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Yet another "which oscope to buy" thread...

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s_mack

Posted: Jun 14, 2012 - 09:05 PM

Joined: Oct 15, 2010
Posts: 317

I've been told enough times that I need an oscilloscope, so I guess I'll get one.

I've read several dozen similar threads, but many are several years old and (perhaps) out dated.

With a budget of $450 or less, I know I'm restricted to Chinese models. I read a LOT of people suggesting the Rigol 1052e, and that's fine... but then those same people are quick to call other brands "chinese crap" (etc), but the Rigol is Chinese too so I'm not understanding the bias.

Anyway, I'm fine with getting something that every says to get... but then I see the Aktakom ADS-2111M (aka Owon SDS7102 I think) and am attracted to the much larger (and wider) screen, 10 Mpts per channel memory depth vs 500kpts/ch for the Rigol (that's 20x as much... not that I really understand the significance), included external trigger (whatever that means), and additional math function (divide). Mostly, its the screen that appeals to me I guess. Cost is very similar and under my budget.

I'm also NOT looking at spending my budget if I don't have to! I see things like the DSO Nano and wonder... is that good enough?

So to help with that, you'll need to know what I need it for, right? Honestly, I'm not sure. For the most part, its simple things like confirming a pin is high/low or that I'm generating a PWM of 400hz like I think I am, etc. I can't imagine why I'd need 100Mhz capability... but it'll probably come up some day. I don't want to spend $450 if I don't have to, but I also don't want to waste $100 if I'm going to have to spend $450 later anyway.

Note - in the foreseeable future, I don't expect to work with anything > 20V so I'm not concerned with high voltage ratings.

Cheers.

- Steven

smkipus

Posted: Jun 14, 2012 - 10:07 PM

Joined: Jun 13, 2009
Posts: 307
Location: Ann Arbor, MI

I picked up a PM3394A Philips 200MHz scope off of craigslist for like $400 complete with a recent calibration sticker! The thing doesn't stop working, analog and digital modes, and every other peripheral you can imagine. I didn't like the idea of used first, but it seems to work awesome and I'm sure I could have beat the seller down lower on his price if I wanted to. I believe this scope new went for a few thousand and it hadn't hardly been used...

Here's my Oscope thread from last year, the geniuses told me what speed I need based on the types of signals to analyze somewhere in it. It's all about rise time and having a scope be 10 times faster is what I think someone said...

http://www.avrfreaks.net/index.php?name ... highlight=

Last edited by smkipus on Jun 14, 2012 - 10:09 PM; edited 1 time in total

dryanhuston

Posted: Jun 14, 2012 - 10:09 PM

Joined: Mar 19, 2010
Posts: 52
Location: California

I have two older dual trace tektronixs oscopes (american made). Picked them up from a local electronics surplus store for about $100 each. One is from the 80's (250mhz) the other 90's (100mhz).

I am a hobbyist so they work for me. You might look into the surplus market.

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s_mack

Posted: Jun 14, 2012 - 10:58 PM

Joined: Oct 15, 2010
Posts: 317

If something falls on my lap, I'll consider used... I have no particular hangup there. But I'm in a relatively remote area in Canada without easy access to the same kind of markets most Americans enjoy. I suspect I'd be better off getting something new. Just easier if nothing else.

After reading a bunch more threads, I think I'm leaning toward the Owon SDS7102. It got a bad rap early on but it sounds like most issues were fixed over a year ago. I'll check out that thread in case it was something I missed, so thanks.

I still wonder if the "toy" devices like the DSO Nano, etc, are worth considering.

valusoft

Posted: Jun 15, 2012 - 01:49 AM

Joined: Jul 02, 2005
Posts: 5949
Location: Melbourne, Australia

s_mack wrote:

I still wonder if the "toy" devices like the DSO Nano, etc, are worth considering.

Are you planning on "playing" or "working" in the field?

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Ross McKenzie
ValuSoft
Melbourne Australia

DocJC

Posted: Jun 15, 2012 - 02:05 AM

Joined: Dec 11, 2007
Posts: 6851
Location: Cleveland, OH

Quote:

It's all about rise time and having a scope be 10 times faster is what I think someone said...

Yes. If you want to look at a square wave of 10 kHz, the fundamental frequency making up the square wave is a sin wave of 10 kHz. You need to have an adequate bandwidth to see about the first 10 harmonics of the fundamental frequency to adeuately reproduce the waveform in the time domain, i.e. on an Oscope screen.

