Author Topic: Siglent SDG1020 square signal "dirty"  (Read 14705 times)

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Offline Xyphro

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Siglent SDG1020 square signal "dirty"
« on: April 14, 2013, 02:34:35 pm »
Hi!

Did anybody ever have a close look at the Siglent SDG1020 square wave output at low frequencies?

Settings: 1 Hz, Square, 50% duty. Zoom in to the rising or falling edges. Output 1 (right BNC connector).

Looks like a bug in the DDS section (see attached picture).

Output 2 is free of this problem.
Other waveforms look fine at Output 1...

It could be a feature which is useful at sine wave output, but useless and nasty for square wave output: Dithering of the phase accumulator for low frequencies?!?

Best regards,

Kai


« Last Edit: April 14, 2013, 02:36:08 pm by Xyphro »
 

Offline rf-loop

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Re: Siglent SDG1020 square signal "dirty"
« Reply #1 on: April 14, 2013, 03:05:49 pm »
It have discussed also earlier.

Your image do not look like 50% duty.
Out from 50% this situation is more bad than 50%.

It is not DDS problem and/or FW problem at all.

Square wave is special case.  It is derived from internal sinewave using PECL comparators. (and this principle is not only Siglent special)
 This make square wave function different as all other functions.

On some HW's PECL comparator hysteresis setting is not optimum and in some cases hysteresis setting resistor value  change may give some amount better result.

Of course there may be some other problem in some individual unit if this signal pathway to comparator is noisy (example some component failure what is related to this signal noise)
Now if use low frequency and specially other than 50% duty this small noise may lead to wrong comparator "switch" specially if comparator hysteresis window is too narrow.

It is explained littlebit more here.

And here.
If need better signal quality specially for low frequencies  it is better to use pulse than square.
« Last Edit: April 14, 2013, 03:42:09 pm by rf-loop »
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Offline Xyphro

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Re: Siglent SDG1020 square signal "dirty"
« Reply #2 on: April 14, 2013, 03:15:00 pm »
tak, rf-loop!

I just also noticed, that the pulse mode is clean and was wondering why.

Offline bmwnomad

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Re: Siglent SDG1020 square signal "dirty"
« Reply #3 on: April 14, 2013, 03:54:10 pm »
Is this the same thing you guys are talking about? 

I have an SDG1025 and was going to send it back under warranty for a replacement, but if they are all like that then maybe I'll have to live with it.

Attached are scope snapshots.  Yellow are channel 1, 1khz square wave and blue is channel 2, 1khz square wave.  I set it on infinite persistance for a few seconds to show the glitches.

Channel 2 is fine, as is channel 1 pulsed output(not shown), it's just channel 1 square wave that looks like crap.

Steve
« Last Edit: April 14, 2013, 04:02:17 pm by bmwnomad »
 

Offline rf-loop

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Re: Siglent SDG1020 square signal "dirty"
« Reply #4 on: April 14, 2013, 04:18:20 pm »
This difference between channels is now strange.
If practice and theory is not equal it tells that used application of theory is wrong or the theory itself is wrong.
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Offline Xyphro

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Re: Siglent SDG1020 square signal "dirty"
« Reply #5 on: April 14, 2013, 05:16:07 pm »

Yes, it is the same issue.

Output 2 is also fine with my generator, while Output1 shows this behaviour.

Offline bmwnomad

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Re: Siglent SDG1020 square signal "dirty"
« Reply #6 on: April 14, 2013, 05:17:18 pm »
Thanks, no use in returning it then if I'll just get another one with the same issue.

Steve
 

Offline Bored@Work

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Re: Siglent SDG1020 square signal "dirty"
« Reply #7 on: April 14, 2013, 05:40:44 pm »
Thanks, no use in returning it then if I'll just get another one with the same issue.

Steve

But returning it could be useful when you want to get your money back. And next time the resident Siglent sockpupets tell you how great Siglent/Atten quality is, you know the truth.
I delete PMs unread. If you have something to say, say it in public.
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Offline Wuerstchenhund

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Re: Siglent SDG1020 square signal "dirty"
« Reply #8 on: April 14, 2013, 07:11:19 pm »
But returning it could be useful when you want to get your money back. And next time the resident Siglent sockpupets tell you how great Siglent/Atten quality is, you know the truth.

The problem is that the alternatives in this price range are hardly better. And to be honest, the general hardware quality of the Siglent SDG1000 Series is not *that* bad, and if they would sort out the jitter issue then this could be a decent low-cost AWG for hobby use.

Of course Siglent should be deeply ashamed to release a product with such a design flaw on the market, and they should fix the issue for the owners of these generators (which won't happen).
 

Offline rf-loop

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Re: Siglent SDG1020 square signal "dirty"
« Reply #9 on: April 16, 2013, 06:58:30 pm »
I have tested SDG1020  + some SDG1010
All are same HW version (I forget all data to workshop) and same latest FW version .27

SDG1010 have no any kind of sign about this issue. Also glitch level in square wave is less than before. These works just ok.

SDG1020 is totally as from different world in quick test. But all tests are not ready yet.

CH1 square wave (not other func) very bad timing jitter and very bad glitches as someone show here before. This is problem specially in low frequencies. Higher frequencies better. (naturally due to circuit principle)

And more:

CH2 have much better square wave. (not as good as SDG1010 and not as good as SDG1025 what I have tested before. Difference is not big.

But then CH2 have other issue in unit what I have tested..

Square, ramp, sine etc. All fails but looks like only if use 50ohm and highes voltage band. Specially it can most easy look with square or pulse. After signal rise it looks like go flat but just after corner it sart "oscillate".

Oh well, if you look it with slow oscilloscope it looks just ok or like only "noise level in signal top is more than bottom. Take fast oscilloscope and ... oops.
Signal top (not bottom) have high level some kind of oscillation with high frequencies. Something like over 200MHz!

