Tachymeter (watch)

A tachymeter is a scale sometimes inscribed around the rim of an analog watch with a chronograph. It can be used to conveniently compute the frequency in hours of an event of a known second-defined period, such as speed based on travel time, or measure distance based on speed. The spacings between the marks on the tachymeter dial are therefore proportional to 1⁄t, where t is the elapsed time.


A tachymeter is a scale sometimes inscribed around the rim of an analog watch with a chronograph. It can be used to conveniently compute the frequency in hours of an event of a known second-defined period, such as speed based on travel time, or measure distance based on speed. The spacings between the marks on the tachymeter dial are therefore proportional to 1⁄t, where t is the elapsed time.
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