If the bandwidth isn't wide enough, then the higher frequency components of the signal are attenuated, or lost altogether, and the square wave won't look very square.

I would be reluctant to buy a single channel Oscope. I find that I am often comparing the timing of two signals, or for analog work the input and output of a circuit, and having two channels makes this much easier.

Make sure a good pair of probes are included in the package, or be sure to include that within your budget.

A scope without a good probe is a lot like a radio without a good antenna.

JC

s_mack

Posted: Jun 15, 2012 - 02:19 AM

Joined: Oct 15, 2010
Posts: 317

valusoft wrote:

s_mack wrote:

I still wonder if the "toy" devices like the DSO Nano, etc, are worth considering.

Are you planning on "playing" or "working" in the field?

Excellent question.

I fall in between. And also beside Smile

I have no aspirations of being an EE or even a hobbiest really. I am an entrepreneur. I find niche market needs and I fill them with "clever" products that larger companies either haven't thought of or, more often, aren't willing to bother with because its too small of a market.

More often than not, they involve electronics.

Depending on the project, I hire the design out or I give it a go myself. The determining factors on that decision include: how quickly I want to get to market; how much outsourcing will cost; how big the total value of the project is expected to be.

My projects have varied from industrial washing machines to automotive electronics, where I had my biggest successes. Most recently, I've been working on a few related products for a new hobby of mine - r/c aircraft. These tend to be lower margin items where cost control is critical. As an example, I developed a electro-mechanical for a specific automobile a few years ago. The per-unit cost is aroung $28 and they sell for over $450 - so obviously there was room in there for outsourcing the electronics design (but I am proud to say I learned and did all the injection molded plastics design myself! As well as the PIC firmware having zero PIC experience at the time. I also personally did all the CANBUS analysis, which was considerable - again, with no experience). The last product I did, on the other hand, cost me $18 and I sell them for $35. I've sold 2000 of them so far, but even still had I paid someone $30k to do the design, it wouldn't have been much of a venture! In this case, it was my first foray into AVR and I did the entire "design" myself... however I can't take too much credit, as a good chunk of it was adapted from an openharware project and the rest was pretty much following datasheet typical application circuits. Still, I did it myself.

The future holds more of the same. As I learn things, I build my toolbox as does anyone else. But if I seek to learn it all, then too much time is spent apart from my core competencies - which is management, conception, procurement and, ultimately, sales.

So is that "playing" or is that "working"? Smile

I tend to believe I'll always be closer to what you envision as "playing" - I just expect to make good money at it.

- Steven

s_mack

Posted: Jun 15, 2012 - 02:25 AM

Joined: Oct 15, 2010
Posts: 317

DocJC wrote:

that entire paragraph is beyond my brain's bandwidth.

DocJC wrote:

If the bandwidth isn't wide enough, then the higher frequency components of the signal are attenuated, or lost altogether, and the square wave won't look very square.

That, I think, I understood Smile

DocJC wrote:

I would be reluctant to buy a single channel Oscope. I find that I am often comparing the timing of two signals, or for analog work the input and output of a circuit, and having two channels makes this much easier.

I already figured 2 channel would be the way to go unless I was spending "toy" money. I see that 4 channel are just too expensive except for the DSO quad, but again we're back to toys, right?

DocJC wrote:

Make sure a good pair of probes are included in the package, or be sure to include that within your budget.

A scope without a good probe is a lot like a radio without a good antenna.

JC

Thanks for that. How does one tell what is a "good" probe??

toalan

Posted: Jun 15, 2012 - 04:00 AM

Joined: Jul 21, 2005
Posts: 1373

I would consider Rigol as a reliable and dependable brand, they OEM for Agilent so their quality must be ok.

I have the Rigol DS1052E, 50 mhz bandwidth. I paid around $400 two years ago. Good scope for the money.

In another thread a few months ago someone posted about this scope, http://www.eevblog.com/forum/general-ch ... -for-free/
It runs linux and is better speced than the Rigol, but costs around $550 USD. If I could do it again, I would get that linux scope.

I do have a few complaints about my Rigol:

-When looking at small signals at DC, at certain amplifications the waveform looks totally fucked up. It looks fine when I use AC.

-Too many functions and not enough buttons, this is probably a common problem with most entry level DSO scopes though regardless of brand. You will eventually bump and grind your way to the right settings provided you push enough buttons.

-The PC software/USB interface to connect your PC the scope is dog slow. It is a complete slideshow. IIRC the resolution you see on the PC screen is the same as on the scope, ~320x240 (I think), you can not even maximize the screen so the image on your PC screen is no easier on the eyes than the LCD on the scope.

