Cheap USB scopes

[kelemvor]

Greetings.  Noob here.  I couldn't find this exact question in another post, although I'm sure it's a common idea. I thought I'd just go ahead and ask.

So, I'm just a hobbyist.  I had some electronics training about 25 years ago - actually have an aa in electronics tech.  But I proceeded to get a job writing code for a large firm and haven't done anything with electronics in all that time. I've forgotten almost everything.   Lately I'm messing with it as a hobby.

Now then.  I just plopped down about $250usd on a 121gw.  My first good meter.  Actually I bought a fluke 117 about 2 days before I ordered the 121gw.  Decided to return the fluke and pony up for the better meter.  I've been using the one they issued me in school (which I later looked up and found that it was about a $10 meter).  Needless to say that the 121gw should last me until one of us dies.

I've always really wanted a scope.  Mostly I want to do basic things. I want to look at the signal from my UPS devices and see if the wave is any good.  I want to look at the waveform in my SLA 3d printer as there's some concern about noise causing problems with them that results in imperfect results at 20 micron.  All of those things should be within range of any crappy scope..I think.

So... having just spent so much on a DMM, I think SWMBO would freak if I plopped down $350 on a Rigol DS1054Z.

Is there any value at all in the cheap USB scopes for doing stuff like looking at a 60hz waveform or looking for noise in the signal for low power stepper motors?   Yes, I've read the scope chart to the best of my ability.  Clearly the usb scopes aren't very good and are not comparable to a rigol.  What I can't extrapolate from all that data is this:  Are these things totally useless or can a home gamer get by with one for basic use?

Honestly, I barely even remember how to use a scope and will probably be watching some training videos to re learn.

[schmitt trigger]

I am sure you will receive 100 different answers. And will be OK, but seen from a different perspective based on the unique experience.

To me, the really cheap USB scopes have been disappointing in more than one way. There are some excellent USB scopes like Pico, which won't break the bank and their hardware capabilities and its software interface are far superior.

[hexreader]

Rigol DS1054z is cheap and does USB

That would be my choice......

..... but then again, I would rarely waste time on the USB options for hobby use

YMMV

[kelemvor]

Rigol DS1054z is cheap and does USB

That would be my choice......

..... but then again, I would rarely waste time on the USB options for hobby use

YMMV

I'm not after USB connectivity on a regular scope.  I'm after cheap.  There are some scopes with no interface that just connect to a PC for display and control.  The picoscope that Mr. trigger mentioned is one such example.  It's like $140.  Honestly I was thinking of something like the $65 hantek 6022BE.

[FuzzyOnion]

I'll echo the two previous posts.  I've been looking at scopes, both standalone and USB for the past 3 months.  I don't mean to sound like an ass, but if $250 for your dmm gave you pause, then scopes will give you apoplexy.  There are a lot of choices and as you have perceived, not all of them good.  There are some standalone Chinese scopes for under $300 if you can go that route.  I'm like Hexreader and prefer something not tethered to a computer.  Ultimately, you'll have to set a firm budget and then ask the question again.

Good luck

[Jan Audio]

Real scopes last longer, windows is garbage.

[hexreader]

Do not make the same mistake that I nearly made, in assuming that USB-only scope must be cheaper than traditional scope. You would think that there would be a huge saving by having no screen, but it does not seem to work that way.

1054Z cannot be beaten on bangs-per-buck IHMO, but if that is too much money, then brace yourself for disappointment with anything cheaper. Settle for making-do.

You should have bought a $50 DMM and put he other $200 towards Scope IHMO.   ...   no, I lie...  You bought a great DMM and will always treasure it

[Peabody]

If you want really cheap without USB, you can get a single-channel DSO150 kit from Banggood for $18 shipped from China.  But you'll also need a "real" probe ($7) and a 9V power supply ($8?).  You don't want to be connecting this to mains (I guess 10x mode might work), but I have found it to be surprisingly useful for things like steppers and servos, PWM, any audio stuff, other slow things.

They are coming out with a new 2-channel version called the Wave2, but I don't think it's quite ready to ship yet.  And it's a good bit more expensive - about $80 from the manufacturer, which appears to be the lowest price.   So the Hantek would be cheaper, but you have to deal with USB.

The DSO150 is not battery powered, but there's a long-winded forum thread on how to convert it, which I was able to do, and it's quite convenient.  The Wave2 is battery powered but the battery itself is not included in the kit version, only the assembled version.

[rf-loop]

Greetings.  Noob here.  I couldn't find this exact question in another post, although I'm sure it's a common idea. I thought I'd just go ahead and ask.

So, I'm just a hobbyist.  I had some electronics training about 25 years ago - actually have an aa in electronics tech.  But I proceeded to get a job writing code for a large firm and haven't done anything with electronics in all that time. I've forgotten almost everything.   Lately I'm messing with it as a hobby.

