Scoposcopy: Trigger Source "LINE" and 60Hz Mains Line Hum
Here’s a quick demo of what happens when you have an improper Signal Ground for the scope. You will often get 60 (or 50) Hz hum from the mains supply superimposed on your signal of interest.
The scope’s LINE trigger source can help you identify this problem if you are seeing unexpected weirdness on your signal of interest and you suspect bad grounding on your singnal input to the oscilloscope.
The Interstate F43 function generator has a Signal Ground isolation switch on the back panel to isolate the BNC grounds from the chassis and mains ground. I’ve moved this very useful switch to the front panel to make it easier to get to.
Of course if one uses a BNC patch cord to connect the FG to some other, non-isolated instrument, this cancels the “isolation” setting of the switch and grounds the FG’s signal grounds anyhow, so one needs to be careful using this feature.