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eevBLAB #5 - Are Mixed Signal (MSO) Oscilloscopes Worth The Money?
Posted by EEVblog on 18 Jan, 2015 09:11 -
Dave answers a forum question about whether the Rigol MSO1074Z mixed signal oscilloscope is worth double the price of the DS1054Z. Or whether it's better to buy the DSO and separate USB logic analyser.
But this applies to any mixed signal oscilloscope.
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Pretty much sums it up. I have two 4ch MSOs but don't use the LA capability very much, having four analogue channels is usually enough, as you rightly say so much is on serial busses these days.
When I was looking for a field scope though, I want to minimise the amount of kit I have with me, hence I bought an MSO1074Z-S, which has the two channel AWG too. Interestingly, I use its AWG function more than the scope. I've only used the LA function once for real work in the three months I've had it! And you're dead right, the screen gets cramped.
Couple of other things to note, the LA on the MSO1000Z is split into either 8 or 16 channels. With 8 channels, it deprives you of one of the analogue channels, and with 16 you're down to two.
Also, although not specific to the LA, the serial decode only decodes what's on the screen, and even then you need to have the timebase set fast enough for it to sample sufficiently to give results. At best you might only get 8 or 10 bytes of decode at any one time. This renders the event table feature useless.
But on the positive side, having all that stuff in one box for field use is handy, but I'd say not everyone has that requirement. -
Couple of other things to note, the LA on the MSO1000Z is split into either 8 or 16 channels. With 8 channels, it deprives you of one of the analogue channels, and with 16 you're down to two.
Wow, didn't know that!
Kinda obvious though having shared memory for that, I didn't think of checking.
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Given the subject I think this would have made a suitable EEVBlog video. It was too long (IMHO) for a blab and with a bit of actual bench work demonstrating the MSO in actual use it would have been ideal for EEVBlog video.
As mentioned, I don't have the Rigol MSO scope in question.QuoteAlso I was thinking given the recent review of the Digilent Analog Discovery you might have been able to contrast it with a device like that. Particularly since you were targeting your advice towards the value conscious demographic.
That takes the video in much wider (and longer) direction.
I just wanted to answer one question.QuotePlus, I saw a few edits creeping in as it got longer.
If you followed me on twitter you'd know why there are edits. -
that rigol is for 350$
crap country i live in , here a Chinese no name crap oscilloscope cost around 750$ 
i just saw the review about that LA "analog discovery" 99$ ... 250$ when i saw it
about the blab can't agree more ... most signals are bus signal and an oscilloscope can do the job , i can't see any good reason for investing money on LA if you don't really have the need to one.
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I saw similar advice for stand alone logic analyzers when I was researching this years ago and another plus of the two systems is separate failures and replacements if one becomes outdated.
Also just wanted to say how good the 1080p60fps videos look. Night and day difference, I can't believe other youtubers don't use that setting. Keep up the good work Dave!
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And here's me still trying to work out whether I should get the 50Mhz or 70Mhz version.
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Also just wanted to say how good the 1080p60fps videos look. Night and day difference, I can't believe other youtubers don't use that setting. Keep up the good work Dave!
Thanks.
I still need a lot more light. Considering a lighting upgrade specifically for that bench talking head shot. -
And here's me still trying to work out whether I should get the 50Mhz or 70Mhz version.
Get the 50Mhz.
70MHz doesn't offer much more for the price difference.
And it can be hacked if that's your thing. -
Dave, when are you going to start shaming manufacturers to include basic serial decoders as standard in 2015?
Might run into trouble with only two probes, but rs232? -
1st of all, thanks Dave for the whole 1000Z series comprehensive review/tear-down/trouble shooting saga
. I was waiting for this from the time he had a quick look at this scope in 
.
I would appreciate if Dave could share his thoughts on DS-1000z-S series (with Integrated Signal Generator). Is the AWG capable of recording from inputs and playing it? (Like theAgilentK-S 2000/3000 series)
Is the extra $419 (comparing DS1054Z & DS1074Z-S) worth the 2 channel signal generator
?
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1st of all, thanks Dave for the whole 1000Z series comprehensive review/tear-down/trouble shooting saga
. I was waiting for this from the time he had a quick look at this scope in .
I would appreciate if Dave could share his thoughts on DS-1000z-S series (with Integrated Signal Generator). Is the AWG capable of recording from inputs and playing it? (Like theAgilentK-S 2000/3000 series)
Is the extra (comparing DS1054Z & DS1074Z-S) worth the 2 channel signal generator?
You can get the DG1032Z for $680. I've no idea what the functional improvement is with the dedicated unit though, although a cursory glance suggests you get more arbitrary waveforms and higher maximum output frequency. -
One thing i missed in the blab or teardown /review (or i missed it) no mention of protocol triggering capabilites.
