Others have mentioned the Analog Discovery 2, a multi-function usb device. There's a nearly identical product made by Analog Devices called ADALM 2000. The hardware and software spec's are on par, but the price is about half. I managed to snag one off ebay for $50, and it's worked great for me so far.
The grounding on cheap DSO's and USB scopes can be risky (though the grounding on line powered scopes can be a problem also unless it is a differential scope, sometimes it is a bad idea to clip an earth ground onto a circuit ground). With a USB scope you are counting on a inexpensive device to protect your valuable laptop computer and it can be inconvenient to use the computer for other purposes (you would have to stop a video render to use it as a scope for example). If you can afford it a low end Owon or Rigol is a much better investment. If it's just for fun with audio signals a software scope that uses a computers mic/line input may be good enough. If you want to view lissajous curves get a two channel analog scope (used on eBay or new starting around $200), most cheap digital scopes don't have a fast enough graphics capability to draw smooth lissajous curves. The frequency range of signals is often a deciding factor in scope choice, if what you want to view is 100MHz signals (or signals that include 100Mhz components/artifacts such as short spikes) then you need a scope that can handle that, if you just want to view audio signals any scope is probably good enough. The ability to capture and store signals can be useful to capturing one time events for analysis. The ability to store screenshots can be useful if you need to publish images of signals.
To me, the choice at the low end for an oscilloscope rather than a USB dongle is between Siglent and GW Instek with Rigol being a touch more expensive.
It used to be that the Siglent and GW Instek actually had slightly better specs relative to the Rigol's--which was quite irritating given that the Rigol's were more expensive. In addition, the Siglent and Instek used to come with serial decode while Rigol would charge for it as an add-on.
Due to the semiconductor supply chain issues, what was in stock varied wildly. I don't know if that has settled down.
If you keep your eyes open, you can generally find any one of them being cheaper than the other due to specials, shipping, discounts, etc.
I use 4 analog channels (vs 2) a LOT, and that's also enough that you can do basic serial decodes. I recommend stumping up for the 4 channels.
I don't put a lot of stock in MSO. I have an MSO on my big Agilent, but I use a $10 Logic Analyzer way more often for digital since it's a lot more convenient. I also don't worry about accidentally putting too much voltage on it as if I fry the analyzer, it's just another $10.
I like the GW Instek scopes because they have dials per channel. Having to multiplex controls irritates me to no end. YMMV.
We had a thread on this the other day. https://news.ycombinator.com/item?id=32365449 I personally bought a DS-100 (aka. "DSO Nano v3") afterwards, successfully switched it to English, and obtained firmware and manuals. http://pratyeka.org/ds100.zip Haven't really put it through its paces yet as I use a Rigol DS-1000 series 4-channel with decodes and LXI (so useful) on the bench but next week have a perfect project which will require off-bench work. DS-100 easy screenshot functionality is a draw: just hold down two buttons and it stores a BMP, later plug it via USB and it becomes a mass storage device. I think the Seeed Studio link Justin shared sells preconfigured English ones for the international market.
Small and cheap oscilloscope is normally the PC based oscilloscope. Early this week someone posted this review of a cheap USD$60 portable PC based oscilloscope [1].
On related note, if you want to understand the inner workings of oscilloscope, there is an excellent book on sales now at Springer Link (50% back to school discount). It also covers PC based oscilloscope technology.
I like my Picoscope, beware it has no display or physical controls, it’s entirely computer controlled. It’s very small physically if that’s what you meant.
Owon vds 1022I served me well for basic stuff. PC oscilloscopes are pretty decent for the $ cost. There's definitely better out there, but if you're in the market for a budget scope, I recommend that one.
Korg has a semi-DIY oscilloscope now, the NTS-2. Is it good? I don't know. It's pretty clearly meant to fit into a modular synth setup. But it's definitely small.
+1 for the AD2. Its sort of like a pocketknife tool (e.g. obv not the best available for any price but very versatile) and is easily scriptable in c++/python.