Now then.  I just plopped down about $250usd on a 121gw.  My first good meter.  Actually I bought a fluke 117 about 2 days before I ordered the 121gw.  Decided to return the fluke and pony up for the better meter.  I've been using the one they issued me in school (which I later looked up and found that it was about a $10 meter).  Needless to say that the 121gw should last me until one of us dies.

I've always really wanted a scope.  Mostly I want to do basic things. I want to look at the signal from my UPS devices and see if the wave is any good.  I want to look at the waveform in my SLA 3d printer as there's some concern about noise causing problems with them that results in imperfect results at 20 micron.  All of those things should be within range of any crappy scope..I think.

So... having just spent so much on a DMM, I think SWMBO would freak if I plopped down $350 on a Rigol DS1054Z.

Is there any value at all in the cheap USB scopes for doing stuff like looking at a 60hz waveform or looking for noise in the signal for low power stepper motors?   Yes, I've read the scope chart to the best of my ability.  Clearly the usb scopes aren't very good and are not comparable to a rigol.  What I can't extrapolate from all that data is this:  Are these things totally useless or can a home gamer get by with one for basic use?

Honestly, I barely even remember how to use a scope and will probably be watching some training videos to re learn.

You can find some opinions and facts here.
https://www.eevblog.com/forum/testgear/owon-vds1022i-quick-teardown-(versus-the-hantek-6022be)/

My experience (with other products) is that Owon hardware building quality have been clearly better than Hantek. (and I do not talk about how they looks internally also true documented failures in real life)

[kelemvor]

If you want really cheap without USB, you can get a single-channel DSO150 kit from Banggood for $18 shipped from China.  But you'll also need a "real" probe ($7) and a 9V power supply ($8?).  You don't want to be connecting this to mains (I guess 10x mode might work), but I have found it to be surprisingly useful for things like steppers and servos, PWM, any audio stuff, other slow things.

They are coming out with a new 2-channel version called the Wave2, but I don't think it's quite ready to ship yet.  And it's a good bit more expensive - about $80 from the manufacturer, which appears to be the lowest price.   So the Hantek would be cheaper, but you have to deal with USB.

The DSO150 is not battery powered, but there's a long-winded forum thread on how to convert it, which I was able to do, and it's quite convenient.  The Wave2 is battery powered but the battery itself is not included in the kit version, only the assembled version.

I didn't even think to consider the low input voltage maximums on the usb scopes.  One of the things on my to-do list for a scope is examining 120v outputs from my UPS units.  I guess I'm going to have to bite the bullet and buy the rigol or not do it at all.

Thanks very much for the input, everyone!

[2N3055]

If you want really cheap without USB, you can get a single-channel DSO150 kit from Banggood for $18 shipped from China.  But you'll also need a "real" probe ($7) and a 9V power supply ($8?).  You don't want to be connecting this to mains (I guess 10x mode might work), but I have found it to be surprisingly useful for things like steppers and servos, PWM, any audio stuff, other slow things.

They are coming out with a new 2-channel version called the Wave2, but I don't think it's quite ready to ship yet.  And it's a good bit more expensive - about $80 from the manufacturer, which appears to be the lowest price.   So the Hantek would be cheaper, but you have to deal with USB.

The DSO150 is not battery powered, but there's a long-winded forum thread on how to convert it, which I was able to do, and it's quite convenient.  The Wave2 is battery powered but the battery itself is not included in the kit version, only the assembled version.

I didn't even think to consider the low input voltage maximums on the usb scopes.  One of the things on my to-do list for a scope is examining 120v outputs from my UPS units.  I guess I'm going to have to bite the bullet and buy the rigol or not do it at all.

Thanks very much for the input, everyone!

You cannot measure 120 AC with normal scope+normal scope probe !!!!

You either have to have special (expensive!) scope with galvanically isolated input channels, or you have to have a normal oscilloscope and special high voltage differential probe.

None of the solutions are on the cheap like you would like it.
Buying a Rigol and cheap Micsig HV diff probe is cheapest way to get something that actually works properly for measuring 120 VAC.

Apart from that, Rigol 1000Z is cheapest real scope. Period.

[rf-loop]

You cannot measure 120 AC with normal scope+normal scope probe !!!!

Can you explain?

But yes, if you talk for noobs, yes stay away from live mains with normal scope with normal probes (even when they can use if really know things and understand these things)

Educated professional can  use normal CAT II 600V rated passive probes for 120 - 230VAC (if environment/circuit is CAT II class and follow all safety instructions and rules)

Today I'm retired but after ~1970  I have done it thousands of times including real industrial professional work except that here we have 230Vac mains. We do not stay there for playing, our job is keep factory running 24/7/365 even when some things need repair "on the fly". I have get also HV working safety education and education for maintenance and repair work on live installations. Even when my main job have been with electronics and automation. 