I would not recommend getting a used analog scope unless you find something dirt cheap that is local to you, it costs more to ship such a beast than it is worth.

I would also not recommend getting really low end stuff like usb PC scopes and the DSO nano. A scope is a tool, you need something that is of good quality and you also must be confident that it is of good quality.

The Owon does look nice, better than nice, it looks gorgeous, it also has a VGA output and an ethernet lan port. Seems like a winner on paper.

I would suggest you get a Rigol, it will be under your budget, with the extra money get some nice probes or a logic analyser.

smkipus

Posted: Jun 15, 2012 - 04:35 AM

Joined: Jun 13, 2009
Posts: 307
Location: Ann Arbor, MI

I smile and get dizzy when thinking of one day buying my very own logic analyzer... or better a spectrum analyzer or best a network analyzer

jwatte

Posted: Jun 15, 2012 - 04:38 AM

Joined: Apr 28, 2012
Posts: 70

I've used the Rigol at TechShop, and I'm friends with it. I wouldn't mind having one at home, but I don't pay for one.

For me, I mostly do digital logic, for which a logic analyzer is much better. I ended up buying the Salae Logic (8 channels,) for $149, and it's fantastic! The software works superbly, even in Linux, and it can decode various serial and parallel protocols. For $299 you can get 16 channels instead of 8, if you're into very wide systems.

If you're doing analog voltages that are more of the "control voltage between 0 and 5V" type, and less of the "accurately represented analog signal" type, then a voltmeter, or a cheap pocket or USB scope may be good enough, but the moment you want to actually look at something for real in the analog domain, it won't be good enough anymore.

valusoft

Posted: Jun 15, 2012 - 05:29 AM

Joined: Jul 02, 2005
Posts: 5949
Location: Melbourne, Australia

s_mack wrote:

So is that "playing" or is that "working"? Smile

I tend to believe I'll always be closer to what you envision as "playing" - I just expect to make good money at it.

- Steven

Steven,

I would call it "working". Don't short-change yourself or your tools.

Cheers,

Ross

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ValuSoft
Melbourne Australia

s_mack

Posted: Jun 15, 2012 - 05:48 AM

Joined: Oct 15, 2010
Posts: 317

Fine advice. Still a question of "which one" Smile

Now that I'm reading up on logic analyzers... wow, that seems so much more useful for what I've needed a scope for thus far, but I recognize its not at all useful for some of the things I may need a scope for in the future. Are there any that do both? I saw a chart comparing scopes somewhere and there was brief mention in it that the Rigol supported "up to 16 digital channels" but its a 2-channel so I don't get what it was referring to.

gchapman

Posted: Jun 15, 2012 - 06:11 AM

Joined: Jan 09, 2007
Posts: 1877
Location: Arlington, Texas, U.S.A.

DocJC wrote:

If you want to look at a square wave ... You need to have an adequate bandwidth to see about the first 10 harmonics of the fundamental frequency to adeuately reproduce the waveform in the time domain, i.e. on an Oscope screen.

That can get expensive.
Rules of thumb:
1. 0.5/rise-time is enough (maybe more than enough).
2. 5, or preferably 7, times the square wave's fundamental frequency.
3. 10_000USD/GHz.
AVR32's rise-time is approximately 1ns; CD4000-series CMOS is 10ns (IIRC). AVR is in-between those two.
Ref.
Erroneous Harmonics, Dr. Howard Johnson.
Take the Fifth, Dr. Howard Johnson.
Probing High-Speed Digital Designs, Dr. Howard Johnson.

gchapman

Posted: Jun 15, 2012 - 06:24 AM

Joined: Jan 09, 2007
Posts: 1877
Location: Arlington, Texas, U.S.A.

s_mack wrote:

Are there any that do both?

Yes and kinda popular with embedded systems engineers. Use the analog part for signal integrity analysis, triggering, plant's signals (usually analog) then use the logic analyzer part to connect to one of the MCU's 8-bit ports for application debug and the remainder to the board's digital signals. But, I'd use a good scope combined with an off-scope inexpensive logic analyzer and a shared trigger signal. But for field usage, an all-in-one instrument appeals if one can afford the extra cost.

meslomp

Posted: Jun 15, 2012 - 07:03 AM

Joined: May 02, 2007
Posts: 3022
Location: Nieuwegein, Netherlands

s_mack,

as Ross said, consider it work.
This means that you can write it off over a larger period of time and multiple projects.
What good is a scope that is not doing what it needs to do.