This is first time I have tested SDG1020. (becouse Teledyne do not have this version), they have 1010, 1025 and 1050 only.  (2012, 2022, 2052)

What is this problem, I do not know anything more now.
(I do not sell this 1020 model at all before whole this issue is solved)

Please, who have this issue in SDG1020 model:
HW version, FW version and whole serial number exept last 3 digits  as xxx.
(I think posibility that this issue is in some manufacturing lot.)

« Last Edit: April 29, 2013, 04:57:36 am by rf-loop »
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Offline rf-loop

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Re: Siglent SDG1020 square signal "dirty"
« Reply #10 on: April 17, 2013, 05:38:58 pm »
Here SDG1020 some tests using Square wave.
Serial SDG00001130xxx
HW:02-00-00-21-24
FW: 1.01.01.27

Also compared to SDG1010 (not only one unit)
same serial (exept xxx)
same HW
same FW

also I have earlier tested other SDG1010 and SDG1025  and not at all this problem what I can see in tested SDG1020. SDG1020 tests looks just as someone others have also find.

Connection to scope 50ohm coaxials and 50ohm terminators
SDG1020 CH1 glitches in images.
If use more low frequency there  can see  also full random width level pulses near rising edge (not picture here)

There is also problem in CH2 if use 50ohm load adn if use over 1Vpp. High frequency oscillating in signal upper levels. This oscillation can see also in other waveforms. (280MHz! oscillation with this setting)

pictures filename also explain settings.

« Last Edit: April 17, 2013, 06:12:40 pm by rf-loop »
If practice and theory is not equal it tells that used application of theory is wrong or the theory itself is wrong.
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Offline commongrounder

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Re: Siglent SDG1020 square signal "dirty"
« Reply #11 on: April 17, 2013, 06:42:54 pm »
I checked this issue on my SDG1005 (FW..27), just to add another model number to the list.  I set up my generator and scope as rf-loop did, and I have the same problem with glitches on low frequency square waves on channel 1 only. It only begins to clear up above about 10khz on my unit.  Channel 2 is very stable with only a little noise at the bottom of the waveform (no HF oscillations).  I set up my scope for infinite persistence and triggered off of channel 2 to show the severe timing jitter between the channels, over 70us peak.  About 30 second capture time.  Would not want to use dual channel square wave mode for any phase related work!  Pulse is definitely better.   Oh well.  Better to find this stuff out and understand the limitations now, rather than banging your head against the wall trying to figure out a crazy output from a DUT.
 

Offline rf-loop

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Re: Siglent SDG1020 square signal "dirty"
« Reply #12 on: April 17, 2013, 07:23:12 pm »
I checked this issue on my SDG1005 (FW..27), just to add another model number to the list.  I set up my generator and scope as rf-loop did, and I have the same problem with glitches on low frequency square waves on channel 1 only. It only begins to clear up above about 10khz on my unit.  Channel 2 is very stable with only a little noise at the bottom of the waveform (no HF oscillations).  I set up my scope for infinite persistence and triggered off of channel 2 to show the severe timing jitter between the channels, over 70us peak.  About 30 second capture time.  Would not want to use dual channel square wave mode for any phase related work!  Pulse is definitely better.   Oh well.  Better to find this stuff out and understand the limitations now, rather than banging your head against the wall trying to figure out a crazy output from a DUT.


Timing jitter is different case. (there you see now channel - channel total. (both channels have just individual random jitter. Also it is good to know that most of manufacturer  tell rms jitter. And it is just different case becouse jitter is gaussian random distribution)

Check channels so that look generator CH1 alone. Then look CH2 alone.
Timing jitter is specified: 0.1% of period(typical,1kHz,1Vpp)
And there is not specified lower freq jitter.

50Hz period is 20ms. Jitter (typical) 20us. Jitter from "0" line (ideal time)  to positive direction 20us and to negative direction 20us.
It can measure so that trig rising edge. Go to next rising edge and look timing jitter.
(also this is NOT channel to channel jitter)

These glitches is best to look so that trig rising edge and keep peristence on, in this case timing jitter do not overwrite on oscilloscope screen these glitches.

If need less jitter specially with low frequencies it is better to use "Pulse" function and not "Square".  Pulse have 8ns p-p jitter  independent of pulse freq.
It is not so user friendly becouse if set duty, it do not keep %. All time need adjust duty agen if change freq.

 
(SDG5000 serie is totally different animal. )

SDG1000 series Square principle:


« Last Edit: April 17, 2013, 07:36:07 pm by rf-loop »
If practice and theory is not equal it tells that used application of theory is wrong or the theory itself is wrong.
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Offline commongrounder

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Re: Siglent SDG1020 square signal "dirty"
« Reply #13 on: April 17, 2013, 08:19:57 pm »
Yes, indeed I got off on a tangent about jitter, which, while different than the glitches showing up from the sine to square conversion, do combine to aggravate the problem.  My unit does have about +/- 25us peak (worst case) jitter at 50hz (1vp-p into 50ohm scope termination), observing the next rising edge after the triggered edge.  I did my best to set the trigger point above the top of the glitches to avoid having that influence the observed jitter.  It is clearly visible even when observing several wave repetitions on the screen (on my Rigol DS4012, anyway).  CH 2 has +/- 10us under the same conditions, and none of the glitching.

Thank you for your thoughts on this, rf-loop.
 

Offline nixxon

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Re: Siglent SDG1020 square signal "dirty"
« Reply #14 on: April 17, 2013, 09:55:53 pm »
Here is a screenshot of my DSG1020 @ 1 kHz square wave 50% 4 Vpp (high Z) straight coax (50 ohm) after almost 90 minutes persistent display logging on my rigol DS1102. Nothing special or close to the horror images in previous post(s).