But, I do not recommend anything with danger voltages and danger currents for uneducated hobbyists or even professionals who do not have special training for working with live high voltage circuits. And of course we use there also more safe HV probes when need, or other methods, depending situation. But claim that these normal probes can not use for 120VAC (if also look that other related things are still safe) , it is false - if only definition is this voltage.

[Gyro]

But claim that these normal probes can not use for 120VAC (if also look that other related things are still safe) , it is false - if only definition is this voltage.

@rf-loop:  Can you explain to the OP where he should put the probe ground clip then? [Edit: He's talking about monitoring the output of his UPS!]

[kelemvor]

You cannot measure 120 AC with normal scope+normal scope probe !!!!

You either have to have special (expensive!) scope with galvanically isolated input channels, or you have to have a normal oscilloscope and special high voltage differential probe.

Can you elaborate on that any?  120v seems to be within the specs according to the manual: Analog Channel: CAT I 300 Vrms, CAT II 100 Vrms, Transient Overvoltage 1000 Vpk Digital channel: CAT I 40Vrms, Transient Overvoltage 800 Vpk

A quick google search shows a lot of folks responding to the idea much like you.  I.e. don't do it with a varying number of exclamation marks. 
Other folks seem to be doing it, they include screenshots and photos of this very thing.  Example: https://electronics.stackexchange.com/questions/98656/using-oscilloscope-safely-with-ac-mains

Measuring 120v with a meter, even my crappy $10 meter is the norm. Heck it's the main thing I've used my meter for over the years..when working on my home wiring inside the breaker panel, or replacing/installing outlets etc.  Why so much more dangerous with a scope?

I did look up differential probes such as the eevblog hvp70, but they seem to cost more than the rigol scope.   Know where I can find an inexpensive one?

[Gyro]

The problem is that a DMM is a battery operated 2 probe insulated hand held device. The outer shield of the scope's BNC connector and the scope probe ground clip are connected to the protective ground pin of its mains plug.

https://youtu.be/xaELqAo4kkQ

[rf-loop]

But claim that these normal probes can not use for 120VAC (if also look that other related things are still safe) , it is false - if only definition is this voltage.

@rf-loop:  Can you explain to the OP where he should put the probe ground clip then? [Edit: In his original post he's talking about monitoring the output of his UPS!]

My answer was for 3055 one quoted sentence.

For OP, please do not. If you need ask it, please do not do it even if someone answer and remotely (example internet)  give some instructions how to connect. People who need ask this question do not know enough for safety working in this case. Period.

Perhaps I can do it (depending UPS circuit details) but I'm not so stupid that I try here tell how to do it or how to look if this is even possible sao that it is enough safe (safety depend also who is doing...) . Because... it do not happen under my eyes, under my full control and because I do not know exactly what is situation and circuit and so on even if I look situation in real life with my eyes and thinking it is possible I do conclusion that it is not safe or possible to do with safety. It depends many things.   But 120VAC itself and normal oscilloscope probe itself do not themselves make it impossible at all. 

So, my previous answer is valid only for this my quoted sentence from 2N3055. Not for OP original question.

[Gyro]

So, my previous answer is valid only for this my quoted sentence from 2N3055. Not for OP original question.

It is rather more helpful to relate your answer to what the OP is actually asking don't you think?    The rest of us, at least the experienced ones, already know the nitpicking one - let's keep the quotes in context!

[2N3055]

You cannot measure 120 AC with normal scope+normal scope probe !!!!

Can you explain?

But yes, if you talk for noobs, yes stay away from live mains with normal scope with normal probes (even when they can use if really know things and understand these things)

Educated professional can  use normal CAT II 600V rated passive probes for 120 - 230VAC (if environment/circuit is CAT II class and follow all safety instructions and rules)

Today I'm retired but after ~1970  I have done it thousands of times including real industrial professional work except that here we have 230Vac mains. We do not stay there for playing, our job is keep factory running 24/7/365 even when some things need repair "on the fly". I have get also HV working safety education and education for maintenance and repair work on live installations. Even when my main job have been with electronics and automation. 

But, I do not recommend anything with danger voltages and danger currents for uneducated hobbyists or even professionals who do not have special training for working with live high voltage circuits. And of course we use there also more safe HV probes when need, or other methods, depending situation. But claim that these normal probes can not use for 120VAC (if also look that other related things are still safe) , it is false - if only definition is this voltage.

Yes I can explain. I take the normal probe, and (with a tongue at the right angle) i look at the power outlet. I have this one pointy thing and a crocodile thing... And then I randomly (Russian roulette style) decide which one I stick to the left hole in the outlet and which one to the right.
Because, power outlets are NOT defined which one is live and whic one is neutral. Even if you stick grounded side of the probe (scope) to the neutral, there is no guarantee there are no stray voltages between power neutral and earth circuit.

