I have a cheap handheld oscilloscope (ZOYI ZT703S, ~$80) that I find very convenient to have around. It's the size of a multimeter, runs on a battery and works

I have a cheap handheld oscilloscope (ZOYI ZT703S, ~$80) that I find very convenient to have around. It's the size of a multimeter, runs on a battery and works well enough that I don't feel too limited by it.