Use for ground coupling on scope?

[Phaedrus]

So I use my scope's AC and DC coupling modes quite a bit for all the usual tasks, but I've never found a use for GND coupling. Maybe once I get my 2465a in good shape it will be useful? But on my DSO I can't find any use in it. Is there something I'm missing? Or is this feature only included out of tradition?

[w2aew]

So I use my scope's AC and DC coupling modes quite a bit for all the usual tasks, but I've never found a use for GND coupling. Maybe once I get my 2465a in good shape it will be useful? But on my DSO I can't find any use in it. Is there something I'm missing? Or is this feature only included out of tradition?

It is useful to "pre-charge" the AC coupling cap with the DC content of the signal - at least that's how many of the old Tek scopes worked. Then, when you switched to AC coupling, the signal would be steady on-screen rather than "settle" from above or below the screen at the blocking cap gets charged.  I'd have to check to see if the new scopes work this way too...

[T3sl4co1l]

Not really "useful"... it's kind of intentionally anti-useful, really.  That's not to say useless; much like matter and antimatter, neither one is altogether null.

On analog scopes, the main purpose is to zero the trace to quickly see where it's referenced to, or if it needs adjustment, to give a flat line so you can line it up with the graticule.

On digital scopes, it's more either to clear an extra waveform without shutting off the channel, or to sanity-check the converter (a crapped out converter might read the ~mV noise on GND and convert it to nonsense, rather than a correct ~zero reading).

Tim