So basically pure luck if it goes boom.

I have normal (grounded) 100x probes that I use on 1000V on a grounded circuit inside device.

And I also had occasionally measured something on a primary side of the switcher. With probe safely connected to grounded side of circuit.
Once, a crocodile slipped, and on it's way to the desk it touched live circuit. It was old school Hitachi scope, it survived, mains fuse was blown, and I was the village idiot for some time until somebody else made something stupid and my colleagues moved on, making fun of somebody else..

Point is, even if you exactly know what are you doing, there can still be mistakes.
And OP, by it's own admission (it is a sign of a smart person to know your limitations) is a complete beginner.

So, yeah, I stand by what I said. In these circumstances I gave him best advice.

I make it a point to make  a distinction between what is possible and what is a smart way to do it.

If you take a stick of dynamite and a lighter, and slowly heat one point of the stick, dynamite won't explode. It will, in fact, start burning with a yellowish smokey flame and quite slow. You might use it as a torch...  Despite that fact, smart people will probably want to use a candle or a battery hand torch for light.. It's kinda less extreme.

[nctnico]

I did look up differential probes such as the eevblog hvp70, but they seem to cost more than the rigol scope.   Know where I can find an inexpensive one?

MicSig produces good (and good value for money too) differential probes. They still cost over $100 though but better safe than sorry. You won't be the first to do a self-electrocution.

[2N3055]

But claim that these normal probes can not use for 120VAC (if also look that other related things are still safe) , it is false - if only definition is this voltage.

@rf-loop:  Can you explain to the OP where he should put the probe ground clip then? [Edit: In his original post he's talking about monitoring the output of his UPS!]

My answer was for 3055 one quoted sentence.

For OP, please do not. If you need ask it, please do not do it even if someone answer and remotely (example internet)  give some instructions how to connect. People who need ask this question do not know enough for safety working in this case. Period.

Perhaps I can do it (depending UPS circuit details) but I'm not so stupid that I try here tell how to do it or how to look if this is even possible sao that it is enough safe (safety depend also who is doing...) . Because... it do not happen under my eyes, under my full control and because I do not know exactly what is situation and circuit and so on even if I look situation in real life with my eyes and thinking it is possible I do conclusion that it is not safe or possible to do with safety. It depends many things.   But 120VAC itself and normal oscilloscope probe itself do not themselves make it impossible at all. 

So, my previous answer is valid only for this my quoted sentence from 2N3055. Not for OP original question.

No, you are nitpicking. And you also don't know why I wrote it EXACTLY like that.
OP is from USA and 120 VAC  is what is how people colloquially call what comes from power outlet on the wall.

In this context it is what it means to the OP, not a general statement of 120 V of alternating current in some circuit in a textbook.

I repeated his words to make sure he understands me.

You and me exchanged enough of messages on this forum that you damn well know I know the difference between seconds and siemens (s an S) and that I'm not a complete idiot.

I also make a difference who I talk to. To a beginner, I give simplified version that is conductive for him staying alive and not blowing up expensive equipment. To you I don't talk like that, because you know all there is to know. But you (and people like you and me) don't ask questions like this on the forum. We know how it's done through professional training and years of experience.

I prefer to err on the safe side, when it's other people. It is my responsibility.

On my own time, I can choose to accept any level of risk I damn want. It's my ass on the line.

Regards,

[kelemvor]

Thanks again, guys. I really appreciate your taking the time to lay it out for me.

[kelemvor]

Decision made... I always get that queasy feeling when I spend too much... like just now.

I ordered the Rigol scope and the micsig differential probe...toys arrive Sunday.

Thanks again for your assistance, folks.

[maginnovision]

Decision made... I always get that queasy feeling when I spend too much... like just now.

I ordered the Rigol scope and the micsig differential probe...toys arrive Sunday.

Thanks again for your assistance, folks.

You made the safe choice. As long as you can afford them you won't be disappointed. Don't forget to change probe multiplier on scope to match probe if you want sane numbers.

[schmitt trigger]

Ditto for what maginnovision said.

[2N3055]

Decision made... I always get that queasy feeling when I spend too much... like just now.

I ordered the Rigol scope and the micsig differential probe...toys arrive Sunday.

Thanks again for your assistance, folks.

I'm sorry that you had to spend that much..
OTOH, you won't regret it in a long run.
Be safe and have fun learning stuff.
And yes, RTFM...
Regards,

[kelemvor]

It'll be fun for sure.  I've forgotten almost everything I learned in college.  Not only that but I've never even seen a digital scope in person.  All the scopes we had were analog, mostly 20Mhz.  There was a 40Mhz scope but you had to be the first person to get to class in order to score it for the day.  The Rigol looks so tiny in Dave's reviews, hard to believe that's an entire oscilloscope.  From what I read this thing is up-gradable to 100Mhz.  It's hard to believe, really.