I worked at a company where they always wanted things cheap. I needed a scope and I had made a list of features I wanted on that scope to be able to do my job now(at that time) and in the future. I had made a list of 3 or 4 scopes in the 10K euro price range that had all the stuff I knew I needed.
When coming back from a holiday I found a big box on my desk with a scope that was only 8K and lacked a large number of features. reason it was a lot cheaper. After some time I needed to do a lot of measurements and would have saved me a lot of time if I would have had some of the features. I calculated that it would cost me over a month to do all the measurements then as I could not automate things and had to do it all by hand.
The manager then decided that the options needed to be bought ( same manager that first removed the options to be cheaper) cost then of all the options needed 3K and those where not all the options. The director was not very pleased when I had to explain that it was decided that the options where not needed... as it had cost him over 1K in the end. It became even worst when I later needed another option and thus had to pay again.

So trying to save money now on a piece of equipment you are going to use for a long time will be money bad spend in the end.

So you need to think:
- how many analog channels do I need 2 or 4
I would go for 4 most of the times 2 is enough, but I have a 2 channel scope at home and sometimes really lack a 3rd or 4th channel.

- Do I need digital and how many channels
This is then your logic analyzer. I do not have it, but this also is very handy at times and will save you time. Less needed though if you have 4 channel scope.

- what is the highest frequency I need to be able to measure.
Scope suppliers tell us that you need at least 3 times more band with on your scope then you have on your system. But here the trick question is what is your max frequency needed. 20MHz AVR or 150MHz FPGA. This will be a real money maker The higher the bandwith needed the higher the price

If you are not sure, you have to ask for a demonstration. Then you can play with it (having a feeling with a scope and how to use it is also a thing you need to have) nice scope but terrible user interface will also ensure you will not want to use it, hence waste of time as it is needed to save you time in measureing.

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s_mack

Posted: Jun 15, 2012 - 07:24 AM

Joined: Oct 15, 2010
Posts: 317

thanks for that.

Anyone see the QA100? Looks kind of bang-on for what I'm looking for?

"20MHz AVR or 150MHz FPGA"?? I have no idea what an FPGA is so I'm gonna say "probably not". 20Mhz AVR? Sure... why not. But I'm still not getting how that determines the frequency I need in a scope. Can't I take it for granted that my 20Mhz crystal is actually humming along at 20Mhz? Its worked so far without needing a scope. So far, the things people have told me "get a scope" for have been to confirm an output is high/low and to confirm my math was correct on a PWM and it was actually outputting at 400Hz like I thought it was. Beyond that, I can see needing to debug UART signals (9600 baud) or similar, but that's well below uC clock speed. I'm sure I'm missing things.

meslomp

Posted: Jun 15, 2012 - 08:16 AM

Joined: May 02, 2007
Posts: 3022
Location: Nieuwegein, Netherlands

if your crystal is not doing it's thing then indeed you have other problems.
but if you want to measure lets say a 20MHz square wave.
this square wave is build up out of a sine of 20Mhz, 40MHz, 60mHz, 80MHz......
Now if you measure that square wave with your scope of 20MHz the signal will look like a sine wave and not a square wave.
if you have a 100MHz scope it will look like a square wave.
so if you have a problem with a signal that is not getting high fast enough and your scope is to 'slow' then you might think it is because of the signal not being square but only slowly rising, although the square wave is a square wave, but you have a problem in another part of the circuit.
That is why you need a 'fast' scope.

I hope this clarifies a bit.

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s_mack

Posted: Jun 15, 2012 - 04:23 PM

Joined: Oct 15, 2010
Posts: 317

It does, thank you!

david.prentice

Posted: Jun 15, 2012 - 04:37 PM

Joined: Feb 12, 2005
Posts: 16323
Location: Wormshill, England

jwatte wrote:

I agree 100%. You will use a Logic Analyser. The scope will gather dust.

Of course if your main interest is in analog signals, your mileage may vary.

David.

s_mack

Posted: Jun 15, 2012 - 04:42 PM

Joined: Oct 15, 2010
Posts: 317

My gut tends to agree... however the vast majority of recommendations out there disagree it seems. Just about everything I've read on the subject says its the other way round. That an LA can be "nice to have" but the scope is a daily use item.

