Owon SDS7102: How do I use slope trigger?

[AndrejaKo]

Hi!

I'm trying to understand how slope triggering works on this oscilloscope (examples for other units are also welcome!).

I can't really understand what the manual says about the slope trigger, because it only says the names of the controls and that's about it.


From settings, I have basically two important menus:

When menu:
In it I can select rising or falling slope. Further, I have 3 options marked with > = and <. There's a time value for every option which I can adjust. Now my understanding is that when I select the >, I set the scope to trigger when it takes more than written amount of time to move the signal from the lower value to the upper value. When I select =, it means that it takes that much time exactly and when I select <, it takes less than written amount of time.

Threshold&SlewRate menu:
I have a High level (T1 on screen) and a Low level (T2 on screen) options to set the voltage. If I understand how this works correctly, this is the place to set the levels which will be used to measure the time set in the When menu.

Now my problem: I'm trying to use slew rate trigger with the attached wave. The section I'd like to trigger on rises from -980 mV to 900 mV, so I set the levels in Threshold menu to -980 mV and 900 mV. Next, the time it takes for the wave to rise is 5.6  ns. I don't have that low option, so I choose less than 30 ns in the When menu.

Next, I let the scope run and it stays in auto trigger. Single/normal mode will result in to trigger at all.


So I switched it from < 30 ns mode to > 30 ns mode and then it triggered on a falling edge of a wave with a very small amplitude! When I switched it from rising to falling edge, it triggered on a rising edge.

So did I get the theoretical part correctly and am having a buggy scope or is the problem between keyboard and chair?