Higher End Oscilloscope for Inverter work? - Page 1
Forum section: electronics / testgear

author: TSOL
author_rank: Contributor
timestamp: February 12, 2025, 11:51:29 pm
content: Ok. I'm going to try and make this thread as useful as possible so that it's different from all the other "what scope should I buy?" threads.Price range: ~1600$ USD. Could be convinced to go as high as ~2300, but either has to be a helluva deal or a helluva scope.Work: This scope is for home use. This budget is very likely overkill for home use, but I have a reason for it I'll explain later. I want to work on inverters (I want to design BLDC inverters for fun) and so bandwidth requirements aren't crazy high, just a few dozen megahertz to ensure I get transients captured.My biggest concern is with UI, actually. My Alma mater university (as of 2 months ago) is fitted out with brand new Tektronix scopes (can't remember the model but probably 10" touch screen, realm of ~3k$ each), and I absolutely hated them. They were slow to everything you tried to do with them, zooming in too far out/in would cause them to update so infrequently it felt like it stalled. Features were fine, but I genuinely had to swap between our old Tek digital scopes and the new ones for a test I needed to run that determined the latency between when a button was read and when the MCU output a signal. The OLD scopes could read it just fine, the new ones nearly stalled. It was infuriating, because the new ones had to be used for a DIFFERENT test because the old ones couldn't do it.Tl;Dr, I'm over scopes having terrible UI and I'm willing to pay for one that has good UI. Keysight dsox2000 series has been the obvious choice, but I've read quite a few people say (and even Dave's review) where he ran out of memory accidentally on a screen capture. For an instrument that I'm paying 2k for, it isn't inspiring a whole lot of confidence that I'll want to keep this device (without a supplementary scope) for, say, 20 years. Maybe they're the best option still, I'm not sure.There are other scopes (like siglent 2000 series and rigol dho 900x) that people rave about, but I've got PTSD from those Tek scopes, so I'd need to see some footage of either of those two scopes with all 4 channels being used to make sure they're usable.Another option I've had a liking for is the Micsig MHO3-2504 (or something like that). In fact, I like this one so much I may just buy it when funds allow, but I've never heard of Micsig until I got here and them being entirely China based has me a bit concerned about their long term support of their products. Their UI appears to be really snappy though on this model.Anyways, if anyone has videos of their scope (any of the above) at home in this price range with ~200MHZ bandwidth, 4 channels, 15-20+ MPT memory, and all that jazz, I'd greatly appreciate it as I've been relentlessly searching for about a week to very little avail.Thanks!Tsol

author: tautech
author_rank: Super Contributor
timestamp: February 13, 2025, 12:01:05 am
content: Grab the cheap 2ch SDS802X HD or 4ch SDS804X HD and try out the PA option, especially for inverter analysis but to use it to full advantage the differential and current modes will cost way more than the scope.Then you can make an informed decision if the larger display models with the same PA option will be a good fit for your needs.

author: benseno
author_rank: Regular Contributor
timestamp: February 13, 2025, 12:22:00 am
content: Is this project about small BLDC motors like used in quadcopters, or the bigger ones connected to the mains? the latter may ask for isolated probes too.

author: bdunham7
author_rank: Super Contributor
timestamp: February 13, 2025, 12:50:05 am
content: Quote from: TSOL on February 12, 2025, 11:51:29 pmWhat exactly would you like to see in a video?Given your description of your frustration and description of the scope "stalling", I suspect you are what I call a "knob twiddler".A knob twiddler is someone who adjusts their scope by turning the knobs as they watch the trace on the screen or lack thereof, in which case they curse and grumble. Knob twiddlers are sometimes people who are used to using analog scopes and perhaps working on old televisions. They also can be people that overdo the espresso or are generally impatient. Certainly some scopes are more responsive than others and the Keysight model you mention do have a reputation of behaving in the "live" manner that some prefer.I'm not a knob twiddler, so it is hard for me to give usable advice to someone who wants a "snappy" UI. I want a well thought out UI with lots of useful features, preferrably the one that I happen to need at the moment. I rarely press buttons or turn encoders faster than about 1 input per second. Some people want to tap on their screens like they are frantically texting someone while sitting at a stoplight. I personally find the Siglent SDS2000X+ series to be quite usable with a reasonably thought out UI. I can adjust the horizontal timebase pretty rapidly and it keeps up, but of course if I accidentally overdo it and zoom out to 10s/div or something then there will be a long delay before anything appears on the screen. I don't like the MATH implementation and there are a few other minor things I'd have done differently, but 500MHz, 200M of memory and the big screen make up for a lot.IDK which Tek scope you didn't like--perhaps post the model so we understand what you are complaining about there.