All I can really go by is what I could have used one for in the past, and I'm pretty sure most of it would have been the LA. The only thing I think a scope would have been useful where an LA would not have, was when I was troubleshooting an EL driver chip. I was following the typical application schematic exactly but was getting very little brightness. I would have liked to confirm the frequencies of the output signals but it was out of the range of my multimeter. Other than that, I think an LA would have been useful a few times.

I ask again about the QA100 - which appears to do both for a very reasonable amount. Its frequency isn't that high though.

DocJC

Posted: Jun 15, 2012 - 06:09 PM

Joined: Dec 11, 2007
Posts: 6851
Location: Cleveland, OH

QA100 Mixed Signal O'scope

Certainly a nice looking advertising page.

At 25 MHz bandwidth it is well above most toy scopes, but well below most professional scopes these days.

It might well meet your current needs, which you mentioned above, low speed bus analysis and some low frequency analog signals.

I can certainly see where having a mixed signal, (analog Oscope & LA) in one package would be very useful.

JC

s_mack

Posted: Jun 15, 2012 - 06:55 PM

Joined: Oct 15, 2010
Posts: 317

I looked into it more. One thing I noticed was their marketing and support material is well written in English. So at first I thought it was an American company. Its not. they are based in China and its produced in China. But the software and support services are out of the US. Does that matter? No, not really except that it means I can read and hopefully have a chance at understanding the material. I've looked at their support forum and answers are reasonably quick and extremely detailed.

They explain the lower Mhz as being a deliberate design decision and state that the hardware could be "opened up" to higher speeds, but at the expense of [a bunch of stuff I didn't understand]. It appears they're deliberately going after a specific segment and, according to them, not throwing out huge numbers just to look better.

I like that approach: "don't look better... be better". Whether or not its b/s I have no idea.

At this point though, I think that's the way I'm going to go. I think I'll take a chance on it and hope it hits everything I need. Since I don't know what I need, I'm not sure I'm really doing much better getting a "normal" scope anyway. At this moment, I think a $99 DSO would work for my needs but I can easily see that would be a waste at some point in the (probably near) future. Well, it also appears that $400 now is a waste when I need a $4000 one later. And that's a waste when I need the $40k one further down the road because I hire some engineer that won't work with cheap stuff Smile

So perhaps I should focus on the "now" and not worry so much about the future. This QA100 seems like a not bad way to go in that regard.

Still open to suggestions and thoughts though, because they are sold out at the moment anyway.

- Steven

valusoft

Posted: Jun 15, 2012 - 10:08 PM

Joined: Jul 02, 2005
Posts: 5949
Location: Melbourne, Australia

Steven,

While you are waiting, you might like to examine the scanlogic logic analyser/signal generator ( http://www.ikalogicstore.com/ ). Not expensive. I am a happy user.

Cheers,

Ross

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ValuSoft
Melbourne Australia

s_mack

Posted: Jun 15, 2012 - 11:39 PM

Joined: Oct 15, 2010
Posts: 317

Interesting, thanks! At first appearance they charge VAT incorrectly, but once you go through the checkout process, they do knock it off if you're not in the EU. So around $75 shipped to Canada... that's not bad if its a useful tool.

toalan

Posted: Jun 17, 2012 - 05:29 AM

Joined: Jul 21, 2005
Posts: 1373

I found this

http://www.aliexpress.com/product-fm/57 ... alers.html

If it lives up to half the listed specs, it is a great deal.

valusoft

Posted: Jun 17, 2012 - 06:34 AM

Joined: Jul 02, 2005
Posts: 5949
Location: Melbourne, Australia

toalan wrote:

I found this

http://www.aliexpress.com/product-fm/57 ... alers.html

If it lives up to half the listed specs, it is a great deal.

Alan, I think the "Bandwidth 3 MHz" specification is very poor. If it is half that ... well let's not even discuss it.

_________________
Ross McKenzie
ValuSoft
Melbourne Australia

meteor

Posted: Jun 17, 2012 - 05:52 PM

Joined: Dec 11, 2010
Posts: 166

Having owned my Rigol DS1052E for over a year now, I would agree with Alan's recommendation to buy one.

I would like to clarify/correct one point he made, however:

toalan wrote:

I do have a few complaints about my Rigol:

[...]

-The PC software/USB interface to connect your PC the scope is dog slow. It is a complete slideshow. IIRC the resolution you see on the PC screen is the same as on the scope, ~320x240 (I think), you can not even maximize the screen so the image on your PC screen is no easier on the eyes than the LCD on the scope.

I'm a full-time GNU/Linux guy so, before today, I had only run this Windows-based "Ultrascope" software (which is what Alan presumably refers to) once, shortly after buying the scope. My recollection and notes from back then show that the Ultrascope app is less-than-ideal, putting it kindly.

