1、Copyright 1998 IEEE All Rights Reserved 1ANSI/IEEE Std 945-1984 (R2008)An American National StandardIEEE Recommended Practice for Preferred Metric Units for Use in Electrical and Electronics Science and TechnologySponsorIEEE Standards Coordinating Committee 14 on Quantities and UnitsReaffirmed Septe
2、mber 25, 2008Approved March 10, 1982IEEE Standards BoardApproved July 22, 1983American National Standards Institute Copyright 1984 byThe Institute of Electrical and Electronics Engineers, Inc 345 East 47th Street, New York, NY 10017, USANo part of this publication may be reproduced in any form, in a
3、n electronic retrieval system or otherwise, without theprior written permission of the publisher.Acceptance NoticeThis non-Government document was adopted on 25 September 1984, and is approved for use by the DoD. Theindicated industry group has furnished the clearances required by existing regulatio
4、ns. Copies of the document arestocked by DoD Single Stock Point, Naval Publications and Forms Center, Philadelphia, PA 19120, for issue to DoDactivities only. Contractors and industry groups must obtain copies directly from IEEE, 345 East 47th Street, NewYork, NY 10017.Title of Document: IEEE Recomm
5、ended Practice for Preferred Metric Units for Use in Electrical andElectronics Science and TechnologyDocument No: ANSI/IEEE Std 945-1984 Date of Specic Issue Adopted: September 25, 1984Releasing Industry Group: The Institute of Electrical and Electronics Engineers, IncCustodians:Army ARNavy SHAir Fo
6、rce 11Military Coordinating Activity:Army ARProject MISC-0038NOTICE: When reafrmation, amendment, revision, or cancellation of this standard is initially proposed, the industrygroup responsible for this standard shall inform the military coordinating activity of the proposed change and requestpartic
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15、Secretary, IEEE Standards Board345 East 47th StreetNew York, NY 10017USAivCLAUSE PAGE1. Purpose12. Space and Time.23. Periodic and Related Phenomena44. Mechanics .45. Heat .86. Electricity and Magnetism 107. Light and Related Electromagnetic Radiations.148. Acoustics.15Copyright 1984 IEEE All Rights
16、 Reserved1An American National StandardIEEE Recommended Practice for Preferred Metric Units for Use in Electrical and Electronics Science and Technology1. PurposeThe purpose of this recommended practice is to aid in the selection of metric units so as to promote uniformity in theuse of metric units
17、and to limit the number of different metric units that will be used in electrical and electronicsscience and technology. ANSI/IEEE Std 268-1982, American National Standard Metric Practice, prescribes howmetric units are to be used and gives guidance concerning correct metric practice.Table 1Multiple
18、s and Submultiples of SI UnitsMultiplying Factor PrefixLetterSymbol1 000 000 000 000 000 000 = 1018exa E1 000 000 000 000 000 = 1015peta P1 000 000 000 000 = 1012tera T1 000 000 000 = 109giga G1 000 000 = 106mega M1 000 = 103kilo k100 = 102hecto*To be avoided where practical. See ANSI/IEEE Std 268-1
19、982 .h10 = 101deka*da0.1 = 10-1deci*d0.01 = 10-2centi*c0.001 = 10-3milli m0.000 001 = 10-6microm0.000 000 001 = 10-9nano n0.000 000 000 001 = 10-12pico p0.000 000 000 000 001 = 10-15femto f0.000 000 000 000 000 001 = 10-18atto a2Copyright 1984 IEEE All Rights ReservedANSI/IEEE Std 945-1984 IEEE RECO
20、MMENDED PRACTICE FOR PREFERRED METRIC UNITS FOR USE2. Space and TimeItem QuantitySI Symbol(Unit)Preferred Multiplesof the SI UnitsOther UnitsPermitted forUse with SITypical and RecommendedApplications andExplanatory Notes2.1plane angle rad (radian) Engineering and scientific calculations(degree) Mea
21、surement of angles in surveys, plans, electrical calculations(Use of decimal divisions of degrees instead of minutes and seconds is encouraged)2.2solid angle sr (steradian) Engineering and scientific calculations2.3length (width, height, thickness, radius, diameter, depth)m (meter) km (kilometer) Wh
22、en coverting to SI, the meter generally replaces the yard and foot, the kilometer replaces the mile, the centimeter replaces the inch, and smaller submultiples replace the fractions of an inch. The hectometer, dekameter, and decimeter are used only rarely and are not recommended for general use.cm (
