Cheap USB scopes

[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.