That said, I was curious about the screen update rate with Ultrascope, so I dug out that HDD and fired it up on a spare PC under WinXP.

I'm especially interested since I was very recently doing some testing under Slackware Linux using 'libusb' to pull LCD screen snapshots from this oscilloscope. (BTW, the LCD screen capture resolution is exactly 320x234 pixels.) With a USB connection to the scope, I timed Ultrascope's "Virtual Panel" as doing 50 screen updates (for which it is doing an LCD screen grab of 74890 bytes each time) in 36 seconds for an average of 0.72 seconds per refresh. My own 'libusb'-based Linux software takes roughly 0.8 seconds to pull a screenshot, but that includes time to do some extra processing. So, AFAICT, the Ultrascope software is pulling screenshots as fast as the scope will send them.

@Alan: As for not being able to zoom in, you might want to check for an update. My Ultrascope version reports "00.01.07" and the "Virtual Panel" window has a "Zoom" toggle (see upper middle part of attached snapshot) which doubles the size of the LCD shown on the PC screen.

I still hate the Ultrascope user interface. For example, every time there's a "refresh" (automated or manual) on a maximized waveform window, it annoyingly un-maximizes the window! And if you try to use the Virtual Panel window, you cannot interact with any other Ultrascope windows without closing it first! Furthermore, things as simple as changing the waveform window refresh rate cause the app to disconnect from the scope forcing you to manually reconnect!

In short, the Windows-based "Ultrascope" software is pretty bad overall. But the Rigol DS1052E is still a nice scope.

Edited to add: my Dec 2011 post about Rigol DS1052E and DS1102E

I've attached screenshots of both the "Virtual Panel" window and the Ultrascope application itself (with a single waveform data window open) for reference (and for any future surfers of this thread looking for a good scope).

jwatte

Posted: Jun 17, 2012 - 09:01 PM

Joined: Apr 28, 2012
Posts: 70

Quote:

the Ultrascope software is pulling screenshots as fast as the scope will send them.

Right -- but that doesn't make it any better Smile

I think the main problem is that the Ultrascope is scraping screen bits, rather than just sending the raw capture data, and letting the PC format it and scroll through it using the rather higher-end CPU and display capability available there. It's just Doing It Wrong (tm).

meteor

Posted: Jun 17, 2012 - 11:37 PM

Joined: Dec 11, 2010
Posts: 166

jwatte wrote:

Quote:

the Ultrascope software is pulling screenshots as fast as the scope will send them.

Right -- but that doesn't make it any better Smile

I won't defend Ultrascope, but I think you may be somewhat confused about what it's doing.

jwatte wrote:

I would agree with you if it was happening the way you say, but it's slightly more complex than that. Allow me to clarify this a bit. Ultrascope actually does both.

If you use the "Virtual Panel" window (see the upper of my 2 attached images), it's actually grabbing the raw video data (320x234x1 [8-bit color] bytes) -- i.e. it's just a screen capture, so there's no point in using it unless the physical scope is not visible at your PC. It refreshes this screen at about 0.72 seconds per update (~1.4 Hz).
Ultrascope also allows you to open multiple windows (despite the fact that I've only shown 1 open in my 2nd attached image above) showing the processed waveform data, so it's receiving the raw waveform data from the scope to do it. The Rigol DS1052E allows multiple settings to control the depth of the waveform data, but for all I know, the Ultrascope software may be programming the scope for lesser depth before issuing the ":WAVeform:DATA?" query command. I haven't done much testing with Ultrascope to be sure about that last bit. I don't think Ultrascope allows any scrolling of the waveform, but I honestly haven't played with it much. But I am certain that Ultrascope is pulling the raw waveform data. Oh, and the maximum user-selectable update rate of those waveform data windows is 1 Hz.

Ultrascope does some other things that I haven't shown or addressed. My initial post was mostly done to clarify what Alan wrote about it and to show people what it looks like.

jwatte

Posted: Jun 18, 2012 - 12:12 AM

Joined: Apr 28, 2012
Posts: 70

Quote:

it's receiving the raw waveform data from the scope to do it.