Analog Ch  State   Scale    Position   Coupling  BW Limit  Invert
CH1        On      100mV/    2.00V     DC        Off       Off

Analog Ch  Impedance   Probe
CH1        1M Ohm      1X

Time    Time Ref    Main Scale    Delay
Main    Center      5.000us/      -25.00000us

Trigger  Source      Slope    Mode      Coupling     Level    Holdoff
Edge     CH1         Rising   Auto      DC           -1.40V   500ns

Acquisition    Sampling    Memory Depth    Sample Rate
Normal         Realtime    Normal          50.00MSa   
 

Offline nixxon

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Re: Siglent SDG1020 square signal "dirty"
« Reply #15 on: April 17, 2013, 10:02:56 pm »
The difference between 500mV/Div and 200mV/Div on my Rigol DS1102E is strange though. Can anyone explain why I get such different low level trace on the very same signal from my Siglent SDG1020 (as in my previous post)?

500mV/Div
Analog Ch  State   Scale    Position   Coupling  BW Limit  Invert
CH1        On      500mV/    2.00V     DC        Off       Off

Analog Ch  Impedance   Probe
CH1        1M Ohm      1X

Time    Time Ref    Main Scale    Delay
Main    Center      50.00us/      -250.0000us

Trigger  Source      Slope    Mode      Coupling     Level    Holdoff
Edge     CH1         Rising   Auto      DC            264mV   500ns

Acquisition    Sampling    Memory Depth    Sample Rate
Normal         Realtime    Normal          5.000MSa   

200mV/Div
Analog Ch  State   Scale    Position   Coupling  BW Limit  Invert
CH1        On      200mV/    2.00V     DC        Off       Off

Analog Ch  Impedance   Probe
CH1        1M Ohm      1X

Time    Time Ref    Main Scale    Delay
Main    Center      50.00us/      -250.0000us

Trigger  Source      Slope    Mode      Coupling     Level    Holdoff
Edge     CH1         Rising   Auto      DC           -800mV   500ns

Acquisition    Sampling    Memory Depth    Sample Rate
Normal         Realtime    Normal          5.000MSa
« Last Edit: April 19, 2013, 02:08:37 pm by nixxon »
 

Offline nixxon

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Re: Siglent SDG1020 square signal "dirty"
« Reply #16 on: April 17, 2013, 10:19:50 pm »
This is strange. Stepping up in 0.1 Vpp increments from 3.0 --> 4.0 Vpp and 2.00 --> 4.00 Vpp respectively:
 

Offline nixxon

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Re: Siglent SDG1020 square signal "dirty"
« Reply #17 on: April 17, 2013, 10:37:11 pm »
My Rigol was reaching bodily temperatures. That could explain it all  :-BROKE

(actually all the hotspots on the Rigol are the shiny, low emissivity BNC Connectors (+ test signal/Ground rightmost), so I guess the higher temperature is actually reflected from the overhead 5 spot 12V Halogen light bulbs)

Edit: Just as rf-loop suggested, the BNC connectors actually were warmer than the rest of the front panel. There was no significant IR reflection from the Halogen lights above. The panel just around the BNC connectors is slightly warmer than the rest of the front panel, due to thermal radiation and thermal conduction, and maybe even thermal convection (above the BNC connectors).

I have added an IR close up of the BNC connectors.
« Last Edit: April 20, 2013, 08:03:41 am by nixxon »
 

Offline rf-loop

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Re: Siglent SDG1020 square signal "dirty"
« Reply #18 on: April 18, 2013, 04:30:24 am »
Can you tell your SDG1020  HW version, FW version and serial number SDGnnnnnnnnxxx (no need last three digits (xxx)
In your pictures can not see any strange from SDG.
(but test is very limited)

--------

This temperature in Rigol input BNC is normal. Analog front end convert electric to heat ( smile )) and you see then BNC connectors temp rise. This front end circuit is hot inside oscilloscope. Some chips there produce lot of heat (also without any signal), and it is normal.



In picture you have  200mV/div. Signal level is example 4Vpp. It means your signal peak to peak is 20div. Then you add around 10div offset and you think now signal bottom is on the oscilloscope center line - but it is not ideal machine. With some levels it reacxh its limits. (I do not remember numbers)

Are you sure your Rigol analog front end can perfect handle this. No, it can not. It is going to its limits. It is perhaps out from its linear working area.
My opinion is that nothing is wrong in your Rigol. It works as it is designed. You need know your instruments and they limits.

(I have tested Rigol long time ago and I do not remember exatly these numbers but I remember well how it looks in signal. And this looks like just same what I remember (in my head image memory). (your signal top is out of range what it can handle and it affect also to bottom part of signal what is visible on screen)

It can say, here test equipment and device under test is swapped. Wagons drag horse. With SDG1020 you now test Rigol but originally you think you test SDG using Rigol.

In this test you find Rigol front end "features".   

« Last Edit: April 18, 2013, 04:59:00 am by rf-loop »
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Offline nixxon

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Re: Siglent SDG1020 square signal "dirty"
« Reply #19 on: April 18, 2013, 10:44:28 am »
Thank you, rf-loop, for much useful info and for calming me down regarding my equipment.

It seems my SDG1020 is OK at low freq. square Waves (compared to the horrific examples shown above in this thread).

Here is some more info about my unit:

Original configuration:
 Software version: 1.01.01.20
 Hardware version: 01-00-00-17-23
 Serial number: SDG00002120XXX

Previous configuration (after 1.01.01.23 update):
 Software version: 1.01.01.23
 Hardware version: 01-00-00-19-23
 Serial number: SDG00002120XXX

Current configuration (after 1.01.01.27 update):
 Software version: 1.01.01.27
 Hardware version: 01-00-00-21-23
 Serial number: SDG00002120XXX
« Last Edit: April 18, 2013, 11:21:59 am by nixxon »
 

Offline rf-loop

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Re: Siglent SDG1020 square signal "dirty"
« Reply #20 on: April 18, 2013, 12:16:17 pm »
Thank you about this information. Your SDG is older and without more knowldge it can also suspect that problem is in more new HW version.
I find this problem in quite fresh version from factory.

