Digilent Analog Discovery or budget oscilloscope.

[Howardlong]

To add: I just measured the ADC quantization with the high gain switched in, it is 400uV irrespective of V/div setting. (The analogue noise floor however is about 5mV p-p with both differential inputs grounded, and about the same with the BNC adapter and a terminator).

It looks like the low gain switches in at 1V/div by viewing the noise floor and adjusting the vertical range. This would make sense, the documentation refers to the high gain being in use up to Vdiff<7V, at 1V/div the maximum viewable on screen is 10V.

So at 500mV/div (5V total vertical resolution), with an ADC resolution of 400uV, there are 12,500 possible ADC values (5/400e-6). This is satisfyingly close to and within 14 bit resolution.

Here are the screen vertical resolutions I calculated for each V/div setting in the software:

Code: [Select]

ADC Quantization V/lsb
High res 400.00E-6
Low res 4.24E-3

V/div V/max Steps High/Low
5E+0 50E+0 11792 Low
2E+0 20E+0 4717 Low
1E+0 10E+0 2358 Low
500E-3 5E+0 12500 High
200E-3 2E+0 5000 High
100E-3 1E+0 2500 High
50E-3 500E-3 1250 High
20E-3 200E-3 500 High
10E-3 100E-3 250 High
5E-3 50E-3 125 High
2E-3 20E-3 50 High
1E-3 10E-3 25 High
500E-6 5E-3 12.5 High
200E-6 2E-3 5 High
100E-6 1E-3 2.5 High


Note that this is raw ADC resolution. Where there is oversampling at lower timebase settings, these resolutions will increase accordingly.

[Smokey]

Budget scope.  100%.  And by that I mean a Rigol DS1054Z, not an Owon thing or DSO Nano or things like that.  At 400USD for the Rigol, it will last you a really long time if you are just starting.  If you HAVE to have a logic analyzer (with more than 4 channels since you can use the scope) then just about any cheap LA is as good as the Analog Discovery.

Analog Discovery is a fun little toy but it will drive you nuts as a general purpose tool.  If nothing else, the jumper header interface sucks.

Working with with audio, 48dB extra dynamic range (theoretical difference between 8 and 14 bit), differential inputs and proper sweeps with bode plots and dual channel gen is very good to have. None of this you get with a bench scope below 20000usd AFAIK.

These functions is usually much more important than an increased bandwith from 5MHz to 100MHz or whatever.

You can suck a deep memory data capture from the bench scope and perform all the same functionality with a little bit of hoop jumping at better resolution probably. 
The "Bode plot" functionality of the Analog discovery is just:
1) Apply fixed amplitude sine wave at frequency X, measure amplitude of output voltage.
2) Increase input frequency. 
3) If less than max frequency goto 1, else stop.

You can recreate that with a scope and function gen you can script pretty easily with higher resolution and take less time.  Dave did a whole video on how to cheat and use a frequency sweep with a single shot scope capture to make a bode plot.

[Howardlong]

Budget scope.  100%.  And by that I mean a Rigol DS1054Z, not an Owon thing or DSO Nano or things like that.  At 400USD for the Rigol, it will last you a really long time if you are just starting.  If you HAVE to have a logic analyzer (with more than 4 channels since you can use the scope) then just about any cheap LA is as good as the Analog Discovery.

Analog Discovery is a fun little toy but it will drive you nuts as a general purpose tool.  If nothing else, the jumper header interface sucks.

Working with with audio, 48dB extra dynamic range (theoretical difference between 8 and 14 bit), differential inputs and proper sweeps with bode plots and dual channel gen is very good to have. None of this you get with a bench scope below 20000usd AFAIK.

These functions is usually much more important than an increased bandwith from 5MHz to 100MHz or whatever.

You can suck a deep memory data capture from the bench scope and perform all the same functionality with a little bit of hoop jumping at better resolution probably. 
The "Bode plot" functionality of the Analog discovery is just:
1) Apply fixed amplitude sine wave at frequency X, measure amplitude of output voltage.
2) Increase input frequency. 
3) If less than max frequency goto 1, else stop.

You can recreate that with a scope and function gen you can script pretty easily with higher resolution and take less time.  Dave did a whole video on how to cheat and use a frequency sweep with a single shot scope capture to make a bode plot.

Was that for magnitude and phase or just magnitude?

[Smokey]

True on the phase.  I forgot that part of the procedure. 
The AD also checks the phase offset from input to output when it measures the amplitude.  You can do this on the bench scope by having the input waveform on channel 1 and the output on channel 2 and sucking both traces out of the scope for analysis (or use the built in phase and amplitude measurements) on both phases.

[nctnico]

Ofcourse there are other ways of getting somewhere using different gear. IMHO the DAD is a very nifty tool judging from Dave's extensive video. If you can buy it for the student discount price then I'd go for it and postpone getting a 'real' oscilloscope. But even after getting a 'real' oscilloscope I'm pretty sure the DAD won't be forgotten. It has a nifty bag of tricks which you don't get that easely from other test equipment.

