It's obvious that a sound card is the most affordable oscilloscope, the obvious downside being quite limited sample rate. You would expect that an oscilloscope

It's obvious that a sound card is the most affordable oscilloscope, the obvious downside being quite limited sample rate. You would expect that an oscilloscope would go into MHz. But if it works for you, fine. I remember an article about ball mice disassembled and used as a cheap reliable rotation sensor somewhere in oil pipeline industry.