Siglent SDG1020 Arbitrary FunGen- First Impressions and a possible Signal Glitch - Page 1
Forum section: electronics / testgear

author: BlueLaser
author_rank: Contributor
timestamp: January 19, 2013, 10:08:29 pm
content: I purchased the Siglent SDG1020 just yesterday and thought I would offer up some thoughts and bring up a possible concern.First, the unit seems to be built quite nicely. Good shielding and solid chassis, bright screen that is easily view-able and not washed out. etc. User interface is managable but could definitely be improved with a firmware update. There are many settings that I would like to see be toggled using the rotary encoder rather than having to press the soft key at the side of the screen multiple times. The voltage accuracy seems very good as well. I particularly like the DC output option which seems very close to spot on at voltages above about 10mV. The DC output is fully adjustable from 1mV upto 10V. I measured it with a Uni-T UT61Eand the 1-5 mV range was off by upto 0.4mV. After that, the values all the way through the full range were almost always +/- 1mV. Nice!So naturally, I am interested in this unit for testing of devices which requires non-DC signals so I hooked it up to my (also) new DS2072 and found a strange glitch. I had it set to 4V pk2pk Square wave and At 100kHz on Channel 1 only, there were a number of glitches which begin occurring about -50ns before trigger and continue past about +40ns. They seem pretty significant and are not present at all frequencies. I have attached pictures to get others' thoughts. One minor other thought is I found the jitter between channel 1 and 2 to be pretty significant (and above the listed spec of 6ns) but I assume the spec sheet was referring to the jitter of the channel with respect to itself. They must have completely different synthesizers as they do not seem correlated. Either way, kind of strange and may cause problems for some measurements. I think when I get a second, I will compare it to the TTL out to figure out what is going on. I wanted to know what others thought and it this is just an issue with my unit. I just emailed Siglent and am hoping to hear back from them soon. All the best.UpdateA number of SDG1000 Series units seem to suffer from a glitching/jitter phenomenon when viewed carefully along the rising or falling edge of the SQUARE wave function. The issue is most visible in the low frequency area <1MHz. This issue only seems to affect the square wave as it stems from hysteresis on the ADCMP562 Comparator located near the fan on the main board. A solution recommended by Siglent to me was to replace R82 and R87 (located very close to the ventilation fan on the board) with 20k ohmwell matched0603 resistors. The existing resistors seem to be 40k in some units and are VERY closely matched (Mine were <0.1% tolerance) so when replacing, I manually binned the 5% resistors I had to ensure similar response on each channel. It should be noted that I only experienced improvement in the upper frequency range >2-4MHz after this repair. Please observe strict ESD protection rules if you are attempting this repair. For vastly improved jitter and no glitching, the pulse function should be used instead setting the duty cycle to 50%. The pulse function is limited to 5MHz, however.

author: saturation
author_rank: Super Contributor
timestamp: January 19, 2013, 10:38:53 pm
content: I don't own this unit, but at only 100kHz it abnormal; waveforms should be pristine in appearance and stability, as this FG is rated to 20MHz. Beyond a flaw, and if one isn't so worried about voiding a warranty, I'd tear it down and check the construction quality to make sure its not something easily user fixable caused by poor assembly.

author: BlueLaser
author_rank: Contributor
timestamp: January 19, 2013, 11:28:56 pm
content: Hmm, yeah. This is what I suspected. The glitches are pretty significant. Let me see what the manufacturer says and what the seller will do? As long as I am keeping the unit, I would definitely be willing to crack it open and see if there is soldering error that could be resulting in the error. That said, I don't want to do anything until I know they're not going to ask for it back.Regarding firmware, from what I understand, you must also contact the manufacturer directly? Does anyone know if there are any hardware differences between the different models of the SDG1000 series? (Is it just software crippled for sub 50MHz models?)

author: pauln
author_rank: Contributor
timestamp: January 20, 2013, 10:41:58 am
content: I have this exact same AWG. FWIW I have duplicated your settings into my old Owon DSO anddo notget the glitches shown in your pictures.In case you are not aware there is a known issue when using the 1020 with dbm units - the output jumps dramatically at certain points. Sorry I cant remember the exact points. I have written several emails to Siglent, starting last August 2012 asking when it will be sorted and have only received 1 response saying "wait" it is under test. The sudden output increase when using dbm units could cause a problem or 2 - so be aware.Paul

author: Mark
author_rank: Frequent Contributor
timestamp: January 20, 2013, 11:03:11 am
content: Quote from: pauln on January 20, 2013, 10:41:58 amSame here with the same equipment as you. No glitches with the OP's settings.

author: BlueLaser
author_rank: Contributor
timestamp: January 20, 2013, 03:11:46 pm
content: Thanks Mark and Pauln. I did want to point out that the glitches do not occur on every trace. They are probably about 1 out of 500 or so traces with a glitch but luckily I can keep my ds2072 on infinite persistence and the 50,000 wfms/s helps too!I'll wait to see if Siglent tells me anything. Otherwise, I guess I'll leave it up to the sales channel to see if I can get an exchange or get fully or partially compensated.

author: andy1
author_rank: Contributor
timestamp: January 20, 2013, 10:08:57 pm
content: I have the SDG1010 so not exactly the same model but with this frequency there shouldn't be that much difference, no glitch for me either when capturing for ~30min with infinite persistence with my hantek DSO so I think with even the much lower capture rate than the nice Rigol I should have seen something.