author: LinuxGuy123
author_rank: Regular Contributor
timestamp: February 13, 2025, 01:16:20 am
content: If you are going to build BLDC inverters, you'll be doing a lot of embedded and power work. You'll want to see the power waveforms at the same time you see digital waveforms.I do similar work from time to time. I have a Rigol MSO5000 and love it because it's got 4 analog channels and 16 digital channels all on the same screen. It also has a 2 channel arb waveform generator and can be controlled really well from a computer screen using VNC.4 analog channels is almost a must with any scope for serious work. The 16 digital channels will let you watch things like gate drive signals of your H bridges while you watch the current and voltage waveforms going into the BLDC motor.I highly recommend you get (or make) some differential probes and some current sensors (clamps).The only thing I wish was better on my MSO5000 is the screen. Nothing wrong with it, but I wish it was bigger as in more pixels. It's easily viewable it's just that it gets very crowded from time to time. It would be nice if the VNC output was more pixel area, but its not. The output has the same pixels as the scope screen.The VNC control is fantastic. I couldn't got without this now that I've had it.Good luck. Let us know how you make out.

author: TSOL
author_rank: Contributor
timestamp: February 13, 2025, 03:35:33 am
content: Quote from: bdunham7 on February 13, 2025, 12:50:05 amI most certainly am a "knob twiddler", not gonna hide it. I play competitive games on the side (not well) as a for-fun activity, and so good UI is something I'm used to and not willing to compromise on. I am well aware that an oscilloscope isn't going to compete in that space at all, and I'm not really looking for it to. It just frustrates me to no end that a purchase that is financially significant should have a poor user experience. It also gives me the impression that the processing power of the scope is artificially limiting my ability to see the waveform because it isn't fast enough to update (which may not entirely be incorrect if the wfms/sec rate drops). Maybe its not the core function of the device to be user friendly, but I expect poor performance out of a 20$ Chinese meter, not a 2000$ scope.It has been a while since I have worked with these Tek oscilloscopes, but I vaguely remember 100MHZ, it certainly was 4 channel, I absolutely do remember the layout of the device, so my guess is that it is the Tektronix TBS2104B.As far as what I'd like to see in a video, nothing super complex. Just view a signal on two of the inputs (a sine wave on ch1 and square wave on ch2, for example), maybe throw a math function between the two in to really push it, and just zoom in and out (maybe on the rising edge of the square wave, to simulate looking at the rising edge of a FET gate) to see how well it responds. If there is major stuttering (5+ seconds for an input to register), that is not something I want in a scope I intend to keep for a very long time (10+ years if it lasts that long, idk why it wouldn't).Quote from: LinuxGuy123 on February 13, 2025, 01:16:20 amCertainly. I am basically only considering scopes with 4 analog channels. Hadn't considered using digital channels to monitor gate drive signals, that is quite the good idea if it is as simple as you say. Do Digital channels typically have a 5V limit on them? I don't want to blow them up by sending 20V to them.Quote from: benseno on February 13, 2025, 12:22:00 amFor the immediate future, small BLDC motors are what this scope is being bought for. I have distant plans to do an EV conversion on an antique car our family owns, but there's no reason doing that kind of work if I can't even design a BLDC driver. Yes, I am familiar with how much work actually goes into that, they're very complex, but electronics doesn't get any easier as power scales up. I made a brushed DC driver for a class, and it DID work, but due to some anomalies(i'd imagine ringing? I could never catch it on an oscilloscope, it always worked when it was hooked up to it) the FETs that were conducting would permanently get shorted on and the motor would permanently get stuck spinning in one direction (never a shoot-through condition oddly). I need a tool to diagnose this before I diagnose more expensive projects.Point is, Differential probes and current clamps that have BNC connectors are going to be their own budget later on. I am aware that they are very expensive, so the justification for this scope being purchased "now" is that I can immediately use it on small projects (RC BLDC driver) to build my practical knowledge before tackling larger stuff (like an ebike).Quote from: tautech on February 13, 2025, 12:01:05 amI've seen the prices. They're not pretty. However, Hioki has some ~500$ current clamps with an old design that do 500A (on the used market). They need their own supply, but this is its own topic. As noted above, these probes are likely going to be so expensive that the grand total will outweigh the scope by quite a bit. This post was to make sure that whatever scope I choose is sufficient for the equipment that would need to be plugged into it.

