Products > Test Equipment
Show us your square wave
TunerSandwich:
YIKES!!!
That Rigol "25MHz square wave" is pretty useless.....I wonder just how bad the ds2000A-S gen is @ 15MHz. My plots showed some serious issues, but I assumed they were more related to cabling and the fact that the "specAN" in the MXi isn't a "real" discreet spectral analysis tool.....you don't happen to have a ds2000A-S in house do you?
My guess is running the built-in gen on the a-s at it's "limit" is producing useless data (in terms of analyzing the cabling and acquisition tool.
You have far nicer spectrum analyzer package than anything i have kicking around....
Pjotr:
--- Quote from: TunerSandwich on January 28, 2015, 07:46:29 pm ---YIKES!!!
That Rigol "25MHz square wave" is pretty useless.....I wonder just how bad the ds2000A-S gen is @ 15MHz. My plots showed some serious issues, but I assumed they were more related to cabling and the fact that the "specAN" in the MXi isn't a "real" discreet spectral analysis tool.....you don't happen to have a ds2000A-S in house do you?
--- End quote ---
There are many more issues here, like PCB layout and PSU pulse response/decoupling at the output drivers. Capacitors and inductors are as always, everywhere and ring as they like.
Wuerstchenhund:
--- Quote from: TunerSandwich on January 28, 2015, 07:46:29 pm ---YIKES!!!
That Rigol "25MHz square wave" is pretty useless.....I wonder just how bad the ds2000A-S gen is @ 15MHz. My plots showed some serious issues, but I assumed they were more related to cabling and the fact that the "specAN" in the MXi isn't a "real" discreet spectral analysis tool.....
--- End quote ---
Don't underestimate your scope ;) The WRXi-SPECTRUM option should turn your scope into a "real" spectrum analyzer, although a vector one and not an old-style swept one (which isn't necessarily a disadvantage), and of course with only 600MHz bandwidth.
--- Quote ---you don't happen to have a ds2000A-S in house do you?
--- End quote ---
No, and what I've seen from Rigol so far nowadays I probably wouldn't touch another of their products with a bargepole. Admittedly some Rigol devices aren't as bad as say, Siglent, but after the DG1062z I've decided to stay with the big names.
--- Quote ---You have far nicer spectrum analyzer package than anything i have kicking around....
--- End quote ---
You haven't seen my R&S CMU200 yet ;)
But seriously, the E7495A/Bs are great devices, where else can you get a portable Spectrum Analyzer (500kHz to 2.7GHz) that also comes with an RF generator (IIRC 200MHz to 2.7GHz), a power meter and a cable tester (1-port and 2-port measurements), all in a rugged and weatherproof case, for less than $1500?
It run Linux so there might even be a chance to extend the functionality by "hacking".
TunerSandwich:
--- Quote from: Wuerstchenhund on January 28, 2015, 07:45:08 pm ---
I know, but I thought I should highlight the RIS issue anyways to avoid that someone takes the screenshot too literally.
A perfect square wave can't exist, it's physically impossible as it assumes a indefinitely fast transition between low and high (which in this analog world is not possble). All we can get are more or less close approximations.
--- End quote ---
Yes, I had brought that up when one gentleman said the "1THz bandwidth" of the FFT function was impressive.....considering it can only be achieved with RIS and sin x/x I think it's a somewhat "useless" measure.
My main point in this whole discussion, is really regarding the original post. In which it was sort of implied "use all of the horsepower you've got". At least in my situation all that "horsepower" doesn't lead to anything of real value. It's all interpolated and based on signal processing, and has very little bearing on the actual analog front end characteristics of the 64MXi.
I think that is a very important point to drive home....that the more bells and whistles and interpolations of the actual signal, the farther we get away from anything of merit or value. In some ways the more impressive results are those showing as little interpolation and augmentation of the "true signal" as possible. Which obviously can get VERY resource intensive ($$$$). Cabling, true quality of source, post ADC "artifacts" etc....at some point I wonder just how useful a DSO is in regards to truly "characterizing" the "quality" of the sigGen.
Seems like they are great for looking at the impulse responses (phase issues/ringing).....but for truly analyzing the "rise time" of the sigGen....hmmmm, seems like it's not so cut and dry....
TunerSandwich:
--- Quote from: Pjotr on January 28, 2015, 07:56:19 pm ---
--- Quote from: TunerSandwich on January 28, 2015, 07:46:29 pm ---YIKES!!!
That Rigol "25MHz square wave" is pretty useless.....I wonder just how bad the ds2000A-S gen is @ 15MHz. My plots showed some serious issues, but I assumed they were more related to cabling and the fact that the "specAN" in the MXi isn't a "real" discreet spectral analysis tool.....you don't happen to have a ds2000A-S in house do you?
--- End quote ---
There are many more issues here, like PCB layout and PSU pulse response/decoupling at the output drivers. Capacitors and inductors are as always, everywhere and ring as they like.
--- End quote ---
absolutely.....I have to assume that is a given....I can't imagine any scope based FFT/specAn is going to have the clarity/fidelity of a dedicated device....which focuses it's investment resources on doing one thing "as good as it can"
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