$100 – Analog Discovery
It’s a 2 channel Oscilloscope, Function Generator, Logic Analyzer, Communication Bus Intrepreter, Network Analyzer, and Spectrum Analyzer w/ Tracking Generator all in one small usb device that can be carried in your backpack and plugged into a laptop. It does have it’s limitations though, a small bandwidth and low sampling speed compared to its table top equivalent. But realistically, for the slow speed signals that we work with, it’s an amazing value for the price. I wish this had existed when I was a student.
$50-$100 Second-Hand Analog Oscilloscope
From Ebay, Craigslist, or anywhere that might be getting rid of one. There is nothing wrong with an older analog scope. As long as it is in reasonable condition and still works, I’ll gladly work with one of these great machines. Keep a lookout on ebay and you should be able to score an older Tektronix, Philips, Hitachi, Hameg, etc.. on ebay at a reasonable $50 price tag. See this link for one my favorites, Dave Jones from EEVBlog, discussing this topic.
$300 – $400 Rigol DS1102E 100MHz Digital Oscilloscope
If I wanted to buy a new oscilloscope, for the price, nothing beats this one. They make a 50Mhz bandwidth version that is a little cheaper and you might be able to get a deal on ebay. I wouldn’t bother buying the cheaper variants like the sigilent/owan, and I definitely wouldn’t bother buying a handheld or usb junk oscilloscope.
Here, Dave Jones from EEVBlog does a teardown.