23、centimetermm (millimeter)mm (micrometer)nm (nanometer)In many engineering applications the centimeter is avoided for fear of confusion or of proliferation of different unit multiples. Thus, all dimensions on mechanical engineering drawings are expressed in millimeters; dimensions for construction pr
24、ojects are expressed in meters or millimeters, but not in centimeters.2.4area m2(square meter) Area of floors, walls, and small property sizeha (hectare) Surveying and land measurementkm2(square kilometer) Drainage area, watershed, or lake areacm2(square centimeter)mm2(square millimeter)Cross sectio
25、nal area of conductors2.5volume m3(cubic meter) All volumesThe expression of 106m3should be used for volumes of reservoirsdm3(cubic decimeter) L (liter) 1 dm3= 1 L1 mL = 1 cm3cm3(cubic centimeter) mL (milliliter) NOTE: Use of the liter is restricted to volumetric capacity, dry measure, and measure o
26、f fluids (both liquid and gases).mm3(cubic millimeter)mL (microliter)Copyright 1984 IEEE All Rights Reserved3IN ELECTRICAL AND ELECTRONICS SCIENCE AND TECHNOLOGY ANSI/IEEE Std 945-19842.6time s (second) Preferred unit for all time derivative functions for engineering and scientific measurements and
27、calculations.ms (millisecond) Geophysical measurements, electrical device operating timems (microsecond) Ultrasonic testing, electrical transientsns (nanosecond)ps (picosecond)Computer and communications technologya (year) Statistics, planningmonthweekWork time, statisticsd (day)h (hour)min (minute)
28、Work time, statisticsNOTE: In engineering measurements and calculations, these non-SI units should be used in time derivative functions only when second related quantities become impractical.2.7angular velocity rad/s (radian per second) Engineering calculationsNOTE: See also 3.3, rotational frequenc
29、y2.8velocity m/s (meter per second) Conveyor speed, wind and water speed, ventilation, hoist speed, crane travel speed, elevator speed, and engineering calculationscm/s (centimeter per second)Tape speeds and recordersmm/s (millimeter per second)Wire feed for welding, chart speedsmm/a (millimeter per
30、 year)Wear rates of motor brushes, bearings, etcmm/d (millimeter per day)Chart speedskm/h (kilometer per hour)Vehicle speed, wind speed (meteorological)2.9acceleration m/s2(meter per second squared)mm/s2(millimeter per second squaredMechanical vibrations, engineering calculationsmm/s2(micrometer per
31、 second squared)2.10angular acceleration rad/s2(radian per second squaredEngineering calculations, design, and analysis of machinesNOTE: See also 3.5, rotational accelerationItem QuantitySI Symbol(Unit)Preferred Multiplesof the SI UnitsOther UnitsPermitted forUse with SITypical and RecommendedApplic
32、ations andExplanatory Notes4Copyright 1984 IEEE All Rights ReservedANSI/IEEE Std 945-1984 IEEE RECOMMENDED PRACTICE FOR PREFERRED METRIC UNITS FOR USE3. Periodic and Related Phenomena4. MechanicsItem QuantitySI Symbol(Unit)Preferred Multiplesof the SI UnitsOther UnitsPermitted forUse with SITypical
33、and RecommendedApplications andExplanatory Notes3.1period(See also item 8.1)s (second) ms (millisecond) NOTE: Many unit multiples are used for this quantity, as appropriate. The conversion to SI has no effect on current practice.3.2frequency(See also item 8.2)Hz (hertz) GHz (gigahertz) NOTE: Many un
34、it multiples are used for this quantity, as appropriate. The conversion to SI has no effect on current practice.MHz (megahertz)kHz (kilohertz)3.3rotational frequency s-1(1 per second) Not favoredr/s (revolution per second)Preferred for rotating machine speeds; electrical, hydraulic, or pneumatic too
35、ls; automatic control instruments.r/min (revolution per minute)3.4wavelength m (meter) cm (centimeter) NOTE: Many unit multiples are used for this quantity, as appropriate. The conversion to SI has no effect on current practice.mm (millimeter)nm (nanometer)See also 7.1 and 8.33.5rotational accelerat
36、ionr/s2(revolution per second squared)Rotating machineryItem QuantitySI Symbol(Unit)Preferred Multiplesof the SI UnitsOther UnitsPermitted forUse with SITypical and RecommendedApplications andExplanatory Notes4.1mass kg (kilogram) Equipment and materials, transport and handling, construction elevato
