SDS1104X-E, backup power supply  - Page 1
Forum section: electronics / testgear

author: Linwood
author_rank: Contributor
timestamp: February 13, 2023, 11:51:20 pm
content: I have an SDS1104X-E due in any moment (though thinking Amazon let me down); my thanks to all the info here that helped me decide (and yes, should have gotten an X-U and saved the $100 but in absence of real knowledge I figured I might one day appreciate those extra features or ADC). Anyway...Most of what I want to do is hunting for low voltage issues in astro gear, but...I have a standby generator for the house and am curious how clean its output is. Now when I run it, I mostly turn off expensive electronic stuff just in case. I have a EV now also, and conceivably one day might need to charge from it (I am in hurricane prone florida) but using dirty power could be an seriously expensive mistake there.This is NOT a question about how to test safely - please assume I can (or that I will be dead and not bother you further).To put any even modest load on that generator I have to turn off utility power to the house (it's a panel interlock). I then have two choices to power the scope: consumer quality UPS's which are going to have a nasty square wave, or the generator itself.I do know that the generator's RMS voltage is good, whether idle or under load. I know its frequency is 60 +/-1 from a frequency counter in prior tests. It is properly installed, grounded appropriately in coordination with the house. It is a 10k/13k-surge non-inverter generator, so my gut tells me it has a decent sine wave, but I really don't know, hence my wanting to look. I also realize there are better tools than a scope -- but none that I have access to.My question is two pieces:Does low quality power to the scope risk damage, e.g. a consumer grade Cyber Power UPS? My guess is no, no more than any SPS powered gear like computers.But perhaps more importantly - Does low quality input power to the scope affect its measurements? Will I end up seeing a horrible result that is really from the input power not the measurement? Assume a solid ground throughout, will confirm or modify as needed the UPS.I should note a third option is go buy a good sine wave output UPS, but trying to be cheap since I just splurged on the scope.I have searched and have seen mixed answers, most simply saying "don't need a UPS", a few saying 'won't hurt it", but none seeming to authoritatively address whether it impacted the results.Advice welcomed.Linwood

author: TomKatt
author_rank: Frequent Contributor
timestamp: February 14, 2023, 12:04:16 pm
content: I half expected modern EV's to feature some form of ac power outlet in them - seems almost standard these days for all variety of vehicles... Can you do that ?

author: Linwood
author_rank: Contributor
timestamp: February 14, 2023, 12:43:30 pm
content: Quote from: TomKatt on February 14, 2023, 12:04:16 pmYou know, I did not even consider that, and it's known to have a pretty good sinewave output. By default it will be floating but I could just arrange to ground it in this case and I have my sine wave output UPS.Mine (Kia EV6) in the US only provides a standard 110v/15a (or maybe it's 20a, don't remember) output, but that's perfect for this use. I had been ignoring it for home outages since it was so light duty and kind of forgot about it.That's a great idea that avoids the whole issue. Never solve a problem you can go around.Thank you.

author: TomKatt
author_rank: Frequent Contributor
timestamp: February 14, 2023, 12:54:20 pm
content: Sometimes you just need someone who isn't too close to the problemThat's what makes a forum like this so great!And I'm not sure I would classify 15A ac source as "light duty"That's a pretty nice feature to have, though I'm not surprised EV's can offer that power level as compared to conventional ICE vehicles.Edit - I know you said you knew what you were doing, but please do be carefulScoping mains seems so straightforward - it's anything but. Good luck!

author: Fungus
author_rank: Super Contributor
timestamp: February 14, 2023, 01:54:12 pm
content: Quote from: Linwood on February 13, 2023, 11:51:20 pmI'd guess that, too. Switching supplies don't really care.People around here have evenrun their 'scopes off DC voltageand they still work (usually about 48V). That's switched-mode supplies for you.Quote from: Linwood on February 13, 2023, 11:51:20 pmI'd say "no" - see above. The power has been been highly "processed" by the time it gets through the SMPS. A slightly-less-than-perfect sine wave won't make much difference. It's easy to test though, just do the experiment on a battery powered signal (eg. laptop computer sound?)Worry more about the wall warts and LED lights in the room:

author: TomKatt
author_rank: Frequent Contributor
timestamp: February 14, 2023, 02:30:07 pm
content: Quote from: Fungus on February 14, 2023, 01:54:12 pmConsidering that the first thing power hits in a SMPS is a bridge rectifier, they can pretty much run off anything with sufficient voltage to trigger the oscillator.I doubt gear like this takes all that much power - I'm surprised I haven't stumbled across a true 12v supply solution for them... Mobile portability would be really handy!

