Micrometre

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"Micron" redirects here. For other uses, see Micron (disambiguation).
"Microscale" redirects here. For other uses, see Microscale (disambiguation).
For the measuring instrument, see Micrometer.
1 micrometre =
SI units
1.0000×10^−6 m 1.00000 μm
US customary / Imperial units
3.2808×10^−6 ft 39.370×10^−6 in
Look up micrometre in Wiktionary, the free dictionary.

The micrometre (International spelling as used by the International Bureau of Weights and Measures; SI symbol: µm) or micrometer (American spelling) is an SI derived unit of length equaling 1×10−6 of a metre (SI standard prefix "micro-" = 10−6); that is, one-millionth of a metre (or one-thousandth of a millimetre, 0.001 mm, or about 0.000039 inch). The symbol µm is sometimes rendered as um if the symbol µ cannot be used, or if the writer is not aware of the distinction.

The micrometre is a common unit of measurement for wavelengths of infrared radiation as well as sizes of cells and bacteria and is also commonly used in plastics manufacturing.[1]

Microns are the standard for grading wool (referring to the diameter of wool fibres). Any wool finer than 25 microns can be used for garments, while coarser grades are used for outerwear, rugs and carpets.

The symbol for the SI prefix micro-, µ, is a Greek lowercase mu, μ. In Unicode, it has the codepoint U+00B5, distinct from that of the Greek letter lowercase mu so that machines can recognize it as the SI prefix symbol rather than as a letter. Many fonts use the same glyph for the two characters.

SI standardisation

The term micron representing the micrometre, was officially accepted between 1879 and 1967, but officially revoked by the International System of Units (SI) in 1967.[2]

Nevertheless, in practice, "micron" remains a widely used term in preference to "micrometre" in many English-speaking countries, both in academic science (including geology, biology, physics, and astronomy) and in applied science and industry (including machining, the semiconductor industry, and plastics manufacturing).[citation needed] Additionally, in American English the use of "micron" helps differentiate the unit from the micrometer, a measuring device, because the unit's name in mainstream American spelling is a homograph of the device's name.

See also

For examples of things measuring between one and ten micrometres, see 1 micrometre.

References

  1. ↑ "micrometre" Encyclopædia Britannica Online, accessed 17 March 2012
  2. ↑ BIPM - Resolution 7 of the 13th CGPM (1967/68), "Abrogation of earlier decisions (micron, new candle.)"
SI units of length
yoctometre <<< zeptometre <<< attometre <<< femtometre <<< picometre <<< nanometre <<< micrometre <<<
millimetre < centimetre < decimetre < metre < decametre < hectometre < kilometre
<<< megametre <<< gigametre <<< terametre <<< petametre <<< exametre <<< zettametre <<< yottametre

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