37、r loadsMg (megagram) t (metric ton) Mass of coal and other bulk materialsNOTE: The name metric tonmay be used as an alternative to megagramg (gram)mg (milligram)Mass of small items4.2linear density (mass per unit length)kg/m (kilogram per meter)g/m (gram per meter)mg/m (milligram per meter)Mass load
38、 on conveyor belt or on a beamConductor mass per unit length4.3area density (mass per unit area)kg/m2(kilogram per square meter)Mass loads on floorg/m2(gram per square meter)Metallic coatings, platingCopyright 1984 IEEE All Rights Reserved5IN ELECTRICAL AND ELECTRONICS SCIENCE AND TECHNOLOGY ANSI/IE
39、EE Std 945-19844.4density (mass per unit volume)kg/m3(kilogram per cubic meter)Mass density of gases, solids or liquids4.4.1mass concentration(mass per unit volume)mg/m3(milligram per cubic meter)Air pollution datag/L (gram per liter) Mass concentrations in liquids4.4.2mass per unit energy kg/J (kil
40、ogram per joule)g/GJ (gram per gigajoule)Contaminent production related to fuel burning process4.4.3relative density 1 (one) NOTE: The terms specific weightand specific gravityshould be replaced by the term relative density.Mercury has a relative density of 13.6, meaning that it is 13.6 times as den
41、se as water. Water is implied as the reference substance unless indicated otherwise. Relative density is a ratio and has no units; it is always just a number.4.5momentum kgm/s (kilogram meter per second)4.6moment of momentumkgm2/s (kilogram meter squared per second)4.7moment of inertia(See also item
42、 4.13)kgm2(kilogram meter squared)4.8force N (newton)MN (meganewton) Reactions on structureskN (kilonewton) Forces in columns, conductor tension, loading on insulators, braces, and strutsmN (millinewton)mN (micronewton)Forces of small magnitude4.8.1force per unit length N/m (newton per meter) Wind l
43、oading on conductors4.9moment of force, torqueNm (newton meter) Engineering calculations, bolt tightening torque, motor torqueMNm (meganewton meter)Bending moments on structureskNm (kilonewton meter)Bending moments on structuresNOTE: This unit can result in confusion with the unit for work or energy
44、 (see 4.20) which is also newton meter but which in the later case is called the joule. It is important to recognize the difference between torque and energy; the joule should never be used to express torque.Item QuantitySI Symbol(Unit)Preferred Multiplesof the SI UnitsOther UnitsPermitted forUse wi
45、th SITypical and RecommendedApplications andExplanatory Notes6Copyright 1984 IEEE All Rights ReservedANSI/IEEE Std 945-1984 IEEE RECOMMENDED PRACTICE FOR PREFERRED METRIC UNITS FOR USE4.10pressure Pa (pascal) Both gauge pressure and absolute pressure are properly expressed in pascals, using SI prefi
46、xes as appropriate.kPa (kilopascal) The kilopascal (kPa) is the unit recommended for fluid pressure for almost all fields of use, such as barometric pressure, tire pressure, water pressure, and steam pressure. A notable exception is in air conditioning, where pressure differentials in air ducts are
47、more conveniently measured in pascals (Pa).4.11stress Pa (pascal)MPa(megapascal) Compressive, tensile, and shear stresses on structuresN/mm2(newton per square millimeter)1 N/mm2= 1 MPakPa (kilopascal) Static and dynamic stresses in low-strength materials (wood). Dynamic stresses on stator bar packin
48、g4.12modulus of elasticity Pa (pascal)MPa (megapascal) Elastic moduli of structural materials4.13second moment of aream4(meter to the fourth power)cm4(centimeter to the fourth power)mm4(millimeter to the fourth power)Properties of structural shapes4.14section modulus m3(meter cubed) cm3(centimeter c
49、ubed)mm3(millimeter cubed)Properties of structural shapes4.15viscosity (dynamic) Pas (pascal second) NOTE: Use of the centipoise is to be avoided.mPas (millipascal second)Hydraulic model studies lubrication1 mPas = 1 cP (centipoise)4.16kinematic viscosity m2/s (meter squared per second)NOTE: Use of the centistokes is to be avoidedmm2/s (millimeter squared per second)Hydraulic model studies, lubrication, viscosity of oils and other liquids1 mm2/s = 1 cSt (centi-stokes)4.17surface tension N/m (newton per meter)Item QuantitySI Symbol(Unit)Preferred M