author: Linwood
author_rank: Contributor
timestamp: February 14, 2023, 03:06:14 pm
content: Quote from: TomKatt on February 14, 2023, 12:54:20 pmWith 77kwh stored and a system that can charge in the multi-hundred KW range, outputting <2kw is handy as a single item UPS, but hardly living up to its potential for vehicle-to-house. Some do better. The same one in Europe does 220v @ 15a, so with just a bit of wiring change could probably give twice the power here.But yes, quite handy, and will run a LONG time, and more convenient than trying to use a computer UPS.Quote from: TomKatt on February 14, 2023, 12:54:20 pmI wouldn't say I know what I am doing, just that I understand well enough not to hurt myself or the scope from handling the grounding incorrectly. Lots of experience around line voltage and the NEC, but haven't used a scope since the early 70's -- I hear a few things may have changed.In terms of whether I can actually learning anything from looking at the generator ... remains to be seen.-----Everyone else, thanks. My GUESS was the SPS would fairly well isolate the scope from line both relative to damage and to noise, glad to have some knowledge to substitute for that guess.This place has been a great resource. It may cost me money though, jeep stumbling across things and thinking "Hmm... I could have used that". I still struggle with the whole "need" vs "want" thing, a lifelong problem.

author: Fungus
author_rank: Super Contributor
timestamp: February 14, 2023, 03:22:30 pm
content: Quote from: TomKatt on February 14, 2023, 02:30:07 pm12V probably isn't enough to trigger the supply. I'm sure you could do it with a 12V to 48V DC converter though.

author: Fungus
author_rank: Super Contributor
timestamp: February 14, 2023, 03:27:17 pm
content: Quote from: Linwood on February 14, 2023, 03:06:14 pmMake sure your probe is set to 10x.Me? I'd get a fixed 10x or even fixed 100x probe. Those little probe switches are a liability for work like this.(and 100x probes usually have better insulation)

author: 2N3055
author_rank: Super Contributor
timestamp: February 14, 2023, 03:50:14 pm
content: Quote from: Fungus on February 14, 2023, 03:22:30 pmPSU in these are 90-240V AC RMS, roughly...Running it a too low voltage would be hard on PSU (needs more current).....It is not approved by manufacturer and any damage won't be in warranty.And converter 12>220 that doesn't put out too much voltage spikes would do...

author: TomKatt
author_rank: Frequent Contributor
timestamp: February 14, 2023, 04:17:22 pm
content: Quote from: 2N3055 on February 14, 2023, 03:50:14 pmI understand that 12v won't work on the mains psu inside. I'm thinking more along the lines of a "replacement" psu that runs off 12v and creates the +15v, +6.5v and -9.5v rails used by the SDS1104X-E... I can't imagine any of those require significant current. Shouldn't be too hard to design a 12v based power supply that generates those voltages in a package small enough to fit inside the scope... The manual specs power consumption at up to 25 watts, but I suspect it's less than that.

author: tautech
author_rank: Super Contributor
timestamp: February 14, 2023, 07:05:52 pm
content: Quote from: Fungus on February 14, 2023, 03:22:30 pmYou can't.Recently tried and pushed 100VDC @ 3A into mine and it wouldn't start.However it is a first generation build SN# 0013 and there is a chance the PSU has been changed IDK.

author: Linwood
author_rank: Contributor
timestamp: February 14, 2023, 10:18:13 pm
content: Quote from: Fungus on February 14, 2023, 03:27:17 pmThanks. Honestly I can't see why I want to do this more than once, for that generator (or if I replace it). I know my cheap UPS' are crap, I know utility power is a sine wave, I don't need to look at it every week to see those things have not changed.My main use case (yet to be seen if useful) is when I get interference patterns and other issues in my astro imaging gear, to get some insight into what parts are noisy and how and when. Secondarily about once I hear I build some esp8266 or rPi thing (light, weather component, etc.) and occasionally have struggled to figure out what I was doing that was dumb limited to a DVM.Definitely not a power supply builder or some such that needs to probe high voltage on a regular basis.LinwoodPS. Amazon finally delivered it, then an hour later sent me a note that said they were trying to find it and get it shipped to me, so I might get two.Four probes adjusted, four channels come on and show a square wave, so happy so far. Need to break out some old 8266 device and poke around a bit just to learn. Dragging out the generator will wait for a better day when I feel like actually working (since when done I need to "winterize" it for storage, drain all the fuel, etc. ).

author: JeremyC
author_rank: Regular Contributor
timestamp: February 15, 2023, 04:24:37 am
content: @LinwoodYou need double-conversion UPS, but they are expensive. I doubt you will be able to find 1000 VA below $700. Example in link belowhttps://www.amazon.com/Maruson-Tacoma-TAC-LV1K-1000VA-Online/dp/B01ELPJJQA/ref=sr_1_4?keywords=double%2Bconversion%2BUPS&qid=1676433875&refinements=p_72%3A1248879011&s=pc&sr=1-4&th=1Standard UPS (line-interactive) connects power from battery inverter only when the main power will fail, otherwise is acting as pass trough with some filtering. It applies to the “true sine wave” too.

author: Linwood
author_rank: Contributor
timestamp: February 15, 2023, 04:40:28 am
content: Quote from: JeremyC on February 15, 2023, 04:24:37 amWell, I don't "need" one, really, which is why I have some cheap ones running my network gear so (for example) VoIP phone works when the power is out, at least for a while. I might like to have one, but it does not seem worth it.Unless you are saying I need one for the scope when power is out, but the suggestion to use the EV car seemed viable.

