The trigger level controls at what voltage the left side of the trace starts. If the trigger level is set too high, it will not synchronize and you get a running wave. You should be able to stabilize the trace by lowering the trigger voltage. On a digital scope, the level is shown by a dotted line and once it enters the waveform, it should stabilize. DSO's can be a bitch to use, there are so many settings. You need to look at the trigger settings and mess with them until you get it to work.

Bob

Thank you, Bob, I will check that. I use O-scopes once in a blue moon, since my job is rather electrical in nature. Almost every time I have to use a different model of the O-scope, whatever is available on the site. I downloaded the manual for this one, so I have a homework to do )
Thanks to everyone!

 

Your signal generators seem to have output frequencies slightly diferring from each other.

While keeping the same channel, say No 1, to always trigger both channels, make sure both generators have the same nominal frequency selected.

Once there, apply generator A to ch. 1 and generator B to ch. 2. Note which one is running and to where (left or right).
Now do the swapping with gen A to ch. 2 and gen B to ch. 1.

If they actually difer in frequency you will see the same channel running but now in the other direction.

Nice moment to play Lissajous.

 

make sure both generators have the same nominal frequency selected.

And also set to the same amplitude.

 

And also set to the same amplitude.

If I understand this right, they only need to have the necessary to trigger the scope but not to be the same.

 

If I understand this right, they only need to have the necessary to trigger the scope but not to be the same.

That all depends on the trigger level setting (and other settings like filters and coupling). What may work for high input voltage may not work for low voltage input.