I'm preparing to purchase a digital storage oscilloscope, to complement my 100 MHz analog oscilloscope. I've been demoing units and narrowing down the choices.
The EEVBlog tutorial on DSOs advises that the three most important properties of DSOs are:
- Analog bandwidth
- Sample rate
- Memory depth
I am looking at a couple of two-channel 100 MHz DSOs, the Tektronix TDS2012C and the Rigol DS2102. Some other features aside, these two appear to have identical performance in terms of analog bandwidth and real time sample rate.
However, the Tektronix oscilloscope's memory depth is a paltry 2,500 points compared to the Rigol's generous 14 million points (expandable to 56 million). This seems like a major reason to opt for the Rigol. (Not to mention it is ~$200 less.)
Is there a reason not to weigh memory depth heavily? Perhaps some reason that the Tektronix doesn't need as much?
I know I want to be able to capture multiple digital events/waveforms from microcontrollers and look for things that change over time, etc. Ample memory depth is needed for this. The fact that the Rigol and Tektronix differ by orders of magnitude concerns me. Tektronix has a superb reputation, whereas Rigol is new to me. The vast difference in memory depth seems to be the final word. Should it be?
Best Answer
NOTE: A lot of this is now outdated, as Tektronix have released some interesting scopes lately (2015).
This started out as a comment, but I'm expanding it to an answer:
Basically, Tektronix is not competitive in the digital oscilloscope market any more.
Your comparison is fundamentally flawed too. You are comparing Tektronix's bottom-of-the range scope to Rigol's middle-of-the-range model.
The actual Rigol scope that best matches that Tektronix scope is the DS1102E.
Note that the Rigol scope listed above is only US$400!
Really, if you're shopping for a US$500-US$3000 DSO, the only two players on the market even worth bothering to look at (at least at the current time) are Rigol and Agilent. They are the only two people on the market that offer intensity grading (Rigol call it "Ultravision" and Agilent call it "InfiniiVision").
This is a technique that actually measures the time the input waveform spends at each ADC value per X-axis time-step, and actually varies the intensity of the drawn scope trace to reflect the period of time the input spent at that voltage. This produces a display that actually somewhat resembles a traditional cathode-ray oscilloscope. It is absolutely a excellent feature, and I, at least personally wouldn't even consider a DSO that lacked it at this point.
Basically, Tektronix are just not producing DSOs worth looking at. They did have some good DSOs in the early 2000s: they produced a nice, primitive DSO, garnered a significant chunk of market share, and basically then sat there resting on their laurels and stopped innovating. This is supported by the teardowns I've seen of some of their late-model scopes, which were using rather ancient silicon for their processing. Note that this is changing, but only for Tektronix's higher end. They're doing some really cool stuff with their MSO devices (mixed-signal oscilloscopes). They basically combine a spectrum analyzer and a DSO, and for RF work, they look excellent. They're also $50K+.
Then, Agilent came along and basically completely wiped the floor with them in short order, with their much deeper memory scopes, and introduced intensity grading.
Now, Rigol have subsequently come out with a competitive mid-range scope line that makes them also worth considering, together with Agilent.
As far as I can tell, Tektronix's superb reputation should only really be applied to cathode-ray oscilloscopes (I have several, all Tektronix). They really didn't take the transition to digital, and its high innovation rate well at all.
If I were buying a scope now, I would look for:
Absolutely essential at ANY price-point:
Absolutely essential a >~$1K price-point:
Nice to have: