How to tell if your scroll wheel is faulty
Test your mouse scroll wheel. This scroll test counts wheel notches per second, splits scrolling up from scrolling down, and helps you spot a worn wheel encoder that skips or scrolls the wrong way. Page scrolling is paused while your pointer is over the pad, so every notch is counted.
A mouse wheel reports its movement through a small encoder. When the encoder wears or collects dust, slow scrolling in one direction can register as a jump the other way, or notches can be skipped. Scroll slowly in Endless mode and watch the up and down counters separately: in a healthy wheel only one counter moves at a time.
