (Sequence_RT_50MHz_Mod_40kHz)




We can clearly see 7 individual traces, with nice and evenly spaced amplitudes due to the ramp modulation.

Without sequence mode, we get a little more under otherwise same conditions (Standard_50MHz_Mod_40kHz)




The full range of amplitudes is run through 40000 times per second and we can see 7 traces. And despite dots display, all 7 traces don’t show any gaps.
At 10kHz modulation frequency we can assume it would be four times as much traces, hence 28 – and we still don’t see any noticeable gaps.

So this won’t get us very far. But what if we just reduce the modulation frequency to the point were we don’t get a nicely filled sinewave anymore, but observe some discontinuity instead?

Down to 300Hz everything looked just fine. At 200Hz the picture suddenly changed (Sequence_RT_50MHz_Mod_200Hz)




First we need to remember that we need about 300ms to fill the memory with 80000 segments (for Ch. 4 that is). So even a low modulation frequency of just 300Hz yields about 100 full modulation periods in memory. And this is about the lowest frequency that gives a correct modulation display without vertical gaps.
In normal mode, we don’t get any gaps even with just 100Hz of modulation frequency.

So while this doesn’t answer your question as how many waveforms make it to the screen, it is certainly a proof that not all waveforms are displayed, hence sequence mode cannot serve as a secret trick to have a very high waveform update rate that would not miss anything despite the slow screen update of just about 3 per second…

Mark_O:

--- Quote from: rf-loop on January 05, 2016, 03:15:43 pm ---...with some settings and Sequence mode in use it can capture  over  300ksegment/s continuously (10s average).

...In this case inside one sequence segment speed is 545ksegment/s.  This amazing speed is reached using CH1 + CH2 on, 10ns/div (segment lenght is 140pts and sampling rate 1GSa/s) , 50MHz signal in and Sinc off, display dots.

--- End quote ---

So let me check that I'm following correctly.  At 545k segs/s, that means 1.83 us/segment.  Since each triggered acquisition runs for 140 ns, it doesn't trip again for 1.69 us afterwards.  That's the inter-segment dead-time, where the trigger hasn't been rearmed yet.  Even though your 50 MHz signal is providing another trigger event every 20 ns.

Then at the end of the segment burst, there is a second time gap, where it sets up to grab the next burst (clear and reset).  With 330k segs/sec, that means the  average time between segments has increased to 3.03 us, from the 1.83 us, or a 1.2 us delta/seg.  Since each burst here is 80k segments, that means the inter-burst gap is 9.6 ms.


Of course, as Performa01 said, we don't use Sequence Mode to look at rapidly repeating, continuous signals like this in real life.  However, tests such as these are useful in determining the capabilities of the test instrument.  The most interesting from my perspective being the dead-time that occurs between segments, while the unit re-arms to catch the next trigger.  Which has been demonstrated here to be ~1.7 us.  Which isn't bad performance at all. 

If the events you're trying to capture are always spaced further apart than that, even if they only occur maybe once per millisecond, or even once per second, then ALL of them will be captured if no two are closer together than 1.7 us.  That's good to know.  Plus a big win for Sequence Mode.  And conversely, if not, then they all won't, and some will be missed.

rf-loop:
Perhaps this explain better what is going on.

(it need of course also note that dead time inside sequence burst phase between segments is much higher what is example with 50ns/div where segment lenght is 700ns or 1400ns depending samplerate. If look maximum 500ksegm/s speed previously measured using CH1 and 50ns/div. There is (quite exactly) 2000ns interval in burst phase. There segment time is 700ns and between segments dead time 1300ns.)

But here this case where long time average go over 300ksegment/s speed and speed during Sequence mode segment acquisition burst over 540ksegment/s. (here 80000 segments, CH1+CH2 open, 10ns/div)

Images tell more.



Snap shot during Sequence acquisition, running continuously over and over (not one shot at this time).
Just at snap shot random time there was going segment number 48659 and display waveform is from previous Sequence. (Settings: Sinc OFF, Display Dots, Trig normal, rising edge, Holdoff closed)






Here second scope (SDS1202X) CH1 is connected to scope under test (SDS2304) Trigger Out signal.
There can see Sequence segment acquisition burst and then scope busy time when it processes all nessessary things before it start next period (visible in top window right side).  SDS1202X trigger event based counter show around 310kHz frequency. (I do not know how this counter exactly work but freq display is jumping around between 300 and 325kHz  but mostly near 310kHz.   Because this, I also check it using HP 53131 for counting pulses over 10s gate time (not as frequency calculating mode but just as simple pulse counter, what is better mode for this case. Result certify this result in image if we tell average speed is ~310ksegment/s.

Whole period time here is 258ms.   80000 segments acquisition burst time is  141.5ms and oscilloscope busy time is 111.5ms.  This busy time is valid only for this instance.







And here scope stopped for looking captured seqments. Segment number 1. Also to image cloned segment number 80000 timestamp.




Still even with long busy time between Sequence periods it give over 300ksegment/s average speed  and here inside segment acquisition phase (80000 segment burst) speed is ~545ksegment/s.

I believe here is reached some of this SDS2000 series some upper possible limit values.
(with current FW)




--- Quote ---Segmented Memory Acquisition for
InfiniiVision Series Oscilloscopes

Number of segments
1 to 2000 (5000, 6000, and 7000 Series)
1 to 1000 (3000 and 4000 X-Series)
1 to 250 (2000 X-Series)

Re-arm time
(minimum time between trigger events)
5000, 6000, 7000: 6 ?s
3000 and 4000 X-Series: 1 ?s
2000 X-Series: 20 ?s

Data sheet: Agilent 5989-7833EN
--- End quote ---




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