For examlle : trigger on a missing acq in i2c, or trigger on a write of a specific register in 82c , or a soecific address.
Here is an examlle. I have a dac driving an analog block. I want to measure the settling time.
At that point an mso is a must. You need not only time correlation but also bus activity trigger. Simple packet decoding is not enough the packet decoding needs ro be real time and filters need to be able to be set. I only want to trigger if a the dac is addressed. The scope should not trigger on any other device being addressed.
You dont need deep memory for that. You need realtime decoding of the packet and trigger launch.
Do the cheap machines even have such a thing ? The packet decoding is most likely done in post processing.
As comparison : the keysight 4000/5000/6000/7000 series have such trigger capability. Sont know about the 2000 or 3000.
Do the rigols ?
Even the old. 54622d has that. It can even do it on usb, can and a whole range of other busses.
I use that feature of the mso the most. Hook it up, set a filter on the transport , hide the digital channels and look at the analogs.
That is where the real strength of an MSO lies. The ability to trigger of a serial bus. -
One thing i missed in the blab or teardown /review (or i missed it) no mention of protocol triggering capabilites.
For examlle : trigger on a missing acq in i2c, or trigger on a write of a specific register in 82c , or a soecific address.
Yes, it will do all those things, or at least they are there in the trigger menu. You can also select H/L/X in each bit position in address and data (up to five successive bytes after the address), and whether it's a read, write, or either.
I have only used the trigger on SPI so far, I am not yet convinced that it always triggered: I am not saying it doesn't work, it does, but I never went back to check if it really did consistently trigger. Happy for others to give further insight. -
Recently my old 70ies vintage Tek Scope died and thus, I had to get a new scope. The stuff that I want to measure with a scope often incorporate checking digital signals as well. So I also asked myself the same question: Does it make sense to get an Digital Oscilloscope plus - maybe later - an external logic analyzer or directly go for a mixed signal oscilloscope. In the end I did not really "decide it", because I had the occasion to get a used 2 analog channel Mixed Signal Oscilloscope at an affordable price, so I stopped thinking about it and went for that option. So far I'm happy with that solution. I guess, though, that I'll probably never really need all 16 digital channels. Speaking of my own projects, I don't see a situation where 16 individual channels really need to be exactly related in the time domain to debug something. And when it is about a digital parallel bus and really capturing transferred data (btw: playing around with an old Apple II ), 16 channels might be not enough (data and adress lines, Chip Select and Read/Write-Signals...).
One thing that interests me in terms of the "combination solution" (DSO with a LA): How good (or bad) is the jitter produced by the external trigger output of Oscilloscopes? It would be really interesting to feed the External Trigger output back into one analog channel of the same scope to evaluate the jitter and the fixed portion of the delay that this external output produces. How suitable is this trigger output really to get exact analog/digital time relations from the combination of those two instruments? It would be nice to see how different scopes "behave" in this regard, especially when they're triggering on irregular signals. Maybe thats an idea for a future episode of the EEV Blog? :-) -
Ok, just quickly tested this :-) With the MSOX3000, I get a super stable 30ns delay between the actual trigger and measured trigger out beeing fed back to the same scope. No visible jitter. But when not triggered (Auto mode), there is +/- 10ns jitter visible but of course this is not a really relevant finding. (Theoretically shouldn't happen, though...)
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Be careful with the lower end Agilent mso's. I bought a msox2024 thinking I could look at i2c with he main 4 analog channels. That is locked out by agilent. Decoding must be done on the main analog channels. It's a stupid project managers attempt at differentiating ever model step.
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Nearly 40 years ago, whilst developing my Z80 based system, I'd have thought I'd died and gone to heaven had I had an MDO.
Fortunately the Z80 used static memory so one could pulse the single phase clock manually. This allowed a simple 32 way latchable LED buffer circuit together with my second hand 2ch scope (which has long since departed to the junk yard in the sky - I can't even remember the make or model) to allow debugging.
I was taught eyes first, then think and be darn sure before actually doing. Now as then that's not bad advice. Of course sometimes there is no alternative to having the right piece of equipment.
The truth is 'worth the money' depends on your circumstances. -
I have a general question about those PC-based USB logic analyzers.
Several years ago I was trying to use one of those inexpensive ones to reverse engineer some LCD display protocol. The analyzer was based on some Cypress USB chip + buffer. That attempt failed miserably because of the crosstalk between the non-shielded probe wires that connect the logic analyzer to my device under test. There were tons of false transitions shown on the traces that did not exist in reality, and that prevented me from using it at all.
