why use low frequency signal to trigger high frequency?

[mpig09]

Dear all:

I have a question on scope?
==>If there are two signals need to measure on a scpoe, one is low frequency signal
and another is high frequency signal, why we need to choose the low frequency
signal as trigger source?

Thanks.
mpig

 

[flatulent]

That way the low one will be stationary on the display. If you triggered on the high one the low one would be at a different phase each sweep and be seen as a blur.

 

[mpig09]

Dear flatulent:

Do you mean when I use low frequency signal as trigger source, each trigger edge will sweep the high frequency signal on the scope, so I can see these two signal more stationary?

If I am wrong, could you help me to describe more detail?

mpig