author: rf-loop
author_rank: Super Contributor
timestamp: January 21, 2013, 09:04:15 am
content: First you can look these tests (specially about jitter)In these some tests have used SDG1010 and 1025.In most of things they are same.Look there jitter image 6. Made with two channels and ~93kHz square.Then look image 4 and then image 7 with lower frequancies.Also image 7 is made for jitter test so it is not good for look inside corner where signal rising edge start. I will test and take later some images with better settings for look inside this corner. (I have something allready but I can not use these - becouse images have something (done in third party lab) where I need follow NDA)There are (of course) lot of "glitches" due to natural jitter and filtering. typically they stay "typically" below ~10% of signal level and around jitter p-p time before rising edge start (are not equally spaced throughout the time domain, but the emphasis on close to the rising edge (statistical distribution)).For OP, please read also Agilent paper about this type of DDS generators principle. This is simple DDS generator and jitter is natural with this principle.If you have real glitches what levels are nearly 50% (as shown in your one image) from signal level something is badly wrong. Something is wrong in your measurement OR something is wrong in your Siglent SDG OR both. Also you can set your oscilloscope trigger to level where it do not meet these "glitches". And for jitter, look next rising edge from triggering rising edge.After I have enough time for do some tests with Siglent SDG I will show lot of better images about this corner before square rising edge in this image. This image here is not for this purpose, it is made for characterize amount of typical peak to peak jitter.(it is typically as manufacturer specified). Filtering is always compromise but still it perhaps can do better without hop to next price group. Some amount of this corner impurity need accept. Just as we need also accept corners wobbling aliasing in oscilloscopes and many other natural things. If <0.5k$ machine is not enough good it can always buy 5k$ or 50k$ unit. But also if you get more accurate test equipments you find still (but more small) "errors" there. It is one important part of experience and knowledge to characterize what is fail and what is normal.Also of course there is channel to channel jitter becouse both channels signal have jitter and now if you synchronize to other channel and look how other channel have jitter related to other channel - it is basic fundamental in this type of generator principle.If need generator what do not have this this type of jitter then this generator type is wrong for your use. Also there are some golden frequancies where do not need "hop" for example adjust frequency or period (remember sampling rate).If there isreallythis level of glitches what your image show then your generator have some fail. Simply talking - then your generator is broken.----(Yes I'm also aghp (well known seller as "brand" in my country and specially in some group of peoples)but nowIFI find something what these companies do not want publish (data/hack/modification or other this kind of things) for Owon/Siglent I can not at all publish these becouse I'm both companies accepted reseller and service - if this is unethical - sorry, I keep these in my head. ; )But original "accident" happend after some old customer and friend ask me why I'm rf-loop in EEVblog becouse I'm "aghp"... after 3 minute "thinking" it was ready... ok: now I'm aghp, satisfied now? What rf-loop or aghp have talk here: there is not any kind of discrepancy.I did not destroy rf-loop account becouse I thinkit may be useful in futuresome situations IF there come data or something what seller can not publish without loose deal with manufacturer. ; ) ) Then also sometimes becouse I have several computers (some have same IP behind NAT and some in other locations and even some in China sometimes) Sometimes have happend accident that I open PC and go to EEVblog and I have not looked login (automatic) and just start write without thinkin who I'm becouse I'm myself always.All know outside of equipment are not secrets.. and same for inside... all can measure and test these. But inside there may be things where can use some given information about repair service work.Of course I can still publish errors and all information what is normal from seller who do not sell only "nice boxes".- rf-loop (aka and "official": aghp or aghp55)

author: rf-loop
author_rank: Super Contributor
timestamp: January 21, 2013, 04:23:04 pm
content: Here some images made with HPSiglent SDG1025 connected to HP's 50ohm input. (it is 500MHz old work horse)SDG software version is: 1.01.01.23 and HW version 0f-00-00-19-23Images have explanation.But look carefully scales and remember signal frequency.Remember: SDG samplerate is 125MSa/s. One sample every 8ns.It is good to note what happend if think reverse. Take oscilloscope what have example 50MHz analog bw and it have 125MSa/s sampling rate. Then try look sguare with example 6ns rising time. What you see (if all is ok). You see corners wobbling. Something littlebit like this 100kHz rising.But then... what happend 10kHz. I do not know.Level is under 10% mostly but sometimes higher but NOT nerly 50%.I do not know what this OP measuring method may affect or what is going on in Rigol "image makeup" process.My first suspect is that OP's SDG is somehow broken. These glitches are lot of too high.Is it possible analyze real sampled data points so that Rigol signal makeup process do not "destroy" real data.In these HP images there is raw real data without any "show nice image" manipulation.NOTE images vertical and horizontal scale and signal under test dimensions.100kHz signal period is 10000ns! and 10kHz signal 100000ns! and signal level is 3.5Vp-p but on the scope screen is only 800mV (100mV/div)For images 4 and 5. remeber that SDG ample perior is 8ns!

