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Siglent SDG1020 Arbitrary FunGen- First Impressions and a possible Signal Glitch

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BlueLaser:
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 UT61E  :-DMM  and 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. 

Update
A 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 ohm well matched 0603 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. 

saturation:
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.

BlueLaser:
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?)

pauln:
I have this exact same AWG.  FWIW I have duplicated your settings into my old Owon DSO and do not get 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 

Mark:

--- Quote from: pauln on January 20, 2013, 10:41:58 am ---I have this exact same AWG.  FWIW I have duplicated your settings into my old Owon DSO and do not get the glitches shown in your pictures.

--- End quote ---

Same here with the same equipment as you.  No glitches with the OP's settings.   

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