[J-R]

For anyone wanting an answer that adheres to the original query:

I picked up the two channel Owon VDS1022I (isolated) USB scope from the Amazon Warehouse for $80 last year.  It is rated at 400V peak to peak directly on the inputs and comes with X10 probes so I have no trouble using it to look at waveforms from UPSs and inverters.  I can easily see the quality of the output and how it performs under various loads.  Most units just put out an alternating square wave at around 450V p-p.

With regard to safety, I think the simple explanation of don't let your body complete any circuit is adequate...

[james_s]

I have an old Bitscope and have used several other USB scopes and was not impressed by any of them. The Rigol is certainly a better value, although for someone on a tight budget who just wants to poke around and do simple stuff, there are plenty of old analog scopes out there that can be had for a song, they work just as well now as they did back when they were new.

A DSO is certainly far superior for working with digital stuff though, makes debugging microcontroller projects a lot easier and you can capture single shot events.

I don't think I'd have bought tools just to look at the output of a UPS though. You'll look at the waveform out of every UPS in the house in one evening and once you've seen it there's no real reason to look again.

[2N3055]

For anyone wanting an answer that adheres to the original query:

I picked up the two channel Owon VDS1022I (isolated) USB scope from the Amazon Warehouse for $80 last year.  It is rated at 400V peak to peak directly on the inputs and comes with X10 probes so I have no trouble using it to look at waveforms from UPSs and inverters.  I can easily see the quality of the output and how it performs under various loads.  Most units just put out an alternating square wave at around 450V p-p.

With regard to safety, I think the simple explanation of don't let your body complete any circuit is adequate...

Things can explode in your face while your looking at it, not even touching it..

Also, 10x probe didn't make it safe until 4000V. It might easily be that probe has worse safety rating than scope input itself. Also max probe voltage drops rapidly at higher frequencies..And rated voltages are for continuous use, you might as well measure higher voltage than rated and it might not explode immediately. It can slowly degrade probe to the point of problems.

Also, Owon VDS1022I, as far as I know, doesn't have isolated inputs but isolated USB. It means it is not really isolated, because scope chassis and both scope input grounds are connected together. Which means you can still make boom if you connect two channels at the wrong places, and also means that probe from one channel can electrocute you while you measure something with other channel.
What are you doing is exact equivalent to floating the scope with isolation transformers. Not a safe practice.
That USB isolation is there to avoid ground loops and for limited floating measurements on low voltages.

[2N3055]

I have an old Bitscope and have used several other USB scopes and was not impressed by any of them. The Rigol is certainly a better value, although for someone on a tight budget who just wants to poke around and do simple stuff, there are plenty of old analog scopes out there that can be had for a song, they work just as well now as they did back when they were new.

A DSO is certainly far superior for working with digital stuff though, makes debugging microcontroller projects a lot easier and you can capture single shot events.

I don't think I'd have bought tools just to look at the output of a UPS though. You'll look at the waveform out of every UPS in the house in one evening and once you've seen it there's no real reason to look again.

Old analog scopes are just that. Old.  I personally think it is a bad advice to a beginner to get something that likely doesn't work right, that he/she doesn't know how to verify if it is working OK, or to repair it if needed.
Old analog scopes are most of the time a project, not a working instruments. You will need another, working, scope to repair it, together with a signal generator and calibrator ..., And a few more of the same analog scopes as part donors..

Smart thing to do is to get one functional scope that will be your workhorse that you trust. And if you like that green analog CRT nostalgia that's fine.
As you said, as they can be had for few bucks, go ahead and buy them in addition to the one (or few) that are guaranteed to work.

But they are, when you first get them,  most of the time not a tool that you use to repair other stuff, but a repair project by itself.
For someone with equipped lab (with scopes and everything needed) and experience it's a fun project.
For a beginner, a frustration that he bought electronic waste. And even if they work when you get them they can die at any moment. Frustration.

All of those are way past their designed lifetime. They are oldtimer Sunday cars, collectibles.. We all love them, but rely on modern Toyotas to get us to work.

They survive on luck and enthusiasm of their owners. But they are not workhorses they used to be. They are cherished museum pieces. Everybody wants one.

But even little DS1000Z is infinitely more capable and appropriate for today's electronics. And cheap and has 3 year warranty.

And, best thing, you can use it to repair that old analog CRT scope that you just got the other day for a few bucks, you know, the one you always wanted because they are so cool...

Regards,

[james_s]

I don't know what makes you think old analog scopes don't work right, I have several of them that all work perfectly, they're not my daily use scope anymore but I do still use them occasionally and they still work just fine.

But then I also drive a 30 year old car as my daily transportation, it's meticulously maintained and rock solid dependable. I take good care of my stuff and it lasts. Old does not necessarily mean worn out or bad, quite often older stuff was much better built than modern devices that are much cheaper.

