Review of USB oscilloscopes

[vsam0987]

Hello All,

Dave had posted a really nice review of USB oscilloscopes a couple of years back.  Looks like things have moved on since then and there are many USB scopes for the picking.

One particular entry which caught my attention was the MSO-28 USB Oscilloscope and the logic analyser.  If one compares this with the RIGOL DS1052E, it puts up a pretty good fight.  It has a decent sampling rate (200MS/s) and analog bandwidth (60MHz) and also boasts of a logic analyser.  All these specs, though not upto RIGOL, are something that a newbie could benefit from.

Now, if I had a tight budget of around 300$ and could not affort a RIGOL, it appears that there are few choices.  Some of the more promising entry-level USB scopes, which have a decent sampling rate / bandwidth / logic analyser are Quantum Analysis QA100, Bitscope 10U (new model) and Link Instruments MSO-28.   Can anyone comment which one would be the best for a newbie?  Portability and multi-functionality are must and cost is a huge penatly.

Appreciate your inputs,
Thanks in advance
Sam

[Mechatrommer]

MSO-28 USB Oscilloscope and the logic analyser.  If one compares this with the RIGOL DS1052E, it puts up a pretty good fight.  It has a decent sampling rate (200MS/s) and analog bandwidth (60MHz) and also boasts of a logic analyser.  All these specs, though not upto RIGOL, are something that a newbie could benefit from.

search and read about DSO sampling rate here in eevblog, you are in the wrong direction.

[Armin_Balija]

The 1052E is now $350.00. Really no reason not to spend the extra 50 dollars and buy yourself an actual oscilloscope in my opinion.

[JoeyP]

The QA100 seems expensive to me for the toy-like performance it offers. The data sheet reveals some interesting points: First is the statement "All specs are typical". That means not warranted, but trust us, we saw one meet these numbers in the lab.

The analog accuracy is spec'd at 5%? With lowest v/div setting of 10mv, the analog range is missing a decade since many/most scopes these days offer 1mv/div. The specified noise level of 10mvpp is the highest I've ever seen, and it's specified at 250KHz sample rate which means it's probably much higher at 100MHz rate.

The max sample rate of 100MHz is kind of 1990's, and there's no mention of equivalent-time sampling (which almost all scopes use these days to increase sample rates to the GHz range for repetitive signals). 

The logic analyzer apparently doesn't have an adjustable threshold, and there's no input capacitance spec. mentioned. Missing specs usually mean so bad that we're embarrassed to publish.

The arbitrary waveform generator is spec'd as maximum freq of ~10KHz? Either that's a typo (maybe should say ~10MHz), or it's extremely limited. I would guess it's just a digital PWM output with a low pass filter.

Seems like a product that -almost- does a lot of things.

[EEVblog]

Seems like a product that -almost- does a lot of things.

Bingo, and that's what makes it a toy, just like most other low cost USB scopes.
And at $300 you'd be crazy to buy it when a Rigol (and other decent entry level bench scopes) is only $350.

Dave.

[vsam0987]

Hello Guys,

Thanks a lot everyone for taking time to answer my question.

I am a newbie and thought it would be a good idea to get a multi-purpose portable tool to learn before buying a more serious and dedicated benchtop scope.  The reason I looked at MSO-28 is that it was offering a logic analyser as well at 325$.  The same on RIGOL with their D series is far to expensive.

I saw some of the posts and got a better understanding of how to interpret the specs.  @Mechatrommer, thanks for pointing that out.

I am starting off on basic hobby projects (mostly robotics / mechatronics, with little bit of USB development).  How important is a logic analyser in my case.  Can I still learn and also be effective at debugging using just an oscilloscope?

I would be glad if someone can comment on whether the Link instrument MSO-28 would be a good starting point in my case.

Thanks,
Sam

[EEVblog]

I am starting off on basic hobby projects (mostly robotics / mechatronics, with little bit of USB development).  How important is a logic analyser in my case.  Can I still learn and also be effective at debugging using just an oscilloscope?

Yes, you can do wonders with a basic deep memory scope.
I rarely have to use a logic analyser, although everyone's needs are different.
You can buy a cheap USB logic analyser though, and they are good value and work great.
The same can't be said for USB scopes though.
You pay a real premium for a bench scope with built in logic analyser, and generally speaking, unless you need the mixed signal integration, they aren't good value for money.

Dave.

