To put things into perspective I did same stuff on heavily outgunned old soapbox called Pico 2205 MSO. Guess could have done it on any Tek, Agilent etc also and gotten pretty much the same. It is what you expect from properly programmed DSO:
Test setup:
25MHz sine signal,
90' phase diff.
Test 2-1: 50ns timebase,
100MS/s sampling
"2205MSO_25MHz_50ns_100MS_.png"
Take note that poor soapbox is totally outgunned (5x worse sampling rate, operating at max analog freq) but manges display value with same abs error. Avg value is rock solid as it should be with 128 count avg.
Test 2-2: 20us timebase,
100MS/s sampling.
"2205MSO_25MHz_20us_100MS_zoom_.png"
Nothing changes about measurements when I zoom in/out since it's all calculated from actual data. Zoom is just UI feature as it should be. This pic is 500x zoom, with honest datapoint display.
Measurement values are
exactly same as they are on other timebases with same sampling rate. And another time: Measurements
do not (should not, cannot) depend on timebase, do not depend on zoom. They only depend on sampling rate and datapoints (more points - better averaging).
Edit:
Test 2-3: 20us timebase,
100MS/s sampling.
"2205MSO_25MHz_20us_100MS_.png"
Forgot no-zoom pic from 20us timebase. All measurements same as any other 100MS/s case.
So what's the bottom line. Why bashing the
Z-box? Because it wastes human resources. Maybe "pixel math off the screen" seems normal to someone coming from CRO. It's not normal for someone buying his fifth scope after using properly programmed DSOs for years. You wont be expecting s*it like that. It will waste your time and ruin your day.
Also as former pro programmer (now exec) I can ensure you that problem is not hardware here, it's just GUI/core logic is made a** inside out. I know the programmer type that does this. I have personally fired about 5 like this and another 5 in outsourced company f*cked a project worth millions. Worst case is when Haxx0r-aces manage it to senior programmer stage by luck or coincidence, more collateral when you fire these.