[rf-loop]

I don't know what makes you think old analog scopes don't work right, I have several of them that all work perfectly, they're not my daily use scope anymore but I do still use them occasionally and they still work just fine.

But then I also drive a 30 year old car as my daily transportation, it's meticulously maintained and rock solid dependable. I take good care of my stuff and it lasts. Old does not necessarily mean worn out or bad, quite often older stuff was much better built than modern devices that are much cheaper.

My most reliable and "perfect" (analog)scopes (after I leave Tek 7000 series analogs) are Tek 2465A-DM and Tek 2246A and true mint condition Tek AN/USM-488.  What ever digital mess these new scopes show, these old analogs can trust in every situation (of course inside they specifications). And they are most fast to use and adjust in real service repair situation where is not time to playing in some menu  and wonder digital miracles and bullshits on the screen, no aliasing, no gibbs ears no this and that, no clipping or overload recovery like digitals...full bandwidth even down to slowest timebase, XY mode works better than in any my budget digital... But of course they have also big disadvantages... can not see 10ns pulses with 1s period etc... )
They are old ans still even today if I send these to get cal cert with data they pass. Every single button and adjustemnts works like new out from box. After these years. 
If someone want manufature these today they are so expensive that...
Still 500 dollar chinese cheap scope can do many more things, what these old beauties can not even dream but, still I can say, if I am really in troubles in some hurry repair case and need fast scope what do not fool me in some situation... I weak up one of these oldies. Even when all others fails, these works like old RocwellCollins or Racal..

[2N3055]

I don't know what makes you think old analog scopes don't work right, I have several of them that all work perfectly, they're not my daily use scope anymore but I do still use them occasionally and they still work just fine.

But then I also drive a 30 year old car as my daily transportation, it's meticulously maintained and rock solid dependable. I take good care of my stuff and it lasts. Old does not necessarily mean worn out or bad, quite often older stuff was much better built than modern devices that are much cheaper.

No, they do work just fine, if they do, like an old car will if it does. And old doesn't necessarily mean worn out and bad. 

But it does mean that generally and usually, old stuff is simply old crap.

Amount of old analog scopes that are :

1. one of the model numbers and brands that were very good in a first place, one of the desirable ones
2. that are not worn out, broken and generally garbage
3. that will, being the unicorn and a coveted thing for analog scope connoisseurs, for sale, and not kept like you keep your good ones.

Realistically, chances for you to find one today that will, in fact, be cheaper that brand new entry level Rigol or Siglent are basically NIL.

Same with cars, and other stuff.
If it is old, and special and good, it's not going to be cheap. It is going to be very expensive.

So yeah, if you want to sell one of your Tektronix 2465A that are fully restored and  in a great shape for 50 USD I'll take one, please.
But you probably have no intention to do so.. So is everybody else that have a nice specimen.

So we end up that old analog scopes that are worth having cannot be had for 50 USD. They are much more expensive and you can get a nice new modern scope for less money.

With that being said, situation in USA is a bit better for old scopes, market is better. In EU, you can't have a good one without almost 1000€

Regards,

[J-R]

For anyone wanting an answer that adheres to the original query:

I picked up the two channel Owon VDS1022I (isolated) USB scope from the Amazon Warehouse for $80 last year.  It is rated at 400V peak to peak directly on the inputs and comes with X10 probes so I have no trouble using it to look at waveforms from UPSs and inverters.  I can easily see the quality of the output and how it performs under various loads.  Most units just put out an alternating square wave at around 450V p-p.

With regard to safety, I think the simple explanation of don't let your body complete any circuit is adequate...

Things can explode in your face while your looking at it, not even touching it..

Also, 10x probe didn't make it safe until 4000V. It might easily be that probe has worse safety rating than scope input itself. Also max probe voltage drops rapidly at higher frequencies..And rated voltages are for continuous use, you might as well measure higher voltage than rated and it might not explode immediately. It can slowly degrade probe to the point of problems.

Also, Owon VDS1022I, as far as I know, doesn't have isolated inputs but isolated USB. It means it is not really isolated, because scope chassis and both scope input grounds are connected together. Which means you can still make boom if you connect two channels at the wrong places, and also means that probe from one channel can electrocute you while you measure something with other channel.
What are you doing is exact equivalent to floating the scope with isolation transformers. Not a safe practice.
That USB isolation is there to avoid ground loops and for limited floating measurements on low voltages.

Might as well just stay in bed, then?  I'm not sure what your point here is because I'm sure I could walk up to your bench and start a fire or cause an explosion in seconds.  So is that because you have the wrong equipment or because I'm using it incorrectly?

While the chassis is made of metal, it is not connected to anything.  The scope chassis does have a ground clip which is the same as both probe grounds.  As stated before, the scope has isolated USB but yes, all the grounds are connected.  The probes that come with the scope are rated to 600V and 60MHz on the X10 setting.

