One may say Rigal is "cheating" in the DS1000Z, and strictly speaking that's probably correct. But what difference does it make for the average hobby user working on audio or low-speed microcontroller stuff? I guess the result is still good enough for the job, if something better is really necessary, the options are plentiful.
To add more to the confusion, here are some screenshots of my "liberated" 1054Z, fed with a signal from a Leo Bodnar fast edge square generator through a 50R BNC terminator to channel 1 (the other channels perform identical). The scope was configured in dot mode and fine vertical control. The single input divider relay of the DS1000Z switches between 330 and 335mV/div and this makes a big difference: at 335mV selection, the input amplifier "sees" much less signal and the VGA integrated in the A/D converter is adjusted at high gain. I kept that as a reference trace while I changed input sensitivity to 330mV, resulting in the input amp being driven with a much larger signal. The trace shapes and rise times differ by more than 1ns, but both appear to be well within the 100MHz range.
I also took a reading at 250MSa/s. Funny enough, the input divider relay is now actuated between 250 and 245mV/div. The difference of the rise time between the two settings now is neglible but something ugly goes on with the sin(X)/x trace reconstruction. It becomes obvious that even in dot mode (not only vector display), the 'scope uses this correction function (or something else...maybe a high pass filter to compensate for the input amp's high frequency dropoff) to modify the data readings. Unfortunately, the sin(x)/x "optimization" can only be disabled at 250MSa/s so it's difficult to get a better understanding of what kind of mathematical methods are used (see the third and fourth screenshots).
One may say Rigal is "cheating" in the DS1000Z, and strictly speaking that's probably correct. But what difference does it make for the average hobby user working on audio or low-speed microcontroller stuff? I guess the result is still good enough for the job, if something better is really necessary, the options are plentiful.
Are there any differences between the DS1054Z and DS1104Z models hardware-wise? Possible, but I doubt it. The instrument is too inexpensive for the manufacturer to go through the hassle of component or instrument selection.
Cheers,
Thomas
Your measurements show a plus or minus 1.3 dB difference between the all the different conditions at the highest frequency.
Your measurements show a plus or minus 1.3 dB difference between the all the different conditions at the highest frequency.
Did you even look at PDF?
@100MHz
3.500V gen out displayed.
Demod reports 3.147V on gen (scope not connected), 2.841V on scope connector. Note that demod lowers value and is for relative not absolute measurements.
Scope reads:
3.440V at 1GSa/s, Sinc
2.080V at 250MSa/s, w/o Sinc
Sink it in. ~2V vs ~3.5V!!! When twisting knobs that should only affect signal fidelity, not amplitude.
I will write a direct message to the Rigol and ask whether it is possible to hack ds1054z and what consequences
I will write a direct message to the Rigol and ask whether it is possible to hack ds1054z and what consequences
Your measurements show a plus or minus 1.3 dB difference between the all the different conditions at the highest frequency.
Did you even look at PDF?
@100MHz
3.500V gen out displayed.
Demod reports 3.147V on gen (scope not connected), 2.841V on scope connector. Note that demod lowers value and is for relative not absolute measurements.
Scope reads:
3.440V at 1GSa/s, Sinc
2.080V at 250MSa/s, w/o Sinc
Sink it in. ~2V vs ~3.5V!!! When twisting knobs that should only affect signal fidelity, not amplitude.
...
200n-dots-sinxOff.png
100n-dots-sinxOff.png
* 20 MHz sine wave (I can't generate a 70MHz sine wave easily)
Because I want know truth and also I want of course change my opinion about this situation if the new information overrides the old one.
Most probably sin(x)/x was on when testing, or some other acquisition settings were different between the two 'scopes.
Because I want know truth and also I want of course change my opinion about this situation if the new information overrides the old one.
Dunno why, have a feeling that you will only change your opinion once you become a Rigol distributor, instead of current Siglent, really wish one day you carry both at your shop, as I respect your technical experiences at oscilloscopes especially at the boat anchor types.
I sell also Owon and have previously sold Hantek and Rigol.
(also Owon have very low failure rate but not exatly zero but ~1%)
Hantek - so much warranty time problems and also so much just DOA units from factory. Never want this catastroph repeating. In worst phase incoming Hanteks failure percent in my quality control was well over 25% (~40%). (depending how to count lots). It was finally - game over.
Rigol - long time ago I sell also R. - never get any answer from Rigol for solve any problems. So, I stopped. In my own use for some dedicated purpose I have also new Rigol (1000Z series) but I do not even think to sell these.
Scope reads:
3.440V at 1GSa/s, Sinc
2.080V at 250MSa/s, w/o Sinc
Sink it in. ~2V vs ~3.5V!!! When twisting knobs that should only affect signal fidelity, not amplitude.
First 3 images:
200ns/div ; Sin(x)/x OFF scope show normal level (as also with more low speeds)
100ns/div ; Sin(x)/x OFF level drops down and then stay same level from this speed down to 5ns/s
005ns/div ; Sin(x)/x OFF level drops down
Next 3 images:
200ns/div ; Sin(x)/x ON level ok (as also with more low speeds)
100ns/div ; Sin(x)/x ON level ok
005ns/div ; Sin(x)/x ON level ok
Also if think typical criteria for sin(x)/x interpolation there is 250MSa/s and input is 70MHz sinewave. Samplerate/input frequency = 3.57 what is ok. Even with 100MHz it is still in acceptable range (2.5)
Now they need name it Rig(x)/x
to arrange dishonestly for the result of something, for example an election, to be changed
* 20 MHz sine wave (I can't generate a 70MHz sine wave easily)
What you're saying is that when you sample a signal then don't do a proper sinc reconstruction, the answer is wrong? Is that correct?
Are you implying that "proper sinc reconstruction" is rising signal level over 4dB compared to actual recorded sample points?
Also you seem to be on position that signal max amplitude should be somehow related to sampling rate (of course given some minimal sufficient set of points to account for aliasing etc).
Is it so?
Where are you getting "actual recorded sample points" from?
Quote from: Fungus link=topic=36920.msg1806275#msg1806275Where are you getting "actual recorded sample points" from?
One should be getting then from Sinc=OFF trace...
Did you even look at PDF?
It would be more interesting if I knew more about your test setup and equipment. What's the uncertainty of the signal flatness and then of the system? Are you relying on the flatness of a signal generator sweep or are you leveling at the input?
Yes, but but it's not a legal requirement and we know that in this particular case one isn't.