author: tautech
author_rank: Super Contributor
timestamp: February 13, 2025, 03:49:02 am
content: Quote from: TSOL on February 13, 2025, 03:35:33 amYet one must have the right tools/accessories to make full use of any equipment.Hunted out an older post with images of the PA mode UI:https://www.eevblog.com/forum/testgear/siglent-sds800x-hd-12-bit-dsos-coming/msg5385866/#msg5385866

author: bdunham7
author_rank: Super Contributor
timestamp: February 13, 2025, 04:23:26 am
content: Quote from: TSOL on February 13, 2025, 03:35:33 amTBS2014B is actually a pretty decent scope and certainly not known for a bad UI. IDK how quick it is, I haven't used one enough to notice any hang time on inputs. I'd expect most responses and screen refreshes to take place in a fraction of a second unless you have long acquisition times in which case there's no getting around the delay. The TBS2104B had a long memory (10M IIRC) and you could easily end up with a very long acquisition time depending on the setup. I certainly don't expect to see a little spinning hourglass as I wait for something to happen, other than booting up.I should add that the scopes we're talking about in your budget range are not "higher end" at all, they are one notch above entry level or educational types and they offer vastly more capability than you could dream about just decade or so ago. For the work you want to do, a $100k scope and $200k in probes would do a better job, but I suspect you'll just have to make do like most of the rest of us.QuoteTwo videos for you here. One is pretty much what you requested, in and out of zoom mode. You'll see it isn't absolutely instant, but it doesn't stutter, stall, hang or whatever. The other is me demonstrating quickly setting the scope up to make a capture of a single event. The scope is first returned to it's "default" condition, essentially a reset to how it turns on out of the box. Then the sig-gen is configured to deliver a 0 to 1V 25µs pulse once every 10 seconds. Once I press the output button I have ten seconds to properly configure the scope to capture this pulse. I set the vertical to 500mV/div, horizontal to 20µs/div, trigger to between 0 and 1V and NORMAL (or SINGLE if it really was just one pulse) and a few seconds later it captures the pulse just as planned. That's the non-twiddler method. You'll see that I'm able to set that all up in less than ten seconds.https://youtu.be/yE3W7KIpdg0https://youtu.be/QYzPGdMX8eg

author: 2N3055
author_rank: Super Contributor
timestamp: February 13, 2025, 11:03:51 am
content: Quote from: tautech on February 13, 2025, 12:01:05 amSDS804X HD is definitely on the faster side. I would recommend OP to try it. Videos don't really show response.

author: TSOL
author_rank: Contributor
timestamp: February 13, 2025, 03:28:41 pm
content: Quote from: bdunham7 on February 13, 2025, 04:23:26 amI'd have to go check the assignment again to figure out what was causing me so much grief to see if I can repeat it. I don't have the microcontroller anymore, as it was part of a class, but I should be able to repeat the test with an ESP32 as (iirc) it is just about an order of magnitude faster than the one we used for class. I don't believe it had anything to do with being zoomed out, but I'd really need to check that assignment again.And yeah, I'm under no illusions of how deep the oscilloscope rabbit hole goes. Keysight has one for over $1mil iirc. The scopes I'm referring to are typically "higher end" than what a lot of hobbyists will buy, but its nearly entry level tier when a company/university is considering them. I meant they were "high end" from a hobbyist's perspective, and I know that Dave made a video saying 800$ is maybe a little overkill for a hobbyist scope... well I'm nearly double that.Quote from: 2N3055 on February 13, 2025, 11:03:51 amI am kinda new to this whole thing, how do you suppose I "try" a scope? I don't have any test equipment depots near me, do you literally just mean buy it on amazon and return it if I don't like it? I wouldn't mind doing that at all, this isn't a super urgent need for a scope (I have heard of people getting their amazon accounts suspended if they do this a lot, and that would be really bad as I share this account with a family member who really needs to use it). I have ambiently needed one for years but never had the funds. Just started a real job a few months ago and decided its time to start filling in the test equipment holes in my life.Also, I looked at a few reviews of the SDS804 and DHO800/900, and I gotta say, they're pretty close to what I want in a scope. Really eyeing the Rigol but will see where I end up. What does paying more in a scope get you these days anyways? If there are $400 scopes you can upgrade to 200MHz, 4 channel, sub 100uV noise, what is the draw for getting a scope in the 1500$ range? Is it literally just higher bandwidth and more MPts/sec? I've looked through probably 30 different scope models in the past week and honestly I have a hard time telling what the difference between the entry tier and "step up" tier other than bandwidth and memory depth. I don't need crazy amounts of either of those things, I just wanted a snappy UI. 100MHz-200MHz is what I'd need, and low noise so I can attach external probes down the line.