[Mechatrommer]

The reason I looked at MSO-28 is that it was offering a logic analyser as well at 325$.  The same on RIGOL with their D series is far to expensive.

buy ds1052E series (real scope) for $300 and you can get USB LA for $15 (cheap chinese) - $300 (saleae) (20MSps - 200MSps), they are all pretty acceptable to hobbiest community. dedicated bench LA (real LA) is far too expensive for us. you may check my thread here, recently i also looking for one. PC USB Logic Analyzer - Who Has The Best Software

[JoeyP]

I would be glad if someone can comment on whether the Link instrument MSO-28 would be a good starting point in my case.

The MSO-28 has a slightly different set of deficiencies, which make it no less of a toy. The lowest analog range is even worse at 50mv/div (!). The capture depth is only 1000 samples (!) which would make it -just- usable as a scope. I can't imagine trying to use it for logic analysis (it doesn't even have sample compression as many of the other low-cost analyzers do). 

The analog channel noise spec is missing (read high). Max input spec of 20v for analog channels also sounds pretty fragile.

It does at least have equivalent-time sampling up to 2GHz, but they are advertising that as the banner sample rate, which is a bit misleading since most manufacturers advertise the real-time sample rate (which is only 200MHz for this product).

Save your money. I don't think there's a competent "all in one" in this price range. You'd be far better off to buy a decent scope, and then back-fill with a separate logic analyzer as your needs become more defined.

[EEVblog]

I would be glad if someone can comment on whether the Link instrument MSO-28 would be a good starting point in my case.

The MSO-28 has a slightly different set of deficiencies, which make it no less of a toy. The lowest analog range is even worse at 50mv/div (!). The capture depth is only 1000 samples (!) which would make it -just- usable as a scope. I can't imagine trying to use it for logic analysis (it doesn't even have sample compression as many of the other low-cost analyzers do). 

The analog channel noise spec is missing (read high). Max input spec of 20v for analog channels also sounds pretty fragile.

It does at least have equivalent-time sampling up to 2GHz, but they are advertising that as the banner sample rate, which is a bit misleading since most manufacturers advertise the real-time sample rate (which is only 200MHz for this product).

Save your money. I don't think there's a competent "all in one" in this price range. You'd be far better off to buy a decent scope, and then back-fill with a separate logic analyzer as your needs become more defined.

Spot on.
Don't buy it, it's waste of money.
It appears attractive to a beginner, but that's all it is, appearances.
Bang-per-buck is terrible, and it's barely usable as a general purpose scope.
Bench scope + USB logic analyzer as required is the best way to go.

You aren't the first person to ask this, in fact I get at least several emails a week asking exactly the same question about these cheap USB scopes. The answer is always the same, don't buy them.

Dave.

[vsam0987]

Hello Dave and JoeyP,

Your advice is greatly appreciated.  I do realize that most USB-based DSO manufacturers are flaunting incomplete specs (if not the wrong ones).  Maybe some are intentionally cheating on less-aware folks like me  .  These are especially misleading for beginners/hobbyists who are trying to find a simple solution for their projects.

I am so glad that the user forums are selflessly defending the cause of less-informed amateurs and coming to their rescue.

Thanks again,
Sam

PS:  I will make sure that I dig deeper into the archives before posting questions.  I guess it take a good deal of everyone's effort to reply.

[EEVblog]

Your advice is greatly appreciated.  I do realize that most USB-based DSO manufacturers are flaunting incomplete specs (if not the wrong ones).  Maybe some are intentionally cheating on less-aware folks like me  .  These are especially misleading for beginners/hobbyists who are trying to find a simple solution for their projects.

I wouldn't say they are misleading, as I rarely see figures that are actually fraudulent. You just have to be aware of how the specs relate to common usage, and how to compare them with a similar price bench scope.
The numbers and specs are almost always there in black and white to do comparisons.
It's not really the job of a manufacturer of USB scopes to inform you that a bench meter offers better bang-per-buck and is more usable than their USB scope 

Dave.

[seattle]

I have a QA100. I also have a Rigol DS1102E. And a USBee SX. They are all different tools used for different reasons. The QA100 can do a lot the Rigol and USBee cannot do, and vice versa. If you aren't doing much embedded software work, and are just doing basic EE stuff, then probably a standalone scope is best because the prices cannot be beat. But if you are doing a lot of embedded software work, and need to decode protocols AND see how things change in the analog realm while triggering in the digital realm then you can't beat an MSO. Anything else is like viewing the world through a pinhole.