ARB Function Generator - 25Mhz good enough or 100Mhz+ required? - Page 1
Forum section: electronics / testgear

author: Mecanix
author_rank: Frequent Contributor
timestamp: July 08, 2020, 02:48:39 pm
content: Hey guysStill in the process of empowering the R&D eShop with equipment and moving on to the waveform generator. Looking at several; all offering rather similar arb features and resolutions although timings varies a lot and so is the end cost.Under what circumstance(s) I would completely fail to design a circuit shall I omit getting the full 1 gazillion frequency super duper model? At the moment the shop focus on the automotive industry however there are days when I see expanding this to building intergalactic space ships' electronics too.Same question put in a different way; are you suffering that much with your 25MHz sine and 10MHz sq waves gen?

author: Bassman59
author_rank: Super Contributor
timestamp: July 08, 2020, 04:36:22 pm
content: Quote from: Mecanix on July 08, 2020, 02:48:39 pmI'm not sure how useful 25 millihertz sine waves are in real life.

author: tv84
author_rank: Super Contributor
timestamp: July 08, 2020, 04:46:46 pm
content: Quote from: Bassman59 on July 08, 2020, 04:36:22 pmAstronomers used them frequently... OP was talking on building spaceships, so he must be thinking in buying something future-proof.

author: Mecanix
author_rank: Frequent Contributor
timestamp: July 08, 2020, 05:02:15 pm
content: Quote from: tv84 on July 08, 2020, 04:46:46 pmIs that how they do it? Looks like I've unintentionally managed to dig out their ultimate secret! There, some progress...(typo corrected lol)What if we limit those space geeks to 25Mhz and 10Mhz waveforms, will they ever reach to another galaxy or remain clueless and well below our stratosphere?

author: Elasia
author_rank: Frequent Contributor
timestamp: July 08, 2020, 05:12:23 pm
content: Biggest thing in an arb is what frequency range do you want to generate, at what bit resolution, and length of waveformanswer those three then tack on whatever bells and whistles you wantYou could go from 50 bucks to tens of thousands in a hurryActually since you mentioned auto... i do off highway which is pretty close.. i've never had much reason to go over 100Mhz, i use several siglent SDG2000X unitsAlthough at home im thinking of swapping to a SDG6000X.... just because i like shinnies and do not go to TEA lol

author: tv84
author_rank: Super Contributor
timestamp: July 08, 2020, 05:18:29 pm
content: Quote from: Mecanix on July 08, 2020, 05:02:15 pmProbably you won't get off the launchpad... Starthere. You can have a cheap model that can be "upgraded" big. Not the best in the world, but when you reach a flight-ready stage you can buy something better.

author: Mecanix
author_rank: Frequent Contributor
timestamp: July 08, 2020, 05:34:53 pm
content: Quote from: tv84 on July 08, 2020, 05:18:29 pmHmm, that's what I thought. Thanks for confirming thisDamn you hacked that thingy good lol!!! Just browsed a few posts to get in the context and if I've understood you can beef up an entry Rigol up to 100MHz? Correct? if so that's pretty insane and something to consider (THANKS MAN).Before I get deeper though hope you don't mind me asking; will this hack retain its factory calibration or if not have you noticed anything major or of concern? Second question (sorry), why would I go for a 16bits vs all the other 14bits models I was looking at a few hours ago? Is this 16bits what really enables space warp?!(ps: man that rigol enclosure shape & design uh, that futuristic space age is already built-in... go figure)edit: right. ignore my Q this is already answered in that thread and looking quite good in fact. Additional thanks to members timber23 & TurboTom for the tests. Worth a look!

author: tv84
author_rank: Super Contributor
timestamp: July 08, 2020, 05:51:31 pm
content: Correct and the problem with that (being unable, for now, to do our own calibration) is that it is only 100% accurate up to 40 MHz. See the thread as there are many testimonies. But, I think, in the future there will be a way to calibrate it ourselves.For $200 is hard to go wrong. Believe me, the shape was what made me suggest it to you!