What's the current state of affairs in this regard? Are there any inexpensive logic analyzers with the shielded coaxial probes? This is usually not listed in the specs, and it is hard to tell from the product photos. -
I personally wouldn't rely on getting a useful time correlation between Rigol DS1074Z output trigger and an external logic analyzer like Dave suggested in his video. The problem is in Rigol's trigger output.
I own a 1074Z for a year now and one of the ideas I had in the past was to connect 1074Z trigger output to 1052E trigger input and effectively get a 6 channel scope. DS1052E has an estimated stable delay of around 2ns on trigger input which is great. The problem is the trigger output on 1074Z which has around 70ns delay and quite a substantial jitter. Ok, I could compensate the 70ns (hopefully I remembered the nanoseconds correctly) delay but there's no way to get rid of the jitter.
Right now I don't know which firmware version (still the one it came with) I have on the scope, but I'll let you know if someone is going to pursue this issue.
I know Rigol had some jitter related issues not so long ago but don't know if the problems are related. I haven't updated my scope yet. -
Hi Dave,
I am pretty much with you on this one (unless I have an MDO with 16 chan _ CLK+Qualifier+RF SA to 6GHz).
The USBee DX looks good especially for the serial decode. It seems that there are clones of these all over eBay.
However if you can quantify the trigger delay to trigger out you can use that to trigger a real Logic Analyzer like a HP1660 series or 16500 or similar which can be had really inexpensive on eBay. Often times these analyzers can be found with a complete set of pods and clips.
I found a 1660C complete with all of the pods and 132 clips at a local hamfest for 50.00. I bought a 1660AS with the scope option on ebay (no pods or clips) for 25.00 on ebay. I hope to get the time to see if I can move the scope board into the C version to make it a CS. I am not sure I can do that but I am going to give it the old college try.
Sam
W3OHM
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Quote
Given the Digilent is essentially a MSO, I would agree with this poster, if there was time to mention other standalone logic analyzers, 30 seconds mentioning the Digilent would have been appropriate.QuoteAlso I was thinking given the recent review of the Digilent Analog Discovery you might have been able to contrast it with a device like that. Particularly since you were targeting your advice towards the value conscious demographic.
That takes the video in much wider (and longer) direction.
I just wanted to answer one question.
I just picked up a Digilent inexpensively ($100), and as I had neither a scope nor a LA, it was the perfect purchase for someone who only needs it on rare occasion. What a difference from the scope I last owned (20 yrs ago) a Tek 2236 (which I paid $2200 for used).
As for the other poster who said "This is probably long enough to be a full EEVblog episode, and I agree. The 15-20 min episodes are often quite useful; and I don't really think it's worth splitting the blabs out, they've been good watching so far.
keep up the good work Dave.
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Time correlation can be a big factor. Just finished debugging a brushless DC motor drive with Hall feedback that had internment commutation and I cant imagine doing this with anything other than a MSO as 6 correlated channels was required. It comes down to what you are doing and the amount of time you have to do it.
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Given the Digilent is essentially a MSO, I would agree with this poster, if there was time to mention other standalone logic analyzers, 30 seconds mentioning the Digilent would have been appropriate.
Sure, but I honestly didn't give it a thought. I just grabbed a couple of dedicated logic analysers that were sitting together on my shelf to flash around on camera and pressed record.
I guess the Digilent doesn't register with my subconscious as a go-to logic analyser.
But the whole point of the video was not to recommend a logic analyser, it was simply to answer the OP's question of whether or not to buy an MSO.
But you are of course right, the Digilent would have been appropriate as well. -
As for the other poster who said "This is probably long enough to be a full EEVblog episode, and I agree. The 15-20 min episodes are often quite useful; and I don't really think it's worth splitting the blabs out, they've been good watching so far.
The problem is one of a production difference between a blab video and a regular video. Blab videos are designed to be a zero thought, grab camera, press record, one take, upload.
They are designed to be quick and efficient, and expectations of them are low.
On the other hand once a decide to do a regular video, I go into regular video mode and start to think about stuff to include, experiments, demos, and extra tangent information that is appropriate etc. And a shoot it in an entirely different with dozens and dozens of different shorter clips.
It essentially takes all day to shoot and edit and muck around with even the simplest one of those.
And for a simple question like this I wanted to answer, if I decided to make it into a regular video it most likely wouldn't have because:
a) I didn't have enough time that day, and I hate shooting stuff over multiple days and avoid it wherever possible.
b) It would have screwed up my timeline because I would have to finish it today (Monday) so I probably would have done it in lieu of a Mailbag (yet again)
So I hope that gives some insight into how and why I shoot certain video. It was likely either a quick blab, or it was nothing.