Jones Counterとは 意味・読み方・使い方

The Jones Counter is a device fitted to the front wheel of a bicycle which counts the revolutions of the wheel. It was invented in 1971 by Alan Jones in order to measure the length of road running race courses. It has gears that drive a mechanical digital counter. Depending on the gear ratio used, one count typically corresponds to about 1/20th of a wheel revolution. This provides a resolution of about 10 cm in course length, although overall accuracy, depending on calibration and other factors, is lower, but normally better than 1 part in 1000.