author: BlueLaser
author_rank: Contributor
timestamp: January 21, 2013, 04:40:51 pm
content: RF-loop, Thank you so much for all the insight. You made me worried about my new DS2072 so I decided to check it with my DS1102e and sure enough, the glitch is there. BADLY! There is DEFINITELY something wrong with my particular unit. I understand the nature of DDS will introduce glitches based on the true internal sampling rate. The problem I am having is that they are orders of magnitude larger than the jitter specification. Please see the included pictures. For these, I decided to turn ON sync in the utility menu and can now see that channel 2 also exhibits some (but not as severe) glitching. I mean, this is 4us of glitches!!!(Not ns or ps) That was on a 1kHz square wave.Okay, so besides that, I was wondering if someone could chime in on the impedance switching. When I switch form High-Z to 50ohms, the voltage amplitude seems to double. Is this a normal response or yet another problem? Thanks again everyone!

author: PA0PBZ
author_rank: Super Contributor
timestamp: January 21, 2013, 04:45:46 pm
content: Quote from: BlueLaser on January 21, 2013, 04:40:51 pmWhen set to 50 Ohms you should terminate 'the other side' with 50 Ohms, I guess you will find that the amplitude will be correct again

author: BlueLaser
author_rank: Contributor
timestamp: January 21, 2013, 04:58:20 pm
content: lol, I guess I slept through too much of my electrical engineering classes!When I get back to the bench, I'll try matching the impedance. I'm 99% sure that's what I was missing. Thanks.

author: rf-loop
author_rank: Super Contributor
timestamp: January 21, 2013, 05:17:19 pm
content: Glitches before rising edge, there is some but they need be quite low level! It can not at all accept if these glitches level is 30% or even 50% from signal pp. 10-15% is maybe normal for this kind of unit.Jitter is totally different case.Most easy way look jitter is (just as Agilent do).Trig to rising edge. Go to look NEXT rising edge. Zoom in. Wait enough time. Finally you find peak to peak value for jitter. It is highly related to square wave frequency (period).100kHz square long time jitter here in image. This data have collected long time leaving scope with infinite prsistence alone. Trigger point is 10us (one cycle) before (rising edge)If some manufacturer tell (as someones do) jitter rms value.. or typical value... nice numbers and they do not lie..(and for Owon owners here... all these can also look with Owon)

author: rf-loop
author_rank: Super Contributor
timestamp: January 21, 2013, 08:12:17 pm
content: Quote from: Mark on January 20, 2013, 11:03:11 amWith Owon, of course it can see (but with 100kHz square just same as with HP images before.)Here image (not best possible due to lack of time to do it) how Owon see these "glitches" using SDG1025 with 4Vp-p square and10kHzfrequency.Note that image show only around 900mV area from 4V rising edge.And bottom line (after last falling edge is around 50000ns. Glitches are inside 120ns before rising edge and most them are inside 30ns.Nice to see also that Rigol have learn something from Owon front end and also it seems they have take exactly same RuiFeng ADC. But of course Rigol have developed nice and totally different product.

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: January 23, 2013, 06:18:18 am
content: I, too, have a Siglent SDG1020 AWG (HW 02-00-00-19-24, SW 1.01.01.23), and because of this thread I did some tests yesterday. And low and behold, my unit does show the same glitches at 100kHz 4Vp-p square wave as BlueLaser's one. I never noticed the glitches because I only use the unit for sinus and pulse signals, and occasionally for square waves in the MHz range.However, I am not so sure that this is a hardware problem. I did some few more tests with other signal forms (pulses, sinus), and lower and higher frequencies. What I found was that the glitchesonlyshow up in square wave mode, they don't however come up in other modes (i.e. pulse mode with 50% duty cycle), and that it gets worse if the frequency gets lower. But at 1Mhz or more the signal is perfectly stable.Ch 2 doesn't show any glitches in square wave mode.This leads me to believe that the issue may as well be a firmware bug, which perhaps only shows up on specific hardware variants.BlueLaser, Pauln and Mark, maybe you can post your HW and SW versions?

author: rf-loop
author_rank: Super Contributor
timestamp: January 23, 2013, 09:13:49 am
content: Quote from: Wuerstchenhund on January 23, 2013, 06:18:18 amPlease can you show image about these glitches. Trig to rising edge around 70% of full level.Use (example) 100kHz symmetric square (not pulse)Look just before rising edge... something example 30 - 100ns area before rising.Use 4Vpp set in generator (50ohm) and 50ohm input with oscilloscope.What is maximum glitch level? (do not use any "Sinx-like" cosmetics in scope. Real sampled points.How about 3VppThen use 400mVpp signal from SDG all other same. Max glitches level?(this level is "direct" in output stages)Can you confirm with just equal settings (note CH1 and CH2 output limits) that CH2 do not have glitches but CH1 have.Here is table about level ranges inside HW. (for these there are set of attenuators and also fixed 20dB amplifier in HW) They are used combination what also depends about offset setting range (<=3V and >3V)

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: January 23, 2013, 09:36:36 am
content: Quote from: rf-loop on January 23, 2013, 09:13:49 amGetting images may be difficult as the only scope I have at the moment is a HP 54510A 2Ch 250MHz 1GSa/s DSO for which I don't have any screen capture utility (Agilent's IntuiLink software doesn't work with this scope), and my 54542A which can capture screen shots is currently out of order due to a PSU problem.But I guess I could try to make some old-fashioned photos.I'll have a look when I am back home tonight.Update: Sorry, something more important came along so I had't time to play around with the AWG. If it's still of interest I can do that within the next days.

