I'm considering buying a 220X series scope, but I'm a bit confused about the sampling rates - maybe you could clarify it for me?
For reference, I'm planning on measuring digital signals up to around 1MHz, and analog signals up to around 100kHz.
The 'Equivalent Time Sampling' (ETS) I think I understand - it's used when you have a repetitive signal, the scope always triggers at the same part of the waveform, and then takes samples at different offsets from that trigger point to build up a better picture of the waveform. This won't be useful to me because my data signals will come in bursts, not repetitive.
The 'streaming sampling rate' is what should be useful to me. This is 1MS/sec on all 220X models. What confuses me here is the "2M sample limit". Does this mean that it stops 2M samples after triggering? Or that it will display continuously on the screen, but if I press 'pause', I will only be able to "scroll back" 2M samples? If it's streaming the data, then surely these samples are held in the PC's memory which is likely to be a few GB, in that case why such a small limit?
The 'block mode': if I understand this correctly, it reads a number of samples and then stops reading to transmit the data, leaving gaps in your data - I can't really see how this is useful? It's just for looking at data immediately following a trigger?
The 'maximum real time sampling rate'. This is neither the streaming rate or the ETS rate but somewhere in the middle - is this the rate for block-mode measurements? Is this used with triggers, so that if I set up a trigger using say the 2203, then it would read 8000 samples at 40MS/s, then stop?
One last question - this time about grounding. I have read the warning about the ground potential, but I don't really understand what I can do about it. If my circuit is powered by some power supply other than the PC (eg a bench power supply or external switched-mode power supply), how do I safely connect the scope? I must admit to ignoring this warning on other devices because I just don't know what can be done about it!
Thanks for any help you can provide,