author: TurboTom
author_rank: Super Contributor
timestamp: July 08, 2020, 05:54:57 pm
content: I agree -- currently, a hacked DG811 is probably the best bang-for-buck "decent" AWG.What can be found written about sampling rate and DAC resolution is partially BS. All the DG800, DG900 and DG2000 share exactly the same hardware, which means they are all 250MSa/s and 16bit. Calibration is an issue with the DG800 models -- their amplitude is accurate per spec up to approx. 70MHz, to 100MHz they drop by just shy of 3dB. If we had the calibration instructions, I'm sure we could get them accurate over the full range.One thing you should consider before buying a DG811 to be used in a harsh environment, is that, since it isn't equipped with a fan, it has quite large cooling air gills all around the enclosure which may permit the entry of (smallish) foreign particles, that, if electrically conductive or hygroscopic, will eventually lead to some trouble...P.S. @tv84 beat me on that answer... Anyway, I publish it

author: tv84
author_rank: Super Contributor
timestamp: July 08, 2020, 06:10:32 pm
content: Quote from: TurboTom on July 08, 2020, 05:54:57 pmTiming isn't everything. Your answer has more weight!

author: TurboTom
author_rank: Super Contributor
timestamp: July 08, 2020, 06:12:52 pm
content: Not only my answer (I guess...)(working on that)

author: Mecanix
author_rank: Frequent Contributor
timestamp: July 08, 2020, 06:14:27 pm
content: I'm guessing as long as it retains its original spec/accuracy around that 25MHz range then I don't see a major problem. And I agree, for that sort of money this got to be the best deal around right now (jeez!!!). I'll see if I can crack a deal on this bad boy and report backQuote from: tv84 on July 08, 2020, 05:51:31 pmlol no kidd, I get the sentiment!Quote from: TurboTom on July 08, 2020, 05:54:57 pmActually the first concern that came to my mind when I saw the openings on the top. But then, its designed for Space (from the look of it) and there is Zero Gravity there so dust particles and other space junks won't be a problem... so all good

author: tv84
author_rank: Super Contributor
timestamp: July 08, 2020, 06:30:59 pm
content: Quote from: Mecanix on July 08, 2020, 06:14:27 pmNot so!Because in 0-G there is no convection as on Earth's surface, you MUST include a fan. Or else the design won't ensure the necessary cooling.

author: Mecanix
author_rank: Frequent Contributor
timestamp: July 08, 2020, 06:47:10 pm
content: Ah! true. Sorry bit of a noob, but I'll get there a way or another. Few mHz at a timeHave to say; thanks for that firmware tweak you made available to us. Less stressful to jump in the fire "right now" and considering I don't need to cash out $760 anymore. Probably will have to dosh out another $2000+ in 24 months as our knowledge and circuit designs evolved both in features & precision anyway. But for now I think I'm confident to give that wicked rigol spacebox a try. Thanks again for all your help and community support

author: TurboTom
author_rank: Super Contributor
timestamp: July 08, 2020, 07:05:44 pm
content: Just design your engines so they provide 1 G (or more...) of acceleration continuously and your cooling problem is mute

author: Elasia
author_rank: Frequent Contributor
timestamp: July 08, 2020, 07:47:36 pm
content: Quote from: TurboTom on July 08, 2020, 07:05:44 pmOr you could just cool it with a turbo encabulator

author: james_s
author_rank: Super Contributor
timestamp: July 08, 2020, 07:58:53 pm
content: I have a 15MHz 33120A, it has done everything I need it to do. If I need higher frequencies I'll get an RF generator but so far that hasn't been needed.As with anything, it depends greatly on what you're trying to do. Most of the things I use a function generator for are in the audio range up to a few tens of kHz.

author: Mecanix
author_rank: Frequent Contributor
timestamp: July 09, 2020, 01:10:15 am
content: Quote from: james_s on July 08, 2020, 07:58:53 pmThanks James, reassuring to hear. In all seriousness I am "initially" hoping to at least be able to validate/characterize some common passives and simulate some basic circuits (e.g. opamps, filters, etc). Optimization capability and analyzing straight from the lab's benchtop is a feature I'm looking forward too, constantly going back and forth from the lab to the DUT is tiring! All-in-all nothing too SpaceX to be perfectly honestLooking forward! As always thanks for all your input and recommendations guys, appreciated.