author: rf-loop
author_rank: Super Contributor
timestamp: January 23, 2013, 05:11:20 pm
content: After very small HW modification in analog circuit.Changed one component value.Measurement just all as my earlier hp image 1.(also it can see that hp scope trig is more stable after this mod. (look rising edge)20minute time with infinite peristence as also before.Perhaps now better?I have not tested all functions fully butlooks likenot any bad efect in other signal modes and features.But this test show clearly where in circuit this problem is hiding.... (partially or fully)Images before test mod and after test modNote: Signal top level is 3.5V and here is only bottom corner before rising.Now glitches are inside 70ns before rise and under 150mV (what can find with this oscilloscope using 20minute)Before around 140ns area and 400mV (with used around 10kHz square.)

author: BlueLaser
author_rank: Contributor
timestamp: January 23, 2013, 09:28:08 pm
content: My unit is versioned as follows:Boot Strap Number: 1Software Version: 1.01.01.23R1HardWare Version: 02-00-00-19-24Model: SDG1020RF-loop, what change did you make. I can't see your image of the circuit you're referring to.I find this interesting because Siglent got back to my seller and said the problem may require changing R87 on the board to a 20kohm resistor. I am really not sure what this will do because I was then advised in the next email to NOT open the case as it may complicate the return/exchange process. I'm currently in the process of either getting replacement unit or board from the seller. And yes, I seem to only see these glitches when in square wave mode. I do still see them at higher frequencies (>1MHz) but they are much less pronounced and do not go back as far in time. It guess this does show signs of a firmware issue but I wonder if it has to do with the square generator or filter. If someone has one that is out of warranty or are okay opening, what is the current value is R87 anyway? Thanks a bunch guys.

author: rf-loop
author_rank: Super Contributor
timestamp: January 23, 2013, 10:45:41 pm
content: Nice to hear that someone else have also find solution.Yes resistors R87 (for CH1) and R82 (for CH2)can change.Original resistance may be different in different manufacture versions.Original may be normally 40k (40.2k) as example in image.And it is too high in my opinion.Change to 20k may help enough but this hp oscilloscope image was from test with around 9k.My opinion is that some value between 7k - 33k is ok for most of uses. (perhaps this 20k is compromize with less glitches but minimum other efects. I have not tested what possible things it affects in some other things.. phase accuracy etc.. Lack of time to do full tests.(but remember, my test was with 10kHz, not 100kHz as original post here and also I have looked 100Hz and really lot of better than without change. As we know example 1MHz there is very small amount of glitches. More low freq and more wide "time window" for glitches before rising edge. This is natural with this circuit principle.)This image show original, NOT modified!

author: nixxon
author_rank: Frequent Contributor
timestamp: January 23, 2013, 11:06:03 pm
content: I did some tests on my SDG1020 with newest firmware 1.01.01.23 this evening with my Rigol DS1102E.Square wave, 50% duty cycle, 100 kHz, 50 ohm terminated inside SDG1020 and at scope BNC input (T-connector).Amplitude 3 Vpp, as CH2 only goes up to 3 Vpp."Exposure" time: approx. 13 minutes for both runs (SDG1020 Ch1 and Ch2).When I saved the screenshot from output Ch1, the triggering was not stopped on the scope and there was a bad connection between the 50ohm termination and T-connector at the scope end. Thus the amplitude increased a bit and got captured on the screenshot. I have crossed out the wrong part (in red color).All measurements done in basement "lab" @ 10 degrees Celcius. Equipment was not warmed up at all, other than during the tests that took an hour or so in total.Rigol settings:Analog Ch State Scale Position Coupling BW Limit InvertCH1 On 500mV/ 0.00uV DC Off OffAnalog Ch Impedance ProbeCH1 1M Ohm 1XTime Time Ref Main Scale DelayMain Center 5.000ns/ 0.000000sTrigger Source Slope Mode Coupling Level HoldoffEdge CH1 Rising Auto DC 460mV 500nsAcquisition Sampling Memory Depth Sample RateNormal Realtime Long Memory 500.0MSa

author: nixxon
author_rank: Frequent Contributor
timestamp: January 23, 2013, 11:21:20 pm
content: Some DC measurements of the SDG1020, using my Fluke 87 (and 83-5)DC out ------> Reading Fluke 87+1 ------> 1.006-1 ------> -0.999+2 ------> 2.000-2 ------> -1.981+5 ------> 5.00-5 ------> -4.96Some mV readings:DC out ------> Reading Fluke 870.000 ------> 0.001 (+0.001V)0.001 ------> 0.0020.002 ------> 0.003(etc. (+0.001V) all the way up to:)0.133 ------> 0.1340.134 ------> 0.1350.135 ------> 0.137 (+0.002V)0.136 ------> 0.138(etc (+0.002) then some bigger steps0.200 ------> 0.2020.300 ------> 0.303 (+0.003V)0.400 ------> 0.4030.500 ------> 0.5030.600 ------> 0.6040.700 ------> 0.7030.800 ------> 0.804 (+0.004V)0.900 ------> 0.905 (+0.005V)1.000 ------> 1.006 (+0.006V)Pretty accurate DC output and within specs: 1% +3mVEDIT: See enclosed table for %-errorsEDIT 2: Corrected wrong numbers in table

