Best arbitrary waveform generator for around $500 - Page 1
Forum section: electronics / testgear

author: nbritton
author_rank: Frequent Contributor
timestamp: September 16, 2015, 03:53:17 am
content: I'm thinking about getting a 300 MHz scope and I'd like to get an arbitrary waveform generator that is matched for the scope. The system bandwidth of the scope is about 230 MHz, and dividing that by ten yields 23 MHz... thus I'm thinking that I should be looking for AWG that can generate up to 25 MHz square waves. What do you recommend? I'd like to stay under $500. Any thoughts on the Siglent SDG2042X?Edit: also what are the practical advantages of an arbitrary waveform generator vs a regular arbitrary function generator? Is it worth spending a little extra to get the AWG functionality?

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: September 16, 2015, 05:21:32 am
content: Quote from: nbritton on September 16, 2015, 03:53:17 amIt depends on what you want, really. In this price class you'll get good basic functionality but the AWG function is often pretty basic, and the included software is mostly crap.Have a look at the Siglent SDG1025, it should fit your budget and can do square up to 25MHz. Plus it has been on the market for a long time and is now pretty mature.QuoteWell, it's not even available yet, but the basic specs look ok. The listed 1GSa/s sample rate seems a bit bogus as it looks to be a 4x oversampled 300MSa/s signal, plus it's only for the standard waveforms (sine, square, pulse, triangle), the arbitrary sample rate is much lower (but that's the case with many low end AWGs). Plus there's the risk of all Siglent gear that it's firmware will be full of bugs and it will them take forever to sort that out, as it has been the case with other Siglent devices.QuoteAs the name says, a AWG can produce arbitrary waveforms, i.e. non-standard waveforms, while a function generator only generates standard waveforms like sine, square and triangle. An AWG allows you to define your own waveforms and load them into the AWG.QuoteDepends on what you want to do.

author: dkozel
author_rank: Regular Contributor
timestamp: September 16, 2015, 07:52:17 am
content: I just bought a Siglent SDG1025 so I'm in agreement with Wuerstchenhund. For me the second channel was a big feature. It's cheaper than your budget and doesn't have too many quirks. Even with the 800 line and the upcoming 2042X they've put out a firmware update recently, and bonus, it has a menu for bandwidth upgrading. The upgrades aren't available, so either there's an announcement coming or the firmware is being shared with the upcoming line which would be great.For me the arbitrary function was a matter of flexibility. Being able to generate simple baseband IQ signals or record a signal with an oscilloscope and play it back are really nifty features, and very useful for some applications.

author: dadler
author_rank: Unknown
timestamp: September 16, 2015, 10:18:45 pm
content: Out of your price range, but here are my votes:Rigol DG4062Rigol DG1032Z (I used to have one of these, thought it was a great generator! Upgraded to an Agilent)

author: nbritton
author_rank: Frequent Contributor
timestamp: September 17, 2015, 02:13:51 am
content: Quote from: Wuerstchenhund on March 21, 2013, 08:34:56 pmWhy are you giving the SDG1000 praise in this thread and bashing in the other thread?

author: nbritton
author_rank: Frequent Contributor
timestamp: September 17, 2015, 02:54:26 am
content: Is the 125 MSa/s on the SDG1000 enough fidelity to reproduce a sine or other arbitrary waveform at 25 MHz? That would seem to only be 5 samples per clock at 25 MHz. Doesn't seem like enough.Is $500 a reasonable amount for this type of device, or should I up my budget?

author: jhufford
author_rank: Contributor
timestamp: September 17, 2015, 03:43:20 am
content: I'm in the market for a function gen too. And I'm considering the SDG1025 as well as the 2000 models. I'm willing to spend the $900 for the 2122X model, if it's worth it.Why does the 2000 series have such a measly arb sample rate (75MSa/S), while sporting a 1.2GSa/S rate on the built-in waves. But the 1000 series has 125MSa/S for both. The 5000 series has 500MSa/S for both. Ideas?Thanks.