[tautech]

The probes that come with the scope are rated to 600V and 60MHz on the X10 setting.

At low frequencies yes but add some fast spikes or something unexpected then the clearances in the ordinary 10x probe are insufficient to protect the user.
I gave up using 10x probes for anything 150V+ years ago.

100x probes are cheap insurance.
Play safe !

[J-R]

I don't know what makes you think old analog scopes don't work right, I have several of them that all work perfectly, they're not my daily use scope anymore but I do still use them occasionally and they still work just fine.

But then I also drive a 30 year old car as my daily transportation, it's meticulously maintained and rock solid dependable. I take good care of my stuff and it lasts. Old does not necessarily mean worn out or bad, quite often older stuff was much better built than modern devices that are much cheaper.

I have one of these from my grandfather:

https://www.oscilloscopemuseum.com/oscilloscope-philco-7019-s6133.html

He gave it to me as my first scope maybe 30 years ago and it was his first scope too (it's from the 40's).

The first thing I did when I got the Owon and one of those dirt cheap DSO kits was to connect all of them up to a function generator to see how well they got along.  Well enough!

[BravoV]

For anyone wanting an answer that adheres to the original query:

I picked up the two channel Owon VDS1022I (isolated) USB scope from the Amazon Warehouse for $80 last year.  It is rated at 400V peak to peak directly on the inputs and comes with X10 probes so I have no trouble using it to look at waveforms from UPSs and inverters.  I can easily see the quality of the output and how it performs under various loads.  Most units just put out an alternating square wave at around 450V p-p.

With regard to safety, I think the simple explanation of don't let your body complete any circuit is adequate...

Things can explode in your face while your looking at it, not even touching it..

Also, 10x probe didn't make it safe until 4000V. It might easily be that probe has worse safety rating than scope input itself. Also max probe voltage drops rapidly at higher frequencies..And rated voltages are for continuous use, you might as well measure higher voltage than rated and it might not explode immediately. It can slowly degrade probe to the point of problems.

Also, Owon VDS1022I, as far as I know, doesn't have isolated inputs but isolated USB. It means it is not really isolated, because scope chassis and both scope input grounds are connected together. Which means you can still make boom if you connect two channels at the wrong places, and also means that probe from one channel can electrocute you while you measure something with other channel.
What are you doing is exact equivalent to floating the scope with isolation transformers. Not a safe practice.
That USB isolation is there to avoid ground loops and for limited floating measurements on low voltages.

Might as well just stay in bed, then?  I'm not sure what your point here is because I'm sure I could walk up to your bench and start a fire or cause an explosion in seconds.  So is that because you have the wrong equipment or because I'm using it incorrectly?

While the chassis is made of metal, it is not connected to anything.  The scope chassis does have a ground clip which is the same as both probe grounds.  As stated before, the scope has isolated USB but yes, all the grounds are connected.  The probes that come with the scope are rated to 600V and 60MHz on the X10 setting.

That Owon VDS1022I scope is not a properly designed scope for HV work, as both channels are not isolated. Here the illustration how a "proper" isolated scope was designed n made from the 1st place.


Probing mistakes happened, and we have to admit that, and for HV stuff, one single mistake is enough to make really serious damage or even kills.

Say an example for this below case, a proper isolated scope will work as as expected and will show you the relation between primary vs secondary, while using your Owon, it simply short the primary to secondary side, just don't dare to imagine if this is a critical circuit, say that is controlling a big factory machines. 


Doing a HV probing just because "it has an isolated USB" so you're safe watching the signals at the computer(USB) side, is not a good excuse, as a good practice of probing, beside it must protect the operator, its also must protect the circuit under test from the operator's mistake. Your Owon scope shared grounds is a timed bomb that waiting to explode, if the operator did just one single fatal mistake in clipping both ground clips at the wrong points ... KABOOOM. 

[0culus]

Yeah I would NOT be using that Owon setup for probing anything that can deliver serious energy in a fault situation. CAT ratings are there for a reason, and stuff that connects to your computer via USB is not designed for that sort of use.

[J-R]

The Owon VDS1022I is well within design specifications when connected to US wall power and inverter/UPS outputs. The probe's ground connection shouldn't be connected to neutral, since there may be voltage present, although as stated previously that doesn't energize the scope chassis anyway since they are not connected.  I don't see why someone would be thinking it's right to be squeezing an alligator clip with your fingers to make a high voltage connection...

If you are sticking things into sockets or operating equipment with the cover off, then isn't it obvious you should know what you are doing?

And who are these imaginary people connecting their $100 Owon scope to "big factory machines"??  You guys strain credulity...

[0culus]

People do dumb stuff all the time. And people have been killed probing around industrial equipment with all the right gear. Even your home AC circuits can deliver a good 15-20 amps before the breaker cuts it off in a mishap (hopefully in time). The service from the pole and beyond including the type of service that plants and other industry have is a whole new ball game in terms of how much energy can be delivered to a short circuit.

