@w2aew;
"To test this hypothesis on your scope, setup the 100k or 1MHz square wave and make the rise time measurement. Without changing the horizontal controls, simply change the square wave frequency on the FG down to 100Hz. You should still have a rising edge on the screen, and it should still be reading the same fast rise time. This is the true rise time. "
Exactly! Same rising edge & same rise time.
As usual, thank you very much for your detailed explanation.
Regards.
It is very unfortunate that your scope LIES to you at the lower sweep speeds. Better digital scopes will at LEAST tell you that they have "low resolution" or "insufficient sample rate" for a given measurement in these types of cases. It's good that you now know about this characteristic of your scope.
as the manufacturer of his DSO designed their first model (2008), it was a 1:1 TDS2000 (A/B) series clone. I have here one,
and even with chinese firmware on it, knowing TEK, i can completly blind navigate through almost all menus. And gues what this DSO can, yes, it shows (a chinsese character) when measured values can not be properly calculated.
I have no idea why the "current" model, which was however designed already 3.5yrs ago, is not having such simple functionality.
Maybe simply lazy developer. I did reversed (partialy) their firmware and i know that they at least analyzing waveform risetime before they applying filters - so the data "valid, not valid, value" is there somewhere.
But this is exactly the "small" difference between some old known manufacturers and the rest of the world.
Or maybe simple question of price (diff between Hantek and Tek is already >500USD) ?
Maybe both, but this is what all the beginners out there should realize before they buy anything.