[LaurenceW]

Wonna, Let's try and answer your ORIGINAL question! Either/or for a beginner, you ask. I'd say the Analogue Discovery is a useful lot of electronics in one little box, it's at a bargain price and it will suit beginners well. It does things that some more expensive 'scopes cannot, but then the reverse is also true. I own BOTH, and find uses and needs for both, but then I am not a beginner.

Sure, it doesn't go from DC to light (no, wait - it does go from DC!), it doesn't go down (well) to very small voltage levels, and it doesn't do fancy triggers or advanced protocol decoding. I have other gear when I need to do those things, and these aren't what most "beginners" actually begin with, anyway. It also doesn't put out the cat (wife's job), or remind me when her birthday is coming up (wife, not cat). But it does have a very serviceable signal generator, and the buit in (low current) power supply is just fine for powering your little two-chip project. 

Yes, the interface connector is a bit "budget", and I too recommend the BNC break-out board. You won't find this little board in many "professional" electronics workshops, but as a first "lab in a box" I reckon it's neat. In a few years' time, you'll know whether you want to trade up to a decent 'scope, signal gen and power supply.

My 2 Volts' worth.

[wonna]

Wonna, Let's try and answer your ORIGINAL question! Either/or for a beginner, you ask. I'd say the Analogue Discovery is a useful lot of electronics in one little box, it's at a bargain price and it will suit beginners well. It does things that some more expensive 'scopes cannot, but then the reverse is also true. I own BOTH, and find uses and needs for both, but then I am not a beginner.

The consensus of opinion seems to be going towards the Analog Discovery, just to confirm the 'budget' scope I would be looking at is the Rigol DS1054Z. Thank you all for your opinions, it has helped a great deal.

[Howardlong]

Wonna, Let's try and answer your ORIGINAL question! Either/or for a beginner, you ask. I'd say the Analogue Discovery is a useful lot of electronics in one little box, it's at a bargain price and it will suit beginners well. It does things that some more expensive 'scopes cannot, but then the reverse is also true. I own BOTH, and find uses and needs for both, but then I am not a beginner.

The consensus of opinion seems to be going towards the Analog Discovery, just to confirm the 'budget' scope I would be looking at is the Rigol DS1054Z. Thank you all for your opinions, it has helped a great deal.

Yikes, that's a different kettle of fish. I incorrectly assumed your budget was about £140. As a scope, the DS1054Z is far, far better than the Analog Discovery. If you are only interested in a scope and not waveform generation, get the DS1054Z. No brainer. Or get both :-)

To achieve the full 14 bit resolution of the Analog Discovery s going to need some jiggery pokery in acquisition settings or post processing, the noise floor is already about 3 or 4 bits' worth. Remember that the DS1054Z already offers 12 bits in high resolution by oversampling.

[wonna]

Yikes, that's a different kettle of fish. I incorrectly assumed your budget was about £140. As a scope, the DS1054Z is far, far better than the Analog Discovery. If you are only interested in a scope and not waveform generation, get the DS1054Z. No brainer. Or get both :-)

Sorry to cause confusion, I should have specified the model in my original post. The price for the DAD was £230 and the Rigol £301 when I originally posted but later found an academic price of £140 for the DAD, so originally there was a £70 difference... I was just staying within my original budget of about £300 for the scope.

Thanks again for your replies.

[wonna]

I don't think price should be the deciding factor when comparing these two products.

That's one of the main reason's I initially stated a budget oscilloscope but it is nice to get an opinion about the Rigol vs the DAD too. I do understand the comparison is really about the advantage of an 'all in one' unit vs a relatively budget scope.

[R_G_B_]

A good feature of the analogue discovery is the ability to export waveform and network analyzer data into LT spice and Microsoft office and other such programs. Being able to characterise a transfer function of a unknown process is also another good reason to own one.

[R_G_B_]

And you can also do this
http://m.instructables.com/id/WaveForms-Analog-Discovery-on-Zybo/

[pascal_sweden]

And you can also do this
http://m.instructables.com/id/WaveForms-Analog-Discovery-on-Zybo/

What are they achieving with this setup? It is not clear to me from the instructable.
Is it some kind of automated testing? Or can you explain the experiment? =)

[tggzzz]

And you can also do this
http://m.instructables.com/id/WaveForms-Analog-Discovery-on-Zybo/

What are they achieving with this setup? It is not clear to me from the instructable.
Is it some kind of automated testing? Or can you explain the experiment? =)

It looks like they are running the waveforms software on a development board that consists of ARM processors and an FPGA. The significance is that is nothing like a conventonal WIntel nor Linux PC. That is vaguely similar in concept to the Red Pitaya, although there are very significant differences.

Whether that is a benefit for you is up to you to decide.

[Howardlong]

Yes it had me scratching my head as to what the benefit is.

