Thanks Dave, I had failed to find bench scopes with that sort of memory depth. I am using a UK sourced Datamane 150 megs USB scope right now, but 3 rhings against it make me want to try something else.
1: Only 15k memory depth
2: Not fully isolated and floating inputs, I work on some historic race cars with early ECU's that are poorly protected, often having the original software for mapping lost or incapable of running on none bespoke hardware, and therefore I am in fear of damaging one.
3: USB scopes can be a PITA as I worry about all the cabling, my laptop getting bust, and whether the battery is going flat, or the laptop is plain somewhere else.
I thought I would try a bench scope, as 90% of the time these cars are in the workshop and portability of equipment is not really an issue. I would like to be able to connect a bench scope to a BIG monitor though, as it makes working on a loom or engine much safer and easier if you aren't having to peer at a small screen as well as fiddle with moving or hot parts. I believe quite a few have a VGA output port these days? My budget certainly won't run to the big Agilent in your link, realistically I am probably looking at used, up to a max of £1200 UK pounds, about $1800 Aus.
Finding a bench scope that meets the requirements is proving hard as I have very limited knowledge of scopes. I am unclear as to how much memory depth I need, versus bandwidth of the scope.
I am also unclear how my current, and other, scope's "Roll Mode" works. I asked this question on the makers forum, but haven't had a reply yet:
"In automotive diagnostics we are often measuring what I call very slow waveforms, often in the sub 800 Hz region, sometimes down to 8Hz. Viewing such slow waveforms and seeing any glitches is proving tricky, so a while ago I bought the Roll Mode upgrade from you. I have been paying with it using an old signal generator I have, giving a square wave signal at 2 to 600 Hz, and capturing various sets of data at different speeds via the roll mode. By means of roll mode it is much easier to see all of the waveform over extended periods. But what effect does running out of internal memory buffer at these low frequencies have on the stored signal? When the red line has crossed the screen I believe this shows the buffer is full? After that, what is occurring? is the buffer plain full, and stays full, and the rest of the data is caught in real time on the PC? Or is the buffer emptied very fast and it refills? I assume the former as no glitch is evident in the traces. What I am getting at is when the buffer is filled, at these low frequencies will roll mode continue to store accurate traces and be reliable for seeing glitches from missed or corrupted injection or spark events, for example? To what sort of frequencies will roll mode store useful data once the buffer is filled? Apologies if the questions are naive, but the more I learn unfortunately the more questions I seem to have. Thanks."
Does Roll Mode in any way take the place of deep memory for automotive type measurements where frequencies are relatively low?
Great forum, thanks for your videos Dave, I look forward to them, and good luck with the new lab, at least you aren't paying rent on it, good move!