Your FFT display is exactly what I would expect.
Why would you not expect the FFT computation to be dependent on the acquired dataset and the filtering/windowing imposed?
I sincerely hope that this bug does not discourage hobbyists from purchasing this scope. I bought the scope last week and immediately put it through the paces of debugging a relatively sophisticated amateur radio application I designed using both SPI and I2C data busses. Never a problem and very impressive performance. I also have an Agilent 7014B right beside it and the only fault I can find is somewhat sluggish operation with everything enabled (triggering/decoding), and the smallish fonts. Yes, there are few other things with persistence (forgetting settings when powered on e.g. measurement font) but for $380 (Tequipment with eevblog discount and free shipping), this thing could lose three channels and I would still be thrilled.
Indeed, it is the best thing going for the hobbyist. I am thinking of purchasing three more for the robotics class I teach. What a bargain!
dan W7NGA
Sure, but as we asked in another thread... which display is "more correct" then? If you expect to see some "even harmonic energy" due to the slow risetime, why does that show up in the "Normal" mode but not in the "High Resolution" mode? Would one not expect it to be the other way around?
I get the feeling you'll be seeing plenty of used units up for sale soon.
Thank you for posting those spectra. Indeed, the spectrum analyzer tells the tale. The even-numbered peaks in the Rigol's FFT of its Calibrator signal when in "Normal" acquisition mode are spurious.
Thank you for posting those spectra. Indeed, the spectrum analyzer tells the tale. The even-numbered peaks in the Rigol's FFT of its Calibrator signal when in "Normal" acquisition mode are spurious.
In "Normal" acquisition at 5Msps when you are only set to 120Ksps sample rate it means you are throwing away 97.6 percent of the sample data so it's producing peaks where none exists.
You really need to set your scope to high-res for FFTs.
In "Normal" acquisition at 5Msps when you are only set to 120Ksps sample rate it means you are throwing away 97.6 percent of the sample data so it's producing peaks where none exists.
You really need to set your scope to high-res for FFTs.Well, that's clear enough.... now. Is that "feature" mentioned in the User's Manual somewhere?
Tips
- You can use HORIZONTAL SCALE to adjust the center frequency
and horizontal scale at the same time.
- Signals with DC components or deviation would cause error or deviation of
the FFT waveform components. To reduce the DC components, set the
“Channel Coupling” to “AC”.
- To reduce the random noise and aliasing frequency components of
repetitive or single pulse, set the “Acquisition Mode” of the oscilloscope
to “Average”.
Can reproduce the freeze bug on .04.02 SP4 board 0.1.1 with all options (except 500microvolt/d) enabled. The mem setting is saved with 1 channel on, but reverts to auto if the scope is powered off with 4 channels enabled and set to power on last.
Edit: Just upgraded to .04.03, and somewhat the same problem. Inputting a 1MHz sine wave instantly locks up the scope after switching the persistence. But inputting a 1KHz sine wave does not. I can change the persistence to all the different settings. I can also increase the frequency to 1MHz again and change the persistence around. But if I exit the zoom mode and enter it again at 1MHz it locks up. Basically, if the scope does not initially crash after switching the persistence mode in zoom mode, I can change the frequency to whatever I want, 5Hz and 25MHz for example, and also change the persistence to whatever I want. Tried to enter at 500KHz and it locked up, seems to be a specific frequency and up that it locks up.
In "Normal" acquisition at 5Msps when you are only set to 120Ksps sample rate it means you are throwing away 97.6 percent of the sample data so it's producing peaks where none exists.
You really need to set your scope to high-res for FFTs.Well, that's clear enough.... now. Is that "feature" mentioned in the User's Manual somewhere?
Yes:QuoteTips
? You can use HORIZONTAL SCALE to adjust the center frequency
and horizontal scale at the same time.
? Signals with DC components or deviation would cause error or deviation of
the FFT waveform components. To reduce the DC components, set the
“Channel Coupling” to “AC”.
? To reduce the random noise and aliasing frequency components of
repetitive or single pulse, set the “Acquisition Mode” of the oscilloscope
to “Average”.
Well, that's clear enough.... now. Is that "feature" mentioned in the User's Manual somewhere? "Thrown away sample data" causing peaks to appear where none exists.... That's interesting. I would have expected that "thrown away data" would cause peaks that _should appear_, to be missing or attenuated, not the other way around. Would you call this an aliasing problem.... which isn't affected by the "anti-aliasing" setting at all..... ?
Thanks for doing that comparison. Yes, I agree that the DS1054Z is a great bargain, an excellent scope for beginners like me.
Hopefully you will make up a handout to notify your students about the conditions for lock-up and what settings are "poison" on your new ones, and how to recover from a locked-on-startup condition. Or maybe you can select new ones that don't lock up, from your vendor's stock. After all, you have slightly less than a 50 percent chance of getting scopes that don't show this bug. Or maybe Rigol will have issued another firmware update that fixes this bug by the time you return to your classes.
Just curious ... is it possible to get the Tek TDS 2014B to start up "frozen" and unresponsive to all controls, after being shut down in a running, fully operational state?
Thanks for doing that comparison. Yes, I agree that the DS1054Z is a great bargain, an excellent scope for beginners like me.
Hopefully you will make up a handout to notify your students about the conditions for lock-up and what settings are "poison" on your new ones, and how to recover from a locked-on-startup condition. Or maybe you can select new ones that don't lock up, from your vendor's stock. After all, you have slightly less than a 50 percent chance of getting scopes that don't show this bug. Or maybe Rigol will have issued another firmware update that fixes this bug by the time you return to your classes.
Just curious ... is it possible to get the Tek TDS 2014B to start up "frozen" and unresponsive to all controls, after being shut down in a running, fully operational state?
Maybe you should consider selling your DS1054Z -- or start using it, to work on some nice, cool projects?
Spending all your electronics hobby time searching for flies in the ointment can't be good for you...