What is ground coupling used for on an oscilloscope?

Question

I read that it disconnected the input signal from the oscilloscope and draws a horizontal line at 0V. Why would I want to do that?

doug-

When I adjust the horizontal position in the first place there is a small marker on the left-hand side of the scope screen. I thought the marker itself represented 0V. I usually position that in the middle of the display and count divisions upward from there. Checking with the measurement features yields the same results... Clearly I'm missing something here- if you can see what it is please let me know!

Answer 1

So you can -- adjust-- the horizontal trace line to be exactly behind the zero line on the graticule of the CRT ☺

Doug