author: JeremyC
author_rank: Regular Contributor
timestamp: February 15, 2023, 05:25:32 am
content: Quote from: Linwood on February 15, 2023, 04:40:28 amQuoteIt was only suggestion how to condition the electricity delivered from your generator.Sorry for the understatement.

author: Linwood
author_rank: Contributor
timestamp: February 15, 2023, 12:47:07 pm
content: QuoteAh... got the context now... yes.I was thinking in terms of brief power outages, which is where the UPS' now come into play (but not the generator as it is a bit of an ordeal to get it set up, outside and running -- it's not stationary, but sort-of portable). Utility power is clean enough a double-conversion is not needed.But for the generator, if I look and it's really ugly power, you are of course correct, cleaning it up would require double conversion.I'm hoping I will find a nice more or less smooth sine wave since it has a fairly large generator body, but haven't looked.Sorry for the first reply, it now makes all kind of sense.

author: TomKatt
author_rank: Frequent Contributor
timestamp: February 15, 2023, 12:57:41 pm
content: Quote from: Linwood on February 15, 2023, 12:47:07 pmIf you're talking about one of those 'utility' generators that sits in a metal tube frame with wheels, don't expect much. They're typically pretty crappy. I had a 'decent quality' Generac branded version and my furnace fan motor made some horrible sounds when I ran it off the generator. I eventually got a sinewave generator for the furnace fan.Those kind of units also tend to have quite a frequency variance in them beyond the spurious noise.

author: robert.rozee
author_rank: Frequent Contributor
timestamp: February 15, 2023, 01:30:02 pm
content: Quote from: TomKatt on February 14, 2023, 04:17:22 pmi've been working on replacing the toasted PSU in a friend's Hantek DSO5072P, where the main supply rails draw 2A @ +5v, 400mA @ +14v, and 200mA @ -8v. i would expect the Siglent to be similar, with the highest current draw being from your +6.5v rail. in the case of the Hantek, i had considered converting it to battery operation, but in the end have just modified a salvaged PSU from an old DVD player instead.an interesting idea: there will be three schottky diodes in the Siglent's PSU, one for each of the three rails. take a wire from each (on the sideawayfrom the transformer) along with ground to a 4-pin connector located somewhere on the back of the scope. you can now feed regulated power into here, making use of the filter capacitors and chokes already in the PSU.a small external box can then house switching converts: buck input down to +6.5v, then boost this back up to +/-15v. finally use a 3-terminal negative regulator to bring the -15v back to -9.5v. size the buck converter large, to handle 5A or thereabouts. this gives you the ability to run the scope on anything from 8v up to 27v. if keen, add an under-voltage lockout.cheers,rob :-)

author: Linwood
author_rank: Contributor
timestamp: February 15, 2023, 05:35:33 pm
content: Quote from: TomKatt on February 15, 2023, 12:57:41 pmIt is one of those.I have put a frequency counter on it (my DVM has one) and it's pretty steady even when adding and shedding load, as is the voltage. I don't think I saw more than +/- 1 hz (though it has been a long time) and maybe +/- 5v rms.It's a Northstar (Northern Hydraulic now Northern Tools) 13k surge / 10k continuous from somewhere around 2017, nice Honda engine, but few details on what's inside the generator portion, just "rotor" and such.To date it has been through three hurricanes here, and served its purpose -- it prevented me from loosing power. Even Ian, which was almost a direct hit here and wiped out whole communities on all sides did not take our power (we were without water for about 2-3 weeks). Like taking an umbrella out prevents rain.So I consider it well worth the money -- without being prepared I would have lost power and maybe still not have it back.But how well it works... Maybe in a day or two will drag it out and get set up to run it. Having fun now looking at noise induced by PWM power to telescope dew heaters with various power supplies. I have no idea what to make of all the info I see, but it's drawing really cool images. Fun to look at.

author: Linwood
author_rank: Contributor
timestamp: March 04, 2023, 08:39:56 pm
content: I just wanted to follow up.My thanks to @TomKatt for the EV solution. I also discovered I had a sine wave UPS but the EV was a lot easier. Well, mostly -- Kia has some weird ideas how that thing works, and how to turn it off (stopping requires hitting the door unlock -- not the charger door, the driver door unlock -- to stop using the adapter). Anyway...Anyway, just for a bit of closure....First, I did not die, and neither did the scope.The generator has a surprisingly clean output as below. It's not perfect but decent. This is just one leg, I didn't want to chase down an extension cord to find the other leg. The green is neutral. The little blips are millivolts, I had looked more closely and forgot to expand them for the photo.This was under a mild load, a large burner on the stove on. Voltage is pretty accurate, frequency is a bit off (62.3) but did not change when I went from no-load to probably 1.5kw or so.Anyway, no real questions here, just a bit of closure and thank you.