author: nixxon
author_rank: Frequent Contributor
timestamp: January 23, 2013, 11:27:02 pm
content: I also enclose a 25 minute sample from Ch1 output @ 3.5Vpp (same settings as above)I'll enclose the scope settings (25minp.txt) for this screenshot in case I missed any details:Analog Ch State Scale Position Coupling BW Limit InvertCH1 On 500mV/ 0.00uV DC Off OffAnalog Ch Impedance ProbeCH1 1M Ohm 1XTime Time Ref Main Scale DelayMain Center 5.000ns/ 0.000000sTrigger Source Slope Mode Coupling Level HoldoffEdge CH1 Rising Auto DC 1.00V 500nsAcquisition Sampling Memory Depth Sample RateNormal Realtime Long Memory 500.0MSa

author: rf-loop
author_rank: Super Contributor
timestamp: January 24, 2013, 07:15:19 am
content: There are more glitches with lower frequency.You can look example 10kHz and 1kHz.Also note that example in my images there is 100mV/div but signal from SDG is 3.5V.Only looked bottom corner beforer signal rising edge (for better visibility)Why there is glitches more if use more low frequency.Answer is simple but it need pen and paper to explain whole "theory and practice".But it can understand as know that squarewave is produced from sinewave.More slow wave there is more time where input to comparator is just very very near to treshold before input crosses the threshold. Now, in practice and in theory all signals have more or less noise. There is not "ideal" sinewave. Also we know how sinewave is produced. With 14bit DAC where some lowest bits are also "noisy". Comparator whole environment is "noisy", also littlebit itself comparator Analog Devices ADCMP562 (Dual High Speed PECL Comparator).Quote from: Analog Devices datasheet"Resistor what need change is just for set this hysteresis.It is also possible that optimum value is different in some units.If want do lot of more then also internal sinewave used for square may need more filtering if want really good. But it need think compromize. Also it is possible that comparator enviroment (powers and GNDs need cleaning etc etc) This is cheap generator. Not high-end generator. If want high-end generator it need build totally all agen...or buy different generator (with different price)EDit/AddI get beter smd resistor values set for this purpose and later I will do some more and better tests.

author: nixxon
author_rank: Frequent Contributor
timestamp: January 24, 2013, 06:15:29 pm
content: I will do some tests with the recommended setup:Signal generator: 4Vpp, Square wave, 50% duty cycle, 1 kHz or 10 kHz (or maybe 12.345678 kHz)Rigol: Horizontal scale 20 ns/div, Vertical scale 100 mV/div (& place trace to the right and bottom of screen)Maybe I will capture more glitches if I setMemory Depthto "Normal" (16kpts@1GS/s) rather than "Long memory" (1Mpts@500MS/s). I dont't believe I need that MegaZoom-like feature at all. (If I scroll sideways, the persist-image disappears) I think reducing memory depth also may reduce the blind time and increase the waveform capture (or update) rate. Or maybe this makes no difference when measuring low frequencies.If I capture the same signal with both Memory Depth settings (Normal and Long Memory), can anyone predict how the 2 screenshots will differ from each other?

author: nixxon
author_rank: Frequent Contributor
timestamp: January 24, 2013, 11:13:05 pm
content: Here are 2 x 15 minute persistent "exposures" from my DS1102ESDG1020 at 4Vpp, Square wave, 50% duty cycle, 10 kHz, 50 ohm terminated both ends (and 50 ohm impedance RG58 cable).At 10 kHz there was much more noise, compared to that at 100 kHz. As expected.Not too much difference between the pictures at Long and Normal memory depth. A few, bigger glitches was captured on the long memory depth measurement.Settings Rigol DS1102E for picture file "15_long.bmp":Analog Ch State Scale Position Coupling BW Limit InvertCH1 On 100mV/ 1.73V DC Off OffAnalog Ch Impedance ProbeCH1 1M Ohm 1XTime Time Ref Main Scale DelayMain Center 20.00ns/ -100.0000nsTrigger Source Slope Mode Coupling Level HoldoffEdge CH1 Rising Auto DC -1.13V 500nsAcquisition Sampling Memory Depth Sample RateNormal Realtime Long Memory 500.0MSaSettings Rigol DS1102E for picture file "15normal.bmp":Analog Ch State Scale Position Coupling BW Limit InvertCH1 On 100mV/ 1.77V DC Off OffAnalog Ch Impedance ProbeCH1 1M Ohm 1XTime Time Ref Main Scale DelayMain Center 20.00ns/ -100.0000nsTrigger Source Slope Mode Coupling Level HoldoffEdge CH1 Rising Auto DC -1.17V 500nsAcquisition Sampling Memory Depth Sample RateNormal Realtime Normal 1.000GSa

author: nixxon
author_rank: Frequent Contributor
timestamp: January 24, 2013, 11:25:03 pm
content: Here is a 5 min "exposure" of the 1 kHz signal from SDG1020.It's only 5 min, as my scope froze when I tried to save the first time (a 15 min exposure). I had to power off and restart.Only frequency was changed on the waveform generator (other settings, see previous post).I had to expand the horizontal time base by a factor of 5, from 20 ns/div to 100 ns/div to capture most of the noise. That also made the sample rate on the scope go down from 1 GS/s to 500 MS/s. Memory depth normal.Settings Rigol DS1102E for picture file "5mi_1khz.bmp":Analog Ch State Scale Position Coupling BW Limit InvertCH1 On 100mV/ 1.59V DC Off OffAnalog Ch Impedance ProbeCH1 1M Ohm 1XTime Time Ref Main Scale DelayMain Center 100.0ns/ -500.0000nsTrigger Source Slope Mode Coupling Level HoldoffEdge CH1 Rising Auto DC -992mV 500nsAcquisition Sampling Memory Depth Sample RateNormal Realtime Normal 500.0MSa

