Physics Education Volume 46, Number 4, ISSN 0031-9120
A very low-cost, easy-to-make stopwatch is presented to support various experiments in mechanics. The high-resolution stopwatch is based on two photodetectors connected directly to the microphone input of a sound card. Dedicated free open-source software has been developed and made available to download. The efficiency is demonstrated by a free fall experiment. (Contains 4 figures.)
Gingl, Z. & Kopasz, K. (2011). A High-Resolution Stopwatch for Cents. Physics Education, 46(4), 430-432.