spend ~700$ for Rigol 2000a or spend 500$ more and get the R&S RTB 2000for ~1200

[nctnico]

Ok but that sounds to me like you're looking for an awful lot of memory (5 seconds at what Bitrate? I2C is not rally fast) And then you're offloading the data to a computer or are you looking at this much data on the oscilloscope?

I recently had a problem like this, a test box does some 10 seconds of SPI, and even though I could record it on a scope it was highly impractical to browse through it. I ended up using A logic analyzer and had the person who requested the data install the analyzer software to browse through the data. Much easier on the PC.

On a decent scope you can save the decoded data to a CSV file for analysis on a PC.

[ChuckDarwin]

Specs aside, if you are concentrating on new (or factory refurb), many T&M companies have ed discounts or run educational specials.  Some directly to students and some via a department (dept orders w/ your payment info).  Check with the the companies of interest directly--distributors aren't always aware of all the offered programs.  Also consider factory refurb/demo w/ factory warranty directly from the manufacturer (Keysight, Siglent, Rigol, Instek, R&S?, Tek?).  Of course used can offer some outstanding deals, if you are comfortable going in that direction.

[MrW0lf]

On a decent scope you can save the decoded data to a CSV file for analysis on a PC.

This is why I like USB gear - if for any "advanced" stuff need PC connection anyway, may as well skip the knobs. It may be forgotten but originally PC was intended for data processing, not browsing forums or enjoying (cat) videos

[Keysight DanielBogdanoff]

I did not experience any limitation due to having small capture memory.  I just change the Timebase and recapture if I want to see the details.

What if it's a one-time event? Or only happens every 53 minutes? 

I'm not going to derail the discussion any further  , but no scope out there will capture 53 minutes of data at full sample rate. Period. Segmented memory or normal trigger mode instead of auto trigger mode .

[nctnico]

I did not experience any limitation due to having small capture memory.  I just change the Timebase and recapture if I want to see the details.

What if it's a one-time event? Or only happens every 53 minutes? 

I'm not going to derail the discussion any further  , but no scope out there will capture 53 minutes of data at full sample rate. Period. Segmented memory or normal trigger mode instead of auto trigger mode .

Nobody claims that but having more memory for segmented recording makes it easier to capture a rare event because you have more segments.  This is especially true if you have to stop the recording manually and don't want to babysit the test setup all the time. Again, triggering on a runt or malformed signal won't work because you don't know what the actual problem is.

[TK]

Again, triggering on a runt or malformed signal won't work because you don't know what the actual problem is.

I am trying to understand your point, but it is getting harder... I understand that you don't know what the actual problem is, because if you knew, you won't need any TEST equipment after all.  But you must have a vague idea or suspicion.  If not, then you need infinite channels, infinite memory and infinite time to be able to capture and analyze the fault in a system.  If you have a suspicion and you place a probe on the place, then you must also have an idea of what the signal should look like or behave.  What you are suggesting is brute force diagnostics.

[nctnico]

Again, triggering on a runt or malformed signal won't work because you don't know what the actual problem is.

I am trying to understand your point, but it is getting harder... I understand that you don't know what the actual problem is, because if you knew, you won't need any TEST equipment after all.  But you must have a vague idea or suspicion.  If not, then you need infinite channels, infinite memory and infinite time to be able to capture and analyze the fault in a system.  If you have a suspicion and you place a probe on the place, then you must also have an idea of what the signal should look like or behave.  What you are suggesting is brute force diagnostics.

If you get a black box with a problem description the best thing to do is to trace information from the source to the destination. Doing this based on suspicion (=fantasising -I'm avoiding the word speculation here-) and start at a random spot somewhere in the signal chain is likely to end up in a wild goose chase because you might be looking at multiple problems with unrelated causes.

For one of such problems I had to figure out is why a PC application shows a weird spike in a graph once in an hour. The source of that information was an I2C chip in a circuit which measured something. So I measured what information is coming from the I2C chip and correlate that to the time at which the spike happens in the PC application. This turned out to be a problem in how the I2C was bit-banged but the next step would have been to check the communication between the PC and the circuit and see if information is messed up there.

[Fungus]

I did not experience any limitation due to having small capture memory.  I just change the Timebase and recapture if I want to see the details.

What if it's a one-time event? Or only happens every 53 minutes? 

I'm not going to derail the discussion any further  , but no scope out there will capture 53 minutes of data at full sample rate. Period. Segmented memory or normal trigger mode instead of auto trigger mode .

That wasn't the point being made.

The claim was that when you see something weird on a 'scope with small memory you can simply change the timebase and recapture it to see more detail.

This isn't possible if the event is rare.

[TK]

The claim was that when you see something weird on a 'scope with small memory you can simply change the timebase and recapture it to see more detail.

Again, You are misinterpreting my post, I did not make any claim.  I just wrote about my experience and I think this use case can be similar to what other beginners might need.

[MrW0lf]

Overall more is better. If you do not need all of it, can always use less. If only have less cannot use more. But if only thing you ever had is less then brain auto-adapts into "I do not need more" mode, because otherwise one would be under constant stress. So all quite normal, just better not to generalize.