<P> Calipers without a vernier scale originated in ancient China as early as the Qin dynasty (AD 9). The secondary scale, which contributed extra precision, was invented in 1631 by French mathematician Pierre Vernier (1580--1637). Its use was described in detail in English in Navigatio Britannica (1750) by mathematician and historian John Barrow . While calipers are the most typical use of Vernier scales today, they were originally developed for angle - measuring instruments such as astronomical quadrants . </P> <P> In some languages, the Vernier scale is called a nonius, a precursor to the Vernier scale developed by Portuguese mathematician, cosmographer Pedro Nunes (1502--1578), latinised as Petrus Nonius . It was known by this name in English until the end of the 18th century . </P> <P> The name "vernier" was popularised by the French astronomer Jérôme Lalande (1732--1807) through his Traité d'astronomie (2 vols) (1764). </P> <P> In the following, N is the number of divisions the maker wishes to show at a finer level of measure . </P>

When is a vernier caliper said to be free from zero error