The point is the impress upon newbies that you have to think about the capabilities of your gear before you ever connect it to anything. Especially something that could kill you. It's something I think about all the time even with relatively safe circuits. And I generally try to avoid situations where I have to probe high potentials. But if I have to, I get the right tools and think about what I'm doing before I do it.

[Gyro]

Might as well just stay in bed, then?  I'm not sure what your point here is because I'm sure I could walk up to your bench and start a fire or cause an explosion in seconds.  So is that because you have the wrong equipment or because I'm using it incorrectly?

While the chassis is made of metal, it is not connected to anything.  The scope chassis does have a ground clip which is the same as both probe grounds.  As stated before, the scope has isolated USB but yes, all the grounds are connected.  The probes that come with the scope are rated to 600V and 60MHz on the X10 setting.

No, no, no!

The VDS1022I is designed to break USB ground loops, not for floating at mains!

I did the original teardown thread on the VDS1022I and can tell you that (aside from a few early revisions) the metal case IS connected to the probe grounds! Even on the ones without the (copper foil strip) case grounding, the PCB track clearances from PCB to case were nothing like enough for mains isolation. The USB interface has decent galvanic isolation, BUT THAT'S ALL!

https://www.eevblog.com/forum/testgear/owon-vds1022i-quick-teardown-(versus-the-hantek-6022be)/


P.S. The supplied P6060 probes are switchable X1 / X10. Accidentally catch the switch and flip it to X1 and sh*t will happen really fast. For this reason , they are sensibly rated CAT I. You also need to read up on probe frequency/voltage de-rating curves. You don't get 600V and 60MHz, this is very relevant to fast edged signals and transients.

[Electro Detective]

 

Here we go again, punters wanting a cheap gadget to view mains voltages
and probe the unknown in a suspect inverter circuit full of HV capacitors and banks of daisy chained 12 volt -BANG- batteries

Come on guys, air conditioned hospital rooms and funeral services cost a lot more than a cheap scope or meter,
and your family and friends have enough on their plate 
without having to grieve at your first and final electronical blunder   

When you decide to cluelessly probe mains potential voltages, the power company is happy to oblige with no questions asked 
supplying all the current your unfortunate body and gear can handle...and then some 

Electro Nanny advice aside, most stuff can be done on the cheap,
but only by those who are clued up and prepared for unexpected snafus,
especially when troubleshooting faulty gear with possible miswired power sources and or cabling,
and other insane stuff you would never imagine   

It's unreasonable to expect seasoned members here to offer an easy solution to a dangerous ever changing scenario,
and read minds   

[frogg]

Is there any value at all in the cheap USB scopes for doing stuff like looking at a 60hz waveform or looking for noise in the signal for low power stepper motors?

Just my opinion, but given the tricky choice between an expensive DMM and a cheap oscilloscope, I would recommend the cheap oscilloscope first.

That said, 60hz signals are very low frequency. Any USB scope with the requisite specs for your application (no matter how cheap) should be much more useful than your DMM. I have both an 87V and a 289 and neither are as versatile as  a cheap oscilloscope. Even the cheap $100 self-triggering portable scopes are significantly more useful than either of the "premium" DMM's I have.

The big decider with USB scopes is the software. That is the key. Make sure that whatever hardware you get is matched by good software support.

[schmitt trigger]

The big decider with USB scopes is the software. That is the key. Make sure that whatever hardware you get is matched by good software support.

I could not have spelled it better.
Not only the user interface should NOT be a PITA to use (*), but the company should be solid enough such that when Microsoft releases their next Windows iteration, it should plan to support it.

(*) Note: PITA interfaces are not the sole domain of USB scopes. Many standalone scopes suffer from the same flaw. I understand that a key to reduce hardware complexity and thus cost, is to replace physical buttons with softkeys, but that is where the design engineers must really give a lot of thought to the user interface.

[Old Printer]

The big decider with USB scopes is the software. That is the key. Make sure that whatever hardware you get is matched by good software support.

I could not have spelled it better.
Not only the user interface should NOT be a PITA to use (*), but the company should be solid enough such that when Microsoft releases their next Windows iteration, it should plan to support it.

(*) Note: PITA interfaces are not the sole domain of USB scopes. Many standalone scopes suffer from the same flaw. I understand that a key to reduce hardware complexity and thus cost, is to replace physical buttons with softkeys, but that is where the design engineers must really give a lot of thought to the user interface.

Sound advice about the software with a USB scope, it usually is the weak link because good software is expensive to write. Pico & Digilent (Analog Discovery) come to mind, but neither are cheap. The Analog Discovery offers a lot of extra tools in the package and makes a great starting point for a hobbyist, though certainly not for poking around mains voltages without proper probes and training.