It is very nice if some others who have SDG1020 problem (showed in this thread) give this version information also.
If practice and theory is not equal it tells that used application of theory is wrong or the theory itself is wrong.
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Offline commongrounder

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Re: Siglent SDG1020 square signal "dirty"
« Reply #21 on: April 18, 2013, 01:33:36 pm »
Mine, as noted previously, is an SDG1005, but I will contribute my unit info for what it is worth.
From the info screen:
Boot Strap number 14
SW 1.01.01.27
HW 02-00-00-21-24
SN SDG00004120xxx

Thank you rf-loop for your interest in this issue!
 

Offline BlueLaser

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Re: Siglent SDG1020 square signal "dirty"
« Reply #22 on: April 18, 2013, 03:13:41 pm »
I have had similar problems and noted them down on my post:  https://www.eevblog.com/forum/testgear/siglent-sdg1020-arbitrary-fungen-first-impressions-and-a-possible-signal-glitch/  Do note that there are some modifications you can make to the board including replacement of resistors and addition of capacitors.  I found that rf-loop's advice of using the pulse function has resulted in signals clean enough for me to use for my application.  Since I did not need the extra frequency range--it worked out in my case. 
 

Offline commongrounder

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Re: Siglent SDG1020 square signal "dirty"
« Reply #23 on: April 18, 2013, 04:03:39 pm »
BlueLaser:  I did see, and appreciate, your post with the modifications that can be done.  Thanks!  I hesitate to crack the case until my warranty is done, however, to cover myself if the thing decides to die completely!  Pulse mode works for most of my applications as well, thankfully.
 

Offline rf-loop

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Re: Siglent SDG1020 square signal "dirty"
« Reply #24 on: April 18, 2013, 04:42:06 pm »
I have had similar problems and noted them down on my post:  https://www.eevblog.com/forum/testgear/siglent-sdg1020-arbitrary-fungen-first-impressions-and-a-possible-signal-glitch/  Do note that there are some modifications you can make to the board including replacement of resistors and addition of capacitors.  I found that rf-loop's advice of using the pulse function has resulted in signals clean enough for me to use for my application.  Since I did not need the extra frequency range--it worked out in my case.

What is your HW version?

It is also possible this issue is different.
This issue is not just same what I have seen before. There is something same but then also very different.

If practice and theory is not equal it tells that used application of theory is wrong or the theory itself is wrong.
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Offline Mike Warren

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Re: Siglent SDG1020 square signal "dirty"
« Reply #25 on: April 18, 2013, 10:12:06 pm »
I received a SDG1020 yesterday. Same as others, channel 2 square wave is good, but channel 1 is so full of glitches that my scope won't trigger properly.

Software: 1.01.01.27
Hardware: 02-00-00-21-24
Serial: SDG0000113xxxx
 

Offline Tepe

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Re: Siglent SDG1020 square signal "dirty"
« Reply #26 on: April 20, 2013, 08:49:32 pm »
SDG 1020

Software Version: 1.01.01.27
Hardware Version: 0f-00-00-21-22
Serial Number: SDG00001120xxx

1 Hz square wave with 50% duty cycle on channel 1:
« Last Edit: April 21, 2013, 06:09:50 am by Tepe »
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Offline rf-loop

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Re: Siglent SDG1020 square signal "dirty"
« Reply #27 on: April 21, 2013, 08:11:39 am »
SDG 1020

Software Version: 1.01.01.27
Hardware Version: 0f-00-00-21-22
Serial Number: SDG00001120xxx

1 Hz square wave with 50% duty cycle on channel 1:


All we know that electronics is art and it also can be and need be fun.



Square risetime is <10ns (typically 6-8ns in this Siglent model)
In your image you perhaps have one sample every 2us. 2us is 2000ns.

(with 16k sampling buffer your Rigol  have 0.5MSa/s with 500us horizontal speed)
It can draw straight line between 2 sample points (just as your rising edge in zoomed window if there is good luck that real rising edge is just between these sample points)

You really can not see any glitches there due to this extremely low samplerate.

And for jitter. You are looking same rising edge where is your trigger. Yes you can test your oscilloscope trigger quality/jitter but not signal source timing jitter with this method.
This 0.5MSa/s sampling rate is too low for all this kind of purpose. But yes, it produce nice art draw on the screen.  For analyzing 1Hz square wave timing jitter: nearly impossible with your scope.
You need reliable trigger on rising edge and then go to look next riring edge! 1 second! How you do it if thewre need enough resolution for reliable jitter measurement. You have max 1M memory. With 1s period theoretical maximum is 1MSa/s. With 500ksa/s you have 2 second. Can you set trigger to rising adge and take next rising edge on the screen... and there you have 2us time resolution. Is it enough? Yes it is if think that specified jitter for Sqrwave is 0.1% of period (@ 1kHz typical)  But wait...  50ms/div and more slow your Rigol go to scroll mode!
So, game over for real jitter measurement with Rigol DS1000E for 1Hz square.


Btw.. you are looking 1Hz square and your input is AC coupled. (yes you can see this rising edge but if you turn to speed where you can see whole cycle... well you see only peaks up and down where is rising and falling edges. But yes with only this short time period it can do.


-----------------------

This your SDG1020 is old version.

I have not tested this version SDG1020 but I have tested this same version SDG1010 and 1025. They did not have this special CH1 square wave  problem where it out "burst" of pulses before real edges using low frequencies + high level of glitches near rising and falling starting  corners. (when these glitches duration is enough long and high they make siggle or several random burst of real flat top pulses.


Strange here is that these new glitches  with high level can see in different time position than this other "glitch" issue what is talked earlier an where PECL comparator hysteris setting was wrong (too narrow).  Typically this was common to both channels and around same. Also these special glitches looks reduced in these new versions. 


It looks more and more like it is in SDG1020 and if it is PCB version 02. (until find opposite information) and  they are made 2013.

I have tested several SDG1010 with this new PCB 02- version and no any sign about this issue.
Also new SDG1010 where is PCB version 02-: it looks that square corner glitches level is more low than units what I have tested before. (dependent of FW there may read HW 0f- or 00-)
PCB version is first two digits in HW version string.

