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A variety of rulers A carpenter's rule Retractable flexible rule or tape measure A closeup of a steel ruler A ruler in combination with a letter scale. A ruler, sometimes called a rule, scale or a line gauge or metre/meter stick, is an instrument used to make length measurements, whereby a length is read from a series of markings called "rules" along an edge of the device. [1]
An early definition of the metre was one ten-millionth of the Earth quadrant, the distance from the North Pole to the Equator, measured along a meridian through Paris.. The history of the metre starts with the Scientific Revolution that is considered to have begun with Nicolaus Copernicus's publication of De revolutionibus orbium coelestium in 1543.
The metre (or meter in US spelling; symbol: m) is the base unit of length in the International System of Units (SI). Since 2019, the metre has been defined as the length of the path travelled by light in vacuum during a time interval of 1 / 299 792 458 of a second, where the second is defined by a hyperfine transition frequency of caesium.
The ruler the simplest kind of length measurement tool: lengths are defined by printed marks or engravings on a stick. The metre was initially defined using a ruler before more accurate methods became available. Gauge blocks are a common method for precise measurement or calibration of measurement tools.
The accuracy for the end of a retractable tape measure is dependent on the hook's sliding mechanism and thickness. The European Commission (EC) has standardised a non-compulsory classification system for certifying tape measure accuracy, with certified tapes falling into one of three classes of accuracy: Classes I, II, and III. [ 32 ]
The formal definition of calibration by the International Bureau of Weights and Measures (BIPM) is the following: "Operation that, under specified conditions, in a first step, establishes a relation between the quantity values with measurement uncertainties provided by measurement standards and corresponding indications with associated measurement uncertainties (of the calibrated instrument or ...
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A metre-stick, metrestick (or meter-stick and meterstick as alternative spellings); [1] or yardstick [2] is either a straightedge or foldable ruler used to measure length, and is especially common in the construction industry. They are often made of wood or plastic, and often have metal or plastic joints so that they can be folded together.