author: nixxon
author_rank: Frequent Contributor
timestamp: January 25, 2013, 11:55:31 am
content: I just turned some pages in the SDG1000 series manual and on page 70 it is mentioned a function that is supposed to initiate a self calibration: --> "Test/Cal" --> "SelfAdjust"The manual just mentiones this option, but does not describe it any further. Does anyone know what happens when you select "SelfAdjust"? Does the AWG perform better afterwards?

author: BlueLaser
author_rank: Contributor
timestamp: January 25, 2013, 03:37:54 pm
content: I'm awaiting official instruction on the channel 2 repair. I guess I got the go ahead to remove the void warranty sticker!At any rate, Nixxon had suggested doing the self-cal which for some reason I never considered. I had a set of images on the decades of channel 1 and 2 performance while triggering on the sync out signal locked to channel 1. The self-cal without a doubt has greatly improved the higher frequency performance. The low frequency is still riddled with glitches BUT... the glitches are now occurring in a more regular (less random fashion) and aligning on the trace. Just a note, that on my unit the Channel 1 to Channel 2 phase error at 100Hz can be as large as 18 microseconds!!!Crazy!!!! It's like they're not even on the same clock and it seems totally random. I sure hope these resistors magically address all these issues.As for the repair, I need to go and buy some 0603 resistors to modify the circuit. I only have 1206 and 0805 in my parts bin now. I sure hope I get compensated for all this diagnostic and debug work for the Siglent.Teardown pictures to come. I know some people wanted to see all the parts and it doesn't look like any of mine have been sanded down.P.S. If anyone is wondering why I don't test the 10MHz range, it's because the output sync signal can only go upto 2MHz for some reason???

author: nixxon
author_rank: Frequent Contributor
timestamp: January 25, 2013, 04:39:38 pm
content: Quote from: BlueLaser on January 25, 2013, 03:37:54 pmCould you describe what happened when you selected "SelfAdjust"? Did it take long? Did the relays click? I wonder if it is required to short the outputs to ground or anything else...On the first screen captures of yours, it seems that 120mV trigger level is a bit low. Looks like the scope has triggered on lots of the noise/glitches. Maybe a trigger level of 500 or 1000 mV is better and will give a more intelligible picture. (stay above of the noise/glitches and trigger only on the actual rising edge of the trace). Maybe changing the trace from line to dots would be better as well. (for some reason, the trace "dots" of my DS1102E aren't only the bright yellow dots, there is a trail of a few pixels (dim yellow).

author: BlueLaser
author_rank: Contributor
timestamp: January 25, 2013, 05:17:58 pm
content: @Nixxon, The self-cal procedure takes about 20-30 s. During the process, you can hear a number of relays clicking. Because I was not sure if the cal procedure works for both or each channel, I repeated it twice (once for each channel). I had all inputs and outputs floating during the procedure.As for the traces, I only have a 2 channel oscilloscope so what you can't see is the triggering on the Sync out signal from the back of the SDG1020. The signal is relatively low but even the low trigger level is more than sufficient to trigger correctly IF the signal output is correct. Even if I trigger on Channel 1 or 2 rising edge, the same result will be seen. By using the sync out signal, I am trying to demonstrate the jitter with respect to the internal clock as opposed to the jitter from channel 1 to 2 or vice-vera. If the picture looks unintelligible, that is because that is how bad the jitter and glitch problem is! I captured using infinite persistence for only 10-15s at a rate of up to 10kwfms/s.

author: nixxon
author_rank: Frequent Contributor
timestamp: January 25, 2013, 06:51:20 pm
content: Maybe you could try some screen captures in persistance mode with trigger on the waveform itself rather than the sync signal. That gives one less source of error.I have noticed that the sync signal on my SDG1020 is not at the beginning of a waveform. It is rather in the middle of the waveform somewhere.10kwfms/s is pretty nice. I have read somewhere that the DS1000E series has ~800 wfms/s.

author: rf-loop
author_rank: Super Contributor
timestamp: January 25, 2013, 06:54:50 pm
content: Quote from: BlueLaser on January 25, 2013, 03:37:54 pmNo, these reistors change do not change this timing jitter. It affect voltage glitches there before rising edge in images.Also these do not help phase error.Just specially square wave is exeption...It is also why there in specifications read:(and note word "typical!")Is it typical if 97.5% of samples show under 0.1% time error and all rest show example max 0.3%?And this is jitter +- time from exactly right.Of course becouse jitter is random it may show Channel to Channel peak error double.But if jitter type time error... long time frequency is just as accurate as freq reference. Using external reference for SDG and frequency counter can proof it very easy.Jitter (in this square wave and specially only in it) come from system how it is produced.Square wave is derived using PECL comparator from internal sinewave what is produced in DDS system as also normal sinewave out. In Square function system produce sinewave frequency (what freq you set for sqr) with fixed level and it go to comparator. This comparator method is not very accurate due to many type of error sources... sivevawe have noise... all have noise... and then there come slowly changing (lo freq) sinewave and comparator look if it go over voltage treshold. (this voltage treshold is also used for adjust duty%)Sinewave to comparator other input.Treshold (Duty% adjust) to other input.Out square.These resistors affect ONLY to PECL Comparator hysteresis. Changing this hysteresis can reduce voltage glitches, as shown in test images before.PECL is:Analog Devices ADCMP562If need square wave but better accuracy... I recommend use pulse mode.Here is what datasheet tell about square.

