Hi All,
I've been doing electronics as a hobby since I was a teenager 40+ years ago, and decided it was finally time to retire my 1970s Tektronix 2-channel CRT scope. After a few minutes of on-line research I ordered a Rigol DS 1054Z (with 24 Msamples memory and all possible options enabled the price was still low) which arrived earlier today. I've been playing around with it for a couple of hours, and am impressed by what it can do.
One odd thing I have noticed: if I look at the built-in calibration signal (1kHz square wave, 3v amplitude) the horizontal traces at 0 and 3v look broader than in the manual. If I zoom in on them, I can see that they are each made of a pair of lines of equal brightness, separated in amplitude by tens of mV. I'm not sure how many bits are used internally, but I guess this might be quantization noise from the input ADC. I can also see this if I (electronically) ground the input. I would have hoped that the electronics noise at the input is not enough to dither the ADC. I've also noticed that as I shift the position of the trace vertically, the relationship between the two lines shifts and distorts.
My question: is this behavior "normal" or did I get a scope with a bad input amplifier or noisy ADC? Easy to send it back now, if that's the case.
Cheers,
Bruce
Edit: when I shift the vertical gain from 500mV per division to 200mV, I can hear a relay click shut internally. That's when the shape of trace near zero distorts and becomes dependent on the Y-axis offset. I don't think this should happen, is it "normal"? Also, I can see the doubling of the horizontal trace lines when the gain is set so that 3V is full scale, so it's got to be at least 30 mV, meaning that it's in the 8th or 9th bit of an ADC.
Here's a photo of the calibrator signal, I have turned off the display grid to make the structure more visible:
![Rigol DS 1054Z behavior: normal or defective?](https://www.eevblog.com/forum/index.php?action=dlattach;topic=261628.0;attach=1118456;image)