I work on mostly older (60's-90's) European cars and would like to be able to carry out some of the tests I see in factory literature, an example is attached. I do not know much about scopes but for occasional hobby use have been recommended a few made in china brands such as Rigol ($200-300 used) or a ~$100 new micro scope such as
https://www.sainsmart.com/products/dso212-2-ch-handheld-mini-digital-oscilloscope
I don't want to over-buy - I have used a very simple <$100 VOM for decades for a huge variety of automotive work and don't want a larger, plug-in scope if a handheld battery powered will do. Problem is I have no idea what I don't know and the test I used as an example doesn't indicate frequency, only shape of wave form.
Can someone help me figure out what a 'good enough' scope would be to verify the function of things like fuel injectors, sensors, etc? Current stable includes '73 Alfa & '91 911 but like any car guy I'm always buying and selling.
In your example, set frequency is basically impossible to determine. I'd assume that's a crank position sensor based on the waveform; distance between top dead center marks (the shape at figure 2) is not a set number, as engine rpm varies even within a single 720 degree revolution of the engine. I suppose one could calculate a frequency graph, as picoscope does with math channels, but unless you're trying to get fancy it's not going to tell you anything the tachometer isn't.
I have 3 scopes, the Uscope, a generation 1 snap on Modis, and a Picoscope 4425. They all have their place. The Uscope master kit was $400? Came with amp clamp, some leads and accessories. I buy backprobes in bulk on amazon. The gen-1 Modis was a craigslist deal at $350, and includes a scanner updated to whatever year, in my case 2010. Includes 4 short leads, gators and a probe or two. You will need to buy actual back probes, amp clamps, or secondary ignition stuff. It also functions as a volt meter with a big *** screen. Used snap on is the big value item IF you are willing to sit around and wait for a deal. Secondary ignition is okay for consistent-ish misfire, zooming is counter intuitive. Glitch capture is okay, not great. Picoscope makes the previous scopes look like literal children toys, but will cost you $1200+ for a scope and USB cable. No leads, no laptop to run the scope. "Value" is low, but it's extremely powerful. It absolutely stomps on the Modis, can zoom 1000X if you like, on a 5min+ per division capture over an hours time. Stupid resolution and lots of cool features like math channels, the waveform library, guided testing (mainly for those learning).
The Uscope tells you that you indeed have a signal, and the shape of it. It cannot record and then zoom, unless you save the file and view later on a laptop. Uscope is fantastic for go/no-go signal checks, basic current probe testing of DC motors, "quick peek" sort of things. It ***** at secondary ignition unless you have a dead hole, and it ***** at intermittent. Neither are what such a tool is designed for.
Modis is where you get review capability, and cursors. You kinda need cursors if you want to do the test you listed in the OP; both for time between events and height/amplitude. Great for dragging through interiors, quick test drives, it's a good unit.
Pico is the big gun. Stupid intermittent stuff, extreme detail, long time bases. More detail than you'd ever ask for.
Neither is the correct option, they all have their place. Define your budget, then see what exists within that budget, and whether that will meet your needs. Multiple channels are nice, although on older stuff I doubt you'd need them frequently.