author: nixxon
author_rank: Frequent Contributor
timestamp: January 25, 2013, 07:29:40 pm
content: Att: rf-loopDo you know how to perform a SelfAdjust procedure properly?Do you know the specs of the sync signal of the SD1000 series?I have noticed that the sync signal is a pretty short pulse (manual: ">50ns") that is occuringsomewhereduring anarbitrarywaveform. I do not recall where it occurs during a built in wavfeorm.Siglent should supply us with a FW update that - among other things - gives us more sync signal options. I wish generally that Siglent were open for suggestions and had the ability to improve their equipment's user experience. It seems like a one way street with Siglent.

author: BlueLaser
author_rank: Contributor
timestamp: January 25, 2013, 07:42:40 pm
content: Yeah, RF-loop, I have to say, you're amazingly knowledgeable and familiar with this system. If I didn't know any better, I would say you were a consultant! So it would seem that you're describing a square wave formed from comparator filtering of a sine wave--thus amplifying any error in the sine generation. I wonder why they chose the square wave to be generated like this instead of DDS. So at least pulse mode allows the DDS generation of the signal but unfortunately, that is limited to 5MHz in stead of 20.I too noticed the very short and low sync pulse which is not aligned to the edge of the actual square wave... but that now makes sense based on how rf-loop described the generation of the square wave. That must be the trigger point for the ADCMP562. I also agree with nixxon that the unit has some pretty nice high spec parts inside. I found mine has exclusively Rubycon 105°C Aluminium caps inside which quite nice. I feel a little bit of firmware work could really take this generator to the next level. I should probably talk to them some more but I need to buy some resistors to get this repair job done first.

author: nixxon
author_rank: Frequent Contributor
timestamp: January 25, 2013, 08:27:07 pm
content: Quote from: BlueLaser on January 25, 2013, 07:42:40 pmI understand that RF-loop, among other brands, is a supplier of Siglent gear in Finland.I was thinking of user: aghp.By the way, I don't know anything about high spec parts inside the Siglent AWG's. I have never opened my unit and I don't know much about the internals.However, after some research before I bought an AWG, the Siglent came out pretty good. Just a hairs width better than Rigols DG1022. I did not (and do not) believe, that Atten is the principal in the Atten-Siglent relationship. I believe Siglent is.So, LULU and Jelin Wei @ Siglent: You travel the World on behalf of Siglent, you attendElectronicain Munich, Germany, you communicate with your customer and hopefully with your company's decision* makers: Keep it up, and polish your FW in particular and customer relations in general! We demand more of your good stuff*the selection between possible actions

author: nixxon
author_rank: Frequent Contributor
timestamp: January 25, 2013, 11:07:47 pm
content: I activated "SelfAdjust" and now the DC output is exactly 1 mV more off than before.There has to be a correct way to perform this "SelfAdjust" procedure...I wonder what will happen if both channels are shorted to ground while doing it? As I do it, I will measure current between signal and ground as I "SelfAdjust"...EDIT: With DMM in mA/A mode connected between CH1 signal and GND, nothing was registered on my DMM (Fluke 87) while "SelfAdjusingt" the SD1020.

author: rf-loop
author_rank: Super Contributor
timestamp: January 26, 2013, 10:34:54 am
content: Quote from: nixxon on January 25, 2013, 11:07:47 pmSelfcalibration (or perhaps "self adjusting" is better) do not use any external references. It is fully internal process and its meaning is partially compensate components drifts and offsets from nominal. There are lot of components together and many things cross affect each others. There is filter networks, amplifiers, attenuators etc etc. Self calibration do lot of things but of course there is still many errors left after sefcal. Your SDG go littlebit worse with one parameter. Did you check all combinations what go better?Always also drift may be to good direction or to bad direction. If it have gone to good direction then selfcal return it to littlebit bad direction. Also selfcal, as all things, is not "ideal" and repeating selfcal every result may be littlebit different. It is just how it randomly go (there is random things affecting). Also internal reference, timebase and voltage reference(s) may drift and may have more or less initial errors (including they noise) to nominal value and who knows if they drift to good or bad direction or randomly both direction. World is full of errors and all what you see is sum of all errors, including (small part) also your measurement errors.Siglent specifications tell that 100kHz sinewave 1Vpp is inside specs if it is ~995.5mV to ~1004.5mVand if follow this specs 10mVpp same signal... it is 8.965 - 11.035(±(0.3dB+1mVpp of setting value)And then flatness ±0.3 dB compared to 100kHz (specified using 5Vpp signal) (so if you measure other than 100kHz there can add this flatness error. It means that there is +-0.6dB "window" (+- this 1mV) for level.Example: If set output to 50Hz and 10mVpp and someone tell that there is 12mVpp. 20% more than setting. It is still inside specifications.DC output accuracy is not separately specified and we can only believe it is somehow in same kind of accuracy class as vertical accuracy is specified.If read as it can read.. DC frequency is zero. Vertical accuracy is specified by 100kHz and then there is specified flatness. Flatness is relative error to value in specified frequency.If 100kHz is maximum off, example -0.3dB (and 1mV) and if we go to lower or higher freq with flatnes specs +-0.3dB we can see that total can be -0.6dBIn low end of frequency there is 0Hz, 1uHz, 2uHz etc.. and we call this oHz as DC. We have no any method for look if there is extremely low frequency or just zero... of course if we have 1uHz it is easy to see just wait 1000000 second for whole phase. But if you measure (and do not know any other things that voltage you see... how it can know it is DC or extremely low freq AC - (I do not know any method)With this thinking we can stretch thinking from Siglent specs for 100kHz to DC and think it is maybe in specs if it have 0.6dB +1mV errorwithout loadingand AC is same if there is not resistive or reactive loading..If need more accurate dc (or ac), just adjust it together with measurement in system where it is use.This is always normal everyday practice in lab works where need more accuracy that specs limits.

