This project is a great example. [Scott Daniels] takes a look at the other voltage measurement options available to AVR chips used by Arduino.

I've just come across a no-name non-contact, high-precision 80 GHz mmWave radar sensor for liquid level detection with a 40m ...

It’s an easy to build high voltage power supply that interfaces with an Arduino. After harvesting a flyback from the power board of a CRT, [Andrew Moser] added a new primary coil to the transformer.