-----------

But for low frequencies. WHY use square wave function at all? There is pulse function up to 5MHz.
After 5MHz up to 20 or 25MHz there can use Square function typically without problems.
Perhaps Siglent can shut off this Square function example under some some frequency... example 100kHz or something like it.   
Btw, with higher frequencies timing jitter is less than pulse mode what have always 8ns due to 125MHz clock and  simple machine principle.

Example. How much is 1MHz square wave timing jitter? (even with these units what have problem)
1ns or something like this from ideal edge time?

With pulse function 8ns

1kHz square wave (in good condition normal unit)
0.1% from cycle time   1us  = 1000ns  (and becouse not explained, it can not say if it is from ideal time point or peak-peak. (my measurements looks like from ideal time point)

1kHz pulse 8ns p-p (+ some small other kind of jitter if look more deep in practicde and theory)


----------------------------------------------

Open recommendation to Siglent:

Simple free solution what may solve many problems:

Please: In next FW update, shut off Square wave function example  <100kHz freq.
And then write new specs sheet.

Square wave: 100kHz - 5, 10, 20, 25MHz depending model.

There is no any need for special square wave function under 100kHz.
For under 100kHz there can use Pulse function.

« Last Edit: April 21, 2013, 08:23:35 am by rf-loop »
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Offline Wuerstchenhund

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Re: Siglent SDG1020 square signal "dirty"
« Reply #28 on: April 21, 2013, 12:54:17 pm »
It looks more and more like it is in SDG1020 and if it is PCB version 02. (until find opposite information) and  they are made 2013.

This does not only affect generators made in 2013. My SDG1020 has been bought in December 2012 and suffers from the same problem.

Quote
Simple free solution what may solve many problems:

Please: In next FW update, shut off Square wave function example  <100kHz freq.
And then write new specs sheet.

Great idea, artificially limit the functionality and fiddle the specs to cover what is a major design omission which should have never passed any quality control (assuming there is one in Siglent, that is, which I doubt).

The appropriate way to react to this would to provide affected owners with a free board replacement with a fixed new board revision, offer a partial refund, or allow them to trade-in the affected generators for a different model at a hugely discounted price. In fact, this could be a good opportunity for a Chinese manufacturer to shine and show that customer satisfaction is actually important to them, and that they are more than one of many slave shops putting out cheap crap (I'm not holding my breath, though).

Your suggestion goes exactly in the opposite direction, a very good way to burn a brand name for good in this industry.

Quote
For under 100kHz there can use Pulse function.

Well, no, as at least on my unit square wave is still shit at 100kHz.
« Last Edit: April 21, 2013, 12:56:04 pm by Wuerstchenhund »
 

Offline rf-loop

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Re: Siglent SDG1020 square signal "dirty"
« Reply #29 on: April 21, 2013, 02:39:23 pm »

Your suggestion goes exactly in the opposite direction,

It (recommendation) was my try for some kind of sarcasm... but it is difficult.

Your unit HW  version is 02-  ?
Made 2012.
Before I have seen only 2013 made HW 02- 


And your problem is exactly this CH2 new more bad problem or is it  this old glitch issue what typically was in both channels.?

And simply, with this principle can not easy produce clean variable duty square, or circuit need be more complex. 
(my opinion is that these are two different internal problem in units)

I have not yet analysed it in circuit. I'm waiting some comment first from Siglent engineers.
 
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Offline rf-loop

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Re: Siglent SDG1020 square signal "dirty"
« Reply #30 on: April 21, 2013, 03:42:06 pm »
..... on my unit square wave is still shit at 100kHz.


Here is pictures from some test with Siglent SDG (unit what works normally).

1.6V pp  Square, 50% duty, 100kHz
first rising corner. Near corner before rising, acceptable level of "glitches".
Oscilloscope trigger from this same rising edge what is in display.
Cycle time is 10us.
There can not see any this kind of signs about severe glitches what can name as "issue"

Next same setting in SDG
Oscilloscope trigger is rising edge one cycle before.
(there is also cumulated oscilloscope trigger jitter (what is not markable here))

It can see that cycle-cycle jitter time is well in specs and not any kind of "issue".

In both images infinite prsistence and watching time 15 minutes.
(btw, for rms jitter calculation there is normal used 10000 events and many manufacturers give rms jitter... of course rms jitter may be "nice number".)

Of course this kind of square is shit  but then if look all functions, signal quality in this class of equipments and building quality and then take also price. What is better with all features in this price class if do not look old second hand professional equipments but look new units.

But this is BAD they have shipped some units what have really problem. This is bad. Really bad.
So, it is better to buy from sellers who really know what they sell and not only nice boxes.
Factory need better QC and not only that units looks like work but also they need watch this kind of problems. But then... also as long as chinese manufacturers are as they are... distributors need do control. Example I do not sell any individual unit what I have not chcked. (still there may be some rare problems sometimes)
« Last Edit: April 21, 2013, 04:17:35 pm by rf-loop »
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Offline Tepe

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Re: Siglent SDG1020 square signal "dirty"
« Reply #31 on: April 21, 2013, 03:57:35 pm »
1 kHz square wave, 4 Vpp from channel 1:


The same, but with DC coupling:


An attempt at duplicating Xyphro's first screenshot with a non-50% duty cycle and 877.2 Hz, 1 Vpp:


And finally 50 Hz, 600 mVpp like what rf-loop posted earlier:
« Last Edit: April 21, 2013, 04:01:01 pm by Tepe »
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Offline commongrounder

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Re: Siglent SDG1020 square signal "dirty"
« Reply #32 on: April 21, 2013, 06:27:06 pm »
Yeah.  I got curious and had to go back and check my SDG1005 square wave at 100khz, 50%, too.  I set up like rf-loop for the "glitches" at the trigger point and the jitter at the one cycle down from the trigger.  I set the trigger threshold above the jitter peaks to get as stable a trigger as possible on just the "real" square wave rising edge.  What do people thing about the periodic nature of the glitching?  There seems to be about 2.3ns between the peaks, 435mhz.  Does that relate harmonically to any clock frequency in the generator?  I am noticing that the height of the glitches varies, depending on how warmed up it is, warmer=less.  They do not ever go away entirely, however. :(
 