author: rf-loop
author_rank: Super Contributor
timestamp: September 17, 2015, 05:02:50 am
content: Quote from: jhufford on September 17, 2015, 03:43:20 am2000X working principle is totally different compared to SDG800, 1000 and 5000 series!SDG2000X do not jump over data points. It is not ordinary fixed clock and fixed Arb memory lenght as Siglent model series without X and many other brands DDS Arb what use this simple working principle. There is good to read articles available example from Agilent (Keyshit)If think ordinary DDS Arb with fixed 125 or 100 or 500 or 250 or what ever sampling speed there is allways one sample period time jitter (exept example with sine wave or some other waveforms what are not generated from arb data point table at all.SDG1000. Lets go tto over simplified but it may give some idea what is going on there...Maximum Arb frequency is 5MHz. Arb memory lenght is fixed 16kpoints. It "walk" over this 16000 memory up to 5000000 times in one second. Lets calculate first thing.16000 x 5000000. It is 80000000000.Do it have time to set output level 80000000000 times in one second? (Sampling speed is fixed 125000000 times in one second.) Really not at all.What is going on... 80000000000/125000000=640. Oh no and wow...what a hell...Do it mean it can read only every 640th point in arb memory.... or what. How it is possible. (and endless loop of noobs questions)At this time you can go and read theory books how Arb generators different working principles do it. Reading only is not enough. These need also understand.SDS1000 have 125MSa/s system... and with max arb freq 5MHz there is just one 8ns "time slice" for 640 memory points. Only solution is that it NEED jump over Arb memory points. And in practice, it do it, and many of other brand simple DDS Arb generators do just same.SDS2000X have only 75MSa/s and there is claim it do not miss sample points...How it is possible? Its working principle is NOT fixed clock and fixed memory lenght... just as before, now is time to go study more about how different Arb working principles solve this.And also 7 points wink: SDS2000X DAC's works out with 1.2Gsa/s.A. Study, get experience, study, get experience, study.. Repeat A until individual time for dementia start. (kind of sarc.)

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: September 17, 2015, 05:28:35 am
content: Quote from: rf-loop on September 17, 2015, 05:02:50 amIt's been a long time when I had an SDG1000 so I can't really remember (and I didn't make much out it's arbitrary function anyways) but being able to use variable sample clock and a variable amount of sample memory on the SDG2000X is really nothing new, even in this price class. The Rigol DG1000z can do that, and I'm sure the DG4000 (which has been on the market for a pretty long time now) can as well. It's also pretty standard for the AWGs from the big brands (except maybe LeCroy, as they are selling rebranded Siglent SDG1000/5000 AWGs).So you're saying that even the Siglent SDG5000 uses a fixed clock and memory only? If so then this makes me really glad I didn't buy one.

author: rf-loop
author_rank: Super Contributor
timestamp: September 17, 2015, 07:03:33 am
content: Quote from: Wuerstchenhund on September 17, 2015, 05:28:35 amWho have told it is something new?It is new in Siglent series of generators and Siglent have done it with they own way.Do you know that my own 40 years ago made pulse generator is very good. My 30kEur Agilent spectrum analyzatror is total crap junk...etc. What is good or crap and junk depends what we hope and need.Why I buy SDG1000 if I can not accept 8ns cycle-cycle arb or pulse mode designed jitter what is specified. If I need less than 0.1ns jitter and I buy SDS1000 for this need I can not tel SDS1000 is crap junk. I can tel I'm stupid and crap when I do not understand what I'm buying and so lazy that do not first study and design and after then do.My opinion is that SDG1000 is still good for many purposes and one of best in its price class overall.Many many times I personally need much much better equipment but many times also SDG1000 is well enough.

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: September 17, 2015, 11:02:05 am
content: Quote from: rf-loop on September 17, 2015, 07:03:33 amNot sure what you're getting so excited about. I certainly don't blame the SDG1000 for what it is, its specs or the sample clock and memory size limitations, because I think for its age (it's an older design now after all) and its price range its still a good offering.However, I would have thought that the SDG5000, which much newer and more expensive and supposed to be in the same class as the Rigol DG4000, wouldn't suffer from the same limitations re. sample clock and memory length, and the fact that it seems to do is pretty poor.Just out of curiosity, I guess the AWG in the SDS2000 comes with a similar sample rate/fixed memory length limitation as the SDG1000?QuoteWhat model would that be?

author: fanOfeeDIY
author_rank: Unknown
timestamp: September 18, 2015, 03:59:38 pm
content: I am not good at arbitrary function generator but I see this model at the shop with reasonable price.GW Instek AFG-2000http://www.gwinstek.com/en-global/products/Signal_Sources/Arbitrary_Function_Generators/AFG-2100_AFG-2000

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: September 18, 2015, 05:17:01 pm
content: Quote from: fanOfeeDIY on September 18, 2015, 03:59:38 pm20MSa/s sample rate and 4k memory? Wow, that's pretty pathetic for a device that in its cheapest variant (5MHz) costs around $300:http://www.newark.com/gw-instek/afg-2005/signal-generator-arb-function/dp/79T9494?ost=GW+Instek+Afg-2005Even the cheapest Siglent AWG (SDG805) goes for $50 less and offers much better specs:http://www.tequipment.net/Siglent/SDG805/Function-Generator/Plus GW Instek's support generally sucks. Not just like Siglent and Rigol (which take care of easier problems although there's a lot of room for improvement), it really sucks, i.e. close no non-existent.

