Dave has taken a break, he posted a note in the "Announcements" forum saying he's going walkabout for a while. I'm sure the deluge of e-mails and consistent output of quality video blogs has been taxing his time for a while now!
You're saying it's 20% slower maximum, but that's actually the minimum. The maximum would be 600 MS/s slower with both scopes in single channel operation, and 300 MS/s with both scopes in dual channel operation. That's 50% and 50% maximum difference. The minimum difference would be 20% with the DS1052E in dual-channel operation and the C model in single channel operation.
I do say this makes a huge difference in performance, I operated them side by side to test my modifications and the noise in the C model made the readings far worse than even my 50 MHz unmodified channel.
I'm surprised to hear that Dave made that claim. Especially since it's not true. You don't need 10-times oversampling to be able to accurately reconstruct a waveshape. Assuming a gaussian-distribution (the normal case), you can exactly reconstruct any arbitrary waveform, using sin(x)/x with as little as 2.5x oversampling. However, to accomplish that requires very good filters (i.e., expensive), and with the quality of filtering on most consumer-grade instruments, you actually need ~4x oversampling to achieve the same results. (To get technical, it varies, depending on the instrument, from 3-5x... but 4x is a good rule-of-thumb.)
But 10x is really overkill. Thus even the 400MSa on the earlier 100MHz 1000C-series was perfectly fine. Based on your claim, they'd only be good to 40 MHz (and the 100 MHz-version of the 1000E would top out at 50 MHz).
One issue with applying the Nyquist-Shannon sampling theory to DSO's is that the theory talks about the total bandwidth of the signal. The bandwidth of an oscilloscope is the -3dB point. The bandwidth in the sampling theory is the highest frequency component. This would require a hard cut-off above 100MHz, as opposed to the Gaussian roll-off that's normal for oscilloscopes. Some of the high-end oscilloscopes, which do oversample less than 10x because they can't make the ADC's and memory fast enough, have a much sharper input filter (there's an Agilent appnote about this). Because your signal may have higher frequency components, you can't treat it like a simple Nyquist reconstruction, so more samples are useful.
Agilent did a paper on noise in digital scopes a while back, and it was quite illuminating. Even very expensive scopes can exhibit surprisingly high levels of relative noise, under some circumstances as much as 50% of one vertical division on a peak-to-peak basis! Turn on infinite Persistence, and things can get pretty ugly.
Agilent did a paper on noise in digital scopes a while back, and it was quite illuminating. Even very expensive scopes can exhibit surprisingly high levels of relative noise, under some circumstances as much as 50% of one vertical division on a peak-to-peak basis! Turn on infinite Persistence, and things can get pretty ugly.
They also did a nice job of dispelling the myth that digital scopes are intrinsically "noiser" than analog scopes. At first look, it seems obvious that the signals on a digital scope are much noiser, but that's attributable mostly to the difference in acquisition and display methods. I.e., the higher peak-to-peak noise levels you see on your digital scope are captured and displayed instantaneously. The exact same signal displayed on an analog scope will show much less noise, simply because of the persistence of the phosphor.
I.e., the random peak-to-peak fluctuations don't occur with sufficient frequency to continually repaint on the screen... so you don't see them. What you do see are those parts of the signal that occur over and over again. Or in other words, the analog scope has built-in automatic averaging. Turn averaging on with your Rigol (or any DSO), and see how much cleaner things look! Almost analog-like. As little as 4x can make a big difference.
- Mark
I beg to differ my rigol is noisy and the only way to cure it is use the inernal filtering and hope you don't have to measure in the same band as the noise
Damn, the post notification mail didn't work, and I discovered the news just today!
I just made the mod myself, and IT WORKS GREAT!! Thanks everyone... I should add a few info about my experience:
The correct method is to changhe the serial number first, then the model number, then you can power cycle the scope. Keep your fingers away from the "enter" key!! If you press it instead of the alt+010 combination, it will add a line return at the end of the serial number. Always double check the results of the query commands before power cycling.
My father did some tests with a professional signal generator, you can see the data and graphs in the attached document. Somehow excel won't let me set the horizontal scale to logarithmic, so I left everything as-is.
I'm happy!
I connected pulse generator directly to the scope and there is no ringing any more
you can see the data and graphs in the attached document.
..some tests with a professional signal generator....
I was swapping back and forth between 100mhz to 50mhz doing some testing and accidently left the E off the model number and the scope still booted up fine to my surprise. I never noticed I have left the E off the model number until I looked at the scope wondering why the model number was wrong It fired up with DS1102 as 100mhz ok luckily.
I ask becouse there is something wrong!
there is minimum 3 posibilities:
1. Test configuration is bad? (bad cable/missing or fail termination.)
2. Your oscilloscope is fail. (not my first opinion becouse both channels equal)
3. Signal generator is fail. (leveling defect)
What makes me think, maybe we should try to rename the scope as DS1152E or DS1202E and get even more from it
P.S. BTW, I wanted to say "thanks" for those exceptional detailed photos you did of the Rigol internals. The combined panoramic shots were phenominally good, and extremely well lit. Really amazing. Thanks!
Or maybe 1204D, and suddenly two additional BNC and a SCSI like connector blossom up on the front