In that case, why would you do a screen capture at all? You can re-create the same screen capture PC-side if needed, and it will be a *lot* faster.
I've used the 1052E as a stand-alone scope, and it's a fine scope for that use. However, I've been looking at USB scopes like the QA100 to use at my workbench, where I always have at least one PC/monitor on.
If the 1052E can be made to read only raw data, and not bother with the screen capture, and that data can be fed into some analysis/scope software at reasonable data rates (10 Hz and up) then that'd be a really nifty feature! I haven't seen any mention of the actuals of this in the 1052E literature.
(I also notice online that the 1102E is down to $399, replacing the 1052E)

meteor

Posted: Jun 18, 2012 - 01:46 AM

Joined: Dec 11, 2010
Posts: 166

jwatte wrote:

Quote:

it's receiving the raw waveform data from the scope to do it.

In that case, why would you do a screen capture at all? You can re-create the same screen capture PC-side if needed, and it will be a *lot* faster.

Because a screen capture often includes things that are not present in the raw waveform data, including, for example, the table of measurement values or the cursors or (most importantly) the menus that appear in the screen, controlled with the "soft" buttons. The virtual scope screen effectively has to do the screen capture to easily show the menus, allowing the remote control via PC. Yes, grabbing the raw waveform data would be faster, but it's only good to recreate the waveform. The scope presents more information than just the waveform in many situations.

The point is that both screen capture and waveform capture each have their purposes. It's useful to be able to do both and the Rigol DS1052E supports both.

jwatte wrote:

If the 1052E can be made to read only raw data, [...]

It can. I've done it (under GNU/Linux).

jwatte wrote:

[...] and not bother with the screen capture, [...]

But, as I hope I've made clear, there are good reasons to sometimes capture the screen itself.

jwatte wrote:

[...] and that data can be fed into some analysis/scope software at reasonable data rates (10 Hz and up) then that'd be a really nifty feature! I haven't seen any mention of the actuals of this in the 1052E literature.

The rate at which you can capture the raw waveform data depends on the depth, which is controlled by the ":ACQuire:MEMDepth xxx" and ":WAVeform:POINts:MODE xxx" commands (or the equivalent menu settings). I don't recall how fast you can capture at each permutation of memory depth settings, though.

jwatte wrote:

(I also notice online that the 1102E is down to $399, replacing the 1052E)

I mentioned that in the thread linked to in my 1st post. Actually, the 1052E is still available last time I looked, but it's now cheaper.

jwatte

Posted: Jun 18, 2012 - 06:18 PM

Joined: Apr 28, 2012
Posts: 70

So, at $329, the 1052E is actually a real contended to the QA100 for a reasonably priced USB scope -- superior specs, on-device display, slightly higher price, and no logic analyzer. (But I already have a Saleae Logic, which has fantastic Linux software!)

meteor

Posted: Jun 18, 2012 - 08:00 PM

Joined: Dec 11, 2010
Posts: 166

jwatte wrote:

So, at $329, the 1052E is actually a real [contender] to the QA100 for a reasonably priced USB scope -- superior specs, on-device display, slightly higher price, and no logic analyzer.

I should have mentioned this in my earlier post.... Unless you put the Rigol DS1052E scope into "STOP" mode, you're only going to be getting 600 bytes of raw waveform data per active channel. If you stop the scope before issuing the ":WAVEFORM:DATA?" query, you'll get anywhere from 600 bytes to 1M bytes per channel, depending on: memory depth settings (described in my previous post), number of active channels, and whether "MATH" mode is enabled. I think that's all of the conditions. Smile

I hadn't run any timing tests because when I grab data from the scope, I can always stop it and am rarely trying to grab raw waveform data in realtime. If a measly 600 bytes per channel is adequate, you could probably grab that quite frequently, since the scope can be kept running. At the other extreme, there's no way you'll be grabbing 1M bytes at 10 Hz (even without having to stop the scope! Smile

).

So, the USB QA100 may still be the better tool for someone more interested in a continuous, realtime grab of raw waveform data. With the Rigol, grabbing low-depth, raw waveform data in realtime is more of a convenient bonus, but not primarily how I'd use the scope.

Aww, what the heck... Motivated by this discussion, and at the calculated-but-acceptable risk of boring everyone else following this thread Smile

, I went ahead and did some crude timing tests on grabbing raw waveform data at various depths:

600 bytes = 13 msec (~77 Hz)
8K bytes = 29 msec (~34 Hz)
16K bytes = 47 msec (~21 Hz)
512K bytes = 2546 msec (~0.4 Hz)
1M bytes = 5296 msec (~0.2 Hz)

Note: Only the '600 byte' grabs are done in realtime, i.e. without first stopping the scope. On the other hand, all the other grabs require stopping the scope and the times/rates I show above only reflect the time to grab the data, not any time to stop the scope and restart it (let alone allowing any [unknown amount of] required "settling" time after doing so). So take those numbers with a large grain of salt. Smile

jwatte wrote:

(But I already have a Saleae Logic, which has fantastic Linux software!)