author: nctnico
author_rank: Super Contributor
timestamp: September 18, 2015, 05:24:16 pm
content: Generally speaking: every time I looked at GW instek I noticed it is very expensive rebranded low end (far below Siglent and Rigol) gear.

author: wraper
author_rank: Unknown
timestamp: September 18, 2015, 06:08:18 pm
content: Quote from: nctnico on September 18, 2015, 05:24:16 pmCan you say what particularly? I'm not aware of GW instek rebranding anything, only the opposite way - GW instek gets rebranded and sold under more expensive brands. Also QC at instek is far better than both Rigol and Siglent.

author: BloodyCactus
author_rank: Frequent Contributor
timestamp: September 18, 2015, 06:27:58 pm
content: Id take instek > rigol + siglent any day for comparative gear.saying that, I have a Rigol 1032Z, I dont use the arbitrary much so cant comment on it, but its square wave beyond say 10mhz is crap. at its max supported 15mhz is pure crap, its just a sine wave! it has great memory depth for its arbitrary stuff but not really the bandwidth/speed to do precision stuff thats non sine!

author: nctnico
author_rank: Super Contributor
timestamp: September 18, 2015, 06:33:39 pm
content: Quote from: wraper on September 18, 2015, 06:08:18 pmwww.ebay.com/itm/LCD-VARIABLE-REGULATED-DIGITAL-DC-POWER-SUPPLY-30V-3A-/110674399053http://uk.farnell.com/gw-instek/gps-3030d/power-supply-dc-30v-90w/dp/2071104

author: wraper
author_rank: Unknown
timestamp: September 18, 2015, 08:43:01 pm
content: Quote from: nctnico on September 18, 2015, 06:33:39 pmThey are completely different power supplies of completely different quality. Don't you see completely different displays, additional switch for current ranges? Nothing similar on the back too. This is 20 years old model BTW. Rigol didn't even exist back then.

author: nctnico
author_rank: Super Contributor
timestamp: September 18, 2015, 09:14:31 pm
content: They look similar enough to come from the same factory. Minor differences between the models don't change the factory where they are made!

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: September 18, 2015, 09:45:09 pm
content: Quote from: BloodyCactus on September 18, 2015, 06:27:58 pmI wouldn't, and I'm not exactly a fan of Siglent or Rigol. And that is if there even is any comparative gear, which often there isn't because the GW Instek counterparts comes with outdated specs from a bygone era.QuoteHow exactly did you come to the conclusion that it is a sine wave? If your DG1032z produces really a sine wave when in square mode then it's defective, or you're doing something very wrong. At the moment my money is on the latter as my DG1062z (which has similar performance specs) produces a perfectly fine square wave within the limits of its specifications.

author: tautech
author_rank: Super Contributor
timestamp: September 18, 2015, 09:46:01 pm
content: Quote from: wraper on September 18, 2015, 06:08:18 pmNot wanting to get into a shit fightbut your evidence for this claim?Equipment failure % ? Component quality? Build quality?

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: September 18, 2015, 09:48:00 pm
content: Quote from: nctnico on September 18, 2015, 05:24:16 pmGW Instek gear always reminds me on kit I've seen from other brands 15 years ago, and the specs are often from a similar era.I also can't remember that they ever came up with something remarkable.Quote from: wraper on September 18, 2015, 06:08:18 pmNo, it isn't. In my direct environment there are quite a few GW Instek devices, and while the general build quality is OK-ish (not great, still better than Atten), I've seen quite a few of QC issues (i.e. loose missing screws on a scope, loose PSU on another, and a good number of DOAs). The support was also less than stellar (actually pretty much the worst in T&M I've ever seen, and I've seen a lot!) and pretty much for most part really didn't give a shit. Rigol and Siglent are far from perfect and leave a lot to be desired, but in terms of QC where they are today is a much better place than where GW Instek has ever been in its existence.Seriously, I wouldn't know why anyone would ever consider them, unless you're a Taiwanese who wants to shop patriotically. Their gear's specs are from OK-ish to awful, the prices are at least as expensive (usually even more) than better-spec'd gear from other brands, the quality often isn't up to standard and the support is poor. If they were to close tomorrow, I don't think it would be a huge loss.

