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Oscilloscope number of probes
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Yaroooo:
Hi all,

I've read a lot of topics with some people that advise 4 probes with less bandwidth (100Mhz) and some 2 with higher bandwidth (300Mhz). With a fixed budget I must choose one of this options.

People that advice 4 probes used this feature to analyze SPI and multi signals. But I've through about speed of this signals and purpose of the oscilloscope. If I exclude space or 2in1 pros where for me are not a problem. Isn't better to have a more reliable oscilloscope on this speeds and check each signal at time? Once I've found that they act correctly without disturbance I can analyze/read them with a Logic Analyzer that allow me more I/Os.

Same apply for all signals that must be analyzed on logic level. Once checked, they can be actually read by a logic analyzer that also simulate a counterpart.

I just want to expose what are my consideration on my use of this instrument. On lower budgets that seems more logical. I'd like to know also other opinions about this.
rstofer:
It is certainly possible to get along with a two channel scope (and 2 probes of equivalent bandwidth), it was done that way for decades.  It's a fairly recent development that 4 channels isn't a lot more expensive than 2 channels.

Given a 2 channel scope, you can make the case for a logic analyzer and, in fact, if you had more than 4 signals to watch, it wouldn't matter which scope you had, if it didn't include a logic analyzer, you would have to buy one extra.

A good logic analyzer of some kind is quite helpful in digital electronics whether you have a scope or not.

Your approach of using a high bandwidth 2 channel scope to check signal integrity (and timing) and following up with a logic analyzer is correct.

I used a 2 channel scope off and on for over 50 years and I still have a 350 MHz Tektronix 485 for the high speed stuff.  My 4 channel Rigol DS1054Z was a nice addition.  Today, I would be looking at the 200 MHz Siglent offerings.  I would probably still go for 4 channels.  More is always better.
TheHolyHorse:
I just ordered an oscilloscope I was choosing between the siglent SDS1202X-E(2 channel) and the SDS1104X-E(4 channel). I went with the 1104 because it wasn't that much more. 400~ vs 500~ euro. If you're gonna spend 400 what's another 100, if you can't afford that right now I'd wait and save up some more. Better to have too many channels than too few.

An oscilloscope is something that wont be obsolete in 5 years unlike PC hw. So it could be worth spending a bit more, it would suck if you realized later that you really needed those 4 channels.
tggzzz:
The OP has a better grasp of the important fundamentals than most people on this forum!

Use a scope to ensure signal integrity, I.e. that the analogue voltage/current transmitted between chips will be correctly interpreted as a digital signal by the receiver. Once that is true, switch to debugging digital signals using analogic analyser and printf() statements.

Hence the key parameter of a scope is it's bandwidth. The key issues with logic analysers are the sampling rate and the ability to filter out irrelevant logic levels so that you can see the signal's of interest.
rstofer:
And the 1104 can be unlocked to 200 MHz, details elsewhere.  Number of channels is the most important consideration - except for bandwidth.
I already have the Rigol but if I were in the market today, that Siglent SDS1104X-E would be on my very short list.  In fact, it would probably already be on my bench.  Unlocked, of course...

I don't think I would consider the SDS1102X-E - I really want 4 channels and price isn't the biggest factor.


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