Offline commongrounder

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Re: Siglent SDG1020 square signal "dirty"
« Reply #33 on: April 21, 2013, 06:49:50 pm »
Another quick note:  Changing the frequency does not seem to affect the spacing of the glitches (except for how far away they are from the base of the rising edge) until crossing over certain frequencies. Crossing below 25khz changes the spacing to around 1.8ns.  The wave shape is the same, but is much more cluttered.  Given time, the persistent buildup on the scope screen is filled in.  The amplitude of these is incredible!:

 
 

Offline MasterOfNone

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Re: Siglent SDG1020 square signal "dirty"
« Reply #34 on: April 21, 2013, 07:10:52 pm »
I’ve also got an SDG105 in my home lab, but it doesn’t have the glitch problem on any of the channels. It is an older model so it looks like rf-loop is right about the problem being introduced recently:
SW 1.01.01.27
HW 0f-00-00-21-22
SN SDG00004110xxx
Since the glitches are cause by the comparator hysteresis, does it happen on the falling edge as well?
 

Offline rf-loop

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Re: Siglent SDG1020 square signal "dirty"
« Reply #35 on: April 21, 2013, 07:22:32 pm »
Since the glitches are cause by the comparator hysteresis, does it happen on the falling edge as well?

Yes, this glitch problem what is related to PECL hysteresis (and PECL comparator itself other things)  is around same in falling edge but of course now upside down.
If practice and theory is not equal it tells that used application of theory is wrong or the theory itself is wrong.
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Offline commongrounder

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Re: Siglent SDG1020 square signal "dirty"
« Reply #36 on: April 21, 2013, 07:25:13 pm »
It is an exact inverse of the positive going.  The same action is occurring on both transitions.
"Newer is Better" is becoming one of the most hollow sounding catch phrases around, these days. :(
 

Offline Tepe

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Re: Siglent SDG1020 square signal "dirty"
« Reply #37 on: April 21, 2013, 07:26:40 pm »
For comparison with rf-loop's test. 100 kHz, 50% duty cycle, 1.6 Vpp, channel 1, one cycle to the right of the trigger:


edit: Just for fun, a comparison with a Thurlby-Thandar TG210 at ~100 kHz. There is less jitter but the rise time is longer (but well within the <100 ns specified).
« Last Edit: April 22, 2013, 11:07:40 am by Tepe »
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Offline commongrounder

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Re: Siglent SDG1020 square signal "dirty"
« Reply #38 on: April 21, 2013, 08:06:25 pm »
Tepe's Channel 1 output looks like my Channel 2 output.  Better.  Channel 2 has less drive capability, but it can certainly be used more reliably for square waves if one understands the limitations.
 

Offline Mike Warren

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Re: Siglent SDG1020 square signal "dirty"
« Reply #39 on: April 24, 2013, 03:09:45 am »
I have been communicating with Jie Wang at Siglent and he advised the best cure for this problem is to fit a 47pF capacitor in parallel with R194. I've just done that and I'm now happy with the performance.

Jie also said that changing the value of R87 to 20K could be done instead of adding the capacitor, but the capacitor was the preferred fix.

Don't do both mods, just one or the other.

I found Siglent to be very responsive. I received replies to my emails within 24 hours.

« Last Edit: April 24, 2013, 05:07:32 am by Mike Warren »
 

Offline bmwnomad

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Re: Siglent SDG1020 square signal "dirty"
« Reply #40 on: April 24, 2013, 05:03:43 am »
Thanks Mike!

I can confirm that putting the 47pf cap in parallel with R194 fixes the square wave on channel 1.  I haven't done any extensive tests, just 1khz, 4vpp, 50% duty, but so far the glitches are gone.

SDG1025
SW 1.01.01.27
HW 02-00-00-21-24

Steve
« Last Edit: April 24, 2013, 05:38:03 am by bmwnomad »
 

Offline Mike Warren

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Re: Siglent SDG1020 square signal "dirty"
« Reply #41 on: April 24, 2013, 05:08:07 am »
 

Offline pickle9000

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Re: Siglent SDG1020 square signal "dirty"
« Reply #42 on: April 24, 2013, 07:26:28 am »
Siglent just earned a bonus point, maybe even two. First they talk to a customer then suggest a fix. I sure wish I could see more of this kind of stuff.
 

Offline Fennec

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Re: Siglent SDG1020 square signal "dirty"
« Reply #43 on: April 24, 2013, 11:51:35 am »
The same crap with mine, but on both channels. No difference between Ch1 & Ch2   :o   :scared:

4Vpp,  50%, 1kHz, no load (my T-adapter saw this "signal" and must be went away to the dark side of Moon. Can't find it.)


300mV !!  >:(

SDG1020
SW. 1.01.01.27
HW 0f-00-00-21-23
SDG00003120xxx
 

Offline Mike Warren

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Re: Siglent SDG1020 square signal "dirty"
« Reply #44 on: April 24, 2013, 12:07:36 pm »
The same crap with mine, but on both channels. No difference between Ch1 & Ch2   :o   :scared:

4Vpp,  50%, 1kHz, no load (my T-adapter saw this "signal" and must be went away to the dark side of Moon. Can't find it.)


300mV !!  >:(

SDG1020
SW. 1.01.01.27
HW 0f-00-00-21-23
SDG00003120xxx

That doesn't look like the glitch problem being discussed here. It just looks like a lot of noise.  I notice you have older hardware, which based on posts here doesn't seem to suffer from the glitch problem.

These signal generators aren't particularly quiet, so what you are seeing might be perfectly normal; at least 22 dB down.
 