author: wraper
author_rank: Unknown
timestamp: September 18, 2015, 09:49:14 pm
content: Quote from: nctnico on September 18, 2015, 09:14:31 pmLOL. Power supplies in this form factor come from dozens of Chinese factories.EDIT: considering the age of these series of Instek PSU's, quiet likely that others just cloned their look. That Mastech one is quiet decent among them actually. Most of them are useless and dangerous crap. BTW Instek gear is produced in Taiwan unlike those Chinese cheapies.Similar???

author: wraper
author_rank: Unknown
timestamp: September 18, 2015, 10:00:04 pm
content: Quote from: Wuerstchenhund on September 18, 2015, 09:48:00 pmLook at their new GDS-1000B series oscilloscopes (if not considering hacking, beats DS1000Z in almost every way including price, unfortunately no options for purchase available), GDS-2000A oscilloscopes. But yes, they were slow to update their product lines when Rigol DS2000 series came but their entry level scopes remained like DS1000E for many years.

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: September 18, 2015, 10:18:36 pm
content: Quote from: wraper on September 18, 2015, 10:00:04 pmNot sure the GDS1000B really beats the DS1000z in almost every way, as the Rigol has more memory (12/24Mpts vs 10Mpts on the GDS1000B), plus it's also cheaper:http://www.newark.com/gw-instek/gds-1054b/oscilloscope-4-ch-50mhz-1gsps/dp/51Y5253http://www.tequipment.net/Rigol/DS1054Z/Digital-Oscilloscopes/The only positive I can see on the GDS1000B is that FFT uses up to 1Mpts compared to a few thousand points with the Rigols (all of them up to the DS6000) and the digital filter, and I haven't yet seen a GDS1000B in the wild but I'd guess FFT at full 1Mpts will be dog slow due to the large amount of data that needs processing (which the processors found in these low-cost bottom-of-the-barrel scopes can't perform in reasonable speed). The GDS1000B is listed with a higher waveform rate (50k vs 30k for the Rigol) but I doubt that makes much of a difference. Plus based on what I've seen with other GW Instek products I would trust them with their firmware even less than Siglent or Rigol.QuoteYes, but the DS1000E offered the right amount of features for its time and was priced right, both which isn't often the case with GW Instek gear.

author: wraper
author_rank: Unknown
timestamp: September 18, 2015, 10:30:50 pm
content: Quote from: Wuerstchenhund on September 18, 2015, 10:18:36 pmComparing apples vs apples, not newark prices?http://www.tequipment.net/Instek/GDS-1054B/Digital-Oscilloscopes/?v=0QuoteFFT is not slow and actually becomes a usable feature in the scope. It has faster waveform update rates too.

author: jhufford
author_rank: Contributor
timestamp: September 18, 2015, 10:50:18 pm
content: Wow, thanks for the info rf-loop! You're correct, I need to study, I don't know much about function gens, haven't used one since the circuits 101 days in college, and I've never played with an arb gen. But I'm trying to learn now as I finding myself needing a function gen, so thanks again for the info! it helped send me down the right path.

author: BloodyCactus
author_rank: Frequent Contributor
timestamp: September 18, 2015, 11:48:32 pm
content: Quote from: Wuerstchenhund on September 18, 2015, 09:45:09 pm

author: dadler
author_rank: Unknown
timestamp: September 19, 2015, 12:35:15 am
content: What does it look like @ 1Vpp (assuming proper termination)?Rigol specs: Square Rise/Fall Time Typical (1 Vpp) <10nsFWIW: I tested the internal AWG on my DSOX3000T, and I see similar results (rise time is about 18ns). This was 5Vpp@10MHz as the internal AWG maxes out at 10MHz for square wave output.

author: nbritton
author_rank: Frequent Contributor
timestamp: September 19, 2015, 05:20:12 am
content: Quote from: jhufford on September 17, 2015, 03:43:20 amIt appears that the SDG2000X has two arbitrary waveform modes, TrueArb mode (low jitter) which is 75 MSa/s and DDS mode (normal jitter) which is quoted as 300 MSa/s minimum. In the datasheet it also states that the device can do 20 MHz in arbitrary mode, whereas the SDG1000 is limited to 5 MHz. Additionally it appears that the modulation speeds are significantly faster. On the SDG2000X it quotes a max of 1 MHz, whereas on the SDG1000 it quotes a max of 20 KHz.