If it was wrapped up in a box with knobs etc or a touch screen interface I would get it, otherwise as it stands it's even more junk on the bench with a statement "because you can".

[tggzzz]

Yes it had me scratching my head as to what the benefit is.

If it was wrapped up in a box with knobs etc or a touch screen interface I would get it, otherwise as it stands it's even more junk on the bench with a statement "because you can".

The Red Pitaya can ensure a tight fast loop between a scope's input and output to some special purpose hardware, with feedback algorithms in either FPGA hardware or software. I doubt that's possible with the Zybo/Waveforms, since the javascript interpreter would be in the loop.

I'd have thought the main beneficiary of Waveforms-ARM-Linux would be RPi class machines.

Of course "because I can and I want to" is always sufficient justification But it would be courteous to have a paragraph describing the benefits of doing it!

[Smokey]

Since they released the API I've had the feeling the analog discovery would make a good poor man's data acquisition system coupled with a test fixture.  Just plug the unit into a pin header on the fixture and away you go with analog and digital source/measurement.

[RoboTechEd]

Another thing that nobody mentioned about the discovery is how low profile it is. If you are a student, you can bring it to class with you, or put it on your desk. This was a HUGE plus for me in college. I had it in my backpack for when I needed it (debugging a project in the library after the labs closed down, etc). Also, if you are just starting and don't have a dedicated workspace, it can help you keep your area manageable. Big boy tools are great, but they take up a lot of real-estate that nto eveyrone has

[tggzzz]

Since they released the API I've had the feeling the analog discovery would make a good poor man's data acquisition system coupled with a test fixture.  Just plug the unit into a pin header on the fixture and away you go with analog and digital source/measurement.

Digilent is, I believe, now owned by National Instruments, so I suspect others have had the same idea.

[Howardlong]

Since they released the API I've had the feeling the analog discovery would make a good poor man's data acquisition system coupled with a test fixture.  Just plug the unit into a pin header on the fixture and away you go with analog and digital source/measurement.

Digilent is, I believe, now owned by National Instruments, so I suspect others have had the same idea.

Indeed, and it remains to be seen how long it will be before NI bean counters and MBAs are let loose start seeing "value by tampering" and "synergies" with them, so far the pencil necks seem to have been kept under control.

[nuno]

Personally I don't like "usb scopes", for the simple fact that you need a computer for them to be useful, and I already have my computer busy with other stuff and a small working desk. For me that is a PITA, but you millage may vary. Usability issues. Just to add another POV.

[tggzzz]

Since they released the API I've had the feeling the analog discovery would make a good poor man's data acquisition system coupled with a test fixture.  Just plug the unit into a pin header on the fixture and away you go with analog and digital source/measurement.

Digilent is, I believe, now owned by National Instruments, so I suspect others have had the same idea.

Indeed, and it remains to be seen how long it will be before NI bean counters and MBAs are let loose start seeing "value by tampering" and "synergies" with them, so far the pencil necks seem to have been kept under control.

The worst possibility is, arguably, the "everlasting match" syndrome. In other words a small company develops the proverbial everlasting match, and - in order to protect their continuing profits - it is promptly bought and borged by a wooden match company.

[mtdoc]

Personally I don't like "usb scopes", for the simple fact that you need a computer for them to be useful, and I already have my computer busy with other stuff and a small working desk. For me that is a PITA, but you millage may vary. Usability issues. Just to add another POV.

As mentioned before, the question is not which is the best scope. Clearly, the answer to that question is the Rigol.

The question is which instrument is best for a beginner starting out.  I would argue that given the price and all the included instruments - the DAD is the best choice - unless one can afford all the instruments from the start. 

I say start with the DAD then add a real scope, power supply, AWG, etc as you can afford them. The beauty of the DAD is that it will remain useful even after you have those things because of it's portability and other features as previously discussed.

[Muxr]

Personally I don't like "usb scopes", for the simple fact that you need a computer for them to be useful, and I already have my computer busy with other stuff and a small working desk. For me that is a PITA, but you millage may vary. Usability issues. Just to add another POV.

Personally I wouldn't mind a PC based oscilloscope, it would clear up my desk which already has a computer on it, but they mostly have poor software, price per performance is also poor. The analog front end is inferior and the general responsiveness and speed is not there. That's been my experience with all the ones I tried.

Perhaps one day we will have a Rigol of PC based scopes but we're not there yet.

[tggzzz]

Personally I don't like "usb scopes", for the simple fact that you need a computer for them to be useful, and I already have my computer busy with other stuff and a small working desk. For me that is a PITA, but you millage may vary. Usability issues. Just to add another POV.

Personally I wouldn't mind a PC based oscilloscope, it would clear up my desk which already has a computer on it, but they mostly have poor software, price per performance is also poor. The analog front end is inferior and the general responsiveness and speed is not there. That's been my experience with all the ones I tried.

That would be more helpful if you stated the ones you have tried.

In what way do you regard the AFEs as being inferior in ways not stated in their specification?