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Anglicky v odbornch pedmtech"Support of teaching technical subjects in EnglishTutorial:Engineering metrology

Topic: Measuring units

Prepared by: Ing. Pavel Roek

Projekt Anglicky v odbornch pedmtech, CZ.1.07/1.3.09/04.0002je spolufinancovn Evropskm socilnm fondem a sttnm rozpotem esk republiky.

Measuring units

Main idea of metric system units system based on meter and kilogramme it was originated during French revolution when 2 platinum referential meter and kilogramme standards were made in 1799 - they were stored in French National Archive in Paris.

Later, they were called archive meter and archive kilogramme.International system of units, SI (Le Systme International Units).

The condition of quantification possibility in the made quantity system is making of corresponding measuring system.

Conference of general scales and measures (CGPM) introduced International system of units SI in 1960 as complete system of units.Measuring units

Nowadays, SI system is made by 7 basic units which make together with derived units complete system of units.Basic SI unitsQuantityBasic unitSignLengthMeterMWeigthKilogrammekgTimesecondsElectric currentampereAThermodynamic temperaturekelvinKAmount of substancemoleMolLuminositycandelacd

Basic unit meter is the length of way through which light in vacuum travels in 1/299 792 458 second.

Basic unit kilogramme is weigth of international kilogramme prototype.

Basic unit second is the time which equals to 9 192 631 770 radiation periods, corresponding with 2 very fine structure levels transition of basic caesium 133 atom condition.

Basic unit ampere is constant electric current which, at 2 linear parallel conductors passage of infinite ways and insignificant cross-section placed in distance of 1 meter in vacuum, causes force equal to 2 x 10-7 newton to 1 meter of conductor length.Basic SI units definition

Basic unit kelvine is 1/273,16 part of triple water point thermodynamics temperature.

Basic unit mole is amount of substance which contains as many elementar entities as there are atoms in 0,012 carbon isotope kilogramme 12C. It is necessary to specify elementary entities at amount of substance setting, there can be atoms, molecules, ions, electrones, other particles or more specified particles clusters.

Basic unit luminosity candela it is luminosity source which in given direction transmits monochromatic radiation with frequency 540 x 1012 hertz and whose radiant capacity in this direction is 1/683 watts to steradian.Basic units SI definition

Derived SI units are derived from basic SI units in accordance with physical relationships among given quantities.

Derived units are made of basic units using maths signs for multiplication and division.Derived SI unitsExamples of derived SI units expressed in basic SI unitsSee following table.

Derived quantityDerived unitSignAreaSquare metermcapacitycubic metermspeedMeter per secondm s-1accelerationMeter per square secondm s-2Anglular speedRadian per secondrad s-1Angular accelerationRadian per square secondrad s-2densitykilogramme to cubic meterkg m-3Magnetic field intensityamper to meterA m-1Electric field intensityamper to square meterA m-2Moment of forcenewton meterN mElectric field intensityvolt to meterV m-1permeabilityhenry to meterH m-1permittivityfarad to meterF m-1Amount of substance concentrationmole to square metermol m-3luminositycandela to square metercd m-2

Units which are used together with SI units because they are commonly used or they are used in specific branches.Out-of-system unitsquantityunitsignValue in SI unitstimeminutemin1 min = 60 shourh1 h = 3600 sdayd1 d = 24 hPlane angledegree1 = (/180) radminute1 = (1/60) = (/10 800) radsecond1 = (1/60) = (/ 648 000) radgradegon1 gon = (/200) radareaHectareha1 ha = 1 hm = 10 mcapacityLiterl ; L1 L = 1 l = 1 dm = 10 cm = 10 mweight tonet1 t = 10 kg

Prefixes are mostly related to 10-to-power (not 2-to-power).Example: 1 kilobit represents1000 bits not 1024 bits at all

Prefixes must be written without gaps before unit sign.Example: Centimeter must be written cm not c m at all

Prefixes can not be combined.Example: 10 kg must be written1 mg not 1 kg

We can not write prefix individually.Example: 109/m can not be written as G/mRules for right prefixes usage

Explain the meaning of measuring units and SI system meaning in engineering metrology.Question 1:Question 2:Name out-of-system units and explain their usage in practice.

Metrologie v kostce: Tet upraven a doplnn vydn. tet. Praha 2009: Boivoj Klenk, PhDr. Q-art., 2009. Dostupn z: k volnmu prohlen a staen

26. vodn kurz METROLOGIE: K 381-07. 2007. esk metrologick spolenost: MS, Praha 1.

Translation:www.seznam.czwww.slovnik.czJANATA, Petr. Handy slovnk technick anglicko-esk a esko-anglick. Plze: Nakladatelstv Fraus, 2000. ISBN 80-7238-075-3Lingea LEXIKON 5, Technick slovnk anglicko-esk a esko-anglick. 2010.

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