I want to make myself a fast, at least 30fps screen update multimeter, which will have no range switching (either manual or automatic), and will have decent resolution in 0.1V-600V range. I already built one using built-in ADC of PIC16F1939, but 10 bits of resolution are definitely not good enough.

By fast sampling the input voltage, I guess, I can measure AC voltage too, without additional losses caused by rectification.