Siglent SDG1010 Low Frequency Square Wave Issues - Page 1
Forum section: electronics / testgear

author: logictom
author_rank: Unknown
timestamp: December 07, 2015, 04:05:06 am
content: I was hoping to use a SDG1010 at work to generate a nice slow square wave as an in input to my test however when I go below around 5Hz, (5Vpp 2.5Voffset), I get multiple edges at the transition which my test will pick up as it is happy with at least 100Hz input.What spec would I be looking at in the datasheet to check if this is within normal operation?link to datasheetIs this type of output expected at low frequencies when running the output as a square wave?

author: tautech
author_rank: Super Contributor
timestamp: December 07, 2015, 04:18:51 am
content: Quote from: logictom on December 07, 2015, 04:05:06 amI'll get mine out and check for you but IIRC it should go much slower tha 1 Hz.While you're waiting can you check the FW # you have installed?

author: rf-loop
author_rank: Super Contributor
timestamp: December 07, 2015, 04:51:34 am
content: Quote from: logictom on December 07, 2015, 04:05:06 amHow old is yout SDG1010?On some older units there may exist some higher level glitches just before rising start corner and just before start of falling edge corner.In some older units there was more these. Later this was solved (it is HW thing)Later this problem was solved and these glitches pekaks reduced typically under 10% of level and also time before corner where they exist was reduced.This problem exist only in low frequencies SQUARE wave function. Square wave is derived from internal sinewave (system generates example 5Hz sinewave internally and then use harware PECL comparator for make square from sine. This have advantages and disadvantages. In some older units PECL comparator hysteresis window was too narrow. Also in some cases internal sinewave need bit more filtering before PECL due to system generated and natural noise.If it is old unit and have this special HW "problem", there is available knowledge how to make it bit better. (need SMD resistor/capacitor rework)If it is new unit what works normally there is still these some small clitches and if your system is sensitive enough for detect these and you want go over this problem, look where is your system treshold for detect/count pulses and can you rise this treshold so it is near half of level. Normal digital logick system tresholds for 1 or 0 are well defined in data books. If build some equipment these definitions are not wise to break.Simpest "solution" in practice for generate better (more clean) low frequency square waves with SDG1010 is:Do not use Square function!Use Pulse function for generate Square waves. there you can also set 50% duty so it is square wave. (or of course other dyty % or pulse width)With higher frequencies (I mean example hundreds of kHz or MHz range) Square give better result if look signal cycle to cycle time jitter. (Pulse mode have system 8ns jitter)

author: logictom
author_rank: Unknown
timestamp: December 07, 2015, 06:32:15 am
content: I upgraded the firmware to 1.01.0137R3 today with no change.The hardware is 02-00-00-23-24 if that means anything to you.I just tried it on the pulse function and it works a treat, thanks

author: rf-loop
author_rank: Super Contributor
timestamp: December 07, 2015, 11:11:03 am
content: I believe that your version is not at all these very old units where some individuals may have much more bad clitch issue in Square using low frequencies.These are measured from units what are made after Siglent regognize problem and made small component changes in HW.These are 1kHz. These corner clitches grow some amount when go more low frequencies, not so much if look levels but much more wide time window before corner. Of course comparator method can make much better but we talk still now very low price equipment.I have not here in my current location available test images using much lower frequencies.But perhaps these still can tell something about this thing.Measured with SDG1010 and if I remember right HW version starting number 2.(FW do affect anything with this special thing. It is pure HW thing)

author: logictom
author_rank: Unknown
timestamp: December 09, 2015, 12:00:01 am
content: The function generator seems to have gone totally out of whack since I upgraded it.I set it to 5Vpp, 2.5Voffset and I get 10.5Vpp out of the thing, if I switch between a few of the modes and back to square wave it is then set to 10Vpp 5Voff, then when I put it back to 5Vpp, 2.5Voff it then starts behaving itself better but then I still have to set the output to 3.9Vpp to get 5Vpp on the scope - very bizarre operation