author: bdunham7
author_rank: Super Contributor
timestamp: February 13, 2025, 04:47:46 pm
content: Quote from: TSOL on February 13, 2025, 03:28:41 pmIt definitely sounds like one of the entry-level 12-bit scopes would be right for you at this point. You're giving up a larger screen, some sample rate and BW, very long memory and perhaps some features that won't matter to you. Some of the entry level Siglents have an issue with low-frequency square waves as shown here:https://www.eevblog.com/forum/beginners/probe-compensated-but-level-of-square-signal-gt-20ms-not-looking-good/msg5523046/#msg5523046If you have time, read the whole thread and the links in my post above:https://www.eevblog.com/forum/beginners/probe-compensated-but-level-of-square-signal-gt-20ms-not-looking-good/msg5519191/#msg5519191I don't know what bug-features the Rigols might have and I'm not recommending you avoid the Siglent just based on this unless you think it would bother you. Remember that when in doubt, you rarely go wrong by keeping your money in your pocket, so as I said you should probably start with a $400 entry-level model.

author: PwrElectronics
author_rank: Regular Contributor
timestamp: February 13, 2025, 05:35:08 pm
content: If sluggish UI is a issue, don't get a Tek TPS2024. We have a couple of them at work and they can be infurating. Seems like the response to knob or buttons can randomly take a few seconds to respond.I probably classify as a "knob twiddler" but when you have to whisper 1001-1002-1003 for each button press to wait for it and not overshoot your goal it gets a little out of hand!

author: TSOL
author_rank: Contributor
timestamp: February 13, 2025, 07:41:11 pm
content: Quote from: PwrElectronics on February 13, 2025, 05:35:08 pmHonestly you're the third person I've heard say that (I'm the first, and another guy from a different thread was talking about the $10k scopes he was looking at. From what I can tell, Tek was by far the slowest). Its starting to appear more and more like this is less of a "cheap scopes" problem and is more of a "Tektronix cheap scopes" problem. I guess until I'm proven otherwise, I'm staying away from Tektronix.Maybe I should make a "knob twiddlers anonymous" thread for all us nerds who are too impatient

author: bdunham7
author_rank: Super Contributor
timestamp: February 13, 2025, 07:57:51 pm
content: Quote from: PwrElectronics on February 13, 2025, 05:35:08 pmTPS or TBS? Those are two entirely different animals.

author: PwrElectronics
author_rank: Regular Contributor
timestamp: February 13, 2025, 10:04:59 pm
content: QuoteTPS. I work in a group that does power electronics (including inverters) and we got those in some years ago as they have 4 isolated inputs and can run on battery for possible floating measurements. Hardly anyone uses them though and during the pandemic I had one checked out to me (as it was available) to use in my home lab on my then project so got to spend too much time with it. Those also are old now and use a CF card for storage but the card eject mechanism is easily broken.We had a bunch of TDS3034C scopes but those are getting old too. Some newer stuff has come in but I have not used it. I am still fond of the Lecroy scope I spec'd in 2008 (104Mxi). We use differential probes on all our HV projects.

author: bdunham7
author_rank: Super Contributor
timestamp: February 13, 2025, 10:24:47 pm
content: Quote from: PwrElectronics on February 13, 2025, 10:04:59 pmI have one (TPS2024) that I repaired (3d printed that eject mechanism, replaced some encoders, etc) and yes it is pretty old although I don't find slowness to be the main drawback. But it is only useful because of its fairly rare HV isolation capability and battery operation. Everything else is decades past its prime--1/4VGA, 2.5k memory, etc. I think they only recently stopped selling its most recent iteration.