I'm glad you added this comment -- thanks! I bought the Rigol without the logic analyzer (LA) capability because I'd read that their LA was inferior to others and that it would be a better value overall to buy the Rigol and a separate LA. Ability to use hardware under Linux is a must for me and I've collected several good comments about the Saleae Logic LA.

toalan

Posted: Jun 18, 2012 - 10:48 PM

Joined: Jul 21, 2005
Posts: 1373

valusoft wrote:

toalan wrote:

I found this

http://www.aliexpress.com/product-fm/57 ... alers.html

If it lives up to half the listed specs, it is a great deal.

Alan, I think the "Bandwidth 3 MHz" specification is very poor. If it is half that ... well let's not even discuss it.

For $50 I think it is good tool. It's sample rate is 16Msps, and their advertised bandwidth is 3mhz. That is quite honest IMHO, some USB scope advertise 100Msps and claim 100Mhz bandwidth.

You also get LA function too.

I think I will get one, I just want to see if they use onboard ADC ports of the micro and if so what is the brand of the micro. 16Msps is quite a feat if it is part of a uC peripheral set.

jwatte

Posted: Jun 19, 2012 - 04:57 AM

Joined: Apr 28, 2012
Posts: 70

Note that what looks like essentially the same box is also sold as something named a "Saleae" that's not related to the Saleae Logic. That's pretty low, but not at all uncommon for Chinese clones. (You know that "CE marked" means Chinese Export, right? Wink

http://www.aliexpress.com/product-fm/54 ... alers.html

davef

Posted: Jun 19, 2012 - 06:07 AM

Joined: Sep 03, 2005
Posts: 795
Location: Christchurch, NZ

This 'scope
http://www.hotmcu.com/xzl-studio-dx-mixed-signal-oscilloscope-logic-analyzer-p-13.html?cPath=3_26&zenid=1u4cajvajc2afcqma3l1c063b4
has links to USBee. Do I assume this is also a "knock-off"? Does one just go the USBee site to download all the software you need? Seems rather odd to me.

david.prentice

Posted: Jun 19, 2012 - 07:44 AM

Joined: Feb 12, 2005
Posts: 16323
Location: Wormshill, England

Both USBee and Saleae use incredibly cheap hardware. They just use a Cypress chip. Hence the cheap Chinese clones.

The usability depends on the quality of the software.
Both Saleae and USBee have excellent software. This justifies the selling price.

Saleae software will work with clones harmlessly.

Current USBee software detects a clone, destroys the firmware and cripples your hardware.

I presume that the Chinese may have cracked USBee software but I do not know whether they can recover firmware that the official USBee software has destroyed.

David.

davef

Posted: Jun 19, 2012 - 11:14 AM

Joined: Sep 03, 2005
Posts: 795
Location: Christchurch, NZ

Thank you for the "heads-up".

toalan

Posted: Jul 11, 2012 - 09:10 PM

Joined: Jul 21, 2005
Posts: 1373

davef wrote:

I got the scope/LA today. It is a verbatim rip of the USBee AX product. The unit uses a cypress part for USB and digital stuff, it looks like it uses an external ADC for analog sampling, probably connected via SPI. The big issue with the clone and the original is that there is really only 1 analog channel, though they advertise 2. There are 2 physical analog inputs but it looks like it just gets muxed to a single ADC pin.

I am guessing the parts cost of the unit is around $20, the PCB and soldering look to be of good quality. There looks to be TVS suppression on each of the inputs.

There looks to be a clone of the USBee Dx product for ~85. The USBee Dx looks like it has 2 real analog channels, but I guess you really do not know until you have the actual hardware and test it for yourself.

The USBee software for the AX and DX looks pretty crude, though it seems functional and did not exhibit any problems when I tested it for a few minutes.

The only other contender in the same price range is the POScope, from my own experience the POS prefix stands for Piece Of Sh*t.

I am against a blatant copy job like this, I am guilty of buying it but I only wanted to see what was on the inside. I realize the end result is the same; the cloner makes money and USBee does not.

Seems like USBee has totally stopped selling the AX and DX models, probably due to the clones.

If you are going to buy a USBee clone, get the $80 clone of the DX and not the $40 clone of the AX, as you will get 2 real analog channels.

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