My new project is going to involve testing and designing electronics, and so I find myself in need of a bunch of tools I don’t have. Foremost among them, is an oscilloscope, so I can probe circuits in devices to try and understand how they work, and why they don’t work.
My overall electronics aptitude is pretty mediocre. I had a job soldering connectors to serial cables when I was a kid, but my soldering skill isn’t very high and most of the electronic theory I learned in my introductory physics course in college is long forgotten. I have used an oscilloscope though. I used one when I learned about electrophysiology techniques for looking at the activity of individual cells, and I also used one to tune the video system of a cell-florescence microscope to take full advantage of its dynamic range.
More important than what I’ve done with oscilloscopes is that I know what I’d use one for now. I think it will come in handy for looking at the operation of DC-DC power supplies, and just generally for probing circuits. Beyond that though, I’m a novice, and so I went looking a place to get advice. Actually, I didn’t have to look, because I’d already found the EEVBlog Forum, which even has a special section where people are supposed to go easy on beginners for asking dumb questions. Still, they ask that you provide plenty of information when you ask a question, so I had to do some shopping on my own, so I could get a sense of the questions I should ask, and the background I should give.
My first stop was to see what Sparkfun and Adafruit, two online stores that specialize in electronics for hobbyists, were offering. Adafruit has two options, one a 50MHz, two-channel Rigol DS1052E digital storage oscilloscope, the other, a Rigol DS1102, is very similar, but has 100MHz bandwidth. Sparkfun offers the Gratten GA1102CAL, which is also a 100MHz, 2-channel digital scope. They also have two USB scopes for use with your computer, the MSO-19, and MSO-28 from link instruments. Sparkfun and Adafruit also both carry the small, inexpensive DSO Nano and/or DSO Quad.
I’d been considering a DSO Nano or Quad because of their low price and compact size, but people who seem to know better hate them, first because their user interfaces are difficult to use compared to a real oscilloscope, but also because they can’t actually do much. Of course, my needs, as I understand them, aren’t that demanding. I think the signals I’ll be looking at are in the 1-2MHz range, which should be within the capabilities of the DSO Quad, but it doesn’t leave a lot of headroom, and at $200 bucks, its a bit too expensive given that you could get a more capable used analog scope for less, or a new digital scope for another $50-100 more.
I also considered a USB scope. They are more compact, and I also assumed they’d be cheaper, since they didn’t have to include a screen or UI, and I also thought it might make it easier to work with the data on a computer. I was wrong on multiple counts. USB Scopes are a bit of a niche item when compared to a benchtop scope, because regular O’scope users find physical knobs and buttons more productive and easier to use than the often poor software that ships with USB scopes. As a result, volumes are lower, and there is less competition to drive prices down. Moreover, screens are pretty cheap these days, so eliminating one isn’t a huge cost savings. Put the two together, and a decent USB scope is about as expensive as a dedicated scope with similar specs, and you can hook most dedicated scopes up over USB if you need to anyway.
Exploring the existing options helped me think through what I needed and why. I was ready to ask the experts over on EEVBlog. I’ll cover that in my next blog post.