Themicrometre(Commonwealth English) as used by theInternational Bureau of Weights and Measures;[1]SIsymbol:μm) ormicrometer(American English), also commonly known by the non-SI termmicron,[2]is a unit oflengthin theInternational System of Units(SI) equalling1×10−6metre(SI standard prefix "micro-"=10−6); that is, one millionth of ametre(or one thousandth of amillimetre,0.001 mm,or about0.00004inch).[1]
| micrometre | |
|---|---|
 A 6 μm diametercarbon filamentabove a 50 μm diameter human hair | |
| General information | |
| Unit system | SI |
| Unit of | length |
| Symbol | μm |
| Conversions | |
| 1 μmin... | ... is equal to... |
| SI base units | 10−6m |
| Natural units | 1.8897×104a0 |
| imperial/USunits | 3.9370×10−5in |
The nearest smaller commonSI unitis thenanometre,equivalent to one thousandth of a micrometre, one millionth of a millimetre or one billionth of a metre (0.000000001m).
The micrometre is a common unit ofmeasurementforwavelengthsofinfrared radiationas well as sizes of biologicalcellsandbacteria,[1]and for gradingwoolby the diameter of the fibres.[3]The width of a singlehuman hairranges from approximately 20 to200 μm.
Examples
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Between 1 μm and 10 μm:
- 1–10 μm – length of a typicalbacterium
- 3–8 μm – width of strand ofspider web silk[4]
- 5 μm – length of a typical humanspermatozoon's head[5]
- 10 μm – size offungal hyphae
- about 10 μm – size of afog,mist,orcloudwater droplet
Between 10 μm and 100 μm:
- about 10–12 μm – thickness ofplastic wrap (cling wrap)
- 10 to 55 μm – width ofwoolfibre[6]
- 17 to 181 μm – diameter of human hair[7]
- 70 to 180 μm – thickness of paper
SI standardization
editThe termmicronandthe symbol μwere officially accepted for use in isolation to denote the micrometre in 1879, but officially revoked by theInternational System of Units(SI) in 1967.[8]This became necessary because the older usage was incompatible with the official adoption of the unit prefixmicro-,denoted μ, during the creation of the SI in 1960.
In the SI, the systematic namemicrometrebecame the official name of the unit, and μm became the official unit symbol.
InAmerican English,the use of "micron" helps differentiate the unit from themicrometer,a measuring device, because the unit's name in mainstreamAmerican spellingis ahomographof the device's name. In spoken English, they may be distinguished by pronunciation, as the name of the measuring device is often stressed on the second syllable (/maɪˈkrɒmɪtər/my-KROM-it-ər), whereas the systematic pronunciation of the unit name, in accordance with the convention for pronouncing SI units in English, places the stress on the first syllable (/ˈmaɪkroʊmiːtər/MY-kroh-meet-ər).
The plural ofmicronis normallymicrons,thoughmicrawas occasionally used before 1950.[9][10][11]
Symbol
editThe official symbol for theSI prefixmicro-is aGreek lowercase mu.[12]Unicodehas inheritedU+00B5µMICRO SIGNfromISO/IEC 8859-1,distinct from thecode pointU+03BCμGREEK SMALL LETTER MU.According to theUnicode Consortium,the Greek letter character is preferred,[13]but implementations must recognize the micro sign as well forcompatibility with legacy character sets.Most fonts use the sameglyphfor the twocharacters.
Beforedesktop publishingbecame commonplace, it was customary to render the symbol μ in texts produced with mechanicaltypewritersby combining a slightly lowered slash with the letteru.For example, "15 μm" would appear as "15/um".This gave rise in earlyword processingto substituting just the letterufor the symbol if the Greek letter μ was not available, as in "15 um".[14]
The UnicodeCJK Compatibilityblock contains square forms of some Japanesekatakanameasure and currency units. U+3348㍈SQUARE MIKURONcorresponds toミクロンmikuron.
See also
editNotes and references
edit- ^abc"micrometre".Encyclopædia Britannica Online.Retrieved18 May2014.
- ^"Writing with SI (Metric System) Units".NIST.13 January 2010.
- ^"Wool Fibre".NSW Department of Education and Communities.Archived fromthe original(Word Document download)on 17 June 2016.Retrieved18 May2014.
- ^Ramel, Gordon."Spider Silk".Archivedfrom the original on 4 December 2008.Retrieved14 December2008.
A typical strand of garden spider silk has a diameter of about 0.003 mm... Dragline silk (about.00032 inch (.008 mm) inNephila)
- ^Smith, D.J.; Gaffney, E.A.; Blake, J.R.; Kirkman-Brown, J.C. (25 February 2009)."Human sperm accumulation near surfaces: a simulation study"(PDF).Journal of Fluid Mechanics.621.Cambridge University Press:295.Bibcode:2009JFM...621..289S.doi:10.1017/S0022112008004953.S2CID3942426.Archived fromthe original(PDF)on 6 November 2013.
- ^"Fibreshape applications".IST - Innovative Sintering Technologies Ltd.Retrieved4 December2008.
Histogram of Fiber Thickness [micrometre]
- ^Thediameterof human hair ranges from 17 to 181 μm.Ley, Brian (1999). Elert, Glenn (ed.)."Diameter of a human hair".The Physics Factbook.Retrieved8 December2018.
- ^BIPM - Resolution 7 of the 13th CGPM 1967/68),"Abrogation of earlier decisions (micron, new candle.)"
- ^Proceedings of the Royal Society of Queensland.Part I. Vol. XIX. H. Pole & Co. 1907 – via Google Books.
- ^Bigalow, Edward Fuller; Agassiz Association (1905).The Observer.Vol. 7–8 – via Google Books.
- ^10 micra/10 microns(Start at 1885; before that, the word "micron", singular or plural, was rare)
- ^"Prefixes of the International System of Units".International Bureau of Weights and Measures.Archived fromthe originalon 23 May 2018.Retrieved9 May2016.
- ^Beeton, Barbara; Freytag, Asmus; Sargent, Murray III (30 May 2017)."Unicode Technical Report #25".Unicode Technical Reports.Unicode Consortium.p. 11.
- ^John C. Mutchler, ed. (1999).The American Directory of Writer's Guidelines: A Compilation of Information for Freelancers from More Than 1,300 Magazine Editors and Book Publishers(2 ed.). Quill Driver Books. p. 47.ISBN978-1-884956-08-9.
External links
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The dictionary definition ofmicrometreat Wiktionary