author: Armxnian
author_rank: Regular Contributor
timestamp: September 19, 2015, 06:12:14 am
content: Quote from: dadler on September 19, 2015, 12:35:15 amRise time seems to stay constant on the sdg1025. About 7ns for a square, which is pretty good. But the performance starts to fall off after 1MHz @1vpp. At 25MHz the square wave is almost indistinguishable from a sine wave. Amplitude doesn't affect performance that much.The spec Siglent publishes is correct, but it's kind of meaningless if the square wave rated for 25MHz starts to transform after 1MHz.

author: nbritton
author_rank: Frequent Contributor
timestamp: September 19, 2015, 08:53:39 am
content: What about the Hantek HDG2000B series. The HDG2002B is a bargain at $300 and it can be hacked to 100 MHz.

author: Groucho2005
author_rank: Regular Contributor
timestamp: September 19, 2015, 09:04:04 am
content: Quote from: Armxnian on September 19, 2015, 06:12:14 amWhat scope did you use? Some SDG1025 screen shots taken with a reasonably fast scope:https://www.eevblog.com/forum/testgear/show-us-your-square-wave/msg588973/?topicseen#msg588973The 25 MHz signal is certainly no square but also far from a sinusoid.

author: wraper
author_rank: Unknown
timestamp: September 19, 2015, 10:55:05 am
content: Quote from: Wuerstchenhund on September 18, 2015, 09:48:00 pmI had to deal with Rigol warranty in EU. Can say it's almost non existent too. Then how about 2 Rigol DM3068 multimeters of almost the same date code and same PCB revision. One has two bodge wires on PCB and multiple ICs hand soldered (after a week developed strange AC range failure affecting precision), the other does not have all of that mess. Seems the first one had some issues at production and was heavily reworked. Huge quantity of flux residues were not cleaned too, and all of that over the places where guard rings are present. I have disassembled Instek gear and PCBs where very nice and clean.

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: September 19, 2015, 11:50:37 am
content: Quote from: wraper on September 18, 2015, 10:30:50 pmStrange, it didn't show up when I searched, But I stand corrected.QuoteAs I said I haven't seen any GDS1000B in the wild (people here are pretty much cured from GW Instek) but I'd be really surprised if this $400 scope could handle 1Mpts of FFT data with its processor, something which puts even many more powerful scopes under visible strain.

author: wraper
author_rank: Unknown
timestamp: September 19, 2015, 11:57:29 am
content: Quote from: Wuerstchenhund on September 19, 2015, 11:50:37 amOn the video FFT on GSD-1000B is much faster than on DS-1000Z. Should be done in the FPGA.

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: September 19, 2015, 12:26:50 pm
content: Quote from: BloodyCactus on September 18, 2015, 11:48:32 pmNo, it isn't. It's not a perfect square but it's far from being a sine wave (and even less os a pure sine, which doesn't occur in reality anyways).BTW, my DG1062z shows the same, which is not surprising considering the similarities:1MHz:15MHz:A quick view on the signal's frequency spectrum not only shows that this clearly isn't a sine wave but also explains why the 15MHz square wave looks like it does:It's clearly visible that the 15MHz signal contains non-harmonic components, plus some of the expected harmonics are missing.A check with a proper spectrum analyzer confirms the malformations increasing with the frequency increasing:1MHz:3MHz:5MHz:10MHz:15MHz:However, that's an imperfection that the DG1000z shares with many other AWGs in that price class, and if you believe that a GW Instek device performs any better then I'd say you're deluding yourself.There simply are limits what one can expect when buying low end gear, and that's true for AWGs as well. Maybe the new Siglent SDG2000X does better in this regard, but I'm not holding my breath.Edit:I forgot to mention, the scope used is a LeCroy WavePro 7300A (3Ghz 20GSa/s 48Mpts) connected via a 50ohms BNC cable (tested to 2.7GHz) directly into the scope. The spectrum Analyzer is a Rohde & Schwarz FSP7 (7Ghz), again using the same cable setup plus a Pasternack BNC-to-N adapter.

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: September 19, 2015, 12:34:17 pm
content: Quote from: wraper on September 19, 2015, 11:57:29 amYes, on a promotional video made by GW Instek, with no visibility of the test parameters and scope settings.No thanks, I'd wait until I see some independent confirmation before I believe them.Plus it seems GW Instek still shoots it's videos on an old VHS camcorder, but hey at least it's in color and not black & white.On the other side, the care GW Instek shows to their online representation does very well reflect the care they show towards their customers.

author: wraper
author_rank: Unknown
timestamp: September 19, 2015, 02:25:31 pm
content: Quote from: Wuerstchenhund on September 19, 2015, 12:34:17 pmYou were concerned about FFT being very slow. IMO that video is completely enough to see that it is not the case.

