Rigol MSO1074 - current FFT status?

[vwegert]

Hi all,

I'm thinking about buying a Rigol scope - perhaps a MSO1074Z-S or something in that range. I recently watched the eevBlog #845 episode, and the built-in FFT function of the Rigol really didn't look too good. HOWEVER:

1. The video is three years old and referring to different scopes. Has the situation changed in the meantime, perhaps through software upgrades or new hardware revisione?

2. Dave is using a 1 MHz carrier signal - I have no intention of using FFT in that frequency range. I'll probably staying in the audio frequency range. Even if the FFT isn't stellar, is it more usable in this range?

Thanks y'all
  Volker

[Fungus]

a) There's been a firmware update since then that improves the FFT. It's still not awesome but it's a lot better than in that video.

b) Do you need a standalone device? You sound like a candidate for an Analog Discovery II. More bits in the ADC is everything when you're doing FFTs.

[vwegert]

Thanks, Fungus. As for b) - it's a hobby, I'm nowhere near professional application, so "need" is not really the word I'd be using...

I'm a bit reluctant to consider scopes that require an external computer - for a number of reasons. At the moment I only have a Raspi permanently installed in my workshop - enough to lookup datasheets and upload code to an arduino, but nothing more. I don't want to leave one of my more powerful systems in the area because it's not a pure electronics workshop - things do get dirty from time to time. Setting up a laptop with power brick and an external scope and packing things back up all the time just seemed a lot less convenient...

The second issue is long-term support. If Rigol or any other software manufacturer stopped releasing scope firmware upgrades, the scopes would still keep working the way they were. For host-based systems these days, pretty much constant software updates are required to keep up with the "improvements" that Microsoft, Apple or even the Linux community come up with (already got that issue with some of my audio devices). I'd rather spend a little more on an integrated device that I can pull off the shelf in 5 or 10 years time, turn on and It Just Works[tm] than save a little money now and end up with an expensive brick if the manufacturer goes belly-up or decides to drop support in favor of a New And Improved product.

However, nothing's been decided yet - thanks for the heads-up, I might look into these options as well.

[Fungus]

If you have a Raspberry PI then it has an audio output that could be used as the signal generator. That way you could buy a (much cheaper) DS1054Z, or maybe the 2-channel Siglent (which costs a few $ more but has a slightly better FFT).

[rsjsouza]

Volker, I completely understand your argument regarding PC-based gear, but since you are interested in audio AND is concerned about the FFT, then becomes a matter of actually doing something useful with your equipment. The Rigol will give you a waveform visualization and measurements (where it shines) but it will be more concerning with low level signals (noisy analog inputs) and a very rough estimate of the frequency components and sinewave purity (due to the very limited FFT). Other oscilloscopes have better FFT (Siglent SDS1202X-E, for example), bit I am not familiar with their analog performance.

I would try to take into consideration the extra resolution of the Discovery and its post processing capabilities. However, for audio there is also the alternative of choosing a software and a sound card.

[bd139]

FFT on the DS1054Z (same platform) is certainly acceptable at audio frequencies. Quick contrived example I happened to have floating around on the bench ....

LM358 crossover distortion. 2v p-p 5KHz sine.



And the FFT output. You can see the harmonics. Centre frequency is 5KHz and you can see the next harmonics. You can zoom out here easily to see the remainder of the harmonic products.



I've used it for RF up to about 14MHz as well. It's acceptable there. If you want a real bit of kit here you will have to fish out for an expensive dynamic signal analyser or spectrum analyser. Or just buy a decent sound card (I used M-Audio Audiophile 2496) and use some software but then you have line level and impedance hell to deal with.

[Old Printer]

Vwegert, Not sure I understand your long term concerns for the Analog Discovery. The software platform is very mature at this point, though Digilent still occasionally releases updates. Regardless of the company's future, I don't see the AD becoming useless. There is a USB issue that prevents the AD from running on the RP but it will run on the Beaglebone. Mine runs quite nicely on a 10 year old Win box running Win 7 Home that my employer was recycling. I picked up my second AD, the original version 1, on eBay for $50 last year. It is the same as the AD2 except for the PS.

[tautech]

Dave had a quick look at the FFT performance of the current low priced DSO's:

[vwegert]

Going through the Analog Discovery videos right now, and I'm starting to like the idea. I was thinking about replacing the Raspi with some second-hand PC running Linux. Too bad the system requirements for the Waveforms software seem to be a classified military secret, though...

[egonotto]

Hello,

I like the Analog Discovery.
 
But the USB connection is damageable.
And there are only 2 true sensitivities. If I remember right +- 2.5V and +- 25V. All other sensitivities are digital zoom.

 
The system requirements for the Waveforms software are not so secret.

In https://reference.digilentinc.com/reference/software/waveforms/waveforms-3/reference-manual?redirect=1#installer
you find:

"For Linux®, the application is available in DEB and RPM packages for 32 and 64-bit systems. The required Digilent Adept Runtime must be installed separately."

If you are a student you can bye one for about 170€ at https://shop.trenz-electronic.de/de/27070-Analog-Discovery-2-Akademisch
Or for about 265€ at https://shop.trenz-electronic.de/de/27069-Analog-Discovery-2?c=29


Best regard
egonotto

[TK]

Another option is the Analog Devices ADALM-2000.  It is similar to the Analog Discovery but priced at around $100-$150.  I think software is open source and it is almost ready to use on Windows and compile from source on Linux / Mac OS X.

[Old Printer]

Going through the Analog Discovery videos right now, and I'm starting to like the idea. I was thinking about replacing the Raspi with some second-hand PC running Linux. Too bad the system requirements for the Waveforms software seem to be a classified military secret, though...

Dig a little deeper, Digilent puts out extremely detailed info and their tech support through the forum is excellent. You will find pretty much anything you want to know about the AD's in the forum. Be aware that though they claim excellent compatibility with Apple OS's some users have had problems. Unfortunately I am clueless on Linux, but their Windows compatibility is excellent. And be kind to that little USB connector as has been mentioned, as well as the 25 volt input limit. If you have old eyes(i am 66) spreading a scope and AWG across dual 25 inch screens is really nice.