Products > Test Equipment
MSOs
FrankT:
I'm a hobbiest, with limited budget. I currently have a Dynon Instruments elab-080 USB scope. It's an all in one device with 2 analog channels, 16 digital channels, AWG, 4 digital outputs, 2 output clocks and 2 output "power supplies" (total 60mA output).
It has served me well, but recently I've struggled with its limited capture memory, 32k, slow usb (version 1), and its been playing up a lot - I'm using the AWG, and I get some strange results. The software is pretty dated, and doesn't have any protocol decoding.
So, I'm looking to replace it, either with a single device, or multiple, to provide 2 channel DSO, LA, AWG and digital outputs (and lots more sample memory).
I couldn't find much info on the forums about MSOs, except that some people that have MSOs say the wouldn't buy another. The posters don't elaborate, so I'm wondering if they are just not useful, too expensive, or can you do mixed signal analysis with a DSO and logic analyser? If so how do you combine the results?
I like the USB scope, probably because I've never owned a standalone unit. I rarely use it away from my desk, or if I do its easy enough to connect it to my lap top. Panning and zooming on a 25" monitor is hard to beat.
And budget - the elab-080 was about $500, but I know I'm looking at over $1k.
Any thoughts?
Electro Fan:
Hi FrankT,
I don't have the answers to your questions, but I liked your post a lot. I have many of the same questions.
I haven't read about anyone with a MSO saying they wouldn't buy another, but I'd be interested to hear more about such experiences and such a line of thinking. Like you, I'm up for trying to understand if it is it because MSO's are somehow not useful (kind of hard/very hard to believe), or is it because they are too expensive (perhaps when compared to separate DSO and LA units)? And similar to your question - how hard (and/or how useful) is it to combine the results if you use a DSO + a separate logic analyzer?
So far, it seems to me that a Rigol 2072 + an Intronix LogicPort (or some other similar DSO and LA) would be a very good and cost-effective combination, but I'd like to hear from people who have a $1500 to $3000 MSO that provides better utility to find out what that better utility consists of.
I'n my case I'm not as interested in an AWG (I'd like one, but except for the abitrary functionality I'm getting by with a BK4040A); and here again Rigol seems to make a pretty nice family of AWGs - including one for under $400 and about four others for under $1k.
I started a thread with some questions similar to yours that has now bumped down lower in this forum and there were some good replies and comments but we never really seemed to get to a definitive answer. Maybe a more definitive way to ask the question is, "to beat a Rigol 2072 plus an Intronix LogicPort, how far up the food chain do you have to go on MSOs?" And when you get there, what are the key advantages of the MSO?
Having tried to ask the questions(s), here are my guesses at the answers. (I hope I don't get beat too bad if they are wrong - I am clearly stating they are just guesses.)
1. A high end MSO might provide more memory, but I can't quite see how it would provide more memory or storage than a PC attached to a LA; having said that, it looks like the LogicPort is limited to 2048 samples per each of 34 channels - so maybe for long signals that need examination or for signals with lots of changes that are difficult to compress 2048 samples could be a limitation?
2. A high end MSO might provide both timing analysis and state analysis, but for example so does the $389 LogicPort.
3. A high end MSO might run at a higher clock speed (the LogicPort is limted to 500MHz for internal clock with timing mode, and 200MHz external clock for state mode.) Probably depends on what you are building, testing, debugging?
4. A high end MSO might support more protocols, but it appears that protocols often cost still more $ on MSOs; on the LogicPort about 10 or 12 popular protocols seem to be included; I think I saw another standalone LA that supported many more protocols for about $500.
Net, net: the only reasons I can come up for not using a separate LA are 1) if you need to debug things that exceed the speed/sampling/memory limitations of a standalone LA, or 2) if there is a notable benefit from being able to see the analog wave forms and the digital signals at the same time on the same screen - I'm wondering in what types of applications and how often this 2nd situation turns out be valuable?
It appears that for relatively low end / low speed work (I2C on Arduinos, etc.) that a DSO like the 2072 and a LogicPort (or even a Saleae if you don't need more than basic triggering) that the only thing missing is the simultaneous view of the analog and digital signals? Yes or No? And if yes, how valuable or cool is it to have the simultaneous analog and digital view?
Thanks to any forum members who can shed light on this stuff.
FrankT:
--- Quote from: Electro Fan on April 27, 2013, 03:59:26 am ---1. A high end MSO might provide more memory, but I can't quite see how it would provide more memory or storage than a PC attached to a LA; having said that, it looks like the LogicPort is limited to 2048 samples per each of 34 channels - so maybe for long signals that need examination or for signals with lots of changes that are difficult to compress 2048 samples could be a limitation?
--- End quote ---
There are a few logic analysers that have small amounts of memory and rely on a fast connection to the PC to provide storage. The Saleae Logic analyser (http://www.saleae.com/logic) claims 24M samples per second on each channel, but that is dependant on how well your pc and usb bus is working. The specs (http://www.saleae.com/logic/specs) say....
--- Quote ---Note that achieving the highest sample rates requires low USB latency; this may not be achievable on all computers. Performance may improve with the removal of other USB devices, using a different USB host controller, or increasing the software's process priority.
--- End quote ---
They also claim 10B sample memory, but...
--- Quote ---10B samples. Absolute max depends on data compressibility, available RAM and operating system. 10B samples assumes reasonably high compressibility.
--- End quote ---
I'm concerned the LogicPort has these issues.
Picotech make some nice usb scopes. One has a USB 3 interface so is cable of very fast transfer back to the PC.
Electro Fan:
Looks like the new buyers leading the new buyers here :)
but regarding this,
"The Saleae Logic analyser (http://www.saleae.com/logic) claims 24M samples per second on each channel, but that is dependant on how well your pc and usb bus is working. The specs (http://www.saleae.com/logic/specs) say...."
If the USB connection is the only issue a user could have a dedicated "low latency" PC (and to your earlier point, for good panning and zooming it could have a big screen - much more so than what would come with any scope); it could simply have a dedicated USB port or at least a decent USB bus; or perhaps we will see a new generation of USB LAs with USB 3.0 if this is really a notable issue.
I just don't think the USB latency/reliability issue is the numero uno issue; I can believe that other factors related to the ability to support the required sample size could be an issue for users that require mondo sample sizes. But if a USB LA was architected properly I think neither speed or sample size should be an issue.
Saleae gets lots of good reviews from users but their triggering options don't look quite as extensive as perhaps they could be. Likewise the Intronix gets very good reviews but occassionally users indicate they might like more/better sampling.
Any way you cut it, I think the next generation of LAs (both USB based and MSO based) should be very good; and as each segment gets stronger that will create competition/stimulus for the other segment to keep pace.
We know hardware is going to get faster and less expensive, and it seems that we are starting to head toward some consenus on what ths software should do. I think we are headed toward ever nicer abilities to surface stuff that was previously hard to see.
A little off topic, but here is an interesting post about an Arduino user chasing some issues with a LA (happens to be with a LogicPort): http://arduinococo.blogspot.com/?m=1
FrankT:
--- Quote from: Electro Fan on April 27, 2013, 06:09:43 am ---A little off topic, but here is an interesting post about an Arduino user chasing some issues with a LA (happens to be with a LogicPort): http://arduinococo.blogspot.com/?m=1
--- End quote ---
That's freaky, because the project I'm working on at the moment is a device to read the tapes of a CoCo (TRS-80 color computer). It was trying to play back some of the waveforms using the AWG and monitor the wave and use digital outputs for debugging. The attached image shows the waveform, the zero crossing detection, and when I think I've located a bit.
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