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: September 19, 2015, 02:50:39 pm
content: Quote from: wraper on September 19, 2015, 02:25:31 pmNo, I was concerned aboutFFT over 1Mptsbeing slow.QuoteNo, it isn't. All it does is show the scope doing some FFT over an unknown number of points (and any scope is fast at FFT if the number of points is sufficiently low). And thanks to the crap low resolution video it's even impossible to see what the actual settings are.As a demonstration of the claimed capabilities of the GDS1000B the video is pretty much worthless.

author: Armxnian
author_rank: Regular Contributor
timestamp: September 19, 2015, 06:58:43 pm
content: Quote from: Groucho2005 on September 19, 2015, 09:04:04 am25MHz Sine:25MHz Square:What itshouldlook more like, 1MHz Square:

author: nbritton
author_rank: Frequent Contributor
timestamp: September 19, 2015, 07:18:17 pm
content: It appears you're using the DS1054Z. You do realize you would need at least 225 MHz of bandwidth to faithfully reproduce a 25 MHz square wave on your scope. You would need to capture at least the 9th harmonic, which you can't do on the DS1054Z.Fundamental: 25 MHz3rd Harmonic: 75 MHz5th Harmonic: 125 MHz7th Harmonic: 175 MHz9th Harmonic: 225 MHz

author: Armxnian
author_rank: Regular Contributor
timestamp: September 19, 2015, 07:30:11 pm
content: At 25MHz, the 9th harmonic doesn't even exist. That's the point we're trying to make. At that frequency, it's transforming into a sine wave. As Wuerstchenhund showed, the spectral content of the square wave at the high frequency does indeed contain characteristics of a square wave, but not as much as you would like, at least on the sdg1025.

author: nctnico
author_rank: Super Contributor
timestamp: September 19, 2015, 07:45:53 pm
content: Well a square wave has an infinite number of harmonics so there is no signal generator to create the perfect square wave and there is no oscilloscope to view it. What is the point of all this?

author: Groucho2005
author_rank: Regular Contributor
timestamp: September 19, 2015, 08:27:07 pm
content: Quote from: Armxnian on September 19, 2015, 06:58:43 pmWithout knowing the bandwidth of the scope and how you measured this (probe or a properly terminated 50 Ohm cable) it's impossible to comment.

author: Armxnian
author_rank: Regular Contributor
timestamp: September 19, 2015, 09:07:03 pm
content: Quote from: Groucho2005 on September 19, 2015, 08:27:07 pmOutput is terminated into 50ohms on a 100MHz scope. But it doesn't matter, because I checked beforehand with a 1.5GHz SA and the content after the 3rd harmonic barely resembles a square wave.After 8MHz, which you can easily view on a 100MHz scope, you can see that the square starts to transform into a sine. Even after 1MHz you can see curves instead of sharply rising and falling edges. The scope does not lie. Sub 1MHz the output is great, not so much after. All of the other functions perform great, but the square suffers. IMO, if you're going to claim a "square" wave output at 25MHz, it better look something like it does in my 1MHz screen capture.

author: nbritton
author_rank: Frequent Contributor
timestamp: September 19, 2015, 09:08:17 pm
content: Quote from: Groucho2005 on September 19, 2015, 08:27:07 pmJudging by the screenshot he is using a Rigol DS1000Z. I see another critical problem with his measurement, on the screenshot you can see he is using a 1X probe. IIRC the Rigol probe derates in 1X mode to around 7 MHz of usable bandwidth. Furthermore, the DS1000Z doesn't have 50 Ohm termination, you would have to put the SDG1025 into Hi-Z mode and then plug the scope's 10X probe directly into the SDG1025's BNC connector.1000Z Bandwidth:Frequency Amplitude10 MHz 0.0 dBm100 MHz -1.5 dBm150 MHz -3.0 dBm393 MHz -10.0 dBm447 MHz -20.0 dBmThe system bandwidth (scope + probe) on the DS100Z is calculated at 83.2 MHz, in the dBm measurements above I don't know if they were taken using the scope's probe or using a BNC cable, it makes a difference.1/sqrt((1/scope bandwidth)^2+(1/probe bandwidth)^2) = system bandwidth1/sqrt((1/100 MHz)^2+(1/150 MHz)^2) = 83.2050294338 MHzSquare Wave:Fundamental: 25 MHz3rd Harmonic: 75 MHz5th Harmonic: 125 MHz7th Harmonic: 175 MHz9th Harmonic: 225 MHz11th Harmonic: 275 MHz13th Harmonic: 325 MHz