author: nixxon
author_rank: Frequent Contributor
timestamp: January 27, 2013, 02:42:21 pm
content: Does anybody know how many mA the DC output of the SDG1000 series can handle?And how does the unit handle a short?I guess it is not supposed to be used as a PSU.

author: rf-loop
author_rank: Super Contributor
timestamp: January 27, 2013, 03:26:39 pm
content: Quote from: nixxon on January 27, 2013, 02:42:21 pmSame as what ever signal from SDG BNC.Source impedance is 50ohm (always), no exeption.If you load it with 50ohm you get half compared to "open".If you set SDG output for 50ohm it correct display to show voltage to 50 ohm load.5V and short circuit: current is around 100mACH1 output amplifier is TI3095CH2 output amp is Intersil EL5166Between out amp and BNC out there are 50ohm resistor.It can say it is short circuit protected but still I do not recommend continuous short circuit.It can also find in user manual.....it is a good idea to read at least once even if it is really poorly written."SDG1000 Series has a fixed 50? Series Impendence. No matter what valuethe set parameter is, if the real load is different from the set one, the displayedvoltage will not equal the real voltage"

author: rf-loop
author_rank: Super Contributor
timestamp: January 30, 2013, 08:20:32 am
content: I will later make some more tests and explanations (nearly total lack of time now and also waiting some components)You find more info here about Square wave in SDG1000 series.Quote from: nixxon on January 25, 2013, 07:29:40 pmHere more about SDG1000 series SyncOut "secrets" and "freaks"

author: rf-loop
author_rank: Super Contributor
timestamp: January 31, 2013, 11:55:01 am
content: I will update explanations here later after it is "ready". If I slowly add and edit it here it is nearly as "spamming" here so I will avoid this.(first I will add more and more tests and explanations about SyncOut (and TrigOut) to this before linked other place. I can not do this all at once so I will first edit and add all info slowly to this other place becouse I can use only small time slices for this work. You can follow up this work there.)

author: BlueLaser
author_rank: Contributor
timestamp: February 04, 2013, 08:19:09 pm
content: So I finally got the replacement 20k 0603 resistors for R82 and R87. I forgot why I never order smaller than 0805 for hand soldering. After much care, I managed to get the new parts in placeand tested the output. Here is the brief synopsis and results:Old values 40 k? (40.02 k? and 40.03 k? measured),New Values 20 k? (19.907 k? and 19.914 k? measured)I de-soldered the old parts and measured them using a Uni-Trend UT61E multimeter and found them to be in very good agreement and very close to the listed value of 40k. This is probably because the hysteresis response should be as similar as possible between the two channels. I only had 5% resistors which I could find for cheap so I decided to manually bin them and measured about 20 values and found a pair which were off by only 7 ohms (<0.05% variance, ?0.5% tolerance). As I said before, I think the variance is more important than the tolerance. I found that the high frequency response (>2MHz) is definitely corrected and acceptable but the low frequency response (while having fewer random glitches) has more full transitions. There is a bit more ringing than before in the output signal at higher frequencies but the lower seem to have less overshoot and pre-shoot. As RF-loop said, at lower frequencies the Pulse function does work far better as it is DSS.I've also included pictures of parts of the board. I have to warn those who might want to do this repair, it is not for the faint of heart. I have a hot air rework tool but was afraid of overheating the board. I decided to use a blade soldering tip to get the parts on and off but being so small, it was very difficult. I wore 2 esd straps and worked on a static mat the entire time.

author: BlueLaser
author_rank: Contributor
timestamp: February 04, 2013, 08:25:02 pm
content: Sorry, PDF seems to have not attached correctly, here are scans.

author: rf-loop
author_rank: Super Contributor
timestamp: February 05, 2013, 09:06:36 am
content: My opinion for measuring glitches and jitter.Use CH1 for trig directly from signal itself.Measuring trig out or syncout jitter related to signal is other case.

author: nixxon
author_rank: Frequent Contributor
timestamp: February 05, 2013, 02:36:12 pm
content: Agree. Set scope settings to Horizontal scale = 20 ns/div and Vertical = 100mV/div.Show one trace only. Trigger on the trace itself and not the sync signal.