Offline commongrounder

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Re: Siglent SDG1020 square signal "dirty"
« Reply #45 on: April 24, 2013, 03:22:33 pm »
Thank you Mike Warren, for working with Siglent on this.  Despite my reluctance to open up a brand new unit, I am going to proceed with the capacitor mod, since it is a recommended solution directly from Siglent.  I expect I will see the same improvement on my SDG1005.  I have a little more space to work in because there is no fan to get in the way on the 5mhz version.
 

Offline bmwnomad

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Re: Siglent SDG1020 square signal "dirty"
« Reply #46 on: April 24, 2013, 03:38:52 pm »
Yeah, I had to remove the fan to give me clearance to get in there with the tweezers and soldering iron.  :)

Steve
 

Offline rf-loop

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Re: Siglent SDG1020 square signal "dirty"
« Reply #47 on: April 24, 2013, 03:41:42 pm »
The same crap with mine, but on both channels. No difference between Ch1 & Ch2   :o   :scared:

4Vpp,  50%, 1kHz, no load (my T-adapter saw this "signal" and must be went away to the dark side of Moon. Can't find it.)


300mV !!  >:(

SDG1020
SW. 1.01.01.27
HW 0f-00-00-21-23
SDG00003120xxx

It have also handled here.
http://siglent.freeforums.org/old-sdg1000-possible-improvement-for-square-wave-quality-t27.html

and more here
https://www.eevblog.com/forum/testgear/siglent-sdg1020-arbitrary-fungen-first-impressions-and-a-possible-signal-glitch/

Your square wave corner noise is <10% from signal p-p

If you want more clean square for under 5MHz
Just do not push "Square" but push "Pulse"  what you can read as "Pulse and sguare wave functions"

With "pulse" you can of course do square wave but there is also more features and it have always around 8ns p-p timing jitter what is only related to 125MHz sampling speed.


Why use Square function if need "square wave" between 500uHz to 5MHz and specially below 100-200kHz.


Here is one reason why NOT use Square function:
 
Square: jitter in specs: 0.1% cycle time.  (@1kHz typical)

1Hz cycle is 1000000000ns
Square function:  square wave cycle time jitter may be  something like 1000000ns
Pulse function:  square wave cycle time jitter may be 8ns peak to peak.
(and corner clitches...  try find)

Just use Pulse function and use Square function only if really need it in special cases.
(with higher frequencies it have less time jitter than 8ns p-p)

http://siglent.freeforums.org/sdg1000-square-wave-t43.html

Also today I get recommendation directly from Siglent for this special CH1 problem where it have extremely high level glitches and even full level random pulses and high time jitter.   1st solution for this is add 47pF capacitor as Mike Warren have told and also he have made nice pictures for this. Nice work!  Tnx!

Notes for work.  All know it but still: Remember ESD protection!
SDG 1000 series service manual is also good for read.. It is available directly from Siglent sides (whoever can downlod and no need any registration)

(Old units with not this problem but where both channels have some amount too high level gliches before rising and falling edges, there is old Siglent recommended change for comparator hysteris setting resistor value.)




« Last Edit: April 24, 2013, 04:00:20 pm by rf-loop »
If practice and theory is not equal it tells that used application of theory is wrong or the theory itself is wrong.
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Offline Mike Warren

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Re: Siglent SDG1020 square signal "dirty"
« Reply #48 on: April 24, 2013, 09:58:44 pm »
Yeah, I had to remove the fan to give me clearance to get in there with the tweezers and soldering iron.  :)

You just need to hold your tongue at the right angle. :)
 
 

Offline rf-loop

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Re: Siglent SDG1020 square signal "dirty"
« Reply #49 on: April 29, 2013, 06:52:41 am »
SDG1020

CH2 parasitic oscillation problem in some situations.


But then CH2 have other issue in unit what I have tested..

Square, ramp, sine etc. All fails but looks like only if use 50ohm and highes voltage band. Specially it can most easy look with square or pulse. After signal rise it looks like go flat but just after corner it sart "oscillate".

Oh well, if you look it with slow oscilloscope it looks just ok or like only "noise level in signal top is more than bottom. Take fast oscilloscope and ... oops.
Signal top (not bottom) have high level some kind of oscillation with high frequencies. Something like over 200MHz!

This is first time I have tested SDG1020. (becouse Teledyne do not have this version), they have 1010, 1025 and 1050 only.  (2012, 2022, 2052)

What is this problem, I do not know anything more now.
(I do not sell this 1020 model at all before whole this issue is solved)

Please, who have this issue in SDG1020 model:
HW version, FW version and whole serial number exept last 3 digits  as xxx.
(I think posibility that this issue is in some manufacturing lot.)


This oscillation problem is solved by Siglent:

(due to Holiday in China, there is now open question how they support these who have this problem. If you have this problem, please contact your Siglent distributor / seller for get after sales customer care.)

CH2 have two end amplifiers.  One (a) for low voltage levels and one (b) for high levels.
(with high levels both of these are in use. (a is preamplifier for b))


Problem is in some units CH2 high level end emplifier (b).

This  amplifier (b) is Texas Instruments OPA695 (it is used in some units).
It need change to Intersil EL5166ISZ
(also Siglent have used CLC1606 in some units and this also looks like ok
EDIT/ADD: in problem case also this need change to Intersil EL5166ISZ  )

I have tested this repair and it solve this problem as 1-0

OPA695 is problem only in this CH2 high level end amplifier. (if there is OPA695 in other circuits it is not problem)

There do not need any kind of other component changes if change this amplifier.

How to test if there is this problem.

CH2 sine or square.
Output 50 ohm
Frequency depends your oscilloscope. Try example with 10kHz
Level 2Vp-p   (shift 0V)
Connect  >1m 50ohm coaxial cable to oscilloscope input using 50ohm "simple" termination. 
(this test NEED that there is oscilloscope input capasitive reactance together with 50ohm termination, If 50 ohm termoination is wide freq band enough pure 50ohm impedance  this problem is perhaps not visible)

Now look this signal top. (use peak mode)

If top looks very "noisy" (trace is "fat") then zoom to this fat area. You may see there high frequency oscillation (if square wave, it may start littlebit after signal rising edge)
If you change level between 1.00V and 1.01V you can hear also inside SDG internal relay voice becouse here it change to upper voltage band. Lower Voltage range  is clean but upper Voltage range is problem.  In my tests maximum oscillating level is somewhere half way this highest voltage band where this amplifier is added to signal pathway.

