Editing Tachometer (section)

==History==
The first tachometer was described by [[Bryan Donkin]] in a paper to the [[Royal Society of Arts]] in 1810 for which he was awarded the [[Gold medal]] of the society. This consisted of a bowl of mercury constructed in such a way that centrifugal force caused the level in a central tube to fall when it rotated and brought down the level in a narrower tube above filled with coloured spirit. The bowl was connected to the machinery to be measured by pulleys.<ref>{{cite journal |last1=Donkin |first1=Bryan |title=An instrument to ascertain the velocities of machine, called a Tachometer |journal=Transactions of the Society, Instituted at London, for the Encouragement of Arts, Manufactures, and Commerce |date=April 1810 |volume=28 |pages=185–191 |jstor=41325817 |url=https://www.jstor.org/stable/41325817 |access-date=23 August 2021}}</ref>

The first mechanical tachometers were based on measuring the [[centrifugal force]], similar to the operation of a [[centrifugal governor]]. The inventor is assumed to be the German engineer [[Diedrich Uhlhorn|Dietrich Uhlhorn]]; he used it for measuring the speed of machines in 1817.<ref>[http://digital.ub.uni-duesseldorf.de/urn/urn:nbn:de:hbz:061:1-492968 Theoretische und praktische Abhandlung über einen neuerfundenen Tachometer oder Geschwindigkeitsmesser : zunächst für Mechaniker, Fabrikanten, Baumeister und Andere]</ref> Since 1840, it has been used to measure the speed of [[locomotive]]s.