author: Armxnian
author_rank: Regular Contributor
timestamp: September 19, 2015, 09:28:55 pm
content: Quote from: nbritton on September 19, 2015, 09:08:17 pmI see that reading comprehension is a challenge for you.I set the scope to 1x to show that I was using a 1Vpp signal. I'm not using a probe, I'm using a BNC cable that goes into a T-connector with one side terminated into 50ohms. You don't need to view 13 harmonics to judge the performance of a wave.I was trying to help you make a purchase. If square wave performance was important to you I would have recommended to perhaps try something other than the SDG1025. But it seems you're more interested in finding errors in my simple setup. Good luck.

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: September 19, 2015, 09:32:25 pm
content: Quote from: nctnico on September 19, 2015, 07:45:53 pmThat is absolutely true.QuoteI guess the point is that at higher frequencies (i.e. >10MHz) the square wave produced by the Rigol DG1000z and Siglent SDG1000 is pretty crap, but this is true for most (all?) low end AWGs and a limitation that comes with the low purchase price.Quote from: Armxnian on September 19, 2015, 09:28:55 pmIf square wave performance is important then you have to invest a lot more money than the several hundred bucks for a low end AWG and you're probably looking into serious mid-range AWGs from Keysight or Tektronix which will set you back several grand.As the old saying goes, you get what you pay for.

author: nbritton
author_rank: Frequent Contributor
timestamp: September 19, 2015, 09:51:03 pm
content: Quote from: Armxnian on September 19, 2015, 09:28:55 pmWhere in your original post did you state the conditions of your test? You just posted a screenshot with no words, I can't read minds. Thank you for taking the time to test this, I was simply trying to make sure the test was setup properly.

author: dadler
author_rank: Unknown
timestamp: September 19, 2015, 09:57:01 pm
content: If you want fast edges, you have to pay for them. There aren't really any free lunches in AWGs.Square wave on my 33522B meets the rise time specs of 8.4ns (fixed, based on the implementation of the generator) all the way to 30MHz. But this is an expensive generator, and 8.4ns isn't even that fast.For the money, these low-end generators from Siglent and Rigol do offer good performance. If you need** fast edges, buy a higher end generator.**I can't imagine anyone buying an entry level generator "needs" super-fast edges.

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: September 19, 2015, 10:13:15 pm
content: Quote from: nbritton on September 17, 2015, 02:13:51 amYou're pulling stuff out of context. For a start,the posting you quoted is from 2013, and at that time some SDG1000 (including mine) were suffering from excessive jitter. Siglent later published instructions for a hardware fix, and that cured the problem. This most certainly isn't an issue for any SDG1000 bought today (or even in 2014).The other thing you would probably only understand if you read all my postings regarding the SDG1000 and AWGs in general is that my requirements even for personal T&M gear are probably much more stringent than for the average hobbyist, and bluntly spoken that simply means that stuff in the low end class is unlikely to be anything more than a toy for me. I bought the SDG1020 mostly out of curiosity of what you can get for the few hundred Pounds the thing did cost at the time, which is why when I wrote the posting in 2013 I didn't really care if my experiment with the firmware would brick my SDG1020 or not. Well, it didn't, and I later fixed the jitter problem, and my old SDG1020 now serves with a happy beginner.However, I'm also well aware that my own requirements aren't necessarily the same ones other people have, plus I know pretty well what you can get for your money. This also means that just because the SDG1000 didn't satisfymyrequirements (which it was unlikely to do anyways, even the more expensive Rigol DG1062z didn't do that!) doesn't mean it won't do for others. Considering what else is out there in this bottom-of-the-barrel price range, the SDG1000 is actually a pretty good offering.So yeah, I wouldn't buy a Siglent SDG1000 (or a Rigol DG1000z) again, but that doesn't mean they're also a bad purchase for everyone else!

author: Groucho2005
author_rank: Regular Contributor
timestamp: September 19, 2015, 10:33:33 pm
content: Quote from: dadler on September 19, 2015, 09:57:01 pmOr a dedicated pulse generator. Although these are getting rare.

author: nctnico
author_rank: Super Contributor
timestamp: September 19, 2015, 10:43:30 pm
content: Quote from: Wuerstchenhund on September 19, 2015, 10:13:15 pmI'm quite happy with mine but my typical use isn't very demanding on a function generator. I didn't even bother to fix the jitter problem and I don't take the AWG function serious. If I ever find myself in a situation where I need something better I simply buy something better.