If you want see this oscillation signal you need 1GSa/s or more wiith this horizontal speed what you are using and oscilloscope analog front end need be enough good for far over 200MHz, in other case you may see only "some kind of noise".  in real world this is nice sinewave.

« Last Edit: May 03, 2013, 08:17:21 am by rf-loop »
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Offline Wuerstchenhund

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Re: Siglent SDG1020 square signal "dirty"
« Reply #50 on: April 29, 2013, 09:26:36 am »
This oscillation problem is solved by Siglent:

(due to Holiday in China, there is now open question how they support these who have this problem. If you have this problem, please contact your Siglent distributor / seller for get after sales customer care.)

Unfortunately that doesn't work for me as my seller is of no help. But then since I added the SMD capacitor the main issue (excessive square wave jitter) seems to be gone now.

After opening up my unit I found that the general hardware design looked perfectly fine but that there was some sloppyness during assembly which lead to the PSU cable being damaged (insulation cut off by sharp corner with wires exposed) as it was stuck between parts of the housing. Oh well, at least it didn't cause any damage and was easily fixable.

Since you sell this stuff for a living, have you seen any SDG5000 yet? Spec-wise it looks very interesting (aside from the missing LAN port) but I wonder how it performs in the real world.
 

Offline rf-loop

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Re: Siglent SDG1020 square signal "dirty"
« Reply #51 on: April 29, 2013, 09:56:35 am »
This oscillation problem is solved by Siglent:

(due to Holiday in China, there is now open question how they support these who have this problem. If you have this problem, please contact your Siglent distributor / seller for get after sales customer care.)

Unfortunately that doesn't work for me as my seller is of no help. But then since I added the SMD capacitor the main issue (excessive square wave jitter) seems to be gone now.

After opening up my unit I found that the general hardware design looked perfectly fine but that there was some sloppyness during assembly which lead to the PSU cable being damaged (insulation cut off by sharp corner with wires exposed) as it was stuck between parts of the housing. Oh well, at least it didn't cause any damage and was easily fixable.

Since you sell this stuff for a living, have you seen any SDG5000 yet? Spec-wise it looks very interesting (aside from the missing LAN port) but I wonder how it performs in the real world.

I have not seen any SDG5000 yet.
Under tests now.


Last time I order lot from Siglent I think if I get one for tests but somehow I have learned that what ever machine is I littlebit afraid first versions.
If it is washing machine, if it is car, if it is TV, etc.
Mostly they are not mature when they first come on market. Least it is good to short time look around what kind of comments are available.
Of course this may lead wrong also becouse if there is some problems... and related to this some negative opinions and then lot of peoples do not buy also later versions becouse there is now "bad opinions" over this brand. If later come more mature version... peoples still keep they first opinions and everywhere can read these and then every corner they talk that this name/model  is bad and now also these other peoples who never have made any tests repeat also these bad opinions what they have heard perhaps time ago.
« Last Edit: June 04, 2013, 02:23:14 pm by rf-loop »
If practice and theory is not equal it tells that used application of theory is wrong or the theory itself is wrong.
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Offline rf-loop

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Re: Siglent SDG1020 square signal "dirty"
« Reply #52 on: June 22, 2013, 04:06:03 pm »
Original message from wrong thread (SDG5000 series test thread is wrong place)
Hi,
Did you see this review ?

interesting moments:  49:30 ,  54:45 and 57:30 - what happen ?

I know, SDG1020 is low budget waveform generator, but it is still Siglent (maybe I'm wrong)
I may have difficulty understanding some sentences, but the waveforms look very strange.




Yes, this is well known and many times here and there handled and also circuits analyzed some amount. Also there have been improvement for this glitch issue.



https://www.eevblog.com/forum/testgear/siglent-sdg1020-arbitrary-fungen-first-impressions-and-a-possible-signal-glitch/msg185396/#msg185396


and here many things: http://siglent.freeforums.org/sdg1000-arbitrary-multifunction-generators-f13.html   

(also some wink for modify)



But other things like square wave glitch have handled lot of and littlebit more.
Then 54.45.  Sampling frequency is 125MSa/s. It reads also in specifications.
125MSa/s period is just 8ns.
This kind of equipment circuit principle need do it. (it depends frequency(period) and pulse width.
More advanced (and typically more expensive) equipments have some methods for avoid this.
Square wave is then special case becouse it is derived from internal sinewave using cheap simple comparator solution. For low frequencies, better square can do using pulse function.

57.30 and after then this "gameboy" playing - for what kind of purpose.  Perhaps nothing useful to do - perhaps if this, then coffee break is perhaps better use for time. ;)
Of course sometimes this kind of playing can do ecample for finding bugs what leads to system crash.


Please continue this discussing here. Not about this case in SDG5000 test thread, please.

« Last Edit: June 22, 2013, 05:34:06 pm by rf-loop »
If practice and theory is not equal it tells that used application of theory is wrong or the theory itself is wrong.
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Offline Siglent

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    • SIGLENT TECHNOLOGIES
Re: Siglent SDG1020 square signal "dirty"
« Reply #53 on: June 26, 2013, 02:23:34 am »
Is this the same thing you guys are talking about? 

I have an SDG1025 and was going to send it back under warranty for a replacement, but if they are all like that then maybe I'll have to live with it.

Attached are scope snapshots.  Yellow are channel 1, 1khz square wave and blue is channel 2, 1khz square wave.  I set it on infinite persistance for a few seconds to show the glitches.

Channel 2 is fine, as is channel 1 pulsed output(not shown), it's just channel 1 square wave that looks like crap.

Steve

The question is due to changes the circuit, in the new version has been resolved (increasing the capacitance), it will be updated in the latter.


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