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 Posted: Jun 15, 2012 - 04:42 PM |
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Joined: Oct 15, 2010
Posts: 317
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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. |
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Posted: Jun 15, 2012 - 06:09 PM |
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Joined: Dec 11, 2007
Posts: 6849
Location: Cleveland, OH
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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 |
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Posted: Jun 15, 2012 - 06:55 PM |
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Joined: Oct 15, 2010
Posts: 317
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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 
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 |
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Posted: Jun 15, 2012 - 10:08 PM |
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Joined: Jul 02, 2005
Posts: 5945
Location: Melbourne, Australia
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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 |
_________________
Ross McKenzie
ValuSoft
Melbourne Australia
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Posted: Jun 15, 2012 - 11:39 PM |
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Joined: Oct 15, 2010
Posts: 317
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| 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. |
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Posted: Jun 17, 2012 - 05:29 AM |
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Joined: Jul 21, 2005
Posts: 1373
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Posted: Jun 17, 2012 - 06:34 AM |
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Joined: Jul 02, 2005
Posts: 5945
Location: Melbourne, Australia
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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.
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_________________
Ross McKenzie
ValuSoft
Melbourne Australia
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Posted: Jun 17, 2012 - 05:52 PM |
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Joined: Dec 11, 2010
Posts: 166
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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). |
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Posted: Jun 17, 2012 - 09:01 PM |
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Joined: Apr 28, 2012
Posts: 70
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Quote:
the Ultrascope software is pulling screenshots as fast as the scope will send them.
Right -- but that doesn't make it any better
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). |
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Posted: Jun 17, 2012 - 11:37 PM |
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Joined: Dec 11, 2010
Posts: 166
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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
I won't defend Ultrascope, but I think you may be somewhat confused about what it's doing.
jwatte wrote:
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).
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. |
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Posted: Jun 18, 2012 - 12:12 AM |
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Joined: Apr 28, 2012
Posts: 70
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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) |
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Posted: Jun 18, 2012 - 01:46 AM |
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Joined: Dec 11, 2010
Posts: 166
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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. |
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Posted: Jun 18, 2012 - 06:18 PM |
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Joined: Apr 28, 2012
Posts: 70
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| 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!) |
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Posted: Jun 18, 2012 - 08:00 PM |
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Joined: Dec 11, 2010
Posts: 166
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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. 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! ).
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 , 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.
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. |
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Posted: Jun 18, 2012 - 10:48 PM |
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Joined: Jul 21, 2005
Posts: 1373
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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. |
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Posted: Jun 19, 2012 - 04:57 AM |
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Joined: Apr 28, 2012
Posts: 70
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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? 
http://www.aliexpress.com/product-fm/54 ... alers.html |
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Posted: Jun 19, 2012 - 06:07 AM |
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Joined: Sep 03, 2005
Posts: 795
Location: Christchurch, NZ
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Posted: Jun 19, 2012 - 07:44 AM |
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Joined: Feb 12, 2005
Posts: 16308
Location: Wormshill, England
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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. |
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Posted: Jun 19, 2012 - 11:14 AM |
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Joined: Sep 03, 2005
Posts: 795
Location: Christchurch, NZ
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| Thank you for the "heads-up". |
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Posted: Jul 11, 2012 - 09:10 PM |
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Joined: Jul 21, 2005
Posts: 1373
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davef wrote:
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.
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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