author: nbritton
author_rank: Frequent Contributor
timestamp: September 20, 2015, 12:40:10 am
content: I'm mulling over the idea of going with the Hantek HDG2002B. This is a ~$300 5 MHz AWG that can be hacked to 100 MHz. Its datasheet says it's 16 bit with a 250 MSa/s and 64M memory depth. From what I understand its square wave output is similar to the units we have talked about in this thread, which is to say it's mediocre. However, its sine wave output appears good all the way up to 100 MHz. If I need high frequency square waves I'm thinking I could build a square wave generator circuit that is clocked using the sine wave output from the AWG.Also it apparently has 16 digital output channels, but I'm perplexed as to how these work... is it just a square wave output?Here is the datasheet for it, are the other specs comparable to the other units we discussed?:http://hantek.com/en/ProductDetail_12_149.htmlhttps://www.eevblog.com/forum/testgear/hantek-hdg2002b-awg-5mhz-or-100mhz-let's-see!/

author: nbritton
author_rank: Frequent Contributor
timestamp: September 20, 2015, 02:26:06 am
content: Which AWGs can I program with mathematical functions? i.g. algebra, trigonometry, and calculus.Edit: Also the HDG2002B runs Linux, does anyone know if I can drive the signal gen directly from a shell prompt or python script?Edit 2: Do you know of a signal gen that can be driven directly from a shell script?

author: nbritton
author_rank: Frequent Contributor
timestamp: September 20, 2015, 03:11:57 am
content: Why can't you just wrap a USB interface around a 18-bit DAC and call it done? I'm not understanding why these AWGs are so expensive.

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: September 20, 2015, 07:22:09 am
content: Quote from: nbritton on September 20, 2015, 12:40:10 amIt also seems to be highly unreliable, plus you don't even know how good its specs are above the guranteed 5MHz. Just because it can be made to output a something that looks like a 100MHz sine doesn't necessarily mean it's a true sine wave with low jitter. But I guess it depends on how much reliability you want and if you can afford to throw away $300.QuoteDon't underestimate the amount of effort required to generate a good square wave that isn't crap at with these low end AWGs.QuoteAny of them, just not on the device directly. An AWG reproduces a waveform it receives in binary (or proprietary) form, which aside from a number of built-in predefined arbitrary waveforms is usually created outside the instrument, i.e. on a PC running a waveform editor (which with cheap AWGs is also crap), or generated from MathLab or Excel.QuoteShell on what? On an external PC? Yes, you should be able do that with any AWG that comes with a remote control interface (LAN, USB, GPIB) and which supports some standard communication protocol like SCPI.QuoteSure you can, if you don't care about jitter or other distortions.QuoteThey're expensive because generating valid waveforms is a pretty complicated thing, even more so for square waves. Just converting some bitstream into an analog signal isn't enough.

author: wojt
author_rank: Newbie
timestamp: September 21, 2015, 04:29:17 pm
content: Quote from: Wuerstchenhund on September 20, 2015, 07:22:09 amPeople who hacked it to 100 MHz have also prepared calibration for this range. I have done it on my HDG and it works as good as I can measure and need.

author: nctnico
author_rank: Super Contributor
timestamp: September 21, 2015, 07:21:11 pm
content: That HDG2002B looks mighty nice when hacked to 100MHz. Can both channels do 20Vpp in the low frequency range?Edit: never mind. Seems the firmware is crap.

author: Howardlong
author_rank: Super Contributor
timestamp: September 21, 2015, 08:56:13 pm
content: Quote from: nctnico on September 21, 2015, 07:21:11 pmIt is. Although if you're into aftermarket adjustments, there's plenty to tinker with. As well as liberating it, I added an external serial port to mine, ethernet magnetics and RJ45, and a high speed frequency divider for use as a counter into the GHz. The hardware's not too bad, but you can't easily polish the turd that is the software.

author: jhufford
author_rank: Contributor
timestamp: September 22, 2015, 07:41:38 pm
content: Is it possible to make a relatively cheap circuit that can take a signal input and re-output it with really fast edges? In other words, if the edges aren't sharp enough, can you run it through another circuit to sharpen them up? My initial guess is this would work, but might make for some jitter due to imperfect triggering of the edge shaper. So maybe lower freq square waves (jitter is low % of fundamental) but with super sharp edges... Anyone?

author: nctnico
author_rank: Super Contributor
timestamp: September 22, 2015, 07:45:01 pm
content: Something like that is called a comparator. The low end ones have an open collector output, the fast ones have a push-pull output. Another option is to use an LVDS to CMOS receiver.